The Periodontal Ligament Health And Social Care Essay

The periodontic ligament has assorted maps, in peculiar tooth support and eruption, related to its structurally complex administration. This is shown through its extended development trusting on the timing of events such as dentine formation so that the cells of the dental follicle can distinguish into those cells required to bring forth the periodontic ligament. The organisation of these cells in the mature periodontic ligament is indispensable in giving the tissue structural unity every bit good as enabling it to be compressed, which is of import to let for orthodontic motion every bit good as in maps such as chew. The fibroblast can be seen to be peculiarly of import in bring forthing the collagen fibres indispensable for back uping the construction as a whole. The PDL is hence seen is a complex specialised conjunction tissue, with much that still remains unknown about it.1. IntroductionThe periodontium are the tissues that environment and back up the dentition, dwelling of: the g um, periodontic ligament, cementum and alveolar bone. The periodontic ligament ( PDL ) is a specialised connective tissue formed of cells and fibers embedded in a land substance incorporating cells, blood vass and nervousnesss. It is located between the root cementum of the tooth and alveolar bone covering the socket wall ; the country it occupies is the periodontic infinite. The ligament is uninterrupted with connective tissue of the gum every bit good as the mush chamber. The PDL is of involvement due to its importance in organizing an fond regard between the tooth and alveolar bone, which means that disease, can distribute easy from the unwritten pit through the back uping constructions of the dentition ( via the PDL/periodontium ) . Figure 1 – The PDL is shown in blue ( Nagal et al 2008 ) . 2. Function Tooth support mechanism The PDL is a robust tissue fond regard between the tooth and alveolar bone. It acts as a daze absorber to defy any occlusal forces and masticatory tonss, whilst protecting underlying tissues such as the root vertex. There are three chief constructions commanding tooth support: collagen fibers, land substance and vasculature. Experiments carried out by Kawada, Komatsu et Al ( 2000 ) on rat molar dentition show that collagen fibers can bear a high mechanical burden Fibres attach to the cementum of the tooth on one side and to the alveolar bone on the other side. They have a wavy orientation or ‘crimp ‘ due to cross-linking of the proteoglycans ( Gathercole, Keller et Al, 1983 ) . In burden, fibres uncrimp so stretch. It is suggested folds are involved in the initial phases of burden, leting some motion before the tissue is placed under tenseness. Fibroblasts are parallel to the collagen fibers. They attach to collagen via a fibronexus fond regard called plaque and can orientate the extracellular matrix ( Harris, Stopak, Wild et Al, 1981 ) . Fibroblasts are indispensable in tooth support due to their high rate of collagen turnover ; if they are damaged there is a rapid loss of back uping tissue of the tooth. Proteoglycans found in land substance lessening in molecular-weight fraction when tonss are applied. This is shown by an experiment carried out by Picton, Stanbury et Al ( 1987 ) on macae monkey dentition. There was a lessening in peak size of proteoglycans on application of tonss of 1N and a farther lessening in peak size by about 0.15 A280 unit with tonss of 4N. After a three hr recovery period there was an addition in molecular size of proteoglycans. It has been said the PDL is a suspensory ligament so the tonss are spread through oblique fibers running across the ligament to the alveolar bone. This theory relies on Hooke ‘s jurisprudence of elastic kick proposing if the tooth is pushed, it would react to the force proportionately. Therefore, the PDL responds elastically to coerce being applied. However, I do non believe this is feasible because of surveies carried out on nomadic dentitions by Parfitt et Al ( 1960 ) where a human upper jaw incisor was taken and the place of it measured at intervals before, during and after load application. The response produced a curving graph of burden against supplanting as shown in figure 2, whereas if the response was elastic a consecutive lined graph would be produced. This suggests that hysteresis is the likely method of tooth support as there is deficiency of supplanting with increased force because the system has memory. An experiment carried out by Moxham et Al ( 1989 ) on incisor dentitions of guinea hogs suggests dentitions exhibit a viscoelastic response to axial directed tonss. This is because the response of burden application is biphasic ; ab initio there is an elastic response followed by a slower, gradual response demoing a syrupy stage. Figure 2 – this graph is an axial load/mobility curve for a human upper jaw incisor to demo hysteresis. Consecutive tonss pass along different waies ( hysteresis cringles ) . ( Parfitt et al 1960 ) . The first stage demoing an elastic more additive response can be seen, every bit good as the 2nd more gradual syrupy stage. 2.2 Tooth eruption and impetus mechanisms For eruption to happen there must be a mechanism to bring forth the eruptive forces, processes where these forces are transferred to environing tissues enabling the tooth to be supported in place, so reconstructing of the periodontium to prolong the tooth. The periodontium is likely to be the beginning of the force for eruption. One position suggests that the force is produced by fibroblast contractibility whereas another position suggests that vascular hydrostatic force per unit areas are responsible. It has besides been proposed that a ‘zone of shear ‘ is a site of remodelling during eruption. Fibroblast contractility hypothesis Fibroblasts with smooth musculus cells such as ?-smooth musculus actin are called myofibroblasts. These make connexions with extracellular matrix through fibronexus. Myofibroblasts are thought to exercise tenseness on their extracellular matrix doing tooth eruption. When a fibroblast is placed in civilization with a piece of root dentine it can travel the piece of dentine. Therefore it has been suggested contraction of fibroblasts in the development PDL is responsible for ‘pulling ‘ the tooth into the unwritten pit. Opposing grounds for this, such as an experiment carried out by the usage of lathyrogens ( drugs that inhibits collagen cross ) , in gnawer incisors showed that eruption was unaffected so collagen fibers are non required for eruption ( Berkovitz, Moxham, Newham et Al, 1995 ) . Vascular hydrostatic force per unit area hypothesis This hypothesis suggests that an eruptive force is generated by blood force per unit area act uponing the periodontic tissue hydrostatic force per unit areas. Position of dentitions can alter in synchronism with arterial pulsation ( movements up to 0.4um Berkovitz et Al ( 2008 ) and when arterial pulsation is zero, eruption does non happen farther back uping this hypothesis. Experimentally, utilizing hypotensive drugs there is an addition in eruptive motion due to an addition in periodontic hydrostatic force per unit areas. Stimulation of the sympathetic nervous system causes vasoconstriction therefore a reduced periodontic tissue force per unit area and decreased tooth eruption, but eruption starts once more one time the stimulation is removed. I think there is cogency in both hypotheses as tooth motion, whether it is eruption or impetus, could be caused by both of these. Although there is important grounds against the fibroblast hypothesis, it may still lend to tooth motion, but may non entirely be the cause of tooth eruption. 2. 3 Formation, care and fix of alveolar bone and cementum Cells are contained within the ligament in a reservoir and are available when needed for tissue homeostasis and repair/ regeneration. These are uniform mesenchymal cells which are produced to equilibrate out cells migrating out of the PDL or cells that dice. These cells include cementoblasts, cementoclasts, bone-forming cells and osteoclasts. Changes in forces involved in growing and impetus stimulate bone and cementum formation or reabsorption. Figure 3: Histological position of the Bone remodelling sequence ( Grigoriadis A, 2008 ) . Osteoblasts form bone whereas the osteoclasts resorb it. Extrinsic Sharpey fibers enter bone sheer from chief fibers of the PDL. Stem cells for bone-forming cells are found in the PDL. Osteoblasts are bone organizing cells that line the tooth socket, they synthesise collagen matrix and go enclosed in the matrix. They besides produce growing factors and may play a function in osteoclast map. Cementum is easy formed throughout life leting reattachment of PDL fibers, which are seen as a calcified portion of the cementum. Aceullar extrinsic fiber cementum as shown in figure 5 is derived from PDL Sharpey ‘s fibers that run into precementum. These are good mineralised extrinsic fibers and organize the matrix of cementum. 2. 4 Control of chew Sensory nervus fibers of the PDL are associated with mechanoreception via mechanoreceptors that have a low threshold and can be activated with tonss of 0.01 N ( Berkovitz et al, 2008 ) . Endings of mechanoreceptors are Ruffini-like and react proportionately to coerce applied. Mechanoreceptors are involved in masticatory and salivary physiological reactions. Sensory nerves from anterior dentitions convey information about contact between nutrient and the dentition, hence changing the force needed to pull strings the nutrient between dentitions. They modulate activity of the motor nerve cells of the nervus hypoglosus nervus involved in commanding the place of the lingua in chew. The PDL is involved in the jaw opening nonvoluntary physiological reaction which is triggered by mechanical or electrical stimulations being applied to unwritten mucous membrane, PDL or dentitions. A stronger stimulation produces a greater response. This is one theory that controls chew, another is that it is consciously controlled through instructions from the motor cerebral mantle. The beat generator theory suggests chew relies on cardinal spiel generators within the brain-stem. Fibroblast contractility is involved in chew as it allows for growing of the jaw. Their association with peculiar constituents of the matrix allows them to react to alterations in tenseness and compaction of extracellular matrix. Integrins are mechanostransducers that bind to extracellular matrix constituents to convey this stimulation to fibroblasts. Fibroblasts besides realign collagen filaments by drawing them back towards the cell. Fibroblasts and collagen fibers align parallel to the way of strain in the matrix. 3. DEVELOPMENT Overview The PDL signifiers after root formation begins. The internal and external epithelial tissue proliferate to organize Hertwig ‘s epithelial root sheath ( HERS ) . HERS fragments due to growing alterations and organize epithelial cell remainders of Malassez ( ERM ) . Now during tooth development, PDL formation begins ( in the cap phase ) . The enamel organ and HERS are surrounded by a dental pouch formed of condensed cells called the dental follicle. Cells of the dental follicle differentiate into cementoblasts, fibroblasts and bone-forming cells. Fibroblasts synthesise fibers and land substance of the PDL. Fibres become embedded in cementum ( formed by cementoblasts ) next to the dentine and in the bone laid down by the bone-forming cells at the other terminal. The PDL infinite is filled with an unorganized connective tissue between bone and cementum. This is remodeled by the extracellular matrix and is replaced by packages of fibers which become reorganized tissue, uninterrupted across the ligament infinite to procure fond regard of the tooth. This initial fond regard is modified after tooth eruption and one time occlusion establishes. 3.1 Embryonic Development The nervous tubing ( embryo ‘s precursor to the CNS ) develops via introversion of the exoderm into mesenchyme, following this nervous crest cells migrate to the dorsal midplane of nervous tubing and occupy the developing branchial arches Bronner-Fraser et Al ( 1995 ) . These ectomesenchymal cells when concentrated form the dental papilla and dental follicle Moxham et Al ( 1995 ) . Interactions between matrix adhesion molecules, syndecan and tenascin cut down migration and promote collection of ectomesenchymal cells promoting formation of the dental papilla and follicle Vainio, Thesleff et Al ( 1992 ) . The dental papilla is involved in formation of the tooth root including odontoblasts and dental mush. The dental follicle differentiates organizing the PDL cells every bit good as other cells of the periodontium, such as bone-forming cells and cementoblasts ( Yao, Pan, Wise et Al, 2008 ) . The dental follicle is seeable in the cap phase ( embryologic twenty-four hours 15 ) of development and signifiers from cranial nervous crest cells ( Chai et al, 2000 ) . It is required for eruption as it regulates osteoclastogenesis and osteogenesis ( Marks and Cahill et Al, 1984 ) ( Wise et al, 2005 ) . Evidence for development of the periodontium was proven by Nanci A et Al ( 1971 ) when tooth buds were labeled with tritiated thymidine and transplanted. Cementoblasts and fibroblasts in the development cell were labeled demoing that they originated from the transplanted tooth bud and as the dental follicle was merely transported with the tooth bud so it must be the beginning of primogenitor cells for the cementum, bone and fibroblasts. Work carried out by Palmer and Lumsden et Al ( 1987 ) confirmed this. Figure 4 shows the Cap phase of tooth development ( Cho and Garant at al 2000 ) This is the 2nd phase of development after the bud phase where the epithelial invaginates into the mesenchyme. At the cap phase the epithelial-mesenchymal interactions are still happening, but there is a greater difference between the cell types of the enamel organ. Centrally the cells are more rounded, whereas peripherally the cells are set uping themselves to organize the external and internal epithelial tissue. By late cap phase ( 12th hebdomad ) , the cardinal cells become detached merely keeping contact by desmosomes. This tissue is called the stellate Reticulum and develops further in the bell phase. The EEE remains cubelike whereas the IEE becomes columnar. The mesenchyme below the IEE is called the alveolar consonant papilla and that environing the tooth source is the dental follicle. Development of the PDL relies on the formation of root dentine and synthesis of cementum. As HERS encloses the dental papilla, distinction of odontoblasts is initiated from cells at the fringe of the dental papilla and formation of root dentine and atomization of the epithelial root sheath allows migration of dental follicle cells towards dentine and allows distinction into cementoblasts ( Cho and Garant et Al, 1988 ) . There are two chief cells types of the PDL ; mesenchymal cells of the dental follicle perifollicular mesenchymal cells Cells of the perifollicular mesenchyme are stellate-shaped, little, indiscriminately orientated, widely spaced. They have a little cytol incorporating unsmooth endoplasmic Reticulum, free ribosomes and long cytoplasmatic procedures to link with adjacent cells. As root formation progresses these cells addition in mutual opposition and man-made activity. They become extended with increased protein releasing cell organs enabling them to synthesize and lodge collagen filaments and glycoproteins in the development PDL ( Cho, Garant et Al, 1996 ) . 3.2 Development of the Fibres of the PDL Chief fibers of the PDL organize the chief part of the ligament and are found at the freshly formed root dentine, associated with fibroblasts. Collagen fibers are tightly packed by cementoblasts during development of noncellular extrinsic fiber cementum. In tooth eruption, fibers spread and merge across the breadth of the ligament to organize chief fibre packages. In the center of the ligament collagen fibers are less tightly packed. The bulk of chief fibers are coronal fibers running from the cementum to cram organizing the oblique fibers, which occupies two tierces of the ligament ( Grant, Berwich et al, 1972 ) . Agreement of oblique fibers allows for forces of chew to be absorbed. Histologically there are distinguishable fibre types shown in figure 7. As the root develops chief fibers become uninterrupted as Sharpey ‘s fibers in mineralised bone and noncellular cementum. Sharpey fibers are cemented into bone or cementum by a nonfibrillar matrix. Principal fibres develop earl ier in deciduous dentitions. All right brush-like fibers radiate from cementum, merely a few fibers project from the alveolar bone and widen into the unorganised collagenic cardinal zone. Sharpey fibers are thicker and more widely spaced than cementum fibers. They emerge from bone and widen towards the tooth, unknoting as they go. Cemented fibers still remain short. Alveolar fibers extend farther into the cardinal zone to fall in the length of the cemental fibers. With occlusal map, chief fibres become thicker and more uninterrupted ( Grant, Berwich et al, 1972 ) . 3.3 Development of the Cells of the PDL Tissues of the dental follicle in the developing root have three beds. Inner layer following to HERS. It is derived from the ectomesenchyme ( nervous crest beginning ) Outer bed next to the developing alveolar bone ( mesoblastic beginning ) Middle bed ( mesoblastic beginning ) Cells of the dental follicle give rise to cementoblasts, fibroblasts and bone-forming cells of the PDL. Fibroblasts are the chief cell type of the PDL and metabolize extracellular constituents. Osteoblast-like fibroblasts have besides been found incorporating alkalic phosphatase ( Lie, Yacobi, Savion, Narayan, Pitaru et Al, 1997 ) . These cells form bone cells and cementoblasts and bring forth aceullar extrinsic fiber cementum in the mature PDL ( Groeneveld, Everts et Al, 1995 ) . In eruption there may be alterations in non-fibrous extracellular matrix and the vascularity of PDL. Osteoclasts appear at the alveolar bone surface leting bone to reconstruct in association with tooth eruption and bone growing. Undifferentiated root cells are besides found as the PDL develops and once it is mature. These can distinguish into bone-forming cells, cementoblasts and fibroblasts. Research suggests these root cells are found in perivascular sites and in next endosteal infinites. They mature farther after migration into bone or cementum surfaces ( Mcculloch et al, 1993 ) . Further research needs to be carried out to find whether there is a common primogenitor cell for cementoblasts, fibroblasts and bone-forming cells. Some say cementoblasts arise from HERS every bit good as the dental follicle ( Zeichner-David et Al, 2003 ) others say that all of the cementoblasts arise from the dental follicle ( Diekwisch, 2001 ) . 3.4 Development of the Vasculature of the PDL Nerve fibers are seen in the mush, nevertheless few are found in the lower dental follicle that will organize the PDL. With root formation and eruption, nervousnesss adjacent to the bone grow into the PDL with blood. Centripetal excitation is established one time the ligament is to the full organised after eruption. Blood vass are derived from the periapical country from which they enter and pass upwards in the ligament. During eruption the tooth receives vass from the gum and capillaries of these dentitions may be extremely fenestrated.. 3.5 Molecular Mechanisms Development of the PDL is dependent on the extracellular matrix which regulates collagen filament formation ( McCulloch et al, 2000 ) . Small leucine rich proteoglycans such as lumican and decorin regulate administration of collagen filaments in development which was proven in decorin deficient mice by Matheson et Al ( 2005 ) . In contrast to this, Yamada et Al ( 2001, 2007 ) found that PDL-associated protein is specifically expressed in the dental follicle and mature PDL, which interacts with bone morphogenetic protein-2 to suppress the mineralisation of the PDL. Periostin is an adhesion protein which is expressed in the dental follicle, Rios et Al ( 2005 ) and Kia et Al ( 2006 ) suggest it is required for care of the PDL and is involved in the oncoming of periodontic disease. This is from research on periostin deficient mice demoing disorganized PDL and alveolar bone reabsorption.TGF?1/2 and BMP-4 are critical regulators in distinction of connective tissues such as the PDL ( Vainio et al, 1993 ) . 4. ANATOMY The PDL is the specialised connective tissue between the cementum covering the root of the tooth and the bone organizing the socket wall. It ranges in breadth from 0.15mm to 0.38mm Berkovitz et Al ( 2008 ) . The thinnest part is around the in-between tierce of the root which decreases in thickness with age. The mature PDL is subdivided into three parts ( Sloan, Carter et al, 1995 ) . – Bone-related part rich in cells and blood vass, – Cementum-related part with heavy well-ordered collagen packages – Center zone incorporating fewer cells and dilutant collagen filaments Dentine- side of PDL Bone- side of PDL Figure 5: Sharpey ‘s fibers extend into the dentine and alveolar bone on both sides. These are extensions of the chief fibers widening across the PDL infinite Fibroblasts Blood vass Extracellular Matrix ( I ) Collagen fibers Collagen is a quaternate protein formed of amino acids, glycine and proline, that coil into a ternary spiral to organize strong fibers found in connective tissues of ligaments and sinews. Collagen fibres consist of microfibrils composed of tropocollagen molecules. Collagen packages are found in the PDL embedded in an formless ( shapeless ) background stuff, land substance ( Nanci and Bosshardt et Al, 2006 ) . Hempen collagens The bulk of collagen is present as Type 1 and Type III hempen collagens in a ratio of 3:1 ( Berkovitz et al, 2008 ) . Approximately 70-80 % of PDL collagen is type 1 ( Wagle et al, 2005 ) .This is a major constituent of most connective tissues, such as tegument and bone. Type III collagen is found at the fringe of Sharpey ‘s fibers and close nervousnesss and blood vass, every bit good as high sums being found in immature developing tissues and in granulation tissue Berkovitz et Al ( 2004 ) . 15 % of collagen is found to be type III collagen of unknown map. However it is associated with sites of the organic structure with a rapid turnover and is found covalently linked to type I collagen throughout the PDL ( Berkovitz, Holland, Moxham, 1992 ) . Non -fibrous collagens Type V, VI, XII – Type VI collagen is absent from the center of the ligament during the eruptive stage, whereas Type XII collagen appears after eruption tardily in development. There may be increased Type V collagen in periodontic disease. Type IV, VII -these are basement membrane collagens of blood vass and epithelial cell remainders. Non -fibrous collagens act to keep hempen collagens in a 3-dimensional web. Evidence of this was seen in transgenic mice ( DNA from another being ) with a mutant of collagen type Twelve where there is a break of the agreement of collagen fibers ( Berkovitz, Holland Moxham et Al, 1992 ) . The diameter of collagen filaments is little, with a mean of 50 nanometer. There are no age-related alterations, but the diameter may alter with periodontic disease. A specialised characteristic of collagen in the PDL is its high rate of turnover which may be the fastest in anyplace in the organic structure, these characteristics are quantified in Figure 6. The turnover is non related to functional considerations ( Berkovitz et al, 2004 ) . Figure 6 – This qualitatively shows the specialised characteristics of the PDL compared to the gingival tissue ( Berkovitz et al 2004 ) . It can be seen that the turnover rate in the PDL is five times every bit fast as that in the gum, which is related to the increased sum of Type III collagen. Chief fibers These are about 5micron collagen fiber bundles that run across the PDL and infix into cementum and bone on each terminal. The alveolar crest group – attached to the cementum below the CEJ. They run downwards and outwards to infix into the air sac. The horizontal group – apical to the alveolar crest group. Run at right angles to the long axis of the tooth from the cementum to the bone. The oblique group – the most legion group. They run from the cementum sidelong to infix into bone coronally. The apical group – radiate from the cementum around the vertex of the root to the bone. They form the base of the socket The interradicular group – are found between the roots of multirooted dentitions. They run from the cementum into the bone organizing the crest of the interradicular septum. Figure 7 – Chief fibre groups of the PDL ( Nanci A EL Al Oral Histology P.266 ( 2003 ) ( A ) Transseptal, ( B ) Alveolar crest, ( C ) Horizontal, ( D ) Oblique ( Tocopherol ) Apical ( F ) Interradicular There is contention over the extent of the single fibers traversing the breadth of the PDL. Position 1 There are distinguishable tooth-related and bone-related fibers that intercalate near the center of the ligament as an intermediate rete. This rete explains how the forces of tooth eruption may be sustained However this may be an artifact related to collagen fibers in turning incisors looking as sheets instead than packages. Position 2 This is a more recent position proposing the fibers cross the full breadth of the periodontic infinite but subdivision en path and articulation neighbouring fibers to organize a complex 3-dimensional web. I think a complex web of fibers is more likely in the PDL due to the functional demands placed on it and for it to carry through its maps of tooth support and eruption. Sharpey ‘s Fibers The part of chief fibers embedded into bone or cementum are known as Sharpey ‘s fiber. In primary noncellular cementun fibers are to the full mineralised, nevertheless those in cellular cementum and bone are partly mineralised at their fringe. Sharpey ‘s fibers can infix uninterrupted into the bone of the alveolar procedure and continue as chief fibers of an next PDL fond regard. They have a complex construction and lace-like form and can widen buccally and linguistically with fibers of the periosteum. The gingival ligament is besides involved in keeping functional unity and is formed of groups found in the lamina propria of the gum. Figure 8- Sharpey ‘s fibers hypertext transfer protocol: //www.bu.edu/histology/p/10003loa.htm ( 28/02.10, 23.19 ) 4.1 ( two ) Oxytalan fibers These are pre-elastin fibers organizing about 3 % of all fibers of the PDL ( Berkovitz et al, 2004 ) . They are attached into the cementum of the tooth and cross out as a delicate web into the PDL. They are concentrated in the cervical part of the ligament where they run parallel to the gingival group of collagen fibers. In the chief portion of the PDL they are longitudinal and traverse the oblique fibres sheer. The oxytalan fibres terminate around blood vas. These fibers increase in figure and thickness in dentitions that carry abnormally high tonss such as abutment dentitions for Bridgess. They may hold some function in tooth support in relation to vasculature. Oxytalan microfibrils are similar in construction and map to fibronectin filaments. These are involved in adhesion and migration of fibroblasts. Due to their snap from the elastin fibers formed by fibroblasts, they are able to react to tenseness. Figure 9 – Oxytalan fibre hypertext transfer protocol: //www.dentistry.ucla.edu/PIC/members/force/index.html 28/02/10 23.22 ( A ) Cementum, ( B ) Principal oxytalan fiber ( C ) Oxytalan piece of land ( D ) Periodontal vas. 4.1 ( three ) Land Substance The PDL is composed of 60 % land substance by volume ( Berkovitz et al, 2004 ) dwelling of glycosaminogylcans, proteoglycans and glycoproteins secreted by fibroblasts. Hyaluran is a gylycosaminoglycan consisting a big volume of the land substance. It affects the permeableness and motility of the PDL tissue. The two chief proteoglycans are proteodermatan sulfate and a proteoglycan containing chondroitin sulphate/dermatan sulfate loanblends. Proteodermatan sulfate is related to decorin which increases the strength of collagen filaments. Land substance can besides change collagen orientation. Glycoproteins such as fibronectin are involved in cell migration, orientation and fond regard. Tenascin is another glycoprotein, besides found in the immature PDL. It is non found throughout the PDL like fibronectin, but is located in parts near alveolar bone and cementum. Employee turnover rate of land substance is greater than collagen and it is involved in ion and H2O binding every bit good as exchange of substances such as adhering growing factor. Tissue unstable force per unit area is high in the PDL at 10 millimeters Hg above atmospheric force per unit area, hence impacting tooth support and eruption mechanisms. Land substance inhibits mineralisation of the PDL. Experiments where enzymes that degrade the land substance, such as spreading factor and chondroitinase are applied to the PDL followed by mineralizing solution prove this, as mineral crystals appear. Calcium adhering proteins such as S100A4 in extracellular matrix besides prevent mineralisation ( Berkovitz et al, 2004 ) . In periodontic disease there is a lessening in dermatan sulfate and an addition in chondroitin sulfate. Remodeling of the PDL occurs in deficiency of occlusal operation, where there is a lessening in chondroitin sulfate, decorin and Lipo-Hepin sulfate. Changes in the land substance could measure the patterned advance of disease, such as in measuring the gingival crevicular fluid for these proteins. 4.2 Cells 4.2 ( I ) Fibroblasts Poundal fibroblasts are big cells with an extended cytol and many cell organs associated with protein synthesis and secretion- unsmooth endoplasmic Reticulum, Golgi composite, chondriosome and secretory cysts. This reflects their high rate of collagen and land substance synthesis. They have a developed cytoskeleton with adherens and spread junctions due to their functional function. Fibroblasts are aligned along the way the fiber packages are in and widen cytoplasmatic procedures that wrap around collagen packages. Collagen fibrils in packages are invariably being remodeled as fibroblasts are capable of both synthesising and degrading collagen. Evidence for this is seen in the presence of intracellular collagen profile within cells ( Chris everts, Zee, Creemers, Beertsen et Al, 1996 ) . The profiles contain collagen in changing visual aspects, from normal banded filaments to unbanded filaments. Cellular activities of fibroblasts are controlled by modulatory molecules such as growing factors and cytokines. IGFI, BMPs, PDGF, IL-1, TGF? stimulate synthesis of collagen and inhibit synthesis of metalloproteinases, for illustration collegenase. Tissue harm relates to an addition in cytokines to forestall debasement. Fibroblasts besides produce factors that inhibit osteoclastic distinction, such as osteoprotegerin which inhibits bone reabsorption. Alkaline phosphatase is an enzyme related to the formation of aceullar cementum found in fibroblasts. It has receptors to epidermal growing factor that inhibit the fibroblast from distinguishing into cementoblasts or bone-forming cells. Other molecules such as TGF? , IGFI, BMP-2, BMP-7 and FGF-2 regulate proliferation and distinction of fibroblasts, bone-forming cells and cementoblasts. Figure 10 – Conventional representation of a fibroblast hypertext transfer protocol: //www.tiho-hannover.de/einricht/anat/lit/mwenth/conntis 28/02/10 23.55 Poundal fibroblasts are able to degrade and synthesize collagen. Degradation occurs through phagocytic activity happening through the intraceullular collagen vacuoles in fibroblasts that ingest the collagen from the extracellular environment ( Berkovitz, Newham 1995 ) . Degradation involves acerb phosphatase and cathepsins. Synthesis of collagen occurs via the protein releasing organels round in the fibroblasts. Fibrils form via wadding of single tropocollagen molecules. Figure11 – Fibroblasts in cell civilization from a mouse embryo ( Todaro et al 1963 ) 4.2 ( two ) Bone and cementum cells These cells are situated within the PDL, but are involved in organizing difficult tissues. Cementoblasts These are cement organizing cells that line the surface of cementum. They are little and cubelike in form packed with cell organs involved in secernment. These cells become trapped in Howship ‘s blank one time the cementum has been laid down. Osteoblasts These are bone organizing cells that line the tooth socket. They are cubelike in form and have a secretory function. Cementoclasts and osteoclasts These reabsorb cementum and bone and originate from macrophage-derived cells. They sit in Howship ‘s blank where a coppice boundary line develops. Figure 12 demoing the basic construction of an Osteoclast ( Grigoriadis A, 2008 ) 4.2 ( three ) Defence cells Defence cells found in the PDL consist chiefly of mast cells and macrophages. Mast cells are found near to blood vass as they degranulate in hypersensitivity type 1 reaction. Eosinophils can besides be found. 4.2 ( four ) Epithelial remainders of Malassez Epithelial cells found in the PDL are leftovers of HERS. They are found nigh cementum as a bunch of cells that form an epithelial web. More of these cells are found in forking countries, at the vertex of deciduous dentitions and in the gum of older dentitions. They may hold a function in periodontic repair/regeneration as they can be stimulated to proliferate. 4.2 ( V ) Stem Cells and Precursors Undifferentiated mesenchymal cells are required due to changeless omission of cells by programmed cell death, which needs to be balanced by production of new cells in order to keep homeostasis. In lesion mending these cells differentiate to mend the ligament itself, but besides produce cells to reconstruct the lost bone and cementum ( Beersten, Van den Bos, Everts et Al, 1997 ) . They have a perivascular location and may besides be found in endosteal infinites of alveolar bone. Different stimuli recruit primogenitors bring forthing different cell types, such as bone-forming cells in orthodontic burden. Recently root cells found in the PDL have been isolated turn outing their presence ( Seo, Miura, Gronthos, Bartold, Batouli, Brahim, Young, Robey, Wang, Shi et Al, 2004 ) . 4.3 Vascularization 4.3 ( I ) Blood supply The PDL is highly vascularised. Major blood vass are postcapillary venulas that run between chief fiber packages and shut to alveolar bone. Fenestrated capillaries allow diffusion and filtration ; this may be connected to high tissue fluid force per unit area. The sum of fenestrations alterations harmonizing to the phase of eruption ( Berkovitz, Newham, Moxham et Al, 1995 ) . 4.3 ( two ) Nerve supply The PDL is associated with many sensory and autonomic nervousnesss. Centripetal nervousnesss are associated with nociception and mechanoreception ( chew ) , whereas autonomic nervus fibers are associated with supply of blood vass. Nerve bundles enter near the root vertex or through the center and cervical parts of the PDL as finer subdivisions through the alveolar bone. Fibers can be myelinated if they are centripetal nervus fibers, unmyelinated fibers can be both centripetal and autonomic. Sensory nervus terminations in the PDL besides release neuropeptides, for illustration substance P and vaso-active intestinal. These substances affect blood vass and are upregulated in redness and orthodontias. 5. Clinical Indication Periodonticss Periodontic diseases cause a loss of collagen fibroblasts. This is because in redness there is an addition of tissue inhibitors i.e. matrix metalloproteinases expressed that destroy collagen. TIMP ‘s can be found of course produced by PDL fibroblasts themselves. Periodontic disease could be controlled by suppressing matrix metalloproteinases, hence diminishing tissue devastation. Drugs such as Achromycin and Vibramycin act in this manner. At the initial phase of periodontic disease there is redness of the country, nevertheless due to the high turnover rate of the tissue, regeneration can happen. If there is a loss of fond regard there is no continuity with the gum leting more bacteriums to colonize pockets and hence disease progresses. Symptoms such as Mobile, floating dentitions that are prone to falling out in are seen in advanced periodontal disease. More type V collagen every bit good as a alteration in fibril diameter can be found in the PDL. 5.2 Orthodonticss The PDL regulates motion of dentitions under tonss and is involved in conveying mechanical forces to cram. The ligament shows viscoelasticity and hysteresis every bit explained in figure 2. After application of a force the tooth moves a short distance and so halt. This is because of little deformation of alveolar bone and compaction of PDL fibers. Alveolar bone will reabsorb preferentially over cementum and the tooth moves in the way of the force being applied Certain countries of the PDL are compressed and others are under tenseness and it is these alterations that result in bone remodelling and tooth motion. Remodeling involves dislocation of the matrix of the ligament that connects the bone and cementum. The 3D-meshwork of fibers adapt to emphasiss through realignment of the collagen fibers arranged in land substance Mechanical emphasiss produced by orthodontic contraptions, alter fractal dimension of the periodontic – bone interface. This is a step of the ability of an object to make full infinite, the more infinites it fills the greater the fractal dimension. The alteration is relative to the size of force applied. Fractal dimension was measured at the vertex of maxillary grinders to demo the response of mechanical burden ( Wagle, DO, Yu, Burke et Al ) . Decisions were that fractal dimension increased along the full root length connoting that these alterations are due to physical burden as opposed to a cellular response. This is one position point nevertheless others suggest both a physical and a cellular response of reconstructing. A cellular response means osteoblastic /osteoclastic activity, such as the osteoblastic instead than fibroblastic response following orthodontic loading- bone-forming cells respond to the force per unit area and reabsorb alveolar bone. Endodonticss Irritation of the PDL can happen in root canal intervention due to overextension of the file beyond the apical bottleneck during the process. This forces dust and fluid towards the periapical tissues, which can inflame. A periapical abscess can develop around the root vertexs of the septic tooth and do farther redness. Root canal sealants can be cytotoxic to the PDL fibroblasts and ‘Canals ‘ was the most toxic sealant as proven by an experiment carried out by Chang et Al ( 2010 ) . 6. Decision This undertaking was carried out to explicate the maps, development and anatomy of the PDL. The function of fibroblasts in peculiar I found is indispensable in all of these parametric quantities. This is due to them bring forthing the collagen fibres that history for keeping the structural unity of the tissue for tooth support every bit good as theories of fibroblast contractility in tooth eruption. Clinically the absence of the fibroblast in periodontias could finally take to exfoliation of dentitions. The mechanisms by which the alveolar consonant follicle differentiates into the cementoblasts, bone-forming cells and fibroblasts of the periodontium is relevant non merely to the PDL but to the periodontium in general. Developmentally, molecular mechanisms that modulate the activity of the cells come from the original PDL cells themselves, which contributes to functions of care, fix and regeneration. Although the importance of the construction of the PDL can be seen, there is still a batch that remains unknown such as the intent of the type III collagen fibers and why these are associated with the tissue have a high turnover rate, every bit good as the intent of oxytalan fibres. The relevancy of this connective tissue can be seen clinically in many different instances, hence holding a good apprehension of its construction has helped me appreciate the effects of, for illustration periodontic disease, on the PDL from a clinical point of position.

Hilton hotels Corporate Governance Essay

Hilton Hotels and Resorts is an international chain of full service hotels and resorts and it’s a flagship brand of Hilton Worldwide. The original company was founded by Conrad Hilton and is now owned by Hilton Worldwide. Hilton hotels are owned, managed, or franchised to independent operators by Hilton Worldwide. Hilton Hotels became the first coast-to-coast hotel chain of the United States in 1943. As of 2013, there are now over 540 Hilton branded hotels across the world in 78 countries across six continents. The Hilton Hotels brand remains one of the company’s flagship brands and one of the largest hotel brands in the world. The company places marketing emphasis on both business travel and leisure travel with locations in major city centers, near airports, convention centers, and a number of vacation resorts and leisure-oriented hotels in popular vacation destinations around the world. Since being founded in 1919, Hilton Worldwide has been a leader in the hospitality industry. Today, Hilton Worldwide remains a beacon of innovation, quality, and success. And it comprehended the importance of corporate governance and formulated very systematic corporate governance guidelines. And I have disseminated its corporate governance in India, United States and United Kingdom. CORPORATE GOVERANCE AND ITS IMPORTANCE: The system of rules, practices and processes by which a company is directed and controlled. Corporate governance essentially involves balancing the interests of the many stakeholders in a company – these include its shareholders, management, customers, suppliers, financiers, government and the community. Since corporate governance also provides the framework for attaining a company’s objectives, it encompasses practically every sphere of management, from action plans and internal controls to performance measurement and corporate disclosure. Corporate governance became a pressing issue from 2002 introduction of the Sarbanes-Oxley Act in the U.S., which was ushered in to restore public confidence in companies and markets after accounting fraud bankrupted high-profile companies such as Enron and WorldCom. Most companies strive to have a high level of corporate governance. These  days, it is not enough for a company to merely be profitable; it also needs to demonstrate good corporate citizenship through environmental awareness, ethical behavior and sound corporate governance practices. HILTON WORLDWIDE’S CORPORATE GOVERNANCE: Hilton Worldwide has divided its division of corporate governance into four major classifieds, such as guidelines, Code of conduct, Ethical code, and management. These are clearly explained below: HILTON WORLDWIDE CORPORATE GUIDELINES: The Nominating Corporate Governance Committee of the Board of Directors (the â€Å"Board†) of Hilton Worldwide Holdings Inc. (the â€Å"Company†) and the Board have developed, and the Board has adopted, these governance guidelines, which describe the principles and practices that the Board is expected to follow in carrying out its responsibilities. It is expected that these guidelines will be reviewed by the Governance Committee from time to time to ensure that they effectively promote the best interests of both the Company and the Company’s stockholders and that they comply with all applicable laws, regulations and the requirements of the New York Stock Exchange and other national stock exchanges of its incorporation. These guidelines should be interpreted in the context of all applicable laws and the Company’s Certificate of Incorporation, bylaws and other corporate governance documents (each as amended, restated and in effect). These guidelines are intended to serve as a flexible framework within which the Board may conduct its business and not as a set of legally binding obligations. The Board may modify these guidelines from time to time. It provides guidelines on Board roles and responsibilities Board composition, structure, policies Board meetings Exceptions of Directors Management succession plan Evaluation of board performance Board composition Communication with non-managing directors CODE OF CONDUCT: Statement of Policy The reputation of Hilton and each of our Hotels is the key to our past, present and future success. Every Team Member is personally responsible to act with integrity to enhance Hilton’s reputation as well as to maintain a desirable work environment. Integrity means doing what’s right, all the time, and encouraging those around us to do the same. In some instances, the Code of Conduct contains rules that must be strictly observed, and in other instances it provides general guidelines. In all instances, compliance with the Code of Conduct is required. We expect Team Members to uphold the highest standards of ethical conduct in every action taken on Hilton’s behalf. Team Members must not only avoid improper activities, but also activities that create the appearance of impropriety. This Code of Conduct provides guidance about how Hilton and Team Members must work together to achieve the highest ethical standards in the hospitality business. This Code of Conduct is applicable to all employees of Hilton Worldwide, Inc. and its subsidiaries and to the employees of all hotels owned, operated or managed by Hilton Worldwide , whether or not they are employed by Hilton Worldwide. The code of conduct provides policies on the following Personal accountability Respecting and valuing diversity Maintaining harassment free work force Maintaining safe and healthy work space Drug and alcohol free workspace Violence- free workspace Restricting unacceptable behavior Business ethics Personal investment of employees Policies for conflict of interest Personal information privacy policy of employees, customers, etc. Family members and relationship Outside business and employment Reportable interests Financial obligation Business courtesies Proprietary, confidential and trade secrets Maintaining global corporate citizenship These are crucial aspects covered in code of conduct of Hilton worldwide. PRIME FEATURES OF INDIAN, UK, US CORPORATE GOVERNANCE: An effective board to provide leadership †¢ A single board with members collectively responsible for the long-term success of the company. †¢ A clear division of responsibilities for running the board and running the company with a separate chairman and chief executive. †¢ An appropriate balance of skills, experience and independence on the board and its committees. †¢ Formal and transparent procedures for appointing directors, with all appointments and re-appointments to be ratified by shareholders. †¢ Regular evaluation of the effectiveness of the board, its committees and individual directors. Accountability The board must present a balanced assessment of the company’s position. The board must determine the nature and extent of the significant risks it is willing to take, and oversee sound risk management and internal control systems. Formal and transparent procedures for carrying out these responsibilities, including an audit committee made up of independent directors and with the necessary experience. Remuneration Formal and transparent procedures for setting executive remuneration, including a remuneration committee made up of independent directors and an advisory vote for shareholders. A significant proportion of remuneration to be linked to performance conditions designed to promote the long-term success of the company. Relations with shareholders Regular contact with shareholders to understand their opinions and concerns. Separate resolutions on all substantial issues at general meetings. Shareholders to monitor and engage with the companies in which they invest. Insider trading law in US: Section 17(a) of the Securities Act,1933 prohibits fraudulent practices with the offer or sale of any security SEC Rule 14e-3, under Section 14(e) of the Exchange Act and Insider Trading Act, 1984 (ITSA) permits the SEC to bring suit against anyone violating the Exchange Act by â€Å"trading a security while in possession of material nonpublic information.† ITSA provides for penalties of up to three times the profits gained or loss avoided by the insider trading and authorizes a criminal penalty for insider trading of up to $100,000. Last few years have been significant strengthening of corporate governance in India. Hilton worldwide is listed in Indian stock exchange regulators and it adopts the guidelines of SEBI and MCA in India. Key aspects are mentioned below: Share Holding pattern Committee of corporate governance Yearly corporate governance report CONCLUSION: Since the Wall Street crash in 1929 and recent Lehman Brothers scandal, with every corporate scandal, corporate governance in corporate world is getting better. And the field of corporate governance has attracted great attention and enhancements in almost all facets. Hilton Worldwide is maintaining its market leadership with a well-structured corporate governance policies and practices. As Hiltons business based on hospitality, it’s very crucial to satisfy its stakeholders and corporate governance plays a crucial part in doing so.

Sociology Definitions

Culture: All that human beings learn to do, to use, to produce, to know, and to believe as they grow to maturity and live out their lives in the social groups to which they belong. Culture Shock: The reaction people may have when encountering cultural traditions different from their own. Culture Universal: Forms or patterns for resolving the common, basic, human problems that are found in all cultures. Culture universals include the division of labor, the incest taboo, marriage, the family, rites of passage, and ideology. Material Culture: All the things human beings make and use, from small handheld tools to skyscrapers. Non-Material Culture: The totality of knowledge, beliefs, values, and rules for appropriate behavior that specifies how people should interact and how people may solve their problems. Norms: Specific rules of behavior that are agreed upon and shared within a culture to prescribe limits of acceptable behavior. Mores: Strongly held norms that usually have a moral connotation and are based on the central values of the culture. Folkways: Norms that permit a rather wide degree of individual interpretation as long as certain limits are not overstepped. Folkways change with time and vary from culture to culture. Ideal Norms: Expectations of what people should do under perfect conditions. The norm that marriage will last â€Å"until death do us part† is an ideal norm in American society. Real Norms: Norms that allow for differences in individual behavior. Real norms specify how people actually behave, not how they should behave under ideal circumstances. Value: A culture’s general orientations toward life; its notion of what is good and bad, what is desirable and undesirable. Sapir-Whorf Hypothesis: A hypothesis that argues that the language a person uses determines his or her perception of reality. Cultural Lag: A situation that develops when new patterns of behavior conflict with traditional values. Cultural lag can occur when technological change (material change) is more rapid than are changes in norms and values (nonmaterial cultural). Subculture: The distinctive lifestyles, values, norms, and beliefs of certain segments of the population within a society. Types of subcultures are religious, age, regional, deviant, occupational. Rites of Passage: Standardized rituals that mark the transition from one stage of life to another. Ways that Culture is transmitted- Mechanism of Cultural Change-Diffusion: The movement of cultural traits from one culture to another. Reformulation: A trait is modified in some way so that it fits better in its new context. Innovation: Any practice or tool that becomes widely accepted in a society. Selectivity: A process that defines some aspects of the world as important and others as unimportant. Selectivity is reflected in the vocabulary and grammar of language. Taboo: A sacred prohibition against touching, mentioning, of looking at certain objects, acts, or people. Symbol: Objects that represents other things. Unlike signs, symbols need not share ant of the qualities of whatever they represent. Ethnocentrism: The tendency to judge other cultures in terms of one’s own customs and values. Cultural Relativism: The positions that social scientists doing cross-cultural research should view and analyze behaviors and customs within the cultural context in which they occur. Ideology: A set or interrelated religious or secular beliefs, values, and norms justifying the pursuit of a given set of goals through a given set of means.

Identify how a UK company could convince shareholders and the Essay

Identify how a UK company could convince shareholders and the regulator that it had complied with the five main principles of the UK Corporate Governance Code - Essay Example More importantly, their neutrality and lack of vested bias should be illustrated their lack of previous/present personal/professional connections. By satisfactorily adhering to this principle, a UK company can convince shareholders and the regulator about its compliance with the Code. The second main principle relates to executive remuneration. The growing discontent with the trend of exorbitant top-executive compensation has brought the issue to the notice of Financial Reporting Council. Consequently, the principle of ‘performance related pay’ is included in the Code, whereby the rules already stated in the Companies Act of 2006 will be enacted more effectively. The principle also suggests the ideal composition of the remuneration committee, where non-executive directors will play a major role, especially in ascertaining director remuneration. Another key principle set out in the Code is Accountability and Audit standards. It is suggested that only independent non-executive directors are appointed to the Audit Committee. This makes sense in the context of some major corporate scandals across the Atlantic, where conflict of interest for members of the audit committee can lead to disastrous consequences for shareholders. The fourth main principle concerns the role played by institutional investors. The salience of this principle arises from the fact that the UK is a major financial hub in the world and ethical investment/trading practices are imperative to uphold the integrity of the system. Hence all companies (especially those in the financial sector) in the UK should comply with the guidelines given in the Code. Finally, another key principle in the Code is regarding shareholder relations. Under this section, best practices and recommendations for maintaining a strong and honest relationship with shareholders are given. The principle has at its core the need for shareholders

PROPOSAL Assignment Example | Topics and Well Written Essays - 2000 words

PROPOSAL - Assignment Example The chief question of the peer reviewer was about the measures that can help solving the problem of gender gap in education In response to the peer reviewer concerns, questions and assessment it has been understood that there is essential need of thinking about the solution of the problem rather emphasizing much upon the problem itself. Hence, there are some major changed made in the proposal and considerable portion of material has been added that speak about the strategies and suggestions that can help in reducing the gender gap in education. After making these changes, it is requested from the instructor to have look at the proposal and inform about its contents. 2. Organizing your argument into appropriate sections This assignment follows a report format for formal proposals. You must organize the content of your proposal into four major sections. Each section has a specific task or purpose. (See the assignment outline under the "Drafting your Proposal" heading above.) Using sect ions creates a reader-friendly report that allows readers to access the points of your argument quickly and easily. As you revise, you may need to rearrange some of the content of your proposal. Highlight your rearrangements and revisions so your instructor will see what you've done. Finally, if you are still unsure of what content belongs in which section, ask your instructor questions about the required organization. The proposal has been organized in these sections. Introductions, Problem definition, proposed solution, reasoning, conclusion 3. Completing your research and filling in the gaps By the end of this week, you must have completed all of your research. As you revise your draft, incorporate ALL the primary fieldwork and any secondary research that you plan to use to support your arguments in this proposal. Highlight your additions/revisions so your instructor will see what you've done. There are some adjustments made in the proposal as per the comments of the instructor. The new changes have been highlighted 4. Evaluating your evidence, supporting quotes/paraphrases. Supporting evidence can't speak for itself. Ask yourself: How well-connected is each piece of evidence in your draft—each example, observation, fact, or quote from an interviewee or survey—to your overall claim? You need to add explanation or commentary with each piece of evidence so that readers can see how and why your supporting evidence is significant. Don't leave readers guessing or assume those points of connection are obvious. In each body paragraph of your draft make specific revisions/additions to add explanation for how each piece of evidence you offer is significant to your overall proposal argument. Highlight your additions/revisions so your instructor will see what you've done. The evidenced are supported by the proper references and in-text citations 5. Acknowledging available alternatives and counterarguments In your first draft, you might not have worked ou t how you would address these issues. How much or how little you will need to address alternatives or counterarguments depends on the nature of your proposal topic and on how well received (or not) your solution will be by your intended audience. If you believe that you need to respond to alternatives or counterarguments, the place to do so is in Section 3 of your proposal. Now is the time to consider adding this discussion to your draft of Section 3. Highlight your

Low in business Essay Example | Topics and Well Written Essays - 2000 words

Low in business - Essay Example In the UK, â€Å"Product liability law defines a defective product as existing when the safety of the product is below that which consumers are entitled to expect†¦The standard of proof required by the court is such that the person claiming compensation must be able to show†¦that the defect in the product caused the injury or damage† (â€Å"UK Product Liability Law,† 2009). In one case of product liability, â€Å"[an individual] helped his mother attach [a] product to his younger brothers pushchair. One of the elastic straps slipped and lashed back. The buckle attached to the elastic strap hit him in the eye causing serious, permanent damage. The claimant sued Mothercare, the supplier of the product, claiming damages in negligence and also under the Consumer Protection Act† (â€Å"Abouzaid v. Mothercare (UK) Ltd.,† 2009). Brian is a budding semi-professional roller skater, and ha been practising for a national roller skating competition in which he was the favourite to win a 5000-pound prize. Albert asked James (Phillip’s younger brother and sales associate at Cretins Ltd.) whether the store had any skates suitable for semi-professional skating. Not only did Brian fall, but he brought his father down with him. Brain sustained a broken ankle, which would prevent him from skating for a year—while Albert sustained a broken arm in the accident. This is an incidence of where product liability would come into play. â€Å"Products liability refers to the liability of any or all parties along the chain of manufacture of any product for damage caused by that product. This includes the manufacturer of component parts (at the top of the chain), an assembling manufacturer, the wholesaler, and the retail store owner† (â€Å"Product Liability—US,† 2009). There are multiple possibilities. â€Å"Products liability law consists of a mixture of tort law and contract law†¦Aspects that relate to

Panama Canal expansion Essay Example | Topics and Well Written Essays - 3000 words

Panama Canal expansion - Essay Example This research will begin with the statement that most infrastructural mega projects are prone to suffer from cost overruns, delays, poor performance or inability to give customer satisfaction if inadequately managed. Interaction of several factors such as governance of such projects, their financing, human management, and financing can cause complexities which can either promote their success or inhibit it depending on how they are approached. It is, therefore, crucial for project managers to thus critically analyze a mega project before undertaking it. This report takes an in-depth assessment of the expansion of the Panama Canal which is one of the busiest waterways internationally. Panama expansion project is also of key interest given that it plays a critical role in maritime trade and brings together international concerns. The initial construction of Panama Canal went underway in 1880 under the leadership of Ferdinand de Lesseps who built Suez Canal. This was a large scale proje ct undertaken by people who had little prior experience in canal construction. They faced several challenges including minimal workforce, diseases and lack of funding. The geology of the region also posed a challenge to the construction work. A second company, the Compagnie Nouvelle du Canal de Panama, was contracted to complete the construction. After the American government the requested French machinery for construction, work officially began in 1904. Despite the challenges encountered in constructing the canal, Panama Canal was completed a decade later.

Personal project and Scoop management plan for my personal project Assignment

Personal project and Scoop management plan for my personal project - Assignment Example I would like to urge the management of the company to consider investing in Dream Chaserâ„ ¢ Vehicle. It is a new project that if adequately supported, will make the company to go a step further. I propose that a lot of funds should be allocated so as to enable me and my team to conduct a thorough research so as to ensure that the new brand of vehicle will be the best one in the market. If it is equipped with all the necessary features, it will become so comfortable to the users. For this reason, they will do all that they can to purchase it. By this, the company will not only rebuild its reputation, but increase its revenues. This demonstrates that even if the project has been created by me, it will not succeed if not supported by others. In order for the Dream Chaserâ„ ¢ Vehicle project to be a success, well-thought feasible and manageable plan need to implement. This plan will include strategies that can enable the project to achieve its objectives. First, I would like to suggest that the project should be executed by a team of professionals. In order to cope up with the stiff competition in this field, Sierra Nevada Corporation needs to come up with novel ideas. Meaning, it should incorporate the input of well trained professionals to carry out all the activities. The other strategy to be adopted is the production of high quality products. As already hinted, the auto industry has become so competitive. So, for the company to succeed in this project, it needs to manufacture exceptionally high quality vehicle that will appeal to the target clients and win their confidence. Besides, producing high quality vehicles will help in making the company to stand as outstanding manufacturer in the midst of others. Lastly, I would like to suggest that the project should be given enough time, finances and resources. As a new product, the company should be ready to incur all the expenses it requires. Apart from allocating

Economics Quiz of Supply and Demand Case Study Example | Topics and Well Written Essays - 250 words

Economics Quiz of Supply and Demand - Case Study Example With regards to the illustrated situation and the â€Å"ancient internet cable†, the cost can be allocated amongst the three parties equitably in the following way.   Due to the fact that the cable that exists in Judah and Eastern Jerusalem accounts for 39 billion in investment, this represents a 40% share of the total project cost as a function of the total being 98 billion Judaic coin.   Similarly, the Turkish line represents a further 50% of the total cost of the project with the final 10 percent being build out to the island of Rhodes.   In this way, total price can be marginally distributed by ensuring that each responsible party pays according to the percentage rates that their part of the project has necessitated with Turkey paying the highest rate followed by Jerusalem/Judah at ten percent less and finally Rhodes at 40% less than Turkey.

Latin American Religions Essay Example for Free

Latin American Religions Essay What are some major attributes of Latin American Catholicism? Identify and describe at least two distinctions and include how they are distinct from Catholicism elsewhere. The Central American War had changed the priorities of the Catholic Church in Latin America. In the 1980’s, the clergy’s had decided to go against the Catholic Church mainly the Vatican despite the various threats, and began to help the poor which were struggling for their equality and their rights. The Catholic activism was in support of the change; however, it did influence guerilla movements in certain parts of Latin America such as Nicaragua, Salvador, Guatemala. This had introduced moral and spiritual justification. â€Å"Throughout Latin America and the Caribbean, a wing of the church surfaced as a powerful ideological force in the struggle to end authoritarian regimes,† (Meade, T., 2010). In what ways have African religions influenced Latin American Catholicism? â€Å"Latinos are comprised of a great conglomeration of ethnicities, traditions, and customs, which are traditionally, expressed by a common language (Spanish) and religion (Catholocism). For instance, Latin American values and traditions received a great influence from Catholicism and indigenous beliefs. Similarly, African traditions also permeated the Latin American culture, especially in the Caribbean region. This unique syncretism between Catholicism, and indigenous and African traditions allowed the survival of folk traditions, which led to the creation of several healing approaches,† (www.egochicagoschools.com, 2012). Should Latin American Catholicism be considered polytheistic? Why or why not? There are various polytheistic religions that are practiced today. Many of the religions today outside of Catholicism believe in more than one God. However, the Catholics believe in one God and one God only. I do think the Catholicism needs to be consistent meaning the Catholicism that is being practices within Latin American needs to be the same everywhere else. Once others start to deviate from Catholicism then it begins to start a new religion and moves away from the beliefs of the Catholicism. Only the Vatican may assess and make changes within the Catholic Religions. How have churches fostered or hindered social changes in Latin America? After the civil war, Latin Americans had turned to other religions. For over 500 years, many Latin Americans were considered loyal to the Catholic religions. However, it quickly turned to be a stronghold to Protestants. In the Liberation area other religions had developed such as Evangelical and Pentecostal. These religions are very different from the Catholicism. These religions speak in tongue, rely on baptism, accept the Holy Spirit, and emotional rituals. With these new religions developing the social changes in Latin America does provide a much broader outlook on their beliefs. There are various groups or community gatherings within the particular religion. Each religion unites and brings together their faith and social aspects within their own community. How has Protestantism spread in Latin America in the past? Is it different than the factors that are promoting the current growth in Protestantism in this region? How and why? The Protestantism had spread in Latin America in the past due to the fact of various discrepancies within the Catholic Religion. For instance, in 1980’s, the Guatemalan’s had begun to change their beliefs and lean more to the Protestants. This was proven in 2005, when a massive amount of members of the Catholic Church had begun to leave the church as rapid growth. The new leading religion was the Pentecostal church. Many of the new religions were still created by using the Catholic religion as their foundation. Reference: A History of Modern Latin America. 1800 to the Present, Meade, T., 2010 http://ego.thechicagoschool.edu/s/843/index.aspx?sid=843gid=3pgid=760

The effects unemployment has on crime

The effects unemployment has on crime Unemployment occurs when people are without jobs and they have actively looked for  work  within the past four weeks.  The unemployment rate is a measure of the prevalence of unemployment and it is calculated as a percentage by dividing the number of unemployed individuals by all individuals currently in the  labour force (the  International Labour Organization). There never occurs full employment in the country. But there are different methods of combating unemployment. There are some countries that reached a minimum unemployment figure. A good example of this are the post World War II era when there was a huge economic growth occurring. e.g. the United Kingdom in the 1950s and 60s when the average unemployment rate was at about 1.6 % (John Sloman (2004).  Economics. Penguin. p.  811), and in Australia in the 1945  government established a policy of full employment, which lasted until the 1970s when the government ran out of money. The latest statistics for UK unempl oyment is The unemployment rate stands at 7.7% down 0.1% over the quarter. 29.19 million people were in work in July to September according to the labour force survey (LFS). The number of people employed was up by 167,000 this quarter and up by nearly 300,000 from last year. (HRM Guide, 13 October 2010) As anyone can derive, there is a relationship between crime and unemployment. There have been a lot of studies into this topic as a low level of crime is socially desirable. Therefore, governments of all countries have tried to combat the problem of rising crime levels. A good example of the latter is post Soviet Russia. Crime rate in the 1980s increased to very high levels. This was the outcome of the collapse of the Soviet Union, because with it everything collapsed the law enforcement systems, social security, and minimal standard of living. And, obviously, these are the perfect conditions for an outbreak of crime. Extreme poverty and unpaid wages, which resulted from a suffering economy, have led to property crimes, theft and counterfeiting. By the early 1990s, theft, burglary, and other property crimes accounted for nearly two-thirds of all crime in the country.  There was a rapid growth of violent crime, including homicides.( Crime in the Soviet Era  Federal Research Division,  Library of Congress). In present times, though, Russia has done well in fighting this nightmare of crime. There are many other countries that have fought and are still combating this problem. By the use of the example of Russia, I wanted to show that unemployment is considered a very important cause of crime in any country, together with law enforcement problems and also labour market opportunities. Economic theories of the effect of crime on unemployment  « how many resources and how much punishment should  be used to enforce different kinds of legislation? Put equivalently, although more strangely, how many offenses should  be permitted and how many offenders should go unpunished. Gary Becker (1968). Becker (1968) is considered to be the first work which formally analyses the issue of crime using an economic model. Becker links the problem of crime to social welfare. It is assumed that criminals are as rational as any other person. And, therefore, if they are involved i n crime activities, it means that they are better off by doing so. The issue of opportunity cost comes up quite frequently in these discussions. If a potential offender, despite the knowledge that he has about the punishment he will get if he commits a crime, still goes and does it it means that the reward that he is aiming at justifies the probability of him getting caught and convicted. When looking at crime, the concept of rationality is applied not only to criminals, but to all parties involved judges, policemen, legislators and potential victims. So, when the institutions that control crime are designed, their main concern is not the crimes that are committed and how much they weigh, but the costs that occur to the society. As an example, if it takes half of the population to be turned into judges, policemen, etc in order to decrease the crime rate by 70%, it would probably not happen in the real life, because the cost of doing so is too high. Becker constructed a model, which identifies optimal levels of punishment by minimising the social c ost induced by both combating crime and crimes themselves. This model predicts the aggregated supply of offences. The number of offences a criminal would commit, according to Becker, would be negatively related to the probability of apprehension and the severity of punishment. It also includes a certain u term, which includes all other variables that can influence the predicted outcome e.g. income from legal and illegal activities, education, risk aversion, etc. But, this variable u is not explicitly studied by Becker. This work was later on continued by Ehrlich (1972, 1973). Ehrlich states that a person is able to spend time on both legal and illegal activities, but the amount of time that one dedicates to any of those activities depends on the amount of utility (return) that he gets from it. By 1973, Ehrlich designed a mathematical model that describes this relationship. Ehrlich bases his model on the decision making under uncertainty theory. The assumption used is that a person can switch between legal and illegal activities during their lifetime, depending, as I have mentioned earlier, on the amount of utility they get from them (activities). There is no training and no costs involved in changing between the two. So, it is obvious, that an increase in opportunities in the legal market, e.g. higher probability of employment and higher wages would increase the expected utility gained from legal activities and so and individual, being rational, would spend more time on legal, rather than illegal deeds. Therefore, keeping a low level of unemployment, in theory will decrease the crime level. Cohen and Felson (1979) have proposed that in order for a crime to be done, it need three factors to be satisfied: motivated offenders, suitable victims and the lack of effective legal punishment system. Leading from this, the increase in crime production is caused by an increase in the first two factors under the third an ineffective legal system. This argument only supports the prediction made in Ehrlichs model. We can deduce a positive relationship between the rate of unemployment and the crime rate. On the other side of the argument, Cantor and Land (1985) have predicted a negative relationship between the rate of unemployment and crime based on the works of Cohen and Felson. They suggested that the higher the unemployment, the less people there are in the second category (suitable victims). If there are more unemployed, those who lost their jobs stay at home and therefore avoid the risk of having their house robbed, for example. Also, a higher rate of unemployment is a sign of a recession, which means that there is less for the offenders to steal, for example. So, higher unemployment may reduce property crimes. Also, using the same logic, we can deduce a reduction in violent crimes again through a reduction in that second factor suitable victims. Statistically, most violent crimes are committed by strangers, so if you stay at home, you avoid that risk. Cantor and Land have designed an empirical model which tests the motivation and opportunity effects of unemployment rate on crime. There are several equations under estimation. The dependant variables include the differentiated levels of crimes like homicide, rape, assault, robbery, theft, burglary, etc. Independent variables are either up to date or differentiated unemployment rates. The argument in this paper is that in case of a financial crisis those that become unemployed will receive some unemployment benefits, etc. And therefore they might not turn to criminal activities straight away, but after they are under financial pressure in case unemployment benefits or an alternative source of income expires. This model has been criticized by several researchers in this area. For example, Greenberg in 2001 has argued that those who become unemployed might not have the sufficient resources to keep themselves, while out of work. This factor might make them engage in illegal activities, which contradicts the outcomes on the Cantor and Land model. He also questioned the mathematical approach of the model. Greenberg (2001) claimed that it is mathematically unacceptable if the differencing procedure is only carried out on the crime rates but not the explanatory variables. Also, Hale and Sabbagh (1991) have questioned mainly the empirical work of Cantor and Land. The ideas of integration and cointegration were introduced to show that their models  are mis-specified. Leading from this, it is argued that any conclusions drawn from their work are probably unreliable. There are other papers that only try to derive the net effect of unemployment on crime, rather than taking into account motivation and opportunity costs. A good example is a paper written by Fleisher (1963). In it, the author argues that there is a positive correlation between parent unemployment and youth crime. If there is a high level of unemployment in the country, adults become unemployed and it becomes very hard for them to provide for their children, who, therefore, might turn to illegal activities. Fleisher uses time series data to test this relationship because it gives a more thorough view of the relationship of different variable in a long period of time. The prediction of the model is justified using an OLS estimation and shows a positive and significant correlation between unemployment rate and youth crime. Some researchers preferred to use panel data to investigate this area. For example, a paper written by Raphael and Winter-Ebmer (2001) uses this approach. The argument in this paper is that there is a dependent relationship between crime and unemployment. One might be the cause of the other. E.g. high crime rates in the country will deter investment and so add to an increase in unemployment, which is what happens in countries like Russia. Because Russia is known for white-collar crime, it is a serious obstacle to foreign direct investment. (Forbes.com). Also, people who have had a criminal record might find it very difficult to find a job a so remain unemployed. The results of the OLS estimations of the model are the following: there is a positive relationship between unemployment and property crimes, but, on the other hand, there are insignificant results regarding the relationship between unemployment and more severe crimes like rape and murder. Although, one very interesting point of findings of this paper is the negative relationship between unemployment and murder. The explanation of this can potentially be found in Ehrlichs three factor model. Unemployment could decrease the potential interaction between a criminal and a victim.

Malaysian construction industry system

Malaysian construction industry system INTRODUCTION The Malaysian construction industry is undergoing a transitional change from an industry employing conventional technology to a more systematic and mechanized system. This new system is now known as the Industrialized Building System (IBS). This new method of construction can increase productivity and quality of work through the use of better construction machinery, equipment, materials and extensive pre-project planning. This study becomes very necessary since there is yet no organized body, which can provide the necessary information on the building cost comparison between the conventional system and industrialized building system in Malaysias construction industry. This study also addresses the building cost comparison of the conventional system and industrialized building system of formwork system. It provides the details building cost between the conventional system and the formwork system and indicates which of the two is cheaper. The data were collected through questionnaire s urvey and case study, which consisting of institutional buildings. Through the statistical testt-test it is shown that there is a significant difference in cost saving for the conventional system as compared to the formwork system (industrialized building system). The Malaysian construction industry is undergoing a transitional change from an industry employing conventional technologies to a more systematic and mechanized system employing the latest computer and communication technologies. This is vital for the future health of the industry, given the trend towards global competition and the advent of the k-economy. The Industrialized Building System (IBS) has been introduced in Malaysia since the 60s by the use of precast concrete beam-column elements. Since the demand of building construction has increased rapidly, it is necessary to innovate a construction method, which speeds up the building construction process. To sum-up, in general, the IBS is a methodology whereby a local construction industry is driven towards the adoption of an integrated and encouraging key players in the construction industry to produce and utilize pre-fabricated and mass production of the building at their work sites. This will help to enhance the efficiency of construction process, allowing a higher productivity, and quality, time and cost saving. The construction cost of a building using precast components should be assessed in its overall context. The traditional method of costing by material quantities with a fixed factor for labor cost can lead to incorrect estimation. For example, if labor usage is halved, this will more than compensate for a 10% material increase. More importantly, there is saving in time. Also, if properly designed and executed, precast can lead to much better quality of work. The overall cost impact of precast has therefore to take all these factors into consideration. With the rising costs of labor and less assurance of dependable skilled manpower, the trend is that precast construction will become increasingly competitive compared to cast-in-place construction? PRECAST CONCRETE CONSTRUCTION Introduction Every construction material system has its own characteristics which to a greater or less extend influence the layout, span length, construction depth, stability system, etc. This is also the case for precast concrete, not only in comparison to steel, wood, masonry structures, but also with respect to cast in-situ concrete. Theoretically, all joints between the precast units could be made in such a way that the completed precast structure has the same monolithic concept as a in-situ one. However, this is a wrong approach one, which is very labour intensive costly. If the full advantages of precast concrete are to be realized, the structure should be conceived according to its specific design philosophy: Long spans, appropriate stability concept, simple details, etc. Designers should from the very outset of the project consider the possibilities, restrictions advantages of precast concrete, its detailing, manufacturer, transport, erection serviceability stages before completing a design in precast concrete. Precast concrete system enables faster programmed times not affected by weather or labour shortages. Improves buildability early enclosure of dry envelope enables follow-on trades to start sooner. Produces a high standard of workmanship in factory conditions reduces potential for accidents, addresses on-site skill shortage. Has a high quality finish that can be left exposed concretes thermal properties can be exploited in low-energy buildings. PRIMARY FUNCTIONS Keep water out Prevent air leakage Control light Control radiation of heat Control conduction of heat Control sound SECONDARY FUNCTIONS Resist wind forces Control water vapor Adjust to movement Thermal and moisture expansion or contraction Structural movements Resist fire Weather gracefully Easy to install Architectural precast concrete provides architects with an exciting medium when designing facades for a wide range of buildings, from healthcare facilities to shopping malls, commercial office buildings to sports stadiums. Precast concrete provides: Complete thermal protection Continuous air/vapour barrier Effective rain screens Superior lifespan Reduced construction schedule and on-site labour High quality control standards Numerous finish options and colours CATEGORIES OF PRECAST BUILDING SYSTEMS Precast buildings constitute a significant fraction of the building stock in the republics of the former Soviet Union and Eastern European countries. Depending on the load-bearing structure, precast systems can be divided into the following categories: Large-panel systems Frame systems Slab-column systems with walls Precast concrete floor Large-Panel Systems The designation â€Å"large-panel system† refers to multistory structures composed of large wall and floor concrete panels connected in the vertical and horizontal directions so that the wall panels enclose appropriate spaces for the rooms within a building. These panels form a box-like structure (see Figure 1). Both vertical and horizontal panels resist gravity load. Wall panels are usually one story high. Horizontal floor and roof panels span either as one-way or two-way slabs. When properly joined together, these horizontal elements act as diaphragms that transfer the lateral loads to the walls. Depending on the wall layout, there are three basic configurations of large-panel buildings: Cross-wall system. The main walls that resist gravity and lateral loads are placed in the short direction of the building. Longitudinal-wall system. The walls resisting gravity and lateral loads are placed in the longitudinal direction; usually, there is only one longitudinal wall, except for the system with two longitudinal walls. Two-way system. The walls are placed in both directions. Thickness of wall panels ranges from 120 mm for interior walls to 300 mm for exterior walls. Floor panel thickness is 60 mm. Wall panel length is equal to the room length, typically on the order of 2.7m to 3.6 m. In some cases, there are no exterior wall panels and the faà §ade walls are made of lightweight concrete. A typical interior wall panel is shown in Figure 2. Panel connections represent the key structural components in these systems. Based on their location within a building, these connections can be classified into vertical and horizontal joints. Vertical joints connect the vertical faces of adjoining wall panels and primarily resist vertical seismic shear forces. Horizontal joints connect the horizontal faces of the adjoining wall and floor panels and resist both gravity and seismic loads. Depending on the construction method, these joints can be classified as wet and dry. Wet joints are constructed with cast-in-place concrete poured between the precast panels. To ensure structural continuity, protruding reinforcing bars from the panels (dowels) are welded, looped, or otherwise connected in the joint region before the concrete is placed. Dry joints are constructed by bolting or welding together steel plates or other steel inserts cast into the ends of the precast panels for this purpose. Wet joints more closely approximate cast-in-place construction, whereas the force transfer in structures with dry joints is accomplished at discrete points. Frame Systems Precast frames can be constructed using either linear elements or spatial beam-column subassemblages. Precast beam-column subassemblages have the advantage that the connecting faces between the subassemblages can be placed away from the critical frame regions; however, linear elements are generally preferred because of the difficulties associated with forming, handling, and erecting spatial elements. The use of linear elements generally means placing the connecting faces at the beam-column junctions. The beams can be seated on corbels at the columns, for ease of construction and to aid the shear transfer from the beam to the column. The beam-column joints accomplished in this way are hinged. However, rigid beam-column connections are used in some cases, when the continuity of longitudinal reinforcement through the beam-column joint needs to be ensured. The load-bearing structure consists of a precast reinforced concrete space frame and precast floor slabs. The space frame is construc ted using two main modular elements: a cruciform element and a linear beam element. The cruciform element consists of the transverse frame joint with half of the adjacent beam and column lengths. The longitudinal frames are constructed by installing the precast beam elements in between the transverse frame joints. The precast elements are joined by welding the projected reinforcement bars (dowels) and casting the concrete in place. Slab-Column Systems with Shear Walls These systems rely on shear walls to sustain lateral load effects, whereas the slab-column structure resists mainly gravity loads. There are two main systems in this category: Lift-slab system with walls Prestressed slab-column system Precast columns are usually two stories high. All precast structural elements are assembled by means of special joints. Reinforced concrete slabs are poured on the ground in forms, one on top of the other. Precast concrete floor slabs are lifted from the ground up to the final height by lifting cranes. The slab panels are lifted to the top of the column and then moved downwards to the final position. Temporary supports are used to keep the slabs in the position until the connection with the columns has been achieved. In the connections, the steel bars (dowels) that project from the edges of the slabs are welded to the dowels of the adjacent components and transverse reinforcement bars are installed in place. The connections are then filled with concrete that is poured at the site. Most buildings of this type have some kind of lateral load-resisting elements, mainly consisting of cast-in-place or precast shear walls, etc. In case lateral load-resisting elements (shear walls, etc.) are not present, the lateral load path depends on the ability of the slab-column connections to transfer bending moments. When the connections have been poorly constructed, this is not possible, and the lateral load path may be incomplete. Another type of precast system is a slab-column system that uses horizontal prestressing in two orthogonal directions to achieve continuity. The precast concrete column elements are 1 to 3 stories high. The reinforced concrete floor slabs fit the clear span between columns. After erecting the slabs and columns of a story, the columns and floor slabs are prestressed by means of prestressing tendons that pass through ducts in the columns at the floor level and along the gaps left between adjacent slabs. After prestressing, the gaps between the slabs are filled with in situ concrete and the tendons then become bonded with the spans. Seismic loads are resisted mainly by the shear walls (precast or cast-in-place) positioned between the columns at appropri ate locations. Precast concrete Floor The principle advantages of precast floors are speed of construction, absence of scaffolding, large variety of types, large span capacity, economy. Precast floors can also be classified according to their manufacture into totally partially precast floors. Totally precast floors are composed of units, which are totally cast at the plant. After erection, the units are connected to the structure the longitudinal joints are grouted. In some cases a cast in-situ structural topping screed is added. Partially precast floors are composed of a precast part a cast in-situ part. Both parts are working together at the final stage to achieve the composite structural capacity. The main totally precast floor roof types are described hereafter. CONVENTIONAL IN-SITU CONSTRUCTION Conventional Construction Method Conventional construction encompasses traditional forms of structural load-bearing elements; typically composed of concrete, brickwork and structural steel. We are well-versed in all forms of conventional construction and have substantial in-house capacity. The majority of our commercial and unique residential products to date have utilized conventional methods of construction. A number of designers that we have worked with tend to express the structural elements of the construction, from exposed beams, cantilevered slabs and stairs, to exposed structural steelwork. This requires a high degree of accuracy as well as a high level of workmanship; both of which are easily attained using our in-house skills. Conventional building method is defined as components of the building that are pre-fabricated on site through the processes or timber or plywood formwork installation, steel reinforcement and cast in-situ. Conventional buildings are, mostly built of reinforced concrete frames. The tr aditional construction method uses wooden formwork. It is much more costly for construction, which includes labor, raw material, transportation and low speed of construction time. Cast-in-situ Construction Method This system is suitable for a country where unskilled labor is limited. There is no heavy machinery or high technology involved. The system is technically applicable to almost all types of building. Formwork is used as a mould, where wet concrete, is poured into a temporary system. The temporary system also acts as a temporary support for the structures. The objective of in-situ method is to eliminate and to reduce the traditional site based trades like traditional timber formwork, brickwork, and plastering and to reduce labor content. A carefully planned in-situ work can maximize the productivity, speed and accuracy of prefabricated construction. Cast in-situ method uses lightweight prefabricated formwork made of steel/fiberglass/aluminum that is easily erected and dismantled. The steel reinforcement is placed within the formwork as they are being erected and concrete is poured into the mould. When the concrete is set according to the required strength the mould is dismantled. The w orkers can be trained easily to erect the moulds and set the steel reinforcement. Its advantages over the traditional construction method are, its low skill requirement, can be quickly constructed, maintenance is low, structure is durable and cost can be less. In-situ method is to eliminate and reduce the traditional site based trades like traditional timber formwork, brickwork, plastering and to reduce labor content. Carefully planned in-situ work can maximize the productivity, speed and accuracy of prefabricated construction. The formwork system is based on the combination of pre-fabrication and in-situ conventional construction, which features the utilization of permanent concrete for elements instead of conventional timber formwork. Differences Between In situ and Precast Construction Method Labour   Ã‚  Ã‚  Ã‚  Ã‚  Precast construction method only use semi-skilled workers and dont use skill or unskilled- worker in construction process. Economies are generated through reduced requirements for formwork, access scaffolding and less reliance on wet trades. Reduced on-site supervision by the main contractor is also a saving. So for precast construction method, labours are not use 100 percent for making formwork, access scaffolding, and handle wet concrete. Due to speed of construction, gives earlier return on investment, freeing up the project critical path and allowing earlier completion. It is estimated that a precast structure takes up to 20% less time to construct than a similar cast in situ structure, using labour can be late because of rest time and energy of a labour. For quality and accuracy, precast construction methods will more quality n accuracy than in situ. This ensures that reinforcement bars are accurately located and that clients receive high quality products man ufactured to controlled dimensional tolerances. Precast method delivers a high performance product with a quality appearance. Have a high quality finish that can be left exposed concretes thermal properties can be exploited in low-energy buildings because all of the equipment are made up in factory.   Ã‚  Ã‚  Ã‚  Ã‚  In situ construction method use skilled worker, semi-skilled worker, and un-skilled worker in construction process. Labour can amenable to almost any design and labour can alteration the design in last minute construction process. Design can proceed as the structure is built because labour takes a time to build. Construction can proceed independently of weather conditions because workers still can proceed the work even though whether are not good. Construction process is easily used for two way structural systems because labour used two ways structural system in construction process. It is not necessary to pay for crane on site because of labour can take instead of crane functions. Wastage Environmental and manufacturing conditions at a precast concrete plant are easily monitored. The production of precast concrete elements takes place under controlled conditions in enclosed factories. This makes the control of manufacturing, waste, emissions, noise levels, etc. easy compared with the same processes at a building site. The raw material consumption is similar for similar qualities of concrete, whether the production takes place in a factory, at a ready-mix plant or at a building site. The raw material waste in precast concrete production is very small. The process of preparing mild steel reinforcement may be the same for a precaster as for a contractor at a building site, except that precasters will usually have less waste. This results in better utilization of the steel and less consumption of natural resources. Surplus materials are generated during the production of precast elements. Much surplus material is recyclable, and consists mainly of hardened concrete with or without reinforcement, steel reinforcement and pieces of structural steel, plywood and other wooden materials, fresh concrete (from production and washing of equipment), slurry from the sawing of concrete, insulating materials (mineral wool and polystyrene), oil etc. from machinery and paper and other packaging materials. The amount of surplus material varies between factories and different types of production. Studies in the Scandinavian countries have shown that the magnitude is typically about 100 kg of surplus material per m3 of concrete produced. About 40% of the surplus material is fresh and hardened concrete and about 45% is wastewater from washing equipment and sawing slurry generated during hollow core slab production. It is possible to collect and sort different types of surplus materials in precast plants. Excess materials that can be recycled and reused include steel, wood, insulating materials, oil, paper and other packaging materials. Wood can be sorted out, cut and used as industrial firewood, or used for other construction purposes. Buildings are constructed with traditional cast in-situ concrete, using timber formworks. Building that timber formwork was the major contributor to construction waste, accounting for 30% of the total identified waste. Wet trades, such as concreting, masonry, plastering and tiling on-site were considered as the second major waste generator, accounting for 20% of the total on-site waste generated. A recent study demonstrated that the ‘off-cuts from cutting materials were a major cause of wastage during construction. Waste also arises as a result of design concepts and decisions. Case studies in Sri Lanka In the construction industry, it is well known that there is a relatively large volume of material being wasted due to a variety of reasons. The problem of material waste on construction sites is not an isolated issue and is of environmental concern. Therefore, waste minimization has become an important issue in the construction industry. The aim of this research was mainly to identify the pre-cast contribution to the construction waste minimization in the Sri Lankan construction industry, through a comparison of material waste arising from pre-cast, ready-mixed and site-mixed concrete. Data were collected from 27 building construction projects and three concrete elements: slabs, beams, and columns, were considered to quantify construction waste. To compare the wastage due to pre-cast involvement with other types, three categories of building projects were used, including projects using pre-cast concrete elements, in situ concrete elements site mix, and in- situ concrete elements ready mix. The data for the study were collected from 27 multi-storey housing constructions projects, of which, seven projects used pre-cast construction and 20 projects used in situ construction. The wastage was compared between the basic materials used for three types of concrete elements are columns, beams and slabs. In this study, material wastage includes waste arising from manufacturing process at the factory level to the site level. For instance, material waste of pre-cast and ready-mixed concrete were quantified considering the waste arising from manufacturing process at factory level to usage at construction site. However, it was identified that waste during the transportation of ready-mix concrete and pre-cast elements is negligible. Further, waste of pre-cast elements at the site level was also noted as almost zero and, hence only the factory level waste was considered for the analysis. Techniques of material reconciliation were used to analyse the waste of ready-mix concrete and pre -cast elements at the site level, while work studies were used to quantify the waste of site-mixed concrete at the site level and wastage of ready-mix concrete and pre-cast concrete at the factory level. Pre-cast concrete waste The mean wastages of cement, sand and metal amounted to 5.34 per cent, 13.86 per cent and 7.62 per cent respectively showing the lower values compared with the material wastages in the other two situations (Table III). Further, it was shown that there is a noticeable difference in the generation of material waste between pre-casts and in situ (Figures 1 and 2). The main reason behind this may be due to the negligible wastes arisen during transportation and installation at the site. The pre-cast concrete elements transported to the site were stored unit wise by during transportation had been minimized and identified as zero. Since pre-cast elements were supplied according to the required length, waste arising during installation of elements was at a minimum level and waste occurring due to over ordering of materials was also eliminated. Further, the pre-cast elements were produced at factories under proper supervision using steel moulds which can be formed of different sizes. Therefor e, the wastage of materials during manufacturing also reduced to a considerable amount. Site-mixed concrete waste In site-mix concrete, the mean wastages of cement, sand and metal amounted to 14.39 per cent, 25.70 per cent and 16.11 per cent respectively showing higher values compared with the material wastages in other situations (Table III). This large quantity of wastage was identified due to the lack of supervision, inaccurate mixing methods, inappropriate type of equipment used, poor storage of materials and poor quality workmanship and this led to higher waste of materials in ways of excess cement being used to accelerate the curing process, excess concrete being used due to the breaking of form work, higher waste in transit and handling of metal and sand and excess concrete being used in uneven surfaces (e.g. attached concrete column). Ready-mixed concrete waste The mean wastages of cement, sand and metal amounted to 6.61 per cent, 22.31 per cent and 13.01 per cent respectively showing the higher values than material wastages of pre-cast concrete and lower values than material wastages of site-mixed concrete (Table II). Although there was lower wastage at the factory level, the overall wastage of ready-mixed concrete showed higher values. The main reason behind this is the excess ordering of materials, large quantity of concrete remains in pump car and pump pipe and poor quality workmanship at the site level such as breaking of formwork. Case studies in Hong Kong The questionnaire survey revealed that the construction activities were closely related to the amount of waste generated. Timber formwork is the major contributor to construction waste. The wet trades associated with finishing work such as screeding, plastering and tile laying are identified as the second major set of waste generation processes in the construction of buildings. Concrete work and masonry work are the next most significant groups. Site activities need to be emphasised in order to reduce building waste. In general, it was estimated that about 5-10 per cent of materials ended up as waste on building sites. Pecaform foundation formwork is made by laminating a layer of polyethylene to each side of a high tensile steel wire mesh. This combination creates a material that is both light and structurally strong, making it very easy to handle. It can be used for constructing ground beams, pile caps, footings, curved structures, ribbed and waffle slabs. The formwork is cut-to-size and bent to shape at a factory and arrives at site ready for installation. There is no need to strip the formwork after the concrete has cured. Very little waste is produced. A clean and neat site can be obtained in the foundation stage. Large panel formwork compared with traditional timber formwork, metal panel system formwork has several advantages. The use of large panel formwork can save time and labour in erecting, striking and re-erecting the formwork as the panel is handled as one unit. It can also produce a concrete surface much neater than conventional timber formwork and the surface essentially needs no additional applied finishes for levelling. So far, steel is the most popular material used for the formwork and the reusability of steel formwork can be as high as 100 times, and therefore much formwork waste is reduced. On-site waste audit also indicated that large panel formwork was effective in reducing concrete waste generated by loss in concreting and broken formwork, which usually accounts for about 30 per cent of the total concrete waste Prefabricated steel reinforcement system is tailor-made in plants where steel bars are mechanically cut, bent and fabricated. The completed systems are then transported to the sites for use. During the manufacturing process, the steel bars are cut and bent in a more systematic and accurate manner so that the wastage is kept to a minimum. Precast cladding is a new construction method for tiling works in the corridors of public housing projects in Hong Kong. The cladding panels are manufactured in the precast factory. The production processes are: place wall tiles onto the steel mould face down, pour lightweight concrete onto the back of the tiles, and demould after hardening. The tiles are thus cast integrally with the lightweight concrete and no traditional tile fixing by cement mortar or adhesive is required. At the construction site, the positions for holding brackets will be set out, and cladding panels levelled and fixed. The advantages of precast cladding panels are: reduced requirements on skilled labour with better end product quality, less wastage of raw materials and waste generation as wet trades on site such as plastering and tiling are eliminated, flexible time control as no setting and curing time are needed on site, and a cleaner and safer working environment. Machinery sprayed plaster was originally used in civil engineering applications. It now replaces the traditional cement mortar in some building projects. The major difference between the mechanised plaster and the traditional cement mortar is that the former is mixed and applied by means of a mechanised operation whilst the latter is applied and trowelled smooth by hand. The use of machinery sprayed plaster has the benefits of high productivity, low labour demand and less waste. Precast bathroom is an innovative feature in the construction of public housing. The wall, floor and ceiling of the bathroom are prefabricated with concrete as a whole unit and finished with tiles in the factory. PVC sleeves are also left in the structure for the future fixing of drainpipes. It is then transported to the site and installed into the final position of the building structure with the help of a crane. The only work required on site is to install the sanitary fittings, connect plumbing and electricity wiring to the building mains. Wet trades are avoided on site and this reduces material damages and wastage. Pre-cast external wall panels. Traditionally, external wall panels in high-rise residential buildings have been constructed in-situ with concrete panels finished with mosaic tiles. Pre-casting external wall panels enables panels to be pre-finished with the mosaic tiles attached together with windows and louvres installed. Building services provision can also be included. The finishes are fixed in the factory, production is not affected by the weather, a cleaner safer production environment results in stronger bonding and less tile wastage. Pre-fabricated fibre glass water tank. This type of pre-fabrication is an example of saving construction waste by materials substitution. All residential housing units of the New Harmony type include water storage on the roof of the building; the normal design solution is a cast in-situ concrete tank. An alternative to the construction of the cast-in-situ concrete water tank on the roof of the building is the adoption of a pre-fabricated fibre glass tank. Pre-fabricated internal wall panels e.g. dry wall partitions, and gypsum boards may be used to replace concrete or brick walls which are then finished by plastering in-situ. This has the potential to make significant savings in construction waste because a typical residential building would have some 452m2 of internal walls per floor and typically there would be 32 or 40 floors per building. The adoption of this form of construction has minimal impact on the design tasks because the pre-fabricate