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

Uranium/ special nuclear material :: essays research papers fc

SPECIAL NUCLEAR MATERIA L "Special nuclear material" (SNM) is defined by Title I of the Atomic Energy Act of 1954 as plutonium, uranium-233, or uranium enriched in the isotopes uranium-233 or uranium-235. In 1789, Uranium was discovered in the mineral called pitchblende, by a German chemist named Martin Klaproth. It was named after the planet Uranus, which had been discovered eight years earlier. Uranium-233 and plutonium are formed in nuclear reactors because they do not occur naturally. It has to be taken from highly radioactive spent fuel by chemical separation. Uranium-233 can be produced in special reactors that use thorium as fuel. Only small quantities of uranium-233 have ever been made in the United States. No U.S. commercial plutonium reprocessing plant is currently licensed by the U.S. Nuclear Regulatory Commission for operation. Uranium enriched in uranium-235 is created by an enrichment facility. The NRC regulates two gaseous diffusion enrichment plants operated by the U.S. Enrichment Co rporation. The gaseous diffusion process is the current method used by the United States to enrich uranium. There are two gaseous diffusion plants in the United States. One is located in Portsmouth, Ohio but was shut down in March 2001, and the other is in Paducah, Kentucky. This plant has produced enriched uranium continuously since November 1952. It is operated by the United States Enrichment Corporation (USEC) which was created as a government corporation under the Energy Act of 1992 and privatized by legislation in 1996 Natural uranium contains 99% U238 and only about 0.7% U235 by weight. Gaseous Diffusion The uranium enriched in uranium-235 is required in commercial light water reactors to produce a controlled nuclear reaction. Gaseous diffusion is one way to enrich uranium. The gas separates by slowly flowing through small holes. (molecular effusion) In a vessel containing a mixture of two gases, molecules of the gas with lower molecular weight travel faster and strike the walls of the vessel more frequently. The walls of the vessel can be penetrated, so more of the lighter molecules flow through the barrier than the heavier molecules. The gas that escapes the vessel is enriched in the lighter isotope. One barrier isn’t enough to do the job, though. It takes many hundreds of barriers, one after the other, before the UF6 gas contains enough uranium-235 to be used in reactors. At the end of the process, the enriched UF6 gas is withdrawn from the pipelines and condensed back into a liquid that is poured into containers.

The Pathogenesis of Down’s Syndrome Essay -- Science Medical Genetics

The Pathogenesis of Down’s Syndrome Down’s syndrome (DS) is the most common cause of mental retardation in the United States. It occurs with a frequency of one in 700 live births. The disease is caused by the presence of three copies of chromosome 21 as a result of chromosomal mutation (95% nondisjunction, 5% translocation) during cell division, leading to a total of 47 chromosomes instead of the normal number, 46. There are no individuals with the clinical signs of DS who do not have at least partial trisomy of chromosome 21. Conversely, there are no cases of people with trisomy 21 who do not have DS (Patterson, 1987). Patients suffer from a variety of physical and mental problems. Physically, the disease manifests itself in epicanthic folds of the eyes, flattened facial features, unusual palm creases, muscular flaccidity and short stature (Patterson, 1987). Many are born with congenital heart defects and increased risk for cataracts, leukemia and Alzheimer’s disease. In addition to the anatomical abnorm alities, DS patients suffer from biochemical imbalances including elevated levels of purines - a condition that can by itself lead to neurological impairment, mental retardation, and immunodeficiencies. The life expectancy for DS patients is approximately 30 years. However, with advancing medical care and therapy more patients are living to the age of 50. All individuals with DS over the age of 35 develop the same kind of abnormal microscopic plaques and neurofibrillary tangles in the brain as people who die from Alzheimer’s disease, the major cause of presenile dementia. Although a vast amount of literature exists on DS, little is known about why the presence of an extra chromosome causes mental retardation. In addition to ... ...ogy and Experimental Neurology, 49: 509-518. Ferrer, I., Gullotta, F. (1990): Down’s Syndrome and Alzheimer’s Disease: Dendritic Spine Counts in the Hippocampus. Acta Neuropathol, 79: 680--685. Mann, D. M. A., Brown, A., Prinja, D., Davies, C. A., Landon, M., Masters, C. L., Beyreuthers, K. (1989): An Analysis of the Morphology of Senile Plaques in Down’s Syndrome Patients of Different Ages Using Immunocytochemical and Lectin Histochemical Techniques. Neuropathology and Applied Neurobiology, 15: 317-329. Patterson, D. (1987): The Causes of Down Syndrome. Scientific American, 255: 52-60. Takashima, S., Ieshima, A., Nakamura, H., Becker, L. (1989): Dendrites, Dementia and the Down Syndrome. Brain Development, 11: 131-133. Wisniewski, K., Bobinski, M. (1991): Hypothalamic Abnormalities in Down Syndrome. The Morphogenesis of Down Syndrome., 153-167. The Pathogenesis of Down’s Syndrome Essay -- Science Medical Genetics The Pathogenesis of Down’s Syndrome Down’s syndrome (DS) is the most common cause of mental retardation in the United States. It occurs with a frequency of one in 700 live births. The disease is caused by the presence of three copies of chromosome 21 as a result of chromosomal mutation (95% nondisjunction, 5% translocation) during cell division, leading to a total of 47 chromosomes instead of the normal number, 46. There are no individuals with the clinical signs of DS who do not have at least partial trisomy of chromosome 21. Conversely, there are no cases of people with trisomy 21 who do not have DS (Patterson, 1987). Patients suffer from a variety of physical and mental problems. Physically, the disease manifests itself in epicanthic folds of the eyes, flattened facial features, unusual palm creases, muscular flaccidity and short stature (Patterson, 1987). Many are born with congenital heart defects and increased risk for cataracts, leukemia and Alzheimer’s disease. In addition to the anatomical abnorm alities, DS patients suffer from biochemical imbalances including elevated levels of purines - a condition that can by itself lead to neurological impairment, mental retardation, and immunodeficiencies. The life expectancy for DS patients is approximately 30 years. However, with advancing medical care and therapy more patients are living to the age of 50. All individuals with DS over the age of 35 develop the same kind of abnormal microscopic plaques and neurofibrillary tangles in the brain as people who die from Alzheimer’s disease, the major cause of presenile dementia. Although a vast amount of literature exists on DS, little is known about why the presence of an extra chromosome causes mental retardation. In addition to ... ...ogy and Experimental Neurology, 49: 509-518. Ferrer, I., Gullotta, F. (1990): Down’s Syndrome and Alzheimer’s Disease: Dendritic Spine Counts in the Hippocampus. Acta Neuropathol, 79: 680--685. Mann, D. M. A., Brown, A., Prinja, D., Davies, C. A., Landon, M., Masters, C. L., Beyreuthers, K. (1989): An Analysis of the Morphology of Senile Plaques in Down’s Syndrome Patients of Different Ages Using Immunocytochemical and Lectin Histochemical Techniques. Neuropathology and Applied Neurobiology, 15: 317-329. Patterson, D. (1987): The Causes of Down Syndrome. Scientific American, 255: 52-60. Takashima, S., Ieshima, A., Nakamura, H., Becker, L. (1989): Dendrites, Dementia and the Down Syndrome. Brain Development, 11: 131-133. Wisniewski, K., Bobinski, M. (1991): Hypothalamic Abnormalities in Down Syndrome. The Morphogenesis of Down Syndrome., 153-167.

Explain how and why the meaning Essay

There are many terms used in respect to World Development, common terms include â€Å"Less Developed Countries†, â€Å"Third World† and â€Å"Developed Countries†. There is also the more recent and politically correct MEDC’s and LEDC’s, both being introduced as a sign of the growing awareness that poverty is not just about economic status. At one time it was strongly thought that a countries development was purely based on its wealth. This led to the North/South divide where the northern hemisphere was predominantly developed and the southern hemisphere mostly underdeveloped. This relationship can clearly be seen in the diagram below, the main exception to the rule being Australia and New Zealand. World GNP 1997 It was however suggested that these underdeveloped countries would follow a route of economic growth as illustrated by Rostow’s 1960 model. The model was based on a study of 15 mainly European countries, the main prospective being on industrialisation and economic position. The model proposes that a country can break the cycle of poverty and underdevelopment by following a succession of linear stages, five to be exact. Rostow’s Model of Economic Growth   Stage 1 – Traditional Society This stage of the model is dominated by subsistence economics where little if any productivity is consumed by those who produced it rather than being sold. Agriculture being the primary industry at this stage is produced with little capital and on a labour intensive basis. Stage 2 – Preconditions for Take-Off Also known as the transitional stage this is where people desire a higher standard of life and so change their aims and goals to increase production and begin to trade. This process can also be triggered by external sources where forces help to aid the transition. * Stage 3 – Take-Off Industrialisation dramatically increases with the population’s attention shifting from farming and agriculture to manufacturing. This effect is normally concentrated and leads to an improvement in infrastructure and the initiation of rural to urban migration. * Stage 4 – Drive to Maturity The economic growth spurred in stage 3 starts to spread across the country, there is also a multiplier effect where the amount and diversity of industry increases. The emphasis is now on technological advancement as rural populations and agriculture are further put in decline. * Stage 5 – High Mass Consumption Personal incomes grow and so the demand for tertiary industry intensifies. There will therefore be an increase in tertiary employment as manufacturing now begins to decline. Basic amenities are now common place and the country should have a stable infrastructure, political situation and a high GNP. Rostow’s model would require substantial investment in capital, unless there is external intervention it would be very difficult for a country to leave stage 1. Barke and O’Hare who themselves made a development model were the first to publicly reject the ‘Rostow’ model, in 1984 they argued that the model was too ‘Eurocentric’ expecting all countries to follow the west (America and Britain etc. ). They agreed that yes a country can and some already had passed through the 5 stages, but it is unlikely for a country to take off without structural and social change. Other criticisms of Rostow’s model include the model assuming all countries start off from the same level, and that it does not take into consideration the debt a country can gather from aid to help it transcend from stage 1 to 2. Africa is a perfect example of this, where the country’s debts have prevented it from further developing. By the 1990’s people were for the first time trying to redefine the term development, after the failure of the ‘Three World Model’ which was seen as an inappropriate way of viewing global development, the world bank identified and took up the challenge. They believed that development should not just be about economic growth but it should have a more multi-dimensional prospective, they believed that development was also the challenge to improve quality of life taking into account the following factors: – The right to a better education. – Individual/Political freedom. – More equality of opportunity. – Higher standards of health and nutrition. – Strong culture. This brought about three core values of development, sustenance, self-esteem and freedom to choose. This new prospective also resulted in many quotes, one that sums up this new way of thinking is by ‘Moorish’ written in 1998: â€Å"Development is not simply concerned with wealth, but with many other aspects of life such as health, education, housing and employment. † However, as much as people wanted countries to develop there was also great concern about the cost it was having on the environment to fuel this process, and so a new approach was introduced, a ‘greening’ of development. This meant that although a countries natural resources would still be needed for it to develop, it should be done so in a sustainable way as to not compromising the ability for future generations to meet their own needs. This ‘greening’ of development initiated numerous schemes such as in the Amazon Rain Forest, where for every tree that was to be cut-down another would be replanted. It is this sustainable approach to development that is still being implemented today, with concerns about global warming and a lack of crude oil to name but a few. Although Rostow explained the development of western countries well he failed to consider the different cultures and traditions each country has. As quoted by Mark Tully in 1993, â€Å"Development is more than mere economics†, he was right, it is about much more than that. Social, economic and political factors need to be taken into account for a true projection of how much a country really is developed, and so the new meaning of development is defined as, ‘the progressive improvements in the standards of living and quality of life for an increasing proportion of the population’.

Not a Good Day

The classroom was stuffy. The lesson was boring. There was a heavy atmosphere in the room; everyone was tense wondering if the teacher was going to explode again, ranting and raving. The teacher, Mr Perry, was being as annoying as possible, talking in a deep, slow, flat voice, pronouncing each word as slowly and perfectly as possible. â€Å"So, if you multiply together these two numbers, and divide the answer by six, you get the answer to the question.† It hadn't been a good day for him so far today. His car had broken down this morning, he had loads of overdue marking to do, his year eight class earlier in the day had caused him a load of hassle and he had a meeting with his boss after he had finished teaching and he knew it wasn't going to be good news. It was the end of the day and no-one wanted to be in the lesson. It was one of those beautiful, warm sunny summer afternoons outside, but inside it felt like the calm before the storm. Earlier on in the lesson it hadn't been pleasant. Anna had just been sitting at the back keeping herself to herself, at least she had been pretending to be, but when there's an interesting piece of gossip going round, it has to be thoroughly discussed and looked at from every angle. It's not really the best idea to write the note on a fluorescent pink post-it note, its not exactly subtle. Of course, he saw the note, stormed over, snatched it away and of course read it out loud to the class. The note had just been from one of Anna's friends and it had just been asking if she was going shopping on Saturday. It was something innocent, luckily it had been, seeing as it was read out to the entire class. That had been about half an hour earlier. â€Å"Sir, can I open the window please? I feel as if I'm about to faint.† whined Cassie. â€Å"No.† was the short, sharp simple reply. â€Å"Sir, can I pull the blinds down?† â€Å"No.† All of a sudden there was a loud crash. Someone had knocked their tin on the floor. Anna quickly bent down to retrieve her tin, it had been an accident, she didn't mean to knock it on the floor. â€Å"Who did that?† Mr Perry boomed, his voice echoing around the room, making everyone wake up. All of a sudden everyone was awake and alert and tense again wondering what his reaction would be. His first reaction made the situation worse. He was silent, he did nothing. Then slowly, he stood up and walked towards Anna, with his eyes boring deep into hers, cold and icy. â€Å"Anna, could you come here a minute please?† he said as sweetly and non-threateningly as he could. â€Å"Er, sir, do I have to? The look he gave her in reply gave her the answer loud and clear. He marched over towards the door, and opened it and politely said â€Å"after you.† There was a muffled whisper of good luck from the back of the room as Anna disappeared out of sight. There was more air out in the corridor, the fresh summer breeze felt good on her face, it was easier to breathe, and she went and stood by the open window, a luxury they weren't allowed in the classroom. â€Å"What do you want sir?† Anna wanted to get straight to the point and know what she had done wrong. â€Å"Is there something wrong Anna, at school, or at home maybe?† â€Å"No, why?† † I just wanted to know if there was something bothering you, something that you wanted to take your mind off. You seem to be becoming a persistent troublemaker and I don't want you to be because you're a good student the majority of the time. Recently though your behaviour has been starting to slip, you're letting your standards drop. I don't like troublemakers in my lessons. If you think that you are going to get away with any of this bad behaviour, you can think again about coming back to my lessons. You can go back inside now.† He had a very strange expression on his face as he was saying this, he was frowning, it was as if something was puzzling him, and he just stood there completely upright with his hands on his hips. Anna on the other hand looked completely shocked as if she couldn't believe what she was hearing, and what he was saying about her. Her mouth hung open a little bit and her eyes were wide and starring straight at Mr Perry. She was slouching and her arms just hung by her sides, as if she had no control over them and she couldn't move. Anna was left standing there, shocked and not entirely sure what to think or say. She wasn't thinking straight now. Anger was boiling up inside her, and she didn't know when she was going to explode. She walked back into the classroom as if she was on autopilot, and collapsed into her seat. She stayed like that for the next ten minutes or so and then†¦Ã¢â‚¬ ¦Ã¢â‚¬ ¦Ã¢â‚¬ ¦Ã¢â‚¬ ¦Ã¢â‚¬ ¦Ã¢â‚¬ ¦Ã¢â‚¬ ¦. â€Å"Sir, I don't know what you think you were talking about out there. I am not a persistent troublemaker, I don't have any problems here or home, and you know what? I have been thinking about what you said and it is my pleasure to tell you that I will not be coming to any more of your lessons. You must be joking to think that I'd actually want to spend an hour each day with you, an hour of your bad tempers, an hour or your rude and insulting comments, an hour of your yelling and shouting.† Mr Perry looked up sharply, surprised and not expecting this sudden outburst. He wasn't in the mood for dealing with troublesome teenagers. He was going through a bit of a rough patch, he had bills piling up, he was possibly going to get evicted from his flat, and he had his boss constantly hanging around and watching his every move. He wasn't really thinking straight and he just snapped. â€Å"THAT IS ENOUGH. GET OUT OF HERE NOW.† He stood up from his desk and strode over to where she sat. He gave her that evil glare again but this time it was full of evil and hatred. He towered over her, shaking with anger â€Å"I SAID ANNA TAILOR, GET OUT OF HERE NOW.† He raised his fist, and that did it for Anna, she leapt out of her seat, and ran to the door screaming â€Å"You haven't heard the last of this, I'll be back you know, I swear that I'm going to get you fired.† Mr Perry stood there, perfectly still and silent, realising what he had done as he stared at Anna disappearing down the corridor out of sight. The rest of the class was shocked, no-one said a word, no-one moved. Work was the last thing on everyone's mind. Luckily, the bell went. Time seemed to have disappeared. Everyone packed their bags in silence and just crept out of the room. Mr Perry still stood in the exact same place, not moving at all with a frozen expression fixed on his face.

Alternative communication system during disaster Essay

PSTN or the public switched telephone network is the prime network responsible for transmitting and receiving voice, fax and data. All government and private offices, police stations, fire stations, hospitals and majority of homes and business places are serviced by the PSTN line. . Amateur Radio operation does not use ground based infrastructure. Moreover these have limited power needs which can easily be met by batteries and generations. Therefore, it has been experienced that Amateur Radio has worked successfully when no other communication worked. A radio wave is an electromagnetic wave propagated by an antenna. The floods in 2004 in Assam and Bihar submerged telephone exchanges and damaged telephone exchanges thereby disrupting roads and railways communication. This is the reason why the district headquarters got totally out off from the state headquarters and neighbouring districts. A major natural disaster or emergency situation like earthquake, cyclone, flood, etc., leaves the public wired and wireless mobile telephone infrastructure damaged and non-functional. This is a transmission towers or disrupted power supply to operate telephone exchanges and cellular transmission towers also affect the radio communication network of police and civil authorities. Satellite based communication systems refer to communication systems designed for users on the earth but have some equipment in space called a satellite. Various jobs such as taking weather pictures or finding accurate positions are amongst the different job performed by different satellites. These are sometimes refered to as COSMAT’s and are essentially radio relay stations in space. Geo-stationary orbit satellites are stationed above the earth at a position around 36000 kms above the equator. The images of weather forecasts and cyclone observations that we see on our television are made with the help of images from weather satellites. A major disaster (flood, earthquake, etc.) or emergency situation affects telephone exchanges and communication networks thereby disconnecting the affected areas from other parts of the world. In such situations, the urgent needs of disaster affected population are not communicated to government authorities, voluntary organizations and other unaffected people. This result in severe loss of human lives, livestock, property etc. This situation calls for reliable alternate communication links, to ensure that the right resources are provided to the right people at the right time. Asynchronous Orbit Satellites – These satellites are positioned in the lowerorbits around the earth. These continuously change their position with respect to the earth. The different kinds of asynchronous orbit satellites are : a) Science satellites: These orbit in altitudes of 4800 to 9700 kms. These send their research data to earth via radio telemetry signals. b) Observation Satellites: These are used for tasks like search and rescue satellites, photography. These act as relay stations to rebroadcast emergency radio-beacon signals from a downed aircraft or ship in trouble. These orbit at altitudes from 480 to 970 kms. c) Global Positioning System Satellites: Orbiting at altitudes of 9600 to 19200 kms, these are used to determine in terms of latitude ad longitude to determine the exact geographic location. The two prime communication networks of government of India are NIC and BSNL. Following are the functions of them: NIC or the National Information Centre, an organization of the Government of India is a premier science and technology organization of the Government of India is a premier science and technology organization in the field of informat ics services and information technology applications. To facilitate information and communication applications in government departments at central, state and districts, it has established a nationwide ICT network i.e. NICNET. The Government has designated NICNET as the Government Network. It has gateway modes in Central Government Departments, 35 state and union territories secretariats and 602 district collect orates of India for IT services. BSNL : The Department of Telephone Operations, Government of India was incorporated on 1st October, 2000 and was named Bharat Sanchar Nigam Limited. BSNL is today the largest public sector undertaking in India with a network of over 45 million lines, covering 5000 towns with over 35 million telephone connections, it has become the country’s leading telecommunication company expansion of telecom network, improvement of the quality of telecom in rural areas are some of its major responsibilities.

Motivational Strategy and Action Plan Essay

Determine the motivational strategy or strategies that would likely be most appropriate for each of your three employees on basis of their individual characteristics. Indicate how you would leverage their employee evaluations to motivate each of the three employees. Describe one or more of the motivational theories and explain how the theories connect to each of your selected motivational strategies. Team Member Name Summary of Individual Characteristics Motivational Strategy and Action Plan Relevant Theory Tina Engaged Passionate Persistent Inspirational Leader Happy Emotional stable This employee would not really need much motivation, since already in engaged, passionate and is a leader at work. I would suggest that the employee uses an action plan to continue with positive attitude. Also since the employee has passed reviews, to advance in progress with promotions in the company. McClelland theory is relevant to this situation. It relates to this situation because for the most part the employee is happy at the job. Brittany Competitive Good communicator Influential Independent Emotional Quick thinker This employee shouldn’t much motivation since she is so competitive. However we could motivate her to be more engaged and happy at job since so emotional. An action plan for this strategy would be to assign her to do task she is interested and likes to do that are easy and take little thought since she is a quick thinker. This situation relates to the self-efficiency theory because employee is independent. She likes to do things on her own and feels she can. Denise Timid Considerate Neutral decision maker Eager Happy with job Encouraging This employee needs motivation in company involvement in communication since timid and shy. She can demonstrate these skills in an action plan by being more involved in conferences, presentations, and meetings. This situation could be also related to the McClelland theory because for the employee is happy with job, but there is room for opportunity.