Composite resins have been advocated as a reinforcing build-up material for badly damaged endodontically treated teeth with flared canals. However, the control of an autocuring composite resin is difficult because it polymerizes rapidly within the root canal. While the light-curing composite resins are more user friendly, their polymerization can be a problem deep in the root canal. Light-transmitting plastic posts allow the transmission of light into the root canal and enable intraradicular composite resin reconstitution and reinforcement of weakened roots. At the same time, the light-transmitting plastic post forms an optimal post canal in the rehabilitated root and can accurately fit a matching retentive final post. These light-transmitting posts are a useful addition to the dental armamentarium.
In this study, the depth of cure of composite resins cured within simulated root canals by means of light-transmitting plastic posts was compared to that achieved by the conventional light-curing method. Six sizes of posts with diameters of 1.05 mm, 1.20 mm, 1.35 mm, 1.50 mm, 1.65 mm, and 1.80 mm were investigated. In general, the larger the post diameter, the greater was the depth of cure. There were significant differences in the depth of cure between the control and all sizes of posts investigated. There were also significant differences between the various post diameters except for the 1.35 mm and 1.50 mm diameter posts. It was possible to achieve a depth of cure exceeding 11 mm using these light-transmitting posts.
Deaths due to plastic bag suffocation or plastic bag asphyxia are not reported in Malaysia. In the West many suicides by plastic bag asphyxia, particularly in the elderly and those who are chronically and terminally ill, have been reported. Accidental deaths too are not uncommon in the West, both among small children who play with shopping bags and adolescents who are solvent abusers. Another well-known but not so common form of accidental death from plastic bag asphyxia is sexual asphyxia, which is mostly seen among adult males. Homicide by plastic bag asphyxia too is reported in the West and the victims are invariably infants or adults who are frail or terminally ill and who cannot struggle. Two deaths due to plastic bag asphyxia are presented. Both the autopsies were performed at the University Hospital Mortuary, Kuala Lumpur. Both victims were 50-year old married Chinese males. One death was diagnosed as suicide and the other as sexual asphyxia. Sexual asphyxia is generally believed to be a problem associated exclusively with the West. Specific autopsy findings are often absent in deaths due to plastic bag asphyxia and therefore such deaths could be missed when some interested parties have altered the scene and most importantly have removed the plastic bag. A visit to the scene of death is invariably useful.
A study was undertaken to determine the effect of polyethylene and polystyrene used in the manufacture of plastic items on colour perception. Colour vision was assessed using the Ishihara plates, panel 015 test and the Farnsworth Munsell 100-Hue test. Two factories were chosen at random. One factory (referred here as factory A) used virgin resin in pellet form (polyethylene) in the manufacturing of plastic containers to store consumer edible oil. The other factory (referred as factory B) used polystyrene to make plastic bags. A total of 39 healthy employees from factory A (mean age 26.4 :t 8.2 years) and 40 healthy employees from factory B (mean age 26.8 :t 9.6 years) were recruited in this study. A control group of 27 normal healthy subjects (mean age 27.4 :t 4.3 years) who were employees of UKM with no occupational involvement with petroleum derivatives were also recruited in this study and they performed the same colour vision tests. All subjects passed the Ishihara plates test showing that none of the subjects (employees of factory A and B, and control subjects) had a congenital red-green defect. All control subjects passed all of the colour vision tests whilst some employees of factories A and B failed the 015 and FM100 Hue tests. For employees from factory A results from the 015 test showed that 7 (17.9%) had a tritan (blue-yellow) type of defect and 1 (2.6%) had a complex type of defect. The FM 100 Hue results of factory A employees showed that 51.3% (n=20) had a complex type of defect. Total error scores (TES) calculated from the FM 100 Hue test revealed that employees from factory A had a statistically significant higher mean TES of 65.13:!: 48.31 compared to that of control subjects with a mean TES of 31.26:!: 14.93. For employees in factory B, 10 employees (25.0%) had a tritan (blue-yellow) type of defect and 2 (5.0%) had a complex type of defect. Results of the FM 100 Hue test showed that 4 employees (1.0%) had a tritan type of defect whereas 22 (55.0%) had a complex type of defect. Mean total error scores (TES) calculated from the FM 100 Hue test revealed that employees from factory B had a statistically significant higher mean TES of 71.54 :t 54.63 compared with that of control subjects with a mean TES of 31.26 :t. 14.93
The above results show that employees of the plastic factories studies are associated with a higher risk of acquiring colour vision defects as compared to normal subjects who are not engaged in the plastic manufacturing industry. This may have an implication towards the future retinal health of employees in petrod1emical-based industries.
A cross sectional study to determine the exposure of heat and its biological effects on the workers in a plastic factory located in the Shah Alam Industrial Estate, Selangor, Malaysia. Forty five respondents from the polymer section in the factory were selected as the respondents. Variables measured were the environmental temperature (WBGTin), air velocity, relative humidity, body temperature, average heart and recovery heart rate. QUESTEMP°34 Area Heat Stress Monitor was used to measure the environmental temperature in °C (WBGTin) and relative humidity (%). Velocicheck Model TSI 8830 was used to measure the air velocity in meter per second (m/s) while the OMRON Blood Pressure Monitor Model T3, was used to measure average heart rate and recovery heart rate. Body temperature (°C) was measured by the Instant Ear Thermometer-OMRON Gentle Temperature Model MC509. Interviews using questionnaires were used to determine respondents’ socioeconomic background, previous risk factors on heat exposure and other information related to heat stress. Results showed that the mean environmental temperature for the exposed group was 28.75°C, the mean air velocity was 0.15 m/s and the mean relative humidity was 58.1%. These production workers were exposed occasionally to heat when loading plastic powder into the molds as well as demolding the finished plastic products from the molds. The average time of monitoring was 2 hours for intermittent exposure and 8 hours duration for overall exposure. Maximum demand for work load was measured 1 minute after work activities were stopped at the demolding section. There was a significant difference between body temperature and average heart rate before work, after 2 hours of work and after 8 hours of work ( p < 0.001). The mean recovery heart rate after 1 min was 88.0 ± 12.0 beat per min. (bpm), indicating that there is no excessive physiological demand. Body temperature (36.8 ± 0.40°C) and average heart rate after 8 hours (78 ± 12 bpm) indicated a good body control of heat exposure. Five out of six workplaces monitored had temperatures of greater than 28°C (ACGIH TLV). The workers were exposed to moderate heat stress during the study period, however, body temperature and average heart rate measurement did not reach unacceptable level of physiologic strain.
Percolation theory has been used with great interest in understanding the design and characterization of dosage forms. In this study, work has been carried out to investigate the behavior of binary mixture tablets containing excipients of similar and different deformation properties. The binary mixture tablets were prepared by direct compression using lactose, polyvinyl chloride (PVC), Eudragit RS 100, and microcrystalline cellulose (MCC). The application of percolation theory on the relationships between compactibility, Pmax, or compression susceptibility (compressibility), gamma, and mixture compositions reveals the presence of percolation thresholds even for mixtures of similar deformation properties. The results showed that all mixture compositions exhibited at least one discreet change in the slope, which was referred to as the percolation threshold. The PVC/Eudragit RS100 mixture compositions showed significant percolation threshold at 80% (w/w) PVC loading. Two percolation thresholds were observed from a series of binary mixtures containing similar plastic deformation materials (PVC/MCC). The percolation thresholds were determined at 20% (w/w) and 80% (w/w) PVC loading. These are areas where one of the components percolates throughout the system and the properties of the tablets are expected to experience a sudden change. Experimental results, however, showed that total disruption of the tablet physical properties at the specified percolation thresholds can be observed for PVC/lactose mixtures at 20-30% (w/w) loading while only minor changes in the tablets' strength for PVC/MCC or PVC/Eudragit RS 100 mixtures were observed.
The process for the production of biodegradable plastic material (polyhydroxyalkanoates, PHAs) from microbial cells by mixed-bacterial cultivation using readily available waste (renewable resources) is the main consideration nowadays. These observations have shown impressive results typically under high carbon fraction, COD/N and COD/P (usually described as nutrient-limiting conditions) and warmest temperature (moderate condition). Therefore, the aim of this work is predominantly to select mixed cultures under high storage responded by cultivation on a substrate - non limited in a single batch reactor with shortest period for feeding and to characterize their storage response by using specific and kinetics determination. In that case, the selected-fixed temperature is 30 degrees C to establish tropical conditions. During the accumulated steady-state period, the cell growth was inhibited by high PHA content within the cells because of the carbon reserve consumption. From the experiments, there is no doubt about the PHA accumulation even at high carbon fraction ratio. Apparently, the best accumulation occurred at carbon fraction, 160 +/- 7.97 g COD/g N (PHAmean, = 44.54% of dried cells). Unfortunately, the highest PHA productivity was achieved at the high carbon fraction, 560 +/- 1.62 g COD/g N (0.152 +/- 0.17 g/l. min). Overall results showed that with high carbon fraction induced to the cultivation, the PO4 and NO3 can remove up to 20% in single cultivation.
An optical code generating device for a portable optical access-card system was constructed using the plastic optical fibre (POF) waveguide coupler. The newly constructed device provided output light intensities which were used as optical codes in a portable optical access-card system. The construction of a basic 1 × 2 waveguide design combined two major components which were the asymmetric Y-junction splitter and the linear taper. A hollow waveguide structure was utilized as it provided more flexibility in guiding light rays. A basic 1 × 2 waveguide coupler was designed using the CAD tool and then the ray was traced using the non-sequential ray tracing tool. A linear relationship between the tap-off ratio and the waveguide tap-width enabled a higher-level hollow waveguide coupler to be designed using the simple cascading technique. Construction of a 1 × 4 and higher level waveguide coupler was easily realized using the basic 1 × 2 waveguide coupler design together with a simple cascading technique.
This study was carried out in Agricultural Park, Teluk Cempedak and Bukit Pelindung at Kuantan, Pahang in October 2007. These three areas were different in ecological characteristic, Agricultural Park is a lowland region in Kuantan rural area, Teluk Cempedak is Kuantan’s most famous beach, and Bukit Pelindung is a reserved rainforest which is 200 meters from the sea level. Fly specimens were collected using four different kinds of baits: dry prawn, salted fish, pork and mango. Each of these baits was placed in a plastic container and exposed for one hour to attract flies. Within 5 minutes, flies started swarming around the baits. The flies were more attracted to the pork and salted fish compared to the other two baits. Fifty one flies, one moth (Lepidoptera) and one wasp (Hymenoptera) were collected. In Agricultural Park, two Lucilia cuprina, one Chrysomya megacephala and one Sarcophaga sp. were collected. For Teluk Cempedak beach, there were two Sarcophagids, 31 Chrysomya megacephala, five Musca domestica, one Lucilia cuprina and one moth were caught. Flies collected from Bukit Pelindung included five C.megacephala, two Sarcophagids, one Musca domestica and one wasp. Most C.megacephala were attracted to the pork and salted fish.
The present project investigated the potential of utilizing corncobs and sugar cane waste as viscosivier in drilling fluid. For this purpose, the synthetic-based drilling fluid, Sarapar 147, was used as the base fluid. Both the materials were subjected to pre-treatment of drying, dehumidifying, grinding and sieving process prior to rheological tests. The rheological tests were conducted in accordance with the API 13B specifications to measure mud density, plastic viscosity, yield point, 10-second and 10-minute gel strength. The study found that plastic viscosity and yield point had a direct relationship with the amount of materials added. To drill fluid additive with corn cobs, the density, plastic viscosity and yield point were increased when the amount of additives were increased. Based on these experiments, both additives were found to have the potential to be used as additive in drilling fluid. In particular, they were able to improve its rheological properties by increasing the density, plastic viscosity and yield point. The suitable concentration for the corn cobs and sugar cane is 6.45 lb/bbl and 9.43 lb/bbl, respectively.
Polyethylene is a widely used packaging material, but its non-biodegradable nature can lead to waste
disposal problems. This increases the concern in research and development of biodegradable plastics from natural resource as alternatives to petroleum-derived plastics. In this study, biodegradable plastic composites were prepared by blending thermoplastic starch with natural rubber in the present of glycerol as plasticizer. Local sago starch was cast with 0.5 to 10% of natural rubber to prepare the bioplastic. The products were characterized by differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR), water absorption test, biodegradable test, hydrolysis test, and mechanical analysis. Meanwhile, composite with natural rubber latex was increased from 0.5 to 10% showing that the melting temperature is in the range of 120 to 150˚C, but with no significant difference. The water absorption characteristics, biodegradability, and tensile strength decreased by 11.21%, 30.18%, and 20.733 MPa, respectively. However, the elongation at break was increased from 26.67 to 503.3%. The findings of this study showed that sago starch has a great potential in bioplastic production with good miscibility and compatibility.
An attempt was made in this investigation to trace the dynamic response of roller compacted concrete dam, which is subjected to horizontal ground motion by considering the interactions between flexible foundations, reservoir water, and bottom reservoir sediments. Two-dimensional finiteinfinite element was used for the non-linear elasto-plastic dynamic analysis. In this analysis, special emphasis was given to the non-linear behaviour of discontinuities along RCC dam-bedding rock foundation which was modelled by thin layer interface. Analysis was first carried out under static loading (self-weight and hydrostatic pressure), and this this was followed by seismic analysis, with hydrodynamic pressure effect in a dam-reservoir system. Based on the numerical dynamic results, it is concluded that the bottom reservoir sediment has significant effect on the seismic response of the RCC gravity dam. Moreover, there is a redistribution of the stresses at thin layer interface with significant stresses reduction, which is resulted from the release of energy through different modes of deformation in this region.
With the world facing depletion of its oil reserves, attention is being focused on how the plastics industry will address shortages and price increases in its crucial raw materials. One renewable resource is that of vegetable oils and fats and about a dozen crop plants make up the main vegetable oil-seed market. The main constituents of these oils are saturated and unsaturated fatty acids that are unique to the plant in which they have been developed. Moreover, technological processes can produce more well-defined and pure oils, and the fatty acid contents in the vegetable oils can be altered with modern crop development techniques. This article describes recent advances in utilising such vegetable oils in sourcing new polymeric materials. It also gives the context for the development of polymers based on renewable materials in general.
Cosmos caudatus Kunth. (Asteraceae), commonly known as ulam raja, is widely grown as an herbal aromatic shrub. In Malaysia, its young leaves are popularly eaten raw as salad with other greens and have been reported to possess extremely high antioxidant properties, which may be partly responsible for some of its believed medicinal functions. In early 2010, a suspected powdery mildew was observed on ulam raja plants at the Agricultural Park of Universiti Putra Malaysia. Initially, individual, white, superficial colonies were small and almost circular. Later, they enlarged and coalesced to cover the whole abaxial leaf surface. With development of the disease, all green parts (leaves, stems, and petioles) became covered with a continuous mat of mildew, giving a dusty appearance. Newly emerged leaves rapidly became infected. Diseased leaves ultimately senesced and dried up, making them aesthetically unattractive and unmarketable. The pathogen produced conidia in short chains (four to six conidia) on erect conidiophores. Conidiophores were unbranched, cylindrical, 125 to 240 μm long, with a slightly swollen foot cell. Individual conidia were hyaline, ellipsoid, and 25 to 30 (27.5) × 15 to 20 (17.5) μm with fibrosin inclusions. Morphological descriptions were consistent with those described for Sphaerotheca fuliginea or S. fusca, which has lately been reclassified as Podosphaera fusca (1). From extracted genomic DNA of P. fusca UPM UR1, the internal transcribed spacer (ITS) region was amplified with ITS1 (5'-TCCGTAGGTGAACCTGCGG-3') and ITS4 (5'-TCCTCCGCTTATTGATATGC-3'). A BLAST search of GenBank with an ITS rDNA sequence of this fungus (GenBank Accession No. HQ589357) showed a maximum identity of 98% to the sequences of two P. fusca isolates (GenBank Accession Nos. AB525915.1 and AB525914.1). To satisfy Koch's postulates, the pathogenicity of fungal strain UPM UR1 was verified on 4-week-old plants. Inoculation was carried out by gently rubbing infected leaves onto healthy plants of C. caudatus. Ten pots of inoculated plants were kept under a plastic humid chamber and 10 pots of noninoculated plants, placed under another chamber, served as controls. After 48 h, the plants were then placed under natural conditions (25 to 28°C). Powdery mildew symptoms, similar to those on diseased field plants, appeared after 7 days on all inoculated plants. The white, superficial colonies enlarged and merged to cover large areas within 2 weeks. The infected leaf tissues became necrotic 6 to 8 days after the appearance of the first symptoms. Sporulation of P. fusca was observed on all infected leaves and stems. No symptoms were seen on the control plants. To our knowledge, this is the first report of P. fusca causing powdery mildew on C. caudatus in Malaysia. This pathogen has also been reported previously to be economically important on a number of other hosts. With ulam raja plants, more attention should be given to prevention and control measures to help manage this disease. Reference: (1) U. Braun and S. Takamatsu. Schlechtendalia 4:1, 2000.
Waste plastics contain a substantial number of valuable chemicals. The wastes from post-consumer as well as from industrial production can be recycled to valuable chemical feedstock, which can be used in refineries and/or petrochemical industries. This chemical recycling process is an ideal approach in recycling the waste for a better environment. Polymer cracking using a laboratory fluidized bed reactor concentrated on the used highly contaminated catalyst, E-Cat 2. Even though E-Cat 2 had low activity due to fewer acid sites, the products yielded were similar with amorphous ASA and were far better than thermal cracking. The high levels of heavy metals, namely nickel and vanadium, deposited during their lifetime as an FCC catalyst, did not greatly affect on the catalyst activity. It was also shown that E-Cat 2 could be used with and without regeneration. Although there was more deactivation when there was no regeneration step, the yield of gases (C(2)-C(7)) remained fairly constant. For the first time, these results indicate that "waste" FCC catalyst (E-Cat) is a good candidate for future feedstock recycling of polymer waste. The major benefits of using E-Cat are a low market price, the ability to tolerate reuse and regeneration capacity.
We quantified Campylobacter jejuni transferred from naturally contaminated raw chicken fillets and skins to similar cooked chicken parts via standard rubberwood (RW) and polyethylene cutting boards (PE).
The electrical resistivity and flexural strength of plastic composites reinforced with pineapple leaf particles (PCPLP) is presented. PCPLP were produced using different plastic materials; Polyethylene (PE) and Polypropylene (PP), and different plastic pineapple leaf particle ratios; 50:50 and 70:30. The PCPLP were tested and evaluated with respect to electrical resistivity and flexural strength according to ASTM D257 and D790, respectively. The results indicate that PCPLP made from PP exhibits better electrical resistance than PE, which may be attributed to the better frequency insulation behaviour ofPP. PCPLP using the higher ratio of 70:30 also exhibited better electrical resistance than the lower 50:50 ratio. Cellulose materials inherently influence the electrical resistance of plastic composites, due to their natural propensity to absorb moisture. The PCPLP produced using a ratio of 50:50 for both PP and PE composites exhibited better MOE results than the 70:30 composites, however the converse is true with respect to the MOR. MOE of PCPLP was increased with increasing pineapple leaf particles content due to the greater matrix stiffness of this natural particle with respect to plastic matrix. However, high percentage offiller particles in the matrix (70:30 ratio) has reduced the toughness in the composite structure due to the lost ofphysical contact between high accumulated particles.
Compliance to delivery of orthodontic appliances within specified times and factors which influenced compliance by dental technicians in Selangor was evaluated. This is a prospective 8-month study of 18 trainee/ trained technicians from 4 main government dental laboratories in Kajang, Klang, Tanjong Karang and Shah Alam. Delivery times specified by orthodontists were 1 day for plastic retainer, 3 days acrylic retainer, 5 days active plates (URA), 10 days functional appliances (FA), 10 days transpalatal arch (TPA) and 10 days for quadhelix. Punctual delivery was recorded as ‘compliant’. Compliance was compared between appliances, clinics, technicians, orthodontists and seniority of technicians. The sample comprised appliances from 365 patients; 38 (10.4%) Tanjong.Karang, 114 (31.2%) Kajang, 191 (52.3%) Klang and 22 (6.0%) Shah Alam. The majority of appliances were retainers (66.3%), followed by URA (13.4%), functionals (9.3%), TPA (9.0%) and quadhelix (1.9%). Mean compliance for all appliances in Selangor was 55%. Plastic retainers had highest compliance (77.8%), followed by acrylic retainers (59.9%), quadhelix (57.1%), FA (47.1%), TPA (45.5%) and URA (24.5%). Senior technicians (>3 years in service) were more compliant than juniors (
In this work, poly(lactic acid) (PLA) a fully biodegradable thermoplastic polymer matrix was melt blended with three different epoxidized palm oil (EPO). The aim of this research was to enhance the flexibility, mechanical and thermal properties of PLA. The blends were prepared at various EPO contents of 1, 2, 3, 4 and 5 wt% and characterized. The SEM analysis evidenced successful modification on the neat PLA brittle morphology. Tensile tests indicate that the addition of 1 wt% EPO is sufficient to improve the strength and flexibility compared to neat PLA. Additionally, the flexural and impact properties were also enhanced. Further, DSC analysis showed that the addition of EPO results in a decrease in T(g), which implies an increase in the PLA chain mobility. In the presence of 1 wt% EPO, TGA results revealed significant increase in the thermal stability by 27%. Among the three EPOs used, EPO(3) showed the best mechanical and thermal properties compared to the other EPO's, with an optimum loading of 1 wt%. Conclusively, EPO showed a promising outcome to overcome the brittleness and improve the overall properties of neat PLA, thus can be considered as a potential plasticizer.
Starch is a biodegradable polymer produced in abundance from many renewable resources. This study examined the influence of citric acid (0-40% w/wt%) ) and water (0-40% w/wt%) as secondary additive and glycerol as plasticizer on the mechanical properties of bio-plastic starch (BPS) from Malaysian sago. The CA content varies from 0 to 40 w/wt% while water was also varied from 0 to 40 w/wt%. FT-IR spectroscopy showed that acid citric improve the properties of BPS and water give negative effects to the carbon hydrogenbond. It is obvious that the addition of the CA at 30 wt/wt% improve the mechanical property of BPS to more than 40% compare to the addition of water.