Displaying publications 1 - 20 of 173 in total

  1. Ahmad, M.H., Norzaie, J., Al Qbadi, F., Daniel, B.D.
    ASM Science Journal, 2009;3(1):17-26.
    The functions of dams are for water supply, flood control and hydroelectric power generation. A concrete faced rockfill dam (CFRD) is preferred by dam consultants due to its many advantages. It is designed to withstand all applied loads, namely gravity load due to its massive weight and hydrostatic load due to water thrust from the reservoir. The structural response of the Bakun CFRD which is the second highest dam in the world after the Shuibuya Dam, was analyzed using finite element method. A two-dimensional plane strain finite element analysis of the non-linear Duncan-Chang hyperbolic model was used in the study of the dam in respect to the deformation and stresses of the main dam of Bakun CFRD project. The Dead-Birth-Ghost element technique was used to simulate sequences of the construction of the dam. The comparison of rigid and flexible foundation on the behaviour of the dam is discussed in this study. In the finite element modeling, the concrete slab on the upstream was represented through a six-noded element, while the interface characteristic between the dam body and the concrete slab was modeled using an interface element. The maximum settlement and stresses of the cross-section were found and their distribution was discussed and tabulated in the form of contours. The effect of reservoir filling loading had a gradual effect on the dam response behaviour. Comparisons with no water impoundment in the dam were also discussed.
  2. Al-Bayaty, F.H., Al-Tay, B.O., Al-Kushali, S.S., Mahmmod, L.
    ASM Science Journal, 2009;3(1):45-50.
    A study was undertaken to estimate the histological changes of gingival enlargement induced by
    Cyclosporin A (CsA) and Nifedipine, separately and in combination. Twelve adult rabbits were divided equally into four main groups. The first group received 10 mg/kg/day Nifedipine, the second received 10 mg/kg/day CsA, and the third received a combination of 10 mg/kg /day Nifedipine and CsA by gastric feeding. The fourth was regarded as a control group. Animals were given the drugs from day 1 of the experiment until day 70. They were then sacrificed for histological purposes. Results showed increase in the thickness of the epithelium with keratosis and acanthosis, and also increased vascularity. Collagen fibres and fibroblasts at different rates in the three histological groups were observed. Significant alveolar bone resorption with increased marrow spaces filled with fatty tissue were found in the CsA group. Non-significant changes in the alveolar bone of the Nifedipine group while subsequent bone resorption and bone deposition were seen in the combination group. These changes could be due to the effect of both drugs. Significant changes in the gingiva and the alveolar bone were shown in the three experimental groups compared with the control group.
  3. Harun, S.W., Sulaiman, A.H., Ahmad, H.
    ASM Science Journal, 2009;3(1):27-30.
    We demonstrate a multi-wavelength light source using a semiconductor optical amplifier (SOA) in conjunction with an array waveguide grating (AWG). The experimental results showed more than 20 channels with a wavelength separation of 0.8 nm and an optical signal-to-noise ratio of more than 10 dB under room temperature. The channels operated at the wavelength region from 1530.4 nm to 1548.6 nm, which corresponded to AWG filtering wavelengths with SOA drive current of 350 mA. The proposed light source had the advantages of a simple and compact structure, multi-wavelength operation and the system could be upgraded to generate more wavelengths.
  4. Momani, M.A., Yatim, B., Ali, M.A.M., Abdullah, M.
    ASM Science Journal, 2009;3(2):121-130.
    The paper examines the propagation direction and speed of large scale travelling ionospheric disturbances (LSTIDs) obtained from GPS observations of extreme geomagnetic storms during the 23rd solar cycle; these are the October 2003 and November 2003 geomagnetic storms. In the analysis, the time delay between total electron content (TEC) structures at Scott Base station (SBA) (Lat. –77.85º, Long. 166.76º), McMurdo (McM4), (Lat. –77.84º, Long. 166.95º), Davis (DAV1), (Lat. –68.58º, Long. 77.97º) and Casey station (CAS1) (Lat. –66.28º, Long. 110.52º) GPS stations as well as the distance between these stations were employed in the analysis. The measurements during the October 2003 storm showed obvious time delay between the TEC enhancement occurrences at SBA/MCM4, DAV1 and CAS1 stations. The time delay indicated a movement of the ionospheric structures from higher to lower latitudes in a velocity ranging between 0.8 km/s – 1.2 km/s. The first sudden TEC enhancement was observed at SBA/McM4 (Lat. –75.84º) followed by CAS1 station (Lat. –66.28º) and the final TEC enhancement was seen at DAV1 station (Lat. –68.58º) with TEC magnitude decreasing while moving from higher to lower latitudes. One important observation was that although the latitude of the CAS1 station was lower than the DAV1 station, the TEC enhancement was firstly seen at the CAS1 station due to the shorter distance between SBA and CAS1 compared with the distance between SBA and CAS1 of about 500 km. The TEC measurements during the November 2003 storm showed an opposite propagation direction (i.e. poleward direction from lower to higher latitudes) which was seen with a velocity ranging between 0.3 km/s – 0.4 km/s. As similar response was observed using vertical TEC measurements obtained from individual PRN satellites but with higher velocity ranges (1.2 km/s – 2.4 km/s during October
    and 0.5 km/s – 0.7 km/s during November). The equatorward or poleward expansion of LSTIDs during the October and November 2003 storms was probably caused by the disturbances in the neutral temperature which occurred close to the dayside convection throat or due to the neutral wind oscillation induced by atmospheric gravity waves launched from the aurora region.
  5. Omar, S., Alias, S.A., Smykla, J., Moreano, H., Guerra, M.L., Ming, C.Y.
    ASM Science Journal, 2009;3(2):184-194.
    Results of a biodiversity study of Antarctic microfungi from ornithogenic soils are presented in this paper. A wide range of soil habitats within and adjacent to active and abandoned penguin rookeries were sampled in order to examine relationships between environmental factors and the biodiversity of soil microfungi. Soil samples were collected from two contrasting Antarctic locations: (1) Beaufort Island (Ross Sea, Continental Antarctica), which is largely ice- and snow-covered, isolated, difficult to access and infrequently visited, and (2) Barrientos Island (maritime Antarctica) which is mostly ice-free during summer and is often visited by scientists and tourists. Soil sampling at Beaufort and Barrientos Islands was completed during the austral summer seasons of 2004/05 and 2006/07, respectively. Warcup’s soil method was used for fungi cultivation. A total of 27 fungal taxa were isolated from the two study sites, consisting of 11 ascomycetes, 13 hyphomycetes
    and three yeasts. Only three taxa — Geomyces sp., a pink and a white yeast — occurred on both sites. The isolated fungi were classified according to their thermal characteristics in culture, with seven psychrophilic, 10 psychrotrophic and 10 mesophilic fungi being isolated. Thelebolus microspores, Thelebolus sp., Geomyces sp. and Antarctomyces sp., were the most frequently isolated fungi. A total of 10 taxa were isolated from the 20 soil samples from Beaufort Island, consisting of five psychrophilic, four psychrotrophic and one mesophilic fungi. Thelebolus microsporus, Thelebolus sp., Asco BI8 and Phoma sp. were the most frequently obtained fungi
    (20%–27% of isolates). A total of 22 fungal taxa were isolated from 23 soil samples from Barrientos Island, consisting of four psychrophilic, six psychrotrophic and 12 mesophilic fungi. Geomyces sp. and Antarctomyces sp. were the most frequently isolated taxa. Thus, the fungal diversity of Beaufort Island was dominated by Ascomycetes while that of Barrientos Island was dominated by hyphomycetes.
  6. Suparta, W., Samah, A.A., Harper, A.R.
    ASM Science Journal, 2009;3(2):152-160.
    Katabatic winds dramatically affect the polar climate. Their activity depends on density of air and temperature in the source region. This paper presents for first time an analysis of the precipitable water vapour (PWV) variability and its relation to a katabatic event at Scott Base station, Antarctica. A significant effect in their characteristics toward calculation of a reliable user accuracy in GPS applications is addressed. Our investigations using the data between 21st and 30th of November 2002 showed that the PWV profile exhibited an irregular pattern with a maximum value of 7.38 mm (~ 6 mm on average), and was more strongly influenced by relative humidity than by wind speed activity. The dominant wind flow during this period was from the North-Northeast (blowing from the Ross Sea) with a median speed of 4.96 ms–1. The PWV was high when the temperature was between –15ºC and –11ºC. During the dates identified as a katabatic event between 21:30 UT of 28th November and 18:40 UT on 29th November, the wind blew from the Southeast-South direction (from the Ross Ice Shelf) with a maximum speed of 10.92 ms–1. The PWV increased ~1.4 mm (23%) from the mean value, indicating severe wind during this event which had pronounced effect on GPS observations.
  7. Wong, C.M.V.L., Chung, H.H., Aisyah, S., Omar, S., Cheah, Y.K., Maria de, L.G., et al.
    ASM Science Journal, 2009;3(2):107-112.
    There are relatively little data on bacteria with antimicrobial activities from Antarctic, especially from the South Shetland Islands when compared to the other parts of the world. Hence, this project was set to isolate and characterize bacteria that produce anti-microbial compounds from Greenwich Island (one of the South Shetland Islands), Antarctica. A total of 356 strains of bacteria were isolated from Greenwich Island. They were screened for antimicrobial activities against 13 Gram-negative and one Gram-positive indicator food-borne pathogens. Two out of the 356 Antarctic bacterial strains exhibited an antagonistic effect on the indicator strains, Escherichia coli, Salmonella spp., Klebsiella pneumoniae, Enterobacter cloacae, Vibrio parahaemolyticus and Bacillus cereus. The two Antarctic bacterial strains were designated as SS157 and SR13. Biochemical and 16S rDNA analysis indicated that the strain SS157 was closely related to Pseudomonas congelans while the strain SR13 was closely related to Pseudomonas tremae. The anti-microbial compounds produced by the two Antarctic bacteria were not sensitive to temperature and were not degraded by trypsin or pronase indicating that they were likely to be chemical compounds or antibiotics. Antimicrobial compounds from strains SS157 and SR13 were broad spectrum, and targeted both Gram-positive and negative pathogens.
  8. Al-Mansoori, M.H., Mahdi, M.A., Iqbal, S.J., Abdullah, M.K.
    ASM Science Journal, 2008;2(2):107-113.
    In this paper, the tuning range characteristics of a multiwavelength L-band Brillouin-erbium fibre laser utilizing a linear cavity is described. The dependency of the Stokes signal tuning range on the laser’s pumping power and single mode fibre length is elaborated. The proposed laser configuration exhibited a wide tuning range of 11 nm from 1599 nm to 1610 nm. The maximum number of 28 output channels with a spacing of 10.5 GHz was achieved by setting the Brillouin pump wavelength and power at 1603.1 nm and 1.1 mW, respectively. The wider tuning range and higher number of Brillouin Stokes contributed to the higher efficiency of doublepass amplification in the erbium gain medium and also to the bidirectional generation of Brillouin Stokes in the single-mode fibre.
  9. Bidin, N.
    ASM Science Journal, 2008;2(2):179-182.
    The laser technology laboratory (LTL) of the Physics Department, University of Technology Malaysia was established in 1989 to support research and development activities. The laboratory provides activities for short- and long-term projects to serve final year undergraduate and post-graduate students in masters and PhD programmes.
  10. Shaari, S., Ehsan, A.A., Abd-Rahman, M.K.
    ASM Science Journal, 2008;2(2):153-161.
    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.
  11. Mahmood, A.A., Hapipah, M.A., Noor, S.M., Kuppusamy, U.R., Salmah, I., Salmah, I., et al.
    ASM Science Journal, 2009;3(1):51-57.
    The effects of topical application of Orthosiphon stamineus leaf extract on the rate of wound healing and histology of the healed wound were assessed. Four groups of adult male Sprague Dawley rats were experimentally wounded in the posterior neck area. A thin layer of blank placebo was applied topically to wounds of Group 1 rats. Wounds of experimental animals (Group 2 and 3) were dressed with placebo containing 5% and 10% O. stamineus extract, respectively. A thin layer of Intrasite gel® was applied topically to wounds of Group 4 animals as reference. Macroscopically, wounds dressed with placebo containing 5% (healed on day 14.50 ± 0.43) and 10% (healed on day 13.83 ± 0.21) O. stamineus extract each or Intrasite gel® (healed on day 13.13 ± 0.42) significantly accelerated the rate of wound healing compared to wounds dressed with blank placebo. Histological analysis of healed wounds confirmed the results. Wounds dressed with placebo containing 5%, 10% O.stamineus or Intrasite gel® showed markedly less scar width at wound enclosure and granulating tissue contained markedly more collagen, proliferating fibroblast with angiogenesis, and no inflammatory cells compared to wounds dressed with blank placebo. In conclusion, placebo containing 5% or 10% O. stamineus on extract-dressed wounds significantly accelerated the rate of wound healing in rats.
  12. Marghany, M., Cracknell, A.P., Hashim, M.
    ASM Science Journal, 2009;3(1):7-16.
    This paper introduces a method for modification of the formula of the fractal box counting dimension. The method is based on the utilization of the probability distribution formula in the fractal box count. The purpose of this method is to use it for the discrimination of oil spill areas from the surrounding features e.g. sea surface and look-alikes in RADARSAT-1 SAR data. The result showed that the new formula of the fractal box counting dimension was able to discriminate between oil spills and look-alike areas. The low wind area had the highest fractal dimension peak of 2.9, as compared to the oil slick and the surrounding rough sea. The maximum error standard deviation of the low wind area was 0.68 which performed with a 2.9 fractal dimension value.
  13. Tan, C.T., Chua, K.B., Wong, K.T.
    ASM Science Journal, 2009;3(1):91-96.
    The Nipah virus was first discovered in 1999, following a severe outbreak of viral encephalitis among pig farm workers in Malaysia. The virus was thought to have spread from Pteropus bats to pigs, then from infected pigs to humans by close contact. Mortality of the disease was high at about 40%. The main necropsy finding was disseminated microinfarction associated with vasculitis and direct neuronal involvement. Relapsed encephalitis was seen in approximately 10% of those who survived the initial illness. Since its first recorded emergence in peninsular Malaysia, 10 outbreaks of Nipah virus encephalitis have been reported in Bangladesh and West Bengal in India. The outbreaks occurred from January to May, with Pteropus giganteus as the reservoir of the virus. In Bangladesh, evidence indicated that the virus transmitted directly from bats to human, with human to human transmission as an important mode of spread. The mortality of the illness was higher in Bangladesh which stood at around 70%. This was likely to be due to genetic variation of the virus.
  14. Abdul-Rashid, H.A., Al-Qdah, M.T., Chuah, H.T., Tayahi, M.
    ASM Science Journal, 2008;2(2):129-132.
    The operating principle and the performance of chromatic dispersion (CD) measurement technique are discussed through developed numerical models. The performance of the CD measurement technique was studied in terms of the measurement range and sensitivity as the wavelength separation was varied. Based on the numerical model, the technique sensitivity increased with wavelength separation. However, this increase in sensitivity was traded off with a narrower measurement range. The measurement technique was optimized at 5.0 GHz wavelength separation with a sensitivity of 0.009 (dB/ps/nm) and measurement range of 2500 ps/nm.
  15. Lee, L., Sidek, R.M., Jamuar, S.S., Khatun, S.
    ASM Science Journal, 2009;3(1):59-69.
    A 2.4 GHz variable-gain low noise amplifier (VGLNA) intended for use in a Wide-band Code Division
    Multiple Access receiver was designed in 0.18 um CMOS process for low voltage and low power applications. Rivaling classical designs using voltage mode approach, this design used the current mode approach, utilizing the current mirror principle to obtain a controllable gain range from 8.26 dB to 16.95 dB with good input and output return losses. By varying the current through the widths of transistors and a bias resistor, the VGLNA was capable of exhibiting 8 dB gain tuning range without degrading the noise figure. Therefore, higher gain was possible at lower current and thus at lower power consumption. Total power consumption simulated was 4.63 mW from a 1 V supply and this gave a gain/power quotient of 3.66 dB/mW. Comparing this with available published data, it was observed that this work demonstrated a good gain tuning range and the lowest noise figure with such power consumption.
  16. Low, K.H., Zain, S.M., Abas, M.R., Ali Mohd, M.
    ASM Science Journal, 2009;3(1):71-76.
    Fractional factorial design was utilized to evaluate the effect of combinations of nitric acid, hydrogen peroxide, hydrochloric acid and water for microwave digestion of fish muscle. Upon digestion, copper, iron and zinc were determined by flame atomic absorption spectroscopy. H2O2 and HCl volumes were found to be the most significant parameters which resulted in good metal recoveries. This is especially so for the effect of HCl on Fe recovery. The results indicated that the combination of 4 mL 65% HNO3, 2 mL 30% H2O2 and 2 mL 30% HCl gave the most satisfactory percentage recovery. There was good agreement between measured and certified values for all metals with respect to the DORM-3 fish protein.
  17. Omar, N.Y.M., Rahman, N.A., Zain, S.M.
    ASM Science Journal, 2009;3(1):77-90.
    Computational chemistry is a discipline that concerns the computing of physical and chemical properties of atoms and molecules using the fundamentals of quantum mechanics. The expense of computational chemistry calculations is significant and limited by available computational capabilities. The use of high-performance computing clusters alleviate such calculations. However, as high-performance computing (HPC) clusters have always required a balance between four major factors: raw computing power, memory size, I/O capacity, and communication capacity. In this paper, we present the results of standard HPC benchmarks in order to help assess the performance characteristics of the various hardware and software components of a home-built commodity-class Linux cluster. We optimized a range of TCP/MPICH parameters and achieved a maximum MPICH bandwidth of 666 Mbps. The bandwidth and latency of GA put/get operations were better than the corresponding MPICH send/receive ones. We also examined the NFS, PVFS2, and Lustre parallel filesystems and Lustre provided the best read/write bandwidths with more than 90% of those of the local filesystem.
  18. Rosli, Y., Maddess, T.L., James, A.C., Goh, X.L.
    ASM Science Journal, 2009;3(1):31-37.
    Responses were recorded from normal healthy subjects and age-related macular degeneration (AMD) patients and evaluated, using a new variant of mfVEP. Subjects information was recorded using 64 EEG channels with a computer-based acquisition system. The stimulus layout was a 84 region corticallyscaled dartboard comprising 12 sectors and seven concentric rings subtending a diameter of 23º, presented dichoptically at 60 Hz. Data from the control and AMD patients were statistically compared when fitted concurrently into the multiple regression analysis. The Pattern-pulse mfVEP technique could distinguish between normal eyes and those with a definite diagnosis of dry and wet AMD when responses from the macula were considered.
  19. Zakri, A.H.
    ASM Science Journal, 2009;3(2):200-202.
    Recent studies by the United Nations University - Institute of Advanced Studies (UNU-IAS) demonstrate that bioprospecting is taking place in Antarctica and the Southern Ocean and that related commercial applications were being marketed. The bioprospectors’ interest in Antarctica stems from two reasons. First, the lack of knowledge surrounding Antarctic biota provides opportunities to discover novel organisms of potential use to biotechnology. Second, Antarctica’s environmental extremes, such as cold temperatures, extreme aridity and salinity present conditions in which biota have evolved unique characteristics for survival (UNU-IAS 2003). Thus bioprospecting opportunities include, inter alia, the discovery of novel bioactives in species found in cold and dry lithic habitat, novel pigments found in hyper-saline lakes and antifreezes in sea-lakes (Cheng & Cheng 1999).
  20. Abdullah, Z., Halim, Z.I.A., Bakar, M.A.A., Idris, A.M.
    ASM Science Journal, 2009;3(1):39-44.
    3-Nitro-2-phenoxypyridine and 3-nitro-2-(4-methyl)phenoxypyridine were obtained when 2-chloro-3-nitropyridine was treated with phenol and p-cresol, respectively. Fluorescence studies were carried out in various solvents, in capped and uncapped conditions and for differing concentrations. Both 3-nitro-2-phenoxypyridine and 3-nitro-2-(4-methyl)phenoxypyridine were fluorescent compounds but 3-Nitro-2-(4-methyl)phenoxypyridine was more fluorescent than 3-nitro-2-phenoxypyridine in all the solvents used. The fluorescence intensity decreased with concentration and time.
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