[en] Suitability of Parmotrema praesorediosum as a biological indicator of air pollution was studied by determining toxic elements using instrumental neutron activation analysis. Lichen samples were obtained at UKM (National Univ. of Malaysia), BBB (Bandar Baru Bangi), Shah Alam and Kajang. Seven elements were determined i.e. As, Co, Cr, La, Sb, Sc and Zn, with an average concentration of 6.79, 0.80, 11.02, 2.77, 0.77, o.85 and 42.98 ppm respectively. The study showed that most toxic elemental concentration were highest at BBB, followed by Kajang, Shah Alam and UKM campus. Concentration difference of these elements in lichen Parmotrema praesorediosum as influenced by their environmental activity indicate it's possibility as a biological indicator for monitoring an air quality

[en] A phyto chemical investigation on the acetone extract of the stem bark of Shorea faguetiana was conducted. The isolation of the chemical compounds was carried out by different chromatographic techniques and their structures were elucidated by spectroscopic methods including UV, IR, NMR and MS, and also by comparison with the literature. Five oligo stilbenes were isolated and identified as (-)-ε-viniferin, (-)-α-viniferin, (-)-laevifonol, (-)-ampelopsin E and (-)-hopeaphenol. (author)

[en] Titanium oxide (TiO₂) nano tubes were successfully formed by anodization of pure titanium foil in a standard two-electrode bath consisting of ethylene glycol solution containing 5 wt % NH₄F. The pH of the solution was ∼7 and the anodization voltage was 60 V. It was observed that such anodization condition results in ordered arrays of TiO₂ nano tubes with smooth surface and a very high aspect ratio. It was observed that a minimum of 1 wt % water addition was required to form well ordered TiO₂ nano tubes with length of approximately 18.5 μm. As-anodized sample, the self-organized TiO₂ nano tubes have amorphous structure and annealing at 500 degree Celsius of the nano tubes promote formation of anatase and rutile phase. Photo catalytic activity of well ordered TiO₂ nano tubes with two different lengths was evaluated by measuring the degradation of methyl orange (MO). The elaboration of this observation is described in detail in this paper. (author)

[en] The mechanical parameters such as Poisson ratio are input parameter for rock engineering especially in numerical modeling computer software. Seismic methods were utilized to determine Poisson's ratio for fresh (grade I), slightly weathered (grade II), moderately weathered (grade III) and highly weathered (grade IV) rock masses. Poisson's ratio for each layer of rock mass was determined based on average value of compressive wave (Vp) and shear wave (Vs) velocities at respective depth. Compressive wave velocities (Vp) were determined by seismic refraction method and shear wave velocities (Vs) were determined by spectral analysis of surface wave (SASW) method or multichannel analysis of surface wave (MASW) method. A total of 66 seismic tests were carried out on 9 rock mass slopes comprising 6 tests on 1 granitic rock mass slope at Quarry JKR, Bukit Penggorak, Kuantan, Pahang; 26 tests on 4 granitic rock mass slopes at Kuari Kajang Rock, Semenyih, Ulu Langat, Selangor; 12 tests on 1 granitic rock mass slope at Lebuhraya Silk Kajang (km 14.6) Selangor; 14 tests on 2 schistose rock mass slopes at Jalan Kuala Kubu Baru-Bukit Fraser (km 15), Selangor and 8 tests on 1 quartzitic rock mass slope at Section U10, Bukit Cherakah, Shah Alam, Selangor. From the seismic tests, the maximum values of Poissons ratio for grade I, II, III and IV rock masses were 0.295, 0.335, 0.355 and 0.364. The minimum values of Poissons ratio for grade I, II, III and IV rock masses were 0.215, 0.299, 0.334 and 0.337. The average values of Poissons ratio for grade I, II, III and IV rock masses were 0.274, 0.320, 0.345 and 0.345. The values of Poissons ratio for rock masses were increased when the weathering grade increased. The average values of Poisson's ratio for grade II, III and IV rock masses increased 16.8 %, 25.9 % and 25.9 % if compare to grade I rock mass. This scenario occurred because fracture changes on grade I rock mass were bigger when experienced weathering processes. The fracture changes became smaller when experienced weathering processes further on. No fracture change occurred on grade III rock mass when became grade IV rock mass. (author)

[en] Long-wavelength vertical-cavity surface-emitting lasers (LW-VCSELs) have profound advantages compared to traditional edge-emitting lasers offering improved properties with respect to mode selectivity, fibre coupling, threshold currents and integration into 2D arrays or with other electronic devices. Its commercialization is gaining momentum as the local and access network in optical communication system expand. Numerical modeling of LW-VCSEL utilizing wafer-fused InP-based multi-quantum wells (MQW) and GaAs-based distributed Bragg reflectors (DBRs) is presented in this paper. Emphasis is on the device and mesa/pillar diameter design parameter comparison and its effect on the device characteristics. (author)

[en] Four chromium based oxo-trinuclear carboxylate complexes were prepared by reacting chromium(III) nitrate nonahydrate with acetic acid and substituted carboxylic acids. They were characterized using infrared spectroscopy (FT-IR). Chromium content of the complexes was determined by titrimetry method. The chromium(III) monochloroacetate complex, [Cr₃O(ClCH₂COO)₆.3H₂O]NO₃.3H₂O in combination with diethylaluminium chloride formed heterogeneous catalyst system for ethylene polymerization. Both Al/ Cr ratio and temperature influenced the catalytic activity. The maximum activity was 1768 gPE/ gCr/ hr/ atm, achieved by polymerizing at 29 degree Celsius and monomer pressure around 1 atm, with Al/ Cr ratio 30.8. Effect of chloro-substituent groups on carboxylic ligand was studied by comparing the catalytic activities of chromium(III) monochloroacetate, chromium(III) dichloroacetate, chromium(III) trichloroacetate and chromium(III) acetate.The polymerization reaction was found to be first order with respect to the monomer during the initial stage. The activity decreases very rapidly presumably due to fast decay of the active sites. The polyethylene was characterized using FT-IR and DSC, and the results showed that it was of high density and crystallinity. (author)

[en] The seeds of C. cleomifolia (locally known as kacang hantu) collected along Simpang Pulai - Berinchang Road, Cameron Highlands, was defatted with hexane and the resulting oil was analysed for their physico-chemical properties. The percentage yield of the oil was calculated as 5.3 %. The acid value (1.2 %), iodine value (85), peroxide value (0.6), saponification value (192.0) and unsaponifiable matter (2.3 %) were determined to assess the quality of the oil. The physico-chemical characterisation showed that C. cleomifolia seeds oil is unsaturated semi-drying oil, with high saponification and acidic values. The fatty acid composition of C. cleomifolia seed oil was determined by Gas Chromatography and Gas Chromatography-Mass Spectrometry (ToF). The seed oil of C. cleomifolia contained linoleic acid (57.59 %) and palmitic acid (5.07 %), the most abundant unsaturated and saturated fatty acids, respectively. The polyunsaturated triacylglycerol (TAG) in C. cleomifolia seed oil determined by reverse phase High performance Liquid Chromatography; contained as PLL (18.04 %) followed by POL + SLL (11.92 %), OOL (7.04 %) and PLLn (6.31 %). The melting and cooling point of the oil were 16.22 degree Celsius and -33.54 degree Celsius, respectively. (author)

[en] The steady two-dimensional stagnation point flow of an incompressible viscous and electrically conducting fluid, subject to a transverse uniform magnetic field, towards a stretching sheet is investigated. The governing system of partial differential equations are transformed to ordinary differential equations, which are then solved numerically using a finite difference scheme known as the Keller-box method. The effects of the governing parameters on the flow field and heat transfer characteristics are obtained and discussed. It is found that the heat transfer rate at the surface increases with the magnetic parameter when the free stream velocity exceeds the stretching velocity, for example ε>1, and the opposite is observed when ε<1. (author)

[en] The phytochemicals investigation on the fruit peel of Goniothalamus scortechinii (Selayar Raja Ubat) obtained from Gunung Stong, Kelantan has resulted in the isolation of five compounds namely pinocembrine, altholactone, goniofufurone, goniotriol and goniopypyrone. Their structures were determined extensive ultra violet (UV), infrared (IR), nuclear magnetic resonance (NMR) spectroscopy and gas chromatography-mass spectrum (GCMS) analysis. (author)

[en] The objective of this study is to perform an exergy and economic analysis on proton electrolyte membrane fuel cell power system (PEMFC) known as exegoeconomic. A 5 kW PEMFC was taken as case study. The fuel cell includes the hydrogen processing system and a fuel cell stack. The hydrogen processing system consisted of an auto-thermal reactor (ATR), a water gas shift reactor (WGS), tubular ceramic membrane module (TCR) and a pressure swing adsorber (PSA). The fuel cell stack was the main power generator. It was obseved that TCM and PSA have low energy efficiency of 0.29 % and 0.09 % respectively. Energy efficiency for the auto-thermal reactor and fuel cell stack were higher at 22.44 % and 31.97 % respectively and both values are comparable with other studies. The exergoeconomics for the 5kW fuel cell system was determined as RM4756.62 per GJ. From the analysis, it is also found that the fuel cell cost can more competitive, if the cost of operation, maintenance and fuel can be reduced. (author)