Sains Malaysiana

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Simulated GARCH(1,1)-t, the gray region indicates data points used for out-of-sample forecast evaluation. 
In this paper we introduce an analyzing procedure using the Kullback-Leibler information criteria (KLIC) as a statistical tool to evaluate and compare the predictive abilities of possibly misspecified density forecast models. The main advantage of this statistical tool is that we use the censored likelihood functions to compute the tail minimum of the KLIC, to compare the performance of a density forecast models in the tails. Use of KLIC is practically attractive as well as convenient, given its equivalent of the widely used LR test. We include an illustrative simulation to compare a set of distributions, including symmetric and asymmetric distribution, and a family of GARCH volatility models. Our results on simulated data show that the choice of the conditional distribution appears to be a more dominant factor in determining the adequacy and accuracy (quality) of density forecasts than the choice of volatility model.
 
Vehicle license plate recognition has been intensively studied in many countries. Due to the different types of license plates being used, the requirement of an automatic license plate recognition system is different for each country. In this paper, an automatic license plate recognition system is proposed for Malaysian vehicles with standard license plates based on image processing, clustering, feature extraction and neural networks.The image processing library is developed in-house which referred to as Vision System Development Platform (VSDP). Fixed filter, Minimum filter, Median Filter and Homomorphic Filtering are used in image enhancement process. After applying image enhancement, the image is segmented using blob analysis, horizontal scan line profiles, clustering and run length smoothing algorithm approach to identify the location of the license plate. Thoroughly each image is transformed into blob objects and its important information such as total of blobs, location, height and width, are being analyzed for the purpose of cluster exercising and choosing the best cluster with winner blobs. Here, new algorithm called Cluster Run Length Smoothing Algorithm (CRLSA) approach was applied to locate the license plate at the right position. CRLSA consisted of two separate new proposed algorithm which applied new edge detector algorithm using 3×3 kernel masks and 128 grayscale offset plus a new way (3D method) to calculate run length smoothing algorithm (RLSA), which can improve clustering techniques in segmentation phase. Three separate experiments were performed; Cluster and Threshold value 130 (CT130) and CRLSA with Threshold value 1 (CCT1). From those experiments, analysis of error tables based on segmentation errors were constructed. The prototyped system has an accuracy more than 96% and suggestions to further improve the system are discussed in this paper pertaining to analysis of the error.
 
xrD pattern of In 2-x Fe x O 3 thin film (x=00, 0.05, 0.25, 0.35, 0.45) 2 theta (degree)
Absorption coefficient vs wavelength for In 2-x Fe x O 3 thin film (x=00, 0.05, 0.25, 0.35, 0.45)
The lattice parameter, relative reliability, crystal size, grain size, root mean square roughness, thickness and energy band gap of (In 1-x Fe x ) 2 O 3 (x=00, 0.05, 0.25, 0.35, 0.45) thin films
High quality indium oxide and iron doped indium oxide nanocrystalline films were prepared by the sol-gel method followed by a spin coating technique. The samples were characterized by an X-ray diffractometer, an atomic force microscopy and a UV-vis spectroscopy. All samples had good crystallinity with a preferred orientation in the (222) direction. The crystallite size increased from 12.1 nm for the pure sample to 16.1 nm for the sample with x=0.35 and then decreased to 12.1 nm for the sample with x=0.45. All samples contained nanometer grain sizes with a smooth surface. All films showed a high transmission of over 91% in the wavelength range of 200-800 nm.
 
X-ray powder diffraction patterns of La 1.851.5x Sr 0.15+1.5x Cu 1-x Mn x O 4 (x = 0, 0.02, 0.04)
The effects of mixed-valence Mn substitution at the Cu site on the superconducting and elastic properties of La1.85-1.5xSr0.15+1.5xCu1-xMnxO4 (x = 0, 0.02 and 0.04) were studied. The samples were characterized by X-ray diffraction (XRD) method, temperature-dependent resistance measurements, scanning electron microscopy (SEM) and sound velocity measurements at room temperature. An elastic softening and a decrease in the critical temperature Tc was observed as Mn was substituted for Cu. The Debye temperature θD for x = 0 and 0.02 void free samples were calculated to be 459 K and 430 K, respectively. Internal lattice strain which is related to lattice parameter ratio a/c did not correlate with Tc. The electron-phonon coupling estimated using the conventional Bardeen-Cooper-Schrieffer (BCS) theory was λ = 0.367 (x = 0) and 0.368 (x = 0.02). The electron-phonon coupling in two-dimensional van Hove scenario was calculated to be λvH = 0.0148 (x = 0) and 0.0149 (x = 0.02). These results were compared with other cuprates and related superconductors. The comparison showed that other than electron-phonon coupling, the elastic moduli might play an important role in the mechanism of superconductivity in these materials. © 2018 Penerbit Universiti Kebangsaan Malaysia. All Rights Reserved..
 
Superkonduktor fasa (Tl0.5Pb0.5)Sr2Ca(Cu2-xCrx)O7-δ (Tl-1212) bagi x = 0 hingga 0.100 telah disediakan menggunakan kaedah tindak balas keadaan pepejal. Tujuan kajian ini ialah menentukan suhu optimum untuk pembentukan fasa Tl-1212 dengan komposisi ini. Sampel telah disediakan dalam aliran gas oksigen dalam tiga suhu berlainan iaitu 850 °C dalam kerajang perak selama 5 jam, dan 950 °C dan 1000 °C selama 4 min. Bahan telah diciri menggunakan kaedah pembelauan sinar-X untuk mengenal pasti fasa dan pengukuran rintangan elektrik (R) untuk menentukan suhu genting. Sampel yang dipanaskan pada 950 °C menunjukkan pecahan isi padu fasa Tl-1212 yang tertinggi (94% bagi x = 0). Sampel yang dipanaskan pada 1000 °C menunjukkan suhu genting yang tertinggi dengan x = 0.100 menunjukkan suhu genting mula, Tc mula tertinggi iaitu 102 K. Terbitan rintangan melawan suhu (T), dR/dT menunjukkan sampel yang dipanaskan pada 1000 °C (x = 0.015 - 0.100) mempunyai puncak yang hampir sama iaitu Tp1 = Tp2. Ini menunjukkan suhu kesuperkonduksian intrabutiran (Tp1) dan antara butiran (Tp2) berlaku adalah sama. Hasil kajian ini menunjukkan suhu pemanasan 950 °C adalah suhu optimum untuk pembentukan fasa Tl-1212 sementara 1000 °C adalah suhu optimum untuk mendapatkan suhu genting tertinggi.
 
The heat-treatable 6XXX series wrought aluminium alloys need to undergo various thermomechanical processes before they can be used as external car body skin. A lengthy natural aging at room temperature is detrimental to the age hardening of these alloys. Many researchers introduced an additional step such as pre-aging to offset the detrimental effects of the natural aging. The present work is aimed to improve the age-hardening response of the Al-1.2Si-0. 5Mg-0.25Fe sheet alloy through Zr additions between 0.02 to 0.30 wt %. The alloys were water-quenched to room temperature and naturally aged for 14 days before undergoing heat-treatment at 180°C for 30 minutes and 11 hours. Microhardness of Al-1.2Si-0.5Mg-0.25Fe alloy without Zr is 80.2 VHN for the 30 minutes heat-treatment and 105.0 VHN for the 11 hours heat-treatment. Microhardness, ultimate tensile strength and yield strength values for alloys containing Zr heat-treated at 180°C for 11 hours are far more superior compared to the same set of alloys heat-treated for 30 minutes. Nevertheless, alloy containing 0.30 wt %. Zr which was heat-treated for 30 minutes have higher microhardness, ultimate tensile strength and yield strength compared to the alloy without Zr which was heat-treated for 11 hours. Increment in the mechanical properties reported is attributed to grain refinement phenomenon.
 
Samples of La1-xSrxMnO3 (LSMO) complex solution with 0 ≤ x ≤ 0.25 were prepared using the Pechini method. The LSMO solution was then deposited on a quartz substrate using the spin coating technique and annealed at 750°C for an hour. The X-ray diffraction pattern for films with Sr matches with the R3c rhombohedral structure. The surface morphology of the film shows a different structure for a different x with more surface crack formation with Sr increment. The magnetic properties at room temperature showed hysteresis curves for all samples. La1-xSr xMnO3 thin film samples with x = 0.00, 0.05 and 0.10 showed weak ferromagnetic properties while films with x = 0.15, 0.20 and 0.25 are paramagnetic. The sample with x = 0.10 has the highest magnetization value at 12 kOe, which is 0.48 emu/g.
 
Solder joint is important for providing mechanical support and functionality of electronic packaging. Established solder joint should be able to withstand in device service operation and the environment without significant changes in terms of their microstructural evolution and mechanical properties. This study investigates the effect of the coating element (Sn and Ni) on the joining stability of Sn-0.3Ag-0.7Cu solder joint. The solder joints were exposed to different aging test for 1000 h to observed microstructure and micromechanical properties changes. Microstructural observation by means of intermetallic compound layer thickness due to the aging temperature effect. Joining stability by means of micromechanical changes were studied using nanoindentation approach. It was found that the elastic behavior, reduced modulus, and hardness of Sn-0.3Ag-0.7Cu solder joint has reduced due to aging test. However, the plastic behavior of Sn-0.3Ag-0.7Cu solder joint has increased with the increase of the aging temperature. It is observed that the Ni coating has a significant effect and a more stable solder joint achieved. This can be evidenced from small changes in intermetallic compound layer thickness and micromechanical properties were achieved using Ni coating as compared to Sn coating after subjected to the aging test for 1000 h.
 
Ba 0.6Sr 0.4TiO 3 (BST) thin films were prepared on TiO 2 buffer layers. The buffer layers were prepared using sol-gel method, followed by annealing process at different temperature from 300 to 550°C with 50°C interval for 30 min in air. The microstructure and electrical properties of BST were then investigated. Increasing the annealing temperature increased. The buffer layer thickness BST films prepared on thicker buffer layer showed improved crystallinity. Without the buffer layer, BST crystallization cannot occur at 700°C. However with buffer layer, 700°C is sufficient for the process to occur. The BST grain size increased with the buffer grains increment. The existence of TiO 2 buffer layer increased the current density. The dielectric constant, ε r′ and dielectric loss were not affected much by the buffer layer except at frequency around 1 kHz that showed an increment in the ε r' value with the increment of the annealing temperature.
 
In this study TiO 2 films have been prepared using two different techniques i.e. sol-gel and electron gun evaporation (e-gun) techniques. The films were annealed at 300, 350 and 400oC in air. The microstructure study using field emission scanning electron microscope and x-ray diffractometer showed nanometer grains size and only the film prepared by sol-gel and annealed at 400oC has anatase phase while others are amorphous. To study the effect of the films (as buffer layer) onto the dielectric bolometer Ba 0.6Sr 0.4TiO 3 as distance sensor, sensors with the configuration of Al/BST/TiO 2/RuO 2/SiO 2/Si were built. Two different measurements i.e. with and without infrared source were carried out to measure the sensitivity and repeatability of the sensors. The sensors which contained sol-gel TiO 2 films gave reading for both type of measurements, indicating that the sensor can act as active and passive sensors. However, the sensors which contained e-gun TiO 2 films only gave responses when the IR source was used, indicating that they can only act as passive sensors. The most sensitive sensor was TiO 2 film prepared by sol gel and annealed at 350°C. In general sensors which contained TiO 2 films prepared by sol gel showed good repeatability.
 
Polycrystalline samples of (Pr 1-xNdx) 0.67Ba0.33MnO3 with × = 0.0, 0.167, 0.33, 0.5, 0.67, 0.833, and 1.0 have been prepared using the solid state reaction. The samples were calcined at 900°C for 12 hours, pelletized and sintered at 1300°C for 24 hours. The structures were investigated via X-ray diffraction (XRD) method. XRD patterns shiowed orthorliombic distorted perovskite structures. The scanning electron microscopy (SEM) micrographs showed the disorder of the structure in all substitutions. This influenced the value of the magnetoresistance (MR). The MR effects are measured using the four point probe technique with a magnetic field of B < IT at temperatures of 90, 100, 150, 200, 250, 270 and 300 K. Overall, the MR increased as the temperature decreased. All doping concentrations gave a small variation range (10% to 56%). The highest MR value of 56.5 % is observed at 100 K for a sample with X= 1.0. The influence of disorder on the magnetoresistance in (Pr1-× Ndx)0.67Ba0.33MnO3 manganites at low temperatures was also discussed in this paper.
 
The influence of bismuth (Bi) addition on wettability, thickness of interfacial intermetallic compound (IMC), and microhardness properties of Sn-0.7Cu + xBi solder alloy using different types of substrate were examined. The 0.5, 1.0, 1.5, and 2.0 wt. % Bi was added into Sn-0.7Cu and fabricated using the casting process. The result shows that the influence of 1.5 wt. % Bi in the Sn-0.7Cu solder soldered on copper organic solderability preservative (Cu-OSP) and immersion tin (Im-Sn) surface finish has improved the wettability and microhardness. Subsequently, the IMC thickness of Sn-0.7Cu+1.5Bi solder alloy on Im-Sn surface finish gives a better result than reflowed on Cu-OSP. Generally, with the addition of 1.5 wt. % Bi in Sn-0.7Cu solder alloy reflowed on the Im-Sn surface finish had enhanced the performance in terms of wettability, thickness of IMC and microhardness properties compared to on Cu-OSP surface finish.
 
Aloi pateri bebas plumbum telah digunakan secara meluas sebagai bahan antarasambungan bagi peranti elektronik yang memberikan sambungan elektrik bagi kebolehfungsian dan sokongan mekanik bagi integriti struktur. Rawatan termomekanik merupakan proses metalurgi yang melibatkan gabungan rawatan terma dan pembebanan mekanik. Kajian ini bertujuan untuk mengkaji kesan rawatan termomekanik dengan mampatan tunggal ke atas perubahan mikrostruktur dan sifat mikromekanik aloi pateri Sn-0.7Cu. Aloi pateri Sn-0.7Cu berbentuk bar dipotong kepada lapan sampel berbentuk kiub dengan ukuran 6 mm (p) × 6 mm (l) × 10 mm (t). Empat sampel yang pertama menjalani rawatan haba pada suhu 30 ℃, 60 ℃, 90 ℃ dan 120 ℃ selama 20 minit, diikuti dengan proses mampatan tunggal sebanyak 20% dan pelindapan di dalam medium air. Empat sampel yang berikutnya hanya didedahkan pada rawatan haba sahaja, diikuti pelindapan di dalam medium air digunakan sebagai sampel kawalan. Cerapan mikrostruktur menunjukkan butiran yang kecil dan seragam aloi pateri Sn-0.7Cu terbentuk dengan rawatan termomekanik mampatan tunggal pada suhu 120 °C akibat daripada penghabluran semula butiran. Keputusan kekerasan bagi aloi pateri Sn-0.7Cu selepas rawatan termomekanik mampatan tunggal pada suhu 120 °C telah menunjukkan perubahan yang sedikit iaitu sebanyak 19% berbanding sampel rawatan haba sebanyak 64%. Keputusan modulus terkurang juga menunjukkan tren yang sama iaitu perubahan yang lebih rendah bagi sampel dengan rawatan termomekanik mampatan tunggal pada suhu 120 °C sebanyak 52% manakala sampel rawatan haba sebanyak 69%. Penemuan kajian ini menunjukkan bahawa kesan suhu dalam rawatan termomekanik mampatan tunggal berupaya untuk mengubah suai mikrostruktur dan memberikan kestabilan sifat mikromekanik aloi pateri Sn-0.7Cu berbanding dengan rawatan haba.
 
The regulation of immune mechanisms is controlled by major histocompatibility complex/human leukocyte antigen (MHC/HLA). Polymorphisms of the HLA region have an impact on susceptibility to complex infectious and autoimmune diseases. The present study was carried out to determine the frequencies of ASMA, AMA, ANA, dsDNA, and anti-LKM-1 auto-antibodies in hepatitis C patients and to determine their association with the HLA DRβ1 (*04) locus. It was a cross-sectional, analytical study, and 86 patients with chronic HCV were recruited. The presence of auto-antibodies (ASMA, AMA, ANA, dsDNA, and anti-LKM-1) was determined by indirect immunofluorescence and ELISA, while the HLA DRβ1 (*04) allele was assessed by sequence-specific conventional PCR. ANA was detected in 41%, ASMA in 17.4%, AMA in 7%, LKM-1 in 5.8% dsDNA in 4.6% of CHC patients while HLA-DRβ1 (*04) was present in 3.5% of patients, but this was not significantly associated with these auto-antibodies.
 
crystal data and structure refi nement parameters for 2BrBT
experimental and calculated uV-Vis absorption data for 2BrBT measured in ethanol
Comparison of the experimental (solid line) and calculated (dashed line) uV-Vis absorption spectra of 2BrBT in ethanol. Inset: the close-in image of the curve at 320-400 nm 
A benzoylthiourea molecule namely 1,1-dibenzyl-3-(2-bromobenzoyl)thiourea (2BrBT) was synthesized and characterized by C, H, N and S elemental, mass spectrometry and spectroscopic analyses (infrared, ultraviolet-visible and nuclear magnetic resonance). The 2BrBT compound crystallized in a tetragonal system with the space group P43 and exhibits an acentric crystalline packing due to the presence of intermolecular H-bonding network that forms a self-assembly of 1D helical motif. The asymmetric delocalisation of electrons in the molecule retains its transparency throughout the visible and near-infrared region and hence, essentially propagates the macroscopic helical motif in the solid state. The highest-occupied and lowest-unoccupied molecular orbital (HOMO/LUMO) are mainly found on the thiourea moiety and the benzoylthiourea fragment, respectively and shows an optical bandgap of 3.50 eV. The influence of its geometrical characteristics to the optical properties of 2BrBT is established and discussed in view of nonlinear optical (NLO) application.
 
A new series of lanthanum dialkyldithiocarbamate complexes with 1,10-phenantroline were successfully synthesized using in situ methods. These complexes were characterized using elemental analysis, infrared, thermogravimetric analysis and conductivity. Microelemental analysis data were in agreement with the general formula La(S2CNR'R")3phen (R'=ethyl, methyl; R"=butyl, heptyl, isopropyl, isobutyl, benzyl and cyclohexyl; phen = 1,10-phenantroline). Infrared spectra of complexes showed the thioureide v(C-N) bands were in the region of 1450-1482 cm-1. The single v(C-S) bands appeared in the region of 959-997 cm-1 and v(C-H) bands in the region of 2918-2955 cm-1. The crystal structure of tris(N,N- ethylbenzyldithiocarbamate)(1,10-phenantroline)lantanum(III) adopts an orthorombic system (space group Pccn) with a distorted dodecahedron geometry with a = 19.865(5) Å, b = 42.803(10) Å, c = 10.657(3) Å, α = β = γ= 90° and Z = 9. Three dithiocarbamates and one phenanthroline ligands were coordinated to the central La atom in bidentate manner.
 
A new series of gadolinium complexes with mixed ligands, dialkyl dithiocarbamate and 1,10-Phenantroline were successfully synthesized using "in situ" methods. Microelemental analysis data of complexes are in agreement with the general formula Gd[S2 CNR'R"]3Phen (R'=ethyl, methyl; R" = butyl, heptyl, isopropyl, isobutyl, benzyl and cyclohexyl; Phen = 1,10-phenantroline). These complexes have been characterized using elemental analysis, infrared, thermogravimetric analysis, conductivity and magnetic measurements. Infrared spectra of complexes showed the thioureide v(C-N) bands were in the region of 1450-1490 cm-1. The single v(C-S) bands appeared in the region of 959-1003 cm-1 and v(C-H) bands in the region of 2853-2931 cm-1. The crystal structure of tris(N,N-methylbenzyldithiocarbamate) (1,10-phenantroline) gadolinium(III) adopts a triclinic system (space group P?) with a distorted dodecahedron geometry with a = 11.04(6) Å, b = 12.65(7) Å, c = 17.13(10) Å, c = 73.86°(8) β = 74.54°(8) γ = 72.34°(8) and Z = 2. Three dithiocarbamates and one phenanthroline ligands were coordinated to the central Gd atom in bidentate manner.
 
Seven promethium (Pr) complexes with 1,10-phenantroline were successfully synthesized using in situ methods from the reactions of eight amines with praseodymium(III) salts together with carbon disulphide. Methatesis and condensation were the most successful methods to prepare praseodymium dithiocarbamate 1,10-phenantroline complexes with general formula Pr[S 2CNR1R2J3 phen (R1 = ethyl, methyl: R2 = butyl, heptyl, isopropyl, isobutyl, benzyl and cyclohexyl; phen= 1,10-phenantroline). These complexes were characterized using elemental analysis, infrared, thermogravimetric analysis and conductivity. Microelemental analysis data were in agreement with the general formula. Infrared spectra of complexes showed the thioureide v(C-N) bands were in the region of 1454-1484 cm-1 and v(C-H) bands in the region of 2853-2973 cm-1. The single v(C-S) bands appeared in the region of 959 - 999 cm-1 has proved to be bidentate bonding. The 13C NMR spectroscopic data for these complexes showed that the carbon signal from NCS2 moiety were in the range of 192 - 212 ppm. The crystal structure of Pr[S2CN(CH3)(C7H7)] 3phen adopts triclinic system (space group P1) with a distorted dodecahedron geometry with a = 10.7165(16) Å , b = 12.2897(19) Å, c = 16.586(2) Å, α = 73.887(2)°, β = 74.879(2)° and γ = 71.837(2)° and Z = 2. Three dithiocarbamates and one phenanthroline ligands were coordinated to the central Pr atom in bidentate manner.
 
1 H-NMR spectrum (500 MHz, CD 3 CN) and peak assignments of C 2 in the aromatic region between ? = 7.0 and ? = 9.1 ppm [(CD 3 CN solvent, TMS reference] 
Three novel ruthenium(II) complexes of the general formula [Ru(II)(bpy)2L]2+ were synthesized, where L = 1,10-phenanthroline derivatives of position 2 imidazole having 3,4-didecyloxy-phenyl (ddip), 3,4-ditetradecyloxy-phenyl (dtip) and 3,4-dihexadecyloxy-phenyl (dhip). All complexes were characterized by elemental analysis, 1H-nmr and esi-ms. Their photophysical properties have also been studied by UV-visible spectroscopy and fluorescence spectroscopy. The complexes exhibit Ru(II) metal centered emission at approximately 610 nm in acetonitrile solution at room temperature. dna binding studies were carried out by UV-visible titration, luminescence titration and viscosity studies. The results indicated that [Ru(bpy)2(ddip)]2+ binds to c t-dna by partial intercalation mode, while [Ru(bpy)2(dtip)]2+ and [Ru(bpy)2(dhip)]2+ bind intercalatively via extended ligands.
 
A series of metal modified dolomite catalysts (10%Ni-20%Cu/Dol, 10%Co-20%Cu/Dol, 10%Fe-20%Cu/Dol, 10%Zn-20%Cu/DolNi) were synthesized via method of impregnation, later calcined at 500 ℃ and reduced by 5%H2 at 600 ℃. Those catalysts were formerly tested for their physico-chemical properties by BET, BJH, XRD, H2-TPR, NH3–TPD, CO2-TPD and SEM, and followed by evaluation in catalytic performance of glycerol hydrogenolysis to 1,2-propanediol (1,2-PDO). Among the examined catalysts, 10%Ni-20%Cu/Dol showed optimum hydrogenolysis activity owing to the good copper-nickel-dolomite interaction. The outcomes from the characterizations disclosed that the presence of nickel-copper species which principally enriched on dolomite surface thereby enhanced the properties of the catalyst in terms of good metal reducibility along with the presence of adequate catalyst acidity. All the good features of 10%Ni-20%Cu/Dolcatalyst added to its high activity with 83.5% glycerol conversion (GC) and 75% 1,2-PDO with low methanol as side reaction product under 200 ℃, 4 MPa H2 and 10 h duration test, 1 g catalyst dosage and 20 wt% glycerol concentration.
 
Tris (1-carboxyl-2-phenyl-1,2-ethylenodithiolenic-S,S′) tungsten complex is one of the most promising photocatalyst to be used in photolysis of water to produce hydrogen. The first step of the synthesis involves a metathesis reaction of tetrapropylammonium bromide [{(C3H7)4 N}Br] and ammonium tetrathiotungstate [(NH4)2WS4] to form a tetrapropylammonium tetrathiotungstate [{(C3 H7)4N}2WS4] (precursor). Then, the precursor was reacted with phenylacetylenecarboxylic acid (C9H6O2) to form tris(1-carboxyl-2-phenyl-1,2-ethylenodithiolenic-S,S′) tungsten complex (C27H18 O2S6W). The infra-red, ultra violet/visible (UV/ Vis) spectrum, nuclear magnetic resonance (NMR) and elemental micro-analysis of C, H, Nand S agreed with the characteristic of the tris(1-carboxyl-2-phenyl-1,2-ethylenodithiolenic-S,S′) tungsten complex. The (W-S), (C-S) and (C=O) stretching frequencies were detected at 511, (1470 and 1035) and 1655 cm-1, respectively. The 1H NMR spectrum showed six protons in the complex. The 13C NMR showed only 7 signals for carbon atom in the benzene ring, ethylene groups and carboxylic acid pendant group due to the symmetry of the molecules. The reaction yield was about 50 %. Photolysis of acetone spiked H2O showed that the catalyst was able to produced 1.8μmol/h hydrogen.
 
Acetic acid bacteria (AAB) isolated from natural resources and fermented plant beverages were screened to produce 1,3-dihydroxyacetone (DHA) from non-detoxified crude glycerol. Among them, the isolate NKC115 was identified as Gluconobacter frateurii and produced the highest amounts of DHA. Subsequently, the effects of growth-medium conditions (initial pH, crude glycerol concentration and nitrogen sources) on growth and DHA-production capability were examined. The results showed that the crude glycerol concentration increase to above 100 g/L suppressed growth and DHA production. The highest amount of DHA obtained was 27.50 g/L, from an initial crude glycerol concentration of 100 g/L. Meanwhile, an initial pH of 5.5-7.5 in the YPGc medium did not significantly affect the bacterial growth and DHA production. The optimal nitrogen source was peptone, with DHA production at 34.70 g/L. Furthermore, overexpression of the nhaK2 gene encoding for the Na+(K+)/H+ antiporter from Acetobactor tropicalis SKU1100 in G. frateurii NKC115 improved growth and increased the accumulation of DHA (37.25 g/L) from an initial crude glycerol concentration of 20%. These results indicated that the expression of this antiporter might maintain an optimal intracellular pH and concentration of Na+ or K+, leading to the cells' ability to tolerate high concentrations of crude glycerol. © 2018 Penerbit Universiti Kebangsaan Malaysia. All Rights Reserved.
 
Selenocompounds have been widely synthesized for their potential in pharmacology. Ebselen, a selenazole oxide, is a glutathione peroxidase mimic which is known to possess high antioxidant activity. Four derivatives of 3-(2-amino-1,3-selenazol-4-yl)-2H-chromen-2-ones were synthesized by reacting 3-(2-bromoacetyl)-chromen-2-one derivatives with selenourea through Hantzsch reaction using NaF as a catalyst in methanol-water (1:1) at room temperature. These reactions were completed in 30 min and purified using column chromatography eluted with n-hexane-ethyl acetate (7:3) to give 50-83% yields. All the compounds were successfully characterized using IR, 1H and 13C NMR as well as mass spectrometry. The synthesized compounds were tested with DPPH assay to determine the free radical scavenging activity and were compared to gallic and ascorbic acids as standard. Nonetheless, all compounds exhibited weak free radical scavenging activity with IC50 value ranging from 672.13 to 984.03 μM signifying that the derivatives may possess weak antioxidant activities. © 2018 Penerbit Universiti Kebangsaan Malaysia. All rights reserved.
 
The rising concern regarding the negative impact of synthetic pesticides has led to the search for alternative means of pest control. Vermicomposting the mixture of oil palm empty fruit bunch and neem (Azadirachta indica) leaves, with the latter known to have pesticidal value, is therefore of great interest and significance to be studied. The present study was conducted to evaluate the chitinase, protease and β-1,3-glucanase activity of neem leaf-based vermicompost as an indication of its biocontrol properties. The total microbial population of different composition of the vermicompost was also investigated. The results showed that at 10% neem composition, an increment in microbial population, chitinase and protease activities was observed in the end product. A higher concentration of neem exerted a suppressive effect on the microbial population as well as enzymatic activity. This study suggested that the addition of an appropriate composition of neem leaves as one of the raw materials for vermicomposting would potentially enhance the performance of vermicompost as biofertilizer as well as biopesticide.
 
The presence of two different chromophores in benzothiazole molecule namely benzothiazole and aromatic rings lead to interesting chemical and biological properties that attract more researches on the compounds. Three new benzothiazolyl-benzoythiourea compounds namely 1-(1,3-benzothiazol-2-yl)-3-(benzoylthiourea) (BBT), 1-(1,3-benzothiazol-2-yl)-3-(4-chlorobenzoylthiourea) (BBT-4Cl) and 1-(1,3-benzothiazol-2-yl)-3-(4-methoxybenzoylthiourea) (BBT-4OCH3) with different electron withdrawing substituents (R) at the para positions on the benzene ring of benzoylthiourea ring have been synthesized from the reaction of R-benzoyl isothiocyanate (R= H, Cl, and OCH3) and 2-aminobenzothiazole. The compounds were characterized by spectroscopic techniques (infrared, ¹H proton NMR and UV-Vis). The IR spectra showed the frequency signals of n (C=O), n (C=S), n (N-H) at 1664-1673, 1238-1249 and 3031-3055 cm⁻¹, respectively. The ¹H proton NMR spectra showed the presence of N-H amine and amide signals in the region of (12.14-12.35) and (14.17-14.43) ppm, respectively. The proton signals of the two benzothiazole and benzoylthiourea moieties appear at 7.08-8.16 ppm. A theoretical study based on Density Functional Theory (DFT) and Time-Dependent (TD) DFT was conducted to optimize the geometrical structure and investigate the electronic properties of title compounds. The highest occupied molecular orbital (HOMO) was found on the benzothiazole moiety; while, the lowest-unoccupied molecular orbital (LUMO) was located at the benzoylthiourea fragment. The DFT optimized structures possessed an intramolecular hydrogen bonding and the types of para substituents used influenced the properties of hydrogen bonding. © 2018 Penerbit Universiti Kebangsaan Malaysia. All Rights Reserved.
 
Crystallographic data of compound 4
SCHEME 1. Synthesis of borylated porphyrin (i) Synthesis of dipyrromethane catalyzed by trifluoroacetic acid (38%) (ii) Synthesis of 5,15-porphyrin (A 2 B 2 type) by Lindsey condensation reaction (30%) (iii) Bromination reaction (67%) (iv) Borylation by Suzuki cross coupling reaction (40%)
Borylated porphyrin is one of building blocks in coupling reactions to obtain the multiporphyrin containing two, three or more subunits of porphyrins. In this study, one of borylated porphyrin derivatives, 5-(4,4,5,5 – tetramethyl – 1,3,2 – dioxoborolane) -10,20 – diphenylporphyrin (B-DPP) was synthesized through four steps of reactions. The building block of porphyrin, dipyrromethane was synthesized through a condensation reaction in the presence of trifluoroacetic acid as catalyst. Subsequently, A2B2 type of porphyrin was obtained by Lindsey condensation reaction followed by bromination reaction to produce porphyrin halide. Suzuki cross coupling reaction between porphyrin halide and pinacolborane with Pd (II) catalyst afforded 40% of borylayed porphyrin. The product was successfully characterized by using nuclear magnetic resonance spectroscopy (NMR) and UV-Visible spectroscopy (UV-Vis). This compound crystallized from a mixture of dichloromethane/methanol to give violet needle-like crystal. Crystallographic studies showed this compound crystallized in monoclinic system with space group of P21/c. © 2018 Penerbit Universiti Kebangsaan Malaysia. All rights reserved.
 
A novel rapid ion colorimetric sensing material for iron(III) ions was developed from poly(γ-glutamic acid) and 3,4-dihydro-3-(2′-ethyl hydroxyl)-6-ethyl-1,3,2H-benzoxazine (ethyl-Bx). The benzoxazine as an ionophore segment was grafted into γ-PGA backbone via the esterification reaction, which is a simple and effective reaction. The structure of γ-PGA-graft- ethyl-Bx was characterized by using FT-IR and 1H-NMR. The most attainable degree of conversion was 25%. The γ-PGA-graft-ethyl-Bx showed a highly selective and sensitive recognition toward iron(III), which was clearly observable with the naked eye. The iron(III) ions sensing property of γ-PGA-graft-ethyl-Bx was further examined by using photometric titration method. After the interaction between the γ-PGA-graft-ethyl-Bx and iron(III) ions was formed, the solution of the polymer in dimethyl sulfoxide was changed from clear and colorless to red color, resulting in the shift of the maximum wavelength from UV to visible range.
 
1-(5-Mercapto-1,3,4-oxadiazol-2-yl)-2-(pyridine-2-ylamino)ethanone (3), has been synthesized from 2-(pyridine-2-ylamino)acetohydrazide (2). A yellow colored compound (2) was reacted with carbon disulfide and potassium hydroxide in absolute ethanol to obtain the 1-(5-mercapto-1,3,4-oxadiazol-2-yl)-2- (pyridine-2-ylamino)ethanone. Structures of the synthesized compounds were supported by means of IR, NMR, MS spectroscopic and elemental analysis. The synthesized compounds were evaluated for their antimicrobial activity and were expressed as the corresponding minimum inhibitory concentration (MIC). A brown colored compound (3) with 90% yield has been successfully synthesized. This compound was found to have significant antimicrobial activity with MIC value ranging from 30.2-43.2 μg cm-3. The findings of the present study indicate that cyclization of hydrazide acid group of 2-(pyridine-2-ylamino) acetohydrazide (2) into 1,3,4-oxadiazole nucleus resulted in increased antimicrobial activity.
 
The aim of this study was to observe the pattern of lactate dehydrogenase (LDH) activity in GCF and the rate of tooth movement at two different orthodontic forces (1.0 N and 1.5 N). Twelve subjects participated in this study and was chosen based on the inclusion criteria. Each subject received forces of 1.0 N and 1.5 N for tooth movement either on the left or right side of the maxillary canine. GCF sample was collected at mesial and distal sites of the canines before applying the appliance (week 0) and every week for 5 weeks after tooth movement (week 1 to week 5) where baseline activity served as control. LDH activity was assayed spectrophotometically at 340 nm. The tooth movements were measured from casted study models. LDH specific activity at mesial sites in 1.0 N and 1.5 N force groups, respectively increased significantly (p<0.05) only on week four and throughout the treatment when compared with baseline. At distal sites, LDH specific activity with 1.5 N was higher than 1.0 N throughout the five weeks of tooth movement. LDH specific activity with 1.5 N force increased at both mesial (week 2) and distal sites (week 3) with significant different (p<0.05) when compared with 1.0 N force. The tooth movement with 1.5 N showed significantly faster (p<0.05) at the end of week 5 when compared with 1.0 N. LDH has the potential as a biological marker of inflammation during tooth movement. A force of 1 N was more suitable to be used although less tooth movement was produced because less inflammation caused by the force can be useful in orthodontic treatment for patients with stabilised periodontal diseases compared with 1.5 N force.
 
Tocotrienol mixtures have been shown to exert anabolic actions on the skeletal system in animal studies, but it is unclear which tocotrienol isomer shows the most prominent effects. This study aims to investigate the most active tocotrienol isomers using hFOB 1.19 human osteoblasts cultured on a bovine bone scaffold. The bovine trabecular bone was sectioned, demineralised and freeze-dried to form the scaffold. hFOB 1.19 osteoblasts were cultured on the bone scaffolds in humidified condition at 37 °C and 5% carbon dioxide with vitamin E isomers (alpha-, beta-, gamma-, delta-tocotrienol and alpha-tocopherol). The cell differentiation capacity of tocotrienol isomers was investigated through morphological observation, alkaline phosphatase (ALP) activity and osteocalcin expression. Changes in the bone scaffolds were determined using histomorphometry methods. Osteoblast culture treated with gamma- and delta-tocotrienols showed a significant increase in ALP activity and osteocalcin expression. Bone structural histomorphometry analysis showed that bone scaffolds treated with gamma- and delta-tocotrienol showed significant increases in bone volume and trabecular thickness. In conclusion, gamma- and delta-tocotrienol show the most prominent bone anabolic effects by increasing osteoblast differentiation and enhancing bone microstructure.
 
FTIR peak values and different functional groups in fraction A and B
The galls of Quercus infectoria (QI) have been reported to possess numerous medicinal values and give a positive effect on bone metabolism. This study investigated the effects of semi-purified fractions of QI gall extract on the proliferation, alkaline phosphatase (ALP) activity, and mineralisation of human foetal osteoblast cell line (hFOB1.19). The semi-purified fractions (fraction A and B) were prepared by column chromatography methods. MTT assay was used to measure cell proliferation activity to obtain half maximal concentration (EC50) of the cells treated with fraction A (phenolic components and contained amide), fraction B (phenolic components with the presence of alkene), and pamidronate (drug control). The most potent or lowest EC50 was further used to measure ALP activity in the treated and untreated cells at day 1, 3, 7, 10, and 14 by ELISA. Cell mineralisation was determined by von Kossa staining for phosphate depositions and Alizarin Red S staining for calcium depositions. The EC50 values for fraction A and B were 8.86 and 9.92 μg/mL, respectively, which showed a greater effect compared to the pamidronate (15.27 μg/mL). The ALPactivity of both fractions in the treated cells were also greater compared to the two control groups (cells treated with pamidronate and untreated cells), starting from day 3 onwards. The calcium depositions appeared as red spots, while phosphate depositions appeared as black spots. Interestingly, the calcium depositions of cells treated with both fractions were higher than those of the two control groups. In conclusion, semi-purified fractions of QI gall extract enhanced proliferation, improved mineralisation, and increased ALP activity of hFOB 1.19 cells.
 
Sn-Ag based solder alloy seems to be a promising lead-free solder for the application on electronic assembly. The corrosion behavior of different lead free solder alloys such as Sn-3.0Ag, Sn-1.0Ag-0.5Cu and Sn-3.0Ag-0.5Cu was investigated in 3.5% NaCl solution by potentiodynamic polarization and electrochemical impedance spectroscopy. Scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX) and X-ray diffraction (XRD) were used to characterize the samples after the tests. The results showed that the addition of 0.5 wt. % copper with Sn-3.0 Ag solder alloy led to a better corrosion resistance while lowering of Ag content from 3.0 to 1.0 wt. % decreased the resistance. Sn-3.0Ag-0.5Cu exhibits a better corrosion resistance in terms of increased charge transfer resistance and impedance values as well as the lowest capacitance. These characteristics signify its suitability for the application in electronic packaging.
 
Endothelial-to-mesenchymal transition (EndoMT) is a common phenomenon in vascular diseases, while the role of endothelial dysfunction in central vascular disease remains to be further investigated. MiR-122 is an inflammation-associated non-coding RNA that participates in multiple human disease, but whether miR-122 plays as a critical role in EndoMT induced by ischaemic stroke is unknown. Although BAI2 is known as a brain-specific inhibitor protein of angiogenesis, few studies of BAI2 examined EndoMT. This study investigated the mechanism of EndoMT and the miR-122/BAI2 axis in oxygen-glucose deprivation/reperfusion (OGD/R)-mediated EndoMT. A transient middle cerebral artery occlusion (tMCAO) model and OGD/R treatment were used to mimic the ischaemia-reperfusion injury. The colocalization of CD31 and α-SMA was elevated in the peri-infarct area of tMCAO mice. The expression of miR-122 was decreased in the peri-infarct area of tMCAO mice. Downregulation of miR-122, Occludin, and ZO-1 was observed in human brain microvascular endothelial cells (HBMECs) after OGD/R treatment, while α-SMA expression was increased in HBMECs after OGD/R treatment. MiR-122 overexpression reduced the decrease of Occludin and ZO-1 expression and the increase of α-SMA expression induced by OGD/R. MiR-122 negatively regulated BAI2 expression, and OGD/R treatment enhanced BAI2 expression. Knockdown the expression of BAI2 suppressed the decrease of Occludin and ZO-1 expression and the increase of α-SMA expression induced by OGD/R. In conclusion, miR-122 overexpression attenuates OGD/R-mediated EndoMT by targeting BAI2.
 
This study was conducted to characterize the selected marine fish species using partial sequence of mtDNA 12S and 16S rRNA gene. PCR amplification of 12S and 16S rRNA generated PCR amplicons at 350 and 440 bp lengths, respectively. Sequence analysis was performed using BioEdit software. Phylogenetic tree was constructed using MEGA software. Two reference species have been used namely Gobio gobio (AB239596 and EF112528) and Pentapodus caninus (DQ533268 and DQ532933). Based on the result obtained, mtDNA 12S and 16S rRNA were found to be useful as molecular markers for fish species identification. These markers will provide correct identification of fish species when considered along with morphological characteristics.
 
The electronic band structure, density of states (DOS) and carrier concentration of a (13,13) metallic and a (13,0) semiconducting Single Wall Carbon Nanotube (SWCNT) have been estimated and simulated by using the Fermi-Dirac distribution function. The energy dispersion E(k) relation for metallic SWCNT near the minimum energy is linear and the Fermi level was independent of temperature (T). On the other hand for semiconducting SWCNT the E(k) relation is parabolic. The normalized Fermi-Energy (EF - E C) in the nondegenerate regime is a weak (logarithmic) function of carrier concentration and varies linearly with T In the degenerate condition, the Fermi level was independent of T and was a strong function of carrier concentration.
 
Bi 3Zn 2Ta 3O 14, 'P', was crystallised in a cubic unit cell with lattice parameter of a=105437 (9) Å. The material had permittivity, ε', of around 58 and dielectric loss, tan δ, of 2.3 x 10 -3 at 30°C, 1 MHz; temperature coefficient of capacitance (TCC) of-156 ppm/°C in the range of 30°C to 300°C at 1 MHz. Chemical doping was carried out at either A (Bi 15Zn 05-xM x) (Zn 05Ta 15)O 7, or B site (Bi 15Zn 05)(Zn 05-xM xTa 15)O 7 in search of better performance materials. Various divalent cations such as Cd 2+, Ca 2+, Mg 2+, Ni 2+, Pb 2+, and Cu 2+ were used as dopants. Solid solutions formed were: Bi 3Zn 2-XCd xTa 3O 14 (0≤x≤05), Bi 3Zn 2-XMg xTa 3O 14(0≤x≤0.2), Bi 3Zn 2-xNi xTa 3O 14 (0≤x≤0.4), Bi 3Zn 2-xPb xTa 3O 14 (0≤x≤0.3), Bi 3Zn 2-xCa xTa 3O 14 (0≤x≤03) and Bi 3Zn 2-xCu xTa 3O 14 (0≤x≤0.1). Electrical properties of the materials were investigated using impedance spectroscopy. Conductivities of the solid solutions were higher than that of the parent material Bi3Zn2Ta3O14. These doped materials exhibited similar behaviour as Bi 3Zn 2Ta 3O 14, showing a high degree of dispersion of permittivity at low frequencies (<1 kHz) and at temperatures above 500°C. Between 100 kHz and 1000 kHz, non-frequency dependence was observed in the range of 100-300°C. An increase in dielectric loss below 10 kHz was observed. Dielectric loss decreased with frequencies when temperature was above 500°C. Dielectric loss of all divalent cation doped materials was higher than that of the parent material; maximum permittivity value of 68 was recorded at x = 03 in Bi 3Zn 2-xCa xTa 3O 14 TCC obtained in this study had negative values; no obvious correlation between TCC and composition of the doped materials can be deduced.
 
The decolorization of reactive orange 16 dye (RO16)from aqueous solution by CuO/H2O2 was investigated. The amount of dye removed was determined by measuring the concentration of the dye at its characteristic wavelengths by UV-Vis spectrophotometer. The effects of CuO dose, H 2O2 concentration and UV light on the decolorization of the dye were investigated. It was found that the removal rate increased with increasing mass of CuO and increasing concentration of H2O 2. The combination of CuO, H2O2 and UV light was the best system with dye removal of 100% after 6 h. The removal efficiency observed was in the order: CuO/UV/H2O2 > CuO/H 2O2 > CuO/UV = CuO > UV/H2O2 > H2O2 > UV.
 
The performance of charcoal composite electrodes, by using commercial activated charcoal and charcoals from coconut trunk, mangrove wood, rubber wood, and sugarcane, was compared in an attempt to fabricate effective and low cost electrodes for wastewater treatment in textile industries. Reactive Orange 16 was chosen as a model dye because of its high resistance towards conventional treatment methods, while sodium chloride was selected as a supporting electrolyte. The electrode efficiencies were determined based on the percentage of Reactive Orange 16 decolourisation. The charcoals used, duration of electrolysis, functional groups present in charcoals, Brunauer-Emmett-Teller surface area and production of hypochlorite ion that contribute to the effectiveness of the electrodes were examined. The coconut trunk, rubber wood, sugarcane, mangrove wood, and commercially available activated charcoals that were incorporated into tin composite electrodes were able to degrade Reactive Orange 16 until 98.5%, 96.2%, 83.0%, 71.2%, and 29.6%, respectively, after 20 min of electrolysis. The degradation increases with duration of electrolysis. This study illustrated that the production of hypochlorite ion from sodium chloride in solution was the main factor that enhanced the Reactive Orange 16 colour removal. Adsorption process on the electrode surface did not play any significant role in the dye decolourisation. © 2019 Penerbit Universiti Kebangsaan Malaysia. All rights reserved.
 
In this paper, a method of defining the even-even deformed nuclei inertial parameters is suggested. Calculations for isotopes 162-168Hf and 164-176Yb are listed. The parameters of inertia of rotational nuclei are also defined. Dependence of the parameters of inertia on the nucleons number is shown.
 
In this paper, a method of defining the even-even deformed nuclei inertial parameters is suggested. Calculations for isotopes Hf162-168 and Yb164-176 are listed. The parameters of inertia of rotational nuclei are also defined. Dependence of the parameters of inertia on the nucleons number is shown.
 
This study aimed to determine phylogenetic relationship between and among selected species of sea cucumbers (Echinodermata: Holothuroidea) using 16S mitochondrial ribosomal RNA (rRNA) gene. Phylogenetic analyses of 37 partial sequences of 16S mitochondrial rRNA gene using three main methods namely neighbour joining (NJ), maximum parsimony (MP) and maximum likelihood (ML) showed the presence of five main genera of sea cucumbers: Molpadia from order Molpadiida and four genera of order Aspidochirotida namely Holothuria, Stichopus, Bohadschia and Actinopyga. All of the 17 species obtained from Malaysia distributed among the main genera except within Actinopyga. Interestingly, Holothuria excellens was out of Holothuria group causing Holothuria to be paraphyletic. High bootstrap value and consistent clustering made Molpadia, Stichopus, Bohadschia and Actinopyga monophyletic. The relationship of Actinopyga with the other genera was unclarified and Stichopus was sister to Molpadia. The latter finding caused the resolution at order level unclear. The pairwise genetic distance calculated using Kimura 2-parameter model further supported and verified findings from the phylogenetic trees. Further studies with more samples and different mitochondrial DNA genes need to be done to get a better view and verification on the molecular phylogeny of sea cucumbers.
 
Sample collection sites in Selangor, Malaysia. Name of region, number of positive samples/number of samples, were stated in the figure. Five of 105 samples were uncultured Leptospira-positive
16s rRNA sequences of positive samples submitted to GenBank
This study attempted to identify and determine distribution of Leptospira spp. in environmental samples using 16S rRNA and rpoβ genes amplification. The samples were collected from high risk areas in Selangor, Malaysia. A total of 105 environmental samples consisting of soil and water were subjected to direct DNA extraction and PCR reaction. PCR products were analysed using gel electrophoresis and subjected to sequence analysis. Thirteen out of 105 (12.38%) samples were amplified for 16S rRNA with an expected amplicon size of 330 bp, while 50 out of 105 (47.62%) samples showed amplification using rpoβ primers, but were not of expected size. Of the 13 16S rRNA amplified samples, only 5 were identified as Leptospira in the gene sequence analysis and clustered under uncultured group via phylogenetic tree. This study showed the DNA-based approach using PCR and sequence analysis is able to detect the presence of Leptospira, although environmental samples may contain diverse microbial populations that may complicate the detection. Overall, the study suggested the importance of surveillance for Leptospira from environmental samples. © 2018 Penerbit Universiti Kebangsaan Malaysia. All Rights Reserved..
 
Potentiodynamic polarization curves of 17-4 PH stainless steel aged at different conditions in artificial saliva
Chemical composition of the 17-4PH stainless steel
The corrosion behavior of the sintered 17-4PH stainless steel samples aged at different conditions in artificial saliva was studied using the method of electrochemical and weight loss after exposure for various periods of time. The results showed that the samples aged at 480 °C for 1 h exhibited the highest corrosion resistance.The pitting corrosion was predominantly initiated from existing, isolated pores and further accelerated. The corrosion kinetics trend is found to be more consistent with a bimodal function form rather than the classical power-law function.
 
Top-cited authors
Anuar Ishak
  • Universiti Kebangsaan Malaysia
Chin-hua Chia
  • Univeriti Kebangsaan Malaysia (National University of Malaysia)
Wan Aida Wan mustapha
  • Universiti Kebangsaan Malaysia
Sarani Zakaria
  • Universiti Kebangsaan Malaysia
Abdul Aziz Jemain
  • Universiti Kebangsaan Malaysia