Browse publications by year: 2014

  1. Komala T, Tan. C. Khun
    Sains Malaysiana, 2014;43:1149-1156.
    Bacillus pumilis was isolated and identified from limestone and the ability towards carbon dioxide (CO) sequestration was demonstrated. B . pumilus (S3 SC_1), isolated from Gua Tempurung, Gopeng, Perak was able to form calcite in the presence of calcium ions. B. pumilus was successfully characterized by using conventional biochemical characterization and 16s rDNA sequencing. Three types of experimental systems with B. pumilus, without B. pumilus and without continuous supply of CO2 with the presence of B. pumilus which could produce extracellular carbonic were studied to determine the effects of bacterially produced carbonic anhydrase (CA) by B. pumilus in removing CO2 as calcite. Through our current study, CO2 sequestration ability of B . pumilus was proven.
    MeSH terms: Bacillus; Bacteria; Calcium Carbonate; Carbon; Carbon Dioxide; Carbonic Anhydrases; DNA, Ribosomal; Ions; Carbon Sequestration
  2. Shariza Azizan, Wan KL, Adura Mohd-Adnan
    Sains Malaysiana, 2014;43:1139-1148.
    The lysosomal aspartic proteinase cathepsin D is an acute phase protein involved in various physiological processes, including vitellogenesis, yolk processing and immune responses. In this study, we characterised the cathepsin D from the Asian seabass Lates calcarifer and examined its expression profile during infection. The complete coding sequence of L. calcarifer cathepsin D consists of 1191 nucleotides, encoding a 396 amino acid protein molecule that is made up of a putative signal peptide, a leader peptide and a mature peptide. Phylogenetic analyses showed that two types of cathepsin D are present in the teleost lineage i.e. cathepsin D1 and D2, whereas higher vertebrates possess only one type of cathepsin D. L. calcarifer cathepsin D was clustered together with cathepsin D1 from other teleosts. Compared to mammalian sequences, L. calcarifer cathepsin D lacks the β-hairpin loop that forms the double chain and is present as a single chain peptide with conserved aspartic active sites like other fish. Both multiple sequence alignment and phylogenetic analysis indicated that the L. calcarifer cathepsin D sequence codes for cathepsin D1 and suggested that it shares the same functions with cathepsin D from other fish. Expression profiling analysis of cathepsin D in L. calcarifer infected with Aeromonas hydrophila showed that it is up-regulated in immune-related tissues such as gills, spleen and liver, suggesting that cathepsin D plays an important role in the innate immune response of L. calcarifer against pathogens.
  3. Lai WH, Leo TK, Zainal Z, Daud F
    Sains Malaysiana, 2014;43:1133-1138.
    Tiger’s Milk mushrooms (Lignosus rhinocerus) are polypores with three distinct parts: cap (pileus), stem (stipe) and tuber (sclerotium). The stem of this medicinal mushroom is centrally connected to the brownish woody cap that grows out from the tuber underground rather than from the wood. To date, the biotic and abiotic factors that induce the growth of this mushroom are unclear and information regarding its development is scanty. Hence, the differential protein expressions of vegetative dikaryotic mycelial and primordial cells of this mushroom were investigated. Six two dimensional-sodium dodecyl sulfate-polyacrylamide gel electrophoresis (2D-SDS-PAGE) of 13 cm with pH3-10 containing the intracellular proteins of vegetative mycelial and primordial cells of L. rhinocerus were obtained. Analysis of 2D-SDS-PAGE using Progenesis Samespot version 4.1 yielded approximately 1000 distinct protein spots in the proteome of vegetative mycelial cells, while primordial proteome contained nearly 100 spots. Further comparison between the vegetative mycelial and primordial proteomes yielded significant up-regulation of protein expression of 5 primordial cells proteins that were labeled as P1, P2, P3, P4 and P5. These protein spots were excised, trypsin digested and submitted to mass spectrometry. Protein identification through MASCOT yielded significant identification with P1 and P2 as DnaJ domain protein, P3 and P5 as hypothetical protein while P4 as AP-2rep transcription factor. The present results suggested that P3, P4 and P5 are novel proteins that involved in the initiation of L. rhinocerus primordia. Our findings also suggested that stress response mechanism is present during fruitification of this mushroom.
    MeSH terms: Agaricales; Malaysia; Plants, Medicinal
  4. Chong MM, Chang SY, Noraiham Muhammad, Zulkifli Mord Rosli, Qumrul Ahsan
    Sains Malaysiana, 2014;43:959-966.
    Dry sliding wear of polyester hybrid composites containing carboxylic functionalized multi-walled carbon nanotubes (cNT) and microparticles, silica (Si02) was studied at different sliding distances. An attempt has been made to produce uniform dispersion of nano- and micro- particles in the test samples by ultrasonication. The tribological properties of the hybrid composites were performed by using pin-on-disc (POD) tester against grey cast iron countersurface. The dry sliding wear tests were carried out under pressure-velocity (pv) condition of 0.4 MPa and 4 m/s for total sliding distance of 28800 m and at an interval of every sliding distance of 3600 m, wear properties and behavior were studied. The samples containing 10 wt.% silica (microparticles) with and without CNT always show increase in coefficient of friction at the expense of wear rate. However, samples containing only ci'rr have the lowest wear rate with the increase in coefficient of friction. Sliding distance studies also provide the information on wear rates which were ever changing at different sliding distances whereas average coefficient of friction did not vary throughout the tests. SEM observations of wear surfaces showed different wear morphologies when reinforcement (cNT or Si02) incorporated into the composites either alone or in combination.
    MeSH terms: Clothing; Dental Materials; Iron; Polyesters; Pressure; Silicon Dioxide; Friction; Nanotubes, Carbon
  5. Chiu W, Too S, Daud S, Rashid N, Chia M, Rahman S, et al.
    Sains Malaysiana, 2014;43:941-945.
    In the present study, we report the size distribution study on the iron oxide (Fe304) magnetic nanocrystals (Ncs), which have been synthesized by using green chemistry approach with palm-oil based carboxylic compound (oleic acid) as capping ligands . The Fe304 Ncs were prepared by one pot reaction under non-hydrolytic approach. With the assistance of oleic acid that plays the role as effective capping-ligands , we showed that the Fe304 NCs that are highly monodispersed in size and shape can be synthesized by scrupulously controlling the reaction time. The diameter of Fe304 Ncs can be tuned within the range of 4.0-18.0 nm and exhibit very uniform morphology, which are spherical in shape. Current synthetic approach offers a cheap, environmentally benign and excellent repeatability route in large-scale production of high-quality magnetic Fe304 Ncs if compared to the preceding reports.
    MeSH terms: Ferric Compounds; Ligands; Magnetics; Reaction Time; Oleic Acid; Nanoparticles; Physical Phenomena
  6. Mohamad N, Jalar A, Othman N
    Sains Malaysiana, 2014;43:935-940.
    Aluminum alloys have extensive applications in engineering structures like aircraft due to their high strength-to-weight ratio. However, these alloys are very reactive and prone to corrosion attack. Paddy waste is one of the beneficial natural sources that have a potential contribution on inhibiting the corrosion attack. At 600°C, silica was obtained from rice husk ash. The chemical reaction between silica powders with concentrated alkali generates formulation of potential silicate-based corrosion inhibitor. The potentiodynamic polarization, optical microscope (om) , infinite focus microscope (IFM) and scanning electron microscopy (SEM) were employed to investigate the corrosion behaviour of Al 6061 through electrochemical and surface study. The electrochemical measurement showed that the existence of silicate-based corrosion inhibitor in 0.5 M hydrochloric acid medium significantly mitigates the corrosion rates. SEM, IFM and OM showed that the morphology of untreated Al 6061 contributes more damage on the sample surface than that of Al 6061 treated with silicate-base corrosion inhibitor. The aim of this study was to attain better understanding of surface study on corrosion behaviour of aluminum alloy in acidic medium after treated and untreated with silicate-based corrosion inhibitor from paddy residue.
  7. Leow T, Leong P, Eeu T, Ibrahim Z, Hussin R
    Sains Malaysiana, 2014;43:929-934.
    Study of a series of lead lithium borophosphate glass samples was performed to determine the structural and luminescence properties. The glass samples containing the composition of 20Pb0-xLi20-30B 20 3-(50-x)P 20 5-2TiO 2 (where x = 0, 5, 10, 15, 20) system were prepared using melt-quenching technique. The Pb0-Li20-B 20 3-P20 5-Ti0 2 samples were investigated for structural properties using Fourier transform infrared and photoluminescence spectroscopy for studies of luminescence properties. The results from FTIR showed the presence of trigonal and tetrahedral PO4' PO3, BO4 and B03 groups within the host network structure. The samples exhibit luminescence emission centered at 420, 482 and 496 nm when excited at 300 nm wavelength. The emission peak at 420 nm were assigned to F center emission and charge-transfer transition of Ti4+ ions. The results showed that emission intensity was dependent on lithium contents in Ti-doped lead lithium borophosphate glass composition.
    MeSH terms: Fourier Analysis; Glass; Ions; Lithium; Titanium; Spectroscopy, Fourier Transform Infrared; Luminescence
  8. Leong PM, Eeu TY, Leow TQ, Pang XG, Zuhairi Ibrahim, Rosli Hussin
    Sains Malaysiana, 2014;43:915-922.
    Structural and luminescence properties of borophosphate glasses with different modifier doped with transition metal ions have been investigated in this study. The glass sample from the series of xPb 30 4:0 .2Sb20 3:0.3B 20 3:(0 .5-x)P 20 5 and ySb 20 3:0 .2Pb 30 4:(0 .5-y)B 20 3:0 .3P 20 5where x 20 mol% and 0 y 0 .1 5mol% , respectively, were doped with 0.01 mol% of Fe 20 3 system have been prepared using the melt-quenching technique. The structural properties of samples had been studied using fourier transform infrared (FT-m) spectroscopy. The FT-IR study showed the network structure of the studied glasses based on the B 20 3-P 20 5host with the 5b203 and Pb203 modifiers. The results of FT-IR showed traces of B03 and B04 with the introduction of 5b203 and Pb203 modifiers. With the increasing content of B203 which replacing content of P205 in the glass network, the intensity of the borate band decreases and shifted to lower frequency. uv-Vis spectroscopy analysed the transition of Fe3+ from ground state to excited state in the ultraviolet spectral region. The photoluminescence of samples were studied using photoluminescence spectroscopy. The result of photoluminescence spectroscopy showed the effect of photoluminescence enhancement by doping Fe3+ as activator.
    MeSH terms: Borates; Fourier Analysis; Glass; Ions; Metals; Spectroscopy, Fourier Transform Infrared; Transition Elements; Luminescence
  9. Noor Ashikin Mohd Rashid, Wan Nor Liza Wan Mahadi
    Sains Malaysiana, 2014;43:909-914.
    Evaluation of magnetic properties of electrical steel is vital in improving the quality of electrical machinery since it is used as magnetic cores for transformers, motors and generators. A double yoke single sheet tester (ssT) was modeled using two identical C-cores wound with copper wires at limb side in horizontal arrangement. The magnetic properties for electrical steels, grade M4 and M19 were tested under a frequency of 50 Hz with the current ranging from 02 to 2.4A. The effects of the sample dimension and anisotropy on magnetic measurements were investigated. Evaluation on specimen dimensions indicate that the non-uniformity of sample magnetization in overhang sample can attribute to the flux leakage between the yoke legs. The stray flux is also increased with the overhang sample. However, the so-called fit-in sample which is fitted nicely between the yoke end poles can minimize the effect of stray flux. One way ANOVA and T-test were used as statistical methods and executed at the 5% significance level. It is statistically proven that the magnetic properties of both magnetic materials are influenced by their anisotropy.
    MeSH terms: Analysis of Variance; Copper; Electricity; Extremities; Magnetics; Steel; Anisotropy; Magnets
  10. Khan A, Karimov KS, Zubair Armad, Khaulah Sulaiman, Shah M, Moiz S
    Sains Malaysiana, 2014;43:903-908.
    In this paper, fabrication and investigation of organic pressure sensor based on AlICIVT-VO 2(3j7)ICu composite is reported. The active layer of the composite was deposited by drop-casting of the blend CN'T-VO 2 (3fl) on a glass substrate (with prefabricated copper (Cu) electrode). The thin film of the blend consists of carbon nanotube CNT, (2.55 wt. %) and vanadium oxide (VO 2 (3fl)) micropowder, (3 wt. %) in benzol (1 mL). The thickness of the composite was in the range of 20-40 ,um. It was found that the fabricated sensor was sensitive to pressure and showed good repeatability. The decrease in resistance of the sensor was observed by increasing the external uniaxial pressure up to 50 kNm-2 . The experimentally obtained results were compared with the simulated results and showed reasonable agreement with each other.
    MeSH terms: Benzene; Copper; Electrodes; Glass; Oxides; Vanadium; Nanotubes, Carbon; Intracellular Signaling Peptides and Proteins
  11. Halimah M, Chiew W, Sidek H, Daud W, Wahab Z, Khamirul A, et al.
    Sains Malaysiana, 2014;43:899-902.
    A series of (Li20)x(B203)1-x has been synthesized with mole fraction x=0.10, 0.15,020,025 and 0.30 mol% using melt quenching method. The structure of the glass system was determined by FTIR and X-ray diffraction. The density and molar volume were determined and the density increases with Li20 content whereas molar volume decreases with Li20. Refractive index of glass samples were measured by ellipsometer. Refractive index increases with increase of Li20. The absorption spectra of the studied glass showed that position of fundamental absorption edge shifts to longer wavelength with Li20. Optical band gap varies from 0.10 to 222 eV and Urbach energy varies from 2.91 to 1.55 eV. The variation in optical band gap and Urbach energy were due to the variation in the glass structure.
    MeSH terms: Glass; Molar; Refractometry; X-Ray Diffraction; Spectroscopy, Fourier Transform Infrared; Physical Phenomena
  12. Hussain S, Mehmood H, Ali G
    Sains Malaysiana, 2014;43:895-898.
    A novel thin-film multijunction solar cell based on nanocrystalline silicon (nc-Si:H) is presented in this paper. Existing thin-film double junction solar cells are based on amorphous silicon carbide (aSiC:H) and amorphous silicon layers. Such solar cells have limited efficiency due to lower absorption and poor charge transport properties of the a-SiC:H layer. These solar cells have maximum achieved efficiency of about 8.8%. In this work, a-SiC:H has been replaced with nc-Si:H layer and the double junction solar cell has been redesigned. The proposed structure has been simulated with Silvaco TCAD (ATLAS). The simulated results indicated a step increase in the performance of the solar cell with open circuit voltage Voc=2 .096 V and efficiency 77 = 102%. It was proven that the nc-Si:H is a suitable material for the development of an efficient thin film multijunction solar cell.
    MeSH terms: Cell Count; Intercellular Junctions; Silicon; Carbon Compounds, Inorganic; Silicon Compounds
  13. Ho M, Khiew P, Isa D, Tan T, Chiu W, Chia C, et al.
    Sains Malaysiana, 2014;43:885-894.
    In this study, a symmetric supercapacitor has been fabricated by adopting the nanostructured iron oxide (Fe304)-activated carbon (Ac) composite as the core electrode materials. The composite electrodes were prepared via a facile mechanical mixing process and PTFE polymeric solution has been used as the electrode material binder. Structural analysis of the nanocomposite electrodes were characterized by scanning electron microscopy ( sEm) and Brunauer-Emmett-Teller (BET) analysis. The electrochemical performances of the prepared supercapacitor were studied using cyclic voltammetry (cv) and electrochemical impedance spectroscopy (Eis) in 1.0 M Na2S03 and 1.0 M Na2SO4 aqueous solutions, respectively. The experimental results showed that the highest specific capacitance of 43 FIg is achieved with a fairly low Fe304 nanomaterials loading (4 wt. %) in 1 M Na2S03. It is clear that the low concentration of nanostructured Fe304 has improved the capacitive performance of the composite via pseudocapacitance charge storage mechanism as well as the enhancement on the specific surface areas of the electrode. However, further increasing of the Fe304 content in the electrode is found to distort the capacitive performance and deteriorate the specific surface area of the electrode, mainly due to the aggregation of the Fe304 particles within the composite. Additionally, the cv results showed that the Fe3041Ac nanocomposite electrode in Na2S03 electrolyte exhibits a better charge storage performance if compared with Na2SO4 solution. It is believed that Fe304 nanoparticles can provide favourable surface adsorption sites for sulphite (S032-) anions which act as catalysts for subsequent redox and intercalation reactions.
    MeSH terms: Adsorption; Anions; Carbon; Electrodes; Electrolytes; Ferric Compounds; Microscopy, Electron, Scanning; Oxidation-Reduction; Polytetrafluoroethylene; Sulfites; Electric Capacitance; Ficus; Nanoparticles; Nanocomposites; Dielectric Spectroscopy
  14. Siti Khatijah Deraman, Nor Sabirin Mohamed, Ri Hanum Yahaya Subban
    Sains Malaysiana, 2014;43:877-883.
    This paper is focussed on conductivity and dielectric properties of Poly (vinyl) chloride (Pvc)- ammonium triflate (NH4CF3SO3) - butyltrimethyl ammonium bis (trifluoromethyl sulfonyl) imide (Bu3MeNTf2N) ionic liquid, electrolyte system. The electrolyte is prepared by solution cast technique. In this work, the sample containing 30 wt. % NH4CF3SO3 exhibits the highest room temperature conductivity of 2.50 x 10-7 S cm' . Ionic liquid is added in various quantities to the 70 wt. % Pvc-30 wt. % NH4CF3SO3 composition in order to enhance the conductivity of the sample. The highest conductivity at room temperature is obtained for the sample containing 15 wt. % Bu3MeNTf2N with a value of 1.56 x 10 -4 S cm' . The effects of ionic liquid addition on the frequency dependent dielectric properties of PVC based electrolytes is investigated by electrochemical impedance spectroscopy (Eis) at room temperature. The values of dielectric constant were found to increase with increasing conductivity of the samples. Analysis of the ac conductivity data showed the electrolytes to be of the non-Debye type.
    MeSH terms: Electrolytes; Imides; Ions; Paper; Polyvinyl Chloride; Temperature; Vinyl Chloride; Ionic Liquids; Dielectric Spectroscopy; Ammonium Compounds
  15. Chaudhry AR, Armed R, Irfan A, Shaari A, Maarof H, Abdullah GAS
    Sains Malaysiana, 2014;43:867-875.
    We have designed new derivatives of naphtha [2 ,1-b:6 ,5-13V difuran as DPNDF-CN1 and DPNDF-CN2. The molecular structures of DPNDF, its derivatives DPNDF-CN1 and DPNDF-CN2 have been optimized at the ground (So) and first excited (S1) states using density functional theory (DFT) and time-dependent density functional theory (TD-DFT), respectively. Then the highest occupied molecular orbitals (HOMOs), the lowest unoccupied molecular orbitals (Lumos), photoluminescence properties, electron affinities (EELS), reorganization energies (.1.$) and ionization potentials (iPs) have been investigated. The balanced A(h) and A(e) showed that DPNDF, DPNDF-CN1 and DPNDF-CN2 would be better charge transport materials for both hole and electron. The effect of attached acceptors on the geometrical parameters, electronic, optical and charge transfer properties have also been investigated.
    MeSH terms: Alkanes; Animals; Eels; Electrons; Solvents; Molecular Structure; Physical Phenomena
  16. Hossein Mohammadi, Huda Abdullah, Chang FD
    Sains Malaysiana, 2014;43:861-866.
    This paper attempts to give a detailed review and provide a complete description on the technology, physics and modeling of various Multi-Gate MOSFETs. It consists of a synopsis of mathematical depiction of the potential distribution along the channel of various MG-MOSFETS which can be made to enable fast computer analysis of device behavior. This serves a link between process technology and circuit design. This review demonstrates that this technology is strongly desired in nanoscale domain and there is a plenty demand for analytical model which can explain the physics and operation of the devices perfectly.
    MeSH terms: Physics; Technology; Craving; Perfectionism
  17. Syuhada N, Huang N, Vijay Kumar S, Lim H, Rahman S, Thien G, et al.
    Sains Malaysiana, 2014;43:851-859.
    Nanocomposite thin films of chitosanlgraphene oxide (cs/Go) and chitosanl EDTA-GO (CSIEDTA-GO) were prepared by environmental friendly method and the properties were compared. The experimental results showed fine dispersion of GO and EDTA-GO in CS matrix and some interaction occur between the filler and the CS matrix that leads to better distribution of stress transfer. At 0.5 wt. %, both CSIGO and CSIEDTA-GO experienced maximum tensile stress by 51 and 71% compared with CS. Moreover, the elongation at break for both nanocomposites increases and the amount of filler increases.
    MeSH terms: Edetic Acid; Excipients; Organic Chemicals; Oxides; Nanocomposites
  18. Baki S, Tan L, Kan C, Kamari H, Noor A, Mardi M
    Sains Malaysiana, 2014;43:843-850.
    Multicomposition of Er3+ -Y11-3+ codoped tellurite oxide, Te02-ZnO-PbO-Ti02-Na20 glass has been investigated. A detailed spectroscopic study of the Judd-Ofelt analysis has been performed from the measured absorption spectrum in order to obtain the intensity parameters S2, (t=2, 4, 6). The calculated S2, values were then utilized in the determination of transition probabilities, radiative lifetimes and branching ratios of the Er3+ transitions between the J(upper)-J'(lower) manifolds. Both visible upconversion and near-infrared spectra were characterized under the 980 nm laser diode excitation at room temperature.
    MeSH terms: Glass; Oxides; Probability; Spectrum Analysis; Tellurium; Temperature; Zinc Oxide
  19. Wan Nasarudin Wan Jalal, Huda Abdullah, Mohd Syafiq Zulfakar, Sahbudin Shaari, Mohammad Thariqul Islam, Badariah Bais
    Sains Malaysiana, 2014;43:833-842.
    CaxZn(1_x)Al204thin films (x = 0.00; 0 .05 ; 0.10; 0.15 and 0.20) were prepared by sol-gel method with the substitution of Zn2+ by Ca" in the framework of ZnAl204. The effect of Ca addition on the structure and morphology of CaZnAl204thin films was investigated by x-ray diffraction (xRD), field-emission scanning electron microscope (FESEM), energy-dispersive x-ray spectroscopy (EDx), ultra-violet visible (uv-Vis) and atomic force microscope (AFM). The xRD patterns showed the characteristic peaks of face-centred cubic (fcc)ZnAl204and CaZnAl204. The addition of Ca increased the crystallite size from 8.9 to 302 nm. The bandgap of CaxZnuld204 thin film was found in the range of 3.40 to 3.84 eV. sEm micrograph shows the morphology of all thin films is sphere-like, with the grain size increased from 33 to 123 nm. The AFM images show the roughness of surface morphology increased. The substitution of Zn2+ by Ca" increased the crystallite size, grain size and surface roughness which evidently increased the density (4.59 to 4.64 glcm3) and dielectric constant (8.48 to 9.54). The composition of CaxZn(1_x)Al204is considered as suitable material for GPS patch antennas.
    MeSH terms: Mass Media; Microscopy, Electron, Scanning; Spectrometry, X-Ray Emission; X-Ray Diffraction; X-Rays
  20. Siew PF, Wan Yusmawati Wan Yusoff, Azman Jalar
    Sains Malaysiana, 2014;43:827-832.
    The physical properties and structural stability of the Quad Flat No-Leads (QFN) package with different gamma radiation doses have been investigated. The packages were irradiated with Co-60 gamma radiation with varying doses of 5 Gy, 50 Gy, 500 Gy, 5 kGy and 50 kGy with operating dose of 2.54 kGylh at room temperature. The infinite focus microscope (IFM) was used to measure the dimensional change and slantinglwarpage behaviour, while the 3D CT Scan X-ray machine was used to determine the occurrence of deflection on a wire in package due to exposure. It is believed that radiation effect on ceramic filler in the epoxy mold compound (EMC) plays an important role to induce the defects and resulted in swelling of the package. The slantinglwarpage behaviour is believed to be caused by the swelling behaviour of ceramic filler and further induced structural stability. The induced stress on the EMC structural after the dimensional change and slantinglwarpage failure leads to the occurrence of wire sweep. The finding suggests that defect production in swelled ceramic filler leads to the occurrence of dimensional and structure instability.
    MeSH terms: Ceramics; Drug Packaging; Epoxy Resins; Fungi; Gamma Rays; Radiation Injuries; Radiography; Temperature; Tomography, X-Ray Computed; X-Rays
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