Displaying publications 141 - 160 of 2561 in total

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  1. Yang SR, Yeh YL
    Sains Malaysiana, 2015;44:1677-1683.
    Countering the dangers associated the present extreme climate not only requires continuous improvement of local disaster
    prevention engineering infrastructure but also needs an enhanced understanding of the causes of the disasters. This study
    investigates the geologic hazard risk of 53 slopeland villages in Pingtung county of southern Taiwan. First, remote sensing
    (RS) techniques were utilized to interpret environmental geology and geologic hazard zonation, including dip slope, fault,
    landslide and debris flow. GIS map overlay analysis was used to further identify the extent of the geologic hazard zonation.
    As a final step, field investigation is used to comprehend geologic, topographic conditions and the geologic hazard risk
    specific to each locality. Based on data analysis and field investigation results, this study successfully integrates RS, GIS
    and GPS techniques to construct a geologic hazard risk assessment method of slopeland village. The results of this study
    can be used to promote support for future disaster prevention and disaster mitigation efforts.
  2. Yang ES, Kim YS, Park CY, Kim JD, Song HJ
    Sains Malaysiana, 2015;44:1653-1659.
    Anemia of chronic disease (ACD) frequently occurred in patients with chronic inflammatory diseases and can be treated
    by treating the underlying disease. On the other hand, iron-deficiency anemia (IDA), the most common type of anemia,
    occurred with iron loss or when the iron requirement of the body was increased. Since the treatment methods for ACD
    and IDA differ, it is important to clinically distinguish between the two types of anemia. In this study, we investigated and
    evaluated the performance of a number of biomarkers, including ferritin, soluble transferrin receptor (sTfR), hepcidin,
    C-reactive protein (CRP) and combination markers containing ferritin for the diagnosis of IDA using serum samples from
    Korean patients (80 ACD and 48 IDA Korean patients). Among the single markers, ferritin exhibited the best performance
    with 98.58% AUC and 97.50% sensitivity. In this study, a combination of two biomarkers was used to differentially
    diagnose IDA and ACD. Among the combination markers, ferritin + sTfR showed the best performance with 99.51% AUC
    and 98.75% sensitivity. We found that the ferritin + sTfR combination showed the best diagnostic performance with
    1.25% higher SN than ferritin alone. Moreover, it also showed 10% better diagnostic performance than the single ferritin
    marker within the data range where the distinction between ACD and IDA is unclear. We propose that using combination
    markers containing ferritin may diagnose IDA more accurately and facilitate the determination of the appropriate anemia
    treatment to expedite patient recovery.
  3. Yam F, Hassan Z, Omar K
    This article reports on the studies of structural and optical properties of nanoporous GaN prepared by Pt assisted electro chemical etching. The porous GaN samples were investigated by scanning electron microscopy (SEM), atomic force microscopy (AFM), and optical transmission (OT). SEM images liang indicated that the density of the pores increased with etching duration, however, the etching duration has no significant effect on the size and shape of the pores. AFM measurements exhibited that the surface roughness was increased with etching durations, however, for long etching duration, the increase of the surface roughness became insignificant. OT measurements revealed that the increase of pore density would lead to the reduction of light transmission. The studies showed that the porosity could influence the structural and optical properties of the GaN.
  4. Yahya M.D., Lung C, Pinnas YL
    Sains Malaysiana, 1996;25(1):77-86.
    The levels of malondialdehyde (MDA)-specific antibodies in lupus-prone MRL/ lpr mice of different ages were compared to those against DNA. These mice elicited anti-MDA antibodies earlier and in higher levels that anti-DNA antibodies. The levels of immune complexes containing MDA adducts were also higher in these mice when compared to 3 other non-lupus strains. MDA binding to a 100 kDa serum protein was observed in 3 and 5 month old mice. Immune complexes involving anti-MDA antibodies and MDA adducts may represent an additional mechanism that contributes to disease pathogenesis in these mice.
  5. Yaacob WA, Noor Azhraa Sabri, Nur Shafiqa Abdullah
    Sains Malaysiana, 2017;46:1285-1288.
    A new compound namely 2-[(1′E)-3′-hydroxyl-1′-methyl-1′-propen-1′-yl]-6-methoxy-7-[(2′′-methylheptyl)oxy]-5-benzofurancarboxylic acid and three known compounds of β-sitosterol, γ-taraxasterol and stigmasterol were isolated from the n-hexane extracts of the rhizomes and fruits of Johannesteijsmannia altifrons using vacuum liquid, column and radial chromatography. The structures of the isolated compounds were determined by means of 1D and 2D NMR, FT-IR, UV-VIS spectroscopy and mass spectrometry.
  6. YEAMIN HOSSAIN M, MOSADDEQUR RAHMAN M, ABDALLAH EM, JUN O
    Sains Malaysiana, 2013;42:1571-1580.
    The present study describes population structure (length-frequency distribution-LFD) and biometric relationships including length-weight relationship (LWR), length-length relationship (LLR), Fulton’s condition factor (K), relative weight (Wr) and form factor (a3.0) of Puntius sophore wild populations from three major rivers of different geographical locations of Bangladesh. A total of 784 specimens were caught by traditional fishing gear from March 2010 to February 2011. For each individual, the total length (TL), fork length (FL) and standard length (SL) were measured by digital slide calipers. Individual body weight (BW) was also taken by a digital balance. The results showed significant differences in TL-frequency distributions among populations (p<0.05), with larger mean TL size (6.92 ± 1.21 cm) was recorded from the Rupsha River. The coefficient b of the LWR was close to the isometric value (b≈3.000) in these rivers of Bangladesh, although it suggested negative allometric growth in the Padma River (b≈2.900). The results also indicated that the LWRs were highly correlated (r2>0.921). Fulton’s condition factor (K) showed significant variations (p<0.001) among the populations, with best performance by the Padma River, followed by the Jamuna and Rupsha River; whereas, relative weight (Wr) was close to 100 for all the populations, indicating the balance habitat with food availability relative to the presence of predators. The estimated values of a3.0 were as 0.0158, 0.0142 and 0.0152 for P. sophore in the Jamuna, Padma and Rupsha River. These results will be useful for fishery biologists and conservationists to suggest adequate regulations for sustainable fishery management and conservation its numerous stocks in the region.
  7. YAP C, CHENG W, ONG C, TAN S
    Sains Malaysiana, 2013;42:1557-1564.
    A total of 19 polymorphic microsatellite loci were used to analyze the levels of genetic variations for six geographical populations of green-lipped Perna viridis collected from the coastal waters of Peninsular Malaysia. In addition, the total soft tissues of all mussel populations were determined for heavy metals (Cd, Cu, Pb and Zn). FST values revealed that all the six populations of P. viridis in Peninsular Malaysia were categorized as showing ‘moderate genetic differentiation’ according to the classification of Wright (1978). Cluster analysis revealed that three populations which were located in the western part of the Johor Causeway were clustered differently from the other three populations located in the eastern part. Hierarchical F-statistics and cluster analysis indicated that the Johor Causeway which blocked the free flow of the pelagic larvae swimmers of P. viridis and a distinct effect of heavy metal contamination on the Kg. Pasir Puteh population, were the two main causal agents for the genetic differentiation of the P. viridis populations investigated in this study.
  8. YAHYA S, OTHMAN N, DAUD A, JALAR A
    Sains Malaysiana, 2013;42:1793-1798.
    The effect of corrosion inhibition of low carbon steel in water based medium containing lignin was investigated via weight loss method. The evolution of surface morphology has been carried out for 7 to 42 days via optical microscopy (OM), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX) and X-ray photoelectron microscopy (XPS). Immersion of metal specimen without lignin shows that significant increase in the surface roughness. The longer the immersion time, the more the oxide crust formed. The surface degradation of metal specimen was well protected by immersion in lignin solution. A protective layer containing of lignin was formed on the surface of metal specimens after 7 and 21 days immersion. The corrosion inhibition gives about 13 and 53% inhibition for both 7 and 21 days immersion, respectively. The protective layers were spalling and separated from the metal surface after 42 days immersion in lignin solution possibly due to the increase in corrosion attack after long time immersion according to the increase in dissolved oxygen and may also due to the thermal mismatch between oxide and substrate. The adsorption of protective layer containing lignin was temporary adsorbed on the surface.
  9. Xuwang Wei, Yang Yang, Jinfeng Ma
    Sains Malaysiana, 2017;46:2133-2142.
    CCUS (Carbon Capture, Utilization and Storage) now is a lead way to reduce greenhouse effect such as carbon dioxide emission in the world. This paper presents an integrated overview of seismic monitoring technology when CO2 injection process. Mainly is time-lapse seismic method .Time-lapse seismic method is a feasible way to monitor CO2 injection process when CO2 interaction with minerals, which is proved an effective method in CCUS experiments. AVAZ (Amplitude versus Azimuth) seismic method is proved a useful tool to indentify CO2 injection process, which can detect fluid-induced seismic anisotropic response and locating where CO2 flow to in reservoirs, therefore, it’s an effective way to monitor CO2 flow in CO2 monitoring process. Since we develop AVAZ modelling experiment base on rock physics theory to modeling the time-lapse AVAZ seismic reservoir response. The research show fluid saturation and pressure behave two main factors influence modeling seismic AVAZ response. Meanwhile the AVAZ response can also be detect by seismic AVAZ data.
  10. Xu-hui Zhang, Lei Liang, Xiao-yan Wang, Li Zhang, Yan-xin Zheng, Hong-zhu Deng, et al.
    Sains Malaysiana, 2016;45:109-113.
    We investigated the antitumor effects of the combination of matrine-a purified alkaloid extracted from Sophora flavescence-and 5-fluorouracil (5-FU) on SW480 cells. This combination inhibited the growth of SW480 cells in a synergistic or additive manner by disrupting their progression through the cell cycle. Exposure of SW480 cells to matrine and 5-FU was followed by an increased rate of expression for caspase-3, caspase-9 and poly-ADP ribose polymerase (PARP) and inhibited the subcutaneous transplantation of SW480 tumors into Balb/c nude mice. Histopathological analysis showed that this effect was most pronounced in the spleens of treated animals. Typical cytotoxic effects observed in 5-FU-treated mice included fibrosis and lymphopenia, whereas in mice treated with 5-FU combined with matrine, the spleen ultrastructure remained intact. These findings indicate that matrine may enhance the therapeutic effectiveness of 5-FU in SW480 tumors by enhancing apoptosis and overcome the threat to immunocompetence associated with 5-FU.
  11. Xu L, Kaopong R, Nualkaew S, Chullasara A, Phongdara A
    Sains Malaysiana, 2017;46:1491-1498.
    soflavonoids are the main compound in White Kwao Krua (Pueraria mirifica), which is an effective folk medicinal plant endemic to Thailand. It has been widely used for improving human physical and treating diseases. There are substances with estrogenic activities have been isolated from P. mirifica, such as puerarin, daidzein and genistein. Isoflavone synthase (IFS) is one of the key enzymes in Leguminous plants to convert liquiritigenin, liquiritigenin C-glucoside and naringenin chalcone to isoflavonoids. The aim of this research was to enhance the production of isoflavonoids by metabolic engineering. Transgenic plants were constructed by introducing P450 gene (EgP450) which is similar to IFS from oil palm (Elaeis guineensis), into P. mirifica by a biolistic method. After the transgenic plants had proved successfully, isoflavonoids of each group plants were determined by HPLC. The contents of daidzein and genistein in transgenic plants were higher than the control plants
  12. Xin Tong, Xiao-ye Shen, Cheng-lin Hou
    Sains Malaysiana, 2018;47:1685-1692.
    Fungi associated with Vaccinium species play important roles in plant growth and disease control, especially in the final
    blueberry production. Vaccinium dunalianum var. urophyllum (Ericaceae) is a well-known medicinal plant in Southern
    China used to treat inflammation and microbial infections. The endophytic fungi from these plants are therefore anticipated
    as potential new sources of antimicrobials. In this report, the inhibitory effects of endophytes against clinical bacteria
    and yeast were comprehensively screened and 11 isolates indicated high bioactivity by the agar diffusion method. The
    corresponding crude extracts of these fungi under submerged fermentation also demonstrated distinct differences and
    n-butyl alcohol displayed the lowest extraction efficiency among the extracts. The ethyl acetate and dichloromethane
    extracts of filtrates from the Colletotrichum sp. VD001, Epicoccum nigrum VD021 and E. nigrum VD022 strains
    displayed good properties against pathogenic microorganisms according to disc diffusion assays and minimal inhibitory
    concentration (MIC). This study is the first indicating that cultivable endophytic fungi associated with blueberry plants
    produce potential compounds against clinical pathogens.
  13. Xiaolei Wang, Qirong Qin, Cunhui Fan
    Sains Malaysiana, 2017;46:2041-2048.
    In mining process, the height of water flowing fractured zone is important significance to prevent mine of water and gas, in order to further research the failure characteristic of the overlying strata. Taking certain coal mine with 5.82 m mining height as the experimental face, by using the equipment which is sealed two ends by capsules in borehole, affused measurable water between the two capsules and borehole televiewer system, ground penetrating radar, microseismic monitoring system in underground coal mine, the height of water flowing fractured zone of fully-mechanized top caving are monitored, a numerical simulation experiment on the failure process was conducted, a similarity simulation experiment on the cracks evolution was conducted, at the same time, empirical formula of traditional was modified, The results showed that the height of caving and fractured zones were respectively 43.1 and 86.7 m in fully mechanized sub-level caving mining. The data difference of each test method of caving, fractured and water flowing fractured zones were respectively less than 4.5%, 7.1% and 9.0%. The degree of fracture development was low before mining, the number of fissures was obviously increased after mining, the degree of fracture development increased. The fractures cluster region mainly focuses near the coal wall. The fractures density distribution curves of overlying strata like sanke-shapes. The new and adapt to certain coal mine geological conditions empirical formula of water flowing fractured zone height is proposed.
  14. Xiaofeng Tian, Linsong Cheng, Wenqi Zhao, Yiqun Yan, Xiaohui He, Qiang Guo
    Sains Malaysiana, 2015;44:719-725.
    In this paper, seven permeability stress sensitivity experiments were conducted to show the features of permeability stress
    sensitivity. The cores in the experiments were taken from the tight sandstone oil reservoir in Ordos Basin. Then advanced
    technologies, such as casting thin section, scanning electron microscope and rate-controlled mercury penetration, were
    applied to explain the mechanism of permeability stress sensitivity in tight oil reservoirs. The results indicated that
    the permeability reduction and recovery in gas permeability stress sensitivity increases as the permeability decreases.
    This was resulted from the maximal throat radius. The permeability reduction in liquid permeability stress sensitivity
    increases at first and then decreases as the permeability decreases. The permeability recovery decreases to zero as the
    permeability decreases. Additionally, the differences between gas and liquid permeability stress sensitivity become greater
    as the permeability decreases. These were resulted from the effect of the critical throat radius. This paper corrects the
    mistakes about the stress sensitivity in tight oil reservoirs from gas permeability stress sensitivity experiments which is
    significant to the development of tight sandstone oil reservoirs.
  15. Xiaochun Wang, Zongshan Li, Keping Ma
    Sains Malaysiana, 2014;43:9-19.
    The climatic regime shift that occurred in the North Pacific Basin during 1976/’77 have been linked to a decadal mode of climate variability, which long-term behavior could be reconstructed from tree-ring records. We analyzed radial growth patterns of five subtropical tree species in Southeast China in relation to air and sea surface temperature, the Pacific Decadal Oscillation (PDO) and El Niño-Southern Oscillation (ENSO) indices 25 years before and after 1977. In 1953-1977, tree-ring chronologies showed higher correlations with air temperature than in 1978-2002, so that their time-series graphs showed divergence after 1977. The first principal component of the five tree-ring chronologies was significantly correlated with ENSO and PDO indices in 1978-2002, while it had no significant correlations with these variables during 1953-1977. Correlation maps of PC1, PDO and ENSO indices with surface air temperature showed different patterns before and after 1977. Based on these comparisons, altered sensitivity of tree growth to temperature in recent decades could depend on basin-wide climatic shift in the North Pacific, which either changed the effects of local climatic factors on tree growth or modified the relationships between local and regional climate.
  16. Xiangsheng Bao, Quanwen Liu, Haiyan Zhou
    Sains Malaysiana, 2017;46:2169-2177.
    Subei basin is the most promising onshore oil and gas bearing basin in South China. With the deepening of exploration, subtle hydrocarbon reservoirs have gradually become the major target of exploration. Seismic record often shows low signal to noise ratio (SNR), resulting that conventional seismic records have three shortcomings in the identification of subtle reservoirs: difficult to identify small faults; difficult to show the distribution law of sand body; and difficult to find traps. In order to solve this problem, we conducted the research on signal synthesis and decomposition. The research results showed that seismic record of different frequency bands can be restored from original seismic record and both of them contain real stratigraphic information. Based on this, when a certain band or several bands in the original seismic record is affected by noise and result in the reduction of SNR of seismic record, seismic information seriously affected by noise can be abandoned, leaving only less affected seismic information to obtain seismic record with higher SNR. In the collection of actual seismic record, the low and high band seismic information is seriously affected by noise, while medium-band seismic information is less affected. Therefore, based on this, the medium-band seismic information can be restored from the original seismic record to be new record, which is called predominant frequency band seismic record. In this paper, based on the research result, the predominant frequency band seismic record was applied to the two areas of Subei basin and the result showed the research result can be used as a good instruction on well placement and the improvement of drilling success rate.
  17. Wun Fui Mark-lee, Ng KH, Lorna Jeffery Minggu, Khuzaimah Arifin, Mohammad Kassim
    Sains Malaysiana, 2017;46:2461-2467.
    Kompleks Ru(II), [Ru(bpy)2(pypzH)](PF6)2 dengan bpy = 2,2’-bipiridil dan pypzH= 2-(1H-pirazol-3-il)piridin, telah berjaya disintesis dan dicirikan dengan teknik spektroskopi transformasi Fourier inframerah (FTIR), ultralembayung dan cahaya nampak (UV-Vis), resonans magnet nukleus (RMN), serta spektrometer jisim. Pengiraan dengan kaedah teori fungsi ketumpatan (DFT) dan DFT bersandar masa (TD) telah dijalankan untuk membangunkan struktur optimum dan elektronik kompleks Ru(II). Data yang diperoleh menunjukkan orbital molekul terisi dengan tenaga tertinggi (HOMO) disetempatkan pada logam Ru(II) dan ligan pypzH, manakala orbital molekul tidak terisi dengan tenaga terendah (LUMO) didapati tersebar secara menyeluruh pada kedua-dua struktur ligan bpy. Aktiviti fotomangkin kompleks telah diuji terhadap penguruaian pewarna tekstil bromotimol biru (BTB) disebabkan aktiviti foto [Ru(bpy)2(pypzH)](PF6)2 di bawah sinaran lampu xenon 450W (AM 1.5, penapis inframerah). Kadar dan tertib tindak balas foto-uraian BTB dikenal pasti dan dibincangkan bersama dengan mekanisma foto-uraian BTB.
  18. Wun Fui Mark-Lee, Mohammad B. Kassim, Mohd Faizal Md Nasir
    Sains Malaysiana, 2018;47:741-747.
    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.
  19. Wun FML, Chong YY, Law KP, Ishak Ahmad, Mohammad Kassim
    Sains Malaysiana, 2018;47:1491-1499.
    The Re(I) complex, [Re(PyPzH)(CO)3
    Cl] where PyPzH = 2-(1H-pyrazol-3-yl)pyridine, was successfully synthesised
    and characterised with an infrared (IR), ultraviolet-visible (UV-Vis), 1
    H and 13C nuclear magnetic resonance (NMR)
    spectroscopies and X-ray crystallography. The IR spectrum featured three n(C≡O), n(N-H), n(C=N) and n(C=C) signals
    at (1860-2020), 3137, 1614 and 1513 cm-1, respectively. The UV-Vis spectrum of the complex exhibited ligand-centred
    (π®>*) electronic excitations [λmax = 227 nm, ε = 1.942 x 104 M-1cm-1; lmax = 292 nm, ε = 0.853 x 104 M-1cm-1] and
    a metal-to-ligand charge transfer (MLCT) band [lmax = 331 nm, ε = 0.467 x 104 M-1cm-1]. The 13C and 1
    H-NMR spectra
    exhibited the characteristic signals of the three C≡O (189.0 – 199.0 ppm) and NH (14.84 ppm), respectively. The X-ray
    structure of [Re(PyPzH)(CO)3
    Cl] showed the crystal adopted a monoclinic system with a C2/c space group [unit cell
    dimensions: a = 27.7422(14) Å, b = 11.1456(5) Å, c = 9.2461(4) Å with α = γ = 90º and β = 92.552(2)º]. Density
    functional theory (DFT) and time-dependent (TD) DFT calculations were performed to investigate the optimised structural
    geometry and electronic properties of the title complex. The results showed that the highest-occupied molecular orbital
    (HOMO) was predominantly found on the dπ-orbitals of Re(I), Cl and CO. While the lowest-unoccupied molecular orbital
    (LUMO) was located on the PyPzH moiety. The structural and photophysical properties of the [Re(PyPzH)(CO)3
    Cl] were
    established and the reaction enthalpies for the dissociation of Cl atom in the formation of [Re(PyPzH)(CO)3
    ]•
    were
    discussed in view of its potential application for photocatalytic CO2
    reduction.
  20. Wun FML, Muhd Hafizi Zainal, Syahidah Mohd Tahir, Ishak B. Ahmad, Mohammad B. Kassim
    Sains Malaysiana, 2018;47:923-929.
    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 benzothiazolylbenzoythiourea
    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, 1
    H 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 1
    H
    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.
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