Displaying publications 421 - 440 of 9926 in total

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  1. Noorain Mohd Isa, Ahmad Zaharin Aris
    Sains Malaysiana, 2012;41:23-32.
    Classified as a small island, Kapas Island experiences major problems especially in supplying freshwater where groundwater abstraction is the only way to meet the demand of drinking water and domestic use. Groundwater samples were collected from seven constructed boreholes to examine the hydrochemistry properties of major ions and in-situ parameters as these could provide a basis for future reference. The chemical composition showed strong and significant correlation for each studied parameter; an indication of the effect of environmental variables to the groundwater composition. The composition changed from Ca-rich to Na-rich are explained mostly by mixing and cation exchange processes. This study provided an input for water management at Kapas Island where groundwater is a crucial resource to maintain the hydrogeological balance of the island.
  2. IBRAHIM N, AL-SHOMAR S, AHMAD S
    Sains Malaysiana, 2013;42:1781-1786.
    Undoped zinc oxide (ZnO) thin films were prepared by a sol-gel method. The effect of annealing temperature from 500 to 700°C on the structural and optical properties of the fi lms was studied. The films nanostructure characterized by the X-ray diffraction method showed that the films were single phase ZnO with wurtzite structure. The surface morphology studied using the field emission scanning electron microscope showed that the thickness of the films increased with the increment of annealing temperature. The grain size of the films increased with the increment of the annealing temperature. The film surface roughness measured using the atomic force microscope showed that the surface roughness of the film decreased (from 2.3 to 1.02 nm ), when the annealing temperature increased from 500 to 600°C then it increased to 3.06 nm at 700°C. The optical properties were studied by the UV-Vis spectrophotometer. The results showed that the films had high transmittance (above 80%) in the visible range and the exciton absorption occurred at a wavelength of 379 nm. The energy gap decreased with the increment of annealing temperature.
  3. Riaz Ahmad Afridi, Muhammad Azim Khan
    Sains Malaysiana, 2015;44:693-699.
    Laboratory and pot experiments were conducted at the Department of Weed Science, The University of Agriculture
    Peshawar, Pakistan during fall 2011 and repeated in 2012. Allelopathic plants were used against wheat and associated
    weeds. Allelopathic plants showed significant activity against three selected species - Triticum aestivum, Avena fatua
    and Rumex crispus. Aqueous extracts of Parthenium hysterophorus and Datura alba showed significant effect against
    weeds of Triticum aestivum although aqueous extract of Phragmites australis possessed moderate activity. It was noted
    that aqueous extract of Oryza sativa and control were comparable for all parameters studied. Aqueous extract of P.
    hysterophorus and D. alba decreased seed germination, shoot length, fresh and dry biomass as compared to the rest
    of the treatments. The degree of toxicity of different treatments can be placed in the following order of inhibition: P.
    hysterophorus > D. alba > P. australis > O. sativa ≥ control. The present studies showed that the plants used contain water
    soluble allelochemicals that retard or inhibit the germination, growth and biomass of other species. These experiments
    suggests that P. hysterophorus, D. alba and P. australis extracts may have negative effect on major weeds like A. fatua
    and R. crispus. Thus there is a possibility of using these plant extracts for weed management. However, more extensive
    studies is required to identify the allelopathins responsible for inhibitory effects on seed germination and plant growth.
  4. Ting T, Crouse K, Ahmad H
    Sains Malaysiana, 2015;44:619-628.
    Three novel ruthenium(II) complexes of the general formula [Ru(II)(bpy)2
    L]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, 1
    H-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 CT-DNA by partial intercalation mode, while [Ru(bpy)2
    (dtip)]2+ and [Ru(bpy)2
    (dhip)]2+
    bind intercalatively via extended ligands.
  5. Mansoor Saburov, Mohd Ali Khameini Ahmad
    Sains Malaysiana, 2015;44:635-641.
    We provide a solvability criterion for a cubic equation in domains , 3
    , and 3
    .
  6. Ahmad Zorin Sahalan, Engku Sharmila, Nazahiyah Sulaiman
    Jurnal Sains Kesihatan Malaysia, 2018;16(101):83-87.
    MyJurnal
    Recently, epidermal mucus of fish has been identified as a rich biological source of various bioactive substances, particularly antibacterial peptides. This study was conducted to identify the potential of epidermal mucosa of Clarias batrachus as a source of antibacterial material. Mucosal samples were collected from C. batrachus epidermis and extracted using an aqueous extraction method. Antibacterial activity of the crude epidermal mucus extract was determined by using spectrophotometric method. As a result there was antibacterial activity by the mucus extract against Escherichia coli (ATCC 25922) and Pseudomonas aeruginosa (ATCC 27853). The results of this study supports the role of mucus as a part of body immune system with antibacterial peptide as a component of innate body immune system. Hence, these findings can be used as one of the first steps towards the development of new class antibiotics.
  7. Desa A, Ahmad A, Sharkawi Z
    Jurnal Psikologi Malaysia, 2009;olume 23:19-25.
    This study explores whether differences in levels of psychological well-being exist between the Orang Asli in Pertak and those in Gerachi Jaya. Field studies were conductecl on orang Asli in both these villages by using structured interviews. Psychological well-being questionnaires were modified by the researcher based on the Psychological Well-being Scale (Ryff 1989). Psychological well-being was measured in terms of autonomy, control environment, personal development and positive relationships. This study involved 40 Orang Asli from Gerachi City and 35 Orang Asli from Pertak. Data were analyzed with SPSS software using t-tests. Results show that the levels of psychological well-being between the two groups were not significantly different (t= 0.339, k> 0.05). Implications are also discussed.
  8. Zulaikah Mohamed, Nazlina Ibrahim, Ismail Ahmad
    Sains Malaysiana, 2008;37(1):107-113.
    Methanol extract of Melastoma malabathricum leaves inhibited the growth of Staphylococcus aureus and six clinical isolates of Methicilin Resistant Stapyhlococcus aureus (MRSA 1-6). The minimum inhibitory concentration (MIC) of test substance was 1.565mg/ml and the minimum bacteriocidal concentration (MBC) was 3.125 mg/ml. The methanol extract suppressed RNA synthesis at 10 mg/ml as shown by RNA profile which was devoid of three bands compared to the control. Reverse transcriptase-polymerase chain reaction (RT-PCR) analysis using seven primer pairs was only successful in amplifying four cDNA amplicons. The failure to amplify three cDNA amplicons for three primer pairs corresponding to gyrA, femA and nuc genes, implied the possibility of suppression of the corresponding mRNA. Electrophoretic separation of endogenous and exogenuos bacterial proteins showed that three and five protein, respectively were not expressed. One endogenous and three exogenous proteins were over-expressed in treated MRSA compared with untreated control. The results of the molecular and proteomic analyses are in agreement, and based on primers being used, methanol extract of M. malabathricum leaves possibly inhibits MRSA growth through inhibition of DNA synthesis, peptidoglycan production, and nuclease production.
    Keywords: Methicillin resistant Staphylococcus aureus; Melastoma malabathricum; gene expression; protein production
  9. AHMAD SHAHIR BIN JAMALUDIN, ABDULLAH BIN YASSIN
    Sains Malaysiana, 2013;42:1727-1733.
    Invention of milling combined laser sintering system (MLSS) is able to reduce the mould manufacturing time and improve the mould accuracy. Thus, more study is needed to increase the understanding for the laser sintered material machining characteristic to gain benefit from the invention of MLSS. This paper clarified the analysis of laser sintered material machinability with the application of Finite Element Method (FEM). Mild steel AISI1055 was applied in developing the Finite Element model in this study due to its popularity in machinability test and adequate level of data availability. 2D orthogonal cutting was employed on edge design tools with updated Lagrangian coupled thermo mechanical plane strain model. Adaptive meshing, tool edge radius and various types of friction models were assigned to obtain efficient simulations and precise cutting results. Cutting force and cutting-edge temperature estimated by Finite Element Method are validated against corresponding experimental values by previous researchers. In the study, cutting force increases when radial depth increases and lowest error acquired when the shear friction factor of 0.8 was applied. Machining simulation for laser sintered materials estimated lower cutting force compared with mild steel AISI1055 due to lower Young modulus. Higher cutting temperature estimated for machining simulation laser sintered material compared with machining simulation mild steel AISI1055 due to its low thermal conductivity.
  10. Azlina Ahmad-Annuar, Ai Sze Ching
    Sains Malaysiana, 2015;44:1481-1488.
    As researchers seek to determine the cellular mechanisms underlying biological processes, they have turned to analyze the functional role of microRNAs to understand this process in details. Here, we investigated the expression pattern of two microRNAs, miR-124 and -134 in maturing neurons and found that the choice of endogenous controls influenced the observed expression levels of these microRNAs. We have cultured rat hippocampal neurons and performed quantitative PCR on the microRNAs using Taqman gene expression assays. The expression of miRNAs was normalised with selected endogenous controls. Using BestKeeper and NormFinder software, we found that 18S rRNA and 5S rRNA to be unsuitable as endogenous controls in this system, while normalising to U6 snRNA produced more consistent results. Our study would like to highlight the importance of empirically testing proposed endogenous controls in any model system before data interpretation is carried out.
  11. Rita Sundari, Musa Ahmad, Lee YH
    Sains Malaysiana, 2006;35:67-73.
    An equation modeling on Sembulan river, Sabah, Malaysia, has been undertaken using a backward stepwise multiple linear regression. A good performance has been obtained using a log transformation on water quality data designated as predictors and dependent variable. The regression model is in accordance with the ANOVA result. The temperature, biochemical oxygen demand (BOD), Echerichia Coli, Pb and nitrate were described as continuous predictors, while the river location (downstream, municipal and upstream) was designated as independent string grouping variable, and the chemical oxygen demand (COD) was set up as the dependent variable. The string grouping variable was converted to its dummy variable, which in turn led to design of a three-equation model with respect to river location. The results show that BOD has a strong effect on COD, while Pb and nitrate show less effect on COD. The temperature gives little negative effect on COD, while other variables such as pH, salinity and Cd are excluded from the river modeling since they induce insignificant effects based on backward criterion probability of F-value ≥ 0.100. Using the general linear model with LSD mode, it is revealed that predictor(s) show a remarkable discriminant effect between upstream and municipal/downstream on the 0.05 level. The most effect came from salinity indicated by the canonical discriminant function based on Wilks’ lambda.
  12. Rosmawani Mohammad, Musa Ahmad, Jamaluddin Mohd Daud
    Sensor optik pH berasaskan reagen kurkumin terpegun dalam matriks hibrid sol-gel/kitosan melamin telah dibangunkan dalam kajian ini. Sensor optik pH ini memberikan rangsangan linear pada julat pH 9-13 (R2 = 0.9846). Seterusnya, nilai RSD kebolehulangan adalah 7.38% - 9.65%, manakala nilai RSD kebolehasilan pula adalah 2.18% - 4.72%. Kestabilanfoto yang baik bagi reagen kurkumin terpegun diperolehi apabila filem disimpan dalam persekitaran gelap dengan nilai RSD 3.69% untuk tempoh kajian 3 minggu. Tiada kesan histerisis diperhatikan apabila sensor digunakan untuk mengukur pH dalam kitaran pH 2-12-2. Masa rangsangan sensor adalah 10-20 saat. Penentuan nilai pH bagi beberapa sampel sebenar menggunakan sensor pH yang dihasilkan dalam kajian ini menunjukkan tiada perbezaan secara signifikan pada nilai pH yang diperolehi apabila dibandingkan dengan keputusan yang diperolehi menggunakan meter pH.
  13. Ishak Ahmad, Mohd Suzeren Jamil, Ibrahim Abdullah
    Kesan penambahan pengisi sekam padi dan tanah liat ke dalam matriks getah asli getah asli cecair polietilena berketumpatan tinggi (NR/LNR/HDPE), NR/HDPE dan HDPE terhadap sifat mekanik dan morfologi adunan telah dikaji. Pemprosesan adunan dilakukan pada suhu 140°C dan kadar percampuran 50 r.p.m. selama 16 minit. Pra-pemanasan pengisi selama 4 minit pada suhu 80°C dilakukan sebelum pengadunan dengan matriks bagi meminimumkan kesan lembapan. Getah asli cecair digunakan sebagai agen pengserasi dalam adunan komposit. Pengisian sekam padi (SP) dan tanah liat (TL) dalam matrik HDPE, NR/HDPE serta NR/LNR/HDPE umumnya menurunkan nilai kekuatan tensil dan kekuatan hentaman tetapi meningkatkan nilai modulus. Kehomogenan adunan komposit berpengisi yang dikenal pasti melalui pemeriksaan morfologi menggunakan mikroskop imbasan elektron (SEM) menunjukkan masalah aglomerasi dan interaksi antara muka dalam komposit berlaku. Kelikatan leburan dan interaksi antara bahan menentukan arah pergerakan serta serakan pengisi dalam komposit. Daripada keputusan yang diperolehi dan merujuk kedua-dua sifat pengisi, SP adalah lebih serasi dengan NR disebabkan potensi interaksi antara kumpulan berfungsi permukaan pengisi selulosa (SP) seperti –OH dengan ikatan ganda dua NR berbanding TL. Ciri fizik permukaan TL yang kurang bersifat hidrofilik berbanding SP pula menyebabkan TL lebih cenderung berinteraksi dan tersebar dengan baik dalam HDPE.
  14. Shuhaimi-Othman M, Azmah M, Ahmad A
    Biomonitor Multispesies Air Tawar (Multispecies Freshwater Biomonitor®) (MFB) menggunakan pengukuran dan analisis pelbagai kelakuan daripada pelbagai jenis organisma akuatik untuk memantau kualiti air dalam ekosistem air tawar. Kajian ini dijalankan di dalam makmal bagi menentukan respons spesifik udang air tawar (Macrobrachium lanchesteri) dan ikan gapi (Poecilia reticulata) terhadap logam berat kadmium (Cd). Kepekatan Cd yang berbeza didedahkan kepada M. lanchesteri (1 ppb dan 10 ppb) dan P. reticulata (100 ppb dan 560 ppb) dan perubahan perilaku setiap organisma direkod dengan MFB selama 2 jam. Hasil yang diperolehi menunjukkan peningkatan respons pergerakan dan ventilasi udang air tawar dan ikan dengan peningkatan kepekatan pendedahan kepada logam Cd. Kajian ini menunjukkan udang memberi respons yang lebih sensitif kepada logam Cd berbanding ikan gapi dan spesies tempatan ini sesuai digunakan sebagai organisma penunjuk untuk MFB.
  15. Liow CH, Sahrim Ahmad, Khairiah Badri
    In-situ polymerization method was used to prepare palm-based polyurethane (PU) composites loading with 15 wt% magnetite (Fe3O4), polyaniline (PANI) and Fe3O4 coated with PANI labeled as PU15, PP and PPM, respectively. FTIR spectroscopy analysis indicated a shift in the carbonyl, C=O and NH in PP. The shift of the peak indicated that there was hydrogen bonding between the C=O (proton acceptor) of urethane with NH (proton-donator) of PANI. PPM gave the highest impact and flexural strengths at 4875 kJ/ m2 and 42 MPa, respectively but with the lowest flexural modulus (1050 MPa). Two-stage degradation behavior was observed in the TGA thermogram.
  16. Ili NN, Omar Z, Ahmad A
    Jurnal Psikologi Malaysia, 2014;olume 28:39-62.
    Employee deviance has received increasing attention in the past decade. Past research have reported that work environment related factors such as organizational support, supervisory support, role conflict, and job demand were associated with deviant behavior The purpose of this paper is to examine the relationship between job demand (psychological job demand), and job resources (social support), and employee workplace deviant behavior. This study adopts a cross-sectional correlation study design. A total of 315 employees were selected using cluster sampling technique participated in this study. Data were collected using a self-administered questionnaire using the drop and collect method. Data were analyzed using descriptive analysis (mean, standard deviation, frequency distribution) to describe the demographic profile and study variables. Correlation and regression analysis was performed to test the relationship between psychological job demand, and social support, and employee workplace deviant behaviors. The result revealed that lack of social support has significant positive influence on employee workplace deviant behavior. The findings suggest that lack of job resources such as social support may drive employees to engage in deviant work behavior. However, high job demand experienced by employees does not drive them towards engaging in deviant work behavior.
  17. Shuhaimi-Othman M, Ahmad A, Norziana G
    Kajian kepekatan logam dalam air di Tasik Bukit Merah telah dijalankan pada April 2009. Lima belas stesen persampelan telah dipilih dan sampel air permukaan bagi penentuan logam telah diambil. Beberapa parameter kualiti air seperti suhu, konduktiviti, oksigen terlarut, pH dan keliatan air telah ditentukan di setiap stesen. Sebanyak 11 jenis logam iaitu kadmium, zink, plumbum, kuprum, nikel, ferum, kobalt, aluminium, barium, kromium dan mangan (Mn) telah ditentukan dalam sampel air. Keputusan menunjukkan kepekatan semua logam kajian berada di bawah kepekatan maksimum yang dicadangkan oleh piawaian Malaysia dan antarabangsa bagi melindungi hidupan akuatik kecuali bagi logam Fe dan Al. Bagi parameter kualiti air, kajian menunjukkan semua parameter berada dalam julat kepekatan semula jadi (kelas I) berdasarkan Piawaian Kualiti Air Kebangsaan (NWQS Malaysia) kecuali oksigen terlarut dan pH di beberapa stesen persampelan terutama di bahagian timur tasik yang didapati dipengaruhi oleh faktor-faktor semula jadi dan antropogenik.
  18. Zulfahmi Ali Rahman, Umar Hamzah, Noorulakma Ahmad
    Hydrocarbon is a light-non aqueous phase liquid or known as LNAPL. It poses environmental hazard if accidentally spilled out into the soil and water systems as a result of its insoluble nature in water. LNAPL component infiltrates into soil through pore spaces and afloat at the top of groundwater level. Some of this hydrocarbon would trap and clog within the voids, difficult to remove and costly to clean. The occurence of hydrocarbon in the soil definitely degraded the behaviour of soils in terms of engineering properties. This study aimed to investigate the engineering properties of oil-contaminated soil for two different residual soils originally developed from in-situ weathering of granitic and metasedimentary rocks. The physical characterisations of the soil were determined including particle size distribution, specific gravity test and x-ray diffraction (XRD). The engineering parameters for the contaminated and uncontaminated soils were Atterberg limits, compaction and soil shear strength (UU tests). The amounts of hydrocarbon added to soil were varied at 0%, 4%, 8%, 12% and 16% of dried weigth of soil samples. The results from the particle size distribution analysis showed that residual soil from granitic rock comprises of 38% sand, 33% silt and 4% clay while metasedimentary soil consists of 4% sand, 43% silt dan 29% clay. The mean values of specific gravity for the granitic and metasedimentary soils were 2.56 and 2.61, respectively. The types of minerals present in granitic soil sample were quartz, kaolinite and gibbsite while metasedimentary soil consists of quartz and kaolinite. The Atterberg limits value decreased as a result of increasing amount of added hydrocarbon into the soil. A similar behaviouir was observed with the values of maximum dry density and optimum water content with increasing hydrocarbon content. The overall unconsolidated undrained shear strength, Cu showed a decreasing trend with the increase in hydrocarbon content.
  19. Zulham, Jusuf AA, Indarti J, Lisnawati
    Papanicolaou test is a diagnostic test for uterine cervical cancer screening and routinely examined. It has limitations. A better technique is needed to identify true cervical malignancy process. Molecular cancer marker detection may have high the sensitivity and specificity in detecting cancer. Survivin, a marker candidate, is upregulated in many malignancy processes. Ninety women have joined in this cross sectional study by consecutive sampling. Survivin expression was examined by indirect immunoperoxidase method. It was predominantly found in metaplastic cells. Correlation between survivin expression and Papanicolaou test results was calculated by Fischer’s-exact test. Using Papanicolaou test result as an indicator for the presence of uterine cervical abnormalities, the performance indicators were calculated. Fischer’s-exact test showed that survivin expression was not significantly useful as cervical cancer molecular marker. Survivin expression of the uterine cervical exfoliative cells cannot be used as a diagnostic test for uterine cervical malignancy process.
  20. Nurhidayaty Mokhtar, Mustaffa Abdullah, Sahrim Ahmad
    Sains Malaysiana, 2012;41:1125-1131.
    Structural and magnetic properties of type-M barium ferrite (BaFe12O19) nanoparticles (~ 20 nm) embedded in nonmagnetic thermoplastic natural rubber (TPNR) matrices were investigated. The TPNR matrices were prepared from high density polyethylene (HDPE) and natural rubber (NR) in the weight ratios of 80:20 and 60:40, respectively, with 10 wt% of NR in the form of liquid natural rubber (LNR) which act as a compatibiliser. BaFe12O19 – filled nanocomposites with 2 – 12 wt% BaFe12O19 ferrite were prepared using a melt- blending technique. Magnetic hysteresis was measured using a vibrating sample magnetometer (VSM) in a maximum field of 10 kOe at room temperature (25oC). The saturation magnetisation (MS), remanence (MR) and coercivity (Hc) were derived from the hysteresis loops. The results show that the structural and magnetic properties of nanocomposites depend on both the ferrite content and the composition of the natural rubber or plastic in the nanocomposites. All the nanocomposites exhibit an exchange bias-like phenomenon
    resulting from the exchange coupling of spins at the interface between the core ferrimagnetic region and the disordered surface region of the nanoparticles.
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