Displaying publications 1 - 20 of 2561 in total

  1. S.A. Hanifah, N.A. Rahman, A.M.N. Zani, A. Ahmad
    Sains Malaysiana, 2015;44:995-1001.
    An interpenetrating polymer network (IPN), N-isopropylacrylamide/O-nitrochitosan (NONK) was developed in the presence of ammonium persulfate using solution polymerization technique. O-nitrochitosan (ONK) was synthesized from chitosan, before it was further reacted with N-isopropylacrylamide. A new vibration of the C-N bond formed between the NH from ONK and the CH2 from NIPAAm was detected at the peak 1154 and 1171 cm-1 using attenuated total reflection Fouriertransform infrared (ATR-FTIR) spectroscopy. In the polymerization, the primary amine became a secondary amine and the peaks of the amide I (C=O peak) and amide II (N–H) were broadened. The structure of ONK was confirmed using nuclear magnetic resonance (NMR). At 10°C, the result from swelling test was found that IPN poly(NONK82) had the highest swelling percentage, 1171%, compared to poly (NIPAAm) at 467%. Micrograph from scanning electron microscopy (SEM) indicated the pore size of IPN NONK increased with an increasing ratio of ONK.
  2. Wan A. Yaacob, Bohari M. Yamin, Hasliza Yusof, Laily B. Din, Nazlina Ibrahim, A. Latiff
    Sains Malaysiana, 2015;44:1125-1128.
    Chromatographic purification of chloroform extract of the twigs of Ellipeia cuneifolia has led to the discovery of three compounds comprising of 2´,4´-dihydroxy-4,6´-dimethoxychalcone; tepanone; and O-methylmoschatoline. Structures of the compounds were established by interpreting their spectral data and by comparing them with those of the literature. Two of them showed antibacterial activities.
  3. Shafika Sultan Abdullah, M.A. Malek, Namiq Sultan Abdullah, A. Mustapha
    Sains Malaysiana, 2015;44:1053-1059.
    Water scarcity is a global concern, as the demand for water is increasing tremendously and poor management of water resources will accelerates dramatically the depletion of available water. The precise prediction of evapotranspiration (ET), that consumes almost 100% of the supplied irrigation water, is one of the goals that should be adopted in order to avoid more squandering of water especially in arid and semiarid regions. The capabilities of feedforward backpropagation neural networks (FFBP) in predicting reference evapotranspiration (ET0) are evaluated in this paper in comparison with the empirical FAO Penman-Monteith (P-M) equation, later a model of FFBP+Genetic Algorithm (GA) is implemented for the same evaluation purpose. The study location is the main station in Iraq, namely Baghdad Station. Records of weather variables from the related meteorological station, including monthly mean records of maximum air temperature (Tmax), minimum air temperature (Tmin), sunshine hours (Rn), relative humidity (Rh) and wind speed (U2), from the related meteorological station are used in the prediction of ET0 values. The performance of both simulation models were evaluated using statistical coefficients such as the root of mean squared error (RMSE), mean absolute error (MAE) and coefficient of determination (R2). The results of both models are promising, however the hybrid model shows higher efficiency in predicting ET0 and could be recommended for modeling of ET0 in arid and semiarid regions.
  4. Munirah Ismail, Choong Yin Chun, Noor Aini Mohd Yusoff, Suzana Shahar, Zahara Abdul Manaf, Roslee Rajikan, et al.
    Sains Malaysiana, 2013;42:373-380.
    In thalassaemic patients, the impact of the disease especially on quality of life (QOL) of the caregivers in Malaysia has not been established. This study was conducted to assess the health-related quality of life (HRQOL) of thalassaemia patients and their caregivers in order to explore factors affecting their QOL. A cross-sectional study was conducted on 75 thalassaemic children and adolescents aged between 7 and 18 years old and their caregivers. The PedsQLTM 4.0
    generic core scales questionnaire was administered to both thalassaemic children and their caregivers while the health questionnaire EQ 5D was given to caregivers only. The subjects were recruited from Hospital Kuala Lumpur (HKL) and Universiti Kebangsaan Malaysia Medical Centre (UKMMC). The results revealed that the mean of psychosocial HRQOL score in patients (63.91±14.65) was significantly lower than parent proxy reports (67.14±10.48) (p=0.008). The
    school functioning score (50.59±15.31) was the lowest of the psychosocial measure, followed by emotional functioning (59.92±16.83) and social functioning (78.01±13.92) score. The patients’ pre-transfusion haemoglobin concentration was significantly associated with their QOL (p=0.02). Having more children, higher numbers of thalassaemic children and lower educational level of caregivers were associated with poorer QOL. In conclusion, caregivers underestimated
    the QOL of their thalassaemic children. The school functioning domain was affected the most domain. There is a need to improve the QOL of thalassaemic children and their caregivers.
  5. S.Z. Satari, Y.Z. Zubairi, S.F. Hassan, A.G. Hussin
    Sains Malaysiana, 2015;44:1521-1530.
    The statistical characteristics of wind direction that was recorded at maximum wind speed in Peninsular Malaysia for two monsoons from 1999 to 2008 for seven stations were analyzed in this study. Modeled by von Mises distribution, the change in parameters values namely mean direction and concentration parameter was measured. Statistical summary, graphical representations, Watson-William Test and linear-circular correlation are used in the analysis. It is found that there is a significant change in the mean direction of wind over the period of ten years for most stations in Peninsular Malaysia. However, there is a weak relationship between wind direction and wind speed. This study suggested the presence of prominent direction of wind that blows in Peninsular Malaysia by monsoon. This finding may provide useful information on giving a better understanding of the behavior of the wind in Peninsular Malaysia and the potential use of wind as an alternative source of energy.
  6. M. Nor-Fazilla, A. Samat, A.G. Mazlan
    Sains Malaysiana, 2013;42:737-742.
    Satu penyelidikan telah dijalankan untuk mengesan struktur halus organ deria-elektro (Ampullae of Lorenzini) pada Carcharhinus melanopterus, C. limbatus dan Chiloscyllium griseum. Organ ini amat peka terhadap beberapa bentuk rangsangan terutamanya untuk mengesan kedudukan mangsa, penentuan arah dan mengawan. Di dalam makmal, suatu bahagian organ deria ini dipisahkan daripada lapisan dermis kepala ikan yu. Pemerhatian dan pengambilan imej struktur organ deria telah dibuat menggunakan mikroskop elektron imbasan (SEM). Imej-imej yang diperoleh jelas menunjukkan organ deria pada Carcharhinus melanopterus, C. limbatus dan Chiloscyllium griseum berbentuk ampulari terkumpul di dalam kluster. Saluran-saluran deria yang menghubungkan ampula dengan pori didapati mempunyai orientasi panjang dan susunan yang berbeza-beza pada spesies yang berlainan.
  7. Yulita Molliq R, Noorani M, Ahmad R, A.K. Alomari
    Sains Malaysiana, 2013;42:347-358.
    In this paper, a new reliable method called the step variational iteration method (SVIM) based on an adaptation of the variational iteration method (VIM) is presented to solve non–chaotic and chaotic systems. The SVIM uses the general Lagrange multipliers for constructing the correction functional for the problems. The SVIM yields a step analytical solution of the form of a rapidly convergent infinite power series with easily computable terms and obtain a good approximate solution for larger intervals. The accuracy of the presented solution obtained is in an excellent agreement with the previously published solutions.
  8. A.N. Yusoff
    Sains Malaysiana, 2013;42:765-771.
    Kajian pengimejan resonans magnet kefungsian (fMRI) subjek tunggal ini menyelidiki interaksi psikofisiologi (PPI) antara girus presentral (PCG) dan lobus parietal superior (SPL) kanan semasa tepikan jari rentak sendiri secara bilateral. Model kehubungan efektif antara PCG dan SPL kanan dibina menggunakan analisis PPI dengan mengambil daya dan laju tepikan sebagai faktor uji kaji. Keputusan menunjukkan bahawa peningkatan daya dan laju tepikan masing-masing mengaktifkan PCG bilateral dan SPL kanan secara bererti (p<0.05). PCG dan SPL kanan didapati saling berhubungan semasa tepikan jari dilakukan dengan daya dan laju tepikan sebagai faktor uji kaji yang mempengaruhi kehubungan efektif antara mereka. Kajian ini telah mendedahkan maklumat asas berguna untuk kajian fMRI pada masa depan ke atas koordinasi motor dan boleh digunakan untuk mengkaji ketaktertiban otak misalnya strok.
    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. Mohammad Moneruzzaman Khandaker, Normaniza Osman, Golam Faruq, Amru Nasrulhaq Boyce, ABM Sharif Hossain
    Sains Malaysiana, 2015;44:1431-1439.
    In this study, we investigated the effects of 2,4-Dichlorophenoxy acetic acid (2,4-D) treatment on selected physiological parameters and fruit quality of wax apple fruits under field conditions. Foliar spray of 2,4-D at 0, 5, 10 and 20 mg L-1 concentrations were used from bud stage to the 3rd week of fruit development. Physiological parameters determined included net photosynthesis, stomatal conductivity, chlorophyll content and chlorophyll fluorescence. Net photosynthetic rate and photosynthetic efficiency via chlorophyll fluorescence significantly (p≤0.05) increased with 5 and 10 mg L-1 2, 4-D treatments. Furthermore, 5 mg L-1 2,4-D reduced bud and fruit drop, increased fruit weight and dry matter content in leaves. An improved fruit set, enhanced fruit growth, faster color development and advanced maturity were also recorded in treated plants. In addition, fruit yield increased by 39 and 48% with 5 and 10 mg L-1 2,4-D treatments, respectively. Fruit K+ content, total sugar, protein content and chalcone synthase (CHS) activities increased with 2,4-D treatments. Increased leaf soluble protein and elevated sucrose phosphate synthase (SPS) activity were also observed in 5 mg L-1 treated plants. Positive correlation between photosynthesis rate and SPS activity of leaves (R2=0.98) and between CHS activity and color development of fruits (R2=0.98) were recorded in 5 mg L-1 treatments. The results also suggested that 5 and 10 mg L-1 2,4-D treatments are promising for enhancing plant productivity and fruit quality in wax apple trees under field conditions.
    Sains Malaysiana, 2013;42:1819-1826.
    This study aims to describe the pattern of sexual behaviour among methamphetamine and heroin users. It describes the pattern of sexual behaviour based on aspects of sex such as desire, interest, drive and obsession in relation to the drug use. A cross-sectional study was carried out among attendees of drug rehabilitation programmes in Kota Kinabalu, Kota Bharu and Kuala Lumpur. All subjects were living in the community with satisfactory psychosocial functioning. This study was primarily based on a validated sexual behaviour self-rated questionnaire followed by face-to-face interview. A total of 227 subjects were included with 124 (54.6%) using methamphetamine while 103 (45.4%) using heroin. Majority (218; 96%) were heterosexuals with 104 (45.8%) reported having been involved in high risk sexual behaviour. More methamphetamine than heroin subjects agreed that their sexual thoughts, feelings and behaviours were often associated with the drug (p<0.05). Methamphetamine subjects agreed that the use of methamphetamine caused them to be more obsessed with sex and they found themselves to be preoccupied with sexual thoughts while being under the influence of the drug (p<0.05). Heroin subjects mainly reported on negative effects of the drug on their sexual behaviour. Methamphetamine subjects reported that the use of drug had positively affected their sexual interest and drive (p<0.05). Methamphetamine subjects were also 1.97 times more likely than heroin subjects to be involved in risky sexual behaviour. The results of this study can be utilized to improve the drug treatment and rehabilitation programme. Methamphetamine subjects were more likely than heroin subjects to be involved in risky sexual behaviour.
    Sains Malaysiana, 2013;42:1815-1818.
    Working environmental conditions in automotive industry are very challenging to the human workers. Meanwhile, products quality is very much dependent on workers’ health, safety and comfort in their working environment. Environmental factors, such as temperature, illuminance and humidity levels have significant effect on workers’ performance at the production line. In this experiment, temperature, humidity, illuminance levels and productivity rate were observed in a control room. An automotive manufacturing firm production line was chosen to be simulated in the control room to observe the temperature, relative humidity, illuminance and worker’s productivity rate. The experimental data collected was analyzed using Response Surface Method (RSM). RSM is an analysis technique, which combined statistical systems and mathematical methods. It can be applied for research and development, reform and optimize a process, which involves several design variables. As a result, the combined effect of temperature, illuminance and humidity toward productivity can be clearly seen. Optimum environmental factor cannot be predicted using first order RSM analysis because it gives low reliability for obtaining the optimum level. Thus, a second order RSM analysis was generated for obtaining the optimum level of environmental factors.
    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.
    Sains Malaysiana, 2012;41:431-437.
    Ciri inokulum bagi pengkulturan kulat oleaginus pencilan tempatan, Cunninghamella bainieri 2A1 dibangunkan dengan mengenal pasti kesan jenis, umur dan saiz inokulum terhadap pertumbuhan, penghasilan lipid dan GLA. Pengkulturan dijalankan pada suhu 30ºC dengan kadar goncangan 250 rpm dalam kelalang goncangan 500 mL yang mengandungi 200 mL medium terhad nitrogen. Inokulum spora didapati lebih sesuai berdasarkan produktiviti penghasilan lipid yang tinggi iaitu 0.71 (g/L/hari) berbanding penggunaan inokulum sel vegetatif vegetatif 24 jam dan 48 jam yang masingmasing memberikan produktiviti hanya 0.51 dan 0.45 (g/L/hari). Selain itu, penghasilan GLA (5.3 × 10-2 g/g biojisim tanpa lipid) dalam kultur yang dimulakan dengan inokulum spora (1 × 105 spora/mL) didapati lebih tinggi sebanyak 23% berbanding inokulum sel vegetatif. Kepekatan spora sebanyak 1 × 103 spora/mL menghasilkan morfologi pellet bersaiz 1.04 mm dan berkadaran dengan kandungan lipid dan GLA masing-masing sebanyak 40% (g/g biojisim) dan 8.34 × 10-2 (g/g biojisim tanpa lipid).
    Sains Malaysiana, 2013;42:1647-1654.
    According to the classical theory of viscoelasticity, a linear viscoelastic (LVE) function can be converted into another viscoelastic function even though they emphasize different information. In this study, dynamic tests were conducted on different conventional penetration grade bitumens using a dynamic shear rheometer (DSR) in the LVE region. The results showed that the dynamic data in the frequency domain can be converted into the time domain functions using a numerical technique. This was done with the aid of the non-linear regularization (NLREG) computer program. The NLREG software is a computer program for solving nonlinear ill-posed problem and is based on non-linear Tikhonov regularization method. The use of data interconversion equation is found suitable for converting from the frequency domain into the time domain of conventional penetration grade bitumens.
  16. Shukurov E, Nabiyev M, ALI-ZADE V
    Sains Malaysiana, 2013;42:1467-1471.
    The purpose of the investigation was to study the early spring plant diversity distributed in different vegetation types and their life forms, in relation to different altitudes. The investigation was carried out in accordance with itinerary method beginning from the shoreline up to the mountain. The results showed that 100% of the totally collected plants from the desert vegetation were therophytes; 100% from steppe vegetation were geophytes; 50 from forest were geophytes and the other 50% were hemicryptophytes. It is concluded that the life forms of early spring plants change depending on the altitude corresponding to changes in the air temperature as well as climatic and edaphic factors.
    Sains Malaysiana, 2013;42:1641-1646.
    Organic rice using different cultivation methods namely system of rice intensification (SRI) and local organic rice (BOT) were studied and compared with conventional non organic rice (BBO). One kg of the SRI organic rice was obtained from research plot in Tunjung, Kelantan. Physical and cooking properties were determined using the average weight of 100 kernel, length-breadth ratio (L/B ratio), minimum cooking time, water uptake ratio and percentage of gruel solid loss. Amylose content was determined by iodine-binding method. Thiamine and niacin content were determined by HPLC. Results of the study showed that weight of non organic rice (21.2 mg) was significantly higher (p≤0.05) than SRI organic rice (19.7 mg) or conventional (19.4 mg). Minimum cooking time of SRI organic rice was 19.5 min. The amylose content of conventional rice was the highest (16.6%) followed by SRI organic rice (15.6%) and conventional organic rice (15.3%). Vitamin B1 and B3 contents of organic rice were higher than non-organic rice. The means sensory score of all attributes of SRI cooked rice were the highest. Thus it can be concluded that rice cultivated using SRI resulted in comparatively better physicochemical characteristics and sensory quality compared with other methods.
  18. Ling Ty, Lee Nyanti, Theresa Muan, Jongkar Grinang, Siong-fong Sim, Aazani Mujahid
    Sains Malaysiana, 2016;45:157-166.
    Determining the water quality of Bakun Reservoir 13 months after it operates at full supply level is crucial for better understanding of changes in the physicochemical parameters, which may enable the prediction of its effects on the survival of aquatic life in the reservoir. This study determined 13 physicochemical parameters at six stations within the reservoir at fixed depths. The results showed that the minimum 5 mg/L of dissolved oxygen (DO) required for sensitive aquatic organisms was recorded at 6 m depth. However, DO was not detectable at depths exceeding 7 m. The water was acidic at depths of more than 10 m. Turbidity and total suspended solids increased corresponding with depth. Inorganic nitrogen were predominantly in the form of ammonia-nitrogen, creating an unhealthy environment for aquatic life. Concentration of Chl-a was significantly higher at the subsurface water than 30 m depth in four out of six stations. The present study shows changes in water quality as compared to the pre-impounded period and 15 months after the filling phase, in particular, stratification of dissolved oxygen, thermocline conditions and alkalinity. The changes varied according to the distance from the dam and may have been influenced by existing land developments within the area such as the construction of the Murum Hydroelectric Dam, oil palm plantations and timber concessionares. Though the water quality might have deteriorated, further study is needed to determine if this condition will prolong.
  19. Muhamad Saiful Bahri Yusoff, Ahmad Fuad Abdul Rahim, Abdul Aziz Baba, Shaiful Bahari Ismail, Hatta Sidi, Ab Rahman Esa
    Sains Malaysiana, 2013;42:423-428.
    The study of medicine is often regarded by students as a stressful environment particularly during examination period. Studies found a high percentage of medical students experience significant psychological distress during the examination period. This study compared percentage and level of psychological distress between two batches of first year medical students who underwent different selection admission processes during a stressful examination period. A comparative
    cross-sectional study was done on two batches of first year medical students; one group selected based on academic merit (2008/2009 batch) and the other selected based on academic merit, psychometric tests and interview (2009/2010 batch). The psychological distress was measured by the 12-item general health questionnaire (GHQ-12). The data were collected right after the final examinations. A total of 99 (46.05%) medical students of the 2008/2009 batch and 196 (100%) medical students of the 2009/2010 batch participated. The percentage of medical students who had psychological distress of the 2008/2009 and the 2009/2010 batches were 58.59% and 42.3%, respectively. The mean GHQ-12 score and percentage of psychological distress were significantly different between the two batches (p< 0.01). The older batch had 2.01 times higher risk for developing psychological distress compared with the newer batch (p< 0.01). The newer batch
    of medical students had better psychological health status and was less likely to develop psychological distress during the stressful period compared with older batch.
  20. H-E. Khoo, Azlan A, Ismail A, Abas F
    Sains Malaysiana, 2013;42:949-954.
    This study aimed to determine the total phenolics and antioxidant capacity of defatted dabai parts based on liquid extraction and optimized using response surface methodology (RSM). A two-level factorial design was applied to determine the effect of two independent variables (extraction time: X1 and % methanol: X2) on three response variables (total phenolic content: Y1, total flavonoid/anthocyanin content: Y2 and Trolox equivalent antioxidant capacity: Y3). The optimum conditions for extraction time and percent methanol were 36 min or 1 min and 62.25% or 53% for the defatted dabai pulp or peel, respectively. The RSM optimized extraction was compared with sonication-assisted extraction. Optimization results showed that defatted dabai parts had high total phenolic content and antioxidant capacity. Sonication-assisted extraction utilized the optimized extraction conditions had further increased the total phenolic content and antioxidant capacity of defatted dabai peel, but not in the pulp. Therefore, optimization of different extraction methods for the defatted fruit parts is recommended for future studies.
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