Displaying publications 1 - 20 of 2561 in total

  1. Wan-Norafikah O, Nazni W, Noramiza S, Shafa’ar-Ko’ohar S, Heah S, Nor-Azlina A, et al.
    Sains Malaysiana, 2012;41:1309-1313.
    Aedes aegypti and Aedes albopictus are the principle dengue vectors in Malaysia. The presence and distribution of Aedes larvae were studied in three different localities in Kelantan, Terengganu and Sabah, Malaysia in October 2008, November 2008 and June 2009. Two hundred (200) ovitraps per locality were placed randomly indoors and outdoors, depending on the environment of each locality. The highest mean number of Ae. aegypti and Ae. albopictus larvae per recovered ovitrap for both indoors and outdoors was obtained from Kg. Paya Rambai, Kelantan. The indoor populations of Ae. aegypti as well as the indoor and outdoor populations of Ae. albopictus in Kg. Paya Rambai, Kelantan were significantly higher than the other two study sites (p<0.05) by 1.03- and 4.67-folds, 2.36- and 5.84-folds and 1.98- and 4.00-folds, respectively. Both Ae. aegypti and Ae. albopictus were also found to breed within the same ovitraps placed indoors and outdoors in all study sites ranging from 15.22% to 31.82% of the total positive ovitraps. This study showed that both species could serve as the vectors of dengue in all study sites as indicated by the high populations recorded. The reliability and sensitivity of ovitraps in Aedes surveillance was also proven.
  2. Chung F, Noroul Asyikeen Z, Ma'aruf A
    Sains Malaysiana, 2012;41:1315-1324.
    Kajian ini dijalankan untuk menentukan keupayaan yis (Saccharomyces cerevisiae) yang telah dipencil daripada buahbuahan tempatan iaitu duku langsat (Lansium domesticum), rambutan (Nephelium lappaceum), mangga Chokanan (Mangifera indica cv. Chokanan) dan rebung buluh minyak (Bambusa vulgaris) sebagai agen penaik roti berbanding roti kawalan penambahan yis komersial. Isi padu tertentu roti kawalan menunjukkan perbezaan bererti (p<0.05) dengan semua roti kajian. Roti yang difermentasi oleh yis rebung buluh menunjukkan isi padu tertentu yang paling tinggi, diikuti oleh roti yang difermentasi oleh yis mangga dan yis duku langsat dan ketiga-tiga yis tersebut juga mempunyai isi padu tertentu yang lebih tinggi secara bererti (p<0.05) dengan roti kawalan. Roti yang difermentasi oleh yis rebung buluh dan yis mangga mempunyai tekstur yang lebih lembut berbanding roti kawalan. Peningkatan dalam isi padu tertentu roti boleh meningkatkan kelembutan tekstur roti. Peratus kandungan kelembapan kulit dan isi roti yang difermentasi oleh yis rebung buluh adalah paling tinggi manakala roti yang difermentasi oleh yis rambutan menunjukkan peratus kandungan kelembapan yang paling rendah. Peningkatan peratus kandungan kelembapan juga boleh meningkatkan kelembutan tesktur roti dan sebaliknya. Daripada segi warna kulit, hanya kecerahan warna kulit (L*) roti yang difermentasi oleh yis rebung buluh tidak menunjukkan perbezaan bererti (p>0.05) dengan warna kulit roti kawalan. Kecerahan warna isi (L*) roti kawalan pula menunjukkan perbezaan bererti (p<0.05) dengan semua isi roti kajian. Selain itu, didapati semakin kecil dan padat liang udara, semakin putih warna isi roti. Keseragaman taburan liang udara juga menghasilkan isi roti yang lebih putih. Secara keseluruhan, kesemua yis yang dipencil berpotensi untuk dijadikan sebagai agen penaik. Yis rebung buluh dan yis mangga dapat menghasilkan kualiti roti putih yang lebih baik daripada yis komersial.
  3. Muhammad Taher, Nur Aizura Mat Alewi, Deny S, Zaitunnatakhin Zamli, Norazsida Ramli, Nurulwahida Saad
    Sains Malaysiana, 2012;41:1423-1429.
    Sapium baccatum is usually used as a timber in Malaysia. Its medicinal values are not well known and very little research has been conducted concerning the plant. Consequently, this study was conducted to observe toxicity effects of hexane extract of stem bark of S. baccatum. The toxicity effects were assessed through observation of physiological changes of the rats as well as through gross and histological examinations of its livers. The doses for the treated groups were given intraperitoneally for T2, T3 and T4 group which were given 100, 250 and 500 mg/kg, respectively. Meanwhile, control group (T1) was administered with 80% PEG 200 only. The observation period was 14 days. If the rat died, it was dissected and the liver was removed and examined. Some physiological effects observed include ataxia and hind-legs paralysis. The gross observations of the livers, growth of abnormal spots and connective tissues attachment to lobes of the livers were observed. The experiment was followed byhistopathological observation, which indicated the presence of abnormal hepatocytes with a distorted shape and undefined cell linings for T2 group. Results also indicated an increase in the distortion of hepatocytes, presence of massive cytoplasm and necrosis of hepatocytes for T3 and T4 groups. The results suggest that non polar extract of the stem bark of S. baccatum may promote toxic effects to the animals.
  4. Nurain Aziman, Noriham Abdullah, Zainon Mohd Noor, Khairusy Syakirah Zulkifli, Wan Saidatul Syida W
    Sains Malaysiana, 2012;41:1437-1444.
    Phytochemical compounds, antioxidant and antibacterial activities of selected ethanolic aromatic Malaysian herbal extracts namely Persicaria hydropiper, Citrus hystrix, Murraya koenigii, Etlingera elatior, Cymbopogon citratus and Kaempferia galanga were screened and determined. Antioxidant activities were analysed using Ferric Reducing Antioxidant Power (FRAP), β-carotene bleaching and Oxygen Radical Absorbance Capacity (ORAC) assays. Disc diffusion assay was used to determine antibacterial activity against six bacteria strains. Alkaloids, flavonoids, saponins, tannins, terpenoids and steroids were detected in the herb extracts. P. hydropiper extract had the highest antioxidant activities in FRAP and ORAC assays in which 1676.67 mM TE/g EW and 11.20 mmol TE/g EW were obtained, respectively. However, M. koenigii extract showed 61.8% inhibition in β-carotene bleaching assay among samples but lower than BHA/BHT standard. M. koenigii extract showed the most effective antibacterial activity against three Gram-positive bacteria. Aromatic Malaysian herbs such as P. hydropiper and M. koenigii were found to exhibit high antioxidant and antibacterial activities.
  5. Annazirin Eli, Mardhiyyah Shaffie, Wan Zawiah W
    Sains Malaysiana, 2012;41:1403-1410.
    Statistical modeling of extreme rainfall is essential since the results can often facilitate civil engineers and planners to estimate the ability of building structures to survive under the utmost extreme conditions. Data comprising of annual maximum series (AMS) of extreme rainfall in Alor Setar were fitted to Generalized Extreme Value (GEV) distribution using method of maximum likelihood (ML) and Bayesian Markov Chain Monte Carlo (MCMC) simulations. The weakness of ML method in handling small sample is hoped to be tackled by means of Bayesian MCMC simulations in this study. In order to obtain the posterior densities, non-informative and independent priors were employed. Performances of parameter estimations were verified by conducting several goodness-of-fit tests. The results showed that Bayesian MCMC method was slightly better than ML method in estimating GEV parameters.
  6. Wah SH, Halimatun Muhamad, Tangang FT, Liew J
    Sains Malaysiana, 2012;41:1411-1422.
    The historical and future storm surge climate over the South China Sea Sunda Shelf was derived using a barotropic two dimensional model. The atmospheric forcings were obtained from the UKMO regional climate modeling system, PRECIS (Providing Regional Climates for Impacts Studies), forced at the boundary by the ECHAM4 simulation output under the SRES A2 emission experiment. In general, the model simulates historical sea surface elevation characteristics satisfactory although there is a substantial underestimation for the sea level elevation at local scales. The climate change analysis suggests that the storm surge extreme over the Sunda Shelf is expected to increase along the coastal area of the Gulf of Thailand and east coast of Peninsular Malaysia in the future (2071-2100). The projected increment is averagely ~9% over the Sunda Shelf region by the end of the 21st century corresponding to about 5% stronger wind speed as compare to the baseline period of 1961-1990.
  7. Thanh ND, Nguyen QT, Trinh TL, Vu TH, Phan VT, Pham VC
    Sains Malaysiana, 2012;41:1325-1334.
    This study presents a preliminary attempt to assess future climate conditions in the Red River Delta (RRD) region. Outputs of the Community Climate System Model version 3.0 (CCSM3) are dynamically downscaled using the Regional Climate Model version 3 (RegCM3). Numerical experiments and analysis are realized for the baseline 1980-1999 and the future 2030-2049 periods with the A1B and A2 emissions scenarios. We first examine the capability of the model in simulating the 20 years mean climate. Temperature and precipitation outputs for the baseline period are compared with observations at the 17 selected meteorological stations in RRD. Results show that temperature patterns are fairly well reproduced but with systematic cold biases. Precipitation is also well simulated during winter - spring and largely underestimated during summer - autumn. Estimation of the future changes of temperature and precipitation as compared to those of the baseline period reveals that annual temperature of the 2030-2049 appears to be warmer than the baseline temperature of about 1.4±0.2ºC. Summer temperature is likely to increase faster than winter temperature in the future. We also notice that precipitation generally decreases throughout the RRD region except the future JJA rainfall projected by the A2 scenario.
  8. Norshahida Shaadan, Sayang Mohd Deni, Abd Aziz Jemain
    Sains Malaysiana, 2012;41:1335-1344.
    This study highlights the advantage of functional data approach in assessing and comparing the PM10 pollutant behaviour as an alternative statistical approach during and between the two extreme haze years (1997 and 2005) that have been reported in Selangor, state of Malaysia. The aim of the study was to improvise the current conventional methods used in air quality assessment so that any unforeseen implicit information can be revealed and the previous research findings can be justified. An analysis based on the daily diurnal curves in place of discrete point values was performed. The
    analysis results provided evidences of the influence of the change in the climate (due to the El-Nino event), the different levels of different emission sources and meteorological conditions on the severity of the PM10 problem. By means of the cummulative exceedence index and the functional depth method, most of the monitoring stations for the year 2005 experienced the worst day of critical exceedences on the 10th of August, while for the year 1997 it occurred between 13th and 26th September inclusively at different dates among the stations.
  9. Noratiqah Mohd Ariff, Abdul Aziz Jemain
    Sains Malaysiana, 2012;41:1377-1387.
    Rainfalls data have been broadly used in researches including in hydrological and meteorological areas. Two common ways in extracting observations from hourly rainfalls data are the window-based analysis (WBA) and storm-event analysis (SEA) approach. However, the differences in the qualitative and quantitative properties of both methods are still vaguely discussed. The aim of studying these dissimilarities is to understand the effects of each approach in modelling and analysis. The qualitative difference is due to the way the two analyses define the accumulated rainfalls for observations which are referred to as rainfall and storm depths, respectively. The repetitiveness of rainfall depths provide nested structure while the storm depths are considered independent. The quantitative comparisons include their statistical and scaling properties that are linked by the self-similarity concept from simple scaling characteristics. If self-similarity concept
    holds, then the rainfall or storm depths follow simple scaling and the analysis would be simplified. The rainfall depths showed clearer simple scaling characteristics compared to the storm depths. Though the storm depths do not yield self-similarity for a large range of storm duration but the characteristics of simple scaling can be observed for a reduced range of the considered duration. In general, the context of the research and the region of the time interval and duration will be an important aspects to consider in choosing which method is best to use for analyzing the data.
  10. Ling WS, Noriszura Ismail
    Sains Malaysiana, 2012;41:1389-1401.
    This paper aims to estimate the Generalized Pareto Distribution (GPD) parameters and predicts the T-year return levels of extreme rainfall events using the Partial Duration Series (PDS) method based on the hourly rainfall data of five stations in Peninsular Malaysia. In particular, the GPD parameters are estimated using five methods namely the method of Moments (MOM), the probability weighted moments (PWM), the L-moments (LMOM), the Trimmed L-moments (TLMOM) and the Maximum Likelihood (ML) and the performance of the T-year return level of each estimation method is analyzed based on the RMSE measure obtained from Monte Carlo simulation. In addition, we suggest the weighted average model, a model which assigns the inverse variance of several methods as weights, to estimate the T-year return level. This paper contributes to the hydrological literatures in terms of three main elements. Firstly, we suggest the use
    of hourly rainfall data as an alternative to provide a more detailed and valuable information for the analysis of extreme rainfall events. Secondly, this study applies five methods of parametric approach for estimating the GPD parameters and predicting the T-year return level. Finally, in this study we propose the weighted average model, a model that assigns the inverse variance of several methods as weights, for the estimation of the T-year return level.
  11. Wahidah Sanusi, Kamarulzaman Ibrahim
    Sains Malaysiana, 2012;41:1345-1353.
    Climate changes have become serious issues that have been widely discussed by researchers. One of the issues concerns with the study in changes of rainfall patterns. Changes in rainfall patterns affect the dryness and wetness conditions of a region. In this study, the three-dimensional loglinear model was used to fit the observed frequencies and to model the expected frequencies of wet class transition on eight rainfall stations in Peninsular Malaysia. The expected frequency values could be employed to determine the odds value of wet classes of each station. Further, the odds values were used to estimate the wet class of the following month if the wet class of the previous month and current month were identified. The wet classification based on SPI index (Standardized Precipitation Index). For station that was analyzed, there was no difference found were between estimated and observed wet classes. It was concluded that the loglinear models can be used to estimate the wetness classes through the estimates of odds values.
  12. Muzirah Musa, Kamarulzaman Ibrahim
    Sains Malaysiana, 2012;41:1367-1376.
    Long-memory is often observed in time series data. The existence of long-memory in a data set implies that the successive data points are strongly correlated i.e. they remain persistent for quite some time. A commonly used approach in modellingthe time series data such as the Box and Jenkins models are no longer appropriate since the assumption of stationary is not satisfied. Thus, the scaling analysis is particularly suitable to be used for identifying the existence of long-memory as well as the extent of persistent data. In this study, an analysis was carried out on the observed daily mean per hour of ozone concentration that were available at six monitoring stations located in the urban areas of Peninsular Malaysia from 1998 to 2006. In order to investigate the existence of long-memory, a preliminary analysis was done based on plots of autocorrelation function (ACF) of the observed data. Scaling analysis involving five methods which included rescaled range, rescaled variance, dispersional, linear and bridge detrending techniques of scaled windowed variance were applied to estimate the hurst coefficient (H) at each station. The results revealed that the ACF plots indicated a slow decay as the number lag increased. Based on the scaling analysis, the estimated H values lay within 0.7 and 0.9, indicating the existence of long-memory in the ozone time series data. In addition, it was also found that the data were persistent for the period of up to 150 days.
  13. Adi Ainurzaman Jamaludin, Noor Zalina Mahmood, Noorlidah Abdullah
    Sains Malaysiana, 2012;41:1445-1450.
    Vermicomposting for 140 days by using Lumbricus rubellus was conducted after 21 days of natural pre-composting. Five treatments in different ratio of goat manure: spent mushroom substrate were prepared as feed materials with four replicates for each treatment namely; 20:80 (TA), 40:60 (TB), 50:50 (TC), 60:40 (TD) and 80:20 (TE). As for control, each treatment without earthworm was prepared. On the basis of nutrient elements, goat manure and spent mushroom substrate can be decomposed through both methods of vermicomposting and natural composting. Findings of this study indicated that the higher usage of goat manure with longer duration resulted in the production of improved organic fertilizer.
  14. Halimah Muhamad, Mohd Izwarie Ramli, Tan YA, Zuriati Zakaria, Ismail Sahid
    Sains Malaysiana, 2012;41:1451-1459.
    The objective of this study was to develop a method for the determination of diuron (3-(3,4-dichlorophenyl)-1,1-dimethyl urea) residue in crude palm oil (CPO) and crude palm kernel oil (CPKO) matrices. The method involves the extraction of the herbicide from the oil matrix using low temperature precipitation and solid phase extraction techniques, detected by high performance liquid chromatography-ultra violet (HPLC-UV). The HPLC separation was carried out on an Ascentis
    TMRP-Amide column and elution with acetonitrile (solvent A) and water-methanol (2:1, v/v) (solvent B) as a suitable solvent system, at ratio of 4:6 (v/v). The optimum volume of acetonitrile for the extraction of diuron was 30 mL and 4 mL was obtained as the optimum volume of the solvent for elution analyte through the SPE cartridge. A linear correlation was obtained for the concentration of diuron from 0.05–1.0 µg mL-1 with a correlation coefficient of 0.99. The recovery of diuron from CPO was 83.2–101.4% with a relative standard deviation of 1.4–9.9% and 79.4–87.9% with relative standard deviation of 0.9–5.6% for CPKO. The method detection limit and limit of quantification obtained were 0.018 µg g-1 and 0.058 µg g-1, respectively. The method was used to determine diuron residues in palm oil from different refineries situated at different locations throughout Malaysia.
  15. Khan Y, Smarda Z
    Sains Malaysiana, 2012;41:1489-1493.
    This paper proposed an efficient modification of homotopy perturbation transform method (HPTM), namely modified homotopy perturbation transform method (MHPTM) for the solution of third order boundary layer equation on semi-infinite domain. The technique was based on the application of Laplace transform to boundary layers in fluid mechanics. The nonlinear terms can be easily handled by the use of He’s polynomials. The Pade´ approximants, that often show superior performance over series approximations, were effectively used in the analysis to capture the essential behavior of the boundary layer equation on infinity. We then conduct a comparative study between the MHPTM and the existing results with the help of third order boundary layer equation. The results obtained indicated that the MHPTM was effective and promising.
  16. Zhen L, Zhang ZW, Wang YJ, Wang PC, Xu YR, Zhou ZX
    Sains Malaysiana, 2012;41:1495-1501.
    Relationship between understory plant diversity and anthropogenic disturbances in urban forests of Wuhan City, Central China, was analyzed by diversity analysis and detrended canonical correspondence analysis (DCCA). The results showed that: understory species diversity was higher in suburban area than in urban area. From forest center to edge, species diversity of Luojia hill, Shizi hill and Maan hill forests gradually increased, however, that of Hong hill gradually decreased. Anthropogenic disturbances gradient resulted from visitors flowrate, shrub coverage, aspect and adjacent land types had significant effects on species diversity of shrub and herb layers in urban forests. High anthropogenic disturbances might increase similar non-native herb species in urban area and low disturbances might promote co-existence of wood species in suburban area. Further analysis on types of anthropogenic disturbances and plant functional groups in urban-suburban gradient should be taken into a consideration.
  17. Rosca NC, Grosan T, Pop I
    Sains Malaysiana, 2012;41:1271-1279.
    A numerical study has been conducted to investigate the steady forced convection stagnation point-flow and mass transfer past a permeable stretching/shrinking sheet placed in a copper (Cu)- water based nanofluid. The system of partial differential equations is transformed, using appropriate transformations, into two ordinary differential equations, which are solved numerically using bvp4c function from Matlab. The results are obtained for the reduced skin-friction and reduced Sherwood number as well as for the velocity and concentration profiles for some values of the governing parameters. These results indicate that dual solutions exist for the shrinking sheet case (λ < 0). It is shown that for a regular fluid (f = 0) a very good agreement exists between the present numerical results and those reported in the open literature.
  18. Shekholeslami M, Ashorynejad HR, Domairry D, Ishak Hashim
    Sains Malaysiana, 2012;41:1281-1285.
    In this paper, the problem of laminar viscous flow in a semi-porous channel in the presence of transverse magnetic field is studied. The Optimal Homotopy Asymptotic Method (OHAM) is employed to approximate the solution of the system of nonlinear differential equations governing the problem. The influence of the Hartmann number (Ha) and the Reynolds number (Re) on the flow was investigated. The results of the OHAM were compared with homotopy analysis method (HAM) and variation iteration method (VIM) results.
  19. Al-awfi S
    Sains Malaysiana, 2012;41:1461-1466.
    We give details about how a surface plasmons with phase singularities can be produced when a Bessel beam light is totally reflected internally at the planar surface of a dielectric on which an infinitesimally thin film has been deposited. The characteristic property of such a light is the exponential decay with distance in a vacuum which can basically provide a two-dimensional surface plasmons with phase singularities with attractive enhancements. Such a phenomenon is governable by altering the incident angle and the order of the Bessel beam.
  20. Seyed Ehsan Saffari, Robiah Adnan
    Sains Malaysiana, 2012;41:1483-1487.
    A Poisson model typically is assumed for count data, but when there are so many zeroes in the response variable, because of overdispersion, a negative binomial regression is suggested as a count regression instead of Poisson regression. In this paper, a zero-inflated negative binomial regression model with right truncation count data was developed. In this model, we considered a response variable and one or more than one explanatory variables. The estimation of regression
    parameters using the maximum likelihood method was discussed and the goodness-of-fit for the regression model was examined. We studied the effects of truncation in terms of parameters estimation, their standard errors and the goodnessof-fit statistics via real data. The results showed a better fit by using a truncated zero-inflated negative binomial regression model when the response variable has many zeros and it was right truncated.
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