Displaying publications 1 - 20 of 2561 in total

  1. Andi R. Rosandy, Seng JL, Jalifah Latip, Muntaz A. Bakar, Rozida M. Khalid, Munir A. Murad A, et al.
    Sains Malaysiana, 2018;47:2693-2698.
    A new dipeptide, (-)-glaciantarcin (1) and three known compounds, cyclo(-Pro-Gly) (2), 1-(2-deoxypentofuranosyl)-5-
    methyl-2,4(1H,3H)-pyrimidinedione (3) and vidarabine (Ara-A) (4), were isolated from Glaciozyma antarctica PI12,
    a cold-adapted yeast. The chemical structures were elucidated by FT-IR, NMR and mass spectrometry. The cytotoxicity
    and antioxidant activities of compounds 1-4 were evaluated by using the MTT bioassay on MCF-7 (human breast cancer
    cell line), PC-3 (human prostate cancer cell line) and HEK-293 (normal human embryonic kidney cell line) and DPPH
    free radical scavenging activity, respectively. At concentration of 400 µM, all compounds showed the highest activity
    on MCF-7, with compound 1 at 65%, compound 2 (70%), compound 3 (66%) and compound 4 (58%) cell viability. All
    compounds exhibited weak antioxidant properties. To the best of our knowledge, this is the first report of compounds
    1-4 from Glaciozyma antactica.
  2. Al-Sabahi E, Abdul Rahim Samsudin, Wan Zuhairi Wan Yaccob, Umar Hamzah
    A 2D electrical resistivity survey was conducted to investigate the subsurface contamination underneath a domestic waste disposal site at Ampar Tenang, Dengkil, Selangor. The resistivity imaging technique was used in this study to locate the vertical and horizontal extend of contamination plumes underneath the site. A total of six 2-D resistivity imaging lines were established with two of them located outside the landfill area while one of them located in inactive landfill site. Another three lines were situated in the active landfill site. The results of the survey show that the resistivity value of the decomposed waste material in the inactive site of landfill is relatively low and the contaminated leachate plumes has low resistivity value of less than 2 Ωm. Characterisation of subsurface resisitivity and its relation to lithology was interpreted based on the available borehole data.
  3. Nudrat Aisha Akram, Shamim Kausar, Naila Farid, Muhammad Ashraf, Muhammad Ashraf, Fahad Al-Qurainy
    Sains Malaysiana, 2018;47:661-670.
    The production of wheat crop is below average in many regions of the world which is ascribed to adverse environmental
    conditions including drought stress. The present study was conducted to appraise the beneficial role of exogenouslyapplied
    5-aminolevulinic acid (ALA) on growth, yield and some key physio-biochemical characteristics of two commercially
    important wheat cultivars (Shafaq-06 and Uqab-2000) under well watered [100% field capacity (FC)] and water-deficit
    (60 and 80% FC) conditions. Imposition of varying water regimes significantly decreased fresh and dry weights of shoots,
    photosynthetic pigments (a and b), non-photochemical quenching of chlorophyll fluorescence (NPQ), quenching coefficient
    for non-photochemical (N) of chlorophyll fluorescence (qN), K+ (potassium ion), Ca2+ (calcium ion) and P (phosphorus)
    accumulation in shoot and root and yield-related attributes. In contrast, water deficit regimes caused improvement in
    Fv/Fm (chlorophyll fluorescence measurement), coefficient of photochemical quenching (qP), proline, glycinebetaine
    (GB) and hydrogen peroxide (H2O2) contents. Foliar spray of ALA at the rate of 50, 100 and 150 mg/Lalong with control
    (no spray (NS) and/or water spray (WS)) significantly enhanced chlorophyll a and b pigments, qN, NPQ, qP, K+, Ca2+
    and P accumulation in both roots and shoots, proline, GB, total phenolics and malondialdehyde (MDA) contents and
    yield. The wheat Shafaq-06 was better in shoot dry weight, qN, NPQ and Fv/Fm, shoot and root K+, root Ca2+, proline,
    GB accumulation and yield attributes, while Uqab-2000 was better in chlorophyll a contents, root P and MDA contents.
    Overall, better growth and yield of Shafaq-06 than Uqab-2000 under water deficit regimes was found to be associated
    with ALA improved leaf fluorescence (qN, NPQ and Fv/Fm), shoot and root K+, root Ca2+, proline and GB accumulation.
  4. Siti Atiqah Ishak, Iskandar Shahrim, Siti KAR, Azhar A. Alrahman
    Sains Malaysiana, 2017;46:303-308.
    The aim of this study was to evaluate properties of normoxic polymer gel 2-Hydroxyethyl methacrylate monomer (HEMAG)
    as a point dosimeter by using optical properties evaluation techniques. HEMAG were prepared from seven different
    radiation dose within five different depths of HEMAG dosimeters. These HEMAG dosimeters were irradiated by linear
    accelerator with 6 MV photon beams. The absorption spectra were measured by using a UV-visible spectrophotometer in
    the wavelength range from 300 to 800 nm. Then, the data was analysed to determine the optical energy band gap (Eg
    and Urbach’s energy (∆E). The result showed that Eg
    and ∆E were dependent on radiation dose and percentage of depth
    dose (PDD). In additional, Eg
    with indirect transition of HEMAG decreased as radiation dose increased and increased
    with traversing of depth. ∆E of HEMAG increased as the dose increased and decreased with traversing depth of monomer.
    There was a shift in the Eg
    values towards lower energy as the dose increased and led to a shift of the ∆E value towards
    the higher energy with increasing dose. This observation supported the increase of structured disorder of the polymer
    with increasing radiation dose, which resulted in the lower energy transitions that was feasible and reduced the values
    of Eg
    . In conclusion, HEMAG has a potential to be used as a dosimeter at low radiation dose in the clinical radiotherapy
  5. Darah I., Teo M, Ibrahim C.O.
    Atratoxin B1 which was extracted from a local sea cucumber, Holothuria atra is a potential antifungal agent against dermatophytes. Exposure of Microsporum canis mycelia inoculated into Sabouraud glucose agar medium to the 10 mg/ml atratoxin B1 solution, resulted in complete suppression of the fungal growth. Prolonged exposure to the atratoxin B] (72 hours) resulted with necrosis in a substantial portion of the existing hyphae. The main anomalies noted were the abnormally shaped hyphae and the alterations in its morphology and cytology.
    Atratoksin B] yang diekstrak daripada timun laut tempatan, Holothuria atra, adalah suatu agen antikulat yang berpotensi terhadap dermatofit. Pendedahan miselium Microsporum canis yang diinokulat ke dalam medium agar glukosa Sabouraud kepada larutan atratoksin B] berkepekatan 10 mg/ml, mengakibatkan penindasan lengkap dalam pertumbuhannya. Pendedahan yang lebih lama kepada larutan atratoksin B] (72 jam) mengakibatkan nekrosis berlaku pada sebahagian besar hifanya. Keganjilan yang jelas berlaku adalah ketidaknormalan pada bentuk hifanya dan juga pengubahsuaian yang terjadi pada morfologi dan sitologinya.
  6. Seuk-Yen Phoong, Mohd Tahir Ismail
    Sains Malaysiana, 2015;44:1033-1039.
    Over the years, maximum likelihood estimation and Bayesian method became popular statistical tools in which applied to fit finite mixture model. These trends begin with the advent of computer technology during the last decades. Moreover, the asymptotic properties for both statistical methods also act as one of the main reasons that boost the popularity of the methods. The difference between these two approaches is that the parameters for maximum likelihood estimation are fixed, but unknown meanwhile the parameters for Bayesian method act as random variables with known prior distributions. In the present paper, both the maximum likelihood estimation and Bayesian method are applied to investigate the relationship between exchange rate and the rubber price for Malaysia, Thailand, Philippines and Indonesia. In order to identify the most plausible method between Bayesian method and maximum likelihood estimation of time series data, Akaike Information Criterion and Bayesian Information Criterion are adopted in this paper. The result depicts that the Bayesian method performs better than maximum likelihood estimation on financial data.
  7. Nuryazmin Ahmat Zainuri, Abdul Aziz Jemain, Nora Muda
    Sains Malaysiana, 2015;44:449-456.
    This paper presents various imputation methods for air quality data specifically in Malaysia. The main objective was to
    select the best method of imputation and to compare whether there was any difference in the methods used between stations
    in Peninsular Malaysia. Missing data for various cases are randomly simulated with 5, 10, 15, 20, 25 and 30% missing.
    Six methods used in this paper were mean and median substitution, expectation-maximization (EM) method, singular
    value decomposition (SVD), K-nearest neighbour (KNN) method and sequential K-nearest neighbour (SKNN) method. The
    performance of the imputations is compared using the performance indicator: The correlation coefficient (R), the index
    of agreement (d) and the mean absolute error (MAE). Based on the result obtained, it can be concluded that EM, KNN
    and SKNN are the three best methods. The same result are obtained for all the eight monitoring station used in this study.
  8. Suwanda Idris
    Total Variance (TV) and Generalized Variance (GV) are commonly used as a measure multivariate dispersion. However, these two statistics has some drawbacks. This paper proposes a new measure of multivariate dispersion, named Vectorial Variance (VV) an inner product for set of operators defined on a Hilbert-Smith space. Since, the exact sampling distribution of VV is difficult to find, therefore the asymptotic sampling distribution is obtained.
    [Jumlah Varians dan Varians Teritlak kebiasaannya digunakan sebagai ukuran dispersi multivariate. Namun begitu, kedua-dua statistik ini mempunyai beberapa kelemahan. Dalam tulisan ini akan dicadankgan satu ukuran dispersi multivariate yang baru, dikenali sebagai varians bervektor (VV) yang merupakan suatu hasil darab terkedalam bagi set pengoperasi yang tertakrif ke atas suatu ruang Hilbert-Smith. Oleh kerana taburan pensampilan tepat dari statistik vv tersebut sangat sukar untuk ditentukan, maka taburan pensampilan asimtot telah diperolehi].
  9. Borza M, Rambely A, Saraj M
    Sains Malaysiana, 2012;41:1651-1656.
    In this paper, two approaches were introduced to obtain Stackelberg solutions for two-level linear fractional programming problems with interval coefficients in the objective functions. The approaches were based on the Kth best method and the method for solving linear fractional programming problems with interval coefficients in the objective function. In the first approach, linear fractional programming with interval coefficients in the objective function and linear programming were utilized to obtain Stackelberg solution, but in the second approach only linear programming is used. Since a linear fractional programming with interval coefficients can be equivalently transformed into a linear programming, therefore both of approaches have same results. Numerical examples demonstrate the feasibility and effectiveness of the methods.
  10. Noppakun T, Wuttichai S, Angkana B
    Sains Malaysiana, 2016;45:1565-1572.
    This study involves testing the equality of several normal means under unequal variances, which is the setup of one-way analysis of variances (one-way ANOVA). Several tests are available in the literature, however, most of them perform poorly in terms of type I error rate under unequal variances. In fact, Type I errors can be highly inflated for some of the commonly used tests, a serious issue that seems to have been overlooked. Even though several tests have been proposed to overcome the problem, most of them show difficulty in calculation. Accordingly, the test for ANOVA with estimation of parameters using Bayesian approach is proposed as an alternative to such tests. The proposed test is compared with four existing tests such as the original test, James’s test, Welch’s test and the parametric bootstrap (PB) test. Type I error rates and powers of the tests are evaluated using Monte Carlo simulation. Our results indicated that the performance of the proposed test is superior to the original test and is comparable to James’s test, Welch’s test and the PB test, controlling Type I error rate quite well and showing high power of the test. Our study suggested that the proposed test has high performance and should be used as an alternative to the four existing tests due to its simple formula.
  11. Ozturk M, Sakcali S, Celik A
    Sains Malaysiana, 2013;42:1371-1376.
    Diplotaxis tenuifolia is a medicinally important perennial plant species, distributed widely alongside the roads in Turkey. The samples were collected from 54 sites, including highways, sideways, industrial areas, urban centres and rural environs. Both the plant and soil samples were analysed to determine the concentrations of different metals using AAS. The results showed that in the soil samples copper and lead were highest near highway 45.533 and 2.865 mg/kg, respectively; but lowest values of copper were determined around industrial areas (3.514 mg/kg), latter however showed higher concentrations of cadmium (0.726 mg/kg) and iron (82.766 mg/kg). The lead as well as iron were the lowest around sideways 1.917 mg/kg and 54.073 mg/kg, respectively, whereas chromium concentrations in the soils were highest near sideways (18.397 mg/kg) and lowest around industrial areas (0.182 mg/kg). The sideways showed very low nickel concentrations (0.271 mg/kg), as compared to the rural areas which had higher nickel concentrations (0.726 mg/kg). No cadmium was detected in the urban soil samples. In the plants copper and chromium were higher in the urban areas 50.130 and 0.238 mg/kg, respectively. The former was lowest around sideways (32.377 mg/kg) and latter around highways (0.114 mg/kg). Both nickel and cadmium were higher in the samples from industrial areas 0.238 and 0.016 mg/kg, respectively. Their values around the highways were lowest 0.182 and 0.005 mg/kg. The samples from urban sites revealed highest values of lead (3.474 mg/kg) and iron (61.304 mg/kg), but the values of lead were lowest around sideways (2.420 mg/kg) and those of iron in the vicinity of industrial areas (20.600 mg/kg). All these findings depict that there is some aerial deposition of these metals on the leaves. A significant correlation is seen between the plants and the soils.
  12. Rozainah M
    Sains Malaysiana, 2006;35:55-62.
    A survey on coastal vegetation of Pahang in some localities from Sg. Balok in Kuantan southwards to Kuala Endau in Rompin was conducted from middle 2004 to early 2005. A total of 88 species of plants were recorded and identified mostly to the generic or species level. The usual vegetation types were sand and mudflat beach vegetations like Pandanus odoratissimus, Ipomoea pes capre and Casuarina equisetifolia and mangrove vegetation like Sonneratia caseolaris, Rhizophora mucronata and Avicennia marina. This paper also reports some unique heath-type forest vegetation like Hopea spp. in Menchali area.
  13. Siti Mazlina Mustapa Kamal, Khairul Faezah Md. Yunos, Norhafizah Abdullah
    Sains Malaysiana, 2018;47:309-318.
    Tilapia is a popular freshwater fish and among the important cultured fish grown worldwide. In this study, fish protein
    hydrolysate was produced from tilapia (Oreochromis niloticus) by-product (TB) and tilapia muscle (TM) through enzymatic
    hydrolysis using alcalase. The TB and TM protein hydrolysates were evaluated for its characteristics in terms of angiotensin
    I-converting enzyme (ACE) inhibition activity, peptide size distribution, and functional properties. Hydrolysis for 1 h for
    TB and TM successfully produced low molecular weight peptides (<14.2kDa) with the highest ACE inhibitory activities.
    The findings also demonstrated that both samples have high nitrogen solubility (>80% at pH2-9) and good emulsifying,
    water and oil holding capacities. The study indicated that tilapia protein hydrolysates have the potential to be used as
    functional food products.
  14. Yap C, Al-Barwani S
    Sains Malaysiana, 2012;41:1063-1069.
    This study compared some allometric parameters (shell length, shell width, shell height, total dry weight of soft tissues, condition index and heavy metals (Cd, Cu, Pb and Zn) in the different soft tissues of Perna viridis collected from Sebatu and Muar estuary. It was found that the total dry weight of soft tissues and condition index of mussels collected from Sebatu were significantly (p<0.05) higher than those in Muar. The significantly (p<0.05) higher concentrations of Cu in most soft tissues and some of Cd indicated a higher bioavailability of Cu and Cd at Muar than Sebatu. In addition, the significantly (p<0.05) higher levels of Cu, Cd, Zn and Pb in surface sediments collected from Muar supported the observable anthropogenic impacts at Muar than Sebatu and hence, higher metal contamination at Muar than Sebatu. The higher condition index value in mussels recorded in Sebatu than in Muar was believed to be a result of higher metal contamination at Muar estuary.
  15. Wan Zin Wan Zawiah, Abdul Aziz Jemain, Kamarulzaman Ibrahim, Jamaludin Suhaila, Mohd Deni Sayang
    Statistical distributions of annual extreme (AE) and partial duration (PD) for rainfall events are analysed using a database of 50 rain-gauge stations in Peninsular Malaysia, involving records of time series data which extend from 1975 to 2004. The generalised extreme value (GEV) and generalised Pareto (GP) distributions are considered to model the series of annual extreme and partial duration. In both cases, the three parameter models such as GEV and GP distributions are fitted by means of L-moments method, which is one of the commonly used methods for robust estimation. The goodness-of-fit of the theoretical distribution to the data is then evaluated by means of L-moment ratio diagram and several goodness-of-fit (GOF) tests for each of the 50 stations. It is found that for the majority of stations, the AE and PD series are well fitted by the GEV and GP models, respectively. Based on the models that have been identified, we can reasonably predict the risks associated with extreme rainfall for various return periods.
  16. Mei Siang Ma, Zalini Yunus, Zukri Ahmad, Farizah Abdul Fatah
    Sains Malaysiana, 2015;44:187-192.
    Water from the dental unit waterlines (DUWLs) is known to contaminate with microbial from the biofilm that formed in the tubing system. The water quality from DUWLs is important to patients and dental health care professionals as they could be infected either directly from the contaminated water or aerosol that is generated during dental procedures. Suppliers claimed that dental units supplied to the hospital can only use a specific disinfectant which is uneconomic compared with the others. The aims of this study were to evaluate and compare the efficacy of different disinfectant on the water quality of DUWLs. Four disinfectants (Calbenium, A-dec ICX tablet, Dentel 5, Metassys) and distil water were evaluated. 350 mL water sample was collected separately, from the outlet of high-speed handpiece, scaler, 3-ways syringe and cup filler into a sterile thiosulfate bag on the 1st, 2nd, 4th, 8th, 12th and 24th weeks of the study. The samples were tested on the following day for total viable count (TVC). There is significant difference in the efficacies of the different disinfectants. Only one disinfectant consistently produces water quality within the recommended level of American Dental Association (ADA). Within the limitation of this study, it was found that there is alternative disinfectant that can reduce the TVC to the level recommended by ADA. However, the water qualities produced with these disinfectants were not consistent although they did not cause any technical problem to the dental units during the period of study.
  17. Abdul Ghapor Hussin, Norli Anida Abdullah, Ibrahim Mohamed
    This paper gives a comprehensive discussion on complex regression model by extending the idea of regression model to circular variables. Various aspect have been considered such as the biasness of parameters, error assumptions and model checking. The advantage of this approach is that it allows the use of usual technique available in ordinary linear regression for the regression of circular variables. The quality of the estimates and the feasibility of the approach were illustrated via simulation. The model was then applied to the wave direction data.
  18. Atikah C, Nihayah M, Omar B, Leonard J, Noor Ibrahim M, Zurkarnain M, et al.
    Sains Malaysiana, 2015;44:1461-1466.
    Fire fighting is one of the most strenuous activities in the hazardous fire service industry. Firefighters have to be physically fit in order to provide an effective and safe fire prevention to the afflicted community and as well as to themselves. The aimed of this cross-sectional study was to evaluate the physical fitness among Malaysian firefighters. The hand grip test to evaluate hand and muscular strength was measured using hand dynamometer and one-minute sit ups and one-minute push ups were conducted to measure abdominal muscle endurance. The sit and reach test was carried out to measure lower back and hamstring flexibility. VO2 max was assessed by a 20 meter shuttle run test to measure cardiorespiratory fitness. A total of 385 subjects were participated and the results showed that 77.1% (n=297) and 84.8% (n=325) of them had very poor scores for hand grip strength and VO2 max, respectively. For one-minute sit ups, 40.8% (n=157) of subjects scored excellent. Meanwhile, 32.7% (n=126) subjects scored average for one-minute push ups. For flexibility test, 53.2% (n=205) subjects had poor flexibilty. The results showed there were significantly difference between one-minute sit ups (p<0.001), one-minute push ups (p<0.05), flexibility (p<0.05) and VO2 max (p<0.001) according to age. As a conclusion, this study provides representative data on physical fitness among Malaysian firefighters. These findings suggested the needs to explore the issues behind low physical fitness among Malaysian firefighters and to find ways to improve them.
  19. Idham Arif Alias
    A map on a group is not necessarily an automorphism on the group. In this paper we determined the necessary and sufficient conditions of a map on a split metacyclic p-group to be an automorphism, where we only considered p as an odd prime number. The metacyclic group can be defined by a presentation and it will be beneficial to have a direct relation between the parameters in the presentation and an automorphism of the group. We considered the action of an automorphism on the generators of the group mentioned. Since any element of a metacyclic group will be mapped to an element of the group by an automorphism, we can conveniently represent the automorphism in a matrix notation. We then used the relations and the regularity of the split metacyclic p-group to find conditions on each entry of the matrix in terms of the parameters in its presentation so that such a matrix does indeed represent an automorphism.
  20. Fanhui-Zeng, Jianchun-Guo, Yuxuan-Liu
    Sains Malaysiana, 2015;44:1377-1388.
    Hydraulic fracturing becomes more difficult when confronted with a formation of high fracturing pressure. In such formations, acidizing before the main fracturing treatment provide a method to reduce fracture pressure. The aim of this paper was to investigate the evolution of fracture pressure in a wellbore with acidizing. Five experiments were conducted to study the mechanisms of acid damage on reservoir minerals and cementing materials properties. Consequently, a mathematical model to predict fracture pressure with acidizing has been established and verified by field data. The analysis results showed that it is possible to reduce fracture pressure with decreased rock strength and fracture critical stress intensity factor by means of acid damage. Acid damage destroys the crystal structure of mineral particles, breaks the crystalline layers in cementing materials, increases rock porosity and reduces the rock strength. In addition, as the acid concentration, formation temperature and acid treatment time increased, it was useful to reduce fracture pressure in the wellbore. Using the proposed model, we were able to select the optimal acid damage construction parameters to reduce fracture pressure.
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