Displaying publications 141 - 160 of 2561 in total

Abstract:
Sort:
  1. Hu YG, Bachir Goudia Daoura, Iqbal Saeed, Quanhao Song, Yang Yang, Liang Chen
    Sains Malaysiana, 2018;47:235-242.
    The activities of key C4 photosynthetic enzymes including phosphoenolpyruvate carboxylase (PEPcase), NADP-malic
    enzyme (NADP-ME), malate dehydrogenase (MDH) and pyruvate phosphate dikinase (PPDK) were assayed in flag leaves
    at three major growth stages (heading, anthesis and grain filling) among 59 winter wheat genotypes grown in field
    conditions. All C4 enzymes expressed in the flag leaves and their activation showed a wide range of variation in relation
    to different growth stages in all the genotypes. PEPcase, NADP-ME and MDH displayed the highest mean activities of
    1.018, 0.758 and 0.731 µmol. min–1.mg–1 protein at heading stage, respectively; while PPDK showed the highest mean
    activity (0.888 µmol. min–1.mg–1 protein) at grain filling stage. The activities of PEPcase and PPDK were higher at
    heading stage, decreased at anthesis and again increased at grain filling stage, while NADP-ME and MDH exhibited a
    decreasing trend at the three stages. The results of the current study could be valuable and useful for wheat researchers
    in improving photosynthetic capacity of wheat.
  2. Khan S, Jameel R, Razak F, Bakri M
    Sains Malaysiana, 2018;47:531-536.
    The potential of using saliva as a diagnostic fluid is well documented. The aim of this study was to assess the quality and
    quantity of saliva DNA of alcoholic and non-alcoholic participants using three saliva collection methods; DNA-SalTM (Oasis
    Diagnostics, USA), Oragene-DNA (DNA Genotek Inc, Ontario, Canada) and whole saliva collection method. Saliva DNA
    of non-alcoholic (n=30) and alcoholic participants (n=10) age between 25 and 35 years was assessed qualitatively and
    quantitatively using spectrophotometry. Saliva DNA quantity was the highest for all participants when using the DNA-Sal TM
    saliva collection kit (p<0.05). The use of a mechanical scraper provided only in the DNA-Sal TM kit may have contributed
    to the highest DNA yield for all participants. The quantity of saliva DNA when assessed using spectrophotometer was found
    to be significantly lower (p<0.05) for the alcoholic (16±3.57 ng/μL) than non-alcoholic participants (19.92±6.18 ng/
    μL). To determine the integrity of the DNA samples, PCR amplification of the Alcohol Dehydrogenase gene, ADH1B was
    carried out and the PCR was found to be successful. For all participants, the DNA quality of the saliva collected using the
    three saliva collection methods was found to be in the acceptable range considered as pure DNA. The DNA quality and
    quantity of saliva collected from the three saliva collection methods were considered suitable for research purposes.
  3. Mohammad Zahirul Islam, Mahmuda Akter Mele, Ho-Min Kang
    Sains Malaysiana, 2018;47:537-542.
    Salicylic acid (SA) is a plant hormone that has functional effects in plant. This study was conducted to find out the effects
    of salicylic acid (SA) on cherry tomato fruit quality and shelf life. Different concentrations (0.13, 0.25, 0.50 and 1.00
    mM) SA were added in nutrient solution of hydroponic system in plants vegetation and fruits development stage. Lightred
    maturity stage of cherry tomato fruits was harvested to measure the harvest time fruit quality and stored at 5℃ to
    measure the postharvest quality and shelf life. Ethylene production and respiration rate of tomato fruit at the harvest
    time and after storage was effectively reduced by the 0.50 mM SA treatment. Increased acetaldehyde (p≤0.05) as well
    as ethanol (p≤0.001) was performed in the 0.50 mM SA treatment at after storage. The 0.50 mM SA treatment showed
    the lowest fresh weight loss 3.08% and the longest shelf life 25 days by reducing decay, fruits softening and fungal
    infection. Significantly lower fungal incidence (p≤0.001) was observed in the 0.50 mM SA treatment. Final storage day
    color development and lycopene content was lower in the 0.50 mM SA treatment compare with other treatments. The 0.50
    mM SA treatment obtained the highest firmness at harvest time and it retain after storage. Comparatively higher vitamin
    C and lower soluble solids was showed at the harvest time and after storage. Therefore, the 0.50 mM SA treatment is
    effective in increasing the quality and shelf life of cherry tomato fruit.
  4. Lam SM, Sin JC, Abdul Rahman Mohamed
    Sains Malaysiana, 2018;47:253-259.
    With the rapid civilization and industrialization, water pollution is becoming more and more intricate. Heterogeneous photocatalysis using metal oxide loaded ZnO nanorods is a well-known environmental technology to degrade toxic organic pollutants. In this study, Cr2O3 particles anchored on the ZnO nanorods (Cr2O3/ZnO) were successfully synthesized by a hydrothermal-deposition technique. Microscopic and crystallographic analyses indicated that the synthesized samples consisted of two-phase heterostructure of Cr2O3 and ZnO. The photocatalytic results showed that the phenol degradation by Cr2O3 /ZnO heterostructures was higher than those of pure ZnO and commercial TiO2. The synergetic effect between Cr2O3 and ZnO was the pivotal reason for the improvement of photoactivity as proven by the photoluminescence and terephthalic acid–photoluminescence analyses.
  5. Yongvanich N, Wangwanich N, Phomwana N
    Sains Malaysiana, 2018;47:581-587.
    Ceramic colour pigments based on the malayaite structure was synthesized by sol-gel with an aim to obtain homogeneous
    powder systems. The formulation was Ca(Sn1-xCrx
    )SiO5
    where x = 0, 0.02 and 0.05. Thermogravimetric analysis and
    infrared spectroscopy suggested suitable calcination temperatures to be > 1000°C. Formation of malayaite phase was
    found to be very difficult; high calcination temperatures up to 1400°C was required which was typical for this particular
    phase. Nevertheless, small amounts of impurities were still present and were found to be both wollastonite (CaSiO3
    ) and
    cassiterite (SnO2
    ). The oxidation state of chromium was found to be mainly 4+. The obtained pigment particles were
    in the range of 1-5 micron with a high degree of agglomeration due to sintering. UV-vis spectra demonstrated broad
    absorbance peak in the 550-600 nm range which could be attributed to both Cr(III) and Cr(IV). The colour parameters in
    the CIELab system showed a red tone (more positive a* values whereas b* remained relatively constant) when chromium
    was doped into the malayaite host. Preliminary interaction testing with a low-fire glaze displayed an even improvement
    in the a* parameter (getting more red tone). Microscopic studies showed a certain degree of chromium diffusion out
    of the pigment powders toward the glaze matrix. These results have demonstrated a great potential for this refractory
    colour pigments to be possibly utilized in other kinds of glazes as well.
  6. Xin Tong, Xiao-ye Shen, Cheng-lin Hou
    Sains Malaysiana, 2018;47:1685-1692.
    Fungi associated with Vaccinium species play important roles in plant growth and disease control, especially in the final
    blueberry production. Vaccinium dunalianum var. urophyllum (Ericaceae) is a well-known medicinal plant in Southern
    China used to treat inflammation and microbial infections. The endophytic fungi from these plants are therefore anticipated
    as potential new sources of antimicrobials. In this report, the inhibitory effects of endophytes against clinical bacteria
    and yeast were comprehensively screened and 11 isolates indicated high bioactivity by the agar diffusion method. The
    corresponding crude extracts of these fungi under submerged fermentation also demonstrated distinct differences and
    n-butyl alcohol displayed the lowest extraction efficiency among the extracts. The ethyl acetate and dichloromethane
    extracts of filtrates from the Colletotrichum sp. VD001, Epicoccum nigrum VD021 and E. nigrum VD022 strains
    displayed good properties against pathogenic microorganisms according to disc diffusion assays and minimal inhibitory
    concentration (MIC). This study is the first indicating that cultivable endophytic fungi associated with blueberry plants
    produce potential compounds against clinical pathogens.
  7. Nurazira Mohd Nor, Darfizzi Derawi, Jumat Salimon
    Sains Malaysiana, 2018;47:1359-1367.
    The epoxidation process of RBD palm oil was carried out using in situ generated performic acid. The effect of various
    process variables such as the formic acid towards hydrogen peroxide mole ratio, the reaction temperature and the
    reaction time were optimized by using response surface methodology (RSM). The D-optimal design was used to evaluate
    the influence of process variables and their interaction in order to obtain the process optimum conditions. The results
    showed that the optimum conditions of the epoxidation process were at 5.91 mole ratio of formic acid towards 3.60 mole
    of hydrogen peroxide, reaction temperature of 40ºC and reaction time of 2.55 h. At the optimum condition, the epoxidised
    RBD palm oil (EPO) yield was 86% with oxirane oxygen content (OOC) of 3.46%. The results showed in good agreement
    with the predicted values from the RSM model.
  8. Li Tian, Qiang-Sheng Wu, Kamil Ku?a, Mohammed Mahabubur Rahman
    Sains Malaysiana, 2018;47:1693-1700.
    China is one of the largest citrus producers in Asia, where Phytophthora parasitica infection has become the major
    threat in sustaining long term citrus production. The proposed study examined the effects of P. parasitica on Citrus junos,
    C. limon, C. tangerina and Poncirus trifoliata to evaluate the resisted rootstock to Phytophthora root rot. P. parasitica
    infection notably decreased plant growth, root morphology and activities of pathogenesis-related proteins (PRs) in
    C. limon and C. tangerina. Root β-1,3-glucanase, chitinase and phenylalanine ammonialyase activities significantly
    increased in C. junos and P. trifoliata after infection with P. parasitica. P. parasitica infection notably decreased root
    salicylic acid concentrations in C. limon, C. tangerina and P. trifoliata, while increasing it in C. junos. An opposite
    trend was observed in root jasmonic acid levels after infection with P. parasitica, relative to root salicylic acid. Root
    nitric oxide and calmodulin concentrations were significantly increased in P. parasitica-infected C. junos, C. tangerina
    and P. trifoliata, while C. limon exhibited a decrease. These results demonstrated that citrus species like C. junos and P.
    trifoliata displayed a much higher resistance to Phytophthora-induced root rot, and C. limon and C. tangerina showed
    a comparatively lower degree of resistance.
  9. Masniza Mohamed@Mahmood, Wan Ramli Wan Daud, Masturah Markom, Che Nurul Ain Nadirah Che Mansor
    Sains Malaysiana, 2018;47:1741-1747.
    In this work, a preliminary study was conducted to study the effects of different types and concentrations of cosolvents
    based on the total yield and antioxidants capacity prior to supercritical fluid extraction (SFE) of Orthosiphon stamineus
    (locally referred as misai kucing). Initially, a comparison was made by cold maceration technique with nine types of
    different cosolvents, namely water, pure ethanol, 25% (v/v) of ethanol in water, 50% (v/v) of ethanol in water, 75% (v/v) of
    ethanol in water, pure methanol, 25% (v/v) of methanol in water, 50% (v/v) of methanol in water and 75% (v/v) of methanol
    in water. The antioxidant capacity was analysed by free radical scavenging activity of 2,2-diphenyl-1-picrylhydrazyl
    (DPPH), total phenolic content (TPC) and total flavonoid content (TFC). Aqueous ethanolic solvent of 50% (v/v) ethanol in
    water showed the highest total yield of extract of 4.64 ± 0.02%. All antioxidant assays of TPC and TFC showed the highest
    value of 3.42 ± 0.08 mg GAE g−1 extract, 4.7 ± 0.14 mg CAE g−1 extract, respectively and IC50 value for DPPH was 0.625
    µg/mL for 50% (v/v) ethanol in water extract. Based on the overall result, ethanolic solvents gave a better result for all
    antioxidant assays compared to those of methanolic solvents. Using the selected cosolvent, the identification of target
    compounds, which were rosmarinic acid, eupatorin and sinensetin from supercritical fluid extraction was determined
    by using HPLC. In conclusion, ethanol-water solvent was efficient in extracting bioactive compounds in O. stamineus
    and also improved the total yield, thus the usage of ethanolic solvent in different concentrations should be considered
    for further optimisation of SFE with cosolvent studies.
  10. Ainul Mardhiyah Mohd Razib, Goh TL, Nur Amanina Mazlan, Muhammad Fahmi Abdul Ghani, Tuan Rusli Tuan Mohamed, Abdul Ghani Rafek, et al.
    Sains Malaysiana, 2018;47:1413-1421.
    The stability of the limestone cliff at Gunung Kandu, Gopeng, Perak, Malaysia was assessed based on the Slope Mass
    Rating (SMR) system on 53 cross sections of the Gunung Kandu hill slopes. The slopes of Gunung Kandu were identified
    as class I (very good) to IV (poor). The kinematic analysis showed that 12 out of 53 hill slopes of Gunung Kandu were
    identified as having potential wedge, planar and toppling failures. The assessment showed that the stability of the western
    flanks can be classified as stable to unstable with the probability of failure from 0.2 to 0.6. The stability of the eastern and
    southern flanks range from very stable to partially stable with the probability of failure from 0.0 to 0.4. While the stability
    of northern flanks are from very stable to stable with the probability of failure of 0.0 - 0.2. This systematic approach
    offers a practical method especially for large area of rock slope stability assessment and the results from probability of
    failure values will help engineers to design adequate mitigation measures.
  11. Nur Suhana Mohamad Ripim, Nuraini Fazil, Saidatul Nadrah Kholid Ibrahim, Adibah Ahamad Bahtiar, Yip Chee Wai, Nazlina Ibrahim, et al.
    Sains Malaysiana, 2018;47:1725-1730.
    A study was conducted to investigate the antiviral activity of aqueous extracts from Orthosiphon stamineus (OS).
    Extraction was done using different parts of OS. The whole plant except root (WPOS), leaves (LOS) and flowers (FOS) of
    OS were extracted using aqueous extraction method. Cytotoxicity was assessed using 3-(4,5-dimethylthiazol-2,5-diphenyl
    tetrazolium bromide (MTT) assay. Plaque reduction assays were carried out to evaluate the antiviral activity of OS extract
    against herpes simplex virus type 1 (HSV-1). These include post-treatment, pre-treatment and virucidal assays. High
    antiviral activity was observed in post-treatment and virucidal assay with 100% reduction of HSV-1 plaque at 0.39 mg/
    mL in LOS, FOS and WPOS. In pre-treatment assay, 79%, 84% and 97% plaque reduction using the same concentration
    was observed in FOS, LOS and WPOS, respectively. In conclusion, this study showed that OS aqueous extract has promising
    potential to be explored as anti-HSV-1 agent regardless of the mode of treatment.
  12. Marina Zainal Abidin, Ahmad Abas Kutty, Tukimat Lihan, Nurul Akhma Zakaria
    Sains Malaysiana, 2018;47:1401-1411.
    This study attempts to assess the impact of various types of land use along Sungai Langat and describes hydrological
    change and water quality variation along this river. This study also determines water quality of Sungai Langat based on
    low flow dry period Q100,7 using the application of QUAL2K. Dissolved oxygen (DO), pH, temperature and conductivity
    were measured in situ. Biochemical oxygen demand (BOD5
    ), ammonia nitrogen (NH3
    -N) and total suspended solid (TSS)
    were analysed according to the standard methods (APHA). Water quality data was referred to National Water Quality
    Standards for Malaysia (NWQS) proposed by Malaysian Department of Environment (DOE) to estimate Sungai Langat
    water quality status. Four important water quality parameters namely DO, BOD5, NH3
    -N and TSS were simulated with
    QUAL2K version 2.07 for 83.67 km. As regard to individual parameter, DO classified this river into class III, BOD5 in
    Class II, NH3
    -N in Class IV and TSS in Class I. Based on QUAL2K simulation for low flow scenario, the results clearly
    demonstrates a gradually reduction of DO and BOD5 whereas NH3
    -N and TSS display opposite. Only NH3
    -N was found
    significantly increase which cause low water quality class towards the downstream. Three parameters namely DO, BOD5
    and NH3
    -N show effects of industrial which approximately located at the middle of river stretch. The TSS was contributed
    to the river system at the upstream and downstream of the river stretch which most likely from sand mining activity which
    located at Sungai Long, Cheras (near R5) and Sungai Semenyih (R11).
  13. Rahimah Mahat, Noraihan Afiqah Rawi, Sharidan Shafie, Abdul Rahman Mohd Kasim
    Sains Malaysiana, 2018;47:1617-1623.
    The purpose of this study was to examine the effect of viscous dissipation on mixed convection flow of viscoelastic
    nanofluid past a horizontal circular cylinder. Carboxymethyl cellulose solution (CMC) is chosen as the base fluid and
    copper as a nanoparticle with the Prandtl number Pr = 6.2. The transformed boundary layer equations for momentum
    and temperature subject to the appropriate boundary conditions are solved numerically by using Keller-box method. The
    influenced of the dimensionless parameters such as Eckert number, mixed convection parameter, nanoparticles volume
    fraction and viscoelastic parameter on the flow and heat transfer characteristics is analyzed in detail and presented
    graphically. The results come out with the velocity profiles are increased while the temperature profiles are decreased
    by increasing the values of nanoparticles volume fraction and viscoelastic parameter, respectively. The graph shows
    that, increasing Eckert number the skin friction is also increases. The values of skin friction are increased by increasing
    mixed convection parameter, but the values of Nusselt number produce an opposite behavior. The present study has many
    applications especially in heat exchangers technology and oceanography. Therefore, in future, it is hoping to study the
    viscoelastic nanofluid flow past a different geometric such as sphere and cylindrical cone.
  14. Farah Shafawati Mohd-taib, Siti Nabilah Ishak, Mohammad Saiful Mansor, Shukor Md-nor
    Sains Malaysiana, 2018;47:1645-1656.
    Despite the increasing numbers of hydrodam worldwide, only a handful of studies evaluated their impacts on biodiversity.
    Compared to terrestrial animals, birds were thought to be less affected by inundation process, following impoundment. At
    the Hulu Terengganu Hydroelectric Dam in Peninsular Malaysia, our study compared species assemblages and diversity
    of birds within the dam area (i.e. the dam reservoir and catchment area) after recent logging and inundation in relation
    to a nearby forest logged 30 years ago. Using point count and mist-netting techniques, we recorded a total of 64 species
    (Shannon Index (H’) = 3.827) in the dam area and 91 species (H’=3.99) in historically-logged forests. Insectivore species
    richness was significantly higher in the historically-logged forests (Mann-Whitney: Z=4.339, N=205, p<0.005). These
    results indicated that richness and diversity of bird species assemblages appear to decline following recent inundation
    phase. Nevertheless, the forests in the dam area still harbour charismatic species such as eagles (Family: Accipitridae)
    and hornbills (Family: Bucerotidae) which suggests that this habitat is relatively important for birds.
  15. Phuchiwan Suriyawong, Elizabeth A. Bergey
    Sains Malaysiana, 2018;47:1379-1386.
    A series of check dams (or small dams in shallow streams) have been placed on many streams throughout Thailand and
    the number of them continue to increase. Check dam construction activities have been emphasized by the government
    and private sector entities over the last decade to prevent severe flood or drought due to changes in rainfall patterns. This
    study evaluated distribution of functional feeding groups (FFG) in a stream with a high density of check dams. Twelve
    sampling sites at three altitudes (500, 900 and 1500 m asl) included undammed and nearby dammed sections (above
    and below check dams) were used. Aquatic insects were collected monthly at each site for a year and categorized into
    FFG. Aquatic insect composition of undammed and above dam sites was different. Abundance within each FFG at above
    dam sites significantly differed from undammed sites. Taxonomic richness at 1500 and 900 m altitudes was decreased
    at above dam sites compared with the corresponding undammed sites, whereas above dam sites of 500 m altitude had
    higher richness than undammed site. High abundance of predators and collector-gatherers associated with reservoirs
    and fine sediment accumulation above dams, where filter-feeders were scarce. Shredder abundance varied among sites
    and was highest where leaf packs were most abundant. Scrapers were least abundant group and inconsistent with the
    dams. Distribution of FFG was similar to changes in other regulated streams. The composition of FFG reflected the
    stream ecosystem conditions through adaptation of communities to stream habitat and food resources, including those
    associated with check dam construction.
  16. Sains Malaysiana, 2018;47:1393-1400.
    Numerous studies have shown that parasites potentially become bio-accumulators for heavy metals. The heavy metals
    content in parasite-infected fish was reported to be lower compared to the parasite non-infected fish. Evaluation of heavy
    metal content in Nemipterus peronii and Paraphilometroides nemipteri was performed using ICP-OES. Our result has
    shown that arsenic was the most abundance heavy metal content in muscle N. peronii and P. nemipteri, suggesting that
    the parasite has the ability to accumulate heavy metals. Heavy metals were reported to induce oxidative stress where
    glutathione and p38 protein may be involved. Thus, expression of the p38 protein was determined using western blot
    technique and glutathione content was measured fluorometrically. The p38 expression in P. nemipteri of Pulau Kambing
    was higher compared to P. nemipteri of Besut has shown that the parasite may exposed to stress. Glutathione content
    showed no significant changes due to detoxification mechanism occurred in the parasite. In this study, we could conclude
    that P. nemipteri could be a bio-accumulator, whereas p38 protein and glutathione as indicator of stress level in the
    parasite that exposed to the heavy metals.
  17. Mohd-Ridwan A, Nurul Farah Diyana Ahmad Tahir, Mohamad Haikal Bin Eshak, Faisal Ali Anwarali Khan, Jayasilan Mohd-Azlan, Gábor Csorba & Tamás Görföl
    Sains Malaysiana, 2018;47:1349-1357.
    Bat surveys at Gunung Gading National Park (GGNP) were conducted for 29 non-consecutive nights, which consisted
    of five separate sampling sessions from November 2011 until November 2015. A total of 378 individuals representing
    36 species from six families were captured, from an accumulated effort of 435 trapping nights. This corresponds to
    approximately 39% (n=36) of the total species recorded in Borneo. The most commonly captured species in GGNP for
    insectivorous bats was Rhinolophus affinis (20.1%), whereas for frugivorous bats Penthetor lucasi (14.3%) dominated the
    capture. Species accumulation curve reached asymptote on the 24th sampling night suggesting that sampling saturation
    has been achieved for the trapping sites studied here. The species diversity (H’= 2.75) showed relatively high diversity
    of bat species in the park compared to other actively surveyed sites in western Sarawak including Bako National Park
    (Bako NP), Kubah National Park (Kubah NP) and Mount Penrisen (Mt Penrisen). This was further supported through
    rarefaction analysis showing that GGNP has largest value of estimated species compared to other actively surveyed
    sites in western Sarawak. Lunar phase and bat capture rate correlation analysis showed that there is no statistically
    significant relationship between lunar phase and the bat capture rate at GGNP. This suggests that bat activity reported
    here were not affected by moonlight. The results from these surveys provided the most comprehensive list of bats for
    GGNP. Our study highlights the importance of GGNP as an important habitat for bat conservation including the rare bat
    species found in Borneo, Phoniscus atrox.
  18. Dewi Hidayati, Ismail B, Shuhaimi-Othman M, Norela Sulaiman
    Sains Malaysiana, 2018;47:1665-1674.
    LUSI (Lumpur“mud”-Sidoarjo) is the mud volcanic which was initiated by the failed gas drilling exploration activities
    carried out near an urban area. The evaluation of the LUSI mud volcanic emission and its dried mud effects on air pollution
    and human health was carried out from 2011 to 2012. The concentrations of particulate matter (PM2
    .
    5
    ), hazardous
    gases (H2
    S, SO2
    , NO2
    ), volatile organic compounds (VOC): Including total hydrocarbons (THC)), toluene (C6
    H5
    CH3
    ) and
    benzene (C6
    H6
    ) as well as heavy metals (Pb, Cr and Cd) were measured following standard methods. The results showed
    that the average concentration of PM2.5 ranged from 24.0-399.9 μg/m3
    , H2
    S: 1.53-2.92 ppm; SO2
    : 0.021-1.321 ppm and
    NO2
    : 0.007-0.076 ppm. The VOC included total hydrocarbons from 0.57-0.96 ppm, toluene 0.33-0.92 ppm and benzene
    0.33-0.40 ppm. Furthermore, heavy metal concentrations were as follows: Pb 2.6-37.34 μg/m3
    ; Cr 0.14-12.8 μg/m3
    and
    Cd 0.78-4.16 μg/m3
    . LUSI contributed to increased air pollution primarily through H2
    S, SO2 and PM2.5. The Air Quality
    Index (AQI) of PM2.5 (164-217) and SO2
    (235-291) showed that the air quality at the disaster area was ‘very unhealthy’.
    Backward trajectories indicated that the wind direction may have had an impact on the air pollution load.
  19. Syazwani Mohd Zokri, Nur Syamilah Arifin, Muhammad Khairul Anuar Mohamed, Abdul Rahman Mohd Kasim, Mohd Zuki Salleh, Nurul Farahain Mohammad
    Sains Malaysiana, 2018;47:1607-1615.
    This paper delves into the problem of mixed convection boundary layer flow from a horizontal circular cylinder filled in
    a Jeffrey fluid with viscous dissipation effect. Both cases of cooled and heated cylinders are discussed. The governing
    equations which have been converted into a dimensionless form using the appropriate non-dimensional variables are solved
    numerically through the Keller-box method. A comparative study is performed and authentication of the present results
    with documented outcomes from formerly published works is excellently achieved. Tabular and graphical representations
    of the numerical results are executed for the specified distributions, considering the mixed convection parameter, Jeffrey
    fluid parameters and the Prandtl and Eckert numbers. Interestingly, boundary layer separation for mixed convection
    parameter happens for some positive (assisting flow) and negative (opposing flow) values. Strong assisting flow means
    the cylinder is heated, which causes the delay in boundary layer separation, whereas strong opposing flow means the
    cylinder is cooled, which conveys the separation point close to the lower stagnation point. Contradictory behaviours
    of both Jeffrey fluid parameters are observed over the velocity and temperature profiles together with the skin friction
    coefficient and Nusselt number. The increase of the Prandtl number leads to the decrement of the temperature profile,
    while the increase of the Eckert number results in the slight increment of the skin friction coefficient and decrement of
    the Nusselt number. Both velocity and temperature profiles of Eckert number show no effects at the lower stagnation
    point of the cylinder.
  20. Arifah Bahar, Siti Rohani Mohd Nor, Fadhilah Yusof
    Sains Malaysiana, 2018;47:1337-1347.
    The growing number of multi-population mortality models in the recent years signifies the mortality improvement in
    developed countries. In this case, there exists a narrowing gap of sex-differential in life expectancy between populations;
    hence multi-population mortality models are designed to assimilate the correlation between populations. The present
    study considers two extensions of the single-population Lee-Carter model, namely the independent model and augmented
    common factor model. The independent model incorporates the information between male and female separately
    whereas the augmented common factor model incorporates the information between male and female simultaneously.
    The methods are demonstrated in two perspectives: First is by applying them to Malaysian mortality data and second
    is by comparing the significance of the methods to the annuity pricing. The performances of the two methods are then
    compared in which has been found that the augmented common factor model is more superior in terms of historical fit,
    forecast performance, and annuity pricing.
Filters
Contact Us

Please provide feedback to Administrator (afdal@afpm.org.my)

External Links