Displaying all 16 publications

  1. Lim LK, Yap SL, Bradley DA
    PLoS One, 2018;13(1):e0188009.
    PMID: 29309425 DOI: 10.1371/journal.pone.0188009
    The plasma focus device discussed herein is a Z-pinch pulsed-plasma arrangement. In this, the plasma is heated and compressed into a cylindrical column, producing a typical density of > 1025 particles/m3 and a temperature of (1-3) × 107 oC. The plasma focus has been widely investigated as a radiation source, including as ion-beams, electron-beams and as a source of x-ray and neutron production, providing considerable scope for use in a variety of technological situations. Thus said, the nature of the radiation emission depends on the dynamics of the plasma pinch. In this study of the characteristics of deuteron-beam emission, in terms of energy, fluence and angular distribution were analyzed. The 2.7 kJ plasma focus discharge has been made to operate at a pressure of less than 1 mbar rather than at its more conventional operating pressure of a few mbar. Faraday cup were used to determine deuteron-beam energy and deuteron-beam fluence per shot while CR-39 solid-state nuclear track detectors were employed in studying the angular distribution of deuteron emission. Beam energy and deuteron-beam fluence per shot have been found to be pressure dependent. The largest value of average deuteron energy measured for present conditions was found to be (52 ± 7) keV, while the deuteron-beam fluence per shot was of the order of 1015 ions/m2 when operated at a pressure of 0.2 mbar. The deuteron-beam emission is in the forward direction and is observed to be highly anisotropic.
  2. Nga AD, Yap SL, Samsudin A, Abdul-Rahman PS, Hashim OH, Mimiwati Z
    BMC Ophthalmol, 2014;14:33.
    PMID: 24655889 DOI: 10.1186/1471-2415-14-33
    Altered levels of specific matrix metalloproteinases (MMPs) and tissue inhibitors of metalloproteinases (TIMPs) in the aqueous humour of primary open-angle glaucoma (POAG) eyes have been described. In this study, levels of specific MMPs and TIMPs in the aqueous humour of primary angle-closure glaucoma (PACG) eyes were measured and compared with those of POAG as well as non-glaucoma control eyes.
  3. Hashim SA, Samsudin FN, Wong CS, Abu Bakar K, Yap SL, Mohd Zin MF
    Arch Biochem Biophys, 2016 09 01;605:34-40.
    PMID: 27056469 DOI: 10.1016/j.abb.2016.03.032
    A modular typed dielectric barrier discharge (DBD) device is designed and tested for air and water remediation. The module is made of a number of DBD tubes that can be arranged in series or parallel. Each of the DBD tubes comprises inner electrode enclosed with dielectric barrier and arranged as such to provide a gap for the passage of gases. Non-thermal plasma generated in the gap effectively creates gaseous chemical reactions. Its efficacy in the remediation of gas stream containing high NOx, similar to diesel emission and wastewater containing latex, are presented. A six tubes DBD module has successfully removed more than 80% of nitric oxide from the gas stream. In another arrangement, oxygen was fed into a two tubes DBD to generate ozone for treatment of wastewater. Samples of wastewater were collected from a treatment pond of a rubber vulcanization pilot plant. The water pollution load was evaluated by the chemical oxygen demand (COD) and biological oxygen demand (BOD5) values. Preliminary results showed some improvement (about 13%) on the COD after treatment and at the same time had increased the BOD5 by 42%. This results in higher BOD5/COD ratio after ozonation which indicate better biodegradability of the wastewater.
  4. Mohd Nasir N, Lee BK, Yap SS, Thong KL, Yap SL
    Arch Biochem Biophys, 2016 09 01;605:76-85.
    PMID: 27046340 DOI: 10.1016/j.abb.2016.03.033
    Cold plasma is partly ionized non-thermal plasma generated at atmospheric pressure. It has been recognized as an alternative approach in medicine for sterilization of wounds, promotion of wound healing, topical treatment of skin diseases with microbial involvement and treatment of cancer. Cold plasma used in wound therapy inhibits microbes in chronic wound due to its antiseptic effects, while promoting healing by stimulation of cell proliferation and migration of wound relating skin cells. In this study, two types of plasma systems are employed to generate cold plasma: a parallel plate dielectric barrier discharge and a capillary-guided corona discharge. Parameters such as applied voltage, discharge frequency, treatment time and the flow of the carrier gas influence the cold plasma chemistry and therefore change the composition and concentration of plasma species that react with the target sample. Chronic wound that fails to heal often infected by multidrug resistant organisms makes them recalcitrant to healing. Methicillin-resistant Staphylococcus aureus (MRSA) and Pseudomonas aeruginosa (Pseudomonas aeruginosa) are two common bacteria in infected and clinically non-infected wounds. The efficacies of the cold plasma generated by the two designs on the inactivation of three different isolates of MRSA and four isolates of P. aeruginosa are reported here.
  5. Chee WS, Suriah AR, Zaitun Y, Chan SP, Yap SL, Chan YM
    Asia Pac J Clin Nutr, 2002;11(2):142-6.
    PMID: 12074181
    The objective of this study was to compare the dietary calcium intakes assessed by a quantitative food frequency questionnaire (FFQ) and the three-day food record method in 230 Chinese postmenopausal women aged 50-65 years in Kuala Lumpur. The results showed that the mean calcium intake from the dietary records was 447+/-168 mg/day and 499+/-211 mg/day from the FFQ. The mean difference in intake by the two methods was 51.3 mg (95% CI = -30.8-77.9; SD = 181.2, P>0.05), which did not differ significantly from zero. Pearson's correlation coefficient of 0.56 was obtained between the two methods. Ninety-five percent of the individuals classified by food records fell into the same or within-one-quartile category when classified by FFQ. Forty-eight percent were classified into the same quartile by both methods. No subjects were grossly misclassified by the FFQ. The FFQ correctly identified subjects with calcium intakes below the Malaysian recommended daily allowance (450 mg/day) with 60% specificity and with 92% specificity for women consuming less than 800 mg calcium/day. In conclusion, the FFQ developed was a useful, rapid clinical tool for assessing calcium intake and identifying postmenopausal Chinese women with low calcium intakes in Malaysia.
  6. Babji AS, Alina AR, Seri Chempaka MY, Sharmini T, Basker R, Yap SL
    Int J Food Sci Nutr, 1998 Sep;49(5):327-32.
    PMID: 10367001
    Four formulations of burgers, prepared with 65% lean meat and 15% fat consisting of RBD palm stearin (PS), Socfat 4000P and Socfat 4100P and beef fat (BF) as control were evaluated for solid fat content (SFC), slip melting point (SMP), cooking loss, proximate analysis (moisture, fat and protein), colour, i.e. lightness ('L'), redness ('a') and yellowness ('b'), free fatty acid (FFA), iodine value (IV), thiobarbituric acid (TBA) and texture profile analysis (TPA). Sensory evaluation was carried out for texture, juiciness, aroma, oiliness and overall acceptance. SFC and SMP for raw and cooked SF4000P beef burgers were closest to BF control burgers, falling into the range of 35-40 degrees C. Cooking loss was highest for PS burgers, there were no significant differences (P > 0.05) amongst BF, SF4000P and SF4100P burgers. Proximate analysis on raw burgers showed SF4000P to contain high fat and lowest moisture contents. Objective textural measurements using texture profile analysis (TPA) for all cooked burgers showed no significant differences (P > 0.05) for springiness and cohesiveness. Variation of values among the formulations for hardness, gumminess and chewiness are explained by the differences of SFC for beef burgers with various types of fats. Raw and cooked PS burgers have the lightest 'L' values compared with other fat-substituted burgers while BF, SF4000P and SF4100P indicated no significant differences (P > 0.05) for 'L', 'a' and 'b' values. Beef fat showed the highest amount of free fatty acids (FFA) compared to palm oil samples. For the iodine value (IV), SF4000P showed the highest value which means that it contained the highest level of unsaturated fatty acids followed by PS, BF and SF4100P successively. SF4000P had the highest TBA values followed successively by BF, PS and SF4100P. For sensory evaluation, PS burgers had the least oily taste. This may be due to its high cooking loss. Taste panelists could not differentiate burgers with substituted vegetable fats against the control burgers.
  7. Yap SL, Wong SS, Chew KS, Kueh JS, Siew KL
    Asian Pac J Cancer Prev, 2020 Oct 01;21(10):3077-3083.
    PMID: 33112570 DOI: 10.31557/APJCP.2020.21.10.3077
    BACKGROUND: Patient's financial ability is always the most critical imputes to treatment choice and adherence; as it translates into health outcomes such as survival rate and quality of life. Cancer care is likely to affect the patient's financial well-being, putting huge financial pressure to the families. Therefore, it is imperative to understand the confounding factors of financial toxicity among cancer survivors along the course of survivorship.

    METHODS: This study was designed in the form of cross-sectional analysis, in which, cancer survivors were recruited from the Sarawak General Hospital, the largest tertiary and referral public hospital in Sarawak. To capture the financial toxicity of the cancer survivors, the Comprehensive Score for Financial Toxicity (COST) instrument in its validated form was adopted. Multivariable logistic regression analysis was applied to determine the relationship between financial toxicity (FT) and its predictors.

    RESULTS: The median age of the 461 cancer survivors was 56 while the median score of COST was 22.0. Besides, finding from multivariable logistic regression revealed that low income households (OR: 6.893, 95% CI, 3.109-15.281) were susceptible to higher risk of financial toxicity, while elderly survivors above 50 years old reported a lower risk in financial toxicity. Also, survivors with secondary schooling (OR:0.240; 95%CI, 0.110-0.519) and above [College or university (OR: 0.242; 95% CI, 0.090-0.646)] suffer a lower risk of FT.

    CONCLUSION: Financial toxicity was found to be associated with survivors age, household income and educational level. In the context of cancer treatment within public health facility, younger survivors, households from B40 group and individual with educational attainment below the first level schooling in the Malaysian system of education are prone to greater financial toxicity. Therefore, it is crucial for healthcare policymakers and clinicians to deliberate the plausible risk of financial toxicity borne by the patient amidst the treatment process.

  8. Nee CH, Yap SL, Tou TY, Chang HC, Yap SS
    Sci Rep, 2016 Sep 23;6:33966.
    PMID: 27659184 DOI: 10.1038/srep33966
    Carbon nanomaterials exhibit novel characteristics including enhanced thermal, electrical, mechanical, and biological properties. Nanodiamonds; first discovered in meteorites are found to be biocompatible, non-toxic and have distinct optical properties. Here we show that nanodiamonds with the size of <5 nm are formed directly from ethanol via 1025 nm femtosecond laser irradiation. The absorption of laser energy by ethanol increased non-linearly above 100 μJ accompanied by a white light continuum arises from fs laser filamentation. At laser energy higher than 300 μJ, emission spectra of C, O and H in the plasma were detected, indicating the dissociation of C2H5OH. Nucleation of the carbon species in the confined plasma within the laser filaments leads to the formation of nanodiamonds. The energy dependence and the roles of the nonlinear phenomenon to the formation of homogeneous nanodiamonds are discussed. This work brings new possibility for bottom-up nanomaterials synthesis based on nano and ultrafast laser physics.
  9. Yong TSM, Panting AJ, Juatan N, Perialathan K, Ahmad M, Ahmad Sanusi NH, et al.
    Vet Med Sci, 2021 Sep;7(5):1558-1563.
    PMID: 34137200 DOI: 10.1002/vms3.547
    BACKGROUND: Zoonoses among household pets are recognized as disease and infections transmitted between animals and humans. World Health Organization-estimated zoonotic diseases have contributed about one billion cases of illness and millions of mortalities every year. Despite the emerging and re-emerging zoonotic disease, most pet owners are unaware of the risks posed by their pets. As there are a lack of studies assessing infections at home, this study aimed to develop and validate a cognitive, affective and behaviour questionnaire (CAB-ZDQ) to assess household pets' zoonotic diseases.

    METHODS: This paper covers detailed explanation on the various developmental and validation process stages of the CAB zoonotic disease questionnaire development. The development phase comprised thorough literature search, focus group discussion, expert panel assessment and review. The validation process included pre-test and pilot testing, data analysis of results, analysis of internal consistency and the development of the final version of the questionnaire. Participants selected represented main ethnicities, gender, levels of education and population type (urban/rural) in the Klang Valley area.

    RESULTS: The items in the questionnaire has undergone various changes in structurally and linguistically. The final refined CAB questionnaire consists of 14 items cognitive (no items removed at pilot phase), nine items affective (one item removed at pilot phase) and five items behaviour (no items removed from pre-test phase), respectively. Reliability analysis revealed Cronbach's alpha values were 0.700 (cognitive) and 0.606 (affective) which indicated good internal consistency after item reduction.

    CONCLUSIONS: The developed questionnaire has proved its feasibility in assessing the Malaysian general population cognitive, affective and behavior regarding the household pets' zoonotic diseases.

  10. Zhang Q, Wang PI, Ong GL, Tan SH, Tan ZW, Hii YH, et al.
    Polymers (Basel), 2019 May 09;11(5).
    PMID: 31075895 DOI: 10.3390/polym11050840
    In this work, polymers of poly[(9,9-dioctylfluorenyl-2,7-diyl)-co-triphenylamine] with side chains containing: pyrene (C1), diphenyl (C2), naphthalene (C3), and isopropyl (C6) structures were synthesized via a Suzuki coupling reaction. The structures were verified using NMR and cyclic voltammetry measurements provide the HOMO and LUMO of the polymers. The polymer with pyrene (C1) and naphthalene (C3) produced photoluminescence in the green while the polymer with the side chain containing diphenyl (C2) and isopropyl (C6) produce dual emission peaks of blue-green photoluminescence (PL). In order to examine the electroluminescence properties of the polymers, the solutions were spin-coated onto patterned ITO anode, dried, and subsequently coated with an Al cathode layer to form pristine single layer polymer LEDs. The results are compared to a standard PFO sample. The electroluminescence spectra resemble the PL spectra for C1 and C3. The devices of C2, C3, and C6 exhibit voltage-dependent EL. An additional red emission peak was detected for C2 and C6, resulting in spectra with peaks at 435 nm, 490 nm, and 625 nm. The effects of the side chains on the spectral characteristics of the polymer are discussed.
  11. Bakar KA, Muhamad NA, Sarpin MA, Shaharudin S, Sidhu S, Yap SL, et al.
    Pediatr Nephrol, 2023 Jun;38(6):1897-1905.
    PMID: 36272027 DOI: 10.1007/s00467-022-05774-0
    BACKGROUND: The PedsQL 3.0 End Stage Renal Disease (ESRD) Module is a well-accepted instrument internationally but it is not available in the local language. We aimed to validate the Bahasa Melayu (Malay language) version and determine the health-related quality of life (HRQoL) scores amongst children with CKD in Malaysia.

    METHODS: The source questionnaire in English was translated into Bahasa Melayu. Linguistic validation guidelines by the MAPI Research Institute were followed. The already validated Bahasa Melayu PedsQL 4.0 Generic Core Scales was used for comparison. Sociodemographic data were collected during the interview. Statistical analyses were performed using SPSS version 25.0.

    RESULTS: Sixty-nine children aged 8 to 18 with CKD stages 4 and 5, with or without dialysis, and their caregivers were recruited. Mean age was 12.62 ± 2.77 (SD). Evaluation of the PedsQL 3.0 ESRD Module Bahasa Melayu version demonstrated good internal consistency (Cronbach alpha 0.82). There was good agreement between child self-report and parent proxy report in all domains; average intraclass correlation coefficients (ICC) were 0.78, 95% CI (0.71, 0.84). Scores obtained from Generic 4.0 scales correlated with the disease-specific ESRD 3.0 scale, Spearman's rho = 0.32, p = 0.007. The Kruskal-Wallis H test indicated that there were no significant differences between stages of CKD and their respective mean HRQoL score, χ2(2) = 2.88, p = 0.236.

    CONCLUSIONS: The PedsQL 3.0 ESRD Module Bahasa Melayu version is a reliable and feasible tool for cross-cultural adaptation. A longer prospective study may help better illustrate the quality of life in this group of children.

  12. Xu H, Detto M, Fang S, Chazdon RL, Li Y, Hau BCH, et al.
    Commun Biol, 2020 06 19;3(1):317.
    PMID: 32561898 DOI: 10.1038/s42003-020-1041-y
    Legumes provide an essential service to ecosystems by capturing nitrogen from the atmosphere and delivering it to the soil, where it may then be available to other plants. However, this facilitation by legumes has not been widely studied in global tropical forests. Demographic data from 11 large forest plots (16-60 ha) ranging from 5.25° S to 29.25° N latitude show that within forests, leguminous trees have a larger effect on neighbor diversity than non-legumes. Where soil nitrogen is high, most legume species have higher neighbor diversity than non-legumes. Where soil nitrogen is low, most legumes have lower neighbor diversity than non-legumes. No facilitation effect on neighbor basal area was observed in either high or low soil N conditions. The legume-soil nitrogen positive feedback that promotes tree diversity has both theoretical implications for understanding species coexistence in diverse forests, and practical implications for the utilization of legumes in forest restoration.
  13. Russo SE, McMahon SM, Detto M, Ledder G, Wright SJ, Condit RS, et al.
    Nat Ecol Evol, 2021 Feb;5(2):174-183.
    PMID: 33199870 DOI: 10.1038/s41559-020-01340-9
    Resource allocation within trees is a zero-sum game. Unavoidable trade-offs dictate that allocation to growth-promoting functions curtails other functions, generating a gradient of investment in growth versus survival along which tree species align, known as the interspecific growth-mortality trade-off. This paradigm is widely accepted but not well established. Using demographic data for 1,111 tree species across ten tropical forests, we tested the generality of the growth-mortality trade-off and evaluated its underlying drivers using two species-specific parameters describing resource allocation strategies: tolerance of resource limitation and responsiveness of allocation to resource access. Globally, a canonical growth-mortality trade-off emerged, but the trade-off was strongly observed only in less disturbance-prone forests, which contained diverse resource allocation strategies. Only half of disturbance-prone forests, which lacked tolerant species, exhibited the trade-off. Supported by a theoretical model, our findings raise questions about whether the growth-mortality trade-off is a universally applicable organizing framework for understanding tropical forest community structure.
  14. Needham JF, Johnson DJ, Anderson-Teixeira KJ, Bourg N, Bunyavejchewin S, Butt N, et al.
    Glob Chang Biol, 2022 Jan 25.
    PMID: 35080088 DOI: 10.1111/gcb.16100
    The growth and survival of individual trees determine the physical structure of a forest with important consequences for forest function. However, given the diversity of tree species and forest biomes, quantifying the multitude of demographic strategies within and across forests and the way that they translate into forest structure and function remains a significant challenge. Here, we quantify the demographic rates of 1,961 tree species from temperate and tropical forests and evaluate how demographic diversity (DD) and demographic composition (DC) differ across forests, and how these differences in demography relate to species richness, aboveground biomass, and carbon residence time. We find wide variation in DD and DC across forest plots, patterns that are not explained by species richness or climate variables alone. There is no evidence that DD has an effect on either aboveground biomass or carbon residence time. Rather, the DC of forests, specifically the relative abundance of large statured species, predicted both biomass and carbon residence time. Our results demonstrate the distinct demographic compositions of globally distributed forests, reflecting biogeography, recent history, and current plot conditions. Linking the demographic composition of forests to resilience or vulnerability to climate change, will improve the precision and accuracy of predictions of future forest composition, structure and function.
  15. Slik JW, Arroyo-Rodríguez V, Aiba S, Alvarez-Loayza P, Alves LF, Ashton P, et al.
    Proc Natl Acad Sci U S A, 2015 Jun 16;112(24):7472-7.
    PMID: 26034279 DOI: 10.1073/pnas.1423147112
    The high species richness of tropical forests has long been recognized, yet there remains substantial uncertainty regarding the actual number of tropical tree species. Using a pantropical tree inventory database from closed canopy forests, consisting of 657,630 trees belonging to 11,371 species, we use a fitted value of Fisher's alpha and an approximate pantropical stem total to estimate the minimum number of tropical forest tree species to fall between ∼ 40,000 and ∼ 53,000, i.e., at the high end of previous estimates. Contrary to common assumption, the Indo-Pacific region was found to be as species-rich as the Neotropics, with both regions having a minimum of ∼ 19,000-25,000 tree species. Continental Africa is relatively depauperate with a minimum of ∼ 4,500-6,000 tree species. Very few species are shared among the African, American, and the Indo-Pacific regions. We provide a methodological framework for estimating species richness in trees that may help refine species richness estimates of tree-dependent taxa.
  16. Slik JWF, Franklin J, Arroyo-Rodríguez V, Field R, Aguilar S, Aguirre N, et al.
    Proc Natl Acad Sci U S A, 2018 02 20;115(8):1837-1842.
    PMID: 29432167 DOI: 10.1073/pnas.1714977115
    Knowledge about the biogeographic affinities of the world's tropical forests helps to better understand regional differences in forest structure, diversity, composition, and dynamics. Such understanding will enable anticipation of region-specific responses to global environmental change. Modern phylogenies, in combination with broad coverage of species inventory data, now allow for global biogeographic analyses that take species evolutionary distance into account. Here we present a classification of the world's tropical forests based on their phylogenetic similarity. We identify five principal floristic regions and their floristic relationships: (i) Indo-Pacific, (ii) Subtropical, (iii) African, (iv) American, and (v) Dry forests. Our results do not support the traditional neo- versus paleotropical forest division but instead separate the combined American and African forests from their Indo-Pacific counterparts. We also find indications for the existence of a global dry forest region, with representatives in America, Africa, Madagascar, and India. Additionally, a northern-hemisphere Subtropical forest region was identified with representatives in Asia and America, providing support for a link between Asian and American northern-hemisphere forests.
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