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  1. Fulltext Challenges and Opportunities in the Malaysian Health Care System
    Mohd Tahir NA, Li SC, Thomas P
    Value Health, 2014 Nov;17(7):A802.
    PMID: 27203017 DOI: 10.1016/j.jval.2014.08.499
  2. Ionic composition of rainwater at selected sites of Kuantan, Pahang, Malaysia: a preliminary study
    Tay JH, Jaafar S, Mohd Tahir N
    Bull Environ Contam Toxicol, 2014 Mar;92(3):329-33.
    PMID: 24435136 DOI: 10.1007/s00128-014-1203-z
    A short-term investigation on the chemical composition of rainwater was carried out at five selected sampling stations in Kuantan district, Pahang, Malaysia. Sampling of rainwater was conducted by event basis between September and November 2011. Rainwater samples were collected using polyethylene containers and the parameters measured were cations (sodium, potassium, ammonium, calcium and magnesium) and anions (chlorides, nitrates and sulphates). The average pH value for rainwater samples was 6.0 ± 0.57 in which most of the sampling sites exhibited pH values >5.6. Calcium and sulphate were the most abundant cation and anion, respectively, whilst the concentrations of other major ions varied according to sampling location.
  3. Composition and sources of aliphatic lipids and sterols in sediments of a tropical island, southern South China Sea: preliminary assessment
    Mohd Tahir N, Pang SY, Abdullah NA, Suratman S
    Environ Monit Assess, 2013 Dec;185(12):10209-16.
    PMID: 23856812 DOI: 10.1007/s10661-013-3325-x
    Near-shore surface sediment was collected from five stations off Redang Island located on the eastern coast of Peninsular Malaysia. Freeze-dried sediments were Soxhlet extracted and then fractionated using column chromatography into aliphatic and polar fractions. Determination of these fractions was carried out using gas chromatography mass spectrometry. The concentration of total resolved aliphatic hydrocarbons in sediments ranged from 157 to 308 ng/g. The distribution of aliphatic fraction showed the presence of n-alkanes ranging from nC15 to nC33 with a minor odd-to-even predominance exhibiting carbon maximum, depending on station, at nC17, nC26, nC29 or nC31. Calculation of Carbon Preference Index (CPI) for CPI(15-33) gave values ranging from 1.09 to 1.46. n-Alkanol in all sediment exhibits even-to-odd carbon predominance ranging from nC16 to nC28 and maximising at nC22. n-Fatty acids distribution ranged from nC14 to nC24 with a dominant maximum at nC16 and exhibiting high values of short chain fatty acids (≤nC20) to long chain fatty acids (>nC20) ratios. Unsaturated fatty acids, particularly nC16:1 and nC18:1 is also ubiquitous in all samples. Cholesterol is the most abundant compound amongst the sterol group ranging from 42.8 to 62.6% of the total sterols. β-Sitosterol, brassicasterol and stigmasterol, are also present but of relatively lower amount. These observations suggest that the aliphatic lipids and sterols in the study area originate, mainly, from biogenic sources of marine microbial with minor contribution from epiticular waxes of terrestrial plants.
  4. Economic burden of osteoporosis-related hip fracture in Asia: a systematic review
    Mohd-Tahir NA, Li SC
    Osteoporos Int, 2017 07;28(7):2035-2044.
    PMID: 28314898 DOI: 10.1007/s00198-017-3985-4
    This review analyzes the economic costs of HF in Asia. The availability and quality of studies on the burden of osteoporosis in Asia are very scarce. There is a need to encourage more quality cost of osteoporosis studies based on standardized methods to convince healthcare authorities in implementing appropriate strategies.
    INTRODUCTION: Osteoporosis fractures, especially hip fractures, impose large economic costs to governments and societies. This review aimed to systematically analyze available evidence on healthcare costs associated with osteoporosis-related hip fractures (HF) in Asia.
    METHODS: Articles were systematically sought from databases including PubMed, EMBASE, and EBSCOHost between 2000 and 2015. Total costs associated with HF care, the cost components, and length of stays were retrieved and analyzed. Study designs were also qualitatively analyzed.
    RESULTS: The availability of published studies on economic burden of HF in Asia is severely lacking with only 15 articles met the inclusion criteria. Even among the included studies, only two studies reported comprehensive costs evaluating all costs including indirect or intangible costs. Most studies satisfactorily reported criteria for conducting economic evaluation, but large variations existed in the methodological design. Due to study design and other influencing factors, large variation in the cost of HF treatment from US$774 to US$14,198.90 (median S$2943), representing an average of 18.95% (range: 3.58-57.05%) of the countries' 2014 GDP/capita, was observed. This highlighted the heavy burden of managing HF in Asia with about 40% of the included studies reported using more than one third of GDP/capita.
    CONCLUSION: There is a paucity of burden of illness studies of osteoporosis in the Asian region. For the few available studies, there was a lack of standardization in methodological approach in evaluating the economic burden of the disease. There is a need to encourage more quality burden of illness studies of osteoporosis to inform policymakers in healthcare planning.
  5. Degradation and mineralization kinetics of acephate in humid tropic soils of Malaysia
    Chai LK, Wong MH, Mohd-Tahir N, Hansen HC
    Chemosphere, 2010 Apr;79(4):434-40.
    PMID: 20189217 DOI: 10.1016/j.chemosphere.2010.01.046
    Acephate is poorly sorbed to soil, thus the risk of leaching to the aquatic environment is high if it is not quickly degraded. The effect of soil moisture, temperature, microbial activity and application rate on acephate degradation has been studied in three Malaysian soils to examine and identify critical variables determining its degradation and mineralization kinetics. First-order kinetics could be used to describe degradation in all cases (r(2)>0.91). Acephate degraded faster in air-dry (t((1/2)) 9-11 d) and field capacity (t((1/2)) 10-16d) soils than in the wet soils (t((1/2)) 32-77 d). The activation energy of degradation was in the range 17-28 kJ mol(-1) and significantly higher for the soil with higher pH and lower clay and iron oxide contents. Soil sterilization caused a 3- to 10-fold decrease in degradation rates compared to non-sterile soils (t((1/2)) 53-116 d) demonstrating that acephate degradation is mainly governed by microbial processes. At 5-fold increase in application rates (25 microg g(-1)), half-life increased slightly (t((1/2)) 13-19 d) or was unaffected. Half-life from acephate mineralization was similar to those from degradation but much longer at the 5-fold increase in acephate application rates (t((1/2)) 41-96 d) demonstrating that degradation of metabolites is rate limiting. Thus, application of acephate should be restricted or avoided during wet seasons with heavy rainfall and flooded soil as in paddy cultivation. Sandy soils with low microbial activity are more prone to acephate leaching than clay soils rich in humic matter.
  6. A preliminary study of the distribution of selected trace metals in the Besut River basin, Terengganu, Malaysia
    Suratman S, Hang HC, Shazili NA, Mohd Tahir N
    Bull Environ Contam Toxicol, 2009 Jan;82(1):16-9.
    PMID: 18665317 DOI: 10.1007/s00128-008-9507-5
    This paper presents a preliminary result carried out in the Besut River basin, Terengganu, Malaysia to determine the selected trace metal concentrations. Concentrations of dissolved Pb, Cu, and Fe during the present study were in the range of 3.3-8.3 microg/L Pb, 0.1-0.3 microg/L Cu, and 1.1-12.3 microg/L Fe. For the particulate fraction concentrations of Pb, Cu, and Fe ranged from 1.0 to 3.6 microg/L, 0.3 to 2.8 microg/L, and 114 to 1,537 microg/L, respectively. The concentrations of metals in this study area, in general, were lower than those reported for other study areas. Higher metal concentrations measured in the wet monsoon season suggest that the input was mainly due to terrestrial runoff.
  7. Dissipation of acephate, chlorpyrifos, cypermethrin and their metabolites in a humid-tropical vegetable production system
    Chai LK, Mohd-Tahir N, Bruun Hansen HC
    Pest Manag Sci, 2009 Feb;65(2):189-96.
    PMID: 18979521 DOI: 10.1002/ps.1667
    High amounts of insecticides are often used in intensive tropical vegetable production systems. Their persistence and residues in vegetables and soils need to be studied to ensure food safety and environmental stability. The dissipation of acephate, chlorpyrifos, cypermethrin and their metabolites was studied in green mustard [Brassica juncea (L.) Coss.] and soils. Two treatments, Impact 75 (acephate) and Agent 505 (cypermethrin plus chlorpyrifos), were applied 4 times at weekly intervals.
  8. Investigation of aliphatic hydrocarbons in core sediments of Brunei Bay, East Malaysia
    Pang SY, Suratman S, Tay JH, Mohd Tahir N
    Mar Pollut Bull, 2021 Oct;171:112736.
    PMID: 34325152 DOI: 10.1016/j.marpolbul.2021.112736
    The distribution of aliphatic hydrocarbons in three sediment cores from Brunei Bay was investigated in order to understand their sources and the biogeochemical processes of these hydrocarbons. The total concentrations of C15 to C37n-alkanes ranged from 0.70 to 16.5 μg g-1. Traces of hopanes with C29-C31 carbon homologs were detected in the study area. The carbon preference index (CPI15-37) ranged from 1.23 to 3.42 coupled with the natural n-alkane ratio (NAR19-32) ratios (1.52 to 5.34), and the presence of unresolved complex mixtures and hopanes, suggested slight contamination by anthropogenic hydrocarbons, presumably derived from activities along the coasts. The presence of C27 trisnorhopene and diploptene, as well as their association with long-chain and short-chain n-alkanes, revealed a depositional environment of organic matter in the sediment cores.
  9. Comparing retainers constructed on conventional stone models and on 3D printed models: a randomized crossover clinical study
    Mohd Tahir N, Wan Hassan WN, Saub R
    Eur J Orthod, 2019 08 08;41(4):370-380.
    PMID: 30321319 DOI: 10.1093/ejo/cjy063
    OBJECTIVES: The aim of this study was to compare vacuum-formed thermoplastic retainers (VFRs) constructed on stone models (VFR-CV) and those constructed on three-dimensional (3D) printed models (VFR-3D) based on patients' perspective and post-treatment stability.

    STUDY DESIGN: The research was designed as a crossover, randomized control trial.

    MATERIALS AND METHODS: Subjects comprised patients receiving fixed appliances at a teaching institution and indicated for VFRs. Post-treatment stone models were scanned with a structured-light scanner. A fused deposition modelling machine was used to construct acrylonitrile-butadiene-styrene (ABS)-based replicas from the 3D scanned images. VFRs were fabricated on the original stone and printed models. Analysis comprised independent t-tests and repeated measures analysis of variance.

    RANDOMIZATION: Subjects were allocated to two groups using Latin squares methods and simple randomization. A week after debond, subjects received either VFR-CV first (group A) or VFR-3D first (group B) for 3 months, then the interventions were crossed over for another 3 months.

    BLINDING: In this single-blinded study, subjects were assigned a blinding code for data entry; data were analysed by a third party.

    OUTCOME MEASURES: The primary outcome measured was oral health-related quality of life (OHRQoL) based on Oral Health Impact Profile-14 (OHIP-14). Secondary outcome was post-treatment stability measured using Little's Irregularity Index (LII).

    RESULTS: A total of 30 subjects (15 in each group) were recruited but 3 dropped out. Analysis included 13 subjects from group A and 14 subjects from group B. Group A showed an increase in LII (P < 0.05) after wearing VFR-CV and VFR-3D, whereas group B had no significant increase in LII after wearing both VFRs. Both groups reported significant improvement in OHRQoL after the first intervention but no significant differences after the second intervention. LII changes and OHIP-14 scores at T2 and T3 between groups, and overall between the retainers were not significantly different. No harm was reported during the study.

    CONCLUSION: VFRs made on ABS-based 3D printed models showed no differences in terms of patients' OHRQoL and stability compared with conventionally made retainers.

    REGISTRATION: NCT02866617 (ClinicalTrials.gov).

  10. Nutrient availability in the Setiu Wetland Lagoon, Malaysia: trends, possible causes and environmental impacts
    Poh SC, Ng NCW, Suratman S, Mathew D, Mohd Tahir N
    Environ Monit Assess, 2018 Dec 04;191(1):3.
    PMID: 30515582 DOI: 10.1007/s10661-018-7128-y
    The objective of this study was to identify the spatial and temporal variabilities of selected nutrients in the Setiu Wetlands Lagoon (SWL), Malaysia. Water samples were collected quarterly at ten monitoring sites. This study presents results from a 10-year field investigation (2003 to 2010 and 2014 to 2015) of water quality in the SWL. For the spatial pattern, four clusters were identified with hierarchical cluster analysis. Analysis of the temporal trend shows that the high total suspended solid loading in 2010 was due to large-scale land clearing upstream of the SWL. The enrichment of ammonium after 2010 could plausibly be due to land-based aquaculture diffuse discharges. In 2005-2007, expansion of oil palm plantations within the Setiu catchment had doubled the phosphorus concentration in the SWL. The natural and anthropogenic alterations of the lagoon inlets profoundly influenced the spatial distribution patterns of nutrients in the SWL. These results suggest that intense anthropogenic disturbances close to the SWL accounted for the water quality deterioration.
  11. A green solvent holder in electro-mediated microextraction for the extraction of phenols in water
    Chong YT, Mohd Ariffin M, Mohd Tahir N, Loh SH
    Talanta, 2018 Jan 01;176:558-564.
    PMID: 28917790 DOI: 10.1016/j.talanta.2017.08.068
    Electro-mediated microextraction (EMM) combined with micro-high performance liquid chromatography-ultraviolet detection was successfully developed for the determination of selected phenols, namely 4-chlorophenol (4CP), 2-nitrophenol (2NP) and 2,4-dichlorophenols (2,4 DCP) in water. A solvent-impregnated agarose gel disc was utilized as a solvent holder in this study. Under optimum extraction conditions, the method showed good linearity in the range of 0.1-250µgL-1, 0.3-250µgL-1and 0.2-500µgL-1for 4CP, 2NP and 2,4 DCP, respectively with correlation coefficients of ≥ 0.9975, ultra-trace LODs (0.03-0.1µgL-1) and satisfactory relative recovery average (85.0-114.1%) for the analysis of selected phenols. The proposed method was rapid and eco-friendly as the solvent holder was constructed using minute amounts of extraction solvent immobilized within the biodegradable agarose gel disc. A comparative microextraction technique termed solvent-impregnated agarose gel liquid phase microextraction (AG-LPME) was re-optimized and validated for the extraction of phenols in water. The method offered good linearity, ultra-trace LODs ranging 0.1-0.5µgL-1and satisfactory average of relative recovery (86.1-114.1%). The EMM was superior in terms of sensitivity and time-effectiveness compared to AG-LPME. Both techniques combine extraction and pre-concentration in mini-scaled approaches using an eco-friendly solvent holder that fulfil the green chemistry concept.
  12. Dissipation and leaching of acephate, chlorpyrifos, and their main metabolites in field soils of Malaysia
    Chai LK, Mohd-Tahir N, Hansen S, Hansen HC
    J Environ Qual, 2009 Apr 27;38(3):1160-9.
    PMID: 19398513 DOI: 10.2134/jeq2007.0644
    Preventive treatment with insecticides at high dosing rates before planting of a new crop- soil drenching- is a common practice in some tropical intensive cropping systems, which may increase the risk of leaching, soil functioning, and pesticide uptake in the next crop. The degradation rates and migration of acephate and chlorpyrifos and their primary metabolites, methamidophos and 3,5,6-trichloropyridinol (TCP), have been studied in clayey red yellow podzolic (Typic Paleudults), alluvial (Typic Udorthents), and red yellow podzolic soils (Typic Kandiudults) of Malaysia under field conditions. The initial concentrations of acephate and chlorpyrifos in topsoils were found to strongly depend on solar radiation. Both pesticides and their metabolites were detected in subsoils at the deepest sampling depth monitored (50 cm) and with maximum concentrations up to 2.3 mg kg(-1) at soil depths of 10 to 20 cm. Extraordinary high dissipation rates for weakly sorbed acephate was in part attributed to preferential flow which was activated due to the high moisture content of the soils, high precipitation and the presence of conducting macropores running from below the A horizons to at least 1 m, as seen from a dye tracer experiment. Transport of chlorpyrifos and TCP which both sorb strongly to soil organic matter was attributed to macropore transport with soil particles. The half-lives for acephate in topsoils were 0.4 to 2.6 d while substantially longer half-lives of between 12.6 and 19.8 d were observed for chlorpyrifos. The transport through preferential flow of strongly sorbed pesticides is of concern in the tropics.
  13. Source identification of particulate matter in a semi-urban area of Malaysia using multivariate techniques
    Wahid NB, Latif MT, Suan LS, Dominick D, Sahani M, Jaafar SA, et al.
    Bull Environ Contam Toxicol, 2014 Mar;92(3):317-22.
    PMID: 24435135 DOI: 10.1007/s00128-014-1201-1
    This study aims to determine the composition and sources of particulate matter with an aerodynamic diameter of 10 μm or less (PM10) in a semi-urban area. PM10 samples were collected using a high volume sampler. Heavy metals (Fe, Zn, Pb, Mn, Cu, Cd and Ni) and cations (Na(+), K(+), Ca(2+) and Mg(2+)) were detected using inductively coupled plasma mass spectrometry, while anions (SO4 (2-), NO3 (-), Cl(-) and F(-)) were analysed using Ion Chromatography. Principle component analysis and multiple linear regressions were used to identify the source apportionment of PM10. Results showed the average concentration of PM10 was 29.5 ± 5.1 μg/m(3). The heavy metals found were dominated by Fe, followed by Zn, Pb, Cu, Mn, Cd and Ni. Na(+) was the dominant cation, followed by Ca(2+), K(+) and Mg(2+), whereas SO4 (2-) was the dominant anion, followed by NO3 (-), Cl(-) and F(-). The main sources of PM10 were the Earth's crust/road dust, followed by vehicle emissions, industrial emissions/road activity, and construction/biomass burning.
  14. Determination of trace metals in airborne particulate matter of Kuala Terengganu, Malaysia
    Mohd Tahir N, Poh SC, Suratman S, Ariffin MM, Shazali NA, Yunus K
    Bull Environ Contam Toxicol, 2009 Aug;83(2):199-203.
    PMID: 19436928 DOI: 10.1007/s00128-009-9751-3
    Results from the present study in Kuala Terengganu, Malaysia indicated a significant spatial variation but generally the total suspended particulate concentrations (mean = 17.2-148 microg/m(3)) recorded were below the recommended Malaysia guideline for total suspended particulate (mean of 24-h measurement = 260 microg/m(3)). Some of the elemental composition of particulate aerosol is clearly affected by non crustal sources, e.g. vehicular emission sources. Based on correlation and enrichment analyses, the elements could be grouped into two i.e. Pb, Cd and Zn group with sources from vehicular emission (r > 0.6; enrichment factor > 10) and Al, Fe, Mn and Cr group that appears to be of crustal origin (r > 0.6; enrichment factor < 10). It can also be concluded that the mean levels of Pb (1 ng/m(3)), Cd (0.02 ng/m(3)) and Zn (2 ng/m(3)) in the study area are generally lower than other urban areas in Malaysia (Pb < 181 ng/m(3); Cd < 6 ng/m(3); Zn < 192 ng/m(3)).
  15. Input of organic matter in Brunei Bay, East Malaysia, as indicated by sedimentary steroids and multivariate statistics
    Pang SY, Tay JH, Suratman S, Simoneit BRT, Mohd Tahir N
    Mar Pollut Bull, 2020 Jul;156:111269.
    PMID: 32510409 DOI: 10.1016/j.marpolbul.2020.111269
    Brunei Bay is one of the most important marine environments of East Malaysia (South China Sea), covering many productive ecosystems with activities including fisheries, tourism, and main shipping lanes for petroleum transfers. Evaluation of the sources and distributions of steroids in the surface sedimentary organic matter was carried out by gas chromatography-mass spectrometry (GC-MS). The concentrations of the total identified sterols (TIS) ranged between 0.81 and 12.69 μg g-1 dry weight, and the total sterones were between 0.11 and 5.66 μg g-1 dry weight. The coprostanol level was comparatively low (<0.10 μg g-1), and the multi-biomarker proxies indicated that the region did not exhibit significant contamination from sewage effluents. Principal component analysis (PCA) revealed the coastal environment of the study area was dominated by allochthonous (mainly terrestrial) organic matter input.
  16. Fulltext The significance of pyrogenic polycyclic aromatic hydrocarbons in Borneo peat core for the reconstruction of fire history
    Kong SR, Yamamoto M, Shaari H, Hayashi R, Seki O, Mohd Tahir N, et al.
    PLoS One, 2021;16(9):e0256853.
    PMID: 34495997 DOI: 10.1371/journal.pone.0256853
    The reconstruction of fire history is essential to understand the palaeoclimate and human history. Polycyclic aromatic hydrocarbons (PAHs) have been extensively used as a fire marker. In this work, the distribution of PAHs in Borneo peat archives was investigated to understand how PAHs reflect the palaeo-fire activity. In total, 52 peat samples were analysed from a Borneo peat core for the PAH analysis. Pyrogenic PAHs consist of 2-7 aromatic rings, some of which have methyl and ethyl groups. The results reveal that the concentration of pyrogenic PAHs fluctuated with the core depth. Compared to low-molecular-weight (LMW) PAHs, the high-molecular-weight (HMW) PAHs had a more similar depth variation to the charcoal abundance. This finding also suggests that the HMW PAHs were mainly formed at a local fire near the study area, while the LMW PAHs could be transported from remote locations.
  17. Polycyclic aromatic hydrocarbons in coastal sediments of Southern Terengganu, South China Sea, Malaysia: source assessment using diagnostic ratios and multivariate statistic
    Pang SY, Suratman S, Latif MT, Khan MF, Simoneit BRT, Mohd Tahir N
    Environ Sci Pollut Res Int, 2022 Mar;29(11):15849-15862.
    PMID: 34636003 DOI: 10.1007/s11356-021-16762-6
    Surface sediments along the Southern Terengganu coast (≤7 km from the coast) were analyzed for polycyclic aromatic hydrocarbons (PAHs). The concentrations of 16 USEPA priority polycyclic aromatic hydrocarbons (ΣPAH16) ranged from 2.59 to 155 ng g-1 and their respective alkylated ranged between 8.80 and 24.90 ng g-1. Traces of acephenanthrylene, benzo[c]phenanthrene, thiophenic PAH, and benzonaphthofuran were identified. PAH diagnostic ratios and cross-plots revealed that these sedimentary PAH compounds are derived mainly from pyrogenic sources, primarily from biomass burning and petroleum combustion residues with minor petrogenic input. The high correlations between pyrogenic PAHs to total PAHs (r >0.73, p <0.5), and the Bap/Bep ratio to total PAHs (r = 0.88, p <0.5), suggest that atmospheric deposition and urban runoff are the main deposition pathways. The concentrations of the PAHs in the southern South China Sea fall in the moderate contamination range of 100-1000 ng g-1.
  18. Fulltext The effect of live demonstration and flipped classroom with continuous formative assessment on dental students' orthodontic wire-bending performance
    Sivarajan S, Soh EX, Zakaria NN, Kamarudin Y, Lau MN, Bahar AD, et al.
    BMC Med Educ, 2021 Jun 07;21(1):326.
    PMID: 34098931 DOI: 10.1186/s12909-021-02717-5
    BACKGROUND: Wire-bending skills is commonly taught through live demonstrations (LD) though flipped classroom (FC) method has gained popularity. Continuous formative assessment promotes personalised learning via closely monitored progress, with the identification of students' strengths and weaknesses. This study aims to evaluate the effects of LD and FC teaching methods, supplemented with continuous formative assessment, on dental students' learning of wire-bending skills for six types of removable orthodontic appliance components. A deeper understanding of the relative effectiveness between LD and FC teaching methods can help identify the most appropriate method to achieve student learning objectives, which is especially important given the current Covid-19 pandemic.

    METHODS: Forty third-year undergraduate dental students were randomly assigned into FC (n = 20) or LD (n = 20) cohort. Each student attended six teaching sessions, each to teach students' competency in fabricating one type of wire component, for a total competency in fabricating six wire components over the course of six teaching sessions. Either LD or FC teaching methods were used. After each session, wire assignments had to be submitted. Wire assignments were then evaluated using a blinded wire-bending assessment protocol. As part of their formative assessment, the assessment results were distributed to students, lecturers, and technicians before the next session. After the first session (T0) and at the end of all six sessions (T1), students completed a self-reported questionnaire.

    RESULTS: The mean wire-bending scores for FC were significantly higher than LD for two of the six assignments, namely the Adams clasp (p 

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