Displaying publications 1 - 20 of 129 in total

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  1. Nourouzi MM, Chuah TG, Choong TS, Rabiei F
    J Environ Sci Health B, 2012;47(5):455-65.
    PMID: 22424071 DOI: 10.1080/03601234.2012.663603
    An artificial neural network (ANN) model was developed to simulate the biodegradation of herbicide glyphosate [2-(Phosphonomethylamino) acetic acid] in a solution with varying parameters pH, inoculum size and initial glyphosate concentration. The predictive ability of ANN model was also compared with Monod model. The result showed that ANN model was able to accurately predict the experimental results. A low ratio of self-inhibition and half saturation constants of Haldane equations (< 8) exhibited the inhibitory effect of glyphosate on bacteria growth. The value of K(i)/K(s) increased when the mixed inoculum size was increased from 10(4) to 10(6) bacteria/mL. It was found that the percentage of glyphosate degradation reached a maximum value of 99% at an optimum pH 6-7 while for pH values higher than 9 or lower than 4, no degradation was observed.
  2. Nourouzi MM, Chuah TG, Choong TS
    Water Sci. Technol., 2011;63(5):984-94.
    PMID: 21411950 DOI: 10.2166/wst.2011.280
    The removal of Reactive Black 5 dye in an aqueous solution by electrocoagulation (EC) as well as addition of flocculant was investigated. The effect of operational parameters, i.e. current density, treatment time, solution conductivity and polymer dosage, was investigated. Two models, namely the artificial neural network (ANN) and the response surface method (RSM), were used to model the effect of independent variables on percentage of dye removal. The findings of this work showed that current density, treatment time and dosage of polymer had the most significant effect on percentage of dye removal (p<0.001). In addition, interaction between time and current density, time and dosage of polymer, current density and dosage of polymer also significantly affected the percentage of dye removal (p=0.034, 0.003 and 0.024, respectively). It was shown that both the ANN and RSM models were able to predict well the experimental results (R(2)>0.8).
  3. Choong TS, Wong TN, Chuah TG, Idris A
    J Colloid Interface Sci, 2006 Sep 15;301(2):436-40.
    PMID: 16814316
    The rate of dye adsorption from aqueous effluents onto palm kernel shell (PKS) activated carbon has been studied experimentally using the batch adsorption method. The adsorption rates of methylene blue on PKS for systems of different initial dye concentrations are modeled using a film-pore-concentration dependent surface diffusion (FPCDSD) model. The FPCDSD model is sufficiently general and can be reduced easily to describe other simplified models. Using the FPCDSD model, only a single set of mass transfer parameters is required to describe the methylene blue/PKS system for different initial concentrations. A different set of mass transfer parameters are needed to obtain the best fitting if the pore diffusion is not included in the model.
  4. Venkataraman VV, Kraft TS, Dominy NJ, Endicott KM
    Proc. Natl. Acad. Sci. U.S.A., 2017 03 21;114(12):3097-3102.
    PMID: 28265058 DOI: 10.1073/pnas.1617542114
    The residential mobility patterns of modern hunter-gatherers broadly reflect local resource availability, but the proximate ecological and social forces that determine the timing of camp movements are poorly known. We tested the hypothesis that the timing of such moves maximizes foraging efficiency as hunter-gatherers move across the landscape. The marginal value theorem predicts when a group should depart a camp and its associated foraging area and move to another based on declining marginal return rates. This influential model has yet to be directly applied in a population of hunter-gatherers, primarily because the shape of gain curves (cumulative resource acquisition through time) and travel times between patches have been difficult to estimate in ethnographic settings. We tested the predictions of the marginal value theorem in the context of hunter-gatherer residential mobility using historical foraging data from nomadic, socially egalitarian Batek hunter-gatherers (n = 93 d across 11 residential camps) living in the tropical rainforests of Peninsular Malaysia. We characterized the gain functions for all resources acquired by the Batek at daily timescales and examined how patterns of individual foraging related to the emergent property of residential movements. Patterns of camp residence times conformed well with the predictions of the marginal value theorem, indicating that communal perceptions of resource depletion are closely linked to collective movement decisions. Despite (and perhaps because of) a protracted process of deliberation and argument about when to depart camps, Batek residential mobility seems to maximize group-level foraging efficiency.
  5. Thomas S, Balan A, Balaram P
    Dent Res J (Isfahan), 2015 Jul-Aug;12(4):307-14.
    PMID: 26288619 DOI: 10.4103/1735-3327.161427
    The role of retinoblastoma (Rb) protein in cell cycle regulation prompted us to take up this study with the aim of assessing its role in the progression of oral cancer and to correlate with various clinicopathological parameters, including habits such as smoking, Paan chewing, and alcoholism.
  6. Thomas S, Beh L, Nordin RB
    J Public Health Afr, 2011 Sep 05;2(2):e23.
    PMID: 28299064 DOI: 10.4081/jphia.2011.e23
    Since 1957, there has been major reorganization of health care services in Malaysia. This article assesses the changes and challenges in health care delivery in Malaysia and how the management in health care processes has evolved over the years including equitable health care and health care financing. The health care service in Malaysia is changing towards wellness service as opposed to illness service. The Malaysian Ministry of Health (MOH), being the main provider of health services, may need to manage and mobilize better health care services by providing better health care financing mechanisms. It is recommended that partnership between public and private sectors with the extension of traditional medicine complementing western medicine in medical therapy continues in the delivery of health care.
  7. Khan MA, Ngabura M, Choong TS, Masood H, Chuah LA
    Bioresour. Technol., 2012 Jan;103(1):35-42.
    PMID: 22055093 DOI: 10.1016/j.biortech.2011.09.065
    Biosorption potential of mustard oil cake (MOC) for Ni(II) from aqueous medium was studied. Spectroscopic studies showed possible involvement of acidic (hydroxyl, carbonyl and carboxyl) groups in biosorption. Optimum biosorption was observed at pH 8. Contact time, reaction temperature, biosorbent dose and adsorbate concentration showed significant influence. Linear and non-linear isotherms comparison suggests applicability of Temkin model at 303 and 313 K and Freundlich model at 323K. Kinetics studies revealed applicability of Pseudo-second-order model. The process was endothermic and spontaneous. Freundlich constant (n) and activation energy (Ea) values confirm physical nature of the process. The breakthrough and exhaustive capacities for 5 mg/L initial Ni(II) concentration were 0.25 and 4.5 mg/g, while for 10 mg/L initial Ni(II) concentration were 4.5 and 9.5 mg/g, respectively. Batch desorption studies showed maximum Ni(II) recovery in acidic medium. Regeneration studies by batch and column process confirmed reutilization of biomass without appreciable loss in biosorption.
  8. Koay GF, Chuah TG, Zainal-Abidin S, Ahmad S, Choong TS
    J Oleo Sci, 2011;60(5):237-65.
    PMID: 21502724
    Hydroxyl fatty acids and their derivatives are of high value due to their wide range of industrial application, including cosmetic, food, personal care and pharmaceutical products. Realizing the importance of hydroxyl fatty acids, and yet due to the absence of the conventional starting raw materials, Malaysia has developed 9,10-dihydroxystearic acid (9,10-DHSA) and its derivatives from locally abundant palm based oils. The aim of this article is to provide a general description of the works that have thus far being done on palm based 9,10-DHSA: starting from its conception and production from commercial grade palm based crude oleic acid via epoxidation and hydrolysis, purification through solvent crystallization and characterization through wet and analytical chemistry, moving on to developmental works done on producing its derivatives through blending, esterification, amidation and polymerization, and completing with applications of 9,10-DHSA and its derivatives, e.g. DHSA-stearates and DHSA-estolides, in commercial products such as soaps, deodorant sticks and shampoos. This article incorporates some of the patent filed technological knowhow on 9,10-DHSA and its derivatives, and will also point out some of the shortcomings in previously published documents and provide some recommendations for future research works in mitigating these shortcomings.
  9. Chang TS, Yunus R, Rashid U, Choong TS, Awang Biak DR, Syam AM
    J Oleo Sci, 2015;64(2):143-51.
    PMID: 25748374 DOI: 10.5650/jos.ess14162
    Trimethylolpropane triesters are biodegradable synthetic lubricant base oil alternative to mineral oils, polyalphaolefins and diesters. These oils can be produced from trimethylolpropane (TMP) and fatty acid methyl esters via chemical or enzymatic catalyzed synthesis methods. In the present study, a commercial palm oil derived winter grade biodiesel (ME18) was evaluated as a viable and sustainable methyl ester source for the synthesis of high oleic trimethylolpropane triesters (HO-TMPTE). ME18 has fatty acid profile containing 86.8% oleic acid, 8.7% linoleic acid with the remaining minor concentration of palmitic acid, stearic acid and linolenic acid. It's high oleic property makes it superior to produce synthetic lubricant base oil that fulfills both the good low temperature property as well as good oxidative stability. The synthetic base oil produced had a viscosity of 44.3 mm(2)/s at 40°C meeting the needs for ISO 46 oils. It also exhibited an excellent viscosity index of 219 that is higher than some other commercial brands of trimethylolpropane trioleate. Properties of base oil such as cloud point, density, acid value, demulsibility and soap content were also examined. The oil was then used in the formulation of tapping oil and appraised in term of adaptability, stability and field test performance.
  10. Sun W, McCrory TS, Khaw WY, Petzing S, Myers T, Schmitt AP
    J. Virol., 2014 Nov;88(22):13099-110.
    PMID: 25210190 DOI: 10.1128/JVI.02103-14
    Paramyxoviruses and other negative-strand RNA viruses encode matrix proteins that coordinate the virus assembly process. The matrix proteins link the viral glycoproteins and the viral ribonucleoproteins at virus assembly sites and often recruit host machinery that facilitates the budding process. Using a co-affinity purification strategy, we have identified the beta subunit of the AP-3 adapter protein complex, AP3B1, as a binding partner for the M proteins of the zoonotic paramyxoviruses Nipah virus and Hendra virus. Binding function was localized to the serine-rich and acidic Hinge domain of AP3B1, and a 29-amino-acid Hinge-derived polypeptide was sufficient for M protein binding in coimmunoprecipitation assays. Virus-like particle (VLP) production assays were used to assess the relationship between AP3B1 binding and M protein function. We found that for both Nipah virus and Hendra virus, M protein expression in the absence of any other viral proteins led to the efficient production of VLPs in transfected cells, and this VLP production was potently inhibited upon overexpression of short M-binding polypeptides derived from the Hinge region of AP3B1. Both human and bat (Pteropus alecto) AP3B1-derived polypeptides were highly effective at inhibiting the production of VLPs. VLP production was also impaired through small interfering RNA (siRNA)-mediated depletion of AP3B1 from cells. These findings suggest that AP-3-directed trafficking processes are important for henipavirus particle production and identify a new host protein-virus protein binding interface that could become a useful target in future efforts to develop small molecule inhibitors to combat paramyxoviral infections.
  11. Bello MM, Nourouzi MM, Abdullah LC, Choong TS, Koay YS, Keshani S
    J. Hazard. Mater., 2013 Nov 15;262:106-13.
    PMID: 24021163 DOI: 10.1016/j.jhazmat.2013.06.053
    As Malaysia is one of the world's largest producer of palm oil, large amounts of palm oil mill effluent (POME) is generated. It was found that negatively charged components are accountable for POME color. An attempt was made to remove residual contaminants after conventional treatment using anion base resin. Adsorption experiments were carried out in fixed bed column. Various models such as the Thomas, the Yoon-Nelson, the Wolborska and BDST model were used to fit the experimental data. It was found that only the BDST model was fitted well at the initial breakthrough time. A wavelet neural network model (WNN) was developed to model the breakthrough curves in fixed bed column for multicomponent system. The results showed that the WNN model described breakthrough curves better than the commonly used models. The effects of pH, flow rate and bed depth on column performance were investigated. It was found that the highest uptake capacity was obtained at pH 3. The exhaustion time appeared to increase with increase in bed length and decrease in flow rate.
  12. Kraft TS, Venkataraman VV, Tacey I, Dominy NJ, Endicott KM
    Hum Nat, 2019 Mar;30(1):71-97.
    PMID: 30552578 DOI: 10.1007/s12110-018-9334-2
    Identifying the determinants of reproductive success in small-scale societies is critical for understanding how natural selection has shaped human evolution and behavior. The available evidence suggests that status-accruing behaviors such as hunting and prosociality are pathways to reproductive success, but social egalitarianism may diminish this pathway. Here we introduce a mixed longitudinal/cross-sectional dataset based on 45 years of research with the Batek, a population of egalitarian rain forest hunter-gatherers in Peninsular Malaysia, and use it to test the effects of four predictors of lifetime reproductive success: (i) foraging return rate, (ii) sharing proclivity, (iii) cooperative foraging tendency, and (iv) kin presence. We found that none of these factors can explain variation in lifetime reproduction among males or females. We suggest that social egalitarianism, combined with strikingly low infant and juvenile mortality rates, can mediate the pathway between foraging, status-accruing behavior, and reproductive success. Our approach advocates for greater theoretical and empirical attention to quantitative social network measures, female foraging, and fitness outcomes.
  13. Venkataraman VV, Yegian AK, Wallace IJ, Holowka NB, Tacey I, Gurven M, et al.
    Proc. Biol. Sci., 2018 11 07;285(1890).
    PMID: 30404871 DOI: 10.1098/rspb.2018.1492
    The convergent evolution of the human pygmy phenotype in tropical rainforests is widely assumed to reflect adaptation in response to the distinct ecological challenges of this habitat (e.g. high levels of heat and humidity, high pathogen load, low food availability, and dense forest structure), yet few precise adaptive benefits of this phenotype have been proposed. Here, we describe and test a biomechanical model of how the rainforest environment can alter gait kinematics such that short stature is advantageous in dense habitats. We hypothesized that environmental constraints on step length in rainforests alter walking mechanics such that taller individuals are expected to walk more slowly due to their inability to achieve preferred step lengths in the rainforest. We tested predictions from this model with experimental field data from two short-statured populations that regularly forage in the rainforest: the Batek of Peninsular Malaysia and the Tsimane of the Bolivian Amazon. In accordance with model expectations, we found stature-dependent constraints on step length in the rainforest and concomitant reductions in walking speed that are expected to compromise foraging efficiency. These results provide the first evidence that the human pygmy phenotype is beneficial in terms of locomotor performance and highlight the value of applying laboratory-derived biomechanical models to field settings for testing evolutionary hypotheses.
  14. Omale SO, Choong TSY, Abdullah LC, Siajam SI, Yip MW
    Heliyon, 2019 Oct;5(10):e02602.
    PMID: 31667417 DOI: 10.1016/j.heliyon.2019.e02602
    Iron and steel industries are among the contributors of CO2 emission in large volume into the atmosphere, causing detrimental effects to the environment and the ecosystem at large scale. These industries also generate solid wastes in the form of electric arc furnace (EAF) slag during operations which result in about 10-15% slag wastes per ton of steel produced. In this study, the EAF slags from an iron and steel-making factory in Klang, Malaysia was utilized for CO2 sequestration through direct aqueous mineral carbonation. According to the surface area analysis, the fresh EAF slag has a mesoporous structure, its elemental composition shows the presence of 20.91 wt.% of CaO that was used for the sequestration of CO2 through carbonation. The sequestration capacity was found to be 58.36 g CO2/kg of slag at ambient temperature in 3 h, with the liquid/solid (L/S) ratio of 5:1 and using <63μm particle size. Moreover, the shrinking core model (SCM) was used to analyze the solid-fluid reaction in a heterogeneous phase and the CO2 sequestration shows to be controlled by the product layer phase. The EAF slag is demonstrated to have the potential of CO2 sequestration at ambient temperature.
  15. Thomas S, Subramaniam S, Abraham M, Too L, Beh L
    BMC Res Notes, 2011;4:337.
    PMID: 21902839 DOI: 10.1186/1756-0500-4-337
    This is a pilot cross sectional study using both quantitative and qualitative approach towards tutors teaching large classes in private universities in the Klang Valley (comprising Kuala Lumpur, its suburbs, adjoining towns in the State of Selangor) and the State of Negeri Sembilan, Malaysia. The general aim of this study is to determine the difficulties faced by tutors when teaching large group of students and to outline appropriate recommendations in overcoming them.
  16. Rajisha KR, Maria HJ, Pothan LA, Ahmad Z, Thomas S
    Int. J. Biol. Macromol., 2014 Jun;67:147-53.
    PMID: 24657376 DOI: 10.1016/j.ijbiomac.2014.03.013
    Potato starch nanocrystals were found to serve as an effective reinforcing agent for natural rubber (NR). Starch nanocrystals were obtained by the sulfuric acid hydrolysis of potato starch granules. After mixing the latex and the starch nanocrystals, the resulting aqueous suspension was cast into film by solvent evaporation method. The composite samples were successfully prepared by varying filler loadings, using a colloidal suspension of starch nanocrystals and NR latex. The morphology of the nanocomposite prepared was analyzed by field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM). FESEM analysis revealed the size and shape of the crystal and their homogeneous dispersion in the composites. The crystallinity of the nanocomposites was studied using XRD analysis which indicated an overall increase in crystallinity with filler content. The mechanical properties of the nanocomposites such as stress-strain behavior, tensile strength, tensile modulus and elongation at break were measured according to ASTM standards. The tensile strength and modulus of the composites were found to improve tremendously with increasing nanocrystal content. This dramatic increase observed can be attributed to the formation of starch nanocrystal network. This network immobilizes the polymer chains leading to an increase in the modulus and other mechanical properties.
  17. Eseyin OA, Daniel A, Paul TS, Attih E, Emmanuel E, Ekarika J, et al.
    Nat. Prod. Res., 2018 Feb;32(4):444-447.
    PMID: 28361553 DOI: 10.1080/14786419.2017.1308366
    The 2,2-diphenyl-1-picryl hydrazyl (DPPH) radical, nitric oxide, reducing power, hydrogen peroxide scavenging, and total antioxidant activities of the methanol extract, n-hexane, dichloromethane, ethyl acetate, butanol and aqueous fractions of the seed of Telfairia occidentalis were evaluated. Total phenolic content was determined using the Folin-Ciocalteu method. The dichloromethane fraction exhibited the highest DPPH radical scavenging, reducing power and total antioxidant activities. Two pure compounds which were identified by FTIR, H-and 2D NMR and Mass spectroscopy as 9-octadecenoic acid (TOS B) and 10-hydroxyoctadecanoic acid (TOS C) and four oily isolates, TOS A, TOS D, TOS E and TOS F were obtained from the dichloromethane fraction. TOS E had the highest DPPH radical scavening activity comparable to that of ascorbic acid. GC-MS analysis revealed the major compounds in TOS E as 4-(2,2-Dimethyl-6-methylene cyclohexylidene)-2-butanol; 3-(3-hydroxybutyl)-2,4,4-trimethyl-2-cyclohexene-1-one and 1,2-Benzenedicarboxylic acid disooctyl ester. Thus, the seed of T. occidentalis can be consumed for its antioxidant property.
  18. Ghosal K, Das A, Das SK, Mahmood S, Ramadan MAM, Thomas S
    Int. J. Biol. Macromol., 2019 Jun 01;130:645-654.
    PMID: 30797807 DOI: 10.1016/j.ijbiomac.2019.02.117
    This study aimed to develop and characterize the calcium alginate films loaded with diclofenac sodium and other hydrophilic polymers with different degrees of cross-linking obtained by external gelation process. To the formed films different physicochemical evaluation were performed which showed an initial character of the films. The films produced by this external gelation process were found thicker (0.031-0.038 mm) and stronger (51.9-52.9 MPa) but less elastic (2.3%) than those non-cross-linked films (0.029 mm; 39.7 MPa; 4.4%). The lower water vapor permeability (WVP) values of the films were obtained where maximum level of crosslinking occurs. Composite films can be cross-linked in presence of external crosslinking agent to improve the quality of the produced matrices for various uses. The characterization of the film was performed using Differential Scanning Calorimetry (DSC) and Fourier-Transform Infrared Spectroscopy (FT-IR) analysis. The Scanning Electron Microscopy (SEM) study showed the morphology of treated composite films. The kinetic release studies showed a sustained release of the drug from the formulated films as it can be prolonged in composite film. The prepared biodegradable Ca-Alginate bio-composite film may be of clinical importance for its therapeutic benefit.
  19. Ninan N, Muthiah M, Bt Yahaya NA, Park IK, Elain A, Wong TW, et al.
    Colloids Surf B Biointerfaces, 2014 Mar 1;115:244-52.
    PMID: 24362063 DOI: 10.1016/j.colsurfb.2013.11.048
    In this article, gelatin/copper activated faujasites (CAF) composite scaffolds were fabricated by lyophilisation technique for promoting partial thickness wound healing. The optimised scaffold with 0.5% (w/w) of CAF, G (0.5%), demonstrated pore size in the range of 10-350 μm. Agar disc diffusion tests verified the antibacterial role of G (0.5%) and further supported that bacterial lysis was due to copper released from the core of CAF embedded in the gelatin matrix. The change in morphology of bacteria as a function of CAF content in gelatin scaffold was studied using SEM analysis. The confocal images revealed the increase in mortality rate of bacteria with increase in concentration of incorporated CAF in gelatin matrix. Proficient oxygen supply to needy cells is a continuing hurdle faced by tissue engineering scaffolds. The dissolved oxygen measurements revealed that CAF embedded in the scaffold were capable of increasing oxygen supply and thereby promote cell proliferation. Also, G (0.5%) exhibited highest cell viability on NIH 3T3 fibroblast cells which was mainly attributed to the highly porous architecture and its ability to enhance oxygen supply to cells. In vivo studies conducted on Sprague Dawley rats revealed the ability of G (0.5%) to promote skin regeneration in 20 days. Thus, the obtained data suggest that G (0.5%) is an ideal candidate for wound healing applications.
  20. M H, Chong EWN, Jafarzadeh S, Paridah MT, Gopakumar DA, Tajarudin HA, et al.
    Polymers (Basel), 2019 Jan 26;11(2).
    PMID: 30960194 DOI: 10.3390/polym11020210
    This study aimed to compare the performance of fabricated microbially induced precipitated calcium carbonate⁻ (MB⁻CaCO₃) based red seaweed (Kappaphycus alvarezii) bio-polymer film and commercial calcium carbonate⁻ (C⁻CaCO₃) based red seaweed bio-film with the conventional biodegradable mulch film. To the best of our knowledge, there has been limited research on the application of commercial CaCO₃ (C⁻CaCO₃) and microbially induced CaCO₃ (MB⁻CaCO₃) as fillers for the preparation of films from seaweed bio-polymer and comparison with biodegradable commercial plasticulture packaging. The results revealed that the mechanical, contact angle, and biodegradability properties of the polymer composite films incorporated with C⁻CaCO₃ and MB⁻CaCO₃ fillers were comparable or even superior than the conventional biodegradable mulch film. The seaweed polymer film incorporated with MB⁻CaCO₃ showed the highest contact angle of 100.94°, whereas conventional biodegradable mulch film showed a contact angle of 90.25°. The enhanced contact angle of MB⁻CaCO₃ resulted in high barrier properties, which is highly desired in the current scenario for plasticulture packaging application. The water vapor permeability of MB⁻CaCO₃ based seaweed films was low (2.05 ± 1.06 g·m/m²·s·Pa) when compared to conventional mulch film (2.68 ± 0.35 g·m/m²·s·Pa), which makes the fabricated film an ideal candidate for plasticulture application. The highest tensile strength (TS) was achieved by seaweed-based film filled with commercial CaCO₃ (84.92% higher than conventional mulch film). SEM images of the fractured surfaces of the fabricated films revealed the strong interaction between seaweed and fillers. Furthermore, composite films incorporated with MB⁻CaCO₃ promote brighter film, better water barrier, hydrophobicity, and biodegradability compared to C⁻CaCO₃ based seaweed polymer film and conventional mulch film. From this demonstrated work, it can be concluded that the fabricated MB⁻CaCO₃ based seaweed biopolymer film will be a promising candidate for plasticulture and agricultural application.
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