Displaying publications 1 - 20 of 602 in total

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  1. Koh HL, Lim PE, Midun Z
    Environ Monit Assess, 1991 Oct;19(1-3):349-59.
    PMID: 24233952 DOI: 10.1007/BF00401324
    Coastal waters in South Johore, Malaysia are polluted to various degrees. The major pollution sources are domestric wastes from human settlements, agro-based wastes from palm oil mills and rubber processing factories, industrial effluents from industrial estates and discharges from animal farms. These pollution problems have adversely affected resources such as fisheries, recreational potential as well as the general aesthetic quality of the coastal environment particularly the Inner Johore Strait. Hence proper management and control measures are urgently needed to protect and further enhance the water quality to ensure environmentally sustainable development. This study examines various management options to control the pollution in the Inner Johore Strait. The options involve partial opening as well as complete removal of the Causeway to improve the tidal flow for more effective dilution and dispersion of pollutants. Computer simulation models are used to assess the impacts of the proposed options.
    Matched MeSH terms: Computer Simulation
  2. Spohr MH, Wright NH, Herm J
    Medinfo, 1995;8 Pt 2:1639.
    PMID: 8591525
    We developed a computer model which measures the impact of disease on a population, has the ability to track changes in disease incidence over time, and incorporates costs of disease prevention and treatment. This model was developed with data for Malaysia and used by the Ministry of Health in the development of their national health plan. The model uses the DHLL (DALY) measure which incorporates morbidity and mortality impacts of disease. The ability of the model to adjust for changes in disease incidence over a period of years allows health planners to accurately reflect demographic and development related changes in disease incidence. This model is of value to health planners because in incorporates information on population health status, costs of prevention and treatment, and changes in health status over time. It produces an evaluation of the cost effectiveness of possible interventions that can be used by health planners in making decisions on resource allocation.
    Matched MeSH terms: Computer Simulation*
  3. Cheah YN, Abidi SS
    PMID: 10724990
    In this paper we suggest that the healthcare enterprise needs to be more conscious of its vast knowledge resources vis-à-vis the exploitation of knowledge management techniques to efficiently manage its knowledge. The development of healthcare enterprise memory is suggested as a solution, together with a novel approach advocating the operationalisation of healthcare enterprise memories leading to the modelling of healthcare processes for strategic planning. As an example, we present a simulation of Service Delivery Time in a hospital's OPD.
    Matched MeSH terms: Computer Simulation
  4. Lim TA, Inbasegaran K
    Br J Anaesth, 2001 Mar;86(3):422-4.
    PMID: 11573534
    We derived the predicted effect compartment concentration of thiopental, at loss of the eyelash reflex, following three different injection regimens. Sixty patients were given thiopental for induction of anaesthesia. Twenty patients received multiple small boluses, 20 patients received a single bolus and 20 patients received an infusion. Computer simulation was then used to derive the effect compartment concentration. The median concentration was not significantly different between the three groups. EC50, derived after combining all three groups was 11.3 microg ml(-1). The EC05-EC95 range was 6.9-18.3 microg ml(-1), suggesting wide inter-individual variation.
    Matched MeSH terms: Computer Simulation
  5. Kueh R, Rahman NA, Merican AF
    J Mol Model, 2003 Apr;9(2):88-98.
    PMID: 12707802
    The arginine repressor (ArgR) of Escherichia coli binds to six L-arginine molecules that act as its co-repressor in order to bind to DNA. The binding of L-arginine molecules as well as its structural analogues is compared by means of computational docking. A grid-based energy evaluation method combined with a Monte Carlo simulated annealing process was used in the automated docking. For all ligands, the docking procedure proposed more than one binding site in the C-terminal domain of ArgR (ArgRc). Interaction patterns of ArgRc with L-arginine were also observed for L-canavanine and L-citrulline. L-lysine and L-homoarginine, on the other hand, were shown to bind poorly at the binding site. Figure A general overview of the sites found from docking the various ligands into ArgRc ( grey ribbons). Red coloured sticks: residues in binding site H that was selected for docking
    Matched MeSH terms: Computer Simulation*
  6. Lim TA
    Br J Anaesth, 2003 Nov;91(5):730-2.
    PMID: 14570797
    BACKGROUND: Calculation of the effect compartment concentration (Ce) in non-steady-state conditions requires the equilibrium rate constant, keo. Most studies of propofol derive the keo using EEG measurements. This study investigated an alternative method. Starting from a predicted concentration-time profile, a keo value was included so that the predicted Ce at a specific pharmacodynamic end-point was the same when using three different methods of injection.

    METHODS: Seventy-five patients were given propofol for induction of anaesthesia. Twenty-five patients received a single bolus, 25 patients received an infusion, and 25 patients received a bolus followed by an infusion. Computer simulation was used to derive the central compartment concentration. The keo that brought about the same value for Ce at loss of the eyelash reflex using the three methods of injection was derived.

    RESULTS: Keo was found to be 0.80 min(-1). Mean (SD) Ce at loss of the eyelash reflex was 2.27 (0.69) microg ml(-1).

    CONCLUSIONS: The effect compartment equilibrium rate constant and concentration at loss of the eyelash reflex can be derived without the use of electronic central nervous system monitors.

    Matched MeSH terms: Computer Simulation
  7. Asi AM, Rahman NA, Merican AF
    J Mol Graph Model, 2004 Mar;22(4):249-62.
    PMID: 15177077
    Protein-ligand binding free energy values of wild-type and mutant C-terminal domain of Escherichia coli arginine repressor (ArgRc) protein systems bound to L-arginine or L-citrulline molecules were calculated using the linear interaction energy (LIE) method by molecular dynamics (MD) simulation. The binding behaviour predicted by the dissociation constant (K(d)) calculations from the binding free energy values showed preferences for binding of L-arginine to the wild-type ArgRc but not to the mutant ArgRc(D128N). On the other hand, L-citrulline do not favour binding to wild-type ArgRc but prefer binding to mutant ArgRc(D128N). The dissociation constant for the wild-type ArgRc-L-arginine complex obtained in this study is in agreement with reported experimental results. Our results also support the experimental data for the binding of L-citrulline to the mutant ArgRc(D128N). These showed that LIE method for protein-ligand binding free energy calculation could be applied to the wild-type and the mutant E. coli ArgRc-L-arginine and ArgRc-L-citrulline protein-ligand complexes and possibly to other transcriptional repressor-co-repressor systems as well.
    Matched MeSH terms: Computer Simulation*
  8. Loo CK, Rajeswari M, Rao MV
    IEEE Trans Neural Netw, 2004 Nov;15(6):1378-95.
    PMID: 15565767
    This paper presents two novel approaches to determine optimum growing multi-experts network (GMN) structure. The first method called direct method deals with expertise domain and levels in connection with local experts. The growing neural gas (GNG) algorithm is used to cluster the local experts. The concept of error distribution is used to apportion error among the local experts. After reaching the specified size of the network, redundant experts removal algorithm is invoked to prune the size of the network based on the ranking of the experts. However, GMN is not ergonomic due to too many network control parameters. Therefore, a self-regulating GMN (SGMN) algorithm is proposed. SGMN adopts self-adaptive learning rates for gradient-descent learning rules. In addition, SGMN adopts a more rigorous clustering method called fully self-organized simplified adaptive resonance theory in a modified form. Experimental results show SGMN obtains comparative or even better performance than GMN in four benchmark examples, with reduced sensitivity to learning parameters setting. Moreover, both GMN and SGMN outperform the other neural networks and statistical models. The efficacy of SGMN is further justified in three industrial applications and a control problem. It provides consistent results besides holding out a profound potential and promise for building a novel type of nonlinear model consisting of several local linear models.
    Matched MeSH terms: Computer Simulation
  9. Teo J, Abbass HA
    Evol Comput, 2004;12(3):355-94.
    PMID: 15355605
    In this paper, we investigate the use of a self-adaptive Pareto evolutionary multi-objective optimization (EMO) approach for evolving the controllers of virtual embodied organisms. The objective of this paper is to demonstrate the trade-off between quality of solutions and computational cost. We show empirically that evolving controllers using the proposed algorithm incurs significantly less computational cost when compared to a self-adaptive weighted sum EMO algorithm, a self-adaptive single-objective evolutionary algorithm (EA) and a hand-tuned Pareto EMO algorithm. The main contribution of the self-adaptive Pareto EMO approach is its ability to produce sufficiently good controllers with different locomotion capabilities in a single run, thereby reducing the evolutionary computational cost and allowing the designer to explore the space of good solutions simultaneously. Our results also show that self-adaptation was found to be highly beneficial in reducing redundancy when compared against the other algorithms. Moreover, it was also shown that genetic diversity was being maintained naturally by virtue of the system's inherent multi-objectivity.
    Matched MeSH terms: Computer Simulation
  10. Al-Zuhair S
    Biotechnol Prog, 2005 Sep-Oct;21(5):1442-8.
    PMID: 16209548
    Kinetics of production of biodiesel by enzymatic methanolysis of vegetable oils using lipase has been investigated. A mathematical model taking into account the mechanism of the methanolysis reaction starting from the vegetable oil as substrate, rather than the free fatty acids, has been developed. The kinetic parameters were estimated by fitting the experimental data of the enzymatic reaction of sunflower oil by two types of lipases, namely, Rhizomucor miehei lipase (RM) immobilized on ion-exchange resins and Thermomyces lanuginosa lipase (TL) immobilized on silica gel. There was a good agreement between the experimental results of the initial rate of reaction and those predicted by the proposed model equations, for both enzymes. From the proposed model equations, the regions where the effect of alcohol inhibition fades, at different substrate concentrations, were identified. The proposed model equation can be used to predict the rate of methanolysis of vegetable oils in a batch or a continuous reactor and to determine the optimal conditions for biodiesel production.
    Matched MeSH terms: Computer Simulation
  11. Ismail BS, Ngan CK
    J Environ Sci Health B, 2005;40(2):341-53.
    PMID: 15825685
    A comparison of dissipation of chlorothalonil, chlorpyrifos, and profenofos in a Malaysian agricultural soil between the field experiment and simulation by the PERSIST model was studied. A plot of sweet pea (Pisum sativum) from a farm in the Cameron Highlands was selected for the field experiment. The plot was treated with chlorothalonil, chlorpyrifos, and profenofos. Core soil collection was conducted according to the sampling schedule. Residues of the three pesticides were analyzed in the laboratory. Simulations of the three pesticides' persistency were also conducted using a computer-run software PERSIST. Generally, predicted data obtained using PERSIST were found to be high for the three pesticides except for one field measurement of chlorpyrifos. The predicted data for profenofos, which is the most mobile of the three pesticides tested, was not well matched with the observed data compared to chlorothalonil and chlorpyrifos.
    Matched MeSH terms: Computer Simulation
  12. Fazlena H, Kamaruddin AH, Zulkali MM
    Bioprocess Biosyst Eng, 2006 Mar;28(4):227-33.
    PMID: 16215728
    A lipase catalysed enantioselective hydrolysis process under in situ racemization of the remaining (R)-ibuprofen ester substrate with sodium hydroxide as the catalyst was developed for the production of S-ibuprofen from (R,S)-ibuprofen ester in isooctane. Detailed investigations on parameters study indicated that 0.5 M NaOH, addition of 20% (v/v) co-solvent (dimethyl sulphoxide), operating temperature of 45 degrees C, and 40 mmol/L substrate gave 86% conversion and 99.4% optical purity of S-ibuprofen in dynamic kinetic resolution. Meanwhile, in common enzymatic kinetic resolution process, only 42% conversion of the racemate and 93% enantiomeric excess of the product was obtained which are of lower values as compared to dynamic kinetic resolution. The S-ibuprofen produced during each process was evaluated and approximately 50% increment in concentration of S-acid product was produced when dynamic kinetic resolution was applied into the process.
    Matched MeSH terms: Computer Simulation
  13. Chong TT, Hashim R, Bryce RA
    J Phys Chem B, 2006 Mar 16;110(10):4978-84.
    PMID: 16526739
    Comparative molecular dynamics simulations of n-octyl-beta-D-galactopyranoside (beta-C8Gal) and n-octyl-beta-D-glucopyranoside (beta-C8Glc) micelles in aqueous solution have been performed to explore the influence of carbohydrate stereochemistry on glycolipid properties at the atomic level. In particular, we explore the hypothesis that differences in T(m) and T(c) for beta-C8Gal and beta-C8Glc in lyotropic systems arise from a more extensive hydrogen bonding network between beta-C8Gal headgroups relative to beta-C8Glc, due to the axial 4-OH group in beta-C8Gal. Good agreement of the 13 ns micelle-water simulations with available experimental information is found. The micelles exhibit a similar shape, size, and degree of exposed alkyl chain surface area. We find net inter- and intra-headgroup hydrogen bonding is also similar for beta-C8Gal and beta-C8Glc, although n-octyl-beta-D-galactopyranoside micelles do exhibit a slightly greater degree of inter- and intra-headgroup hydrogen bonding. However, the main distinction in the calculated microscopic behavior of beta-C8Glc and beta-C8Gal micelles lies in solvent interactions, where beta-d-glucosyl headgroups are considerably more solvated (mainly at the equatorial O4 oxygen). These results agree with preceding theoretical and experimental studies of monosaccharides in aqueous solution. A number of long water residence times are found for solvent surrounding both micelle types, the largest of which are associated with surface protrusions involving headgroup clusters. Our simulations, therefore, predict differences in hydrogen bonding for the two headgroup stereochemistries, including a small difference in inter-headgroup interactions, which may contribute to the higher T(m) and T(c) values of beta-C8Gal surfactants relative to beta-C8Glc in lyotropic systems.
    Matched MeSH terms: Computer Simulation*
  14. Ibrahim Z, Tsuboi Y, Ono O
    IEEE Trans Nanobioscience, 2006 Jun;5(2):103-9.
    PMID: 16805106
    Previously, direct-proportional length-based DNA computing (DPLB-DNAC) for solving weighted graph problems has been reported. The proposed DPLB-DNAC has been successfully applied to solve the shortest path problem, which is an instance of weighted graph problems. The design and development of DPLB-DNAC is important in order to extend the capability of DNA computing for solving numerical optimization problem. According to DPLB-DNAC, after the initial pool generation, the initial solution is subjected to amplification by polymerase chain reaction and, finally, the output of the computation is visualized by gel electrophoresis. In this paper, however, we give more attention to the initial pool generation of DPLB-DNAC. For this purpose, two kinds of initial pool generation methods, which are generally used for solving weighted graph problems, are evaluated. Those methods are hybridization-ligation and parallel overlap assembly (POA). It is found that for DPLB-DNAC, POA is better than that of the hybridization-ligation method, in terms of population size, generation time, material usage, and efficiency, as supported by the results of actual experiments.
    Matched MeSH terms: Computer Simulation
  15. Serri NA, Kamaruddin AH, Long WS
    Bioprocess Biosyst Eng, 2006 Oct;29(4):253-60.
    PMID: 16868763
    Immobilized Candida rugosa lipase was used for the synthesis of citronellyl laurate from citronellol and lauric acid. Screening of different types of support (Amberlite MB-1 and Celite) for immobilization of lipase and solvent (n-hexane, n-heptane, and iso-octane) and optimization of reaction conditions, such as catalyst loading, effect of substrates molar ratio and temperature, have been studied. The maximum enzyme activity was obtained at 310 K. The immobilized C. rugosa lipase onto Amberlite MB-1 support was found to be the best support with a conversion of 89% of citronellyl laurate ester in iso-octane compared to Celite 545. Deactivation of C. rugosa lipase at 313, 318 and 323 K were observed. Ordered bi bi mechanism with dead end complex of lauric acid was found to fit the initial rate data and the kinetic parameters were obtained by non-linear regression analysis.
    Matched MeSH terms: Computer Simulation
  16. Lim TA, Wong WH, Lim KY
    J Anesth, 2006;20(2):153-5.
    PMID: 16633780
    The effect-compartment concentration (C(e)) of a drug at a specific pharmacodynamic endpoint should be independent of the rate of drug injection. We used this assumption to derive an effect-compartment equilibrium rate constant (k(eo)) for propofol during induction of anesthesia, using a target controlled infusion device (Diprifusor). Eighteen unpremedicated patients were induced with a target blood propofol concentration of 5 microg x ml(-1) (group 1), while another 18 were induced with a target concentration of 6 microg x ml(-1) (group 2). The time at loss of the eyelash reflex was recorded. Computer simulation was used to derive the rate constant (k(eo)) that resulted in the mean C(e) at loss of the eyelash reflex in group 1 being equal to that in group 2. Using this population technique, we found the k(eo) to be 0.57 min(-1). The mean (SD) effect compartment concentration at loss of the eyelash reflex was 2.39 (0.70) microg x ml(-1). This means that to achieve a desired C(e) within 3 min of induction, the initial target blood concentration should be set at 1.67 times that of the desired C(e) for 1 min, after which it should revert to the desired concentration.
    Matched MeSH terms: Computer Simulation
  17. Zanariah Abdul Majid, Mohamed Suleiman
    Sains Malaysiana, 2006;35:63-68.
    In this paper, a direct integration implicit variable step size method in the form of Adams Moulton Method is developed for solving directly the second order system of ordinary differential equations (ODEs) using variable step size. The existing multistep method involves the computations of the divided differences and integration coefficients in the code when using the variable step size or variable step size and order. The idea of developing this method is to store all the coefficients involved in the code. Thus, this strategy can avoid the lengthy computation of the coefficients during the implementation of the code as well as to improve the execution time. Numerical results are given to compare the efficiency of the developed method with the 1-point method of variable step size and order code (1PDVSO) in Omar (1999).
    Matched MeSH terms: Computer Simulation
  18. Idrose AM, Adnan WA, Villa GF, Abdullah AH
    Emerg Med J, 2007 Jan;24(1):7-11.
    PMID: 17183034
    There is a dire need to have complementary form of disaster training which is cost effective, relatively easy to conduct, comprehensive, effective and acceptable. This will complement field drills training. A classroom-based training and simulation module was built by combining multiple tools: Powerpoint lectures, simulations utilising the Kuala Lumpur International Airport (KLIA) schematic module into 'floortop' model and video show of previous disaster drill. 76 participants made up of medical responders, categorised as Level 1 (specialists and doctors), Level 2 (paramedics), Level 3 (assistant paramedics) and Level 4 (health attendants and drivers) were trained using this module. A pre-test with validated questions on current airport disaster plans was carried out before the training. At the end of training, participants answered similar questions as post-test. Participants also answered questionnaire for assessment of training's acceptance. There was a mean rise from 47.3 (18.8%) to 84.0 (18.7%) in post-test (p<0.05). For Levels 1, 2, 3 and 4 the scores were 94.8 (6.3)%, 90.1 (11)%, 80.3 (20.1)% and 65 (23.4)% respectively. Nevertheless Level 4 group gained most increase in knowledge rise from baseline pre-test score (51.4%). Feedback from the questionnaire showed that the training module was highly acceptable. A classroom-based training can be enhanced with favourable results. The use of classroom training and simulation effectively improves the knowledge of disaster plan significantly on the back of its low cost, relatively-easy to conduct, fun and holistic nature. All Levels of participants (from specialists to drivers) can be grouped together for training. Classroom training and simulation can overcome the problem of "dead-document" phenomenon or "paper-plan syndrome".
    Matched MeSH terms: Computer Simulation*
  19. Shamsir MS, Dalby AR
    Biophys J, 2007 Mar 15;92(6):2080-9.
    PMID: 17172295
    Previous molecular dynamic simulations have reported elongation of the existing beta-sheet in prion proteins. Detailed examination has shown that these elongations do not extend beyond the proline residues flanking these beta-sheets. In addition, proline has also been suggested to possess a possible structural role in preserving protein interaction sites by preventing invasion of neighboring secondary structures. In this work, we have studied the possible structural role of the flanking proline residues by simulating mutant structures with alternate substitution of the proline residues with valine. Simulations showed a directional inhibition of elongation, with the elongation progressing in the direction of valine including evident inhibition of elongation by existing proline residues. This suggests that the flanking proline residues in prion proteins may have a containment role and would confine the beta-sheet within a specific length.
    Matched MeSH terms: Computer Simulation
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