Displaying publications 21 - 40 of 192 in total

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  1. Fulltext Highly accurate prediction of flammability limits of chemical compounds using novel integrated hybrid models
    El-Harbawi M, Samir BB, El Blidi L, Ben Ghanem O
    PLoS One, 2019;14(11):e0224807.
    PMID: 31725738 DOI: 10.1371/journal.pone.0224807
    Two novel and highly accurate hybrid models were developed for the prediction of the flammability limits (lower flammability limit (LFL) and upper flammability limit (UFL)) of pure compounds using a quantitative structure-property relationship approach. The two models were developed using a dataset obtained from the DIPPR Project 801 database, which comprises 1057 and 515 literature data for the LFL and UFL, respectively. Multiple linear regression (MLR), logarithmic, and polynomial models were used to develop the models according to an algorithm and code written using the MATLAB software. The results indicated that the proposed models were capable of predicting LFL and UFL values with accuracies that were among the best (i.e. most optimised) reported in the literature (LFL: R2 = 99.72%, with an average absolute relative deviation (AARD) of 0.8%; UFL: R2 = 99.64%, with an AARD of 1.41%). These hybrid models are unique in that they were developed using a modified mathematical technique combined three conventional methods. These models afford good practicability and can be used as cost-effective alternatives to experimental measurements of LFL and UFL values for a wide range of pure compounds.
    Matched MeSH terms: Models, Chemical*
  2. Influence of parameters and radical scavengers on the visible-light-induced degradation of ciprofloxacin in ZnO/SnS2 nanocomposite suspension: Identification of transformation products
    Makama AB, Salmiaton A, Choong TSY, Hamid MRA, Abdullah N, Saion E
    Chemosphere, 2020 Aug;253:126689.
    PMID: 32304862 DOI: 10.1016/j.chemosphere.2020.126689
    Removal of ciprofloxacin (CIP) pollutant from wastewater using conventional process is particularly challenging due to poor removal efficiency. In this work, CIP was photocatalytically degraded using a porous ZnO/SnS2 photocatalyst prepared via microwaves. The influence of process parameters (e.g., pH, catalyst mass and initial CIP concentration) and radical scavengers on visible-light induced degradation of CIP on the catalyst was investigated. From the study, it was found that visible-light induced degradation of CIP on ZnO/SnS2 is a surface-mediated process and the reaction kinetics followed the Langmuir-Hinshelwood first-order kinetics. It was found that the optimum condition for CIP degradation was at pH of 6.1 and catalyst dosage of 500 mg L-1. Higher catalyst dosage however led to a decline in reaction rate due to light scattering effect and reduction in light penetration.
    Matched MeSH terms: Models, Chemical*
  3. Assessing GPCR homology models constructed from templates of various transmembrane sequence identities: Binding mode prediction and docking enrichment
    Loo JSE, Emtage AL, Ng KW, Yong ASJ, Doughty SW
    J Mol Graph Model, 2017 Dec 29;80:38-47.
    PMID: 29306746 DOI: 10.1016/j.jmgm.2017.12.017
    GPCR crystal structures have become more readily accessible in recent years. However, homology models of GPCRs continue to play an important role as many GPCR structures remain unsolved. The new crystal structures now available provide not only additional templates for homology modelling but also the opportunity to assess the performance of homology models against their respective crystal structures and gain insight into the performance of such models. In this study we have constructed homology models from templates of various transmembrane sequence identities for eight GPCR targets to better understand the relationship between transmembrane sequence identity and model quality. Model quality was assessed relative to the crystal structure in terms of structural accuracy as well as performance in two typical structure-based drug design applications: ligand binding pose prediction and docking enrichment in virtual screening. Crystal structures significantly outperformed homology models in both assessments. Accurate ligand binding pose prediction was possible but difficult to achieve using homology models, even with the use of induced fit docking. In virtual screening using homology models still conferred significant enrichment compared to random selection, with a clear benefit also observed in using models optimized through induced fit docking. Our results indicate that while homology models that are reasonably accurate structurally can be constructed, without significant refinement homology models will be outperformed by crystal structures in ligand binding pose prediction and docking enrichment regardless of the template used, primarily due to the extremely high level of structural accuracy needed for such applications.
    Matched MeSH terms: Models, Chemical
  4. Fulltext Approximating non linear higher order ODEs by a three point block algorithm
    Rasedee AFN, Abdul Sathar MH, Othman KI, Hamzah SR, Ishak N
    PLoS One, 2021;16(2):e0246904.
    PMID: 33577619 DOI: 10.1371/journal.pone.0246904
    Differential equations are commonly used to model various types of real life applications. The complexity of these models may often hinder the ability to acquire an analytical solution. To overcome this drawback, numerical methods were introduced to approximate the solutions. Initially when developing a numerical algorithm, researchers focused on the key aspect which is accuracy of the method. As numerical methods becomes more and more robust, accuracy alone is not sufficient hence begins the pursuit of efficiency which warrants the need for reducing computational cost. The current research proposes a numerical algorithm for solving initial value higher order ordinary differential equations (ODEs). The proposed algorithm is derived as a three point block multistep method, developed in an Adams type formulae (3PBCS) and will be used to solve various types of ODEs and systems of ODEs. Type of ODEs that are selected varies from linear to nonlinear, artificial and real life problems. Results will illustrate the accuracy and efficiency of the proposed three point block method. Order, stability and convergence of the method are also presented in the study.
    Matched MeSH terms: Models, Chemical
  5. Fulltext Artificial neural network modelling of photodegradation in suspension of manganese doped zinc oxide nanoparticles under visible-light irradiation
    Abdollahi Y, Zakaria A, Sairi NA, Matori KA, Masoumi HR, Sadrolhosseini AR, et al.
    ScientificWorldJournal, 2014;2014:726101.
    PMID: 25538962 DOI: 10.1155/2014/726101
    The artificial neural network (ANN) modeling of m-cresol photodegradation was carried out for determination of the optimum and importance values of the effective variables to achieve the maximum efficiency. The photodegradation was carried out in the suspension of synthesized manganese doped ZnO nanoparticles under visible-light irradiation. The input considered effective variables of the photodegradation were irradiation time, pH, photocatalyst amount, and concentration of m-cresol while the efficiency was the only response as output. The performed experiments were designed into three data sets such as training, testing, and validation that were randomly splitted by the software's option. To obtain the optimum topologies, ANN was trained by quick propagation (QP), Incremental Back Propagation (IBP), Batch Back Propagation (BBP), and Levenberg-Marquardt (LM) algorithms for testing data set. The topologies were determined by the indicator of minimized root mean squared error (RMSE) for each algorithm. According to the indicator, the QP-4-8-1, IBP-4-15-1, BBP-4-6-1, and LM-4-10-1 were selected as the optimized topologies. Among the topologies, QP-4-8-1 has presented the minimum RMSE and absolute average deviation as well as maximum R-squared. Therefore, QP-4-8-1 was selected as final model for validation test and navigation of the process. The model was used for determination of the optimum values of the effective variables by a few three-dimensional plots. The optimum points of the variables were confirmed by further validated experiments. Moreover, the model predicted the relative importance of the variables which showed none of them was neglectable in this work.
    Matched MeSH terms: Models, Chemical*
  6. Fulltext A comparison of central composite design and Taguchi method for optimizing Fenton process
    Asghar A, Abdul Raman AA, Daud WM
    ScientificWorldJournal, 2014;2014:869120.
    PMID: 25258741 DOI: 10.1155/2014/869120
    In the present study, a comparison of central composite design (CCD) and Taguchi method was established for Fenton oxidation. [Dye]ini, Dye:Fe(+2), H2O2:Fe(+2), and pH were identified control variables while COD and decolorization efficiency were selected responses. L 9 orthogonal array and face-centered CCD were used for the experimental design. Maximum 99% decolorization and 80% COD removal efficiency were obtained under optimum conditions. R squared values of 0.97 and 0.95 for CCD and Taguchi method, respectively, indicate that both models are statistically significant and are in well agreement with each other. Furthermore, Prob > F less than 0.0500 and ANOVA results indicate the good fitting of selected model with experimental results. Nevertheless, possibility of ranking of input variables in terms of percent contribution to the response value has made Taguchi method a suitable approach for scrutinizing the operating parameters. For present case, pH with percent contribution of 87.62% and 66.2% was ranked as the most contributing and significant factor. This finding of Taguchi method was also verified by 3D contour plots of CCD. Therefore, from this comparative study, it is concluded that Taguchi method with 9 experimental runs and simple interaction plots is a suitable alternative to CCD for several chemical engineering applications.
    Matched MeSH terms: Models, Chemical*
  7. Fulltext Kinetic modeling of a heterogeneous Fenton oxidative treatment of petroleum refining wastewater
    Hasan DB, Abdul Raman AA, Daud WM
    ScientificWorldJournal, 2014;2014:252491.
    PMID: 24592152 DOI: 10.1155/2014/252491
    The mineralisation kinetics of petroleum refinery effluent (PRE) by Fenton oxidation were evaluated. Within the ambit of the experimental data generated, first-order kinetic model (FKM), generalised lumped kinetic model (GLKM), and generalized kinetic model (GKM) were tested. The obtained apparent kinetic rate constants for the initial oxidation step (k'2), their final oxidation step (k'1), and the direct conversion to endproducts step (k3') were 10.12, 3.78, and 0.24 min(-1) for GKM; 0.98, 0.98, and nil min(-1) for GLKM; and nil, nil, and >0.005 min(-1) for FKM. The findings showed that GKM is superior in estimating the mineralization kinetics.
    Matched MeSH terms: Models, Chemical*
  8. Fulltext Chemodynamics of methyl parathion and ethyl parathion: adsorption models for sustainable agriculture
    Tabassum N, Rafique U, Balkhair KS, Ashraf MA
    Biomed Res Int, 2014;2014:831989.
    PMID: 24689059 DOI: 10.1155/2014/831989
    The toxicity of organophosphate insecticides for nontarget organism has been the subject of extensive research for sustainable agriculture. Pakistan has banned the use of methyl/ethyl parathions, but they are still illegally used. The present study is an attempt to estimate the residual concentration and to suggest remedial solution of adsorption by different types of soils collected and characterized for physicochemical parameters. Sorption of pesticides in soil or other porous media is an important process regulating pesticide transport and degradation. The percentage removal of methyl parathion and ethyl parathion was determined through UV-Visible spectrophotometer at 276 nm and 277 nm, respectively. The results indicate that agricultural soil as compared to barren soil is more efficient adsorbent for both insecticides, at optimum batch condition of pH 7. The equilibrium between adsorbate and adsorbent was attained in 12 hours. Methyl parathion is removed more efficiently (by seven orders of magnitude) than ethyl parathion. It may be attributed to more available binding sites and less steric hindrance of methyl parathion. Adsorption kinetics indicates that a good correlation exists between distribution coefficient (Kd) and soil organic carbon. A general increase in Kd is noted with increase in induced concentration due to the formation of bound or aged residue.
    Matched MeSH terms: Models, Chemical*
  9. Fulltext An experimental study on pile spacing effects under lateral loading in sand
    Khari M, Kassim KA, Adnan A
    ScientificWorldJournal, 2013;2013:734292.
    PMID: 24453900 DOI: 10.1155/2013/734292
    Grouped and single pile behavior differs owing to the impacts of the pile-to-pile interaction. Ultimate lateral resistance and lateral subgrade modulus within a pile group are known as the key parameters in the soil-pile interaction phenomenon. In this study, a series of experimental investigation was carried out on single and group pile subjected to monotonic lateral loadings. Experimental investigations were conducted on twelve model pile groups of configurations 1 × 2, 1 × 3, 2 × 2, 3 × 3, and 3 × 2 for embedded length-to-diameter ratio l/d = 32 into loose and dense sand, spacing from 3 to 6 pile diameter, in parallel and series arrangement. The tests were performed in dry sand from Johor Bahru, Malaysia. To reconstruct the sand samples, the new designed apparatus, Mobile Pluviator, was adopted. The ultimate lateral load is increased 53% in increasing of s/d from 3 to 6 owing to effects of sand relative density. An increasing of the number of piles in-group decreases the group efficiency owing to the increasing of overlapped stress zones and active wedges. A ratio of s/d more than 6d is large enough to eliminate the pile-to-pile interaction and the group effects. It may be more in the loose sand.
    Matched MeSH terms: Models, Chemical*
  10. Extent and severity of groundwater contamination based on hydrochemistry mechanism of sandy tropical coastal aquifer
    Isa NM, Aris AZ, Sulaiman WN
    Sci Total Environ, 2012 Nov 1;438:414-25.
    PMID: 23022725 DOI: 10.1016/j.scitotenv.2012.08.069
    Small islands are susceptible to anthropogenic and natural activities, especially in respect of their freshwater supply. The freshwater supply in small islands may be threatened by the encroachment of seawater into freshwater aquifers, usually caused by over pumping. This study focused on the hydrochemistry of the Kapas Island aquifer, which controls the groundwater composition. Groundwater samples were taken from six constructed boreholes for the analysis and measurement of its in-situ and major ions. The experimental results show a positive and significant correlation between Na-Cl (r=0.907; p<0.01), which can be defined as the effect of salinization. The mechanisms involved in groundwater chemistry changes were ion exchange and mineralization. These processes can be demonstrated using Piper's diagram in which the water type has shifted into a Na-HCO(3) water type from a Ca-HCO(3) water type. Saturation indices have been calculated in order to determine the saturation condition related to dissolution or the precipitation state of the aquifer bedrock. About 76% of collected data (n=108) were found to be in the dissolution process of carbonate minerals. Moreover, the correlation between total CEC and Ca shows a positive and strong relationship (r=0.995; p<0.01). This indicates that the major mineral component in Kapas Island is Ca ion, which contributes to the groundwater chemical composition. The output of this research explains the chemical mechanism attributed to the groundwater condition of the Kapas Island aquifer.
    Matched MeSH terms: Models, Chemical*
  11. Using D-optimal experimental design to optimise remazol black B mineralisation by Fenton-like peroxidation
    Hasan DB, Abdul Aziz AR, Daud WM
    Environ Technol, 2012 Jun;33(10-12):1111-21.
    PMID: 22856280
    The mineralisation of remazol black B (RBB) was studied at concentrations ranging from 20-1000 mgL(-1). The work was aimed at investigating the Fenton-like peroxidation of RBB at a concentration typically obtained in Batik cottage industries. Other response parameters were degradation and colour removal efficiencies. The parameters that were measured included total organic carbon (TOC), chemical oxygen demand (COD) as well as absorbance for mineralisation, degradation and colour. To optimise the process, the interaction effects of several controlling variables on the treatment process were examined using dispersion matrix-optimal design and response surface analysis. Four specific variables: initial dye concentration (Dye)o; the molar ratio of oxidant to dye organic strength (H2O2):(COD); the mass ratio of the oxidant to the catalyst (H2O2):(Fe3+) and reaction time (t(r)), were observed. Three reduced empirical models, one for each response, were developed for describing the treatment process. For 20, 510 and 1000 mgL(-1), the optimum %TOC reduction and oxidation times were 44% for 95 min, 52% for 52.5 min and 68% for 10 min corresponding to 67, 81 and 75% COD reduction, respectively. The optimum COD reduction and oxidation times were 89% for 95 min, 91% for 10 min and 84% for 95 min for concentrations of 20, 510 and 1000 mg L(-1), respectively. For all concentrations, total colour removal was achieved. A comparison of the results obtained in this study with literature values for traditional Fenton, photo-Fenton and photo-Fenton-like oxidation indicated that the TOC reduction obtained using the Fenton-like process was satisfactory.
    Matched MeSH terms: Models, Chemical*
  12. The evaluation of various kinetic models for base-catalyzed ethanolysis of palm oil
    Shahla S, Ngoh GC, Yusoff R
    Bioresour Technol, 2012 Jan;104:1-5.
    PMID: 22154586 DOI: 10.1016/j.biortech.2011.11.010
    In this paper, the kinetics of palm oil ethanolysis with various models have been investigated in a temperature range of 25-55 °C. The highest yield was achieved when the conversion to ethyl ester was 97.5±0.5% in the stated temperature range, using ethanol:oil molar ratio of 12:1, and 1.0 wt.% sodium ethoxide. The level of conformity of the reaction with reversible second order, irreversible second order and first order kinetic models were evaluated by means of the R(2) values of the linear curves. The ethanolysis showed the best conformity with irreversible second order kinetic model with 92-98% level of confidence. The reaction rate constants were within 0.018-0.088 dm(3)/mol min and the activation energy of the reaction was 42.36 kJ/mol.
    Matched MeSH terms: Models, Chemical*
  13. Simplex-centroid mixture formulation for optimised composting of kitchen waste
    Abdullah N, Chin NL
    Bioresour Technol, 2010 Nov;101(21):8205-10.
    PMID: 20624604 DOI: 10.1016/j.biortech.2010.05.068
    Composting is a good recycling method to fully utilise all the organic wastes present in kitchen waste due to its high nutritious matter within the waste. In this present study, the optimised mixture proportions of kitchen waste containing vegetable scraps (V), fish processing waste (F) and newspaper (N) or onion peels (O) were determined by applying the simplex-centroid mixture design method to achieve the desired initial moisture content and carbon-to-nitrogen (CN) ratio for effective composting process. The best mixture was at 48.5% V, 17.7% F and 33.7% N for blends with newspaper while for blends with onion peels, the mixture proportion was 44.0% V, 19.7% F and 36.2% O. The predicted responses from these mixture proportions fall in the acceptable limits of moisture content of 50% to 65% and CN ratio of 20-40 and were also validated experimentally.
    Matched MeSH terms: Models, Chemical*
  14. Removal Rate of Organic Matter Using Natural Cellulose via Adsorption Isotherm and Kinetic Studies
    Din MF, Ponraj M, Low WP, Fulazzaky MA, Iwao K, Songip AR, et al.
    Water Environ Res, 2016 Feb;88(2):118-30.
    PMID: 26803100 DOI: 10.2175/106143015X14362865227913
    In this study, the removal of natural organic matter (NOM) using coconut fiber (CF) and palm oil fiber (POF) was investigated. Preliminary analysis was performed using a jar test for the selection of optimal medium before the fabricated column model experiment. The equilibrium studies on isotherms and kinetic models for NOM adsorption were analyzed using linearized correlation coefficient. Results showed that the equilibrium data were fitted to Langmuir isotherm model for both CF and POF. The most suitable adsorption model was the pseudo-first-order kinetic model for POF and pseudo-second-order kinetic model for CF. The adsorption capacities achieved by the CF and POF were 15.67 and 30.8 mg/g respectively. Based on this investigation, it can be concluded that the POF is the most suitable material for the removal of NOM in semi polluted river water.
    Matched MeSH terms: Models, Chemical*
  15. Morphology and kinetic modeling of molecularly imprinted organosilanol polymer matrix for specific uptake of creatinine
    Ang QY, Low SC
    Anal Bioanal Chem, 2015 Sep;407(22):6747-58.
    PMID: 26163132 DOI: 10.1007/s00216-015-8841-9
    Molecular imprinting is an emerging technique to create imprinted polymers that can be applied in affinity-based separation, in particular, biomimetic sensors. In this study, the matrix of siloxane bonds prepared from the polycondensation of hydrolyzed tetraethoxysilane (TEOS) was employed as the inorganic monomer for the formation of a creatinine (Cre)-based molecularly imprinted polymer (MIP). Doped aluminium ion (Al(3+)) was used as the functional cross-linker that generated Lewis acid sites in the confined silica matrix to interact with Cre via sharing of lone pair electrons. Surface morphologies and pore characteristics of the synthesized MIP were determined by field emission scanning electron microscopy (FESEM) and Brunauer-Emmet-Teller (BET) analyses, respectively. The imprinting efficiency of MIPs was then evaluated through the adsorption of Cre with regard to molar ratios of Al(3+). A Cre adsorption capacity of up to 17.40 mg Cre g(-1) MIP was obtained and adsorption selectivity of Cre to its analogues creatine (Cr) and N-hydroxysuccinimide (N-hyd) were found to be 3.90 ± 0.61 and 4.17 ± 3.09, respectively. Of all the studied MIP systems, chemisorption was predicted as the rate-limiting step in the binding of Cre. The pseudo-second-order chemical reaction kinetic provides the best correlation of the experimental data. Furthermore, the equilibrium adsorption capacity of MIP fit well with a Freundlich isotherm (R (2) = 0.98) in which the heterogeneous surface was defined.
    Matched MeSH terms: Models, Chemical*
  16. An ultrasound-assisted system for the optimization of biodiesel production from chicken fat oil using a genetic algorithm and response surface methodology
    Fayyazi E, Ghobadian B, Najafi G, Hosseinzadeh B, Mamat R, Hosseinzadeh J
    Ultrason Sonochem, 2015 Sep;26:312-20.
    PMID: 25870003 DOI: 10.1016/j.ultsonch.2015.03.007
    Biodiesel is a green (clean), renewable energy source and is an alternative for diesel fuel. Biodiesel can be produced from vegetable oil, animal fat and waste cooking oil or fat. Fats and oils react with alcohol to produce methyl ester, which is generally known as biodiesel. Because vegetable oil and animal fat wastes are cheaper, the tendency to produce biodiesel from these materials is increasing. In this research, the effect of some parameters such as the alcohol-to-oil molar ratio (4:1, 6:1, 8:1), the catalyst concentration (0.75%, 1% and 1.25% w/w) and the time for the transesterification reaction using ultrasonication on the rate of the fatty acids-to-methyl ester (biodiesel) conversion percentage have been studied (3, 6 and 9 min). In biodiesel production from chicken fat, when increasing the catalyst concentration up to 1%, the oil-to-biodiesel conversion percentage was first increased and then decreased. Upon increasing the molar ratio from 4:1 to 6:1 and then to 8:1, the oil-to-biodiesel conversion percentage increased by 21.9% and then 22.8%, respectively. The optimal point is determined by response surface methodology (RSM) and genetic algorithms (GAs). The biodiesel production from chicken fat by ultrasonic waves with a 1% w/w catalyst percentage, 7:1 alcohol-to-oil molar ratio and 9 min reaction time was equal to 94.8%. For biodiesel that was produced by ultrasonic waves under a similar conversion percentage condition compared to the conventional method, the reaction time was decreased by approximately 87.5%. The time reduction for the ultrasonic method compared to the conventional method makes the ultrasonic method superior.
    Matched MeSH terms: Models, Chemical*
  17. Modeling and optimization of lipase-catalyzed production of succinic acid ester using central composite design analysis
    Abdul Rahman MB, Jarmi NI, Chaibakhsh N, Basri M
    J Ind Microbiol Biotechnol, 2011 Jan;38(1):229-34.
    PMID: 20803246 DOI: 10.1007/s10295-010-0817-3
    Esterification of succinic acid with oleyl alcohol catalyzed by immobilized Candida antarctica lipase B (Novozym 435) was investigated in this study. Response surface methodology (RSM) based on a five-level, four-variable central composite design (CCD) was used to model and analyze the reaction. A total of 21 experiments representing different combinations of the four parameters including temperature (35-65°C), time (30-450 min), enzyme amount (20-400 mg), and alcohol:acid molar ratio (1:1-8:1) were generated. A partial cubic equation could accurately model the response surface with a R(2) of 0.9853. The effect and interactions of the variables on the ester synthesis were also studied. Temperature was found to be the most significant parameter that influenced the succinate ester synthesis. At the optimal conditions of 41.1°C, 272.8 min, 20 mg enzyme amount and 7.8:1 alcohol:acid molar ratio, the esterification percentage was 85.0%. The model can present a rapid means for estimating the conversion yield of succinate ester within the selected ranges.
    Matched MeSH terms: Models, Chemical*
  18. Rapid adsorption of toxic Pb(II) ions from aqueous solution using multiwall carbon nanotubes synthesized by microwave chemical vapor deposition technique
    Mubarak NM, Sahu JN, Abdullah EC, Jayakumar NS
    J Environ Sci (China), 2016 Jul;45:143-55.
    PMID: 27372128 DOI: 10.1016/j.jes.2015.12.025
    Multiwall carbon nanotubes (MWCNTs) were synthesized using a tubular microwave chemical vapor deposition technique, using acetylene and hydrogen as the precursor gases and ferrocene as catalyst. The novel MWCNT samples were tested for their performance in terms of Pb(II) binding. The synthesized MWCNT samples were characterized using Fourier Transform Infrared (FT-IR), Brunauer, Emmett and Teller (BET), Field Emission Scanning Electron Microscopy (FESEM) analysis, and the adsorption of Pb(II) was studied as a function of pH, initial Pb(II) concentration, MWCNT dosage, agitation speed, and adsorption time, and process parameters were optimized. The adsorption data followed both Freundlich and Langmuir isotherms. On the basis of the Langmuir model, Qmax was calculated to be 104.2mg/g for the microwave-synthesized MWCNTs. In order to investigate the dynamic behavior of MWCNTs as an adsorbent, the kinetic data were modeled using pseudo first-order and pseudo second-order equations. Different thermodynamic parameters, viz., ∆H(0), ∆S(0) and ∆G(0) were evaluated and it was found that the adsorption was feasible, spontaneous and endothermic in nature. The statistical analysis revealed that the optimum conditions for the highest removal (99.9%) of Pb(II) are at pH5, MWCNT dosage 0.1g, agitation speed 160r/min and time of 22.5min with the initial concentration of 10mg/L. Our results proved that microwave-synthesized MWCNTs can be used as an effective Pb(II) adsorbent due to their high adsorption capacity as well as the short adsorption time needed to achieve equilibrium.
    Matched MeSH terms: Models, Chemical*
  19. Fulltext AnkPlex: algorithmic structure for refinement of near-native ankyrin-protein docking
    Wisitponchai T, Shoombuatong W, Lee VS, Kitidee K, Tayapiwatana C
    BMC Bioinformatics, 2017 Apr 19;18(1):220.
    PMID: 28424069 DOI: 10.1186/s12859-017-1628-6
    BACKGROUND: Computational analysis of protein-protein interaction provided the crucial information to increase the binding affinity without a change in basic conformation. Several docking programs were used to predict the near-native poses of the protein-protein complex in 10 top-rankings. The universal criteria for discriminating the near-native pose are not available since there are several classes of recognition protein. Currently, the explicit criteria for identifying the near-native pose of ankyrin-protein complexes (APKs) have not been reported yet.

    RESULTS: In this study, we established an ensemble computational model for discriminating the near-native docking pose of APKs named "AnkPlex". A dataset of APKs was generated from seven X-ray APKs, which consisted of 3 internal domains, using the reliable docking tool ZDOCK. The dataset was composed of 669 and 44,334 near-native and non-near-native poses, respectively, and it was used to generate eleven informative features. Subsequently, a re-scoring rank was generated by AnkPlex using a combination of a decision tree algorithm and logistic regression. AnkPlex achieved superior efficiency with ≥1 near-native complexes in the 10 top-rankings for nine X-ray complexes compared to ZDOCK, which only obtained six X-ray complexes. In addition, feature analysis demonstrated that the van der Waals feature was the dominant near-native pose out of the potential ankyrin-protein docking poses.

    CONCLUSION: The AnkPlex model achieved a success at predicting near-native docking poses and led to the discovery of informative characteristics that could further improve our understanding of the ankyrin-protein complex. Our computational study could be useful for predicting the near-native poses of binding proteins and desired targets, especially for ankyrin-protein complexes. The AnkPlex web server is freely accessible at http://ankplex.ams.cmu.ac.th .

    Matched MeSH terms: Models, Chemical*
  20. Catalytic CO2 gasification of rubber seed shell-derived hydrochar: reactivity and kinetic studies
    Lahijani P, Mohammadi M, Mohamed AR
    Environ Sci Pollut Res Int, 2019 Apr;26(12):11767-11780.
    PMID: 30815812 DOI: 10.1007/s11356-019-04613-4
    In this study, hydrothermal carbonization (HTC) of a biomass was used as a means to improve the physicochemical properties of rubber seed shell (RSS) and enhance its reactivity in the char-CO2 gasification reaction, known as the Boudouard reaction (C + CO2 ↔ 2CO). Hydrochar samples were developed by hydrothermal treatment of RSS, without separating the solid residue from the liquid product, at 433, 473, 513, and 553 K under autogenous pressure. The CO2 gasification reactivity of the developed hydrochars was then investigated at different heating rates (5, 10, 20, and 30 K/min) by the non-isothermal thermogravimetric method. The hydrochars revealed higher reactivity and improved gasification characteristics compared to the untreated biomass, while the hydrochar which was filtered from the liquid slurry showed lower reactivity compared to the untreated biomass. This was due to the chemical and structural evolutions of the biomass during hydrothermal treatment as indicated by various analyses. The gasification reactivity of the hydrochar was substantially enhanced by introduction of a catalyst (NaNO3) during HTC. Kinetic analysis of the char-CO2 gasification reaction was carried out by applying Flynn-Wall-Ozawa (FWO), Kissinger-Akahira-Sunose (KAS), and Starink isoconversional methods, and thermodynamic parameters were also determined. The activation energy of the Na-loaded RSS hydrochar in CO2 gasification (120-154 kJ/mol) was considerably lower than that of the untreated biomass (153-172 kJ/mol). Thermodynamic studies also confirmed the promoting effect of hydrothermal treatment and catalyst impregnation on enhancement of reactivity of the virgin biomass and reduction of gasification temperature.
    Matched MeSH terms: Models, Chemical*
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