Preparation of O/W Pickering emulsion with oxygen plasma treated carbon nanotubes as surfactants

Wenbao Chen,김형일,Xuyan Liu,Yangshuo Liu,Youngkil Bang 한국공업화학회 2011 Journal of Industrial and Engineering Chemistry Vol.17 No.3

The stable oil-in-water Pickering emulsions were prepared using oxygen plasma treated carbon nanotubes (CNTs) as stabilizers. Some hydrophilic groups such as hydroxyl and carboxyl groups were introduced on the surface of the CNTs by plasma treatment. The plasma treated CNTs showed the improvement in dispersion stability in water as well as cyclohexane for a long time. The Raman spectra showed that the original properties of CNTs were retained after the plasma treatment differently from other chemical modification methods. The plasma treated CNTs had a favorable interfacial interaction with water to form the stable O/W Pickering emulsions. The formation of stable O/W Pickering emulsion was dependent on the CNT concentration, the plasma treatment period, and the sonication time.

Novel Synthesis of Silica/Polypyrrole Hybrid Nanocomposites via Microemulsion Polymerization with a Vapor Monomer Feeding System

Wenbao Chen,Xuyan Liu,Yangshuo Liu,방영길,김형일 한국고분자학회 2011 Macromolecular Research Vol.19 No.1

Silica/polypyrrole hybrid nanoparticles were synthesized by microemulsion polymerization using a vapor monomer feeding system. In contrast to the traditional monomer feeding methods of microemulsion polymerization,this study examined the monomer feeding as a vapor phase. The silica modified with 3-(trimethoxysilyl)propyl methacrylate had a hydrophobic surface was used as template. Polymerization of the pyrrole monomers occurred at the surface of the modified silica. By controlling the vapor feeding speed, the pyrrole monomer could be dispersed in the reaction system quite well. The modification of silica and the formation of silica/polypyrrole nanoparticles were characterized by Fourier transform infrared spectroscopy and thermogravimetric analysis. The silica/polypyrrole hybrid morphology was confirmed by transmission electron microscopy and scanning electron microscopy. Through a comparison with the nanoparticles made by traditional microemulsion polymerization, uniform and smaller nanoparticles of the silica/polypyrrole hybrid nanocomposite were prepared using a lower surfactant content. The size of the silica/polypyrrole nanocomposites decreased with increasing surfactant content and decreasing pyrrole monomer content.

A Multi-dimensional Evidence-based Trust Evaluation Model and Algorithm

Wenbao Jiang,Qijing Li,Wenliang Chen 보안공학연구지원센터 2015 International Journal of Security and Its Applicat Vol.9 No.5

Trust evaluation is increasingly important for collaboration in the Internet today. We propose a multi-dimensional evidence-Based trust evaluation model named EBTrust model, which expands the types and sources of evidence. We put both transaction feedback and the network operating behavior information into this model. And we improve the D-S evidence theory and propose a new rule of evidence synthesis that based on the conflict intensity (G) and efficient conflict (Gh), so we call it G-Gh synthesis rule, which can not only solve the high confliction and complete conflict feature of multi-dimensional evidences but also the problem of uncertainty in the process of trust evaluation. The example analysis and experimental results show that the EBTrust model can resist conspiracy and malicious comment behavior.

A modified area under the ROC curve and its application to marker selection and classification

WenBao Yu,Yuan-chin Ivan Chang,Eun-Sik Park 한국통계학회 2014 Journal of the Korean Statistical Society Vol.43 No.2

sificationscores of a diseased subject is larger than that of a non-diseased subject for arandomly sampled pair of subjects. From the perspective of classification, we want to finda way to separate two groups as distinctly as possible via AUC. When the difference ofthe scores of a marker is small, its impact on classification is less important. Thus, a newdiagnostic/classification measure based on a modified area under the ROC curve (mAUC)is proposed, which is defined as a weighted sum of two AUCs, where the AUC with thesmaller difference is assigned a lower weight, and vice versa. Using mAUC is robust in thesense that mAUC gets larger as AUC gets larger as long as they are not equal. Moreover, inmany diagnostic situations, only a specific range of specificity is of interest. Under normaldistributions, we show that if the AUCs of two markers are within similar ranges, the largermAUC implies the larger partial AUC for a given specificity. This property of mAUC will helpto identify the marker with the higher partial AUC, even when the AUCs are similar. Twononparametric estimates of an mAUC and their variances are given.Wealso suggest the useof mAUC as the objective function for classification, and the use of the gradient Lasso algorithmfor classifier construction and marker selection. Application to simulation datasetsand real microarray gene expression datasets show that our method finds a linear classifierwith a higher ROC curve than some other existing linear classifiers, especially in the rangeof low false positive rates.

Few-layered graphene oxides as superior adsorbents for the removal of Pb(II) ions from aqueous solutions

Wenbao Jia,Songsheng Lu 한국화학공학회 2014 Korean Journal of Chemical Engineering Vol.31 No.7

Few-layered graphene oxides (GOs) were successfully synthesized from graphite using Hummers’ method. The synthesized GOs were characterized in detail by SEM, AFM, XRD, and FTIR spectroscopy. The prepared GOswere used as adsorbents to preconcentrate Pb(II) ions from large volumes of aqueous solutions. The effects of pH, ionicstrength and temperature on the removal of Pb(II) ions from solution to GOs were investigated. The sorption of Pb(II)on GOs was dependent on pH values and independent of ionic strength, which suggested that Pb(II) sorption on GOswas mainly dominated by strong inner-sphere surface complexation. The maximum adsorption capacities (Csmax) ofPb(II) on GOs were calculated to be 344 mg/g at 293 K, 487 mg/g at 308 K, and 758mg/g at 333 K, respectively. TheCsmax values are the highest sorption capacities of today’s materials for the sorption of Pb(II) ions from aqueous solutions. The thermodynamic parameters were calculated from the temperature-dependent sorption isotherms, and the resultsindicated that Pb(II) sorption on GOs was spontaneous and endothermic. The results suggested that the GOs were promisingmaterials for the preconcentration of Pb(II) and other kinds of heavy metal ions from aqueous solutions in environmentalpollution cleanup in real work.

A unified model based multifactor dimensionality reduction framework for detecting gene–gene interactions

Yu, Wenbao,Lee, Seungyeoun,Park, Taesung Oxford University Press 2016 Bioinformatics Vol.32 No.17

<P>Motivation: Gene-gene interaction (GGI) is one of the most popular approaches for finding and explaining the missing heritability of common complex traits in genome-wide association studies. The multifactor dimensionality reduction (MDR) method has been widely studied for detecting GGI effects. However, there are several disadvantages of the existing MDR-based approaches, such as the lack of an efficient way of evaluating the significance of multi-locus models and the high computational burden due to intensive permutation. Furthermore, the MDR method does not distinguish marginal effects from pure interaction effects. Methods: We propose a two-step unified model based MDR approach (UM-MDR), in which, the significance of a multi-locus model, even a high-order model, can be easily obtained through a regression framework with a semi-parametric correction procedure for controlling Type I error rates. In comparison to the conventional permutation approach, the proposed semi-parametric correction procedure avoids heavy computation in order to achieve the significance of a multi-locus model. The proposed UM-MDR approach is flexible in the sense that it is able to incorporate different types of traits and evaluate significances of the existing MDR extensions. Results: The simulation studies and the analysis of a real example are provided to demonstrate the utility of the proposed method. UM-MDR can achieve at least the same power as MDR for most scenarios, and it outperforms MDR especially when there are some single nucleotide polymorphisms that only have marginal effects, which masks the detection of causal epistasis for the existing MDR approaches. Conclusions: UM-MDR provides a very good supplement of existing MDR method due to its efficiency in achieving significance for every multi-locus model, its power and its flexibility of handling different types of traits.</P>

Applying a modified AUC to gene ranking

Yu, Wenbao,Chang, Yuan-Chin Ivan,Park, Eunsik The Korean Statistical Society 2018 Communications for statistical applications and me Vol.25 No.3

High-throughput technologies enable the simultaneous evaluation of thousands of genes that could discriminate different subclasses of complex diseases. Ranking genes according to differential expression is an important screening step for follow-up analysis. Many statistical measures have been proposed for this purpose. A good ranked list should provide a stable rank (at least for top-ranked gene), and the top ranked genes should have a high power in differentiating different disease status. However, there is a lack of emphasis in the literature on ranking genes based on these two criteria simultaneously. To achieve the above two criteria simultaneously, we proposed to apply a previously reported metric, the modified area under the receiver operating characteristic cure, to gene ranking. The proposed ranking method is found to be promising in leading to a stable ranking list and good prediction performances of top ranked genes. The findings are illustrated through studies on both synthesized data and real microarray gene expression data. The proposed method is recommended for ranking genes or other biomarkers for high-dimensional omics studies.

Synthesis of microcapsules with polystyrene/ZnO hybrid shell by Pickering emulsion polymerization

Chen, Wenbao,Liu, Xuyan,Liu, Yangshuo,Kim, Hyung-Il Springer-Verlag 2010 Colloid and Polymer Science Vol.288 No.14

Fabrication and characterization of microcapsules with polyamide–polyurea as hybrid shell

Chen, Wenbao,Liu, Xuyan,Lee, Dong Weon Springer-Verlag 2012 JOURNAL OF MATERIALS SCIENCE - Vol.47 No.4

Gene-Gene Interaction Analysis for the Accelerated Failure Time Model Using a Unified Model-Based Multifactor Dimensionality Reduction Method

이승연,손동희,Wenbao Yu,박태성 한국유전체학회 2016 Genomics & informatics Vol.14 No.4

Although a large number of genetic variants have been identified to be associated with common diseases through genome-wide association studies, there still exits limitations in explaining the missing heritability. One approach to solving this missing heritability problem is to investigate gene-gene interactions, rather than a single-locus approach. For gene-gene interaction analysis, the multifactor dimensionality reduction (MDR) method has been widely applied, since the constructive induction algorithm of MDR efficiently reduces high-order dimensions into one dimension by classifying multi-level genotypes into high- and low-risk groups. The MDR method has been extended to various phenotypes and has been improved to provide a significance test for gene-gene interactions. In this paper, we propose a simple method, called accelerated failure time (AFT) UM-MDR, in which the idea of a unified model-based MDR is extended to the survival phenotype by incorporating AFT-MDR into the classification step. The proposed AFT UM-MDR method is compared with AFT-MDR through simulation studies, and a short discussion is given.