bluuebunny/crossref_metadata_2025_split huggingface dataset:
Comparative HPLC Enantioseparation of Thirty‐Six Aromatic Compounds on Four Columns of the Lux® Series: Impact of Substituents, Shapes and Electronic Properties
Authors: Peluso Paola , Cossu Sergio 
Published: July 2013

ABSTRACTWith the aim to define a combined computational/chromatographic empirical approach useful for the high‐performance liquid chromatography (HPLC) method development of new chiral compounds, 36 racemic aromatic compounds with different chemical structures were used as test probes on four polysaccharide‐based chiral stationary phases (CSPs) of the Lux series, namely Lux Cellulose‐1, Lux Cellulose‐2, Lux Cellulose‐4, and Lux Amylose‐2, using classical n‐hexane/2‐propanol mixtures as mobile phase. Electrostatic potential surfaces (EPSs) determined using Density Functional Theory (DFT) calculations were used to derive size, shape, and electronic properties of each analyte. Then a comparative HPLC screening was carried out in order to evaluate the impact of substituents, shapes, and electronic properties of the analytes on the chromatographic behavior as the column changes. The four CSPs showed good complementary recognition ability. The elution sequence was determined in 30 cases out of 36. The success rate to afford baseline separations (Rs ≥ 1.5) was estimated: 29 compounds out of 36 showed baseline enantioseparation on at least one of the four selected CSPs. The combined computational‐chromatographic screening furnished useful collective structure‐chromatographic behavior relationships and a map of the chiral discrimination abilities of the considered CSPs towards the analytes. On this basis, the chromatographic behavior of new analytes on a set of polysaccharide‐based CSPs can be mapped through the qualitative correlation of chromatographic parameters (k, α, Rs) to computed molecular properties of the analytes. Chirality 25:709–718, 2013. © 2013 Wiley Periodicals, Inc.
Study on Lithium Insertion in Lepidocrocite and λ‐MnO2 Type TiO2: A First‐Principles Prediction
Authors: Liu Yahui , Wu Jingyi , Zhao Wei , Chu Jinglong , Qi Tao 
Published: July 2013

AbstractTiO2 is a latent anode material for rechargeable lithium batteries. Our simulation models, basing lepidocrocite and λ‐MnO2 type TiO2, were investigated by density functional theory (DFT). The key issues are focused on the lithium insertion sites, electronic structures, and the conducting paths of Li+ ions. Our calculated data indicate the calculated voltage of λ‐MnO2 type TiO2 is higher than that of lepidocrocite type TiO2. The Li+ ion migration energy barrier of lepidocrocite type TiO2 along the [1 0 0] direction (0.45 eV) is lower than that of along the [1 1 0] direction (0.57 eV). The energy barriers of λ‐MnO2 type TiO2 to move a Li+ ion among the adjacent embedded sites (16c or 8a sites) is 0.68 eV.
Preparation of Monodispersed Copper Nanoparticles by an Environmentally Friendly Chemical Reduction
Authors: Li Meijuan , Xiang Kun , Luo Guoqiang , Gong Daoren , Shen Qiang , Zhang Lianmeng 
Published: July 2013

AbstractIn this paper, highly dispersive nanosized copper particles with a mean particle size of less than 6 nm are prepared by an environmentally friendly chemical reduction method. Non‐toxic L‐ascorbic acid acts as both reducing agent and antioxidant in ethylene glycol in the absence of any other capping agent. Transmission electron microscopy (TEM) is used to characterize the size and morphology of Cu nanoparticles. The results of UV‐Vis spectroscopy (UV‐Vis), energy dispersive spectroscopy (EDS) and high resolution TEM (HRTEM) illustrate that the resultant product is pure Cu nanocrystals. The size of Cu nanoparticles is remarkably impacted by the order of reagent addition, and the investigation reveals the reaction procedure of Cu2+ ions and L‐ascorbic acid.
Cu(I)‐Catalyzed Synthesis of 2‐Substituted Benzimidazoles from 2‐Iodoanilines and Amides
Authors: Yuan Hua , Chen Yongxin , Song Jinli , Chen Chunxia , Chen Baohua 
Published: July 2013

AbstractA novel and efficient approach to the synthesis of 2‐substituted benzimidazoles has been developed via CuI/DMEDA‐catalyzed coupling reaction and post‐cyclization with glacial acetic acid from readily available 2‐iodoanilines and amides. This method is suitable for the construction of a variety of benzimidazoles in moderate to good yields under short reaction times.
Asymmetric Synthesis, Antifungal Activity and Molecular Modeling of Iodiconazole Isomers
Authors: Zhang Yongqiang , Wang Shengzheng , Miao Zhenyuan , Yao Jianzhong , Zhang Wannian , Sheng Chunquan 
Published: July 2013

AbstractIodiconazole is a novel antifungal agent that was developed in its racemic form. In order to investigate the effects of the chiral center on the antifungal activity, R‐ and S‐isomers of iodiconazole were prepared on the basis of the asymmetric Sharpless epoxidation. (S)‐Iodiconazole was proved to have better antifungal activity than the (R)‐isomer. The binding modes of the two isomers with lanosterol 14α‐demethylase were clarified by molecular docking.
Backward‐in‐Time Selection of the Order of Dynamic Regression Prediction Model
Authors: Vlachos Ioannis , Kugiumtzis Dimitris 
Published: July 2013

ABSTRACTWe investigate the optimal structure of dynamic regression models used in multivariate time series prediction and propose a scheme to form the lagged variable structure called Backward‐in‐Time Selection (BTS), which takes into account feedback and multicollinearity, often present in multivariate time series. We compare BTS to other known methods, also in conjunction with regularization techniques used for the estimation of model parameters, namely principal components, partial least squares and ridge regression estimation. The predictive efficiency of the different models is assessed by means of Monte Carlo simulations for different settings of feedback and multicollinearity. The results show that BTS has consistently good prediction performance, while other popular methods have varying and often inferior performance. The prediction performance of BTS was also found the best when tested on human electroencephalograms of an epileptic seizure, and for the prediction of returns of indices of world financial markets.Copyright © 2013 John Wiley & Sons, Ltd.
Performance of the Direct Methanol Carbonate Fuel Cell Using Anion Exchange Materials and Non‐Noble Metal Cathode Catalyst
Authors: Wang X. , Yu E. H. , Horsfall J. , Scott K. 
Published: July 2013

AbstractA direct methanol fuel cell using a mixture of O2 and CO2 at the cathode was evaluated using anion exchange materials and cathode catalysts of Pt and a non‐Pt catalyst. The MEA based on non‐noble metal catalyst Acta 4020 showed superior performance than Pt/C based MEA in terms of open circuit potential and power density in carbonate environment. The fuel cell performance was improved by applying anion exchange ionomer in the catalyst layer. A maximum power density of 4.5 mW cm–2 was achieved at 50 °C using 6.0 M methanol and 2.0 M K2CO3.
Toxicity of graphene nanoflakes evaluated by cell‐based electrochemical impedance biosensing
Authors: Yoon Ok Ja , Kim Insu , Sohn Il Yung , Kieu Truong Thuy , Lee Nae‐Eung 
Published: July 2013

AbstractGraphene nanoflake toxicity was analyzed using cell‐based electrochemical impedance biosensing with interdigitated indium tin oxide (ITO) electrodes installed in a custom‐built mini‐ incubator positioned on an inverted optical microscope. Sensing with electrochemical measurements from interdigitated ITO electrodes was highly linear (R2 = 0.93 and 0.96 for anodic peak current (Ipa) and cathodic peak current (Ipc), respectively). Size‐dependent analysis of Graphene nanoflake toxicity was carried out in a mini‐incubator system with cultured HeLa cells treated with Graphene nanoflakes having an average size of 80 or 30 nm for one day. Biological assays of cell proliferation and viability complemented electrochemical impedance measurements. The increased toxicity of smaller Graphene nanoflakes (30 nm) as measured by electrochemical impedance sensing and optical monitoring of treated cells was consistent with the biological assay results. Cell‐based electrochemical impedance biosensing can be used to assess the toxicity of nanomaterials with different biomedical and environmental applications. © 2013 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 102A: 2288–2294, 2014.
Polyethyleneimine‐poly(ethylene glycol)‐star‐copolymers as efficient and biodegradable vectors for mammalian cell transfection
Authors: Ladewig Katharina , Xu Zhi Ping , Gray Peter , (Max) Lu G. Q. 
Published: July 2013

AbstractHigh molecular weight (MW) polyethyleneimine (PEI) has been successfully used for the transfection of a broad variety of cell lines. In contrast to low MW PEI, which exhibits low transfection efficiencies but also low cytotoxicity, high MW PEI‐mediated transfection achieves much higher efficiencies but at the cost of cell viability; therefore its use in commercial scale transfection and clinical application is limited. In this work we address this problem by constructing biodegradable high MW PEI mimics built from low MW PEI building blocks. The end‐groups of small 5‐arm star polyethylene glycol (PEG) prepolymers were decorated with linear oligo‐ethyleneimine (OEI)/PEI arms of various MW via azomethine linkages. The resultant PEI‐PEG‐star‐copolymers were investigated for their ability to complex plasmid DNA. Polymer/DNA complexes were characterized using techniques such as dynamic light scattering and transmission electron microscopy. Having established their cytotoxicity limits, they were tested as gene delivery vehicles for the transfection of suspension adapted Chinese hamster ovary (CHO‐S) cells under serum‐free conditions and adherent human embryonic kidney cells (HEK293T) in serum containing medium. Our PEI‐PEG‐star‐copolymers showed a reduced cytotoxicity compared to high MW PEI while maintaining the ability to complex plasmid DNA and transfect mammalian cells, with significant transfection efficiencies. The effects of the optimum parameters on the transfection of mammalian cells using such novel polymers are discussed. © 2013 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 102A: 2137–2146, 2014.
Interaction between mesenchymal stem cells and Ti‐30Ta alloy after surface treatment
Authors: Capellato Patricia , Escada Ana L. A. , Popat Ketul C. , Claro Ana P. R. Alves 
Published: July 2013

AbstractIn this study, in vitro cytocompatibility was investigated in the Ti‐30Ta alloy after two kinds of surfaces treatments: alkaline and biomimetic treatment. Each condition was evaluated by scanning electron microscopy/energy‐dispersive X‐ray spectroscopy. Cellular adhesion, viability, protein expression, morphology, and differentiation were evaluated with Bone marrow stromal cells (MSCs) to investigate the short and long‐term cellular response by fluorescence microscope imaging and colorimetric assays techniques. Two treatments exhibited similar results with respect to total protein content and enzyme activity as compared with alloy without treatment. However, it was observed improved of the biomineralization, bone matrix formation, enzyme activity, and MSCs functionality after biomimetic treatment. These results indicate that the biomimetic surface treatment has a high potential for enhanced osseointegration. © 2013 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 102A: 2147–2156, 2014.
Effects of DS‐modified agarose gels on neurite extension in 3D scaffold through mechanisms other than changing the pore radius of the gels
Authors: Peng Jin , Pan Qian , Zhang Wei , Yang Hao , Zhou Xue , Jiang Hua 
Published: July 2013

AbstractDermatan sulfate is widely distributed as glycosaminoglycan side chains of proteoglycans, which are the main components of glial scar and inhibit neurite regeneration after nerve injury. However its role in the inhibiting process is not clear. Understanding neurite extension in three‐dimensional scaffolds is critical for neural tissue engineering. This study used agarose gels modified with dermatan sulfate as the three‐dimensional culture scaffold. We explored structure–function relationship between the three‐dimensional scaffold and neurite extension and examined the role of dermatan sulfate on neurite extension in the three‐dimensional scaffold. A range of agarose concentrations was used to generate varied gel physical structures and the corresponding neurite extension of embryonic day (E9) chick dorsal root ganglia was examined. We measured gel stiffness and gel pore size to determine whether dermatan sulfate changed the gels' conformation. As gel concentration increased, neurite length and gel pore size decreased, and gel stiffness increased. At 1.00 and 1.25% (wt/vol) concentrations, dermatan sulfates both immobilized with agarose gels and dissolved in culture medium inhibit neurite extension. While at 1.50 and 1.75% (wt/vol) concentrations, only immobilized dermatan sulfate worked. Immobilized dermatan sulfate could modify molecular shape of agarose gels, decrease gel pore size statistically, but did not influence gel stiffness. We have proved that the decrease of gel pore size is insufficient to inhibit neurite extension. These results indicate that dermatan sulfate inhibits neurite extension not through forming a mechanical barrier. Maybe its interaction with neuron membrane is the key factor in neurite extension. © 2013 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 102A: 2157–2162, 2014.
One‐Pot Synthesis of CdSe Quantum Dots in Aqueous Solution for Biological Labeling
Authors: Dong Meiting , Fu Shasha , Liu Shuxian , Xu Jingyi , Huang Chaobiao 
Published: July 2013

AbstractThe one‐pot synthesis of water‐soluble and biologically compatible yellow CdSe quantum dots (QDs) featuring the use of glutathione (GSH) as the capping and reducing agent was achieved under aqueous conditions at 150 °C. The synthesized yellow CdSe QDs with quantum yield (QY) up to 20% exhibit zinc blende cubic structure particles with an average diameter of 4‐5 nm. It was found that both molar ratio of Se/Cd and reaction time had a significant effect on size distribution of GSH‐CdSe QDs. Meanwhile, the interaction of QDs bioconjugated to bovine hemoglobin (BHb) was studied by absorption and fluorescence(FL) spectra. With addition of BHb, the FL intensity of CdSe QDs largely quenched due to the static mechanism. The linear range is 5.0 × 10−8 mol/L to 3.0 × 10−6 mol/L, and the correlation coefficient is 0.9991, suggesting that could be used as a probe to label biological molecules and bacterial cells.
Spatial and diurnal variability in reactive nitrogen oxide chemistry as reflected in the isotopic composition of atmospheric nitrate: Results from the CalNex 2010 field study
Authors: Vicars W. C. , Morin S. , Savarino J. , Wagner N. L. , Erbland J. , Vince E. , Martins J. M. F. , Lerner B. M. , Quinn P. K. , Coffman D. J. , Williams E. J. , Brown S. S. 
Published: July 2013

AbstractHere we present measurements of the size‐resolved concentration and isotopic composition of atmospheric nitrate (NO3−) collected during a cruise in coastal California. Significant differences in air mass origin and atmospheric chemistry were observed in the two main regions of this cruise (South and Central Coast) with corresponding differences in NO3− concentration and isotope ratios. Measurements of the 17O‐excess (Δ17O) of NO3− suggest that nocturnal chemistry played an important role in terms of total NO3− production (~ 50%) in the coastal Los Angeles region (South Coast), where NO3− concentrations were elevated due to the influence of sea breeze / land breeze recirculation and Δ17O(NO3−) averaged (25.3 ± 1.6)‰. Conversely, Δ17O(NO3−) averaged (22.3 ± 1.8)‰ in the Central Coast region, suggesting that the daytime OH + NO2 reaction was responsible for 60–85% of NO3− production in the marine air sampled in this area. A strong diurnal signal was observed for both the Δ17O and δ15N of NO3−. In the case of Δ17O, this trend is interpreted quantitatively in terms of the relative proportions of daytime and nighttime production and the atmospheric lifetime of NO3−. For δ15N, which had an average value of (0.0 ± 3.2)‰, the observed diurnality suggests a combined effect of isotopic exchange between gas‐phase precursors and variability in reactive nitrogen sources. These findings represent a significant advance in our understanding of the isotope dynamics of nitrate and its precursor molecules, with potentially important implications for air quality modeling.
Long‐term survival after hepatic and pulmonary resection of colorectal cancer metastases
Authors: Sourrouille Isabelle , Mordant Pierre , Maggiori Léon , Dokmak Safi , Lesèche Guy , Panis Yves , Belghiti Jacques , Castier Yves 
Published: July 2013

AbstractBackgroundRecent changes in adjuvant therapies improved the prognosis of metastatic colorectal cancers. Curative resection may be considered, even for both pulmonary and hepatic metastases, but prognostic factors are not well identified.MethodsFrom 1995 to 2010, 69 patients had curative resection of pulmonary metastases of colorectal cancer; 31 had also hepatic metastases. Pulmonary and hepatic resection occurred in 2 steps (87%). We studied overall and disease‐free survival and prognostic factors.ResultsPrimary tumor location was the rectum in 10 cases (32%). Pulmonary metastases were synchronous in 5 (16%) and bilateral in 6 (19%). One patient (3%) died after pulmonary surgery. One (3%) had positive surgical margins for pulmonary metastases. Median overall survival was 44 months (5‐year rate = 36%); median disease‐free survival was 22 months (5‐year rate = 10%). Factors linked to impaired survival were rectal primary tumor (P = 0.04) and bilateral pulmonary metastases (P = 0.02) for overall survival, and pulmonary metastase≥20 mm (P = 0.04) for disease‐free survival.ConclusionWhen associated to adjuvant therapy, complete resection of pulmonary and hepatic metastases of colorectal cancer allows long‐term survival in one third of the patients. J. Surg. Oncol. 2013 108:220–224. © 2013 Wiley Periodicals, Inc.
Fabrication methods of 3D periodic metallic nano/microstructures for photonics applications
Authors: Hossain Md Muntasir , Gu Min 
Published: July 2013

AbstractPeriodic metallic nano/microstructures have received a great a deal of attention in the photonics research community over the last few decades due to their intriguing optical properties. Three‐dimensional metallic nano/microstructures such as metallic photonic crystals, metamaterials, and plasmonic devices possess unique characteristics of tailored thermal radiation, negative refraction and deep subwavelength confinement of light. In this article, the recent progress on the experimental methods for the realisation of three‐dimensional periodic metallic and thin metal film coated dielectric nano/microstructures operating from optical to mid‐infrared frequencies has been reviewed. Advancement of the state‐of‐the‐art nanofabrication methods over the last few decades have led to the development of metallic nano/microstructures of diverse geometries, high resolution features and large scale production. The recent progress in the novel fabrication methods have inspired the development of functional and exciting photonic devices based on periodic metallic nano/microstructures with various applications in photonics including communications, photovoltaics, and biophotonics.
Dispersion of Silver Nanoparticles into Polymer Matrix Dry Adhesives to Achieve Antibacterial Properties, Increased Adhesion, and Optical Absorption
Authors: Bovero Enrico , Magee Kaylee E. A. , Young Edgar C. , Menon Carlo 
Published: July 2013

AbstractThe fabrication and characterization of dry adhesives treated with silver (Ag) nanoparticles presenting enhanced adhesion and antibacterial properties is described. A one‐step procedure for the dispersion of Ag nanoparticles in polydimethylsiloxane (PDMS) is implemented, achieving a uniform distribution of particles within the polymer with an average particle size of 40 nm. An order‐of‐magnitude increase in adhesion is observed for both flat and structured polymers treated with silver, in comparison with adhesives consisting of PDMS without silver. An average reduction of bacterial growth of 2 log‐units is observed upon exposure to Ag treated polymers in comparison to polymers without silver. This indicates the potential for employing this material in environments where avoidance of bacterial contamination is crucial.
Efficient Sustainable Tool for Monitoring Chemical Reactions and Structure Determination in Ionic Liquids by ESI‐MS
Authors: Khemchyan Levon L. , Khokhlova Elena A. , Seitkalieva Marina M. , Ananikov Valentine P. 
Published: July 2013

AbstractAn easy and convenient procedure is described for monitoring chemical reactions and characterization of compounds dissolved in ionic liquids using the well‐known tandem mass spectrometry (MS/MS) technique. Generation of wastes was avoided by utilizing an easy procedure for analysis of ionic liquid systems without preliminary isolation and purification. The described procedure also decreased the risk of plausible contamination and damage of the ESI‐MS hardware and increased sensitivity and accuracy of the measurements. ESI‐MS detection in MS/MS mode was shown to be efficient in ionic liquids systems for structural and mechanistic studies, which are rather difficult otherwise. The developed ESI‐MS/MS approach was applied to study samples corresponding to peptide systems in ionic liquids and to platform chemical directed biomass conversion in ionic liquids.
The Effects of Green Cards on the Wages and Innovations of New PhDs
Authors: Lan Xiaohuan 
Published: July 2013

AbstractVisa policies in the United States restrict job opportunities and job mobility for U.S.‐trained PhDs who hold a temporary visa, a group that accounts for 40 percent of newly graduated PhDs in science and engineering. The Chinese Student Protection Act of 1992 (CSPA) allowed Chinese students to be eligible for permanent residence in the United States. Many CSPA beneficiaries, Chinese students who became permanent residents, did not pursue postdoctoral training and instead entered the public or private sector directly. This supply shift increased the relative wage of native postdocs to non‐postdocs. Four to eight years after graduation, CSPA beneficiaries earned 9 percent more than the comparison group, were less likely to work in academia, published fewer research articles, and produced more patents.