bluuebunny/crossref_metadata_2025_split huggingface dataset:
Metacognitions about smoking: a preliminary investigation
Authors: Nikčević Ana V. , Spada Marcantonio M. 
Published: February 2010

AbstractPreliminary research has indicated that metacognitions are involved in smoking. In the present study, we aimed to investigate whether specific facets of metacognition play a role in explaining smoking initiation and perseveration. Twelve individuals, self‐identified as regular smokers and scoring a positive value on the Fagerström Test of Nicotine Dependence, were assessed using a semi‐structured interview to investigate the following: (1) whether they held positive and/or negative metacognitive beliefs about smoking; (2) what their main goal in smoking was, and how they knew if they had achieved their goal; (3) how they directed their focus of attention when smoking; and (4) what they perceived the advantages and disadvantages of these attentional strategies to be. Results indicated that participants endorsed both positive and negative metacognitive beliefs about smoking and that the goal of smoking was to regulate negative emotion and/or to enhance cognitive functioning. Participants reported that they relied either on an internal signal, such as improvement in the emotional/cognitive state, or on a physical sign, in the form of a finished cigarette, to determine if they had achieved their goal. During an episode of smoking, half of the participants reported focusing their attention internally on thoughts and feelings or the sensations of smoking. The remainder of participants reported either an exclusively external focus of attention (e.g., the environment) or a varied focus of attention. Most participants were able to identify advantages to their attentional strategies, whereas two reported perceived disadvantages. The implications of the findings are discussed. Copyright © 2010 John Wiley & Sons, Ltd.Key Practitioner Message• Cognitive‐attentional profiling that may aid assessment and conceptualisation of smoking behaviour.
Sustainable development: the role of network communication
Authors: Nielsen Anne Ellerup , Thomsen Christa 
Published: February 2010

AbstractResearch within the field of sustainable development has documented a number of network initiatives taken by corporations in order to manage financial, social, and environmental pressures. So far, the focus of the research has been to address the concerns raised by a number of external stakeholders. As such, research attention has been paid to the reactive corporate response rather than to the proactive communication of the sustainability message with the purpose of developing and driving corporate social responsibility (CSR) and sustainability. Only recently, a few papers have emerged on the issue. The purpose of this paper is to contribute to the field by proposing a theoretical analysis of the organizational and communicative bases of CSR and sustainability networks. Resource dependence theory and social network theory are used to form the theoretical framework set up for understanding how governments build relations with local networks, including corporations. The framework is tested on an example from Denmark. Copyright © 2010 John Wiley & Sons, Ltd and ERP Environment.
New biological investigations on 3‐bromophenyl 6‐acetoxymethyl‐2‐oxo‐2H‐1‐benzopyran‐3‐carboxylate as anti‐angiogenic agent
Authors: Hemmer Marc , Kempen Isabelle , de Tullio Pascal , Frankenne Françis , Lambert Vincent , Blacher Silvia , Bueb Jean‐Luc , Foidart Jean‐Michel , Noël Agnès , Tschirhart Eric , Pirotte Bernard 
Published: February 2010

AbstractThe development of blood vessels inside tumors is required to provide the nutrients and oxygen needed for tumor growth and to allow the spread of cancer cells at a distance to form metastasis. Angiogenesis is also implicated in ocular diseases like age‐related macular degeneration. The present work describes the potential anti‐angiogenic properties of a coumarinic derivative, 3‐bromophenyl 6‐acetoxymethyl‐2‐oxo‐2H‐1‐benzopyran‐3‐carboxylate (IK9), previously described as a potent inhibitor of HT 1080 fibrosarcoma cell invasion in vitro and tumor growth in vivo. In vivo, ex vivo, and in vitro models were used to delineate the anti‐angiogenic properties of IK9. The anti‐angiogenic effect of IK9 was demonstrated in vivo in a choroidal neovascularization mice model and additionally ex vivo in a rat aortic ring assay where it was more active than the known matrix metalloproteinase inhibitor Ro 28‐2653. IK9 did not affect apoptosis, proliferation, or endothelial cell invasiveness in vitro. These findings suggest a complex mechanism of action of the compound via direct or indirect effects on endothelial cell properties. This study identifies IK9 as a new potent inhibitor of angiogenesis and suggests its potential use as a therapeutic agent. Drug Dev Res 71, 2010. © 2010 Wiley‐Liss, Inc.
A validated stability‐indicating gas chromatography method for determination of divalproex sodium impurities in pharmaceutical preparation
Authors: Subasranjan Acharya , Suresh Pulluru , Srinivasulu C. , Hemant Raoutray 
Published: February 2010

AbstractA stability‐indicating gas chromatography (GC) method has been developed and validated for the quantitative determination of divalproex sodium impurities in pharmaceutical preparation. A technique has been developed whereby the peak purity of a compound with poor UV detection can be determined using a gas chromatograph coupled with a mass spectrometer. The drug products were subjected to hydrolysis, oxidation, photolysis, and heat to apply stress conditions. The stability‐indicating nature of the method has been proven by establishing peak purity of all stressed samples. The chromatographic separation was performed on a fused silica capillary (Quadrex‐FFAP, 30 meter, 0.32 mm and 1 µm film thickness) column. The method validation results indicate that the method is specific, accurate, linear, reproducible, rugged, and robust. The effectiveness of the technique was demonstrated with stability sample analysis of divalproex sodium in its pharmaceutical preparation. Copyright © 2010 John Wiley & Sons, Ltd.
Spectrophotometric and spectrodensitometric determination of triamterene and xipamide in pure form and in pharmaceutical formulation
Authors: Wagieh Nour E. , Abbas Samah S. , Abdelkawy M. , Abdelrahman Maha M. 
Published: February 2010

AbstractSensitive and validated UV‐spectrophotometric, chemometric and TLC‐densitometric methods were developed for determination of triamterene (TRM) and xipamide (XIP) in their binary mixture, formulated for use as a diuretic, without previous separation. Method A is the isoabsorptive point spectrophotometry, in which TRM concentration alone can be determined at its λmax while XIP concentration can be determined by measuring total concentration of TRM and XIP at their isoabsorptive point followed by subtraction. Method B is the ratio subtraction spectrophotometry, where XIP can be determined by dividing the spectrum of the mixture by the spectrum of TRM (as a divisor) followed by subtracting the constant absorbance value of the plateau region, then finally multiplying the produced spectrum by the spectrum of the divisor, while TRM concentration can be determined at its λmax. Method C is a chemometric‐assisted spectrophotometry where classical least squares, principal component regression, and partial least squares were applied. Method D is a TLC‐densitometry; this method depends on quantitative densitometric separation of thin layer chromatogram of TRM and XIP using silica gel plates at 254 nm. The proposed methods were successfully applied for the analysis of TRM and XIP in their pharmaceutical formulation and the results were statistically compared with the established HPLC method. Copyright © 2010 John Wiley & Sons, Ltd.
Influence of the semi‐permeable membrane on the performance of dynamic field gradient focusing
Authors: Burke Jeffrey M. , Ivory Cornelius F. 
Published: February 2010

AbstractThis paper is part of our continued effort to understand the underlying principles of dynamic field gradient focusing. In this investigation, we examined three problems associated with the use of a semi‐permeable membrane. First, the influence of steric and ionic exclusion of current carrying ions through the membrane was examined. It was found that resistance to the transport of ions across the membrane resulted in a shallowing of the electric field profile and an increase in the size of the defocusing zone, which is where the slope of the electric field is reversed so that it disperses rather than concentrates solutes. These problems could be reduced by using a membrane with large pores relative to the size of the buffering ions and completely void of fixed charges. Next, a numerical simulation was used to investigate concentration polarization of protein onto the surface of the membrane. Due to the presence of a transverse electric field, species were pulled toward the membrane. If the membrane is restrictive to those species, a concentrated, polarized layer will form on the surface. The simulation showed that by decreasing the channel to a depth of 20 μm, the concentrated region next to the membrane could be reduced. Finally, it was found that changes in column volume due to loss of membrane structural integrity could be mitigated by including a porous ceramic support. The variation in peak elution times was decreased from greater than 20% to less than 3%.
Protein adsorption‐dependent electro‐kinetic pore flow: Modeling of ion‐exchange electrochromatography with an oscillatory transverse electric field
Authors: Yuan Wei , Zhao Yan‐Pu , Zhang Qiang , Sun Yan 
Published: February 2010

AbstractElectro‐kinetic acceleration of protein mass transfer was studied by dynamic chromatographic experiments and computer simulations on IEC with an oscillatory transverse electric field (EF) perpendicular to the mobile‐phase flow (pIEEC). The breakthrough behavior of BSA was investigated at different electric current densities. A two‐dimensional mathematical model has been established to describe the electro‐kinetic convection‐diffusion behavior of protein adsorption in a single adsorbent particle. The equation was coupled with the axial dispersion model to simulate the dynamic adsorption process in the pIEEC. The model parameters were determined by independent experiments or calculations. It was found that protein adsorption led to an exponential decrease of intraparticle electro‐kinetic flow with increasing protein adsorption. Taking this effect into consideration, the model calculations could well describe dynamic breakthrough curves. Moreover, protein distribution in adsorbents was observed to present excursion along the periodical oscillatory EF direction. At the beginning of pIEEC, intraparticle convection caused by the EF contributed more to the enhancement of dynamic binding capacity. Finally, it was confirmed that both the EOF and electrophoresis contributed to the acceleration of mass transfer.
Numerical studies of electrokinetic control of DNA concentration in a closed‐end microchannel
Authors: Daghighi Yasaman , Li Dongqing 
Published: February 2010

AbstractA major challenge in lab‐on‐a‐chip devices is how to concentrate sample molecules from a dilute solution, which is critical to the effectiveness and the detection limit of on‐chip bio‐chemical reactions. A numerical study of sample concentration control by electrokinetic microfluidic means in a closed‐end microchannel is presented in this paper. The present method provides a simple and efficient way of concentration control by using electrokinetic trapping of a charged species of interest, controlling liquid flow and separating different sample molecules in the microchannel. The electrokinetic‐concentration process and the controlled transport of the sample molecules are numerically studied. In this system, in addition to the electroosmotic flow and the electrophoresis, the closed‐end of the chamber causes velocity variation at both ends of the channel and induces a pressure gradient and the associated fluid movement in the channel. The combined effects determine the final concentration field of the sample molecules. The influences of a number of parameters such as the channel dimensions, electrode size and the applied electric field are investigated.
High‐throughput log P determination by MEEKC coupled with UV and MS detections
Authors: Henchoz Yveline , Romand Stéphanie , Schappler Julie , Rudaz Serge , Veuthey Jean‐Luc , Carrupt Pierre‐Alain 
Published: February 2010

AbstractA high‐throughput screening method using MEEKC was developed for the determination of 1‐octanol‐water partition coefficients (log Poct). Two approaches were carried out to decrease determination times to about 20 min per compound: (i) a dynamically coated capillary was used to increase the EOF at low pH, allowing the measurement of log Poct of acidic compounds and (ii) a short‐end injection was performed to reduce the capillary effective length. The analytical conditions were optimized to determine the lipophilicity of neutral, basic, and acidic compounds with log Poct ranging from 0 to 5. The developed method was first applied to a well‐balanced set of 35 reference compounds, and second to a set of 21 acidic and 29 basic pharmaceutical compounds. Finally, determinations were achieved with MS detection, allowing a 20‐fold throughput increase thanks to sample pooling. An atmospheric pressure photoionization source was selected to advantageously replace ESI as it was less affected by the non‐volatile BGE additives used in MEEKC.
Optimization of charged species separation by autogenous electric field‐flow fractionation in nano‐scale channels
Authors: Griffiths Stewart K. , Nilson Robert H. 
Published: February 2010

AbstractNumerical methods are employed to examine the resolution and optimization of a relatively new technique for charged species separation that is based on flow along nano‐scale channels having an electric double‐layer thickness comparable to the channel size. In such channels, the electric field inherent to the double‐layer produces transverse species distributions that depend on the species charge. Flow along the channel thus yields mean axial species speeds that also depend on the species charge, enabling species separation and identification. Building on earlier work describing retention and plate heights, here we characterize this new type of field‐flow fractionation via the classic metric of resolution. Sample results are presented and discussed for a wide range of conditions for both pressure‐driven and electroosmotic flows. Optimum design and operating conditions are also examined. We find that resolution is maximized for optimum values of the ζ potential and Debye layer thickness and that these optima depend strongly on the species charge or range of charges of interest. Under optimum conditions, acceptable resolution can be obtained over a wide range of species charges for pressure‐driven flows. This separable range of charges is much smaller for electroosmotic flows. Finally, sample calculations are presented showing that all species in the range of charge between −8 to 10 can be separated simultaneously with resolutions above unity, and this is possible in less than 6 s under optimum conditions that are readily achievable.
Analyte transport in liquid junction nano‐electrospray interface between capillary electrophoresis and mass spectrometry
Authors: Klepárník Karel , Otevřel Marek 
Published: February 2010

AbstractThe optimization of working parameters controlling the transfer of an analyte from the separation into the spray capillary at the liquid junction interface is a complex problem. The numerical models of hydrodynamic flow, electric field strength and the consequential mass transfer provide a valuable insight into the function of the miniaturized device. The results revealed that the most important parameter is the electric field strength inside the gap between the separation and spray capillaries. In a strong electric field, the analyte leaving the separation capillary is immediately transferred into the spray capillary at its maximum concentration. Although the losses of analyte outside the interface are dominant in this case, the sprayed concentration determines the detection sensitivity. Since only a small amount of the sprayed material enters mass spectrometer, the losses at the interface do not influence the sensitivity. At low electric field strength the total amount of analytes is transferred into the spray capillary. In this case, however, the analytes enter the capillary slowly and, as a result, are significantly diluted. The electric field strength, pressure and dimensions determine the mass transfer in the interface and must be considered when the optimum conditions of an analysis are chosen. Several fold improvement in sensitivity and efficiency of the method can be expected when working under the optimum conditions.
Electrochromatographic retention of peptides on strong cation‐exchange stationary phases
Authors: Nischang Ivo , Höltzel Alexandra , Tallarek Ulrich 
Published: February 2010

AbstractWe analyze the systematic and substantial electrical field‐dependence of electrochromatographic retention for four counterionic peptides ([Met5]enkephalin, oxytocin, [Arg8]vasopressin, and luteinizing hormone releasing hormone (LHRH) ) on a strong cation‐exchange (SCX) stationary phase. Our experiments show that retention behavior in the studied system depends on the charge‐selectivity of the stationary phase particles, the applied voltage, and the peptides' net charge. Retention factors of twice positively charged peptides ([Arg8]vasopressin and LHRH at pH 2.7) decrease with increasing applied voltage, whereas lower charged peptides (oxytocin and [Met5]enkephalin at pH 2.7, [Arg8]vasopressin and LHRH at pH 7.0) show a concomitant increase in their retention factors. The observed behavior is explained on the basis of electrical field‐induced concentration polarization (CP) that develops around the SCX particles of the packing. The intraparticle concentration of charged species (buffer ions, peptides) increases with increasing applied voltage due to diffusive backflux from the enriched CP zone associated with each SCX particle. For twice charged and on the SCX phase strongly retained peptides the local increase in mobile phase ionic strength reduces the electrostatic interactions with the stationary phase, which explains the decrease of retention factors with increasing applied voltage and CP intensity. Lower charged and weaker retained peptides experience a much stronger relative intraparticle enrichment than the twice‐charged peptides, which results in a net increase of retention factors with increasing applied voltage. The CP‐related contribution to electrochromatographic retention of peptides on the SCX stationary phase is modulated by the applied voltage, the mobile phase ionic strength, and the peptides' net charge and could be used for selectivity tuning in difficult separations.
Characterization of nanoparticles by capillary electromigration separation techniques
Authors: Pyell Ute 
Published: February 2010

AbstractConsidering the large number of papers presented in the last years in the field of CE and plate gel electrophoresis (PGE) of nanoparticles and nanoparticle−biomolecule conjugates, this review article gives an overview on the application of capillary electromigration separation techniques for the separation of nanoparticles and nanoparticle−biomolecule conjugates according to differences in size and/or ζ potential and for the determination of several physicochemical parameters characterizing a population of nanoparticles. A brief introduction is given into the theoretical background of the size‐selective electrophoretic separation of nanospheres in free‐solution and sieving media including involvement of interparticle interactions. Some aspects of colloidal system stability are discussed. Applications of capillary electromigration techniques in the field of size‐selective and/or surface charge density‐selective separation of nanoparticles and nanoparticle−biomolecule conjugates are described, including free‐solution CE, CGE, IEF, and ITP, complemented by an overview on the application of (semipreparative) PGE in the field of nanotechnology and nanobiotechnology. The review also includes actual developments regarding the coupling of capillary electromigration techniques to (wavelength‐resolved) LIF and other selective detection methods and studies concerning individual‐particle CE.
Development of a membrane‐less dynamic field gradient focusing device for the separation of low‐molecular‐weight molecules
Authors: Burke Jeffrey M. , Smith Colin D. , Ivory Cornelius F. 
Published: February 2010

AbstractDynamic field gradient focusing uses an electric field gradient generated by controlling the voltage profile of an electrode array to separate and concentrate charged analytes according to their individual electrophoretic mobilities. This study describes a new instrument in which the electrodes have been placed within the separation channel. The major challenge faced with this device is that when applied voltages to the electrodes are larger than the redox potential of water, electrolysis will occur, producing hydrogen ions (H+) plus oxygen gas on the anodes and hydroxide (OH–) plus hydrogen gas on the cathodes. The resulting gas bubbles and pH excursions can cause problems with system performance and reproducibility. An on‐column, degassing system that can remove gas bubbles “on‐the‐fly” is described. In addition, the use of a high capacity, low‐conductivity buffer to address the problem of the pH shift that occurs due to the production of H+ on the anodes is illustrated. Finally, the successful separation of three, low‐molecular‐weight dyes (amaranth, bromophenol blue and methyl red) is described.
Investigation of the stereodynamics of molecules and catalyzed reactions by CE
Authors: Trapp Oliver 
Published: February 2010

AbstractThe investigation of the molecular dynamics of stereoisomers and the study of the kinetics of reactions, in particular of catalyzed reactions, is of fundamental interest in chemistry, biochemistry, and medicine. Understanding how to control the transition state of a reaction allows for a directed design of new catalysts and benign processes. The integration of reactions and capillary or microchip‐based electrophoretic separations is highly attractive to perform on‐column derivatizations or enzymatic on‐column digests of peptides and proteins for further characterization. The present review article focuses on the recent advances to study the stereodynamics of molecules and reaction kinetics of catalyzed processes by means of CE. Models and algorithms to evaluate interconversion profiles obtained by electrophoretic separation techniques are discussed with respect to the challenging demands of high separation efficiencies typical for electrophoretic techniques. Models used for evaluation are based on iterative computer simulation algorithms using the theoretical plate model or stochastic model of chromatography, empirical calculation methods, derived from equations used in chemical engineering, namely Damköhler analysis, and direct access with the approximation function and more recently with the unified equation, which can be applied to all kinds of first‐order reactions taking place during a chromatographic or a electrophoretic separation. Furthermore, areas of applications are presented and discussed to give a guideline for using dynamic CE and on‐column reaction electrophoresis to study kinetics of reactions and dynamic processes.