bluuebunny/crossref_metadata_2025_split huggingface dataset:
Separation of basic and acidic compounds by capillary electrochromatography using monolithic silica capillary columns with zwitterionic stationary phase
Authors: Hu Jiwei , Xie Chuanhui , Tian Ruijun , He Zhike , Zou Hanfa 
Published: March 2007

AbstractA novel monolithic silica column with zwitterionic stationary phase was prepared by in‐situ covalent attachment of phenylalanine to a 3‐glycidoxypropyltriethoxysilane‐modified silica monolith. Due to the zwitterionic nature of the resulting stationary phase, the density and sign of the net surface charge, and accordingly the direction and magnitude of electroosmotic flow in this column during capillary electrochromatography could be manipulated by adjusting the pH values of the mobile phase. CEC separations of various acidic and basic compounds were performed on the prepared column in anodic and weakly cathodic EOF modes, respectively. The peak tailing of basic compounds in CEC on a silica column could be alleviated at optimized buffer compositions. Besides the electrophoretic mechanism and weak hydrophobic interaction, weak cation‐ and anion‐exchange interactions are also involved in the separations of acids and bases, respectively, on the zwitterionic column.
Potential of solid phase microextraction and gas chromatography for quarantine‐required detection of wood packaging in shipping containers
Authors: More Nicole A. , Braggins Terry J. , Goldson Stephen L. 
Published: March 2007

AbstractSolid phase microextraction (SPME) coupled with gas chromatography (GC) was used to detect terpene hydrocarbons inside shipping containers entering New Zealand. The utility of this system for the rapid detection of undeclared wood packaging for quarantine purposes was demonstrated. A portable dynamic air‐sampling device was built to house a SPME fibre and allow the air from shipping containers to be sampled. The effects of sample flow rate and sampling time were investigated and sampling conditions of 100 mL/min for 30 s were chosen to keep sampling within the linear range. A CV of less than 15% (n = 12) was obtained for all the compounds analysed under these conditions. To obtain an estimate for the limit of detection (LOD) for the terpene hydrocarbons of interest, small quantities of lime oil were placed in an empty shipping container and the air inside was analysed. LOD (S/N = 3) was estimated to be in the order of 50–100 ng/L of air using GC with flame ionisation detection (GC‐FID). Finally, the device was tested in fully laden containers and was shown to be effective for trapping terpene hydrocarbons indicative of wood packaging.
Fabrication of a poly(styrene–octadecene–divinylbenzene) monolithic column and its comparison with a poly(styrene–divinylbenzene) monolithic column for the separation of proteins
Authors: Gu Congying , Lin Li , Chen Xiaodong , Jia Jinping , Ren Jicun , Fang Nenghu 
Published: March 2007

AbstractIn this paper, a poly(styrene‐octadecene‐divinylbenzene) (PS‐OD‐DVB) monolithic column was prepared in one step by introducing a C18 carbon chain as monomer. N,N‐Dimethylformamide and decanol served as porogens to make a homogeneous polymerization mixture in a fused silica capillary (320 μm inner diameter). Its physical and chromatographic properties were compared with those of poly(styrene‐divinylbenzene) (PS‐DVB) monolithic column, which was also fabricated by in‐situ polymerization in a fused silica capillary with the same inner diameter. Six standard proteins were used to evaluate the columns and their potential application for the separation of human hemoglobin was also discussed. It was shown that the PS‐OD‐DVB and PS‐DVB monoliths appeared to have similar efficiency for rapid separation of six proteins within 3.5 min. The PS‐OD‐DVB monolith was found to have higher loading capacity and higher resolution for the separation of α and β chains of hemoglobin because of the introduction of C18 carbon chains, and shows great potential for the separation of bio‐macromolecules.
Development and validation of a stability‐indicating liquid chromatographic method for determination of emtricitabine and related impurities in drug substance
Authors: Seshachalam Unnam , Haribabu Bodepudi , Chandrasekhar Kottapalli B. 
Published: March 2007

AbstractA novel stability‐indicating high‐performance liquid chromatographic (HPLC) method was developed and validated for assay and determination of impurities of emtricitabine in drug substance. Emtricitabine was found to be degraded under acidic, alkaline, and oxidative stress conditions and to be more labile under oxidative conditions. The drug proved to be stable to dry heat and photolytic degradation. Resolution of major and minor degradation impurities was achieved on an Intersil ODS‐3V column utilizing 10 mM sodium phosphate buffer and methanol (85:15) as mobile phase. Detection was at 280 nm. Validation studies were performed as per ICH recommended conditions. The developed method was found to be linear, accurate, specific, selective, precise, and robust.
A new procedure for separation of complex mixtures of pesticides by multidimensional planar chromatography
Authors: Tuzimski Tomasz 
Published: March 2007

AbstractThe objective of this communication is to report a new procedure for the separation of complex mixtures of pesticides by a combination of different modes of multidimensional planar chromatography. Complete separation of a mixture of pesticides was carried out by multidimensional planar chromatography on silica gel plates. The plates were videoscanned to show a real picture of the experimental results. Complete separation of all compounds was not possible by a single development on silica gel. The separation can be characterized as [PC×(nPC + PC + PC + PC)]. With the aid of this new procedure a complex mixture of fourteen compounds was separated on a 10×10 cm TLC plate.
Sensitive capillary electrophoretic determination of mercury species with amperometric detection at a copper electrode after cation exchange preconcentration
Authors: Kubáň Petr , Houserová Pavlína , Kubáň Pavel , Hauser Peter C. , Kubáň Vlastimil 
Published: March 2007

AbstractA capillary electrophoretic method for the separation of four mercury species with amperometric detection was developed. Inorganic Hg2+, methyl‐, ethyl‐, and phenylmercury were complexed with L‐cysteine and separated in a counterelectroosmotic mode in an electrolyte solution comprised of 20 mM sodium tetraborate at pH 9.5. Amperometric detection of separated species was achieved at passivated copper electrode under electrocatalytic oxidation conditions. The four mercury species were separated in less than 8 min with LODs ranging from 170 to 450 μg/L. Cation exchange preconcentration was used to decrease the LODs down to 1.7 μg/L.
Study on the Phase Behavior of High Density Polyethylene – Ethylene Octene Copolymer Blends
Authors: Mileva Daniela , Radusch Hans‐Joachim , Betchev Christo 
Published: March 2007

AbstractThe processes of melting and crystallization of blends based on HDPE and EOC were investigated. DSC thermograms showed that a separate crystallization and co‐crystallization occurred in the blends studied. Avrami approach was used to analyze the kinetics of crystallization in the blends. It is shown that the Avrami exponent depends on the EOC concentration of the samples studied. The difference in the Avrami parameters for HDPE, EOC and the blends indicated that the nucleation mechanism and dimension of the spherulite growth of the blends were different from that of HDPE to some extent. The crystal growth was examined in the context of the Lauritzen‐Hoffman theory. DSC traces obtained at different cooling rates were used for analyzing the non‐isothermal crystallization. It was found that the Ozawa model was rather inapplicable for the materials studied. In contrast, the Avrami equation modified by Jeziorny can be used more efficiently to describe the non‐isothermal crystallization behavior of HDPE‐EOC blends.magnified image
Polymer/Phenanthrene‐Derivative Host‐Guest Systems: Rheological, Optical and Thermal Properties
Authors: Hanemann Thomas , Böhm Johannes , Honnef Kirsten , Ritzhaupt‐Kleissl Eberhard , Haußelt Jürgen 
Published: March 2007

AbstractStarting from commercially‐available, polymer‐based reactive resins like acrylates or unsaturated polyesters, a systematic investigation was carried out as to the influence organic dopants like phenanthrene and its derivatives have on the optical and thermal properties of the mixtures resulting from curing to the final thermoplastic polymer. The refractive index of PMMA at 633 nm can be increased, starting from 1.49 for the pure polymer, up to a value of around 1.55, and, in the case of the polyester, from 1.565 up to 1.6. The transmittance in the visible range is slightly affected at a lower dopant concentration of up to 10 wt.‐%, and remains better than 80% for a sample with a thickness of 1 mm, in the range between 500 and 800 nm. An unwanted side‐effect of larger dopant concentrations is to lower the glass transition temperature significantly.magnified image
Effect of Surface Modification on the Synthesis of Pore‐Filling Polymeric Monoliths in Microfiltration Membranes Made from Poly(propylene) and Poly(ethylene terephthalate)
Authors: Salam Abdus , Ulbricht Mathias 
Published: March 2007

AbstractThe effect of pre‐modification on the interaction of macroporous substrates (membranes) with mainly micro‐ and mesoporous polymer monoliths has been studied. Bulk, porous polymer monoliths were synthesized to optimize the synthesis conditions and their pore morphology, and the data were used as benchmark for this study. Pre‐modification of the entire pore surface of PP microfiltration membranes and PET track‐etched membranes by UV‐initiated grafting with PEGMA was performed using well‐established methods, including coating with the photo‐initiator, benzophenone. Subsequently, these membranes were functionalized by filling the pores with porous polymer monoliths from MAA and EDMA and compared with membranes that had been functionalized without the pre‐modification step. The materials were characterized mainly by the degree of grafting, SEM and by the gas‐adsorption‐isotherm method. The DG values, after composite‐membrane preparation under identical conditions, were not influenced by the pre‐modification. However, it could be clearly seen from the SEM images that the pre‐modification step prevents the formation of voids at the monolith‐membrane pore interface. Larger specific surface area and pore volume values for composite membranes, prepared after pre‐modification, fully support the SEM results. Especially large differences in pore structure between the two different composite membranes were found in the mesopore range. The results of this study indicate that it is possible to prepare porous, composite membranes where the trans‐membrane transport is exclusively controlled by the pore and surface structure of a functional polymeric monolith, for example, made from a molecularly‐imprinted polymer.magnified image
An Algorithm Based on Simple Rules for the Determination of the Architecture of Branched Polymer Molecules from the Number of Branching Points per Molecule
Authors: Majesté Jean‐Charles , Carrot Christian , Stanescu Paul‐Octavian , Mardon Coralie 
Published: March 2007

AbstractA general simple algorithm is proposed to determine the average architecture of an acyclic branched polymer macromolecule from its number of branching points, whatever their functionality. The number of branching points can be derived from SEC measurements using a coupling of viscosimetric and refractometric detectors through the use of the Zimm‐Stockmayer equation. Since various isomers can be built for a given number of branching points, some basic rules are proposed in order to select the structures that are physically meaningful; the possibility of structural isomers has been also investigated and a probability of presence is assigned to each species starting from the compactness of the molecule. For each species corresponding to a given molecular weight in the sample, the average structure is then obtained from the number of branching points and the universal probability distribution of the isomers.magnified image
The Effect of Pressure on the Microphase Separation of Diblock Copolymer Melts Studied by Dynamic Density Functional Theory Based on Equation of State
Authors: Xu Hui , Liu Honglai , Hu Ying 
Published: March 2007

AbstractThe effect of pressure on the microphase separation of diblock copolymer melts was investigated by dynamic density functional theory based on equation of state. The results correspond well with experiment data. With the application of high pressure, all of the phase regions corresponding to the different ordered morphologies become narrower. However, the pressure dependence of the order‐disorder transition temperature (TODT) relies on the symmetry of the diblock copolymer. In the very non‐symmetrical case when f is small, TODT decreases with increasing pressure, while in the symmetrical case when f = 0.5, TODT increases with increasing pressure. For the latter case, the increase in the total bead number of the system at the ODT is found, which is in good accordance with the experimental phenomenon that there is an increase in volume accompanying with the transition from ordered to disordered state. In contrast to the temperature, the pressure does not influence the starting time and the duration of microphase separation.magnified image
Conformational Study of Short Peptoid Models for Future Applications as Potent Antimicrobial Compounds
Authors: Nandel Fateh Singh , Saini Avneet 
Published: March 2007

AbstractDevelopment of peptides as clinically useful drugs is limited by their poor metabolic stability and low bioavailability. Recent progresses in chemical synthesis and design have led to several strategies for producing potent mimetics. This study aims to analyze sequence/structure requirements and composition for antimicrobial peptoid designs, as use of peptoids is one of the most representative approaches to meet the goal of biomimicry. Analysis of the designs showed that for maximum activity and minimum hemolysis, the plane of the aromatic residues should be at an angle between 0 and 90 ° with respect to membranes, cationic residues need not be at the terminal position, and central positions should be uniform in NIle, NLys, and NPhe residues.magnified image
Solving singularly perturbed advection–reaction equations via non‐standard finite difference methods
Authors: Lubuma Jean M.‐S. , Patidar Kailash C. 
Published: March 2007

AbstractWe design and implement two non‐standard finite difference methods (NSFDMs) to solve singularly perturbed advection–reaction equations (SPARE). Our methods constitute a big plus to the class of those ‘rare’ fitted operator methods, which can be extended to singularly perturbed partial differential equations. Unlike the standard finite difference methods (SFDMs), the NSFDMs designed in this paper allow the time and the space step sizes to vary independently of one another and of the parameter ε in the SPARE under consideration. The NSFDMs replicate the linear stability properties of the fixed points of the continuous problem. Furthermore, these methods preserve the positivity and boundedness properties of the exact solution. Numerical simulations that confirm the theoretical results are presented. Copyright © 2007 John Wiley & Sons, Ltd.
A fourth‐order parabolic equation in two space dimensions
Authors: Liu Changchun 
Published: March 2007

AbstractIn this paper, we consider an initial‐boundary problem for a fourth‐order nonlinear parabolic equations. The problem as a model arises in epitaxial growth of nanoscale thin films. Based on the Lp type estimates and Schauder type estimates, we prove the global existence of classical solutions for the problem in two space dimensions. Copyright © 2007 John Wiley & Sons, Ltd.
Asymptotic waveform evaluation for scattering by inhomogeneous dielectric bodies of revolution
Authors: Kucharski Andrzej A. 
Published: March 2007

AbstractIn this article, an application of the asymptotic waveform evaluation technique to accelerate wideband scattering analysis by lossless dielectric objects is given. The solution is based on the volume integral equation together with the method‐of‐moments. Computational examples for so‐called bodies‐of‐revolution are given. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 1028–1031, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22326
Broadband integrated DTV antenna for USB dongle application
Authors: Li Wei‐Yu , Wong Kin‐Lu , Su Saou‐Wen 
Published: March 2007

AbstractA novel broadband planar antenna integrated in the USB dongle for digital television (DTV) signal reception is presented. The planar antenna is printed on a dielectric substrate and electrically connected to the system ground plane of the USB dongle. When in operation, the planar antenna is swung upward to be perpendicular to the system ground plane and can provide a wide operating bandwidth (2.5:1 VSWR) of larger than 50% centered at about 630 MHz, allowing it to cover the DTV signal reception in the 470–806‐MHz band. While not in operation, the planar antenna can be swung downward and attached onto the housing of the USB dongle, keeping the aesthetic appearance of the device. Detailed design considerations of the proposed antenna are described, and obtained experimental and simulation results are presented and discussed. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 1018–1021, 2007; Published online in Wiley InterScience (www.interscience.wiley.com).DOI 10.1002/mop.22329
A novel filter based on zeroth‐order resonance by means of CRLH transmission line
Authors: Sun Yuanyuan , Zhang Yewen , Liu Fuqiang , He Li , Li Hongqiang , Chen Hong 
Published: March 2007

AbstractA novel band‐pass filter based on zeroth‐order resonance is presented in this article. The filter offers a 68% size reduction compared to the traditional coupled‐line filter, while keeping the same performance. The experimental results of the filter are in good agreement with the Advanced Design System simulation results. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 1015–1018, 2007; Published online in Wiley InterScience (www.interscience.wiley.com).DOI 10.1002/mop.22332
Robust GMRES recursive method for fast finite element analysis of 3D electromagnetic problems
Authors: Rui P. L. , Chen R. S. 
Published: March 2007

AbstractA robust generalized minimal residual recursive (GMRESR) iterative method is proposed to solve a large system of linear equations resulting from the use of an un‐gauged vector‐potential formulation of finite element method (FEM). This method involves an outer generalized conjugate residual (GCR) method and an inner generalized minimal residual (GMRES) method, where the inner GMRES acts as a variable preconditioning for the outer GCR. The efficient implementation of symmetric successive overrelaxation (SSOR) preconditioned GMRESR (SSOR‐GMRESR) algorithm is described in details for complex coefficient matrix equation. On several three‐dimensional electromagnetic problems, the resulting SSOR‐GMRESR approach converges in CPU time, which is 14.2–71.3 times shorter with respect to conventional conjugate gradient (CG) approach. By comparison with other popularly preconditioned CG methods, the results demonstrate that SSOR‐GMRESR is especially effective and robust when the A‐V formulation of FEM is applied to solve large‐scale time harmonic electromagnetic field problems. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 1010–1015, 2007; Published online in Wiley InterScience (www.interscience.wiley.com).DOI 10.1002/mop.22333
Electromagnetic scattering from high order inhomogeneous impedance cylinder of arbitrary shape by using physical optics
Authors: Tezel Necmi Serkan 
Published: March 2007

AbstractIn this study, physical optics (PO) method have been applied to electromagnetic scattering problem related to high order inhomogeneous impedance cylinder of arbitrary shape. In the solution, induced electric and magnetic currents on the illuminated region of surface are expressed by means of incident field and high order inhomogeneous impedance boundary condition then scattered field is calculated using Huygens type Green's formula. Obtained scattering width results are compared with those obtained by other analytical and numeric methods and good agreements are observed especially monostatic case. Because of the fact that PO method does not need matrix inversion, which requires high CPU time, PO method also significantly reduces computer calculation time according the other methods. In this study, TM case is considered, but similar procedure can be easily applied to TE case and even also three‐dimensional inhomogeneous impedance objects using dyadic Green's functions as well. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 1031–1036, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22339
Ultra wideband printed monopole antenna
Authors: Thomas K. George , Lenin N. 
Published: March 2007

AbstractAn ultra wideband printed planar elliptical monopole is reported. The antenna has a simple printed structure, mounted perpendicular to a small metallic ground plane. The proposed antenna can be used for multiband operation, with omnidirectional radiation pattern in azimuth plane. The antenna operates over an extremely wide impedance bandwidth of more than 25:1, determined by 10 dB return loss and covers almost all present day wireless communication systems: Advanced mobile phone system, global system for mobile communication, digital communication system, universal mobile telecommunication system, and broadband wireless metropolitan area network system for operation in the 2–11 GHz band. This article presents the design, analysis, and experimental results for the proposed antenna. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 1082–1085, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI.10.1002/mop.22343
Novel power divider with fixed strip width using offset double‐sided parallel‐strip lines
Authors: Chen Jian‐Xin , Chin Ching‐Hong K. , Xue Quan 
Published: March 2007

AbstractA novel power divider with fixed strip width using offset double‐sided parallel‐strip lines (DSPSL) is proposed. The offset double‐sided parallel‐strip lines allows an additional design freedom, i.e., offset distance between the top and bottom strips of the offset double‐sided parallel‐strip lines for characteristic impedance besides the strip width. This can reduce the discontinuities effectively resulting from the change of the strip width and improve the power‐handling capability of the proposed power divider. The simulated and measured results are presented and show good agreement. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 1109–1111, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI.10.1002/mop.22346
Coupled‐mode analysis of nonlinear fiber couplers with different core parameters
Authors: Liu Min 
Published: March 2007

AbstractA nonlinear two‐core fiber coupler with unequal cores (phase‐mismatched) is analyzed by using coupled‐mode theory. Based on the solutions of the coupled‐mode equations, it is demonstrated that even though there is a difference in core diameter, the unequal‐core fiber coupler (phase‐mismatched) can function as a twin‐core fiber coupler (phase‐matched) by increasing the refractive index of the small core. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49:1051–1053, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22350