bluuebunny/crossref_metadata_2025_split huggingface dataset:
Flow‐through partial‐filling affinity capillary electrophoresis can estimate binding constants of neutral ligands to receptors via a competitive assay technique
Authors: Kaddis John , Mito Erica , Heintz Joseph , Plazas Alfredo , Gomez Frank A. 
Published: March 2003

AbstractThis work evaluates the use of a competitive binding assay using flow‐through partial‐filling affinity capillary electrophoresis (FTPFACE) to estimate binding constants of neutral ligands to a receptor. We demonstrate this technique using, as a model system, carbonic anhydrase B (CAB, EC 4.2.1.1) and arylsulfonamides. In this technique, the capillary is first partially filled with a negatively charged ligand, a sample containing CAB and two noninteracting standards, and a neutral ligand, then electrophoresed. Upon application of a voltage the sample plug migrates into the plug of negatively charged ligand (L–) resulting in the formation of a CAB‐L– complex. Continued electrophoresis results in mixing between the neutral ligand (L0) and the CAB‐L– complex. L0 successfully competes out L– to form the new CAB‐L0 complex. Analysis of the change in the relative migration time ratio (RMTR) of CAB relative to the noninteracting standards, as a function of neutral ligand concentration, yields a value for the binding constant. These values are in agreement with those estimated using other binding and ACE techniques. Data demonstrating the quantitative potential of this method is presented.
Electrophoretically mediated reaction of glycosidases at a nanoliter scale
Authors: Kanie Yoshimi , Kanie Osamu 
Published: March 2003

AbstractWe have investigated electrophoretically mediated microanalysis (EMMA) for the assay of a native glyco‐enzyme. As a representative of this class of enzyme, β‐glucosidase was selected, and the reaction was analyzed. Our EMMA was based on the plug‐plug interaction of enzyme and substrate plugs, which is essential to reduce quantities of materials. Furthermore, we have addressed the problem of incompatibility of the enzymatic reaction and separation of the reactants. As a result, EMMA of native glycosidase was achieved with a reaction volume of ∼ 20 nL and the Michaelis constant was estimated according to the Lineweaver‐Burk plot. The current method may have advantages over traditional assay methods, especially in terms of the amount of enzyme (ng order) and substrate (pmol order) required for a reaction*.
On‐line coupling of size‐exclusion chromatography and capillary zone electrophoresis via a reversed‐phase C18 trapping column for the determination of peptides in biological samples
Authors: Stroink Thom , Schravendijk Pim , Wiese Gerard , Teeuwsen Jan , Lingeman Henk , Waterval Joop C. M. , Bult Auke , de Jong Gerhardus J. , Underberg Willy J. M. 
Published: March 2003

AbstractSince biologically active peptides usually exhibit their effects in low concentrations, the development of sensitive analytical methods has become a challenge. In this paper, a multidimensional system is presented, consisting of a size‐exclusion chromatographic (SEC) separation followed by a trapping procedure on a 4 mm×3 mm ID reversed‐phase C18 (RP18) column with subsequent elution of the trapped fraction and separation by capillary zone electrophoresis (CZE). The system has been tested with mixtures of six enkephalins and albumin, mimicking biological matrices such as plasma and cerebrospinal fluid. After separation of albumin from the enkephalins in the SEC dimension a heart‐cut of 200 μL, containing the enkephalin peak, is taken, concentrated on the RP18 microcolumn and, after elution with a 20 μL plug of 80% acetonitrile, electrokinetically injected into the CZE system, where stacking and separation is achieved. While validation shows generally good linearity and reproducibility, the quantitation limit with UV detection is acceptable (2.5 μg/ mL with an injection volume of 50 μL).
Advances in capillary electrochromatography and micro‐high performance liquid chromatography monolithic columns for separation science
Authors: Legido‐Quigley Cristina , Marlin Nicola D. , Melin Virginie , Manz Andreas , Smith Norman W. 
Published: March 2003

AbstractOver the last decade, monoliths or continuous beds have emerged as an alternative to traditional packed‐bed columns for use in capillary electrochromatography (CEC) and micro‐high performance liquid chromatography (μ‐HPLC). Monolithic columns can be divided into two categories: silica‐based monolithic columns and rigid organic polymer‐based monolithic columns resulting from the polymerization of acrylamide, styrene, acrylate or methacrylate monomers. In this paper, the chemistry and most recent applications of these various types of monoliths in both CEC and μ‐HPLC are presented.
Separation of selected humic degradation compounds by capillary electrochromatography with monolithic and packed columns
Authors: Ping Guichen , Schmitt‐Kopplin Philippe , Hertkorn Norbert , Zhang Weibing , Zhang Yukui , Kettrup Antonius 
Published: March 2003

AbstractThe separation of selected lignin/humic substance (HS) degradation compounds by capillary electrochromatography (CEC) with a methacrylate‐based monolithic column and a conventional column packed with 5 μm octadecyl silica (ODS) particles is presented. The effects of organic modifier concentration, pH of the mobile phase, ionic strength, applied voltage, and temperature on the separation were investigated to determine the optimal separation conditions. With the increase of pH in the mobile phase, some of analytes start to ionize and both chromatographic partition and electrophoresis can play roles in separation simultaneously. Accordingly, different selectivity from high‐performance liquid chromatography (HPLC) and capillary electrophoresis (CE) could be achieved. The performances of both kinds of columns were compared. The results showed that the peaks of compounds obtained on the former column were much wider than those on the latter one, although good separation efficiency of alkylbenzenes could be readily achieved; the most probable reasons for this behavior and method to solve this problem were briefly discussed. The CEC of a soil fulvic acid with a monolithic column produced partly resolved broad bands; by means of nuclear magnetic resonance (NMR) analysis a wide range of oxygen derived aromatic substitution patterns was found with prominent contributions from phenolic and carboxylic groups.
Capillary electrochromatographic analysis of aliphatic mono‐ and polycarboxylic acids
Authors: Chen Wei‐Hsi , Lin Chun‐Chi , Chen Tse‐Shien , Misra Tarun K. , Liu Chuen‐Ying 
Published: March 2003

AbstractThe parameters influencing the electrochromatographic separation of aliphatic organic acids in a capillary column with a wall‐coated macrocyclic polyamine have been studied. Indirect detection using chromate, pyromellitate, trimellitate, o‐phthalate, benzoate and acetate as background electrolytes has been tested. A complete separation of polyprotic acids could be achieved with pyromellitate buffer (7.5 mM, pH 6.5), and satisfactory results for the simultaneous separation of monoprotic acids and polyprotic acids were found using a capillary column of 70 cm (50 cm effective length)×75 μm inner diameter, electrokinetic injection (–10 kV, 10 s), benzoate buffer (6 mM, pH 4.6), separation voltage of –10 kV, and detection at 220 nm. For the separation of the geometric isomers fumarate and maleate, acetate buffer was found the best choice among the background electrolytes tested. The method so established has been applied to the determination of organic acids in soy sauce, brandy, lemon juice, spinach juice and cigarette. From the retention behavior, it was found that the separation mechanism on the bonded phase was influenced by the macrocyclic effect, electrostatic attraction, hydrogen bonding, van der Waals forces, and anion exchange, in addition to the differences in electrophoretic mobility.
Comparison of the retention characteristics of different pseudostationary phases for microemulsion and micellar electrokinetic chromatography of betamethasone and derivatives
Authors: Lucangioli Silvia E. , Carducci Clyde N. , Scioscia Silvia L. , Carlucci Adriana , Bregni Carlos , Kenndler Ernst 
Published: March 2003

AbstractFive electrokinetic chromatography systems were compared concerning retention behavior and lipophilicity. Comparison was based on capacity (retention) factors of some steroidal drugs, and on log POW values derived by the aid of reference substances. In all systems the aqueous buffer consisted of phosphate (20 mM, pH 7.5). Two systems had micelles, three systems microdroplets as negatively charged pseudostationary phases. The micelles were formed by sodium dodecyl sulfate (SDS) and sodium cholate, respectively. One microemulsion consisted (as usual) from octane as oil, butanol as cosurfactant and SDS as charged tenside. Two microemulsions were made from biosurfactants (phosphatidylcholine, isopropylmyristate) to better simulate biopartitioning of the drugs. Even for noncharged analytes a change in migration sequence and thus in log POW was observed for the systems consisting of the biosurfactants, compared to the others. For the former systems, log POW derived from the capacity factors agree for all analytes with those obtained from calculation by computer software based on the structure of the drugs, and with experimental data directly obtained from octanol/water partitioning.
Microemulsion electrokinetic chromatography applied for separation of levetiracetam from other antiepileptic drugs in polypharmacy
Authors: Ivanova Mariela , Piunti Alessandra , Marziali Ettore , Komarova Natalja , Raggi Maria Augusta , Kenndler Ernst 
Published: March 2003

AbstractMicroemulsion electrokinetic chromatography was applied for the separation of levetiracetam from other antiepileptic drugs (primidone, phenobarbital, phenytoin, lamotrigine and carbamazepine) that are potentially coadministered in therapy of patients. The influence of the composition of the microemulsion system (with sodium dodecyl sulfate as charged surfactant) was investigated, modifying the kind of cosurfactant (lower alcohols from C3 to C5), the pH (and salinity) of the aqueous background electrolyte, and the ratio of aqueous phase to organic constituents forming the microdroplets of the oil‐in‐water emulsion. Separation selectivity was depending on all these parameters, resulting even in changes of the migration sequence of the analytes. Only moderate correlation was observed for the microemulsion system compared with a micellar system, both consisting of the aqueous borate buffer (pH 9.2) and SDS as micelle former (linear correlation coefficient for analyte mobilities is 0.974). The sample solvent plays an important role on the shape of the resulting chromatograms: methanol at concentrations higher than 35% impairs peak shape and separation efficiency. The microemulsion method (with 93.76% aqueous borate buffer (pH 9.2, 10 mM), 0.48% n‐octane, 1.80% SDS, 3.96% 1‐butanol, all w/w) is suitable for the determination of levetiracetam in human plasma (combined with a sample pretreatment based on solid‐phase extraction).
Three‐dimensional transient free‐surface flow of viscous fluids inside cavities of arbitrary shape
Authors: Kim Kyu‐Tae , Khayat Roger E. 
Published: March 2003

AbstractThe three‐dimensional transient free‐surface flow inside cavities of arbitrary shape is examined in this study. An adaptive (Lagrangian) boundary‐element approach is proposed for the general three‐dimensional simulation of confined free‐surface flow of viscous incompressible fluids. The method is stable as it includes remeshing capabilities of the deforming free‐surface, and thus can handle large deformations. A simple algorithm is developed for mesh refinement of the deforming free‐surface mesh. Smooth transition between large and small elements is achieved without significant degradation of the aspect ratio of the elements in the mesh. The method is used to determine the flow field and free‐surface evolution inside cubic, rectangular and cylindrical containers. These problems illustrate the transient nature of the flow during the mixing process. Surface tension effects are also explored. Copyright © 2003 John Wiley & Sons, Ltd.
Anisotropic Cartesian grid method for steady inviscid shocked flow computation
Authors: Wu Zi‐Niu , Li Ke 
Published: March 2003

AbstractThe anisotropic Cartesian grid method, initially developed by Z.N. Wu (ICNMFD 15, 1996; CFD Review 1998, pp. 93–113) several years ago for efficiently capturing the anisotropic nature of a viscous boundary layer, is applied here to steady shocked flow computation. A finite‐difference method is proposed for treating the slip wall conditions. Copyright © 2003 John Wiley & Sons, Ltd.
Numerical approximation of generalized Newtonian fluids using Powell–Sabin–Heindl elements: I. theoretical estimates
Authors: Chow S.‐S. , Carey G. F. 
Published: March 2003

AbstractIn this paper we consider the numerical approximation of steady and unsteady generalized Newtonian fluid flows using divergence free finite elements generated by the Powell–Sabin–Heindl elements. We derive a priori and a posteriori finite element error estimates and prove convergence of the method of successive approximations for the steady flow case. A priori error estimates of unsteady flows are also considered. These results provide a theoretical foundation and supporting numerical studies are to be provided in Part II. Copyright © 2003 John Wiley & Sons, Ltd.
Large‐eddy simulation with complex 2‐D geometries using a parallel finite‐element/spectral algorithm
Authors: Snyder D. O. , Degrez G. 
Published: March 2003

AbstractA parallel stabilized finite‐element/spectral formulation is presented for incompressible large‐eddy simulation with complex 2‐D geometries. A unique discretization scheme is developed consisting of a streamline‐upwind Petrov–Galerkin/Pressure‐Stabilized Petrov–Galerkin (SUPG/PSPG) finite‐element discretization in the 2‐D plane with a collocated spectral/pseudospectral discretization in the out‐of‐plane direction. This formulation provides an efficient approach for solving 3‐D flows over arbitrary 2‐D geometries. Utilizing this discretization and through explicit temporal treatment of the non‐linear terms, the system of equations for each Fourier mode is decoupled within each time step. A novel parallelization approach is then taken, where the computational work is partitioned in Fourier space. A validation of the algorithm is presented via comparison of results for flow past a circular cylinder with published values for Re=195, 300, and 3900. Copyright © 2003 John Wiley & Sons, Ltd.
Numerical simulation of vortical ideal fluid flow through curved channel
Authors: Moshkin N. P. , Mounnamprang P. 
Published: March 2003

AbstractA numerical algorithm to study the boundary‐value problem in which the governing equations are the steady Euler equations and the vorticity is given on the inflow parts of the domain boundary is developed. The Euler equations are implemented in terms of the stream function and vorticity. An irregular physical domain is transformed into a rectangle in the computational domain and the Euler equations are rewritten with respect to a curvilinear co‐ordinate system. The convergence of the finite‐difference equations to the exact solution is shown experimentally for the test problems by comparing the computational results with the exact solutions on the sequence of grids. To find the pressure from the known vorticity and stream function, the Euler equations are utilized in the Gromeka–Lamb form. The numerical algorithm is illustrated with several examples of steady flow through a two‐dimensional channel with curved walls. The analysis of calculations shows strong dependence of the pressure field on the vorticity given at the inflow parts of the boundary. Plots of the flow structure and isobars, for different geometries of channel and for different values of vorticity on entrance, are also presented. Copyright © 2003 John Wiley & Sons, Ltd.
Riemann solvers and boundary conditions for two‐dimensional shallow water simulations
Authors: Guinot Vincent 
Published: March 2003

AbstractMost existing algorithms for two‐dimensional shallow water simulations treat multi‐dimensional waves using wave splitting or time splitting. This often results in anisotropy of the computed flow. Both wave splitting and time splitting are based on a local decomposition of the multi‐dimensional problem into one‐dimensional, orthogonal problems. Therefore, these algorithms handle boundary conditions in a very similar way to classical one‐dimensional algorithms. This should be expected to trigger a dependence of the number of boundary conditions on the direction of the flow at the boundaries. However, most computational codes based on alternate directions do not exhibit such sensitivity, which seems to contradict the theory of existence and uniqueness of the solution. The present paper addresses these issues. A Riemann solver is presented that aims to convert two‐dimensional Riemann problems into a one‐dimensional equivalent Riemann problem (ERP) at the interfaces between the computational cells. The ERP is derived by applying the theory of bicharacteristics at each end of the interface and by performing a linear averaging along the interface. The proposed approach is tested against the traditional one‐dimensional approach on the classical circular dambreak problem. The results show that the proposed solver allows the isotropy of the solution to be better preserved. Use of the two‐dimensional solver with a first‐order scheme may give better results than use of a second‐order scheme with a one‐dimensional solver. The theory of bicharacteristics is also used to discuss the issue of boundary conditions. It is shown that, when the flow is subcritical, the number of boundary conditions affects the accuracy of the solution, but not its existence and uniqueness. When only one boundary condition is to be prescribed, it should not be the velocity in the direction parallel to the boundary. When two boundary conditions are to be prescribed, at least one of them should involve the component of the velocity in the direction parallel to the boundary. Copyright © 2003 John Wiley & Sons, Ltd.
A robust multi‐grid pressure‐based algorithm for multi‐fluid flow at all speeds
Authors: Darwish M. , Moukalled F. , Sekar B. 
Published: March 2003

AbstractThis paper reports on the implementation and testing, within a full non‐linear multi‐grid environment, of a new pressure‐based algorithm for the prediction of multi‐fluid flow at all speeds. The algorithm is part of the mass conservation‐based algorithms (MCBA) group in which the pressure correction equation is derived from overall mass conservation. The performance of the new method is assessed by solving a series of two‐dimensional two‐fluid flow test problems varying from turbulent low Mach number to supersonic flows, and from very low to high fluid density ratios. Solutions are generated for several grid sizes using the single grid (SG), the prolongation grid (PG), and the full non‐linear multi‐grid (FMG) methods. The main outcomes of this study are: (i) a clear demonstration of the ability of the FMG method to tackle the added non‐linearity of multi‐fluid flows, which is manifested through the performance jump observed when using the non‐linear multi‐grid approach as compared to the SG and PG methods; (ii) the extension of the FMG method to predict turbulent multi‐fluid flows at all speeds. The convergence history plots and CPU‐times presented indicate that the FMG method is far more efficient than the PG method and accelerates the convergence rate over the SG method, for the problems solved and the grids used, by a factor reaching a value as high as 15. Copyright © 2003 John Wiley & Sons, Ltd.
Role of the α‐chemokine stromal cell‐derived factor (SDF‐1) in the developing and mature central nervous system
Authors: Lazarini Françoise , Tham To Nam , Casanova Philippe , Arenzana‐Seisdedos Fernando , Dubois‐Dalcq Monique 
Published: March 2003

Abstractα‐chemokines, which control the activation and directed migration of leukocytes, participate in the inflammatory processes in host defense response. One of the α‐chemokines, CXCL12 or stromal cell‐derived factor 1 (SDF‐1), not only regulates cell growth and migration of hematopoietic stem cells but may also play a central role in brain development as we discuss here. SDF‐1 indeed activates the CXCR4 receptor expressed in a variety of neural cells, and this signaling results in diverse biological effects. It enhances migration and proliferation of cerebellar granule cells, chemoattracts microglia, and stimulates cytokine production and glutamate release by astrocytes. Moreover, it elicits postsynaptic currents in Purkinje cells, triggers migration of cortical neuron progenitors, and produces pain by directly exciting nociceptive neurons. By modulating cell signaling and survival during neuroinflammation, SDF‐1 may also play a role in the pathogenesis of brain tumors, experimental allergic encephalitis, and the nervous system dysfunction associated with acquired immunodeficiency syndrome. GLIA 42:139–148, 2003. © 2003 Wiley‐Liss, Inc.
Acute downregulation of Cx43 alters P2Y receptor expression levels in mouse spinal cord astrocytes
Authors: Suadicani Sylvia O. , De Pina‐Benabou Mara Helena , Urban‐Maldonado Marcia , Spray David C. , Scemes Eliana 
Published: March 2003

AbstractPropagation of intercellular calcium waves (ICW) between astrocytes depends on the diffusion of signaling molecules through gap junction channels and diffusion through the extracellular space of neuroactive substances acting on plasmalemmal receptors. The relative contributions of these two pathways vary in different brain regions and under certain pathological conditions. We have previously shown that in wild‐type spinal cord astrocytes, ICW are primarily gap junction‐dependent, but that deletion of the main gap junction protein (Cx43) by homologous recombination results in a switch in mode of ICW propagation to a purinoceptor‐dependent mechanism. Such a compensatory mechanism for ICW propagation was related to changes in the pharmacological profile of P2Y receptors, from an adenine‐sensitive P2Y1, in wild‐type, to a uridine‐sensitive P2U receptor subtype, in Cx43 knockout (KO) astrocytes. Using oligonucleotide antisense to Cx43 mRNA for acute downregulation of connexin43 expression levels, we provide evidence for the molecular nature of such compensatory mechanism. Pharmacological studies and Western blot analysis indicate that there is a reciprocal regulation of P2Y1 and P2Y4 expression levels, such that downregulation of Cx43 leads to decreased expression of the adenine‐sensitive P2Y1 receptor and increased expression of the uridine‐sensitive P2Y4 receptor. This change in functional expression of the P2Y receptor subtype population in acutely downregulated Cx43 was paralleled by changes in the mode of ICW propagation, similar to that previously observed for Cx43 KO spinal cord astrocytes. On the basis of these results, we propose that Cx43 regulates both modes of ICW by altering P2Y receptor subtype expression in addition to providing intercellular coupling. GLIA 42:160–171, 2003. © 2003 Wiley‐Liss, Inc.