bluuebunny/crossref_metadata_2025_split huggingface dataset:
Preparation and characterization of monolithic columns for capillary electrochromatography with weak electroosmotic flow
Authors: Zhang Lingyi , Ping Guichen , Zhang Lihua , Zhang Weibing , Zhang Yukui 
Published: March 2003

AbstractMonolithic columns of capillary electrochromatography (CEC) with weak electroosmotic flow (EOF) have been prepared by in situ polymerization of butyl methacrylate and ethylene dimethacrylate, without any charged groups in the reaction mixture. The reproducibility of such columns has been proved good no matter whether they are prepared in the same batch or in different batches. In the case of BMA‐EDMA monoliths, besides the traditional ternary mixture – 1‐propanol, 1,4‐butanediol, and water, binary porogenic solvents with only alcohols have also been adopted. Compared with ternary porogenic solvents, the design with binary ones allows for fine control of the pore diameter and the formation of the specific surface of the monolithic polymers. The composition of porogenic reagents has also been shown to have an effect on EOF in the column systems. In addition, the Joule heat effect in such columns has been studied by varying the inner diameter of columns. Through the separation of acidic compounds, monolithic columns with low EOF have shown potential in the analysis of charged samples.
Nonlinear artificial boundary conditions with pointwise error estimates for the exterior three dimensional Navier–Stokes problem
Authors: Nazarov Sergej A. , Specovius–Neugebauer Maria 
Published: April 2003

AbstractOn a three–dimensional exterior domain Ω we consider the Dirichlet problem for the stationary Navier–Stokes system. We construct an approximation problem on the domain ΩR, which is the intersection of Ω with a sufficiently large ball, while we create nonlinear, but local artificial boundary conditions on the truncation boundary. We prove existence and uniqueness of the solutions to the approximating problem together with asymptotically precise pointwise error estimates as R tends to infinity.
Ordering in Stretched Bernoullian Copolymers
Authors: Litmanovich Arkady D. , Kudryavtsev Yaroslav V. , Kriksin Yury A. , Kononenko Oleg A. 
Published: March 2003

AbstractA new approach is suggested to estimate the theoretical maximum capability to order for stretched Bernoullian copolymers AB, provided interchain AB contacts are unfavorable. A simple Monte Carlo procedure simulating the ordering of such copolymers via rotation of ring‐shaped chains reveals the capability to order even for quite long copolymer chains. The analytical probabilistic consideration is elaborated, which enables one to interpret the ordering via rotation in terms of a sliding of periodic Bernoullian chains. Using both the probabilistic analysis and Monte Carlo simulations it is shown that estimations of a capability to order given by the rotation procedure are also good for a sliding of true Bernoullian copolymers. Therefore, the simple Monte Carlo procedure seems suitable for estimating ordering in other classes of copolymers for which an analytical approach is more complicated. Such estimations might be useful for a consideration of various properties of irregular copolymers connected with their tendency to order.Ordering by rotation of rings. As an example, an ordering for M = 10 000 chains of length N = 20 and composition p = 0.50 (p is the mole fraction of A units) is shown. See text.imageOrdering by rotation of rings. As an example, an ordering for M = 10 000 chains of length N = 20 and composition p = 0.50 (p is the mole fraction of A units) is shown. See text.
Molecular Weight Development during Simultaneous Chain Scission, Long‐Chain Branching and Crosslinking, 1
Authors: Tobita Hidetaka 
Published: March 2003

AbstractA general matrix formula is proposed for the weight‐average molecular weights of the polymer systems formed through simultaneous scission, branching and crosslinking of N types of chains, assuming the chain connection statistics are Markovian. For the polymerization systems in which chains are generated consecutively, such as for free‐radical polymerization, the present theory can be applied by increasing the number of chain types N to infinity, by considering the chains formed at different times as different types of chains. The gel point determination reduces to the eigenvalue problem and the present theory extends the classical gelation theory to non‐random, history‐dependent reaction systems. From the mathematical point of view, this theory is capable of describing complex molecular build‐up processes through end‐linking, T‐ and H‐shaped chain connections, irrespective of reaction/reactor types used.
Schematic representation of the 0th generation segment and the connection to the 1st generation segments.imageSchematic representation of the 0th generation segment and the connection to the 1st generation segments.
Applikationsfelder organischer Funktionspolymere, Polymeraktoren und Polymertransistoren
Authors: Roth H.‐K. , Schrödner M. 
Published: March 2003

AbstractDer Artikel gibt einen kurzen allgemeinen Überblick über zukünftige Hochtechnologieprodukte, in denen leitfähige Polymere und andere Polymere mit speziellen elektronischen Eigenschaften Anwendung finden werden oder bereits angewendet werden. Solche Produkte sind z. B. Polymeraktoren, organische Feldeffekttransistoren (OFET's) und integrierte Polymerschaltkreise, organische Leuchtdioden (OLED's), Polymersolarzellen bzw. Photovoltaikelemente, Membranen für Brennstoffzellen, Polymerbatterien sowie verschiedene Varianten von Polymersensoren.Es wird kurz informiert über Strukturen und Eigenschaften von intrinsisch leitfähigen Polymeren und etwas detaillierter über elektro‐chemo‐mechanische Polymeraktoren und über polymere Feldeffekttransistoren.
High‐Tech‐Cellulose‐Funktionspolymere nach dem ALCERU®‐Verfahren
Authors: Meister F. , Vorbach D. , Niemz F. , Schulze T. 
Published: March 2003

AbstractCellulose gehört zu einem der ältesten Werkstoffe der Menschheit. Standen dabei die Nutzung als Konstruktionswerkstoff bzw. als Textilrohstoff im Vordergrund, so erweitert sich das Anwendungsprofil durch die Nutzung des ALCERU®‐Verfahrens zunehmend auch auf Funktionswerkstoffe.Dabei gestattet die Verspinnung von Cellulose‐NMMNO‐Lösungen die Herstellung von Polster‐ und Filterwerkstoffen sowie von bioabbaubaren Feinstfolienbändchen mit exakten Formkörperquerschnitten. Nutzt man verschiedene Techniken zur Regenerierung lassen sich vielseitig verwendbare Cellulosefibride herstellen.Ein großes Feld innovativer cellulosischer Funktionspolymere erschließt sich bei der Zugabe von funktionalen Additiven zur Celluloselösung. Beim Zusatz von keramischen Pulvern lassen sich so piezo‐elektrische Fasern oder aber auch Hochtemperaturfilterwerkstoffe generieren. Insbesondere PZT‐Grünfasern finden zunehmend Anwendung in sehr modernen Sensor‐ und Aktuatoranwendungen. Auf dem gleichen Weg erhält man durch die Zugabe von Leitfähigkeitsrußen elektrisch leitfähige Cellulosefasern, die gleichzeitig textil verarbeitet werden können. Durch den definierten Zusatz verschiedener Mengen an Ruß lassen sich Cellulosewerkstoffe mit genau an den Verwendungszweck angepaßten elektrischen Eigenschaften gewinnen. Schließlich erhält man durch die Variation der Verformungstechnik Celluloseperlen mit variablen Partikel‐ bzw. Porendurchmessern, die über ein attraktives Eigenschaftsspektrum für Anwendungen im Bereich der Blutwäsche sowie der affinitätschromatographischen Nutzung besitzen.
Möglichkeiten der Geruchsmessung und ‐minderung bei Naturfaserverbunden
Authors: Bledzki A. K. , Sperber V. E. , Wolff S. 
Published: March 2003

AbstractDie kritische Einstellung der deutschen Öffentlichkeit zu Umweltfragen hat auch die Welt der Gerüche erfasst.In den letzten Jahren haben die Bewertung und Verminderung von Gerüchen bei der Anwendung von Kunststoffen zunehmend an Bedeutung gewonnen. War es zunächst die Verpackungsbranche, die Produkte für Lebensmittelverpackungen olfaktometrisch untersuchte, so zeigt in den letzten Jahren die Automobilindustrie zunehmendes Interesse für Geruchsbestimmung und Messung, nicht zuletzt wegen des zunehmenden Einsatzes von naturfaserverstärkten Werkstoffen im Fahrzeuginnenraum.Naturfaserverstärkte Kunststoffe haben neben Vorteilen gegenüber glas‐ und kohlefaserverstärkten Systemen (mechanisches Verhalten/Gewicht, ausgeglichene CO2‐Bilanz) auch Eigenschaften, die das Anwendungsspektrum einschränken können. Hierzu werden Emissionen und Geruchsentwicklung gezählt, die unter bestimmten Temperatur‐ und Feuchtigkeitsbedingungen auftreten können. Auch bei Verbundmaterialien stellt sich die Frage, welche Einzelkomponenten, Verfahrensschritte oder Kombinationen beider für einen bestimmten Geruch verantwortlich sind.Der Weg zur Geruchsneutralität von Kunststoffen ist generell schwierig, da geeignete Herstellungsmethoden oder auch Zusätze nur in langen Versuchsketten ermittelt werden können und nach wie vor die menschliche Nase wichtiger als alle physikalischelektronischen Messverfahren ist.Die Frage der Herkunft von Gerüchen und nach deren Bedeutung für Wohlbefinden und Gesundheit wird gestellt und zwingt nicht nur die Kunststoffindustrie zur Reaktion. Deshalb sind beide, Kunststoff‐ und Automobilindustrie, bemüht, auf die Tendenzen des Marktes zu reagieren, und es ist das Ziel der Autohersteller möglichst geruchsneutrale Neuwagen auszuliefern.
Modifizierung organischer Konstruktionswerkstoffe für technische Anwendungen
Authors: Heinemann K. , Meusel E. , Riedel B. , Müller W. , Strubl R. , Gottlöber R.‐P. , Seyfarth H.‐E. , Taeger E. 
Published: March 2003

AbstractBerichtet wird über Experimente zur Synthese neuartiger reaktiver, thermotroper flüssig‐kristalliner Polymere (LCPs) sowie über Untersuchungen zum Einsatz dieser LCPs als Blendkomponente bei der Herstellung derart modifizierter Polyamid‐ und Polyesterfasern und deren Eigenschaften.Diese reaktiven LCPs sind synthetisch leicht zugängliche Polyesterimidanhydride (PEIA), die sowohl seitenständige als auch endständige Anhydridgruppen besitzen. Die mittlere Zahl an Anhydridgruppen ist zwischen 4 und 18 variierbar. Es konten Produkte mit Molmassen von etwa 30 kg/mol bis hin zu 80 kg/mol erhalten werden.Beim Mischen der Reaktiv‐LCPs mit Polyamid 6 [PA 6] oder Polyethylenterephthalat [PET] in einem Extruder unter Schmelzebedingungen reagieren beide Komponenten innerhalb weniger Minuten zu Pfropf‐Blockcopolymeren, an deren LCP‐Rückgratketten sich seiten‐ und endständige Polyamid‐ beziehungsweise Polyesterblöcke befinden. Diese schnell verlaufenden Modifizierungsreaktionen bilden die Basis für die industrielle Nutzanwendung in Form eines kontinuierlilch gestaltbaren “reactive blending‐spinning‐drawing”‐Prozesses.Die auf diesem Wege im Sinne eines “reactive blending” synthetisierten Pfropf‐Blockcopolymeren sind zusammen mit dem jeweils adäquaten Matrixmaterial Polyamid 6 oder Polyester zu reckbaren Filamenten verarbeitbar. Nach Spinn‐ und Reckprozeduren unter geeigneten Bedingungen lassen sich in den erhaltenen Filamenten mit Molekülen des Basispolymers modifizierte lc‐PEIA‐Fibrillen mit Durchmessern von weniger als 500 nm nachweisen. Die angestrebte Mikrophasenverteilung der PA‐ beziehungsweise PET‐modifizierten lc‐PEIA‐Makromoleküle als verstärkungswirksame Systemkomponenten konnte erreicht werden. Zudem zeichnen sich die durch das “reactive blending” in‐situ entstehenden Pfropf‐Blockcopolymere auf Grund ihrer chemischen Ähnlichkeit zur Primärstruktur der jeweiligen Matrixmaterialien durch eine hohe thermodynamische Verträglichkeit aus, woraus ein relativ hoher Verstärkungseffekt resultiert.Diese beiden Aspekte sowie die bei den Reckprozessen stattfindende Orientierung der lc‐PEIA‐Mikrophasen verursachen, obwohl Optimierungsversuche noch ausstehen, bemerkenswerte Steigerungen der Zugfestigkeiten sowie deutlich verbesserte Anfangsmoduli bei gleichzeitig erhöhter Reckfähigkeit der lc‐PEIA‐modifizierten Polyamid‐ und Polyesterfilamente. Diese Effekte lassen sich bereits mit PEIA‐Anteilen von weniger als 5 Masseprozent erreichen.
Propagation characteristics of transmission‐line transformers with different impedance variation patterns on substrates with very high dielectric constant
Authors: Carvalho M. C. R. , Conrado L. F. M. , Demenicis L. S. , Seixas D. L. A. 
Published: March 2003

AbstractTransmission‐line transformers with different impedance variation patterns and printed on substrates with very high dielectric constant (εr = 80) are compared and the influence of the total length is studied. The propagation characteristics of the tapered lines were investigated using the finite‐element method. Dispersion effects and impedance variation with respect to the frequency have been taken into account in the analysis. The obtained results are in good agreement with theoretical predictions for ideal tapers, especially at low frequencies. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 37: 174–177, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10859
Computation of Sommerfeld integrals using tanh transformation
Authors: Singh Surendra , Singh Ritu 
Published: March 2003

AbstractA variable transformation is utilized in the computation of Sommerfeld integrals, which arise in the analysis of antennas radiating over a dielectric half‐space. The method involves a change of variable, which transforms the integrand into a rapidly converging one. Several numerical examples, which illustrate the effectiveness of the method, are presented and the results are compared with those reported in the literature. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 37: 177–180, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10860
Coupled BORs scattering via an efficient MoM solution of CFIE
Authors: Bolli P. , Gentili G. G. , Nesti R. , Pelosi G. 
Published: March 2003

AbstractIn this work a numerical technique for an accurate modelling of the coupling among neighbouring bodies of revolution (BORs) is proposed. This problem is of high interest in modern applications, where clusters of feeds are being used more frequently in antenna systems to increase performances. The scattering problem, both for a stand‐alone body of revolution (BoR) and for coupled BoRs, has been solved using the combined field integral equation (CFIE) approach and the method of moments (MoM), with an efficient set of expansion functions whose validity is limited to BoR. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 37: 180–183, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10861
Error control of the translation operator in 3D MLFMA
Authors: Hastriter Michael Larkin , Ohnuki Shinichiro , Chew Weng Cho 
Published: March 2003

AbstractThis paper presents an extension of a new approach to select the truncation number for translation operators in a 3D multilevel fast multipole algorithm (MLFMA). Although error is harder to control in 3D than in 2D problems, this recently developed new approach provides better error control in 3D problems over the excess bandwidth formula. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 37: 184–188, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10862
High‐order finite‐element analysis of periodic absorbers
Authors: Lou Zheng , Jin Jian‐Ming 
Published: March 2003

AbstractA high‐order vector finite‐element‐method (FEM) analysis of periodic absorbers is presented. By the virtue of the FEM, accurate modeling of complicated absorber structures is made possible. For a given accuracy, high‐order elements are used to reduce the number of unknowns and hence the computing time and memory consumption. The FEM is further combined with the asymptotic waveform evalaution (AWE) technique to produce fast‐frequency sweep. Both singly and doubly periodic absorbers are modeled and the accuracy of the method is demonstrated by comparisons with analytical solutions and published data. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 37: 203–207, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10869
A dual‐band printed L‐shaped monopole for WLAN applications
Authors: Lin Yi‐Fang , Chen Horng‐Dean , Chen Hua‐Ming 
Published: March 2003

AbstractA novel microstrip‐fed dual‐band L‐shaped monopole antenna has been developed for WLAN applications in the 2.4‐GHz and 5.2‐GHz bands. The antenna has a single L‐shaped radiator and is easy to construct. The obtained impedance bandwidth (1:1.5 VSWR) reaches 15.6% and 12.6% for the 2.4 and 5.2 GHz, respectively. Omnidirectional patterns, vertical null in the antenna patterns, and good efficiency of the two operating frequencies are given for the proposed antenna. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 37: 214–216, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10873
Triple‐band triangular‐shaped meander monopole antenna with two coupled lines
Authors: Chen Horng‐Dean 
Published: March 2003

AbstractA novel compact monopole antenna for triple‐band operation is proposed in this paper. The proposed antenna is designed to operate at 900, 1800, and 2450 MHz, and is realized by loading two coupled lines on a triangular‐shaped meander line. The longer coupled line controls the excitations of the first two resonant modes, and the shorter one controls the excitation of the third resonant mode. Good impedance bandwidth performance for the three bands is observed. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 37: 232–234, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10879
Reproducibility study of 3D geometrical reconstruction of the human carotid bifurcation from magnetic resonance images
Authors: Long Q. , Ariff B. , Zhao S.Z. , Thom S.A. , Hughes A.D. , Xu X.Y. 
Published: March 2003

AbstractThe combined magnetic resonance imaging (MRI) and computational fluid dynamics (CFD) modeling approach is playing an increasingly important role in advancing our understanding of the relationship between hemodynamics and arterial disease. Nevertheless, such a modeling approach involves a number of uncertainties associated with various stages of the process. The present study is concerned with the reproducibility of geometry reconstruction, one of the most crucial steps in the modeling process. The reproducibility test was conducted on the right carotid bifurcation of eight normal human subjects, each of whom were scanned twice using the same MR protocol with an in‐plane resolution of 0.625 mm. Models constructed from different scans of the same subject were compared and assessed using four quantitative measures: centerline distance, cross‐sectional area, contour shape factors, and mean radius difference. The difference in the maximum carotid bulb area between the two scans was found to be <8.1% for all subjects. Shape factors (measuring the dissimilarity between two contours) of <10% were achieved in most of the common carotid arteries (CCAs) and internal carotid arteries (ICAs). The mean radius difference between the two scans was <0.4 mm for all subjects. Among the three vessels, the geometry of CCA was well reproduced by the reconstruction procedure in most of the cases, while the external carotid artery (ECA) showed the worst reproducibility. The impact of geometrical differences on CFD‐predicted flow patterns and wall shear stress (WSS) will be investigated and discussed in a separate paper. Magn Reson Med 49:665–674, 2003. © 2003 Wiley‐Liss, Inc.
In vivo oxygen detection using exogenous hemoglobin as a contrast agent in magnetic resonance microscopy
Authors: Sun Phillip Z. , Schoening Zachary B. , Jasanoff Alan 
Published: March 2003

AbstractIn this work we show that exogenous molecular hemoglobin (Hb) is an effective indicator of relative local oxygen tension in magnetic resonance (MR) microscopy studies in vivo. This approach is more sensitive than other MRI oximetry methods; it can be used at higher resolutions and in specimens with no blood oxygen level‐dependent (BOLD) effects. Using injection studies in flies, we show that Hb can permeate through relatively dense neural tissue, and that it is not obviously disruptive to physiology. Hb‐injected flies show large changes in signal intensity (40–50%) when external O2 levels are manipulated artificially from 0% to 21%. Oxygen‐dependent contrast changes produced by exogenous Hb are detected in T2‐weighted imaging experiments, and can be roughly calibrated if necessary. These studies demonstrate the feasibility of a contrast agent technique that may be useful for functional MRI (fMRI) studies of metabolism at tens of microns resolution. Magn Reson Med 49:609–614, 2003. © 2003 Wiley‐Liss, Inc.
Quantitative tumor oxymetric images from 4D electron paramagnetic resonance imaging (EPRI): Methodology and comparison with blood oxygen level‐dependent (BOLD) MRI
Authors: Elas Martyna , Williams Benjamin B. , Parasca Adrian , Mailer Colin , Pelizzari Charles A. , Lewis Marta A. , River Jonathan N. , Karczmar Gregory S. , Barth Eugene D. , Halpern Howard J. 
Published: March 2003

AbstractThis work presents a methodology for obtaining quantitative oxygen concentration images in the tumor‐bearing legs of living C3H mice. The method uses high‐resolution electron paramagnetic resonance imaging (EPRI). Enabling aspects of the methodology include the use of injectable, narrow, single‐line triaryl methyl spin probes and an accurate model of overmodulated spectra. Both of these increase the signal‐to‐noise ratio (SNR), resulting in high resolution in space (1 mm)3 and oxygen concentrations (∼3 torr). Thresholding at 15% the maximum spectral amplitude gives leg/tumor shapes that reproduce those in photographs. The EPRI appears to give reasonable oxygen partial pressures, showing hypoxia (∼0–6 torr, 0–103 Pa) in many of the tumor voxels. EPRI was able to detect statistically significant changes in oxygen concentrations in the tumor with administration of carbogen, although the changes were not increased uniformly. As a demonstration of the method, EPRI was compared with nearly concurrent (same anesthesia) T/blood oxygen level‐dependent (BOLD) MRI. There was a good spatial correlation between EPRI and MRI. Homogeneous and heterogeneous T/BOLD MRI correlated well with the quantitative EPRI. This work demonstrates the potential for EPRI to display, at high spatial resolution, quantitative oxygen tension changes in the physiologic response to environmental changes. Magn Reson Med 49:682–691, 2003. © 2003 Wiley‐Liss, Inc.
An analytical solution for the SSFP signal in MRI
Authors: Hänicke Wolfgang , Vogel Horst U. 
Published: March 2003

AbstractAmong previous analyses of the steady‐state free‐precession (SSFP) signal in rapid MRI, one treatment resulted in equations that require the evaluation of infinite binomial series. Here, an analytical solution is derived by a transformation into the power series expansion of the derivative of the inverse sine function, which is essentially a root. The treatment is extended to include higher‐order signals. The results demonstrate the identity of the vastly different equations for the SSFP signals reported so far. Applications consist of the derivation of closed expressions for the signal in echo‐shifted MRI and a corresponding analysis of TrueFISP sequences. Magn Reson Med 49:771–775, 2003. © 2003 Wiley‐Liss, Inc.