bluuebunny/crossref_metadata_2025_split huggingface dataset:
Wavelength Flexibility in Photoinitiated Cationic Polymerization
Authors: Yagci Yusuf 
Published: September 2004

AbstractThe spectral sensitivity of onium salt photoinitiators in cationic polymerization can be tuned from the short wavelength region of the UV spectrum to wavelengths up to the visible region by using direct and indirect activation, respectively. Indirect activation is based on the electron transfer reactions between onium salts and free radical photoinitiators, appropriate sensitizers and compounds capable of forming charge transfer complexes. Bisacylphosphine oxides, dimanganese decacarbonyl in conjunction with alkyl halides and titanocene type photoinitiators such as Irgacure 784 were shown to be useful free radical promoters providing the possibility of performing cationic polymerization in the long wavelength and visible region. The synthetic routes to prepare block copolymers by using electron transfer photosensitization and free radical promoted cationic polymerization are also described.
Ring‐Opening Polymerization of the Cyclic Ester Amide Derived from Adipic Anhydride and 1‐Amino‐6‐hexanol in Melt and in Solution
Authors: Fey Thomas , Keul Helmut , Höcker Hartwig 
Published: September 2004

AbstractThe ring‐opening polymerization (ROP) of the cyclic ester amide (cEA) 5 (systematic name, 1‐oxa‐8‐aza‐cyclotetradecane‐9,14‐dione) ‐ prepared from adipic anhydride and 1‐amino‐6‐hexanol ‐ in the melt at 165 °C and in solution at 100 °C and 120 °C with Bu2Sn(OMe)2 or Ti(OBu)4 as initiator yields the alternating poly(ester amide) (PEA) 4 (systematic name, poly(5‐(6‐oxyhexylcarbamoyl)‐pentanoate) with regular microstructure. Kinetic studies for different monomer‐to‐initiator ratios, different reaction media, initiators and temperatures reveal that the ROP is a first‐order reaction with respect to the monomer. Under suitable polymerization conditions termination and transfer reactions are suppressed. The elementary chain growth reaction proceeds by a coordination insertion mechanism in analogy to the polymerization of lactones. By using monohydroxy‐ and bishydroxy‐functional telechelic poly(ethylene oxide) and Sn(octoate)2 as the initiating system poly(ethylene oxide)‐block‐poly(ester amide)s and poly(ester amide)‐block‐poly(ethylene oxide)‐block‐poly(ester amide)s are obtained. The poly(ester amide) 4 is a semicrystalline material with a melting point of 140 °C, the block copolymers are phase separated systems showing two melting points characteristic for the respective homopolymers.
Recent Developments in the Ring‐Opening Polymerization of ϵ‐Caprolactone and Derivatives Initiated by Tin(IV) Alkoxides
Authors: Lecomte Ph. , Stassin F. , Jérôme R. 
Published: September 2004

AbstractThe macromolecular engineering of aliphatic polyesters by ring‐opening polymerization (ROP) initiated by aluminum alkoxides is now well established. Tin (IV) alkoxides are less popular, mainly because of a poorer control of the chain growth. This paper discusses some recent examples from CERM, showing that tin (IV) alkoxides can advantageously replace the aluminum counterparts as ROP initiators. For instance, they can initiate successfully the Ring‐Opening Polymerization of α‐chloro‐ϵ‐caprolactone and dioxepane‐2‐one. They are also very promising initiators for ROP in supercritical CO2 and for the synthesis of clay/aliphatic polyester nanocomposites.
Functionalization of Living Polymers via Ethoxysilane Based Compounds: Synthesis and Interaction with Silica Particles
Authors: Hoffstetter Joël , Giebeler Ellen , Peter Rolf , Lutz Pierre J. 
Published: September 2004

AbstractTo optimize the reaction of ω‐carbanionic styrene or butadiene/styrene polymers with ethoxysilane based compounds, the influence of several experimental parameters on the orientation of the functionalization reaction and its yield was examined. The resulting end‐functionalized polymers were systematically investigated by SEC, 1H NMR and elementary analysis. The orientation of the reaction was found to be directly depending on the chemical nature of the chain end and / or on the type of additive (ethers, LiCl). Best results were obtained with tetraethoxysilane, provided the functionalization is conducted around 5°C, and the active chain end of isoprenyl type. These reactions were extended to bifunctional polymers, the reaction product of butyllithium with m‐diisopropenylbenzene being used as an initiator. The efficiency of this initiator for the synthesis of well‐defined bifunctionalized polydienes almost quantitatively fitted with three alkoxy functions at both chain ends was demonstrated. Some preliminary results on the mechanical properties of mixtures of functionalized polymers with silica were mentioned.
Reactivities of Carbocations and Carbanions
Authors: Ofial Armin R. , Mayr Herbert 
Published: September 2004

AbstractInitiation and propagation rate constants of carbocationic and carbanionic polymerizations can be predicted by the correlation equation log k20 °C = s(N + E), where E characterizes the electrophilicity of carbocations and electron‐deficient alkenes, and N characterizes the nucleophilicity of carbanions and electron‐rich alkenes. Since the nucleophile‐specific slope parameter s is generally close to 1, it can be neglected in a first approximation, and the two‐dimensional representation in Figure 3 illustrates the gradual change from carbanionic to carbocationic polymerizations with Hall's “initiation by bond‐formation” as the link connecting the two ranges. The value of model studies for understanding ionic polymerizations is illustrated.
Confinement Effects on the Crystallization Kinetics and Self‐Nucleation of Double Crystalline Poly(p‐dioxanone)‐b‐poly(ϵ‐caprolactone) Diblock Copolymers
Authors: Müller Alejandro J. , Albuerne Julio , Esteves Luis M. , Marquez Leni , Raquez Jean‐Marie , Degée Philippe , Dubois Philippe , Collins Stephen , Hamley Ian W. 
Published: September 2004

AbstractThe morphology, crystallization and self nucleation behavior of double crystalline diblock copolymers of poly(p‐dioxanone) (PPDX) and poly(ϵ‐caprolactone) (PCL) with different compositions have been studied by different techniques, including optical microscopy (OM), atomic force microscopy (AFM) and differential scanning calorimetry (DSC). The two blocks crystallize in a single coincident exotherm when cooled from the melt. The self‐nucleation technique is able to separate into two exotherms the crystallization of each block. We have gathered evidences indicating that the PPDX block can nucleate the PCL block within the copolymers regardless of the composition. This effect is responsible for the lack of homogeneous nucleation or fractionated crystallization of the PCL block even when it constitutes a minor phase within the copolymer (25% or less). Nevertheless, we were able to show that decreasing amounts of PCL within the diblock copolymer still produces confinement effects that retard the crystallization kinetics of the PCL component and decrease the Avrami index. On the other hand evidence for confinement was also obtained for the PPDX block, since as its content is reduced within the copolymer, a depression in its self‐nucleation and annealing temperatures were observed.
Advances in the Synthesis and Characterization of Polypeptide‐Based Hybrid Block Copolymers
Authors: Dimitrov Ivaylo , Kukula Hildegard , Cölfen Helmut , Schlaad Helmut 
Published: September 2004

AbstractLinear polystyrene‐block‐poly(Z‐L‐lysine) copolymers with a very narrow molecular weight distribution (polydispersity index < 1.03) could be obtained via the ring‐opening polymerization of Z‐L‐lysine‐N‐carboxyanhydride using ω‐(primary amino hydrochloride)‐polystyrenes as macroinitiators in N,N‐dimethylformamide as the solvent at 40‐80 °C. The block copolymer samples were analyzed by means of NMR, size exclusion chromatography, and analytical ultracentrifugation.
Novel microwave microstrip filters using photonic bandgap ground plane with fractal periodic pattern
Authors: Siakavara K. 
Published: September 2004

AbstractPhotonic bandgap (PBG) structures with slots etched in their ground plane have been proposed recently as a good choice for the design of printed microwave filters, absorbers, reflectors, and antennas for many modern applications. In the present work, a microstrip PBG filter was designed to operate as a multifrequency bandstop filter. The conventional profile of the slot patterns used in previous works was either discrete (with circles), continuous sinusoidal, or triangular. These geometries guide the structure to operate as a single wideband filter. In this work, a different periodic pattern of slots is introduced. The configuration is designed using the fractal technique. The self‐similarity of the fractal geometry is found to excite the PBG structure to act as a wide stop‐band filter in more than one frequency region. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 43: 273–276, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20443
Triangular microstrip array on NiZn substrate in the L‐band
Authors: Kumar Dheeraj , Pourush P. K. S. 
Published: September 2004

AbstractThe radiation characteristics of a microstrip planar array of triangular patch antennas printed on NiZn ferrite substrate with a normal magnetic bias field are described. The extra degree of freedom offered by the biased ferrite can be used to obtain a number of novel characteristics, including switchable and tunable radiations from a microstrip antenna with a single feed point. In such a case, for antenna radiation, most of the power is converted into magnetostatic waves and little power radiates in the air. Under such circumstances, the antennas are off, in the sense that they are effectively absent as radiators. The radiation properties of the present array system in the L‐band (2 GHz) are analyzed. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 43: 286–290, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20447
A study of planar Goubau lines (PGLs) for millimeter‐ and submillimeter‐wave integrated circuits (ICs)
Authors: Xu Yansheng , Bosisio Renato G. 
Published: September 2004

AbstractIn this paper, a new type of planar Goubau line (PGL) for millimeter‐ and submillimeter‐wave applications is proposed for use in wideband integrated circuits. The configurations of these modified Goubau lines are examined and the parameters are provided. The performances of these lines are studied in detail. Characteristics of lines with different dimensions are calculated and displayed. Comparisons with other types of transmission lines are also performed. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 43: 290–293, 2004; Published online in Wiley InterScience (www.interscience.wiley.com).
An active receiving antenna for short‐range wireless automotive communication
Authors: Al‐Khateeb Basim , Rabinovich Victor , Oakley Barbara 
Published: September 2004

AbstractThis paper describes an easily manufactured, reduced‐size, active receiving antenna for automotive applications, which increases short‐range wireless detection in the 315‐MHz band. This compact antenna has an advantage over currently available antennas because can be hidden in a vehicle's interior. The active antenna consists of a low‐noise amplifier coupled to a low‐profile planer meander‐line pattern printed on the dielectric substrate. Experimental verification of the antenna performance and a theoretical calculation for the maximum range of the active antenna are presented. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 43: 293–297, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20448
Multiwavelength ring lasers employing semiconductor optical amplifiers as gain media
Authors: Sun Junqiang 
Published: September 2004

AbstractStable simultaneous multiwavelength lasing is demonstrated with a novel fiber‐ring laser incorporating a semiconductor optical amplifier. Band‐pass comb filtering is constructed in the ring cavity with the combination of a wideband Fabry–Perot comb filter and a bandpass filter. Ten lasing lines with a fixed wavelength spacing of 1.6 nm are implemented and the multiwavelength lasing ranges can be flexibly chosen. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 43: 301–303, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20451
A fast calculation of impedances of dipoles near cylindrical structure by applying asymptotic waveform evaluation in a spectrum of 2D solutions
Authors: Yang Jian , Kildal Per‐Simon 
Published: September 2004

AbstractA spectrum of 2D solutions (S2DS) applies the Fourier transform to 3D currents in the uniform direction of a 2D cylindrical structure to arrive into a spectral‐domain problem which can be solved by 2D spatial techniques. In order to calculate the near fields that are needed for the calculation of impedance, the inverse Fourier transform must be performed. This usually requires a large number of 2D solutions in the spectral domain. By using the asymptotic waveform evaluation (AWE) method in S2DS, the inverse Fourier transform can be performed very efficiently, with only several 2D solutions in the spectral domain. This paper presents the fast calculation of the impedance of a dipole in the vicinity of a 2D cylindrical structure. The cases presented in this paper show that the calculation is accelerated seven times more than by using the direct S2DS method. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 43: 314–317, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20455
FDTD analysis of a symmetric T‐strip fed wideband rectangular microstrip antenna
Authors: Lethakumary B. , Menon Sreedevi K. , Aanandan C. K. , Vasudevan K. , Mohanan P. 
Published: September 2004

AbstractA theoretical analysis of a symmetric T‐shaped microstrip‐fed rectangular microstrip antenna using the finite‐difference time‐domain (FDTD) method is presented in this paper. The resonant frequency, return loss, impedance bandwidth, and radiation patterns are predicted and are in good agreement with the measured results. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 43: 332–334, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20461
Technological evolution and performances improvements of a tunable phase‐shifter using liquid crystal
Authors: Martin Noham , Laurent Paul , Prigent Gaëtan , Gelin Philippe , Huret Fabrice 
Published: September 2004

AbstractThe topic of this paper is the study of electrically tunable phase‐shifters based on the use of liquid crystals. The dielectric characterization of the commercial liquid crystal involved in this study allows us to determine its dielectric permittivities (with and without DC voltage applied) and then its dielectric anisotropy. In this way, two phase‐shifter configurations were studied. Every devices propose inverted microstrip line. The two circuits have been realized with coplanar accesses to be use in the millimeter‐frequency range. With the aim to improve the phase shift parameter (in °/GHz/cm), our work aims to reduce the transmission line. Instead of a rectilinear transmission line, this one is based on a symmetric stub line. The phase shift obtained is enhanced from 0.87°/GHz/cm to 2.77°/GHz/cm. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 43: 338–341, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20463
Effect of spherical aberration on the coupling efficiency between a laser diode and a hemispherically lensed tapered fiber
Authors: Kumaran S. , Faidz A. R. 
Published: September 2004

AbstractThe objective of our work is to conduct a theoretical analysis to determine the coupling efficiency between a laser diode (LD) and a hemispherically lensed tapered single‐mode fiber (SMF), which takes into account the effect of spherical aberration on the lens surface. The results obtained clearly show that our proposed theoretical method provides a good estimation of the experimental data. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 43: 341–343, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20464
Analog predistorter using a Cartesian vector modulator structure
Authors: Jang Dong‐Hee , Cho Kyung‐Joon , Kim Sang‐Hee , Kim Ji‐Yeon , Kim Jong‐Heon , Stapleton Shawn P. 
Published: September 2004

AbstractWe propose an analog predistorter that uses a Cartesian vector modulator structure. The operation principle of the proposed predistorter is analyzed for various gain and phase characteristics. The bandwidth performance of the predistorter is presented as a function of the dominant nonlinearity order. Experiments on several power amplifiers under various test signals were performed on the proposed analog predistorter. The experimental results demonstrate that the predistorter can easily control both the gain and phase characteristics via biasing the two IM generators. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 43: 343–348, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20465
Accurate characterization of MEM inductors on lossy silicon
Authors: Lee Young‐Ho , Lee Sang‐No , Yook Jong‐Gwan , Kim Ji‐Hyuk , Chun Kuk‐Jin 
Published: September 2004

AbstractThis paper presents the performance characteristics of an air‐suspended high‐Q MEM inductor that is characterized based on an open‐short deembedding scheme and used for accurate and reliable evaluation of the parasitic effects experienced from feed lines as well as contact pads. The validity and effectiveness of the de‐embedding method are proven with a fixed‐length MEM transmission line along with various feed‐line topologies. The measured inductances of the 20‐μm elevated transmission line provide consistent data, as compared to the simpler open de‐embedding method. For more realistic and complicated MEM inductors with 1.5 and 2.5 turns, the characterized inductance values agree very well with the calculated data, based on the Greenhouse algorithm. The measured and calculated inductances are within the 5% range. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 43: 355–358, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20468
Brachial plexopathies: Classification, causes, and consequences
Authors: Ferrante Mark A. 
Published: September 2004

AbstractThe brachial plexus, which is the most complex structure of the peripheral nervous system, supplies most of the upper extremity and shoulder. The high incidence of brachial plexopathies reflects its vulnerability to trauma and the tendency of disorders involving adjacent structures to affect it secondarily. The combination of anatomic, pathophysiologic, and neuromuscular knowledge with detailed clinical and ancillary study evaluations provides diagnostic and prognostic information that is important to clinical management. Since most brachial plexus disorders do not involve the entire brachial plexus but, rather, show a regional predilection, a regional approach to assessment of plexopathies is necessary. Muscle Nerve, 2004
Single motor unit variability with threshold stimulation in patients with amyotrophic lateral sclerosis and normal subjects
Authors: Jillapalli Devanand , Shefner Jeremy M. 
Published: September 2004

AbstractRepetitive nerve stimulation often shows responses with an abnormal decrement in patients with amyotrophic lateral sclerosis (ALS), suggesting instability of the neuromuscular junction; however, the pathophysiology and response characteristics of this instability are not clear. We evaluated response variability of 47 single motor units from 16 patients with ALS and 51 units from 10 normal subjects, acquired by delivering threshold stimuli sporadically at 0.5 HZ or less. In addition, in 46 other different single motor units obtained from 21 patients with ALS, variability was studied at both 1‐ and 3‐HZ stimulation rates. Motor units from patients with ALS were significantly more variable than those from normal subjects, even when their larger amplitude was accounted for. This increased variability was not rate dependent. Response variability is a critical measure in the statistical method of motor unit number estimation and is attributed to variability in the number of units activated; the fact that variability of single motor units varies with disease state may be a potentially confounding factor in the application of the technique. Muscle Nerve, 2004
SPICE for SPACE trials, risk analysis, and process improvement
Authors: Cass Ann , Völcker Christian , Ouared Rafik , Dorling Alec , Winzer Lothar , Carranza Juan María 
Published: September 2004

AbstractAs part of a programme for software process improvement sponsored by the European Space Agency (ESA), an ISO 15504 (1998) conformant method for software process assessment has been developed. [Work supported under ESTEC Contract Number 10 662/93/NL/NB CCN5.] Called SPICE for SPACE, or S4S (Völcker and Cass 2002, Cass et al. 2000), the method includes an assessment model based on the ISO/IEC TR 15504 exemplar model with space software practices incorporated.To promote SPICE for SPACE, ESA has sponsored a series of trial assessments using the S4S method. Since February 2000, eight space software suppliers have been assessed in Austria, Belgium, Denmark, Germany, Great Britain, Italy, and Sweden.The first part of this paper describes the trial assessment programme to date, summarising the assessments that have taken place, the assessment results, the improvement efforts initiated in the host organisations, and the feedback gathered to improve the S4S method.The second part of this paper presents a new approach for software process improvement based on a risk analysis of assessment results. Developed within the same initiative, this method sets the basis for integrating process‐oriented risk analysis into the S4S method, where, along with the process and capability dimensions, risk can be considered as a new third dimension. The outcomes of the risk analysis lead to the selection and prioritisation of pre‐defined generic improvement actions. Alternatively, the risk analysis presented here can be applied in the context of supplier evaluation or risk estimation for investors in software organisations. Copyright © 2004 John Wiley & Sons, Ltd.
Role of locus coeruleus α1‐adrenoceptors in motor activity in rats
Authors: Stone Eric A. , Lin Yan , Ahsan Rashedul , Quartermain David 
Published: September 2004

AbstractThe question of whether or not the locus coeruleus (LC) participates in the control of motor activity has been controversial due to difficulties in demonstrating permanent motor deficits after neurotoxic lesions of this nucleus or of the dorsal noradrenergic bundle (DNB). In the present experiments it was shown in rats that acute local blockade (with terazosin) or stimulation (with phenylephrine) of LC α1‐adrenoceptors respectively blocked or stimulated exploratory behavior in a novel cage and the home cage. Moreover, previous lesion of the DNB by i.p. DSP4 abolished the behavioral changes to local LC α1‐receptor manipulation but did not affect motor activity in the novel or home cage by itself. These findings are consistent with the hypothesis that the intact LC does contribute to motor activity control, exerted in part by its α1‐receptors; however, the permanent loss of this nucleus is compensated for by remaining CNS motor structures. Synapse 54:164–172, 2004. © 2004 Wiley‐Liss, Inc.