bluuebunny/crossref_metadata_2025_split huggingface dataset:
Scaling of Yield Stress of Polythiophene Suspensions under Electric Field
Authors: Chotpattananont Datchanee , Sirivat Anuvat , Jamieson Alexander M. 
Published: May 2004

AbstractSummary: Electrorheological properties in steady shear of perchloric acid doped poly(3‐thiopheneacetic acid), PTAA, particles in silicone oil were investigated to determine the effects of field strength, particle concentration, doping degree (conductivity values), operating temperature and nonionic surfactant. The PTAA/silicone oil suspensions show the typical ER response of Bingham flow behavior upon the application of electric field. The yield stress increases with electric field strength, E, and particle volume fraction, ϕ, according to a scaling law of the form, τy ∝ Eα · ϕγ. The scaling exponent α approaches the value of 2, predicted by the polarization model, as the particle volume fraction decreases and when the doping level of the particles decreases. The scaling exponent γ tends to unity, as predicted by the polarization model, when the electric field strength is low. The yield stress under electric field initially increases with temperature up to 25 °C, and then levels off. At electric fields above of 1.5 kV/mm, the yield stress increases significantly by up to 50% on addition of small amounts of a nonionic surfactant.Effect of switching the applied electric field on the viscosity of a 20 wt.‐% highly HClO4 doped polythiophene suspensions during stress sweep test.imageEffect of switching the applied electric field on the viscosity of a 20 wt.‐% highly HClO4 doped polythiophene suspensions during stress sweep test.
Empirical Modeling of Butyl Acrylate/Vinyl Acetate/Acrylic Acid Emulsion‐Based Pressure‐Sensitive Adhesives
Authors: Jovanovic Renata , McKenna Timothy F. , Dubé Marc A. 
Published: May 2004

AbstractSummary: Butyl acrylate/vinyl acetate/acrylic acid (BA/VAc/AA) emulsion latexes were produced in a semi‐batch mode. The objective was to generate polymers with properties favoring their application as pressure‐sensitive adhesives. The influence of the individual monomer concentrations on final properties such as glass transition temperature (Tg), peel strength, shear strength and tack was investigated. To obtain the maximum amount of information in a reasonable number of runs, a constrained three‐component mixture design was used to define the experimental conditions. Latexes were coated onto a polyethylene terephthalate carrier and dried. Different empirical models (e.g. linear, quadratic and cubic mixture models) governing the individual properties (i.e. Tg, peel adhesion, shear resistance and tack) were developed and evaluated. In the given experimental region, no single model was found to fit all of the responses (i.e. the final properties). However, in all models the most significant factor affecting the final properties was the AA concentration, followed by the VAc concentration.Shear strength contour lines over the investigated region.imageShear strength contour lines over the investigated region.
Location of the Catalytic Site in Supported Atom Transfer Radical Polymerization
Authors: Faucher Santiago , Zhu Shiping 
Published: May 2004

AbstractSummary: A supported and highly recyclable catalyst complex, CuBr/HMTETA physically adsorbed to silica gel, was used for the ATRP of MMA to elucidate the nature of the catalytic site. In some polymerizations, the reaction solutions were filtered and compared with their unfiltered references for catalytic activity. The filtered systems had high catalyst activity indicating the presence of active catalyst sites in solution. These sites are the primary catalytic contributors.Conversion versus time and first‐order kinetic plot for the control and filtered polymerizations.magnified imageConversion versus time and first‐order kinetic plot for the control and filtered polymerizations.
Free‐Radical Termination Kinetics Studied Using a Novel SP‐PLP‐ESR Technique
Authors: Buback Michael , Egorov Mark , Junkers Tanja , Panchenko Elena 
Published: May 2004

AbstractSummary: A novel method for measuring termination rate coefficients, kt, in free‐radical polymerization is presented. A single laser pulse is used to instantaneously produce photoinitiator‐derived radicals. During subsequent polymerization, radical concentration is monitored by time‐resolved electron spin resonance (ESR) spectroscopy. The size of the free radicals, which exhibits a narrow distribution increases linearly with time t, which allows the chain‐length dependence of kt to be deduced. The method will be illustrated using dodecyl methacrylate polymerization as an example.Two straight lines provide a very satisfactory representation of the chain‐length dependence of kt over the entire chain‐length region (cR = radical concentration).magnified imageTwo straight lines provide a very satisfactory representation of the chain‐length dependence of kt over the entire chain‐length region (cR = radical concentration).
Temperature‐sensitive poly(vinyl methyl ether) hydrogel beads
Authors: Theiss Daniel , Schmidt Thomas , Arndt Karl‐Friedrich 
Published: May 2004

AbstractTemperature‐sensitive hydrogel beads were prepared by radiation crosslinking of poly(vinyl methyl ether) PVME spheres wrapped in Ca‐alginate. The obtained gel beads have diameters in the sub‐millimeter or millimeter range (depending on the PVME concentration). They were characterized by sol‐gel analysis, swelling measurements, and differential scanning calorimetry.The gel content g increases with increasing radiation dose D. The swelling degree Qv decreases with increasing PVME concentration cp and increasing D. In comparison to PVME bulkgels the phase‐transition temperature of the synthesized PVME gel beads is a little decreased.
Separation of polyelectrolyte chain dynamics and dynamics of counterion attachment by EPR spectroscopy
Authors: Hinderberger Dariush , Spiess Hans Wolfgang , Jeschke Gunnar 
Published: May 2004

AbstractRotational dynamics and local enrichment of counterions close to polyelectrolyte chains were studied by EPR spectroscopy in solvents of different viscosity. The results confirm previous findings (D. Hinderberger, G. Jeschke, and H. W. Spiess, Macromolecules 2002, 35, 9698) that electrostatic attachment of counterions to the chains is dynamic with lifetimes of contact ion pairs shorter than 1 ns. While in low‐viscosity solvents linewidths for a dianionic nitroxide probe and their dependence on polyelectrolyte concentration are dominated by the gradient of local concentration in the vicinity of the chain, they are more strongly influenced by changes in rotational dynamics in a glycerol/water mixture. The slowdown of dynamics at higher viscosity strongly depends on polyelectrolyte concentration, suggesting that the lifetime of the attached state increases. The linewidths of trianionic triarylmethyl probes and of the center line of the nitroxide probes are dominated by local counterion enrichment both at low and high viscosity. Comparison of these linewidths and of the extent to which the lineshapes are non‐Lorentzian indicates build‐up of larger concentration gradients at higher viscosity.
The stability of polyelectrolyte complex systems of poly(diallydimethyl‐ammonium chloride) with different polyanions
Authors: Mende Mandy , Buchhammer Heide‐Marie , Schwarz Simona , Petzold Gudrun , Jaeger Werner 
Published: May 2004

AbstractPolyelectrolyte complex (PEC) dispersions formed by fast ionic exchange reaction between polyelectrolytes (PELs) bearing oppositely charged groups have been characterized by turbidity and dynamic light scattering. The stability of the formed PEC dispersions, the average hydrodynamic particle size dh and the also determined polydispersity index PI of the PEC particles were of special interest. In this study poly(diallyldimethylammonium chloride) (PD) of different molar mass is used in combination with copolymers of maleic acid and α‐methylstyrene (P(MS‐αMeSty)) as well as propene (P(MS‐P)), with a copolymer of acrylamide and sodium acrylate (PR2540UD) and poly(styrene‐p‐sodium sulfonate) (NaPSS).A strong dependence of the PEC stability on the molar charge ratio n−/n+, the mixing conditions and especially on the chemical structures of the used polyanions was found. If the employed polyanion (PA) have a π‐system (phenyl‐) in the polymer chain a higher tendency to instability results. The average hydrodynamic particle sizes dh and the polydispersity indices PIs of the formed stable PEC dispersions determined by dynamic light scattering were strongly influenced by the mixing conditions of the PECs. If we are able to prepare stable complexes where the isoelectric point is exceeded during complex formation which is possible for PD/P(MS‐P) and PD/PR2540UD systems a distinct increase of dh and decrease of PI is observed. The polymer concentration CP and the chain length L of the used PELs have a minor effect on dh and PI.
Aggregation phenomena in polyelectrolyte multilayers made from polyelectrolytes bearing bulky functional, hydrophobic fragments
Authors: Laschewsky André , Mallwitz Frank , Baussard Jean‐François , Cochin Didier , Fischer Peter , Habib Jiwan Jean‐Louis , Wischerhoff Erik 
Published: May 2004

AbstractThe functionalization of polyelectrolyte multilayers often implies the use of bulky functional fragments, attached to a standard polyelectrolyte matrix. Despite of the high density of non‐charged, often hydrophobic substituents, regular film growth by sequential adsorption proceeds easily when an appropriate polyelectrolyte counter ion is chosen. However, the functional fragments may cluster or aggregate. This complication is particularly evident when using chromophores and fluorophores as bulky pendant groups. Attention has to be paid to this phenomenon for the design of functional polyelectrolyte films, as aggregation may modify crucially the properties. The use of charged spacer groups does not necessarily suppress the aggregation of functional side groups. Still, clustering and aggregation depend on the detailed system employed, and are not obligatory. In the case of cationic poly(acrylamide)s labeled with naphthalene and pyrene fluorophores, for instance, the polymers form intramolecular hydrophobic associates in solution, as indicated by strong excimer formation. But the polymers can undergo a conformational rearrangement upon adsorption so that they are decoiled in the adsorbed films. Analogous observations are made for polyanions bearing mesogenic biphenyls fragments. In contrast, polycations functionalized with the dye coumarin 343 show little aggregation in solution, but a marked aggregation in the ESA films.
Sporadic case of dentatorubral pallidoluysian atrophy with no CAG repeat expansion and no intranuclear inclusions
Authors: Munhoz Renato P. , Bergeron Catherine , Lang Anthony E. 
Published: May 2004

AbstractWe present a patient with a 14‐year course beginning at the age of 44 years with hemidystonia followed by generalized choreoathetosis, behavioral, and oculomotor disturbances. Family history and genetic testing were unrevealing. Neuropathological findings were identical to genetic dentatorubral pallidoluysian (DRPLA) except for the lack of intranuclear inclusions. © 2003 Movement Disorder Society
Neuronal globus pallidus activity in patients with generalised dystonia
Authors: Merello Marcelo , Cerquetti Daniel , Cammarota Angel , Tenca Eduardo , Artes Carlos , Antico Julio , Leiguarda Ramon 
Published: May 2004

AbstractWe studied 516 globus pallidus neurons in dystonic patients. The firing rate was analysed. We classified the burst activity into tonic, burst, and pause patterns. Mean ± SD firing rates and tonicity score for internal globus pallidus (GPi) and external globus pallidus (GPe) were 54.6 ± 28.6; 58.01 ± 39.1 and 1.18 ± 0.55; 0.95 ± 0.43, respectively. Differences in percentage appearance of tonic, burst, or paused neurons were not statistically significant for GPi versus GPe. GPi firing features in dystonic patients were closely similar to those of GPe. This could suggest that the abnormally patterned output from GPi would not result from increased differential inhibitory/excitatory input arising from the direct/indirect pathway but rather be transmitted from GPe, striatum, or either centromedian nucleus. © 2003 Movement Disorder Society
Dystonia as a presenting sign of spinocerebellar ataxia type 1
Authors: Wu Yih‐Ru , Lee‐Chen Guey‐Jen , Lang Anthony E. , Chen Chiung‐Mei , Lin Hsuan‐Yuan , Chen Sien‐Tsong 
Published: May 2004

AbstractWe report on a 39‐year‐old man who presented initially with marked blepharospasm, oromandibular dystonia and retrocollis and one year later developed mild ataxia. Our findings suggest that dystonia can be a disabling presenting sign of SCA1 and support the clinical heterogeneity of SCA1, highlighting the importance of considering this entity in patients combining dystonia and cerebellar ataxia. © 2004 Movement Disorder Society
SCA2 presenting as levodopa‐responsive parkinsonism in a young patient from the United Kingdom: A case report
Authors: Wilkins Alastair , Brown Jerry M. , Barker Roger A. 
Published: May 2004

AbstractWe report on a young woman from the United Kingdom with L‐dopa–responsive parkinsonism with a trinucleotide repeat expansion in her spinocerebellar ataxia 2 (SCA2) gene. The case further extends the phenotype of SCA2 and emphasizes the importance of SCA screening in young‐onset parkinsonism, irrespective of ethnic origin. © 2004 Movement Disorder Society
Multifrequency microwave tomography between boreholes
Authors: Tarnus R. , Dérobert X. , Pichot Ch. 
Published: May 2004

AbstractIn order to detect 2D underground heterogeneity between boreholes, a microwave‐imaging technique is presented along with numerical and experimental comparisons. The proposed technique is based on a spectral diffraction tomography technique which enables heterogeneities from the polarized currents induced by the incident field of a simple dipole antenna to be located. Numerical results in both a transverse‐magnetic (TM) and transverse‐electric (TE) modes are compared with a reduced‐scale physical model composed of a water tank with some immersed cylindrical heterogeneities. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 42: 4–8, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20190
Distortion of a square pulse wave with finite rise time in edge‐coupled microstrip lines on LTCC substrate
Authors: Kang Kai , Li Le‐Wei , Yin Wen‐Yan 
Published: May 2004

AbstractThe distortion of a square pulse wave with a finite rise time in edge‐coupled microstrip lines is investigated. These microstrip lines are assumed to be fabricated on a single‐layer low‐temperature co‐fired ceramic (LTCC) substrate which has excellent high‐frequency performance. Parametric studies are performed to show the effects of different physical parameters of the strips and LTCC substrate on the distortion of the propagated pulse waveform, where the effects of the substrate as well as ohmic losses on the pulse‐wave propagation are treated appropriately. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 42: 8–13, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20191
Periodic bandpass filter with near‐ideal filter response based on Sagnac loop interferometer
Authors: Wei Li , Mao Qinghe , Lit John W. Y. 
Published: May 2004

AbstractIn this paper, an analytical analysis is made on a periodic bandpass filter formed by a two‐cavity etalon incorporated into a Sagnac loop interferometer. The general optimum conditions for a quasi‐flat‐top spectrum and a ripple‐free group‐delay response are derived. Our results show that by properly choosing the reflectance of the mirrors, the filter can be designed with a quasi‐flat‐top spectral response that is also free from group‐delay ripples. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 42: 17–21, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20194
A novel design technique for control of defect frequencies of an electromagnetic bandgap (EBG) superstrate for dual‐band directivity enhancement
Authors: Lee Young Ju , Yeo Junho , Ko Kyoung Dae , Mittra Raj , Lee Yoonjae , Park Wee Sang 
Published: May 2004

AbstractIn this paper, we propose a novel design technique to control the defect frequencies of an electromagnetic bandgap (EBG) superstrate with the objective of enhancing the directivity of a patch antenna at two frequencies. Two different defect configurations, the first of which is introduced by the ground plane of the antenna while the other is produced by a row of rods with dissimilar dielectric constants in the EBG structure, are examined in detail in order to achieve dual‐band operation. We begin by investigating the EBG structure and varying several of its parameters to determine the locations of the bandgap and defect frequencies, as well as their controllability. Finally, the promising designs for the EBG superstrates, which provide enhanced directivities for the EBG antenna, are evaluated to validate the proposed design scheme. It is demonstrated that the directivity of the antenna with a 12 × 3 EBG superstrate increases to 18 and 18.5 dBi, respectively, at the two design frequency bands, as compared to that of the antenna alone (maximum 10 dBi) without the superstrate. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 42: 25–31, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20196
Characteristics analysis of a multiband wide‐aperture‐coupled microstrip antenna
Authors: Jang Yong‐Woong , Shin H. S. , Lee C. A. 
Published: May 2004

AbstractIn this paper, we study a rectangular microstripline‐fed wide aperture‐coupled microstrip antenna backed by a ground plane. In this case, a rectangular microstrip feed line and a wide slot lead to good impedance matching in a wide‐frequency band. The 2.0 VSWR impedance bandwidth of the lower mode is 0.29 GHz (0.83–1.12 GHz, 32.2% at the center frequency of 0.9 GHz) and covers the cellular and GSM bands; the band of the upper mode reaches 0.93 GHz (1.69–2.62 GHz, 46.5% at the center frequency of 2.0 GHz) and covers the PCS, IMT‐2000, WLL, and UMTS bands, in respectively. The results obtained for VSWR exhibit multiband characteristic. The peak antenna gain is 7.6 and 10.5 dBi for the lower (Cellular, GSM) and upper (DCS, PCS, IMT‐2000, WLL) operations, respectively. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 42: 37–40, 2004; Published online Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20199
MicroPhotonic reconfigurable RF signal processor
Authors: Alameh Kamal E. , Zheng Rong , Ahderom Selam , Raisi Mehrdad , Eshraghian Kamran 
Published: May 2004

AbstractIn this paper, we present a novel MicroPhotonic RF signal processor that integrates fibre collimators, opto‐VLSI processors, and a WDM combiner within an optical substrate to control various fibre Bragg grating cavities, thus achieving adaptive RF filtering. Results show that a reconfigurable 64‐cavity MicroPhotonic RF processor can generate arbitrary RF responses. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 42: 54–58, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20205
A parallel analysis of the scattering from inhomogeneous dielectric bodies by the volume integral equation and the precorrected‐FFT algorithm
Authors: Wang Yao‐Jun , Nie Xiao‐Chun , Li Le‐Wei , Li Er‐Ping 
Published: May 2004

AbstractIn this paper, a parallel implementation of the precorrected fast Fourier transform (FFT) algorithm is presented to efficiently solve the volume‐integral equation for scattering from inhomogeneous dielectric objects. Several examples are given to demonstrate the efficiency and correctness of the message‐passing interface (MPI)‐based parallelization algorithm. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 42: 77–79, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20214
Stepped‐impedance resonator bandpass diplexers with over‐coupling structures
Authors: Weng Min‐Hung , Pan Chi‐Shiang , Shao Chih‐Wei , Wu Hung‐Wei 
Published: May 2004

AbstractA stepped‐impedance resonator (SIR) bandpass diplexer using over‐coupling structures and tapped input/output (I/O) has been presented. The advantages of this construction are simple design and suppression of spurious response at twice the center frequency (2f0). The tapped I/O creates an extra transmission zero in each filter of the duplexer in order to improve stopband attenuation. The diplexer, designed at 0.9 and 1.8 GHz, is suitable for mobile communication and is easily fabricated in the packing surface. Experimental results of the designed duplexer are in good agreement with the theoretical predictions and simulated results. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 42: 79–82, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20215
A mitochondrial DNA mutation in a patient with an extensive family history of Duchenne muscular dystrophy
Authors: Wong Lee‐Jun C. , Wladyka Christopher , Mardach‐Verdon Rebecca 
Published: May 2004

AbstractOne challenge in the molecular diagnosis of mitochondrial DNA (mtDNA) disorders is detection of a low percentage of mutant heteroplasmy. We report a patient who had a delayed molecular diagnosis of mitochondrial encephalopathy, lactic acidosis, and stroke‐like episodes (MELAS) syndrome due to the complication of an extensive family history of another neuromuscular disease, Duchenne muscular dystrophy, and the failure to detect a low proportion of mutant A3243G mtDNA with a polymerase chain reaction (PCR)/restriction fragment length polymorphism (RFLP)/ethidium bromide detection method. Using an improved, more sensitive allele‐specific oligonucleotide (ASO) radioactive dot‐blot hybridization method, a low degree of A3243G heteroplasmy was detected in several tissues from this patient. This case underscores the importance of a sensitive mutation detection method and the need for a search for mtDNA mutations if the patient's clinical symptoms suggest a mitochondrial disorder despite the family background of another neuromuscular disease. Muscle Nerve 30: 118–122, 2004
Treadmill training–induced adaptations in muscle phenotype in persons with incomplete spinal cord injury
Authors: Stewart Brian G. , Tarnopolsky Mark A. , Hicks Audrey L. , McCartney Neil , Mahoney Douglas J. , Staron Robert S. , Phillips Stuart M. 
Published: May 2004

AbstractBody weight–supported treadmill (BWST) training has been shown to improve ambulatory capacity in persons with a spinal cord injury (SCI); however, the effect that BWST training has on skeletal muscle phenotype is unknown. We aimed to determine whether 6 months (three sessions/week) of BWST training in neurologically stable persons with a traumatic spinal cord injury (ASIA C) alters skeletal muscle phenotype, ambulatory capacity, and blood lipid profile. Externally supported body weight decreased, and walking velocity and duration of the training sessions increased (all P < 0.05) as a result of training. Muscle biopsies revealed increases in the mean muscle‐fiber area of type I and IIa fibers. Training induced a reduction in type IIax/IIx fibers, as well as a decrease in IIX myosin heavy chain, and an increase in type IIa fibers. Maximal citrate synthase and 3‐hydroxy‐acyl‐CoA dehydrogenase activity also increased following training. BWST training brought about reductions in plasma total (−11%) and low‐density lipoprotein (−13%) cholesterol. We conclude that, in patients with a spinal cord injury, BWST training is able to induce an increase in muscle fiber size and bring about increases in muscle oxidative capacity. In addition, BWST training can bring about improvements in ambulatory capacity and antiatherogenic changes in blood lipid profile. Muscle Nerve 30: 61–68, 2004