bluuebunny/crossref_metadata_2025_split huggingface dataset:
π‐complexes of polystyrene with silver salts and their use as facilitated olefin transport membranes
Authors: Kim Jong Hak , Won Jongok , Kang Yong Soo 
Published: May 2004

Abstractπ‐Complexes of silver salts with polystyrene (PS) were prepared and tested in the separation of propylene/propane mixtures. After the incorporation of silver ions into the PS matrix, both the pure propylene gas permeance of the membrane and its olefin selectivity with respect to the propylene/propane mixtures were remarkably higher than those of the pure PS membrane, demonstrating facilitated propylene transport through the solid‐state membrane. The remarkable separation performance of the PS/silver salt membranes was attributable to the unusually high solubility of the silver salts in the PS matrix, which was possibly due to the formation of π‐complexes between the silver ion and aromatic CC bond of PS. The coordination properties and dissolution behavior of the silver salts in PS were investigated with Fourier transform infrared, Fourier transform Raman, and X‐ray photoelectron spectroscopy. The values for the intersegmental d‐spacing, determined by wide‐angle X‐ray scattering, also showed that significant transient crosslinks arose between the PS chains when the silver salts were added to the PS matrix. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 2263–2269, 2004
Numerical simulation of the tensile modulus of nanoclay‐filled polymer composites
Authors: Zhu Linjie , Narh K.A. 
Published: May 2004

AbstractA numerical simulation model that incorporates three phases, polymer matrix, interlayer, and clay platelet, was developed to predict the tensile modulus of nanoclay‐filled polymer composites. The interlayer was introduced to account for the fact that the mechanical properties of the polymer near the clay surface are different from those of the polymer matrix. The effects of the properties of interlayers, the structure of clay clusters, and platelet distributions upon the modulus of elasticity of the nanocomposites, were studied. The simulation results show that a decrease in the interlayer modulus, as well as an increase in the interlayer thickness, would decrease the modulus of the nanocomposites. Furthermore, it was found that the maximum strain, located in the interlayer near the end of the clay platelet, increases significantly with decreasing interlayer modulus. The effects of the distribution of clay platelets upon composite modulus were interpreted in terms of two parameters, platelet overlap length, and the lateral distance between platelets. Comparison of simulation results with experimental data from the literature has confirmed the reliability of the numerical simulation method used in the present study. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 2391–2406, 2004
A stereochemical microstructure‐based attempt to explain the dielectric behavior of poly(vinyl chloride) (PVC)
Authors: Guarrotxena N. , Del Val J.J. , Elicegui A. , Millan J. 
Published: May 2004

AbstractA poly(vinylchloride) (PVC) obtained by bulk polymerization at 70 °C was modified through substitution reaction with sodium benzenethiolate (NaBT) in cyclohexanone solution at 25 °C, at various conversions up to 15 mol %. According to earlier work, this allows to change, in a controlled way, the stereochemical microstructure in terms of mainly the content of mmr (meso, meso, racemic) tetrad termini of isotactic sequences of at least one heptad in length, and of its likely chain conformations. The samples were all studied by Dielectric Relaxation Spectroscopy, which allows to measure the real and the imaginary parts of the complex dielectrical constant in a frequency range between 1 and 106 Hz, and a temperature range between 100 and 600 K. Most of the changes in the physical quantities that can be analyzed by this technique were found to parallel the changes in stereochemical microstructure with substitution extent. The temperature of the maximum of the dipolar losses, which relates to the temperature range where α relaxation occurs, appeared to increase somewhat up to 0.7% molar conversion. Then the tendency is towards stabilization. The relaxation time τ(T) as deduced from the Havriliak‐Negami (NH) function, tends to decrease between 0 and 0.7 substitution percent, and to increase afterwards. The evolution of the Ngai's β parameter with substitution degree is also highly illustrative. It clearly decreases up to 0.7% and then it increases rapidly up to 7% and slowly afterwards. These changes are discussed by taking into account that 0.7 and 7% substitution extents agree with the removal of mmr under GTTG−TT conformation and of the same structure under GTGTTT conformation, respectively. From the results, some original correlations between stereochemical microstructure and molecular dynamic behaviors are proposed. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 2337–2347, 2004
Effects of physical aging on solubility, diffusivity, and permeability of propane and n‐butane in poly(4‐methyl‐2‐pentyne)
Authors: Nagai Kazukiyo , Sugawara Akihito , Kazama Shingo , Freeman Benny D. 
Published: May 2004

AbstractThe effects of physical aging on the solubility, diffusivity, and permeability of propane and n‐butane in a hydrocarbon‐based disubstituted polyacetylene, poly(4‐methyl‐2‐pentyne) (PMP), were studied. As the relative pressure of propane and n‐butane increased, the solubility of both hydrocarbons increased. Like other glassy polymers, the sorption isotherms for propane and n‐butane in all PMP films were concave to the relative pressure axis, indicating dual‐mode sorption behavior. The diffusion of propane and n‐butane in PMP followed typical Fickian diffusion in a plane sheet. The propane diffusivity in both the unaged and aged films increased with increasing concentration of propane sorbed in the film. The n‐butane diffusivity in aged films also increased with increasing n‐butane concentration. However, unaged films showed the opposite behavior: the diffusivity decreased with increasing n‐butane concentration. These diffusion phenomena are a consequence of the interplay between thermodynamic and mobility factors. The permeabilities of propane and n‐butane decreased monotonically with increasing penetrant concentration, similar to the behavior observed in other common glassy polymers. The relaxation of the nonequilibrium excess free volume in PMP films induced the decrease in both solubility and diffusivity. As a result, the permeability of propane and n‐butane in PMP decreased upon physical aging. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 2407–2418, 2004
Transport and magnetic properties of delafossite CuAl1−xMnxO2 ceramics
Authors: Kim Hyoun Soo , Lee Byoung Seon , Ji Sung Hwa , Kim Hyojin , Kim Dojin , Ihm Young Eon , Choo Woong Kil 
Published: May 2004

AbstractWe report on the transport and magnetic properties of Mn‐doped CuAlO2 ceramics (CuAl1−xMnxO2, 0 ≤ x ≤ 0.05) fabricated by standard solid solution method in an air atmosphere at a sintering temperature of 1150 °C. The equilibrium solubility of Mn ions in CuAlO2 was found to be as low as 3 mol%. Non‐doped CuAlO2 ceramics were semiconducting with a hole concentration of ∼5.8 × 1016 cm−3 and an increase of Mn ion rapidly reduced the hole concentration. The magnetization measurements for all CuAl1−xMnxO2 samples showed paramagnetic behaviors and a negative value of the Curie–Weiss temperature corresponding to antiferromagnetic exchange coupling between Mn ions in delafossite CuAlO2 lattice. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Magnetic properties of γ‐Fe2O3 nanoparticles made by coprecipitation method
Authors: Jeong Jong‐Ryul , Lee Seung‐Jun , Kim Jong‐Duk , Shin Sung‐Chul 
Published: May 2004

AbstractWe have synthesized maghemite (γ‐Fe2O3) nanoparticles using chemical coprecipitation technique through a typical pipette drop method (pipette diameter: 2000 μm) and a piezoelectric nozzle method (nozzle size: 50 μm). The size distribution of the maghemite nanoparticles prepared by the pipette drop method is from 5 nm to 8 nm. However, the nanoparticles made by the piezoelectric nozzle method show smaller size and very narrow size distribution from 3 nm to 5 nm. Zero‐Field‐Cooled (ZFC)/Field‐Cooled (FC) magnetization and magnetic hysteresis measurement were performed using a superconducting quantum interference device (SQUID) magnetometer from 5 K to 300 K to investigate the magnetic properties of nanoparticles. The SQUID measurements revealed superparamagnetism of nanoparticles with the blocking temperature of 119.5 K and 94.3 K for the nanoparticles made by the pipette drop method and the piezoelectric nozzle method, respectively. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Spin transport in an FM/Bi/FM junction
Authors: Lee K. I. , Jeun M. H. , Chang J. Y. , Han S. H. , Ha J. G. , Lee W. Y. 
Published: May 2004

AbstractThe spin transport in a spin‐valve device incorporating Bi thin film and two ferromagnetic (FM) contacts is presented. The non‐local output voltage is found to depend upon the relative magnetization state of the two FM electrodes, indicating that the spin‐polarized electrons are injected from the first FM (injector) into Bi and are detected by the second FM (detector) due to spin accumulation. The observed Hanle effect supports the spin injection and detection in our device. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Electronic structure and magnetism of CrAu3 nano films: density functional study
Authors: Kwon Youngsoo , Cho Sunglae , Hong Soon C. 
Published: May 2004

AbstractMagnetism of some CrAu3 nano films [free standing CrAu(001) monolayer, 1(CrAu)/1Au/1(CrAu)(001), 1(CrAu)/3Au/1(CrAu)(001), 1Au/1(CrAu)/1Au, and 1(CrAu)/1Au/1(CrAu)/1Au/1(CrAu)] were investigated using the FLAPW method with the PBE‐version of GGA for exchange‐correlation potential. The nano films were calculated to be stable in an in‐plane antiferromagnetic state. 1(CrAu)/1Au/1(CrAu)/ 1Au/1(CrAu) was calculated to be stable in L12 G‐type antiferromagnetic structure. The calculated magnetic moments of Cr are about 3.9 μB and 3.7 μB at the surface and in the center layer, respectively. For comparison, calculations on bulk CrAu3 have been done for plausible magnetic structures (PM, FM, and some AFM states) for L12 and D022 crystal structures. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
DFT‐EPR study of radiation‐induced radicals in α‐D‐glucose
Authors: Pauwels Ewald , Van Speybroeck Veronique , Vanhaelewyn Gauthier , Callens Freddy , Waroquier Michel 
Published: May 2004

AbstractThe structures of two radiation‐induced radicals in solid‐state α‐D‐glucose have been identified by means of single‐molecule density function theory (DFT) calculations. Using the original crystalline structure as input, several radical models were created and their geometries optimized. Subsequently, electron paramagnetic resonance (EPR) parameters were calculated. During these calculations, the global orientation of the radical structure was kept fixed with respect to the crystal axes reference frame. This was essential to allow for an easy analysis of the hyperfine tensor principal directions, besides the isotropic and anisotropic coupling constants. By comparing these calculated EPR parameters with their experimentally determined counterparts, a plausible identification of two carbon‐centered glucose radicals was possible. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2004
DFT studies on key intermediates in thiamin catalysis
Authors: Friedemann Rudolf , Tittmann Kai , Golbik Ralph , Hübner Gerhard 
Published: May 2004

AbstractThe diphosphate ester (ThDP) of thiamin (vitamin B1) is an important cofactor of enzymes within the carbohydrate metabolism. From experiments of site‐specific variants and nuclear magnetic resonance (NMR) studies, it is known that the protonation of the N1′ atom is a significant step in the coenzyme activation by the enzymatic environment. Therefore, we have performed density functional theory (DFT) calculations on the B3LYP/6‐31G* level of N1′H and N1′CH3 thiamin as model systems to study the protonation and methylation effect on the structure and the electronic properties of the 4′‐amino group. The relaxed rotational barriers related to the C4′‐4′N bond are correlated with findings of 1H NMR studies and proton/deuterium exchange experiments. Moreover, the effect of N1′ protonation was studied in more detail on the hydroxyethyl‐thiamin carbanion (HETh−), a key intermediate during catalysis of some ThDP‐dependent enzymes. The relaxed rotational barriers related to the C2C2α bond and the reaction coordinates of the proton transfer 4′NH→C2α of HETh− and N1′H‐HETh− show that they are significantly determined by the protonation at N1′ of HETh−. The influence of the apoenzyme environment on the active coenzyme conformation is modeled in a very simple way. The characteristic torsion angles ΦT and ΦP are considered to be restricted in terms of their values in the corresponding enzyme as well as free optimization parameters. Frequency calculations were performed to characterize the minima and transition state structures, respectively. The applicability of the DFT method was checked by comparing calculations on the MP2‐HF‐SCF/6‐31G* level. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2004
Random covering of an interval and a variation of Kingman's coalescent
Authors: Bertoin Jean 
Published: May 2004

AbstractWe consider the covering of [0, 1] by a large number of small random intervals. We show that a simple variation of Kingman's coalescent describes the emergence of macroscopic connected components. © 2004 Wiley Periodicals, Inc. Random Struct. Alg. 2004
Simply generated trees, B‐series and Wigner processes
Authors: Mazza Christian 
Published: May 2004

AbstractWe consider simply generated trees, like rooted plane trees, and consider the problem of computing generating functions of so‐called bare functionals, like the tree factorial, using B‐series from Butcher's theory. We exhibit a special class of functionals from probability theory: the associated generating functions can be seen as limiting traces of product of semi‐circular elements. © 2004 Wiley Periodicals, Inc. Random Struct. Alg. 2004
Reconciling sustainability and growth: criteria, indicators, policies
Authors: Spangenberg Joachim H. 
Published: May 2004

AbstractSustainable development is based on the integration of four dimensions: the economic, the environmental, the social and the institutional. For the economic dimension in particular, growth has been considered an essential element of sustainable development.This paper discusses the relationship of social, environmental and institutional sustainability objectives to economic growth and derives social and environmental criteria for growth to be sustainable.One of the most sophisticated sustainability studies developed for Germany is introduced, demonstrating the need and the possibility to reconcile economic, social, environmental and institutional objectives. Integrated politics taking into account all four dimensions when drafting policy plans are a necessary precondition for this behalf.Based on two sustainability scenarios with a different emphasis (growth, integration) five core action zones for policy making are identified.The criteria derived can be used as yardsticks assessing policy proposals at an early stage regarding their impact on key sustainability objectives. Copyright © 2004 John Wiley & Sons, Ltd and ERP Environment.
Unifying proof methodologies of duration calculus and timed linear temporal logic
Authors: Liu Zhiming , Ravn Anders P. , Li Xiaoshan 
Published: May 2004

Abstract.
Linear temporal logic (LTL) has been widely used for specification and verification of reactive systems. Its standard model is sequences of states (or state transitions), and formulas describe sequencing of state transitions. When LTL is used to model real-time systems, a state is extended with a time stamp to record when a state transition takes place. Duration calculus (DC) is another well studied approach for real-time systems development. DC models behaviours of a system by functions from the domain of reals representing time to the system states. This paper extends this time domain to the Cartesian product of the real and the natural numbers. With the extended time domain, we provide the chop modality with a non-overlapping interpretation. This allows some linear temporal operators explicitly dealing with the discrete dimension of time to be derivable from the chop modality in essentially the same way that their continuous-time counterparts are in the classical DC. This provides a nice embedding of some timed LTL (TLTL) modalities into DC to unify the methods from DC and LTL for real-time systems development: Requirements and high level design decisions are interval properties and are therefore specified and reasoned about in DC, while properties of an implementation, as well as the refinement relation between two implementations, are specified and verified compositionally and inductively in LTL. Implementation properties are related to requirement and design properties by rules for lifting LTL formulas to DC formulas.
Enigmas of mammalian gamete form and function
Authors: Bedford J. Michael 
Published: May 2004

ABSTRACTThe gametes of man and some other Eutheria have been manipulated successfully for practical reasons, but many gaps remain in our basic understanding of the way that they function. This situation stems not least from a failure to recognize the extent to which eutherian spermatozoa and eggs, and elements related to their operation, have come to differ from those of other groups. Novel features in the male that reflect this include a radical design of the sperm head with the acrosome seeming to function primarily in egg‐coat binding rather than its lysis, a multifaceted post‐testicular sperm maturation and an androgen/low‐temperature‐regulated system of sperm storage – both tied to the epididymis, a variable male accessory sex gland complex, and descent of the testis and epididymis to a scrotum. In the female, such novelties are represented in a need for sperm capacitation, in an unusual regulation of sperm transport within the oviduct, in the cumulus oophorus and character of the zona pellucida around the small egg, and in a unique configuration of gamete fusion.The collective evidence now suggests that many of these features reflect a new fertilisation strategy or its consequences, with most being causally linked. One initial‘domino’ in this regard appears to be the small yolkless state of the egg and its intolerance for polyspermy, as determinants of the unusual mode of oviductal sperm transport and possibly the existence and form of the cumulus oophorus. However, a particularly influential first‘domino’ appears to be the physical character of the other animal groups by virtue of a resilient elasticity and thickness. These qualities allow this primary and often only coat to stretch and so persist during later expansion of the blastocyst, usually until close to implantation. At the same time, the dimensions, physical character, and particularly the relative protease‐insensitivity of the zona appear to have had profound effects on sperm form and function and, more indirectly, on sperm‐related events in the male and the female tract. Marsupials display some similarities and also some strikingly different features, against which the enigmas of the eutherian situation can be evaluated.
Diverse Phases of Collaboration: Working Together to Improve Community‐Based HIV Interventions for Adolescents
Authors: Harper Gary W. , Bangi Audrey K. , Contreras Richard , Pedraza Ana , Tolliver Michelle , Vess Luule 
Published: May 2004

AbstractAlthough alliances between community‐based organizations (CBOs) and university‐based evaluators provide opportunities to enhance community‐based interventions, such partnerships may be fraught with challenges and obstacles. This paper focuses on the “story” behind a collaborative partnership between a Latino‐focused CBO and a team of university‐based evaluators that was formed to evaluate HIV prevention interventions for Mexican American female adolescents and gay/bisexual/questioning (GBQ) Latino male adolescents. A developmental trajectory of the partnership is detailed, with a focus on the creation and enhancement of a reciprocal and mutually beneficial relationship. In tracing this history, the paper explores challenges that were faced and presents ways in which the partnership attempted to overcome obstacles. Recommendations are offered to assist in the formation and maintenance of collaborative partnerships between CBOs and university‐based evaluators/researchers.
Metabolic changes in the basal ganglia of patients with Huntington's disease: an in situ hybridization study of cytochrome oxidase subunit I mRNA
Authors: Gourfinkel‐An Isabelle , Vila Miquel , Faucheux Baptiste , Duyckaerts Charles , Viallet François , Hauw Jean‐Jacques , Brice Alexis , Agid Yves , Hirsch Etienne C. 
Published: May 2004

AbstractOn the basis of the functional model of the basal ganglia developed in the 1980s and the neuropathological findings in Huntington's disease (HD), changes in the neuronal activity of the basal ganglia have previously been proposed to explain the abnormal movements observed in this pathology. In particular, it has been stated that the neurodegenerative process affecting the basal ganglia in the disease should provoke a hypoactivity in the internal segment of the pallidum (GPi) that could explain choreic movements observed in the disease. To test this functional hypothesis, we performed an in situ hybridization study on control and HD brains postmortem, taking cytochrome oxidase subunit I (COI) mRNAs expression as index of neuronal activity. As most of the HD patients studied were under chronic neuroleptic (NL) treatment, we also studied the brains of non‐HD patients under chronic NL treatment. Our results show that in HD brain the number of neurons expressing COI mRNA tends to be lower in the striatum, GPe and GPi, suggesting a severe involvement of these structures during the neurodegenerative process. Moreover, COI mRNA level of expression was markedly reduced within neurons of the putamen and GPe. Surprisingly, COI mRNA expression was not modified in the GPi in HD brains compared with controls. This paradoxical result in the GPi may be explained by the antagonistic effect of GPe hypoactivity and the degenerative process involving neurons of GPi. Our results indicate that the functional modifications, and consequently the pathophysiology of␣abnormal movements, observed in HD basal ganglia are more complex than expected from the currently accepted model of the basal ganglia organization.