bluuebunny/crossref_metadata_2025_split huggingface dataset:
Epoxy Networks Modified by a New Class of Oligomeric Silsesquioxanes Bearing Multiple Intramolecular Rings Formed through SiOC Bonds
Authors: dell'Erba Ignacio E. , Fasce Diana P. , Williams Roberto J. J. , Erra‐Balsells Rosa , Fukuyama Yuko , Nonami Hiroshi 
Published: April 2004

AbstractSummary: A new class of silsesquioxane (SSO), containing species with two to nine Si atoms bearing multiple intramolecular rings formed through SiOC bonds, was synthesized as a glassy powder. It was characterized by UV‐MALDI‐TOF MS, 29Si NMR and FT IR. Solutions containing different amounts of SSO in the diglycidyl ether of bisphenol A (DGEBA), were homopolymerized in the presence of (4‐dimethylamino)pyridine (DMAP) as initiator, leading to SSO‐modified epoxy networks. SSO species were covalently bonded to the epoxy network without any evidence of phase separation. The SSO addition provoked an increase in the elastic modulus in the glassy state explained by an increase in the cohesive energy density. The SSO addition gave also place to an increase in the intensity of tan δ and a decrease in both the glass transition temperature and the elastic modulus in the rubbery state. This was explained by a decrease in crosslink density associated with the flexibility of SSO structures. DMAP was much more effective than other usual initiators (like benzyldimethylamine, BDMA), in increasing the crosslink density of the resulting epoxy network. This led to high values of the glass transition temperature and the elastic modulus in the rubbery state.Schematic representation of the chemical structure of the most significant species containing three Si atoms, present in the silsesquioxane.imageSchematic representation of the chemical structure of the most significant species containing three Si atoms, present in the silsesquioxane.
Logarithmic residues in the Banach algebra generated by the compact operators and the identity
Authors: Bart Harm , Ehrhardt Torsten , Silbermann Bernd 
Published: April 2004

AbstractA logarithmic residue is a contour integral of the (left or right) logarithmic derivative of an analytic Banach algebra valued function. Logarithmic residues are intimately related to sums of idempotents. The present paper is concerned with logarithmic residues in a specific Banach algebra, namely the one generated by the compact operators and the identity in the case when the underlying Banach space is infinite dimensional. The situation is more complex than encountered in previous investigations concerning logarithmic residues. Logarithmic derivatives may have essential singularities and the geometric properties of the Banach space play a role. Topological properties of the set of logarithmic residues are considered too. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Sums of reciprocal Stekloff eigenvalues
Authors: Dittmar Bodo 
Published: April 2004

AbstractLet 0 = λ1 < λ2 ≤ λ3 ≤ … be the Stekloff eigenvalues of a plane domain. The paper is concerned with formulas for ∑∞2λ(–2)j in simply and doubly connected domains. In the simply connected case it is proven that the disk minimized this sum. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Contractive and optimal sets in modular spaces
Authors: Kamińska Anna , Lewicki Grzegorz 
Published: April 2004

AbstractWe study contractive, existence and optimal sets in modular spaces. We define the analogous classes of sets with respect to a modular and generalize a number of results due to Beauzamy and Maurey [3] and Bruck [9] to modular spaces. We then apply them to show that in certain Köthe sequence spaces all of these notions are equivalent, extending a result of Davis and Enflo [11] for lp spaces, 1 < p < ∞. We also show that in class of Orlicz sequence spaces the theorem that any optimal set in lp spaces, 1 < p < ∞, is an intersection of half‐spaces determined by one‐complemented hyperplanes in lp, is no longer true. We then find a class of optimal sets, called strongly ρ‐optimal, such that this characterization holds true in Musielak‐Orlicz sequence spaces. We provide examples which show that all families of sets discussed in the paper like optimal, existence or contractive with respect to a norm or a modular or their strong counterparts, are not equivalent in general. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Upper and lower Hausdorff dimension estimates for invariant sets of weak k‐1‐endomorphisms
Authors: Qu Chengqin , Zhou Zuoling 
Published: April 2004

AbstractFor a special class of non‐injective maps called the weak k‐1‐endomorphisms on Riemannian manifolds upper and lower bounds for Hausdorff dimensions of invariant sets are given in terms of the singular values of the tangent maps, which generalize Franz's corresponding results. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Improvement of blepharospasm with Zolpidem
Authors: Garretto Nélida Susana , Bueri José A. , Rey Roberto D. , Arakaki Tomoko , Nano Gabriela V. , Mancuso Marcela 
Published: April 2004

AbstractZolpidem (ZLP) is an imidazopyridine that binds to GABA receptors. We report on improvement of blepharospasm in 3 patients treated with ZLP. The GABAergic action of this drug on the output structures of the basal ganglia could explain the improvement of blepharospasm in these patients. © 2004 Movement Disorder Society
Bilateral globus pallidus internus deep brain stimulation in tardive dyskinesia: A case report
Authors: Eltahawy Hazem A. , Feinstein Anthony , Khan Farouk , Saint‐Cyr Jean , Lang Anthony E. , Lozano Andres M. 
Published: April 2004

AbstractThe clinical response of a 53‐year‐old woman with tardive dyskinesia treated with bilateral globus pallidus interna deep brain stimulation is described. At 18 months follow‐up, her Burke–Fahn–Marsden Dystonia Rating Scale score fell from 52 (preoperative) to 21 (60% improvement). © 2004 Movement Disorder Society
Bilateral chorea–ballism associated with hyperthyroidism
Authors: Ristić Aleksandar J. , Svetel Marina , Dragašević Nataša , Žarković Miloš , Koprivšek Katarina , Kostić Vladimir S. 
Published: April 2004

AbstractWe describe a 50‐year‐old patient with four episodes of recurrent bilateral chorea–ballism (BCB) and associated hyperthyroidism. Reappearance of BCB, associated with increased serum levels of thyroid hormones and lack of relevant changes on brain computed tomography/magnetic resonance imaging scans, suggested that the involuntary movements were likely due to thyrotoxicosis‐induced biochemical changes. © 2004 Movement Disorder Society
Synthetic peroxides as antimalarials
Authors: Tang Yuanqing , Dong Yuxiang , Vennerstrom Jonathan L. 
Published: April 2004

AbstractThe discovery of artemisinin in 1971 initiated a new era in antimalarial chemotherapy. Although the clinically useful semisynthetic artemisinin derivatives are rapid acting and potent antimalarial drugs, they have short half‐lives and must be administered over a period of 5–7 days, leading to noncompliance and recrudescence. With this in view, many synthetic antimalarial peroxides have been prepared. Yet, identification of orally active synthetic peroxide drug development candidates that are easily synthesized, inexpensive, and with good biopharmaceutical properties has been surprisingly difficult. In this review, we document the pitfalls and progress made in this endeavor. For each of 15 synthetic peroxide structural classes, we note highlights of the synthetic routes, product stereochemistry, and origin of the peroxide O atoms. Both in vitro and in vivo antimalarial data are then discussed and any SAR noted. Available data indicates that several synthetic 1,2,4‐trioxanes are only marginally less effective than the semisynthetic artemisinins. Within a given peroxide chemical family, the more lipophilic members are more potent and possess better oral antimalarial activity in animal models than their more polar counterparts. This poses a challenge to identify peroxide structures with suitable “drug‐like” physicochemical properties. Nonetheless, substantial progress has been made in the identification of a new generation of synthetic antimalarial peroxides. © 2004 Wiley Periodicals, Inc. Med Res Rev, 24, No. 4, 425–448, 2004
Predicted signs of reduced two‐bond spin–spin coupling constants (2hKX–Y) across X—H—Y hydrogen bonds
Authors: Del Bene Janet E. , Elguero José 
Published: April 2004

AbstractThe reduced two‐bond Fermi‐contact terms and the reduced spin–spin coupling constants 2hKX–Y across X—H—Y hydrogen bonds for complexes stabilized by C—H—N, N—H—N, O—H—N, F—H—N, C—H—O, O—H—O, F—H—O and C—H—F hydrogen bonds are positive. The NMR Triplet Wavefunction Model (NMRTWM) indicates that the signs of the reduced FC terms and 2hKX–Y are determined by excited triplet states that have an odd number of nodes intersecting the X–Y axis between X and Y, thereby leading to an antiparallel alignment of the nuclear magnetic moments of atoms X and Y. Copyright © 2004 John Wiley & Sons, Ltd.
Do metastases metastasize?
Authors: Tait Catherine R , Dodwell D , Horgan K 
Published: April 2004

AbstractMetastatic disease is a major cause of morbidity and mortality. However, it is not clear if all metastases originate from the primary tumour or whether metastases themselves have the capacity to metastasize. In this review, the evidence for the latter phenomenon, and its biological and clinical implications, is discussed. Copyright © 2004 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.
Effects of clay on polymorphism of polypropylene in polypropylene/clay nanocomposites
Authors: Zheng Wenge , Lu Xuehong , Ling Toh Cher , Hua Zheng Tong , He Chaobin 
Published: April 2004

AbstractThe effects of clay on polymorphism of polypropylene (PP) in PP/clay nanocomposites (PPCNs) under various thermomechanical conditions were studied. In extruded PP and PPCN pellet samples, only α‐phase crystallites existed, as they were prepared by rapidly cooling the melt extrudates to room temperature. Under compression, β‐phase crystallites can develop in neat PP under various thermal conditions, of which isothermal crystallizing at 120 °C gave the highest content of β‐phase crystallites. In contrast, no β‐phase crystallite was detected in the PPCN samples prepared under the same conditions. This indicated that clay significantly inhibits the formation of β‐phase crystallites. The likely reason is that the presence of clay in PPCNs greatly sped up the crystallization process of the α phase, whereas it had an insignificant effect on the crystallization rates of the β phase. The results also showed that clay may slightly promote the formation of γ‐phase PP crystallites in PPCNs. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 1810–1816, 2004
Spinodal patterns indicating unstable regime of polymer crystallization
Authors: Nishida Koji , Kaji Keisuke , Kanaya Toshiji , Matsuba Go , Konishi Takashi 
Published: April 2004

AbstractIt has been considered that crystallization of polymer from melt proceeds via the coexistence of molten matrix and growing crystals that have once overcome a nucleation barrier to a critical size. The nucleation process has often been explained analogously with so‐called nucleation and growth (NG) behavior of the phase separation of a binary mixture in metastable conditions, although the crystallization in one‐component polymer is not a real component separation but a phase transition. Among the mechanisms of polymer crystallization, the topic is whether a liquid–liquid transition between states of different densities within one‐component polymers takes place before the aforementioned nucleation process. The liquid–liquid transition between states, which is probably driven by chain orientation, is also categorized into NG and the controversial spinodal decomposition (SD) type processes depending on the quenching depth. This article provides the optical microscopic observations that favor the occurrence of the SD‐like process when a one‐component polymer melt is very rapidly quenched below a stability limit, including a drastic morphological change from a spherulitic to a spinodal pattern at the critical (or spinodal) temperature. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 1817–1822, 2004
Crystal and phase morphology of dynamic‐packing‐injection‐molded high‐density polyethylene/ethylene vinyl acetate blends
Authors: Na Bing , Wang Yong , Du Rongni , Fu Qiang , Men Yongfeng 
Published: April 2004

AbstractThe effect of shear stress, provided by so‐called dynamic‐packing injection molding, on crystal morphology and phase behavior was investigated for high‐density polyethylene (HDPE) in blends with ethylene vinyl acetate (EVA) of various viscosities and vinyl acetate (VA) contents, with the aid of differential scanning calorimetry, two‐dimensional small‐angle X‐ray scattering (2D SAXS), and scanning electron microscopy (SEM). A shish‐kebab pattern was found in the oriented zones of dynamic samples, and the ratio of shish to kebab increased as a function of the EVA content in the blends up to 20 wt %, regardless of the VA content. This showed that molecules of HDPE could easily be stretched to form a shish structure in the presence of EVA. Moreover, a large increase in the long spacing, characterized by 2D SAXS measurements, was achieved because of the presence of EVA. The SEM results showed an obvious decrease in the domain size of the EVA phase under the effect of shear stress. All these results suggested shear‐induced mixing between HDPE and EVA, in that ethylene segments of EVA molecules could be forged in the shish structure during shear and the other fractions of EVA were located in the amorphous regions between the adjacent lamellae of HDPE. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 1831–1840, 2004
Effect of moisture on the dynamic mechanical relaxation of polyamide‐6/clay nanocomposites
Authors: Pramoda K. P. , Liu Tianxi 
Published: April 2004

AbstractThis article investigates the effect of moisture on the dynamic mechanical behavior of polyamide‐6 (PA6)/clay nanocomposites with dynamic mechanical analysis from −130 to 110 °C. The storage moduli increase with the clay loading for dried and moisture‐absorbed samples because of the enhancing effect from the high‐aspect‐ratio nanoclay. Storage moduli for moisture‐exposed samples are lower than those for dried samples; the longer the moisture absorption period is, the lower the moduli are for neat PA6 and PA6/clay nanocomposites. At temperatures below about 10 °C, however, samples exposed to moisture for longer periods tend to be stiffer than dried samples, probably because of the stiffening effect of ice. The peak temperature of the β relaxation shifts from −53 to −65 °C as the moisture content increases. The glass‐transition temperature (Tg) or α relaxation dramatically shifts; its position is significantly lowered from 62 to 17 °C as the moisture content increases (longer moisture absorption period) and from 62 to 50 °C as the clay loading increases. The observed depression of the storage modulus and Tg may be attributed to the plasticization effect of moisture absorption. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 1823–1830, 2004
Dynamic light scattering and small‐angle neutron scattering studies on organogels formed with a gelator
Authors: Okabe Satoshi , Ando Keiichi , Hanabusa Kenji , Shibayama Mitsuhiro 
Published: April 2004

AbstractSmall‐angle neutron scattering (SANS) and light scattering studies were carried out on an organogel consisting of a gelator, coded P‐1, and dimethyl sulfoxide (DMSO). The gelator was made of an oligosiloxane stem and about eight branches of an amino acid derivative combined with a long alkyl chain. The amino acid part,N‐n‐pentanoyl‐L‐isoleucylaminooctadecane, was responsible for intermolecular association via hydrogen bonding between amide groups. After the complete dissolution of P‐1 in DMSO at 85 °C, the solution was cooled, and the variations of the scattered light intensity were monitored as a function of the temperature. The scattered intensity increased drastically at about 40 °C when the P‐1 concentration (C) was 3.5 g/L, and this indicated gel formation. The SANS results showed that the scattering intensity function was a monotonically decreasing function, regardless ofC. A master relationship of the scattering intensity was obtained with respect toC. These scattering studies disclosed the following facts. First, gelation could be monitored as an abrupt increase in the intensity. Second, the gel was composed of randomly oriented bundlelike clusters. Third, the structure factor could be reduced by the gelator concentration, and this indicated the presence of a self‐similar structure across the gelation threshold. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 1841–1848, 2004
Sol–gel transition of methylcellulose in phosphate buffer saline solutions
Authors: Zheng Peijie , Li Lin , Hu Xiao , Zhao Xiongyan 
Published: April 2004

AbstractThe effect of phosphate buffer saline (PBS) on the thermoreversible sol–gel transition of methylcellulose has been systematically investigated with turbidimetric, microcalorimetric, and rheological methods. In the presence of PBS, the cloud points in the sol–gel transition and the clear points in the gel–sol transition shift to lower temperatures with increasing PBS content. This salting‐out effect is considered to be due to the competition between salts and methylcellulose for water molecules involved in the formation or destruction of cagelike water structures. The microcalorimetric studies prove that with increasing PBS content, the endothermic peak temperature decreases, whereas the enthalpy and entropy changes of the sol–gel transition increase. The rheological studies show that the addition of PBS favors the sol–gel transition, but the gel strength is almost independent of the PBS content, indicating an effect of adding salt equivalent to that of increasing the temperature. The results obtained from the rheological, microcalorimetric, and turbidimetric measurements are consistent. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 1849–1860, 2004
Crystal structure of a protein associated with cell division from Mycoplasma pneumoniae (GI: 13508053): A novel fold with a conserved sequence motif
Authors: Chen Shengfeng , Jancrick Jaru , Yokota Hisao , Kim Rosalind , Kim Sung‐Hou 
Published: April 2004

AbstractUPF0040 is a family of proteins implicated in a cellular function of bacteria cell division. There is no structure information available on protein of this family. We have determined the crystal structure of a protein from Mycoplasma pneumoniae that belongs to this family using X‐ray crystallography. Structural homology search reveals that this protein has a novel fold with no significant similarity to any proteins of known three‐dimensional structure. The crystal structures of the protein in three different crystal forms reveal that the protein exists as a ring of octamer. The conserved protein residues, including a highly conserved DXXXR motif, are examined on the basis of crystal structure. Proteins 2004. © 2004 Wiley‐Liss, Inc.
Gas‐phase interaction between DNA and RNA bases and copper (II) ion: A density functional study
Authors: Marino T. , Toscano M. , Russo N. , Grand A. 
Published: April 2004

AbstractThis investigation, performed at Becke's three‐parameter functional with Perdew–Wang correlational functional/6‐311+G(2df,2p) level, can provide information about the geometry of all possible adducts originating from the interaction of Cu2+ cation with the most stable tautomers of DNA and RNA free bases. Several attachment sites for both purine and pyrimidine bases have been taken into account. Monocoordination or bicoordination has been observed in all the obtained complexes. The copper ion (II) has the major affinity for the most stable tautomer of guanine base. We have observed that an interesting behavior occurs when the copper ion interacts with the bases in an apical approach. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2004
Theoretical study of possible ion‐molecule reactions leading to precursors of glycine in the interstellar medium
Authors: Largo Antonio , Redondo Pilar , Barrientos Carmen 
Published: April 2004

AbstractSeveral ion‐molecule reactions that could lead to precursors of interstellar glycine have been theoretically studied. Predictions for their reaction enthalpies have been carried out at the B3LYP (Becke's three‐parameter exchange functional and the gradient‐corrected functional of Lee, Yang, and Parr) QCISD(T) (quadratic configuration interaction method with singles and doubles substitutions followed by a perturbative treatment of triple substitutions), and MP4 (fourth‐order Møller–Plesset perturbation theory including single, double, triple, and quadruple substitution) levels of theory. The reactions of protonated aminomethanol with formic acid and of HCO with methylamine are clearly endothermic and therefore not likely to be feasible under interstellar conditions. On the other hand, different reactions of cationic derivatives of ammonia with acetic acid or the reaction of CH3NH with formic acid are clearly exothermic. One of the most promising processes, based on its exothermicity (about 27 kcal/mol), is the reaction of NH with CH3COOH. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2004
Effects of loop conformation on pKa and ligand binding in DNA gyrase B
Authors: Schechner Martina , Dejaegere Annick P. , Stote Roland H. 
Published: April 2004

AbstractMolecular dynamics simulations of the adenosine triphosphatase (ATPase) subdomain of DNA gyrase B were done to characterize the flexibility of two loops implicated in ligand binding. The simulations show that bound adenosine triphosphate (ATP) stabilizes the conformation of the two loops. Simulations of the ATPase subdomain without ATP show that the loops are more flexible and can assume alternative conformations. We further investigated the dependence of histidine pKa on the loop conformations using continuum dielectric calculations. Using multiple conformations, we showed that the protonation states of titratable groups in the flexible loops can depend on the loop conformation. This, in turn, will affect ligand binding and calculations such as the multiple copy simultaneous search (MCSS) method for small functional group binding. This illustrates the importance of accurately determining the protonation state of the protein prior to the calculation. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2004
High‐level ab initio methods for calculation of potential energy surfaces of van der Waals complexes
Authors: Giese Timothy J. , York Darrin M. 
Published: April 2004

AbstractA systematic series of highly correlated calculations of van der Waals potential energy surfaces (PESs) with large basis sets is presented. Reference data at the coupled‐cluster theory restricted to single, double, and noniterative triple excitations [CCSD(T)] level with large singly augmented correlation‐consistent basis functions, supplementary bond functions, and counterpoise corrections are provided. Results for minimum energy distances, well depths, vibrational frequencies, second virial coefficients, and Boyle temperatures are compared with corresponding experimental values. An extensive discussion of complete basis set extrapolation methods is presented. Here, the effect of extrapolation type, use of uncorrected and counterpoise‐corrected PESs, and direct property extrapolation are analyzed. Last, a new multicoefficient correlation method for van der Waals potential energy surfaces (MCCM‐vdW) is applied to three‐body interactions of helium trimers and to He … H2O interactions. Comparison with high‐level CCSD(T) calculations using large basis sets demonstrates that the MCCM‐vdW method is transferable to systems not considered in its parameterization. The method allows dispersion interactions of much larger systems to be studied reliably at a fraction of computational cost and offers a new tool for applications to rare‐gas clusters and the development of dispersion parameters for molecular simulation force fields. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2004