bluuebunny/crossref_metadata_2025_split huggingface dataset:
Study of complexes of poly(vinyl pyrrolidone) with copper and cobalt on solid state
Authors: Díaz Esperanza , Valenciano Rosa B. , Katime Issa A. 
Published: May 2004

AbstractA polymer–metal complex is a metal complex containing a polymer ligand, showing a remarkably specific structure in which central metal ions are surrounded by a colossal polymer chain. Based on this polymeric ligand, the polymer–metal complex has interesting and important characteristics, especially catalytic activities. This activity is different from that of the corresponding ordinary metal complex of low molecular weight. In this work we studied the synthesis and characterization, in the solid state, of different poly(vinyl pyrrolidone)–cobalt (PVP/Co) and –copper (PVP/Cu) complexes. We used differential thermal analysis and FTIR as the experimental techniques. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 1512–1518, 2004
Kinetics of butylacrylate polymerization in a starved feed reactor
Authors: Cao Gui‐Ping , Zhu Zhong‐Nan , Zhang Ming‐Hua , Yuan Wei‐Kang 
Published: May 2004

AbstractA starved feed reactor (SFR) is a semibatch polymerization reactor where initiator and monomer are fed slowly into a fixed amount of solvent. The polymerization is carried out isothermally at elevated temperatures. The added initiator decomposes instantaneously and the added monomer polymerizes immediately. The molecular weight of the product polymer can be effectively controlled by the feed ratio of monomer to initiator. This article presents a study on the kinetics of butylacrylate polymerization in an SFR. The model parameters are regressed with experimental data. Although the solids fraction in the SFR is high (>50%), viscosity is not high and the “gel effect” is weak because of the low molecular weight of the products. It is found that the termination rate constant is a power function of molecular weight, and the lumped rate constant kp/(k)1/2 can be modeled through an Arrhenius equation. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 1519–1525, 2004
Immobilization of invertase onto dimer acid‐co‐alkyl polyamine
Authors: Tümtürk H. , Tufan Y. 
Published: May 2004

AbstractInvertase was immobilized onto the dimer acid‐co‐alkyl polyamine after activation with 1,2‐diamine ethane and 1,3‐diamine propane. The effects of pH, temperature, substrate concentration, and storage stability on free and immobilized invertase were investigated. Kinetic parameters were calculated as 18.2 mM for Km and 6.43 × 10−5 mol dm−3 min−1 for Vmax of free enzyme and in the range of 23.8–35.3 mM for Km and 7.97–11.71 × 10−5 mol dm−3 min−1 for Vmax of immobilized enzyme. After storage at 4°C for 1 month, the enzyme activities were 21.0 and 60.0–70.0% of the initial activity for free and immobilized enzyme, respectively. The optimum pH values for free and immobilized enzymes were determined as 4.5. The optimum temperatures for free and immobilized enzymes were 45 and 50°C, respectively. After using immobilized enzyme in 3 days for 43 times, it showed 76–80% of its original activity. As a result of immobilization, thermal and storage stabilities were increased. The aim of this study was to increase the storage stability and reuse number of the immobilized enzyme and also to compare this immobilization method with others with respect to storage stability and reuse number. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 1526–1530, 2004
Development of a novel polymer–metal nanocomposite obtained through the route of in situ reduction for integral capacitor application
Authors: Pothukuchi Suresh , Li Yi , Wong C. P. 
Published: May 2004

AbstractMetal nanoparticles exhibit a number of interesting characteristics, including unique physical, chemical, optical, magnetic, and electric properties. Numerous investigations have exploited their properties in a readily usable form by incorporating them into polymers. The current focus of interest is the behavior of such polymer nanocomposites near the percolation loading levels of the metal nanoparticles. This material is particularly suitable for the new integral passive technology. Discrete capacitors are used in many applications, such as noise suppression, filtering, tuning, decoupling, bypassing, termination, and frequency determination, and they occupy a substantial amount of surface area on a substrate. Thus there are limitations in the number of capacitors that can be placed around the chip. Integral passive components are gradually replacing discrete components because of the inherent advantages of improved electrical performance, increased real estate on the printed wiring board, miniaturization of interconnect distance, reduced processing costs, and efficient electronics packaging. For integral capacitors, polymer composite material has emerged as a potential candidate because it meets the requirements of low processing temperature and reasonably high dielectric constant. Yang and Wong, whose patent was filed in 2001, demonstrated novel integral passive component materials with extraordinarily high dielectric constants (K > 1000) and high reliability performance. These materials are characterized by high dielectric constant based on the mechanism of interfacial polarization, although they need precision filler concentration control. The current study overcomes this drawback and produces the composite through an in situ reduction in an epoxy matrix. Material characterization was done through TEM, SEM, X‐ray analysis, and energy‐dispersive analysis for X rays. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 1531–1538, 2004
Studies on glass transition temperature of chitosan with four techniques
Authors: Dong Yanming , Ruan Yonghong , Wang Huiwu , Zhao Yaging , Bi Danxia 
Published: May 2004

AbstractStudies on the glass transition temperature (Tg) of chitosan are difficult to pursue because of the difficulty in sample preparation and the hydroscopicity of samples. There are a few works concerning this principal relaxation of chitosan. Among them, several quite different values (150°C, 161°C, and 203°C) have been reported. In this paper, the Tg of chitosan (140 ∼ 150°C) was determined by means of four techniques, namely, dynamic mechanical thermal analysis (DMTA), differential scanning calorimetry (DSC), thermally simulated current spectroscopy (TSC), and dilatometry (DIL).DSC measurement has been assumed not to be sensitive enough to detect the relaxation temperature of polysaccharides. We propose a new method to improve the sensitivity of the DSC measurement. After a physical aging treatment of samples, the transition in DSC traces became much more distinct because of the enthalpy relaxation. This technique was also used to distinguish the Tg from other relaxations.The Tg of chitosan with different degree of deacetylation (D.D.) was examined by DSC. No influence of D.D. on Tg was found. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 1553–1558, 2004
Chemical structure designing to enhance the yield stress of electrorheological fluids based on modified chitosan compounds
Authors: Ko Young Gun , Choi Ung Su , Sung Bo Hyun 
Published: May 2004

AbstractFor studying the influences of alkyl chain length, end groups of the side chains, and mixture on enhancing the shear stress of electrorheological (ER) fluids, chitosan carboxylates were synthesized for ER particles and prepared ER fluids by dispersing the particles in silicone oil. After comparing the shear stress of all prepared ER fluids, the conclusion obtained was that ER particles having two functional groups showed higher shear stress than those having one functional group. However, after mixing two ER particles having one functional group respectively, the ER fluid having those particles showed a lower shear stress. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 1559–1566, 2004
Phase morphology and compatibilization mechanism in ternary polymer blend systems of polyethylene terephthalate, polyolefin rubber, and ionomer
Authors: Ohishi Hiroshi 
Published: May 2004

AbstractThe phase morphology and the mechanism of the compatibilization in ternary blends of PET/EBM (ethylene buten rubber)/ionomer (partially neutralized ethylene and methyl methacrylic acid copolymer, EMAA) are examined. Applying the repulsion idea in random copolymer, the ionomer was selected as an encapsulating agent to compatibilize PET/EBM blend. As anticipated, the ionomer can encapsulate EBM in PET matrix and effectively compatibilize PET and EBM. The results of droplet sandwich experiments verified that the actual driving force for the encapsulation is wettability. In addition, this wettablility was found to be realized by the contribution of the polar and nonpolar units in the ionomer: The polar units decrease the interfacial tension between PET and the ionomer, and the nonpolar units decrease that between EBM and the ionomer. The metal ions in the ionomer have little influence on the wettability, and consequently EMAA can encapsulate EBM even when unneutralized. The efficiency of the compatibilization, on the other hand, is not determined by the wettability only, and the metal ions play an important role. EMAA can effectively compatibilize EBM and PET only when neutralized. This compatibilization effectiveness of the ionomer is supposedly due to the strong interaction between PET and the metal ions. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 1567–1576, 2004
Organic Chlorine as a Hydrogen‐Bridge Acceptor: Evidence for the Existence of Intramolecular OH⋅⋅⋅ClC Interactions in Somegem‐Alkynols
Authors: Banerjee Rahul , Desiraju Gautam R. , Mondal Raju , Howard Judith A. K. 
Published: May 2004

AbstractThe acceptor capabilities of “organic” halogen, CX (X=F, Cl, Br, I), with respect to hydrogen bonding are controversial, and unactivated organic chlorine is generally deemed to be a poor acceptor. Hydrogen bridges of the type OH⋅⋅⋅ClC are uncommon and occur mainly in an intramolecular situation when the donor group is sterically hindered, so that the formation of intermolecular interactions is difficult. In this paper, intramolecular OH⋅⋅⋅ClC interactions in a series of chloro‐substitutedgem‐alkynols are studied. We describe various features of this interaction using crystallographic, spectroscopic and computational methods. The OH⋅⋅⋅ClC interaction occurs in five of the six compounds under consideration here (CDDA, 14DDDA, 15DDDA, 18DDDA, 15MKA). Solution1H NMR spectroscopy shows that the interaction is intramolecular and that it is a true hydrogen bond. DFT calculations give a stabilisation energy around 4.0 kcal mol−1. In the crystal structures of the compounds studied, the intramolecular OH⋅⋅⋅ClC interactions fit into the overall scheme of cooperative interactions. These structures may be derived from that of the unsubstituted compound DDA by means of synthon exchange and the OH⋅⋅⋅ClC interaction fares surprisingly well in the presence of competing stronger acceptors. The crystal structures show an unusual degree of modularity for compounds that generally form interactions that are weak and variable. It is noteworthy that the so‐called “weak” acceptor, organic chlorine, is able to sustain a good intramolecular hydrogen bridge that is of an attractive and stabilizing nature and which is of potential importance in crystal engineering and supramolecular chemistry.
Actin filament binding by a monomeric IQGAP1 fragment with a single calponin homology domain
Authors: Mateer Scott C. , Morris Leah E. , Cromer Damond A. , Benseñor Lorena B. , Bloom George S. 
Published: May 2004

AbstractIQGAP1 is a homodimeric protein that reversibly associates with F‐actin, calmodulin, activated Cdc42 and Rac1, CLIP‐170, β‐catenin, and E‐cadherin. Its F‐actin binding site includes a calponin homology domain (CHD) located near the N‐terminal of each subunit. Prior studies have implied that medium‐ to high‐affinity F‐actin binding (5–50 μM Kd) requires multiple CHDs located either on an individual polypeptide or on distinct subunits of a multimeric protein. For IQGAP1, a series of six tandem IQGAP coiled‐coil repeats (IRs) located past the C‐terminal of the CHD of each subunit support protein dimerization and, by extension, the IRs or an undefined subset of them were thought to be essential for F‐actin binding mediated by its CHDs. Here we describe efforts to determine the minimal region of IQGAP1 capable of binding F‐actin. Several truncation mutants of IQGAP1, which contain progressive deletions of the IRs and CHD, were assayed for F‐actin binding in vitro. Fragments that contain both the CHD and at least one IR could bind F‐actin and, as expected, removal of all six IRs and the CHD abolished binding. Unexpectedly, a fragment called IQGAP12‐210, which contains the CHD, but lacks IRs, could bind actin filaments. IQGAP12‐210 was found to be monomeric, to bind F‐actin with a Kd of ∼47 μM, to saturate F‐actin at a molar ratio of one IQGAP12‐210 per actin monomer, and to co‐localize with cortical actin filaments when expressed by transfection in cultured cells. These collective results identify the first known example of high‐affinity actin filament binding mediated by a single CHD. Cell Motil. Cytoskeleton 58:231–241, 2004. © 2004 Wiley‐Liss, Inc.
Loss or mismatch of MHC class I is sufficient to trigger NK cell‐mediated rejection of resting lymphocytes in vivo – role of KARAP/DAP12‐dependent and ‐independent pathways
Authors: Öberg Linda , Johansson Sofia , Michaëlsson Jakob , Tomasello Elena , Vivier Eric , Kärre Klas , Höglund Petter 
Published: May 2004

AbstractA prediction from the "missing self" hypothesis is that down‐regulation of MHC class I on resting hematopoietic cells should be sufficient to make them susceptible to NK cell killing. Using a method enabling kinetic and quantitative assessments of NK cell‐mediated rejection responses in vivo, we here show that resting hematopoietic cells from β2‐microglobulin‐deficient (β2m–/–) mice were rapidly rejected in unmanipulated C57BL/6 (B6) mice. In situations of allelic MHC class I mismatches rejection occurred but required longer time. β2m–/– donor cells pre‐activated with concanavalin A were more efficiently eliminated compared to resting cells, as were MHC– tumor cells. When recipient mice were pretreatedwith an IFN inducer to activate NK cells, rejection was also enhanced. The signaling adaptor KARAP/DAP12 was dispensable for rejection of β2m–/– cells (lacking MHC) but critical for rejection of BALB/c cells (mismatched MHC) in unmanipulated B6 recipients. In contrast, B6 recipients with pre‐activated NK cells rejected BALB/c cells in a KARAP/DAP12‐independent fashion. Loss or mismatch of MHC class I in resting cells was thus sufficient to convey susceptibility to NK cell rejection. However, activation of the effector or the target enhanced rejection and shifted the balance between different signaling pathways involved.
The small subset of CD56brightCD16– natural killer cells is selectively responsible for both cell proliferation and interferon‐γ production upon interaction with dendritic cells
Authors: Vitale Massimo , Chiesa Mariella Della , Carlomagno Simona , Romagnani Chiara , Thiel Andreas , Moretta Lorenzo , Moretta Alessandro 
Published: May 2004

AbstractThe encounter of NK cells with dendritic cells (DC) undergoing maturation may result in the induction of NK cell proliferation. Whether such proliferation involves most NK cells or just a subset has yet to be determined. In the present study we analyzed the nature of such proliferating NK cells by combining carboxyfluorescein succinimidyl ester staining and double‐fluorescence cytofluorimetric analysis. Freshly isolated peripheral blood NK cells cultured with LPS and immature DC underwent proliferation; however, proliferating cells were confined to a minor NK cell subset. This subset is characterized by the CD56brightCD16–NKG2A+KIR– surface phenotype (KIR, killer Ig‐like receptor). This was further confirmed by the fact that, after cell sorting, only the CD56bright NK cells were able to proliferate in response to the DC stimulus, whereas the CD56dull were not. We also provide evidence that the CD56bright subset is the main source of IFN‐γ‐producing NK cells, upon interaction with DC. The CD56brightCD16– NK cells express a panel of surface molecules including CD62L, CCR7 and CXCR3 that may allow their homing either to secondary lymphoid compartments or to inflamed tissues. This implies that, in vivo, the interactions between DC undergoing maturation and CD56bright NK cells may occur in different tissues and have different functional implications.
Neural substrates differentiating global/local processing of bilateral visual inputs
Authors: Han Shihui , Jiang Yi , Gu Hua 
Published: May 2004

AbstractWe investigated neural substrates of global/local processing of bilateral hierarchical stimuli using functional magnetic resonance imaging (fMRI). Subjects were presented with two compound letters that were displayed simultaneously in the left and right visual fields, respectively. In a steady‐state, block‐design paradigm, hemodynamic responses were recorded while subjects detected infrequent global or local targets presented in one hemifield in separate epochs of trials. While behavioural responses were more accurate and faster to global than local targets, attention to the global level of bilateral visual inputs induced stronger activations in the left and right temporal cortex relative to attention to the local level. However, attention to the local level generated stronger activations in bilateral superior parietal cortex compared with attention to the global level. The results suggest that distinct neural substrates in the temporal and parietal cortices are preferentially engaged in the global and local processing of bilateral visual inputs, respectively. Hum. Brain Mapping 22:321–328, 2004. © 2004 Wiley‐Liss, Inc.
Fin efficiency of serrated fins. Part 4. Correction factor for inline arrangement
Authors: Hashizume Kenichi , Sato Toshiharu , Matsue Takahiro , Koyama Tetsuya 
Published: May 2004

AbstractA correction factor to the theoretical fin efficiency of serrated fins, reported in Part 1 and Part 2 of this report, was derived for an inline arrangement experimentally. The experiment was performed using an open‐type wind tunnel with six kinds of test finned‐tubes made of copper, carbon steel and stainless steel, which were arranged in one to five rows. Heat transfer measurement was done by the local thermal simulation method. The derived correction factor for the 1st row was the same as for staggered arrangement reported in Part 3, for the 2nd and deeper rows, however, a further correction was needed, which may be caused by the difference in the nonuniformity in heat transfer coefficient over the fin surface. © 2004 Wiley Periodicals, Inc. Heat Trans Asian Res, 33(4): 258–269, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/htj.20008
Contact angle hysteresis on rough solid surfaces
Authors: Wang X.D. , Peng X.F. , Lu J.F. , Liu T. , Wang B.X. 
Published: May 2004

AbstractWith the introduction of an additional interfacial tension (or hysteresis tension) to describe the effect of the surficial roughness on the liquid‐solid contact angle hysteresis, both contact angle and its hysteresis were derived from mechanical equilibrium and were perfectly consistent with thermodynamics. This unifies the mechanical and thermodynamic performance, or removes the contradiction existing in classical mechanical and thermodynamic understanding. By combining the sessile drop method with CCD camera and the digital imaging techniques, the contact angle hysteresis of distilled water, diethylene glycol, and 1‐butyl alcohol on stainless steel surfaces was measured. The results of the experiments agree very well with the predictions of the hysteresis tension model. © 2004 Wiley Periodicals, Inc. Heat Trans Asian Res, 33(4): 201–210, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/htj.20013
Hemocompatibility of nitrogen‐doped, hydrogen‐free diamond‐like carbon prepared by nitrogen plasma immersion ion implantation–deposition
Authors: Kwok Sunny C.H. , Yang Ping , Wang Jin , Liu Xuanyong , Chu Paul K. 
Published: May 2004

AbstractAmorphous hydrogenated carbon (a‐C:H) has been shown to be a potential material in biomedical devices such as artificial heart valves, bone implants, and so on because of its chemical inertness, low coefficient of friction, high wear resistance, and good biocompatibility. However, the biomedical characteristics such as blood compatibility of doped hydrogen‐free diamond‐like carbon (DLC) have not been investigated in details. We recently began to investigate the potential use of nitrogen‐doped, hydrogen‐free DLC in artificial heart valves. In our experiments, a series of hydrogen‐free DLC films doped with nitrogen were synthesized by plasma immersion ion implantation–deposition (PIII‐D) utilizing a pulsed vacuum arc plasma source and different N to Ar (FN/FAr) gas mixtures in the plasma chamber. The structures and properties of the film were evaluated by Raman spectroscopy, Rutherford backscattering spectrometry (RBS), and X‐ray photoelectron spectroscopy (XPS). To assess the blood compatibility of the films and the impact on the blood compatibility by the presence of nitrogen, platelet adhesion tests were conducted. Our results indicate that the blood compatibility of both hydrogen‐free carbon films (a‐C) and amorphous carbon nitride films are better than that of low‐temperature isotropic pyrolytic carbon (LTIC). The experimental results are consistent with the relative theory of interfacial energy and surface tension including both dispersion and polar components. Our results also indicate that an optimal fraction of sp2 bonding is desirable, but an excessively high nitrogen concentration degrades the properties to an extent that the biocompatibility can be worse than that of LTIC. (PACS codes: 81.05Uw, 87.68.+z,52.77.Dq,68.55.Nq.) © 2004 Wiley Periodicals, Inc. J Biomed Mater Res 70A: 107–114, 2004
Nanometer surface roughness increases select osteoblast adhesion on carbon nanofiber compacts
Authors: Price Rachel L. , Ellison Karen , Haberstroh Karen M. , Webster Thomas J. 
Published: May 2004

AbstractCarbon nanofibers have exceptional theoretical mechanical properties (such as low weight‐to‐strength ratios) that, along with possessing nanoscale fiber dimensions similar to crystalline hydroxyapatite found in bone, suggest strong possibilities for use as an orthopedic/dental implant material. To determine, for the first time, cytocompatibility properties pertinent for bone prosthetic applications, osteoblast (bone‐forming cells), fibroblast (cells contributing to callus formation and fibrous encapsulation events that result in implant loosening), chondrocyte (cartilage‐forming cells), and smooth muscle cell (for comparison purposes) adhesion were determined on carbon nanofibers in the present in vitro study. Results provided evidence that, compared to conventional carbon fibers, nanometer dimension carbon fibers promoted select osteoblast adhesion. Moreover, adhesion of other cells was not influenced by carbon fiber dimensions. In fact, smooth muscle cell, fibroblast, and chondrocyte adhesion decreased with an increase in either carbon nanofiber surface energy or simultaneous change in carbon nanofiber chemistry. To determine properties that selectively enhanced osteoblast adhesion, similar cell adhesion assays were performed on polymer (specifically, poly‐lactic‐co‐glycolic; PLGA) casts of carbon fiber compacts previously tested. Compared to PLGA casts of conventional carbon fibers, results provided the first evidence of enhanced select osteoblast adhesion on PLGA casts of nanophase carbon fibers. The summation of these results demonstrate that due to a high degree of nanometer surface roughness, carbon fibers with nanometer dimensions may be optimal materials to selectively increase osteoblast adhesion necessary for successful orthopedic/dental implant applications. © 2004 Wiley Periodicals, Inc. J Biomed Mater Res 70A: 129–138, 2004