bluuebunny/crossref_metadata_2025 huggingface dataset:
Epoxy resin containing the poly(sily ether): Preparation, morphology, and mechanical properties
Authors: Zheng Sixun , Gao Rong , Li Jianhua , Guo Qipeng
Published: April 2003

The poly(sily ether) with pendant chloromethyl groups (PSE) was synthesized by the polyaddition of dichloromethylsilane (DCM) and diglycidylether of bisphenol A (DGEBA) with tetrabutylammonium chloride (TBAC) as a catalyst. This polymer was miscible with diglycidyl ether of bisphenol A (DGEBA), the precursor of epoxy resin. The miscibility is considered to be due mainly to entropy contribution because the molecular weight of DGEBA is quite low. The blends of epoxy resin with PSE were prepared throughin situcuring reaction of diglycidyl ether of bisphenol A (DGEBA) and 4,4′‐diaminodiphenylmethane (DDM) in the presence of PSE. The DDM‐cured epoxy resin/PSE blends with PSE content up to 40 wt % were obtained. The reaction started from the initial homogeneous ternary mixture of DGEBA/DDM/PSE. With curing proceeding, phase separation induced by polymerization occurred. PSE was immiscible with the 4,4′‐diaminodiphenylmethane‐cured epoxy resin (ER) because the blends exhibited two separate glass transition temperatures (Tgs) as revealed by the means of differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA). SEM showed that all the ER/PSE blends are heterogeneous. Depending on blend composition, the blends can display PSE‐ or epoxy‐dispersed morphologies, respectively. The mechanical test showed that the DDM‐cured ER/PSE blend containing 25 wt % PSE displayed a substantial improvement in Izod impact strength, i.e., epoxy resin was significantly toughened. The improvement in impact toughness corresponded to the formation of PSE‐dispersed phase structure. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 505–512, 2003
Unexpected behavior between polystyrene and untreated and silane‐treated glass beads in filled polymeric composites
Authors: Miller A. C. , Berg J. C.
Published: April 2003

Attempting to extend the database of work reported earlier, the practical adhesion between a glass filler, modified by various silane‐coupling agents, and a polystyrene matrix is measured and compared with predictions based on a generalized thermodynamic criterion. Measurements leading to adhesion failure are carried out using the single‐particle composite method, in which a rectangular polymer specimen containing a single untreated or silane‐treated glass bead is subjected to increasing uniaxial tensile stress until interfacial failure, as observed using a microscope, occurs at one of the poles of the sphere. The results show no difference in adhesion strength between an untreated and a silane‐treated glass bead, and the interfacial failure mechanism for the polystyrene composites is markedly different from that observed for previously studied systems. Crazes originate at the particle pole at low values of the applied stress and continue to form along the interface with continued strain. A dye test performed on filled composites confirms that the polystyrene is not wetting the untreated glass beads. More studies must be done to determine the origin of the anomalous failure and wetting behavior. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 521–526, 2003
Dlx1, Dlx2, Pax6, Brn3b, and Chx10 homeobox gene expression defines the retinal ganglion and inner nuclear layers of the developing and adult mouse retina
Authors: de Melo Jimmy , Qiu Xiangguo , Du Guoyan , Cristante Leah , Eisenstat David D.
Published: April 2003

Distal‐less homeobox genes are expressed in the developing forebrain. We assessed Dlx gene expression in the developing and adult mouse retina. Dlx1 and Dlx2 are detected in retinal neuroprogenitors by embryonic day (E) 12.5 (Eisenstat et al. [1999] J. Comp. Neurol. 217–237). At E13.5, the expression of four homeodomain proteins, DLX2, BRN3b, PAX6, and CHX10, define distinct yet overlapping domains in the retinal neuroepithelium. By postnatal day (P) 0, DLX2 is expressed in the neuroblastic layer and the ganglion cell layer (GCL) consisting of ganglion and displaced amacrine cells. DLX1 expression resembles DLX2 to P0 but decreases postnatally. In the adult, DLX2 is localized to ganglion, amacrine, and horizontal cells as determined by coexpression with retinal cell‐specific markers. There is coincident expression of DLX2 with γ‐aminobutyric acid (GABA), glutamic acid decarboxylase (GAD)65, and GAD67 in the inner nuclear layer (INL) and GCL. In the adult, DLX2 is coexpressed with BRN3b in ganglion cells; PAX6 in amacrine, horizontal, and ganglion cells; and Chx10 in some bipolar cells. We predict that a combinatorial code of these homeobox genes and others specify retinal cell fate. Our results support a possible role for Dlx1 and Dlx2 in inner retinal development and in the terminal differentiation and/or maintenance of INL interneurons and ganglion cells in the adult. The correlation of DLX2 with GABA expression in the mouse retina closely mirrors the relationship of DLX2 to GABAergic neuronal differentiation in the embryonic forebrain, including neocortex, olfactory bulb and hippocampus, signifying a conservation of function of Dlx genes in the developing central nervous system. J. Comp. Neurol. 461:187–204, 2003. © 2003 Wiley‐Liss, Inc.
Goα labels ON bipolar cells in the tiger salamander retina
Authors: Zhang Jian , Wu Samuel M.
Published: April 2003

By using double‐label immunocytochemistry and confocal microscopy, we studied rod and cone synaptic contacts, photoreceptor‐bipolar cell convergence, and patterns of axon terminal ramification of ON bipolar cells in the tiger salamander retina. An antibody to recoverin, a calcium‐binding protein found in photoreceptors and other retinal neurons in various vertebrates, differentially labeled rods and cones by lightly staining rod cell bodies, axons, and synaptic pedicles and heavily staining cone cell bodies and pedicles. An antibody to Goα labeled most ON bipolar cells, with axon terminals ramified mainly in strata 6–9 and a minor band in stratum 3 of the inner plexiform layer (IPL). Stratum 10 of the IPL was Goα negative, and previous studies showed that axon terminals of rod‐dominated ON bipolar cells are monostratified in that stratum. The axonal morphology of Goα‐positive cells resembled that of the cone‐dominated (DBCC) or mixed rod and cone ON (DBCM) bipolar cells. The Goα‐positive dendritic processes made close contact with all cone pedicles and superficial contact with some rod pedicles, consistent with the idea that Goα subunits are present in DBCCs and DBCMs. The size and density of these cells were analyzed, and their spatial distributions were determined. To our knowledge, this is the first study to characterize photoreceptor inputs and axon terminal morphology of a population of ON bipolar cell with the use of a Goα antibody as an immunomarker in the salamander retina. J. Comp. Neurol. 461:276–289, 2003. © 2003 Wiley‐Liss, Inc.
CD55/decay accelerating factor is part of the lipopolysaccharide‐induced receptor complex
Authors: Heine Holger , El‐Samalouti Volker T. , Nötzel Corinna , Pfeiffer Alexandra , Lentschat Arnd , Kusumoto Shoichi , Schmitz Gerd , Hamann Lutz , Ulmer Artur J.
Published: April 2003

Recently, we described an 80‐kDa lipopolysaccharide (LPS)‐binding membrane protein to be identical to CD55 [decay accelerating factor (DAF)]. Here, we demonstrate that CD55 is able to contribute to lipopolysaccharide (LPS) signaling. Transfection of Chinese hamster ovary (CHO) cells with human CD55 resulted in a translocation of NF‐κB after stimulation with LPS as well as with free lipid A. In addition, interaction of lipid A and CD55 was shown by co‐immuno‐precipitation of these molecules from CHO‐CD55 cells after incubation with lipid A and anti‐lipid A monoclonal antibody, as well as by fluorescence resonance energy transfer (FRET) analysis in human monocytes. The comparison of LPS‐induced signaling pathways in CHO‐CD55 and CHO‐CD14 cells revealed that p38, JNK and ERK MAP kinases are activated upon LPS stimulation in both cell lines, and that the activation by LPS can be blocked at the level of Toll‐like receptor 4. Finally, through FRET analysis we could demonstrate LPS‐induced clustering of CD55 and CD11/CD18 in human monocytes. Our results imply a new functional role of CD55 as a member of a multimeric LPS receptor complex.
Stable expression of MHC class I heavy chain/HLA‐DO complexes at the plasma membrane
Authors: van Lith Marcel , van Ham Marieke , Neefjes Jacques
Published: April 2003

Major histocompatibility complex (MHC) class I and II molecules present antigenic fragments to the immune system. MHC‐like chaperones, like HLA‐DM, HLA‐DO and tapasin support peptide loading. HLA class I heavy chains require association with β2‐microglobulin and peptide for endoplasmic reticulum (ER) exit. Likewise, HLA‐DO is only able to leave the ER by association to DM. Here we show that HLA‐DO and free MHC class I heavy chains associate into a stable complex early during biosynthesis and are expressed at the plasma membrane as a complex. These DO/heavy chain complexes are found on DO‐transfected cells and on low amounts on human B cells.
Fibrinogen‐CD11b/CD18 interaction activates the NF‐κB pathway and delays apoptosis in human neutrophils
Authors: Rubel Carolina , Gómez Sonia , Fernández Gabriela C. , Isturiz Martín A. , Caamaño Jorge , Palermo Marina S.
Published: April 2003

The regulation of neutrophil half‐life by members of the coagulation cascade is critical for the resolution of the inflammatory response. We have demonstrated that soluble fibrinogen (sFbg) delays human neutrophil (PMN) apoptosis through a mechanism that involves CD11b interactions, and phosphorylation of focal adhesion kinase (FAK) and extracellular signal‐regulated kinase 1/2 (ERK1/2).Since NF‐κB is a key element in the regulation of apoptotic mechanisms in several immune cells, we investigated whether NF‐κB is involved in the control of PMN survival by sFbg. We showthat sFbg triggers inhibitor protein κB (IκB‐α) degradation and NF‐κB activation. Furthermore, pharmacological inhibition of NF‐κB abrogates sFbg effects on apoptosis. In addition, specific inhibition of MAPK ERK1/2 significantly reduces NF‐κB translocation by sFbg, suggesting a relationship between ERK1/2 and NF‐κB activation. Similar results are obtained when granulocytic‐differentiated HL‐60 cells are treated with sFbg, making this model highly attractive for integrin‐induced gene expression studies. It can be concluded that NF‐κB participates in the prevention of apoptosis induced by sFbg with the participation of MAPK ERK1/2. These results shed light on the molecular mechanisms that control human granulocyte apoptosis, and suggest that NF‐κB regulation may be of benefit for the resolution of the inflammatory response.
T cell adhesion lowers the threshold for antigen detection
Authors: Randriamampita Clotilde , Boulla Geneviève , Revy Patrick , Lemaitre Fabrice , Trautmann Alain
Published: April 2003

Antigen detection and initiation of TCR signaling only occur, under physiological conditions, when T cells are adherent, and not in suspension. We show here that T cell adhesion causes an increase in the Ca2+ content of intracellular stores and of the amount of phosphatidylinositol 4,5‐bisphosphate in the plasma membrane, and enhances TCR‐induced Ca2+ signaling. This priming can be observed in freshly isolated T cells, in activated T cells, and in some T cell lines. Stimulation of T cells by specific monomeric MHC‐peptide complexes only triggers Ca2+ responses after T cell adhesion. This solves a controversial issue concerning the minimum valency of activatory TCR ligands. Adhesion‐induced T cell priming not only occurs upon binding to artificial substrates such as immobilized ligands, but also upon interaction with dendritic cells. Thus, this phenomenon is likely to contribute to the high sensitivity of antigen detection by T cells in secondary lymphoid organs.
Chemokines integrate JAK/STAT and G‐protein pathways during chemotaxis and calcium flux responses
Authors: Soriano Silvia F. , Serrano Antonio , Hernanz‐Falcón Patricia , de Ana Ana Martín , Monterrubio María , Martínez‐A Carlos , Rodríguez‐Frade J. Miguel , Mellado Mario
Published: April 2003

The JAK/STAT (Janus kinase / signaling transducer and activator of transcription) signaling pathway is implicated in converting stationary epithelial cells to migratory cells. In mammals, migratory responses are activated by chemoattractant proteins, including chemokines. We found that by binding to seven‐transmembrane G‐protein‐coupled receptors, chemokines activate the JAK/STAT pathwayto trigger chemotactic responses. We show that chemokine‐mediated JAK/STAT activation is critical for G‐protein induction and for phospholipase C‐β dependent Ca2+ flux; in addition, pharmacological inhibition of JAK or mutation of the JAK kinase domain causes defects in both responses. Furthermore, Gαi association with the receptor is dependent on JAK activation, andthe chemokine‐mediated Ca2+ flux that requires phospholipase C‐β activity takes place downstream of JAK kinases. The chemokines thus employ a mechanism that links heterologous signaling pathways — G proteins and tyrosine kinases — in a network that may be essential for mediating their pleiotropic responses.
Synthesis of C1‐Symmetric Tripod Ligands Containing a P,P,N Donor Set − η2‐Coordination in d8‐Metal Complexes
Authors: Faissner Ralf , Huttner Gottfried , Kaifer Elisabeth , Rutsch Peter
Published: April 2003

Tripod ligands RC(CH2X)(CH2Y)(CH2Z) (X, Y, Z = NR2, PR2) are accessible from α,β‐unsaturated esters R(=CH2)COOR′. The key steps in this synthetic approach are Michael additions of amines and phosphanes to produce RCH(COOR′)(CH2X) (X = NR2, PR2) (2 and 3), followed by hydroxymethylation with paraformaldehyde to result in RC(COOR′)(CH2OH)(CH2X) (X = NR2) (4). Standard transformations of this C1‐symmetric precursor allow for the synthesis of tripod ligands such as PhC(CH2pz)(CH2PPh2)(CH2PMes) (11). Coordination of these ligands with d8‐metal ions [nickel(II), palladium(II), rhodium(I)] results in square‐planar complexes with the chelate cycles in half‐chair, twist‐boat or boat conformations, depending on the specific substitution pattern. Coordination through two phosphane donors with the nitrogen donor acting as a dangling arm is generally preferred throughout. Detail preparative procedures and complete characterisation by analytical methods, including X‐ray analysis of the coordination compounds, are given. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
Effect of buffer, electric field, and separation time on detection of aptamer‐ligand complexes for affinity probe capillary electrophoresis
Authors: Buchanan Danielle D. , Jameson Emily E. , Perlette Jon , Malik Abdul , Kennedy Robert T.
Published: April 2003

The separation and detection of complexes of aptamers and protein targets by capillary electrophoresis (CE) with laser‐induced fluorescence was examined. Aptamer‐thrombin and aptamer‐immunoglobulin E (IgE) were used as model systems. Phosphate, 3‐(N‐morpholino)propanesulfonic acid with phosphate, and tris(hydroxyamino)methane‐glycine‐potassium (TGK) buffer at pH 8.4 were tested as electrophoresis media. Buffer had a large effect with TGK providing the most stable complexes for both protein‐aptamer complexes. Conditions that suppressed electroosmotic flow, such as addition of hydroxypropylmethylcellulose to the media or modification of the capillary inner wall with polyacrylamide, were found to prevent detection of complexes. The effect of separation time and electric field were evaluated by monitoring complexes with electric field varied from 150–2850 V/cm and effective column lengths of 3.5 and 7.0 cm. As expected, shorter times on the column greatly increased peak heights for the complexes due to a combination of less dilution by diffusion and less dissociation on the column. High fields were found to have a detrimental effect on detection of complexes. It is concluded that the best conditions for detection of noncovalent complexes involve use of the minimal column length and electric field necessary to achieve separation. The results will be of interest in developing affinity probe CE assays wherein aptamers are used as affinity ligands.
Aragonite Formation in the Chiton (Mollusca) Girdle
Authors: Treves Keren , Traub Wolfie , Weiner Steve , Addadi Lia
Published: April 2003

In the chitons (Polyplacophora, Mollusca), the body is not entirely protected by the shell. Mineralized spicules or scales often, but not always, decorate the exposed part of the girdle. Here, we report a study on the composition and ultrastructural organization of these mineralized skeletal parts in four different chiton species. In all specimens, the mineral component (97–98 wt‐%) is aragonite, and the organic matrix (2–3 wt‐%) consists of highly glycosylated proteins. X‐Ray diffraction and scanning electron microscopy show that the organic matrix fibers are aligned, morphologically and crystallographically, with the prismatic aragonite crystals. Matrix and mineral are thus clearly related. The matrix–mineral composite bundles are, however, assembled in the various skeletal parts examined with widely different degrees of alignment and order. In the same organism, the crystals are aligned within a range of ±15° in one type of spicule, while they are randomly oriented in another type. The wide heterogeneity in shape, density, and ultrastructure suggests that the girdle mineralized tissues do not fulfill a fundamental role necessary for the survival of the organism. This, together with the lack of chitin in the organic matrix, supports the hypothesis that they evolved separately from the other chiton mineralized tissues, namely the shell plates and teeth.
Who's controlling whom? Infant contributions to maternal play behavior
Authors: Dixon Wallace E. , Hull Smith P.
Published: April 2003

Because the way mothers play with their children may have significant impacts on children's social, cognitive, and linguistic development, researchers have become interested in potential predictors of maternal play. In the present study, 40 mother–infant dyads were followed from child age 5–20 months. Five‐month habituation rate and 13 and 20 month temperamental difficulty were found to be predictive of maternal play quality at 20 months. The most parsimonious theoretical model was one in which habituation was mediated by temperamental difficulty in predicting mother play. Consistent with prior speculation in the literature, these data support the possibility that mothers adjust some aspects of their play behaviors to fit their children's cognitive and temperamental capabilities. Copyright © 2003 John Wiley & Sons, Ltd.
Eddy currents and electrical surface charges
Authors: Baum Eckhard , Erb Otto
Published: April 2003

In eddy current calculations, the displacement current in the non‐conducting space surrounding the eddy current region is usually neglected. This assumption enforces that the electric charge density and the accompanying normal components of the eddy current density on the surface of the eddy current region must vanish.

If the field exiting source currents are not accompanied by charges this assumption may yield acceptable results for the eddy current distribution. However, if the field exiting source currents are accompanied by charges, this assumption may lead to totally wrong results for the current distribution in the eddy current region. An example is given which makes plain this point.

To obtain correct results it is not necessary to employ the full set of Maxwell's equations capable to describe wave propagation phenomena also outside the eddy current region. It is shown in the paper that by replacing the displacement current density in the field describing equations by a specifically chosen current density function makes it possible to determine eddy currents and surface charges within the quasi‐stationary calculation scheme for arbitrary field exciting source currents which may or may not be accompanied by charges. The solution obtained in this way is shown to be unique. Copyright © 2003 John Wiley & Sons, Ltd.
Modelling of photonic bandgap devices by the leaky mode propagation method
Authors: Giorgio Agostino , Gina Perri Anna
Published: April 2003

Main modelling approaches used for investigating the Photonic bandgap (PBG) devices are reviewed. In particular, the model based on Leaky Mode Propagation (LMP) method is described.

A complete analysis of the propagation characteristics, including the determination of modal propagation constants, electromagnetic field harmonics and total field distribution, transmission and reflection coefficients, total forward and backward power flow in the structure, guided and radiated power, and total losses, can be carried out by a computer program based on the LMP approach.

The numerical results have been validated by comparisons with those obtained by using other more complex and expensive models.

The new model shows some significant advantages in terms of very low computational time, absence of any a priori theoretical assumptions and approximations, capability of simulating the actual physical behaviour of the device and fast determination of the bandgap position.Copyright © 2003 John Wiley & Sons, Ltd.
Multiresolution model of electromagnetic wave propagation in dispersive materials
Authors: Barba Ismael , Represa José , Fujii Masafumi , Hoefer Wolfgang J. R.
Published: April 2003

A multiresolution time‐domain (MRTD) technique based on Haar wavelets has been applied to model the propagation of waves in dispersive materials, using a discretization of the convolution equation that governs the behaviour of the media. To validate the method, the reflection coefficient at the interface between air and several different linear dispersive media, as well as the propagation of a plane wave towards a non‐linear dispersive medium have been calculated and compared with other numerical techniques and theoretical results. Copyright © 2003 John Wiley & Sons, Ltd.
Thermodynamics of the Double Helix‐Coil Equilibrium in Tetramethylammonium Gellan: High‐Sensitivity Differential Scanning Calorimetry Data
Authors: Grinberg Valerij Ya. , Burova Tatiana V. , Grinberg Natalia V. , Mashkevich Alexander Ya. , Plashchina Irina G. , Usov Anatoly I. , Shusharina Nadezhda P. , Khokhlov Alexei R. , Navarini Luciano , Cesàro Attilio
Published: April 2003

The order–disorder conformational transition in the tetramethylammonium salt of gellan has been studied by high‐sensitivity differential scanning calorimetry as a function of concentration of the background electrolyte, Me4NCl (0.0025–0.5 M). The transition temperature and enthalpy increase with increasing salt concentration following a logarithmic relation. At the same time, there is a linear correlation between the transition enthalpy and temperature with a positive slope of 0.18 J g−1 K−1. According to Kirchhoff's law, the slope can be considered as a heat capacity increment of the transition. This value is much larger than that expected to arise from electrostatic effects. Thus, it has been suggested that the transition is accompanied by an increase in water accessibility to some less hydrophilic fragments of the primary structure of gellan buried in its ordered conformation. The transition has an λ‐like heat capacity profile and can be therefore defined as a second‐order phase transition. This assignment is in agreement with predictions of a matching model of the double helix‐coil transition. The model fits well to the integral transition curve at 0.5 M Me4NCl, assuming a cooperative length of gellan to be about eight repeating units. This value is close to the size of chain corresponding to the persistent length of gellan in the coil state. The cooperativity parameter in the matching model (σ = 0.62 ± 0.01) indicates a small contribution of the stacking effect into the cooperativity of the transition, while a larger contribution apparently originates from the loop factor. The free energy of transition at a reference temperature (273 K) is a logarithmic function of the concentration of the salt, ΔtG(Cs), as predicted by the counter condensation theory and the Poisson–Boltzmann (PB) model. The latter is preferable because of the low linear charge density parameter (ξ < 1) for the double helix of gellan. Analysis of the ΔtG(Cs) function in terms of the PB model showed that the linear charge density of gellan in the coil conformation needs to be higher than that estimated for the fully stretched chain.

Correlation between the transition enthalpy and the transition temperature for the conformational order–disorder transition in the TMA gellan.

magnified image

Correlation between the transition enthalpy and the transition temperature for the conformational order–disorder transition in the TMA gellan.
Studies in ring opening polymerisation, 6. Tertiary base initiated polymerisation of 5‐phenyl‐1,3‐dioxolan‐2,4‐dione
Authors: Smith Ian Joseph , Tighe Brian John
Published: April 2003

5‐Phenyl‐1,3‐dioxolan‐2,4‐dione (the anhydrocarboxylate derivative of mandelic acid) has been shown to undergo polymerisation in the presence of tertiary organic bases such as pyridine in a reaction that has somewhat unusual characteristics. Thus, although the reaction in nitrobenzene shows first‐order kinetic dependence on both monomer and pyridine over a reasonable concentration range, the pyridine is not consumed and does not appear to control the molecular weight of the resultant polymer. The most important factor in controlling molecular weight is the presence of adventitious moisture which enters into the polymerisation process producing poly‐α‐esters that are hydroxyl/carboxyl terminated. The rate of polymerisation increases progressively as pyridine is replaced by 2‐methylpyridine and 2,6‐dimethylpyridine but decreases dramatically when 2‐methoxypyridine is used, indicating the importance of the basicity of the attacking species. The results are interpreted in terms of the interaction of the basic nitrogen and the C‐4 ring carbonyl leading to the formation of a transient charge transfer complex which subsequently decomposes to form pyridine, carbon dioxide and the α‐lactone. The chain growth process involves the interaction of the α‐lactone with any nucleophiles present which control the molecular weight and nature of the end groups.
Polymerisation via macrozwitterions, 1. Ethyl and butyl cyanoacrylates polymerised by triethyl and triphenylphosphines
Authors: Johnston David Samuel , Pepper David Charles
Published: April 2003

Anionic polymerisation of ethyl and butyl cyanoacrylates in THF initiated by triethyl and triphenylphosphines were followed by adiabatic calorimetry at temperatures between 20 and −95°C. The polymers showed UV absorptions characteristic of phosphonium and cyanoacrylate carbanion end groups, indicating that the growing chains were macrozwitterions. Monomer conversion was quantitative and of 1st order in both monomer and initiator. Other criteria of ‘living’ polymerisation were satisfied, e.g. molecular weights corresponded to one chain per initiator molecule, and indicated that monomer added subsequently was incorporated on to previously formed chains. Assuming the overall rate to be that of propagation yielded values of kp = 1 – 3 · 105 dm3 · mol−1 · s−1 at −78°C, with very low activation energies, i.e. 2,2 and 5,5 kJ · mol−1 for ECA and BCA, respectively. Of a range of inert salts only LiBr significantly reduced the rate of polymerisation.
On L1 decay problem for the dissipative wave equation
Authors: Ono Kosuke
Published: April 2003

We study the decay estimates of solutions to the Cauchy problem for the dissipative wave equation in one, two, and three dimensions. The representation formulas of the solutions provide the sharp decay rates on L1 norms and also Lp norms. Copyright © 2003 John Wiley & Sons, Ltd.
On a first‐order hyperbolic coagulation model
Authors: Ackleh Azmy S. , Deng Keng
Published: April 2003

We consider a first‐order hyperbolic initial–boundary value problem that models coagulation of particles. We establish a comparison principle and construct monotone sequences to show the existence and uniqueness of the solution. Copyright © 2003 John Wiley & Sons, Ltd.
Surface modification and in vitro Blood compatibilities of polyurethanes containing γ‐Benzyl L‐glutamate segments in the main chain
Authors: Hyun Jae‐Yong , Meng Wan , Kang Inn‐Kyu , Song Dong‐Ik
Published: April 2003

Poly(ether urethanes) containing γ‐benzyl L‐glutamate segments in the main chains (PUBLG) were synthesized from 4,4′‐diphenylmethyl diisocyanate, poly(tetramethylene glycol) and γ‐benzyl L‐glutamate oligomer as a chain extender. The surface modification of the PUBLG film was carried out by means of a hydrolysis reaction and heparin immobilization. The surface‐modified PUBLGs were then characterized by attenuated total reflection Fourier‐transform infrared (FT‐IR) spectroscopy and electron spectroscopy for chemical analysis. In vitro blood compatibility of surface‐modified PUBLGs was investigated using plasma proteins, platelets and peripheral blood mononuclear cells. Activated partial thromboplastin time was prolonged on heparin‐immobilized PUBLG (PUBLG‐H), suggesting the binding of immobilized heparin to antithrombin III. The release of serotonin from adhering platelets was significantly suppressed on PUBLG‐H when compared to the other substrates. In the peripheral blood mononuclear cells experiments, the adhesion and activation of the cells were significantly suppressed on PUBLG‐H and the amount of interleukin‐6 released from peripheral blood mononuclear cells stimulated with surface‐modified PUBLGs decreased with a decrease in peripheral blood mononuclear cells adhesion. Copyright © 2003 John Wiley & Sons, Ltd.
Morphology of P(BA‐St‐DAAM) latex particles prepared by seeded‐emulsion polymerization
Authors: Li Huaping , Kan Chengyou , Du Yi , Liu Deshan
Published: April 2003

Seed latex particles of P(styrene‐butyl acrylate) with narrow diameter distribution were first prepared by using ammonium persulfate as initiator at 80 °C for 3 h, then seeded‐emulsion polymerization of styrene, butyl acrylate, methacrylic acid and diacetone acrylamide onto the P(styrene‐butyl acrylate) seed particles was carried out at 85 °C in the absent of emulsifier. In order to investigate the relationship between the polymerization conditions and particle morphology, three different processes of batch, swelling and semi‐continuous monomer additions were used. It was found that latex particles prepared using the swelling process showed no signs of multiphase morphology, while both batch and semi‐continuous processes gave a strawberry‐like particle morphology. A series of polymerizations was carried out using the semi‐continuous process. Results showed that the more acrylamide monomer that was used, the more distinct the phase separation was, and that different monomer feed rates resulted in the same type of particle morphology. Copyright © 2003 John Wiley & Sons, Ltd.
Synthesis and characterization of trifluoromethylated poly(aryl ether ketone)s
Authors: Liu Baijun , Hu Wei , Chen Chunhai , Jiang Zhenhua , Zhang Wanjin , Wu Zhongwen
Published: April 2003

Considerable attention has been devoted to the preparation of fluorine‐containing polymers due to their unique properties and high‐temperature performance. In this paper, we report the synthesis of novel fluorine‐containing poly(aryl ether ketone)s with (3‐fluoromethyl)phenyl or (3,5‐difluoromethyl)phenyl moieties. Novel 3F‐polymers and 6F‐polymers are synthesized from fluorinated bisphenols and dihalides via an aromatic nucleophilic substitution reaction. The high‐molecular‐weight polymers could be obtained despite the steric effect of the bulky pendant groups. The Tgs of polymers ranged from 136 °C to 163 °C. All the polymers exhibited high thermal stability. 3F‐PEEK and 6F‐PEEK showed excellent solubility. The strong, flexible and colorless films were easily obtained by solution casting and compression molding. The near‐infrared spectra showed that the films of 3F‐PEEK and 6F‐PEEK had small light absorption at the telecommunication wavelengths of 1.3 µm and 1.55 µm. Furthermore, 3F‐PEEK, 3F‐PEEKK, 6F‐PEEK, and 6F‐PEEKK exhibited low dielectric constants. The dielectric constants were 2.70, 2.76, 2.69 and 2.78 respectively at 1 MHz. Copyright © 2003 John Wiley & Sons, Ltd.
Synthesis and properties of poly(L‐lactide)‐Poly(Ethylene glycol) multiblock copolymers by coupling triblock copolymers
Authors: Chen Wenna , Luo Weijun , Wang Shenguo , Bei Jianzhong
Published: April 2003

A series of multiblock copolymers of PLLA/PEG(PLE) with high molecular weight were synthesized by coupling PLLA‐PEG‐PLLA triblock copolymers with succinic anhydride in the presence of N‐dimethylaminopyridine(DMAP) and dicyclohexylcarbodimide (DCC). The results of the viscometry measurement, GPC and 1H NMR, elucidated that multiblock PLE copolymers with high content of short PEG segments had been successfully obtained. The thermal properties and the crystallinity were investigated by DSC and X‐ray diffraction. When LA/EG molar ratio and the length of PEG segments were the same in both multiblock and triblock copolymers, multiblock copolymers were less crystalline than the corresponding triblock ones. Mechanical testing showed that multiblock copolymers had relatively high tensile strength and large elongation. In a word, the measurements showed that this multiblock PLE copolymers had high content of short PEG segments (Mn = 2000,4000), high molecular weight (Mw∼50 000), high hydrophilicity, and good mechanical properties. The drug (5‐Fluorourecil) release behavior of these PLE multiblock copolymers had been studied in 0.10M pH7.4 phosphate buffer solution (PBS), and the releasing rate could be tailored by adjusting copolymers composition. All of these results indicated that the multiblock PLE copolymers might be useful in medical applications. Copyright © 2003 John Wiley & Sons, Ltd.
Silica‐based hybrid nonlinear optical chromophore‐trapping film prepared by sol‐gel polymerization
Authors: Ji Shengxiang , Li Ze , Zhou Xiaoshu , Cao Ming , Dai Daorong , Zhang Rongben , Li Shaojun , Ye Cheng
Published: April 2003

A new thermal‐resistant second‐order nonlinear optical film has been prepared by in situ poling and sol–gel processing of 1,4‐phenylene bis(4‐trimethoxylsilylethylbenzoate) (PMSE) and Disperse Red 1 (DR1). The monomer, PMSE, was synthesized by Pt‐catalyzed hydrosilylation reaction followed by alcoholysis reaction. The chromophore DR1 was embedded in the crosslinked organosilicon polymeric matrix. The film was characterized by FTIR, differential scanning calorimeter (DSC), and X‐ray diffraction (XRD). The elemental analysis shows the DR1 content of the poled film to be about 11 wt%. The second‐order harmonic generation (SHG) coefficient (d33) of the film is 16.7 pm/v and its thermal stability studies demonstrate that the onset of d33 decay is about 130 °C. Copyright © 2003 John Wiley & Sons, Ltd.
Catalytic behavior of wool–Rh complex in asymmetric hydrogenation of 2‐methyl furan
Authors: He Man , Zhou Da‐Qing , Ge Hong‐Li , Huang Mei‐Yu , Jiang Ying‐Yan
Published: April 2003

A Wool–Rh complex was prepared by the reaction of wool with RhCl3·3H2O in ethanol solution, and was found to be useful as a chiral catalyst for the asymmetric hydrogenation of 2‐methyl furan to (S)‐(+)‐2‐methyl tetrahydrofuran at 28 °C and under atmospheric hydrogen pressure.

When an appropriate Rh content in the Wool–Rh complex was selected, the yield and optical yield amounted to 53.7 and 76.9%, respectively, and the Wool–Rh complex catalyst could be reused several times without any noticeable loss in its optical catalytic activity.

Wool is a very cheap natural biopolymer ligand, and Wool–Rh complex is very easy to prepare, and it is a very active, enantioselective and stable chiral catalyst for asymmetric hydrogenation of 2‐methyl furan. Copyright © 2003 John Wiley & Sons, Ltd.
Preparation of silica‐supported alginic acid‐L‐glutamic acid–Pt complex and its catalytic behaviors in asymmetric hydrogenation of 4‐methyl‐2‐pentanone
Authors: Xue Lei , Li Bao‐Yu , Huang Mei‐Yu , Jiang Ying‐Yan
Published: April 2003

A new chiral polymer–metal complex, silica‐supported alginic acid‐L‐glutamic acid–Pt complex (SiO2‐AA‐L‐Glu‐Pt), has been prepared by a very simple method and has been found to be able to catalyze the asymmetric hydrogenation of 4‐methyl‐2‐pentanone to give (R)‐(−)‐4‐methyl‐2‐pentanol in 90.8% optical yield at 30 °C and under 1 atm H2. The product and optical yields were greatly affected by the Pt content in the complex, the solvent, the 4‐methyl‐2‐pentanone/Pt molar ratio and the reaction temperature. The catalyst could be reused several times without any great change in its optical catalytic activity. Copyright © 2003 John Wiley & Sons, Ltd.
Light‐emitting alternating copolymers and their intramolecular charge transfer state
Authors: Lin Hongzhen , Yang Junlin , Zheng Min , He Qingguo , Huang Hongmin , Bai Fenglian
Published: April 2003

Two light‐emitting conjugated polymers alternatively involving arylenevinylene and a N‐alkyl carbazole moieties in the main chain were investigated. The formation of an intramolecular charge transfer state was probed within the repetition units of the copolymers. A tail absorption band and dual fluorescence were found for one of the copolymers, poly[(9‐(2‐ethyl‐hexyl)‐9H‐carbazol‐3,6‐ylene)‐alt‐(anthracen‐9,10‐ylene) vinylene], Cz‐PAV. Solvent polarity effects were studied by means of steady‐state spectroscopy and fluorescence‐lifetime measurements. Fluorescence emission spectra at 77 K were also explored. All the results show that a photoinduced intramolecular charge transfer state was formed in Cz‐PAV. The formation of this state may be related to the electron affinity of the acceptor group contained in the copolymer and to the molecular conformation of the copolymer. Copyright © 2003 John Wiley & Sons, Ltd.
Controlled synthesis of poly(carbosiloxane)s
Authors: Kawakami Yusuke
Published: April 2003

Dehydrocoupling polymerization of 1,4‐bis(dimethylsilyl)benzene, 1,3‐bis(dimethylsilyl)benzene, 4,4′‐bis(dimethylsilyl)benzene, and 9,9′‐bis[4‐(dimethylsilyl)‐phenyl]fluorene with water was carried out. The sequential regularity of the polymers was estimated by 1H‐NMR spectroscopy. The reactivity of SiH on the dimethylsilyl group in the dehydrocoupling reaction was found to be almost the same without any connection to the structure of the aromatic groups. Stereoregular and optically active polycarbosiloxanes were also synthesized by polyaddition, polycondensation, and ring‐opening polymerization of optically‐active monomers. Their regio‐ and stereoregularity were investigated by the 13C and 29Si‐NMR, and proved to be dependent upon the optical purity of the monomers. Copyright © 2003 John Wiley & Sons, Ltd.
Synthesis and anti‐HIV activity of ­6‐amino‐6‐deoxy‐(1→3)‐β‐D‐curdlan sulfate
Authors: Borjihan Gereltu , Zhong Guiyun , Baigude Huricha , Nakashima Hedeki , Uryu Toshiyuki
Published: April 2003

6‐Amino‐6‐deoxy‐(1→3)‐β‐D‐curdlan sulfate was synthesized in three steps. First, curdlan was azidized by lithium azide (LiN3) and carbon tetrabromide (CBr4) with triphenylphosphine (Ph3P) in dimethylformamide (DMF). Second, the azido group was reduced to an amino group with sodium borohydride (NaBH4) in dimethyl sulfoxide (DMSO) to afford 6‐amino‐6‐deoxy‐(1→3)‐β‐D‐curdlan. Third, sulfation of the amino‐group‐containing curdlan with a sulfur trioxide‐pyridine complex produced a 6‐amino‐6‐deoxy‐(1→3)‐β‐D‐curdlan sufate exhibiting high anti‐HIV (human immunodeficiency virus) activity (EC50 = 0.912 µg/ml) and low cytotoxicity (CC50 = 2512 µg/ml). Copyright © 2003 John Wiley & Sons, Ltd.
Studies on the rheological properties and compatibility of low molecular weightPC and PS polymer alloy
Authors: Liu Jun , Zhang Ji‐Gui
Published: April 2003

The rheological properties and compatibility of PC/PS containing SMA are determined and the possibility of the alloy being used as a new disc material is also discussed in this paper. The results showed that the ηa of the alloy decreased markedly on increasing the temperature, shear rate and PS content in the alloy. In addition, it was confirmed by DSC that PC was partly compatible with PS. The influence of SMA added into PC/PS on the compatibility was also studied. The results showed that SMA has compatibilization, apparent viscosity ηa of the systems could be lowered by the addition of the compatibilizer, and the results of DSC showed that the Tg of the PC phase got closer to the Tg of the PS phase, until it has only one Tg. Using SEM, the microstructure of the polymer alloy was studied. It indicated compatibilization was better, consistent with the result of DSC. Finally, it is discussed whether the PC/PS alloy systems with the compatibilizer could be used as the substrate material for optical disks. Copyright © 2003 John Wiley & Sons, Ltd.
Silica‐supported chitosan–osmium tetroxide complex catalyzed vicinal hydroxylation of olefins using hexacyanoferrate(III) ion as a cooxidant
Authors: Huang Kai , Liu Hong‐Wen , Dou Xi , Huang Mei‐Yu , Jiang Ying‐Yan
Published: April 2003

Silica‐supported chitosan–osmium tetroxide complex was prepared by a very simple method. This complex (SiO2‐CS‐OsO4) has been found to be able to catalyze the dihydroxylation of styrene, α‐methyl‐styrene, 1‐heptene, 1‐octene and 1‐decene to get (R)‐(−)‐1‐phenyl‐1,2‐ethanediol, (R)‐(−)‐2‐phenyl‐1,2‐propanediol, (S)‐(−)‐1,2‐heptanediol, (S)‐(−)‐1,2‐octanediol and (R)‐(+)‐1,2‐decanediol in the presence of K3Fe(CN)6, K2CO3, t‐BuOH and water at room temperature and under atmospheric pressure. The optical yields amounted to 77.3%, 64.8%, 81.3%, 78.2% and 38.4% respectively, and the product yields were 65.5%, 70%, 89.4%, 51% and 49.6% respectively. The experimental results showed that the OsO4 content in the SiO2‐CS‐OsO4 complex greatly affected the optical yield. This new polymer–Os complex was very easy to prepare and could be reused without any appreciable change in optical catalytic activity. Copyright © 2003 John Wiley & Sons, Ltd.
Regulation of comonomer‐Sequenceand stereosequence in radical copolymerization of methyl methacrylate and styrene
Authors: Hirai Hidefumi
Published: April 2003

The radical copolymerization of methyl methacrylate (MMA) and styrene (St) in the presence of various metal halides was conducted to achieve the advanced regulation of comonomer‐sequence and stereosequence in the resulting copolymers. The alternation‐regulating activities of various metal halides were determined quantitatively by the MMA content in the copolymer prepared under the specific conditions. Boron trichloride, aluminum tribromide and ethyl boron dichloride were found to have large alternation‐regulating activities, yielding the strictly alternating MMA‐St copolymers with high regulation of comonomer‐sequence. The cotacticities of the ‐MMA‐St‐ diad, the ‐St‐MMA‐St‐ triad and the­‐MMA‐St‐MMA‐ triad in the alternating copolymer were determined by 1H‐ and 13C‐NMR spectroscopies. The cotacticities depend on the species and the concentrations of the metal halides, and on the polymerization temperatures. The alternating MMA‐St copolymer with the highest coheterotacticity has been prepared by using boron trichloride at − 95 °C. The mechanism of the stereosequence regulation is described in detail. Copyright © 2003 John Wiley & Sons, Ltd.
Effect of filler loading on cure time and swelling behaviour of SMR L/ENR 25 and SMR L/SBR blends
Authors: Ismail Hanafi , Poh B T , Tan K S , Moorthy M
Published: April 2003

The effect of filler loading on the cure time (t90) and swelling behaviour of SMR L/ENR 25 and SMR L/SBR blends has been studied. Carbon black (N330), silica (Vulcasil C) and calcium carbonate were used as fillers and the loading range was from 0 to 40 phr. Results show that for SMR L/ENR 25 blends the cure time decreases with increasing carbon black loading, whereas silica shows an increasing trend, and calcium carbonate does not show significant changes. For SMR L/SBR blends, the cure time of carbon black, silica and calcium carbonate generally decreases with increasing filler loading. The percentage swelling in toluene and ASTM oil no 3 decreases for both blends with increasing filler loading, with calcium carbonate giving the highest value, followed by silica‐ and carbon black‐filled blends. At a fixed filler loading, SMR L/ENR 25 blend shows a lower percentage swelling than SMR L/SBR blends.

© 2003 Society of Chemical Industry
Comparison of properties of acrylic–polyurethane hybrid emulsions prepared by batch and semibatch processes with monomer emulsion feed
Authors: Šebenik Urška , Golob Janvit , Krajnc Matjaž
Published: April 2003

Aqueous acrylic–polyurethane hybrid emulsions were prepared by batch and semibatch polymerization of acrylic monomer mixtures (butyl acrylate, methyl methacrylate and acrylic acid) in the presence of polyurethane dispersion. The acrylic component was introduced in the monomer emulsion feed. The weight ratio between acrylic and polyurethane components was varied to obtain different emulsion properties, microphase structure and mechanical film properties. Scanning electron microscopy, average particle size and molecular weight measurements were performed to characterize the latex systems. Mechanical properties were examined by measuring Koenig hardnesses of dried films. The average particle size increased with the acrylic/polyurethane ratio. Particles of larger than average size and, to some extent, higher than average molecular weights by batch process were formed. Koenig hardnesses decreased with increasing acrylic/polyurethane ratio. Properties of emulsions synthesized by semibatch processes were compared with the results reported for a different polyurethane dispersion. Copyright © 2003 Society of Chemical Industry
Novolak resins: structure elucidation by multidimensional NMR techniques and correlation with lithographic performance
Authors: Roy Debmalya , Basu PK , Raghunathan P , Eswaran SV
Published: April 2003

Photo‐active chemicals blended with novolak resins, solvents and certain other additives serve as photoresists and are the real workhorses of the burgeoning microlithography industry, which plays a key role in making electronic circuits for ICs and VLSIs at micron and sub‐micron levels. It has been realized over the years that the microstructure of these matrix polymers (novolak resins) is very crucial for better lithographic performance. Although various analytical techniques exist for characterizing novolak resins, precise and unambiguous structural details are obtained only through NMR experiments. In this paper, we review the applications of a range of NMR experimental techniques to the structure elucidation of novolak polymers and co‐polymers. Such information is seen to lead to the design of high‐performance photoresists. The optimum percentage of the different phenolic units in novolak resins, which is very crucial for lithographic performance, can also be determined using these spectroscopic techniques. Using DEPT and INEPT 13C NMR spectra of novolak resins, two formulae have been developed for quantitative estimation of the lithographic performance of photoresists. On the basis of a comparison of the NMR spectra of a photoresist before and after photolysis, the mechanism of action of a photoresist can be probed, and this should lead to a deeper insight into the design of high‐performing photoresists. Copyright © 2003 Society of Chemical Industry