bluuebunny/crossref_metadata_2025 huggingface dataset:
Inhibition of apoptosis in Bacteroides fragilis enterotoxin‐stimulated intestinal epithelial cells through the induction of c‐IAP‐2
Authors: Kim Jung Mogg , Lee Jin Young , Kim Yeong‐Jeon
Published: July 2008

Enterotoxigenic Bacteroides fragilis produces an approximately 20‐kDa heat‐labile enterotoxin (BFT) that plays an essential role in generating mucosal inflammation. Although it is well known that proinflammatory signals are expressed in BFT‐stimulated intestinal epithelial cells, cell death processes have not been elucidated. BFT induced apoptosis in HT‐29 cells, but the apoptosis was first apparent 36 h after stimulation. During the early period of BFT stimulation, expression of cellular inhibitor of apoptosis protein‐2 (c‐IAP2) increased, and inhibition of c‐IAP2 augmented the apoptotic cell death. Inhibition of BFT‐induced COX‐2 expression decreased prostaglandin E2 (PGE2) production, which led not only to a decrease of c‐IAP2 activity but also to an enhancement of DNA fragmentation in the early period of BFT stimulation. Furthermore, apoptosis inhibition through PGE2 and c‐IAP2 was mainly regulated by a p38 mitogen‐activated protein kinase (MAPK). These results suggest that the inhibition of apoptosis may be mediated by a sequential pathway, including MAPK, COX‐2, PGE2 and c‐IAP2, in the early period of stimulation. The delay in the onset of epithelial cell apoptosis after enterotoxigenic B. fragilis infection may be important to the host since it can provides sufficient time for epithelial cells to generate signals for the activation of mucosal inflammation and it may increase the chances of bacterial colonization.
DNA fusion gene vaccination mobilizes effective anti‐leukemic cytotoxic T lymphocytes from a tolerized repertoire
Authors: Rice Jason , Dossett Michelle L. , Öhlén Claes , Buchan Sarah L. , Kendall Timothy J. , Dunn Stuart N. , Stevenson Freda K. , Greenberg Philip D.
Published: July 2008

The majority of known human tumor‐associated antigens derive from non‐mutated self proteins. T cell tolerance, essential to prevent autoimmunity, must therefore be cautiously circumvented to generate cytotoxic T cell responses against these targets. Our strategy uses DNA fusion vaccines to activate high levels of peptide‐specific CTL. Key foreign sequences from tetanus toxin activate tolerance‐breaking CD4+ T cell help. Candidate MHC class I‐binding tumor peptide sequences are fused to the C terminus for optimal processing and presentation. To model performance against a leukemia‐associated antigen in a tolerized setting, we constructed a fusion vaccine encoding an immunodominant CTL epitope derived from Friend murine leukemia virus gag protein (FMuLVgag) and vaccinated tolerant FMuLVgag‐transgenic (gag‐Tg) mice. Vaccination with the construct induced epitope‐specific IFN‐γ‐producing CD8+ T cells in normal and gag‐Tg mice. The frequency and avidity of activated cells were reduced in gag‐Tg mice, and no autoimmune injury resulted. However, these CD8+ T cells did exhibit gag‐specific cytotoxicity in vitro and in vivo. Also, epitope‐specific CTL killed FBL‐3 leukemia cells expressing endogenous FMuLVgag antigen and protected against leukemia challenge in vivo. These results demonstrate a simple strategy to engage anti‐microbial T cell help to activate epitope‐specific polyclonal CD8+ T cell responses from a residual tolerized repertoire.
Dysregulation of the host mevalonate pathway during early bacterial infection activates human TCR γδ cells
Authors: Kistowska Magdalena , Rossy Emmanuel , Sansano Sebastiano , Gober Hans‐Jürgen , Landmann Regine , Mori Lucia , De Libero Gennaro
Published: July 2008

Primates, but not rodents, have T cell receptor Vγ9‐Vδ2 T cells bridging innate and adaptive antimicrobial immunity. This T cell population is activated by prenyl pyrophosphates isolated from microbial or eukaryotic cells. Although the microbial metabolites are more active than the cellular ones, their involvement in TCR γδ activation during infection has not been studied. Here, we show that, during the initial phases of infections withEscherichia coliandStaphylococcus aureus, TCR γδ cells are activated by endogenous mevalonate metabolites. Infections with low bacteria inocula up‐regulate the production and accumulation of host‐derived TCR γδ stimulatory antigens within 1 h, which is followed by a peak of TCR γδ cell activation at 5 h. Infections induce the accumulation and dephosphorylation of the hydroxymethylglutaryl‐coenzyme A reductase, the rate‐limiting enzyme of the mevalonate pathway, resulting in increased activity of this enzyme and in increased synthesis of intermediate metabolites. Thus, primates have evolved the ability to readily respond to bacterial infection by sensing the dysregulation of the mevalonate pathway within infected cells, as a mechanism of immediate antimicrobial immunity.

Supporting Information for this article is available at http://www.wiley‐vch.de/contents/jc_2040/2008/38366_s.pdf
Evidence that the KIR2DS5 gene codes for a surface receptor triggering natural killer cell function
Authors: Chiesa Mariella Della , Romeo Elisa , Falco Michela , Balsamo Mirna , Augugliaro Raffaella , Moretta Lorenzo , Bottino Cristina , Moretta Alessandro , Vitale Massimo
Published: July 2008

In this study, after immunization with NK cells from a KIR2DS5+ donor and screening on cell transfectants expressing different members of the killer immunoglobulin‐like receptor (KIR) family, we generated a mAb, DF200, reacting with several KIR2D receptors including KIR2DL1/L2/L3, KIR2DS1/S2 and KIR2DS5. By the analysis of peripheral blood NK cells and in vitro derived NK cell clones, we have demonstrated for the first time that KIR2DS5 is expressed at the cell surface in discrete subsets of NK cells and, after DF200 mAb‐mediated engagement, can induce both cytotoxicity and cytokine release. Using co‐transfection and co‐immunoprecipitation, we found that KIR2DS5 associates with the DAP12 signaling polypeptide. Finally, soluble KIR2DS5‐Fc fusion protein does not bind to cell transfectants expressing different HLA‐C alleles, suggesting that, if KIR2DS5 does recognize HLA‐C molecules, this may only occur in the presence of certain peptides.
The Nlrp3 inflammasome is critical for aluminium hydroxide‐mediated IL‐1β secretion but dispensable for adjuvant activity
Authors: Franchi Luigi , Núñez Gabriel
Published: July 2008

Aluminum hydroxide (alum) is the most widely used adjuvant in human vaccines, but the immune mechanisms that are activated by alum remain poorly understood. Alum has recently been shown to promote caspase‐1 activation and IL‐1β secretion, but the cellular pathways involved remain elusive. Here we report that the release of IL‐1β triggered by alum is abrogated in macrophages deficient in the NLR family, pyrin domain containing 3 (Nlrp3) protein and the apoptosis‐associated speck‐like protein containing a caspase recruitment domain (Asc) but not the NLR family, CARD domain containing 4 (Nlrc4) protein. The requirement of the Nlrp3 inflammasome was specific for IL‐1β in that secretion of TNF‐α was independent of Nlrp3 or Asc. Consistently, processing of pro‐caspase‐1 induced by alum was abolished in macrophages lacking Nlrp3 or Asc. Unlike caspase‐1 processing and IL‐1β secretion triggered by LPS, alum‐mediated activation of the inflammasome did not require exogenous ATP. Importantly, induction of IgG production against human serum albumin by alum was unimpaired in mice deficient in Nlrp3. These results indicate that alum induces IL‐1β via the Nlrp3 inflammasome but this activity is dispensable for alum‐mediated adjuvant activity.

See accompanying article: http://dx.doi.org/10.1002/eji.200838648
Intrasplenic trafficking of natural killer cells is redirected by chemokines upon inflammation
Authors: Grégoire Claude , Cognet Céline , Chasson Lionel , Coupet Charles‐Antoine , Dalod Marc , Reboldi Andrea , Marvel Jacqueline , Sallusto Federica , Vivier Eric , Walzer Thierry
Published: July 2008

The spleen is a major homing site for NK cells. How they traffic to and within this site in homeostatic or inflammatory conditions is, however, mostly unknown. Here we show that NK cells enter the spleen through the marginal sinus and home to the red pulp via a pertussis toxin‐insensitive mechanism. Upon inflammation induced by poly(I:C) injection or mouse cytomegalovirus infection, many NK cells left the red pulp while others transiently entered the white pulp, predominantly the T cell area. This migration was dependent on both CXCR3 and CCL5, suggesting a synergy between CXCR3 and CCR5, and followed the path lined by fibroblastic reticular cells. Thus, the entry of NK cells in the white pulp is limited by the expression of pro‐inflammatory chemokines. This phenomenon ensures the segregation of NK cells outside of the white pulp and might contribute to the control of immunopathology.
An Overview of Palladium Nanocatalysts: Surface and Molecular Reactivity
Authors: Durand Jérôme , Teuma Emmanuelle , Gómez Montserrat
Published: July 2008

The use of metallic nanoparticles in catalysis under homogeneous conditions leads to a discussion of their catalytic nature: whether the catalyst behaves as a molecular species or, on the contrary, the metallic surface is directly involved in the reactivity. This dilemma is intrinsically associated to the kinetic stability of the nanoclusters, favouring their agglomeration, and also to the formation of molecular species by reaction of the atoms placed at low‐coordination positions at the metallic surface. In particular, for palladium‐catalyzed processes, a large number of contributions have been reported in the last decade involving nanoparticles, but few of them analyze the mechanistic aspects. The present review aims to collect the more relevant research carried out in catalysis involving palladium nanoparticles in the liquid phase and addressing the nature of the catalytically active species. This kind of work is mainly focused on hydrogenation and C–C coupling processes.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)
Synthesis and Anion‐Binding Properties of Novel Redox‐Active Calixarene Receptors
Authors: Métay Estelle , Duclos Marie Christine , Pellet‐Rostaing Stéphane , Lemaire Marc , Schulz Jürgen , Kannappan Ramu , Bucher Christophe , Saint‐Aman Eric , Chaix Carole
Published: July 2008

A novel synthetic approach towards redox‐active calixarene‐based receptors is described in which ferrocene fragments were introduced at the lower rim through anion‐binding urea or amide connections. These derivatives were prepared in one pot by treating an amine‐containing calixarene with ferrocenecarboxylic acid in the presence of diphenylphosphoryl azide and diisopropylethylamine. This method allows a convergent approach to these receptors and is readily adaptable to the introduction of other urea substituents. The anion‐binding properties of these artificial receptors have been revealed by NMR spectroscopy and thoroughly investigated by electrochemical methods. We have assessed the importance of the urea–phosphate bonds in the observed electrochemical response by studying receptors in which the ferrocene reporters and binding fragments are closely associated or fully disconnected through a long alkyl chain. The experimental results clearly show the utmost importance of ion‐pairing effects in the electrochemical recognition process, which account for most of the transduction signal in organic apolar media. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)
Remarkable Stability of Imino Macrocycles in Water
Authors: Saggiomo Vittorio , Lüning Ulrich
Published: July 2008

Imines 3, 5 and 7 generated from 4‐methoxypyridine‐2,6‐dicarbaldehyde (1) and several amines 2, 4 and 6 show a remarkable stability in water. The 18‐membered macrocyclic diimine 5 is stable and could be synthesized in good yield by using 2 equiv. of calcium ions as template in pure water, and even the non‐macrocyclic diimine 3 survives in water/methanol (50:50) without any template effect. In a mixture of pyridinedicarbaldehyde 1 and two glycol‐derived diamines 4 and 6, a calcium template ion selects the 18‐membered macrocycle 5 over the 20‐membered one (7). (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)
Have newer cardiovascular drugs reduced hospitalization? Evidence from longitudinal country‐level data on 20 OECD countries, 1995–2003
Authors: Lichtenberg Frank R.
Published: July 2008

This study examines the effect of changes in the vintage distribution of cardiovascular system drugs on hospitalization and mortality due to cardiovascular disease using longitudinal country‐level data. The vintage of a drug is the first year in which it was marketed anywhere in the world. We use annual data on the utilization of over 1100 cardiovascular drugs (active ingredients) in 20 OECD countries during the period 1995–2003.

Countries with larger increases in the share of cardiovascular drug doses that contained post‐1995 ingredients had smaller increases in the cardiovascular disease hospital discharge rate, controlling for the quantity of cardiovascular medications consumed per person, the use of other medical innovations (computed tomography scanners and magnetic resonance imaging units), potential risk factors (average consumption of calories, tobacco, and alcohol), and demographic variables (population size and age structure, income, and educational attainment). The estimates also indicate that the use of newer cardiovascular drugs has reduced the average length of stay and the age‐adjusted cardiovascular mortality rate, but not the number of potential years of life lost due to cardiovascular disease before age 70 per 100 000 population.

The estimates indicate that if drug vintage had not increased during 1995–2004, hospitalization and mortality would have been higher in 2004. We estimate that per capita expenditure on cardiovascular hospital stays would have been 70% ($89) higher in 2004 had drug vintage not increased during 1995–2004. Per capita expenditure on cardiovascular drugs would have been lower in 2004 had drug vintage not increased during 1995–2004. However, our estimate of the increase in expenditure on cardiovascular hospital stays is about 3.7 times as large as our estimate of the reduction in per capita expenditure for cardiovascular drugs that would have occurred ($24). Copyright © 2008 John Wiley & Sons, Ltd.
Chromium supplementation improves glucose tolerance in diabetic Goto‐Kakizaki rats
Authors: Abdourahman Aicha , Edwards John G.
Published: July 2008

Chromium supplementation (Cr) may be useful in the management of diabetes and appears to improve some aspects of glucose handling. However, several studies have used either high doses of Cr supplementation or have placed control animals on a Cr‐deficient diet. We therefore wanted to test whether Cr dosages in the ranges that more closely approximate recommended levels of supplementation in humans are efficacious in glycemic control under normal dietary conditions. Euglycemic Wistar or diabetic Goto‐Kakizaki (GK) rats (a model of nonobese NIDDM) were assigned to water (control) or chromium picolinate (Cr‐P) supplementation (1 or 10 mg/kg/day) groups for up to 32 weeks. Glucose tolerance was tested following an overnight fast by injecting sterile glucose (1.0 g/kg, i.p.) and then measuring blood glucose at select times to determine the sensitivity to glucose by calculation of the area under the curve. Cr‐P did not significantly alter the growth of the animals. In the euglycemic Wistar rats, Cr‐P supplementation did not alter the response to a glucose tolerance test. In the GK rats, Cr‐P supplementation significantly improved glucose tolerance at both levels of Cr‐P supplementation (1 mg/kg/day: H20; 100 ± 11%; Cr‐P 70 ± 8%; 10 mg/kg/day: H20; 100 ± 10%; Cr‐P 66 ± 9 %). Cr‐P supplementation produced a small improvement in some indices of glycemic control. There were no differences observed for the two levels of Cr‐P supplementation suggested that we did not identify a threshold for Cr‐P effects, and future studies may use lower doses to find a threshold effect for improving glucose tolerance in diabetics. © 2008 IUBMB IUBMB Life, 60(8): 541–548, 2008
Versatile laser‐based cell manipulator
Authors: Maghelli Nicola , Tolić‐Nørrelykke Iva M.
Published: July 2008

Here we describe a two‐photon microscope and laser ablation setup combined with optical tweezers. We tested the setup on the fission yeast Schizosaccharomyces pombe, a commonly used model organism. We show that long‐term imaging can be achieved without significant photo‐bleaching or damage of the sample. The setup can precisely ablate sub‐micrometer structures, such as microtubules and mitotic spindles, inside living cells, which remain viable after the manipulation. Longer exposure times lead to ablation, while shorter exposures lead to photo‐bleaching of the target structure. We used optical tweezers to trap intracellular particles and to displace the cell nucleus. Two‐photon fluorescence imaging of the manipulated cell can be performed simultaneously with trapping. The combination of techniques described here may help to solve a variety of problems in cell biology, such as positioning of organelles and the forces exerted by the cytoskeleton. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Zinc oxide: A case study in contemporary computational solid state chemistry
Authors: Catlow C. Richard A. , French Samuel A. , Sokol Alexey A. , Al‐Sunaidi Abdullah A. , Woodley Scott M.
Published: July 2008

Computational techniques have been applied to study a broad range of chemical and physical properties of zinc oxide. Both interatomic‐potential and density functional theory methods are used to investigate structural, thermodynamic, surface, and defect properties. We survey the structures and energies of nano‐particulate zinc oxide. © 2008 Wiley Periodicals, Inc. J Comput Chem 2008
A combined ab initio and Franck‐Condon factor simulation study on the photodetachment spectrum of ScO2−
Authors: Lee Edmond P. F. , Mok Daniel K. W. , Chau Foo‐Tim , Dyke John M.
Published: July 2008

Restricted‐spin coupled‐cluster single‐double plus perturbative triple excitation {RCCSD(T)} potential energy functions (PEFs) of the $ \tilde X $2B2 state of ScO2 and the $ \tilde X $1A1 state of ScO2− were computed, employing the augmented correlation‐consistent polarized‐weighted core‐valence quadruple‐zeta (aug‐cc‐pwCVQZ) basis set for Sc and augmented correlation‐consistent polarized valence quadruple‐zeta (aug‐cc‐pVQZ) basis set for O, and with the outer core Sc 3s23p6 electrons being explicitly correlated. Franck‐Condon factors, which include allowance for Duschinsky rotation and anharmonicity, were calculated using the computed RCCSD(T) PEFs, and were used to simulate the first photodetachment band of ScO2−. The simulated spectrum matches well with the corresponding experimental 355 nm photodetachment spectrum of Wu and Wang, J Phys Chem A 1998, 102, 9129, confirming the assignment of the photodetachment spectrum and the reliability of the RCCSD(T) PEFs used. Further calculations on low‐lying electronic states of ScO2 gave adiabatic relative electronic energies (Te's) of, and vertical excitation energies (Tv's) to, the $ \tilde A $2A1, $ \tilde B $2B1, and $ \tilde C $2A2 states of ScO2 (from the $ \tilde X $2B2 state of ScO2), as well as electron affinities (EAs) and vertical detachment energies (VDEs) to these neutral states from the $ \tilde X $1A1 state of ScO2−. © 2008 Wiley Periodicals, Inc. J Comput Chem, 2009
Enveloping triangulation method for detecting internal cavities in proteins and algorithm for computing their surface areas and volumes
Authors: Buša Ján , Hayryan Shura , Hu Chin‐Kun , Skřivánek Jaroslav , Wu Ming‐Chya
Published: July 2008

Detection and quantitative characterization of the internal cavities in proteins remain an important topic in studying protein structure and function. Here we propose a new analytical method for detecting the existence of cavities in proteins. The method is based on constructing the special enveloping triangulation enclosing the cavities. Based on this method, we develop an algorithm and a fortran package, CAVE, for computing volumes and surface areas of cavities in proteins. We first test our method and algorithm in some artificial systems of spheres and find that the calculated results are consistent with exact results. Then we apply the package to compute volumes and surface areas of cavities for some protein structures in the Protein Data Bank. We compare our calculated results with those obtained by some other methods and find that our approach is reliable. © 2008 Wiley Periodicals, Inc. J Comput Chem, 2009
Force‐field modeling through quantum mechanical calculations: Molecular dynamics simulations of a nematogenic molecule in its condensed phases
Authors: Cacelli Ivo , Lami Carlo Federico , Prampolini Giacomo
Published: July 2008

Interaction energy of the 4‐n‐pentyloxy‐4′‐cyanobiphenyl (5OCB) dimer is computed at MP2 level, for many geometrical arrangements using the Fragmentation Reconstruction Method (FRM). DFT calculations are performed for a number of geometries of the monomer. The resulting database is used to parameterize an atomistic intra‐ and inter‐molecular force‐field suitable for classical bulk simulations. Several structural and dynamical properties in 5OCB isotropic and liquid crystalline phases are computed from molecular dynamics simulation mainly in the NPT ensemble. Lengthy runs (more than 70 ns) and large sample sizes (up to 806 molecules) were used to determine the nematic to isotropic transition temperature up to a precision of few K. Good agreement was found in most of the investigated properties, thus validating the accuracy of the proposed model potential, only derived by quantum mechanical calculations. © 2008 Wiley Periodicals, Inc. J Comput Chem, 2009
Møller–Plesset perturbation energies and distances for HeC20 extrapolated to the complete basis set limit
Authors: Varandas A. J. C.
Published: July 2008

The potential energy surface for the C20–He interaction is extrapolated for three representative cuts to the complete basis set limit using second‐order Møller–Plesset perturbation calculations with correlation consistent basis sets up to the doubly augmented variety. The results both with and without counterpoise correction show consistency with each other, supporting that extrapolation without such a correction provides a reliable scheme to elude the basis‐set‐superposition error. Converged attributes are obtained for the C20– He interaction, which are used to predict the fullerene dimer ones. Time requirements show that the method can be drastically more economical than the counterpoise procedure and even competitive with Kohn‐Sham density functional theory for the title system. © 2008 Wiley Periodicals, Inc. J Comput Chem, 2009
Modeling high pressure reactivity in unsaturated systems: Application to dimethylacetylene
Authors: Mediavilla C. , Tortajada J. , Baonza V. G.
Published: July 2008

A general model is introduced to study pressure‐induced reactivity on unsaturated systems in the condensed state. The model is applied here to dimethylacetylene (DMA) in the solid phase II (C/2m) because it has been proposed that two DMA molecules can react to form tetramethyl‐cyclobutadiene (TMCBD). The proposed reaction process has been modeled by studying the structural and electronic changes undergone by two DMA molecules as they approach each other preserving the crystal symmetry of phase II. Both monodeterminantal (MP2 and DFT) and multideterminantal (CASSCF and MRMP2) methodologies were used to check the reliability of our model in predicting the reactivity of the system under compression. In all cases, structural results are in agreement with low‐temperature diffraction experiments for the solid phase II. Our model indicates that DMA is expected to form the TMCBD dimer at intermolecular distances close to 2 Å. This value is in excellent agreement with previous calculations on the existence of long carbon–carbon bonds. © 2008 Wiley Periodicals, Inc. J Comput Chem, 2009
Application of semiempirical long‐range dispersion corrections to periodic systems in density functional theory
Authors: Kerber Torsten , Sierka Marek , Sauer Joachim
Published: July 2008

Ewald summation is used to apply semiempirical long‐range dispersion corrections (Grimme, J Comput Chem 2006, 27, 1787; 2004, 25, 1463) to periodic systems in density functional theory. Using the parameters determined before for molecules and the Perdew‐Burke‐Ernzerhof functional, structure parameters and binding energies for solid methane, graphite, and vanadium pentoxide are determined in close agreement with observed values. For methane, a lattice constant a of 580 pm and a sublimation energy of 11 kJ mol−1 are calculated. For the layered solids graphite and vanadia, the interlayer distances are 320 pm and 450 pm, respectively, whereas the graphite interlayer energy is −5.5 kJ mol−1 per carbon atom and layer. Only when adding the semiempirical dispersion corrections, realistic values are obtained for the energies of adsorption of C4 alkenes in microporous silica (−66 to −73 kJ mol−1) and the adsorption and chemisorption (alkoxide formation) of isobutene on acidic sites in the micropores of zeolite ferrierite (−78 to −94 kJ mol−1). As expected, errors due to missing self‐interaction correction as in the energy for the proton transfer from the acidic site to the alkene forming a carbenium ion are not affected by the dispersion term. The adsorption and reaction energies are compared with the results from Møller‐Plesset second‐order perturbation theory with basis set extrapolation. © 2008 Wiley Periodicals, Inc. J Comput Chem 2008
Acyclic systems of representatives and acyclic colorings of digraphs
Authors: Aharoni Ron , Berger Eli , Kfir Ori
Published: July 2008

A natural digraph analog of the graph theoretic concept of “an independent set” is that of “an acyclic set of vertices,” namely a set not spanning a directed cycle. By this token, an analog of the notion of coloring of a graph is that of decomposition of a digraph into acyclic sets. We extend some known results on independent sets and colorings in graphs to acyclic sets and acyclic colorings of digraphs. In particular, we prove bounds on the topological connectivity of the complex of acyclic sets, and using them we prove sufficient conditions for the existence of acyclic systems of representatives of a system of sets of vertices. These bounds generalize a result of Tardos and Szabó. We prove a fractional version of a strong‐acyclic‐coloring conjecture for digraphs. © 2008 Wiley Periodicals, Inc. J Graph Theory 59: 177–189, 2008
On planar intersection graphs with forbidden subgraphs
Authors: Pach János , Sharir Micha
Published: July 2008

Let ${\cal C}$ be a family of n compact connected sets in the plane, whose intersection graph $G({\cal C})$ has no complete bipartite subgraph with k vertices in each of its classes. Then $G({\cal C})$ has at most n times a polylogarithmic number of edges, where the exponent of the logarithmic factor depends on k. In the case where ${\cal C}$ consists of convex sets, we improve this bound to O(n log n). If in addition k = 2, the bound can be further improved to O(n). © 2008 Wiley Periodicals, Inc. J Graph Theory 59: 205–214, 2008
Polycyanurate Thermoset Networks with High Thermal, Mechanical, and Hydrolytic Stability Based on Liquid Multifunctional Cyanate Ester Monomers with Bisphenol A and AF Units
Authors: Yameen Basit , Duran Hatice , Best Andreas , Jonas Ulrich , Steinhart Martin , Knoll Wolfgang
Published: July 2008

Two cyanate ester monomers (CEMs) based on oligomeric aryl ether (OAE) derivatives of bisphenol AF and bisphenol A, with multiple reactive cyanate groups, were developed as technologically highly relevant thermosets. These CEMs are liquids processable at room temperature and can be crosslinked by cyclotrimerization of the cyanate groups to form extended polycyanurate (PC) networks at lower temperatures (<265 °C) than many existing CEMs. The cured PCs have high Tgs (>280 °C), with excellent thermal, mechanical, and dielectric properties. PC nanorods with diameters of 65 or 380 nm could be moulded in porous alumina templates from the OAE‐CEMs. The high aspect ratio nanorods with a length in the order of 100 µm were hydrolytically stable upon extended exposure to boiling water.

magnified image
Macromol. Chem. Phys. 14/2008
Authors: Kessler Daniel , Teutsch Carmen , Theato Patrick
Published: July 2008

Cover: Inorganic‐organic hybrid polymers based on poly‐(methylsilsesquioxane) have been synthesized utilizing ATRP. Different polymeric ATRP initiators were prepared by co‐condensation of functionalized trichlorosilanes with methyltrimethoxysilane. Various vinyl monomers have been grafted from the macro initiators. Spin‐coating these hybrid materials onto various substrates resulted in stable and adherent surface coatings exhibiting high contact angles. Further details can be found in the article by D. Kessler, C. Teutsch, and P. Theato* on page 1437.
Dual Electric Field Induced Alignment of Electrospun Nanofibers
Authors: Acharya Manoranjan , Arumugam Ganesh Kumar , Heiden Patricia A.
Published: July 2008

A dual‐field method is described to produce aligned fibers by electrospinning. By applying a secondary electric field perpendicular to the primary field, control over the orientation of the fibers on the collector is obtained. The dual‐field approach is used in conjunction with dual electrodes and a rotating collector. Both approaches were used to electrospin poly(lactic acid) fibers under conditions intended to produce fibers with a diameter greater then 400 nm to aid observation by optical microscopy and digital photography. Digital photography was used to visualize a large area of aligned fiber and image analysis software was used to quantify the degree of alignment. Fibers aligned with the aid of a dual field showed better alignment than those from a single electric field under otherwise identical conditions.

magnified image
On the absolutely continuous spectrum of block operator matrices
Authors: Albeverio Sergio , Konstantinov Alexei
Published: July 2008

We prove an abstract theorem on the preservation of the absolutely continuous spectrum for block operator matrices. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A new constraint qualification for the formula of the subdifferential of composed convex functions in infinite dimensional spaces
Authors: Boţ Radu Ioan , Grad Sorin‐Mihai , Wanka Gert
Published: July 2008

In this paper we work in separated locally convex spaces where we give equivalent statements for the formulae of the conjugate function of the sum of a convex lower‐semicontinuous function and the precomposition of another convex lower‐semicontinuous function which is also K ‐increasing with a K ‐convex K ‐epi‐closed function, where K is a nonempty closed convex cone. These statements prove to be the weakest constraint qualifications given so far under which the formulae for the subdifferential of the mentioned sum of functions are valid. Then we deliver constraint qualifications inspired from them that guarantee some conjugate duality assertions. Two interesting special cases taken from the literature conclude the paper. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Bi‐commutators of fractional integrals on product spaces
Authors: Chen Wengu , Han Yongsheng , Miao Changxing
Published: July 2008

Recently Lacey extended Chanillo's boundedness result of commutators with fractional integrals to a higher parameter setting. In this paper, we extend Lacey's result to higher dimensional spaces by a different method. Our method is in terms of the dual relationship between product BMO and product Hardy space and the maximal function characterization of product Hardy spaces obtained by S.‐Y.Chang and R. Fefferman. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On a generalized dimension of self‐affine fractals
Authors: He Xing‐Gang , Lau Ka‐Sing
Published: July 2008

For ad×dexpanding matrixA, we de.ne a pseudo‐normw(x) in terms ofAand use this pseudo‐norm (instead of the Euclidean norm) to define the Hausdorff measure and the Hausdorff dimension dimwHEfor subsetsEinRd. We show that this new approach gives convenient estimations to the classical Hausdorff dimension dimwHE, and in the case that the eigenvalues ofAhave the same modulus, then dimwHEand dimHEcoincide. This setup is particularly useful to study self‐affine setsTgenerated byϕj(x) =A–1(x+dj),dj∈Rd,j= 1, …,N. We use it to investigate the fractality ofTfor the case that {ϕj}Nj=1satisfying the open set condition as well as the cases without the open set condition. We extend some well‐known results in the self‐similar sets to the self‐af.ne sets. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
An exterior boundary value problem in Minkowski space
Authors: López Rafael
Published: July 2008

In three‐dimensional Lorentz–Minkowski space 𝕃3, we consider a spacelike plane Π and a round disc Ω over Π. In this article we seek the shapes of unbounded surfaces whose boundary is ∂ Ω and its mean curvature is a linear function of the distance to Π. These surfaces, called stationary surfaces, are solutions of a variational problem and governed by the Young–Laplace equation. In this sense, they generalize the surfaces with constant mean curvature in 𝕃3. We shall describe all axially symmetric unbounded stationary surfaces with special attention in the case that the surface is asymptotic to Π at the infinity. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Strong convergence of an iterative method for non‐expansive mappings
Authors: Song Yisheng , Chen Rudong
Published: July 2008

Let E be a real reflexive Banach space having a weakly continuous duality mapping Jφ with a gauge function φ, and let K be a nonempty closed convex subset of E. Suppose that T is a non‐expansive mapping from K into itself such that F (T) ≠ ∅︁. For an arbitrary initial value x0 ∈ K and fixed anchor u ∈ K, define iteratively a sequence {xn } as follows:

xn +1 = αn u + βn xn + γn Txn , n ≥ 0,

where {αn }, {βn }, {γn } ⊂ (0, 1) satisfies αn +βn + γn = 1, (C 1) limn →∞ αn = 0, (C 2) ∑∞n =1 αn = ∞ and (B) 0 < lim infn →∞ βn ≤ lim supn →∞ βn < 1. We prove that {xn } converges strongly to Pu as n → ∞, where P is the unique sunny non‐expansive retraction of K onto F (T). We also prove that the same conclusions still hold in a uniformly convex Banach space with a uniformly Gâteaux differentiable norm or in a uniformly smooth Banach space. Our results extend and improve the corresponding ones by C. E. Chidume and C. O. Chidume [Iterative approximation of fixed points of non‐expansive mappings, J. Math. Anal. Appl. 318, 288–295 (2006)], and develop and complement Theorem 1 of T. H. Kim and H. K. Xu [Strong convergence of modified Mann iterations, Nonlinear Anal. 61, 51–60 (2005)]. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Gauges for the self‐similar sets
Authors: Wen Sheng‐You , Wen Zhi‐Xiong , Wen Zhi‐Ying
Published: July 2008

For a self‐similar set E with the open set condition we completely determine the class of its Hausdorff gauges and the class of its prepacking gauges. Moreover, its Hausdorff measures and its packing premeasures with respect to the corresponding gauges are estimated. Without the open set condition we prove that a doubling gauge function is a packing gauge of E if and only if it is a prepacking gauge of E. Also, we give some extensions and applications of these results. Here a gauge function is called a Hausdorff, a prepacking, and a packing gauge of a set, if with respect to the function the set has positive and finite Hausdorff measure, packing premeasure, and packing measure, respectively. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Some remarks on essential self‐adjointness and ultracontractivity of a class of singular elliptic operators
Authors: Pang Michael M. H.
Published: July 2008

We study the properties of essential self‐adjointness on C∞c (ℝN ) and semigroup ultracontractivity of a class of singular second order elliptic operators

equation image

defined in L2 (ℝN , σ–a –N (x) dx) with Dirichlet boundary conditions, where a, b ∈ ℝ and σ: ℝN → (0, ∞) is a C∞‐function satisfying

c‐1(1 + |x |) ≤ σ (x) ≤ c (1 + |x |) (x ∈ ℝN).

We also obtain sharp short time upper and lower diagonal bounds on the heat kernel of e –Ht. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Functionalization of Crosslinked Vesicles by Co‐Self‐Assembly of a Gelable Diblock Copolymer and Mercaptosilane
Authors: Xiong Ming , Chen Yongming , Maskos Michael
Published: July 2008

Herein, a convenient and general method to simultaneously fix and functionalize polymeric vesicles with sulphydryl groups by the co‐self‐assembly of poly(ethylene oxide)‐block‐poly[3‐(triethoxysilyl)propyl methacrylate] (PEO‐b‐PTESPMA) and 3‐mercaptopropyltrialkoxysilane in an aqueous solution is reported. The presence of sulphydryl groups across the vesicle membrane has been confirmed by using an energy‐filtered technique during TEM analysis and by capturing Au nanoparticles.

magnified image
Macromol. React. Eng. 4/2008
Authors: Zhu Xiaoxiang , Li Bo‐Geng , Wu Linbo , Zheng Yougui , Zhu Shiping , Hungenberg Klaus‐Dieter , Müssig Stefan , Reinhard Birgit
Published: July 2008

Cover: The graft polymerization of vinyl acetate (VAc) from poly(ethylene glycol) (PEG) was investigated by both experiments and modeling work. The graph on the left of the cover picture illustrates the graft copolymer molecular weight as determined by definitive calculation, GPC with PVAc or PEG calibration, and the model prediction. Using the correlated Arrhenius expression of the chain transfer constant to PEG(CPEG), the graft copolymer molecular weights at various temperatures was predicted in the figure on the right. Further details can be found in the article by X. Zhu, B.‐G. Li,* L. Wu, Y. Zheng, S. Zhu,* K.‐D. Hungenberg, S. Müssig, and B. Reinhard on page 321.
Inorganic–organic hybrid alginate beads with LCST near human body temperature for sustained dual‐sensitive drug delivery
Authors: Shi Jun , Liu Lihua , Liu Xiaopei , Sun Ximeng , Cao Shaokui
Published: July 2008

In order to obtain dual‐stimuli‐responsive (temperature/pH) alginate beads that exhibit LCST close to human body temperature for sustained drug release applications, poly (NIPAAm‐co‐AAm) hydrogel (with LCST 37.5°C) were selected and associated with calcium alginate to prepare inorganic–organic hybrid biomineralized polysaccharide alginate beads via a one‐step method in this paper. Scanning electron microscopy (SEM) and energy dispersive X‐ray spectrometer (EDS) results demonstrated that calcium phosphate could not only be found in the surface but also in the cross‐section of biomineralized polysaccharide beads. Both equilibrium swelling and indomethacin release behavior were found to be pH‐ and thermo‐responsive. In addition, indomethacin release profile could be sustained with a inorganic–organic hybrid membrane: the release amount reached 96% within 4 hr for the unmineralized beads, while a drug release of only 64% obtained after subjecting the biomineralized polysaccharide beads to the same treatment. These results indicate that the biomineralized polysaccharide membrane could prevent the permeability of the encapsulated drug and reduce the drug release rate effectively. The studied system has the potential to be used as an effective smart sustainable delivery system for biomedical applications. Copyright © 2008 John Wiley & Sons, Ltd.
Novel PU‐type polymeric photoinitiator comprising side‐chain benzophenone and coinitiator amine for photopolymerization of PU acrylate
Authors: Wei Jun , Liu Fang , Lu Zhimin , Song Ling , Cai Dongdong
Published: July 2008

A novel diamine 3,5‐diamino‐4′‐phenoxylbenzophenone (DAPBP) was synthesized from the reaction of 3,5‐diamino‐4′‐chlorobenzophenone (DACBP) and phenol. Then through the polycondensation of DAPBP, toluene‐2,4‐diisocyanate (TDI), and N‐methyldiethanolamine (MDEA), we obtained a PU‐type polymeric photoinitiator containing side‐chain benzophenone (BP) and tertiary amine in the same macromolecule (PUSOA). Another polymeric photoinitiator without coinitiator amine in polymer chain (PUSO) was also synthesized for comparison. FT‐IR, 1H NMR, and GPC analyses confirmed the structures of monomer and polymeric photoinitiators. The UV–Vis spectra of PUSOA, PUSO, and DAPBP are similar, and all exhibit the maximal absorption near 290 nm. ESR spectra indicate that PUSOA can generate active species most efficiently. The photopolymerization of PU acrylate, initiated by PUSOA, PUSO/MDEA, DAPBP/MDEA, and BP/MDEA, was studied by differential scanning photocalorimetry (photo‐DSC). The results show that the in‐chain coinitiator amine can significantly improve the photoefficiency of the polymeric photoinitiator and the PUSOA is more efficient for the polymerization of PU acrylate than its low‐molecular‐weight counterpart. Copyright © 2008 John Wiley & Sons, Ltd.
Columnar liquid‐crystalline assemblies composed of spiropyran derivatives and sulfonic acids
Authors: Tan Boon‐Hooi , Yoshio Masafumi , Watanabe Kazuki , Hamasaki Atsushi , Ohno Hiroyuki , Kato Takashi
Published: July 2008

A series of fan‐shaped spiropyran derivatives with different length of alkyl chains has been synthesized. Liquid‐crystalline (LC) assemblies of spiropyran derivatives have been formed by the addition of organic sulfonic acids such as trifluoromethylsulfonic acid, 10‐camphorsulfonic acid, 4‐methylbenzenesulfonic acid, and imidazolium‐based ionic liquids (ILs) having a sulfonic acid group. Equimolar mixtures of a fan‐shaped spiropyran derivative with the acidic imidazolium‐based ILs exhibit columnar phases with wider LC temperature ranges as compared to those of other mixtures. The ionic interactions formed by the ionic imidazolium moieties should contribute to the stabilization of the columnar phases. On the other hand, equimolar mixtures of the spiropyran derivative with decane‐1‐sulfonic acid having a long alkyl chain and poly(4‐styrenesulfonic acid) do not show mesomorphism. The chemical structure of organic sulfonic acids is a key factor for the induction and stabilization of the LC phases. Copyright © 2008 John Wiley & Sons, Ltd.
Ionic liquid‐based luminescent composite materials
Authors: Nakashima Takuya , Nonoguchi Yoshiyuki , Kawai Tsuyoshi
Published: July 2008

Luminescent composite materials based on semiconductor nanocrystals (NCs) with ionic liquid and subsequently with an ionic liquid‐based polymer have been prepared. Cationic CdTe NCs passivated with thiocholine bromide (TCB) were prepared in an aqueous phase and easily transferred to hydrophobic ionic liquids by means of a simple biphasic extraction process without using any surfactant. TCB‐capped CdTe NCs were stably dispersed in hydrophobic ionic liquids and their absorption spectra and optical density (extinction coefficient) were maintained even after the extraction. While the emission peak position was also identical with the original one, its intensity increased almost twice. The efficient extraction and photoluminescence enhancement of CdTe NCs were generally observed for the hydrophobic ionic liquids based on both bis(trifluoromethanesulfonyl)imide (TFSI) and hexafluorophosphate (PF6) anions. However, the generation of a trace of hydrofluoric acid gradually collapsed the CdTe NCs in a PF6‐based ionic liquid. A polymerizable ionic liquid which possesses an acrylate group could also extract the CdTe NCs from water and gave a CdTe NC‐polymer composite with strong luminescence by the polymerization of ionic liquid. Copyright © 2008 John Wiley & Sons, Ltd.
Synthesis of oligomer with carbonate and ether unit from phenyl glycidyl ether and carbon dioxide, using immobilized imidazolium salt catalyst
Authors: Shim Hye‐Lim , Lee Mi‐Kyung , Kim Kyung‐Hoon , Park Dae‐Won , Park Sang‐Wook
Published: July 2008

A silica‐supported imidazolium salt (Im‐IM) was proved to be an effective heterogeneous catalyst for the solventless synthesis of oligomer with carbonate and ether unit from phenyl glycidyl ether (PGE) and CO2. Im‐IM catalysts were prepared by sol–gel method. The catalyst prepared with butyl bromide showed the highest conversion of PGE and the highest carbonate content [f(CO2)] and molecular weight for the oligomer. However, they decreased for Im‐IM prepared with longer alkyl chain (hexyl and octyl bromide) probably due to the steric hindrance for the formation of an intermediate between the catalyst and PGE. High reaction temperature increased PGE conversion, polymer formation, and f(CO2). The average molecular weight of the oligomer decreased with increase in reaction temperature. A high CO2 pressure was favorable for the PGE conversion and f(CO2). But a very high pressure decreased both of them. Im‐IM can be reused for the reaction up to four consecutive runs without considerable loss of its catalytic activity. Copyright © 2008 John Wiley & Sons, Ltd.
Propargyl silicon‐cyclopentadiene oligomeric resin with high temperature resistance
Authors: Wang Mingcun , Yang Ming , Zhao Tong
Published: July 2008

Multiple propargyl substituted cyclopentadiene was synthesized by phase transfer reaction between cyclopentadiene and propargyl bromide in an aqueous solution mediated by sodium hydroxide. It was found that propargylated cyclopentadiene (PCp) could be thermally cured with a mass loss of ca 28%, while the cured material showed a high char yield of ca 76% at 900°C. In order to overcome the processing problems of PCp, a condensation reaction between PCp di‐anion and dimethyldichlorosilane was performed to make a silicon‐PCp (SiPCp) oligomeric resin. SiPCp resin has an acceptable processability, attributed to its organosolubility, low viscosity, and broad processing window. SiPCp resin can readily undergo thermal cure via addition polymerization of ethynyl groups in the temperature range of 170–270°C with an exothermic maximum at ca 240°C, and the mass loss upon cure was less than 5%. Evidenced by the results of dynamic mechanical analysis (DMA) and thermogravimetric analysis (TGA) in a nitrogen atmosphere, the cured SiPCp resin exhibited stable thermo‐mechanical properties up to 320°C, and possessed an anerobic char yield of ca 77% at 900°C. The results of TGA in air atmosphere revealed the higher oxidation resistance of SiPCp resin. Copyright © 2008 John Wiley & Sons, Ltd.
Anionic polymerization of methyl methacrylate in an ionic liquid
Authors: Kokubo Hisashi , Watanabe Masayoshi
Published: July 2008

Anionic polymerization reactions of methyl methacrylate (MMA) in ionic liquids were carried out by utilizing alkyl lithium initiators such as n‐butyl lithium (n‐BuLi) and diphenylhexyl lithium (DPHLi). The polymerization in ionic liquids having bis(trifluoromethyl sulfonyl)amide ([NTf2]) anion did not yield poly(MMA) (PMMA), because of the deactivation of the initiator due to an attack on the trifluoromethyl group. By using 1‐butyl‐3‐methylimidazolium hexafluorophosphate ([C4mim][PF6]), the polymerization reactions proceeded. The PMMA prepared in [C4mim][PF6] gave low yields (5–9%), as compared with those (15–62%) obtained for PMMA prepared in tetrahydrofuran (THF), and the prepared PMMA had large polydispersity indices (≅2.0). The results obtained can be attributed to the high reaction temperature (0°C), in comparison to the common anionic polymerization temperature of MMA, −78°C, and the reaction between the initiator and the imidazolium cation. The initiator was considered to be deactivated because the hydrogen atom at the 2‐position of the imidazolium ring was withdrawn by the alkyl lithium initiator. The tacticity of the obtained PMMA, prepared in [C4mim][PF6] by utilizing DPHLi, was rich in mm triads, similar to that polymerized in toluene. Copyright © 2008 John Wiley & Sons, Ltd.