bluuebunny/crossref_metadata_2025_split huggingface dataset:
Polymer–organoclay hybrids by polymerization into montmorillonite‐vinyl monomer interlayers
Authors: Rehab Ahmed , Akelah Ahmed , Agag Tarek , Betiha Mohamed 
Published: September 2007

AbstractA different series of polymer–clay hybrid materials have been prepared by modification of the clay with different vinyl monomers, followed by polymerization of different ratios of vinyl monomers–clay with the monomers, such as methyl methacrylate, hydroxyethyl methacrylate, and styrene‐maleic anhydride. The materials were investigated by IR, which confirmed the intercalation of vinyl‐cation within the clay interlayers, and by TGA, which illustrated that phosphonium cation has high thermal stability than ammonium cation. Swelling studies of these materials in different organic solvents showed that the swelling degree increases as clay ratio decrease, and also showed higher swelling relative to vinyl–clay. X‐ray diffraction illustrated that the nanocomposites were exfoliated up to a 25 wt % content of organoclay relative to the amount of polymer. SEM and TEM examined the micrograph, which showed a good dispersion of the polymers into clay galleries, and formation of nanosize particles ranged 150–300 Å. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007
Thermo gravimetric analysis and morphological behavior of castor oil based polyurethane–polyester nonwoven fabric composites
Authors: Kumar Maddur Nagaraju Satheesh , Siddaramaiah  
Published: September 2007

AbstractCastor oil (CO) based polyurethane (PU)– polyester nonwoven fabric composites were fabricated by impregnating the polyester nonwoven fabric in a reactive composition containing CO and diisocyanate. Composites were fabricated with two different isocyanates such as toluene‐2, 4‐diisocyanate (TDI) and hexamethylene diisocyanate (HMDI). Thermogravimetric analysis (TGA) studies of the composites were performed to establish the thermal stability and their mode of thermal degradation. It was found that degradation of neat PU takes place in two steps and that of polyester nonwoven fabric reinforced PU composites takes place in three steps. From the TGA thermograms, a little improvement in thermal stability incase of polyester nonwoven fabric reinforced PU composites were noticed compared to unreinforced PUs. Degradation kinetic parameters were obtained for the composites using Broido, Coats and Redfern, and Horowitz and Metzger methods. Tensile fractured composite specimens were used to analyze the morphology of the composites by scanning electron microscopic technique. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007
Amphoteric hydrogels for immobilization of enzymes using template polymerization technique
Authors: El‐Masry Mansour M. , Elnashar Magdy M. M. , El‐Sherif Hazem M. 
Published: September 2007

AbstractNovel ionizable amphoteric hydrogels were prepared from poly(acrylic acid) and dimethylaminoethyl methacrylate monomer, employing template polymerization technique. The mode of interaction, as proved by FTIR, was multiple H‐bonding between the tertiary amino group of the monomer and the carboxylic groups of the polymer. The impact of varying equal polymer–monomer feed ratios from 0.1 to 1.1 on the swelling dynamics was examined. Penetrant sorption experiments demonstrated that the swelling behavior depends strongly on the polymer complex composition. The polymer complex of feed ratio 0.5 : 0.5 (polymer : monomer) showed maximum swelling percentage. The mechanism of the polymer complexes swelling was probably a non‐Fickian with n values approaching Fickian behavior. The hydrogels showed maximum swelling efficiencies of 27 folds and 13.5 folds in drastic acidic and basic medium, respectively, using polymer complex of 0.5 : 0.5 feed ratio. Because of reversibility and rapidity of swelling, the gel could be considered as a mechanochemical system. The prepared hydrogel successfully immobilized the industrially used β‐galactosidase as an acidic model enzyme. The novel immobilized enzyme showed a remarkable improvement in its activity (13.8 μmol min−1 mg−1) compared to the free enzyme (3.2 μmol min−1 mg−1). The optimum pH values for free and immobilized enzyme were 4.5–5 and 4, respectively. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007
Evidence for interchange reconnection between a coronal hole and an adjacent emerging flux region
Authors: Baker D. , van Driel‐Gesztelyi L. , Attrill G.D.R. 
Published: September 2007

AbstractCoronal holes are regions of dominantly monopolar magnetic field on the Sun where the field is considered to be ‘open’ towards interplanetary space. Magnetic bipoles emerging in proximity to a coronal hole boundary naturally interact with this surrounding open magnetic field. In the case of oppositely aligned polarities between the active region and the coronal hole, we expect interchange reconnection to take place, driven by the coronal expansion of the emerging bipole as well as occasional eruptive events. Using SOHO/EIT and SOHO/MDI data, we present observational evidence of such interchange reconnection by studying AR 10869 which emerged close to a coronal hole. We find closed loops forming between the active region and the coronal hole leading to the retreat of the hole. At the same time, on the far side of the active region, we see dimming of the corona which we interpret as a signature of field line ‘opening’ there, as a consequence of a topological displacement of the ‘open’ field lines of the coronal hole. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Trans‐Planckian signatures in the cosmic microwave background?
Authors: Lorenz L.C. 
Published: September 2007

AbstractWith the increasingly precise measurement of the cosmic microwave background (CMB), cosmology has entered an era where a model's predictions become testable to percent‐level accuracy. In particular, the CMB spectrum has so far provided impressive support for the scenario of inflation, first invented to solve outstanding problems of standard cosmology. While current data (COBE, WMAP etc.) have already constrained cosmological parameters like Ω0 to high precision, next generation instruments such as the PLANCK satellite should give access to specific characteristics of the inflationary mechanism itself. Another tantalizing idea has been discussed in this context: Given the enormous expansion of the Universe during the phase of inflation, could it be that even Planck scale physics has been stretched to observable distances and is therefore within grasp in the CMB observations? In this contribution, I discuss the possibility of carrying through the calculation of the perturbation spectrum from an ansatz for short distance physics right to its imprint in the CMB. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Magneto‐seismology of the solar atmosphere
Authors: Verth G. 
Published: September 2007

AbstractMagnetohydrodynamic (MHD) waves in solar coronal loops, which were previously only predicted by theory have actually been detected with space‐borne instruments. These observations have given an important and novel tool to measure fundamental parameters in the magnetically embedded solar corona. This paper will illustrate how information about the magnetic and density structure along coronal loops can be determined by measuring the frequency or amplitude profiles of standing fast kink mode oscillations. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Imaging the cool stars in the interacting binaries AE Aqr, BV Cen and V426 Oph
Authors: Watson C.A. , Steeghs D. , Dhillon V.S. , Shahbaz T. 
Published: September 2007

AbstractIt is well known that magnetic activity in late‐type stars increases with increasing rotation rate. Using inversion techniques akin to medical imaging, the rotationally broadened profiles from such stars can be used to reconstruct ‘Doppler images’ of the distribution of cool, dark starspots on their stellar surfaces. Interacting binaries, however, contain some of the most rapidly rotating late‐type stars known and thus provide important tests of stellar dynamo models. Furthermore, magnetic activity is thought to play a key role in their evolution, behaviour and accretion dynamics. Despite this, we know comparatively little about the magnetic activity and its influence on such binaries. In this review we summarise the concepts behind indirect imaging of these systems, and present movies of the starspot distributions on the cool stars in some interacting binaries. We conclude with a look at the future opportunities that such studies may provide. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Study of the effect of metallicity on the amplitudes of Cepheids
Authors: Klagyivik P. , Szabados L. 
Published: September 2007

AbstractResults concerning the dependence of photometric and radial velocity amplitudes on metallicity are presented based on about 200 Galactic classical Cepheids pulsating in the fundamental mode. The Galactic distribution of the [Fe/H] value of Cepheids is also studied. We show that the photometric amplitude ratio AI/AV is independent of metallicity. The observed dependence of this ratio on the pulsation period does not correspond to the theoretical predictions. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Numerical investigation of the orbit of Interball‐1
Authors: Nagy I. , Érdi B. 
Published: September 2007

AbstractWe investigated the motion of the Earth's artificial satellite Interball‐1 by using a method suitable for the computation of large eccentricity orbits. Though the measured and the computed orbital elements differ from each other within the measured error bound, we found a slight tendency for secular decreasing in the semi‐major axis, caused probably by electromagnetic drag. We analysed the dominant role of the Moon in the variations of the orbital eccentricity, leading to zero perigee height and the end of the lifetime of the satellite. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Calcineurin/NFAT signaling in the β‐cell: From diabetes to new therapeutics
Authors: Heit Jeremy J. 
Published: September 2007

AbstractPancreatic β‐cells in the islet of Langerhans produce the hormone insulin, which maintains blood glucose homeostasis. Perturbations in β‐cell function may lead to impairment of insulin production and secretion and the onset of diabetes mellitus. Several essential β‐cell factors have been identified that are required for normal β‐cell function, including six genes that when mutated give rise to inherited forms of diabetes known as Maturity Onset Diabetes of the Young (MODY). However, the intracellular signaling pathways that control expression of MODY and other factors continue to be revealed. Post‐transplant diabetes mellitus in patients taking the calcineurin inhibitors tacrolimus (FK506) or cyclosporin A indicates that calcineurin and its substrate the Nuclear Factor of Activated T‐cells (NFAT) may be required for β‐cell function. Here recent advances in our understanding of calcineurin and NFAT signaling in the β‐cell are reviewed. Novel therapeutic approaches for the treatment of diabetes are also discussed. BioEssays 29:1011–1021, 2007. © 2007 Wiley Periodicals, Inc.
Maternal cyclin B levels “Chk” the onset of DNA replication checkpoint control in Drosophila
Authors: Yellajoshyula Dhananjay , Patterson Ethan S. , Kroll Kristen L. 
Published: September 2007

AbstractIn many animals, early development of the embryo is characterized by synchronous, biphasic cell divisions. These cell divisions are controlled by maternally inherited proteins and RNAs. A critical question in developmental biology is how the embryo transitions to a later pattern of asynchronous cell divisions and transfers the prior maternal control of development to the zygotic genome. The most‐common model regarding how this transition from maternal to zygotic control is regulated posits that this is a consequence of the limitation of maternal gene products, due to their titration during early cell divisions. Here we discuss a recent article by Crest et al.1 that instead proposes that the balance of Cyclin‐dependent Kinase 1 and Cyclin B (Cdk1‐CycB) activity relative to that of the Drosophila checkpoint kinase Chk1 determines when asynchronous divisions begin. BioEssays 29:949–952, 2007. © 2007 Wiley Periodicals, Inc.
Computational studies of CXCR1, the receptor of IL‐8/CXCL8, using molecular dynamics and electrostatics
Authors: Huynh Nicholas , Mallik Buddhadeb , Zhang Li , Martins‐Green Manuela , Morikis Dimitrios 
Published: September 2007

AbstractThe three‐dimensional structure of IL‐8/CXCL8 has been previously determined using NMR spectroscopy and X‐ray crystallography, but the structure of the receptors for this chemokine has not been determined experimentally. We present here the development of a model for the structure of the IL‐8/CXCL8 receptor CXCR1, using a combination of homology modeling and a molecular dynamics simulation. Based on this model, we discuss the analysis of structural, dynamic, and physicochemical properties of CXCR1. We focused on the role of pairwise ionic interactions in local structural stability of CXCR1 and the role of electrostatic potentials in recognition of CXCR1 with IL‐8/CXCL8. We have performed theoretical mutations of six charged amino acids in CXCR1, which abolish binding as suggested by earlier experimental data, to shed light on the effect of charge on association ability. We propose that the observed loss of binding in the six CXCR1 mutants is owed to loss of local structural stability, rather than hindrance of the recognition process because of changes in the overall electrostatic properties of the receptor. Based on further structural analysis, we propose some mutations of charged residues involving ion pairs in different elements of transmembrane helices and extracellular loops, which are expected to alter the local structure and possibly affect binding. © 2007 Wiley Periodicals, Inc. Biopolymers 89: 52–61, 2008.This article was originally published online as an accepted preprint. The “Published Online” date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com
Modelling the long-term cost-effectiveness of endovascular or open repair for abdominal aortic aneurysm
Authors: Epstein D M , Sculpher M J , Manca A , Michaels J , Thompson S G , Brown L C , Powell J T , Buxton M J , Greenhalgh R M 
Published: September 2007

Abstract

Background
Recent randomized trials have shown that endovascular abdominal aortic aneurysm repair (EVAR) has a 3 per cent aneurysm-related survival benefit in patients fit for open surgery, but it also has uncertain long-term outcomes and higher costs. This study assessed the cost-effectiveness of EVAR.

Methods
A decision model was constructed to estimate the lifetime costs and quality-adjusted life years (QALYs) with EVAR and open repair in men aged 74 years. The model includes the risks of death from aneurysm, other cardiovascular and non-cardiovascular causes, secondary reinterventions and non-fatal cardiovascular events. Data were taken largely from the EVAR trial 1 and supplemented from other sources.

Results
Under the base-case (primary) assumptions, EVAR cost £3800 (95 per cent confidence interval (c.i.) £2400 to £5200) more per patient than open repair but produced fewer lifetime QALYs (mean − 0·020 (95 per cent c.i. − 0·189 to 0·165)). These results were sensitive to alternative model assumptions.

Conclusion
EVAR is unlikely to be cost-effective on the basis of existing devices, costs and evidence, but there remains considerable uncertainty.
Role of CYP2C9 and CYP2C19 polymorphisms in patients with atherosclerosis
Authors: Ercan B. , Ayaz L. , Çiçek D. , Tamer L. 
Published: September 2007

AbstractThe arachidonic acid metabolizing CYP enzymes with prominent roles in vascular regulation are epoxygenases of the two gene family which generate epoxyeicosatrienoic acids. Carriers of CYP2C9 mutant alleles exhibit a diminished CYP2C9 metabolic capacity leading to decreased endothelium‐derived hyperpolarizing factors (EDHF) synthesis and an increased risk for atherosclerosis. We investigated whether the polymorphisms of CYP2C9/19 are related with atherosclerosis. We examined 108 patients having angioraphically ≥70 coronary artery narrowing and 90 healthy controls. CYPC2C9/19*2 and CYP2C9/19*3 alleles were investigated in both patients and controls by a real time PCR instrument. There was no significant difference in the distribution of the CYP2C9*2/*3 alleles between cases and the controls. We found that smoker patients having CYP2C9*2 heterozygote genotype have 3.7‐fold risk of developing atherosclerosis. CYP2C19*3 heterozygote alleles are more frequent in patients than in controls (10.2%, 5.6% respectively) and it is related with a three‐fold risk of atherosclerosis (odds ratio (OR) = 3.75, confidence interval (CI) = 0.75–18.65). It becomes clear that cigarette smoking can cause almost all major diseases prevalent today, such as cancer or heart disease. This inter‐subject variability in cigarette‐induced pathologies is partly mediated by genetic variants of genes that may participate in detoxification processes, e.g., cytochrome P450 (CYP), cellular susceptibility to toxins, such as p53, or disease development such as atherosclerosis. Copyright © 2007 John Wiley & Sons, Ltd.
Increasing pH Causes Faster Anion‐ and Cation‐Transport Rates through a Synthetic Ion Channel
Authors: Madhavan Nandita , Gin Mary S. 
Published: September 2007

AbstractIon‐channel mimics are able to transmit electrical signals across phospholipid membranes, and can be envisioned as nanoswitches for molecular electronics. Here, we reported the use of pH to alter ion‐transport rates through a synthetic aminocyclodextrin ion channel. Both cation‐ and anion‐transport rates were found to increase with an increase in pH due to the unique electrostatics of the multiple ammonium groups that line the channel pore. Such pH regulation of ion transport rates is unique and can be exploited for sensing applications.
Investigating the Structural and Functional Consequences of Circular Permutation on Lipase B from Candida Antarctica
Authors: Qian Zhen , Fields Christina J. , Lutz Stefan 
Published: September 2007

AbstractThe engineering of lipase B from Candida antarctica (CALB) by circular permutation has yielded over sixty hydrolase variants, and several show significantly improved catalytic performance. Here we report a detailed characterization of ten selected enzyme variants by kinetic and spectroscopic methods to further elucidate the impact of circular permutation on the structure and function of CALB. Our experiments identify lipase variants with up to 175‐fold enhanced kcat/KM values over wild‐type. In addition, circular permutation does not change the enzymes’ enantiopreference and preserves or even improves their enantioselectivity compared to that of the wild‐type enzyme. Finally, our spectroscopic analyses suggest that the structural effects of circular permutation on CALB are mostly local, concentrating on regions near the native and new protein termini. The observed changes in secondary structure and protein thermostability vary among enzyme variants but directly correlate with the locations of the new termini, a first step towards a predictive framework.
A comparison of different pre‐treatment procedures for reducing heteroscedasticity and other irrelevant features in data prior to modelling of benthic count profiles
Authors: Flåten Geir Rune , Grung Bjørn , Kvalheim Olav M. 
Published: September 2007

AbstractChallenges related to quantifying environmental disturbance biologically from benthic count profiles by using the Community Disturbance Index (CDI) approach are assessed. A pre‐treatment framework incorporating removal of irrelevant features, scaling and converting transformations is proposed. Within this framework the characteristics of benthic count data are discussed and possible consequences for the CDI calculations are shown. It is established that the benthic count data need to be corrected for heteroscedasticity while scaling is found to be unnecessary for the CDI calculations. Copyright © 2007 John Wiley & Sons, Ltd.
A [3]Rotaxane of the Amide Type
Authors: Vögtle Fritz , Dünnwald Thomas , Händel Mirko , Jäger Ralf , Meier Stephan , Harder Gabriele 
Published: September 2007

AbstractTwo new rotaxane types, the [2]rotaxanes 12a,b and the [3]rotaxane 13, have been synthesised by treating the “axle” 7 with the stopper component 9 in the presence of the “wheel” 8. A nonionic template intermediate of type 10 is proposed. The [3]rotaxane 13 was only obtained when the chain of the “axle” had a certain length: with n = 1 only [2]rotaxane 12 a was isolated, whereas with n = 2 the [3]rotaxane 13 was formed besides the [2]rotaxane 12 b. This suggests that more extended rotaxanes and polyrotaxanes can be synthesised by the template strategy.
Microstructured Peptide‐Functionalised Surfaces by Electrochemical Polymerisation
Authors: Heiduschka Peter , Göpel Wolfgang , Beck Werner , Kraas Wolfgang , Kienle Stefan , Jung Günther 
Published: September 2007

AbstractFor the first time, antigenic peptides have been immobilised by electrochemical polymerisation after having been modified with a polymerisable functional group. 3‐Hydroxyphenylacetic acid was chosen as the novel polymerisable group. The synthetic peptides represent epitopes of the bovine foot and mouth disease virus and of the sodium channel of the cardiac muscle. The polymerisation was performed by applying a constant anodic potential or by cyclic voltammetry. A combination of these two methods was also employed, that is, cyclic voltammetry with a delay at the anodic vertex potential. No additional free phenolic monomer was required for the polymerisation. The layers formed by the polymerisation were recognised by specific antibodies. The specific binding of the antibodies to the polymer film could be demonstrated by ELISA, an enzyme‐linked amperometric immunoassay, and electrochemical impedance measurements, as well as by fluorescence‐labelled antibodies. A peptide derived from laminine was also immobilised by electrochemical polymerisation. It could be shown that neuroblastoma cells adhere to this layer.
Biomimetic Ion‐binding Monolayers on Gold and Their Characterization by AC‐Impedance Spectroscopy
Authors: Gafni Yael , Weizman Haim , Libman Jacqueline , Shanzer Abraham , Rubinstein Israel 
Published: September 2007

AbstractNovel ion‐binding monolayers on gold surfaces are presented where the molecular design is based upon the natural ion binder ferrichrome. The new ion binders possess hydroxamate coordinating groups arranged in C2 symmetry (bishydroxamate binder, BHB) or C3 symmetry (trishydroxamate binder, THB), and a separate dialkyl sulfide moiety, which serves as an anchor to the gold substrate. The separation between the ion‐binding cavity and the attachment site to the gold allows each parameter to be controlled separately, namely, cavity size, its symmetry and external envelope, as well as the functional group used for immobilization. The monolayers were characterized with respect to ellipsometric thickness, wettability (advancing and receding contact angles (CAs) for water), and surface coverage; the latter is determined by metal underpotential deposition (UPD). It is shown that the introduction of hydrophobic side chains (i‐butyl) improves the CAs, thickness, and surface coverage of the monolayers. A detailed analysis of the alternating‐current (AC) impedance spectra is presented for THB monolayers on gold electrodes, where the impedance data are fitted to an equivalent circuit model. It is shown that the AC response in a wide frequency range can be used to probe ion binding and release in monolayer systems on electrodes.