bluuebunny/crossref_metadata_2025_split huggingface dataset:
Wrinkling of epoxy powder coatings
Authors: Basu Soumendra K. , Scriven L. E. , Francis L. F. , McCormick A. V. , Reichert Veronica R. 
Published: July 2005

AbstractDifferential scanning calorimetry (DSC) and mechanical profilometry were used to study wrinkle formation in curing epoxy powder coatings. Powder coating formulations were studied that contained solid epoxy resins, methylene disalicylic acid (MDSA) crosslinker, and an amine‐blocked Lewis acid catalyst. Both the crosslinker (MDSA) and the amine‐blocked catalyst are required for wrinkle formation. Evaporation of the blocking amine from the free surface of the coating generated a depthwise gradient in the extent of polymerization and crosslinking, and hence in the degree of solidification, as evidenced by the formation of a mechanical skin prior to wrinkling. It is hypothesized that compressive elastic stress develops in the still swellable skin when unreacted low‐molecular‐weight material from beneath diffuses up into the monomer‐ or oligomer‐depleted crosslinking skin and swells it. This compressive stress, if above a critical value, buckles the skin to produce wrinkles. Experimentally observed compositional requirements for wrinkle formation were consistent with the proposed mechanism. The size of the wrinkles can be controlled by varying formulation parameters such as the amount of catalyst or crosslinker. Increasing the amount of catalyst decreased both the wavelength and the amplitude of the wrinkle pattern. Increasing the amount of crosslinker initially increased the amplitude of the wrinkles; after reaching a maximum level, the wrinkle amplitude decreased. DSC was a useful tool to understand the critical reactions responsible for wrinkling in this system. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 116–129, 2005
Matrix effects on tubule distribution and dielectrics properties of tubule‐based dielectrics
Authors: Chiou Bor‐Sen , Lankford Andrew R. , Mera Ann E. , Zabetakis Dan , Schoen Paul E. 
Published: July 2005

AbstractThe dielectric properties of composites containing copper‐coated tubules in epoxy and polyurethane were characterized and interpreted in terms of contact angle and interfacial tension between the filler and the polymer matrix. The polyurethane samples had larger permittivity values than the epoxy samples over the entire tubule concentration range. The results suggested the tubules in polyurethane were more aggregated than those in epoxy and, consequently, the polyurethane samples were closer to percolation. This was inconsistent with the contact angle and interfacial tension data, because epoxy had larger contact angles and interfacial tension than polyurethane. Therefore, the contact angle and interfacial tension data could not be used to predict tubule distribution in composites. Also, the De Loor model provided a good fit to the permittivity data. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 53–57, 2005
Thermal degradation kinetics of poly(3‐hydroxybutyrate‐co‐3‐hydroxyhexanoate)
Authors: Daly Patricia A. , Bruce David A. , Melik David H. , Harrison Graham M. 
Published: July 2005

AbstractThe degradation kinetics of poly(3‐hydroxybutyrate‐co‐3‐hydroxyhexanoate), a member of the Nodax family of polymers, were investigated using transient constant shear rate and dynamic time sweep rheological tests. The rate of chain scission at several times and temperatures was correlated with viscosity data and verified using molecular weight determination of the degraded samples. The experimental results show that the molecular weight and the viscosity of Nodax decrease with time over the range of temperatures that were studied (155–175°C). The degradation kinetics, which exhibited first‐order behavior, were determined as a function of the flow history and thermal history. An apparent activation energy of 189 ± 5 kJ/mol for thermal degradation was found by modeling variations in the rate with temperature using an Arrhenius law model. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 66–74, 2005
High modulus polypropylene fibers. I. Mechanical properties
Authors: Gregor‐Svetec Diana , Sluga Franci 
Published: July 2005

AbstractExtensive studies concerning the spinning and drawing of polypropylene resulted in a method for production of high modulus fibers under industrially feasible conditions. The fibers were produced in a conventional melt spinning and drawing process that was optimized in order to increase the elastic modulus of fibers. By such optimization of the process, a tensile strength of around 8 cN/dtex, an elastic modulus up to 14.7 GPa, and a dynamic modulus up to 19 GPa were attained. In this study the mechanical properties of polypropylene fibers were investigated, which were spun from fiber grade controlled rheology (CR) polymers and from the blends of a fiber grade CR polymer with a molding grade polymer in the composition range of 10–50 wt %. The addition of the molding grade polymer to the fiber grade CR polymer resulted in lower tensile strength and moduli, with one exception. By blending a CR polymer with 10% of the molding grade polymer, maximization of the elastic and dynamic modulus was achieved. The predicted modulus of a two‐phase blend, calculated from several representative equations, was compared with the elastic modulus of drawn fibers, determined from the specific stress versus strain curve, and the dynamic modulus, obtained from the sound velocity measurements. The best fit was achieved with the Kleiner simplex equation. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 1–8, 2005
Synthesis and characterization of 2‐diethyl‐aminoethyl–dextran–methyl methacrylate graft copolymer for nonviral gene delivery vector
Authors: Onishi Yasuhiko , Eshita Yuki , Murashita Aya , Mizuno Masaaki , Yoshida Jun 
Published: July 2005

AbstractA stable and soapless latex of 2‐diethyl‐aminoethyl (DEAE)–dextran–methyl methacrylate (MMA) graft copolymer (DDMC) was developed for nonviral gene delivery vectors (complex between polycation and nucleic acid). DDMC was newly prepared using MMA and DEAE–dextran. Following a transfection protocol, transfection of HEK 293 cells by DDC1, DDC2, and DDC3 samples was carried out using plasmid DNA. With the transfection efficiency determined using the X‐Gal staining method, a higher value of 5 times or more was confirmed for DDMC samples DDC1 and DDC2 (but not for DDC3) than for the starting DEAE–dextran hydrochloride. The absorption spectrum shift at around 3400 cm−1 of the complexes between DDMC and DNA may support the formation of more compact structures by a Coulomb force between the phosphoric acid of DNA and the DEAE group of DEAE–dextran, concluding in DNA condensation. The specifically designed molecular structure of DDMC to ensure easy entry of DNA into cells needs not only a positive charge and a hydrophilic–hydrophobic microseparated domain but also more compact structures for transfection steps. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 9–14, 2005
Preparation of polystyrene/montmorillonite nanocomposites in supercritical carbon dioxide
Authors: Yan Chong , Ma Li , Yang Jichu 
Published: July 2005

AbstractThe preparation of polystyrene (PS)/montmorillonite (MMT) composites in supercritical carbon dioxide (SCCO2) was studied. Lipophilic organically modified MMT can be produced through an ion‐exchange reaction between native hydrophilic MMT and an intercalating agent (alkyl ammonium). PS/clay composites were prepared by free‐radical precipitation polymerization of styrene containing dispersed clay. X‐ray diffraction and transmission electron microscopy indicated that intercalation of MMT was achieved. PS/clay composites have a higher thermal decomposition temperature and lower glass‐transition temperature than pure PS. The IR spectrum analysis showed that the solvent of SCCO2 did not change the structures of the PS molecules, but there were some chemical interactions between the PS and the clay in the composites. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 22–28, 2005
Preparation and electro‐optical behaviors of polymer stabilized liquid crystal cells with chiral matrices derived from (−)‐camphor
Authors: Liu Jui‐Hsiang , Hung Hsien‐Jung , Wu Dung‐Shin , Hong Shou‐Mau , Fu Andy Y. G. 
Published: July 2005

AbstractNovel chiral monomers derived from (−)‐camphor and difunctional monomers with biphenyl segments were synthesized. The molecular structures were identified using FTIR, NMR, and elemental analyses. Surface pretreated polymer stabilized cholesteric texture (PSCT) cells with various chiral nematic components were prepared. According to theory, they are kind of reversed mode PSCT cells. The helical twisting power (HTP) and pitches of the PSCT cells were evaluated. The polarized optical microscopic (POM) textures and the dependence of the optical properties on the applied voltage of the PSCT cells were investigated. The reflection band of the PSCT cells before and after UV irradiation were estimated. A blue shift of selective reflection of the PSCT cells was obtained after UV irradiation. PSCT cells with various reflecting colors and the dependence of the transmittance of the cells on applied voltage were investigated. Real image recording through a mask as well as the transmittance of PSCT cells controlled by applied voltage were also confirmed. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 88–96, 2005
Follow‐up study of Wiedemann‐Rautenstrauch syndrome: Long‐term survival and comparison with Rautenstrauch's patient “G”
Authors: Arboleda Humberto , Arboleda Gonzalo 
Published: July 2005

AbstractBACKGROUNDWiedemann‐Rautenstrauch syndrome (WRS) characterizes a neonatal progeroid entity. In the last 30 years, 28 cases have been reported. In most cases of WRS, survival is short and long‐term studies are impossible.CASEIn the present report, we describe a patient with WRS followed for 17 years at the Instituto de Genética, Universidad Nacional de Colombia; this is an exceptional survival period for a person with WRS. The information collected through 17 years for the present patient provides new knowledge about the natural evolution of this syndrome. New clinical and laboratory characteristics are compared with those reported for Rautenstrauch's patient “G.”CONCLUSIONSOur results confirm the variability of this syndrome, especially at the neurological level. However, many etiological and pathological aspects of this syndrome remain unknown. Birth Defects Research (Part A), 2005. © 2005 Wiley‐Liss, Inc.
Epidemiology of noncomplex left ventricular outflow tract obstruction malformations (aortic valve stenosis, coarctation of the aorta, hypoplastic left heart syndrome) in Texas, 1999–2001
Authors: McBride Kim L. , Marengo Lisa , Canfield Mark , Langlois Peter , Fixler David , Belmont John W. 
Published: July 2005

AbstractBACKGROUNDThe left ventricular outflow tract (LVOT) malformations aortic valve stenosis (AVS), coarctation of the aorta (CoA), and hypoplastic left heart syndrome (HLHS) contribute significantly to infant mortality due to birth defects. Previous epidemiology data showed rate differences between male and female and white and black ethnic groups. The Texas Birth Defects Registry, an active surveillance program, enables study in a large, diverse population including Hispanics.METHODSRecords of children up to 1 year old with AVS, CoA, and HLHS born in Texas from 1999 to 2001, were collected from the registry. Those including additional heart defects or a chromosomal anomaly were excluded. Multivariate analysis included: infant sex; United States–Mexico border county residence; and maternal age, race/ethnicity, birthplace, and education.RESULTSThere were 910 cases among 1.08 million live births, of which 499 met inclusion criteria. Multivariate modeling of all LVOT malformations combined demonstrated lower prevalence rate ratios (PRRs) for black males (0.26) and Hispanic males (0.70). Similar results were found for CoA but not AVS or HLHS. Higher PRRs were noted for increased maternal age for LVOT (1.3 for 24–34 years; 1.7 for >34 years), AVS, and HLHS, but not CoA, and higher PRRs across all diagnoses for males (LVOT PRR, 2.4) were noted. CoA PRRs were higher in border county vs. non–border county residents (PRR, 2.1). Maternal education and birthplace were not significant factors.CONCLUSIONSThere are rate differences for males among all 3 ethnic groups. Sex and ethnic differences suggest genetic etiologies, where the ethnic differences could be used to find susceptibility loci with mapping by admixture linkage disequilibrium. Increased CoA rates along the U.S.–Mexico border suggest environmental causes that will require further monitoring. Birth Defects Research (Part A), 2005. © 2005 Wiley‐Liss, Inc.
Magnetic resonance imaging, computed tomography, and conventional X‐ray in 3 cases of symmelia
Authors: Dorenbeck Ulrich , Schreyer Andreas G. , Plendl Philipp J. , Hees Herbert , Feuerbach Stefan , Held Paul 
Published: July 2005

AbstractBACKGROUNDSymmelia is a rare birth defect, often combined with severe malformations of the urogenital system and the lower gastrointestinal tract. Additionally, a deformed pelvis and various degrees of separation of the lower limbs are present.CASESWe report the examination findings of 3 autopsy specimens of symmelia using magnetic resonance imaging (MRI) and computed tomography (CT) with 3‐dimensional (3D) reconstructions, and conventional X‐ray.CONCLUSIONSMRI and CT with the addition of 3D visualization can be used additionally with autopsy and conventional X‐ray images in the investigation of such complex anatomical abnormalities. Birth Defects Research (Part A), 2005. © 2005 Wiley‐Liss, Inc.
Transient Structural Ordering of the RNA‐Binding Domain of Carnation Mottle Virus p7 Movement Protein Modulates Nucleic Acid Binding
Authors: Vilar Marçal , Saurí Ana , Marcos Jose F. , Mingarro Ismael , Pérez‐Payá Enrique 
Published: July 2005

AbstractPlant viral movement proteins bind to RNA and participate in the intra‐ and intercellular movement of the RNAs from plant viruses. However, the role and magnitude of the conformational changes associated with the formation of RNA–protein complexes are not yet defined. Here we describe studies on the relevance of a preexisting nascent α‐helix at the C terminus of the RNA‐binding domain of p7, a movement protein from carnation mottle virus, to RNA binding. Synthetic peptide analogues and single amino acid mutation at the RNA‐binding domain of recombinant p7 protein were used to correlate the transient structural order in aqueous solution with RNA‐binding potential.
How Does DNA Compaction Favor Chiral Selectivity with Cationic Species? Higher Selectivity with Lower Cationic Charge
Authors: Zinchenko Anatoly A. , Chen Ning , Murata Shizuaki , Yoshikawa Kenichi 
Published: July 2005

AbstractA single‐molecule study on giant DNA compaction by enantiomeric dications and tetracations demonstrates that strong chiral discrimination in DNA compaction is manifested only if the positive charge on enantiomeric multications is relatively low. The increase in cationicity of the chiral compaction agent inevitably leads to an increase in nonspecific electrostatic interactions and quenching of chiral discrimination in the DNA‐folding phase transition.
Fluorescence‐Based Cloning of a Protein Tyrosine Kinase with a Yeast Tribrid System
Authors: Clark Daniel D. , Peterson Blake R. 
Published: July 2005

AbstractPost‐translational modifications of proteins control myriad biological functions. However, relatively few methods exist for the identification of the enzymes that catalyze these modifications. To expand this repertoire, we report a yeast genetic approach that enables the identification of protein tyrosine kinases (PTKs) from cDNA libraries. Yeasts were transformed with four vectors encoding: 1) a potentially universal PTK substrate fused to the LexA DNA binding domain, 2) the Grb2‐SH2 domain fused to the B42 activation domain, 3) a fluorescent reporter gene controlled by LexA DNA sites, and 4) a Jurkat cDNA library. Transient expression of PTKs, such as the lymphocyte‐specific kinase Fyn, resulted in phosphorylation of the DNA‐bound substrate, recruitment of the Grb2‐SH2 domain, and activation of the fluorescent reporter gene. This brief induction of protein expression circumvented the potential toxicity of PTKs to the yeast. Fluorescence activated cell sorting (FACS) enabled isolation of PTKs, and these enzymes were further characterized by flow cytometry and immunoblotting. This approach provides a potentially general method for the identification and evaluation of enzymes involved in the post‐translational modification of proteins.
Drug‐eluting stents for coronary bifurcations: Bench testing of provisional side‐branch strategies
Authors: Ormiston John A. , Webster Mark W.I. , El Jack Seifeddin , Ruygrok Peter N. , Stewart James T. , Scott Douglas , Currie Erin , Panther Monique J. , Shaw Bronwyn , O'Shaughnessy Barbara 
Published: July 2005

AbstractThe objective of this study was to bench‐test provisional bifurcation stenting strategies to provide insights on how best to perform these with drug‐eluting stents (DESs). Bifurcation stenting with DESs reduces restenosis compared with bare metal stents (BMSs). Outcomes with a single DES are better than with two DESs but if the main branch is stented, there needs to be a reliable strategy for provisionally stenting the side‐branch with full ostial scaffolding and drug application. Stents were photographed in a phantom after deployment with different strategies. With provisional T‐stenting, placement of the side‐branch stent without gaps is difficult. The internal (or reverse) crush strategy fully scaffolds the side‐branch ostium but is experimental. The culotte technique providing excellent side‐branch ostial coverage is easier to perform with open‐cell or large‐cell stent design. In general, kissing balloon postdilatation improves stent expansion, especially at the ostium, and corrects distortion. However, a main‐branch kissing balloon of smaller diameter than the deploying balloon causes distortion. Final main‐branch postdilatation or sequential postdilatation prevents distortion after the internal crush strategy. © 2005 Wiley‐Liss, Inc.
Mechanistic Aspects of the Metal Catalyzed Alternating Copolymerization of Epoxides and Carbon Monoxide
Authors: Allmendinger Markus , Molnar Ferenc , Zintl Manuela , Luinstra Gerrit A. , Preishuber‐Pflügl Peter , Rieger Bernhard 
Published: July 2005

AbstractThe cobalt‐catalyzed alternating copolymerization of epoxides and CO is a novel, direct approach to aliphatic polyesters, such as poly(hydroxybutyrate) (PHB). This reaction was found to be catalyzed by Ph3Si[Co(CO)4] (4) and pyridine affording in a first step the stable mono‐insertion product Ph3Si‐O‐CH(CH3)‐CH2‐CO‐Co(CO)4 (5). However, a profound mechanistic understanding, especially of the role of pyridine as the key component for the polymerization reaction was missing. ATR‐IR online monitoring under catalytic conditions and DFT calculations were used to show that an acylpyridinium cation is formed by cleavage of the cobaltacyl bond of 5 in the presence of pyridine. The Lewis acid thus generated activates the next incoming epoxide monomer for ring opening through [Co(CO)4]−. The catalytic cycle is completed by a subsequent CO insertion in the new cobaltalkyl bond. The calculations are used to explore the energetic hypersurface of the polymerization reaction and are complemented by extended experimental investigations that also support the mechanistic hypotheses.
Biomimetic Hydrolysis of Penicillin G Catalyzed by Dinuclear Zinc(II) Complexes: Structure–Activity Correlations in β‐Lactamase Model Systems
Authors: Bauer‐Siebenlist Bernhard , Dechert Sebastian , Meyer Franc 
Published: July 2005

AbstractA series of highly preorganized pyrazolate‐based dinuclear zinc complexes has been studied as functional synthetic analogues of metallo‐β‐lactamases, a class of bacterial enzymes that cause serious clinical problems because of their degradation of common β‐lactam antibiotics. We have investigated the hydrolytic cleavage of penicillin G mediated by the different dinuclear zinc complexes, and have deduced structure–activity correlations. While cooperative effects of the adjacent metal ions might be operative, these are found to either enhance or diminish β‐lactamase activity with respect to a single free zinc. Drastic differences in activity are ascribed to a lack of accessible binding sites after incorporation of the substrate within the bimetallic pocket of 2 and 4, whereas partial detachment of hemilabile ligand side arms in 1 and 3 opens up available coordination sites for nucleophile activation and/or for binding and polarisation of the β‐lactam amide oxygen atom. This interpretation has been corroborated by NMR spectroscopic and mass spectrometric evidence as well as by X‐ray crystallography of several adducts formed between the pyrazolate‐based dinuclear zinc scaffolds and the small substrate analogue oxazetidinylacetate (oaa), 5–7. In all adducts, the carboxylate group of oaa is the primary anchoring site and is nested in a bridging position within the bimetallic pocket. However, zinc binding of the β‐lactam amide oxygen atom has been confirmed crystallographically for the first time in 7, in which additional open‐site coordination sites are available.
Cyclohexane‐Based Low Molecular Weight Hydrogelators: A Chirality Investigation
Authors: Friggeri Arianna , van der Pol Cornelia , van Bommel Kjeld J. C. , Heeres André , Stuart Marc C. A. , Feringa Ben L. , van Esch Jan 
Published: July 2005

AbstractSeven new 1,3,5‐cyclohexyltricarboxamide‐phenylalanine derivatives were synthesized in order to investigate the effect of the amino acid chirality on the gelating properties of these small molecules in water. Gelation tests have shown that enantiomerically pure homochiral 1,3,5‐cyclohexyltricarboxamide‐L‐phenylalanine is a non‐hydrogelator as it crystallizes from water, whereas the heterochiral derivatives with either two L‐phenylalanine moieties and one D‐phenylalanine (lld), or vice versa (ddl), are very good hydrogelators. Concentration‐dependent gel‐to‐sol transition‐temperature (Tgs) curves for lld or ddl gels show a sigmoidal behaviour, which is in contrast to the logarithmic curves generally observed for gels derived from low molecular weight gelators (LMWGs). Such sigmoidal behaviour can be related to interactions between fibre bundles, which give rise to intertwined bundles of fibres. Transmission electron microscopy (TEM) images of lld and ddl gels show a network of thin, unbranched, fibre bundles with diameters of 20 nm. Right‐handed twisted fibre bundles are present in the lld gel, whereas left‐handed structures can be found in the ddl gel. Each bundle of fibres consists of a finite number of primary fibres. Gels consisting of mixtures of gelators, lld and ddl, and nongelators (lll or ddd) were investigated by means of Tgs measurements, CD spectroscopy and TEM. Results show that the incorporation of nongelator molecules into gel fibres occurs; this leads to higher Tgs values and to changes in the helicity of the fibre bundles. Furthermore, it was found that peripheral functionalization of the homochiral derivatives lll or ddd by means of a second amino acid or a hydrophilic moiety can overcome the effect of chirality; this process in turn leads to good hydrogelators.