bluuebunny/crossref_metadata_2025 huggingface dataset:
In ovo non‐invasive quantification of the myocardial function and mass of chick embryos using magnetic resonance imaging
Authors: Holmes William M. , McCabe Christopher , Mullin Jim M. , Condon Barrie , Bain Maureen M.
Published: March 2009

Magnetic resonance imaging (MRI) has evolved as one of the major non‐invasive tools to study healthy and diseased hearts in animal models, especially rodent models. Even though, the chick embryo has long been used as a model for cardiovascular research, MRI has not yet been used for in vivo cardiac studies. Part of the reason for this is the difficulty in monitoring the ECG and respiration of the chick embryo in the magnet for gating purposes. To overcome this complication, this paper presents the use of retrospective Cine MRI to measure the cardiac function of chick embryos in ovo for the first time, without the need for respiratory or cardiac gating. The resulting left ventricular functional parameters, from six chick embryos at 20 days of incubation, were (mean ± SD) EDV 69 ± 15 µL, ESV 31 ± 7 µL, SV 38 ± 9 µL and EF 54.5 ± 2%. The use of retrospective Cine MRI at earlier stages of development is also discussed and difficulties have been highlighted. Copyright © 2009 John Wiley & Sons, Ltd.
Polyimide molecular composites containing a stiff‐chain polymer derived from 1,5‐diaminonaphathalene and pyromellitic dianhydride
Authors: Khalil Muhammad , Ha Chang‐Sik , Saeed Shaukat , Khan Irum Majeed , Ahmad Zahoor
Published: March 2009

Polyimide molecular composite (MC) films were prepared by embedding a stiff‐chain polyimide (PIS) in the ductile matrix of a flexible‐chain polyimide (PIF) by blending their respective poly(amic acid) precursor solutions, followed by casting, drying, and thermal imidization upto 300°C. The PIS was prepared from pyromellitic dianhydride (PMDA) and 1,5‐diaminonaphathalene (DAN), whereas the PIF was prepared from the same dianhydride and 4,4′‐oxydianiline (ODA). Transparent, tough, and creasable MC films were obtained with 2.5–40 wt% of PIS content. The disruption of crystalline order of PIS in the MC films evidenced its fine dispersion in the matrix. Visco‐elastic measurements showed a single and enhanced value of the glass transition temperature for MC films indicating miscibility of this polyimide pair. Furthermore, the variation of charge transfer (CT) fluorescence intensity with the PIS content in the blends verified complete miscibility upto 30 wt% of PIS loading. These MCs showed a notable enhancement in the mechanical properties. Among all, the blend containing 30 wt% of stiff‐chain molecules gave the best combination of properties when compared with the matrix polyimide: a 50% higher value of tensile modulus, a 17°C rise in the glass transition temperature, and better thermal stability. POLYM. COMPOS., 2010. © 2009 Society of Plastics Engineers
Consolidation of net‐shape random fiber thermoplastic composite preforms
Authors: Jespersen S.T. , Baudry F. , Wakeman M.D. , Michaud V. , Blanchard P. , Norris R. , Månson J‐A.E.
Published: March 2009

A novel thermoplastic composite preforming process has been developed. This thermoplastic programmable powdered preforming process (TP‐P4) uses commingled glass and polypropylene yarns, which are chopped to a desired length and deposited onto a vacuum screen. The as‐placed fibers are then heat‐set for improved handling, before potential preconsolidation, and final conversion with preheating and press forming. This work investigated the effect of using either a double belt lamination preconsolidation stage or using an improved heat‐setting stage. Polymer degradation was examined using gel permeation chromatography analysis, and the void content evolution tracked using image analysis techniques from the heat setting stage until the final part. It was shown that without preconsolidation, preforms prepared for a 2 mm thick final pressed part could be compression molded into a substantially void free, non degraded part. By using the lamination route, this limit could be increased to 4 mm, but without allowing local thickness changes in the preform. POLYM. COMPOS., 2010. © 2009 Society of Plastics Engineers
Fatigue characterization and reliability analysis of wood flour filled polypropylene composites
Authors: Yang Han‐Seung , Qiao Pizhong , Wolcott Michael P.
Published: March 2009

In this article, the flexural fatigue behavior of wood flour filled polypropylene (PP) composite samples was investigated, and a probabilistic approach is presented to evaluate the fatigue reliability. A nondimensional analysis was adopted to establish a prediction equation for the fatigue life of the composites, and the S‐N curves and survivability diagrams are then constructed to evaluate the fatigue reliability for the wood plastic composites. The predicted results in the nondimensional fatigue model are better related to the testing data than the general S‐N curve, and they could be used as the predictive model for fatigue life analysis of the wood plastic composites. The best‐fit S‐N curve and its corresponding bounds based on 95% confidence are provided, and the fatigue data are well distributed within a 95% confidence range. A two‐parameter Weibull distribution function is used to analyze statistically the fatigue life test results of composite samples based on the probability of survival concept which is proposed to incorporate the probability of survival and the fatigue life time of the composites at a specified lifetime. Weibull graphics are plotted for the composite samples used in the fatigue test, and the S‐N curves are then drawn for different reliability index (RI) of 0.01, 0.1, 0.5, 0.9, 0.99, and 0.368 using these data. These S‐N curves are introduced for the identification of the first failure time as reliability and safety limits. It is shown that the nondimensional fatigue model and two‐parameter probability distribution model can be used successfully for reliability evaluation and lifetime estimation of wood plastic composites. POLYM. COMPOS., 2010. © 2009 Society of Plastics Engineers
Proteomics analysis of BHK‐21 cells infected with a fixed strain of rabies virus
Authors: Zandi Fatemeh , Eslami Naser , Soheili Masoomeh , Fayaz Ahmad , Gholami Alireza , Vaziri Behrouz
Published: March 2009

Rabies is a neurotropic virus that causes a life threatening acute viral encephalitis. The complex relationship of rabies virus (RV) with the host leads to its replication and spreading toward the neural network, where viral pathogenic effects appeared as neuronal dysfunction. In order to better understand the molecular basis of this relationship, a proteomics study on baby hamster kidney cells infected with challenge virus standard strain of RV was performed. This cell line is an in vitro model for rabies infection and is commonly used for viral seed preparation. The direct effect of the virus on cellular protein machinery was investigated by 2‐DE proteome mapping of infected versus control cells followed by LC‐MS/MS identification. This analysis revealed significant changes in expression of 14 proteins, seven of these proteins were viral and the remaining were host proteins with different known functions: cytoskeletal (capping protein, vimentin), anti‐oxidative stress (superoxide dismutase), regulatory (Stathmin), and protein synthesis (P0). Despite of limited changes appeared upon rabies infection, they present a set of interesting biochemical pathways for further investigation on viral‐host interaction.
NDRG1 is down‐regulated in the early apoptotic event induced by camptothecin analogs: The potential role in proteolytic activation of PKCδ and apoptosis
Authors: Zheng Ying , Wang Li‐Shun , Xia Li , Han Yu‐Hui , Liao Shi‐Hua , Wang Xiao‐Ling , Cheng Jin‐Ke , Chen Guo‐Qiang
Published: March 2009

We previously reported that NSC606985, a new camptothecin analog, induces apoptosis of acute myeloid leukemic cells, which is triggered by proteolytic activation of protein kinase C delta (PKCδ). Here, we performed quantitative proteomic analysis of NSC606985‐treated and untreated leukemic U937 cells with two‐dimensional fluorescence difference gel electrophoresis (2‐D DIGE) in combination with matrix‐assisted laser desorption/ionization time‐of‐flight/time‐of‐flight tandem mass spectrometry. Thirty‐three proteins were found to be deregulated. Then, we focused on N‐myc downstream regulated gene 1 (NDRG1) down‐regulated during apoptosis induction. The results demonstrated that the down‐regulation of NDRG1 protein but not its mRNA was an early event prior to proteolytic activation of PKCδ in U937 cells under treatments of NSC606985 as well as other camptothecin analogs. With the ectopic expression of NDRG1, the proteolytic activation of PKCδ in NSC606985‐treated leukemic cells was delayed and the cells were less sensitive to apoptosis. On the contrary, the suppression of NDRG1 expression by specific small interfering RNA significantly enhanced NSC606985‐induced activation of PKCδ and apoptosis of U937 cells. In summary, our study suggests that the down‐regulation of NDRG1 is involved in proteolytic activation of PKCδ during apoptosis induction, which would shed new light on the understanding the apoptotic process initiated by camptothecin.
Mapping of O‐linked β‐N‐acetylglucosamine modification sites in key contractile proteins of rat skeletal muscle
Authors: Hédou Julie , Bastide Bruno , Page Adeline , Michalski Jean‐Claude , Morelle Willy
Published: March 2009

O‐linked β‐N‐acetylglucosamine (O‐GlcNAc) is a widespread modification of serine/threonine residues of nucleocytoplasmic proteins. Recently, several key contractile proteins in rat skeletal muscle (i.e., myosin heavy and light chains and actin) were identified as O‐GlcNAc modified. Moreover, it was demonstrated that O‐GlcNAc moieties involved in contractile protein interactions could modulate Ca2+ activation parameters of contraction. In order to better understand how O‐GlcNAc can modulate the contractile activity of muscle fibers, we decided to identify the sites of O‐GlcNAc modification in purified contractile protein homogenates. Using an MS‐based method that relies on mild β‐elimination followed by Michael addition of DTT (BEMAD), we determined the localization of one O‐GlcNAc site in the subdomain four of actin and four O‐GlcNAc sites in the light meromyosin region of myosin heavy chains (MHC). According to previous reports concerning the role of these regions, our data suggest that O‐GlcNAc sites might modulate the actin–tropomyosin interaction, and be involved in MHC polymerization or interactions between MHC and other contractile proteins. Thus, the results suggest that this PTM might be involved in protein–protein interactions but could also modulate the contractile properties of skeletal muscle.
Biomarker discovery in asthma‐related inflammation and remodeling
Authors: Calvo Florence Quesada , Fillet Marianne , de Seny Dominique , Meuwis Marie‐Alice , Maree Raphael , Crahay Céline , Paulissen Geneviève , Rocks Natacha , Gueders Maud , Wehenkel Louis , Merville Marie‐Paule , Louis Renaud , Foidart Jean‐Michel , Noël Agnes , Cataldo Didier
Published: March 2009

Asthma is a complex inflammatory disease of airways. A network of reciprocal interactions between inflammatory cells, peptidic mediators, extracellular matrix components, and proteases is thought to be involved in the installation and maintenance of asthma‐related airway inflammation and remodeling. To date, new proteic mediators displaying significant activity in the pathophysiology of asthma are still to be unveiled. The main objective of this study was to uncover potential target proteins by using surface‐enhanced laser desorption/ionization‐time of flight‐mass spectrometry (SELDI‐TOF‐MS) on lung samples from mouse models of allergen‐induced airway inflammation and remodeling. In this model, we pointed out several protein or peptide peaks that were preferentially expressed in diseased mice as compared to controls. We report the identification of different five proteins: found inflammatory zone 1 or RELMα (FIZZ‐1), calcyclin (S100A6), clara cell secretory protein 10 (CC10), Ubiquitin, and Histone H4.
Towards functional proteomics of minority component of honeybee royal jelly: The effect of post‐translational modifications on the antimicrobial activity of apalbumin2
Authors: Bíliková Katarína , Mirgorodskaya Ekaterina , Bukovská Gabriela , Gobom Johan , Lehrach Hans , Šimúth Jozef
Published: March 2009

This study illustrates multifunctionality of proteins of honeybee royal jelly (RJ) and how their neofunctionalization result from various PTMs of maternal proteins. Major proteins of RJ, designated as apalbumins belong to a protein family consisting of nine members with Mr of 49–87 kDa and they are accompanied by high number of minority homologs derived from maternal apalbumins. In spite of many data on diversity of apalbumins, the molecular study of their individual minority homologous is still missing.

This work is a contribution to functional proteomics of second most abundant protein of RJ apalbumin2 (Mr 52.7 kDa). We have purified a minority protein from RJ; named as apalbumin2a, differ from apalbumin2 in Mr (48.6 kDa), in N‐terminal amino acids sequences – ENSPRN and in N‐linked glycans. Characterization of apalbumin2a by LC‐MALDI TOF/TOF MS revealed that it is a minority homolog of the major basic royal jelly protein, apalbumin2, carrying two fully occupied N‐glycosylation sites, one with high‐mannose structure, HexNAc2Hex9, and another carrying complex type antennary structures, HexNAc4Hex3 and HexNAc5Hex4. We have found that apalbumin2a inhibit growth of Paenibacillus larvae. The obtained data call attention to functional plasticity of RJ proteins with potential impact on functional proteomics in medicine.
The seminal fluid proteome of the honeybee Apis mellifera
Authors: Baer Boris , Heazlewood Joshua L. , Taylor Nicolas L. , Eubel Holger , Millar A. Harvey
Published: March 2009

Ejaculates contain sperm but also seminal fluid, which is increasingly recognized to be of central importance for reproductive success. However, a detailed biochemical composition and physiological understanding of seminal fluid is still elusive. We have used MS to identify the 57 most abundant proteins within the ejaculated seminal fluid of the honeybee Apis mellifera. Their amino acid sequences revealed the presence of diverse functional categories of enzymes, regulators and structural proteins. A number have known or predicted roles in maintaining sperm viability, protecting sperm from microbial infections or interacting with the physiology of the female. A range of putative glycoproteins or glycosylation enzymes were detected among the 57, subsequent fluorescent staining of glycolysation revealed several prominant glycoproteins in seminal fluid, while no glycoproteins were detected in sperm samples. Many of the abundant proteins that accumulate in the seminal fluid did not contain predictable tags for secretion for the cell. Comparison of the honeybee seminal fluid proteins with Drosophila seminal fluid proteins (including secreted accessory gland proteins known as ACPs), and with the human seminal fluid proteome revealed the bee protein set contains a range of newly identified seminal fluid proteins and we noted more similarity of the bee protein set with the current human seminal fluid protein set than with the known Drosophila seminal fluid proteins. The honeybee seminal fluid proteome thus represents an important addition to available data for comparative studies of seminal fluid proteomes in insects.
Synthesis and characterization of L‐leucine containing chiral vinyl monomer and its polymer, poly(2‐(methacryloyloxyamino)‐4‐methyl pentanoic acid)
Authors: Bag Dibyendu S. , Dutta Dhiraj , Shami T. C. , Bhasker Rao K. U.
Published: March 2009

A chiral monomer containing L‐leucine as a pendant group was synthesized from methacryloyl chloride and L‐leucine in presence of sodium hydroxide at 4 °C. The monomer was polymerized by free radical polymerization in propan‐2‐ol at 60 °C using 2,2′‐azobis isobutyronitrile (AIBN) as an initiator under nitrogen atmosphere. The polymer, poly(2‐(Methacryloyloxyamino)‐4‐methyl pentanoic acid) is thus obtained. The molecular weight of the polymer was determined to be: Mw is 6.9 × 103 and Mn is 5.6 × 103. The optical rotation of both chiral monomer and its polymer varies with the solvent polarity. The amplification of optical rotation due to transformation of monomer to polymer is associated with the ordered conformation of chiral monomer unit in the polymeric chain due to some secondary interactions like H‐bonding. The synthesized monomer and polymer exhibit intense Cotton effect at 220 nm. The conformation of the chain segments is sensitive to external stimuli, particularly the pH of the medium. In alkaline medium, the ordered chain conformation is destroyed resulting disordered random coils. The ordered coiling conformation is more firmly present on addition of HCl. The polymer exhibits swelling‐deswelling characteristics with the change of pH of the medium, which is reversible. The Cotton effect decreases linearly with the increase of temperature which is reversible on cooling. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 2228–2242, 2009
Engineering polymer surfaces with variable chemistry and topography
Authors: Muñoz‐Bonilla Alexandra , Ibarboure Emmanuel , Papon Eric , Rodriguez‐Hernandez Juan
Published: March 2009

We describe the preparation of surfaces with controlled surface chemistry and topology combining both surface segregation of block copolymers and “breath figures” formation. For that purpose, an amphiphilic ABC triblock copolymer, that is, poly(2,3,4,5,6‐pentafluorostyrene)‐b‐polystyrene‐b‐poly[poly(ethylene glycol) methyl ether methacrylate] (PS5F21‐b‐PS31‐b‐PPEGMA38) was mixed with high molecular weight polystyrene and spin coated in a moist atmosphere. As demonstrated by X‐ray photoelectron spectroscopy and atomic force microscopy analysis, the surfaces exhibit spherical holes with diameters between 100 and 300 nm. The holes, enriched in triblock copolymer, exhibit variable chemical composition and topography depending on the environmental conditions. The surface functionality could be reversibly modulated: whereas under humid conditions the PPEGMA hydrophilic block reorients towards the surface, annealing to dry air directs the PS5F fluorinated block to the interface. Equally, surfaces annealed to humid air changed their topography from holes to islands depending on the extent of swelling of the PPEGMA block. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 2262–2271, 2009
Ring‐opening polymerization of lactides initiated by magnesium and zinc complexes based on NNO‐tridentate ketiminate ligands: Activity and stereoselectivity studies
Authors: Huang Yong , Hung Wen‐Chou , Liao Ming‐Yuan , Tsai Tsung‐En , Peng Ya‐Liu , Lin Chu‐Chieh
Published: March 2009

Four metal benzylalkoxides, [L2M2(μ‐OBn)2] (M = Mg or Zn), based on NNO‐tridentate ketiminate ligands are synthesized and characterized. X‐ray crystal structural studies of [(L1)2Mg2(μ‐OBn)2] (1a) and [(L1)2Zn2(μ‐OBn)2] (1b) (L1‐H = (Z)‐4‐((2‐(dimethylamino)ethylamino)(phenyl)methylene)‐3‐methyl‐1‐phenyl‐pyrazol‐5‐one) reveal that both complexes 1a and 1b are dinuclear species whereas the geometry around the metal center is penta‐coordinated bridging through the benzylalkoxy oxygen atoms in the solid structure. The activities and stereoselectivities of these four complexes toward the ring‐opening polymerization of L‐lactide and rac‐lactide are investigated. Polymerization of L‐lactide initiated by these four metal benzyloxides proceeds rapidly with good molecular weight control and yields polymer with a very narrow molecular weight distribution. The kinetic studies for the polymerization of L‐lactide with compound 1a show first order in both compound 1a and lactide concentrations with the polymerization rate constant, k, of 6.94 M/min. Besides, experimental results demonstrate that among these metal benzylalkoxides, complex 1a exhibits the highest stereoselectivity with a Pr up to 87% and complex 1b possesses the highest activity indicating that the terminal group of NNO‐tridentate ketimine ligands exerts a significant influence on both the reactivity and stereoselectivity of these complexes. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 2318–2329, 2009
Three‐arm star ring opening metathesis polymers via alkyne‐azide click reaction
Authors: Dag Aydan , Durmaz Hakan , Sirkecioglu Okan , Hizal Gurkan , Tunca Umit
Published: March 2009

The click chemistry strategy is successfully applied for the preparation of three‐arm star (A3) ring opening metathesis polymers. A well‐defined monoazide end‐functionalized poly(N‐ethyl oxanorbornene) and a poly(N‐butyl oxanorbornene) obtained via ring opening metathesis polymerization using first generation Grubbs' catalyst are simply clicked with the trisalkyne core affording the synthesis of target star polymers. The obtained star polymers are characterized via nuclear magnetic resonance spectroscopy and gel permeation chromatography (GPC). The deconvolution analyses of GPC traces reveal that the click reaction efficiency for the star formation strongly depends on the chemical nature and the molecular weight of ROM polymers. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 2344–2351, 2009
Modulated molecular recognition by a temperature‐sensitive molecularly‐imprinted polymer
Authors: Li Songjun , Pilla Srikanth , Gong Shaoqin
Published: March 2009

Modulated molecular recognition was achieved in a temperature‐sensitive molecularly‐imprinted polymer. Using PNIPA as the temperature‐sensitive element, the adenine‐imprinted polymer (i.e., MIP‐S) was prepared and characterized. The MIP‐S exhibited a temperature‐responsive molecular recognition behavior because of the thermal phase‐transition within the MIP‐S network. Specifically, below the transition temperature (e.g., 20 °C), the MIP‐S showed a highly specific recognition for the imprint species (adenine). However, the MIP‐S did not show any significant resolution for the imprint species (adenine) and its analogue (1‐methyladenine) above the transition temperature (e.g., 40 °C). Such temperature‐regulated recognition is comparable to a switch‐on and switch‐off process, thereby making tunable molecular recognition feasible. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 2352–2360, 2009
Preparation and characterization of nematic polyazomethine/single‐walled carbon nanotube composites prepared by in situ polymerization
Authors: Lafuente Esperanza , Piñol Milagros , Martínez María Teresa , Muñoz Edgar , Oriol Luis , Serrano José Luis
Published: March 2009

The synthesis and characterization of a series of nematic SWNT‐polyazomethine composites are described. The composites were prepared by in situ polymerization in the presence of 1 wt % of chemically modified SWNTs in such a way that they were either dispersed or covalently bonded to the polymeric matrix. The presence of the SWNTs did not alter the thermal behavior of the polymer matrix and, therefore, highly oriented fibers could be melt‐extruded from the composites at moderate temperatures, as revealed by structural and morphological studies. Preliminary tests on tensile properties indicate that strength and stiffness were improved when compared with fibers without CNTs, particularly when SWNTs were covalently bonded to the polymeric matrix. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 2361–2372, 2009
Monolithic biocompatible and biodegradable scaffolds for tissue engineering
Authors: Buchmeiser Michael R.
Published: March 2009

The state of the art in polymeric materials for tissue engineering as well as the needs and concerns for future medical applications are outlined and discussed and brought into relation to recent developments in polymer chemistry. Particularly, the recent developments in micro‐ and nano‐structured polymeric monoliths designed for these purposes will be discussed. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 2219–2227, 2009
Linear polyurethanes made from naturally occurring tartaric acid
Authors: Marín Romina , Martínez de Ilarduya Antxon , Muñoz‐Guerra Sebastián
Published: March 2009

Naturally occurring tartaric acid was used as raw material for the synthesis of novel linear polyurethanes (PURs) bearing two carboxylate side‐groups in the repeating unit. Aliphatic and aromatic PURs were obtained by reaction in solution of alkyl and benzyl tartrates with hexamethylene diisocyanate and 4,4′‐methylene‐bis(phenyl isocyanate), respectively. All the novel PURs were thermally stable and optically active. The aliphatic carboxylate‐containing PURs had Mw in the 40–70 kDa range, with PD between 2.1 and 2.5; all were semicrystalline polymers with melting temperatures between 100 and 150 °C and Tg in the 50–80 °C range. The aromatic PURs were amorphous materials with molecular weights between 18 kDa and 25 kDa and Tg above 130 °C. Hydrogenolysis of the PUR made from hexamethylene diisocyanate and benzyl tartrate yielded PURs containing up to 40% of free carboxylic side‐groups. The tartrate‐derived PURs displayed enhanced sensitivity to hydrolysis compared with their unsubstituted 2,6‐PUR homologs. The PURs bearing free carboxylic groups were unique in being degraded by water upon incubation under physiological conditions. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 2391–2407, 2009
Synthesis and characterization of optically active helical vinyl polymers via free radical polymerization
Authors: Zhi Junge , Guan Yan , Cui Jiaxi , Liu Anhua , Zhu Zhiguo , Wan Xinhua , Zhou Qifeng
Published: March 2009

A facile synthetic route to prepare the dual‐functional molecule, 2,5‐bis(4′‐carboxyphenyl)styrene, was developed. The esterification of this compound with chiral alcohols, that is, (S)‐(+)‐sec‐butanol/(R)‐(−)‐sec‐butanol, (S)‐(+)‐sec‐octanol/(R)‐(−)‐sec‐octanol, and D‐(+)‐menthol/L‐(−)‐menthol, respectively, yielded three enantiomeric pairs of novel vinyl monomers, which underwent radical polymerization to obtain helical polymers with an excess screw sense. These polymers exhibited optical rotations as large as fourfold those of the corresponding monomers. Their helical conformations were quite stable as revealed by the almost unchanged chiroptical properties measured at different temperatures. The polymers with linear alkyl tails in the side‐groups formed irreversibly columnar nematic phases in melt although the corresponding monomers were not liquid crystalline. Whereas, the polymers with cyclic tails generated no mesophase. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 2408–2421, 2009
Synthesis and characterization of photocrosslinked poly(ε‐caprolactone)s showing shape‐memory properties
Authors: Nagata Minoru , Yamamoto Yu
Published: March 2009

Poly(ε‐caprolactone) (PCL) with a pendent coumarin group was prepared by solution polycondensation from 7‐(3,5‐dicarboxyphenyl) carbonylmethoxycoumarin dichloride and α, ω‐dihydroxy terminated poly(ε‐caprolactone) with molecular weights of 1250, 3000, and 10,000 g/mol. These photosensitive polymers underwent a rapid reversible photocrosslinking upon exposure to irradiation with alternating wavelengths (>280/254 nm) without a photoinitiator. The thermal and mechanical properties of the photocrosslinked films were examined by means of differential scanning calorimetry and stress–strain measurements. The crosslinked films exhibited elastic properties above the melting temperature of the PCL segment along with significant decrease in the ultimate tensile strength and Young's modulus. Shape‐memory properties such as strain fixity ratio (Rf) and strain recovery ratio (Rr) were determined by means of a cyclic thermomechanical tensile experiments under varying maximum strains (εm = 100, 300, and 500%). The crosslinked ICM/PCL‐3000 and ‐10,000 films exhibited the excellent shape‐memory properties in which both Rf and Rr values were 88–100% for tensile strain of 100–500%; after the deformation, the films recovered their permanent shapes instantaneously. In vitro degradation was performed in a phosphate buffer saline (pH 7.2) at 37 °C with or without the presence of Pseudomonas cepacia lipase. The presence of the pendent coumarin group and the crosslinking of the polymers pronouncedly decreased the degradation rate. The crosslinked biodegradable PCL showing a good shape‐memory property is promising as a new material for biomedical applications. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 2422–2433, 2009
Synthesis and spectroscopic investigation of π‐conjugated (E)‐enyne polycarbazole with different organo‐metallic catalysts from 3,6‐diethynyl‐9‐(2‐ethylhexyl)carbazole
Authors: Moon In Kyu , Kawamoto Masuki , Wada Tatsuo
Published: March 2009

In the present study, a new (E)‐rich‐enyne π‐conjugated polymer containing a carbazole was designed and synthesized. Two different synthesis methods of poly[N‐(2‐ethylhexyl)‐3,6‐carbazolyleneethynylene‐(E)‐vinylene] (PCZEV) have been prepared from 3,6‐diethynyl‐9(2‐ethylhexyl)carbazole by using the palladium‐carbene‐catalyzed reaction and/or by using the organolanthanide‐catalyzed reaction leading to well‐defined polymer, and their general properties were studied. Compared to poly[N‐(2‐ethylhexyl)‐3,6‐carbazolyleneethynylene] (PCE), the UV‐vis absorption and photoluminescence of the PCZEV was red‐shifted, which indicates the extension of conjugation length. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 2434–2442, 2009
Poly(arylene sulfide)s by nucleophilic aromatic substitution polymerization of 2,7‐difluorothianthrene
Authors: Robb Maxwell J. , Knauss Daniel M.
Published: March 2009

Poly(thianthrene phenylene sulfide) and poly(thianthrene sulfide) have been prepared by nucleophilic aromatic substitution polymerization of the activated monomer 2,7‐difluorothianthrene with bis thiophenoxide and sulfide nucleophiles, respectively. The resulting polymers are thermally stable, amorphous materials that have been characterized by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), gel permeation chromatography (GPC), matrix‐assisted laser desorption/ionization‐time‐of‐flight (MALDI‐TOF) mass spectrometry, UV‐Vis spectroscopy, refractometry, and intrinsic viscosity (IV) measurements. The polymers produced exhibit 5% weight loss values approaching 500 °C in inert and air atmospheres and glass transition temperatures that range from 149 to 210 °C. Poly(thianthrene phenylene sulfide) with a number average molecular weight of 22,100 g/mol has been synthesized with an IV in DMPU of 0.62 dL/g at 30 °C. Creasable films of this polymer have been prepared by solvent casting and melt pressing at 250 °C. Films of poly(thianthrene phenylene sulfide) exhibit transparencies greater than 50% at wavelengths exceeding 400 nm and a high refractive index value of 1.692 at a wavelength of 633 nm, making the polymer interesting for optical applications. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 2453–2461, 2009
A comparative study of temperature dependence of induction time and oscillatory frequency in polymer‐immobilized and free catalyst Belousov‐Zhabotinsky reactions
Authors: Pullela Srinivasa R. , Shen Jingyi , Marquez Manuel , Cheng Zhengdong
Published: March 2009

Environment‐sensitive poly(N‐isopropylacrylamide) (PNIPAM) microgel particles with covalently bonded ruthenium(4‐vinyl‐4′‐methyl‐2,2′‐bipyridine) bis (2,2′‐bipyridine) [Ru(vmbipy)(bipy)2] display periodic size changes when placed in Belousov‐Zhabotinsky (BZ) reaction substrates. The temperature dependency of the induction time and oscillatory frequency of the BZ reaction in this polymer‐immobilized catalyst system were compared to the bulk BZ reaction with the catalyst in the solution phase. Prolonged induction times are observed for the immobilized catalyst, compared with free catalyst, while little difference is observed on the oscillation frequency. The Arrhenius frequency factor calculated using the induction time for the immobilized catalyst BZ reaction is about seven times smaller than that for the free catalyst Ru(bipy) case. On the other hand, the Arrhenius frequency factors calculated using the oscillatory frequency are almost the same, showing similar reaction kinetics during the BZ oscillations. The tunability of the induction time using a polymer matrix, as we observed here, while maintaining similar oscillatory behavior, should provide a new dimension to control the self‐assembling of BZ active particles. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 847–854, 2009
Effect of thermal history on the free volume properties of semi‐crystalline poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) membranes by positron annihilation lifetime spectroscopy
Authors: Cheng Mei‐Ling , Sun Yi‐Ming
Published: March 2009

Free volume properties of a series of poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) (PHBV) membranes, which were produced by various nonisothermal crystallization processes (rapid‐, step‐, and slow‐cooling processes), were investigated using positron annihilation lifetime (PAL) spectroscopy over a temperature range of 25–90 °C. From the annihilation lifetime parameters, the temperature dependence of free volume size, amount, size distribution, and fractional free volume and thermal expansion properties of free volume were discussed. A model which assumed that amorphous phase was subdivided into mobile and rigid amorphous fractions (MAF and RAF) in the semicrystalline polymer was considered to interpret the temperature dependence of those free volume properties. Morphological observation of the semicrystalline polymer by small‐angle X‐ray scattering (SAXS) indicated that the rapid‐cooled (cold‐crystallized) membranes showed a much thinner thickness of the repeating lamellar/amorphous layers and most likely higher amount of RAF, which restrained the chain motion, than the step‐ and slow‐cooled (melt‐crystallized) membranes. The difference of free volume properties among various PHBV membranes was created according to the crystalline structure of the polymer from different thermal history. The polymer crystallized with slower cooling rate induced higher crystallinity and resulted in less free volume amount and lower fractional free volume. In addition, the thermal expansion coefficients of free volume size were affected by the crystallization rate of PHBV polymer. Larger distribution of the free volume size of melt‐crystallized membranes was observed as a result of the bimodal distribution of the lamellar periodicity and less amount of RAF than that of the cold‐crystallized membranes. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 855–865, 2009
Effect of EVM/EVA‐g‐MAH ratio on the structure and properties of nylon 1010 blends
Authors: Yu Haiyang , Zhang Yong , Ren Wentan
Published: March 2009

The nylon 1010/ethylene‐vinyl acetate rubber (EVM)/maleated ethylene‐vinyl acetate copolymers (EVA‐g‐MAH) ternary blends were prepared. The effect of EVM/EVA‐g‐MAH ratio on the toughness of blends was examined. A super tough nylon 1010 blends were obtained by the incorporation of both EVM and EVA‐g‐MAH. Impact essential work of fracture (EWF) model was used to characterize the fracture behavior of the blends. The nylon/EVM/EVA‐g‐MAH (80/15/5) blend had the highest total fracture energy at a given ligament length (5 mm) and the highest dissipative energy density among all the studied blends. Scanning electron microscopy images showed the EVM and EVA‐g‐MAH existed as spherical particles in nylon 1010 matrix and their size decreased gradually with increasing EVA‐g‐MAH content. Large plastic deformation was observed on the impact fracture surface of the nylon/EVM/EVA‐g‐MAH (80/15/5) blend and related to its high impact strength. Then with increasing EVA‐g‐MAH proportion, the matrix shear yielding of nylon/EVM/EVA‐g‐MAH blends became less obvious. EVM and EVA‐g‐MAH greatly increased the apparent viscosity of nylon 1010, especially at low shear rates. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 877–887, 2009
A thermodynamic analysis of specific interactions in homoblends of poly(styrene‐co‐4‐vinylpyridine) and poly(styrene‐co‐methacrylic acid)
Authors: Elmiloudi Khaled , Djadoun Said
Published: March 2009

Miscibility and strong specific interactions that occurred within homoblends of poly(styrene‐co‐4‐vinylpyridine) containing 15 mol % of 4‐vinylpyridine (PS4VP15) and poly(styrene‐co‐methacrylic acid) containing 15 mol % of methacrylic acid (PSMA15) have been examined by Fourier Transform infrared spectroscopy and DSC. The observed positive deviation of the glass transition temperature of the blends from the linear average line, was analyzed by the frequently used theoretical conventional approaches including the one very recently proposed by Brostow. A better fit was obtained when this latter is used. A reasonable agreement with experimental values was also obtained when the theoretical fitting parameter free method developed by Coleman, is applied to predict the composition dependence of the Tg of this system. A thermodynamic analysis of hydrogen bonding in this system was carried using the Painter‐Coleman association model and the variation of the Gibbs function of mixing and its different contributions and corresponding phase diagrams as a function of temperature and composition were estimated. This analysis predicted PSMA15 to be miscible with PS4VP15 in the whole composition range up to 150 °C. Above this temperature, a partial miscibility is predicted when the PS4VP15 is in excess. The DSC results are in agreement with these predictions. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 923–931, 2009
Double yielding in PA6/TPV‐MAH blends: Effect of crosslinking degree of the dispersed phase
Authors: Tang Xue‐Gang , Yang Wei , Shan Gui‐Fang , Xie Bang‐Hu , Yang Ming‐Bo , Hou Meng
Published: March 2009

Thermoplastic vulcanizates (TPVs) based on PP and EPDM (the ratio is 5:5) with different crosslinking degrees were prepared using different contents of phenolic resins, and then blended with polyamide 6 (PA6). The results indicated that with an increase in crosslinking degree, the double yielding phenomenon in PA6/TPV blends became more distinct, the yield stress of the first yield point and the yield stress difference of the two yield points decreased; however, the yield strain of the first yield point did not change with the increasing crosslinking degree of the TPV, but the yield strain of the second yield point increased, resulting in a more broadened yield region. The SEM results showed that with an increase in the crosslinking degree of TPV, the diameter of TPV increased in the core layer, and the orientation degree of TPV in the skin and subskin layer deceased, accompanying with a decrease of the ratio of length to diameter (L/D) of the droplets. The morphology evolution of the PA6/TPV blend during the tensile test was also studied, and the results agreed well with the model we proposed. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 912–922, 2009
Compressing the free energy range of substructure stabilities in iso‐1‐cytochrome c
Authors: Duncan Michael G. , Williams Michael D. , Bowler Bruce E.
Published: March 2009

Evolutionary conservation of substructure architecture between yeast iso‐1‐cytochrome c and the well‐characterized horse cytochrome c is studied with limited proteolysis, the alkaline conformational transition and global unfolding with guanidine‐HCl. Mass spectral analysis of limited proteolysis cleavage products for iso‐1‐cytochrome c show that its least stable substructure is the same as horse cytochrome c. The limited proteolysis data yield a free energy of 3.8 ± 0.4 kcal mol−1 to unfold the least stable substructure compared with 5.05 ± 0.30 kcal mol−1 for global unfolding of iso‐1‐cytochrome c. Thus, substructure stabilities of iso‐1‐cytochrome c span only ∼1.2 kcal mol−1 compared with ∼8 kcal mol−1 for horse cytochrome c. Consistent with the less cooperative folding thus expected for the horse protein, the guanidine‐HCl m‐values are ∼3 kcal mol−1M−1 versus ∼4.5 kcal mol−1M−1 for horse versus yeast cytochrome c. The tight free energy spacing of the yeast cytochrome c substructures suggests that its folding has more branch points than for horse cytochrome c. Studies on a variant of iso‐1‐cytochrome c with an H26N mutation indicate that the least and most stable substructures unfold sequentially and the two least stable substructures unfold independently as for horse cytochrome c. Thus, important aspects of the substructure architecture of horse cytochrome c, albeit compressed energetically, are preserved evolutionally in yeast iso‐1‐cytochrome c.
About charge‐transport mechanisms in mesoporous silicon under adsorption of plant viruses
Authors: Vashpanov Yuriy , Son Jung‐Young , Kwack Kae‐Dal , Woo Sun‐Bo , Choi Kyu‐Hwan
Published: March 2009

Changes in the electric parameters and the charge‐transport mechanism in a mesoporous silicon under adsorption of TORSV (tomato ringspot virus) and GFLV (grapevine fan leaf virus) NEPO‐viruses are analyzed. The mechanism influencing the electric characteristics of the mesoporous silicon under adsorption of the plant viruses is related with the changes in parameters of a potential‐barrier system due to redistribution of voltages at the silicon structure. The mechanism of charge transport in the mesoporous silicon is more likely connected to the changes in parameters of isotopic heterojunction barriers under small bias voltages, and it can be interpreted as Poole–Frenkel and tunnel conductivity for large bias. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Defect reduction in non‐polar (11$ \bar 2 $0) GaN grown on (1$ \bar 1 $02) sapphire
Authors: Johnston Carol F. , Kappers Menno J. , Moram Michelle A. , Hollander Jonathan L. , Humphreys Colin J.
Published: March 2009

This work assesses the relative effectiveness of different techniques to reduce defect density in heteroepitaxial, non‐polar, a ‐plane GaN films grown on r ‐plane sapphire by MOVPE. Plan view TEM was used to obtain the defect density of films grown by different methods. The as‐grown material was found to have a high dislocation and basal plane stacking fault (BSF) density (1.9 (± 0.2) × 1011 cm–2 and 1.1 (± 0.9) × 106 cm–1 respectively). The four defect reduction techniques tested were: 3D–2D growth, SiNx interlayers, ScN interlayers and epitaxial lateral overgrowth (ELOG). Both dislocation and BSF density were reduced by all methods compared to the as‐grown material. The lowest defect density was achieved in the (0001) wing of the ELOG sample and was <1 × 106 dislocations cm–2 and 2.0 (± 0.7) × 104 BSFs cm–1. On the wafer scale, ScN interlayers were most effective: A single 5 nm thick ScN interlayer reduced the BSF density to 5.9 (± 0.8) × 105 cm–1 and the dislocation density was reduced by two orders of magnitude to 1.8 (± 0.2) × 109 cm–2 compared to the as‐grown material. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Observation of novel defect structure in 2H‐AlN grown on 6H‐SiC(0001) substrates with 3‐bilayer‐height step‐and‐terrace structures
Authors: Okumura Hironori , Horita Masahiro , Kimoto Tsunenobu , Suda Jun
Published: March 2009

250 nm thick AlN layers without a nucleation layer were grown directly on 6H‐SiC(0001) with 3‐bilayer‐height steps by rf‐plasma‐assisted molecular‐beam epitaxy. The structure and morphology of the AlN layers have been studied using atomic force microscopy, X‐ray diffraction and transmission electron microscopy. Two different types of unique defect structures were observed. Rows of pure‐edge‐type threading dislocations were observed along the pre‐existing step‐edges of the SiC substrate for AlN grown on as‐gas‐etched SiC substrates, while the planar defects threading through the AlN layer were observed at the step‐edges of the substrate for AlN on SiC with sacrificial oxidation. We concluded that these planar defects were the stacking mismatch boundaries due to the difference in stacking sequence of AlN layers on different SiC terraces. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Porous silicon/metal nanocomposite with tailored magnetic properties
Authors: Granitzer Petra , Rumpf Klemens , Poelt Peter , Krenn Heinz
Published: March 2009

Porous silicon (PS) templates in the meso/macro porous regime with oriented pores clearly separated from each other and filled in a galvanic deposition process with various metals, especially ferromagnetic ones are magnetically investigated. The employment of different metals (e.g. Ni, Co, NiCo) together with the variation of the electrochemical deposition parameters modifies the structural characteristics of the PS/metal nanocomposite and thus leads to distinct magnetic properties of the hybrid system. Furthermore the use of different PS‐templates which means a change of the pore‐diameter and interpore spacing results also in various magnetic characteristics, especially influences on the magnetic interactions among the deposited metal nanostructures. Therefore the specimens show tailored magnetic properties like coercivity, squareness and magnetic anisotropy. The achieved nanocomposite merges electronic properties of a semiconductor with nanomagnetism and therefore opens the possibility of integrated spin‐based electronic devices. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Straining of thin Si films by partially oxidized meso‐porous Si substrates
Authors: Lysenko Vladimir , Ostapenko Dmytro , Bluet Jean‐Marie , Regregny Philippe , Mermoux Michel , Boucherif Abderraouf , Marty Olivier , Grenet Genevieve , Skryshevsky Valery , Guillot Gerard
Published: March 2009

A simple and low‐cost technological approach for the straining of thin crystalline silicon (Si) films using porous silicon (PS) as stress generating nanomaterial is reported. Firstly, a technological approach allowing fabrication of thin Si films on a bulk meso‐PS substrate is described. Secondly, low temperature (<700 °C) oxidation of the PS/Si structures provokes a huge mechanical stress at nanoscale level inside the PS substrate. Consequently, the lateral PS straining induces biaxial deformation of the monocrystalline thin Si layer in the (100) plane parallel to the wafer surface. Raman scattering spectroscopy is used for the evaluation of strain values across the strained thin Si films. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Semiconducting half‐Heusler and LiGaGe structure type compounds
Authors: Casper Frederick , Seshadri Ram , Felser Claudia
Published: March 2009

Compounds with LiAlSi (half‐Heusler) and LiGaGe structure types have been investigated by means of band structure calculations. The LiAlSi structure type is known as the half‐Heusler structure type, whereas LiGaGe is a closely related hexagonal variant. A remarkable feature of some XYZ half‐Heusler compounds with 8 and 18 valence electrons is, that despite being composed of only metallic elements, they are semiconductors. More than 100 semiconducting compounds within these structure types are known. LiGaGe compounds have an additional degree of freedom, namely the degree of puckering of the layers. These compounds can become semiconducting at a certain degree of puckering. Half‐metallic behavior is rarely found in this structure type. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)