bluuebunny/crossref_metadata_2025 huggingface dataset:
12/15-Lipoxygenase Counteracts Inflammation and Tissue Damage in Arthritis
Authors: Krönke Gerhard , Katzenbeisser Julia , Uderhardt Stefan , Zaiss Mario M. , Scholtysek Carina , Schabbauer Gernot , Zarbock Alexander , Koenders Marije I. , Axmann Roland , Zwerina Jochen , Baenckler Hans W. , van den Berg Wim , Voll Reinhard E. , Kühn Hartmut , Joosten Leo A. B. , Schett Georg
Published: August 2009

Eicosanoids are essential mediators of the inflammatory response and contribute both to the initiation and the resolution of inflammation. Leukocyte-type 12/15-lipoxygenase (12/15-LO) represents a major enzyme involved in the generation of a subclass of eicosanoids, including the anti-inflammatory lipoxin A4 (LXA4). Nevertheless, the impact of 12/15-LO on chronic inflammatory diseases such as arthritis has remained elusive. By using two experimental models of arthritis, the K/BxN serum-transfer and a TNF transgenic mouse model, we show that deletion of 12/15-LO leads to uncontrolled inflammation and tissue damage. Consistent with these findings, 12/15-LO-deficient mice showed enhanced inflammatory gene expression and decreased levels of LXA4 within their inflamed synovia. In isolated macrophages, the addition of 12/15-LO-derived eicosanoids blocked both phosphorylation of p38MAPK and expression of a subset of proinflammatory genes. Conversely, 12/15-LO-deficient macrophages displayed significantly reduced levels of LXA4, which correlated with increased activation of p38MAPK and an enhanced inflammatory gene expression after stimulation with TNF-α. Taken together, these results support an anti-inflammatory and tissue-protective role of 12/15-LO and its products during chronic inflammatory disorders such as arthritis.
Crucial Contribution of Thymic Sirpα+ Conventional Dendritic Cells to Central Tolerance against Blood-Borne Antigens in a CCR2-Dependent Manner
Authors: Baba Tomohisa , Nakamoto Yasunari , Mukaida Naofumi
Published: August 2009

Thymic dendritic cells (DCs) as well as thymic epithelial cells are presumed to be major sentinels in central tolerance by inducing the apoptosis of autoreactive T progenitor cells. The thymic DC population is composed of heterogeneous subsets including CD11c+B220+ plasmacytoid DCs, CD11c+B220−CD8α+ signal regulatory protein α (Sirpα)− and CD11c+B220−CD8α−Sirpα+ conventional DCs (cDCs). However, the distinctive role of each DC subset remains undefined. We show herein that Sirpα+ cDCs, a minor subpopulation, was disseminated in the thymic cortical area with some of them uniquely localized inside perivascular regions and nearby small vessels in the thymus. The Sirpα+ but not Sirpα− cDC subset can selectively capture blood-circulating Ags. Moreover, in CCR2-deficient mice, the thymic Sirpα+ cDC subset, but not other thymic cell components, was moderately decreased especially in the perivascular regions. Concomitantly, these mice exhibited a modest impairment in intrathymic negative selection against blood-borne Ags, with the reduced capacity to uptake blood-borne Ags. Given their intrathymic cortical localization, CD11c+B220−CD8α−Sirpα+ cDCs can have a unique role in the development of central tolerance against circulating peripheral Ags, at least partially in a CCR2-dependent manner.
Self-Peptides Prolong Survival in Murine Autoimmunity via Reduced IL-2/IL-7-Mediated STAT5 Signaling, CD8 Coreceptor, and Vα2 Down-Regulation
Authors: Gutermuth Jan , Nograles Kristine E. , Miyagawa Fumi , Nelson Emily , Cho Young-Hun , Katz Stephen I.
Published: August 2009

Although the pathogenic role of B cells and CD4 T cells has been studied extensively, less is known about the role of CD8 T cells in autoimmunity and self-tolerance. To evaluate the role of CD8 T cells in autoimmunity and its modulation using self-peptides, we used mice expressing soluble OVA (sOVA) under control of the keratin-14 promoter. Spontaneous autoimmunity occurred when sOVA mice were crossed with OT-I mice, whose CD8 T cells carry a Vα2/Vβ5-transgenic TCR with specificity for the OVA257–264 peptide. Eighty-three percent of OVA/OT-I mice died during the first 2 wk of life due to multiple organ inflammation. In contrast, preventive or therapeutic OVA257–264 peptide injections induced a dose-dependent increase in survival. Healthy survivors exhibited reductions in peripheral CD8 T cells, CD8 coreceptor, and Vα2 expression. Furthermore, CD8 T cells from healthy mice were anergic and could not be activated by exogenous IL-2. A block in IL-2/IL-7 signaling via the STAT5 pathway provided the basis for low surface expression of the CD8 coreceptor and failure of IL-2 to break CD8 T cell anergy. Thus, the soluble TCR ligand triggered multiple tolerance mechanisms in these sOVA/OT-I mice, making this treatment approach a potential paradigm for modulating human autoimmune diseases.
Violence and the Daniel tales in a children’s Bible
Authors: Nel Marius
Published: August 2009

Children enjoy the tales of Daniel and his three friends, whether told in Sunday school, day school, by parents or grandparents. These tales are cast essentially in violent terms. In this article a specific version of the tales in a children’s Bible is analysed to show in what way violence serves as the thread that holds the tales together and to suggest that this might imply that violence is condoned, be it violence committed by God for the sake of his children or by his children for their own sakes. Through ideology, criticism and deconstruction it is shown how a socially engaged reading of the text necessitates narrators of the Daniel tales to criticise violence embedded within the Biblical text, especially when these tales are narrated to children.
Congregational analysis revisited: Empirical approaches
Authors: Nel Malan
Published: August 2009

The research problem of concern here is: What criteria should be used when congregations are analysed? Congregations as faith communities are defined variously. Discerning the local congregation as a defined and as an empirical subject plays a major role in answering the research question. The theological points of departure are that any measure of a local congregation has to deal with issues like faithfulness to the gospel and the missional identity and integrity of the congregation as a contextual faith community. The hypothesis is that, when theologically informed and motivated, congregations can and should be analysed in the process of continuing reformation. This article describes a number of approaches to and outcomes of empirical research related to congregational analysis. Follow-up research to be submitted for publication will deal with the missional identity, the ministerial role-fulfilment of the congregation, and a proposal to analyse these in a way that is theologically faithful and contextually relevant.
Neurobiophysics
Authors: Kolomytkin Oleg V. , Marino Andrew A.
Published: August 2009

Attempts to understand the individual and collective properties of neurons are made from numerous scientific perspectives. We describe the results of traditional approaches that emphasize the importance of physical laws and the elucidation of mechanisms, and discuss recent developments regarding the properties of interacting neuronal systems. The present view of the structure of ion channels is summarized, followed by an explanation of their role in the generation and propagation of action potentials. Important dynamical processes that occur in systems of neurons are treated, including processes that occur in sensory systems, neural networks, and in the volume transmission of electrical and chemical systems in the central nervous system. Uses of nonlinear analysis to characterize brain electrical activity are delineated, and new experimental methods for studying memory and learning are outlined. Further insights into how the nervous system mediates behavior seems likely to emerge from an approach that integrates well‐established reductionistic strategies with reliance on abstract concepts and the use of nonlinear methods.
Molecular Dynamics Computations for Proteins: A Case Study in Membrane Ion Permeation
Authors: Vorobyov Igor , Allen Toby W.
Published: August 2009

Computer simulation can provide an atomic‐level view of protein structure and function that is unattainable with experiments alone. In this chapter, we demonstrate how molecular dynamics (MD) simulation can reveal the microscopic mechanisms of biomolecular activity. In particular, we illustrate the quantitative value of MD simulation by exploring ion channel proteins that allow selective permeation of charged molecules across cell membranes to control our nervous systems and chemical activity in the body. We begin by introducing the basic statistical mechanical formulation and methodological aspects of modern day MD simulations. We then discuss how to analyze a simulation to obtain mechanistic insight through calculation of various molecular properties. Special attention is given to quantitative thermodynamic calculations, which are the driving forces of protein function. We explain how to calculate free energies and equilibrium constants using potential of mean force (PMF) and free energy perturbation (FEP) techniques as well as the use of more advanced sampling approaches. These methods are then used to study ion permeation through the gramicidin A (gA) channel as well as the energetics of arginine side chain translocation across a lipid bilayer to assess models of voltage‐gated ion channel activation.
Chiral
R
aman and Single Molecule Spectroscopy
Authors: Abdali Salim , Blanch Ewan W.
Published: August 2009

Chiral Raman spectroscopy, widely known as
Raman optical activity (ROA)
, is a vibrational tool, which besides information on structure and folding of molecules, provides information on their chirality. This tool has been employed since the early 1970 s; however, it has been limited to very few groups within the vibrational spectroscopy community, because using this tool several requirements for the instrumentation as well as the sample condition and detection have to be fulfilled. Although the first requirement concerns full control of the polarization state of the light, simultaneously for the right‐ and left‐circular polarization states, the latter requirement concerns high concentration of the sample. Consequently and because of the signal collection involving subtraction of the left‐ and right scattered light, the ROA signal is much weaker than the Raman, thus requires much longer acquisition times. After the discovery of the surface‐enhanced Raman scattering (SERS) effect in 1974, the hope of combining SERS with ROA (into surface‐enhanced Raman optical activity (SEROA)) grew high, in that the giant signal provided by SERS was thought to enable much faster ROA measurements and for much lower concentration, even down to the single molecule level. Nevertheless, three decades passed before SEROA studies began to appear in the literature. In spite of the fact that these studies are not yet at the single molecule level, they do provide SEROA from very low concentration (below μM). Here, we introduce SEROA's historical background, theory, instrumentation, and the recent results, achieved by the authors' research groups.
Biosimulation and Computations in Systems Biology
Authors: Sosnovtseva Olga , Laugesen Jakob L. , Mosekilde Erik
Published: August 2009

We give an overview of the physical basics, experimental techniques, and selected applications of single molecule fluorescence in biophysical research. The photophysical principles underlying single molecule fluorescence resonance energy transfer (smFRET) experiments are treated. Its application in protein biophysics, in particular protein folding and conformational dynamics associated with enzymatic activity, is outlined with selected model systems.
R
aman Spectroscopy in Medicine
Authors: Krafft Christoph , Rösch Petra , Popp Jürgen
Published: August 2009

Raman spectroscopy is an emerging tool in medicine to study tissues and body fluids. This contribution gives an overview of experimental techniques and selected applications. The methodological section presents Raman spectra of biomolecules, the near‐infrared advantage, combination with microscopy, Raman imaging, fiber‐optic probes, and signal enhancement principles. Pathological applications of Raman spectroscopy were reported in the context of oncology, for mineralized tissue such as bone, teeth, and calculi in organs, for blood vessels, for skin, and for the visual system. Raman spectroscopy in clinical chemistry was applied to determine glucose in diabetic patients; to analyze serum, hair and nails; and to investigate malaria.
Design of a two‐step pulsed pressure‐swing adsorption‐based oxygen concentrator
Authors: Rao V. Rama , Farooq S. , Krantz W. B.
Published: August 2009

A two‐step pulsed pressure‐swing adsorption (PPSA) process has been modeled to assess the extent to which an oxygen concentrator might be miniaturized for medical applications. The process consists of a single bed of packed adsorbent particles that is alternately pressurized and depressurized at the feed end. An enriched oxygen product is withdrawn at ambient pressure from the product end when the bed is pressurized at the feed end. The product end remains closed during depressurization. The model development addresses the manner in which axial dispersion enters into the describing equations and the formulation of proper boundary conditions, both of which have not been handled rigorously in some prior modeling studies. The describing equations are solved using COMSOL® Multiphysics software. The effect on the performance of the adsorption time, desorption time, bed length, particle diameter, and imposed pressure drop across the bed have been investigated. An interesting novel result is that for a chosen particle size, bed length, and applied pressure drop, there is an optimum combination of adsorption and desorption times that maximizes the product purity. The results suggest that there are operating windows for both 5A and partially Ag‐exchanged Li‐substituted 13X zeolite adsorbents wherein the product oxygen purity is greater than 90%. At a given product flow rate within this operating window, the extent of miniaturization is limited by the (maximum) cycling frequency that is practically achievable. Sizing of an oxygen concentrator for personal medical applications is also discussed. A principal conclusion is that a compact oxygen concentrator capable of producing a highly oxygen‐enriched product is possible using commercially available adsorbents and implementable operating conditions. © 2009 American Institute of Chemical Engineers AIChE J, 2010
Towards a unified classification of the ectodermal dysplasias: Opportunities outweigh challenges
Authors: Irvine Alan D.
Published: August 2009

The ectodermal dysplasias include a complex and highly diverse group of heritable disorders that share in common developmental abnormalities of ectodermal derivatives. The broader definition of ectodermal dysplasias (as heritable disorders involving at least two of the ectodermal derivatives nails, teeth, hair, and eccrine sweat glands) encompasses 170–200 conditions. Some conditions included by this definition are relatively common; others are rare and, in some cases, family‐specific. Classification of the ectodermal dysplasias has largely been approached by categorizing patterns of clinical findings (phenotypic grouping). In the last 2 decades great progress has been made in understanding the molecular pathogenesis and inter‐relatedness of some of these conditions and a new consensus approach to classification that incorporates this new information is needed. A comprehensive and definitive classification of these disorders would be highly valuable for the many stakeholders in ED. As disease‐specific molecular treatments are developed, accurate classification will assume greater importance in designing registries to enable rapid identification of those with rare disorders who may wish to participate in clinical trials. Ideally a working classification of such a disparate collection of conditions would have a design and architecture that would facilitate easy accessibility by each of the key stakeholder groups and would encourage enhanced interaction between these parties. Attaining this objective is a major challenge but is achievable. This article reviews the historical‐clinical perspective and the impact of recent developments in molecular biology in the field. Reflections are offered as to the future direction of classification systems in these disorders. © 2009 Wiley‐Liss, Inc.
Classifying ectodermal dysplasias: Incorporating the molecular basis and pathways (Workshop II)
Authors: Wright J. Timothy , Morris Clark , Clements Suzanne E. , D'Souza Rena , Gaide Olivier , Mikkola Marja , Zonana Jonathan
Published: August 2009

Hereditary conditions are traditionally classified based either on physical/physiological attributes or using the names of the individuals credited with identifying the condition. For the 170 plus conditions classified as ectodermal dysplasias (EDs), both of these nosological systems are used, at times interchangeably. Over the past decade our knowledge of the human genome and the molecular basis of the EDs have greatly expanded providing the impetus to consider alternative classification systems. The incorporation of the molecular basis of hereditary conditions adds important information allowing effective transfer of objective genetic information that can be lacking from traditional classification systems. Molecular information can be added to the nosological system for the EDs through a hierarchical‐ and domain‐based approach that encompasses the condition's name, mode of inheritance, molecular pathway affected, and specific molecular change. As new molecular information becomes available it can be effectively incorporated using this classification approach. Integrating molecular information into the ED classification system, while retaining well‐recognized traditional syndrome names, facilitates communication at and between different groups of people including patients, families, health care providers, and researchers. © 2009 Wiley‐Liss, Inc.
Genetic testing in ectodermal dysplasia: Availability, clinical utility, and the nuts and bolts of ordering a genetic test
Authors: Bale Sherri J. , Mitchell Allison G.
Published: August 2009

“Ectodermal Dysplasia syndromes” comprise a diverse group of heritable conditions characterized by congenital anomalies of one or more ectodermal structures and their appendages: hair, teeth, nails, and sweat glands. Genetic testing is available for many types of ectodermal dysplasia (ED) through clinical and/or research laboratories. We address the distinctions between genetic testing as performed on a clinical versus research basis, and summarize the clinical aspects, testing methodology, and sensitivity for those ED syndromes for which testing is available in a clinical laboratory. Lastly, we leave the laboratory for the clinical setting to discuss the utility of genetic testing for patients and their families, and summarize the practical issues involved in ordering a genetic test. © 2009 Wiley‐Liss, Inc.
New clinico‐genetic classification of trichothiodystrophy
Authors: Morice‐Picard Fanny , Cario‐André Muriel , Rezvani Hamid , Lacombe Didier , Sarasin Alain , Taïeb Alain
Published: August 2009

Trichothiodystrophy (TTD) is a congenital hair dysplasia with autosomal recessive transmission. Cross banding pattern under polarized light plus trichoschisis and a low sulfur content of hair shafts define the disorder, which is associated with variable and neuroectodermal symptoms. So‐called photosensitive forms of TTD (with low level of in vitro UV‐induced DNA repair, not constantly associated with marked clinical photosensitivity) are caused by mutations in genes encoding subunits of the transcription/repair factor IIH (TFIIH). Ten percentage of nonphotosensitive patients are known to have TTDN1 mutations, the specific role of which is unknown. We studied nine patients recruited at our institution and reviewed 79 with molecular analysis out of 122 TTD patients reported in literature with the aim to collect systematically the clinical findings in TTD patients and establish genotype–phenotype correlations. The frequency of congenital ichthyosis, collodion‐baby type, was significantly higher in the TFIIH mutated group. Hypogonadism was significantly more frequent in the non‐photosensitive group. There was no statistical difference regarding osseous anomalies. Mutations in TFIIH sub‐units leading to abnormal expression in genes involved in epidermal differentiation could explain the particular dermatological changes seen in photosensitive cases of TTD. We suggest a new clinico‐genetic classification of TTD, which may help clinicians confused by the current acronyms used (IBIDS, PIBIDS…). Understanding the TTD ichthyotic phenotype could lead to therapeutic advances in the management of TTD and other types of ichthyoses. © 2009 Wiley‐Liss, Inc.
Acute stroke therapy with tissue plasminogen activator (tPA) since it was approved by the U.S. Food and Drug Administration (FDA)
Authors: Zivin Justin A.
Published: August 2009

Tissue plasminogen activator (tPA) for acute ischemic stroke was approved by the U.S. Food and Drug Administration (FDA) in 1996. Since then it has been severely underutilized. At the time when most practitioners were first being exposed to the literature concerning tPA, there were many concerns about safety and the restrictions on use were quite onerous. Since then a good deal of further work has been done to loosen the restrictions and allay concerns about the risks. The true risk to benefit ratio is far better than is generally realized. Now it is mostly economic problems related to the costs of constantly supplying emergency care that is limiting access. Furthermore, in the current litigious environment, failure to treat is likely to be a more hazardous course of action than legal exposure due to poor outcomes. It must be emphasized that the drug is quite safe and highly effective, and current utilization rates are unacceptably low. Ann Neurol 2009;66:6–10
Quick assessment of the thermal decomposition behavior of lignocellulosic biomass by near infrared spectroscopy and its statistical analysis
Authors: Lee Seung‐Hwan , Cho Hyun‐Woo , Labbé Nicole , Jeong Myong K.
Published: August 2009

The application of near infrared (NIR) spectroscopy for the prediction of the thermal decomposition behavior of lignocellulosic biomass (three types of woody biomass and three types of herbaceous biomass) was successfully performed along with statistical analysis. The thermal degradation behaviors of the woody and herbaceous biomass were different because of their different chemical compositions. Herbaceous biomass was degraded at lower temperature than woody biomass. The weight‐loss profiles as a function of temperature were obtained by thermogravimetric analysis (TGA) at a heating rate of 25°C/min under nitrogen gas. The weight‐loss percentage at 10 temperatures in the range 150–600°C was predicted by a wavelet partial least squares (PLS) model, which showed significantly better predictive performance than the ordinary PLS model. The results show that the data predicted by the wavelet PLS model was well fitted to the original data by TGA, in which the root‐mean‐square error in prediction values less than 5.5 suggested that NIR spectroscopy was applicable for rapid analysis to characterize the thermal decomposition behavior of lignocellulosic biomass for energy production. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Experimental characterization and modeling stiffness of polymer/clay nanocomposites within a hierarchical multiscale framework
Authors: Mesbah A. , Zaïri F. , Boutaleb S. , Gloaguen J. M. , Naït‐Abdelaziz M. , Xie S. , Boukharouba T. , Lefebvre J. M.
Published: August 2009

To provide a better understanding of the relationship between nanostructure and overall material stiffness in the case of polymer/clay nanocomposites, both analytical and finite element modeling were considered. A micromechanical analytical approach based on a multiscale framework is presented in which special attention is devoted to the constrained region around reinforcements. The thickness of the constrained region is seen as a characteristic length scale and the effect of particle size is explicitly introduced in the model. Moreover, the constrained region presents graded properties. The hierarchical morphology of intercalated silicate stacks is also explicitly introduced in the micromechanical model from an equivalent stiffness method in which the silicate stacks are replaced by homogeneous particles with constructed equivalent anisotropic stiffness. The orientational averaging process is used to derive the overall stiffness tensor of nanocomposite materials containing randomly oriented reinforcements. The respective influence of volume fraction, aspect ratio, size and orientation of the reinforcements, matrix properties, number of silicate layers per stack, and interlayer spacing on the overall nanocomposite stiffness is analyzed. The overall stiffness of polymer/clay nanocomposite systems is also evaluated by means of finite element simulations and the results compare favorably with model predictions. From an experimental point of view, relevant morphological and mechanical data were obtained on polyamide‐6 nanocomposites prepared using a modified montmorillonite Cloisite 30B and an unmodified sodium montmorillonite Cloisite Na+. The amount of constrained region around reinforcements was estimated using results issued from dynamic mechanical analyses and differential scanning calorimetry. Comparison to the model clearly underlines the contribution of the constrained region to the stiffness improvement. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Characterization of enzyme‐deproteinized skim rubber
Authors: George K. Mariamma , Alex Rosamma , Joseph Susamma , Thomas K. T.
Published: August 2009

Skim natural rubber latex is a protein‐rich byproduct obtained during the centrifugal concentration of natural rubber latex. Skim latex has a very low dry rubber content (4–8%), and the rubber particles are smaller in size. It has a higher proportion of nonrubber solids, which are mostly proteinaceous in nature. It is difficult to coagulate, and it takes more processing time. The proteins in skim latex can be decomposed by proteolytic enzymes. This article discusses the use of stabilized liquid papain from the papaya plant (Carica papaya) for deproteinization followed by creaming for quick and easy coagulation of skim latex. The technological properties and aging characteristics of the deproteinized skim rubber are compared with those of conventionally prepared skim rubber and block rubber. The deproteinized skim rubber showed enhanced quality parameters. Particle size analysis revealed that deproteinization and creaming of the skim latex did not markedly change the particle size. Gel permeation chromatography showed a reduction in the quantity of fatty acids after deproteinization and creaming, which was reflected in the improvement of the aging characteristics in comparison with the control sample. Vulcanizates prepared with the deproteinized skim rubber had higher resilience, lower heat buildup, lower compression set, and good tensile strength and elongation at break in comparison with conventionally prepared skim rubber, and the properties were almost comparable to those of block rubber. The improvement in the mechanical properties and aging characteristics could be attributed to the reduction of the protein content, the partial removal of unsaturated fatty acids, and the removal of metal ions that were pro‐oxidants during the deproteinization and creaming process. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Dielectric properties and solubility of multilayer hyperbranched polyimide/polyhedral oligomeric silsesquioxane nanocomposites
Authors: Somboonsub Bongkoch , Thongyai Supakanok , Praserthdam Piyasan
Published: August 2009

Multilayer hyperbranched polyimide/polyhedral oligomeric silsesquioxane (POSS) nanocomposites were synthesized by the reaction of a bromide‐hyperbranched polyether/POSS and a main‐chain polyimide containing hydroxyl‐functional groups. The first layer was formed through the direct reactions of the main‐chain hydroxyl groups with monochloroisobutyl polyhedral oligomeric silsesquioxane (POSS–Cl). The second and third layers were prepared by the repeated reactions of bromine ether branches that incorporated POSS–Cl with 3,5‐dihydroxybenzyl alcohol. Regardless of the fixed amount of POSS, the higher layers yielded lower dielectric constants. Even when the amount of the POSS loading was reduced 4‐fold, the third layer still had the lowest dielectric constants. The lowest dielectric constant of 2.54 was found in the third layer of the hyperbranched polyimide/POSS nanocomposite because of the large free volume and loose polyimide structures. The densities of the hyperbranched polyimide/POSS nanocomposite corresponded to the dielectric constants. The lower the density was, the higher the free volume was and the lower the dielectric constant was. The experimental results indicated that the hyperbranched polyimide/POSS nanocomposite exhibited increased solubility in comparison with pure polyimide. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Preparation of a crosslinked polyelectrolyte membrane for fuel cells with an allyl methacrylate based two‐step reaction
Authors: Kishi Akira , Umeda Minoru
Published: August 2009

In this study, a proton‐exchange membrane for fuel cells was prepared via a two‐step reaction with an allyl methacrylate (AMA) as an asymmetric crosslinking agent. First, a linear‐chain polymer was synthesized, consisting of hydrophilic 2‐acrylamido‐2‐methylpropanesulfonic acid (AMPS), hydrophobic 2,2,2‐trifluoroethyl methacrylate (TFEMA), and AMA. Subsequently, we crosslinked the linear‐chain polymer by reacting the remaining allyl group during dry heating. The proton conductivity of the prepared membrane was 7 × 10−2 S/cm at room temperature. The membrane was characterized by Fourier transform infrared spectroscopy, differential scanning calorimetry, and atomic force microscopy. The polymer electrolyte membrane fuel cell (PEMFC) performance was evaluated for a membrane electrode assembly composed of the crosslinked AMPS–TFEMA–AMA/ fluoroalkyl graft polymer (FGP) membrane. As a result of a power‐generation test, a maximum power density of 174 mW/cm2 at a current density of 400 mA/cm2 was observed for a PEMFC single cell. Consequently, it was confirmed that the AMPS–TFEMA–AMA/FGP membrane for PEMFC could easily be prepared via a two‐step reaction at a low cost and that PEMFC exhibited a cell performance and that of cells with the Nafion membrane. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
A relatively simple method for calculating Mark‐Houwink parameters using basic definitions
Authors: Braun Jennifer L. , Kadla John F.
Published: August 2009

A method for calculating Mark‐Houwink parameters from intrinsic viscosity, size exclusion, and number‐ or weight‐average molecular weight data using basic definitions was presented. Polydispersity is not an issue and no calibration curve is required as long as all of the aforementioned data are available. Results for polystyrene, cellulose acetate, and polymethylhydrosiloxane are discussed. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Synthesis and characterization of novel fluorine‐containing methacrylate copolymers: Reactivity ratios, thermal properties, and antimicrobial activity
Authors: Erol Ibrahim , Sen Ozkan , Dedelioglu Ayse , Cifci Cemal
Published: August 2009

The free‐radical‐initiated copolymerization of 2‐(4‐acetylphenoxy)‐2‐oxoethyl‐2‐methylacrylate (AOEMA) and 2‐(4‐benzoylphenoxy)‐2‐oxoethyl‐2‐methylacrylate (BOEMA) with 2‐[(4‐fluorophenyoxy]‐2‐oxoethyl‐2‐methylacrylate (FPEMA) were carried out in 1,4‐dioxane solution at 65°C using 2,2′‐azobisisobutyronitrile as an initiator with different monomer‐to‐monomer ratios in the feed. The monomers and copolymers were characterized by FTIR and 1H‐ and 13C‐NMR spectral studies. 1H‐NMR analysis was used to determine the molar fractions of AOEMA, BOEMA, and FPEMA in the copolymers. The reactivity ratios of the monomers were determined by the application of Fineman‐Ross and Kelen‐Tudos methods. The analysis of reactivity ratios revealed that BOEMA and AOEMA are less reactive than FPEMA, and copolymers formed are statistically in nature. The molecular weights (Mw and Mn) and polydispersity index of the polymers were determined using gel permeation chromatography. Thermogravimetric analysis of the polymers reveals that the thermal stability of the copolymers increases with an increase in the mole fraction of FPEMA in the copolymers. Glass transition temperatures of the copolymers were found to decrease with an increase in the mole fraction of FPEMA in the copolymers. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Studies on structure property correlation of cross‐linked glycidyl azide polymer
Authors: Manu S. K. , Varghese T. L. , Mathew S. , Ninan K. N.
Published: August 2009

Glycidyl azide polymer (GAP) has been evaluated for use as binder for solid propellants. The effects of various parameters like cross‐linking conditions, concentration of crosslinker, and the ratio of isocyanate to hydroxyl functional groups (NCO/OH ratio) on the mechanical properties were studied in detail. It was observed that the type of curing agent and the NCO/OH ratio have a strong influence on the gum‐stock properties. Similar impact was seen for cross‐linker concentration also. The swelling characteristics of the cross‐linked binder prepared with different NCO/OH ratios were evaluated with toluene and tetrahydrofuran (THF). The polarity and the solubility parameter of the solvents were found to influence the swelling of GAP. The NCO/OH ratio and cross‐linker concentration of the polymer were also found to affect the swelling characteristics. The sol fraction determined for the polymer was found to follow a similar pattern. The cross‐link density and average molecular weight between crosslinks (Mc) were determined from the swelling studies and also from the stress–strain relationship. The Mc values were found to be influenced by the NCO/OH ratio. Finally, the Mc values determined from the swelling data were correlated to the gum‐stock properties, and the model parameters were estimated. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Effect of crystallinity on surface morphology and light transmittance of poly(vinylidene fluoride‐co‐hexafluoropropylene) thin film
Authors: Lee Sang Goo , Lee Jong Sung , Ha Jong‐Wook , Park In Jun , Lee Soo‐Bok , Lee Jong Dae
Published: August 2009

Homopolymer of vinylidene fluoride and its copolymers containing hexafluoropropylene (HFP) were prepared from free radical solution polymerizations and spin‐coated on the glass slides to fabricate thin film with a thickness of ∼ 1 μm. It was found that the surface morphology of fluorinated thin films was strongly dependent on the crystallinity of polymers. In addition, the surface morphology was the most important factor to determine the optical transmittance of glass coated with the fluoropolymer thin film. As decreasing the crystallinity of the polymer by introducing HFP with a bulky CF3 moiety, the surface of thin film became flattened and the transmittance of visible light was increased by reducing scattering. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
The conduction characteristics of electrical trees in XLPE cable insulation
Authors: Xie Ansheng , Zheng Xiaoquan , Li Shengtao , Chen George
Published: August 2009

Depending on the morphology of the material and applied voltage frequency, three kinds of electrical trees can exist in cross‐linked polyethylene (XLPE) cable insulation, which are conducting, non‐conducting, and mixed trees with different growth mechanisms. It is suggested that when the needle is inserted into large spherulites, conducting trees will form in those spherulites; when it is inserted among spherulites, non‐conducting trees will appear along the boundaries of spherulites. Frequency will accelerate the growth of non‐conducting trees but have little influence on the initiation and growth processes of conducting trees. If the initiation process of non‐conducting trees is too difficult, they will grow into mixed trees. Finally, it is concluded that the space charge limited tiny breakdown around the tips of electrical trees is responsible for the propagation process of conducting trees; on the other hand, fast expansion occurs due to local high temperature and pressure along the boundaries, partial discharge in electrical tree paths and charge recombination, etc., which are the main reason for the growth of non‐conducting trees. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Thermomechanical and optical properties of biodegradable poly(L‐lactide)/silica nanocomposites by melt compounding
Authors: Wen Xin , Lin Ying , Han Changyu , Zhang Kunyu , Ran Xianghai , Li Yuesheng , Dong Lisong
Published: August 2009

Poly(L‐lactide) (PLA)/silica (SiO2) nanocomposites containing 1, 3, 5, 7, and 10 wt % SiO2 nanoparticles were prepared by melt compounding in a Haake mixer. The phase morphology, thermomechanical properties, and optical transparency were investigated and compared to those of neat PLA. Scanning electron microscopy results show that the SiO2 nanoparticles were uniformly distributed in the PLA matrix for filler contents below 5 wt %, whereas some aggregates were detected with further increasing filler concentration. Differential scanning calorimetry analysis revealed that the addition of SiO2 nanoparticles not only remarkably accelerated the crystallization speed but also largely improved the crystallinity of PLA. An initial increase followed by a decrease with higher filler loadings for the storage modulus and glass‐transition temperature were observed according to dynamic mechanical analysis results. Hydrogen bonding interaction involving CO of PLA with SiOH of SiO2 was evidenced by Fourier transform infrared analysis for the first time. From the mechanical tests, we found that the tensile strength and modulus values of the nanocomposites were greatly enhanced by the incorporation of inorganic SiO2 nanoparticles, and the elongation at break and impact strength were slightly improved. The optical transparency of the nanocomposites was excellent, and it seemed independent of the SiO2 concentration; this was mainly attributed to the closed refractive indices between the PLA matrix and nanofillers. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Preparation and characterization of CMCS/PVA blend membranes and its sorption and pervaporation performance (I)
Authors: Shen Jiang‐Nan , Ruan Hui‐Min , Gao Cong‐Jie
Published: August 2009

Novel pervaporation (PV) membranes for ethanol dehydration were prepared by blend poly(vinyl alcohol) (PVA) and carboxymethyl chitosan (CMCS), followed by the crosslinking reaction with glutaraldehyde; the structure and miscibility of the blend membranes were characterized by Fourier transform infrared, X‐ray diffraction, and differential scanning calorimetry; the results indicated that the blends were miscible. The effect of feed concentration, operation temperature, crosslinking agent content, etc. on sorption performance and PV performance of the blend membrane is investigated. The membrane of CMCS/PVA blend ratio of 8 : 2 exhibited a high separation factor of 2959 with a reasonably high water flux value of 0.14 kg m−2h−1 at the azeotropic feed composition (95 wt % of ethanol) at a temperature of 45°C. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Effects of prior aging at 288°C in argon environment on time‐dependent deformation behavior of a thermoset polymer at elevated temperature, Part 2: Modeling with viscoplasticity theory based on overstress
Authors: McClung Amber J. W. , Ruggles‐Wrenn Marina B.
Published: August 2009

The viscoplasticity based on overstress (VBO) is augmented to model the effects of prior isothermal aging in an argon environment on the inelastic deformation behavior of PMR‐15 neat resin, a high‐temperature thermoset polymer. VBO is a unified state variable theory with growth laws for three state variables: the equilibrium stress, the kinematic stress and the isotropic stress. A systematic model characterization procedure based on a limited number of well defined experiments is employed to determine the VBO parameters. Experimental findings presented in Part I reveal the equilibrium stress and the kinematic stress to be affected by prior aging. Based on the experimental results, the isotropic stress is developed as a function of prior aging time. In addition, several VBO model parameters are made dependent on prior aging time. Comparison with experimental data demonstrates that the modified VBO successfully predicts the inelastic deformation behavior of the PMR‐15 polymer subjected to prior isothermal aging for up to 2000 h. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Synthesis and characterization of poly(esteramide‐urethane) from linseed oil as anticorrosive coatings
Authors: Alam Manawwer , Ray Alok R. , Ahmad Sharif
Published: August 2009

Ethylene diamine polyesteramide (Ed‐PEA) was synthesized from N, N‐bis (2‐hydroxy ethyl) linseed oil fattyamide and ethylene diamine tetra acetic acid through condensation polymerization. It was further treated with toluylene 2,4‐diisocyanate (TDI) in different weight percentage to obtain urethane‐modified polyesteramide (Ed‐UPEA). The structural elucidation of Ed‐PEA and Ed‐UPEA were carried out by FTIR, 1H‐NMR, and 13C‐NMR spectroscopic techniques. Thermal studies of these resins were carried by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The coatings of urethane‐modified polyesteramide were prepared on mild steel strips and their anticorrosive behavior of in acid, alkali, water, and xylene were investigated. Thermal stability performance suggests that the system could be safely used upto 200°C. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Silicone‐based cholesteric liquid crystalline polymers: Effect of crosslinking agent on phase transition behavior
Authors: Jana Rabindranath N. , Cho Jae Whan
Published: August 2009

Silicone‐based cholesteric liquid crystalline polymers (ChLCP) were fabricated with variable clearing temperatures as controlled by their chemical compositions. The chemical structures of the mesogenic monomers and ChLCP were confirmed by FTIR and 1H‐NMR spectroscopy. The mesogenic properties and phase behavior were investigated by differential scanning calorimetry, polarizing optical microscopy, and X‐ray diffraction measurements. The experimental results demonstrated that the glass transition temperatures and the clearing points of the liquid crystalline polymers decreased with increasing proportion of mesogenic crosslinking agent up to 12.50 mol % (LCP‐3), and at higher proportion of crosslinking agent, the clearing points disappeared, indicating that the network chains have less chance to orient themselves. Thermogravimetric analysis showed that the LCP‐3 was the most stable up to 230°C. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
A novel intumescent flame‐retardant system for flame‐retarded LLDPE/EVA composites
Authors: Li Bin , Jia He , Guan Limin , Bing Baichun , Dai Jinfeng
Published: August 2009

A new intumescent flame retardant (IFR) system consisting of ammonium polyphosphate (APP) and charing‐foaming agent (CFA) and a little organic montmorillonite (OMMT) was used in low‐density polyethylene (LLDPE)/ethylene‐vinyl acetate (EVA) composite. According to limiting oxygen index (LOI) value and UL‐94 rating obtained from this work, the reasonable mass ratio of APP to CFA was 3 : 1, and OMMT could obviously enhance the flame retardancy of the composites. Cone calorimeter (CONE) and thermogravimetric analysis (TGA) were applied to evaluate the burning behavior and thermal stability of IFR‐LLDPE/EVA (LLDPE/EVA) composites. The results of cone calorimeter showed that heat release rate peak (HRR‐peak) and smoke production rate peak (SPR‐peak) and time to ignition (TTI) of IFR‐LLDPE/EVA composites decreased clearly compared with the pure blend. TGA data showed that IFR could enhance the thermal stability of the composites at high temperature and effectively increase the char residue. The morphological structures of the composites observed by scanning electron microscopy (SEM) and X‐ray diffraction (XRD) demonstrated that OMMT could well disperse in the composites without exfoliation, and obviously improve the compatibility of components of IFR in LLDPE/EVA blend. The morphological structures of char layer obtained from Cone indicated that OMMT make the char layer structure be more homogenous and more stable. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Multiple UPFC damping control scheme using ANN coordinated adaptive controllers
Authors: Ma Tsao‐Tsung
Published: August 2009

This paper presents a novel design of an adaptive damping control scheme using artificial neural network (ANN) coordinated multiple unified power flow controllers (UPFCs). In this study, a centralized global control scheme is proposed in which three UPFCs are first assumed to be strategically installed in the system to achieve a steady state power flow control objective, then utilized to demonstrate the proposed control scheme in enhancing the damping of low frequency electromechanical oscillations exhibited by a three‐area, six‐machine power system. The coordination of controllers is accomplished by a genetic algorithm based tuning process that is based on considering various system operating conditions and minimizing a set of predefined coordinated damping performance indices (CDPI). The task of real‐time adaptation of system uncertainties is carried out using a trained ANN as an adaptive coordinator to achieve the robust control objectives. Copyright © 2009 John Wiley and Sons Asia Pte Ltd and Chinese Automatic Control Society
Handling occlusions in video‐based augmented reality using depth information
Authors: Zhu Jiejie , Pan Zhigeng , Sun Chao , Chen Wenzhi
Published: August 2009

Augmented Reality (AR) composes virtual objects with real scenes in a mixed environment where human–computer interaction has more semantic meanings. To seamlessly merge virtual objects with real scenes, correct occlusion handling is a significant challenge. We present an approach to separate occluded objects in multiple layers by utilizing depth, color, and neighborhood information. Scene depth is obtained by stereo cameras and two Gaussian local kernels are used to represent color, spatial smoothness. These three cues areintelligentlyfused in a probability framework, where the occlusion information can be safely estimated. We apply our method to handle occlusions in video‐based AR where virtual objects are simply overlapped on real scenes. Experiment results show the approach can correctly register virtual and real objects in different depth layers, and provide a spatial‐awareness interaction environment. Copyright © 2009 John Wiley & Sons, Ltd.
Are the Catalytic Properties of Enzymes from Piezophilic Organisms Pressure Adapted?
Authors: Hay Sam , Evans Rhiannon M. , Levy Colin , Loveridge E. Joel , Wang Xi , Leys David , Allemann Rudolf K. , Scrutton Nigel S.
Published: August 2009

We report the crystal structure of dihydrofolate reductase (DHFR) from the psychropiezophilic bacterium Moritella profunda, which was isolated from the deep ocean at 2 °C and 280 bar. The structure is typical of a chromosomal DHFR and we were unable to identify any obvious structural features that would suggest pressure adaptation. In particular, the core regions of the enzyme are virtually identical to those of the DHFR from the mesophile Escherichia coli. The steady‐state rate at pH 9, which is limited by hydride transfer at atmospheric pressure, is roughly constant between 1 and 750 bar, falling at higher pressures. However, the value of KM increases with increasing pressure, and as a result kcat/KM decreases over the entire pressure range studied. Isotope effect studies showed that increasing the pressure causes a change in the rate‐limiting step of the reaction. We therefore see no evidence of pressure adaptation in either the structure or the activity of this enzyme.