bluuebunny/crossref_metadata_2025 huggingface dataset:
Neural network‐based adaptive attitude tracking control for flexible spacecraft with unknown high‐frequency gain
Authors: Hu Qinglei
Published: August 2009

Adaptive control design using neural networks (a) is investigated for attitude tracking and vibration stabilization of a flexible spacecraft, which is operated at highly nonlinear dynamic regimes. The spacecraft considered consists of a rigid body and two flexible appendages, and it is assumed that the system parameters are unknown and the truncated model of the spacecraft has finite but arbitrary dimension as well, for the purpose of design. Based on this nonlinear model, the derivation of an adaptive control law using neural networks (NNs) is treated, when the dynamics of unstructured and state‐dependent nonlinear function are completely unknown. A radial basis function network that is used here for synthesizing the controller and adaptive mechanisms is derived for adjusting the parameters of the network and estimating the unknown parameters. In this derivation, the Nussbaum gain technique is also employed to relax the sign assumption for the high‐frequency gain for the neural adaptive control. Moreover, systematic design procedure is developed for the synthesis of adaptive NN tracking control with L2 ‐gain performance. The resulting closed‐loop system is proven to be globally stable by Lyapunov's theory and the effect of the external disturbances and elastic vibrations on the tracking error can be attenuated to the prescribed level by appropriately choosing the design parameters. Numerical simulations are performed to show that attitude tracking control and vibration suppression are accomplished in spite of the presence of disturbance torque/parameter uncertainty. Copyright © 2009 John Wiley & Sons, Ltd.
Au@pNIPAM Thermosensitive Nanostructures: Control over Shell Cross‐linking, Overall Dimensions, and Core Growth
Authors: Contreras‐Cáceres Rafael , Pacifico Jessica , Pastoriza‐Santos Isabel , Pérez‐Juste Jorge , Fernández‐Barbero Antonio , Liz‐Marzán Luis M.
Published: August 2009

Thermoresponsive nanocomposites comprising a gold nanoparticle core and a poly(N‐isopropylacrylamide) (pNIPAM) shell are synthesized by grafting the gold nanoparticle surface with polystyrene, which allows the coating of an inorganic core with an organic shell. Through careful control of the experimental conditions, the pNIPAM shell cross‐linking density can be varied, and in turn its porosity and stiffness, as well as shell thickness from a few to a few hundred nanometers is tuned. The characterization of these core–shell systems is carried out by photon‐correlation spectroscopy, transmission electron microscopy, and atomic force microscopy. Additionally, the porous pNIPAM shells are found to modulate the catalytic activity, which is demonstrated through the seeded growth of gold cores, either retaining the initial spherical shape or developing a branched morphology. The nanocomposites also present thermally modulated optical properties because of temperature‐induced local changes of the refractive index surrounding the gold cores.
Swelling‐Induced Surface Patterns in Hydrogels with Gradient Crosslinking Density
Authors: Guvendiren Murat , Yang Shu , Burdick Jason A.
Published: August 2009

Hydrogels with controlled surface patterns are useful for a range of applications, including in microdevices, sensors, coatings, and adhesives. In this work, a simple and robust method to generate a wide range of osmotically driven surface patterns, including random, lamellar, peanut, and hexagonal structures is developed. This method does not require the use of organic solvents for swelling, pre‐patterning of the film surface, or coating of a second layer on the gel. The patterns are fabricated by exposing a photocurable formulation to light while open to air and then swelling, using oxygen inhibition of the radical polymerization at the surface to create a gradient of crosslinking with depth, which was confirmed by measuring the double bond conversion at the surface, surface mechanics, and molecule diffusion into the network. The modulus gradient, and hence osmotic pressure, is controlled by the crosslinker concentration, and the characteristic size of the patterns is determined by the initial film thickness. The patterns are stable in both swollen and dry states, creating a versatile approach that is useful for diverse polymers to create complex patterns with long‐range order.
Fabrication of a Macroporous Microwell Array for Surface‐Enhanced Raman Scattering
Authors: Zamuner Martina , Talaga David , Deiss Frédérique , Guieu Valérie , Kuhn Alexander , Ugo Paolo , Sojic Neso
Published: August 2009

Here, a colloidal templating procedure for generating high‐density arrays of gold macroporous microwells, which act as discrete sites for surface‐enhanced Raman scattering (SERS), is reported. Development of such a novel array with discrete macroporous sites requires multiple fabrication steps. First, selective wet‐chemical etching of the distal face of a coherent optical fiber bundle produces a microwell array. The microwells are then selectively filled with a macroporous structure by electroless template synthesis using self‐assembled nanospheres. The fabricated arrays are structured at both the micrometer and nanometer scale on etched imaging bundles. Confocal Raman microscopy is used to detect a benzenethiol monolayer adsorbed on the macroporous gold and to map the spatial distribution of the SERS signal. The Raman enhancement factor of the modified wells is investigated and an average enhancement factor of 4 × 104 is measured. This demonstrates that such nanostructured wells can enhance the local electromagnetic field and lead to a platform of ordered SERS‐active micrometer‐sized spots defined by the initial shape of the etched optical fibers. Since the fabrication steps keep the initial architecture of the optical fiber bundle, such ordered SERS‐active platforms fabricated onto an imaging waveguide open new applications in remote SERS imaging, plasmonic devices, and integrated electro‐optical sensor arrays.
Fabrication of a Superhydrophobic Surface from a Smectic Liquid‐Crystal Defect Array
Authors: Kim Yun Ho , Yoon Dong Ki , Jeong Hyeon Su , Kim Jung Hyun , Yoon Eun Kyoung , Jung Hee‐Tae
Published: August 2009

A novel fabrication method is developed for the preparation of superhydrophobic surfaces. The procedure uses focal conic structures of semi‐fluorinated smectic liquid crystals (LCs) whose periodic toric focal conic domains (TFCDs) are prepared on a surface modified substrate. Reactive ion etching (RIE) on the periodic TFCD surface leads to a superhydrophobic surface with a water contact angle of ∼160° and a sliding angle of ∼2° for a 10 µL water droplet. The results show that this phenomenon is due to the development of a dual‐scale surface roughness arising from the nanoscale protuberance caused by applying the RIE process to the top of the microscale TFCD arrays. The unique surface behavior is further verified by demonstrating that RIE on a flat lamellar liquid crystal film, in which the director is aligned parallel with surface, results in a relatively low hydrophobicity as compared to when periodic TFCDs are subjected to REI. The observations made in this publication suggest that a new approach exists for selecting potential candidates of superhydrophic surface formation based on spontaneous self‐assembly in smectic liquid‐crystalline materials.
Sociodemographic determinants of growth among Malian adolescent females
Authors: Leslie Timothy F. , Pawloski Lisa R.
Published: August 2009

In Africa, research concerning the social determinants of poor nutritional status has typically focused on children under 5 years of age and has used defined categorical boundaries based on international reference standards. In this article, stunting and wasting of 1,157 Malian adolescent girls is measured through both categorical and continuous data. The focus on adolescent girls is significant because there is relatively little literature examining this group, and because adolescence marks the time when girls gain greater workload responsibilities, autonomy of food choices, and, as a result of the adolescent growth spurt, require the greatest amount of caloric intake respective to their weight since infancy. To differentiate stunting and wasting causes, a number of socioeconomic, geographic, and demographic factors are explored. The findings suggest that continuous data provides a basis for modeling stunting and wasting superior to utilizing international reference categories. Estimations show that decreasing age, the presence of servants, a greater number of wives in a compound, and residence in a large urban area correlate with improved nutritional status while wealthier families appear to correlate with greater stunting and wasting, and no correlation exists with estimated energy expenditure. Future studies should incorporate continuous data, and the need exists for greater analysis of social determinants of growth indicators among adolescent females. Further, these findings have significant implications in the development of nutrition intervention programs aimed at the vulnerable population in Mali, leading us to conclude that factors beyond socioeconomic indicators such as household structure and location should be more fully examined. Am. J. Hum. Biol., 2010. © 2009 Wiley‐Liss, Inc.
Support of association between BRD1 and both schizophrenia and bipolar affective disorder
Authors: Nyegaard Mette , Severinsen Jacob E. , Als Thomas D. , Hedemand Anne , Straarup Steen , Nordentoft Merete , McQuillin Andrew , Bass Nicholas , Lawrence Jacob , Thirumalai Srinivasa , Pereira Ana C.P. , Kandaswamy Radhika , Lydall Gregory J. , Sklar Pamela , Scolnick Edward , Purcell Shaun , Curtis David , Gurling Hugh M.D. , Mortensen Preben B. , Mors Ole , Børglum Anders D.
Published: August 2009

A recent study published by our group implicated the bromodomain containing protein 1 (BRD1) gene located at chromosome 22q13.33 with schizophrenia (SZ) and bipolar affective disorder (BPD) susceptibility and provided evidence suggesting a possible role for BRD1 in neurodevelopment. The present study reports an association analysis of BRD1 and the neighboring gene ZBED4 using a Caucasian case–control sample from Denmark and England (UK/DK sample: 490 patients with BPD, 527 patients with SZ, and 601 control individuals), and genotypes obtained from a BPD genome wide association (GWA) study of an overlapping English sample comprising 506 patients with BPD and 510 control individuals (UCL sample). In the UK/DK sample we genotyped 11 SNPs in the BRD1 region, of which six showed association with SZ (minimal single marker P‐values of 0.0014), including two SNPs that previously showed association in a Scottish population [Severinsen et al. (2006); Mol Psychiatry 11(12): 1126–1138]. Haplotype analysis revealed specific risk as well as protective haplotypes with a minimal P‐value of 0.0027. None of the 11 SNPs showed association with BPD. However, analyzing seven BRD1 SNPs obtained from the BPD GWA study, positive associations with BPD was observed with all markers (minimal P‐value of 0.0014). The associations reported add further support for the implication of BRD1 with SZ and BPD susceptibility. © 2009 Wiley‐Liss, Inc.
Adsorption properties of microwave synthesized inorgano–organo montmorillonite
Authors: Emreol Miray , Soycan Nefset , Yapar Saadet
Published: August 2009

The aim of this study is to determine the adsorption properties of microwave synthesized inorgano–organo montmorillonites. Microwave irradiation is preferred because of its low time and energy consumption properties, forming an advantage in industrial applications. In addition to the intercalation of Keggin and hexadecyltrimethylammonium (HDTMA+) cations, the aging process of pillaring solution was also carried out through the microwave irradiation. Both inorgano clays, namely the parents, and their inorgano–organo derivatives, were prepared by using the same amounts of aluminum by keeping the OH−/Al3+ and Al3+/clay ratios constant. The HDTMA+/clay ratio was changed in inorgano‐organo clays (IOCs) during the preparation. The effects of these parameters on the surface properties and adsorption behaviors of the samples were investigated by conducting X‐ray diffraction (XRD), Fourier transform infrared (FTIR) and simultaneous thermal analyses (STA), as well as batch adsorption experiments, in which phenol was used as a model pollutant. The results of XRD analyses reveal that the intercalation is successfully achieved. The existence of the Keggin and HDTMA+ cations was observed in FTIR spectra of the samples. Through the STA, it was determined that the existence of organic layer increases the dehydroxylation temperature and the thermal behavior of inorgano‐organo montmorillonites strongly depends on the structure of the parent clay. An increase in the adsorption efficiencies with increasing HDTMA+/clay ratio was observed, except with the highest ratio. The behavior of this sample was explained by the formation of the second HDTMA+ layer leading to the hydrophilic surface formation. Copyright © 2009 Curtin University of Technology and John Wiley & Sons, Ltd.
The water‐gas shift reaction: from conventional catalytic systems to Pd‐based membrane reactors—a review
Authors: Mendes D. , Mendes A. , Madeira L. M. , Iulianelli A. , Sousa J. M. , Basile A.
Published: August 2009

The water‐gas shift (WGS) reaction is a well‐known step for upgrading carbon monoxide to hydrogen in the production of synthesis gas. For more than 90 years after its first industrial application, many issues in respect of the catalyst, process configuration, reactor design, reaction mechanisms and kinetics have been investigated. More recently, a renewed interest in the WGS reaction carried out in hydrogen perm‐selective membrane reactors (MRs) has been observed because of the growing use of polymeric electrolyte membrane (PEM) fuel cells that operate using high‐purity hydrogen. Moreover, MRs are viewed as an interesting technology in order to overcome the equilibrium conversion limitations in traditional reactors.

This article reviews the most relevant topics of WGS MR technology—catalysis and membrane science. The most used catalysts and relevant progress achieved so far are described and critically reviewed. The effects of the most important parameters affecting the WGS in MRs are detailed. In addition, an overview on the most used membranes in MRs is also presented and discussed. Copyright © 2009 Curtin University of Technology and John Wiley & Sons, Ltd.
Reforming diesel‐fuel distillates with membrane reactors
Authors: Mundschau Michael V. , Gribble David A. , Henton Lee M. , Jentzsch Nicholas R. , Plassmeyer Paul N.
Published: August 2009

A porous‐membrane reactor is used to produce H2 and CO by dry partial oxidation of volatile hydrocarbons distilled from diesel fuel. To eliminate deposition of thermodynamically and kinetically favored carbon onto reactor walls as the fuel is heated, cool air is brought into reactors through porous walls of refractory, zirconia‐based ceramic. Flow of air through reactor walls suppresses alkyl‐radical polymerization that otherwise leads to formation of tar and soot in the reformer heating zone. Diesel fuel is distilled just below 200 °C to avoid cracking of long‐chain n‐alkanes. The volatile distillates enter the reformer in the vapor phase, eliminating need for complex liquid‐fuel injectors and mixers. Volatile distillates are relatively easily reformed, eliminating soot and most naphthalene in the exhaust, converting 88 mole% of carbon in the distillate into CO, 7% into CH4, and 5% into CO2. Approximately 75 mole% of the hydrogen is converted into H2, 13% into CH4, and the remainder into H2O. Synthesis gas produced from diesel fuel distillates could fuel solid‐oxide fuel cells or regenerate NOx traps used in pollution control. Copyright © 2009 Curtin University of Technology and John Wiley & Sons, Ltd.
State of the art of carbon molecular sieves supported on tubular ceramics for gas separation applications
Authors: Briceño Kelly , Garcia‐Valls Ricard , Montané Daniel
Published: August 2009

During recent years, research into alternative power generation and less polluting vehicles has been directed towards the fabrication of compact and efficient devices using hydrogen fuel cells. As a compact viable proposal, membrane reactors (MR) have been studied as means of providing a fuel cell with an on‐board supply device for pure hydrogen streams obtained by reforming hydrocarbons. However, the development of MRs is strongly dependant on the membrane having high permeation flux and high selectivity ratios towards H2 in a mixture of gases. To meet this need, carbon membranes are proposed materials, which have pores that are the same size as the kinetic diameters of syngases. These would provide an alternative to polymers, metals and ceramics in MR applications. Moreover, a tubular shape is a highly recommended configuration for achieving a compact and large reaction surface area. However, it is not easy to obtain a supported and amorphous carbon layer from polymer pyrolysis because the fabrication methods, the type of precursor material, characteristics of the support and pyrolysis conditions are all closely connected. The combination of all these factors and the stability problems of carbon membranes have limited the use of carbon molecular sieves (CMS) in large‐scale applications. This review attempts to provide an overview of the use of carbon membranes in MRs for gas separation. It also reviews the advances in the materials, fabrication methods and characterisation techniques of specific supported carbon molecular sieve membranes that have been supported on tubular carriers so they can take advantage of the high permeation and selectivity values previously reported for unsupported CMS. Copyright © 2009 Curtin University of Technology and John Wiley & Sons, Ltd.
Ionomeric modification of a metallocene‐based polyolefinic elastomer and its influence on the physicomechanical properties: Effects of the crystallinity and pendent chain length
Authors: Biswas Anjan , Bandyopadhyay Abhijit , Singha Nikhil K. , Bhowmick Anil K.
Published: August 2009

A new class of ionomer was developed through the grafting of acrylic acid onto a metallocene‐based poly(ethylene octene) elastomer, followed by its neutralization with zinc acetate. The ionomeric product was characterized through Fourier transform infrared spectroscopy, small‐angle X‐ray scattering, and transmission electron microscopy studies. The effect of the crystallinity and pendent chain length on the ionomeric modification was also studied through the variation of the level and nature of comonomer, respectively. The impact of these ionomeric modifications on various physicomechanical properties was thoroughly investigated with differential scanning calorimetry and mechanical, dynamic mechanical, and thermogravimetric analysis, and the resulting properties were correlated with the structure of the modified elastomers. The ionomerization of the base elastomers caused a significant improvement in the mechanical and thermal properties compared to the corresponding pristine elastomer. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Modification of κ‐carrageenan by graft copolymerization of methacrylic acid: Synthesis and applications
Authors: Tripathy Jasaswini , Mishra Dinesh Kumar , Yadav Mithilesh , Sand Arpit , Behari Kunj
Published: August 2009

In this article, the synthesis of κ‐carrageenan‐g‐methacrylic acid has been reported by free radical polymerization initiated by Potassium peroxymonosulphate/glycolic acid redox pair under nitrogen atmosphere. The reaction conditions have been optimized by varying the reaction conditions, including the concentration of monomer, peroxymonosulphate, glycolic acid, sulphuric acid, κ‐carrageenan along with reaction time and temperature. It has been observed that the maximum yield has been obtained at time 120 min, temperature 40°C, at 20 × 10−2 mol dm−3 concentration of methacrylic acid, 1.0 g dm−3 concentration of κ‐carrageenan and 16 × 10−3 mol dm−3 concentration of peroxymonosulphate. The graft copolymer is characterized by Forier Transform Infrared Spectroscopy and Thermal analysis. Water swelling capacity of graft copolymer has been determined. Intrinsic viscosity has been obtained for both grafted and ungrafted κ‐carrageenan. Metal ion sorption and flocculation performance of synthesized graft copolymer has been studied with respect to the ungrafted substrate. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Synthesis of high metal‐complexation linear elastomers containing sym‐1,2,4,5‐tetrazine rings
Authors: Sayed Abdelwahed R. , Wiggins Jeffrey S.
Published: August 2009

We report the synthesis of polyurethane‐urea elastomers containing 1,2,4,5‐tetrazine covalently reacted within the main chains of the polymers. Our study investigates the synthesis of 3,6‐diamino‐1,2,4,5‐tetrazine (DAT), the polymerization reaction conditions for reacting DAT into the backbone of segmented polyurethane elastomers, and the metal‐complexation capabilities of tetrazine‐containing elastomers with cobalt (II) chloride. Tetrazines are highly colored and electro‐active heterocyclic moieties, which have a very high electron affinity which make them reducible at high to very high potentials. Upon complexation with metals, we observed a strong color shift of the polymers from deep red to blue indicating the binding efficacy for the polymers. We quantified the metal‐complexation capability of the tetrazine elastomers and determined a molar ratio of approximately two metal atoms per tetrazine allowing us to provide a plausible complexation mechanism for the active polymers. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Application of crosslinked carboxymethyl konjac glucomannan in speciation of dissolved Fe(II) and Fe(III) in water samples
Authors: Shen Min , Dai Ke , Wei Xing , Li Shengqing , Xue Aifang , Chen Hao
Published: August 2009

A new solid‐phase extraction technique has been developed for the speciation of trace dissolved Fe(II) and Fe(III) in environmental water samples with a microcolumn packed with crosslinked carboxymethyl konjac glucomannan (CCMKGM) prior to its determination by flame atomic absorption spectrometry (FAAS). Various influencing factors on the separation and preconcentration of Fe(II) and Fe(III), such as the acidity of the aqueous solution, sample flow rate and volume, and eluent concentration and volume, have been investigated systematically and optimized. Fe(III) could be quantitatively retained by CCMKGM in the pH range of 3.0–7.0, then the retained Fe(III) on the CCMKGM was eluted with 5.0 mol L−1 HCl after cleaning with 0.01 mol L−1 HCl to eliminate Fe(II) and determined by FAAS. Total Fe was determined after the oxidation of Fe(II) to Fe(III) by H2O2, and Fe(II) concentration was calculated by subtracting Fe(III) from total iron. The adsorption capacity of CCMKGM for Fe(III) was found to be as high as 162.3 mg g−1. The detection limit (3σ) for Fe(III) was 1.5 μg L−1 and the RSD was 3.5% (n = 11, c = 20 μg L−1) with an enrichment factor of 50. The proposed method has been applied to the speciation of iron in water samples with satisfactory results. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Studies on the preparation and properties of inorganic molecularly imprinted polymer (MIP) based on tetraethoxysilane and silane coupling agents
Authors: Lee Sung‐Chuan , Lin Hui‐Min , Chen Hui
Published: August 2009

Inorganic molecularly imprinted polymer (MIP) based on tetraethoxysilane (TEOS), methyl triethoxysilane (MTEOS), and phenyl triethoxysilane (PTEOS) by sol‐gel process has been developed. The MIP's preparation conditions, H2O/Si molar ratios (R), template removal procedures, calcination temperatures, and quantity of ammonium hydroxide were investigated. The competition experiments of the MIP for template (caffeine, CAF) and analogue (theophylline, TH) were analyzed by high‐performance liquid chromatography (HPLC). The results showed that the AdCAF decreased with an increase of the H2O/Si molar ratios, but the selectivity (α) increased with an increase of the H2O/Si molar ratios in the MIP. In addition, in a comparison of the procedures for removing the template, calcination obtained better efficiency and higher selectivity than extraction. The optimum adsorption and selectivity of MIP were obtained with R = 10 and the template was removed by calcination at 600°C. Moreover, the selectivity of the MIP (283.9) was greater than the nonimprinted polymer (2.45) under optimum preparation conditions. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Effect of molecular weight of epoxidized natural rubber on shear strength of adhesives
Authors: Poh B. T. , Yong A.T.
Published: August 2009

The dependence of shear strength of epoxidized natural rubber (ENR)‐based adhesives on molecular weight of the rubber is studied using coumarone–indene resin, gum rosin, and petro resin as tackifiers. The adhesive was coated on polyethylene terephthalate (PET) film substrate using a SHEEN hand coater at various coating thickness. The shear strength of adhesives was determined by a Texture Analyzer. Results show a maximum at 6.63 × 104 and 4.14 × 104 for ENR 25 and ENR 50, respectively, after which the shear strength decreases with further increases in molecular weight for all the coating thickness. This observation is attributed to varying degree of cohesiveness which culminates at the respective optimum molecular weight of ENR. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Effects of air plasma treatment on tribological properties of hybrid PTFE/Kevlar fabric composite
Authors: Zhang Hui‐Juan , Zhang Zhao‐Zhu , Guo Fang
Published: August 2009

Hybrid PTFE/Kevlar fabric was surface‐modified by air plasma to improve the adhesion to phenolic resin. The tribological properties of fabric composite with or without plasma‐treated hybrid PTFE/Kevlar fabric were investigated in detail. Friction and wear tests showed that friction‐reducing and antiwear ability of hybrid PTFE/Kevlar fabric composite were remarkably improved after plasma treatment. Scanning electron microscopy and X‐ray photoelectron spectroscopy results indicated that the fiber surfaces were etched and the contents of oxygen and nitrogen increased after plasma treatment, which was favorable for improved fiber/resin bonding strength. The enhancement contributed to the improved tribological properties of hybrid PTFE/Kevlar fabric composite after plasma treatment. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Structural changes evidenced by rheology in PPgMA nanocomposites during oxidative ageing
Authors: Fordiani F. , Aubry T. , Grohens Y.
Published: August 2009

Maleic anhydride grafted polypropylene (PPgMA) reinforced by layered silicates was studied using rheological investigation techniques, to probe the degree of exfoliation of the clay particles in the melt state at 190°C. The rheological properties of the composites were investigated as a function of the ageing time and interpreted in terms of degree of dispersion of the clay platelets in the maleic anhydride modified polypropylene matrix. The interpretation in terms of exfoliation degree was confirmed by wide angle X‐ray scattering and nano‐secondary ions mass spectroscopy experiments. Chemical reaction, promoted by oxygen, of maleic anhydride with hydroxyl groups located on clay platelet edges, is one of the major mechanisms involved in the exfoliation process highlighted in this study. PP chain segment thermal motions as well as moderate shear were shown to be required in order to achieve clay exfoliation. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
The effect of copolymer composition on the surface properties of perfluoroalkylethyl acrylates
Authors: Youssef Ali , Pabon Martial , Severac Romain , Gilbert Robert G.
Published: August 2009

The surface properties of two perfluoroalkylethyl acrylic copolymers—aqueous, Zonyl®329 and solvent‐based, Zonyl®225—were studied. Zonyl®329 is a water‐based dispersion and Zonyl®225 a solvent‐based copolymer solution; both polymers have the same perfluoroalkyethyl side chains [F(CF2)nCH2CH2] but have different comonomer compositions. Thin films, prepared by dip coating onto mica and quartz, with and without annealing, were characterized by contact angle and by X‐ray photoelectron spectroscopy (XPS). The contact angle measurements showed little variation with polymer and with substrate, consistent with the supposition that the perfluoroalkylethyl chains aggregate on the surface and thus dominate surface properties, irrespective of the composition of the rest of the polymer. XPS revealed only small variations in surface chemistry for studied films. Annealed films showed improved segregation for solvent‐based Zonyl®225, which has both hydrocarbon alkyl and perfluoroalkylethyl side chains; the presence of hydrocarbon alkyl chains enables the perfluoroalkylethyl chains to reorganize after annealing. Depending on the external conditions, this thermal treatment can enable more perfluoroalkylethyl chains to reach the film surface (solid/air interface), leading to a reduction in the dispersive‐dominant surface and enhancement in perfluoroalkylethyl segregation. This suggested that perfluoroalkylethyl side chains dominate the surface properties, which are thus not dependent on substrate, backbone composition, or formulation. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
N2‐filled hollow glass beads as novel gas carriers for microcellular polyethylene
Authors: Dong Lijie , Huang Jing , Li Rui , Zhang Yi , Pan Minxuan , Xiong Chuanxi
Published: August 2009

N2‐filled hollow glass beads (HGB) were first used as novel gas carriers to prepare microcellular polymers by compression molding. Dicumyl peroxide was acted as crosslink agent to control the produced microcellular structure of low density polyethylene (LDPE)/HGB. The effect of temperature, pressure and the content of gel on the embryo‐foaming, and final‐foaming structure are investigated. Scanning electronic microscopy shows that the average cell size of microcellular LDPE ranges from 0.1 to 10 μm, and the foam density is about 109–1011 cells/cm3. A clear correlation is established between preserving desirable micromorphologies of microcellular LDPE in different processing stage and tuning processing factors. The pertinent foaming mechanism of microcellular materials foamed with HGB is proposed. Because of the good mechanical strength, low density, weak water‐absorption, and excellent heat insulate ability, microcellular LDPE has great potential application in energy building materials. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Electrospun poly(D,L‐lactide) fibers for drug delivery: The influence of cosolvent and the mechanism of drug release
Authors: Xie Zhiwei , Buschle‐Diller Gisela
Published: August 2009

Controlled‐drug release from electrospun fibers has found important biomedical applications in wound healing, transdermal delivery, and tissue engineering. In this study, poly(D,L‐lactide) (PDLLA) was electrospun into ultrafine fibers and loaded with tetracycline (TC) or chlorotetracycline (CTC) as model drugs. The influence of a cosolvent (methanol) at various concentrations was studied regarding physical properties, morphology, and in vitro release profiles of the drugs from the PDLLA nanofibers. Swelling tests in a physiological buffer solution were performed to determine the extent and rate of swelling of the fiber mats. The results showed that for both drugs electrospun fiber diameters decreased with increasing amounts of cosolvent, whereas water contact angles and drug‐loading efficiency increased. However, similar in chemical structure, the two drugs exhibited considerably different release mechanisms. The results indicated that the concentration of methanol changed the release profiles mainly based on the morphology of the resultant nanofibers and the polymer/drug/solvent interaction during the electrospinning and drug release process. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010
Preparation of amphiphilic phenyl–polysucrose microspheres for protein adsorption
Authors: Wang Xiukui , Hou Xin , Wu Yichun , You Shishu
Published: August 2009

In this study, we prepared novel amphiphilic phenyl–polysucrose microspheres by a two‐step pathway. Crosslinked polysucrose microspheres were synthesized with soluble polysucrose and epichlorohydrin by inversed suspension polymerization first. Then, phenyl–polysucrose microspheres were obtained through the reaction between the polysucrose microspheres and glycidyl phenyl ether. Fourier transform infrared spectrometry and X‐ray photoelectron spectroscopy proved that the microspheres had both hydroxyl groups and phenyl ligands. The quantitative determination of the phenyl groups indicated the optimal conditions for synthesis of the phenyl–polysucrose microspheres. The properties of the phenyl–polysucrose beads showed that the dry density increased from 1.38 to 2.29 g/mL, the equilibrium water content decreased from 77.30 to 33.68%, and the hydroxyl content remained at about 41.70 mmol/g when the phenyl content was increased from 0.00 to 2.64 mmol/g. The results of protein adsorption showed that the saturated adsorption capacities of the phenyl–polysucrose microspheres increased with increasing ion strength compared with the polysucrose microspheres. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Electrochemical synthesis of polypyrrole layers doped with glutamic ions
Authors: Meteleva‐Fischer Yulia V. , Von Hauff Elizabeth , Parisi Jürgen
Published: August 2009

Electrochemically synthesized polypyrrole thin films doped with glutamic ions were investigated as interesting materials for potential use as molecularly selective surfaces. Pyrrole and glutamate interact in aqueous solution, resulting in the formation of a prominent band at 240 nm in the absorption spectra of the solution. This feature was assigned to the formation of a complex, which significantly influences the electrochemical deposition of polypyrrole films doped with glutamate. It was also detected that oxidation of these complexes leads to the appearance of a shoulder in the absorption spectrum at 270 nm, which corresponds to the yellowish color of pyrrole aged under influence of air. A mechanism is proposed for polymer film growth in aqueous solutions containing monosodium L‐glutamate and pyrrole. It takes into account the observed influence of the pH of the solution, the concentration of reagents, the zwitterionic properties of glutamate on deposition, and results from spectroscopic measurements. It is also shown that glutamic ions can electrochemically be released from the synthesized polymer layers. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Rheology and viscosity scaling of the polyelectrolyte xanthan gum
Authors: Wyatt Nicholas B. , Liberatore Matthew W.
Published: August 2009

The viscosity as a function of concentration for xanthan gum in both salt‐free solution and in 50 mM NaCl is measured and compared with a scaling theory for polyelectrolytes. In general, the zero shear rate viscosity and the degree of shear thinning increase with polymer concentration. In addition, shear thinning was observed in the dilute regime in both solvents. In salt‐free solution, four concentration regimes of viscosity scaling and three associated critical concentrations were observed (c* ≈ 70 ppm, ce ≈ 400 ppm, and cD ≈ 2000 ppm). In salt solution, only three concentration regimes and two critical concentrations were observed (c* ≈ 200 ppm and ce ≈ 800 ppm). In the presence of salt, the polymer chain structure collapses and occupies much less space resulting in higher values of the critical concentrations. The observed viscosity‐concentration scaling is in very good agreement with theory in the semidilute unentangled and semidilute entangled regimes in both salt‐free and 50 mM NaCl solution. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Crosslinking and thermal stability of thermosets based on novolak and melamine
Authors: Dante Roberto C. , Santamaria Diego A. , Gil Jesús Martín
Published: August 2009

The crosslinking under pressure of a mixture of novolak with melamine resin has been investigated by means of several techniques, including differential scanning calorimetry, thermal gravimetric analysis, X‐ray diffraction, and infrared spectroscopy. The crosslinking of the mixture essentially follows two steps. The former occurs at 150°C and leads to resin networks composed of di‐ and trisubstituted phenols without significant reaction with melamine polymers. The latter, at 200°C, mainly involves the direct crosslinking of melamine polymers with disubstituted phenols. High pressure, applied to the reaction cell, slows down the crosslinking extent, by inhibiting the formation of trisubstituted phenols. This is probably due to the formation of gaseous by‐products of crosslinking. Moreover, a certain structuring effect due to high pressure was observed by means of X‐ray diffraction.© 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Using T‐PODs to assess variations in the occurrence of coastal bottlenose dolphins and harbour porpoises
Authors: Bailey Helen , Clay Gemma , Coates Elizabeth A. , Lusseau David , Senior Bridget , Thompson Paul M.
Published: August 2009

Assessments of anthropogenic impacts on cetaceans are often constrained by limited data on the extent to which these species use particular areas.

Timing porpoise detectors (T‐PODs) are autonomous data recorders for detecting cetacean echolocation clicks, potentially providing cost‐effective opportunities for monitoring cetacean occurrence.

The performance of T‐PODs was assessed in three areas off the Scottish east coast, where the relative occurrence of bottlenose dolphins and harbour porpoises was known to differ. Land‐based observations in one area compared visual and acoustic detections of dolphins, while direct hydrophone recordings of dolphin echolocation clicks were compared with T‐POD detections during boat surveys.

Land‐based surveys recorded 89 groups of dolphins within 900 m of the T‐POD. All groups spending >30 min in the area were detected on the T‐POD, and the probability of detection declined in relation to distance from the recording site.

The number of dolphin clicks recorded on the independent hydrophone system was significantly related to the number detected by a T‐POD. Between pairs of T‐PODs, there was also significant correlation with the numbers of clicks recorded in each hour, both for channels set to detect bottlenose dolphins and for channels set to detect harbour porpoises.

Year‐round deployments of paired T‐PODs detected significant geographical variation in detections for both bottlenose dolphins and harbour porpoises. This pattern reflected published data from visual surveys, where dolphins occurred most regularly within the Moray Firth Special Area of Conservation, and porpoises were sighted more regularly in offshore waters.

T‐PODs do not detect all cetaceans in the area, and care must be taken when interpreting data from mixed species communities. Nevertheless, these results confirm that T‐PODs provide an effective method for monitoring the occurrence of bottlenose dolphins and harbour porpoises, and provide excellent potential for collecting baseline data from poorly studied areas and monitoring long‐term temporal change in key areas of interest. Copyright © 2009 John Wiley & Sons, Ltd.
When forewarning backfires: Paradoxical effects of elaborating social feedback on entrapment in a losing course of action
Authors: Schulz‐Hardt Stefan , Vogelgesang Frank , Pfeiffer Felix , Mojzisch Andreas , Thurow‐Kröning Birgit
Published: August 2009

Entrapment occurs if people persist with losing courses of action. In two experiments, we show how elaborating social feedback (i.e., premature praise or forewarning regarding the chosen course of action) can have paradoxical effects on entrapment. The participants acted as head of a translation department and had to choose one out of four possible translation strategies for their employees. After choosing, they read four arguments (presumably written by former participants) which were either all in favor of the strategy chosen, all against it, or mixed. Half of the participants only read these arguments, whereas the other half elaborated on them by providing written comments (Experiment 1). The results showed that elaborating on other persons' arguments led to stronger entrapment, independently of whether the arguments were positive or negative. This pattern was due to biased argument processing: Whereas confirming thoughts were generated for positive arguments, negative arguments were refuted. Experiment 2 confirmed that this biased argument processing caused subsequent entrapment. These results indicate that elaborating any type of argument can lead to heightened entrapment and, hence, forewarning can backfire. Copyright © 2009 John Wiley & Sons, Ltd.
Possible amelioration of atherogenic diet induced dyslipidemia, hypothyroidism and hyperglycemia by the peel extracts of Mangifera indica, Cucumis melo and Citrullus vulgaris fruits in rats
Authors: Parmar Hamendra Singh , Kar Anand
Published: August 2009

Hitherto unknown efficacy of the peel extracts of Mangifera indica (MI), Cucumis melo (CM) and Citrullus vulgaris (CV) fruits in ameliorating the diet‐induced alterations in dyslipidemia, thyroid dysfunction and diabetes mellitus have been investigated in rats.

In one study, out of 4 different doses (50–300 mg/kg), 200 mg/kg of MI and 100 mg/kg for other two peel extracts could inhibit lipidperoxidation (LPO) maximally in liver. In the second experiment rats were maintained on pre‐standardized atherogenic diet CCT (supplemented with 4 % cholesterol, 1% cholic acid and 0.5% 2‐thiouracil) to induce dyslipidemia, hypothyroidism and diabetes mellitus and the effects of the test peel extracts (200 mg/kg of MI and 100 mg/kg for CM and CV for 10 consecutive days) were studied by examining the changes in tissue LPO (in heart, liver and kidney), concentrations of serum lipids, thyroid hormones, insulin and glucose. Rats, treated simultaneously with either of the peel extracts reversed the CCT‐diet induced increase in the levels of tissue LPO, serum lipids, glucose, creatinine kinase‐MB and decrease in the levels of thyroid hormones and insulin indicating their potential to ameliorate the diet induced alterations in serum lipids, thyroid dysfunctions and hyperglycemia/diabetes mellitus.

A phytochemical analysis indicated the presence of a high amount of polyphenols and ascorbic acid in the test peel extracts suggesting that the beneficial effects could be the result of the rich content of polyphenols and ascorbic acid in the studied peels.
Auraptene, a citrus fruit compound, regulates gene expression as a PPARα agonist in HepG2 hepatocytes
Authors: Takahashi Nobuyuki , Kang Min‐Sook , Kuroyanagi Kayo , Goto Tsuyoshi , Hirai Shizuka , Ohyama Kana , Lee Joo‐Young , Kawada Teruo , Yu Rina , Yano Masamichi , Sasaki Takao , Murakami Shigeru
Published: August 2009

Citrus fruit compounds have various activities that improve pathological conditions in many tissues. In this study, we examined the effect of auraptene contained mainly in the peel of citrus on peroxisome proliferator‐activated receptor‐α (PPARα) activation. To examine effects of auraptene on the PPARα activation in hepatocytes, PPAR ligand assay system was developed using HepG2 hepatocytes, in which the endogenous PPARα expression level is very low. In the PPAR ligand assay, the addition of auraptene showed significant effects on the transactivation of GAL4/PPARα chimera proteins in a dose‐dependent manner. Actually, treatment with auraptene induced the up‐regulation of PPAR target genes, such as acyl‐CoA oxidase (ACO), carnitine‐palmitoyl transferase 1A (CPT1A) and acyl‐CoA synthetase (ACS), in PPARα‐expressing HepG2 hepatocytes. The regulation of gene expression was dependent on PPARα because mock‐transfected HepG2 hepatocytes showed no regulation. The up‐regulation of PPAR target gene expression by auraptene was sufficient to enhance oleic acid uptake into PPARα‐expressing HepG2 hepatocytes. These results indicate that auraptene acts as a PPARα agonist in hepatocytes and that auraptene may improve lipid abnormality through PPARα activation in the liver.
Lipid profile lowering effect of SoyproTM fermented with lactic acid bacteria isolated from Kimchi in high‐fat diet‐induced obese rats
Authors: Kim Na‐Hyung , Kim Hyung‐Min , An Hyo‐Jin , Um Jae‐Young , Moon Phil‐Dong , Kim Su‐Jin , Choi In‐Young , Hong Seung‐Heon , Myung Noh‐Yil , Jeong Hyun‐Ja
Published: August 2009

Lactic acid bacteria are known to exert various physiologic functions in humans. In the current study, we investigated the effects of SoyproTM, a new soymilk fermented with lactic acid bacteria, like Leuconostoc kimchii, Leuconostoc citreum, and Lactobacillus plantarum, isolated from Kimchi, on adipocyte differentiation in preadipocyte 3T3‐L1 cell lines and weight gain or the plasma lipid profile in Sprague‐Dawley rats. Adipocyte 3T3‐L1 cells treated with SoyproTM (10 μg/ml) significantly reduced the contents of cellular triglyceride and inhibited cell differentiation by Oil red O staining. Treatment with SoyproTM (10 μg/ml) for an additional two days in adipocytes inhibited the expression of peroxisome proliferator‐activated receptor‐μ2 and CCAAT/enhancer binding protein‐α, transcription factors of adipocyte differentiation. Based on these in vitro studies, we examined the anti‐obesity effect of SoyproTM in rats for six weeks. SoyproTM had no significant effect on high‐fat diet‐induced increases in body weight, food intake, or feed gain ratio. However, the administration of SoyproTM significantly reduced the concentration of the plasma low density lipoprotein cholesterol. Changes in the plasma levels of total cholesterol and glucose were inclined to decrease in SoyproTM administrated groups compared with saline treated group. Triglyceride and high density lipoprotein cholesterol values in SoyproTM fed groups were similar compared to those of saline fed groups. Although further research is needed, these findings suggest that SoyproTM decreased the levels of low density lipoprotein cholesterol in high‐fat diet‐induced obesity and might partially inhibit the adipocyte differentiation through the suppression of a transcription factors peroxisome proliferator‐activated receptor‐μ2 and CCAAT/enhancer binding protein‐α.
Low serum α‐tocopherol and selenium are associated with accelerated apoptosis in severe sepsis
Authors: Weber Stefan U. , Lehmann Lutz Eric , Schewe Jens‐Christian , Schröder Stefan , Book Malte , Hoeft Andreas , Stüber Frank , Thiele Jens T.
Published: August 2009

During sepsis, a severe systemic disorder, micronutrients often are decreased. Apoptosis is regarded as an important mechanism in the development of often significant immunosuppression in the course of the disease. This study aimed to investigate a‐tocopherol and selenium in reference to apoptosis in patients with sepsis. 16 patients were enrolled as soon as they fulfilled the criteria of severe sepsis. 10 intensive care patients without sepsis and 11 healthy volunteers served as controls. a‐Tocopherol, selenium and nucleosomes were measured in serum. Phosphatidylserine externalization and Bcl‐2 expression were analyzed in T‐cells by flow cytometry. Serum α‐tocopherol and selenium were decreased in severe sepsis but not in non‐septic critically ill patients (p < 0.05). Conversely, markers of apoptosis were increased in sepsis but not in critically ill control patients: Nucleosomes were found to be elevated 3 fold in serum (p < 0.05) and phosphatidylserine was externalized on an expanded subpopulation of T‐cells (p < 0.05) while Bcl‐2 was expressed at lower levels (p < 0.05). The decrease of micronutrients correlated with markers of accelerated apoptosis. Accelerated apoptosis in sepsis is associated with low α‐tocopherol and selenium. The results support the investigation of micronutrient supplementation strategies in severe sepsis.