bluuebunny/crossref_metadata_2025 huggingface dataset:
X‐band circularly polarized antenna gain enhancement with metamaterials
Authors: Kossiavas C. , Zeitler A. , Clementi G. , Migliaccio C. , Staraj R. , Kossiavas G.
Published: May 2011

On board systems are of growing interest for aerospace applications due to the increase of air traffic as well for civil as for military applications. Moreover, the spread out of drones leads to new security issues. On board systems requires not only detection capabilities but also a “sense and avoid” operation mode. This article describes the study of a X‐band antenna that could be suitable for this application. First, a 2 × 2 circularly polarized antenna array is designed, fabricated and measured. Then an optimization process using a micro Genetic Algorithm (mGA) coupled to a “home made” 3D‐TLM electromagnetic software is applied to improve its performances. A metamaterial type Partially Reflective Surface (PRS) is inserted above the whole structure for this purpose. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26150
An analytical characterization of transmission through a building for deterministic propagation modeling
Authors: Soni Sanjay , Bhattacharya Amitabha
Published: May 2011

An accurate deterministic model for propagation through buildings is presented.The proposed model gives significant improvement over earlier predicted results. The application of the proposed model is considered for a single building scenario and urban microcellular scenario to demonstrate its accuracy. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26152
Comments on “The forbidden bandgap characteristic of EBG structures”
Authors: Dang Xiao‐Jie , Yuan Haobo , Wang Nan , Liang Chang‐Hong
Published: May 2011

In a letter by Yang (Microwave Opt Technol Lett 50 (2008), 2965–2967), the bandgap characteristic of a new uniplanar compact electromagnetic bandgap is considered. The authors use the dispersion diagram related to the irreducible Brillouin zone (IBZ) to determine the bandgap. We have already noticed the IBZ used by the letter is not correct, according to the symmetry of the structure. So, the resulted bandgap characteristic is not true. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26153
Design of compact microstrip filter with large reject band using a new multisectioned T‐shaped defected ground structure and multilayer technique
Authors: Al Sharkawy M. , Boutejdar A. , Abd El Aziz D. , Galal E.
Published: May 2011

In this article, a new compact defected ground structure (DGS) low pass filter (LPF) with wide rejection band, low insertion loss in the stopband, and sharp transition from passband to stopband is proposed. The prototype LPF is composed of three repetitive DGS elements with open stubs to act as a compensated capacitance. Each single DGS element consists of multisections of T‐shaped slots. The filter is then realized as a multilayer structure to achieve size reduction and enhance the filter response. The proposed filter has been fabricated and measured. The agreement between the simulated and measured results confirms the effectiveness of the proposed concept. Finally, multilayer LPF is transformed to band pass filter using J‐inverter method. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26157
An infrared negative‐index layer based on single‐species particles in a polaritonic host
Authors: Basilio Lorena I. , Warne Larry K. , Johnson William A. , Langston William L. , Sinclair Michael B
Published: May 2011

For this article, a simple design procedure based on effective‐media analysis (including higher‐order multipoles), simple optimization, full‐wave numerical simulations, and a postprocessing retrieval algorithm is used to synthesize a negative‐index metamaterial based on a single‐species cubic array immersed in a polaritonic host. In order to verify the predicted performance based on effective media and ultimately validate the design methodology, a full‐wave massively‐parallel numerical simulation for a “bulk” (5 layer thick) sample is performed. Published 2011 Wiley Periodicals, Inc.† Microwave Opt Technol Lett, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26159
Frequency reconfigurable antenna for DVB‐H applications
Authors: Canneva F. , Ferrero F. , Ribero J.M. , Staraj R.
Published: May 2011

This article presents a new reconfigurable DVB‐H antenna for a portable TV or a tablet PC device. The antenna consists in a folded monopole loaded by a diode varactor combined with an open stub used to match the antenna. Design procedure and equivalent model are presented. A prototype is realized and measured; return loss and efficiency are presented. A minimal total efficiency of 27% is reported at the whole DVB‐H band. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26160
An ultra‐wideband monopole antenna with water‐wave structure
Authors: Jiang Wen , Gong Shu‐Xi , Cui Sha
Published: May 2011

A novel water‐drop‐shaped monopole antenna that is based on the model from nature is designed to realize ultra‐wideband (UWB). Its UWB‐related characteristics are simulated and experimentally verified. The results show that the proposed antenna has good radiation performances, which illuminates the structure is a good candidate for antenna design. Method of designing antenna using the model from nature will serve as a good candidate for the future antenna design. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26161
Using indirect covariance processing for structure elucidation of small molecules in cases of spectral crowding
Authors: Aspers Ruud L. E. G. , Geutjes Pepijn E. T. J. , Honing Maarten , Jaeger Martin
Published: May 2011

Indirect and unsymmetrical indirect covariance NMR provide powerful tools to compute and visualize correlation information by transforming component spectra into combined spectral data matrices. Sensitive component spectra such as TOCSY, HSQC and NOESY can be quickly converted into experimentally insensitive or time‐consuming correlation spectra such as HSQC‐NOESY. The comparison of illustrative series of spectra from four steroids, dexamethasone, testosterone, allylestrenol and tibolone, renders the effects of resonance overlap on the ease of interpretation visible. The compounds are selected such that signal overlap increases systematically in the proton and carbon domain. Spectra are defined as light, moderate and heavy signal overlap, based on signal density. The investigation suggests that moderate spectral congestion in either proton or carbon domain leads to a number of artifacts that does not hamper signal assignment but lowers the level of confidence on de novo structure elucidation. Since the number of correlations usually increases through covariance processing, component spectra with severe spectral congestion in both dimensions are not suitable for covariance processing and the resulting spectra do not support structure confirmation or structure elucidation. The calculated spectra are compared with the corresponding experimental spectra with respect to their application in structure elucidation laboratory environments. Copyright © 2011 John Wiley & Sons, Ltd.
Modulation of autophagy influences development and apoptosis in mouse embryos developing in vitro
Authors: Lee Seung‐Eun , Hwang Kyu‐Chan , Sun Shao‐Chen , Xu Yong‐Nan , Kim Nam‐Hyung
Published: May 2011

Autophagyis, the bulk degradation of proteins and organelles, is essential for cellular maintenance, cell viability, and development, and is often involved in type II programmed cell death in mammals. This study investigated the expression levels of autophagy‐related genes and the effect of 3‐methyladenine (3‐MA, an autophagy inhibitor) or rapamycin (an autophagy inducer) on the in vitro development and apoptosis of mouse embryos. LC3, which is essential for the formation of autophagosomes, was widely expressed in mouse embryos, and high levels of transcript were present from 1 to 4 cells but gradually decreased through the morula and blastocyst stages. 3‐MA‐treated embryos exhibited significantly reduced developmental rates and total cell numbers, but increased rates of apoptosis. Furthermore, both the expression of Lc3, Gabarap, Atg4A, and Atg4B, and the synthesis of LC3 were significantly reduced at the blastocyst stage. Although rapamycin treatment did not affect developmental rates, cell numbers decreased, and the apoptosis rate increased. Expression of Lc3, Gabarap, Atg4A, and Atg4B, and synthesis of LC3 increased as well. Modulation of Lc3 mRNA and LC3 protein levels using 3‐MA or rapamycin significantly increased apoptotic cell death through the disruption of mitochondrial morphology and reduction of mtDNA copy number at the blastocyst stage. Interestingly, the inner cell mass, detected by immunostaining with POU5F1 (OCT3/4) after 3‐MA or rapamycin treatment of embryos, was significantly increased compared to controls. These results suggest that autophagy influences developmental patterning and apoptosis, and may play a role in early mouse embryogenesis. Mol. Reprod. Dev. 78:498–509, 2011. © 2011 Wiley‐Liss, Inc.
Carbon nanotubes induced microstructure and mechanical properties changes in cocontinuous poly( L‐lactide)/ethylene‐co‐vinyl acetate blends
Authors: Shi Yunyun , Li Yanli , Xiang Fangming , Huang Ting , Chen Chen , Peng Ya , Wang Yong
Published: May 2011

Toughening of poly( L‐lactide) (PLLA) by elastomer attracts much attention in recent years; however, it is usually associated with the deterioration of modulus and/or strength, resulting in limitation in many applications of the material. In this work, functionalized multiwalled carbon nanotubes (FMWCNTs) were introduced into ethylene‐co‐vinyl acetate toughened PLLA blends. The effects of FMWCNTs content on crystalline structure of PLLA matrix and the morphology of the blends, as well as the selective distribution of FMWCNTs in the ternary nanocomposites were investigated using differential scanning calorimetry (DSC), wide angle X‐ray diffraction, scanning electron microscope, and transmission electron microscope. The results show that FMWCNTs exhibit excellent nucleation role in improving the cold crystallization behaviors of PLLA during the annealing and/or DSC heating processes. The results of mechanical property measurements demonstrate that the modulus, strength, and ductility of the blends can be further improved simultaneously through introducing FMWCNTs. Copyright © 2011 John Wiley & Sons, Ltd.
Preparation and characterization of protein‐free natural rubber
Authors: Chaikumpollert Oraphin , Yamamoto Yoshimasa , Suchiva Krisda , Nghia Phan Trung , Kawahara Seiichi
Published: May 2011

Protein‐free natural rubber was prepared by incubation of natural rubber latex with urea and polar organic solvent in the presence of surfactant. Effect of the polar organic solvent on the removal of the proteins was investigated with respect to chemical affinity and concentration of the solvents. Under a suitable condition, nitrogen content of the deproteinized natural rubber (DPNR) was 0.000 wt%, which was less than that of natural rubber deproteinized with proteolytic enzyme or urea in the presence of surfactant. The removal of all proteins from natural rubber was proved through FT‐IR spectroscopy. Changes in morphology of the DPNR were also investigated by transmission electron microscopy. Copyright © 2011 John Wiley & Sons, Ltd.
Functionalization of poly(4‐chloromethylstyrene) with anthraquinone pendants for organic anode‐active materials
Authors: Oyaizu Kenichi , Choi Wonsung , Nishide Hiroyuki
Published: May 2011

Condensation of anthraquinone‐2‐carboxylic acid with poly(4‐chloromethylstyrene) afforded a high‐density redox polymer containing the anthraquinone pendants with reversible charge storage capability at negative potentials near −1 V versus Ag/AgCl. Electrochemically reversible redox response of the polymer, which was ascribed to the reduction of the pendant group to the anion radical and the dianion, suggested that the polymer was sufficiently robust in these redox states for charge storage application. Immobilizing the anthraquinone groups on current collectors was accomplished by the use of the polymer which was swellable and yet insoluble in both aqueous and nonaqueous electrolyte solutions. Such properties allowed the accommodation of external cations from the electrolyte solution to permeate through the polymer layer for electroneutralization of the negative charge produced at the reduced state, which led to the repeatable charging and discharging cycles without degradation of the charge storage capacity. Exploration of the aqueous electrochemistry of anthraquinone, which had been inaccessible by the lack of the solubility of the conjugated and fused‐ring molecule in H2O, became feasible by virtue of the swelling property of the polymer layer in the aqueous electrolyte. While negative charge was relatively difficult to be stored with redox polymers compared to the positive charge due to the enhanced reactivity in their reduced states and small varieties of the appropriate redox sites, the present polymer was characterized as the excellent organic electrode‐active materials that operated at sufficiently negative potentials which was essential for the fabrication of entirely organic batteries. Copyright © 2011 John Wiley & Sons, Ltd.
Chlorinated thermal stabilizer for optically clear PMMA
Authors: Rajkumar Thangamani , Sivasamy Palanichamy , Sreedhar Bojja , Vijayakumar Chinnaswamy Thangavel
Published: May 2011

Optically clear poly(methyl methacrylate) (PMMA) blends with HET‐EG oligoester (synthesized by condensation of chlorendic acid with ethylene glycol) at six different compositions were prepared by bulk polymerization. The effect of HET‐EG in the PMMA matrix on the optical clarity of PMMA blend was measured using ultraviolet‐visible spectroscopic study. The thermal stability of PMMA blends was investigated using differential scanning calorimetric (DSC) and thermogravimetric (TG) analyses. The parameters to deduce the thermal stability of pure PMMA and PMMA blends were calculated from DSC and TG results. The thermal stability of PMMA was found to increase effectively by loading 5% of HET‐EG oligoester without marring optical clarity. The probable physical and chemical actions of HET‐EG oligoester on the thermal stability of PMMA are discussed. Copyright © 2011 John Wiley & Sons, Ltd.
Effect of processing temperature on thermal doping of polyaniline without shear
Authors: Goto Teruya , Awano Hiroshi , Takahashi Tatsuhiro , Yonetake Koichiro , Sukumaran Sathish K.
Published: May 2011

Electrically conducting samples of polyaniline (PANI) were prepared by doping with dodecylbenzene sulfonic acid (DBSA) using a thermal doping method without the application of shear. Besides characterizing the samples using optical microscopy, SEM, UV‐vis‐NIR, the degree of doping and the electrical conductivity were also measured. The pure PANI powder consisted of aggregates of PANI particles and was non‐conducting. In the shear‐free thermal doping of the PANI/DBSA mixture, the original aggregates were progressively broken up into smaller pieces with increasing temperature while maintaining the original primary particle shape and size and which were dispersed rather uniformly in the DBSA matrix. The electrical conductivity of doped PANI increased with increasing doping temperature. This increase strongly mirrored the increase in the levels of DBSA directly associated with PANI and suggested that the increasing levels of PANI doping were directly responsible for the increase in electrical conductivity as a function of the doping temperature. Despite the absence of the absorption peak at around 800 nm, the sample absorbed strongly in the near‐infrared. Moreover, PANI/DBSA samples possessing a higher ratio of absorbance at 2600 nm to that at 800 nm showed higher electrical conductivity. These results suggest that shear‐free thermal doping provides a simple route to controlling the morphology of the mixture by enabling the disintegration of the micron scale aggregates present in the as‐purchased PANI. This in turn can be used to control the degree of doping of the PANI and consequently the conductivity of the sample. Copyright © 2011 John Wiley & Sons, Ltd.
Assessment of nanocomposites based on unsaturated polyester resin/nanoclay under impact loading
Authors: Esfahani Javad Moftakharian , Sabet Ali Reza , Esfandeh Masoud
Published: May 2011

The aim of this study is to investigate the performance of nanoclay reinforced unsaturated polyester (UP) resin under impact loads. Nanocomposite specimens containing nanoclay in 0, 1.5, and 3 (wt%) were prepared by melt mixing method. X‐ray diffraction, transmission electron microscopy analysis, scanning electron microscope photographs, and viscosity changes in liquid state resin confirmed exfoliation and intercalation of the nanoclay in the UP resin system used. Tensile modulus showed an increase with increase in nanoclay content. However, the tensile strength and elongation at break exhibited reducing performance with increase in nanoclay content. Izod impact test results indicated better performance for the specimens containing nanoclay reinforcements, with 1.5 (wt%) of nanoclay specimens showing the highest value. High velocity impact tests were carried out using gas gun in velocity range of 20–100 m/sec and harden steel hemispherical tip projectile with diameter of 8.7 mm and weight of 11.54 g. Results for high velocity impact test indicated better performance by the specimens containing nanoclay, with 1.5 (wt%) nanoclay showing the highest attained value. Damage assessments of impact area for all specimens showed spalling type brittle failure with punch out and sever fragmentation pattern. Copyright © 2011 John Wiley & Sons, Ltd.
Formulation and characterization of leather and rubber wastes composites
Authors: Ferreira Maria J. , Almeida Manuel F. , Freitas Fernanda
Published: May 2011

Residues from footwear roughing and carding operations represent 5–15% (w/w) of the solid wastes generated by shoe‐making companies. These wastes are mainly composed by chromium tanned leather and sole materials, and are mostly land filled. Sometimes leaching tests show these wastes as hazardous due to chromium in the leachate. This work aims at a more sustainable option for these wastes by recycling them in styrene butadiene rubber (SBR) and acrylonitrile butadiene rubber (NBR). Thus, they were charged with: (i) ≤1 mm leather waste fibers in the range of 10–25 parts per hundred parts of rubber (phr); and (ii) leather and soles industrial carding and roughing wastes in the range of 20–100 phr. The leather waste fibers‐rubber composites tear strength is increased till 25 phr and both tension and elongation at break decrease within the acceptable range till 12.5 phr for SBR and 15 phr for NBR. In the case of leather and sole carding and roughing wastes, composites tear strength increases till 100 phr, and tension and elongation decrease within the acceptable range till 20 phr. The composite materials at the end of their life cycle may be considered inert or non‐hazardous wastes. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers
Orientation development in solid‐state extrusion and hot forming of polypropylene tubes
Authors: Elnagmi Mohamed , Jain Mukesh , Britten James F.
Published: May 2011

The use of high‐strength polymer in automotive structural components is limited by insufficient understanding of microscopic aspects of deformation for accurate numerical predictions of the mechanical behavior during forming processes. One approach to meeting these critical data needs is a careful examination of the structure property relationships that directly influence formability. Different hot forming processes (solid‐state extrusion, axial feed hot oil tube forming, and biaxial ball stretching test) are utilized in this work for investigating the effect of process conditions on the molecular orientation of polypropylene (PP) tubes. White‐Spruiell representation of orientation factors based on the results form X‐ray diffraction (XRD) patterns is utilized to analyze the development of orientation under extrusion and various forming conditions. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers
Montmorillonite nanoclay filler effects on electrical conductivity, thermal and mechanical properties of epoxy‐based nanocomposites
Authors: Rashmi  , Renukappa N.M. , Chikkakuntappa Ranganathaiah , Kunigal N. Shivakumar
Published: May 2011

Epoxy‐based nanocomposites with 2, 5, and 7 wt% of montmorillonite (MMT) nanoclay were prepared using high shear melt mixing technique. The microstructural features of the nanocomposites were investigated by transmission electron microscopy (TEM). The thermal and mechanical properties were measured using differential scanning calorimetry (DSC), thermogravimetric analyzer (TGA), and dynamic mechanical analyzer (DMA). Further, the effect of voltage, temperature, seawater aging on the electrical conductivity (σDC) of the nanocomposites was also measured. To understand the free volume behavior upon filler loading, and to observe the connectivity between microstructure and other properties, positron annihilation lifetime spectroscopy was used. The TEM results revealed that MMT nanoparticles were uniformly dispersed in the epoxy matrix. Experimental results showed that the inclusion of 2 wt% MMT nanofiller increased the Tg, electrical conductivity, thermal stability, modulus, free volume of the epoxy nanocomposite significantly. This is well explained from the results of Tg (DSC and DMA), thermal stability, TGA residue, free volume analysis, and electrical conductivity. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers
The role of specific interaction and selective localization of multiwall carbon nanotubes on the electrical conductivity and phase morphology of multicomponent polymer blends
Authors: Bose Suryasarathi , Bhattacharyya Arup R. , Khare Rupesh A. , Kamath Srikanth S. , Kulkarni Ajit R.
Published: May 2011

Multicomponent polymer blends involving polyamide6 (PA6), polypropylene (PP), acrylonitrile‐butadiene‐styrene (ABS) and high density polyethylene (HDPE) with multiwall carbon nanotubes (MWNT) were prepared by melt mixing technique to achieve conducting composites. MWNT were either compounded directly or by employing a masterbatch dilution approach in binary (PA6/ABS), ternary (PA6/PP/ABS) and quaternary (PA6/PP/ABS/HDPE) blends. To facilitate “network‐like'' structure MWNT were pretreated with either sodium salt of 6‐aminohexanoic acid or octadecyl tri‐phenyl phosponium bromide. Multicomponent blends with pretreated MWNT utilizing masterbatch dilution approach showed significant improvements in the bulk electrical conductivity as compared to blends prepared by direct addition approach at 2 wt % MWNT content. Phase morphology of these blends revealed co‐continuous type of morphology wherein MWNT were found to be selectively localized in the PA6 phase. The heteronucleating action of MWNT was manifested in increased crystallization temperature of mainly PA6 phase of the blends indicating preferential localization of MWNT in the PA6 phase. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers
Melt‐compounding of PP/clay nanocomposite and relationship between its microstructure and shear strain in the flow field based on rheological analysis
Authors: Jiang Guo , Huang Han‐Xiong
Published: May 2011

Polypropylene (PP)/clay nanocomposite was melt‐compounded using high shearing/mixing and chaotic mixing, the former provided by kneading block sections in twin‐screw extruder and the latter by a convective screw. Effect of mixing type on rheological behavior and microstructure of nanocomposites was investigated. Rheological property development along twin‐screw extruder was also tested. By numerical simulation, shear strain was calculated. Based on rheological analysis, the relationship between the shear strain and microstructure of nanocomposite was analyzed. Results show that chaotic mixing facilitates the dispersion of clay in PP matrix. Along twin‐screw extruder, the complex viscosity of samples is increased, and melt yield stress of end‐obtained samples is decreased with increase of the feeding rate. Observed from transmission electron microscopy photomicrographs, a better dispersion of clay in PP matrix was found when feeding rate is lowest, and the total strain calculated is largest at the lowest feeding rate. It is deduced that higher strain in flow field is important to obtain better dispersion and properties of polymer/clay nanocomposites. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers.
Rheological properties of cotton pulp cellulose dissolved in 1‐butyl‐3‐methylimidazolium chloride solutions
Authors: Liu Zhen , Wang Hui , Li Zengxi , Lu Xingmei , Zhang Xiangping , Zhang Suojiang , Zhou Kebin
Published: May 2011

Rheological properties of cotton pulp dissolved in 1‐butyl‐3‐methylimidazolium chloride ([Bmim]Cl) solutions were characterized using an advanced rheometer. The complex viscosity, dynamic modulus, and shear viscosity at different temperature were studied. In the steady shear measurements, all the solutions show a shear‐thinning behavior at high shear rates. The complex viscosity as a function of frequency was fitted by extended Carreau–Yasuda model. In all cotton pulp/[Bmim]Cl solutions, the complex dynamic viscosity (η*) and steady shear viscosity (ηa) followed the Cox–Merz rule only at lower frequency. The effects of tested temperature on viscosity and viscoelastic behavior of the solutions were also investigated. The value of activation energy for the dissolution of cotton pulp in ionic liquids was 65.28 kJ/mol at the concentration of 10 wt% and was comparable with the ones for the dissolution of cellulose in NMMO. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers
Surface‐active and associative properties of ionic polymeric surfactants based on carboxymethylcellulose
Authors: Tomanová Vladimíra , Sroková Iva , Ebringerová Anna , Sasinková Vlasta
Published: May 2011

Polymeric biosurfactants were prepared by the transesterification reaction between rapeseed oil triacyl glycerides and carboxymethylcellulose (CMC). The reaction was performed in H2O/N,Ndimethylformamide (DMF) with potassium laurate as catalyst at various reaction conditions using microwave radiation as heating source. The structural features of the obtained water‐soluble CMC derivatives were characterized Fourier‐transform infrared (FT‐IR) spectroscopy and their behavior in dilute aqueous solutions was investigated by surface activity measurements, viscometry and with a polarity probe, the Coomassie Brilliant Blue dye. All derivatives showed a very low esterification extent and moderate surface tension lowering effect. Nevertheless, they exhibited significant emulsifying efficiency comparable to that of the synthetic surfactant, Tween 20. They establish hydrophobic associations in bulk solution while adsorbing on the air/water interface. The presence of hydrophobic substituents in CMC molecules enhanced the hydrophobicity resulting in higher emulsion stability than produced by Tween 20. The results suggested that suitable polymeric biosurfactants applicable as emulsifying agents can be prepared from CMC under microwave heating at low microwave power and reaction times in the range of few minutes, what represents a great advantage in comparison with transesterification reactions lasting up to 6 h at conventional heating. POLYM. ENG. SCI., 2011. ©2011 Society of Plastics Engineers.
A general quantitative structure–property relationship treatment for dielectric constants of polymers
Authors: Xu Jie , Wang Lei , Liang Guijie , Wang Luoxin , Shen Xiaolin
Published: May 2011

The dielectric constant (ε) of a polymer represents the capacitance of the polymer relative to a vacuum and is important in many industrial applications. Nevertheless, accurate experimental ε values of polymers are often unavailable, and current prediction methods lack universality and suitability. Reported here is the development and testing of a new QSPR (quantitative structure property relationship) correlation of ε for polymers. The entire set of 57 polymers was divided into a training set of 45 polymers and a test set of 12 polymers according to Kennard and Stones algorithm. A nine‐descriptor model, with squared correlation coefficient (R2) of 0.9384 and standard error of estimation (s) of 0.0873, was produced by using the stepwise multilinear regression analysis (MLRA) on the training set. The reliability of the proposed model was further illustrated using various evaluation techniques: leave‐one‐out cross‐validation procedure, randomization tests, and validation through the test set. POLYM. ENG. SCI., 2011. ©2011 Society of Plastics Engineers.
The chlorosome of Chlorobaculum tepidum: Size, mass and protein composition revealed by electron microscopy, dynamic light scattering and mass spectrometry‐driven proteomics
Authors: Kouyianou Kalliopi , De Bock Pieter‐Jan , Müller Shirley A. , Nikolaki Antigoni , Rizos Apostolos , Krzyžánek Vladislav , Aktoudianaki Aikaterini , Vandekerckhove Joël , Engel Andreas , Gevaert Kris , Tsiotis Georgios
Published: May 2011

Chlorosomes, the antenna complexes of green bacteria, are unique antenna systems in which pigments are organized in aggregates. Studies on isolated chlorosomes from Chlorobaculum tepidum based on SDS‐PAGE, immunoblotting and molecular biology have revealed that they contain ten chlorosomal proteins, but no comprehensive information is available about the protein composition of the entire organelle. To extend these studies, chlorosomes were isolated from C. tepidum using three related and one independent isolation protocol and characterized by absorption spectroscopy, tricine SDS‐PAGE, dynamic light scattering (DLS) and electron microscopy. Tricine SDS‐PAGE showed the presence of more than 20 proteins with molecular weights ranging between 6 and 70 kDa. The chlorosomes varied in size. Their hydrodynamic radius (Rh) ranged from 51 to 75 nm and electron microscopy indicated that they were on average 140 nm wide and 170 nm long. Furthermore, the mass of 184 whole chlorosome organelles determined by scanning transmission electron microscopy ranged from 27 to 237 MDa being on average 88 (±28) MDa. In contrast their mass‐per‐area was independent of their size, indicating that there is a strict limit to chlorosome thickness. The average protein composition of the C. tepidum chlorosome organelles was obtained by MS/MS‐driven proteomics and for the first time a detailed protein catalogue of the isolated chlorosomal proteome is presented. Based on the proteomics results for chlorosomes isolated by different protocols, four proteins that are involved in the electron or ion transport are proposed to be tightly associated with or incorporated into C. tepidum chlorosomes as well as the ten Csm proteins known to date.
Proteomic changes in articular cartilage of human endemic osteoarthritis in China
Authors: Ma Wei‐Juan , Guo Xiong , Liu Jiang‐Tao , Liu Rui‐Yu , Hu Jian‐Wen , Sun An‐Guo , Yu Yue‐Xiang , Lammi Mikko J.
Published: May 2011

Kashin–Beck disease (KBD) is a chronic endemic osteochondropathy with unclear pathogenesis. It is a degenerative disease similar to osteoarthritis, but with different manifestations of cartilage damage. The aim of this investigation was to show the protein changes in KBD cartilage and to identify the candidate proteins in order to understand the pathogenesis of the disease. Proteins were extracted from the media of primary cell cultures of KBD and normal chondrocytes, and separated by two‐dimensional fluorescence difference gel electrophoresis (2‐D DIGE). MALDI‐TOF/TOF analysis revealed statistically significant differences in 27 proteins from KBD chondrocyte cultures, which consisted of 17 up‐regulated and ten down‐regulated proteins. The results were further validated by Western blot analysis. The proteins identified are mainly involved in cellular redox homeostasis and stress response (MnSOD, Hsp27, Peroxiredoxin‐1, and Cofilin‐1), glycolysis (PGK‐1, PGM‐1, α‐enolase), and cell motility and cytoskeletal organization (Actin, Calponin‐2, and Keratin). These KBD‐associated proteins indicate that cytoskeletal remodeling, glycometabolism, and oxidative stress are abnormal in KBD articular cartilage.
Adhesive and Structural Failures of Oxide Coatings on Plasma‐Treated Polymers
Authors: Yun Jungheum , Lee Sunghun , Bae Tae‐Sung , Yun Youngmok , Lee Seunghoon , Kwon Jung‐Dae , Lee Gun‐Hwan
Published: May 2011

This study discloses (i) the chemical and morphological modifications in acrylate hard‐coat and bare polyethylene terephthalate polymers occurring in the course of Ar plasma treatments and (ii) the effects of these modifications on the adhesion, barrier performance, and cohesion of silicon oxide coatings deposited on the polymers. It is concluded that the deterioration in these coating properties is dominated by the formation of nanoscopic globular polymer protrusions on the polymer surface as a result of plasma treatment. The protrusions evolve even under very mild plasma conditions in which an ion fluence of less than 1 × 1016 ions · cm−2 is applied with low‐energy ion irradiation of 6 eV. The polymer protrusions dictate the nucleation and subsequent growth of a coating by promoting the development of a three‐dimensional granular morphology in the coating. At the initial oxide nucleation stage, the wetting behavior of silicon oxide on the polymer surface in the presence of nanoscopic protrusions is directly limited by the area number density and size of the protrusions. Incomplete wetting of the protrusions with a silicon oxide coating hinders adhesion between the oxide and the polymer surface. The reduction in the contact area between the oxide and the protrusions is identified as the reason that a weak boundary layer forms at the oxide–polymer interface. Furthermore, the formation of nanoscopic defects, predominantly pinholes, is inevitable in the granular coating morphology on the polymer protrusions and weakens the oxide coating's barrier performance and cohesion strength. Variations in the polar surface free energy and chemical composition of the plasma‐treated polymer surface are irrelevant to the wetting dynamics whenever the protrusions develop on the polymer surface. The effects of the polar surface free energy and chemical composition are valid only to the extent that the plasma treatment improves the wettability of a polymer surface without protrusion formation.

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Grain boundary electrochemistry of β‐type Nb–Ti alloy using a scanning droplet cell
Authors: Woldemedhin Michael Teka , Raabe Dierk , Hassel Achim Walter
Published: May 2011

Localized oxide spots were grown at the grain boundaries of a technically relevant 30 at.% Nb–Ti β‐type titanium alloy to study the local electrochemical response. The grain boundaries selected were combinations of grains having different orientations and grain boundary angle. Crystallographic information of the grains and boundary angles were revealed by electron back scattering diffraction (EBSD) technique. Cyclic voltammetry is the electrochemical technique used to grow the oxides starting from 0 V and increasing the potential in steps of 1 V till 8 V at a scan rate of 100 mV s−1 in an acetate buffer of pH 6.0. Electrochemical impedance spectroscopy was used to investigate the electrical properties of the oxide/electrolyte interface in the frequency range between 100 kHz and 100 mHz. Important oxide parameters such as formation factor and dielectric number were determined from these measurements. Significant differences were observed for different grain boundaries. The semiconducting properties of the oxides at the grain boundaries were assessed by using Mott–Schottky analysis on a potentiostatically grown oxide. All the oxides showed n‐type semiconducting properties where the donor concentration varies with the grain boundaries mentioned above. A flat band potential −0.25 ± 0.02 V versus standard hydrogen electrode is more or less the same for all the boundaries studied.

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Optical gain in AlGaN/AlGaN multiple quantum wells grown on high temperature AlN multiple buffers
Authors: Gong Y. P. , Xing K. , Wang T.
Published: May 2011

Amplified spontaneous emission spectra measurements have been carried out on two AlGaN/AlGaN multiple quantum well (MQW) structures grown using two different kinds of high‐temperature AlN buffers, both showing a clear stimulated emission at 340 nm. This allows for investigation of optical gain of the MQWs. Based on a classic method of stripe‐length dependent optical pumping, the gain spectra have been obtained, showing a higher gain along m‐axis than that along a‐axis (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Why are nitride lasers limited to the spectral range from ∼340 to 530 nm?
Authors: Sharma Tarun Kumar , Towe Elias
Published: May 2011

We recently suggested that careful optimization of residual strain in nitride laser structures could be used to extend the operating wavelength into the red and infrared spectral region (Sharma and Towe, J. Appl. Phys. 106, 104509 (2009) and Appl. Phys. Lett. 96, 191105 (2010) [1, 2]). At the other wavelength extreme, in the ultraviolet, non‐optimal residual strain in nitride emitters with AlGaN layers and large crystal‐field splitting energies can cause a switching in emitted light polarization characteristics, leading to less efficient devices. Although Al‐rich AlGaN quantum wells favour shorter emission wavelengths, these structures also exhibit poor carrier confinement. These factors suggest that even in the ultra‐violet, the key limiting constraint for the development of lasers is the amount of residual strain in the structures. To properly resolve these issues, a critical analysis of strain, quantum confinement, and the polarization properties of nitride quantum well structures is warranted (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Electrical and EDX‐analysis of CF4 and Ar plasma treated AlGaN/GaN HEMTs
Authors: Kotara P. , Hilt O. , Kirmse H. , Würfl J. , Neumann W. , Tränkle G.
Published: May 2011

In this paper we have investigated the effect of CF4 plasma treatment on AlGaN/GaN HEMTs and compared it with Ar plasma treated devices. We have investigated the electrical characteristics of the devices using transistor characteristics as wells as CV measurements in order to verify the impacts of the different treatments on the electron concentration in the 2DEG. Furthermore, a TEM‐EDX analysis was performed to find out if any fluorine incorporation in the AlGaN barrier during the CF4 plasma treatment occurs. No significant impact of the fluorine on the threshold voltage could be determined, We conclude that fluorine incorporation is not responsible for the threshold voltage shift. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Intrinsic origin of the breakdown of quasi‐cubic approximation in nitride semiconductors
Authors: Ebihara Yasuhiro , Kamiya Katsumasa , Shiraishi Kenji , Yamaguchi Atsushi A.
Published: May 2011

We investigate the intrinsic origin of the breakdown of the quasi‐cubic approximation in hexagonal GaN (h‐GaN) on the basis of first‐principles calculations. It is found that the breakdown is caused by the third‐nearest‐neighbour interactions as well as deviations from the “ideal wurtzite structure” in the lattice‐constant ratio (c /a) and the internal parameter (u). This means that the breakdown appears even in ideal structures. Furthermore, we investigate large strain effects on the deformation potentials. We find that the potentials of h‐GaN under large biaxial strain are significantly different from those of unstrained material, although no such difference is seen in cubic GaN. It is suggested that the nonlinearity is linked with the internal parameter (u), an additional degree of freedom. These results imply that these effects should be considered in the design of nitride‐based optical devices using strained active layers (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Inhibitory Effects of Secoiridoids from the Roots of Gentiana straminea on Stimulus‐induced Superoxide Generation, Phosphorylation and Translocation of Cytosolic Compounds to Plasma Membrane in Human Neutrophils
Authors: Wei Shihu , Chen Guang , He Wenfei , Chi Haidong , Abe Hideki , Yamashita Koichi , Yokoyama Masanori , Kodama Hiroyuki
Published: May 2011

Gentiana straminea Maxim. has been used widely as a traditional Chinese medicine for the treatment of rheumarthritis, icterepatitis, constipation, pain and hypertension. Five secoiridoids, gentiopicroside (GTP), 6′‐O‐(2‐hydroxy‐3‐O‐β‐d–glucopyranosyl‐benzoyl)‐sweroside (HGBS), 6′‐O‐β‐d‐glucosylgentiopicroside (GGTP), sweroside (SW) and swertiamarin (STM) were isolated from the roots of G. straminea. The effect of these secoiridoids on stimulus‐induced superoxide generation in human neutrophils was assayed by measuring the reduction of ferricytochrome c. Tyrosyl or serine/threonine phosphorylation of neutrophil proteins, and translocation of the cytosolic compounds to the cell membrane were also investigated using specific monoclonal antibodies. The five secoiridoids used in the present experiment suppressed N‐formyl‐methionyl‐leucyl‐phenylalanine (fMLP)‐induced superoxide generation in a concentration dependent manner. GTP and HGBS also suppressed phorbol 12‐myristate 13‐acetate (PMA) and arachidonic acid (AA)‐induced superoxide generation. However, the other three secoiridoids showed no effect on PMA‐ and AA‐induced superoxide generation. fMLP‐, PMA‐ and AA‐induced tyrosyl or serine/threonine phosphorylation and translocation of the cytosolic proteins to the cell membrane were suppressed in parallel with the suppression of the stimulus‐induced superoxide generation. Copyright © 2011 John Wiley & Sons, Ltd.
Curcumin Inhibits Melanogenesis in Human Melanocytes
Authors: Tu Cai‐Xia , Lin Mao , Lu Shan‐Shan , Qi Xiao‐Yi , Zhang Rong‐Xin , Zhang Yun‐Ying
Published: May 2011

Plant derived compounds, as potentially safe and effective skin lightening agents (SLAs), have attracted great attention from many researchers. Curcumin is a plant‐derived polyphenol, which has been reported to suppress melanogenesis in B16 melanoma cells. However, little is known about whether curcumin affects melanogenesis in cultured human melanocytes. In addition, the molecular mechanism for the antimelanogenic effects of curcumin remains largely unknown. The present study assessed the effects of curcumin on melanin synthesis, cellular tyrosinase activity, the expression of melanogenesis‐related proteins (microphthalmia‐associated transcription factor (MITF), tyrosinase, tyrosinase‐related protein 1 and 2 (TRP‐1, TRP‐2)), and activation of melanogenesis‐regulating signals including phosphatidylinositol 3‐kinase (PI3K)/Akt/ glycogen synthase kinase 3 (GSK 3β), extracellular signal‐regulated kinase (ERK) and p38 MAPK in human melanocytes. The results showed that the melanin content and tyrosinase activity, as well as the expression of melanogenesis‐related proteins in human melanocytes, were significantly inhibited by curcumin in a dose dependent manner. In addition, PI3K/Akt/ GSK 3β, ERK and p38 MAPK were activated by curcumin, while inhibitors of these signals attenuated the inhibitory effects of curcumin on melanogenesis. These results suggest that curcumin inhibits melanogenesis in human melanocytes through activation of Akt/GSK 3β, ERK or p38 MAPK signaling pathways. Copyright © 2011 John Wiley & Sons, Ltd.
Inner‐core vacillation cycles during the intensification of Hurricane Katrina
Authors: Nguyen Mai C. , Reeder Michael J. , Davidson Noel E. , Smith Roger K. , Montgomery Michael T.
Published: May 2011

A simulation of Hurricane Katrina (2005) using the Australian Bureau of Meteorology's operational model for tropical‐cyclone prediction (TCLAPS) shows that the simulated vortex vacillates between almost symmetric and highly asymmetric phases. During the symmetric phase, the eyewall comprises elongated convective bands and both the low‐level potential vorticity (PV) and pseudo‐equivalent potential temperature θe fields exhibit a ring structure, with the maximum at some radius from the vortex centre. During this phase the mean flow intensifies comparatively rapidly, as the maximum acceleration of the mean tangential wind occurs near the radius of maximum mean tangential wind (RMW). In contrast, during the asymmetric phase the eyewall is more polygonal, with vortical hot towers (VHTs) located at the vertices. The low‐level PV and θe fields have monopole structures with the maximum at the centre. The intensification rate is lower than during the symmetric phase because the mean tangential wind accelerates most rapidly well within the RMW.

The symmetric‐to‐asymmetric transition is accompanied by the development of VHTs within the eyewall. The VHTs are shown to be initiated by barotropic–convective instability associated with the ring‐like structure of PV in the eyewall where the convective instability is large. During the reverse asymmetric‐to‐symmetric transition, the VHTs weaken as the local vertical wind shear increases and the convective available potential energy is consumed by convection. The weakened VHTs move outwards, similar to vortex Rossby waves, and are stretched by the angular shear of the mean vortex. Simultaneously, the rapid filamentation zone outside the RMW weakens, becoming more favourable for the development of convection. The next symmetric phase emerges as the convection reorganizes into a more symmetric eyewall. It is proposed that vacillation cycles occur in young tropical cyclones and are distinct from the eyewall replacement cycles that tend to occur in strong and mature tropical cyclones. Copyright © 2011 Royal Meteorological Society
Bayesian design of control space for optimal assimilation of observations. Part I: Consistent multiscale formalism
Authors: Bocquet M. , Wu L. , Chevallier F.
Published: May 2011

In geophysical data assimilation, the control space is by definition the set of parameters which are estimated through the assimilation of observations. It has recently been proposed to design the discretizations of control space in order to assimilate observations optimally. The present paper describes the embedding of that formalism in a consistent Bayesian framework. General background errors are now accounted for. Scale‐dependent errors, such as aggregation errors (that lead to representativeness errors) are consistently introduced. The optimal adaptive discretizations of control space minimize a criterion on a dictionary of grids. New criteria are proposed: degrees of freedom for the signal (DFS) built on the averaging kernel operator, and an observation‐dependent criterion.

These concepts and results are applied to atmospheric transport of pollutants. The algorithms are tested on the European tracer experiment (ETEX), and on a prototype of CO2 flux inversion over Europe using a simplified CarboEurope‐IP network. New types of adaptive discretization of control space are tested such as quaternary trees or factorised trees. Quaternary trees are proven to be both economical, in terms of storage and CPU time, and efficient on the test cases. This sets the path for the application of this methodology to high‐dimensional and noisy geophysical systems. Part II of this article will develop asymptotic solutions for the design of control space representations that are obtained analytically and are contenders to exact numerical optimizations. Copyright © 2011 Royal Meteorological Society