bluuebunny/crossref_metadata_2025 huggingface dataset:
Simulation of Fibrillation of PC/LCP/Kevlar Blends and Its Characterizations
Authors: Mukherjee Madhumita , Das Tanya , Bose Saswata , Das Chapal Kumar , Kharitonov Alexander P. , Banik Kaushik , Chung Tham Nguyen , Mennig Gunter
Published: March 2009

Kevlar fiber was fluorinated and oxy‐fluorinated directly in presence of undiluted fluorine and fluorine gas mixture and processed with Polycarbonate and LCP at 320 °C under 20 rpm in a twin‐screw extruder. The composites were then injection molded into dumbbell shaped specimens under different conditions like various mold temperatures, injection temperatures, injection speeds and mold filling rates. Various physico‐chemical characterizations have been performed under definite processing parameter. Orientation of fibers under different injection parameters was evaluated using mold flow simulation technique. Most injection molded or extruded structures however, exhibit non‐uniform fiber orientation across the final parts, with a diverging variety of different local fiber orientation states. Distinct skin and core regions were observed in the injection molded parts and it has also been found out that fiber orientation is different in skin and core region for both unmodified and modified derivative, which affects the flow behavior. Processing parameters significantly affect the fiber orientation pattern in the skin and core region for all blended materials. It is worth mentioning that the maximum fiber orientation occurred during the extrusion process at the wall but different extent of fiber orientation is observed during the injection molding depending on the shape of the dumbbell specimen. This fibrillation has been corroborated by the SEM study in both the skin and core region.
Preparation and Characterization of Poly(Lactic Acid)‐g‐Maleic Anhydride + Starch Blends
Authors: Orozco Victor H. , Brostow Witold , Chonkaew Wunpen , López Betty L.
Published: March 2009

Poly(lactic acid) (PLA) and starch copolymers are obtained by reactive blending ‐ varying the starch compositions from 0 to 60%. PLA is functionalized with maleic anhydride (MA), obtaining PLA‐g‐MA copolymers using dicumyl peroxide as an initiator of grafting in order to improve the compatibility and interfacial adhesion between the constituents. PLA + starch blends without a compatibilizer do not have sufficient interfacial adhesion. Decomposition temperature of PLA is not affected by grafting. Glass transition temperatures and dynamic mechanical properties are affected since MA has a plasticizing effect. Along with an increasing starch content friction decreases while wear loss volume in pin‐on‐disk tribometry has a minimum at nominal 15% wt. starch but increases at higher starch concentrations. The residual depth in scratching and sliding wear testing has a maximum at 15% starch; there is a minimum of storage modulus E′ determined in dynamic mechanical testing at the same concentration. Microhardness results also reflect the plasticization by MA.
Polyacrylamide Grafted Carboxymethyl Tamarind (CMT‐g‐PAM): Development and Application of a Novel Polymeric Flocculant
Authors: Sen Gautam , Pal Sagar
Published: March 2009

Water is scarce commodity now. Recycling of municipal wastewater, industrial and mineral processing effluents require treatment with the inorganic or organic flocculants. Both synthetic and natural polymers are used as flocculants. Natural polymers are biodegradable and are effective at very large dosages but are very shear stable. The synthetic polymers are highly effective flocculants at very small dosages and have high tailorability, but have poor shear stability. In the authors' laboratory, a novel polymeric flocculant has been developed by grafting polyacrylamide onto the backbone of carboxymethyl tamarind (CMT‐g‐PAM). Various grades were developed to optimize the best flocculant. The grafted polymers were characterized by various characterization techniques such as intrinsic viscosity measurement, FTIR spectroscopy, 13C‐NMR spectroscopy, elemental analysis etc. The flocculation studies were carried out using turbidity test as well as settling test. The optimized CMT‐g‐PAM was then compared with some of the commercial flocculants available in national and international markets in colloidal suspensions and it has been found that our synthesized flocculant surpasses most of the commercial flocculants in performance.
FTIR Studies of Doped PMMA ‐ PVC Blend System
Authors: Soman Vijay V. , Kelkar Deepali S.
Published: March 2009

The IR spectroscopy study shows miscibility between PMMA‐PVC blends due to hydrogen bonding between CO of PMMA and hydrogen from CHCl of PVC. This blend system is doped by Camphor Sulphonic Acid (CSA) in the entire composition range. The doping of CSA in PVC, in PMMA and in PMMA‐PVC blends shows changes in FTIR spectra. The interaction between PVC and CSA is through hydrogen bonding between CO of CSA and CHCl of PVC. Doping PMMA with CSA, indicate an interaction between H+ ion of CSA and oxygen atoms of CO and OCH3 of PMMA. Whereas in PMMA–PVC blend interaction between H+ ion of CSA and oxygen atom of CO of PMMA.
A Comparison of the Syntheses of High Molar Mass Epoxy Resins on the Basis of two Groups of Modified Vegetable Oils
Authors: Czub Piotr
Published: March 2009

Application of epoxidized and hydroxylated natural oils as a new group of environmentally friendly and renewable raw materials for the synthesis of high molar mass epoxy resins is described. Selected vegetable oils were first oxidized and next reacted with mono and diethylene glycols. Obtained epoxidized soybean, rapeseed, linseed and sunflower oils were used together with Bisphenol A in the fusion process. Analogously, hydroxylated soybean and rapeseed oils were reacted with commercial grade Bisphenol A‐based low molar mass epoxy resin. The fusion process was carried out in the presence of selected catalysts (i.e., lithium chloride, 2‐methylimidazole, triphenylphosphine and triethanolamine) giving high molar mass epoxies. The relationship between type of modified oil used in the synthesis and reaction conditions and properties of synthesized resins (e.g., value and distribution of average molar mass, contents of epoxy groups and colour) is discussed.
Synthesis and Ex‐situ Characterization of Nafion/TiO2 Composite Membranes for Direct Ethanol Fuel Cell
Authors: Barbora Lepakshi , Acharya Simadri , Verma Anil
Published: March 2009

Nafion/TiO2 composite membranes for different loadings of TiO2 were prepared by casting method for the possible application in direct ethanol fuel cell (DEFC). The properties of the composite membranes were investigated by scanning electron microscopy (SEM), x‐ray diffraction (XRD), thermogravimetric analyser (TGA), ion exchange capacity, water and alcohol uptake, swelling ratio, proton conductivity, and ethanol crossover. The observed characteristics of the membranes were evaluated for DEFC and compared with the direct methanol fuel cell (DMFC) membrane. The analysis reveales a significant influence on the TiO2 surface characteristics, water and alcohol uptake, and swelling of the membrane. The TiO2 composite membranes exhibited a sharp decrease in methanol and ethanol crossover for 5% TiO2 and the proton conductivity was heighest for 1% TiO2 loading. The best compromise between proton conductivity and crossover has been found out with the help of the characteristic factor ϕ. The optimum loading of 5% TiO2 composite membrane has shown the maximum characteristic factor.
Chiral NMR discrimination of the diastereoisomeric salts of the H3‐antagonist 2‐[3‐(1H‐imidazol‐4‐ylmethyl)piperidin‐1‐yl]‐1H‐benzimidazole
Authors: Rivara Mirko , Zuliani Valentina , Fantini Marco , Dallaturca Elisa , Mor Marco
Published: March 2009

Diastereomeric salts with optically pure (S)‐α‐methoxy‐α‐(trifluoromethyl)phenylacetic acid (MTPA) were used to discriminate the enantiomers of the chiral H3‐antagonist 2‐[3‐(1H‐imidazol‐4‐ylmethyl)piperidin‐1‐yl]‐1H‐benzimidazole. Chemical‐shift differences (Δδ) in NMR spectra strongly depend on solvent and stoichiometric ratio. The better observable differentiation occurred for the proton at the 2‐position of the imidazole ring. Copyright © 2009 John Wiley & Sons, Ltd.
Simultaneous quantification of three major triterpenoids in radix asteris by high‐performance liquid chromatography with evaporative light scattering detection
Authors: Tian Yaping , Wang Qiao , Wang Yu , Zhang Xiaowei , Sheng Xiaona , Qi Haitao , Zheng Xuguang , Zhang Lantong
Published: March 2009

Introduction

Radix asteris, with triterpenoids as its main pharmacological effective compounds, has been widely used for moistening the lung, dispersing phlegm and relieving cough. Quantification of the triterpenoids is important for the quality control of Radix asteris.

Objective

To establish a high‐performance liquid chromatography method with evaporative light scattering detection for simultaneous determination of three major triterpenoids, shionone, friedelin and epi‐friedelinol, in Radix asteris.

Methodology

The optimal chromatographic conditions were achieved on an RP18column with gradient elution by acetonitrile and 0.05% acetic acid in 22 min with ELSD set at an evaporating temperature of 40°C. Validation of the method included tests of linearity, sensitivity, precision, repeatability, stability and accuracy.

Results

All calibration curves showed good linear regression (r2 > 0.9991) within test ranges. The established method showed good precision and accuracy with overall intra‐day and inter‐day variations of 1.61–2.97 and 1.74–2.42%, respectively, and overall recoveries of 97.35–101.13% for the three compounds analysed.

Conclusion

The method developed was successfully applied to quantify the main triterpenoids in 14 Radix asteris samples. Copyright © 2009 John Wiley & Sons, Ltd.
Performance of first‐trimester combined screening for trisomy 13 and 18 with the double test taken at a gestational age of 8 + 0 to 13 + 6
Authors: Kirkegaard Ida , Petersen Olav Bjørn , Uldbjerg Niels , Tørring Niels
Published: March 2009

Objective

To evaluate the performance of the combined test for first‐trimester screening for trisomy 18 and 13, when the double test is scheduled weeks before the nuchal translucency scanning.

Methods

The study included all 40 cases of trisomy 18 and 13 from April 2004 to October 2008 in a screening programme, where the double test was measured in gestational weeks 8 + 0 to 13 + 6 and the nuchal translucency in weeks 11 + 2 to 13 + 6.

Results

Twenty‐eight among the 40 cases had complete information on all variables in the first‐trimester screening test. Among 19 cases having the double test taken before 10 + 0 weeks, 10 cases were detected (detection rate (DR) = 53%) and among 9 cases having the double test taken after 10 + 0 weeks, 6 cases were detected (DR 67%). There was no significant difference in the DRs (p = 0.48). A total of 29 cases were detected at the first‐trimester screening, resulting in an overall DR for trisomy 18 and 13 at 73%.

Conclusion

This study showed no significant differences in the trisomy 18/13 DRs when grouped according to having the double test taken before or after 10 + 0 weeks. The DR was 73% at the first‐trimester screening. Copyright © 2009 John Wiley & Sons, Ltd.
Adherence to diagnostic guidelines and quality indicators in asthma and COPD in Swedish primary care
Authors: Weidinger Paolina , Nilsson J. Lars G. , Lindblad Ulf
Published: March 2009

Purpose

To study the clinical evaluation and treatment of patients with asthma and COPD in primary care in Sweden, with a focus on adherence to recommended guidelines and quality indicators.

Methods

All visits at health care centres in Skaraborg, Sweden, are documented in computerized medical records constituting the Skaraborg Primary Care Database (SPCD). In a register‐based retrospective observational study, all patients diagnosed with asthma or COPD during 2000–2005 (n = 12 328) were identified. In a 5% random sample (n = 623), information on performed investigations at initial visits and at follow‐up during 2004–2005 was collected. Compliance with procedures as recommended by national guidelines was used for quality assessment.

Results

Among 499 patients with asthma, 167 (33%) were investigated with spirometry or Peak Expiratory Flow (PEF) during initial visits in agreement with guidelines. Correspondingly, 40 out of 124 patients with COPD (32%) were investigated with spirometry. During follow‐up, evaluation in agreement with guidelines was performed in 130 (60%) of patients with asthma and in 35 patients out of 77 (45%) with COPD. Prescribing of ICS reached quality target, still every second patient made an acute visit during follow‐up.

Conclusion

Adherence to recommended guidelines in asthma/COPD was low. Acute visits were common and despite the prescribing of ICS according to recommendations, patients still seem uncontrolled in their disease. There is a need for quality improvement in the clinical evaluation and treatment of patients with asthma and COPD. Copyright © 2009 John Wiley & Sons, Ltd.
Creating microstructures on silicon wafers using UV‐crosslinked polystyrene thin films
Authors: Knudsen Daniel , Harnish Bernadette , Toth Ramona , Yan Mingdi
Published: March 2009

We report that UV‐crosslinked polystyrene (PS) thin films can be used as an inexpensive wet chemical etch resist to create microstructures on silicon wafers. When spin‐coated PS films were irradiated, the polymer undergoes UV‐induced crosslinking. Patterned PS films were successfully used as the protective layer withstanding chemical etching with the buffered HF solution. Removal of the polymer films by sonicating in water generated microstructures in silicon wafers. This simple and environmentally friendly procedure employs inexpensive commodity polymer and eliminates the use of organic solvents and harsh conditions in the subsequent development process. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers
Profile of native N‐linked glycan structures from human serum using high performance liquid chromatography on a microfluidic chip and time‐of‐flight mass spectrometry
Authors: Chu Caroline S. , Niñonuevo Milady R. , Clowers Brian H. , Perkins Patrick D. , An Hyun Joo , Yin Hongfeng , Killeen Kevin , Miyamoto Suzanne , Grimm Rudolf , Lebrilla Carlito B.
Published: March 2009

Protein glycosylation involves the addition of monosaccharides in a stepwise process requiring no glycan template. Therefore, identifying the numerous glycoforms, including isomers, can help elucidate the biological function(s) of particular glycans. A method to assess the diversity of the N‐linked oligosaccharides released from human serum without derivatization has been developed using on‐line nanoLC and high resolution TOF MS. The N‐linked oligosaccharides were analyzed with MALDI FT‐ICR MS and microchip LC MS (HPLC–Chip/TOF MS). Two microfluidic chips were employed, the glycan chip (40 nL enrichment column, 43×0.075 mm2 i.d. analytical column) and the high capacity chip (160 nL enrichment column, 140×0.075 mm2 i.d. analytical column), both with graphitized carbon as the stationary phase. Both chips offered good sensitivity and reproducibility in separating a heterogeneous mixture of neutral and anionic oligosaccharides between injections. Increasing the length and volume of the enrichment and the analytical columns improved resolution of the peaks. Complex type N‐linked oligosaccharides were the most abundant oligosaccharides in human serum accounting for ∼96% of the total glycans identified, while hybrid and high mannose type oligosaccharides comprise the remaining ∼4%.
Identification of proteins of Neisseria meningitidis induced under iron‐limiting conditions using the isobaric tandem mass tag (TMT) labeling approach
Authors: van Ulsen Peter , Kuhn Karsten , Prinz Thorsten , Legner Harald , Schmid Peter , Baumann Christian , Tommassen Jan
Published: March 2009

Isobaric labeling reagents such as Tandem Mass Tags (TMT®) enable the genome‐wide quantification of protein expression levels under different conditions using a gel‐free MS/MS‐based approach. Here, we applied a TMTduplex approach with two isobaric tags to study the response of the human pathogen Neisseria meningitidis to deprivation of iron, a condition met in the human body. In total, 609 proteins were identified in samples of three independent growth experiments, in which we compared cultures grown in the presence and absence of iron. Expression of 35 proteins was found to be induced or repressed under iron‐limiting conditions, including 11 proteins whose ORFs were not previously identified in DNA array studies as being regulated by iron availability at the transcriptional level. These 11 proteins include proteins likely involved in iron metabolism.
Subcellular proteomics of Trypanosoma cruzi reservosomes
Authors: Sant'Anna Celso , Nakayasu Ernesto S. , Pereira Miria G. , Lourenço Daniela , de Souza Wanderley , Almeida Igor C. , Cunha‐e‐Silva Narcisa L.
Published: March 2009

Reservosomes are the endpoint of the endocytic pathway in Trypanosoma cruzi epimastigotes. These organelles have the particular ability to concentrate proteins and lipids obtained from medium together with the main proteolytic enzymes originated from the secretory pathway, being at the same time a storage organelle and the main site of protein degradation. Subcellular proteomics have been extensively used for profiling organelles in different cell types. Here, we combine cell fractionation and LC‐MS/MS analysis to identify reservosome‐resident proteins. Starting from a purified reservosome fraction, we established a protocol to isolate reservosome membranes. Transmission electron microscopy was applied to confirm the purity of the fractions. To achieve a better coverage of identified proteins we analyzed the fractions separately and combined the results. LC‐MS/MS analysis identified in total 709 T. cruzi‐specific proteins; of these, 456 had predicted function and 253 were classified as hypothetical proteins. We could confirm the presence of most of the proteins validated by previous work and identify new proteins from different classes such as enzymes, proton pumps, transport proteins, and others. The definition of the reservosome protein profile is a good tool to assess their molecular signature, identify molecular markers, and understand their relationship with different organelles.
Contribution of individual histidines to the global stability of human prolactin
Authors: Keeler Camille , Tettamanzi M. Cristina , Meshack Syrus , Hodsdon Michael E.
Published: March 2009

A member of the family of hematopoietic cytokines human prolactin (hPRL) is a 23k kDa polypeptide hormone, which displays pH dependence in its structural and functional properties. The binding affinity of hPRL for the extracellular domain of its receptor decreases 500‐fold over the relatively narrow, physiologic pH range from 8 to 6; whereas, the affinity of human growth hormone (hGH), its closest evolutionary cousin, does not. Similarly, the structural stability of hPRL decreases from 7.6 to 5.6 kcal/mol from pH 8 to 6, respectively, whereas the stability of hGH is slightly increased over this same pH range. hPRL contains nine histidines, compared with hGH's three, and they are likely responsible for hPRL's pH‐dependent behavior. We have systematically mutated each of hPRL's histidines to alanine and measured the effect on pH‐dependent global stability. Surprisingly, a vast majority of these mutations stabilize the native protein, by as much as 2–3 kcal/mol. Changes in the overall pH dependence to hPRL global stability can be rationalized according to the predominant structural interactions of individual histidines in the hPRL tertiary structure. Using double mutant cycles, we detect large interaction free energies within a cluster of nearby histidines, which are both stabilizing and destabilizing to the native state. Finally, by comparing the structural locations of hPRL's nine histidines with their homologous residues in hGH, we speculate on the evolutionary role of replacing structurally stabilizing residues with histidine to introduce pH dependence to cytokine function.
Nanoscale elongating control of the self‐assembled protein filament with the cysteine‐introduced building blocks
Authors: Usui Kengo , Maki Tei , Ito Fuyu , Suenaga Atsushi , Kidoaki Satoru , Itoh Masayoshi , Taiji Makoto , Matsuda Takehisa , Hayashizaki Yoshihide , Suzuki Harukazu
Published: March 2009

Self‐assembly of artificially designed proteins is extremely desirable for nanomaterials. Here we show a novel strategy for the creation of self‐assembling proteins, named “Nanolego.” Nanolego consists of “structural elements” of a structurally stable symmetrical homo‐oligomeric protein and “binding elements,” which are multiple heterointeraction proteins with relatively weak affinity. We have established two key technologies for Nanolego, a stabilization method and a method for terminating the self‐assembly process. The stabilization method is mediated by disulfide bonds between Cysteine‐residues incorporated into the binding elements, and the termination method uses “capping Nanolegos,” in which some of the binding elements in the Nanolego are absent for the self‐assembled ends. With these technologies, we successfully constructed timing‐controlled and size‐regulated filament‐shape complexes via Nanolego self‐assembly. The Nanolego concept and these technologies should pave the way for regulated nanoarchitecture using designed proteins.
Activation of the West Nile virus NS3 protease: Molecular dynamics evidence for a conformational selection mechanism
Authors: Ekonomiuk Dariusz , Caflisch Amedeo
Published: March 2009

The flaviviral nonstructural 3 protease (NS3pro) is essential for virus replication and is therefore a pharmaceutically relevant target to fight Dengue and West Nile virus (WNV). NS3pro is a chymotrypsin‐like serine protease which requires a polypeptide cofactor (NS2B) for activation. Recent X‐ray crystallography studies have led to the suggestion that the substrate binds to the two‐component NS2B‐NS3pro enzyme by an induced‐fit mechanism. Here, multiple explicit water molecular dynamics simulations of the WNV NS2B‐NS3pro enzyme show that the active conformation of the NS2B cofactor (in which its β‐loop is part of the substrate binding site) is stable over a 50‐ns time scale even in the absence of the inhibitor. The partial and reversible opening of the NSB2 β‐loop and its correlated motion with an adjacent NS3pro loop, both observed in the simulations started from the active conformation, are likely to facilitate substrate binding and product release. Moreover, in five of eight simulations without inhibitor (started from two X‐ray structures both with improperly formed oxyanion hole) the Thr132‐Gly133 peptide bond flips spontaneously thereby promoting the formation of the catalytically competent oxyanion hole, which then stays stable until the end of the runs. The simulation results provide evidence at atomic level of detail that the substrate binds to the NS2B‐NS3pro enzyme by conformational selection, rather than induced‐fit mechanism.
Transforming a NEP1 toxin gene into two Fusarium spp. to enhance mycoherbicide activity on Orobanche—failure and success
Authors: Meir Sagit , Amsellem Ziva , Al‐Ahmad Hani , Safran Einat , Gressel Jonathan
Published: March 2009

BACKGROUND: The NEP1 gene encoding a fungal toxin that successfully conferred hypervirulence when transformed into Colletotrichum coccodes (Wallr.) Hughes attacking Abutilon theophrasti (L.) Medic. was tested to ascertain if it would enhance pathogenicity of Fusarium species to Orobanche aegyptiaca Pers. parasitising crops.

RESULTS: None of the Fusarium oxysporum (#CNCM I‐1622) NEP1 transformants was hypervirulent. NEP1 transformants of a new but unnamed Fusarium sp. (#CNCM I‐1621—previously identified as F. arthrosporioides) killed Orobanche more rapidly than the wild type. Transformed lines of both species were NEP1 PCR positive, as was the wild type of F. oxysporum #CNCM I‐1622 and five other formae speciales of F. oxysporum. All six wild‐type formae speciales of F. oxysporum tested excrete minute amounts of immunologically and bioassay‐detectable NEP1‐like protein. NEP1 expression of most F. oxysporum transformants was suppressed, suggesting that the native gene and the transgene silence each other. The sequence of the putative NEP1 gene in Fusarium oxysporum #CNCM I‐1622 differs from the sequence in the toxin‐overproducing strain of F. oxysporum f. sp. erythroxyli in four or five amino acids in the first exon.

CONCLUSION: Wild‐type Fusarium sp. #CNCM I‐1621 does not contain a NEP1‐like gene, explaining why it seemed amenable to transformation with high expression, and its virulence was probably enhanced by not cosuppressing the endogenous gene as occurred with Fusarium oxysporum #CNCM I‐1622. Copyright © 2009 Society of Chemical Industry
Peptide purification by affinity chromatography based on α‐ketoacyl group chemistry
Authors: Hara Toshiaki , Tainosho Akira , Nakamura Ken'ichiroh , Sato Takeshi , Kawakami Toru , Aimoto Saburo
Published: March 2009

Significant advances have been achieved in the fields of peptide/protein synthesis, permitting the preparation of large, complex molecules. Shortcomings, however, continue to exist in the area of peptide purification. This paper details some studies we undertook to develop a new strategy for peptide purification based on a reactivity of α‐ketoacyl groups in peptides. The α‐ketoacyl peptide was generated from Nε‐acyl‐lysyl‐peptide in the solid phase via a transamination reaction using glyoxylic acid and nickel(II) ion. Cleavage of the α‐ketoacyl group with o‐phenylenediamine gave the target peptide in an acceptable yield and purity. We first carried out a careful step‐by‐step optimization of the purification conditions using a model peptide. The strategy was then used in the purification of a transmembrane peptide that could not be effectively purified using a conventional RP‐HPLC system due to the strong hydrophobicity of the peptide and its high tendency to aggregate. Copyright © 2009 European Peptide Society and John Wiley & Sons, Ltd.
Anisotropic donor states in electric field
Authors: Zakrzewski Adam J.
Published: March 2009

In this paper we consider the application of the stabilization method to calculations of the ground state energy and resonance width of shallow donors in a uniform electric field. We show for the first time that within our formulation of this method it is very easy to include various factors influencing electronic structure of shallow impurities, like effective mass anisotropy or magnetic field. We demonstrate that the effective mass anisotropy significantly changes the lifetime of donor bound electrons. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Comparative cathodoluminescence characterization of ultrathin InN wells/GaN matrix MQWs grown on bulk‐GaN and MOVPE‐GaN
Authors: Hwang E. S. , Che S. B. , Ishitani Y. , Yoshikawa A.
Published: March 2009

One monolayer (1 ML) InN/GaN multiple quantum wells (MQWs) grown on bulk‐GaN and MOVPE‐GaN/ sapphire substrates with threading dislocation densities (TDDs) of about 106 cm–2 and 108 cm–2, respectively, were characterized by SEM‐CL measurements to study the effects of TDs on structural quality of InN/GaN MQWs. For the sample grown on bulk‐GaN substrate, step‐flow surface morphology and quite uniform spatial emission were observed as compared to the sample grown on MOVPE‐GaN/sapphire. CL peak energy at 86 K was observed at around 3.2 eV for both MQWs, but CL emission spectra from MQWs on bulk‐GaN substrate were five times stronger with smaller peak energy distribution, and full width at half maximum than those on MOVPE‐GaN substrate. This was caused by low‐TDD of bulk‐GaN substrate. Further, effects of growth temperature on 1 ML InN/GaN MQWs were investigated and it was found that CL peak energy tended to discretely shift to lower energy side, for e.g., from 3.18 eV to 2.9 eV when the growth temperature was decreased from 660 °C to 620 °C. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Innovative lift‐off solar cell made of monocrystalline‐silicon thin film by annealing of ordered macropores
Authors: Depauw Valérie , Gordon Ivan , Beaucarne Guy , Poortmans Jef , Mertens Robert , Celis Jean‐Pierre
Published: March 2009

To answer the challenge of obtaining thinner silicon solar cells, we developed a technique based on the transfer of a thin layer of high‐quality monocrystalline silicon to a foreign low‐cost substrate. The transfer is enabled by the reorganisation of macroporous silicon at high temperature: driven by the minimisation of their surface energy, pores close and, in specific situations, merge to form a large single void, a few micrometers under the wafer surface. As demonstrated in this paper, the micron‐thick film above it may be detached and used to process a solar cell. The difficulty of this approach lies in appropriately ordering the macropores, while its originality is to enable processing of a high‐quality material directly from porous silicon. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Photoluminescence of nanoporous silicon grains in TiO2 matrices
Authors: Frank Otakar , Kavan Ladislav , Kůsová Kateřina , Dohnalová Kateřina , Solovieva Natalia , Cibulka Ondřej , Pelant Ivan
Published: March 2009

The first attempts on introducing luminescent porous silicon agglomerates into various TiO2 thin‐film matrices (amorphous, crystalline and inverse opal) are reported. We describe preparation methods towards such matrices and how to impregnate them with luminescent Si nanocrystals (Si‐ncs). Si‐ncs keep their high luminescent capability in these matrices. Moreover, Si‐ncs embedded in the inverse TiO2 (anatase) opal matrix show marked modifications both in their emission spectrum and in luminescence dynamics. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Grafting stimuli‐responsive polymer brushes to freshly‐etched porous silicon
Authors: Segal Ester , Perelman Loren A. , Moore Troy , Kesselman Ellina , Sailor Michael J.
Published: March 2009

This work describes a simple two‐step method for grafting thermoresponsive amine‐terminated poly(N‐isopropylacrylamide) brushes to thin films of freshly‐etched porous Si. Grafting is achieved by pre‐hydrosilylation of the hydride‐terminated porous Si with undecylenic acid. The end carboxyl groups are activated and reacted with amine‐terminated poly(N‐isopropylacrylamide). Attachment of the polymer to the porous Si is confirmed by Fourier‐transform infrared (FTIR) spectroscopy and atomic force microscopy. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Refractive index contrast in porous silicon multilayers
Authors: Nava R. , de la Mora M. B. , Tagüeña‐Martínez J. , del Río J. A.
Published: March 2009

Two of the most important properties of a porous silicon multilayer for photonic applications are flat interfaces and a relative large refractive index contrast between layers in the optical wavelength range. In this work, we studied the effect of the current density and HF electrolyte concentration on the refractive index of porous silicon. With the purpose of increasing the refractive index contrast in a multilayer, the refractive index of porous silicon produced at low current was studied in detail. The current density applied to produce the low porosity layers was limited in order to keep the electrolyte flow through the multilayer structure and to avoid deformation of layer interfaces. We found that an electrolyte composed of hydrofluoric acid, ethanol and glycerin in a ratio of 3:7:1 gives a refractive index contrast around 1.3/2.8 at 600 nm. Several multilayer structures with this refractive index contrast were fabricated, such as dielectric Bragg mirrors and microcavities. Reflectance spectra of the structures show the photonic quality of porous silicon multilayers produced under these electrochemical conditions. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Porous silicon based microdevice for reversed phase liquid chromatography
Authors: Méry E. , Alekseev S. , Portet‐Koltalo F. , Morin C. , Barbier D. , Zaitsev V. , Desbène P. L.
Published: March 2009

This paper deals with On‐Chip‐Chromatography separation systems micromachined on porous silicon. Reversed phase C18 was prepared on the porous silicon base and characterised by means of FTIR and water contact angle measurements. From this preliminary study, a liquid chromatography microdevice including silanised porous silicon layer was realized and tested for the separation of model mixture of dimethyl‐ and dioctyl phthalates. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Elastic constants of porous silicon superlattices
Authors: Polomska Anna M. , Andrews G. Todd
Published: March 2009

Porous silicon superlattices with constituent layer porosities of ∼30% and ∼60% and modulation wavelengths of 17 nm, 20 nm and 34 nm were fabricated by electrochemical etching in HF‐based electrolytes. The elastic constants of the superlattices were estimated using Brillouin light scattering spectroscopy and compared to those calculated from an effective elastic constants model (M. Grimsditch and F. Nizzoli, Phys. Rev. B 33, 5891 (1986) [1]). The fair agreement between the experimental and calculated constants suggests that the model holds promise for predicting the elastic properties of these and possibly other porous multilayered systems. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Novel phosphors based on porous materials
Authors: Tiginyanu I. M. , Ursaki V. V. , Sirbu L. , Enaki M. , Monaico E.
Published: March 2009

Technological conditions have been developed for the preparation of nanocomposite phosphors based on porous InP, GaP and GaAs semiconductor as well as Al2O3 and TiO2 dielectric templates doped with rare earth and transition metal ions.

Semiconductor and dielectric templates are prepared by electrochemical treatment of bulk semiconductor substrates and metallic plates, respectively. Doping is performed by impregnation from liquid solutions followed by thermal treatment. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Revised δ34S reference values for IAEA sulfur isotope reference materials S‐2 and S‐3
Authors: Mann Jacqueline L. , Vocke Robert D. , Kelly W. Robert
Published: March 2009

Revised δ34S reference values with associated expanded uncertainties (95% confidence interval (C.I.)) are presented for the sulfur isotope reference materials IAEA‐S‐2 (22.62 ± 0.16‰) and IAEA‐S‐3 (−32.49 ± 0.16‰). These revised values are determined using two relative‐difference measurement techniques, gas source isotope ratio mass spectrometry (GIRMS) and double‐spike multi‐collector thermal ionization mass spectrometry (MC‐TIMS). Gas analyses have traditionally been considered the most robust for relative isotopic difference measurements of sulfur. The double‐spike MC‐TIMS technique provides an independent method for value‐assignment validation and produces revised values that are both unbiased and more precise than previous value assignments. Unbiased δ34S values are required to anchor the positive and negative end members of the sulfur delta (δ) scale because they are the basis for reporting both δ34S values and the derived mass‐independent Δ33S and Δ36S values. Published in 2009 by John Wiley & Sons, Ltd.
Longest convex chains
Authors: Ambrus Gergely , Bárány Imre
Published: March 2009

Assume Xn is a random sample of n uniform, independent points from a triangle T. The longest convex chain, Y, of Xn is defined naturally (see the next paragraph). The length |Y| of Y is a random variable, denoted by Ln. In this article, we determine the order of magnitude of the expectation of Ln. We show further that Ln is highly concentrated around its mean, and that the longest convex chains have a limit shape. © 2009 Wiley Periodicals, Inc. Random Struct. Alg., 2009
Distributed timeslot allocation with crossed slots in CDMA‐TDD systems
Authors: Sung Ki Won , Lee Chae Y.
Published: March 2009

Code division multiple access system with time division duplex (CDMA‐TDD) is a promising solution to cope with traffic asymmetry of downlink (DL) and uplink (UL) in multimedia services. When a rate of asymmetry is different in each cell, CDMA‐TDD system may employ crossed slots, where a timeslot is used for different links in cells. However, it may suffer from base station (BS)‐to‐BS and mobile station (MS)‐to‐MS interference problem. Zone division scheme is an efficient way to tackle the crossed slot interference by dividing a cell into inner and outer zones and restricting communication in crossed slots only to inner zone. In this paper, we propose distributed crossed slot resource allocation with zone division in multi‐cell CDMA‐TDD system. Two conditions for crossed slot resource allocation are defined and the bound on the size of inner zone is analyzed mathematically based on the conditions. Relationship between the capacity of crossed slot and the size of inner zone is also analyzed. Then, numerical results of the mathematical analysis are presented; showing that the proposed crossed slot allocation is effective for traffic asymmetry problem. Copyright © 2009 John Wiley & Sons, Ltd.
X‐Ray fluorescence microtomography under various excitation conditions
Authors: Pereira G. R. , Rocha H. S. , Calza C. , Anjos M. J. , Pérez C. A. , Lopes R. T.
Published: March 2009

The main goal of this work is two‐fold: (1) to compare three different excitation conditions in x‐ray fluorescence microtomography (XRFCT) in the analysis of reference samples, and (2) to determine the elemental distribution map for breast tissue samples, in order to verify concentrations of certain elements correlated with characteristics and pathology, using x‐ray transmission microtomography (CT).

The experiments were performed at the X‐Ray Fluorescence Facility (D09B‐XRF) of the Brazilian Synchrotron Light Laboratory (LNLS), Campinas, Brazil. In this work, a multilayer monochromator with photon energies near 12 keV, a monochromatic beam at 9.8 keV using a Si (111) crystal, and the white beam were used for elements excitation of elements inside the sample. The sample was placed on a high‐precision goniometer and translation stages, which allowed for rotation as well as translation perpendicular to the beam. Fluorescence photons were collected by means of an energy dispersive HPGe detector placed at 90° to the incident beam, while transmitted photons were detected with a fast Na(Tl) scintillation counter, placed behind the sample, in the direction of the incoming beam. Transmission CT images were reconstructed using a filtered back‐projection algorithm, and XRFCT images were reconstructed using a filtered back‐projection algorithm with absorption correction. Copyright © 2009 John Wiley & Sons, Ltd.
TXRF cation analysis by anionic membrane collection
Authors: Kallithrakas‐Kontos N. , Hatzistavros V.
Published: March 2009

A new method for the determination of trace levels of cationic ions by anion selective membrane collection is presented. Anion selective membranes containing a few micrograms of different complexing reagents in polyvinyl chloride (PVC) matrix were produced in quartz reflectors. The membranes were immersed in water solutions with low concentrations of cationic metals, Cu, Co, Ni, Zn, and of anionic ligands (CN−, etc.). After the equilibration time the reflectors were left to dry and they were analyzed by Total X‐Ray Fluorescence (TXRF). Many experimental parameters (pH effect, size of the membrane, volume sample) were examined. The minimum detection limits were estimated to be 1 ng/ml for all metallic cations even in seawater. The method needs less working labor than other enrichment procedures, the cations are collected directly on the TXRF reflector surface and very small chemical reagent consumption is needed. Copyright © 2009 John Wiley & Sons, Ltd.
Integrating population size analysis into habitat suitability assessment: implications for giant panda conservation in the Minshan Mountains, China
Authors: Wang Xuezhi , Xu Weihua , Ouyang Zhiyun
Published: March 2009

Compared to conventional approaches, the integration of population size analysis with habitat suitability assessment on a large scale can provide more evidence to explain the mechanisms of habitat isolation and fragmentation, and thus make regional conservation plans. In this paper, we analyzed the habitat suitability for giant pandas in the Minshan Mountains, China, using the ecological‐niche factor analysis (ENFA) method, and then evaluated the current conservation status of this endangered species. The results showed that (1) giant pandas were distributed in a narrow altitudinal range in which vegetation cover was dominated by coniferous forest, mixed coniferous and deciduous broadleaf forest, and deciduous broadleaf forest with scattered bamboo understory, and (2) roads and human settlements had strong negative effects on the panda habitat selection. According to habitat analysis, the total habitat area of giant panda in the Minshan Mountains was 953,173 ha, which was fragmented into 12 habitat units by major roads, rivers, and human settlements. The habitat of the mid‐Minshan was less fragmentized, but was seriously fragmented in the north. The panda population size estimation showed that 676 individuals inhabited the study area, and 94.53% of them were in the mid‐Minshan, but small panda populations less than 30 individuals inhabited the isolated and fragmented habitat patches in the north. The nature reserves in the Minshan Mountains have formed three conservation groups, which covered 41.26% of panda habitat and protected 70.71% of panda population of the study area, but there still exists two conservation gaps, and the connectivity among these reserves is still weak. Due to habitat isolation and extensive human disturbances, giant pandas in the north (i.e., Diebu, Zhouqu, and Wudou) are facing threats of local extinction. In order to protect pandas and their habitats in this area, some effective conservation approaches, such as establishing new reserves in gap areas, creating corridors among patches, and seasonally controlling traffic flux in key roads, should be implemented in the future to link these isolated habitats together.
Valuing time: Moderate download times can improve online goal pursuit
Authors: Sellier Anne Laure , Chattopadhyay Amitava
Published: March 2009

This research examines how the length of time for which a goal is interrupted affects goal pursuit, in an online context. Goal interruption duration in the form of long download time duration has been identified as a significant impediment to electronic commerce. It is believed that a faster download time is always better to motivate web users to keep surfing. We challenge this belief. In three studies, we find that, under certain circumstances, longer rather than shorter download times motivate web users to keep surfing longer. The counterintuitive pattern of effects can be explained by web users' fit experiences (Higgins, 2000) while surfing. In particular, our findings suggest that when online surfing “feels right”, web users think that online information is right.
EVALUATION OF CERTAIN CLASSES OF EISENSTEIN-TYPE SERIES
Authors: TSUMURA HIROFUMI
Published: March 2009

In this paper, we consider certain classes of Eisenstein-type series involving hyperbolic functions, and prove some formulas for them which can be regarded as relevant analogues of our previous results. We can also regard these formulas as certain generalizations of the famous formulas for the ordinary Eisenstein series given by Hurwitz.
THE GENUS OF PERIODIC LINKS WITH RATIONAL QUOTIENTS
Authors: LEE SANG YOUL , SEO MYOUNGSOO
Published: March 2009

In this paper, we prove that if K is any periodic link in S3 whose quotient link is a 2-bridge link, then one half of the degree of the reduced Alexander polynomial, the minimal genus, the free genus and the canonical genus of K are all the same. We also give criteria to determine whether a given periodic link has a 2-bridge link quotient and some properties of this kind of periodic link.
COMMON FACTORS OF RESULTANTS MODULO p
Authors: GOMEZ DOMINGO , GUTIERREZ JAIME , IBEAS ÁLVAR , SEVILLA DAVID
Published: March 2009

We show that the multiplicity of a prime p as a factor of the resultant of two polynomials with integer coefficients is at least the degree of their greatest common divisor modulo p. This answers an open question by Konyagin and Shparlinski.
FINITE GROUPS WITH TWO p-REGULAR CONJUGACY CLASS LENGTHS II
Authors: ALEMANY ELENA , BELTRÁN ANTONIO , JOSÉ FELIPE MARÍA
Published: March 2009

Let G be a finite group. We prove that if the set of p-regular conjugacy class sizes of G has exactly two elements, then G has Abelian p-complement or G=PQ×A, with P∈Sylp(G), Q∈Sylq(G) and A Abelian.
FRÉCHET INTERMEDIATE DIFFERENTIABILITY OF LIPSCHITZ FUNCTIONS ON ASPLUND SPACES
Authors: GILES J. R.
Published: March 2009

The deep Preiss theorem states that a Lipschitz function on a nonempty open subset of an Asplund space is densely Fréchet differentiable. However, the simpler Fabian–Preiss lemma implies that it is Fréchet intermediately differentiable on a dense subset and that for a large class of Lipschitz functions this dense subset is residual. Results are presented for Asplund generated spaces.
The Dividends of Diversion: Mature Democracies’ Proclivity to Use Diversionary Force and the Rewards They Reap from It
Authors: Kisangani Emizet F. , Pickering Jeffrey
Published: March 2009

The diversionary proclivities of democratic and autocratic regimes have been debated in the empirical literature. This new theoretical synthesis on the subject builds upon the insights of the institutional approach, rational choice literature on voting and research on audience costs. It is contended that leaders in mature democracies have more incentive to use diversionary force than leaders in other regimes, and they are more likely to gain domestic political and economic benefits from it. To test this, dynamic generalized method of moments (GMM) models are used to ascertain the reciprocal relationships between domestic political unrest, domestic economic performance and foreign military intervention in 140 countries in 1950–96. The theory is supported since, collectively, mature democracies are more prone to use diversionary force and to benefit from it than non-democracies. Interesting nuances appear when specific types of presidential or parliamentary democracies are analysed.
Relationship between somatic cell count, polymorphonuclear leucocyte count and quality parameters in bovine bulk tank milk
Authors: Wickström Erik , Persson-Waller Karin , Lindmark-Månsson Helena , Östensson Karin , Sternesjö Åse
Published: March 2009

The somatic cell count (SCC) in bovine bulk tank milk is presently used as an indicator of raw milk quality, reflecting the udder health status of the herd. During mastitis, SCC increases, mostly owing to an influx of polymorphonuclear leucocytes (PMN) from blood into milk, with a concomitant change in milk composition. Bulk tank milk samples were categorized according to their SCC, as well as polymorphonuclear leucocyte count (PMNC), to study relationships between SCC, PMNC and various raw milk quality traits, i.e. contents of total protein, whey protein, casein, fat and lactose, casein number, proteolysis and rheological properties. The proportion of PMN, obtained by direct microscopy, was significantly higher in samples with high SCC compared with low SCC samples. SCC and PMNC were strongly correlated, yielding a correlation coefficient of 0·85. High SCC samples had lower lactose and casein contents, lower casein number and more proteolysis than low SCC samples. Samples with high PMNC had a lower casein number than low PMNC samples. Samples with high and low SCC or PMNC did not differ in respect to rheological properties. Our results do not indicate that PMNC is a better biomarker than SCC for raw bulk tank milk quality, as previously proposed.