bluuebunny/crossref_metadata_2025 huggingface dataset:
Computational modeling of flow‐induced anisotropy of polar ice for the EDML deep drilling site, Antarctica: The effect of rotation recrystallization and grain boundary migration
Authors: Bargmann Swantje , Seddik Hakime , Greve Ralf
Published: May 2011

In this contribution we model flow‐induced anisotropy of polar ice in order to gain a better understanding for the underlying microstructure and its influence on the deformation process. In particular, a continuum‐mechanical, anisotropic flow model that is based on an anisotropic flow enhancement factor (CAFFE model) is applied. The polycrystalline ice is regarded as a mixture whose grains are characterized by their orientation. The approach is based on two distinct scales: the underlying microstructure influences the macroscopic material behavior and is taken into account phenomenologically. To achieve this, the orientation mass density is introduced as a mesoscopic field, i.e. it depends on a mesoscopic variable (the orientation) in addition to position and time. The classical flow law of Glen is extended by a scalar, but anisotropic enhancement factor. Four different effects (local rigid body rotation, grain rotation, rotation recrystallization, grain boundary migration) influencing the evolution of the grain orientations are taken into account. All modeling parameters are either measurable in or derivable from field observations or laboratory experiments. A finite volume method is chosen for the discretization procedure. Numerical results simulating the ice flow at the site of the EPICA ice core in Dronning Maud Land (referred to as EDML), Antarctica, are presented. They go beyond earlier results by Seddikit et al. (J. Glaciol. 2008; 54(187):631–642) in which only local rigid body rotation and grain rotation were accounted for. By comparing simulated and observed fabrics, we come up with reference values for the parameters in the constitutive equations for rotation recrystallization and grain boundary migration. Down to 2045 m depth, good agreement can be achieved; however, further down the observed fabric cannot be reproduced well due to numerical issues. Additionally, we study the influence of the two superposed deformation regimes of vertical compression and simple shear separately and demonstrate that the numerical problems are due to the predominant shear regime near the bottom, whereas vertical compression only produces stable results everywhere. Copyright © 2011 John Wiley & Sons, Ltd.
Bladder base/trigone injection is safe and as effective as bladder body injection of onabotulinumtoxinA for idiopathic detrusor overactivity refractory to antimuscarinics
Authors: Kuo Hann‐Chorng
Published: May 2011

Purpose

The purpose of this study was to evaluate the efficacy and safety of onabotulinumtoxinA injections at bladder base/trigone and compare with injections at bladder body or bladder body/trigone for the treatment of idiopathic detrusor overactivity (IDO) refractory to antimuscarinics.

Materials and Methods

A single blind, randomized, paralleled, actively controlled trial was performed in patients with urodynamically proven IDO who failed antimuscarinic therapy. Patients were randomly assigned to receive intravesical injections of 100 U of onabotulinumtoxinA into three different bladder sites. All treatments were evaluated by voiding diary variables, urgency severity score, urodynamic studies, and patient perception of bladder condition. Long‐term success rates over 12 months were also determined.

Results

Among the patients, 37 were randomized to injections in the bladder body, 35 into the bladder body/trigone, and 33 into the bladder base/trigone. Successful results were reported in 76 (72%) patients at 3 months: 26 (70%) in the bladder body group, 26 (74%) in the bladder body/trigone group, and 24 (73%) in the bladder base/trigone group. There were no significant differences in success rates, changes in urgency and urgency incontinence episodes, urodynamic variables, or long‐term success rates among the three subgroups. The incidence of adverse events was similar among three groups. No vesicoureteral reflux was noted in all patients with or without involving trigone injection.

Conclusion

Intravesical onabotulinumtoxinA injection is an effective treatment for IDO regardless of the bladder injection site. Bladder base/trigone injection is as safe and effective as bladder body injections with or without trigone involvement. Neurourol. Urodynam. 30:1242–1248, 2011. © 2011 Wiley‐Liss, Inc.
Detrusor after‐contraction is associated with bladder outlet obstruction
Authors: Cho Sung Yong , Yi Jun‐Seok , Park Ji Hyun , Jeong Min Su , Oh Seung‐June
Published: May 2011

Aims

The aims of this study were to determine how we can differentiate detrusor after‐contraction (DAC) from artifacts, and to understand the clinical implications and significance of DAC.

Materials and Methods

A retrospective analysis was performed on 2,309 patients with neurogenic or non‐neurogenic voiding dysfunction. Investigators asked patients to cough when detrusor contraction occurred following cessation of urinary flow. No simultaneous change of detrusor pressure (Pdet) could confirm that Pdet increase could be regarded as true DAC. Patients were subcategorized according to the presence of large postvoid urine volume, increase of electromyographic activity, the amount of Pdet change, and multiplicity.

Results

Detrusor contraction occurred after cessation of urinary flow in 245 patients (10.6%). The contractions of 57 patients (23.3%) were regarded as artifacts. DAC was identified in 188 patients (132 males, 5.7% and 56 females, 2.4%). The mean increase in Pdet from the initiation of DAC to the maximal Pdet of DAC was 22.6 ± 11.2 cmH2O in males, and 18.6 ± 7.9 cmH2O in females. DAC occurred more frequently as males became older. Detrusor pressures at maximal flow were higher in patients with DAC. Patients of both genders with bladder outlet obstruction (BOO) had an increased risk of developing DAC. Males with benign prostatic hyperplasia had an increased risk of developing DAC.

Conclusions

DAC should be differentiated from artifacts using cough test and the presence of DAC was significantly correlated to the presence of BOO. Neurourol. Urodynam. 30:1361–1365, 2011. © 2011 Wiley‐Liss, Inc.
Effects of voluntary dose escalation in a placebo‐controlled, flexible‐dose trial of fesoterodine in subjects with overactive bladder
Authors: Staskin David , Khullar Vik , Michel Martin C. , Morrow Jon D. , Sun Franklin , Guan Zhonghong , Dmochowski Roger
Published: May 2011

Aims

To characterize the response to fesoterodine treatment for overactive bladder (OAB) in subjects who did or did not choose to dose escalate in a flexible‐dose study.

Methods

Subjects were randomized to fesoterodine 4 mg or placebo. At week 2, subjects could remain on 4 mg (non‐escalators) or choose to increase to 8 mg (escalators) for the remaining 10 weeks (sham escalation for placebo). Subjects completed 3‐day bladder diaries at baseline, week 2 and week 12 noting micturitions, urgency episodes, and urgency urinary incontinence (UUI) episodes.

Results

Sixty‐three per cent of 438 subjects randomized to fesoterodine and 73% of 445 randomized to placebo dose escalated. At baseline, fesoterodine escalators had significantly more micturitions and urgency episodes than fesoterodine non‐escalators (P < 0.001); at week 2, before dose escalation, diary‐dry rate and improvement in micturitions and urgency episodes were significantly greater among fesoterodine non‐escalators versus escalators (P < 0.001); and by week 12, after dose escalation, diary‐dry rate and improvements in micturitions and UUI episodes were similar between fesoterodine non‐escalators and escalators (P > 0.05). The placebo escalator group did not demonstrate a similar response over placebo non‐escalators following the dose escalation decision point.

Conclusion

A rapid and robust response to fesoterodine 4 mg was demonstrated in non‐escalators. Subjects who chose to dose escalate to fesoterodine 8 mg at week 2 showed significant improvement by week 12 versus baseline and week 2 (prior to escalation), as well as versus placebo. Dose escalation to 8 mg fesoterodine provided subjects with efficacy and tolerability similar to those who were satisfied with the 4‐mg dose. Neurourol. Urodynam. Neurourol. Urodynam. 30: 1480–1485, 2011. © 2011 Wiley Periodicals, Inc.
Aberrant succination of proteins in fumarate hydratase‐deficient mice and HLRCC patients is a robust biomarker of mutation status
Authors: Bardella Chiara , El‐Bahrawy Mona , Frizzell Norma , Adam Julie , Ternette Nicola , Hatipoglu Emine , Howarth Kimberley , O'Flaherty Linda , Roberts Ian , Turner Gareth , Taylor Jennifer , Giaslakiotis Konstantinos , Macaulay Valentine M , Harris Adrian L , Chandra Ashish , Lehtonen Heli J , Launonen Virpi , Aaltonen Lauri A , Pugh Christopher W , Mihai Radu , Trudgian David , Kessler Benedikt , Baynes John W , Ratcliffe Peter J , Tomlinson Ian P , Pollard Patrick J
Published: May 2011

Germline mutations in the FH gene encoding the Krebs cycle enzyme fumarate hydratase predispose to hereditary leiomyomatosis and renal cell cancer (HLRCC) syndrome. FH‐deficient cells and tissues accumulate high levels of fumarate, which may act as an oncometabolite and contribute to tumourigenesis. A recently proposed role for fumarate in the covalent modification of cysteine residues to S‐(2‐succinyl) cysteine (2SC) (termed protein succination) prompted us to assess 2SC levels in our existing models of HLRCC. Herein, using a previously characterized antibody against 2SC, we show that genetic ablation of FH causes high levels of protein succination. We next hypothesized that immunohistochemistry for 2SC would serve as a metabolic biomarker for the in situ detection of FH‐deficient tissues. Robust detection of 2SC was observed in Fh1 (murine FH)‐deficient renal cysts and in a retrospective series of HLRCC tumours (n = 16) with established FH mutations. Importantly, 2SC was undetectable in normal tissues (n = 200) and tumour types not associated with HLRCC (n = 1342). In a prospective evaluation of cases referred for genetic testing for HLRCC, the presence of 2SC‐modified proteins (2SCP) correctly predicted genetic alterations in FH in every case. In two series of unselected type II papillary renal cancer (PRCC), prospectively analysed by 2SCP staining followed by genetic analysis, the biomarker accurately identified previously unsuspected FH mutations (2/33 and 1/36). The investigation of whether metabolites in other tumour types produce protein modification signature(s) that can be assayed using similar strategies will be of interest in future studies of cancer. Copyright © 2011 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.
Degradation and accelerated ageing of poly(ether block amide) thermoplastic elastomers
Authors: Dixon D. , Boyd A.
Published: May 2011

Unstabilized poly(ether block amide) (PEBA, PEBAX) of the type used in angioplasty balloons was aged at temperatures of 18–85°C for periods of up to 313 days. Since PEBA is used in safety critical applications, understanding the effects and underlying mechanisms of ageing and the validity of accelerated ageing protocols is vital. Mechanical testing indicated an increase in modulus during ageing consistent with embrittlement. An activation energy (Ea) of 47.3 kJ mol−1 was calculated over the temperature range 18–45°C and increased deviation from linear Arrhenius behavior observed above 45°C. This value of Ea would result in the commonly applied 10°C rule over estimating shelf life. Fourier Transform Infrared Spectroscopy, Gel Permeation Chromatography, and thermal analysis provided evidence that the observed property changes were largely the result of oxidative damage and crystallinity effects. The data presented provides a rational basis for the use of accelerated testing protocols at temperatures of up to 45°C to generate room temperature shelf life estimates. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers
An experimental and theoretical study of the carbazole to carbazole intramolecular energy transfer in N‐vinylcarbazole/vinyl tert‐butyl‐benzoate copolymers of different molar compositions
Authors: Fernández‐Peña Natali , Carmona Thais , Tarazona M. Pilar , Saiz Enrique , Mendicuti Francisco
Published: May 2011

Fluorescence depolarization and quenching measurements of N‐vinyl carbazole/vinyl tert‐butyl‐benzoate copolymers in dilute solution of several fluid solvents and in a rigid poly(methyl methacrylate) matrix were performed to study the effect of copolymer composition on the intramolecular energy transfer (IET) between carbazole groups (Cz) along the polymer chain. IET efficiency, as the amount of CzCz intramolecular excimer formation, monotonically increases with Cz content up to a number average sequence length of carbazole of ca 12 (Cz molar content ≥ 90%). After this value, IET efficiency remains almost constant. Molecular dynamics simulations on isotactic and syndiotactic copolymer fragments of several monomer compositions were used for obtaining different parameters related to the efficiency for the IET process between Cz units along the polymer chain. Copyright © 2011 Society of Chemical Industry
The peroxide stress response of Bacillus licheniformis
Authors: Schroeter Rebecca , Voigt Birgit , Jürgen Britta , Methling Karen , Pöther Dierk‐Christoph , Schäfer Heinrich , Albrecht Dirk , Mostertz Jörg , Mäder Ulrike , Evers Stefan , Maurer Karl‐Heinz , Lalk Michael , Mascher Thorsten , Hecker Michael , Schweder Thomas
Published: May 2011

The oxidative stress response of Bacillus licheniformis after treatment with hydrogen peroxide was investigated at the transcriptome, proteome and metabolome levels. In this comprehensive study, 84 proteins and 467 transcripts were found to be up or downregulated in response to the stressor. Among the upregulated genes were many that are known to have important functions in the oxidative stress response of other organisms, such as catalase, alkylhydroperoxide reductase or the thioredoxin system. Many of these genes could be grouped into putative regulons by genomic mining. The occurrence of oxidative damage to proteins was analyzed by a 2‐DE‐based approach. In addition, we report the induction of genes with hitherto unknown functions, which may be important for the specific oxidative stress response of B. licheniformis. The genes BLi04114 and BLi04115, that are located adjacent to the catalase gene, were massively induced during peroxide stress. Furthermore, the genes BLi04207 and BLi04208, which encode proteins homologous to glyoxylate cycle enzymes, were also induced by peroxide. Metabolomic analyses support the induction of the glyoxylate cycle during oxidative stress in B. licheniformis.
Synthesis of poly(ethylene glycol)/polypeptide/poly(D,L‐lactide) copolymers and their nanoparticles
Authors: Lee Hyunpyo , Park Jun Beum , Chang Ji Young
Published: May 2011

Core‐shell structured nanoparticles of poly(ethylene glycol) (PEG)/polypeptide/poly(D,L‐lactide) (PLA) copolymers were prepared and their properties were investigated. The copolymers had a poly(L‐serine) or poly(L‐phenylalanine) block as a linker between a hydrophilic PEG and a hydrophobic PLA unit. They formed core‐shell structured nanoparticles, where the polypeptide block resided at the interface between a hydrophilic PEG shell and a hydrophobic PLA core. In the synthesis, poly(ethylene glycol)‐b‐poly(L‐serine) (PEG‐PSER) was prepared by ring opening polymerization of N‐carboxyanhydride of O‐(tert‐butyl)‐L‐serine and subsequent removal of tert‐butyl groups. Poly(ethylene glycol)‐b‐poly(L‐phenylalanine) (PEG‐PPA) was obtained by ring opening polymerization of N‐carboxyanhydride of L‐phenylalanine. Methoxy‐poly(ethylene glycol)‐amine with a MW of 5000 was used as an initiator for both polymerizations. The polymerization of D,L‐lactide by initiation with PEG‐PSER and PEG‐PPA produced a comb‐like copolymer, poly(ethylene glycol)‐b‐[poly(L‐serine)‐g‐poly(D,L‐lactide)] (PEG‐PSER‐PLA) and a linear copolymer, poly(ethylene glycol)‐b‐poly(L‐phenylalanine)‐b‐poly(D,L‐lactide) (PEG‐PPA‐PLA), respectively. The nanoparticles obtained from PEG‐PPA‐PLA showed a negative zeta potential value of −16.6 mV, while those of PEG‐PSER‐PLA exhibited a positive value of about 19.3 mV. In pH 7.0 phosphate buffer solution at 36 °C, the nanoparticles of PEG/polypeptide/PLA copolymers showed much better stability than those of a linear PEG‐PLA copolymer having a comparable molecular weight. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011
Samarium powder as catalyst for SET‐LRP of acrylonitrile in 1,1,1,3,3,3‐hexafluoro‐2‐propanol for control of molecular weight and tacticity
Authors: Chen Hou , Zong Guangxi , Chen Lingfang , Zhang Min , Wang Chunhua , Qu Rongjun
Published: May 2011

Samarium powder was applied as a catalyst for single electron transfer‐living radical polymerization (SET‐LRP) of acrylonitrile (AN) in 1,1,1,3,3,3‐hexafluoro‐2‐propanol (HFIP) with 2‐bromopropionitrile as initiator and N,N,N′,N′‐tetramethylethylenediamine as ligand. First‐order kinetics of polymerization with respect to the monomer concentration, linear increase of the molecular weight with monomer conversion, and the highly syndiotactic polyacrylonitrile (PAN) obtained indicate that the SET‐LRP of AN could simultaneously control molecular weight and tacticity of PAN. An increase in syndiotacticity of PAN obtained in HFIP was observed compared with that obtained by SET‐LRP in N,‐N‐dimethylformamide (DMF). The syndiotacticity markedly increased with the HFIP volume. The syndiotacticity of PAN prepared by SET‐LRP of AN using Sm powder as catalyst in DMF was higher than that prepared with Cu powder as catalyst. The increase in syndiotacticity of PAN with Sm content was more pronounced than the increase in its isotacticity. The block copolymer PAN‐b‐polymethyl methacrylate (52,310 molecular weight and 1.34 polydispersity) was successfully prepared. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011
Characterization of Silicon Oxide Films Deposited from a Permanent‐Magnet Helicon Plasma Source
Authors: Jan Der‐Jun , Tang Chiang‐Yao , Ai Chi‐Fong
Published: May 2011

Silicon oxide films were deposited by an individual PM helicon source using HMDSO as a precursor and N2O as the reactive gas at low temperature. The chemical structure and elemental composition of the films are characterized by Fourier transform infrared spectroscopy and X‐ray photoelectron spectroscopy, and the optical and mechanical properties of the films are evaluated by a thin‐film metrology system using reflectance spectra and a nanoindenter. The experimental results show that the N2O ratio in the plasma has a strong impact on the optical and structural characteristics of the deposited films: with increasing N2O flow ratios, the hardness of the deposited films increases while the deposition rate and carbon content decreases. At the same time, the characteristics of the oxide films gradually shift away from those of polymers towards those of SiO2. The technique presented here may find applications in making barrier films for polymer substrates.

magnified image
Selectivity Control in a Microwave Surface‐Wave Plasma Reactor for Hydrocarbon Conversion
Authors: Mora Manuel , García María Carmen , Jiménez‐Sanchidrián Cesar , Romero‐Salguero Francisco José
Published: May 2011

Drastic changes in the selectivity toward different products have been found in the transformation of n‐hexane in a microwave surface‐wave plasma reactor. Either ethylene or hydrogen can be obtained with a high selectivity by selecting some reaction/plasma parameters such as applied microwave power, hydrocarbon flow rate, or feed position. These results have been related to alternative plasma‐chemical routes revealing the high versatility of surface‐wave sustained discharges for the fine control of the hydrocarbon reactivity and so opening the door to new selective plasma‐chemical processes.

magnified image
A mixed molecular modeling‐robotics approach to investigate lipase large molecular motions
Authors: Barbe Sophie , Cortés Juan , Siméon Thierry , Monsan Pierre , Remaud‐Siméon Magali , André Isabelle
Published: May 2011

Large‐scale conformational rearrangement of a lid subdomain is a key event in the interfacial activation of many lipases. We present herein a study in which the large‐scale “open‐to‐closed” movement of Burkholderia cepacia lipase lid has been simulated at the atomic level using a hybrid computational method. The two‐stage approach combines path‐planning algorithms originating from robotics and molecular mechanics methods. In the first stage, a path‐planning approach is used to compute continuous and geometrically feasible pathways between two protein conformational states. Then, an energy minimization procedure using classical molecular mechanics is applied to intermediate conformations in the path. The main advantage of such a combination of methods is that only geometrically feasible solutions are prompted for energy calculation in explicit solvent, which allows the atomic‐scale description of the transition pathway between two extreme conformations of B. cepacia lipase (BCL; open and closed states) within very short computing times (a few hours on a desktop computer). Of interest, computed pathways enable the description of intermediate conformations along the “open‐to‐closed” conformational transition of BCL lid and the identification of bottlenecks during the lid closing. Furthermore, consideration of the solvent effect when computing the transition energy profiles provides valuable information regarding the feasibility and the spontaneity of the movement under the influence of the solvent environment. This new hybrid computational method turned out to be well‐suited for investigating at an atomistic level large‐scale conformational motion and at a qualitative level, the solvent effect on the energy profiles associated with the global motion. Proteins 2011; © 2011 Wiley‐Liss, Inc.
Low impedance surface coatings via nanopillars and conductive polymers
Authors: Sanetra Nils , Feig Vivian , Wolfrum Bernhard , Offenhäusser Andreas , Mayer Dirk
Published: May 2011

Low impedance electrodes are of significant importance for the development of highly sensitive sensors and bioelectronic devices. The integration of biomolecules into these devices enforces high demands on the interface materials in terms of biocompatibility and electronic properties. Here we present the establishment of the well studied conductive polymer (CP) PEDOT/PSS for ultra thin electrode coatings. The polymer film thickness is adjusted via spin coating and reaches film thicknesses well below 100 nm. Thereby, the polymer layer increases the interface capacity and allows a tuning of the electrode impedance. A further reduction of the impedance is achieved by applying CP coatings on gold nanopillar electrode surfaces.

magnified image

Schematic of polymer coated gold nanopillars electrode in a cyclic voltammetry experiment.
On the past and present of carbon nanostructures
Authors: Dresselhaus Mildred S.
Published: May 2011

A personal review is presented on 50 years of my research experiences in working on research on carbon science and carbon‐based nanostructures. The text is based on a talk given in Warsaw, Poland, on this topic, presented at a meeting of the European Materials Research Society in September 2010.
Light emitting diodes based on sidewall m‐plane epitaxy of etched GaN/sapphire templates
Authors: Nepal N. , Frajtag P. , Zavada J. M. , El‐Masry N. A. , Bedair S. M.
Published: May 2011

Light emitting diodes (LEDs) were grown on the etched m‐plane of c‐plane GaN/sapphire templates by metal organic chemical vapor deposition (MOCVD). The LEDs, with InxGa1‐xN/GaN quantum wells (QWs), were studied and current‐voltage measurements show p‐n diode behavior. TEM image analysis established that the QWs are on the {1$ \bar 1 $01} sidewall semi‐polar plane. Electroluminescence measurements on the fabricated LEDs display an emission peak at 487 nm, with a blue shift of only 4 nm on increasing injected current density from 0.3 to 100 A/cm2. The demonstrated sidewall approach significantly reduces the quantum confined Stark Effect found in QWs grown on c‐plane substrates (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Strain relaxation in InxGa1‐xN/GaN quantum well structures
Authors: Emar Ahmed M. , Berkman E. Acar , Zavada J. , El‐Masry Nadia A. , Bedair S. M.
Published: May 2011

We report on the thickness dependence of strain relaxation in InxGa1‐xN/GaN for single and multiple quantum‐well structures. For InGaN wells thicker than a certain value gradual relaxation occurs and can be presented by two relaxation mechanisms. The first is related to the relaxation of the InGaN well, and the second to the relaxation of the whole multiple quantum well structure. We have also found that the onset of relaxation of multiple quantum wells depends on the number of quantum wells (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The nanorod approach: GaN NanoLEDs for solid state lighting
Authors: Waag Andreas , Wang Xue , Fündling Sönke , Ledig Johannes , Erenburg Milena , Neumann Richard , Al Suleiman Mohamed , Merzsch Stephan , Wei Jiandong , Li Shunfeng , Wehmann Hergo H. , Bergbauer Werner , Straßburg Martin , Trampert Achim , Jahn Uwe , Riechert Henning
Published: May 2011

Vertically aligned GaN nanorods have recently obtained substantial interest as a new approach to solid state lighting. In comparison to conventional planar LEDs, 3D NanoLEDs are expected to offer substantial advantageous: very low defect density, quasi free‐standing, no strain due to mismatch of thermal expansion coefficients, no substrate bending even when grown on large area silicon. Core‐shell strategies are another very interesting aspect. The active LED surface per wafer could be increased by more than one order of magnitude. However, most of these advantages have not yet been proven in real devices, which would include a quantitative comparison of light emission. Related to the 3D character, there are also technological risks. In the following we will discuss the main developments which have paved the way up to this point, including a detailed discussion of possible benefits and risks connected with the NanoLED approach (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
MOVPE grown quaternary AlInGaN layers for polarization matched quantum wells and efficient active regions
Authors: Jetter M. , Wächter C. , Meyer A. , Michler P.
Published: May 2011

Quaternary AlInGaN quantum wells in GaN barriers with varying thicknesses were deposited in a pulsed metal‐organic precursor mode by vapor‐phase epitaxy. X‐ray diffraction and photoluminescence measurements show the good quality of the deposited material.

By adjustment of the quaternary composition we can achieve polarization f eld free conditions at the AlInGaN/GaN interface. By using AlInGaN as barrier material for a ternary InGaN QW we could increase the relative quantum eff ciency to 20% at room temperature. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Effects of cladding on the emission of doped plastic optical fibres
Authors: Bikandi I. , Illarramendi M. A. , Zubia J. , Aldabaldetreku G. , Bazzana L.
Published: May 2011

The effect of the cladding on the emission properties of doped plastic optical fibres has been analyzed by using the side‐illumination technique. For that purpose, the photoluminescence spectra of cladded and uncladed plastic optical fibres, both with the same doped core material, have been compared. In particular, we study the dependence of the emitted intensity on the launching angle and on the propagation distance. We also analyze the angular distribution of the emitted light as a function of the propagation distance through the fibres. Using this information, we have characterized the optical losses in both kinds of optical fibres. The study has been performed in plastic optical fibres doped with a conjugated polymer. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Design and construction of a WDM transceiver with VHGT using hybrid integration technology
Authors: Jeřábek Vítězslav , Hüttel Ivan , Prajzler Václav , Bušek Karel , Arciniega J. A.
Published: May 2011

We report about design and construction of WDM bidirectional transceiver module (TRx) for the passive optical network (PON) of a fiber to the home FTTH topology. The TRx uses a microoptics hybrid integration technology with volume holographic Bragg grating triplex filter (VHGT) and a collimation lenses for wavelength multiplexing/demultiplexing. Our optical WDM transceiver TRx has been constructed using system of a four micromodules in the new circle topology. The optical micromodul with VHGT filter, two optoelectronics receivers micromodules for receiving download information (internet and digital TV signals) and optoelectronic transceiver micromodul for transmitting of a upload information (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Ultraviolet holographic recording in photopolymers
Authors: Aleksejeva Jelena , Teteris Janis
Published: May 2011

Norland Optical Adhesive (NOA) acrylate based photopolymers were studied as a medium for Bragg grating fabrication. NOA photopolymers have absorption maximum in near UV region, but they are transparent in visible light region. Photopolymers were irradiated by He‐Cd laser 325 nm line interference patterns during holographic recording. In light irradiated regions photopolymerization takes place and volume grating can be recorded. Diffraction efficiency in dependence on sample thickness, recording beams polarization state and intensity was investigated on transmission mode. Enlargement of sample thickness allows to achieve better angular selectivity of diffracted beam, therefore thickness of prepared samples were up to 2.4 mm. In this work diffraction efficiency over 80% was achieved. The best angular selectivity of diffracted beam was several minutes. Gratings with high diffraction efficiency and good angular selectivity successfully can be used in telecommunications and data storage devices. Advantages of this grating are long term mechanical stability, low dependence on temperature changes, simple and cheap preparation (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Organic near‐infrared photodiodes containing a wide‐bandgap polymer and an n‐type dopant in the active layer
Authors: Ohtani Naoki , Nakajima Kiichiro , Bando Ken‐ichi
Published: May 2011

In this research, organic photodiodes (NIR‐OPDs) operating in the near‐infrared region were fabricated by wet process. Copper(II) 5,9,14,18,23,27,32,36‐octabutoxy‐2,3‐naphthalocyanine (Cu(II)) was used as a photovoltaic material in the active layer, whose λmax is in the NIR region. To improve the dark current property and external quantum efficiency (EQE), a wide‐bandgap polymer and an n‐type dopant material were mixed in the active layer. Consequently, the maximum EQE was observed to be 9% by adjusting the doping ratio of the two materials. In addition, we evaluated ON/OFF ratio as a function of doping densities of the wide‐bandgap polymer and the n‐type dopant material. As a result, the maximum ON/OFF ratio was observed by adjusting the doping densities. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Well‐width dependence of excitonic properties in organic‐inorganic hybrid quantum well materials
Authors: Miura Takemasa , Takeoka Yuko , Sato Mikio , Kunugita Hideyuki , Ema Kazuhiro
Published: May 2011

Optical properties in a single crystal of the organic‐inorganic hybrid perovskite quantum‐well material (C4H9NH3)2(CH3NH3)Pb2Br7 have been investigated. This material has double‐layer sheets of corner‐sharing [PbBr6]4‐ octahedrons constituting the inorganic well. The estimated longitudinal‐transverse (LT) splitting, exciton exchange energy, and biexciton binding energy are about 60 meV, 17 meV and 26 meV respectively. We can also study well‐width dependence in angstroms by comparing with (C4H9NH3)2PbBr4 which has single‐layer sheets comprising the inorganic well. This is the first time the well‐width dependence of excitonic properties in hybrid organic‐inorganic quantum materials is investigated. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Non‐linear optical properties and structure of wide band gap non‐crystalline semiconductors
Authors: Mitsa Vladimir , Holomb Roman , Veres Miklos , Marton Aniko , Rosola Ivan , Fekeshgazi Ishtvan , Koós Margit
Published: May 2011

The non‐linear two‐photon absorption coefficient (TPA) of ternary Ge‐As‐S glasses of different sections (As2S3‐GeS2, As2S3‐Ge2S3, As‐GeS2, As‐Ge2S3) was measured at 690 nm. The obtained data were interpreted based on the evolution of the glass structure and mean coordination number with the composition. Raman spectroscopy was used to investigate the bonding configuration of the glasses and the structural interpretation of the vibrational bands was performed based on DFT calculations of vibrational spectra of different types of As(Ge)nSm clusters and XPS measurements. It was found that the TPA is decreasing near the magic coordination numbers of 2.4 and 2.67. Relationship between TPA and nanophase separation in ternary glasses is discussed. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Present and Last Glacial Maximum climates as states of maximum entropy production
Authors: Herbert Corentin , Paillard Didier , Kageyama Masa , Dubrulle Bérengère
Published: May 2011

The Earth, like other planets with a relatively thick atmosphere, is not locally in radiative equilibrium and the transport of energy by the geophysical fluids (atmosphere and ocean) plays a fundamental role in determining its climate. Using simple energy‐balance models, it was suggested a few decades ago that the meridional energy fluxes might follow a thermodynamic Maximum Entropy Production (MEP) principle. In the present study, we assess the MEP hypothesis in the framework of a minimal climate model based solely on a robust radiative scheme and the MEP principle, with no extra assumptions. Specifically, we show that by choosing an adequate radiative exchange formulation, the Net Exchange Formulation, a rigorous derivation of all the physical parameters can be performed. The MEP principle is also extended to surface energy fluxes, in addition to meridional energy fluxes. The climate model presented here is extremely fast, needs very little empirical data and does not rely on ad hoc parameterizations. We investigate its range of validity by comparing its performances for pre‐industrial climate and Last Glacial Maximum climate with corresponding simulations with the IPSL coupled atmosphere‐ocean General Circulation Model IPSL_CM4, finding reasonable agreement. Beyond the practical interest of this result for climate modelling, it supports the idea that, to a certain extent, climate can be characterized by macroscale features with no need to compute the underlying microscale dynamics. Copyright © 2011 Royal Meteorological Society
Energetics during proton transfer process in hydrated zündel ion complex
Authors: Meraj Gulafroz , Naganathappa Mahadevappa , Chaudhari Ajay
Published: May 2011

Zündel ion (H5O) is one of the two important structures formed during the proton transfer process in aqueous system. This work reports microsolvation of Zündel ion using density functional theory based B3LYP method with aug‐cc‐pVTZ basis set. Interaction of Zündel ion with four water molecules in its first solvation shell is studied using many‐body analysis approach. A change in many‐body energies and their contribution to the binding energy of a complex during the proton transfer process from donor to acceptor water molecule in Zündel ion‐4H2O complex is obtained. For the hydrated Zündel ion complex, the contribution from total two‐body, three‐body, four‐body, five‐body, and relaxation energy to the binding energy is 84.7, 14, 6.87, 1.6, and 4%, respectively, at B3LYP/aug‐cc‐pVTZ level. Relaxation energy and total five‐body energy have repulsive contribution to the binding energy of a hydrated Zündel ion complex. It is found that the relaxation energy and binding energy of a Zündel‐4H2O complex is the maximum and minimum, respectively, when a shared proton is at equal distance from oxygen atom of donor and acceptor water molecules. A significant change in two‐body, three‐body, and four‐body energies for which Zündel ion is one of the many‐body terms is observed during the proton transfer process. A change in total two‐body, total three‐body, total four‐body, and relaxation energy is about 2.6, 1.8, 0.4, and 1.1%, respectively, during the proton transfer process. A change in two‐body, three‐body, and four‐body interaction energies between water molecules is very small during the proton transfer process. © 2011 Wiley Periodicals, Inc. Int J Quantum Chem, 2012
Modification of citrulline residues with 2,3‐butanedione facilitates their detection by liquid chromatography/mass spectrometry
Authors: De Ceuleneer Marlies , De Wit Vanessa , Van Steendam Katleen , Van Nieuwerburgh Filip , Tilleman Kelly , Deforce Dieter
Published: May 2011

Citrullination is a post‐translational modification (PTM) that results from the deimination of the amino acid arginine into citrulline by Peptidyl Arginine Deiminase enzymes and occurs in a wide range of proteins in health and disease. This modification causes a 1 Da mass shift, which can be used to identify citrullination sites in proteins by the use of mass spectrometry. However, other PTMs, such as deamidation from asparagine to aspartic acid or from glutamine to glutamic acid, can also cause a 1 Da mass shift, making correct interpretation of the data more difficult. We developed a chemical tagging strategy which, combined with an open source search application, allowed us to selectively pinpoint citrullinated peptides in a complex mixture after liquid chromatography/mass spectrometry (LC/MS) analysis. After incubation of a peptide mixture with 2,3 butanedione, citrulline residues were covalently modified which resulted in a 50 Da shift in singly charged mass. By comparison of the peptide mass fingerprint from a modified and an unmodified version of the same sample, our in‐house search application was able to identify the citrullinated peptides in the mixture. This strategy was optimized on synthetic peptides and validated on a digest of in vitro citrullinated fibrinogen, where different proteolytic enzymes were used to augment the protein coverage. This new method results in easy detection of citrullinated residues, without the need for complex mass spectrometry equipment. Copyright © 2011 John Wiley & Sons, Ltd.
Evaluation of allergens in propolis by ultra‐performance liquid chromatography/tandem mass spectrometry
Authors: Gardana Claudio , Simonetti Paolo
Published: May 2011

The purified extract of propolis is used as a traditional remedy for the treatment of several diseases. Its beneficial activities are mainly attributed to the polyphenolic fraction. Nevertheless, propolis can cause allergic dermatitis and the sensitization rate in humans is increasing significantly mainly in younger subjects. The aim of this study was to develop and validate a selective and sensitive ultra‐performance liquid chromatography tandem mass spectrometry analysis (UPLC/MS/MS) for the evaluation of the amount of caffeic acid and its esters with allergenic action in raw propolis samples and commercial formulations. The separation was carried out on a 1.7 μm C18 BEH Shield column and the detection performed by means of electrospray ionization in negative ion mode with multiple reaction monitoring. The confirmation of formulae of the precursor and product ions was accomplished by injection into a high‐resolution system (FTICR‐MS) using accurate mass measurements. The error was below 1.4 ppm.The range of the standard curves was 0.5–10 μg/mL and dihydrocaffeic acid was used as internal standard (IS). The lower limit of detection (LLOD) for 3‐methyl‐2‐butenyl‐ (3M2B), 3‐methyl‐3‐butenyl‐ (3M3B), 2‐methyl‐2‐butenyl‐ (2M2B), benzyl‐ (CABE), phenylethylcaffeic acid (CAPE) and for caffeic acid (CA) and the IS was 0.1 and 0.3 μg/mL, respectively. The recoveries were in the range 96–104% and the intra‐ and inter‐day precisions were within 6.2%. In the European (n = 8) and Asiatic (n = 3) propolis the most abundant allergens were CABE>3M2B>CAPE>3M3B>CA>2M2B. These compounds were not found in the red (n = 1) and green (n = 1) Brazilian propolis. Hydroalcoholic extracts (n = 6) and tablets (n = 6) were analyzed by the proposed UPLC/MS/MS method. The results showed that in the commercial products CABE, 3M2B, CAPE and 3M3B were also the most abundant. Copyright © 2011 John Wiley & Sons, Ltd.
Linear temporal logic vehicle routing with applications to multi‐UAV mission planning
Authors: Karaman S. , Frazzoli E.
Published: May 2011

Missions with high combinatorial complexity involving several logical and temporal constraints often arise in cooperative control of multiple Uninhabited Aerial Vehicles. In this paper, we propose a new class of problems that generalizes the standard Vehicle Routing Problem (VRP) by addressing complex tasks and constraints on the mission, called the ‘mission specifications’, expressed in a high‐level specification language. In the generalized problem setup, these mission specifications are naturally specified using the Linear Temporal Logic language LTL−X. Using a novel systematic procedure, the LTL−Xspecification is converted to a set of constraints suitable to a Mixed‐Integer Linear Programming (MILP) formulation, which in turn can be incorporated into two widely‐used MILP formulations of the standard VRP. Solving the resulting MILP provides an optimal plan that satisfies the given mission specification. The paper also presents two mission planning applications. Copyright © 2011 John Wiley & Sons, Ltd.
WATER QUALITY ASSESSMENT AND APPORTIONMENT OF POLLUTION SOURCES OF TIGRIS RIVER (TURKEY) USING MULTIVARIATE STATISTICAL TECHNIQUES—A CASE STUDY
Authors: Varol M. , Gökot B. , Bekleyen A. , Şen B.
Published: May 2011

The Tigris is one of the most important transboundary rivers in western Asia and originates in the Toros mountains of the Eastern Anatolia region of Turkey. Multivariate statistical techniques, such as cluster analysis (CA), principal component analysis (PCA) and factor analysis (FA), were applied for the evaluation of temporal/spatial variations and the interpretation of a water quality data set for the Tigris River, which was obtained during 1 year of monitoring. This study presents the usefulness of multivariate statistical techniques for the evaluation and interpretation of complex water quality data sets and apportionment of pollution sources/factors to obtain better information about water quality and the design of a monitoring network for the effective management of water resources. Hierarchical CA grouped 12 months into two periods (the first and second periods) and classified seven monitoring sites into three groups, that is, less polluted sites, medium polluted sites and highly polluted sites, based on similarities in the water quality characteristics. PCA/FA identified five factors in the data structure, which explained 77.5% of the total variance of the data set. This allowed us to group the selected parameters according to common features and to evaluate the influence of each group on the overall variation in water quality. Varifactors obtained from the factor analysis indicated that the parameters responsible for water quality variation were mainly related to soluble salts (natural), organic pollution and nutrients (anthropogenic). Copyright © 2011 John Wiley & Sons, Ltd.
“Experiments” and the inquiry emphasis conflation in science teacher education
Authors: Gyllenpalm Jakob , Wickman Per‐Olof
Published: May 2011

This article examines the use and role of the term “experiment” in science teacher education as described by teacher students. Data were collected through focus group interviews conducted at seven occasions with 32 students from six well‐known Swedish universities. The theoretical framework is a sociocultural and pragmatist perspective on language and learning with the analysis based on the notion of pivot terms, introduced in an earlier article, to operationalize language use as habit and mediated action. The term “experiment” was found to be conflated with “laboratory task” and referred to as primarily a pedagogical activity in contrast to a research methodology, in line with the previously described inquiry emphasis conflation. The notion of “controlled experiment” was unfamiliar to most students and had not been explicitly discussed in terms of research methodology during their teacher education. The pedagogical meaning given to the term “experiment” is discussed in contrast to its use and function in scientific research. The possible problems of this conflation of terms are discussed in relation to the educational goal of teaching students about the nature of scientific inquiry. Recommendations for teacher education are discussed, and a heuristic model to use pivot terms to facilitate explicit reflection on unexamined customs of science education is introduced. © 2011 Wiley Periodicals, Inc.Sci Ed95:908–926, 2011
Effects of exogenous methionine on arsenic burden and NO metabolism in brain of mice exposed to arsenite through drinking water
Authors: Zhao Fenghong , Wang Yan , Jin Yaping , Zhong Yuan , Yu Xiaoyun , Li Gexin , Lv Xiuqiang , Sun Guifan
Published: May 2011

The aim of this study was to explore the effects of exogenous methionine (Met) on arsenic burden and metabolism of nitric oxide (NO) in the brain of mice exposed to arsenite via drinking water. Mice were exposed to sodium arsenite through drinking water contaminated with 50 mg/L arsenic for four consecutive weeks, and treated intraperitoneally with saline solution, 100 mg/kg body weight (b.w), 200 mg/kg b.w or 400 mg/kg b.w of Met, respectively at the fourth week. Levels of inorganic arsenic (iAs), monomethylarsenic acid (MMAs), and dimethylarsenic acid (DMAs) in the liver, blood and brain were determined by method of hydride generation coupled with atomic absorption spectrophotometry. Nitric oxide synthase (NOS) activities and NO levels in the brain were determined by colorimetric method. Compared with mice exposed to arsenite alone, administration of Met increased significantly the primary methylation ratio in the liver, which resulted in decrease of percent iAs and increase of percent DMAs in the liver, and decrease of iAs, MMAs and total arsenic levels (TAs) in the blood and DMAs and TAs in the brain. NOS activities and NO levels in the brain of mice exposed to arsenite alone were significantly lower than those in control, however administration of Met could increase significantly NO levels. Findings from this study suggested that exogenous Met could benefit the primary arsenic methylation in the liver, which might increase the production of methylated arsenicals and facilitate arsenic excretion. As a consequence, arsenic burden in both blood and brain was reduced, and toxic effects on NO metabolism in the brain were ameliorated. © 2011 Wiley Periodicals, Inc. Environ Toxicol 2012.