bluuebunny/crossref_metadata_2025_split huggingface dataset:
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

AbstractFluorescence 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

AbstractThe 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

AbstractCore‐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

AbstractSamarium 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

AbstractSilicon 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

AbstractDrastic 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

AbstractLarge‐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

AbstractLow 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.
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

AbstractLight 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

AbstractWe 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

AbstractVertically 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

AbstractQuaternary 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

AbstractThe 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

AbstractWe 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

AbstractNorland 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

AbstractIn 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

AbstractOptical 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

AbstractThe 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

AbstractThe 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