bluuebunny/crossref_metadata_2025_split huggingface dataset:
Frequency‐dependent resistivity and magnetoresistivity of iodine doped conducting polyaniline
Authors: Chakraborty G. , Sarkar A. , Ghosh P. , Meikap A.K. , Chowdhury P. 
Published: March 2009

AbstractThe electrical transport properties of hydroiodic acid doped polyaniline in the temperature range 77 ≤ T ≤ 300 K were studied. The magnetic field strength was varied to a maximum of 1T in the frequency range of 20 Hz–1 MHz. The ac conductivity followed the universal dielectric response σ′(f) ∞ fs. The trend in the variation of ‘s’, the temperature dependence of the frequency exponent, indicated that correlated barrier hopping is the dominating charge transport mechanism. The ac conductivity also shows a positive variation with magnetic field, which can be interpreted by Maxwell‐Wagner capacitor model. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers
Ex‐ante environmental and economic evaluation of polymer photovoltaics
Authors: Roes A. L. , Alsema E. A. , Blok K. , Patel M. K. 
Published: March 2009

AbstractThe use of polymer materials for photovoltaic applications is expected to have several advantages over current crystalline silicon technology. In this paper, we perform an environmental and economic assessment of polymer‐based thin film modules with a glass substrate and modules with a flexible substrate and we compare our results with literature data for multicrystalline (mc‐) silicon photovoltaics and other types of PV. The functional unit of this study is ‘25 years of electricity production by PV systems with a power of 1 watt‐peak (Wp)’. Because the lifetime of polymer photovoltaics is at present much lower than of mc‐silicon photovoltaics, we first compared the PV cells per watt‐peak and next determined the minimum required lifetime of polymer PV to arrive at the same environmental impacts as mc‐silicon PV. We found that per watt‐peak of output power, the environmental impacts compared to mc‐silicon are 20–60% lower for polymer PV systems with glass substrate and 80–95% lower for polymer PV with PET as substrate (flexible modules). Also in comparison with thin film CuInSe and thin film silicon, the impacts of polymer modules, per watt‐peak, appeared to be lower. The costs per watt‐peak of polymer PV modules with glass substrate are approximately 20% higher compared to mc‐silicon photovoltaics. However, taking into account uncertainties, this might be an overestimation. For flexible modules, no cost data were available. If the efficiency and lifetime of polymer PV modules increases, both glass‐based and flexible polymer PV could become an environment friendly and cheap alternative to mc‐silicon PV. Copyright © 2009 John Wiley & Sons, Ltd.
Ring‐banded spherulites in PCL and PCL/MWCNT solution‐casting films and effect of compressed CO2 on them
Authors: Hua Chengwu , Chen Zhimin , Xu Qun , He Linghao 
Published: March 2009

AbstractThe ring‐banded spherulites in poly(ε‐caprolactone) (PCL) solution‐casting films in the absence and presence of multi‐walled carbon nanotube (MWCNT) are studied by atomic force microscopy (AFM), polarized optical microscopy (POM), transmission electron microscopy (TEM), and scanning electronic microscopy (SEM). The results indicate that birefringent ring‐banded spherulites of PCL can grow from solution below 50 °C, and the temperature is much lower than that from pure PCL melt. We also find out that the presence of MWCNT apparently widen the temperature range of forming ring‐banded structure. Furthermore, the mechanism for the ring‐banded structure forming is studied, and it is attributed to the twisting of lamellae crystals, and the driving force is suggested including the deflexion of lamellae bundles. In addition, effect of compressed CO2 on the morphology of PCL and PCL/MWCNT solution‐casting film is also investigated, and the results reveal that both PCL and PCL/MWCNT films undergo recrystallization with the treatment of compressed CO2 and accordingly, the related properties can be adjusted. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 784–792, 2009
The solidification behavior of a PBT/PET blend over a wide range of cooling rate
Authors: Stocco Antonio , La Carrubba Vincenzo , Piccarolo Stefano , Brucato Valerio 
Published: March 2009

AbstractIn recent years, much attention has been paid to the development of high‐performance polyester blends, among which blends of polybutylene terephthalate/polyethylene terephthalate (PBT/PET) are expected to exhibit remarkable properties as far as their crystallization behavior is concerned. Through trial and error, appropriate commercial compositions have been chosen which could not be otherwise explained by a suitable interpretation of the mechanisms determining their solidification behavior. The solidification behavior of a 60/40 w/w PBT/PET blend was studied in a wide range of cooling conditions, according to a continuous cooling transformation (CCT) procedure developed previously, aiming at emulating the typical conditions encountered in polymer processing. Several samples characterized by a homogeneous structure were solidified from the melt at various cooling rates and the resulting structure and properties were subsequently evaluated by analyzing the density, microhardness (MH), and wide angle x‐ray diffraction (WAXD). The resulting solidification behavior was then compared to that exhibited by the individual constituents of the blend (i.e., PBT and PET). The blend displayed a unique solidification behavior, conversely to those of the pure components which showed characteristics not recognized in the blend except at certain restricted cooling rates ranges. The cooling rate dependence observed in the blend does not bring similarities to the crystallization behavior of individual constituents since the fall down of density with cooling rate should be related to the rate controlling demixing stage of the two moieties just before crystallization occurs. The kinetics observed is thus a measure of the kinetics of demixing. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 799–810, 2009
Antibody response to Pseudomonas aeruginosa in children with cystic fibrosis
Authors: Milagres Lucimar G. , Castro Tatiana L.A. , Garcia Daniely , Cruz Aline C. , Higa Laurinda , Folescu Tânia , Marques Elizabeth A. 
Published: March 2009

AbstractCystic fibrosis (CF) is the most frequent life threatening autosomal recessive disease in white subjects. The primary cause of morbidity and mortality in children with CF is chronic pulmonary infection, mainly caused by Pseudomonas aeruginosa. The purpose of this study was to assess the value of the measurement of antibodies to P. aeruginosa in diagnosing lung infection by the bacteria in CF patients. We assessed P. aeruginosa antibody titers in CF patients from Rio de Janeiro, Brazil, using cell lysate antigens as well as recombinant PcrV, a Type III Secretion System protein. Sputum (more than 70% of the specimens) or oropharyngeal swabs were obtained whenever patients were regularly followed for their pulmonary disease. Blood samples were obtained with an average interval of 6 months for a period of 2 years. The ELISA cut‐offs were assigned as the positive 95% confidence interval of the mean antibody levels from non‐fibrocystic controls. Our data showed that most CF patients (81%) of whom were not chronically infected by P. aeruginosa (Groups I and II), had their first serology positive for rPcrV. Cell‐lysate ELISA was able to detect P. aeruginosa antibodies before positive culture in the first serum sample of 44% of the patients from Groups I and II. When serum reactivity to rPcrV and cell lysate were combined, 94% of CF patients from Groups I and II (n = 16) had the first serology positive for P. aeruginosa over a mean time of 20 months before the first isolation of P. aeruginosa. In conclusion, longitudinal P. aeruginosa serology should become part of respiratory care follow‐up, in conjunction with other lung parameter functions. Pediatr Pulmonol. 2009; 44:392–401. © 2009 Wiley‐Liss, Inc.
Relationship between antimicrobial proteins and airway inflammation and infection in cystic fibrosis
Authors: Sagel Scott D. , Sontag Marci K. , Accurso Frank J. 
Published: March 2009

AbstractAntimicrobial proteins are important in lung defense and are potential therapeutic agents in chronic airways infection such as seen in cystic fibrosis (CF). In preparation for future clinical studies, we sought (1) to determine levels of three antimicrobial proteins [lactoferrin, lysozyme, and secretory leukoprotease inhibitor (SLPI)] in the CF airway and (2) to examine the relationships between these antimicrobial proteins and airway inflammation and infection. We examined bronchoalveolar lavage fluid (BALF) from 45 individuals with CF and 23 disease control individuals. Airway inflammation was measured through BALF neutrophil counts and neutrophil elastase activity. Infection was assessed through quantitative counts of CF‐related bacterial pathogens. BALF lysozyme activity and lactoferrin levels were elevated in individuals with CF compared to controls whereas SLPI levels were not different between the groups. Among the CF subjects, lysozyme activity and lactoferrin increased with age while SLPI decreased with age. Lysozyme activity and lactoferrin concentrations correlated positively with neutrophil counts but not with bacterial colony counts. SLPI levels were inversely related to both neutrophil counts and bacterial colony counts. This study provides information concerning the levels of antimicrobial proteins present in the CF airway that are relevant to future clinical trials of these compounds and demonstrates clear relationships between antimicrobial protein‐specific levels and airway inflammation and infection. Pediatr Pulmonol. 2009; 44:402–409. © 2009 Wiley‐Liss, Inc.
Relationship Between the Electrostatic Sensitivity of Nitramines and Their Molecular Structure
Authors: Hossein Keshavarz Mohammad , Moghadas Mohammad Hassan , Kavosh Tehrani Masoud 
Published: March 2009

AbstractIn this paper, a new approach is introduced to predict the electrostatic sensitivity of nitramines on the basis of their molecular structure. The ratio of carbon to oxygen and the existence of two specific structural parameters can be used for the prediction of the electrostatic sensitivity of nitramines. The results are also compared with quantum mechanical computations from [9] so that the new method gives better predictions with respect to the measured data. Electrostatic sensitivities calculated by the new method for two new nitramines CL‐20 [2,4,6,8,10,12‐hexanitro‐2,4,6,8,10,12‐hexaazaisowurtzitane] and TNAZ [1,3,3‐trinitroazatidine] are also close to the experimental data.
Epitaxial LSMO films grown on GaAs substrates with MgO buffer layer
Authors: Španková Marianna , Chromik Štefan , Vávra Ivo , Štrbík Vladimír , Liday Jozef , Vogrinčič Peter , Espinós Juan Pedro , Lobotka Peter 
Published: March 2009

AbstractLa0.67Sr0.33MnO3 (LSMO) manganite thin films were deposited using a magnetron dc sputtering on single crystalline GaAs(001) substrates covered by MgO buffer layers with the goal to fabricate, using MEMS technology, a microbolometer operating at room temperature. The crystalline perfection of the thin film structures are characterized by X‐ray diffraction technique, rocking curve measurements, and transmission electron microscopy (TEM). TEM analyses give evidence of the epitaxial growth of the annealed LSMO. Auger Electron Spectroscopy as well as X‐ray Photoemission Spectroscopy are used to investigate compositional properties of the films. The analyses show a stoichiometric LSMO film without any contamination except of the surface where we register some traces of As, C and Mg. The temperature dependence of resistance, measured by a standard four‐probe technique, exhibits a peak at a temperature of 280 K. The maximum temperature coefficient of resistance reaches a value of ∼2.3% K–1 at T = 249 K. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Controlled enlargement of pores by annealing of porous silicon
Authors: Salonen J. , Mäkilä E. , Riikonen J. , Heikkilä T. , Lehto V.‐P. 
Published: March 2009

AbstractIn the present work, a possibility to use thermal annealing of porous silicon to enlarge the pore sizes has been studied. The size of the pores can be increased by controlling the annealing temperature and time. The pore enlargements from 10 nm even up to 100 nm can be obtained without destroying the pore structure. In all studied cases, annealing was found to decrease the surface areas and pore volumes of porous silicon, but the effects of annealing as a function of temperature were found to be strongly dependent on the initial porosity of samples. The crystallinity of the annealed samples was studied with XRD and the obtained results were used to explain differences observed in the pore sizes after the HF treatment of annealed samples. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Photoexcited silicon nanocrystals: mediators for the excitation of organic molecules
Authors: Goller Bernhard , Polisski Sergej , Kovalev Dmitry 
Published: March 2009

AbstractWe report on spin‐flip activation of organic molecules from the ground state to one of the excited states having different electronic spin configurations. Based on photoexcitations in silicon (Si) nanocrystals, stored electronic energy can be transferred to other substances. The huge hydrogen passivated surface being accessible for acceptor molecules, the tunable confinement energy of excitons and their very long radiative lifetime allow Si nanocrystals to act efficiently as photosensitizers. We demonstrate that the energy transfer is governed by electron exchange mechanism. Therefore a good overlap of the electron wave functions, of donor and acceptor, is crucial for the efficiency of this type of interaction. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Ternary magnetic semiconductors: recent developments in physics and technology
Authors: Tsurkan V. , von Nidda H.‐A. Krug , Krimmel A. , Lunkenheimer P. , Hemberger J. , Rudolf T. , Loidl A. 
Published: March 2009

AbstractRecent results in physics and technology of ternary magnetic oxide and chalcogenide spinels AB2X4 (A = Fe, Mn, Co, Cd, Zn, Hg; B = Cr, Co, Sc, Al; X = O, S, Se) are reviewed. Using magnetic susceptibility, specific heat, thermal expansion, electron‐spin resonance, neutron diffraction, broad‐band dielectric spectroscopy, and infrared optical spectroscopy, the spin, charge, orbital, and lattice correlations in these compounds were investigated. The novel magnetic ground states, e.g., spin liquid, spin–orbital liquid, and orbital glass, and in triguing effects, like colossal magnetocapacitive coupling, negative thermal expansion, and spin‐driven Jahn–Teller structural transformations were revealed. In considering the origin of these phenomena, the concept of geometrical and bond frustration is explored. It relates the interplay of charge, spin, and orbital degrees of freedom with the inherent topological frustration and competing exchange interactions between the magnetic ions. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Spatially resolved characterization of chemical species and crystal structures in CuInS2 and CuGax Sey thin films using Raman microscopy
Authors: Schmid Thomas , Camus Christian , Lehmann Sebastian , Abou‐Ras Daniel , Fischer Christian‐Herbert , Lux‐Steiner Martha Christina , Zenobi Renato 
Published: March 2009

AbstractThis study demonstrates the potential of Raman microscopy in the analysis of thin film cross‐sections. Raman maps of the photovoltaic material CuInS2 (CIS), which was prepared by the spray ion layer gas reaction method, revealed the spatial distribution of two different CIS modifications – chalcopyrite‐type and CuAu I‐type CIS – as well as contaminants and segregates with a lateral resolution of approx. 400 nm. Additionally, the chemical heterogeneity of a CuGaSe2/CuGa3Se5 bi‐layer stack was clearly resolved. Raman microscopy provides a convenient way to simultaneously probe the chemical and structural properties of a sample. Based on Raman spectra, chemical species and even different crystal structures of inorganic compounds can be identified. Knowledge of the distribution of different phases and contaminants in thin films is crucial for further improvements of the coating process. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Raman scattering and structural analysis of electrodeposited CuInSe2 and S‐rich quaternary CuIn(S,Se)2 semiconductors for solar cells
Authors: Izquierdo‐Roca Víctor , Saucedo Edgardo , Ruiz Carmen M. , Fontané Xavier , Calvo‐Barrio Lorenzo , Álvarez‐Garcia Jacobo , Grand Pierre‐Philippe , Jaime‐Ferrer Jesus Salvador , Pérez‐Rodríguez Alejandro , Morante Joan Ramón , Bermudez Verónica 
Published: March 2009

AbstractThis work reports the Raman scattering characterisation of CuInSe2 precursors grown by single step electrodeposition and the corresponding layers recrystallised under sulphurising conditions for solar cell devices. The analysis of the spectra measured on the as‐grown precursors has allowed identifying the main secondary phases in these layers with elemental Se, Cu–Se phases and chalcopyrite Cu‐poor ordered vacancy domains. To deepen in the identification of the Cu–Se phases, these measurements have been correlated with the analysis of binary Cu–Se layers. The experimental data indicate that formation of both Se and Cu–Se phases is likely controlled by the Se content in the layers. For values of stoichiometry below 1.15, excess Cu in the layers is accommodated in a phase with very low Raman efficiency (as Cu2Se). Increasing the content of Se leads to an increase in the spectral contribution from both Se and Cu2–x Se, being the formation of these phases likely favoured under high excess Se conditions. The characterisation of the corresponding recrystallised layers has allowed analysing the impact of the presence of the secondary phases in the as‐grown absorbers on the performance of the final solar cells. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Room temperature characterisation of InGaAlAs quantum well laser structures using electro‐modulated reflectance and surface photovoltage spectroscopy
Authors: Fox Natasha E. , Sharma Tarun K. , Sweeney Stephen J. , Hosea T. J. C. 
Published: March 2009

AbstractIn this study, two tri‐metal quaternary InGaAlAs quantum well (QW) laser structures grown on InP are compared to a conventional InGaAsP QW structure, also grown on InP, all designed to lase at 1.55 μm. Several spectroscopic methods are used to study the samples including surface photo‐voltage (SPV) and electro‐modulated reflectance (ER). In the tri‐metal samples the ground‐ and two excited‐state QW transitions are detectable in both types of spectroscopy. The SPV and ER give results in agreement to within a few meV of each other. By comparing the position of the measured QW transitions with those predicted theoretically, the conduction band offsets of the tri‐metal samples can be determined and compared to that in the InGaAsP sample. It is found that the tri‐metal samples have a much larger conduction band offset of ∼66% compared to the ∼40% in the InGaAsP sample. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
GaN‐based nanocolumn LEDs: Impact of strain engineering on the electro‐optical performance
Authors: Veprek Ratko G. , Steiger Sebastian , Witzigmann Bernd 
Published: March 2009

AbstractA computation of the electronic properties of GaN nanocolumn LEDs with optically active InGaN quantum disks is presented. Using the simulation framework AQUA/tdkp, the relaxation of intrinsic strains in the selected 3D structure and its effects on the built‐in piezoelectric potential and strain dependent bandedge shifts are computed.The results show a strong relaxation of the compressive strains in the InGaN quantum disk compared to usual broad area grown structures suggesting that lower wavelength emission can be achieved at considerable lower indium contents (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Asymmetric external field effects on photoluminescence efficiency in a blue (In,Ga)N quantum‐well diode with an additional n ‐type electron reservoir layer
Authors: Fujiwara Kenzo , Katou Hirofumi , Inoue Takao , Sheu Jin‐Kong 
Published: March 2009

AbstractExternal field effects on photoluminescence (PL) spectra of a blue In0.3Ga0.7N multiple‐quantum‐well (MQW) diode with an additional n+‐doped In0.18Ga0.82N electron reservoir layer (ERL) have been investigated at 20 K as a function of bias voltage under direct excitation conditions, where only the MQW and ERL regions are photoexcited. When the reverse bias is increased, the PL emission of MQW is strongly quenched, accompanying a blue‐shift due to compensation of the internal piezo‐fields, while the ERL emission is stable. However, the PL intensity of ERL is significantly decreased with increasing the forward field, showing asymmetric behaviors on the PL efficiency with respect to the field direction. These results indicate that field‐induced escape processes of photogenerated electrons and holes from the excited regions play an important role for determination of the PL efficiency. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Effect of temperature on cryogenic characteristics of AlGaN/GaN MIS‐HEMTs
Authors: Endoh Akira , Watanabe Issei , Yamashita Yoshimi , Mimura Takashi , Matsui Toshiaki 
Published: March 2009

AbstractWe measured the DC and RF characteristics at 300, 220, 150, 77, and 16 K of AlGaN/GaN metal‐insulator‐semiconductor (MIS) high electron mobility transistors (HEMTs) with SiN/SiO2/SiN triple‐layer insulators. The values of the cutoff frequency fT and the maximum transconductance gm_max increased with a decrease in temperature at relatively high temperatures, i.e. between 150 and 300 K. At temperatures below 100 K, the values of fT and gm_max increased slightly. We also carried out Monte Carlo simulations of electron transport in bulk GaN at various temperatures and electric fields. The steady‐state drift velocity of electrons showed a trend similar to those of the values of fT and gm_max. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Anisotropic polarization of non‐polar GaN quantum dot emission
Authors: Mata R. , Garro N. , Cros A. , Budagosky J. A. , García‐Cristóbal A. , Vinattieri A. , Gurioli M. , Founta S. , Bellet‐Amalric E. , Daudin B. 
Published: March 2009

AbstractWe report on experimental and theoretical studies of the polarization selection rules of the emission of non‐polar GaN/AlN self‐assembled quantum dots. Time‐integrated and time‐resolved photoluminescence measurements have been performed to determine the degree of polarization. It is found that the emission of some samples can be predominantly polarized parallel to the wurtzite c axis, in striking difference with the previously reported results for bulk GaN and its heterostructures, in which the emission was preferentially polarized perpendicular to the c axis. Theoretical calculations based on an 8‐band k·p model are used to analyze the relative importance of strain, confinement and quantum dot shape on the polarization selection rules. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)