bluuebunny/crossref_metadata_2025_split huggingface dataset:
Longitudinal MRI studies in the isoflurane‐anesthetized rat: long‐term effects of a short hypoxic episode on regulation of cerebral blood flow as assessed by pulsed arterial spin labelling
Authors: Wegener Susanne , Wong Eric C. 
Published: February 2008

AbstractMRI is a powerful tool for measuring cerebral blood flow (CBF) longitudinally. However, most animal studies require anesthesia, potentially interfering with normal physiology. Isoflurane anesthesia was used here to study CBF regulation during repetitive scanning in rats. MR perfusion images were acquired using FAIR (flow‐sensitive alternating inversion recovery) arterial spin labeling, and absolute CBF was calculated. CBF changes in response to a hypoxic (12% O2) and hypercapnic (5% CO2) gas stimulus were monitored. Hypercapnia led to a robust increase in CBF compared with baseline (195.5 ± 21.5 vs 123.6 ± 17.9 ml/100 g/min), and hypoxia caused a smaller non‐significant increase in mean CBF values (145.4 ± 13.4 ml/100 g/min). Strikingly, when measurements were repeated 5 days later, CBF was dramatically reduced in hypoxia (93.2 ± 8.1 ml/100 g/min) compared with the first imaging session. Without application of the hypoxic and hypercapnic gases during the first MRI, baseline CBF and CBF changes in response to hypoxia at the second MRI were similar to naive rats. Blood gas analyses revealed a slight reduction in arterial oxygenation during the second period of anesthesia compared with the first. These findings indicate that, in isoflurane‐anesthetized rats, even a short hypoxic episode can have long‐lasting effects on cerebrovascular regulation. Copyright © 2008 John Wiley & Sons, Ltd.
19·9%‐efficient ZnO/CdS/CuInGaSe2 solar cell with 81·2% fill factor
Authors: Repins Ingrid , Contreras Miguel A. , Egaas Brian , DeHart Clay , Scharf John , Perkins Craig L. , To Bobby , Noufi Rommel 
Published: February 2008

AbstractWe report a new record total‐area efficiency of 19·9% for CuInGaSe2‐based thin‐film solar cells. Improved performance is due to higher fill factor. The device was made by three‐stage co‐evaporation with a modified surface termination. Growth conditions, device analysis, and basic film characterization are presented. Published in 2008 by John Wiley & Sons, Ltd.
Synthesis and characterization of epoxy‐based semi‐interpenetrating polymer networks sulfonated polyimides proton‐exchange membranes for direct methanol fuel cell applications
Authors: Lee Chi‐Hung , Wang Yen‐Zen 
Published: February 2008

AbstractNovel epoxy‐based semi‐interpenetrating polymer networks (semi‐IPNs) of aromatic polyimide, derived from 2,2‐benzidinedisulfonic acid (BDSA), were prepared through a thermal imidization reaction. Dynamic scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FTIR) were utilized to verify the synchronization of the imidization of sulfonated poly(amic acid) (SPAA) and the crosslinking reactions of epoxy. The semi‐IPNs of epoxy/sulfonated polyimides (SPI‐EPX) exhibit excellent film‐forming characteristics and mechanical integrity at room temperature. Conductivities at 100 °C of 0.0243 S cm−1 (SPI‐EP30) and 0.0141 S cm−1 (SPI‐EP50) were obtained, which are similar to that of the Nafion 117 (0.0287 S cm−1). The increase in the conductivity of SPI‐EP(30,40) with temperature is more rapid than that of Nafion 117. The SPI‐EPX exhibited lower methanol permeability than did Nafion117. The hydrolytic stability of the SPI‐EPX was followed by FTIR spectroscopy at regular intervals. SPI‐EPX prepared using epoxy‐based semi‐IPNs of sulfonated polyimide, SPI‐EP(40,50), exhibited higher hydrolytic stability than the phthalic polyimides (five‐membered ring polyimides).The microstructure was analyzed using atomic force microscopy (AFM) in the tapping mode, which demonstrated that SPI‐EP50 exhibited a nanophase that was separated into an essentially reticulated and venous hydrophobic and hydrophilic domains. Transmission electron microscopy (TEM) confirmed widespread and well‐connected hydrophilic domains, proving the higher hydrolytic stability and strong proton‐transporting properties of the SPI‐EPX membrane. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 2262–2276, 2008
Synthesis of methacrylate derivatives oligomers by dithiobenzoate‐RAFT‐mediated polymerization
Authors: Hosseini Nejad Elham , Castignolles Patrice , Gilbert Robert G. , Guillaneuf Yohann 
Published: February 2008

AbstractReversible addition fragmentation chain transfer (RAFT) was used to synthesize methacrylic acid oligomers and oligo(methacrylic acid)‐b‐poly(methyl methacrylate) (PMAA‐b‐PMMA) with targeted degree of polymerization ≈ 10. Characterization is by size‐exclusion chromatography (SEC) and electrospray mass‐spectrometry. SEC data are presented as hydrodynamic volume distributions (HVDs), the only proper means to present comparative and meaningful SEC data when there is no unique relationship between size and molecular weight. The RAFT agent, (4‐cyanopentanoic acid)‐4‐dithiobenzoate (CPADB), produced dithiobenzoic acid as a side product during the polymerization of methacrylate derivatives. Precipitation in diethyl ether proved to be an easy way to remove this impurity from the PMAA‐RAFT oligomers. Both unpurified and purified macro‐RAFT agent were used to prepare amphiphilic PMAA‐b‐PMMA copolymers. Diblock copolymer prepared from the purified PMAA homopolymer had a narrower HVD in comparison to those obtained from the equivalent unpurified macro‐RAFT agent. This work shows that while cyanoisopropyl‐dithiobenzoate or CPADB are good RAFT agents for methacrylate derivatives, they exhibit some instability under typical polymerization conditions, and thus when oligomers are targeted, optimal control requires checking for the degradation product and appropriate purification steps when necessary (the same effect is present for larger polymers but is unimportant). © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 2277–2289, 2008
Synthesis and photopolymerizations of new phosphonated monomers for dental applications
Authors: Yeniad Bahar , Albayrak Aylin Ziylan , Olcum Nihan Celebi , Avci Duygu 
Published: February 2008

AbstractThree novel phosphonated methacrylate monomers have been synthesized and studied for use in dental applications. Two of the monomers were synthesized from the reactions of glycidyl methacrylate (GMA) with (diethoxy‐phosphoryl)‐acetic acid (monomer 1) and (2‐hydroxy‐ethyl)‐phosphonic acid dimethyl ester (monomer 2). These monomers showed high crosslinking tendencies during thermal bulk and solution polymerizations. The third monomer (monomer 3) was prepared by the reaction of bisphenol A diglycidylether (DER) with (diethoxy‐phosphoryl)‐acetic acid and subsequent conversion of the resulting diol to the methacrylate with methacryloyl chloride. The homopolymerization and copolymerization behaviors of the synthesized monomers were also investigated with glycerol dimethacrylate (GDMA), triethylene glycol dimethacrylate (TEGDMA), and 2,2‐bis[4‐(2‐hydroxy‐3‐methacryloyloxy propyloxy) phenyl] propane (bis‐GMA) using photodifferential scanning calorimetry at 40 °C using 2,2′‐dimethoxy‐2‐phenyl acetophenone (DMPA) as photoinitiator. Monomer 1 showed polymerization rate similar or greater than dimethacrylates studied here but with higher conversion. The maximum rate of polymerizations decreased in the following order: 1∼TEGDMA>GDMA∼bis‐GMA∼3>2. A synergistic effect in the rate of polymerization was observed during copolymerizations. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 2290–2299, 2008
Improvement of the Optical Transmission of Polymer Planar Waveguides by Plasma Treatment
Authors: Airoudj Aissam , Debarnot Dominique , Bêche Bruno , Boulard Brigitte , Poncin‐Epaillard Fabienne 
Published: February 2008

AbstractThe aim of the present work is to reduce the optical losses of glycidyl ether of bisphenol A (SU‐8) polymer planar waveguides using cold plasmas, which allow the substitution of H atoms by F. CF4 and mixtures of CF4/H2 RF plasma treatments were carried out for the surface fluorination of the SU‐8 waveguide. The observed decrease in the optical losses due to propagation in the Si/SiO2/fluorinated SU‐8 planar waveguides has been correlated with the surface fluorination as measured by XPS and CA measurements. In order to understand and to optimize the fluorination process, the plasma phase was analyzed by OES. Finally, the thickness of the fluorinated layer was estimated using modulated incident‐angle XPS.magnified image
Analysis of the residue–residue coevolution network and the functionally important residues in proteins
Authors: Lee Byung‐Chul , Park Keunwan , Kim Dongsup 
Published: February 2008

AbstractIt is a common belief that some residues of a protein are more important than others. In some cases, point mutations of some residues make butterfly effect on the protein structure and function, but in other cases they do not. In addition, the residues important for the protein function tend to be not only conserved but also coevolved with other interacting residues in a protein. Motivated by these observations, the authors propose that there is a network composed of the residues, the residue–residue coevolution network (RRCN), where nodes are residues and links are set when the coevolutionary interaction strengths between residues are sufficiently large. The authors build the RRCN for the 44 diverse protein families. The interaction strengths are calculated by using McBASC algorithm. After constructing the RRCN, the authors identify residues that have high degree of connectivity (hub nodes), and residues that play a central role in network flow of information (CI nodes). The authors show that these residues are likely to be functionally important residues. Moreover, the CI nodes appear to be more relevant to the function than the hub nodes. Unlike other similar methods, the method described in this study is solely based on sequences. Therefore, the method can be applied to the function annotation of a wider range of proteins. Proteins 2008. © 2008 Wiley‐Liss, Inc.
Insights into the role of oligomeric state on the biological activities of crotoxin: Crystal structure of a tetrameric phospholipase A2formed by two isoforms of crotoxin B fromCrotalus durissus terrificusvenom
Authors: Marchi‐Salvador Daniela P. , Corrêa Luiz C. , Magro Angelo J. , Oliveira Clayton Z. , Soares Andreimar M. , Fontes Marcos R. M. 
Published: February 2008

AbstractCrotoxin B (CB or Cdt PLA2) is a basic Asp49‐PLA2found in the venom of Crotalus durissus terrificus and it is one of the subunits that constitute the crotoxin (Cro). This heterodimeric toxin, main component of the C. d. terrificus venom, is completed by an acidic, nontoxic, and nonenzymatic component (crotoxin A, CA or crotapotin), and it is related to important envenomation effects such as neurological disorders, myotoxicity, and renal failure. Although Cro has been crystallized since 1938, no crystal structure of this toxin or its subunits is currently available. In this work, the authors present the crystal structure of a novel tetrameric complex formed by two dimers of crotoxin B isoforms (CB1 and CB2). The results suggest that these assemblies are stable in solution and show that Ser1 and Glu92 of CB1 and CB2, respectively, play an important role in the oligomerization. The tetrameric and dimeric conformations resulting from the association of the isoforms may increase the neurotoxicity of the toxin CB by the creation of new binding sites, which could improve the affinity of the molecular complexes to the presynaptic membrane. Proteins 2008. © 2008 Wiley‐Liss, Inc.
Mycobacterium tuberculosis isocitrate lyase (MtbIcl): Role of divalent cations in modulation of functional and structural properties
Authors: Kumar Ranjeet , Bhakuni Vinod 
Published: February 2008

AbstractIsocitrate lyase (Icl), an enzyme that plays an important role in the regulation of isocitrate flux and anaplerotic replenishment of pool of substrate required for biosynthetic process in Mycobacterium tuberculosis is a potential drug target for the antituberculosis drugs. Divalent cations induce differential effect of activation and inhibition of MtbIcl functional activity. The study for the first time demonstrates that interaction of cations with MtbIcl results in differential modulation of the enzyme structure which is probably the underlying mechanism for differential modulation of functional activity of enzyme by divalent cations. The Mg2+ and Mn2+ ions act as activators of the enzyme and in their absence no enzymatic activity was observed. These cations do not induce any significant structural alteration in the enzyme as observed by far‐UV CD and solvent denaturation studies using chaotropic salts. However, the thermal denaturation studies demonstrate that they do interact with the noncatalytic α/β barrel core domain of the enzyme and destabilize it. The inhibitors Zn2+ and Cd2+ interact directly with the catalytic domain of the enzyme and unfold it as a result of which complete loss of the enzymatic activity is observed in their presence. The results obtained from the studies provide intriguing insight into the possible mechanism of divalent cation‐induced changes in structure, function, and stability of MtbIcl. Proteins 2008. © 2008 Wiley‐Liss, Inc.
Alignment of the energy levels and charge injection barriers at interfaces for spin injection: La0.7Sr0.3MnO3 in contact with organic semiconductors
Authors: Grobosch M. , Knupfer M. , Dörr K. , Gangineni R. B. 
Published: February 2008

AbstractFor determination of the energy‐level alignment at inter‐ faces between La0.7Sr0.3MnO3 films and two typical organic semiconductors, copper‐phthalocyanine (CuPc) and α‐sexithiophene (α‐6T) we have performed a combined X‐ray and ultraviolet photoemission study. La0.7Sr0.3MnO3 thin films were grown by using the pulsed laser deposition (PLD) technique and subsequently ex‐situ cleaned before the organic materials were thermally evaporated. We show that under these conditions the interfaces are free from chemical interaction and are characterized by a short‐range interface dipole and large injection barriers. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Electronic properties of durene crystals: Implications for charge transport
Authors: Ortmann F. , Hannewald K. , Bechstedt F. 
Published: February 2008

AbstractThe electronic structure and charge anisotropy of durene (1,2,4,5‐tetramethylbenzene) crystals is studied by means of the density‐functional theory. Based on a comprehensive analysis of the band structure and effective‐mass tensors, we propose that durene is a high‐mobility material. We find larger bandwidths than those found for the common oligoacenes. Supplemented by an indepth analysis of the electron density, further insight is obtained into the anisotropy of this herringbone‐stacked material. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Measuring carrier mobility in conventional multilayer organic light emitting devices by delayed exciton generation
Authors: Reineke S. , Lindner F. , Huang Q. , Schwartz G. , Walzer K. , Leo K. 
Published: February 2008

AbstractThe authors present an alternative method for the determination of the charge carrier mobility of organic thin films. In contrast to known methods like space charge limited current, field effect transistor and time of flight approaches, we determine the charge carrier mobility of a mixed film, serving as emission layer, within the conventional multilayer device architecture. We make use of a strong delayed generation feature in the electroluminescent decay, following a short voltage pump pulse in a time‐resolved set‐up. Taking into account the preferentially electron transporting properties of the film, the mobility of a N,N ′‐di(naphthalen‐2‐yl)‐N,N ′‐diphenyl‐benzidine (NPB):tris(1‐phenylisoquinoline) iridium [Ir(piq)3] mixed film is found to be on the order of 10–5 cm2 (Vs)–1. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Charge transport parameters of HBC at different temperatures
Authors: Kirkpatrick J. , Marcon V. , Kremer K. , Nelson J. , Andrienko D. 
Published: February 2008

AbstractWe study the dependence on temperature of the charge transport parameters for hexabenzocoronene (HBC). Following from Marcus theory, two charge transport parameters will be calculated: the transfer integral and the difference in site energies. These parameters are strongly dependent on the orientation and position of molecules. Position and orientation of molecules are determined using molecular dynamics. Transfer integrals are calculated from a simplified INDO method. A technique to compute energetic disorder, that is the spread in site energies for the charge carriers, is developed. In the herringbone phase transfer integrals are higher, but so is energetic disorder. We consider three derivatives of HBC with different side chains, which lead to different phase behaviour and distributions of charge transport parameters. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Ultralong‐range radiative excitation transfer between quantum dots in a planar microcavity
Authors: Tarel Guillaume , Parascandolo Gaetano , Savona Vincenzo 
Published: February 2008

AbstractWe study the system of two quantum dots lying on the central plane of a planar semiconductor microcavity. By solving the full Maxwell problem, we demonstrate that the rate of resonant excitation transfer between the two dots decays as d–1/2 as a function of the distance d at long distance. This very longrange mechanism is due to the leaky and guided modes of the microcavity, which act as effective radiative transfer channels. At short distance, the d–3 dependence of the Förster mechanism, induced by the electrostatic dipole–dipole interaction, is recovered. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Second‐order correlation function of entangled photons from a quantum dot in microcavity
Authors: Ajiki Hiroshi , Ishihara Hajime 
Published: February 2008

AbstractWe theoretically study cross‐polarized entangled photon generation from a single quantum dot in microcavity. Generation of co‐polarized non‐entangled photons is suppressed in the strong‐coupling limit due to the photon blockade effect. Normalized second‐order correlation function shows quantum beat resulting from interference between two kinds of entangled photons. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Strongly coupled organic microcavities with vibronic progressions
Authors: Fontanesi L. , La Rocca G. C. 
Published: February 2008

AbstractThe optical properties of an organic polycrystalline film of NTCDA with one vibronic replica, embedded in a microcavity, were measured by Holmes and Forrest in 2004. They observed strong exciton‐photon coupling and hybridization between the cavity mode and both the 0‐0 and 0‐1 vibronic transitions. The purpose of this work is to build a model to describe optical spectra of an organic microcavity with vibronic replicas in both weak and strong coupling regimes between photon and exciton modes. The problem has been handled with two approaches, a microscopic model and a macroscopic one. The active material vibronic spectra have been calculated in the Franck‐Condon framework.With these models we have reproduced the experimental spectra and we have also analyzed more complicated systems such as anisotropic monocrystalline materials. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Spontaneous emission from an exciton in a quantum dot embedded in a microcavity
Authors: Inoue J. , Ochiai T. , Sakoda K. 
Published: February 2008

AbstractSpontaneous emission properties of a quantum dot embedded in a semiconductor microcavity are theoretically investigated. High Q value of the cavity yields both weak and strong coupling states, the former of which is mainly focused. There, spontaneous emission spectrum has doublet shape, which is caused by a quantum interference. This interference is robust against detuning between the excitation of the quantum dot and cavity mode. The time domain analysis is performed for further characterization of the high Q weak coupling state. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Effects of unbound two‐exciton states on entangled photons generated from a cavity biexciton
Authors: Oka Hisaki , Ishihara Hajime 
Published: February 2008

AbstractWe theoretically investigate entangled‐photon generation via biexciton in a planar microcavity. When the exciton‐photon coupling is comparable to the biexciton binding energy, the biexciton can be stably coupled with the cavity photons (referred to as a cavity biexciton). Entangled photons are generated by the cascade decay of the cavity biexciton. We show that high‐efficient generation of entangled photons can be achieved when the superposition state of a cavity biexciton and two cavity polaritons formed by unbound two‐exciton states is realized. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Entanglement and parametric dynamics in quantum optics with interacting polaritons
Authors: Portolan S. , Di Stefano O. , Savasta S. 
Published: February 2008

AbstractWe report on a microscopic investigation of the polariton parametric emission in the presence of coherent and incoherent interaction processes by means of a full quantum description based on a nonequilibrium quantum Langevin approach for open systems applied to interacting‐electron complexes described within the dynamics controlled truncation scheme. It provides an easy recipe to calculate multi‐time correlation functions which are key‐quantities in quantum optics. In particular we report on calculations of polariton intensities (i.e. single time correlators) and spectra (i.e. two times correlators). We apply our scheme to a two‐pumps set‐up in microcavity recently proposed showing a quantitative analysis of the quantum correlation properties of the emitted photons. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Spin‐wave excitation by spin‐polarized current in magnetic nanostructures
Authors: Consolo G. 
Published: February 2008

AbstractA current‐driven magnetic point‐contact device can support both a quasi‐linear propagating spin‐wave mode and a nonlinear self‐localized evanescent spin‐wave bullet mode. In this work we show how the bias field orientation determines the nature of the excited modes. By using a micromagnetic framework we can describe the main properties of the observed modes, deriving also a satisfying agreement with analytical theories. It is also pointed out how the nature of these modes differs in: (i) threshold current of excitation, (ii) precession angle, (iii) frequency spectra, (iv) trajectory of the precessional motion, (v) spatial localization of the spin‐wave amplitude. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)