bluuebunny/crossref_metadata_2025_split huggingface dataset:
Enantiomeric resolution of bifonazole by supercritical fluid chromatography
Authors: Toribio Laura , del Nozal Ma Jesús , Bernal José L. , Alonso Cristina , Jiménez Juan J. 
Published: June 2006

AbstractThe enantiomeric separation of bifonazole by supercritical fluid chromatography on Chiralpak AD has been studied. The effect of different modifiers (methanol, ethanol, 2‐propanol, and acetonitrile) was examined. Enantioseparation was possible with all of them, but the best results were provided by the alcohol‐type ones. The resolution was higher than 5 in all cases. The isoelution temperatures Tiso were calculated from the study of the temperature effect for the different organic modifiers. The value of Tiso was below the working temperature range on using methanol, but above it with ethanol or 2‐propanol.
Botulinum toxin treatment of facial myoclonus in suspected Rasmussen encephalitis
Authors: Browner Nina , Azher Shaheda N. , Jankovic Joseph 
Published: June 2006

AbstractPatients with Rasmussen encephalitis (RE) may develop a variety of involuntary movements. We report a 26‐year‐old woman who presented with a 3‐year history of progressive, continuous myoclonus of the left side of the face and left arm as well as left spastic hemiparesis. Magnetic resonance imaging of the brain showed right hemisphere and basal ganglia atrophy, and 24‐hour electroencephalogram demonstrated diffuse slowing with random sharp waves in both hemispheres. An 18‐fluoro‐deoxy‐glucose positron emission tomography scan indicated hypometabolism of the right cerebral hemisphere, including basal ganglia and thalamus. We successfully treated her myoclonus with injections of botulinum toxin A into the left zygomaticus muscle. © 2006 Movement Disorder Society
Neutrophils and the blood–brain barrier dysfunction after trauma
Authors: Scholz Martin , Cinatl Jindrich , Schädel‐Höpfner Michael , Windolf Joachim 
Published: June 2006

AbstractDespite the fact that neutrophils are essential for the protection from invading pathogens, hyperactive neutrophils may elicit detrimental cerebral damage after severe trauma. The neutrophil interactions with the neurovascular unit entail endothelial dysfunction involving endothelial leakage, formation of edema, coagulation abnormalities, disturbed hemodynamics, tissue infiltration etc. These elements of the “whole body inflammation,” designated systemic inflammatory response syndrome (SIRS) in conjunction with intracerebral proinflammatory activities, are important triggers of post‐traumatic cerebral damage and mortality according to the “second hit” concept. From the immunologic point of view, the brain is an immune privileged site, known to resist autodestructive inflammatory activity much more efficiently than other organs because of the highly efficient diverse functions of the blood–brain barrier (BBB). However, both the underlying strategy of the BBB to maintain cerebral protecting functions against the post‐traumatic neutrophil‐mediated “second hit” and how activated neutrophils may overcome the BBB are currently unknown. Therefore, this review summarizes the current understanding of the “second hit,” the BBB physiology, and its role in the maintenance of cerebral immune privilege, and discusses recent findings that may explain the pathophysiologic neutrophil–BBB interactions occurring after severe trauma, thus offering novel therapeutic options to protect from post‐traumatic brain damage. © 2006 Wiley Periodicals, Inc. Med Res Rev, 27, No. 3, 401–416, 2007
Endogenous 5‐HT2B receptor activation regulates neonatal respiratory activity in vitro
Authors: Günther Silke , Maroteaux Luc , Schwarzacher Stephan W. 
Published: June 2006

AbstractAn implication of 5‐HT2B receptors in central nervous system has not yet been clearly elucidated. We studied the role of different 5‐HT2 receptor subtypes in the medullary breathing center, the pre‐Bötzinger complex, and on hypoglossal motoneurons in rhythmically active transversal slice preparations of neonatal rats and mice. Local microinjection of 5‐HT2 receptor agonists revealed tonic excitation of hypoglossal motoneurons. Excitatory effects of the 5‐HT2B receptor agonist BW723C86 could be blocked by bath application of LY272015, a highly selective 5‐HT2B receptor antagonist. Excitatory effects of the 5‐HT2A/B/C receptor agonist α‐methyl 5‐HT could be blocked by the preferential 5‐HT2A receptor antagonist ketanserin. Therefore, 5‐HT‐induced excitation of hypoglossal motoneurons is mediated by convergent activation of 5‐HT2A and 5‐HT2B receptors. Local microinjection of BW723C86 in the pre‐Bötzinger complex increased respiratory frequency. Bath application of LY272015 blocked respiratory activity, whereas ketanserin had no effect. Therefore, endogenous 5‐HT appears to support tonic action on respiratory rhythm generation via 5‐HT2B receptors. In preparations of 5‐HT2B receptor‐deficient mice, respiratory activity appeared unaltered. Whereas BW723C86 and LY272015 had no effects, bath application of ketanserin disturbed and blocked rhythmic activity. This demonstrates a stimulatory role of endogenous 5‐HT2B receptor activation at the pre‐Bötzinger complex and hypoglossal motoneurons that can be taken up by 5‐HT2A receptors in the absence of 5‐HT2B receptors. The presence of functional 5‐HT2B receptors in the neonatal medullary breathing center indicates a potential convergent regulatory role of 5‐HT2B and ‐2A receptors on the central respiratory network. © 2006 Wiley Periodicals, Inc. J Neurobiol, 2006
Activity‐dependent regulation of synaptic size in Drosophila neuromuscular junctions
Authors: Nakayama Hiroaki , Kazama Hokto , Nose Akinao , Morimoto‐Tanifuji Takako 
Published: June 2006

AbstractOne of the fundamental questions in neural development is how neurons form synapses of the appropriate size for the efficient transfer of information across neural circuits. Here we investigated the mechanisms that bring about the size correlation between synapses and postsynaptic cells during development of Drosophila neuromuscular junctions (NMJs). To do this, we made use of a unique system in which two neighboring muscles (M6 and M7) are innervated by the same neurons. In mature NMJs, synaptic size on M6 is normally larger than that on M7, in accordance with the difference in muscle volume; this ensures the same extent of contraction of both muscles, and we refer to this correspondence as “matching”. We found that matching was apparent in larvae 8 h after hatching, but not in newly hatched larvae despite the difference in muscle volume. When sensory inputs were suppressed by the expression of tetanus toxin in sensory neurons, matching did not occur, although synapses were able to grow. Matching was also suppressed by the inhibition of motoneuronal activity. These results suggest that matching is induced by regulating the rate of synaptic growth on M6 and M7 in an experience‐ and activity‐dependent manner. It seems most likely that retrograde signals from the postsynaptic to the presynaptic cell convey the information about muscle cell size. We thus examined whether a candidate of retrograde signaling in NMJs, BMP signaling, is involved inmatching. However, there was no effect on matching inBMP type II receptor gene mutants, suggesting thatother experience‐driven mechanisms besides BMP signaling are involved in the proper development of synapses. © 2006 Wiley Periodicals, Inc. J Neurobiol, 2006
Reduced metabolites mediate neuroprotective effects of progesterone in the adult rat hippocampus. The synthetic progestin medroxyprogesterone acetate (Provera) is not neuroprotective
Authors: Ciriza Iratxe , Carrero Paloma , Frye Cheryl A. , Garcia‐Segura Luis M. 
Published: June 2006

AbstractThe ovarian hormone progesterone is neuroprotective in different experimental models of neurodegeneration. In the nervous system, progesterone is metabolized to 5α‐dihydroprogesterone (DHP) by the enzyme 5α‐reductase. DHP is subsequently reduced to 3α,5α‐tetrahydroprogesterone (THP) by a reversible reaction catalyzed by the enzyme 3α‐hydroxysteroid dehydrogenase. In this study we have analyzed whether progesterone metabolism is involved in the neuroprotective effect of the hormone in the hilus of the hippocampus of ovariectomized rats injected with kainic acid, an experimental model of excitotoxic cell death. Progesterone increased the levels of DHP and THP in plasma and hippocampus and prevented kainic‐acid‐induced neuronal loss. In contrast to progesterone, the synthetic progestin medroxyprogesterone acetate (MPA, Provera) did not increase DHP and THP levels and did not prevent kainic‐acid‐induced neuronal loss. The administration of the 5α‐reductase inhibitor finasteride prevented the increase in the levels of DHP and THP in plasma and hippocampus as a result of progesterone administration and abolished the neuroprotective effect of progesterone. Both DHP and THP were neuroprotective against kainic acid. However, the administration of indomethacin, a 3α‐hydroxysteroid dehydrogenase inhibitor, blocked the neuroprotective effect of both DHP and THP, suggesting that both metabolites are necessary for the neuroprotective effect of progesterone. In conclusion, our findings indicate that progesterone is neuroprotective against kainic acid excitotoxicityin vivowhile the synthetic progestin MPA is not and suggest that progesterone metabolism to its reduced derivatives DHP and THP is necessary for the neuroprotective effect of the hormone. © 2006 Wiley Periodicals, Inc. J Neurobiol, 2006
The equilibration of intrachain and interchain excitations in aggregates of a cyano‐substituted phenylene vinylene polymer
Authors: Miller Paul F , de Souza Melanie M , Moratti Stephen C , Holmes Andrew B , Samuel Ifor DW , Rumbles Garry 
Published: June 2006

AbstractAggregates formed in dilute solutions of poly[2,2′‐dimethoxy‐5,5′‐di‐(2″,7″‐dimethyloctyloxy)‐dicyano‐di‐p‐phenylene vinylene], OC1C10‐CNPPV, in toluene exhibit emission from both an intrachain and an interchain excitation that equilibrate on the timescale of the excited states. The position of the equilibrium can be adjusted with temperature, and a binding energy of 130 meV for the interchain species has been determined. A repulsion energy of 350 meV demonstrates that the interchain excitation is not bound in the ground state, indicative of an excited dimer or complex. At ambient temperatures the equilibrated state exhibits a mean photoluminescence quantum yield of 19% that actually decreases with a reduction in temperature, but a mean photoluminescence lifetime of 4.2 ns that shows a moderate increase. These counterintuitive observations, which imply a strong dependence upon temperature of the mean natural radiative lifetime, arise from the relative weighting factors of the two individual natural radiative lifetimes of the interacting species and the dependence upon the position of equilibrium. Copyright © 2006 Society of Chemical Industry
Viscoelastic properties of silica‐grafted poly(styrene–acrylonitrile) nanocomposites
Authors: Goel Vivek , Chatterjee Tirtha , Bombalski Lindsay , Yurekli Koray , Matyjaszewski Krzysztof , Krishnamoorti Ramanan 
Published: June 2006

AbstractThe melt state viscoelastic properties of styrene–acrylonitrile random copolymers grafted to silica nanoparticles and prepared by in situ atom transfer radical polymerization are examined. Linear dynamic oscillatory viscoelastic measurements indicate that nanocomposites with silica contents as low as 1.2 vol % exhibit solid‐like response. Steady shear results in considerable alteration to the mesoscale structure and results in the failure of the Cox‐Merz rule. Flow reversal studies confirm the elastic nature of the mesoscale structure and demonstrate that the relaxation of the flow altered structure is slow, non‐Brownian, and possibly cooperative. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 2014–2023, 2006
Decomposition and Ignition of the High‐Nitrogen Compound Triaminoguanidinium Azotetrazolate (TAGzT)
Authors: Tappan Bryce C. , Ali Arif N. , Son Steven F. , Brill Thomas B. 
Published: June 2006

AbstractThe high‐nitrogen compound triaminoguanidinium azotetrazolate (TAGzT) belongs to a class of C, H and N compounds that are free of both oxygen and metal, but retain energetic material properties as a result of their high heat of formation. Its decomposition thus lacks secondary oxidation reactions of carbon and hydrogen. The fact that TAGzT is over 80% nitrogen makes it potentially useful as a gas generant and energetic material with a low flame temperature to increase the impulse in gun or rocket propellants. The burning rate, laser ignition and flash pyrolysis (T‐jump/FTIR spectroscopy) characteristics were determined. It was found that TAGzT exhibits one of the fastest low‐pressure burning rates yet measured for an organic compound. Both the decomposition and ignition behavior of TAGzT are dominated by condensed phase reactions. T‐Jump/FTIR spectroscopy indicates that condensed phase reactions release about 65% of the energy, which helps to explain the high burning rate at low pressure.
Stress and density of defects in Si‐doped GaN
Authors: Chine Z. , Rebey A. , Touati H. , Goovaerts E. , Oueslati M. , Jani B. El , Laugt S. 
Published: June 2006

AbstractWe report a study by photoluminescence (PL), Raman scattering, and highly resolved X‐ray diffraction (HRXRD) of a series of Si‐doped n‐type GaN layers grown by metalorganic vapor phase epitaxy (MOVPE) on sapphire (0001) with the carrier concentration of 2.3 × 1017 – 9 × 1018 cm–3. We found that the band gap reduction deduced from the PL spectra analysis is due to both band gap narrowing (BGN) effect and change of the nature of stress in the GaN:Si layers. The HRXRD spectra show that at high Si‐doping levels (>1.6 × 1018 cm–3) the GaN films become under tensile stress. Progressive decreases of the E2 Raman mode frequency with Si concentration confirm this observation. The stress induced E2 mode frequency shift is estimated to 1.6 cm–1/GPa. Additionally, dislocation densities are determined by HRXRD by employing a model that uses the line width of X‐ray rocking curves. Atomic force microscopy (AFM) is also used to investigate the defect surface structures of GaN:Si layers which are dominated by pinned steps and surface depressions related to threading dislocations. We find that dislocation densities given by AFM measurements are in agreement with those obtained from rocking curve line widths. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Numerical simulation of impedance and admittance of OLEDs
Authors: Nguyen N. D. , Schmeits M. 
Published: June 2006

AbstractIn this issue's Editor's Choice [1], the electrical characteristics of organic light‐emitting diodes (OLEDs) are calculated for the dc and ac regimes by numerically solving the basic semiconductor equations. The cover picture is taken from a diagram showing the steady‐state electron concentration n0 and the hole concentration p0 for an applied voltage V0 = 3 V as well as the real part of the electron amplitude $ \tilde n $
and the hole amplitude $ \tilde p $ for frequencies of 1 Hz and 105 Hz. α‐NPD and Alq3 molecules being used as active hole‐ and electron‐transporting materials, respectively, are inserted.The first author is working as a postdoctoral fellow for an European project on OLEDs. His current research interests are the transport properties of organic semiconductors, where the conduction mechanisms and the role of traps are studied.This issue also contains a second Editor's Choice entitled “AlGaN/AlN distributed bragg reflectors for deep ultraviolet wavelengths” by Craig G. Moe et al. [2] as well as the Feature Article “p‐type transparent conducting oxides” by Su Sheng, Guojia Fang et al. [3].
Spatially resolved cathodoluminescence, photoluminescence, electroluminescence, and reflectance study of GaInN quantum wells on non‐(0001) GaN facets
Authors: Feneberg M. , Schirra M. , Neubert B. , Brückner P. , Scholz F. , Sauer R. , Thonke K. 
Published: June 2006

AbstractGaInN light emitting diodes have been grown on the {1$ \bar 1 $01} and the {11$ \bar 2 $2} facet of selectively overgrown GaN. Different luminescence measurements with high spectral and spatial resolution have been performed which show strong indications that the piezoelectric fields in the processed devices are diminished increasing the overall efficiency and reducing the carrier lifetime. Furthermore, the growth conditions on such facets different from {0001} result in altered In incorporation as analyzed by spatially resolved cathodoluminescence. The spectral features found by different measurement techniques are correlated and yield important information on the material quality. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Dissociation of VGa–ON complexes in HVPE GaN by high pressure and high temperature annealing
Authors: Tuomisto F. , Hautakangas S. , Makkonen I. , Ranki V. , Puska M. J. , Saarinen K. , Bockowski M. , Suski T. , Paskova T. , Monemar B. , Xu X. , Look D. C. 
Published: June 2006

AbstractWe have used positron annihilation spectroscopy to study the high‐pressure annealing induced thermal recovery of vacancy defects in free‐standing GaN grown by hydride vapor phase epitaxy (HVPE). The results show that the in‐grown Ga vacancy complexes recover after annealing at 1500–1700 K. Comparison of the experimental positron data with ab‐initio calculations indicates that the Doppler broadening measurement of the electron momentum distribution is sensitive enough to distinguish between the N and O atoms surrounding the Ga vacancy. We show that the difference between the isolated VGa in electron irradiated GaN and the VGa–ON complexes in highly O‐doped GaN is clear, and the Ga vacancy related defect complexes that start dissociating at 1500 K can be identified as VGa–ON pairs. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The surface diffusion of Ga on an AlGaN/GaN stripe structure in the selective MOVPE
Authors: Narita Tetsuo , Honda Yoshio , Yamaguchi Masahito , Sawaki Nobuhiko 
Published: June 2006

AbstractThe growth of GaN with an AlGaN/GaN heterostructure was attempted on a (111) Si substrate by selective area metal organic vapor phase epitaxy. The GaN obtained was a trapezoidal stripe with (1$ \bar 1 $01) facets on the sides and a (0001) facet on the top. The distribution of the Al composition on the facets was investigated by cathodeluminescence analyses as a function of the position. The surface diffusion of Ga on the (0001) AlGaN facet was studied under various growth conditions. It was found that the diffu‐ sion length is enhanced by elevating the growth temperature or lowering the Al composition. By the temperature dependence of the diffusion length, the activation energy of the Ga species was estimated. The results depended on the Al composition x; 1.23 ± 0.44 eV (x = 0.05), 1.84 ± 0.58 eV (x = 0.10) and 2.72 ± 0.73 eV (x = 0.15). (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Optical and theoretical study of strong electron coupling in double GaN/AlN quantum wells
Authors: Tchernycheva M. , Nevou L. , Doyennette L. , Julien F. H. , Guillot F. , Monroy E. , Remmele T. , Albrecht M. 
Published: June 2006

AbstractThe electronic confinement in GaN quantum wells coupled by an ultra‐thin AlN barrier is investigated both experimentally and theoretically. The strong coupling between the wells is evidenced by the observation of two pronounced intersubband absorptions peaked at around 0.6 and 0.95 eV for 2 monolayer thick AlN coupling barrier. In agreement with calculations, these absorptions are attributed respectively to the transitions between the ground states of the two coupled wells and between the ground state and the excited state delocalized between the two wells. The experimental results provide clear evidence that the potential drop at the GaN/AlN interfaces is not abrupt, but spread over 1 monolayer. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Resonant Raman characterization of InAlGaN/GaN heterostructures
Authors: Cros A. , Cantarero A. , Pelekanos N. T. , Georgakilas A. , Pomeroy J. , Kuball M. 
Published: June 2006

AbstractInAlGaN/GaN heterostructures and thin films with In composition ranging from 0.03 to 0.1 are characterized by means of Raman scattering excited at various energies in the ultra violet range, tuning the laser excitation energy through the band gap of InxAlyGa1–x–yN. It is shown that the addition of In to the AlyGa1–yN alloy diminishes considerably the vibration energy of the A1(LO) phonon mode. The phonon line is asymmetric on the low energy side, and the asymmetry increases with In content, while the main peak shifts to lower energies. A shift of the phonon energy has also been observed when the excitation energy is close to the absorption edge of the InxAlyGa1–x–yN layer. The nature of this shift is discussed in relation with intrinsic and extrinsic inhomogeneities in the quaternary alloy. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Temperature‐dependent growth and characterization of N‐polar InN films by molecular beam epitaxy
Authors: Wang Xinqiang , Che Song‐Bek , Ishitani Yoshihiro , Yoshikawa Akihiko 
Published: June 2006

AbstractN‐polar InN films were grown as a function of temperature (∼440–620 °C) on 500 nm thick GaN template by plasma‐assisted molecular beam epitaxy. InN films grown at different temperatures showed different morphologies that could be roughly divided into two regions. Dendritic morphologies could be observed at temperatures lower than 540 °C while step‐flow‐like morphology could be obtained at temperatures higher than 540 °C. Crystalline quality became better with the increase of growth temperature at temperatures lower than 540 °C and almost saturated at higher temperatures. Strong photoluminescence was observed at room temperature and 13 K with the emission peaks at 0.67 and 0.7 eV, respectively. Based on our results, the growth temperature above 540 °C was recommended for N‐polar InN epitaxy. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Thermodynamics on hydride vapor phase epitaxy of AlN using AlCl3 and NH3
Authors: Kumagai Y. , Takemoto K. , Kikuchi J. , Hasegawa T. , Murakami H. , Koukitu A. 
Published: June 2006

AbstractA thermodynamic analysis on hydride vapor phase epitaxy (HVPE) of AlN using AlCl3 and NH3 was performed. Regardless of the carrier gas used, partial pressures of Al‐containing gaseous species [AlCl3, AlCl2, AlCl and (AlCl3)2] in equilibrium with AlN are significantly low in the temperature range of 500–1500 °C when the input V/III ratio is above 1. This means that the driving force for AlN growth (ΔPAl) becomes almost equal to the input partial pressure of AlCl3, which is quite different from HVPE of GaN. The good agreement between the calculated and experimental growth rates shows that HVPE of AlN is thermodynamically controlled. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Role of band potential roughness on the luminescence properties of InGaN quantum wells grown by MBE on bulk GaN substrates
Authors: Žukauskas A. , Kazlauskas K. , Tamulaitis G. , Pobedinskas P. , Juršėnas S. , Miasojedovas S. , Ivanov V. Yu. , Godlewski M. , Skierbiszewski C. , Siekacz M. , Franssen G. , Perlin P. , Suski T. , Grzegory I. 
Published: June 2006

AbstractRole of band potential roughness on luminescence decay time and stimulated emission in InGaN quantum wells (QWs) grown by rf plasma‐assisted molecular beam epitaxy (MBE) on bulk GaN substrates was studied. A high‐photoexcitation regime used ensured conditions similar to those in operating laser diodes. Standard deviation of the potential fluctuations in different thickness InGaN QWs was found to vary in the range of 13–22 meV as revealed by Monte Carlo simulation of localized exciton hopping. A negligible influence of this variation on the luminescence decay time (∼700 ps) and stimulated emission threshold (∼30 kW/cm2) was observed. We attribute this insensitivity to the low density of localized states (∼1 × 1018 cm–3) estimated in our high‐quality QWs grown by MBE, and therefore, assign extended states to be mainly responsible for the properties of highly‐excited luminescence. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)