bluuebunny/crossref_metadata_2025 huggingface dataset:
Endothelin-3-Induced Relaxation of Isolated Rat Basilar Artery is Mediated by an Endothelial ETB-Type Endothelin Receptor
Authors: Schilling L. , Feger G. I. , Ehrenreich H. , Wahl M.
Published: April 2011

The endothelin (ET) receptor mediating relaxation of cerebral arteries was characterized using ring segments obtained from the rat basilar artery. Under resting tension, ET-3 (>10−8 M) but not the specific ETB receptor agonist IRL 1620 induced contraction. In ring segments precontracted with 3 × 10−6 M prostaglandin (PG) F2α, ET-3 (10−12–10−8 M) and IRL 1620 (10−14–10−6 M) induced concentration-related relaxation. IRL 1620 was more potent than ET-3, the pD2 (-log10EC50) values being 10.002 ± 0.751 (mean ± SD) for IRL 1620 and 8.836 ± 0.415 for ET-3. Relaxation was abolished after preincubation with the nitric oxide (NO) synthase inhibitor NG-nitro-l-arginine (10−5 M) as well as in segments devoid of a functionally intact endothelium. At a concentration above 10−8 M, ET-3 resulted in a further increase of PGF2α-induced contraction that was not observed with IRL 1620. The presumably specific ETB receptor antagonist IRL 1038 (10−7–3 × 10−6 M) diminished or even abolished (3 × 10−6 M) the relaxation induced by ET-3 or IRL 1620. IRL 1038 did not exert any vasomotor effect by itself, and it did not significantly affect ET-3-induced contraction. These results indicate that in the rat isolated basilar artery, the ET-3-induced relaxation is probably due to activation of an ETB-type receptor located on the endothelial cells and mediated by release of nitric oxide.
The Influence of Acidosis on Hypoglycemic Brain Damage
Authors: Kristián Tibor , Gidö Gunilla , Siesjö Bo K.
Published: April 2011

The objective of the study was to explore whether hypoglycemic brain damage is affected by superimposed acidosis. To that end, animals with insulin-induced hypoglycemic coma, defined in terms of a negative DC potential shift, massive release of K+, or cellular uptake of Ca2+, were exposed to excessive hypercapnia (Paco2 ∼200 or ∼300 mm Hg) during the last 25 min of the 30-min coma period. Animals were allowed to survive for 7 days before their brains were fixed by perfusion, and the cell damage was assessed by light microscopy. Other animals were analyzed with respect to changes in extracellular pH (pHe) or extracellular K+ or Ca2+ concentrations (K+e and Ca2+e, respectively). The total CO2 content (Tco2) was also measured to allow derivation of intracellular pH (pHi). The increase in Paco2 to 190 ± 15 and 312 ± 23 mm Hg (means ± SD) reduced the pHe from a predepolarization value of ∼7.4 and a postdepolarization value (after the first 5 min of coma) of ∼7.3 to 6.8 and 6.7, respectively. The corresponding mean pHi values were 6.7 and 6.5. The hypercapnia did not alter the K+e, which rose to 50–60 m M at the onset of hypoglycemic coma, but it increased the Ca2+e from −0.05 to 0.10–0.16 m M. Normocapnic animals with induced hypoglycemic coma of 30-min duration showed the expected neuronal lesions in the neocortex, hippocampus, and caudoputamen. Hypercapnia clearly aggravated this damage, particularly in the caudoputamen, subiculum, and CA1 region of the hippocampus, and caused additional damage to cells in the CA3 region and piriform cortex. A rise in CO2 tension from −200 to 300 mm Hg did not further aggravate the damage. The results thus demonstrate that relative moderate acidosis aggravates damage that is believed to be mostly neuronal, sparing glia cells and vascular tissue.
Spreading Depression Induces Tolerance of Cortical Neurons to Ischemia in Rat Brain
Authors: Kobayashi Shuichi , Harris Valerie A. , Welsh Frank A.
Published: April 2011

Cortical spreading depression (CSD) was induced in male Wistar rats by applying 2 M KCl to the frontal cortex of one hemisphere for 2 h. Saline was applied to the contralateral cortex in the same manner. Following recovery for 24 h, bilateral forebrain ischemia was induced for 6 min, and the animals were permitted to survive for 6 days for assessment of histopathology. The number of necrotic neurons was counted in the cerebral cortex, striatum, and hippocampus of both hemispheres. In separate sets of animals, the effects of KCl application on cortical direct current (DC) potential and regional expression of c- fos mRNA and 72-kDa heat shock protein (hsp72) mRNA were determined. Forebrain ischemia induced selective neuronal necrosis in both hemispheres, but the number of necrotic neurons in the cerebral cortex ipsilateral to the application of KCl was significantly smaller than that in the contralateral cortex ( p < 0.02, Wilcoxon signed rank test, n = 7). In the striatum and hippocampus, there were no significant differences in neuronal necrosis between hemispheres. Application of KCl for 2 h induced 11 ± 2 (mean ± SD, n = 5) negative deflections of DC potential in the ipsilateral cortex; none were detected in the contralateral cortex. Widespread expression of c- fos mRNA was evident in the ipsilateral cortex, while hsp72 mRNA expression was restricted to the KCl application site. The present results demonstrate that CSD induces tolerance of cortical neurons to ischemia by mechanisms unrelated to hsp72.
Lithium acetylides as alkynylating reagents for the enantioselective alkynylation of ketones catalyzed by lithium binaphtholate
Authors: Tanaka Kana , Kukita Kenji , Ichibakase Tomonori , Kotani Shunsuke , Nakajima Makoto
Published: April 2011

Chiral lithium binaphtholate effectively catalyzed the enantioselective alkynylation of ketones using lithium acetylide as an alkynylating agent.
Epitaxial strain and antiferromagnetism in Heusler Fe2VSi thin films
Authors: Fukatani N. , Ueda K. , Asano H.
Published: April 2011

The effects of biaxial strain on the electrical and magnetic properties of an antiferromagnetic Heusler compound Fe2VSi were systematically investigated. A series of epitaxial Fe2VSi thin films on MgAl2O4 and MgO substrates were fabricated with different tensile strains by varying the substrate-lattice mismatch and the film thickness. The strain was characterized by the ratio of the out-of-plane lattice parameter c to the in-plane lattice parameter a; this ratio c/a varied from 0.987 to 0.998 at room temperature. The tensile epitaxial strain was found to increase the antiferromagnetic Neel temperature TN to 193 K, which is 70 K higher than that for the unstrained bulk material. A clear dependence of TN on c/a was observed, which is consistent with theoretical predictions in which the band Jahn-Teller effect plays a significant role.
Spin pumping efficiency from half metallic Co2MnSi
Authors: Chudo H. , Ando K. , Saito K. , Okayasu S. , Haruki R. , Sakuraba Y. , Yasuoka H. , Takanashi K. , Saitoh E.
Published: April 2011

We present spin pumping using a Heusler alloy Co2MnSi/Pt bilayer film. A spin current is produced by a ferromagnetic resonance (FMR) technique. The pure spin current injected into the Pt layer from the Co2MnSi layer is detected by the inverse spin-Hall effect (ISHE), which converts the spin current into an electric current. We estimated a damping constant of the Co2MnSi/Pt bilayer film from an angular dependence of FMR spectra. Using the damping constant efficiency of spin pumping from the Co2MnSi layer is evaluated. We found that a mixing conductance at the Co2MnSi/Pt interface is comparable to that at a permalloy/Pt interface.
An atomistic study of thermal conductance across a metal-graphene nanoribbon interface
Authors: Huang Zhen , Fisher Timothy , Murthy Jayathi
Published: April 2011

This paper presents an atomistic Green’s function study of phonon transport through a heterogeneous interface between bulk TiC substrates and graphene nanoribbons (GNRs). The force constants that govern the lattice dynamical equations are obtained from first-principles density functional theory (DFT) calculations and then optimized for the Green’s function formulation. Phonon vibrational properties of TiC and GNRs are investigated by lattice dynamics calculations with optimized force constants that correlate well to direct DFT results. Thermal conductances of TiC-GNR-TiC systems are studied together with TiC-GNR structures. The conductances of TiC-GNR interfaces are normalized by ribbon width and are found to converge. The converged value is used to estimate the interface resistance of multiwalled carbon nanotubes (MWCNTs) grown on metal catalyst support substrates and is found to be consistent in an order of magnitude sense with experimental results on MWCNT arrays. The results reveal that covalent bonds may be formed during CNT synthesis and quantify the resulting thermal impedance caused by phonon mismatch.
Structural and magnetic properties of NiZn–ferrite thin films prepared by radio frequency magnetron sputtering
Authors: Liu Yingli , Li Yuanxun , Zhang Huaiwu , Chen Daming , Mu Chunhong
Published: April 2011

Polycrystalline NiZn–ferrite thin films were deposited on Si(100) substrate by rf magnetron sputtering, using targets with a nominal composition of Ni0.5Zn0.5Fe2O4. The effects of substrate condition, sputtering pressure, and postannealing on the structure and magnetic properties of thin films have been investigated. Our results show that the preferred orientation of the NiZn spinel film changed from (311) to (400) with increasing the Ar pressure from 0.8 to 1.6 Pa, meanwhile, the grain size also increased. Atomic force microscopy analysis indicates that perfect surface morphology of the film can be obtained at a relatively lower sputtering pressure of 1.0 Pa. The relative percentage of residual oxygen increases significantly on a condition of lower sputtering pressure, and plays an important role in film structure due to the strong molecular adsorption tendency of oxygen on the film surface during the deposition process. A thin film with a typical thickness of 1 μm, a saturation magnetization of 150 emu/cm3, and a coercivity of 8.8 kA/m has been obtained after annealing at 800 °C, which has the potential application in magnetic integrated circuits.
Measurements of magneto-Rayleigh–Taylor instability growth during the implosion of initially solid metal liners
Authors: Sinars D. B. , Slutz S. A. , Herrmann M. C. , McBride R. D. , Cuneo M. E. , Jennings C. A. , Chittenden J. P. , Velikovich A. L. , Peterson K. J. , Vesey R. A. , Nakhleh C. , Waisman E. M. , Blue B. E. , Killebrew K. , Schroen D. , Tomlinson K. , Edens A. D. , Lopez M. R. , Smith I. C. , Shores J. , Bigman V. , Bennett G. R. , Atherton B. W. , Savage M. , Stygar W. A. , Leifeste G. T. , Porter J. L.
Published: April 2011

A recent publication [D. B. Sinars et al., Phys. Rev. Lett. 105, 185001 (2010)] describes the first controlled experiments measuring the growth of the magneto-Rayleigh–Taylor instability in fast (∼100 ns) Z-pinch plasmas formed from initially solid aluminum tubes (liners). Sinusoidal perturbations on the surface of these liners with wavelengths of 25–400 μm were used to seed single-mode instabilities. The evolution of the outer liner surface was captured using multiframe 6.151 keV radiography. The initial paper shows that there is good agreement between the data and 2-D radiation magneto-hydrodynamic simulations down to 50 μm wavelengths. This paper extends the previous one by providing more detailed radiography images, detailed target characterization data, a more accurate comparison to analytic models for the amplitude growth, the first data from a beryllium liner, and comparisons between the data and 3D simulations.
Magnetic properties of MnSb inclusions formed in GaSb matrix directly during molecular beam epitaxial growth
Authors: Lawniczak-Jablonska Krystyna , Wolska Anna , Klepka Marcin T. , Kret Slawomir , Gosk Jacek , Twardowski Andrzej , Wasik Dariusz , Kwiatkowski Adam , Kurowska Boguslawa , Kowalski Bogdan J. , Sadowski Janusz
Published: April 2011

Despite of intensive search for the proper semiconductor base materials for spintronic devices working at room temperature no appropriate material based on ferromagnetic semiconductors has been found so far. We demonstrate that the phase segregated system with MnSb hexagonal inclusions inside the GaSb matrix, formed directly during the molecular beam epitaxial growth reveals the ferromagnetic properties at room temperature and is a good candidate for exploitation in spintronics. Furthermore, the MnSb inclusions with only one crystalline structure were identified in this GaMn:MnSb granular material. The SQUID magnetometry confirmed that this material exhibits ferromagnetic like behavior starting from helium up to room temperature. Moreover, the magnetic anisotropy was found which was present also at room temperature, and it was proved that by choosing a proper substrate it is possible to control the direction of easy axis of inclusions’ magnetization moment between in-plane and out-of-plane; the latter is important in view of potential applications in spintronic devices.
Control of carrier transport in GaAs by longitudinal-optical phonon-carrier scattering using a pair of laser pump pulses
Authors: Hase Muneaki , Hayashi Daisuke , Lee J. D.
Published: April 2011

We demonstrate optical control of the LO phonon-plasmon coupled (LOPC) modes in GaAs by using a femtosecond pump-pulse pair. The relaxation time of the plasmonlike LOPC mode significantly depends on the separation time (Δt) of the pump-pulse pair. Especially it is maximized when Δt becomes simultaneously comparable to the half period of the longitudinal optical (LO) phonon oscillation and resonant to the 3/4 period of the plasmonlike LOPC oscillation. We attribute these observations to the modification of carrier-LO phonon scattering and ballistic motion of the plasmonlike LOPC mode.
Magnetic anomaly around orbital ordering in FeCr2S4
Authors: Shen Chen , Yang Zhaorong , Tong Ran , Zi Zhenfa , Song Wenhai , Sun Yuping , Pi Li , Zhang Yuheng
Published: April 2011

For polycrystalline FeCr2S4, temperature dependence of low-field magnetization shows a step-like transition around orbital ordering temperature Too ∼ 9 K. In this paper, the origin of the magnetic anomaly has been studied. We show that, with increasing magnetic field, the step-like anomaly in M–T curve is gradually suppressed. However, the external magnetic field up to 5 T has no evident influence on orbital ordering transition as revealed by specific heat measurements. Too was increased when an ultrahigh magnetic field, e.g., 14 T, has been applied. Being contrary to the inert response to magnetic field, the Too is sensitive to the variation of external pressure. M(H) curves measured at different temperatures suggest that magnetic anisotropy changes oppositely going across Too. By considering the variation of magnetocrystalline symmetry induced by orbital ordering, the magnetic anomaly around Too has been explained.
Room temperature ferromagnetism and hopping conduction in Pt NCs/Al2O3 films
Authors: Ma Y. W. , Ding J. , Yi J. B. , Chan Lap , Herng T. S. , Huang Stella , Ran M.
Published: April 2011

In this work, Pt nanocrystals (NCs) were embedded into different oxide films by codeposition of Pt and oxide at 400 °C and 10−8 Torr using a pulse laser deposition system. Films of Pt (25 mol. %) NCs embedded in (Al2O3, ZnO, or SnO2) matrix showed room temperature ferromagnetism (RTFM), while Pt (25 mol. %) NCs/(MgO or SiO2) films were not magnetic. The detailed study of Pt NCs/Al2O3 films with different concentrations of Pt revealed that RTFM depended on Pt NC size and conductivity of the film. Resistance-temperature study of this film showed that the hopping conduction may be associated with RTFM.
Demonstration of spin valve effects in silicon nanowires
Authors: Tarun Jean , Huang Shaoyun , Fukuma Yasuhiro , Idzuchi Hiroshi , Otani YoshiChika , Fukata Naoki , Ishibashi Koji , Oda Shunri
Published: April 2011

We have successfully demonstrated a lateral spin valve device using a silicon nanowire for the nonmagnetic channel. Low-temperature transport measurements with in-plane magnetic field were performed in both local and nonlocal configurations. Hysteretic behavior was observed in the local magnetoresistance curves, with a maximum change of 0.18% at 2.4 K. The shape of the magnetoresistance curves indicates spin valve behavior with two switching fields. In the nonlocal voltage configuration, distinct dips were observed when the injector and detector contacts had antiparallel magnetization states.
The contribution of x-ray specular reflectometry to the oxygen-induced magnetic properties in Pt/Co/AlOx
Authors: Garad H. , Ortega L. , Ramos A. Y. , Marcus J. , Gay F. , Fettar F. , Auffret S. , Rodmacq B. , Dieny B.
Published: April 2011

Two key parameters were analyzed in Si/SiO/Pt/Co/AlOx: the oxidation time of the Al layer resulting in AlOx, and the ex situ annealing temperatures varied in the 15 and 55 s and 20, 300, and 450  °C ranges, respectively. For intermediate annealing temperatures (∼300  °C), the quantitative analysis of specular reflectometry data shows that the progressive oxidation of layers by increasing the oxidation time goes along with an improvement of the homogeneity of the alumina layer. This outcome casts new light on the temperature dependence of magnetic properties of the samples. The remarkable temperature variation of the coercive field, extracted from extraordinary Hall effects in the 5–300 K range, is associated with structural change due to Co–oxygen bondings, which leads to strong pinning of Co spins in the low temperature regime.
The influence of hollow structure on the magnetic characteristics for Fe3O4 submicron spheres
Authors: Yan Shaojiu , Tang Jinke , Liu Pan , Gao Qian , Hong Guangyan , Zhen Liang
Published: April 2011

In this paper, nearly monodisperse Fe3O4 hollow and solid submicron spheres were synthesized using a simple solvothermal method. The TEM investigation clearly reveals the successful realization of the hollow structure of magnetite spherical particles by the method. The average diameter of the Fe3O4 hollow and solid submicron spheres is about 300 and 500 nm, respectively. The submicron spheres are composed of nanometer-sized grains, with grain sizes of 21 and 28 nm for the hollow and solid spheres, respectively. Magnetic hysteresis measurements indicate that the hollow structure has higher coercive force and lower saturation magnetization than the solid submicron spheres. Magnetization versus temperature curve shows a peak at 107 K in the zero-field-cooled (ZFC) runs for the hollow structure, which corresponds to the blocking temperature of the nanograins. The blocking temperature correlates well with the volume of the nanograins according to Stoner–Wohlfarth theory. The hollow structure exhibits the magnetic properties of individual nanograins because of the weak coupling among them. However, the above-described feature is absent in the solid spheres, due to stronger magnetic coupling between the grains.
Direction detectable static magnetic field imaging by frequency-modulated magnetic force microscopy with an AC magnetic field driven soft magnetic tip
Authors: Saito Hitoshi , Ito Ryoichi , Egawa Genta , Li Zhenghua , Yoshimura Satoru
Published: April 2011

Direction detectable static magnetic field imaging, which directly distinguishes the up and down direction of static perpendicular magnetic field from a sample surface and the polarity of magnetic charges on the surface, was demonstrated for CoCrPt-SiO2 perpendicular magnetic recording media based on a frequency-modulated magnetic force microscopy (FM-MFM), which uses a frequency modulation of the cantilever oscillation induced by an alternating force from the tip-sample magnetic interaction. In this study, to generate the alternating force, we used a NiFe soft magnetic tip driven by the ac magnetic field of a soft ferrite core and imaged the direction and the amplitude of the static magnetic field from the recorded bits. This method enables measurement of the static magnetic field near a sample surface, which is masked by short range forces of the surface. The present method will be effective in analyzing the microscopic magnetic domain structure of hard magnetic samples.
Sample fabrication effects in exchange bias systems
Authors: Hussain R. , Kaeswurm B. , O’Grady K.
Published: April 2011

In exchange coupled granular films the reversal process is usually that of reverse domain nucleation and domain wall propagation. Local effects such as surface irregularities can affect the nucleation process significantly. We describe the effects of nucleation arising from both sample shape effects and the process used to cut the samples. Cutting techniques such as the use of ultrasonic cutters lead to a large increase in nucleation, which distorts the hysteresis loop. Deposition through masks causes shadowing effects at the edges that also distort the loops. Cutting with a diamond scribe appears to give the best outcome. Implications for devices based on nanoelements are discussed.
Structural and magnetic properties of Tb6Fe1−xCoxBi2 (0 ≤ x ≤ 0.375) compounds
Authors: Jia Lin , Koehler Michael , McCarthy David , McGuire Michael A. , Keppens Veerle
Published: April 2011

Tb6Fe1−xCoxBi2 (x = 0, 0.125, 0.250, 0.375) compounds have been synthesized, and the structural and magnetic properties are reported. All of the compounds crystallize in the hexagonal Zr6CoAs2-type structure at room temperature, but low temperature x-ray diffraction measurements on the Co-doped samples Tb6Fe0.750Co0.250Bi2 and Tb6Fe0.625Co0.375Bi2 show a splitting of the Bragg peaks, indicating a symmetry lowering structural phase transition at ∼40 K. Two magnetic transitions are observed, with TC1 ∼ 250 K and TC2 ∼ 70 K. While the high temperature transition corresponds to the ferromagnetic ordering of the Tb moments, the lower transition is most likely linked to the structural transition.
Modeling flows of confined nematic liquid crystals
Authors: Hernández-Ortiz Juan P. , Gettelfinger Brian T. , Moreno-Razo Jose , de Pablo Juan J.
Published: April 2011

The flow of nematic liquid crystals in tightly confined systems was simulated using a molecular theory and an unsymmetric radial basis function collocation approach. When a nematic liquid crystal is subjected to a cavity flow, we find that moderate flows facilitate the relaxation of the system to the stable defect configuration observed in the absence of flow. Under more extreme flow conditions, e.g., an Ericksen number \documentclass[12pt]{minimal}\begin{document}$\text{Er}=20$\end{document}Er=20, flows can alter the steady-state defect structure observed in the cavity. The proposed numerical method was also used to examine defect annihilation in a thin liquid crystal film. The flows that arise from shear stresses within the system result in a higher velocity for s = +1/2 defect than for the defect of opposing charge. This higher velocity can be attributed to reactive stresses within the deformed liquid crystal, which result in a net flow that favors the motion of one defect. These two examples serve to illustrate the usefulness of radial basis functions methods in the context of liquid crystal dynamics both at and beyond equilibrium.
Quantum size effects in Raman spectra of Si nanocrystals
Authors: Faraci Giuseppe , Gibilisco Santo , Pennisi Agata R. , Faraci Carla
Published: April 2011

First order Raman spectra of Si nanocrystals exhibit large shift and width, strongly exceeding the theoretical calculated values. The disagreement between theory and experiment is dramatically increasing for the smallest nanocrystal sizes. Here, we present a novel theoretical approach showing one-, two-, or three-dimensional quantum effects, due to the limited size of the corresponding coordinate of the quantum structure. The method can be applied to nanosized layers, quantum wires and/or quantum dots. The agreement of the present theory with experimental data is dramatically improved.
Field-emission properties of carbon nanotube composite in side-electron emission configuration
Authors: Kishi Naohiro , Kita Takashi , Magario Akira , Noguchi Toru
Published: April 2011

Field-emission characteristics of a carbon nanotube (CNT)/elastomer composite have been investigated. We performed theoretical calculations of the field distribution in a field emission device structure with the side-electron configuration of the composite sheet. According to the calculation results, the electric field is found to be concentrated at the edge of the composite sheet which leads to an enhancement of the local electric field at the CNT tips protruding from the composite. Furthermore, we calculated the trajectories of emitted electrons. From the obtained results, bright luminescence over 37000 cd/m2 from green phosphor was obtained by optimizing the electrode structure.
Enhanced sensitivity to direct current magnetic field changes in Metglas/Pb(Mg1/3Nb2/3)O3–PbTiO3 laminates
Authors: Gao Junqi , Shen Liangguo , Wang Yaojing , Gray David , Li Jiefang , Viehland D.
Published: April 2011

We have developed Metglas/Pb(Mg1/3Nb2/3)O3–PbTiO3 magnetoelectric (ME) laminates that have notably larger ME coefficients, with maximum values of up to 45 V/cm Oe. Based on this giant ME effect, the dc magnetic field sensitivity for Metglas/PMN–PT laminate sensors was improved by a factor of > 3, relative to that for Metglas/Pb(Zr,Ti)O3 (PZT)-based ones of the same geometry. Our new ME sensor can detect dc magnetic field changes as small as (i) 5 nT at 1 kHz and (ii) 1 nT near the resonant frequency in a shield chamber.
Evaluation of the Faraday angle by numerical methods and comparison with the Tore Supra and JET polarimeter electronics
Authors: Brault C. , Gil C. , Boboc A. , Spuig P. ,   JET-EFDA Contributors
Published: April 2011

On the Tore Supra tokamak, a far infrared polarimeter diagnostic has been routinely used for diagnosing the current density by measuring the Faraday rotation angle. A high precision of measurement is needed to correctly reconstruct the current profile. To reach this precision, electronics used to compute the phase and the amplitude of the detected signals must have a good resilience to the noise in the measurement. In this article, the analogue card's response to the noise coming from the detectors and their impact on the Faraday angle measurements are analyzed, and we present numerical methods to calculate the phase and the amplitude. These validations have been done using real signals acquired by Tore Supra and JET experiments. These methods have been developed to be used in real-time in the future numerical cards that will replace the Tore Supra present analogue ones
Electronic-grade GaN(0001)/Al2O3(0001) grown by reactive DC-magnetron sputter epitaxy using a liquid Ga target
Authors: Junaid M. , Hsiao C.-L. , Palisaitis J. , Jensen J. , Persson P. O. Å. , Hultman L. , Birch J.
Published: April 2011

Electronic-grade GaN (0001) epilayers have been grown directly on Al2O3 (0001) substrates by reactive direct-current-magnetron sputter epitaxy (MSE) using a liquid Ga sputtering target in an Ar/N2 atmosphere. The as-grown GaN epitaxial films exhibit low threading dislocation density on the order of ≤1010 cm−2 determined by transmission electron microscopy and modified Williamson–Hall plot. X-ray rocking curve shows narrow full-width at half maximum (FWHM) of 1054 arc sec of the 0002 reflection. A sharp 4 K photoluminescence peak at 3.474 eV with a FWHM of 6.3 meV is attributed to intrinsic GaN band edge emission. The high structural and optical qualities indicate that MSE-grown GaN epilayers can be used for fabricating high-performance devices without the need of any buffer layer.
Magnetoresistance signature of resonant states in electromigrated Ni nanocontacts
Authors: Beaufrand J.-B. , Dayen J.-F. , Kemp N. T. , Sokolov A. , Doudin B.
Published: April 2011

Fundamental insight is reported into magnetoresistance properties of ballistic-type atomic size Ni nanojunctions obtained at low temperatures. Feedback-controlled electromigration was used to reveal the ballistic nature of the transport and stabilize samples of conductance values in the range of G0 (G0=2e2/h). Bias voltage dependent measurements identify a clear magnetoresistance fingerprint of resonant tunneling, revealing that localized states in the nanojunctions can be responsible for nonlinear behavior in the IV curves and the related magnetoresistance properties.
Al
0.44
Ga
0.56
N
spacer layer to prevent electron accumulation inside barriers in lattice-matched InAlN/AlGaN/AlN/GaN heterostructures
Authors: Akazawa M. , Gao B. , Hashizume T. , Hiroki M. , Yamahata S. , Shigekawa N.
Published: April 2011

The barrier structure in lattice-matched InAlN/GaN heterostructures with AlGaN-based spacer layers grown by metal organic vapor phase epitaxy was studied by the capacitance-voltage (C-V) method. To investigate the characteristics under positive bias, an Al2O3 overlayer was added. The C-V characteristic of a sample with an Al0.38Ga0.62N (5 nm)/AlN (0.75 nm) double spacer layer exhibited an anomalous saturation at a value far below the insulator capacitance under positive bias, which indicated electron accumulation at the InAlN/AlGaN interface. The C-V characteristic of an alternative sample with a single Al0.44Ga0.56N (1.5 nm) spacer layer did not exhibit the anomalous saturation.
UV-B-induced stomatal closure occurs via ethylene-dependent NO generation in Vicia faba
Authors: He Jun-Min , Zhang Zhan , Wang Rui-Bin , Chen Yi-Ping
Published: April 2011

The role of ethylene and the relationship between ethylene and nitric oxide (NO) in ultraviolet B (UV-B)-induced stomatal closure were investigated in Vicia faba L. (broad bean) plants by epidermal strip bioassay, laser-scanning confocal microscopy and assay of ethylene production. In response to UV-B radiation, the rise of NO level in guard cells was after ethylene evolution peak, but preceded stomatal closure. Both UV-B-induced NO generation in guard cells and subsequent stomatal closure were substantially inhibited not only by NO scavenger and nitrate reductase (NR) inhibitors, but also by interfering with ethylene synthesis or perception. Although exogenous NO could reverse the inhibitive effect of interfering with ethylene synthesis or perception on UV-B-induced stomatal closure, the inhibitive effect of NO scavenger and NR inhibitors on UV-B-induced stomatal closure could not be rescued by exogenous ethylene. Taken together, our results clearly show that ethylene participates in the UV-B-induced stomatal closure and acts upstream of the NR source of NO generation in V. faba.
Density of positive Lyapunov exponents for 𝑆𝐿(2,ℝ)-cocycles
Authors: Avila Artur
Published: April 2011

We show that

S
L

(
2
,

R

)

\mathrm {SL}(2,\mathbb {R})

-cocycles with a positive Lyapunov exponent are dense in all regularity classes and for all non-periodic dynamical systems. For Schrödinger cocycles, we show prevalence of potentials for which the Lyapunov exponent is positive for a dense set of energies.
Gentisate and 3-oxoadipate pathways in the yeast Candida parapsilosis: identification and functional analysis of the genes coding for 3-hydroxybenzoate 6-hydroxylase and 4-hydroxybenzoate 1-hydroxylase
Authors: Holesova Zuzana , Jakubkova Michaela , Zavadiakova Ivana , Zeman Igor , Tomaska Lubomir , Nosek Jozef
Published: April 2011

The pathogenic yeast Candida parapsilosis degrades various hydroxy derivatives of benzenes and benzoates by the gentisate and 3-oxoadipate pathways. We identified the genes MNX1, MNX2, MNX3, GDX1, HDX1 and FPH1 that code for enzymes involved in these pathways in the complete genome sequence of C. parapsilosis. Next, we demonstrated that MNX1, MNX2, MNX3 and GDX1 are inducible and transcriptionally controlled by hydroxyaromatic substrates present in cultivation media. Our results indicate that MNX1 and MNX2 code for flavoprotein monooxygenases catalysing the first steps in the 3-oxoadipate and gentisate pathways, respectively (i.e. 4-hydroxybenzoate 1-hydroxylase and 3-hydroxybenzoate 6-hydroxylase). Moreover, we found that the two pathways differ by their intracellular localization. The enzymes of the 3-oxoadipate pathway, Mnx1p and Mnx3p, localize predominantly in the cytosol. In contrast, intracellular localization of the components of the gentisate pathway, Mnx2p and Gdx1p, depends on the substrate in the cultivation medium. In cells growing on glucose these proteins localize in the cytosol, whereas in media containing hydroxyaromatic compounds they associate with mitochondria. Finally, we showed that the overexpression of MNX1 or MNX2 increases the tolerance of C. parapsilosis cells to the antifungal drug terbinafine.
Genomic analysis of the type VI secretion systems in Pseudomonas spp.: novel clusters and putative effectors uncovered
Authors: Barret Matthieu , Egan Frank , Fargier Emilie , Morrissey John P. , O’Gara Fergal
Published: April 2011

Bacteria encode multiple protein secretion systems that are crucial for interaction with the environment and with hosts. In recent years, attention has focused on type VI secretion systems (T6SSs), which are specialized transporters widely encoded in Proteobacteria. The myriad of processes associated with these secretion systems could be explained by subclasses of T6SS, each involved in specialized functions. To assess diversity and predict function associated with different T6SSs, comparative genomic analysis of 34 Pseudomonas genomes was performed. This identified 70 T6SSs, with at least one locus in every strain, except for Pseudomonas stutzeri A1501. By comparing 11 core genes of the T6SS, it was possible to identify five main Pseudomonas phylogenetic clusters, with strains typically carrying T6SSs from more than one clade. In addition, most strains encode additional vgrG and hcp genes, which encode extracellular structural components of the secretion apparatus. Using a combination of phylogenetic and meta-analysis of transcriptome datasets it was possible to associate specific subsets of VgrG and Hcp proteins with each Pseudomonas T6SS clade. Moreover, a closer examination of the genomic context of vgrG genes in multiple strains highlights a number of additional genes associated with these regions. It is proposed that these genes may play a role in secretion or alternatively could be new T6S effectors.
Differential genome-wide profiling of tandem 3′ UTRs among human breast cancer and normal cells by high-throughput sequencing
Authors: Fu Yonggui , Sun Yu , Li Yuxin , Li Jie , Rao Xingqiang , Chen Chong , Xu Anlong
Published: April 2011

Tandem 3′ UTRs produced by alternative polyadenylation (APA) play an important role in gene expression by impacting mRNA stability, translation, and translocation in cells. Several studies have investigated APA site switching in various physiological states; nevertheless, they only focused on either the genes with two known APA sites or several candidate genes. Here, we developed a strategy to study APA sites in a genome-wide fashion with second-generation sequencing technology which could not only identify new polyadenylation sites but also analyze the APA site switching of all genes, especially those with more than two APA sites. We used this strategy to explore the profiling of APA sites in two human breast cancer cell lines, MCF7 and MB231, and one cultured mammary epithelial cell line, MCF10A. More than half of the identified polyadenylation sites are not included in human poly(A) databases. While MCF7 showed shortening 3′ UTRs, more genes in MB231 switched to distal poly(A) sites. Several gene ontology (GO) terms and pathways were enriched in the list of genes with switched APA sites, including cell cycle, apoptosis, and metabolism. These results suggest a more complex regulation of APA sites in cancer cells than previously thought. In short, our novel unbiased method can be a powerful approach to cost-effectively investigate the complex mechanism of 3′ UTR switching in a genome-wide fashion among various physiological processes and diseases.
The availability and age‐appropriateness of medicines authorized for children in the Netherlands
Authors: van Riet‐Nales Diana A. , de Jager Karin E. , Schobben Alfred F.A.M. , Egberts Toine C.G. , Rademaker Carin M.A.
Published: April 2011

WHAT IS ALREADY KNOWN ABOUT THIS SUBJECT

• Children are entitled to safe, efficacious, child and parent friendly (i.e. age‐appropriate) medicines. However, off‐label and unlicensed paediatric prescription rates in hospital range from 36% (surgical and medical wards) to 93% (neonatal wards), which indicates a general lack of age‐appropriate medicines for children. In 2007, the European Union issued the Paediatric Regulation aiming at better medicines for children by, for example, increasing the number of authorized paediatric medicines.

WHAT THIS STUDY ADDS

• This study reviews the availability and age‐appropriateness of medicines for children in the Netherlands, herewith providing a baseline for an estimation of the effect of the European Paediatric Regulation in the near future. This study also provides a tool for the evaluation of the child authorization status of medicines on the basis of the information in the Summary of Product Characteristics (SPC) and for the assessment of key aspects of the age‐appropriateness of paediatric formulations.

AIM To study the number of medicines and active chemical entities that are authorized and commercially available for children in the Netherlands and to evaluate the age‐appropriateness of the available paediatric medicines.

METHODS The availability of paediatric medicines and active chemical entities was studied with the help of a Dutch medicines database and the Summary of Product Characteristics. Medicines were categorized with respect to their route of administration, type of oral dosage form and therapeutic category. The age‐appropriateness was assessed on three aspects: dose capability, suitability of the dosage form and inclusion of potentially harmful excipients.

RESULTS Three thousand five hundred and forty‐two paediatric medicines containing 703 different active chemical entities were identified. This equalled half of all the medicines and chemical entities available for human use. The percentage of paediatric medicines increased with age and varied for the route of administration from 22% (dermal) to 81% (inhalation) and for the therapeutic category from 11% (uro‐genital, sex hormones) to 89% (anti‐parasites). The appropriateness of the paediatric medicines with respect to their authorization status, dose capability and dosage form increased with age from 27–88%. Fifty‐two percent of all oral paediatric liquid formulations contained a potentially harmful excipient.

CONCLUSION This study confirms the limited availability of paediatric medicines for a broad range of therapeutic areas and shows that paediatric medicines may not be age‐appropriate, even if authorized. While confirming the need for a legislative incentive, the results also provide baseline information for an estimation of the effect of the European Paediatric Regulation in the near future.
An accessory protein required for anchoring and assembly of amyloid fibres in B. subtilis biofilms
Authors: Romero Diego , Vlamakis Hera , Losick Richard , Kolter Roberto
Published: April 2011

Cells within Bacillus subtilis biofilms are held in place by an extracellular matrix that contains cell‐anchored amyloid fibres, composed of the amyloidogenic protein TasA. As biofilms age they disassemble because the cells release the amyloid fibres. This release appears to be the consequence of incorporation of d‐tyrosine, d‐leucine, d‐tryptophan and d‐methionine into the cell wall. Here, we characterize the in vivo roles of an accessory protein TapA (TasA anchoring/assembly protein; previously YqxM) that serves both to anchor the fibres to the cell wall and to assemble TasA into fibres. TapA is found in discrete foci in the cell envelope and these foci disappear when cells are treated with a mixture of d‐amino acids. Purified cell wall sacculi retain a functional form of this anchoring protein such that purified fibres can be anchored to the sacculi in vitro. In addition, we show that TapA is essential for the proper assembly of the fibres. Its absence results in a dramatic reduction in TasA levels and what little TasA is left produces only thin fibres that are not anchored to the cell.
Do pH changes in the leaf apoplast contribute to rapid inhibition of leaf elongation rate by water stress? Comparison of stress responses induced by polyethylene glycol and down‐regulation of root hydraulic conductivity
Authors: EHLERT CHRISTINA , PLASSARD CLAUDE , COOKSON SARAH JANE , TARDIEU FRANÇOIS , SIMONNEAU THIERRY
Published: April 2011

We have dissected the influences of apoplastic pH and cell turgor on short‐term responses of leaf growth to plant water status, by using a combination of a double‐barrelled pH‐selective microelectrodes and a cell pressure probe. These techniques were used, together with continuous measurements of leaf elongation rate (LER), in the (hidden) elongating zone of the leaves of intact maize plants while exposing roots to various treatments. Polyethylene glycol (PEG) reduced water availability to roots, while acid load and anoxia decreased root hydraulic conductivity. During the first 30 min, acid load and anoxia induced moderate reductions in leaf growth and turgor, with no effect on leaf apoplastic pH. PEG stopped leaf growth, while turgor was only partially reduced. Rapid alkalinization of the apoplast, from pH 4.9 ± 0.3 to pH 5.8 ± 0.2 within 30 min, may have participated to this rapid growth reduction. After 60 min, leaf growth inhibition correlated well with turgor reduction across all treatments, supporting a growth limitation by hydraulics. We conclude that apoplastic alkalinization may transiently impair the control of leaf growth by cell turgor upon abrupt water stress, whereas direct hydraulic control of growth predominates under moderate conditions and after a 30–60 min delay following imposition of water stress.
The growth of a profession — the strengthening of a voice
Authors: ROBERTSON SANDRA J
Published: April 2011

ABSTRACT  This paper is presented by way of a celebration of the Golden Jubilee of the Royal College of Speech and Language Therapists and is designed to inform delegates to the Conference of some important aspects of the history of the College. The paper will briefly trace the history of the profession in the UK before the establishment of the College and then will identify some of the milestones in the growth and development of the profession and the professional body since its foundation in 1945. Membership of the College has grown steadily throughout its lifetime from a few hundred members to a current membership of almost 7000. The administrative centre of the College has grown accordingly from one part‐time administrator to an establishment of 15 full‐time office staff, including a Professional Director. Several times in its history the College has outgrown its headquarters and, in 1992, moved into prestigious new offices in central London, near to the heart of central government administration. The voice of the profession has become stronger during this period of time also, and the paper will attempt to highlight some of the ways in which the College has made its voice heard over the years. The paper will reflect on the part played by the founder members of the College and its various Councils over the years. It will also discuss briefly the development of clinical specialisms; the interface with legislative, political and professional bodies; the development of education and training; the establishment and publication of professional standards; and the development of research. The author and presenter of the paper is currently engaged in writing a brief history of the College and it is hoped that the publication of this book will coincide with the Golden Jubilee Conference.
Speech and language therapists as reflective practitioners
Authors: REA PRISCILLA , RYAN SHEILA
Published: April 2011

ABSTRACT  Continuing professional development (CPD) is now an integral part of every speech and language therapist's working life and an essential requirement for annual practitioner registration. Traditional taught courses can be a useful part of this process. However, research has shown that the development of a reflective practitioner approach (Schon, 1983), which enhances learning from taught courses, enables the skills and knowledge developed to be transferred to clinical practice in an evaluative manner rather than by rote. In addition, reflection forces practitioners to evaluate their effectiveness in daily practice. The use of a ‘learning journal’ could assist speech and language therapists (SLTs) to reflect on and critically evaluate formal learning and their own clinical experiences. This approach includes the facility to prioritise relevant management information and the practitioner's recognition of the need to change. By use of a variety of examples drawn from the fields of management self‐development and education, the authors argue that the use of their learning journal model, developed for CPD, integrates individual and organisational development to optimum effect (Attwood & Minett, in Burgoyne, Pedlar & Boydell, 1994) and should result in four main outcomes: (1) self‐development; (2) objective setting in performance review (Armstrong, 1994); (3) contributions to clinical knowledge using an action research/case study‐based methodology; (4) production of data to inform providers and purchases of SLT services. The paper explains the way in which the structure of the learning journal leads to the above four outcomes, supported by findings from an inquiry into the use of this model in SLT services within both community and hospital NHS Trusts.
An outcome measure for speech and language therapists
Authors: JOHN ALEXANDRA , ENDERBY PAMELA , SLOAN MARINA
Published: April 2011

ABSTRACT  One aspect of the introduction of the National Health Service (NHS) internal market is the need to target finite funds as effectively as possible. Information from data collection is being used as one means for judging whether purchasers should buy services and, if so, which services. Presently, data collection concentrates on recording inputs, throughputs and so on. Whilst the effectiveness of routine interventions has proved difficult to measure, such measurements are nevertheless necessary because outcomes form an important part of the cycle of quality assurance. In speech and language therapy, single measures of outcome, such as standard tests, have proved inadequate; rather, multiple measures are required, reflecting change in those areas targeted for treatment. Work is required in further developing the methodology to measure outcomes. An example of such a methodology is being developed, based on work by Enderby (1992).