bluuebunny/crossref_metadata_2025 huggingface dataset:
5‐HT4‐elicited positive inotropic response is mediated by cAMP and regulated by PDE3 in failing rat and human cardiac ventricles
Authors: Afzal F , Andressen K W , Mørk H K , Aronsen J M , Sjaastad I , Dahl C P , Skomedal T , Levy F O , Osnes J‐B , Qvigstad E
Published: August 2008

Background and purpose:

The left ventricle in failing hearts becomes sensitive to 5‐HT parallelled by appearance of functional Gs‐coupled 5‐HT4receptors. Here, we have explored the regulatory functions of phosphodiesterases in the 5‐HT4receptor‐mediated functional effects in ventricular muscle from failing rat and human heart.

Experimental approach:

Extensive myocardial infarctions were induced by coronary artery ligation in Wistar rats. Contractility was measured in left ventricular papillary muscles of rat, 6 weeks after surgery and in left ventricular trabeculae from explanted human hearts. cAMP was quantified by RIA.

Key results:

In papillary muscles from postinfarction rat hearts, 5‐HT4stimulation exerted positive inotropic and lusitropic effects and increased cAMP. The inotropic effect was increased by non‐selective PDE inhibition (IBMX, 10 μM) and selective inhibition of PDE3 (cilostamide, 1 μM), but not of PDE2 (EHNA, 10 μM) or PDE4 (rolipram, 10 μM). Combined PDE3 and PDE4 inhibition enhanced inotropic responses beyond the effect of PDE3 inhibition alone, increased the sensitivity to 5‐HT, and also revealed an inotropic response in control (sham‐operated) rat ventricle. Lusitropic effects were increased only during combined PDE inhibition. In failing human ventricle, the 5‐HT4receptor‐mediated positive inotropic response was regulated by PDEs in a manner similar to that in postinfarction rat hearts.

Conclusions and implications:

5‐HT4receptor‐mediated positive inotropic responses in failing rat ventricle were cAMP‐dependent. PDE3 was the main PDE regulating this response and involvement of PDE4 was disclosed by concomitant inhibition of PDE3 in both postinfarction rat and failing human hearts. 5‐HT, PDE3 and PDE4 may have pathophysiological functions in heart failure.

British Journal of Pharmacology(2008)155, 1005–1014; doi:10.1038/bjp.2008.339; published online 1 September 2008
Dexmedetomidine and ST‐91 analgesia in the formalin model is mediated by α2A‐adrenoceptors: a mechanism of action distinct from morphine
Authors: Nazarian A , Christianson C A , Hua X‐Y , Yaksh T L
Published: August 2008

Background and purpose:

Intrathecal administration of α2‐adrenoceptor agonists produces potent analgesia. This study addressed the subtype of spinal α2‐adrenoceptor responsible for the analgesic effects of i.t. dexmedetomidine and ST‐91 in the formalin behavioural model and their effects on primary afferent substance P (SP) release and spinal Fos activation.

Experimental approach:

The analgesic effects of i.t. dexmedetomidine and ST‐91 (α2agonists) were tested on the formalin behavioural model. To determine the subtype of α2‐adrenoceptor involved in the analgesia, i.t. BRL44408 (α2Aantagonist) or ARC239 (α2B/Cantagonist) were given before dexmedetomidine or ST‐91. Moreover, the ability of dexmedetomidine and ST‐91 to inhibit formalin‐induced release of SP from primary afferent terminals was measured by the internalization of neurokinin1(NK1) receptors. Finally, the effects of dexmedetomidine on formalin‐induced Fos expression were assessed in the dorsal horn.

Key results:

Intrathecal administration of dexmedetomidine or ST‐91 dose‐dependently reduced the formalin‐induced paw‐flinching behaviour in rats. BRL44408 dose‐dependently blocked, whereas ARC239 had no effect on the analgesic actions of dexmedetomidine and ST‐91. Dexmedetomidine and ST‐91 had no effect on the formalin‐induced NK1receptor internalization, while morphine significantly reduced the NK1receptor internalization. On the other hand, both dexmedetomidine and morphine diminished the formalin‐induced Fos activation. The effect of dexmedetomidine on formalin‐induced Fos activation was reversed by BRL44408, but not ARC239.

Conclusion and implications:

These findings suggest that α2A‐adrenoceptors mediate dexmedetomidine and ST‐91 analgesia. This effect could be through a mechanism postsynaptic to primary afferent terminals, distinct from that of morphine.

British Journal of Pharmacology(2008)155, 1117–1126; doi:10.1038/bjp.2008.341; published online 1 September 2008
Effect of hypouricaemic and hyperuricaemic drugs on the renal urate efflux transporter, multidrug resistance protein 4
Authors: El‐Sheikh A A K , Van Den Heuvel J J M W , Koenderink J B , Russel F G M
Published: August 2008

Background and purpose:

The xanthine oxidase inhibitors allopurinol and oxypurinol are used to treat hyperuricaemia, whereas loop and thiazide diuretics can cause iatrogenic hyperuricaemia. Some uricosuric drugs and salicylate have a bimodal action on urate renal excretion. The mechanisms of action of these hypo‐ and hyperuricaemic drugs on the handling of urate in renal tubules have not been fully elucidated. Recently, we identified the multidrug resistance protein (MRP) 4 as a luminal efflux transporter for urate in the proximal tubule.

Experimental approach:

Here, we studied the effect of these drugs on [14C]urate transport using human embryonic kidney 293 cells overexpressing human MRP4 and in membrane vesicles isolated from these cells.

Key results:

Allopurinol stimulated MRP4‐mediated cellular urate efflux and allopurinol and oxypurinol both markedly stimulated urate transport by MRP4 in membrane vesicles. Bumetanide and torasemide had no effect, whereas furosemide, chlorothiazide, hydrochlorothiazide, salicylate, benzbromarone and sulfinpyrazone inhibited urate transport, at concentrations ranging from nanomolar up to millimolar. Probenecid stimulated urate transport at 0.1 μMand inhibited transport at higher concentrations.

Conclusions and implications:

These data suggest that inhibition of MRP4‐mediated urate efflux by furosemide and thiazide diuretics could have an important function in their hyperuricaemic mechanisms. Furthermore, stimulation of MRP4‐mediated renal urate efflux could be a new mechanism in the hypouricaemic action of allopurinol and oxypurinol. In conclusion, MRP4 may provide a potential target for drugs affecting urate homoeostasis, which needs to be further evaluatedin vivo.

British Journal of Pharmacology(2008)155, 1066–1075; doi:10.1038/bjp.2008.343; published online 25 August 2008
Importance of serum high‐density lipoprotein levels to aortic valvular disease
Authors: Yontar O C , Yilmaz M B
Published: August 2008

British Journal of Pharmacology (2008) 155, 1163; doi:10.1038/bjp.2008.348; published online 1 September 2008
Role of AQP2 during apoptosis in cortical collecting duct cells
Authors: Flamenco Pilar , Galizia Luciano , Rivarola Valeria , Fernandez Juan , Ford Paula , Capurro Claudia
Published: August 2008

Background information. A major hallmark of apoptosis is cell shrinkage, termed apoptotic volume decrease, due to the cellular outflow of potassium and chloride ions, followed by osmotically obliged water. In many cells, the ionic pathways triggered during the apoptotic volume decrease may be similar to that observed during a regulatory volume decrease response under hypotonic conditions. However, the pathways involved in water loss during apoptosis have been largely ignored. It was recently reported that in some systems this water movement is mediated via specific water channels (aquaporins). Nevertheless, it is important to identify whether this is a ubiquitous aspect of apoptosis as well as to define the mechanisms involved. The aim of the present work was to investigate the role of aquaporin‐2 during apoptosis in renal‐collecting duct cells. We evaluated the putative relationship between aquaporin‐2 expression and the activation of the ionic pathways involved in the regulatory volume response.

Results. Apoptosis was induced by incubating cells with a hypertonic solution or with cycloheximide in two cortical collecting duct cell lines: one not expressing aquaporins and the other stably transfected with aquaporin‐2. Typical features of apoptosis were evaluated with different approaches and the water permeability was measured by fluorescence videomicroscopy. Our results show that the rate of apoptosis is significantly increased in aquaporin‐2 cells and it is linked to the rapid activation of volume‐regulatory potassium and chloride channels. Furthermore, the water permeability of cells expressing aquaporin‐2 was strongly reduced during the apoptotic process and it occurs before DNA degradation.

Conclusions. These results let us propose that under apoptotic stimulation aquaporin‐2 would act as a sensor leading to a co‐ordinated activation of specific ionic channels for potassium and chloride efflux, resulting in both more rapid cell shrinkage and more rapid achievement of adequate levels of ions necessary to activate the enzymatic apoptotic cascade.
Multistability, phase diagrams, and intransitivity in the Lorenz-84 low-order atmospheric circulation model
Authors: Freire Joana G. , Bonatto Cristian , DaCamara Carlos C. , Gallas Jason A. C.
Published: August 2008

We report phase diagrams detailing the intransitivity observed in the climate scenarios supported by a prototype atmospheric general circulation model, namely, the Lorenz-84 low-order model. So far, this model was known to have a pair of coexisting climates described originally by Lorenz. Bifurcation analysis allows the identification of a remarkably wide parameter region where up to four climates coexist simultaneously. In this region the dynamical behavior depends crucially on subtle and minute tuning of the model parameters. This strong parameter sensitivity makes the Lorenz-84 model a promising candidate of testing ground to validate techniques of assessing the sensitivity of low-order models to perturbations of parameters.
Standing wave probes for microassembly
Authors: Woody Shane , Nowakowski Bartosz , Bauza Marcin , Smith Stuart
Published: August 2008

A single standing wave sensor was investigated and experiments demonstrated release capability of glass microscale objects. It is shown that this micrometer scale fiber may be employed as miniaturized tweezers able to pick up specimens and routinely release them when the standing wave is energized. Furthermore, it is demonstrated that the standing wave probe has sensing capability. Both phase and magnitude indicate when the specimen releases, and also provide postrelease information such as mass of sphere and its rotation about its own axis or, surprisingly, about the probe fiber. The current experiments investigated only the release forces acting normal to the sphere/fiber contact interface. Some work was performed by changing the virtual tip from a normally applied force to a tangential applied force. In this condition, the specimen was observed to release differently.
Response of polar nanoregions in 68%Pb(Mg1∕3Nb2∕3)O3-32%PbTiO3 to a [001] electric field
Authors: Wen Jinsheng , Xu Guangyong , Stock C. , Gehring P. M.
Published: August 2008

We report neutron diffuse scattering measurements on a single crystal of 68%Pb(Mg1∕3Nb2∕3)O3-32%PbTiO3. Strong diffuse scattering is observed at low temperatures. An external field applied along the [001] direction affects the diffuse scattering in the (HK0) plane significantly, suggesting a redistribution occurs between polar nanoregions of different polarizations perpendicular to the field. By contrast, the [001] field has no effect on the diffuse scattering in the (H0L) and (0KL) zones.
Scanning picosecond tunable laser system for simulating MeV heavy ion-induced charge collection events as a function of temperature
Authors: Laird Jamie Stuart , Chen Yuan , Scheick Leif , Vo Tuan , Johnston Allan
Published: August 2008

A new methodology for using scanning picosecond laser microscopy to simulate cosmic ray induced radiation effects as a function of temperature is described in detail. The built system is centered on diffraction-limited focusing of the output from a broadband (690–960 nm) ultrafast Ti:sapphire Tsunami laser pumped by a 532 nm Millennia laser. An acousto-optic modulator is used to provide pulse picking down to event rates necessary for the technologies and effects under study. The temperature dependence of the charge generation process for ions and photons is briefly reviewed and the need for wavelength tunability is discussed. An appropriate wavelength selection is critical for proper emulation of ion events over a wide temperature range. The system developed is detailed and illustrated by way of example on a deep-submicron complementary metal-oxide semiconductor test structure.
The role of Debye–Hückel electronic energy levels on the thermodynamic properties of hydrogen plasmas including isentropic coefficients
Authors: Capitelli M. , Giordano D. , Colonna G.
Published: August 2008

A comparison between frozen, reactive, and total specific heats calculated by using energy levels derived from Coulomb and Debye–Hückel potentials is reported. Results for hydrogen plasmas in local thermodynamic equilibrium show that the use of Debye–Hückel energy levels increases the frozen specific heat of the mixture up to 40% as compared with the corresponding quantities obtained by using Coulomb energy levels, having an opposite effect on the reactive specific heat. The total specific heat of the plasma (the sum of frozen and reactive contributions) is less affected due to compensation effects. Results for the isentropic coefficient γ=cp∕cv show a similar trend and warn on neglecting the electronic excitation in this coefficient.
Structural properties of GaAsN∕GaAs quantum wells studied at the atomic scale by cross-sectional scanning tunneling microscopy
Authors: Ulloa J. M. , Koenraad P. M. , Hopkinson M.
Published: August 2008

The nitrogen distribution in GaAsN∕GaAs quantum wells (QWs) grown by molecular beam epitaxy is studied on the atomic scale by cross-sectional scanning tunneling microscopy. No nitrogen clustering is observed in the range of N contents studied (between 1.0% and 2.5%, as measured by counting the individual N atoms inside the QW). Nevertheless, the upper interface roughness increases with the amount of N. A residual N concentration in the GaAs barriers is found, which strongly increases with the amount of N in the QW.
Diffraction and IR/Raman data do not prove tetrahedral water
Authors: Leetmaa Mikael , Wikfeldt Kjartan Thor , Ljungberg Mathias P. , Odelius Michael , Swenson Jan , Nilsson Anders , Pettersson Lars G. M.
Published: August 2008

We use the reverse Monte Carlo modeling technique to fit two extreme structure models for water to available x-ray and neutron diffraction data in q space as well as to the electric field distribution as a representation of the OH stretch Raman spectrum of dilue HOD in D2O; the internal geometries were fitted to a quantum distribution. Forcing the fit to maximize the number of hydrogen (H) bonds results in a tetrahedral model with 74% double H-bond donors (DD) and 21% single donors (SD). Maximizing instead the number of SD species gives 81% SD and 18% DD, while still reproducing the experimental data and losing only 0.7–1.8 kJ/mole interaction energy. By decomposing the simulated Raman spectrum we can relate the models to the observed ultrafast frequency shifts in recent pump-probe measurements. Within the tetrahedral DD structure model the assumed connection between spectrum position and H-bonding indicates ultrafast dynamics in terms of breaking and reforming H bonds while in the strongly distorted model the observed frequency shifts do not necessarily imply H-bond changes. Both pictures are equally valid based on present diffraction and vibrational experimental data. There is thus no strict proof of tetrahedral water based on these data. We also note that the tetrahedral structure model must, to fit diffraction data, be less structured than most models obtained from molecular dynamics simulations.
Medium-sized double magic metal clusters: Al@Cu54− and Al@Ag54−
Authors: Gao Yi , Shao Nan , Zeng X. C.
Published: August 2008

Medium-sized double magic metal clusters, Al@Ag54− and Al@Cu54−, are predicted based on unbiased global search and density functional calculation. Both bimetallic core-shell clusters have icosahedral symmetry, and they are much lower in energies than all other low-lying isomers. In contrast, the icosahedral cluster Al@Au54− is a high-energy isomer. Both Al@Ag54− and Al@Cu54− exhibit appreciable gaps between the highest occupied molecular orbital and the lowest unoccupied molecular orbital, and strong spherical aromaticity, which provide two additional evidences for the likelihood of their high stability. The simulated anion photoelectron spectra and optical absorption spectra are readily compared with future experiments.
Composition-limited spectral response of hybrid photovoltaic cells containing infrared PbSe nanocrystals
Authors: Zhu Ting , Berger Alan , Tan Zhanao , Cui Dehu , Xu Jian , Khanchaitit Paisan , Wang Qing
Published: August 2008

We report the effects of composition on the performance, particularly the spectral response, of hybrid photovoltaic cells made of PbSe nanocrystal quantum dot (NQD)/poly-3(hexylthiophene) nanocomposites. Photocurrent measurements under monochromatic and white light illuminations were employed to characterize devices consisting of thin nanocomposite films with different NQD weight percentages. It was found that at different illumination wavelengths, the short-circuit current of the hybrid device responds diversely to the variation in the NQD loading. The finding is correlated to the optical and morphological properties of the nanocomposite films, which can be further linked to the absorption and carrier-transport properties. In addition, the observed power dependence of photocurrent on intensity has revealed the pseudomonomolecular recombination kinetics in the NQD-polymer nanocomposite, indicating that the efficiency of the hybrid photovoltaic cells can be enhanced by reducing the potential barriers formed by ligand molecules at the nanocrystal surfaces.
Abnormal temperature-dependent stability of on-plastic a-Si:H thin film transistors fabricated at 150 °C
Authors: Chen J. Z. , Cheng I.-C.
Published: August 2008

We investigated the temperature-dependent stability on the inverted-staggered back-channel-etched a-Si:H thin film transistors (TFTs) made at a process temperature of 150 °C on plastic foil substrates. The shift of threshold voltage (ΔVt) increases with the stressing time and the stressing temperature. Different from TFTs made at temperatures of 300 °C or above, our low-temperature processed TFTs show an abnormal saturation of ΔVt at 50 °C (323 K) in a constant gate-bias stress experiment. Around the same temperature, we observed abrupt increases in both the gate leakage current and the off current. Because of the low process temperature, the gate dielectric is less stable and more defective compared to that made at high process temperatures. A substantial amount of charges, trapped inside the dielectric during TFT fabrication and gate-bias stressing, was thermionically emitted into the channel by the Poole–Frenkel emission mechanism at a stressing temperature of 50 °C, leading to the abnormal phenomena.
Monodomain alignment of the smectic-A liquid crystalline phase from the isotropic phase
Authors: Reznikov Mitya , Wall Bentley , Handschy Mark A. , Bos Philip J.
Published: August 2008

The liquid crystal alignment method described here provides uniform orientation of otherwise difficult-to-align smectic-A liquid crystal materials lacking a nematic phase. The smectic-A phase is grown in the presence of a 10–20 K/mm temperature gradient from an air bubble located within a cell by a photolithographically defined channel in the cell substrates. We obtain uniform layer alignment in millimeter-wide smectic regions at growth rates below about 0.05 μm/s even though there is a tendency for spontaneous nucleation of focal-conic defects at higher growth rates once the width of the smectic-A region exceeds the critical value of about 20 μm.
In situ studies on the kinetics of formation and crystal structure of In4Sn3O12 using high-energy x-ray diffraction
Authors: González G. B. , Okasinski J. S. , Mason T. O. , Buslaps T. , Honkimäki V.
Published: August 2008

High-energy x-ray diffraction was utilized to study in situ the formation temperature and crystal structure of the rhombohedral phase In4Sn3O12. The kinetics of In4Sn3O12 formation from bixbyite In2O3 and tetragonal SnO2 nanopowders were investigated during isothermal annealing treatments ranging from 1335 to 1400 °C. The transformation data exhibited two regimes, well described with a two-exponent kinetics model. The first regime followed a Johnson–Mehl–Avrami–Kolmogorov (JMAK) behavior until 75% of the In4Sn3O12 phase formed and was modeled with a modified JMAK equation. The formation of the first grains of In4Sn3O12 at 1345 °C was observed in situ using diffraction two-dimensional images. Structural results obtained from Rietveld analysis include atomic positions, phase analysis compositions of the samples, and lattice parameters during heating, cooling, and isothermal conditions. Linear and volume coefficients of thermal expansion were determined for the In4Sn3O12 phase.
Change in the room temperature magnetic property of ZnO upon Mn doping
Authors: Banerjee S. , Rajendran K. , Gayathri N. , Sardar M. , Senthilkumar S. , Sengodan V.
Published: August 2008

We present in this paper the changes in the room temperature magnetic property of ZnO on Mn doping prepared using solvothermal process. The zero field cooled (ZFC) and field cooled (FC) magnetization of undoped ZnO showed bifurcation and magnetic hysteresis at room temperature. Upon Mn doping the magnetic hysteresis at room temperature and the bifurcation in ZFC-FC magnetization vanish. The results seem to indicate that undoped ZnO is ferromagnetic while on the other hand the Mn doped ZnO is not a ferromagnetic system. We observe that on addition of Mn atoms the system shows antiferromagnetism with very giant magnetic moments.
Wigner oscillators, twisted Hopf algebras, and second quantization
Authors: Castro P. G. , Chakraborty B. , Toppan F.
Published: August 2008

By correctly identifying the role of the central extension in the centrally extended Heisenberg algebra h, we show that it is indeed possible to construct a Hopf algebraic structure on the corresponding enveloping algebra U(h) and eventually deform it through the Drinfeld twist. This Hopf algebraic structure and its deformed version UF(h) are shown to be induced from a more “fundamental” Hopf algebra obtained from the Schrödinger field/oscillator algebra and its deformed version provided that the fields/oscillators are regarded as odd elements of a given superalgebra. We also discuss the possible implications in the context of quantum statistics.
Local strain measurement in a strain-engineered complementary metal-oxide-semiconductor device by geometrical phase analysis in the transmission electron microscope
Authors: Chung Jayhoon , Lian Guoda , Rabenberg Lew
Published: August 2008

Local strains in the channel and source/drain (S/D) of an advanced complementary metal-oxide-semiconductor device were measured by the geometric phase analysis applied to high resolution transmission electron microscope images. Two-dimensional strain maps were reconstructed for a 45nm p-type metal-oxide-semiconductor device which was strain-engineered using a recessed Si0.82Ge0.18 S/D. Lateral strains were uniform across the channel but vertical strains were found to vary considerably in the channel. Measured strains were used to estimate stresses and hole mobility enhancements.
Solutions for confluent and double-confluent Heun equations
Authors: El-Jaick Léa Jaccoud , Figueiredo Bartolomeu D. B.
Published: August 2008

This paper examines some solutions for confluent and double-confluent Heun equations. In the first place, we review two Leaver’s solutions in series of regular and irregular confluent hypergeometric functions for the confluent equation [Leaver, E. W., J. Math. Phys. 27, 1238 (1986)] and introduce an additional expansion in series of irregular confluent hypergeometric functions. Then, we find the conditions under which one of these solutions can be written as a linear combination of the others. In the second place, by means of limiting procedures we generate solutions for the double-confluent equation as well as for special limits of both the confluent and double-confluent equations. Finally, we present some problems which are ruled by one or the other of these four equations.
The electronic and transport properties of a molecular junction studied by an integrated piecewise thermal equilibrium approach
Authors: Tsai M.-H. , Lu T.-H. , Tang Y.-H.
Published: August 2008

An integrated piecewise thermal equilibrium approach based on the first-principles calculation method has been developed to calculate bias dependent electronic structures and current- and differential conductance-voltage characteristics of the gold-benzene-1,4-dithiol-gold molecular junction. The calculated currents and differential conductance have the same order of magnitude as experimental ones. An electron transfer was found between the two electrodes when a bias is applied, which renders the two electrodes to have different local electronic structures. It was also found that when Au 5d electrons were treated as core electrons the calculated currents were overestimated, which can be understood as an underestimate of the Au–S covalent bonding and consequently the contact potential barrier and the replacement of delocalized Au 5d carriers by more itinerant delocalized Au 6sp carriers in the electrodes.
Enhanced broadband near-infrared emission from Bi-doped glasses by codoping with metal oxides
Authors: Qian Q. , Zhang Q. Y. , Yang G. F. , Yang Z. M. , Jiang Z. H.
Published: August 2008

An intense broadband and flat 1.3 μm emission from Bi-doped germanate glass has been measured upon excitation with a commercial laser diode, which makes the glasses more attractive for their use in broadband optical fiber amplifiers. The 1.3 μm emission exhibits a distinctive fine luminescence shape with four bands centered at 1225, 1320, 1370, and 1390 nm, respectively. It is noted that the addition of CeO2 (2 mol %), As2O5 (2 mol %), or Y2O3 (1 mol %) into Bi-doped glasses could remarkably enhance the luminescence intensity by a factor of 4, 12, and 23, respectively. Whereas, no luminescence has been observed for the glass prepared under a controlled redox condition. The optical properties of the Bi-doped glasses and the possible mechanism involved have been explained.
A compact, portable pulse forming line
Authors: Xia Liansheng , Zhang Huang , Shi Jinshui , Zhang Linwen , Deng Jianjun , Liu Hanxing , Cao Minhe
Published: August 2008

Some research has been done on making a compact, portable pulse forming line. A kind of ceramic based on SrTiO3 is used as the dielectric of the planar pulse forming line. The ceramic’s dielectric constant is around 300 and can store more energy than water with the same volume. However, it is not easy to manufacture the large ceramic bulk but we did successfully manufacture 80×10×6 cm3 ceramic bulks. Using this kind of ceramic bulk as the dielectric, we successfully made a compact, portable line that generated a voltage pulse up to 150 kV with a duration of about 92 ns.
Investigation of the nanomechanical properties in relation to the microstructure of Zn1−xBexTe alloys
Authors: Grillo S. E. , Glénat H. , Tite T. , Pages O. , Maksimov O. , Tamargo M. C.
Published: August 2008

A study by nanoindentation has been performed to investigate the variation of the mechanical properties of Zn1−xBexTe alloys as a function of the beryllium content in the range 0≤x≤0.84. Our data show a very marked increase of hardness (H) and a significant increase of the elastic modulus (E) with Be concentration. These trends are related to an increase in the stiffness of the BeTe bond relative to that of the ZnTe bond. Furthermore, discontinuities are unambiguously revealed in the variations of both H and E at the critical Be content of ∼20%. We relate these to Raman studies of the layers’ microstructure and propose an explanation in terms of a percolative behavior.
Carbon reaction and diffusion on Ni(111), Ni(100), and Fe(110): Kinetic parameters from x-ray photoelectron spectroscopy and density functional theory analysis
Authors: Wiltner A. , Linsmeier Ch. , Jacob T.
Published: August 2008

This paper investigates the reactivity of elemental carbon films deposited from the vapor phase with Fe and Ni substrates at room temperature. X-ray photoelectron spectroscopy (XPS) measurements are presented as a method for evaluating kinetic reaction data. Carbon films are deposited on different surface orientations representing geometries from a dense atom packing as in fcc (111) to an open surface structure as in fcc (100). During annealing experiments several reactions are observed (carbon subsurface diffusion, carbide formation, carbide decomposition, and graphite ordering). These reactions and the respective kinetic parameters are analyzed and quantified by XPS measurements performed while annealing at elevated temperatures (620–820 K). The resulting activation barriers for carbon subsurface diffusion are compared with calculated values using the density functional theory. The determined kinetic parameters are used to reproduce the thermal behavior of carbon films on nickel surfaces.
Two-dimensional micron-step probe drive for laboratory plasma measurement
Authors: Collette A. , Gekelman W.
Published: August 2008

Laboratory measurement of small-scale (∼1mm) magnetic phenomena over an extended area is a challenge requiring precise diagnostics. We present a novel two dimensional magnetic probe platform capable of directly measuring the magnetic field over a 36cm2 region at spatial resolutions better than 1mm. The platform is discussed in the context of an experiment at the Large Plasma Device facility at UCLA, designed to measure the magnetic interaction between two counterpropagating laser-produced plasmas. The use of a precise, repeatable positioning platform enables the recovery of information about the interaction using cross-correlation techniques.
A device for calibrating Rogowski coils in time domain
Authors: Lu Liang , Huang Jianjun , Li Yanming
Published: August 2008

In this article a device for calibrating Rogowski coils in time domain is designed, which can obtain the sensitivity and dynamic response of the Rogowski coil by means of measuring currents of long pulse durations and few nanoseconds rise time. Its key device is a current step wave generator, which can generate the output with rise time of <3ns and with duration time of >300ns.
Nanoparticle coagulation in fractionally charged and charge fluctuating dusty plasmas
Authors: Nunomura Shota , Shiratani Masaharu , Koga Kazunori , Kondo Michio , Watanabe Yukio
Published: August 2008

The kinetics of nanoparticle coagulation has been studied in fractionally charged and charge fluctuating dusty plasmas. The coagulation occurs when the mutual collision frequency among nanoparticles exceeds their charging and decharging/neutralization frequency. Interestingly, the coagulation is suppressed while a fraction (several percent) of nanoparticles are negatively charged in a plasma, in which stochastic charging plays an important role. A model is developed to predict a phase diagram of the coagulation and its suppression.
Modal versus energy stability analysis of kinematic dynamos in cylindrical configurations
Authors: Normand C.
Published: August 2008

The kinematic dynamo problem is solved in a cylindrical geometry using Galerkin expansions of the magnetic field components. The difference with the modal Galerkin analysis [L. Marié et al., Phys. Fluids 18, 017102 (2006)] concerns the weighting functions which here belong to the same set as the trial functions. The new procedure allows to determine the magnetic Reynolds number RmE for energy growth. Lower bounds on the value of RmE are derived for magnetic modes of azimuthal wavenumber m. Using a variational principle, more accurate values of RmE are obtained in the case of helical flows. It is found that the threshold value for the axisymmetric magnetic mode m=0 is slightly higher than its value for the antisymmetric mode m=1. Although excluded by Cowling’s theorem the mode m=0 exhibits transient energy growth and could play a role in the nonlinear equilibration of cylindrical dynamos.
Rhombohedral-to-tetragonal phase transformation and thermal depolarization in relaxor-based ferroelectric single crystal
Authors: Chang W. S. , Lim L. C. , Yang P. , Tu C.-S.
Published: August 2008

The rhombohedral-to-tetragonal (R-T) transformation in relaxor single crystals occurs over a temperature range, manifested by the coexistence of rhombohedral (R) and tetragonal (T) microscopic and nanotwin domains, a string of thermal current signals, and continued degradation of dielectric and electromechanical properties. Thermal current and high-resolution x-ray diffraction results suggest TRT≅100–135 °C for [001]-poled PZN-4.5%PT and 90–115 °C for [001]-poled PZN-7%PT. The “TRT” determined from the dielectric permittivity-temperature plot of poled crystals corresponds to the lower bound of TRT, which is also a good indication of the depolarization temperature (TDP) of relaxor ferroelectric single crystals above which perceptible property degradation begins.
Photonic crystal fiber microtaper supporting two selective higher-order modes with high sensitivity to gas molecules
Authors: Monzón-Hernández D. , Minkovich Vladimir P. , Villatoro Joel , Kreuzer Mark P. , Badenes Gonçal
Published: August 2008

A photonic crystal fiber consisting of three rings of air holes was tapered down to 3–5μm. The voids of the fiber were collapsed so a solid microtaper was formed. In this microtaper two selective higher-order modes propagate and interfere. This makes the transmission of the taper to exhibit a sinusoidal pattern with subnanometric width fringes. It was found that the device was highly sensitive to gas molecules. The latter is attributed to surface refractive index changes, number of molecules enveloping the taper, and high sensitivity of the modes participating in the interference.
Band-edge emission enhancement by longitudinal stress field in GaN
Authors: Cai Duanjun , Kang Junyong , Gibart Pierre , Beaumont Bernard , Sekiguchi Takachi , Ito Shun
Published: August 2008

Bright ultraviolet luminescence in the wing region of epitaxial-lateral-overgrowth GaN was studied by cathodoluminescence. Analysis of dislocation bending and movement by transmission electron microscopy demonstrates the emergence of another longitudinal stress field, which effectively enhances the band-edge light emission. Ab initio calculations of interband transition probability provide a model showing that introduction of appropriate additional stress component in the longitudinal direction of GaN will improve the efficiency of band-edge emission.
Direct visualization of dipolar ferromagnetic domain structures in Co nanoparticle monolayers by electron holography
Authors: Yamamoto Kazuo , Majetich Sara A. , McCartney Martha R. , Sachan Madhur , Yamamuro Saeki , Hirayama Tsukasa
Published: August 2008

Electron holography has revealed dipolar ferromagnetic domain structures in ordered monolayer arrays of Co nanoparticles. In zero-field-cooling experiments, we demonstrate the formation of micron-sized magnetically ordered regions with transverse domain walls, and a spatially varying moment order parameter. Truncated vortex structures that can be modified by an applied field are observed near the sample edges. The collectively magnetized state shows soft magnetic properties and long-range order that is stable over times over 1h at 108K.
Tunable anisotropic nonlinearity in superconductors with asymmetric antidot array
Authors: Aladyshkin A. Yu. , Van de Vondel J. , de Souza Silva C. C. , Moshchalkov V. V.
Published: August 2008

The influence of the spatial asymmetry of the pinning potential on the spectral composition of the voltage, induced in perforated superconducting Al bridges by the injection of a sinusoidal bias current, was investigated. The loss of the mirror symmetry of the pinning potential leads to the appearance of even Fourier components in the induced voltage in the vicinity of the superconducting phase transition line on the H-T diagram (H is the external magnetic field, and T is the temperature). Artificially-introduced asymmetry for vortex motion makes it possible to create low-resistive materials, in which nonlinearity depends on the direction of injected electrical currents.
Spatially limited ion acoustic drift soliton in electron-positron-ion magnetoplasma
Authors: Mushtaq A.
Published: August 2008

Ion acoustic drift solitary wave with intermediate parametric range in both linear and nonlinear regimes has been studied in electron-positron-ion magnetoplasma. In the spatially limited region dispersion relation in the linear and Zakharov–Kuznetsov-type equation in the nonlinear regime are derived, respectively. Both equations show the coupling of electrostatic drift and ion acoustic waves. The stationary soliton solution for oblique drift solitary waves with the effect of positron concentration and temperature has been discussed analytically and graphically. The results are relevant for astrophysical observations and diagnostics of laboratory electron-positron-ion magnetoplasmas.
Lifetime of organic light emitting diodes on polymer anodes
Authors: Fehse Karsten , Meerheim Rico , Walzer Karsten , Leo Karl , Lövenich Wilfried , Elschner Andreas
Published: August 2008

We report on the use of a thin layer of poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate) (PEDOT:PSS) as anode for bottom emission organic light emitting diodes (OLEDs). The combination of polymer anodes with OLEDs having either electrically doped or undoped hole transport layers in direct contact with the polymer is shown. We discuss the impact of the annealing conditions of the polymer on the OLED lifetime in comparison to indium tin oxide anodes. Supported by a differential thermal analysis of PEDOT:PSS, a strong influence of residual water in the polymer on the device lifetime is found. Additional heating of the polymer anode in a dry ambient prior to OLED deposition is necessary to achieve high device lifetimes. At a luminance of 260 cd/m2, pin-OLEDs on a PEDOT:PSS anode show no measurable device degradation during 5200 h of operation.
GaNAsSb/GaAs waveguide photodetector with response up to 1.6 μm grown by molecular beam epitaxy
Authors: Loke W. K. , Yoon S. F. , Xu Z. , Tan K. H. , Ng T. K. , Sim Y. K. , Wicaksono S. , Saadsaoud N. , Decoster D. , Chazelas J.
Published: August 2008

We present a GaNAsSb/GaAs p-i-n waveguide photodetector operating in the 1.0–1.6 μm wavelength range with enhanced photoresponsivity compared to a top-illuminated photodetector fabricated using the same material system. The device consists of a strained GaNAsSb layer, with N and Sb contents of 3.5% and 18%, respectively, sandwiched between GaAs:Si (n-type) and GaAs:C (p-type) layers. X-ray reciprocal space map of the GaNAsSb layer before device fabrication showed that the film relaxation is ∼1%. At 1.55 μm, photoresponsivities of 0.25 and 0.29 A/W for devices with 6.5 and 10 μm ridge width, respectively, was demonstrated.
Response of subterranean clover, balansa clover, and gland clover to lime when grown in mixtures on an acid soil
Authors: Hayes R. C. , Dear B. S. , Orchard B. A. , Peoples M. B. , Eberbach P. L.
Published: August 2008

This study compared the relative tolerances of subterranean clover (Trifolium subterraneum L.), balansa clover (T. michelianum Savi.), and gland clover (T. glanduliferum Boiss.) to acid soil conditions. Seed yield, seedling density, herbage production, N2 fixation, and herbage mineral composition of the 3 legumes were assessed when grown on an acid soil (pHCa of 4.3 and 15% exchangeable Al [0–0.10 m]) with and without the addition of lime (CaCO3). Annual legume species were sown in a mixed sward together with burr medic (Medicago polymorpha L.), and in mixtures with either lucerne (Medicago sativa L.), chicory (Cichorium intybus L.), or phalaris (Phalaris aquatica L.). Due to drier than average seasonal conditions, none of the perennial species persisted beyond the first summer.
Lime increased the herbage production of annual legumes by 18–22% and total pasture production by 14% in both 2002 and 2003. Subterranean clover was the most tolerant of the annual legumes to acid soil conditions, showing no visible toxicity symptoms and no response to lime in terms of seed yield. In contrast, both balansa and gland clovers exhibited visual symptoms of manganese toxicity in the absence of lime, with Mn concentrations in the shoots of 817 mg/kg and 626 mg/kg, respectively. Both species responded positively to lime with seed yields increasing by 45% and 124%, respectively. Lime increased the proportion of herbage N derived from N2 fixation by subterranean clover from 29 to 40% and by gland clover from 30 to 43%. Lime had no effect on the proportion of N2 fixed by balansa clover (29–31%), suggesting a suboptimal symbiosis of rhizobia with that species. Adding chicory or phalaris to the pasture mix increased sward herbage production in the establishment year by 39% and 21%, respectively. Based on leaf symptoms and herbage yield responses to lime, Mn toxicity was present in lucerne with tissue levels of up to 916 mg/kg, but no symptoms were observed in chicory (1129 mg/kg) or phalaris (403 mg/kg). Chicory and phalaris were more tolerant of acidity and high levels of Mn than lucerne, gland clover, and balansa clover.
The study highlighted the value of the small-seeded annual legumes, balansa clover and gland clover, to the production of mixed pasture swards even in drier than average seasonal conditions. Although more sensitive to acid soils than subterranean clover, they set a greater number of seeds and, in the case of balansa clover, a greater weight of seed under moisture stress in the establishment year than the larger seeded subterranean clover.
Navigating networks by using homophily and degree
Authors: Şimşek Özgür , Jensen David
Published: August 2008

Many large distributed systems can be characterized as networks where short paths exist between nearly every pair of nodes. These include social, biological, communication, and distribution networks, which often display power-law or small-world structure. A central challenge of distributed systems is directing messages to specific nodes through a sequence of decisions made by individual nodes without global knowledge of the network. We present a probabilistic analysis of this navigation problem that produces a surprisingly simple and effective method for directing messages. This method requires calculating only the product of the two measures widely used to summarize all local information. It outperforms prior approaches reported in the literature by a large margin, and it provides a formal model that may describe how humans make decisions in sociological studies intended to explore the social network as well as how they make decisions in more naturalistic settings.
Formation of gullies on Mars: Link to recent climate history and insolation microenvironments implicate surface water flow origin
Authors: Head James W. , Marchant David R. , Kreslavsky Mikhail A.
Published: August 2008

Features seen in portions of a typical midlatitude Martian impact crater show that gully formation follows a geologically recent period of midlatitude glaciation. Geological evidence indicates that, in the relatively recent past, sufficient snow and ice accumulated on the pole-facing crater wall to cause glacial flow and filling of the crater floor with debris-covered glaciers. As glaciation waned, debris-covered glaciers ceased flowing, accumulation zones lost ice, and newly exposed wall alcoves continued as the location for limited snow/frost deposition, entrapment, and preservation. Analysis of the insolation geometry of this pole-facing crater wall, and similar occurrences in other craters at these latitudes on Mars, shows that they are uniquely favored for accumulation of snow and ice, and a relatively more rapid exposure to warmer summer temperatures. We show that, after the last glaciation, melting of residual snow and ice in alcoves could have formed the fluvial channels and sedimentary fans of the gullies. Recent modeling shows that top-down melting can occur in these microenvironments under conditions similar to those currently observed on Mars, if small amounts of snow or frost accumulate in alcoves and channels. Accumulation and melting is even more favored in the somewhat wetter, relatively recent geological past of Mars, after the period of active glaciation.
Structural basis for suppression of a host antiviral response by influenza A virus
Authors: Das Kalyan , Ma Li-Chung , Xiao Rong , Radvansky Brian , Aramini James , Zhao Li , Marklund Jesper , Kuo Rei-Lin , Twu Karen Y. , Arnold Eddy , Krug Robert M. , Montelione Gaetano T.
Published: August 2008

Influenza A viruses are responsible for seasonal epidemics and high mortality pandemics. A major function of the viral NS1A protein, a virulence factor, is the inhibition of the production of IFN-β mRNA and other antiviral mRNAs. The NS1A protein of the human influenza A/Udorn/72 (Ud) virus inhibits the production of these antiviral mRNAs by binding the cellular 30-kDa subunit of the cleavage and polyadenylation specificity factor (CPSF30), which is required for the 3′ end processing of all cellular pre-mRNAs. Here we report the 1.95-Å resolution X-ray crystal structure of the complex formed between the second and third zinc finger domain (F2F3) of CPSF30 and the C-terminal domain of the Ud NS1A protein. The complex is a tetramer, in which each of two F2F3 molecules wraps around two NS1A effector domains that interact with each other head-to-head. This structure identifies a CPSF30 binding pocket on NS1A comprised of amino acid residues that are highly conserved among human influenza A viruses. Single amino acid changes within this binding pocket eliminate CPSF30 binding, and a recombinant Ud virus expressing an NS1A protein with such a substitution is attenuated and does not inhibit IFN-β pre-mRNA processing. This binding pocket is a potential target for antiviral drug development. The crystal structure also reveals that two amino acids outside of this pocket, F103 and M106, which are highly conserved (>99%) among influenza A viruses isolated from humans, participate in key hydrophobic interactions with F2F3 that stabilize the complex.