bluuebunny/crossref_metadata_2025 huggingface dataset:
Regulation of hepatic insulin sensitivity by activating signal co-integrator-2
Authors: Kim Geun Hyang , Lee Kyung Jin , Oh Gyun-Sik , Yoon Jin , Kim Hae Won , Kim Seung-Whan
Published: August 2012

ASC-2 (activating signal co-integrator-2, also known as AIB3 and NCoA6) is a transcriptional co-activator and regulates insulin secretion and β-cell survival. The present study was performed to elucidate the role of ASC-2 in the regulation of insulin sensitivity. Although islet cells from 10-week-old ASC-2+/− mice secreted less insulin than wild-type islets, there was no significant difference in glucose tolerance between ASC-2+/− and wild-type mice. However, ASC-2+/− mice did show increased insulin sensitivity compared with wild-type mice in insulin tolerance tests. Consistently, the levels of phosphorylated Akt were higher in ASC-2+/− hepatocytes than in wild-type hepatocytes after insulin treatment. Moreover, decreases in phosphoenol pyruvate carboxykinase mRNA in refed mice were more prominent in ASC-2+/− livers than in wild-type livers. Interestingly, the expression levels of SOCS1 (suppressor of cytokine signalling 1) and SOCS3, well-known insulin signalling inhibitors, were decreased in ASC-2+/− hepatocytes and increased in ASC-2-overexpressing hepatocytes. Furthermore, ASC-2 was recruited to the promoter region of SOCS1 and potentiated the transcription by SREBP-1c (sterol-regulatory-element-binding protein-1c). This transcription-activating function of ASC-2 was diminished by mutations of SREBP-1c-binding sites in the SOCS1 promoter. Taken together, these results suggest that ASC-2 negatively affects hepatic insulin sensitivity, at least in part, through induction of the insulin signalling inhibitors SOCS1 and SOCS3.
On the mechanism for breaks in the cosmic ray spectrum
Authors: Malkov M. A. , Diamond P. H. , Sagdeev R. Z.
Published: August 2012

The proof of cosmic ray (CR) origin in supernova remnants (SNR) must hinge on full consistency of the CR acceleration theory with the observations; direct proof is impossible because of the orbit stochasticity of CR particles. Recent observations of a number of galactic SNR strongly support the SNR-CR connection in general and the Fermi mechanism of CR acceleration, in particular. However, many SNR expand into weakly ionized dense gases, and so a significant revision of the mechanism is required to fit the data. We argue that strong ion-neutral collisions in the remnant surrounding lead to the steepening of the energy spectrum of accelerated particles by exactly one power. The spectral break is caused by a partial evanescence of Alfven waves that confine particles to the accelerator. The gamma-ray spectrum generated in collisions of the accelerated protons with the ambient gas is also calculated. Using the recent Fermi spacecraft observation of the SNR W44 as an example, we demonstrate that the parent proton spectrum is a classical test particle power law ∝E−2, steepening to E−3 at Ebr≈7 GeV.
Efficient surface formation route of interstellar hydroxylamine through NO hydrogenation. II. The multilayer regime in interstellar relevant ices
Authors: Fedoseev G. , Ioppolo S. , Lamberts T. , Zhen J. F. , Cuppen H. M. , Linnartz H.
Published: August 2012

Hydroxylamine (NH2OH) is one of the potential precursors of complex pre-biotic species in space. Here, we present a detailed experimental study of hydroxylamine formation through nitric oxide (NO) surface hydrogenation for astronomically relevant conditions. The aim of this work is to investigate hydroxylamine formation efficiencies in polar (water-rich) and non-polar (carbon monoxide-rich) interstellar ice analogues. A complex reaction network involving both final (N2O, NH2OH) and intermediate (HNO, NH2O·, etc.) products is discussed. The main conclusion is that hydroxyl-amine formation takes place via a fast and barrierless mechanism and it is found to be even more abundantly formed in a water-rich environment at lower temperatures. In parallel, we experimentally verify the non-formation of hydroxylamine upon UV photolysis of NO ice at cryogenic temperatures as well as the non-detection of NC- and NCO-bond bearing species after UV processing of NO in carbon monoxide-rich ices. Our results are implemented into an astrochemical reaction model, which shows that NH2OH is abundant in the solid phase under dark molecular cloud conditions. Once NH2OH desorbs from the ice grains, it becomes available to form more complex species (e.g., glycine and β-alanine) in gas phase reaction schemes.
Efficient surface formation route of interstellar hydroxylamine through NO hydrogenation. I. The submonolayer regime on interstellar relevant substrates
Authors: Congiu E. , Chaabouni H. , Laffon C. , Parent P. , Baouche S. , Dulieu F.
Published: August 2012

Dust grains in the interstellar medium are known to serve as the first chemical laboratory where the rich inventory of interstellar molecules are synthesized. Here we present a study of the formation of hydroxylamine—NH2OH—via the non-energetic route NO + H (D) on crystalline H2O and amorphous silicate under conditions relevant to interstellar dense clouds. Formation of nitrous oxide (N2O) and water (H2O, D2O) is also observed and the reaction network is discussed. Hydroxylamine and water results are detected in temperature-programmed desorption (TPD) experiments, while N2O is detected by both reflection-absorption IR spectroscopy and TPD techniques. The solid state NO + H reaction channel proves to be a very efficient pathway to NH2OH formation in space and may be a potential starting point for prebiotic species in dark interstellar clouds. The present findings are an important step forward in understanding the inclusion of interstellar nitrogen into a non-volatile aminated species since NH2OH provides a solid state nitrogen reservoir along the whole evolutionary process of interstellar ices from dark clouds to planetary systems.
Nucleation of ethanol, propanol, butanol, and pentanol: A systematic experimental study along the homologous series
Authors: Manka Alexandra A. , Wedekind Jan , Ghosh David , Höhler Kristina , Wölk Judith , Strey Reinhard
Published: August 2012

We present homogeneous vapor-liquid nucleation rates of the 1-alcohols (CnH2n+1OH, n = 2‑4) measured in the well-established two-valve nucleation pulse chamber as well as in a novel one-piston nucleation pulse chamber at temperatures between 235 and 265 K. The nucleation rates and critical cluster sizes show a very systematic behavior with respect to the hydrocarbon chain length of the alcohol, just as their thermo-physical parameters such as surface tension, vapor pressure, and density would suggest. For all alcohols, except ethanol, predictions of classical nucleation theory lie several orders of magnitude below the experimental results and show a strong temperature-dependence typically found in nucleation experiments. The more recent Reguera-Reiss theory [J. Phys. Chem. B 108(51), 19831 (2004)] achieves reasonably good predictions for 1-propanol, 1-butanol, and 1-pentanol, and independent of the temperature. Ethanol, however, clearly shows the influence of strong association between molecules even in the vapor phase. We also scaled all experimental results with classic nucleation theory to compare our data with other data from the literature. We find the same overall temperature trend for all measurement series together but inverted and inconsistent temperature trends for individual 1‑propanol and 1‑butanol measurements in other devices. Overall, our data establishe a comprehensive and reliable data set that forms an ideal basis for comparison with nucleation theory.
Characterization of a scintillating mini-detector for time-of-flight positron emission tomography with depth-of-interaction
Authors: Cosentino Luigi , Finocchiaro Paolo , Pappalardo Alfio , Garibaldi Franco
Published: August 2012

By exploiting a suitable treatment of the scintillator surfaces, along with silicon photomultiplier photodetectors and specific algorithms for raw data analysis, we achieved a remarkable tradeoff between energy, time, and depth-of-interaction (DOI) resolution, thus supporting the feasibility of a prostate time-of-flight positron emission tomography probe, magnetic resonance imaging compatible, with the required features and performance. In numbers this means a detector element of 1.5 mm × 1.5 mm × 10 mm, promising to achieve at the same time energy resolution around 11.5%, coincidence resolving time around 300 ps corresponding to a space resolution <5 cm along the line of response, and DOI resolution even below 1 mm. We stress that such a time resolution allows to increase significantly the noise equivalent counting rate, and consequently improve the image quality and the lesion detection capability.
Anisotropic lattice relaxation in non-c-plane InGaN/GaN multiple quantum wells
Authors: Nishinaka Junichi , Funato Mitsuru , Kawakami Yoichi
Published: August 2012

We investigate anisotropic lattice relaxation in non-c-plane InGaN/GaN multiple quantum wells (MQWs). Transmission electron microscopy analyses of semipolar (112¯2) MQWs reveal that lattice relaxation preferentially occurs along the [1¯1¯23] direction by introducing misfit dislocations (MDs) with a Burgers vector of ⅓[112¯0]. To theoretically describe this anisotropic relaxation phenomenon, we expand the force-balance model, where the competition between the force induced by lattice mismatch and the tension of dislocations determines the motion of dislocations. Furthermore, because MDs are introduced at the interface between the bottom InGaN QW and the underlying GaN, we propose to treat InGaN/GaN MQWs as InGaN single layers with effective In compositions. Applying this structure model to the theoretical calculation of the critical layer thicknesses reproduces well the experimentally observed lattice relaxation. This achievement enables us to design semipolar InGaN/GaN MQW structures without lattice relaxation, thereby realizing higher internal emission quantum efficiencies.
Fast numerical design of spatial-selective rf pulses in MRI using Krotov and quasi-Newton based optimal control methods
Authors: Vinding Mads S. , Maximov Ivan I. , Tošner Zdeněk , Nielsen Niels Chr.
Published: August 2012

The use of increasingly strong magnetic fields in magnetic resonance imaging (MRI) improves sensitivity, susceptibility contrast, and spatial or spectral resolution for functional and localized spectroscopic imaging applications. However, along with these benefits come the challenges of increasing static field (B0) and rf field (B1) inhomogeneities induced by radial field susceptibility differences and poorer dielectric properties of objects in the scanner. Increasing fields also impose the need for rf irradiation at higher frequencies which may lead to elevated patient energy absorption, eventually posing a safety risk. These reasons have motivated the use of multidimensional rf pulses and parallel rf transmission, and their combination with tailoring of rf pulses for fast and low-power rf performance. For the latter application, analytical and approximate solutions are well-established in linear regimes, however, with increasing nonlinearities and constraints on the rf pulses, numerical iterative methods become attractive. Among such procedures, optimal control methods have recently demonstrated great potential. Here, we present a Krotov-based optimal control approach which as compared to earlier approaches provides very fast, monotonic convergence even without educated initial guesses. This is essential for in vivo MRI applications. The method is compared to a second-order gradient ascent method relying on the Broyden-Fletcher-Goldfarb-Shanno (BFGS) quasi-Newton method, and a hybrid scheme Krotov-BFGS is also introduced in this study. These optimal control approaches are demonstrated by the design of a 2D spatial selective rf pulse exciting the letters “JCP” in a water phantom.
Simple and accurate scheme to compute electrostatic interaction: Zero-dipole summation technique for molecular system and application to bulk water
Authors: Fukuda Ikuo , Kamiya Narutoshi , Yonezawa Yasushige , Nakamura Haruki
Published: August 2012

The zero-dipole summation method was extended to general molecular systems, and then applied to molecular dynamics simulations of an isotropic water system. In our previous paper [I. Fukuda, Y. Yonezawa, and H. Nakamura, J. Chem. Phys. 134, 164107 (2011)10.1063/1.3582791], for evaluating the electrostatic energy of a classical particle system, we proposed the zero-dipole summation method, which conceptually prevents the nonzero-charge and nonzero-dipole states artificially generated by a simple cutoff truncation. Here, we consider the application of this scheme to molecular systems, as well as some fundamental aspects of general cutoff truncation protocols. Introducing an idea to harmonize the bonding interactions and the electrostatic interactions in the scheme, we develop a specific algorithm. As in the previous study, the resulting energy formula is represented by a simple pairwise function sum, enabling facile applications to high-performance computation. The accuracy of the electrostatic energies calculated by the zero-dipole summation method with the atom-based cutoff was numerically investigated, by comparison with those generated by the Ewald method. We obtained an electrostatic energy error of less than 0.01% at a cutoff length longer than 13 Å for a TIP3P isotropic water system, and the errors were quite small, as compared to those obtained by conventional truncation methods. The static property and the stability in an MD simulation were also satisfactory. In addition, the dielectric constants and the distance-dependent Kirkwood factors were measured, and their coincidences with those calculated by the particle mesh Ewald method were confirmed, although such coincidences are not easily attained by truncation methods. We found that the zero damping-factor gave the best results in a practical cutoff distance region. In fact, in contrast to the zero-charge scheme, the damping effect was insensitive in the zero-charge and zero-dipole scheme, in the molecular system we treated. We discussed the origin of this difference between the two schemes and the dependence of this fact on the physical system. The use of the zero damping-factor will enhance the efficiency of practical computations, since the complementary error function is not employed. In addition, utilizing the zero damping-factor provides freedom from the parameter choice, which is not trivial in the zero-charge scheme, and eliminates the error function term, which corresponds to the time-consuming Fourier part under the periodic boundary conditions.
Effect of ionic liquid on the native and denatured state of a protein covalently attached to a probe: Solvation dynamics study
Authors: Chowdhury Rajdeep , Mojumdar Supratik Sen , Chattoraj Shyamtanu , Bhattacharyya Kankan
Published: August 2012

Effect of a room temperature ionic liquid (RTIL, [pmim][Br]) on the solvation dynamics of a probe covalently attached to a protein (human serum albumin (HSA)) has been studied using femtosecond up-conversion. For this study, a solvation probe, 7-diethylamino-3-(4-maleimidophenyl)-4-methylcoumarin (CPM) has been covalently attached to the lone cysteine group (cys-34) of the protein HSA. Addition of 1.5 M RTIL or 6 M GdnHCl causes a red shift of the emission maxima of CPM bound to HSA by 3 nm and 12 nm, respectively. The average solvation time ⟨τs⟩ decreases from 650 ps (in native HSA) to 260 ps (∼2.5 times) in the presence of 1.5 M RTIL and to 60 ps (∼11 times) in the presence of 6 M GdnHCl. This is ascribed to unfolding of the protein by RTIL or GdnHCl and therefore making the probe CPM more exposed. When 1.5 M RTIL is added to the protein denatured by 6 M GdnHCl in advance, a further ∼5 nm red shift along with further ∼2 fold faster solvent relaxation (⟨τ⟩ ∼30 ps) is observed. Our previous fluorescence correlation spectroscopy study [D. K. Sasmal, T. Mondal, S. Sen Mojumdar, A. Choudhury, R. Banerjee, and K. Bhattacharyya, J. Phys. Chem. B 115, 13075 (2011)10.1021/jp207829y] suggests that addition of RTIL to the protein denatured by 6 M GdnHCl causes a reduction in hydrodynamic radius (rh). It is demonstrated that in the presence of RTIL and GdnHCl, though the protein is structurally more compact, the local environment of CPM is very different from that in the native state.
Effect of small cage guests on hydrogen bonding of tetrahydrofuran in binary structure II clathrate hydrates
Authors: Alavi Saman , Ripmeester John A.
Published: August 2012

Molecular dynamics simulations of the pure structure II tetrahydrofuran clathrate hydrate and binary structure II tetrahydrofuran clathrate hydrate with CO2, CH4, H2S, and Xe small cage guests are performed to study the effect of the shape, size, and intermolecular forces of the small cages guests on the structure and dynamics of the hydrate. The simulations show that the number and nature of the guest in the small cage affects the probability of hydrogen bonding of the tetrahydrofuran guest with the large cage water molecules. The effect on hydrogen bonding of tetrahydrofuran occurs despite the fact that the guests in the small cage do not themselves form hydrogen bonds with water. These results indicate that nearest neighbour guest-guest interactions (mediated through the water lattice framework) can affect the clathrate structure and stability. The implications of these subtle small guest effects on clathrate hydrate stability are discussed.
Analytical modeling of stress and strain of symmetrically oxidized metal
Authors: Maharjan S. , Zhang X. C. , Wang Z. D.
Published: August 2012

During high temperature isothermal oxidation, a plane of oxide molecules is inserted in each oxide grain boundary. These oxide scales grow laterally and thicken in a columnar microstructure to generate a lateral growth strain. But as the oxide scales are constrained by the underlying metal, the metal constraint produces a net in plane compressive stress in the oxide scales. To balance a compressive stress in the oxide scales, a net in plane tensile stress is generated in the metal, which results creep elongation of an oxide/metal composite. Based on this mechanism, the present paper provides a simplified modeling approach to predict an evolution of the stresses and strains in the oxide/metal composite considering the lateral growth strain of the oxide and creep strain of the metal and oxide. Oxide stress variation due to the creep properties of the oxide/metal composite such as creep indexes (m and n) and creep constants (Aox and Am) is provided for the notional mechanical properties. Oxide stress variation due to the lateral growth constant Dox and oxide kinetics parabolic constant kp is also discussed. Finally, the modeling results are compared with the experimental results obtained for FeCrALY and Ni alloy to highlight the importance of the proposed modeling.
Reliability issues for a bolometer detector for ITER at high operating temperatures
Authors: Meister H. , Kannamüller M. , Koll J. , Pathak A. , Penzel F. , Trautmann T. , Detemple P. , Schmitt S. , Langer H.
Published: August 2012

The first detector prototypes for the ITER bolometer diagnostic featuring a 12.5 μm thick Pt-absorber have been realized and characterized in laboratory tests. The results show linear dependencies of the calibration parameters and are in line with measurements of prototypes with thinner absorbers. However, thermal cycling tests up to 450 °C of the prototypes with thick absorbers demonstrated that their reliability at these elevated operating temperatures is not yet sufficient. Profilometer measurements showed a deflection of the membrane hinting to stresses due to the deposition processes of the absorber. Finite element analysis (FEA) managed to reproduce the deflection and identified the highest stresses in the membrane in the region around the corners of the absorber. FEA was further used to identify changes in the geometry of the absorber with a positive impact on the intrinsic stresses of the membrane. However, further improvements are still necessary.
Prospects for the Thomson scattering system on NSTX-Upgrade
Authors: Diallo A. , LeBlanc B. P. , Labik G. , Stevens D.
Published: August 2012

The paper discusses the projected configuration of the Thomson system on the National Spherical Torus Experiment (NSTX-U). In this paper, we discuss the projected configuration of the Thomson system on NSTX-U. More specifically, we determine, through both optical modeling of the collection optics and in-vessel measurements, that the collecting fibers are to be displaced by at most 1 cm toward the imaging plane along the optical axis. Finally, we estimate the performance of the Thomson system in measuring the electron temperature for NSTX-U discharges.
High-performance double-filter soft x-ray diagnostic for measurement of electron temperature structure and dynamics
Authors: McGarry M. B. , Franz P. , Den Hartog D. J. , Goetz J. A. , Thomas M. A. , Reyfman M. , Kumar S. T. A.
Published: August 2012

A new soft x-ray (SXR) Te and tomography diagnostic has been developed for MST that can be used for simultaneous SXR spectrum measurement, tomographically reconstructed emissivity, and reconstructed and line-of-sight electron temperature. The diagnostic utilizes high-performance differential transimpedance amplifiers (gain 105−109) to provide fast time response (up to 125 kHz), allowing for the study of plasma structure dynamics. SXR double-foil Te measurements are consistent with Thomson scattering. SXR brightness through a variety of filter thicknesses has been combined with charge exchange recombination spectroscopy (CHERS) impurity density measurements to determine the plasma energy spectrum. Magnetic pickup from the fluctuating magnetic fields in the plasma (\documentclass[12pt]{minimal}\begin{document}$\tilde{B} \sim 20$\end{document}B̃∼20 gauss at 10–20 kHz) has been dramatically reduced by improving the detector and housing design, so that nanoampere diode currents are now measured without interference from the substantial fluctuating magnetic field incident on the plasma facing surface of the probe.
Observation of new Rydberg series in the many-electron transition region of N2
Authors: Lo J.-I. , Tsai M.-H. , Fung H.-S. , Chen Y.-J. , Chu C.-C. , Yih T.-S. , Lee Y.-Y. , Wu C. Y. R. , Judge D. L.
Published: August 2012

Fluorescence excitation spectra produced through photoexcitation of N2 using synchrotron radiation in the spectral region between 50 and 62.5 nm have been obtained with a resolution of 0.004 nm. A broadband detector (in the 115–180 nm region) was employed to monitor fluorescence originated from neutral excited atomic nitrogen fragments which are produced through direct dissociation processes and predissociation from the well-known many-electron excited Rydberg states. We have identified a new Rydberg series (2 2Πg) 4sσ, a better resolved Rydberg (D 2Πg) npσ series, and also the prominent Codling series converging to the D 2Πg, and C 2Σu+ states of N2+, respectively. By normalizing our relative fluorescence intensities to previously measured absolute fluorescence cross-section data we obtain the cross-section data of undispersed fluorescence in the 115–180 nm region. The fluorescence quantum yields for the present photodissociative excitation processes are found to be less than 0.05. The present results may provide important data for our understanding of competitions among the various decay channels of the many-electron transition states of N2.
Compact steady-state and high-flux Falcon ion source for tests of plasma-facing materials
Authors: Girka O. , Bizyukov I. , Sereda K. , Bizyukov A. , Gutkin M. , Sleptsov V.
Published: August 2012

This paper describes the design and operation of the Falcon ion source. It is based on conventional design of anode layer thrusters. This ion source is a versatile, compact, affordable, and highly functional in the research field of the fusion materials. The reversed magnetic field configuration of the source allows precise focusing of the ion beam into small spot of ≈3 mm and also provides the limited capabilities for impurity mass-separation. As the result, the source generates steady-state ion beam, which irradiates surface with high heat (0.3 – 21 MW m−2) and particle fluxes (4 × 1021 – 3 × 1023 m−2s−1), which approaches the upper limit for the flux range expected in ITER.
Mechanism for magnetic field generation and growth in Rayleigh-Taylor unstable inertial confinement fusion plasmas
Authors: Srinivasan Bhuvana , Tang Xian-Zhu
Published: August 2012

Rayleigh-Taylor instabilities (RTI) in inertial confinement fusion (ICF) implosions are expected to generate magnetic fields at the gas-ice interface and at the ice-ablator interface. The focus here is on the gas-ice interface where the temperature gradient is the largest. A Hall-MHD model is used to study the magnetic field generation and growth for 2-D single-mode and multimode RTI in a stratified two-fluid plasma, the two fluids being ions and electrons. Self-generated magnetic fields are observed and these fields grow as the RTI progresses via the ∇ne×∇Te term in the generalized Ohm’s law. Srinivasan et al. [Phys. Rev. Lett. 108, 165002 (2012)] present results of the magnetic field generation and growth, and some scaling studies in 2-dimensions. The results presented here study the mechanism behind the magnetic field generation and growth, which is related to fluid vorticity generation by RTI. The magnetic field wraps around the bubbles and spikes and concentrates in flux bundles at the perturbed gas-ice interface where fluid vorticity is large. Additionally, the results of Srinivasan et al. [Phys. Rev. Lett. 108, 165002 (2012)] are described in greater detail. Additional scaling studies are performed to determine the growth of the self-generated magnetic field as a function of density, acceleration, perturbation wavelength, Atwood number, and ion mass.
Unraveling siRNA unzipping kinetics with graphene
Authors: Mogurampelly Santosh , Panigrahi Swati , Bhattacharyya Dhananjay , Sood A. K. , Maiti Prabal K.
Published: August 2012

Using all atom molecular dynamics simulations, we report spontaneous unzipping and strong binding of small interfering RNA (siRNA) on graphene. Our dispersion corrected density functional theory based calculations suggest that nucleosides of RNA have stronger attractive interactions with graphene as compared to DNA residues. These stronger interactions force the double stranded siRNA to spontaneously unzip and bind to the graphene surface. Unzipping always nucleates at one end of the siRNA and propagates to the other end after few base-pairs get unzipped. While both the ends get unzipped, the middle part remains in double stranded form because of torsional constraint. Unzipping probability distributions fitted to single exponential function give unzipping time (τ) of the order of few nanoseconds which decrease exponentially with temperature. From the temperature variation of unzipping time we estimate the energy barrier to unzipping.
1.3 μm InAs/GaAs quantum dot lasers on Si substrates by low-resistivity, Au-free metal-mediated wafer bonding
Authors: Tatsumi Tomohiko , Tanabe Katsuaki , Watanabe Katsuyuki , Iwamoto Satoshi , Arakawa Yasuhiko
Published: August 2012

Low-resistivity GaAs/Si metal-mediated wafer bonding has been investigated for silicon photonics applications. Ag thin-film bonding agent was found to significantly reduce interfacial resistivity relative to the previous bonding mediated by Au-based alloy. Lowering of the interfacial resistivity was found to saturate at 1–2 h of bonding time. A bonding temperature around 300 °C was found optimal to balance the trade-off between elemental interdiffusion and oxidation. On the basis of the bonding investigation, 1.3 μm InAs/GaAs ridge-type quantum dot lasers on Si substrates with Au-free GaAs/Si heterointerfaces have been fabricated. The laser device exhibited a significantly lower device series resistivity and threshold current density than the previous Au-mediated-bonded and direct-grown lasers.
OMEGA polar-drive target designs
Authors: Radha P. B. , Marozas J. A. , Marshall F. J. , Shvydky A. , Collins T. J. B. , Goncharov V. N. , McCrory R. L. , McKenty P. W. , Meyerhofer D. D. , Sangster T. C. , Skupsky S.
Published: August 2012

Low-adiabat polar-drive (PD) [Skupsky et al., Phys. Plasmas 11, 2763 (2004)] implosion designs for the OMEGA [Boehly et al., Opt. Commun. 133, 495 (1997)] laser are described. These designs for cryogenic deuterium–tritium and warm plastic shells use a temporal laser pulse shape with three pickets followed by a main pulse [Goncharov et al., Phys. Rev. Lett. 104, 165001 (2010)]. The designs are at two different on-target laser intensities, with different in-flight aspect ratios (IFARs). These designs permit studies of implosion energetics and target performance closer to ignition-relevant intensities (∼7 × 1014 W/cm2 at the quarter-critical surface, where nonlocal heat conduction and laser–plasma interactions can play an important role) but at lower values of IFAR ∼ 22 or at lower intensity (∼3 × 1014 W/cm2) but at a higher IFAR (IFAR ∼ 32, where shell instability can play an important role). PD geometry requires repointing of laser beams to improve shell symmetry. The higher-intensity designs optimize target performance by repointing beams to a lesser extent, compensating for the reduced equatorial drive by increasing the energies of the repointed beams. They also use custom beam profiles that improve equatorial illumination at the expense of irradiation at higher latitudes. These latter designs will be studied when new phase plates for the OMEGA Laser System, corresponding to the custom beam profiles, are obtained.
Reduced-magnetohydrodynamic simulations of toroidally and poloidally localized edge localized modes
Authors: Hölzl M. , Günter S. , Wenninger R. P. , Müller W.-C. , Huysmans G. T. A. , Lackner K. , Krebs I. ,   ASDEX Upgrade Team
Published: August 2012

We use the non-linear reduced-magnetohydrodynamic code JOREK to study edge localized modes (ELMs) in the geometry of the ASDEX Upgrade tokamak. Toroidal mode numbers, poloidal filament sizes, and radial propagation speeds of filaments into the scrape-off layer are in good agreement with observations for type-I ELMs in ASDEX Upgrade. The observed instabilities exhibit a toroidal and poloidal localization of perturbations which is compatible with the “solitary magnetic perturbations” recently discovered in ASDEX Upgrade [R. Wenninger et al., “Solitary magnetic perturbations at the ELM onset,” Nucl. Fusion (accepted)]. This localization can only be described in numerical simulations with high toroidal resolution.
Influences of impedance matching network on pulse-modulated radio frequency atmospheric pressure glow discharges
Authors: Huo W. G. , Xu K. , Sun B. , Ding Z. F.
Published: August 2012

Pulse-modulated RF atmospheric pressure glow discharges (APDGs) were investigated in recent years to reduce the thermal accumulation and extend the operation region of the stable alpha glow mode. Different pulse-modulated voltage and current waveforms were acquired in previous experiments, but no attention was paid to the interpretation. We investigated this issue and associated phenomenon via positive and negative feedback effects derived from varying the series capacitor in the inversely L-shaped matching network used in our pulse-modulated RF APGD source. The evolutions of pulse-modulated RF waveforms were found to be associated with the feedback region and the pulsed plasma absorbed RF power. In the positive feedback region, pulse-modulated RF APGDs are relatively stable. In the negative feedback region, wide spikes as well as undershoots occur in RF voltage and current waveforms and the plasma absorbed RF power. In case of a high RF power discharge with a low modulation frequency, the pulse-modulated RF APGD is extinguished and re-ignited due to the enhanced undershoot during the initial pulse phase. The pulse-modulated RF APGD can transit from positive to negative feedback region in a range of series capacitance. Experimental results are discussed by the aid of equivalent circuit, negative and positive feedback effects.
Resistive switching and threshold switching behaviors in La0.1Bi0.9Fe1−xCoxO3 ceramics
Authors: Wang S. Y. , Liu W. F. , Gao J. , Qiu Xue , Feng Yu , Hou X. G. , Yu D. S. , Li D. J.
Published: August 2012

The effects of cobalt doping on the electrical conductivity of La0.1Bi0.9Fe1−xCoxO3 (LBFCO, x = 0, 0.01, 0.03) ceramics were investigated. It is found that the leakage current increases with cobalt dopant concentration in LBFCO. On the application of bias voltage LBFCO ceramics with cobalt doping exhibits resistive switching effects at room temperature and threshold switching effects at elevated temperatures (50 °C and 80 °C). X-ray photoelectron spectroscopy of LBFCO ceramics show that cobalt dopant is bivalent as an acceptor, which induces an enhancement of oxygen vacancy concentration in LBFCO ceramics. Possible mechanisms for both resistive switching and threshold switching effects are discussed on the basis of the interplay of bound ferroelectric charges and mobile charged defects.
Communication: Monte Carlo calculation of the exchange energy
Authors: Baer Roi , Neuhauser Daniel
Published: August 2012

In recent generalized Kohn-Sham (GKS) schemes for density functional theory (DFT) Hartree-Fock type exchange is important. In plane waves and grid approaches the high cost of exchange energy calculations makes these GKS considerably more expensive than Kohn-Sham DFT calculations. We develop a stochastic approach for speeding up the calculation of exchange for large systems. We show that stochastic error per particle does not grow and can even decrease with system size (at a given number of iterations). We discuss several alternative approaches and explain how these ideas can be included in the GKS framework.
Changes in ruminal microbiota due to rumen content processing and incubation in single-flow continuous-culture fermenters
Authors: Soto E. C. , Yáñez-Ruiz D. R. , Cantalapiedra-Hijar G. , Vivas A. , Molina-Alcaide E.
Published: August 2012

The aim of this study was to investigate the impact of rumen content manipulation and its incubation in an in vitro system on the abundance of some microbial groups and the bacterial diversity of goat rumens. Animals and single-flow continuous-culture fermenters were fed diets differing in forage to concentrate ratio (70 : 30; LC and 30 : 70; HC). Rumen contents were sampled after animals’ adaptation to the experimental diets, processed for inoculum preparation and inoculated into fermenters. Fermenter contents were sampled 1 and 7 days after inoculation. Total bacteria, Fibrobacter succinogenes, fungi and methanogen abundances were lower in the fermenter than in goat rumens, but no differences were found for Ruminococcus flavefaciens. The abundances of all these microorganisms were similar at 1 and 7 days of rumen content incubation in fermenters. Bacterial species richness did not change due to rumen content processing or the in vitro incubation. Shannon–Wiener index and Pielou evenness were lower in the fermenter than in rumen only when the enzyme HaeIII was used in terminal-restriction fragment length polymorphism analysis. Non-metric multidimensional scaling analysis, both in denaturing gradient gel electrophoresis and terminal-restriction fragment length polymorphism, showed a segregation of in vivo and in vitro samples, but no trends of grouping for fermenter samples was observed. The HC diet promoted higher abundance of total bacteria than LC in rumen but not in fermenters. Diet only had an effect on bacterial diversity when the enzyme HaeIII was considered. Rumen content processing and incubation in fermenters caused an important decline of the studied ruminal microbial groups although bacterial community structure and diversity did not significantly change.
Characterization of Gellan Gum by Capillary Electrophoresis
Authors: Taylor Danielle L. , Ferris Cameron J. , Maniego Alison R. , Castignolles Patrice , in het Panhuis Marc , Gaborieau Marianne
Published: August 2012

Gellan gums were characterised for the first time using free-solution capillary electrophoresis (CE) or CE under critical conditions (CE-CC). CE-CC is a fast method that separates the polysaccharide. Gellan gums are shown to be heterogeneous in terms of their electrophoretic mobility at 55°C revealing: oligomer peak(s), broad peaks of polymers with a random coil conformation with different degrees of acylation (composition), aggregates, and polymers with double-helix conformation. CE-CC is complementary with the rheological analysis also performed in this work. Sonication of gellan gums is shown to decrease the viscosity of gellan gum mainly by breaking up aggregates. The effect of sonication is stronger on the high-acyl gellan gum since the latter has a far higher tendency to aggregate.
Rapid adjustment in chrysanthemum carbohydrate turnover and growth activity to a change in time-of-day application of light and daylength
Authors: Kjaer Katrine Heinsvig , Poiré Richard , Ottosen Carl-Otto , Walter Achim
Published: August 2012

Diel (24 h) rhythms are believed to be of great importance to plant growth and carbohydrate metabolism in fluctuating environments. However, it is unclear how plants that have evolved to experience regular day–night patterns will respond to irregular light environments that disturb diurnally-regulated parameters related to growth. In this study, chrysanthemum plants were exposed to a change in the time-of-day application of light followed by short days or long days with a night interruption of light. We observed a clear shift in the diel cycle of sucrose turnover and relative leaf expansion, indicating a resetting of these activities with a temporal trigger in the early morning. The starch pool was relatively stable in long-day plants and marginally affected by the change in the time-of-day application in light followed by long days with a night interruption. This was in contrast with an onset of a daily starch turnover by a shift to short days. These results confirm findings from model species on the complex relationship between carbohydrate metabolism, source–sink relations and growth rate and they shed new light on the dynamic processes during acclimation towards altered environmental responses of plants in fluctuating environments.
Influence of rurality on diagnosing dementia in Australian general practice
Authors: Greenway-Crombie Angela , Snow Pamela , Disler Peter , Davis Sam , Pond Dimity
Published: August 2012

This article reviews the literature concerning barriers in making a diagnosis of dementia in general practice and examines these from a rural perspective. It is proposed that the increasing prevalence of dementia in coming years in Australia will be felt most keenly in rural communities where there are already shortages of GPs and dementia-specific services to manage growing demand. Evidence suggests that dementia is often not specifically diagnosed by GPs and that this is a global issue. There are many barriers to the diagnosis of dementia in general practice, including time constraints, diagnostic uncertainty, denial of symptoms by patients and families, and stigma. This review examines these barriers and their impact on making a dementia diagnosis from a rural general practice perspective. Identification of these practice issues and their influence on service delivery is essential to inform relevant policy decisions and to improve dementia management in rural general practice.
Influence of habitat on home-range size in the short-beaked echidna
Authors: Sprent Jenny , Nicol Stewart C.
Published: August 2012

The size of an animal’s home range is strongly influenced by the resources available within it. In productive, resource-rich habitats sufficient resources are obtainable within a smaller area, and for many species, home ranges are smaller in resource-rich habitats than in habitats with lower resource abundance. Location data on 14 male and 27 female echidnas (Tachyglossus aculeatus) fitted with tracking transmitters, in the southern midlands of Tasmania, were used to test the influence of habitat type on home-range size. We hypothesised that as woodland should offer more shelter, food resources and refuges than pasture, echidnas living in woodland would have smaller home ranges than those living in pasture areas. We found significant differences between the sexes. Male echidnas had a significantly larger mean home range than females and a quite different relationship between home-range size and habitat type from females. There was no relationship between the proportion of woodland within male home ranges and home-range size whereas female echidnas had a highly significant negative relationship. This suggests that home-range size of female echidnas is highly influenced by the amount of woodland within it, but the home-range size of male echidnas is controlled by factors other than habitat. This pattern is consistent with the spatial ecology of many other solitary species with a promiscuous mating system. The home ranges of females are scaled to encompass all necessary resources for successfully raising their young within a minimal area, whilst the large home ranges of males are scaled to maximise access to females.
Diversity of MHC class II DAB1 in the koala (Phascolarctos cinereus)
Authors: Jobbins Sarah E. , Sanderson Claire E. , Griffith Joanna E. , Krockenberger Mark B. , Belov Katherine , Higgins Damien P.
Published: August 2012

The host immune response is an important factor determining the outcome of the host–pathogen–environment interaction. At the gateway between the innate and adaptive immune systems are MHC molecules, which facilitate antigen presentation to T lymphocytes, and initiate the adaptive immune response. Despite their integral role in adaptive immunity, the genes encoding class II MHC molecules have not been examined directly in koalas. Furthermore, indirect historical evidence suggests that this species might lack functional diversity in class II MHC genes, with potential implications for disease susceptibility. We have examined diversity in the β chain genes of the koala class II MHC DA gene family and identified 23 alleles, including several atypical alleles. The levels of diversity observed are consistent with other marsupial and eutherian species, and do not support the paucity of variation suggested by the early literature. These findings are relevant to the conservation management of koalas and provide both a benchmark for maintaining population diversity and a platform for further conservation genetic research in this species.
Morphological and acoustic evidence for hybridisation between two broadly sympatric south-eastern Australian tree frogs Litoria ewingii and L. verreauxii (Anura: Hylidae)
Authors: Smith Katie L. , Oliver Paul M. , Littlejohn Murray J.
Published: August 2012

The south-eastern Australian tree frogs Litoria ewingii and L. verreauxii are related species that share a broad zone of sympatry. Despite evidence of reproductive character displacement and positive assortative mating in sympatry, a small number of studies have provided inconclusive evidence that occasional hybridisation may occur. We assessed morphological and acoustic divergence between males from two localities where L. ewingii and L. verreauxii occur in sympatry. Several acoustic and morphological traits were found to be divergent between individuals assigned a priori to parental species based on a single acoustic character of the male advertisement call that was previously identified to be diagnostic (pulse number). In contrast, multivariate analysis indicated that at least five adult males identified a priori as putative hybrids (on the basis of intermediate pulse number) were also intermediate in morphology and other aspects of acoustic structure. The concordance of intermediate morphological and acoustic phenotypes supports the hypothesis that despite strong premating isolation, mismating results in at least a small number of hybrid adult males where these species occur in sympatry. This new evidence of hybridisation between L. ewingii and L. verreauxii underlines that there remains much to learn about this model system for understanding hybrid zone dynamics.
Glochidia ecology in wild fish populations and laboratory determination of competent host fishes for an endemic freshwater mussel of south-western Australia
Authors: Klunzinger Michael W. , Beatty Stephen J. , Morgan David L. , Thomson Gordon J. , Lymbery Alan J.
Published: August 2012

Glochidia (parasitic larvae) of freshwater mussels generally require a fish as a host. Westralunio carteri Iredale, 1934 (Bivalvia : Hyriidae), the only freshwater mussel found in south-western Australia, was listed as Vulnerable, but recently changed to Least Concern (International Union for the Conservation of Nature). Glochidia were found on four alien and seven native species of fish from 18 sites in the South West Coast Drainage Division. On alien fishes, prevalence of glochidia ranged from 0.0 to 41.0% and mean intensity (number of glochidia per infested fish) from 1.0 to 6.0, while on native fishes prevalence was 9.2–90.5% and intensity was 2.3–7.1. Glochidia infestation was greatest on benthic fishes, which may be a consequence of greater encounter rates, but other factors, such as host size, probably also influence glochidia prevalence and intensity. Glochidia were generally restricted to fins of infested fish, and were rarely on gills or the body surface. In the laboratory, four native and one alien fish species were found to be competent hosts for their ability to produce juvenile W. carteri, but two alien fish species were not. The inability of some alien fishes to produce juvenile W. carteri could potentially reduce recruitment success in areas dominated by alien fishes.
Levetiracetam suppresses neuronal network dysfunction and reverses synaptic and cognitive deficits in an Alzheimer’s disease model
Authors: Sanchez Pascal E. , Zhu Lei , Verret Laure , Vossel Keith A. , Orr Anna G. , Cirrito John R. , Devidze Nino , Ho Kaitlyn , Yu Gui-Qiu , Palop Jorge J. , Mucke Lennart
Published: August 2012

In light of the rising prevalence of Alzheimer’s disease (AD), new strategies to prevent, halt, and reverse this condition are needed urgently. Perturbations of brain network activity are observed in AD patients and in conditions that increase the risk of developing AD, suggesting that aberrant network activity might contribute to AD-related cognitive decline. Human amyloid precursor protein (hAPP) transgenic mice simulate key aspects of AD, including pathologically elevated levels of amyloid-β peptides in brain, aberrant neural network activity, remodeling of hippocampal circuits, synaptic deficits, and behavioral abnormalities. Whether these alterations are linked in a causal chain remains unknown. To explore whether hAPP/amyloid-β–induced aberrant network activity contributes to synaptic and cognitive deficits, we treated hAPP mice with different antiepileptic drugs. Among the drugs tested, only levetiracetam (LEV) effectively reduced abnormal spike activity detected by electroencephalography. Chronic treatment with LEV also reversed hippocampal remodeling, behavioral abnormalities, synaptic dysfunction, and deficits in learning and memory in hAPP mice. Our findings support the hypothesis that aberrant network activity contributes causally to synaptic and cognitive deficits in hAPP mice. LEV might also help ameliorate related abnormalities in people who have or are at risk for AD.