bluuebunny/crossref_metadata_2025 huggingface dataset:
Ab initio studies on the mechanism for linear and nonlinear optical effects in YAl3(BO3)4
Authors: He Ran , Lin Z. S. , Lee M.-H. , Chen C. T.
Published: June 2011

First-principles studies of the linear and nonlinear optical properties for YAl3(BO3)4 (YAB) are presented. Based upon the electronic band structure, the optical refractive indices, birefringence, and second harmonic generation (SHG) coefficients of YAB are calculated, which are in good agreement with experimental values. In addition, the SHG-weighted electron density analysis and the real-space atom-cutting method are adopted to elucidate the origin of the linear and nonlinear optical effects in YAB. The results show that the anionic (BO3) groups have dominant contributions to the birefringence. The contribution of the Al cations to the optical effects is negligibly small. However, the Y cations bond to the neighbor O anions and form the deformed (YO6) octahedra, which results in the large SHG effects in YAB.
A method for intermediate strain rate compression testing and study of compressive failure mechanism of Mg-Al-Zn alloy
Authors: Gupta Nikhil , Luong Dung D. , Rohatgi Pradeep K.
Published: June 2011

Obtaining meaningful information from the test results is a challenge in the split-Hopkinson pressure bar (SHPB) test method if the specimen does not fail during the test. Although SHPB method is now widely used for high strain rate testing, this limitation has made it difficult to use it for characterization of materials in the intermediate strain rate range (typically 10−1000 s−1). In the present work, a method is developed to characterize materials in the intermediate strain rate range using SHPB setup. In this method, the specimen is repeatedly tested under compression at a given strain rate until failure is achieved. The stress–strain graphs obtained from each test cycle are used to plot the master stress–strain graph for that strain rate. This method is used to study the strain rate dependence of compressive response of a Mg-Al-Zn alloy in the intermediate strain rate range. A remarkable difference is observed in the failure mechanism of the alloy under quasi-static and intermediate strain rate compression. Matrix cracking is the main failure mechanism under quasi-static compression, whereas shattering of intermetallic precipitates, along with plastic deformation of the matrix, is discovered to become prominent as the strain rate is increased.
Deposition of hard elastic hydrogenated fullerenelike carbon films
Authors: Wang Zhou , Zhang Junyan
Published: June 2011

Hydrogenated fullerenelike carbon (H-FLC) films, with high hardness of 41.7 ± 1.4 GPa and elastic recovery of ∼75.1%, have been uniformly deposited at low temperature by pulse direct current plasma enhanced chemical vapor deposition (pulse DC PECVD). The superior mechanical properties of the H-FLC films are attributed to the unique curvature and interconnection of graphitic basal planes. We propose the fullerenelike structures are formed in the far nonequilibrium pulse plasma environment and stabilized in the sequential fast quenching process. It is expected that the facile deposition of H-FLC films will promote the large-scale low-temperature preparation of engineering protective films for industrial applications.
Magnetic interaction effect on the critical switching current in vortex arrays
Authors: Lu Yao , Zhang Zongzhi , Liu Yaowen
Published: June 2011

In this paper, we investigate the influence of the dipolar magnetic interaction on the current-driven vortex dynamics in a two-dimensional array of nanodisks. A general formula is established for the prediction of the correlation between the restoring force of the target nanodisk and the polarities and circulations of the neighboring vortices. Large numbers of possible magnetization configuration combinations among the target and the surrounding neighbors are reduced into four groups under an extreme condition. The maximum and minimum restoring forces are analytically derived, which can be used to predict the critical switching current dependence on the magnetic configuration combinations of vortices.
Resonant transport through graphene nanoribbon quantum dots
Authors: Xiong Yong-Jian , Xiong Bao-Ku
Published: June 2011

The transport properties of armchair graphene nanoribbons with two structural nanoconstrictions are studied by atomistic simulations. With the appropriate geometry and size, the central region between the two constrictions can behave as a single tunneling quantum dot. Within the low energy range around the Dirac point, the conductance of the structure shows strong resonances that are related to the quasi-bound states localized in the dot. The quasi-bound states are associated with the standing waves confined by the two constrictions, and can be effectively modulated by the geometric parameters of the structure.
In-situ stoichiometry determination using x-ray fluorescence generated by reflection-high-energy-electron-diffraction
Authors: Keenan Cameron , Chandril Sandeep , Myers T. H. , Lederman David
Published: June 2011

A major challenge in the stoichiometric growth of complex oxide compounds is the control of the relative compositions of the constituent materials. A potential avenue for compositional analysis during growth is the use of x-ray fluorescence generated during reflection high energy electron diffraction measurements. Using this technique, relative compositions of Y and Mn in molecular beam epitaxy grown YMnO3 samples were studied. Comparing the results with Rutherford back scattering spectroscopy suggests that the technique has the potential for real-time analysis of elemental fluxes and stoichiometry control during sample growth.
Influence of nanoparticles on the dynamics of miscible Hele-Shaw flows
Authors: Ghesmat Karim , Hassanzadeh Hassan , Abedi Jalal , Chen Zhangxin
Published: June 2011

In this study, we have made an attempt to address how the nanoparticle flows may affect the hydrodynamic instability around a miscible front. In order to explore the role of nanoparticles in such flows, a linear stability analysis was performed to examine the impact of nanoparticle addition for an already unstable miscible displacement. The growth rates of the temporal modes of the instability are determined for different profiles or physical properties of nanoparticles. The results reveal that the diffusion of either the carrier fluids or nanoparticles initially has destabilizing effects, but demonstrates stabilizing effects at longer times, as the cutoff spectrum is initially shifted to larger wavenumbers, but shifted back later. It was found that deposition of nanoparticles into the medium stabilizes the miscible front, such that the maximum growth rates and cutoff wavenumbers increase continuously.
Effective quantum teleportation of an atomic state between two cavities with the cross-Kerr nonlinearity by interference of polarized photons
Authors: Xia Yan , Song Jie , Lu Pei-Min , Song He-Shan
Published: June 2011

In this paper, we propose a protocol for long-distance quantum teleportation of the unknown state of an atom trapped in an optical cavity to a second atom trapped in another distant optical cavity with the help of the cross-Kerr nonlinearity. The setup involves cavities QEDs and linear optical elements, which are feasible with existing experimental technology. More over, in Lame-Dicke limit, the protocol does not require the simultaneous click of the detectors. These make the protocol more realizable in experiments. We also show that the protocol can be successfully realized with a certain probability.
High resolution absorption spectroscopy of exploding wire plasmas using an x-pinch x-ray source and spherically bent crystal
Authors: Knapp P. F. , Pikuz S. A. , Shelkovenko T. A. , Hammer D. A. , Hansen S. B.
Published: June 2011

We present here the use of absorption spectroscopy of the continuum radiation from x-pinch-produced point x-ray sources as a diagnostic to investigate the properties of aluminum plasmas created by pulsed power machines. This technique is being developed to determine the charge state, temperature, and density as a function of time and space under conditions that are inaccessible to x-ray emission spectroscopic diagnostics. The apparatus and its characterization are described, and the spectrometer dispersion, magnification, and resolution are calculated and compared with experimental results. Spectral resolution of about 5000 and spatial resolution of about 20 μm are demonstrated. This spectral resolution is the highest available to date in an absorption experiment. The beneficial properties of the x-pinch x-ray source as the backlighter for this diagnostic are the small source size (<5 μm), smooth continuum radiation, and short pulse duration (<0.1 ns). Results from a closely spaced (1 mm) exploding wire pair are shown and the general features are discussed.
Scattering in an external electric field asymptotically constant in time
Authors: Adachi Tadayoshi , Ishida Atsuhide
Published: June 2011

We show the asymptotic completeness for two-body quantum systems in an external electric field asymptotically non-zero constant in time. One of the main ingredients of this paper is to give some propagation estimates for physical propagators generated by time-dependent Hamiltonians which govern the systems under consideration.
Why a magnetized quantum wire can act as an active laser medium
Authors: Kushwaha Manvir S.
Published: June 2011

The fundamental issues associated with the magnetoplasmon excitations are investigated in a quantum wire characterized by a confining harmonic potential and subjected to a perpendicular magnetic field. Essentially, we embark on the device aspects of the intersubband collective (magnetoroton) excitation which observes a negative group velocity between the maxon and the roton. The computation of the gain coefficient suggests an interesting and important application: the electronic device based on such magnetoroton modes can act as an active laser medium.
A fluctuating quantum model of the CO vibration in carboxyhemoglobin
Authors: Falvo Cyril , Meier Christoph
Published: June 2011

In this paper, we present a theoretical approach to construct a fluctuating quantum model of the CO vibration in heme-CO proteins and its interaction with external laser fields. The methodology consists of mixed quantum-classical calculations for a restricted number of snapshots, which are then used to construct a parametrized quantum model. As an example, we calculate the infrared absorption spectrum of carboxy-hemoglobin, based on a simplified protein model, and found the absorption linewidth in good agreement with the experimental results.
Development of a new variational approach for thermal density matrices
Authors: Roy Tapta Kanchan , Prasad M. Durga
Published: June 2011

A McLachlan-type variational principle is derived for thermal density matrices. In this approach, the trace of the mean square of the differences between the derivatives of the exact and model density matrices is minimized with respect to the parameters in the model Hamiltonian. Applications to model anharmonic systems in the independent particle model show that the method can provide thermodynamic state functions accurately (within 5% of the converged basis set results) and at the same level of accuracy as the results using Feynman-Gibbs-Bogoliubov variational principle at this level of approximation.
Micromorph thin-film silicon solar cells with transparent high-mobility hydrogenated indium oxide front electrodes
Authors: Battaglia Corsin , Erni Lukas , Boccard Mathieu , Barraud Loris , Escarré Jordi , Söderström Karin , Bugnon Grégory , Billet Adrian , Ding Laura , Despeisse Matthieu , Haug Franz-Josef , Wolf Stefaan De , Ballif Christophe
Published: June 2011

We investigate the performance of hydrogenated indium oxide as a transparent front electrode for micromorph thin-film silicon solar cells on glass. Light trapping is achieved by replicating the morphology of state-of-the-art zinc oxide electrodes, known for their outstanding light trapping properties, via ultraviolet nanoimprint lithography. As a result of the high electron mobility and excellent near-infrared transparency of hydrogenated indium oxide, the short-circuit current density of the cells is improved with respect to indium tin oxide and zinc oxide electrodes. We assess the potential for further current gains by identifying remaining sources of parasitic absorption and evaluate the light trapping capacity of each electrode. We further present a method, based on nonabsorbing insulating silicon nitride electrodes, allowing one to directly relate the optical reflectance to the external quantum efficiency. Our method provides a useful experimental tool to evaluate the light trapping potential of novel photonic nanostructures by a simple optical reflectance measurement, avoiding complications with electrical cell performance.
Reactive magnetron sputtering of Cu2O: Dependence on oxygen pressure and interface formation with indium tin oxide
Authors: Deuermeier Jonas , Gassmann Jürgen , Brötz Joachim , Klein Andreas
Published: June 2011

Thin films of copper oxides were prepared by reactive magnetron sputtering and structural, morphological, chemical, and electronic properties were analyzed using x-ray diffraction, atomic force microscopy, in situ photoelectron spectroscopy, and electrical resistance measurements. The deposition conditions for preparation of Cu(I)-oxide (Cu2O) are identified. In addition, the interface formation between Cu2O and Sn-doped In2O3 (ITO) was studied by stepwise deposition of Cu2O onto ITO and vice versa. A type II (staggered) band alignment with a valence band offset ΔEVB = 2.1–2.6 eV depending on interface preparation is observed. The band alignment explains the nonrectifying behavior of p-Cu2O/n-ITO junctions, which have been investigated for thin film solar cells.
Dislocation cross-slip in GaN single crystals under nanoindentation
Authors: Huang J. , Xu K. , Gong X. J. , Wang J. F. , Fan Y. M. , Liu J. Q. , Zeng X. H. , Ren G. Q. , Zhou T. F. , Yang H.
Published: June 2011

The dislocation multiplication and movement mechanism in GaN single crystals has been studied using nanoindentation and cathodoluminescence. Dislocation loops can multiply and move from plane to plane by cross-slip, thus producing a wide plastic deformation in GaN during indentation. This mechanism is further supported by the remarkable movement of indentation induced dislocations during annealing. Furthermore, the so-called pop-in events, in which the indenter suddenly enters deeper into the material without the application of any additional force, can be better understood by considering the cross-slip mechanism.
Nanoconfinement effects on the reversibility of hydrogen storage in ammonia borane: A first-principles study
Authors: Chang Kiseok , Kim Eunja , Weck Philippe F. , Tománek David
Published: June 2011

We investigate atomistic mechanisms governing hydrogen release and uptake processes in ammonia borane (AB) within the framework of the density functional theory. In order to determine the most favorable pathways for the thermal inter-conversion between AB and polyaminoborane plus H2, we calculate potential energy surfaces for the corresponding reactions. We explore the possibility of enclosing AB in narrow carbon nanotubes to limit the formation of undesirable side-products such as the cyclic compound borazine, which hinder subsequent rehydrogenation of the system. We also explore the effects of nanoconfinement on the possible rehydrogenation pathways of AB and suggest the use of photoexcitation as a means to achieve dehydrogenation of AB at low temperatures.
Magnetic ordering and slow dynamics in a Ho-based bulk metallic glass with moderate random magnetic anisotropy
Authors: Luo Q. , Schwarz B. , Mattern N. , Eckert J.
Published: June 2011

Results of magnetic measurements are presented for a Ho-based bulk metallic glass, which shows similarities and differences with conventional spin glasses (SGs), and significant differences with weak random magnetic anisotropy (RMA) systems. Both ac and dc magnetic measurements indicate a single transition from paramagnetic to speromagnetic or spin glasslike state around 5.6 K. The moderate RMA prevents the formation of long- (or quasilong)-range magnetic order and slows down the spin dynamics in the critical region. Further its isothermal remnant magnetization exhibits a small maximum, instead of a gradual increase with field in SGs. The roles of RMA in the magnetic structure and dynamics of disordered and frustrated systems are discussed by comparisons between the weak RMA system, the moderate or strong RMA system, and conventional SG.
Approaching the theoretical limit in periodic local MP2 calculations with atomic-orbital basis sets: The case of LiH
Authors: Usvyat Denis , Civalleri Bartolomeo , Maschio Lorenzo , Dovesi Roberto , Pisani Cesare , Schütz Martin
Published: June 2011

The atomic orbital basis set limit is approached in periodic correlated calculations for solid LiH. The valence correlation energy is evaluated at the level of the local periodic second order Møller-Plesset perturbation theory (MP2), using basis sets of progressively increasing size, and also employing “bond”-centered basis functions in addition to the standard atom-centered ones. Extended basis sets, which contain linear dependencies, are processed only at the MP2 stage via a dual basis set scheme. The local approximation (domain) error has been consistently eliminated by expanding the orbital excitation domains. As a final result, it is demonstrated that the complete basis set limit can be reached for both HF and local MP2 periodic calculations, and a general scheme is outlined for the definition of high-quality atomic-orbital basis sets for solids.
Compact acoustic bandgap material based on a subwavelength collection of detuned Helmholtz resonators
Authors: Fey Jordan , Robertson William M.
Published: June 2011

This study explores the amplitude and phase transmission of audio-frequency sound through a waveguide side-loaded with a series of closely spaced and sequentially tuned Helmholtz resonators. This system exhibits a series of acoustic bandgaps due to the Helmholtz resonance and standing-wave cavity modes. The bandgaps are achieved in a physically compact manner in that the resonators are spaced by much less than a wavelength. The response of the Helmholtz resonator-loaded waveguide is described by a simple adaptation of an existing theory. Finally, within the forbidden transmission regions the system exhibits narrow bands of negative group delay.
Accuracy evaluation of single-electron shuttle transfer in Si nanowire metal-oxide-semiconductor field-effect transistors
Authors: Yamahata Gento , Nishiguchi Katsuhiko , Fujiwara Akira
Published: June 2011

We report on evaluation of transfer accuracy in a single-electron turnstile using silicon nanowire metal-oxide-semiconductor field-effect transistors at 17 K. Single-electron shuttle transfer and single-shot detection of a single electron are used to detect errors of the transfer. Errors for the transfer through an electrostatically formed island are ascribed to thermal processes. We also observed single-electron transfer mediated by a trap level, which exhibits a wide current plateau and a low error rate.
Effect of delayed feedback on the dynamics of a scalar map via a frequency-domain approach
Authors: Gentile Franco S. , Bel Andrea L. , Belén D’Amico M. , Moiola Jorge L.
Published: June 2011

The effect of delayed feedback on the dynamics of a scalar map is studied by using a frequency-domain approach. Explicit conditions for the occurrence of period-doubling and Neimark-Sacker bifurcations in the controlled map are found analytically. The appearance of a 1:2 resonance for certain values of the delay is also formalized, revealing that this phenomenon is independent of the system parameters. A detailed study of the well-known logistic map under delayed feedback is included for illustration.
Observation of the memory steps in graphene at elevated temperatures
Authors: Rumyantsev Sergey L. , Liu Guanxiong , Shur Michael S. , Balandin Alexander A.
Published: June 2011

We found that the current-voltage characteristics of graphene transistors exhibit an intriguing feature—an abrupt change in the current near zero gate bias at temperatures above 500 K. The strength of this effect, which we refer to as the memory step by analogy with the memory dips—known phenomenon in electron glasses, depends on the rate of the gate voltage sweep. The slower the sweep, the more pronounced is the step in the current. Despite differences in examined graphene transistors, the memory step always appears at Vg≈0 V. The observed memory steps are likely related to the slow relaxation processes in graphene. This new phenomenon in graphene can be used for applications in sensors and switches.
An efficient setup for femtosecond stimulated Raman spectroscopy
Authors: Kovalenko S. A. , Dobryakov A. L. , Ernsting N. P.
Published: June 2011

We present an efficient and robust setup for femtosecond stimulated Raman (FSR) spectroscopy with 60 fs and 10 cm−1 resolution. Raman pulses of 0.5–5 ps are tunable between 450–750 nm with energies1–10 μJ. Experimental features of the setup, signal processing, and data treatment are discussed in detail to be readily reproduced in other labs. The setup is tested by measuring FSR spectra of stilbene in solution.
A novel interpretation of reduced density matrix and cumulant for electronic structure theories
Authors: Kong Liguo , Valeev Edward F.
Published: June 2011

We propose a novel interpretation of the reduced density matrix (RDM) and its cumulant that combines linear and exponential parametrizations of the wavefunction. Any n-particle RDM can be written as a weighted average of “configuration interaction” amplitudes. The corresponding n-particle cumulant is represented in terms of two types of contributions: “connected” (statistical averages of substitution amplitudes) and “disconnected” (cross-correlations of substitution amplitudes). A diagonal element of n-RDM represents the average occupation number of the orbital n-tuple. The diagonal elements of 2- and 3-cumulants take particularly elegant forms in the natural spin-orbital basis: they represent the covariances (correlated fluctuations) of the occupation numbers of the orbital pair and triples, respectively. Thus, the diagonal elements of the cumulants quantify the correlation between the orbital occupation numbers. Our interpretation is used to examine the weak to strong correlation transition in the “two electrons in two orbitals” problem.
Immunological mechanisms to establish embryo tolerance in early bovine pregnancy
Authors: Groebner A. E. , Schulke K. , Schefold J. C. , Fusch G. , Sinowatz F. , Reichenbach H. D. , Wolf E. , Meyer H. H. D. , Ulbrich S. E.
Published: June 2011

A well-balanced immunological interaction between mother and the semi-allogenic embryo is of particular importance. The objective of the present study was to analyse mechanisms of immune tolerance in bovine pregnancy during peri-implantation. Simmental heifers inseminated with either cryopreserved spermatozoa or seminal plasma were killed 12, 15 or 18 days after oestrus. Uteri were flushed for the recovery of conceptuses and the ipsilateral intercaruncular endometrium was sampled for gene expression analysis. Indoleamine 2,3-dioxygenase (IDO) mRNA, coding for the initial enzyme of the kynurenine pathway, was 18-fold (P < 0.001) more abundant in the endometrium of Day 18 pregnant v. non-pregnant animals. Tandem mass spectrometry revealed a decrease of endometrial l-tryptophan (P = 0.0008), but an increase of l-kynurenine concentration (P = 0.005) from Day 12 to Day 18, suggesting increasing IDO activity (P < 0.03). An in vitro coculture model of endometrial cells showed an induction of IDO expression following interferon-τ exposure primarily in stroma cells, which was confirmed by in situ hybridisation localising IDO mRNA mainly in deep stroma cells. Immunohistochemical analysis revealed fewer CD45-positive leucocytes in the zona basalis of pregnant animals. Elevated IDO activity may reduce the presence of leucocytes in the pregnant endometrium, providing a possible mechanism for protecting the semi-allogenic conceptus from maternal rejection.
Fluctuations in total antioxidant capacity, catalase activity and hydrogen peroxide levels of follicular fluid during bovine folliculogenesis
Authors: Gupta Sajal , Choi Audrey , Yu Hope Y. , Czerniak Suzanne M. , Holick Emily A. , Paolella Louis J. , Agarwal Ashok , Combelles Catherine M. H.
Published: June 2011

Follicular fluid is an important environment for oocyte development, yet current knowledge regarding its in vivo oxidant and antioxidant levels remains limited. Examining follicular fluid oxidants and antioxidants will improve understanding of their changes in vivo and contribute to optimisation of in vitro maturation conditions. The aim of the present study was to consider selected markers, namely catalase (CAT) enzyme activity, total antioxidant capacity (TAC) and hydrogen peroxide (H2O2) in follicular fluid samples (n = 503) originating from bovine antral follicles. The dynamic changes in two relevant antioxidant measures and one reactive oxygen species (ROS) were measured through stages of bovine follicular development and the oestrous cycle. CAT activity and H2O2 levels decreased significantly as follicle size increased, whereas TAC increased significantly as follicle size increased. Lower TAC and higher H2O2 in small follicles suggest increased ROS in the initial stages of folliculogenesis. Because CAT levels are highest in the follicular fluid of small follicles in the setting of an overall low TAC, CAT may represent a dominant antioxidant defence in the initial stages of folliculogenesis. Future studies must focus on other reactive oxygen species and their various scavenger types during antral folliculogenesis.
Intrinsic functional architecture predicts electrically evoked responses in the human brain
Authors: Keller Corey J. , Bickel Stephan , Entz László , Ulbert Istvan , Milham Michael P. , Kelly Clare , Mehta Ashesh D.
Published: June 2011

Adaptive brain function is characterized by dynamic interactions within and between neuronal circuits, often occurring at the time scale of milliseconds. These complex interactions between adjacent and noncontiguous brain areas depend on a functional architecture that is maintained even in the absence of input. Functional MRI studies carried out during rest (R-fMRI) suggest that this architecture is represented in low-frequency (<0.1 Hz) spontaneous fluctuations in the blood oxygen level-dependent signal that are correlated within spatially distributed networks of brain areas. These networks, collectively referred to as the brain's intrinsic functional architecture, exhibit a remarkable correspondence with patterns of task-evoked coactivation as well as maps of anatomical connectivity. Despite this striking correspondence, there is no direct evidence that this intrinsic architecture forms the scaffold that gives rise to faster processes relevant to information processing and seizure spread. Here, we demonstrate that the spatial distribution and magnitude of temporally correlated low-frequency fluctuations observed with R-fMRI during rest predict the pattern and magnitude of corticocortical evoked potentials elicited within 500 ms after single-pulse electrical stimulation of the cerebral cortex with intracranial electrodes. Across individuals, this relationship was found to be independent of the specific regions and functional systems probed. Our findings bridge the immense divide between the temporal resolutions of these distinct measures of brain function and provide strong support for the idea that the low-frequency signal fluctuations observed with R-fMRI maintain and update the intrinsic architecture underlying the brain's repertoire of functional responses.
Renal phenotype in mice lacking the Kir5.1 (
Kcnj16
) K
+
channel subunit contrasts with that observed in SeSAME/EAST syndrome
Authors: Paulais Marc , Bloch-Faure May , Picard Nicolas , Jacques Thibaut , Ramakrishnan Suresh Krishna , Keck Mathilde , Sohet Fabien , Eladari Dominique , Houillier Pascal , Lourdel Stéphane , Teulon Jacques , Tucker Stephen J.
Published: June 2011

The heteromeric inwardly rectifying Kir4.1/Kir5.1 K
+
channel underlies the basolateral K
+
conductance in the distal nephron and is extremely sensitive to inhibition by intracellular pH. The functional importance of Kir4.1/Kir5.1 in renal ion transport has recently been highlighted by mutations in the human Kir4.1 gene (
KCNJ10
) that result in seizures, sensorineural deafness, ataxia, mental retardation, and electrolyte imbalance (SeSAME)/epilepsy, ataxia, sensorineural deafness, and renal tubulopathy (EAST) syndrome, a complex disorder that includes salt wasting and hypokalemic alkalosis. Here, we investigated the role of the Kir5.1 subunit in mice with a targeted disruption of the Kir5.1 gene (
Kcnj16
). The

Kir5.1
−/−

mice displayed hypokalemic, hyperchloremic metabolic acidosis with hypercalciuria. The short-term responses to hydrochlorothiazide, an inhibitor of ion transport in the distal convoluted tubule (DCT), were also exaggerated, indicating excessive renal Na
+
absorption in this segment. Furthermore, chronic treatment with hydrochlorothiazide normalized urinary excretion of Na
+
and Ca
2+
, and abolished acidosis in

Kir5.1
−/−

mice. Finally, in contrast to WT mice, electrophysiological recording of K
+
channels in the DCT basolateral membrane of

Kir5.1
−/−

mice revealed that, even though Kir5.1 is absent, there is an increased K
+
conductance caused by the decreased pH sensitivity of the remaining homomeric Kir4.1 channels. In conclusion, disruption of
Kcnj16
induces a severe renal phenotype that, apart from hypokalemia, is the opposite of the phenotype seen in SeSAME/EAST syndrome. These results highlight the important role that Kir5.1 plays as a pH-sensitive regulator of salt transport in the DCT, and the implication of these results for the correct genetic diagnosis of renal tubulopathies is discussed.
Structure of the guanylyltransferase domain of human mRNA capping enzyme
Authors: Chu Chun , Das Kalyan , Tyminski James R. , Bauman Joseph D. , Guan Rongjin , Qiu Weihua , Montelione Gaetano T. , Arnold Eddy , Shatkin Aaron J.
Published: June 2011

The enzyme guanylyltransferase (GTase) plays a central role in the three-step catalytic process of adding an
m7
GpppN cap cotranscriptionally to nascent mRNA (pre-mRNAs). The 5′-mRNA capping process is functionally and evolutionarily conserved from unicellular organisms to human. However, the GTases from viruses and yeast have low amino acid sequence identity (∼25%) with GTases from mammals that, in contrast, are highly conserved (∼98%). We have defined by limited proteolysis of human capping enzyme residues 229–567 as comprising the minimum enzymatically active human GTase (hGTase) domain and have determined the structure by X-ray crystallography. Seven related conformational states of hGTase exist in the crystal. The GTP-binding site is evolutionarily and structurally conserved. The positional variations of the oligonucleotide/oligosaccharide binding fold lid domain over the GTP-binding site provide snapshots of the opening and closing of the active site cleft through a swivel motion. The pattern of conserved surface residues in mammals, but not in yeast, supports the finding that the recognition of the capping apparatus by RNA polymerase II and associated transcription factors is highly conserved in mammals, and the mechanism may differ somewhat from that in yeast. The hGTase structure should help in the design of biochemical and molecular biology experiments to explore the
protein
∶
protein
and
protein
∶RNA interactions that ensure regulated transcription of genes in humans and other mammals.
Concerted regulation of myofiber-specific gene expression and muscle performance by the transcriptional repressor Sox6
Authors: Quiat Daniel , Voelker Kevin A. , Pei Jimin , Grishin Nick V. , Grange Robert W. , Bassel-Duby Rhonda , Olson Eric N.
Published: June 2011

In response to physiological stimuli, skeletal muscle alters its myofiber composition to significantly affect muscle performance and metabolism. This process requires concerted regulation of myofiber-specific isoforms of sarcomeric and calcium regulatory proteins that couple action potentials to the generation of contractile force. Here, we identify Sox6 as a fast myofiber-enriched repressor of slow muscle gene expression in vivo. Mice lacking Sox6 specifically in skeletal muscle have an increased number of slow myofibers, elevated mitochondrial activity, and exhibit down-regulation of the fast myofiber gene program, resulting in enhanced muscular endurance. In addition, microarray profiling of Sox6 knockout muscle revealed extensive muscle fiber-type remodeling, and identified numerous genes that display distinctive fiber-type enrichment. Sox6 directly represses the transcription of slow myofiber-enriched genes by binding to conserved
cis
-regulatory elements. These results identify Sox6 as a robust regulator of muscle contractile phenotype and metabolism, and elucidate a mechanism by which functionally related muscle fiber-type specific gene isoforms are collectively controlled.
Seasonal Changes in Habitat Availability and the Distribution and Abundance of Salmonids along a Stream Gradient from Headwaters to Mouth in Coastal Oregon
Authors: Reeves Gordon H. , Sleeper Jack D. , Lang Dirk W.
Published: June 2011

Visual estimation techniques were used to quantify seasonal habitat characteristics, habitat use, and longitudinal distribution of juvenile steelhead Oncorhynchus mykiss, coastal cutthroat trout O. clarkii clarkii and coho salmon O. kisutch in a coastal Oregon basin. At the channel unit scale, fish distribution was not proportional to habitat type availability. Pool habitats contained a disproportionate percentage of the salmonid assemblage, and the percentage of fish in pools increased as flow decreased. Large woody debris formed 57–68% of pool habitats and was significantly correlated with pool volume, maximum pool depth, slow surface velocity in pools, and pieces of small woody debris. At the reach and basin scales, longitudinal distribution of the total salmonid assemblage generally did not differ from habitat distribution seasonally or between years. Abundance in the reaches varied annually, and the fish species were longitudinally segregated within the basin: coastal cutthroat trout occurred in the uppermost reaches, steelhead occupied the lowest reaches, and coho salmon inhabited the middle reaches. This study demonstrates that the basinwide distribution of salmonids varies among species, age‐classes, seasons, and years. These results suggest that our understanding of salmonid distribution and abundance could be greatly enhanced by adopting a basinwide, community, seasonal perspective. In addition, the methods described here offer one way to assess the seasonal distribution and abundance of salmonids in a relatively quick, inexpensive, nondestructive manner.
Archival Tagging Methods for Monkfish
Authors: Richards R. Anne , Moser Joshua , Dunnigan Bridget , Alade Larry A.
Published: June 2011

The purpose of this study was to develop archival tagging methods for goosefish Lophius americanus (more commonly known as monkfish), a species thought to be highly susceptible to capture and tagging mortality and very difficult to maintain in captivity. Archival tags were implanted subcutaneously near the second dorsal fin using sanitary surgical methods. A streamer attached to the tag extended through the skin and provided an externally visible tag. Mortality of both tagged and control fish was high (39–44%) in laboratory experiments but did not differ significantly; thus, tagging did not increase mortality. Tag retention was 100% through 6 weeks, but 38% of the incisions on tagged fish showed possible signs of opening. Two of four tagged fish held for up to 6 months expelled their tags. We hypothesize that the streamer prevented complete healing of the incision and led to tag loss. We conclude that archival tagging of monkfish could be successful but recommend that archival tags be completely enclosed if implanted subcutaneously.
Reversed remanent magnetic configuration in epitaxial La1−xSrxMnO3 films
Authors: Lee J-S , Kao C-C , Santos T S , Negusse E , Arena D A
Published: June 2011

The polar discontinuity which can occur at oxide interfaces can modify the properties of oxide thin films. In such a system, an unusual reversed orientation of the remanent magnetic state was observed recently for La0.7Sr0.3MnO3 on Nb-doped SrTiO3(0 0 1) deposited via pulsed laser deposition (Lee et al 2010 Phys. Rev. Lett.
105 257204). Here, we report on a similar effect for La0.7Sr0.3MnO3 grown via molecular beam epitaxy, a deposition method with different growth kinetics, onto both Nb-doped and undoped SrTiO3 (STO) substrates. The reversed magnetic state occurred in both samples, while enriched Mn3+ regions (intermediate layer) are slightly different. Intriguingly, the onset of the reversed remanent state occurred at different temperatures: ∼125 K for the Nb : STO substrate and ∼240 K for the undoped STO substrate. Our results point to an additional mechanism for controlling the magnetism in mixed-valence oxide films.
Amorphous carbon interlayers for gold on elastomer stretchable conductors
Authors: Manzoor M U , Tuinea-Bobe C L , McKavanagh F , Byrne C P , Dixon D , Maguire P D , Lemoine P
Published: June 2011

Gold on polydimethylsiloxane (PDMS) stretchable conductors were prepared using a novel approach by interlacing an hydrogenated amorphous carbon (a-C : H) layer between the deposited metal layer and the elastomer. AFM analysis of the a-C : H film surface before gold deposition shows nanoscale buckling, the corresponding increase in specific surface area corresponds to a strain compensation for the first 4–6% of bi-axial tensile loading. Without this interlayer, the deposited gold films show much smaller and uni-directional ripples as well as more cracks and delaminations. With a-C : H interlayer, the initial electrical resistivity of the metal film decreases markedly (280-fold decrease to 8 × 10−6 Ω cm). This is not due to conduction within the carbon interlayer; both a-C : H/PDMS and PDMS substrates are electrically insulating. Upon cyclic tensile loading, both films become more resistive, but return to their initial state after 20 tensile cycles up to 60% strain. Profiling experiments using secondary ion mass spectroscopy and x-ray photoelectron spectroscopy indicate that the a-C : H layer intermixes with the PDMS, resulting in a graded layer of decreasing stiffness. We believe that both this graded layer and the surface buckling contribute to the observed improvement in the electrical performance of these stretchable conductors.
Local valence and physical properties of double perovskite Nd2NiMnO6
Authors: Shi Chenyang , Hao Yongmei , Hu Zhongbo
Published: June 2011

A polycrystalline double perovskite Nd2NiMnO6 (NNM) has been synthesized through the solid-state reaction method. Powder x-ray diffraction data can be indexed by the space group P21/n. Double magnetization transition temperatures at 105.12 K and 193.04 K are observed from temperature-dependent magnetization curve and can be ascribed to Ni3+–O–Mn3+ and Ni2+–O–Mn4+ superexchange interactions, respectively. The effective magnetic moment, Curie constant C and paramagnetic Curie–Weiss temperature θ are calculated to be 6.023μB/f.u., 4.529(4) emu K mol−1 Oe−1 and 191.1(9) K, respectively. Mixed valence of Mn ion is further evidenced by x-ray photoelectron spectra and the mole ratio of Mn3+/Mn4+ is determined to be 19.53 : 81.47. The dielectric relaxor behaviour is found in NNM and follows the Vogel–Fulcher relationship with E
a = 0.0264 eV, T
f = 283.2 K and f
0 = 4.66 × 108 Hz. The delocalized carriers in the semiconducting sample may explain the origin of dielectric relaxation.
Spatially and temporally resolved optical spectroscopic investigations inside a self-pulsing micro thin-cathode discharge
Authors: Du Beilei , Aramaki Mitsutoshi , Mohr Sebastian , Celik Yusuf , Luggenhölscher Dirk , Czarnetzki Uwe
Published: June 2011

A fibre probe is developed to investigate the temporal development and the spatial distribution of the population density of argon 1s5 state and the emission in the afterglow in a self-pulsing micro thin-cathode discharge at atmospheric pressure. The fibre probe with a diameter (125 µm) of about half the discharge diameter (200 µm) is moved along the discharge axis. A tunable diode laser beam at 696.73 nm at resonance with the argon 1s5 → 2p2 transition is coupled into the far end of the fibre probe. The spatially differentiated absorbance yields the axial distribution of the 1s5 state. In addition, the fibre is used to determine similarly the spatially resolved optical emission of various argon lines. Both the emission and the absorption profiles confirm that, in the afterglow, the plasma is strongly localized inside the hole of the discharge. Qualitatively, the measurements agree very well with the results of a zero-dimensional simulation. The long living afterglow is related to the high population density of the metastable atoms.
Evolution of plasmonic response in growing silver thin films with pre-percolation non-local conduction and emittance drop
Authors: Earp A A , Smith G B
Published: June 2011

The optical response of growing silver thin films undergoes a transition dominated by three distinct plasmonic modes, two localized and one delocalized. Their admix as a function of added mass is analysed. The onset of the delocalized or Drude mode occurs before the sharp electrical percolation transition so optically the full insulator–metal transition is broadened. A scaling explanation supported by images shows Ag islands only have to link up over 200–300 nm to yield partial delocalization. The localized modes are (i) from silver nano-islands and (ii) a transitional anomalous mode, peaking near the dc critical percolation point, from islands surrounded by network. Growing silver within a multilayer oxide stack is compared with that on glass. The transition in thermal emittance matches that in the delocalized mode. Its broadening enables practical tuning of intermediate emittance by varying mass.
Electrical resistance of complex two-dimensional structures of loops
Authors: Gomes M A F , Hora R R , Brito V P
Published: June 2011

This work presents a study of the dc electrical resistance of a recently discovered hierarchical two-dimensional system which has a complex topology consisting of a distribution of disordered macroscopic loops with no characteristic size and a distribution of several types of contacts between loops. In addition to its intrinsic interest in the important context of low-dimensional systems and crumpled systems, the structures under study are of relevance in a number of areas including soft condensed matter and packing of DNA in viral capsids. In the particular case discussed here, the loops are made of layers of graphite with a height of tens of nanometers deposited on a substrate of cellulose. Experiments with these systems indicate an anomalous electrical resistance of sub-diffusive type. The results reported here are explained with scaling arguments and computer simulation. A comparison with the dc electrical properties of percolation clusters is made, and some other experimental issues as future prospects are commented.
Study on H-mode access at low density with lower hybrid current drive and lithium-wall coatings on the EAST superconducting tokamak
Authors: Xu G.S. , Wan B.N. , Li J.G. , Gong X.Z. , Hu J.S. , Shan J.F. , Li H. , Mansfield D.K. , Humphreys D.A. , Naulinfor EAST team V.
Published: June 2011

The first high-confinement mode (H-mode) with type-III edge localized modes at an H factor of H
IPB98(y,2) ∼ 1 has been obtained with about 1 MW lower hybrid wave power on the EAST superconducting tokamak. The first H-mode plasma appeared after wall conditioning by lithium (Li) evaporation before plasma breakdown and the real-time injection of fine Li powder into the plasma edge. The threshold power for H-mode access follows the international tokamak scaling even in the low density range and a threshold in density has been identified. With increasing accumulation of deposited Li the H-mode duration was gradually extended up to 3.6 s corresponding to ∼30 confinement times, limited only by currently attainable durations of the plasma current flat top. Finally, it was observed that neutral density near the lower X-point was progressively reduced by a factor of 4 with increasing Li accumulation, which is considered the main mechanism for the H-mode power threshold reduction by the Li wall coatings.
Alpha particle-driven toroidal rotation in burning plasmas
Authors: Honda M. , Takizuka T. , Tobita K. , Matsunaga G. , Fukuyama A.
Published: June 2011

The mechanism of a torque intrinsically produced by alpha particles and the subsequent possibility to create significant toroidal rotation and shear are numerically investigated. In steady-state DEMO plasmas, regardless of the magnetic configuration, the orbit-following Monte Carlo code OFMC predicts that co-directed collisional torque and a counter-directed
torque always emerge due to the gradient of the source profile of alpha particles and both of them virtually cancel each other out, as analytically predicted earlier. The magnitude of each torque is enhanced in the reversed shear configuration compared with the normal shear configuration, provided that the source gradient is finite and similar in both cases. The resultant rotation velocity estimated by the TASK/TX transport code is far below the threshold to stabilize resistive wall modes (RWMs) through intrinsic alpha-driven torque alone. It is estimated that a neutral beam injection at a moderate power level may be capable of producing toroidal rotation sufficient to stabilize RWMs.
Intrinsic rotation, hysteresis and back transition in reversed shear internal transport barriers
Authors: Kim S.S. , Jhang Hogun , Diamond P.H. , Terzolo L. , Yi S. , Hahm T.S.
Published: June 2011

A study of intrinsic rotation and hysteresis in ion thermal internal transport barrier (ITB) is presented. Global flux-driven gyrofluid simulations are performed. It is found that significant co-current intrinsic rotation (0.1 ≲ M
th ≲ 0.2, where M
th is the thermal Mach number) can be produced in ITB plasmas. Exploration of the relationship between the intrinsic rotation and the ITB temperature gradient leads to a novel scaling of intrinsic rotation in ITB plasmas. Long time power ramp simulations with self-consistently evolving profiles clearly demonstrate the existence of hysteresis in reversed shear ITBs. It is shown that intrinsic rotation plays an important role in ITB dynamics and is responsible for determining unique properties of ITB hysteresis. A negative feedback mechanism based on destruction of E × B shear prevails in barrier back transition, triggered by an outward momentum transport event during the power ramp down.