bluuebunny/crossref_metadata_2025 huggingface dataset:
Detection of runoff timing changes in pluvial, nival, and glacial rivers of western Canada
Authors: Déry Stephen J. , Stahl K. , Moore R. D. , Whitfield P. H. , Menounos B. , Burford Jason E.
Published: April 2009

Changes in air temperature, precipitation, and, in some cases, glacial runoff affect the timing of river flow in watersheds of western Canada. We present a method to detect streamflow phase shifts in pluvial, nival, and glacial rivers. The Kendall‐Theil robust lines yield monotonic trends in normalized sequent 5‐day means of runoff in nine river basins of western Canada over the period 1960–2006. In comparison to trends in the timing of the date of annual peak flow and the center of volume, two other less robust metrics often used to infer streamflow timing changes, our approach reveals more detailed structure on the nature of these changes. For instance, our trend analyses reveal extension of the warm hydrological season in nival and glacial rivers of western Canada. This feature is marked by an earlier onset of the spring melt, decreases in summer streamflow, and a delay in the onset of enhanced autumn flows. Our method provides information on streamflow timing changes throughout the entire hydrological year, enhancing results from previous methods to assess climate change impacts on the hydrological cycle.
Non‐annular atmospheric circulation change induced by stratospheric ozone depletion and its role in the recent increase of Antarctic sea ice extent
Authors: Turner John , Comiso Josefino C. , Marshall Gareth J. , Lachlan‐Cope Tom A. , Bracegirdle Tom , Maksym Ted , Meredith Michael P. , Wang Zhaomin , Orr Andrew
Published: April 2009

Based on a new analysis of passive microwave satellite data, we demonstrate that the annual mean extent of Antarctic sea ice has increased at a statistically significant rate of 0.97% dec−1 since the late 1970s. The largest increase has been in autumn when there has been a dipole of significant positive and negative trends in the Ross and Amundsen‐Bellingshausen Seas respectively. The autumn increase in the Ross Sea sector is primarily a result of stronger cyclonic atmospheric flow over the Amundsen Sea. Model experiments suggest that the trend towards stronger cyclonic circulation is mainly a result of stratospheric ozone depletion, which has strengthened autumn wind speeds around the continent, deepening the Amundsen Sea Low through flow separation around the high coastal orography. However, statistics derived from a climate model control run suggest that the observed sea ice increase might still be within the range of natural climate variability.
A New Model of Cortical Stroke in the Rhesus Macaque
Authors: West G Alexander , Golshani Kiarash J , Doyle Kristian P , Lessov Nikola S , Hobbs Theodore R , Kohama Steven G , Pike Martin M , Kroenke Christopher D , Grafe Marjorie R , Spector Maxwell D , Tobar Eric T , Simon Roger P , Stenzel-Poore Mary P
Published: April 2009

Primate models are essential tools for translational research in stroke but are reportedly inconsistent in their ability to produce cortical infarcts of reproducible size. Here, we report a new stroke model using a transorbital, reversible, two-vessel occlusion approach in male rhesus macaques that produces consistent and reproducible cortical infarcts. The right middle cerebral artery (distal to the orbitofrontal branch) and both anterior cerebral arteries were occluded with vascular clips. Bilateral occlusion of the anterior cerebral artery was critical for reducing collateral flow to the ipsilateral cortex. Reversible ischemia was induced for 45, 60, or 90 mins ( n = 2/timepoint) and infarct volume and neurologic outcome were evaluated. The infarcts were located predominantly in the cortex and increased in size with extended duration of ischemia determined by T2-weighted magnetic resonance imaging. Infarct volume measured by 2,3,5-triphenyl tetrazolium chloride and cresyl violet staining corroborated magnetic resonance imaging results. Neurologic deficit scores worsened gradually with longer occlusion times. A subset of animals ( n = 5) underwent 60 mins of ischemia resulting in consistent infarct volumes primarily located to the cortex that correlated well with neurologic deficit scores. This approach offers promise for evaluating therapeutic interventions in stroke.
Small Colony Variants and Senescent Bacteria
Authors: Jacob Jaison
Published: April 2009

Small colony variants (SCVs) are bacterial subpopulation that grow slowly and form smaller colonies. They have been described for a wide range of bacterial species, but most extensively studied for Staphylococci. They are considered as mutants that are auxotrophic to hemin, thiamine or thymidine. In the presence of auxotrophic agents, they revert to normal growth. They are tolerant to many antibiotics and are implicated in chronic and persistent infections. In this presentation, it is proposed that most of them are normal senescent bacteria that do not revert in the presence of auxotrophic agents. SCVs can explain the concentration dependent killing property, long post-antibiotic effect and increased resistance to aminoglycosides.
Curation and annotation for BioModels Database, a resource of published quantitative kinetic models
Authors: Vijayalakshmi Chelliah , Endler Lukas , Laibe Camille , Li Chen , Le Novère Nicolas
Published: April 2009

BioModels Database ("http://www.ebi.ac.uk/biomodels/":http://www.ebi.ac.uk/biomodels/) is a free resource for storing, viewing and retrieving published, peer-reviewed, quantitative models of biochemical and cellular systems. As a storage format, BioModels Database uses the Systems Biology Markup Language (SBML), but also allows submission and export of models in various other commonly used formats.To offer scientists reliable information, models are curated to comply with the MIRIAM (Minimal Information Requested In the Annotation of biochemical Models) standard. This curation process involves verification of the model structure, the parameter and variable values and its mathematical relations. Furthermore reproduction of results in the reference publication is checked.The different elements of the models are extensively annotated with references to controlled vocabularies and links to other databases, to allow for identification and search. Those references and links are provided in the exported SBML files as a URN (Uniform Resource Name), identifying the data-type and the data-set, and a qualifier, indicating the relation between the element and the referenced data-set. The URNs follow the MIRIAM scheme and are resolved, for instance to URLs, using the Web Services of MIRIAM Resources ("http://www.ebi.ac.uk/miriam/":http://www.ebi.ac.uk/miriam/).
Terminizer - Assisting Mark-Up of Text Using Ontological Terms
Authors: Hancock David , Morrison Norman , Velarde Giles , Field Dawn
Published: April 2009

We present a tool that automatically detects ontological terms in free text. Once candidate terms have been identified the results are displayed either overlaid on the original text or in a list organised by the ontology and frequency. The user can interactively accept or reject each match, or try to find a more appropriate match by exploring the network of ontology concepts themselves. In typical ontological resources, the parent(s) of a term represent broader concepts whilst the children of a term represent more specific concepts. In this way, the suggested match can used as a starting point for the user to find a more suitable term. The ontology browser interface incorporates a graphical visualisation which uses Flash to present an interactive view of the ontology.The "Terminizer services":http://terminizer.org/ offers the full set of ontologies are obtained from the OBO Foundry, a collection of over 40 biological ontologies in a common format. Any ontology available in the standard OBO format can easily be added to the database. In addition to the interactive mode, the software is also available as a Web service. Both the term detection service and the interactive presentation layer can be incorporated within other Web sites or programs.
The SOL Genomics Network Model: Making Community Annotation Work
Authors: Menda Naama , Tecle Isaak , Pujar Anuradha , Bombarely Aureliano , York Tom , Mills Adri , Gosselin Joseph , Buels Robert , Mueller Lukas
Published: April 2009

The concept of community annotation is a growing discipline for achieving participation of the research community in depositing up‐to‐date knowledge in biological databases.The Solanaceae Genomics Network ("SGN":http://sgn.cornell.edu/) is a clade‐oriented database (COD) focusing on plants of the nightshade family, including tomato, potato, pepper, eggplant, and tobacco, and is one of the bioinformatics nodes of the international tomato genome sequencing project. One of our major efforts is linking Solanaceae phenotype information with the underlying genes, and subsequently the genome. As part of this goal, SGN has introduced a database for locus names and descriptors, and a database for phenotypes of natural and induced variation. These two databases have web interfaces that allow cross references, associations with tomato gene models, and in‐house curated information of sequences, literature, ontologies, gene networks, and the Solanaceae biochemical pathways database ("SolCyc":http://solcyc.sgn.cornell.edu). All of our curator tools are open for online community annotation, through specially assigned “submitter” accounts. Currently the community database consists of 5,548 phenotyped accessions, and 5,739 curated loci, out of which more than 300 loci where contributed or annotated by 66 active submitters, creating a database that is truly community driven.This framework is easily adaptable for other projects working on other taxa (for example see "http://chlamybase.org":http://chlamybase.org), greatly expanding the application of this user‐friendly online annotation system. Community participation is fostered by an active outreach program that includes contacting potential submitters via emails, at meetings and conferences, and by promoting featured user submitted annotations on the SGN homepage. The source code and database schema for all SGN functionalities are freely available. Please contact SGN at "sgn‐feedback[at]sgn.cornell.edu":mailto:sgn-feedback@sgn.cornell.edu for more information.
Text Mining in Full Text Articles -- Methodical and Represenation Issues
Authors: Klinger Roman , Pesch Robert , Mevissen Theo , Fluck Juliane
Published: April 2009

In many cases, information from abstracts of biomedical publications is not sufficient for annotation of database entries. Therefore, text mining systems supporting curators of biodatabases should be able to process full text articles. Beside the technical problems arising from full text parsing, the representation of the annotated full text is an important issue. Journal articles are mostly electronically available in PDF or HTML format. Also with more easily manageable XML formats, readers would like to have a visualisation of annotations and semantic enrichment directly in the PDF or HTML. We summarize the technical problems arising from parsing of HTML and PDF journal full texts and show first results of visualisation in both formats.
Increasing Access To Bioinformatics Resources: Increase Community Curation by Increasing Your Community
Authors: Williams Jennifer
Published: April 2009

The amount of biological data has risen exponentially over the last decade. Along with this rise, the number and types of bioinformatics resources has risen such that the sheer number of bioinformatics resources is overwhelming. For these resources to attain their full potential, they must be efficiently and extensively utilized. But in such a plethora of resources, how does a researcher new to a field find the resources that will meet their needs. Once a resource is found, how does the researcher quickly learn to utilize that resource fully? There are resource lists such as those provided by the journal Nucleic Acid Research (NAR), BioMed Central and the Univ. of Pittsburgh Health Sciences Library, and most resources include their own documentation. But lists and site documentation don’t always cast a wide enough net to catch all users. For a resource to truly maximize their user community, it often takes multiple different outreach approaches. OpenHelix specializes in providing customized outreach services to bioinformatics resources, including those featured on this poster. Based on the conclusions from our Phase I SBIR grant, which tested the efficiency of several methods for training researchers on the use of genomic resources, OpenHelix ("www.openhelix.com":http://www.openhelix.com) has developed, and currently provides up-to-date online training materials on a large number of bioinformatics resources, covering major providers and research areas. Through a Phase II SBIR grant from NHGRI and other funding, we are developing a search portal for online bioinformatics resources. With the search portal, researchers will be able to find the bioinformatics and genomics online databases and resources most relevant to their needs. The search portal will contain an index of hundreds of the most popular and powerful resources, as well as the content of over 100 OpenHelix tutorials. Using various ranking techniques, the portal will be able to provide more relevant results than a simple keyword search. Additionally, as part of an extension of our Phase II grant, we are providing a sponsored suite of Model Organism Database trainings that include GBrowse, FlyBase, MGI, RGD, SGD, WormBase and ZFIN. We are also developing, and will be offering, sponsored live trainings on resources at NCBI as a way of filling the void left by the demise of the NCBI Field Guide outreach programs. Conclusion: OpenHelix aims to increase community curation by helping resources increase their user community
Exchange bias of NiO/FeNi ordered nanocaps on curved substrate
Authors: Zhang Y. J. , Wang Y. X. , Meng X. D. , Liu Y. , Ding X. , Yang J. H.
Published: April 2009

The magnetic NiO/Fe19Ni81 nanostructure bilayer is deposited onto the colloidal spheres grown on a Si wafer by the self-assembly technology. The nanocap and the nanodot arrays form on the spherical surface and the Si substrate, respectively, which are confirmed by scanning electron microscopy and transmission electron microscopy measurements. Compared to the flat bilayer with the same composition deposited on the Si substrate, the exchange bias field HE from the nanocap is twice as large. The enhancement of HE in the nanocap is ascribed to the decreased thickness of the ferromagnetic layer induced by the sphere surface. The size and space of the biased caps are estimated based on the thickness variations induced by the sphere surfaces.
Polynomial fusion rings of W-extended logarithmic minimal models
Authors: Rasmussen Jørgen
Published: April 2009

The countably infinite number of Virasoro representations of the logarithmic minimal model LM(p,p′) can be reorganized into a finite number of W-representations with respect to the extended Virasoro algebra symmetry W. Using a lattice implementation of fusion, we recently determined the fusion algebra of these representations and found that it closes, albeit without an identity for p>1. Here, we provide a fusion-matrix realization of this fusion algebra and identify a fusion ring isomorphic to it. We also consider various extensions of it and quotients thereof and introduce and analyze commutative diagrams with morphisms between the involved fusion algebras and the corresponding quotient polynomial fusion rings. One particular extension is reminiscent of the fundamental fusion algebra of LM(p,p′) and offers a natural way of introducing the missing identity for p>1. Working out explicit fusion matrices is facilitated by a further enlargement based on a pair of mutual Moore–Penrose inverses intertwining between the W-fundamental and enlarged fusion algebras.
Characterization of linear plasma synthetic jet actuators in an initially quiescent medium
Authors: Santhanakrishnan Arvind , Reasor Daniel A. , LeBeau Raymond P.
Published: April 2009

The plasma synthetic jet actuator (PSJA) is a geometrical variant of the aerodynamic plasma actuator that can be used to produce zero-mass flux jets similar to those created by mechanical devices. This jet can be either three-dimensional using annular electrode arrays (annular PSJA) or nearly two dimensional using two rectangular-strip exposed electrodes and one embedded electrode (linear PSJA). Unsteady pulsing of the PSJA at time scales decoupled to the ac input frequency results in a flow field dominated by counter-rotating vortical structures similar to conventional synthetic jets, and the peak velocity and momentum of the jet is found to be affected by a combination of the pulsing frequency and input power. This paper investigates the fluid dynamic characteristics of linear plasma synthetic jet actuators in an initially quiescent medium. Two-dimensional particle image velocimetry measurements on the actuator are used to validate a previously developed numerical model wherein the plasma behavior is introduced into the Navier–Stokes equations as an electrohydrodynamic force term calculated from Maxwell’s equations and solved for the fluid momentum. The numerical model was implemented in an incompressible, unstructured grid code. The results of the simulations are observed to reproduce some aspects of the qualitative and quantitative experimental behavior of the jet for steady and pulsed modes of actuator operation. The self-similarity behavior of plasma synthetic jets are examined and compared to mechanically driven continuous and synthetic jets.
Influence of the centrifugal force and parallel dynamics on the toroidal momentum transport due to small scale turbulence in a tokamak
Authors: Peeters A. G. , Strintzi D. , Camenen Y. , Angioni C. , Casson F. J. , Hornsby W. A. , Snodin A. P.
Published: April 2009

The paper derives the gyro-kinetic equation in the comoving frame of a toroidally rotating plasma, including both the Coriolis drift effect [A. G. Peeters et al., Phys. Rev. Lett. 98, 265003 (2007)] as well as the centrifugal force. The relation with the laboratory frame is discussed. A low field side gyro-fluid model is derived from the gyro-kinetic equation and applied to the description of parallel momentum transport. The model includes the effects of the Coriolis and centrifugal force as well as the parallel dynamics. The latter physics effect allows for a consistent description of both the Coriolis drift effect as well as the ExB shear effect [R. R. Dominguez and G. M. Staebler, Phys. Fluids B 5, 3876 (1993)] on the momentum transport. Strong plasma rotation as well as parallel dynamics reduce the Coriolis (inward) pinch of momentum and can lead to a sign reversal generating an outward pinch velocity. Also, the ExB shear effect is, in a similar manner, reduced by the parallel dynamics and stronger rotation.
Magnetic insulation to improve voltage holding in electrostatic accelerators
Authors: Grisham L. R.
Published: April 2009

Voltage holding in high voltage electrostatic accelerators is a longstanding problem which limits the practically obtainable performance of most systems. This paper proposes an idea for improving the voltage holding in electrostatic accelerators by suppressing breakdowns between successive stages of an accelerator. The idea consists of flowing electric currents along the accelerator electrodes to produce magnetic fields which envelope each electrode and its support structure, so as to prevent very low energy electrons from leaving the surfaces of electrodes and subsequently picking up energy from the electric field. In order to be useful in some applications, this magnetic insulation would only need to produce modest gains in voltage holding capability, and its utility can be easily tested experimentally as described herein.
Astrophysical jets: Observations, numerical simulations, and laboratory experiments
Authors: Bellan P. M. , Livio M. , Kato Y. , Lebedev S. V. , Ray T. P. , Ferrari A. , Hartigan P. , Frank A. , Foster J. M. , Nicolaï P.
Published: April 2009

This paper provides summaries of ten talks on astrophysical jets given at the HEDP/HEDLA-08 International Conference in St. Louis. The talks are topically divided into the areas of observation, numerical modeling, and laboratory experiment. One essential feature of jets, namely, their filamentary (i.e., collimated) nature, can be reproduced in both numerical models and laboratory experiments. Another essential feature of jets, their scalability, is evident from the large number of astrophysical situations where jets occur. This scalability is the reason why laboratory experiments simulating jets are possible and why the same theoretical models can be used for both observed astrophysical jets and laboratory simulations.
Accretion disk dynamics, photoionized plasmas, and stellar opacities
Authors: Mancini R. C. , Bailey J. E. , Hawley J. F. , Kallman T. , Witthoeft M. , Rose S. J. , Takabe H.
Published: April 2009

We present a brief review on the atomic kinetics, modeling and interpretation of astrophysical observations, and laboratory astrophysics experiments. The emphasis is on benchmarking of opacity calculations relevant for solar structure models, photoionized plasmas research, the magnetohydrodynamic numerical simulation of accretion disk dynamics, and a connection between radiation transport effects and plasma source geometry details. Specific cases of application are discussed with relevance to recent and proposed laboratory astrophysics experiments as well as Chandra and X-ray Multi-Mirror Mission Newton observations.
Cellular vortex shedding behind a tapered circular cylinder
Authors: Narasimhamurthy Vagesh D. , Andersson Helge I. , Pettersen Bjørnar
Published: April 2009

Vortex shedding behind a tapered circular cylinder with taper ratio 75 placed normal to the inflow has been studied. The Reynolds numbers based on the uniform inflow velocity and the diameter of the cylinder at the wide and narrow ends were 300 and 102, respectively. In the present direct numerical simulation study it was observed that even with a very long time sampling a discrete cellular shedding pattern prevails. This is in contrast to what Parnaudeau et al. [J. Turbulence 8, 13 (2007)] speculated in their tapered cylinder study, where they suggested that with a longer time sampling a diffused cellular pattern might appear. In the present investigation it was found that streamwise vorticity increases as vortex dislocation occurs, an effect also reported by Piccirillo and Van Atta [J. Fluid Mech. 246, 163 (1993)] in their experimental study. Flow visualizations revealed that both modes A and B secondary flow structures coexist along the span of the present tapered cylinder. The wavelength of mode B is in surprisingly good agreement with the experimental value found by Williamson [J. Fluid Mech. 328, 345 (1996)] for uniform circular cylinders. The present numerical calculation revealed a spanwise secondary motion, both in the front stagnation zone and also in the wake of the cylinder. In the front stagnation zone, the secondary flow was driven by a spanwise pressure gradient. The secondary flow pattern in the wake was found to be rather complex. This complex behavior of the secondary motion was attributed to the intrinsic secondary instabilities induced by the transition process itself. This is in contrast to what Parnaudeau et al. [J. Turbulence 8, 13 (2007)] speculated in their tapered cylinder study, where they attributed this to the oblique and cellular vortex shedding. In spite of this secondary flow in the base region, the local formation length in the present tapered cylinder study is in surprisingly good agreement with the results of uniform circular cylinders.
Foundations of anisotropic relativistic mechanics
Authors: Sonego Sebastiano , Pin Massimo
Published: April 2009

We lay down the foundations of particle dynamics in mechanical theories that satisfy the relativity principle and whose kinematics can be formulated employing reference frames of the type usually adopted in special relativity. Such mechanics allow for the presence of anisotropy, both conventional (due to nonstandard synchronization protocols) and real (leading to detectable chronogeometrical effects, independent of the choice of synchronization). We give a general method for finding the fundamental dynamical quantities (Lagrangian, energy, and momentum) and write their explicit expression in all the kinematics compatible with the basic requirements. We also write the corresponding dispersion relations and outline a formulation of these theories in terms of a pseudo-Finslerian space-time geometry. Although the treatment is restricted to the case of one spatial dimension, an extension to three dimensions is almost straightforward.
Nanometer resolution piezoresponse force microscopy to study deep submicron ferroelectric and ferroelastic domains
Authors: Ivry Yachin , Chu DaPing , Durkan Colm
Published: April 2009

Understanding ferroelectricity at the deep submicron regime is desirable in utilizing it for next generation nonvolatile memory devices, medical imaging systems, and rf filters. Here we show how piezoresponse force microscopy can be enhanced (1 nm resolution). Using this method, we have investigated ferroelectric and ferroelastic domains at the deep submicron regime in polycrystalline lead zirconium titanate thin films. We demonstrate that in the clamped films, periodic pairs of 90° domains are stable even at 10 nm width, challenging recent predictions of minimum domain size, and suggesting ferroelectricity for high-density storage devices (≥10 Tbyte/in2).
Structural analysis of a (Pt/Co)3/IrMn multilayer: Investigation of sub-nanometric layers by tomographic atom probe
Authors: Lardé R. , Lechevallier L. , Zarefy A. , Bostel A. , Juraszek J , Le Breton J. M. , Rodmacq B. , Dieny B.
Published: April 2009

The structure of a Ta3 nm/[(Pt2 nm/Co0.4 nm)3/IrMn7 nm]7/Pt10 nm multilayer exhibiting perpendicular exchange bias has been investigated by x-ray reflectometry and laser-assisted tomographic atom probe (LATAP). A strong intermixing at the Co/IrMn interface is pointed out by x-ray reflectometry, this interface being more diffuse than the IrMn/Pt interface. A direct observation of this intermixing at the atomic scale is obtained thanks to the LATAP in real space. The three-dimensional reconstructions reveal the atomic planes in the Pt layers and the Pt–Co intermixing in the (Pt/Co)3 multilayer. The analysis of the concentration profiles allows to determine the chemical composition of the Co subnanometric layers; thus providing for the first time an accurate structural characterization of such layers leading to an estimation of their thickness, roughness, atomic concentration and width of their interfaces.
Enhancement in electron field emission in ultrananocrystalline and microcrystalline diamond films upon 100 MeV silver ion irradiation
Authors: Chen Huang-Chin , Palnitkar Umesh , Pong Way-Faung , Lin I-Nan , Singh Abhinav Pratap , Kumar Ravi
Published: April 2009

Enhanced electron field emission (EFE) behavior was observed in ultrananocrystalline diamond (UNCD) and microcrystalline diamond (MCD) films upon irradiation with 100 MeV Ag9+-ions in a fluence of 5×1011 ions/cm2. Transmission electron microscopy indicated that while the overall crystallinity of these films remained essentially unaffected, the local microstructure of the materials was tremendously altered due to heavy ion irradiation, which implied that the melting and recrystallization process have occurred along the trajectory of the heavy ions. Such a process induced the formation of interconnected nanocluster networks, facilitating the electron conduction and enhancing the EFE properties for the materials. The enhancement in the EFE is more prominent for MCD films than that for UNCD films, reaching a low turn-on field of E0=3.2 V/μm and large EFE current density of Je=3.04 mA/cm2 for 5×1011 ions/cm2 heavy ion irradiated samples.
Anisotropy of magnetic properties in ferrimagnetic ytterbium iron garnet under high magnetic fields
Authors: Wang Wei , Yue Yuan , Li Deyao
Published: April 2009

The magnetic anisotropy in ytterbium iron garnet (YbIG) is theoretically investigated under high magnetic fields (up to 160 kOe). According to the crystal field effect in ytterbium gallium garnet (YbGaG), a detailed discussion of crystal-field interaction in YbIG is presented where a suitable set of crystal-field parameters is obtained. Meanwhile, the influences of nine crystal-field parameters on the crystal-field energy splitting are analyzed. On the other hand, considering the ytterbium-iron (Yb–Fe) superexchange interaction of YbIG, the spontaneous magnetization is calculated at different temperatures for the [111] direction. In particular, we demonstrate that the Wesis constant λ is the function of 1/T in YbIG. In addition, the field dependences of the magnetization for the [110] and [111] directions are theoretically described where a noticeable anisotropy can be found. Our theory further confirms the great contribution of anisotropic Yb–Fe superexchange interaction to the anisotropy of the magnetization in YbIG. Moreover, our theoretical results are compared with the available experiments.
Shockless compression of z-cut quartz to 7 GPa
Authors: Jaglinski T. , LaLone B. M. , Bakeman C. J. , Gupta Y. M.
Published: April 2009

Using a recently developed compact pulsed power generator (CPPG), z-cut quartz samples were subjected to shockless uniaxial strain compression to 7 GPa peak stress. Over this stress range, the behavior of z-cut quartz under shock compression [J. Appl. Phys. 88, 5671 (2000)] is nonlinear elastic and in good agreement with predictions based on the measured values of the second and third order elastic constants. In-material and free surface velocities were measured in the present work and analyzed, using a Lagrangian analysis, to provide a continuous loading curve for z-cut quartz. The wavelet speed-particle velocity (Cu-u, where Cu≡(Δh/Δt)u) results were somewhat sensitive to the CPPG panel design details, as well as the velocity data acquisition and reduction techniques. Improvements to provide optimal data were discussed and used to provide accurate longitudinal stress-density response to 7 GPa (6% density compression). The Cu-u curves, a more stringent measure of the material response to nonlinear compression, were within 0.6% of the values predicted using shock compression measurements. This excellent agreement demonstrates that the shockless compression response of quartz is indistinguishable from the shock response in the nonlinear elastic regime and provides a good foundation for comparing the inelastic response of solids under shockless and shock compression. The present work also demonstrated the use of the CPPG as a laboratory capability for examining the shockless compression of materials.
Resistance switching behaviors of V-doped La0.67Ca0.33MnO3 thin films on F-doped SnO2 conducting glass
Authors: Zhang Ting , Chen Hongju , Ni Manman , Su Zhaohui , Zhang Weifeng
Published: April 2009

V-doped La0.67Ca0.33MnO3 (LCMO) thin films were prepared on fluorine-doped SnO2 (FTO) conducting glass substrates with a sol-gel technique. The resistance switching properties of Au/V:LCMO/FTO heterostructures investigated by electrochemical workstation showed reproducible resistive switching behaviors at room temperature. The interactions between nonlattice (mobile) oxygen and oxygen vacancies and/or the cationic vacancies contributed to the carrier transport of the LCMO layer sandwiched systems. With proper doping concentration (3% V-doped LCMO), the resistive switching behaviors could be well improved and stabilized. The maximum resistance ratio obtained could be reached up to 700%. The experimental results show a high potential for nonvolatile memory application on amorphous substrates.
Structural, ferroelectric, dielectric, and magnetic properties of BiFeO3/Bi3.15Nd0.85Ti3O12 multilayer films derived by chemical solution deposition
Authors: Xie Dan , Zang Yongyuan , Luo Yafeng , Han Xueguang , Ren Tianling , Liu Litian
Published: April 2009

BiFeO 3 / Bi 3.15 Nd 0.85 Ti 3 O 12 (BFO/BNdT) multilayer films have been grown on Pt-coated silicon substrate by chemical solution deposition. Using Bi3.15Nd0.85Ti3O12 as an inducing layer, ferroelectric properties of BiFeO3 were enhanced significantly. The 2Pr and coercive electric field of the Pt/BFO/BNdT/Pt capacitor were about 22.1 μC/cm2 and 50 kV/cm, respectively. The dielectric constant and the dissipation factor of the multilayer were 373 and 0.05 measured at 105 Hz, respectively. The multilayer capacitors not only exhibited excellent fatigue resistance without polarization reduction after 1010 switching cycles but also showed lower leakage current density (around the order of 10−9–10−7 A/cm2) and negligible data loss due to imprint. The magnetic hysteresis indicated that the multiplayer was antiferromagnetic and the saturated magnetization was about 2.47 emu/cm3.
Indentation size dependent plastic deformation of nanocrystalline and ultrafine grain Cu films at nanoscale
Authors: Cao Z. H. , Lu H. M. , Meng X. K. , Ngan A. H. W.
Published: April 2009

Nanoindentation creep tests were performed in the depth range from about 28 to 190 nm on nanocrystalline (NC) and ultrafine grain (UFG) Cu films. Pronounced indentation size effects on hardness, creep strain rate (ε̇), and strain rate sensitivity (mc) are observed. Both ε̇ and mc are dependent not only on contact depth (hc) but also on grain size. The experiment results and analysis support that the creep deformation of NC and UFG Cu is dominated by grain-boundary-mediated process and diffusion along the interface of tip sample, respectively, under a critical hc and dislocation-mediated process begin to work as hc increases further.
Magnetotransport properties of a percolating network of magnetite crystals embedded in a glass-ceramic matrix
Authors: Allia Paolo , Bretcanu Oana , Vernè Enrica , Celegato Federica , Coisson Marco , Tiberto Paola , Vinai Franco , Spizzo Federico , Tamisari Melissa
Published: April 2009

Electrical resistance, magnetization, and magnetoresistance have been measured as functions of temperature from 50 to 300 K on three ferromagnetic glass ceramics containing different magnetite crystals by preparing conditions and crystal morphology. Magnetite crystals form a percolating network for electrons with weak links at crystal-crystal contact points. All samples exhibit a broadened Verwey transition, peaked at temperatures lower than measured in bulk stoichiometric magnetite. The negative magnetoresistance ratio increases in absolute value with sample cooling from RT down to the Verwey temperature and decreases on further cooling. This behavior indicates that electron transfer between magnetite crystals is achieved through spin-dependent and spin-independent channels acting in parallel. Magnetic correlation states for spins at contact points between magnetite crystals are studied by plotting the magnetoresistance as a function of reduced magnetization. The transition from activated hopping to variable range hopping affects the magnetoresistance versus magnetization curves.
Optically controlled spin polarization in a spin transistor
Authors: Lü Hai-Feng , Guo Yong , Zu Xiao-Tao , Zhang Huai-Wu
Published: April 2009

The authors investigate the spin-polarized transport through a quantum dot irradiated by continuous circularly polarized light. For the two-terminal dot device, it is shown that sign reversal of current polarization can be modulated for a range of bias voltage. The system thus operates as a rectifier for spin-current polarization. A three-terminal device is proposed to optimize the degree of spin polarization, which can be modulated arbitrarily by polarized optical pumping in the relative large bias voltage and high temperature.
Energy transfer enhancement in Eu3+ doped TbPO4 inverse opal photonic crystals
Authors: Yang Zhengwen , Huang Xueguang , Sun Li , Zhou Ji , Yang Gang , Li Bo , Yu Cailan
Published: April 2009

Photoluminescence of Eu3+ doped TbPO4 (TbPO4:Eu) inverse opal photonic crystals was investigated. The results showed that the energy transfer from the donor Tb3+ to the acceptor Eu3+ can be enhanced effectively by the photonic band gaps in the photonic crystals. When the fluorescence emission wavelength of the donor Tb3+ overlapped the photonic band gap, the fluorescence intensity of the acceptor Eu3+ was obviously enhanced due to the inhibition of radiative emission of donor in the inverse opal photonic crystals.
Fluid simulation of the E-H mode transition in inductively coupled plasma
Authors: Zhao Shu-Xia , Xu Xiang , Li Xue-Chun , Wang You-Nian
Published: April 2009

One self-consistent method combined with the electromagnetic theory and fluid model is developed to investigate the E-H mode transition of argon inductively coupled plasma (ICP) by adjusting the external electric parameters of the reactor. ICP dynamic characteristics of radial and axial space are also studied when E and H modes coexist. By regulating the radio-frequency current in the coil and voltage across the powered end of the coil and the ground, the E-H mode transition is observed, accompanied by the substantial variations in the electromagnetic field and plasma parameters (density, temperature, and deposited power). Besides, the evolution characteristics of ICP are examined when the discharge mechanism transforms from an E-mode dominated to an H-mode dominated.
Upconversion properties of Tb3+–Yb3+ codoped fluorophosphate glasses
Authors: Arai Yusuke , Yamashidta Tatsuya , Suzuki Takenobu , Ohishi Yasutake
Published: April 2009

Tb 3 + – Yb 3 + codoped fluorophosphate glasses were synthesized and properties of the visible emission at 0.54 μm were investigated. The upconversion excitation efficiency from Yb3+ to Tb3+ was studied by evaluation of the cooperative energy transfer efficiency from Yb3+ to Tb3+ (ηCET) and the back-transfer efficiency from Tb3+ to Yb3+(ηBT), which gave a positive and negative contribution to upconversion excitation, respectively. The ηCET was as high as 30% and the ηBT was less than 1% in the fluorophosphate glass. This indicates that Tb3+–Yb3+ codoped fluorophosphate glass is promising as laser and gain medium in the 0.54 μm band.
Design of new binary interaction classes in complex plasmas
Authors: Kompaneets R. , Morfill G. E. , Ivlev A. V.
Published: April 2009

A method is proposed to “design” binary interactions between charged “dust” microparticles in weakly ionized plasmas by applying external ac electric fields of various polarizations. The physical idea of the method is that the applied field induces ion flow which distorts the Debye spheres of the compensating plasma charges surrounding microparticles and thus changes the interparticle interactions. To investigate the resulting interactions, we use a self-consistent kinetic description for ions with the Bhatnagar–Gross–Krook ion-neutral collision integral. The analysis shows a variety of interaction classes including positive and negative dipolar interactions, triaxially anisotropic interactions, and isotropic interactions of molecular type (i.e., consisting of a repulsion at short distances and an attraction at larger distances). This technique will make it possible to use three-dimensional complex plasmas as realistic model systems for studying the atomistic dynamics of fluids, including liquid-vapor phase transitions and the behavior near the critical point.
Multispacecraft observations of the electron current sheet, neighboring magnetic islands, and electron acceleration during magnetotail reconnection
Authors: Chen Li-Jen , Bessho Naoki , Lefebvre Bertrand , Vaith Hans , Asnes Arne , Santolik Ondrej , Fazakerley Andrew , Puhl-Quinn Pamela , Bhattacharjee Amitava , Khotyaintsev Yuri , Daly Patrick , Torbert Roy
Published: April 2009

Open questions concerning structures and dynamics of diffusion regions and electron acceleration in collisionless magnetic reconnection are addressed based on data from the four-spacecraft mission Cluster and particle-in-cell simulations. Using time series of electron distribution functions measured by the four spacecraft, distinct electron regions around a reconnection layer are mapped out to set the framework for studying diffusion regions. A spatially extended electron current sheet (ecs), a series of magnetic islands, and bursts of energetic electrons within islands are identified during magnetotail reconnection with no appreciable guide field. The ecs is collocated with a layer of electron-scale electric fields normal to the ecs and pointing toward the ecs center plane. Both the observed electron and ion densities vary by more than a factor of 2 within one ion skin depth north and south of the ecs, and from the ecs into magnetic islands. Within each of the identified islands, there is a burst of suprathermal electrons whose fluxes peak at density compression sites [L.-J. Chen et al., Nat. Phys. 4, 19 (2008)] and whose energy spectra exhibit power laws with indices ranging from 6 to 7.3. These results indicate that the in-plane electric field normal to the ecs can be of the electron scale at certain phases of reconnection, electrons and ions are highly compressible within the ion diffusion region, and for reconnection involving magnetic islands, primary electron acceleration occurs within the islands.
Effective interactions in multisite cells for adsorption in microporous materials
Authors: Demontis Pierfranco , Pazzona Federico G. , Suffritti Giuseppe B.
Published: April 2009

Local, discrete models of self-interacting multisite adsorption cells have been shown to be able to provide a coarse-grained representation of equilibrium properties of small molecules adsorbed in nanoporous materials at the mesoscopic scale. In the present work we show how the essential statistical properties of a host cell of structured sites with multiple adsorption energies and particle-particle interactions (that is the partition function, the average energy, and the average number of guests close to the windows connecting the cell to its surroundings) can be reproduced by a less-structured cell with two occupancy-dependent adsorption energy levels.
Silicon nanowire n-type metal-oxide-semiconductor field-effect transistors and single-electron transistors at room temperature under uniaxial tensile strain
Authors: Jeong YeonJoo , Miyaji Kousuke , Saraya Takuya , Hiramoto Toshiro
Published: April 2009

Uniaxial tensile strain effects on [110]-directed silicon nanowire n-type metal-oxide-semiconductor field-effect transistors and single-electron transistors (SETs) were experimentally studied for the first time. It is found that strain effect is still effective in extremely narrow nanowire n-FETs and that transverse tensile strain offers more favorable effects than longitudinal one in terms of Ion∕Ioff ratio. In SETs, complicated strain effect at oscillation region, attributed to the modulation of potential structure and rearrangement of tunneling condition, is observed.
Extraordinary optical properties of a superconducting periodic multilayer in near-zero-permittivity operation range
Authors: Aly Arafa H. , Hsu Heng-Tung , Yang Tzong-Jer , Wu Chien-Jang , Hwangbo Chang Kwon
Published: April 2009

Optical properties in a one-dimensional periodic multilayer structure consisting of superconducting and dielectric films are rigorously studied. Due to the temperature- and wavelength-dependent refractive index in superconducting films, the design of multiple-resonance Fabry–Perot resonators can be achievable without physically introducing any defects to break the periodicity of the structure. These extraordinary optical properties, different from the regular all-dielectric Bragg reflectors, are mainly attributed to the operation in the near-zero-permittivity range of superconductors. Additionally, while the reflection bandwidth tends to enlarge with increasing angle of incidence for transverse magnetic polarization, it remains unchanged with band edges shifted for transverse electric polarization.
Inkjet printing narrow electrodes with <50 μm line width and channel length for organic thin-film transistors
Authors: Doggart Jason , Wu Yiliang , Zhu Shiping
Published: April 2009

We demonstrate a strategy for inkjet printing high resolution silver electrodes from silver precursor composition for organic thin-film transistors. Line width, channel length, and film uniformity of printed electrodes were investigated as functions of dot-to-dot spacing, solvent composition, and ink viscosity. Both line width and film uniformity were greatly improved by simultaneously optimizing dot-to-dot spacing and solvent composition. Line width and channel length were also significantly decreased by increasing ink viscosity. Source and drain electrodes with both width and channel length of less than 50 μm and near-perfect film uniformity were printed and integrated with poly(3,3‴-didodecylquarter-thiophene) semiconductor as high-performance transistors.
An efficient generalized polyelectron population analysis in orbital spaces: The hole-expansion methodology
Authors: Karafiloglou P.
Published: April 2009

We present relations leading to an efficient generalized population analysis in orbital spaces of usual delocalized molecular orbital wave functions. Besides the calculation of the diagonal elements of the reduced density matrices of any order, one can also calculate efficiently the probabilities (or, in general, the weights) of various occupation schemes of local electronic structures, by using generalized density operators referring to both electrons and electron holes. Within this population analysis, correlated molecular orbital wave functions can be used, and there are no restrictions to the number of the analyzed electrons and electron holes. It is based on the hole-expansion methodology, according to which a given electronic population is expanded in terms involving only electron holes, which as shown, can be calculated very efficiently; usual difficulties arising from the necessity to handle extremely large local determinantal basis sets are avoided, without introducing approximations. Although an emphasis is given for populations in the basis of orthogonal orbital spaces (providing probabilities), the case of nonorthogonal ones is also considered in order to show the connection of the generalized populations and the traditional weights obtained from valence-bond wave functions. Physically meaningful populations can be obtained by using natural orbitals, such as the natural atomic orbitals (NAOs) (orthogonal orbitals) or the pre-NAO’s (nonorthogonal orbitals); numerical applications for pyrrole molecule are presented in the basis of these natural orbitals.
Approximated electron repulsion integrals: Cholesky decomposition versus resolution of the identity methods
Authors: Weigend Florian , Kattannek Marco , Ahlrichs Reinhart
Published: April 2009

We compare two procedures to gain efficiency by approximating two-electron integrals in molecular electronic structure calculations. The first one is based on a Cholesky decomposition (CD) of two-electron integrals, the second one on the use of preoptimized auxiliary or fitting basis sets employed in a “resolution of the identity” (RI) technique. We present and test auxiliary bases for approximating the Coulomb term, which further improves accuracy over previously proposed fitting bases. It is shown that RI methods lead to insignificant errors only, which are partly comparable to or even better than that of CD treatments; but RI procedures are superior in speed. CD methods have certain advantages, however, particularly for extended basis sets.