bluuebunny/crossref_metadata_2025 huggingface dataset:
Global average of air‐sea CO2 transfer velocity from QuikSCAT scatterometer wind speeds
Authors: Boutin J. , Quilfen Y. , Merlivat L. , Piolle J. F.
Published: April 2009

The absolute calibration of the relationship between air‐sea CO2 transfer velocity, k, and wind speed, U, has been a topic of debate for some time, because k global average, 〈k〉, as deduced from Geochemical Ocean Sections Study oceanic 14C inventory has differed from that deduced from experimental k‐U relationships. Recently, new oceanic 14C inventories and inversions have lead to a lower 〈k〉. In addition, new measurements performed at sea in high–wind speed conditions have led to new k‐U relationship. Meanwhile, quality and sampling of satellite wind speeds has greatly improved. The QuikSCAT scatterometer has provided high‐quality wind speeds for more than 7 years. This allows us to estimate the global distributions of k computed using k‐U relationships and temperature‐dependent Schmidt numbers from 1999 to 2006. Given the difficulty of measuring in situ wind speed very accurately, we performed a sensitivity study of the 〈k〉 uncertainty which results from QuikSCAT U uncertainties. New QuikSCAT‐buoy U comparisons in the northern Atlantic Ocean and in the Southern Ocean confirm the excellent precision of QuikSCAT U (RMS difference of about 1 m s−1), but it is possible that QuikSCAT overestimates wind speeds by 5%, leading to a possible overestimation of k derived with quadratic relationships by 10%. The 〈k〉 values obtained with two recent experimental k‐U relationships are very close, between 15.9 and 17.9 cm h−1, and within the error bar of k average deduced from the new oceanic 14C inventory.
Intensified decadal variability in tropical climate during the late 19th century
Authors: Ault Toby R. , Cole Julia E. , Evans Michael N. , Barnett Heidi , Abram Nerilie J. , Tudhope Alexander W. , Linsley Braddock K.
Published: April 2009

To evaluate and extend the record of decadal climate variability, we present a synthesis of 23 coral oxygen isotope records from the tropical Indo‐Pacific that extends back to A.D. 1850. Principal components analysis (PCA) on detrended records reveals a leading pattern of variance with significant interannual (3–5 year) and decadal (9–14 year) variability. The temporal evolution and spatial pattern of this variability closely resembles the El Niño/Southern Oscillation (ENSO) pattern across both time scales, suggesting that this decadal tropical variability is fundamentally related to ENSO. The 19th century experienced stronger decadal tropical climate variability, compared to the 20th. Decadal variability in the tropical oceans thus remains underestimated by analysis of direct observations.
Three‐dimensional numerical models with varied material properties and erosion rates: Implications for the mechanics and kinematics of compressive wedges
Authors: Upton Phaedra , Mueller Karl , Chen Yue‐Gau
Published: April 2009

We develop three‐dimensional mechanical models of a compressive wedge and investigate how the form and kinematics of the outboard wedge are affected by variation in initial topography, material properties, and erosion rate. Inclusion into the wedge of weaker, less dense material affects the form of the wedge, producing a region of steeper average slopes and higher topography while depriving the region further inboard of material. Enhanced erosion has a similar effect. The wedge attempts to replace the eroded material by focusing deformation. The result is a stepped region of lower topography within the outboard of the orogen. We observe that uplift velocities at three points in the orogen vary cyclically from near zero to ∼3 times the average uplift rate over cycles lasting on the order of 15–200,000 model years. Our models, along with analog models and some well‐dated examples from active orogens, suggest that transient accommodation of strain may be common. The cycles observed responded rapidly to changes in the amount of erosion imposed. Our models suggest that orogens may be driven by strong coupling between erosion and strain on temporal scales of 104–105 years and spatial scales comparable to the scale of the erosional perturbation. We compare our models to the Puli Embayment of west central Taiwan, a region of anomalous low topography and suggest that it presence may reflect the presence of weaker and more erodible sediments than those present along strike in the orogen.
Thunder‐induced ground motions: 1. Observations
Authors: Lin Ting‐L. , Langston Charles A.
Published: April 2009

Acoustic pressure from thunder and its induced ground motions were investigated using a small array consisting of five three‐component short‐period surface seismometers, a three‐component borehole seismometer, and five infrasound microphones. We used the array to constrain wave parameters of the incident acoustic and seismic waves. The incident slowness differences between acoustic pressure and ground motions suggest that ground reverberations were first initiated somewhat away from the array. Using slowness inferred from ground motions is preferable to obtain the seismic source parameters. We propose a source equalization procedure for acoustic/seismic deconvolution to generate the time domain transfer function, a procedure similar to that of obtaining teleseismic earthquake receiver functions. The time domain transfer function removes the incident pressure time history from the seismogram. An additional vertical‐to‐radial ground motion transfer function was used to identify the Rayleigh wave propagation mode of induced seismic waves complementing that found using the particle motions and amplitude variations in the borehole. The initial motions obtained by the time domain transfer functions suggest a low Poisson's ratio for the near‐surface layer. The acoustic‐to‐seismic transfer functions show a consistent reverberation series at frequencies near 5 Hz. This gives an empirical measure of site resonance that depends on the ratio of the layer velocity to layer thickness for earthquake P and S waves. The time domain transfer function approach by transferring a spectral division into the time domain provides an alternative method for studying acoustic‐to‐seismic coupling.
Orthoenstatite/clinoenstatite phase transformation in MgSiO3 at high‐pressure and high‐temperature determined by in situ X‐ray diffraction: Implications for nature of the X discontinuity
Authors: Akashi Akihiko , Nishihara Yu , Takahashi Eiichi , Nakajima Yoichi , Tange Yoshinori , Funakoshi Ken‐ichi
Published: April 2009

In the upper mantle, the X discontinuity at the depths of 240 to 340 km is observed in many localities, but its origin is under debate. The phase transformation of (Mg,Fe)SiO3 from orthopyroxene to high‐pressure clinopyroxene has been proposed to cause this discontinuity. In this study, in situ X‐ray diffraction experiments were performed, and the orthoenstatite/high‐pressure clinoenstatite (C2/c) phase boundary in the MgSiO3 system was determined. All the experiments were carried out using a Kawai‐type multianvil apparatus installed at BL04B1 in SPring‐8, Hyogo, Japan. Two types of experiments were carried out: (1) “phase observation experiments” at varying pressures and temperatures and (2) “quench experiments” at fixed pressure and temperature. The phase boundary, determined precisely by integrating the results of both sets of experiments, was found to be P (GPa) = 0.0035T (°C) + 3.7, using a recent MgO pressure scale. The orthoenstatite/high‐pressure clinoenstatite phase boundary at 1400°C determined here is 0.7–1.0 GPa lower than previous reports based on quench experiments. The phase transformation of orthopyroxene is expected to occur at 260 km depth along a typical mantle geotherm, and the shallower part of the observed X discontinuity can be explained by this phase transformation.
Giant impacts on early Mars and the cessation of the Martian dynamo
Authors: Roberts J. H. , Lillis R. J. , Manga M.
Published: April 2009

Although Mars currently has no global dynamo‐driven magnetic field, widespread crustal magnetization provides strong evidence that such a field existed in the past. The absence of magnetization in the younger large Noachian basins suggests that a dynamo operated early in Martian history but stopped in the mid‐Noachian. Within a 100 Ma period, 15 giant impacts occurred coincident with the disappearance of the global magnetic field. Here we investigate a possible causal link between the giant impacts during the early and mid‐Noachian and the cessation of the Martian dynamo at about the same time. Using three‐dimensional spherical mantle convection models, we find that impact heating associated with the largest basins (diameters >2500 km) can cause the global heat flow at the core‐mantle boundary to decrease significantly (10–40%). We suggest that such a reduction in core heat flow may have led to the cessation of the Martian dynamo.
Spatially explicit simulation of hydrologically controlled carbon and nitrogen cycles and associated feedback mechanisms in a boreal ecosystem
Authors: Govind Ajit , Chen Jing Ming , Ju Weimin
Published: April 2009

Ecosystem models that simulate biogeochemical processes usually ignore hydrological controls that govern them. It is quite possible that topographically driven water fluxes significantly influence the spatial distribution of C sources and sinks because of their large contribution to the local water balance. To investigate this, we simulated biogeochemical processes along with the associated feedback mechanisms in a boreal ecosystem using a spatially explicit hydroecological model, boreal ecosystem productivity simulator (BEPS)–TerrainLab V2.0, that has a tight coupling of ecophysiological, hydrological, and biogeochemical processes. First, the simulated dynamics of snowpack, soil temperature, net ecosystem productivity (NEP), and total ecosystem respiration (TER) were validated with high‐frequency measurements for 2 years. The model was able to explain 80% of the variability in NEP and 84% of the variability in TER. Further, we investigated the influence of topographically driven subsurface base flow on soil C and N cycling and on the spatiotemporal patterns of C sources and sinks using three hydrological modeling scenarios that differed in hydrological conceptualizations. In general, the scenarios that had nonexplicit hydrological representation overestimated NEP, as opposed to the scenario that had an explicit (realistic) representation. The key processes controlling the NEP differences were attributed to the combined effects of variations in photosynthesis (due to changes in stomatal conductance and nitrogen (N) availability), heterotrophic respiration, and autotrophic respiration, all of which occur simultaneously affecting NEP. Feedback relationships were also found to exacerbate the differences. We identified six types of NEP differences (biases), of which the most commonly found was due to an underestimation of the existing C sources, highlighting the vulnerability of regional‐scale ecosystem models that ignore hydrological processes.
Post-Ischemic Helium Provides Neuroprotection in Rats Subjected to Middle Cerebral Artery Occlusion-Induced Ischemia by Producing Hypothermia
Authors: David Hélène N , Haelewyn Benoît , Chazalviel Laurent , Lecocq Myriam , Degoulet Mickael , Risso Jean-Jacques , Abraini Jacques H
Published: April 2009

During the past decade, studies on the manipulation of various inhaled inert gases during ischemia and/or reperfusion have led to the conclusion that inert gases may be promising agents for treating acute ischemic stroke and perinatal hypoxia-ischemia insults. Although there is a general consensus that among these gases xenon is a golden standard, the possible widespread clinical use of xenon experiences major obstacles, namely its availability and cost of production. Interestingly, recent findings have shown that helium, which is a cost-efficient inert gas with no anesthetic properties, can provide neuroprotection against acute ischemic stroke in vivo when administered during ischemia and early reperfusion. We have investigated whether helium provides neuroprotection in rats subjected to middle cerebral artery occlusion (MCAO) when administered after reperfusion, a condition prerequisite for the therapeutic viability and possible clinical use of helium. In this study, we show that helium at 75 vol% produces neuroprotection and improvement of neurologic outcome in rats subjected to transient MCAO by producing hypothermia on account of its high specific heat as compared with air.
TAT-Hsp70-Mediated Neuroprotection and Increased Survival of Neuronal Precursor Cells after Focal Cerebral Ischemia in Mice
Authors: Doeppner Thorsten R , Nagel Florian , Dietz Gunnar PH , Weise Jens , Tönges Lars , Schwarting Sönke , Bähr Mathias
Published: April 2009

Cerebral ischemia stimulates endogenous neurogenesis within the subventricular zone and the hippocampal dentate gyrus of the adult rodent brain. However, such newly generated cells soon die after cerebral ischemia. To enhance postischemic survival of neural precursor cells (NPC) and long-lasting neural regeneration, we applied the antiapoptotic chaperone heat shock protein 70 (Hsp70) fused to a cell-penetrating peptide derived from the HIV TAT to ensure delivery across the blood-brain barrier and the cell membrane. After transient focal cerebral ischemia in mice, TAT-Hsp70 was intravenously injected concomitant with reperfusion and additionally on day 14 after stroke. TAT-Hsp70 treatment resulted in smaller infarct size (27.1 ± 9.0 versus 109.0 ± 14.0 and 88.5 ± 26.0 mm3 in controls) and in functional improvement as assessed by the rota rod, tight rope, and water maze tests when compared with saline- and TAT-hemagglutinin-treated controls. In addition, postischemic survival of endogenous doublecortin (Dcx)-positive NPC was improved within the lesioned striatum of TAT-Hsp70-treated animals for up to 4 weeks after stroke without changing overall cell proliferation of BrdU+ cells. Thus, TAT-Hsp70 treatment after stroke may be a promising tool to act neuroprotective and improve postischemic functional outcome, and also to increase survival of endogenous NPC after stroke.
ChlamyCyc - a comprehensive database and web-portal centered on Chlamydomonas reinhardtii
Authors: Christian Jan-Ole , May Patrick , Kempa Stefan , Walther Dirk
Published: April 2009

*Background*

- The unicellular green alga Chlamydomonas reinhardtii is an important eukaryotic model organism for the study of photosynthesis and growth, as well as flagella development and other cellular processes. In the era of high-throughput technologies there is an imperative need to integrate large-scale data sets from high-throughput experimental techniques using computational methods and database resources to provide comprehensive information about the whole cellular system of a single organism.

*Results*

- In the framework of the German Systems Biology initiative GoFORSYS a pathway/genome database and web-portal for Chlamydomonas reinhardtii (ChlamyCyc) was established, which currently features about 270 metabolic pathways with related genes, enzymes, and compound information. ChlamyCyc was assembled using an integrative approach combining the recently published genome sequence, bioinformatics methods, and experimental data from metabolomics and proteomics experiments. We analyzed and integrated a combination of primary and secondary database resources, such as existing genome annotations from JGI, EST collections, orthology information, and MapMan classification.*Conclusion* - Chlamycyc provides a curated and integrated systems biology repository that will enable and assist in systematic studies of fundamental cellular processes in Chlamydomonas reinhardtii. The ChlamyCyc database and web-portal is freely available under http://chlamycyc.mpimp-golm.mpg.de.
The Jena Library of Biological Macromolecules - JenaLib
Authors: Huehne Rolf , Suehnel Juergen
Published: April 2009

The JenaLib database ("www.fli-leibniz.de/IMAGE.html":http://www.fli-leibniz.de/IMAGE.html) offers value-added information for all Protein Data Bank (PDB) and Nucleic Acid Database (NDB) entries. This includes:(1) atlas pages and entry lists, (2) PDB sequence information extracted from atomic coordinates, (3) PDB/UniProt sequence alignments that clearly indicate gaps, mutations, numbering irregularities and modified residues, (4) integration of data on single amino acid polymorphisms (SAPs), PROSITE motifs, exon structure and SCOP/CATH/Pfam domains with PDB, GO and taxonomy information, (5) display of these data in the sequence/alignment viewer and in the Jmol-based molecule viewer Jena3D ("jena3d.fli-leibniz.de":http://jena3d.fli-leibniz.de ); in the latter case both for asymmetric and biological units, (6) a QuickSearch option that allows searching for PDB/NDB code, UniProt ID/accession number and other search terms in one input field, (7) a sequence homology search (BLAST) and pattern search options and (8) SCOP/CATH/Pfam tree browsers.Offering all this information and analysis tools in one place makes JenaLib a unique resource for the dissemination of 3D structural information on biological macromolecules.
A Framework for BioCuration Workflows (part II)
Authors: Krallinger Martin
Published: April 2009

This is the second part of the talk ‘A Framework for BioCuration Workflows’, given by Martin Krallinger from the Spanish National Cancer Research Centre at the 'Text Mining for the BioCuration Workflow' workshop. The first part was held by Gully APC Burns (USC Information Sciences Institute, USA). This presentation covered some of the main general tasks often shared by existing literature biocuration workflows: Identification of relevant articles, identification and normalization of the actual bio-entities, the extraction of the annotation event and the identification of some evidential support (e.g. experimental evidence). Some of the important aspects, bottlenecks and potential text mining approaches were briefly introduced for each general workflow task. This talk provided a short overview of some of the important aspects to integrate text mining systems into a given biocuration workflow and showed how heterogeneous workflows can be even for a relatively straight forward task such as the identification of curation relevant literature. A more detailed example of the biocuration of protein-protein interactions through the workflow followed by the BioGRID database was presented.
WormBase - Nematode Biology and Genomes
Authors: Davis Paul , Consortium WormBase
Published: April 2009

WormBase is the major public online database resource for the Caenorhabditis research community. The database was developed primarily for the nematode C. elegans but expanded to host genomes and biological data from other closely related nematode species including C. briggsae, C. remanei, C. brenneri, C. japonica and Pristionchus pacificus. WormBase has developed tools to mine the data held within the database and compare the hosted species. Over the years we have developed a variety of curation pipelines which often begin in a "first-pass" literature curation step. This involves a brief overview of the literature before directing it to specialised data curators who extract all relevant information. Curators focus on particular data types or experimental techniques such as gene structure changes (see the Sequence curation poster), variations, phenotypes or RNAi and their expertise in these fields make curation efficient. WormBase works with many other groups and consortiums to validate, process and integrate both large and small scale data resources. WormBase also provides data that will be of interest to the wider biomedical and bioinformatics communities allowing researchers to utilise the information and techniques offered by nematodes to study wider aspects including medicine and disease.
BioCatalogue: A Curated Web Service Registry For The Life Science Community
Authors: Goble Carole , Belhajjame Khalid , Tanoh Franck , Bhagat Jiten , Wolstencroft Katy , Stevens Robert , Nzuobontane Eric , McWilliam Hamish , Laurent Thomas , Lopez Rodrigo
Published: April 2009

Web Services have gained a momentum as a means for packaging existing data and computational resources in a form that is amenable for use and composition by third party applications. The life science community is certainly among the first adopters of Web Services. For example, "Taverna":http://www.mygrid.org.uk, a workflow workbench that is popular within the life science community, provides access to over 3500 thousands web services that can be composed by scientists for constructing and enacting their in silico experiments. However, one of the main issues that hinders the wide adoption and use of Web Services is the difficulty in locating the “appropriate” Web Service, i.e., the Web Service that performs the analysis the scientist is interested in. The descriptions of available Web Services are often poor providing little information to the scientist about their usefulness for the analysis s/he is after. With the above issues in mind, the authors have recently initiated the BioCatalogue project ("http://www.biocatalogue.org/":http://www.biocatalogue.org/). BioCatalogue provides a central registry of curated biological Web Services. A place where providers, users and expert curators can register, annotate and search for Web Services. It also acts as a place where the community can contact and meet the experts and maintainers of these services. The project is co-developed by the University of Manchester and the EMBL-EBI.
Developing a Text Mining Prototype for the Comparative Toxicogenomics Database Biocuration Process
Authors: Wiegers Thomas
Published: April 2009

Understanding interactions between environmental chemicals and genes provides insights into the mechanisms of chemical action, disease susceptibility, therapeutic drug interactions, and toxicity. The Comparative Toxicogenomics Database (CTD; http://ctd.mdibl.org) is a web-based resource that integrates diverse information for the cross-species analysis of chemical, gene, and disease relationships. Much of the data contained in CTD is manually gathered by biocurators; CTD integrates data curated manually from over 10,000 scientific documents. CTD biocurators manually curate chemical-gene and chemical/gene-disease interactions from the scientific literature using controlled vocabularies. Unfortunately, there are many more scientific documents available for curation than can actually be curated by CTD staff; consequently, selecting the best documents for curation is very important.To improve the efficacy of CTD biocuration process, a computational text mining prototype was developed to score and rank PubMed abstracts in terms of their desirability for curation. The prototype identifies:• chemical, gene, and disease actors, • specific action terms used to define interaction activity, and • other key factors that contribute to a document’s overall relevancy to CTD.The prototype was then tested using data manually curated by CTD as the control group in order to determine its overall effectiveness; a metric known as mean average precision was used in evaluating the prototype. How was the prototype designed and architected, what 3rd party tools were integrated into the prototype, how was the prototype tested? Were the tools able to identify the same actors as the curators, how were the documents scored and ranked, how effective was the document ranking process? What major problems were encountered? How will the prototype ultimately be integrated into the CTD biocuration process? The answers to these and other questions will be discussed during the workshop.
On-chip characterization of low-noise microstrip-coupled transition edge sensors
Authors: Rostem Karwan , Goldie David J. , Withington Stafford , Glowacka Dorota M. , Tsaneva Vassilka N. , Audley Michael D.
Published: April 2009

Transition edge sensors (TESs) are used extensively in millimeter-wave and submillimeter-wave astronomy. The next technological push is to reduce the noise equivalent powers from 10−17 to 10−20 W Hz−1/2 in order to take full advantage of the exceptionally low backgrounds associated with cooled-aperture space telescopes. We describe a lab-on-a-chip (LoC) for measuring the small-signal and noise properties of ultralow-noise microstrip-coupled TESs. The LoC comprises two suspended SiNx membranes, one of which supports a single-mode, variable-temperature blackbody source, and the other a microstrip-coupled TES. The two devices are connected by a superconducting microstrip transmission line. The temperature of the source is determined by Johnson noise thermometry using superconducting quantum interference device readout. In this paper, we describe the theory, layout, operation, and calibration of the experimental system and report on two prototype devices. The LoC concept has many advantages, and already we have been able to assess the optical efficiencies of our TESs. We have started to gain an appreciation of the losses associated with 100–300 GHz microminiature superconducting microstrip transmission lines at low temperatures. The next phase of our work is to apply the technique to ultralow-noise detectors, to study fluctuation phenomena in multimode devices, and to investigate the behavior of more complicated integrated circuits.
Diagnosing fuel ρR and ρR asymmetries in cryogenic deuterium-tritium implosions using charged-particle spectrometry at OMEGA
Authors: Frenje J. A. , Li C. K. , Séguin F. H. , Casey D. T. , Petrasso R. D. , Sangster T. C. , Betti R. , Glebov V. Yu. , Meyerhofer D. D.
Published: April 2009

Determining fuel areal density (ρR) in moderate-ρR (100–200 mg/cm2) cryogenic deuterium-tritium (DT) implosions is challenging as it requires new spectrometry techniques and analysis methods to be developed. In this paper, we describe a new method for analyzing the spectrum of knock-on deuterons (KO-Ds), elastically scattered by primary DT neutrons, from which a fuel ρR can be inferred for values up to ∼200 mg/cm2. This new analysis method, which uses Monte Carlo modeling of a cryogenic DT implosion, improves significantly the previous analysis method in two fundamental ways. First, it is not affected by significant spatial-yield variations, which degrade the diagnosis of the fuel ρR (spatial yield variations of about ±20% are typically observed), and second, it does not break down when the fuel ρR exceeds ∼70 mg/cm2.
A smart microfour-point probe with ultrasharp in-plane tips
Authors: Kim Ji-Kwan , Zhang Yan , Lee Dong-Weon
Published: April 2009

We propose a smart microfour-point probe (μ4PP) with ultrasharp in-plane tips that are arranged in a square with a spacing of 20 μm. The μ4PP consists of a supporting cantilever and four subcantilevers. The subcantilevers are symmetrically suspended from the square frame at the end of the supporting cantilever. A thermal actuator based on the bimorph effect is also integrated on each subcantilever for functionalization of interest. The unique configuration of the four-terminal tips is very useful for versatile applications of the μ4PP.
Bottlenecks to vibrational energy flow in carbonyl sulfide: Structures and mechanisms
Authors: Paškauskas R. , Chandre C. , Uzer T.
Published: April 2009

Finding the causes for the nonstatistical vibrational energy relaxation in the planar carbonyl sulfide (OCS) molecule is a longstanding problem in chemical physics: Not only is the relaxation incomplete long past the predicted statistical relaxation time but it also consists of a sequence of abrupt transitions between long-lived regions of localized energy modes. We report on the phase space bottlenecks responsible for this slow and uneven vibrational energy flow in this Hamiltonian system with three degrees of freedom. They belong to a particular class of two-dimensional invariant tori which are organized around elliptic periodic orbits. We relate the trapping and transition mechanisms with the linear stability of these structures.
Spin(9) average of SU(N) matrix models
Authors: Hoppe Jens , Lundholm Douglas , Trzetrzelewski Maciej
Published: April 2009

We apply a method of group averaging to states and operators appearing in (truncations of) the Spin(9)×SU(N) invariant matrix models. We find that there is an exact correspondence between the standard supersymmetric Hamiltonian and the Spin (9) average of a relatively simple lower-dimensional model.
Secondary phase segregation in heavily transition metal implanted ZnO
Authors: Schumm Marcel , Koerdel Martin , Müller Sven , Ronning Carsten , Dynowska Elzbieta , Gołacki Zbigniew , Szuszkiewicz Wojciech , Geurts Jean
Published: April 2009

With micro-Raman spectroscopy and x-ray diffraction (XRD), we studied ZnO crystals implanted with Mn, Fe, Co, and Ni, respectively, with implantation concentrations from 4 up to 16 at. %. Using thermal treatments in air up to 700 °C, we analyzed the annealing effect on the ZnO crystal lattice as well as the onset of secondary phases and their microstructure on the sample surface. While the 500 °C treatment induces a considerable annealing, secondary phases are observed for transition metal (TM) concentrations ≥8 at. % after the treatment at 700 °C. Their microstructure strongly depends on the TM species. Various stoichiometric and nonstoichiometric TM oxide precipitates as well as elemental TM clusters are identified by their Raman and XRD signatures and their possible magnetic impact is discussed.
Impact of proton-radiation-induced spacer damage on the dc characteristics degradation in deep-submicron metal-oxide-semiconductor field effect transistors
Authors: Xue Shoubin , Huang Ru , Wang Pengfei , Wang Wenhua , Wu Dake , Pei Yunpeng , Zhang Xing
Published: April 2009

The dc characteristics degradation of 0.18 μm metal-oxide-semiconductor field effect transistors (MOSFETs) after 10 MeV proton irradiation is comprehensively investigated in this paper. The measured results show that the off-state drain current is increased in N-channel MOSFETs, which is due to the turn on of the parasitic transistors induced by the shallow trench isolation regions. While in P-channel MOSFETs, the threshold voltage increase (absolute value), the transconductance degradation, and the saturation drain current decrease are observed. From the analysis, it is concluded that the basic damage mechanism is not ascribed to the gate oxide and the isolation region. The origin of the observed changes may be mainly due to the damage in the spacer oxides of the transistors. In order to verify the assumption, the leakage current passing through the spacer between the gate and the drain is measured before and after irradiation with floated source/substrate and grounded drain. We find that the leakage current is two to three times larger after irradiation. Finally, in order to confirm the extrapolation, 2-dimension (2D) simulation has been performed with Synopsys TCAD (technical computer-aided design) Sentaurus Device Simulation tools (ISE 10.0). The behavior of the simulated charges trapped in the spacers is qualitatively consistent with the experimental results.
Surface structure of strontium titanate
Authors: Wang Jianli , Fu Min , Wu X. S. , Bai Dongmei
Published: April 2009

Perfect and defective surface structures for (001) SrTiO3 are determined in considering a supercell with 11 atomic layers using the first-principles calculations. The amplitude of the surface rumpling for the SrO-terminated surface is much larger than that for the TiO2-terminated surface, although both SrO- and TiO2-terminated surfaces are stable for a comparable range of the TiO2 chemical potential. The distance between the first and second planes compresses while that of the second and third planes expands due to the relaxation of the slab. The top sites of the oxygen atoms of SrO-termined surface and the fourfold symmetry hollow sites of TiO2-termined surface are favorable for Ti or Sr adsorbate. The relative stability of the defect species or reactions varies with the equilibrium conditions. The dominant surface defect is Ti substitutional defect and a TiO–TiO2 double layers may form at the surface, which has been confirmed by experiments.
Physical aspects of colossal dielectric constant material CaCu3Ti4O12 thin films
Authors: Deng Guochu , He Zhangbin , Muralt Paul
Published: April 2009

The underlying physical mechanism of the so-called colossal dielectric constant phenomenon in CaCu3Ti4O12 (CCTO) thin films were investigated by using semiconductor theories and methods. The semiconductivity of CCTO thin films originated from the acceptor defect at a level ∼90 meV higher than valence band. Two contact types, metal-semiconductor and metal-insulator-semiconductor junctions, were observed and their barrier heights, and impurity concentrations were theoretically calculated. Accordingly, the Schottky barrier height of metal-semiconductor contact is about 0.8 eV, and the diffusion barrier height of metal-insulator-semiconductor contact is about 0.4–0.7 eV. The defect concentrations of both samples are quite similar, of the magnitude of 1019 cm−3, indicating an inherent feature of high defect concentration.
Reconstruction of radial thermal conductivity depth profile in case hardened steel rods
Authors: Celorrio Ricardo , Mendioroz Arantza , Apiñaniz Estibaliz , Salazar Agustín , Wang Chinhua , Mandelis Andreas
Published: April 2009

In this work the surface thermal-wave field (ac temperature) of a solid cylinder illuminated by a modulated light beam is calculated first in two cases: a multilayered cylinder and a cylinder the radial thermal conductivity of which varies continuously. It is demonstrated numerically that, using a few layers of different thicknesses, the surface thermal-wave field of a cylindrical sample with continuously varying radial thermal conductivity can be calculated with high accuracy. Next, an inverse procedure based on the multilayered model is used to reconstruct the radial thermal conductivity profile of hardened C1018 steel rods, the surface temperature of which was measured by photothermal radiometry. The reconstructed thermal conductivity depth profile has a similar shape to those found for flat samples of this material and shows a qualitative anticorrelation with the hardness depth profile.
Fine structure and hyperfine perturbations in the pure rotational spectrum of the VCl radical in its X Δ5r state
Authors: Halfen D. T. , Ziurys L. M. , Brown John M.
Published: April 2009

The pure rotational spectrum of the VCl radical in its Δ5r ground state has been recorded in the range 236–417 GHz using millimeter/submillimeter direct absorption techniques. This species was created in an ac discharge of VCl4 and argon. Ten rotational transitions of VC35l were measured in all five Ω ladders; an additional nine transitions of the Ω=1 spin state were recorded in order to evaluate the V51 hyperfine structure. Hyperfine interactions associated with the C35l nucleus were not resolved, consistent with the ionic structure of the molecule. Because of extensive perturbations caused by the low-lying A Π5r excited state, the rotational spectrum of the ground state has been found to be quite irregular. The four lowest Ω ladders exhibit unusually large lambda-doubling interactions, with the Ω=1 component showing the largest splitting, over 2 GHz in magnitude. The Ω=1 transitions are also shifted to higher frequency relative to the other spin components. In addition, the hyperfine structure varies widely between the Ω ladders, and an avoided crossing is observed in two transitions of both the Ω=1e and 2e components. The data have been analyzed with a case (c) Hamiltonian, and effective rotational, lambda-doubling, and hyperfine constants have been determined for VC35l. Higher-order parity-dependent magnetic hyperfine terms dΔ2 and dΔ3 were required in the analysis, derived from perturbation theory, in addition to the usual dΔ parameter. The local perturbations evident in these spectra indicate that the A Π5r excited state lies within the spin-orbit manifold of the ground state, well below the predicted value of 517 cm−1. Mixing of the A Π5r and X Δ5r states apparently causes both local and global perturbations in the ground state spectrum.
Gravity effects on capillary flows in sharp corners
Authors: Ramé Enrique , Weislogel Mark M.
Published: April 2009

We analyze the effect of gravity on capillary flows in sharp corners. We consider gravity perpendicular and parallel to the channel axis. We analyze both steady and unsteady flows. In the steady analysis the main result is a closed form expression for the flow rate as a function of the two gravity components. Good agreement with steady experiments is offered as support of the model. The unsteady analysis is restricted to “small” values of the two gravity parameters and is accomplished using a similarity formulation. The similarity coefficients of the gravity corrections are fully determined by the coefficients of the gravityless problem. The main result of the unsteady analysis is the gravity corrections to the flow rate (or rate of advance) of the liquid in the channel. In addition, we obtain corrections for the liquid height as a function of position and time. We address in detail unsteady problems with select boundary conditions that are representative of typical flow types. In Appendix A we present a new exact solution to one of the gravityless similarity cases, which is analogous to a nonlinear heat conduction equation. In Appendix B we offer dimensional formulas for all the unsteady flow results, which are valuable for systems design and analysis.
The photoelectron spectrum of the isopropoxide anion: Nonadiabatic effects due to conical intersections and the spin-orbit interaction
Authors: Dillon Joseph J. , Yarkony David R.
Published: April 2009

The negative ion photoelectron spectrum of the isopropoxide anion is determined using the multimode vibronic coupling approach. The simulated spectrum is based on a two state quasidiabatic Hamiltonian for the isopropoxy radical, Hd, which includes all terms through second-order order in all internal coordinates and accurately represents the vicinity of the ab initio determined equilibrium geometry of the ground electronic state as well as the minimum energy crossing point (MECP) on the symmetry-allowed A2″−A2′ accidental seam of conical intersection. Hd is centered at the A2″−A2′ MECP and is determined from ab initio gradients and derivative couplings using a normal equations based algorithm. Spin-orbit effects are included using a generalization of a procedure due to Child and Longuet-Higgins. The nonadiabatic interactions coupling the A2″ and A2′ states are very similar to those found in an Exe Jahn–Teller system although the requisite symmetry is absent. The simulated photoelectron spectrum for isopropoxide-h7 is compared to a measured photoelectron spectrum and the results of a dispersed fluorescence experiment on the isopropoxy radical. The nominal Ã A2−X̃ A2 splitting of 68 cm−1 from the dispersed fluorescence experiment is confirmed. This splitting is shown to be a consequence of the accidental Jahn–Teller symmetry and the spin-orbit interaction so that the standard designation of this spectral feature as the Ã−X̃ splitting is not appropriate. This spectral feature is better thought of as the spin-orbit splitting of a nearly degenerate ground state. It is further shown that the intensities and line positions are such that the origin band of the nominal Ã A2 state and that of the X̃ A2 state could not be distinguished with the resolution available in the photoelectron experiment. The photoelectron spectrum of the completely deuterated analog, isopropoxide-d7, is also reported and discussed.
Contact resistance and threshold voltage extraction in n-channel organic thin film transistors on plastic substrates
Authors: Boudinet Damien , Le Blevennec Gilles , Serbutoviez Christophe , Verilhac Jean-Marie , Yan He , Horowitz Gilles
Published: April 2009

n -channel organic thin film transistors were fabricated on polyethylene naphthalate substrates. The first part of the paper is devoted to a critical analysis of eight methods to extract the threshold voltage from the transfer characteristic in the linear regime. Next, to improve electron injection and reduce contact resistance, self-assembled monolayers (SAMs) were deposited on the gold source and drain electrodes. The subsequent modification on the current-voltage characteristics of the transistors is analyzed by the transfer line method, using a threshold-voltage-corrected gate voltage. The improved performance of the device obtained with some of the SAM treatments is attributed to both a better morphology of the semiconductor film, resulting in an increased channel mobility, and to easier electron injection, which manifests itself through a lowering of the contact resistance. Interestingly, the modulation of the contact resistance exactly follows an opposite behavior to what reported in the case of p-channel devices, which brings further evidence for that charge injection is tuned by the direction and magnitude of the dipole moment of the SAM.
Modeling of magnetoelectric effect in polycrystalline multiferroic laminates influenced by the orientations of applied electric/magnetic fields
Authors: Ni Yong , Priya Shashank , Khachaturyan Armen G.
Published: April 2009

By using coarse graining model, the dependence of magnetoelectric (ME) coupling on the mutual orientations of magnetic and electric fields with respect to the orientation of layers in polycrystalline multiferroic laminates is investigated. It is shown that the ME coefficient, described by polarization change in response to the applied magnetic field, is proportional to the trace of effective piezomagnetic strain tensor projected onto laminate interfaces. The piezomagnetic strain significantly depends on the orientation of applied magnetic fields. The results obtained here demonstrate that the magnetoelectric effect in layered composites can be significantly improved by optimizing the configuration of applied electric/magnetic fields.
Different carrier compensation effect in La2−xSrxCu0.94Zn0.06O4 and La2−xSrxCu0.94Ni0.06O4 samples
Authors: Xu Jingtao , Qu Zhe , Tan Shun , Wu Yinghai , Liu Ning , Zhang Yuheng
Published: April 2009

The element substitution for Cu is usually used to investigate the mechanism of the high TC superconductivity in cuprates. However, it is still controversial how substitution suppresses superconductivity. We suggest that the suppression of superconductivity by doping is attributed to the local electrons introduced by the dopant regardless of magnetic or nonmagnetic impurities. Here, the compensation effect has been investigated in the bivalent ions doped La2−xSrxCu0.94Zn0.06O4 (LSCZO) and La2−xSrxCu0.94Ni0.06O4 (LSCNO) systems. It is found that the holes introduced by Sr substitution for La have compensated the local electrons and this results in the reappearance of the superconductivity in LSCNO system, while no trace for the superconductivity is observed in LSCZO system. Interestingly, resistivity for LSCZO system decreases faster with doping level compared to that for LSCNO system. This may be ascribed to the fact that the introduced holes do not compensate the local electrons around Zn impurities but participate in the conductive process. We discuss the possible origin of the different compensation effect between LSCNO and LSCZO systems.
Determining exciton bandwidth and film microstructure in polythiophene films using linear absorption spectroscopy
Authors: Clark Jenny , Chang Jui-Fen , Spano Frank C. , Friend Richard H. , Silva Carlos
Published: April 2009

We analyze the linear absorption spectrum of regioregular poly(3-hexylthiophene) films spun from a variety of solvents to probe directly the film microstructure and how it depends on processing conditions. We estimate the exciton bandwidth and the percentage of the film composed of aggregates quantitatively using a weakly interacting H-aggregate model. This provides a description of the degree and quality of crystallites within the film and is in turn correlated with thin-film field-effect transistor characteristics.
Simulating dynamic crossover behavior of semiflexible linear polymers in solution and in the melt
Authors: Steinhauser M. O. , Schneider J. , Blumen A.
Published: April 2009

We present a molecular dynamics study of the dynamic scaling behavior of linear polymers in solution and in the melt when their character changes from fully flexible to semiflexible. The stiffness of the chains is determined by a bending potential. It is shown that the relaxation times τp characterizing the internal dynamics of the polymer chains as well as the mean square mode amplitudes ⟨χp2⟩ exhibit a clear crossover from Rouse to bending modes with increasing mode number p. For small mode numbers p the well-known p−2 Rouse behavior is observed, whereas large mode numbers exhibit the p−4 scaling, typical of the bending modes of semiflexible chains. We study the extension and the onset of the region where the crossover from p−2 to p−4 behavior occurs. With increasing stiffness of the chains we observe a shift of the crossover domain to smaller p-values. We also investigate the effect of chain stiffness on the monomer dynamics, based on their mean square displacements. Finally, we compare our results to previous simulations, where the scaling behavior of semiflexible chains was studied and which were restricted to a smaller range of persistence lengths lp and p values.
Quasilinearity in tetratomic molecules: An ab initio study of the CHNO family
Authors: Mladenović Mirjana , Elhiyani Mohamed , Lewerenz Marius
Published: April 2009

We present coupled-cluster CCSD(T) all electron results for the equilibrium structure of isofulminic acid, HONC, together with results for the barrier to linearity and the energetics for the four most stable members of the CHNO isomer family, obtained for the ground electronic states by means of large correlation consistent basis sets. Minimum energy paths along the angular coordinates reported for these CHNO isomers are combined with the dominant kinetic energy contributions to predict key rovibrational spectroscopic features which are clearly reminiscent of quasilinear behavior in tetratomic molecules.
Fluorescence decay-time constants in organic liquid scintillators
Authors: Marrodán Undagoitia T. , von Feilitzsch F. , Oberauer L. , Potzel W. , Ulrich A. , Winter J. , Wurm M.
Published: April 2009

The fluorescence decay-time constants have been measured for several scintillator mixtures based on phenyl-o-xylylethane (PXE) and linear alkylbenzene (LAB) solvents. The resulting values are of relevance for the physics performance of the proposed large-volume liquid scintillator detector Low Energy Neutrino Astronomy (LENA). In particular, the impact of the measured values to the search for proton decay via p→K+ν¯ is evaluated in this work.
The importance of anharmonic effects in models that interconnect point defect parameters with bulk properties in solids
Authors: Varotsos P.
Published: April 2009

We point out that the ability of a model that interconnects the defect Gibbs energy gi with bulk properties to reproduce the Al self-diffusion coefficients D up to the melting point stems from the fact that it seems to capture anharmonic effects. This conforms to recent findings that, in the high temperature region, microscopic studies using density-functional theory (DFT) in combination with the quasiharmonic approximation (QHA) reveal that some thermal properties of Al cannot be fully accounted for, probably due to the anharmonic effects not included in QHA. The importance of these effects is also emerged in inelastic neutron scattering experiments, which find an almost quadratic increase in phonon linewidth with temperature. Furthermore, we discuss recent claims that DFT microscopic calculations enable the satisfactory determination of D even in the harmonic approximation.