bluuebunny/crossref_metadata_2025 huggingface dataset:
Some remarks on resolving seamounts in satellite gravity
Authors: Marks K. M. , Smith W. H. F.
Published: February 2007

We examine peak‐to‐trough gravity anomaly amplitudes over seamounts, comparing gravity derived from satellite altimetry with gravity measured by ships. We also compare amplitudes from linear and higher‐order (non‐linear) computations, and conclude that two‐term forward modeling of seamounts should be adequate. Altimetric amplitudes are within 90% of ship amplitudes at seamounts greater than 14 km in characteristic radius. At smaller seamounts, altimetric amplitude is reduced, probably due to smoothing filters used to process the altimeter data. Perhaps fortuitously, this amplitude loss nearly matches the amplitude under‐estimate that occurs if one assumes the forward model should contain only a linear term. Thus bathymetric prediction by linear filtering may do a fairly good job of resolving seamounts much smaller than 14 km in characteristic radius.
Mechanism of deep low frequency earthquakes: Further evidence that deep non‐volcanic tremor is generated by shear slip on the plate interface
Authors: Ide Satoshi , Shelly David R. , Beroza Gregory C.
Published: February 2007

We study the mechanism of low frequency earthquakes (LFEs) in the Nankai Trough in western Shikoku, Japan. Precise locations have previously suggested that they represent shear slip on the plate boundary. In this paper we examine the mechanism of these events. Due to the low signal‐to‐noise ratio, we analyze stacked LFE waveforms and compare them with the waveforms of nearby earthquakes of known mechanism within the subducting Philippine Sea Plate. Analysis of both the focal mechanism using P‐wave first‐motions and the moment tensor using S waveforms indicates that LFEs represent shear slip on a low‐angle thrust fault dipping to the northwest, namely the plate interface. Together with reports that deep tremor consists of a swarm of LFEs, our results suggest that deep tremor is generated directly by shear slip on the plate interface, and as such represents a seismic signature of the accompanying slow slip events.
Staggered‐grid split‐node method for spontaneous rupture simulation
Authors: Dalguer Luis A. , Day Steven M.
Published: February 2007

We adapt the traction‐at‐split‐node method for spontaneous rupture simulations to the velocity‐stress staggered‐grid finite difference scheme. The staggered‐grid implementation introduces both velocity and stress discontinuities via split nodes. The staggered traction components on the fault plane are interpolated to form the traction vector at split nodes, facilitating alignment of the vectors of sliding friction and slip velocity. To simplify the split‐node partitioning of the equations of motion, spatial differencing is reduced from fourth to second order along the fault plane, but in the remainder of the grid the spatial differencing scheme remains identical to conventional spatially fourth‐order three‐dimensional staggered‐grid schemes. The resulting staggered‐grid split node (SGSN) method has convergence rates relative to rupture‐time, final‐slip, and peak‐slip‐velocity metrics that are very similar to the corresponding rates for both a partly staggered split‐node code (DFM) and the boundary integral method. The SGSN method gives very accurate solutions (in the sense that errors are comparable to the uncertainties in the reference solution) when the median resolution of the cohesive zone is 4.4 grid points. Combined with previous results for other grid types and other fault‐discontinuity approximations, the SGSN results demonstrate that accuracy in finite difference solutions to the spontaneous rupture problem is controlled principally by the scheme used to represent the fault discontinuity, and is relatively insensitive to the grid geometry used to represent the continuum. The method provides an efficient and accurate means of adding spontaneous rupture capability to velocity‐stress staggered‐grid finite difference codes, while retaining the computational advantages of those codes for problems of wave propagation in complex media.
Inversion of far‐regional broadband P waves for the estimation of source parameters from shallow depth earthquakes
Authors: Ichinose Gene A. , Goldstein Peter
Published: February 2007

Attempts in separating the earthquake source effect from complex upper mantle wave propagation effects have been unsuccessful due to band‐limited World‐Wide Standardized Seismograph Network data and limitations in the computation of accurate seismograms. In this study, we examine the potential for estimating source parameters using broadband P waves observed between distances of 10° and 30°. We used the reflectivity method, which retains all of the rays, to compute synthetic Green's functions from the Earth‐flattened global AK135 and regional T7 isotropic velocity models. We applied the moment tensor inversion and iterative dislocation grid search methods to estimate seismic moment, moment tensor, focal mechanism, and focal depth for three example seismic events, the 1995 (Mw 5.7) west Texas, 1999 (Mw 5.6) Scotty's Junction, Nevada, and 1999 southern Iran (Mw 4.8) earthquakes. The west Texas and Scotty's Junction earthquakes were well recorded, and they had independently established source parameters. Independent estimates from different data sets and agencies were used to validate the inversion results. We selected the southern Iran earthquake to show the utility of the method at lower magnitudes. Selected vertical and radial component seismograms were windowed about the P wave arrival, corrected for instrument response, and converted to velocity, preserving the absolute amplitudes and periods within approximately 0.5 to 100 s. Both inverse methods were successful in separating the source effect with the use of the AK135 velocity model. The inversion results using the T7 model appear slightly biased and had worse waveform fits compared to AK135. More importantly, the use of two different velocity models resulted in biases in focal depths that were less than ±2 km, thereby providing a robust inverse method for focal depth. Utilizing far‐regional P waves would be most useful for remote earthquakes not adequately recorded locally and too small in magnitude to be recorded beyond epicentral distances of 30° for teleseismic analysis.
Direct and indirect effects of anthropogenic aerosols on regional precipitation over east Asia
Authors: Huang Yan , Chameides William L. , Dickinson Robert E.
Published: February 2007

A regional coupled climate‐chemistry‐aerosol model is developed. It is used to assess the direct and indirect effects of anthropogenic sulfate and carbonaceous aerosols on regional climate over east Asia with a focus on precipitation. The simulated direct and first indirect effects for the most part reduce the solar radiation and hence decrease the surface temperature, while the second indirect effect generates both negative solar forcing and a substantial positive long‐wave forcing. It decreases the precipitation, but because of the cancelling effect, surface temperature does not change very much. With the interactively model‐calculated current aerosol loading and the combined direct/semidirect/first indirect effect, the simulated precipitation is reduced by about 10% in the fall and winter and by about 5% in the spring and summer. The second indirect effect has the largest impact, by itself decreasing the fall and winter precipitation from about 3% to 20%, depending on the autoconversion scheme assumed. The semidirect effect on precipitation is relatively small. An empirical orthogonal function analysis of climatological precipitation over east Asia since the last century shows a decreasing trend of the leading modes over most of China in the fall and winter, which is generally geographically consistent with the distribution of the model‐simulated precipitation reduction from anthropogenic aerosols.
Comparisons of Tropospheric Emission Spectrometer (TES) ozone profiles to ozonesondes: Methods and initial results
Authors: Worden H. M. , Logan J. A. , Worden J. R. , Beer R. , Bowman K. , Clough S. A. , Eldering A. , Fisher B. M. , Gunson M. R. , Herman R. L. , Kulawik S. S. , Lampel M. C. , Luo M. , Megretskaia I. A. , Osterman G. B. , Shephard M. W.
Published: February 2007

The Tropospheric Emission Spectrometer (TES) on the Earth Observing System (EOS)‐Aura spacecraft measures global profiles of atmospheric ozone with vertical resolution of 6–7 km in the troposphere for the nadir view. For a first validation of TES ozone measurements we have compared TES‐retrieved ozone profiles to ozonesondes from fall, 2004. In some cases the ozonesonde data are from dedicated launches timed to match the Aura overpass, while other comparisons are performed with routine data available from the Southern Hemisphere Additional Ozonesonde (SHADOZ) archive and World Ozone and Ultraviolet Data Center (WOUDC) data archives. We account for TES measurement sensitivity and vertical resolution by applying the TES‐averaging kernel and constraint to the ozonesonde data before differencing the profiles. Overall, for V001 data, TES ozone profiles are systematically higher than sondes in the upper troposphere but compare well in the lower troposphere, with respect to estimated errors. These comparisons show that TES is able to detect relative variations in the coarse vertical structure of tropospheric ozone.
Soil‐atmosphere exchange of N2O, CH4, and CO2 and controlling environmental factors for tropical rain forest sites in western Kenya
Authors: Werner Christian , Kiese Ralf , Butterbach‐Bahl Klaus
Published: February 2007

N2O, CH4 and CO2 soil‐atmosphere exchange and controlling environmental factors were studied for a 3‐month period (dry‐wet season transition) at the Kakamega Rain forest, Kenya, Africa, using an automated measurement system. The mean N2O emission was 42.9 ± 0.7 μg N m−2 h−1 (range: 1.1–324.8 μg N m−2 h−1). Considering the duration of dry and wet season the annual N2O emission was estimated at 2.6 ± 1.2 kg N ha−1 yr−1. Large pulse emissions of N2O were observed after the first rainfall events of the wet season, and the magnitude of N2O emissions steadily declined thereafter. A comparable trend in soil CO2 emissions (mean: 71.8 ± 0.3 mg C m−2 h−1) indicates that the rapid mineralization of litter accumulated during the dry period produced the high N2O emissions at the start of the wet season. Manual N2O emission measurements at four additional rain forest sites were comparable to those measured at the main site, whereas N2O emissions measured at a regrowth site were significantly lower. Spatial differences in N2O emissions could be explained by differences in soil texture and topsoil C:N‐ratio (CO2: subsoil C and N concentrations), whereas the temporal variability of N2O and CO2 emissions was primarily driven by soil moisture. Soils predominantly acted as sinks for CH4 (−56.4 ± 0.8 μg C m−2 h−1). For some chamber positions, episodes of net CH4 release were observed, which could be due to high WFPS and/or termite activity. CH4 fluxes were weakly correlated with soil moisture levels but showed no relation to temperature, texture, pH, carbon or nitrogen contents.
Relationship between the origin of precipitation in the Jordan Rift valley and their geochemical composition
Authors: Anker Yaakov , Flexer Akiva , Rosenthal Eliahu , Ganor Eliezer
Published: February 2007

Rainwater was sampled during seven winters at eight sites along the Jordan Rift valley in Israel. The study area is divided into two regions: the northern part located between the Sea of Galilee and the Dead Sea and the southern part between the Dead Sea and the Dead Sea–Red Sea water divide line in the Arava valley. The Dead Sea region is considered as a desert, the northern part of the study area is semidesert whereas the southern region is considered as extreme desert. Good agreement was found between the chemical and isotopic composition of rainwater its sources and air mass trajectories. In the arid areas, the contribution of salts was mainly from local sources (of up to 500 Km in diameter). Significant chemical divergence was found between rainwater deriving from marine air masses characterized by NaCl enrichment and rainwater deriving from continental air masses which are mainly characterized by Ca‐carbonate enrichment. Six main marine and continental air mass trajectories were defined, i.e., northern, northwestern, western, southwestern, eastern and local. The northern air mass trajectories contribute more salts than the southwestern air mass trajectories which exhibit the lowest rainwater salinities. The western trajectory is exclusively marine originating from the Mediterranean, while the eastern trajectory is exclusively continental and originates in the Arabian Desert. Rainwater isotopes revealed three chemically differing systems. The western marine trajectories reflect chemical setting associated with East Mediterranean Meteoric Water Line system; the continental air masses are mainly associated with the Mean Meteoric Water Line system; and whenever the eastern component is significant, a Local Meteoric Water Line prevails.
A Mariner 10 color study of Mercurian craters
Authors: Blewett David T. , Hawke B. Ray , Lucey Paul G. , Robinson Mark S.
Published: February 2007

We have used recalibrated Mariner 10 color image data (UV and orange) to examine spectral trends associated with crater features on the “incoming” hemisphere of Mercury. Spacecraft images of the Moon (Galileo and Clementine) and lunar sample laboratory spectra provide a framework for interpreting the Mercurian data. Two spectral parameter images were constructed. One reveals opaque mineral abundance, and the other provides a map of variations related to optical maturity and FeO content. The crater Kuiper and its rays are bright mainly because they are fresh (immature) but also because Kuiper has excavated material with a lower opaque content than the surroundings. Under the influence of space weathering, Kuiper will eventually lose its rays and evolve into a bright‐floored crater like Lermontov. Lermontov and nearby smaller craters are examples of craters that are likely mature, but remain bright because of the low‐opaque material exposed on their floors. In this portion of the planet, it appears that a surface layer with moderate‐opaque abundance overlies low‐opaque material found at depth. On the basis of estimates of crater excavation depths, we suggest that the moderate‐opaque surface layer is ∼3–4 km thick. This two‐layer stratigraphy is reminiscent of the lunar highland crust and may have originated in similar magma ocean processes. We also describe a feature that exposes dark material with a relatively high opaque content. This feature could be a Mercurian analog to a lunar dark‐halo impact crater or perhaps a pyroclastic deposit. This implies that opaque‐rich, possibly mafic, magmas were generated in the interior and reached the surface through effusive or explosive activity.
Excitotoxic Mechanisms of Ischemic Injury in Myelinated White Matter
Authors: Tekkök Selva Baltan , Ye ZuCheng , Ransom Bruce R
Published: February 2007

Axonal injury and dysfunction in white matter (WM) are caused by many neurologic diseases including ischemia. We characterized ischemic injury and the role of glutamate-mediated excitotoxicity in a purely myelinated WM tract, the mouse optic nerve (MON). For the first time, excitotoxic WM injury was directly correlated with glutamate release. Oxygen and glucose deprivation (OGD) caused duration-dependent loss of axon function in optic nerves from young adult mice. Protection of axon function required blockade of both α-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA) and kainate receptors, or removal of extracellular Ca2+. Blockade of N-methyl-D-aspartate receptors did not preserve axon function. Curiously, even extended periods of direct exposure to glutamate or kainate or AMPA failed to induce axon dysfunction. Brief periods of OGD, however, caused glutamate receptor agonist exposure to become toxic, suggesting that ionic disruption enabled excitotoxic injury. Glutamate release, directly measured using quantitative high-performance liquid chromatography, occurred late during a 60-mins period of OGD and was due to reversal of the glutamate transporter. Brief periods of OGD (i.e., 15 mins) did not cause glutamate release and produced minimal injury. These results suggested that toxic glutamate accumulation during OGD followed the initial ionic changes mediating early loss of excitability. The onset of glutamate release was an important threshold event for irreversible ischemic injury. Regional differences appear to exist in the specific glutamate receptors that mediate WM ischemic injury. Therapy for ischemic WM injury must be designed accordingly.
Evaluation of Four Pyridine Analogs to Characterize 6-OHDA-Induced Modulation of mGluR5 Function in Rat Brain Using microPET Studies
Authors: Zhu Aijun , Wang Xukui , Yu Meixiang , Wang Ji-Quan , Brownell Anna-Liisa
Published: February 2007

Micro-positron emission tomography imaging studies were conducted to characterize modulation of metabotropic glutamate subtype-5 receptor (mGluR5) function in a 6-hydroxydopamine (6-OHDA)-induced rat model of Parkinson's disease using four analogical PET ligands: 2-[11C]methyl-6-(2-phenylethynyl) pyridine ([11C]MPEP), 2-(2-(3-[11C]methoxyphenyl)ethynyl)pyridine ([11C]M-MPEP), 2-(2-(5-[11C]methoxypyridin-3-yl)ethynyl)pyridine ([11C]M-PEPy), and 3-[(2-[18F]methyl-1,3-thiazol-4-yl)ethynyl]pyridine ([18F]M-TEP). A total of 45 positron emission tomography (PET) imaging studies were conducted on nine male Sprague-Dawley rats within 4 to 6 weeks after unilateral 6-OHDA lesioning into the right medial forebrain bundle. The severity of the lesion was determined with [11C]CFT ([11C]2-β-carbomethoxy-3-β-(4-fluorophenyl)tropane), a specific and sensitive ligand for imaging dopamine transporter function. The binding potential (BP) images were processed on pixel-by-pixel basis by using a method of the distribution volume ratio with cerebellum as a reference tissue. The values for BP were determined on striatum, hippocampus, and cortex. [11C]CFT binding was decreased on the lesioned (right) striatum by 35.4% ± 13.4% compared with the intact left striatum, indicating corresponding loss of presynaptic dopamine terminals. On the same areas of the lesioned striatum, three of the four tested mGluR5 ligands showed enhanced binding characteristics. The average differences between the right and left striatum were 4.4% ± 6.5% ( P < 0.05) with [11C]MPEP, 0.1% ± 1.7% ( P > 0.05) with [11C]M-MPEP, 3.9% ± 4.6% ( P < 0.05) with [11C]M-PEPy, and 6.6% ± 2.7% ( P > 0.05) with [18F]M-TEP. The enhanced binding was also observed in the right hippocampus and cortex. These studies showed that glutamatergic neurotransmission might have a complementary role in dopaminergic degeneration, which can be evaluated by in vivo PET imaging.
Static properties of crystallographically aligned Terfenol-D∕polymer composites
Authors: Altin Gokcay , Ho Ken K. , Henry Christopher. P. , Carman Gregory P.
Published: February 2007

Crystallographically aligned [112] magnetostrictive particle (CAMP) composites were characterized quasistatically. Three volume fraction (vf) composites (26%, 37%, and 49%) were manufactured and subjected to compressive stresses ranging from −2to−24MPa, magnetic fields loading up to 400kA∕m, and thermal variations (from 0to30°C). These tests provided property measurement including maximum magnetostrictive strain (εmax), elastic modulus (EH), relative permeability (μr), piezomagnetic coefficient (d33), and coupling coefficient (k33). Results show that the 49% volume fraction CAMP composite produced strains of up to 1600ppm saturation magnetostriction, which is 89% of the monolithic value (1800ppm), and a coupling coefficient of 0.65, which is approximately 75% that of the monolithic, and relative thermal stability over the range of 0–30°C.
Wave propagation in single- and double-walled carbon nanotubes filled with fluids
Authors: Natsuki Toshiaki , Ni Qing-Qing , Endo Morinobu
Published: February 2007

Wave propagation approach of single- and double-walled carbon nanotubes conveying fluid is presented through the use of the continuum mechanics. A simplified Flügge shell equations are proposed as the governing equations of motion for carbon nanotubes studied here. For the double-walled nanotubes, the deflection of nested tubes is considered to be coupled through the van der Waals interaction between two adjacent nanotubes. Effects of filled fluid property and nanotube diameter on the wave propagation are investigated and analyzed based on the proposed elastic continuum model. The theoretical investigation may give a useful reference for potential design and application of nanoelectronics and nanodevices.
rf magnetron sputter deposition of transparent conducting Nb-doped TiO2 films on SrTiO3
Authors: Gillispie Meagen A. , van Hest Maikel F. A. M. , Dabney Matthew S. , Perkins John D. , Ginley David S.
Published: February 2007

rf magnetron sputtering, an established and scalable large area deposition process, is used to deposit Nb:TiO2 and Ta:TiO2 films onto (100) SrTiO3 substrates at temperatures TS ranging from room temperature to 400°C. Optical, electrical, and structural properties similar to those reported for pulsed laser deposition grown films were obtained. In particular, the most conducting Ti0.85Nb0.15O2 films, grown at TS≈375°C, are epitaxially oriented anatase films with conductivity of 3000Scm−1, carrier concentration of 2.4×1021cm−3, Hall mobility of 7.6cm2V−1s−1, and optical transparency T>80% from 400to900nm. The conductivity is strongly correlated with the intensity of the anatase (004) x-ray diffraction peak.
Thermodynamic and transport properties of carbon dioxide from molecular simulation
Authors: Nieto-Draghi Carlos , de Bruin Theodorus , Pérez-Pellitero Javier , Bonet Avalos Josep , Mackie Allan D.
Published: February 2007

Monte Carlo and molecular dynamics simulations have been used in order to test the ability of a three center intermolecular potential for carbon dioxide to reproduce literature experimental thermophysical values. In particular, both the shear viscosity under supercritical conditions and along the phase coexistence line, as well as the thermal conductivity under supercritical conditions, have been calculated. Together with the already reported excellent agreement for the phase coexistence densities, the authors find that the agreement with experimental values is, in general, good, except for the thermal conductivity at low density. Although extended versions of the model were employed, which include an explicit account of bending and vibrational degrees of freedom, a significant difference was still found with respect to the reported experimental value.
Photoluminescence of Si layers grown on oxidized Si surfaces
Authors: Shklyaev A. A. , Nakamura Y. , Ichikawa M.
Published: February 2007

Silicon layers grown on oxidized Si surfaces at temperatures between 400 and 500°C exhibit intense photoluminescence (PL) in the D1 region after annealing at high temperatures (up to 1100°C). This PL is associated with structural defects that are formed due to the mechanisms of Si growth and thermal relaxation. The growth proceeds through the nucleation of epitaxial and nonepitaxial Si islands. Their coalescence occurs with the formation of a number of interfacial defects, which propagate into the Si layer as it grows. Annealing modifies the structure of the defect and makes them efficient for optical emissions. These Si structures are able to produce PL in the D1 region from thin Si layers at room temperature.
Degradation mechanisms in organic light-emitting devices: Metal migration model versus unstable tris(8-hydroxyquinoline) aluminum cationic model
Authors: Luo Yichun , Aziz Hany , Popovic Zoran D. , Xu Gu
Published: February 2007

To resolve the issue of which of the “indium migration” model and the “unstable AlQ3 cationic” model plays a more important role in luminescence degradation of organic light-emitting devices, we investigated the effect of the device structures on device operational stability. The results show that alterations in device layer structures can significantly affect the device operational stability, although they do not appear to noticeably change the magnitude of indium migrations. This suggests that the indium migration model may not play a dominant role in device degradation. On the other hand, the change in device stability with the alteration in the device structures can be plausibly explained by the unstable AlQ3 cationic model.
Strain relaxation in GaN grown on vicinal 4H-SiC(0001) substrates
Authors: Pernot J. , Bustarret E. , Rudziński M. , Hageman P. R. , Larsen P. K.
Published: February 2007

The strain of GaN layers grown by metal organic chemical vapor deposition on three vicinal 4H-SiC substrates (0°, 3.4°, and 8° off cut from [0001] towards [11−20] axis) is investigated by x-ray diffraction, Raman scattering, and cathodoluminescence. The strain relaxation mechanisms are analyzed for each miscut angle. At a microscopic scale, the GaN layer grown on on-axis substrate has a slight and homogeneous tensile in-plane stress due to a uniform distribution of threading dislocations over the whole surface. The GaN layers grown on miscut substrates presented cracks, separating areas which have a stronger tensile in-plane stress but a more elastic strain. The plastic relaxation mechanisms involved in these layers are attributed to the step flow growth on misoriented surfaces (dislocations and stacking faults) and to the macroscopical plastic release of additional thermoelastic stress upon cooling down (cracks).
Observation of ultrafast carrier dynamics in amorphous Ge2Sb2Te5 films induced by femtosecond laser pulses
Authors: Zhang Guangjun , Gan Fuxi , Lysenko Sergiy , Liu Huimin
Published: February 2007

The femtosecond pump-probe technique was used to study the carrier dynamics of amorphous Ge2Sb2Te5 films. With carrier density at around 1020−1021 cm−3, carriers were excited within 1 ps and recovered to the initial state for less than 3 ns. On the picosecond time scale, the carrier relaxation consists of two components: a fast process within 5 ps and a slow process after 5 ps. The relaxation time of the fast component is a function of carrier density, which increases from 1.9 to 4.3 ps for the carrier density changing from 9.7×1020 cm−3 to 3.1×1021 cm−3. A possible interpretation of the relaxation processes is elucidated. In the first 5 ps the relaxation process is dominated by an intraband carrier relaxation and the carrier trapping. It is followed by a recombination process of trapped carriers at later delay time.
Correlation between x-ray reciprocal space maps and magnetic properties of current-induced magnetization switching pseudospin valve structures
Authors: Siffalovic P. , Chitu L. , Halahovets Y. , Jergel M. , Senderak R. , Majkova E. , Luby S.
Published: February 2007

A thorough study of x-ray diffuse scattering from the spin valve structures suitable for current induced magnetization switching is presented. We used complete reciprocal space maps of diffusely scattered x rays to show the effect of bottom Au electrode on the morphology of buried spin valve interfaces. The thickness and roughness of each layer, as well as vertical and lateral roughness correlation lengths, were obtained. The impact of interfaces morphology on the magnetic properties, especially on the increase of spin valve coercivity, was measured and simulated within the frame of Néel magnetostatic coupling model based on the parameters from the x-ray diffuse scattering data. Measurement of x-ray diffuse scattering presents a rapid and nondestructive technique for in-depth and self-contained analysis of spin valve layers and interfaces.
Nonperturbative Adler-Bardeen theorem
Authors: Mastropietro Vieri
Published: February 2007

The Adler-Bardeen theorem has been proven only as a statement valid at all orders in perturbation theory, without any control on the convergence of the series. In this paper we prove a nonperturbative version of the Adler-Bardeen theorem in d=2 by using recently developed technical tools in the theory of Grassmann integration. The proof is based on the assumption that the boson propagator decays fast enough for large momenta. If the boson propagator does not decay, as for Thirring contact interactions, the anomaly in the WI (Ward Identities) is renormalized by higher order contributions.
Electrostatic energy, potential energy, and energy dissipation for a width-variable capacitor system during adiabatic charging
Authors: Nakata Shunji , Katagiri Yoshitada , Matsuno Shun-ichi
Published: February 2007

This paper considers the energy consumed by charging and discharging a width-variable capacitor. The capacitor with plate distance d is coupled with repulsive mechanical potential energy, which is proportional to 1∕dn. In this capacitor model, there is a stable point between attractive electrical force and repulsive mechanical force. All energies, including the electrostatic energy, potential energy, and energy dissipation, are proportional not to the ordinary value V2 but to V2∕(n−1)+2, where V is the abrupt power supply voltage. We apply N-stepwise adiabatic charging to the width-variable capacitor system. It is shown that the energy consumption after charging and discharging (or recycling) can be 1∕N times smaller than that of the conventional abrupt operation. By increasing the step number N, the adiabatic operation can ideally charge and discharge the width-variable capacitor system with absolutely no energy dissipation, although the voltage dependence of energies is quite different from the usual one. Adiabatic charging is very promising for realizing dissipationless operation in the proposed system.
Understanding the advantage of remote femtosecond laser-induced breakdown spectroscopy of metallic targets
Authors: Xu H. L. , Bernhardt J. , Mathieu P. , Roy G. , Chin S. L.
Published: February 2007

We analyze the advantages of remotely sensing metallic targets using femtosecond laser-induced breakdown spectroscopy by studying the temperature and electron density of the plasma ejected from a lead target produced by femtosecond laser pulse filamentation in ambient air. The electron density of 8×1017cm−3 and the plasma temperature of 6794K were obtained for a 20ns time delay with respect to the laser pulse arriving on the target. With these values the signal is high, while the continuum blackbody radiation is low. The continuum emission in the fluorescence spectra is mainly associated with the supercontinuum of the distorted pulse during filamentation (white light laser) in air and this can be controlled. Extrapolation of the single-shot detection limit shows that this technique of filament-induced breakdown spectroscopy could be extended up to the kilometer range, opening up potential applications in metallurgic industry for remote material analysis and process controls.
MeV N+-ion irradiation effects on α-MoO3 thin films
Authors: Sivakumar R. , Sanjeeviraja C. , Jayachandran M. , Gopalakrishnan R. , Sarangi S. N. , Paramanik D. , Som T.
Published: February 2007

In this work, modifications in the structural, vibrational, optical, and surface morphological properties of 2MeV N+-ion irradiated α-MoO3 thin films are studied. Nitrogen irradiation up to the fluence of 1×1015ionscm−2 does not lead to any structural phase change. The irradiation induced formation of nanoscale defect structures at the film surface becomes more prominent at higher irradiation fluences, leading to the enhancement in the optical absorption behavior of the irradiated films. The possible role of energy loss process in the mechanism of modifying the surface morphology has been discussed.
Probing the submonolayer morphology change in epitaxial growth: A simulation study
Authors: Itoh Makoto , Ohno Takahisa
Published: February 2007

The authors point out that in situ probing of the temporal change of island morphology during epitaxial growth is possible by observing a specular intensity of reflection high-energy electron diffraction (RHEED). They take the homoepitaxial growth of GaAs(001) as an example, and show by means of kinetic Monte Carlo simulations that the slope change in the initial decrease of the specular RHEED intensity gives the signal for the transition of island morphology from islands having no more than one trench structure to those with more than one trench structure.
Detection of tumor markers based on extinction spectra of visible light passing through gold nanoholes
Authors: Gao Di , Chen Wilfred , Mulchandani Ashok , Schultz Jerome S.
Published: February 2007

The authors demonstrate that nanometric holes in optically thin gold films on glass slides can be used as biochemical sensors based on extinction spectra of visible light passing through these holes. Binding and adsorption of biomolecules to the surfaces of gold and glass result in a redshift of the localized surface plasmon resonance peak in the extinction spectrum of the gold holes. Selective sensing of antigens such as cancer antigen 19-9 (of less than 1pg on an ∼0.1mm2 probing area) can be realized using this type of devices after functionalizing the gold and glass surfaces with bioreceptors.
Controlled growth of gold nanoparticles induced by ion irradiation: An in situ x-ray diffraction study
Authors: Mishra Y. K. , Avasthi D. K. , Kulriya P. K. , Singh F. , Kabiraj D. , Tripathi A. , Pivin J. C. , Bayer I. S. , Biswas A.
Published: February 2007

Thin silica films containing Au nanoparticles were prepared by cosputtering. The kinetics of the growth of nanoparticles under 90MeV Ni ion irradiation was studied by in situ x-ray diffraction. The growth of nanoparticles from 4 (for pristine) to 9nm at a fluence of 1×1014ions∕cm2 was observed, in accordance with the observations made by transmission electron microscopy analyses. The present study shows that the ion irradiation is an effective tool for tailoring the size of nanoparticles. The results are discussed in the framework of thermal spike model.
Leakage current analysis of diamond Schottky barrier diode
Authors: Umezawa Hitoshi , Saito Takeyasu , Tokuda Norio , Ogura Masahiko , Ri Sung-Gi , Yoshikawa Hiromichi , Shikata Shin-ichi
Published: February 2007

The current-voltage characteristics of non-punch-through-type diamond Schottky barrier diodes (SBDs) are analyzed by using thermionic and thermionic-field emission (TFE) models. Diamond SBD with defects such as nonepitaxial crystallites (NCs) shows shunt path conductance both under forward and reverse bias conditions. However, SBD without NCs shows a low reverse leakage current density of less than 1×10−11A∕cm2, which is more than 12 orders of magnitude smaller than the forward current density. From the fitting of the reverse leakage current of SBD without NCs, TFE current dominates when the reverse electric field is larger than 1.2MV∕cm and its current density value reaches 10−6A∕cm2 even at 1.6MV∕cm, which is lower than the avalanche limit.
Universities, Innovation, and Territorial Development: A Review of the Evidence
Authors: Smith Helen Lawton
Published: February 2007

In many countries, universities are emerging as the focal point for the formulation and delivery of policies on innovation, cluster development, human capital formation and development, entrepreneurship, and governance. The author provides a critique of arguments as to why universities have come to be seen as crucial stakeholders in the innovation process, and, in particular, should be territorial actors. It is argued that ascribing a central role in contemporary innovation systems to universities needs to be done with caution, and cannot be understood in isolation from political pressure.
Residents, Regulators, and Risk in Two Industrial Towns
Authors: Phillimore Peter , Schlüter Achim , Pless-Mulloli Tanja , Bell Patricia
Published: February 2007

To what extent is trust in governance procedures a precondition for public engagement? This work is based on ethnographic research that examined the relationship between regulators and residents in the major chemical and petrochemical centres of Grangemouth (Scotland) and Ludwigshafen (Germany). In Grangemouth a period of rising economic insecurity coupled with intensified public concern about safety has brought regulatory authorities and the town's population into ongoing dialogue. This dialogue has been uneasy, and marked by considerable public suspicion; but it has been a dialogue of sorts, nonetheless. In Ludwigshafen the prevailing mood has remained one of confidence in the town's massive chemical industry: the notion that a routine dialogue between regulators and residents might be either necessary or desirable has rarely been articulated by either side. Questioning the tendency in the literature on public engagement in environmental policy issues to associate such engagement with trust, we suggest that, in these two case studies at least, the opposite applied. It was manifest distrust and frustration which provoked animated public engagement with government and officials in Grangemouth recently. Equally, it was the depth of trust and familiarity, built up over decades, which facilitated public disengagement from issues of environmental regulation and governance in Ludwigshafen.
Agricultural acid sulfate soils: a potential source of volatile sulfur compounds?
Authors: Kinsela Andrew S. , Reynolds Jason K. , Melville Mike D.
Published: February 2007

Environmental context. Acid sulfate soils are important contributors to global environmental problems. Agricultural acid sulfate soils have recently been shown to emit sulfur dioxide, an important gas in global issues of acid rain, cloud formation and climate change. This emission is surprising because these soils tend to be wet and the gas is extremely water-soluble. The potential origins of this gas are not yet understood within the context of acid sulfate soils. Our new study reports the measurement of two potential precursors of sulfur dioxide, dimethylsulfide and ethanethiol, from both a natural and an agricultural acid sulfate soil in eastern Australia. Abstract. Most agricultural soils are generally considered to be a sink for sulfur gases rather than a source; however, recent studies have shown significant emissions of sulfur dioxide and hydrogen sulfide from acid sulfate soils. In the current study, acid sulfate soil samples were taken in northern New South Wales from under sugarcane cropping, as well as from an undisturbed nature reserve. Using gas chromatography/flame photometric detection in conjunction with headspace solid-phase microextraction, we have now determined that these soils are a potential source of the low molecular weight volatile sulfur compounds, dimethylsulfide and ethanethiol. Although the mechanism for their production remains unclear, both compounds are important in the transfer and interconversions of atmospheric and terrestrial sulfur. Therefore, these novel findings have important implications for refining local and regional atmospheric sulfur budgets, as well as for expanding our understanding of sulfur cycling within acid sulfate soils and other sediments.
Influence of organic and mineral fertilisation on organic matter fractions of a Brazilian Acrisol under maize/common bean intercrop
Authors: Leite L. F. C. , Mendonça E. S. , Machado P. L. O. A.
Published: February 2007

In 1984, a field experiment was initiated in Coimbra, State of Minas Gerais, Brazil, involving the combination of 3 levels of mineral fertilisers at control (0); 10 kg N/ha, 15 kg P/ha, and 17 kg K/ha (MF1); 20 kg N/ha, 30 kg P/ha, and 34 kg K/ha (MF2); and 2 levels of organic compost at control (0) and 40 m3/ha (OC) in a maize/common bean intercrop. Soil samples were collected (0–0.10 and 0.10–0.20 m) in 2000 to evaluate the impact of mineral and organic compost on total carbon (TOC) and nitrogen (TN) stocks and on organic carbon pools of a Ferric Acrisol (Chromosol in the Australian Soil Classification). Additional soil samples were collected from an adjacent site covered by secondary Atlantic Forest as a reference. The conversion of forest to agriculture caused a reduction in most of TOC, TN, and microbial biomass carbon, free-light fraction carbon (CLF), and non-labile carbon. The carbon pools in cultivated plot were enhanced by the addition of compost alone. At both depths, TOC and TN stocks were higher (P < 0.05) in the MF2 + OC than MF2 treatment. Compared to soils that have received mineral fertiliser alone or combined with compost, the stocks of labile organic carbon, TN, and CLF were significantly affected (P < 0.05) by the sole application of compost.
Interpretation of a single-point P buffering index for adjusting critical levels of the Colwell soil P test
Authors: Moody P. W.
Published: February 2007

Soil phosphorus (P) buffer capacity is the change in the quantity of sorbed P required per unit change in solution P concentration. Because P availability to crops is mainly determined by solution P concentration, as P buffer capacity increases, so does the quantity of P required to maintain a solution P concentration that is adequate for crop demand. Bicarbonate-extractable P using the Colwell method is the most common soil P test used in Australia, and Colwell-P can be considered to estimate P quantity. Therefore, as P buffer capacity increases, the Colwell-P concentration required for maximum yield also increases. Data from several published and unpublished studies are used to derive relationships between the ‘critical’ Colwell-P value (Colwell-P at 90% maximum yield) and the single-point P buffer index (PBI) for annual medics, soybean, potato, wheat, and temperate pasture. The rate of increase in critical Colwell-P with increasing PBI increases in the order: temperate pasture < medics < wheat < potato. Indicative critical Colwell-P values are given for the 5 crops at each of the PBI categories used to describe soil P buffer capacity as it increases from extremely low to very high.
An electromagnetic induction method for monitoring variation in soil moisture in agroforestry systems
Authors: Huth N. I. , Poulton P. L.
Published: February 2007

An understanding of the spatial and temporal patterns of soil water extraction by trees in agroforestry systems has long been seen as an important step towards understanding their functioning. Traditional methods of soil moisture monitoring have been employed with some success but limitations in utilising them efficiently across both time and space have led to restrictions in their use. An electromagnetic induction (EMI) technique has been evaluated and used to study the patterns of soil water extraction from a Grey Vertosol in fallow or cropped fields alongside a Eucalyptus argophloia windbreak near Warra, Qld (26.93°S, 150.93°E). This technique provides methods for minimising error caused by seasonal variations in temperature and the vertical distributions of both soil water and temperature. The calibration developed in this study was successful in describing the observed variations in total soil moisture in the surface 0.9 m of the soil profile (R2 = 0.93, s.e. = 15.3 mm). We conclude that EMI techniques can provide a quick and efficient means for monitoring soil moisture patterns in agroforestry systems when employed under suitable conditions. This paper describes the techniques developed and where they may be employed, the type of information available from the approach, and the likely methods for employing EMI approaches in a wider range of situations.
Fibroblast growth factor blocks Sonic hedgehog signaling in neuronal precursors and tumor cells
Authors: Fogarty Marie P. , Emmenegger Brian A. , Grasfeder Linda L. , Oliver Trudy G. , Wechsler-Reya Robert J.
Published: February 2007

The Sonic hedgehog (Shh) and FGF signaling pathways regulate growth and differentiation in many regions of the nervous system, but interactions between these pathways have not been studied extensively. Here, we examine the relationship between Shh and FGF signaling in granule cell precursors (GCPs), which are the most abundant neural progenitors in the cerebellum and the putative cell of origin for the childhood brain tumor medulloblastoma. In these cells, Shh induces a potent proliferative response that is abolished by coincubation with basic FGF. FGF also inhibits transcription of Shh target genes and prevents activation of a Gli-responsive promoter in fibroblasts, which suggests that it blocks Shh signaling upstream of Gli-mediated transcription. FGF-mediated inhibition of Shh responses requires activation of FGF receptors and of ERK and JNK kinases, because it can be blocked by inhibitors of these enzymes. Finally, FGF promotes differentiation of GCPs
in vitro
and
in vivo
and halts proliferation of tumor cells from
patched
(
ptc
) mutant mice, a model for medulloblastoma. These findings suggest that FGF is a potent inhibitor of Shh signaling and may be a useful therapy for tumors involving activation of the hedgehog pathway.
Enemy release after introduction of disease-resistant genotypes into plant–pathogen systems
Authors: Godfree Robert C. , Thrall Peter H. , Young Andrew G.
Published: February 2007

Predicting the magnitude of enemy release in host–pathogen systems after introduction of novel disease resistance genes has become a central problem in ecology. Here, we develop a general quantitative framework for predicting changes in realized niche size and intrinsic population growth rate after introgression of disease resistance genes into wild host populations. We then apply this framework to a model host–pathogen system targeted by genetically modified and conventionally bred disease-resistant host lines (
Trifolium repens
lines expressing resistance to
Clover yellow vein potyvirus
) and show that, under a range of ecologically realistic conditions, the introduction of novel pathogen resistance genes into host populations can pose a quantifiable risk to associated nontarget native plant communities. In the host–pathogen system studied, we predict that pathogen release could result in an increase in the intrinsic rate of population growth of up to 15% and the expansion of host populations into some marginal environments. This approach has general applicability to the ecological risk assessment of all novel disease-resistant plant genotypes that target coevolutionary host–pathogen systems for improvement of agricultural productivity.
Evolutionary genomics reveals conserved structural determinants of signaling and adaptation in microbial chemoreceptors
Authors: Alexander Roger P. , Zhulin Igor B.
Published: February 2007

As an important model for transmembrane signaling, methyl-accepting chemotaxis proteins (MCPs) have been extensively studied by using genetic, biochemical, and structural techniques. However, details of the molecular mechanism of signaling are still not well understood. The availability of genomic information for hundreds of species enables the identification of features in protein sequences that are conserved over long evolutionary distances and thus are critically important for function. We carried out a large-scale comparative genomic analysis of the MCP signaling and adaptation domain family and identified features that appear to be critical for receptor structure and function. Based on domain length and sequence conservation, we identified seven major MCP classes and three distinct structural regions within the cytoplasmic domain: signaling, methylation, and flexible bundle subdomains. The flexible bundle subdomain, not previously recognized in MCPs, is a conserved element that appears to be important for signal transduction. Remarkably, the N- and C-terminal helical arms of the cytoplasmic domain maintain symmetry in length and register despite dramatic variation, from 24 to 64 7-aa heptads in overall domain length. Loss of symmetry is observed in some MCPs, where it is concomitant with specific changes in the sensory module. Each major MCP class has a distinct pattern of predicted methylation sites that is well supported by experimental data. Our findings indicate that signaling and adaptation functions within the MCP cytoplasmic domain are tightly coupled, and that their coevolution has contributed to the significant diversity in chemotaxis mechanisms among different organisms.