bluuebunny/crossref_metadata_2025 huggingface dataset:
On the biannually repeating slow‐slip events at the Ryukyu Trench, southwestern Japan
Authors: Heki Kosuke , Kataoka Takeshi
Published: November 2008

Global positioning system data show that about 20 slow‐slip events occurred during 1997–2007 in the southwestern part of the Ryukyu Arc, Japan, where large interplate thrust earthquakes are not known to have occurred in spite of relatively fast plate convergence. They recur fairly regularly on one patch of the subduction fault, which is as deep as 20–40 km and mechanically isolated in an uncoupled subduction zone. They have time constants of a month or so and release seismic moment equivalent of Mw 6.6 on average. This is one of the best recorded sequences of repeating fault slips, with enough events for statistical analyses. They have fairly constant recurrence interval of ∼0.5 year but do not show preferred months of occurrence in a year, suggesting that they are not controlled by seasonal forcing. The correlation between intervals and amounts of fault slip show statistically significant time‐predictable recurrences. There is one significant disruption in the rhythm, but the stress perturbations due to nearby earthquakes do not appear to play a significant role. This part of the fault might be an altered asperity that used to rupture fast but now slips only slowly because of the increased ambient temperature.
Analysis of large‐scale ocean bottom pressure variability in the North Pacific
Authors: Chambers Don P. , Willis Josh K.
Published: November 2008

We use the leading empirical orthogonal functions (EOFs) of ocean bottom pressure (OBP) derived from an ocean model and the technique of EOF reconstruction to reduce noise in the large‐scale OBP variations derived from the Gravity Recovery and Climate Experiment (GRACE). The subsequent OBP variations from the model and GRACE are then examined in the North Pacific between January 2003 and May 2007. Although annual and semiannual variations are similar, GRACE observes large interannual fluctuations poleward of 30°, where OBP increases from a low of nearly 3 cm below normal in early 2003 to normal throughout 2004 and 2005, then an increase of nearly the same magnitude in 2006. These fluctuations have also been observed in OBP inferred from satellite altimetry corrected for steric variations computed from Argo float data. Since GRACE and steric‐corrected altimetry are completely independent observations of OBP, we conclude that the model has errors or deficiencies in predicting the interannual OBP fluctuations in the North Pacific.
Uplift of Saharan dust south of the intertropical discontinuity
Authors: Marsham J. H. , Parker D. J. , Grams C. M. , Taylor C. M. , Haywood J. M.
Published: November 2008

In situ observations from a flight made during the Geostationary Earth Radiation Budget Intercomparison of Longwave and Shortwave Radiation (GERBILS) field campaign (June 2007) show significant dust uplift into the monsoon flow immediately south of the intertropical discontinuity in the western Sahara. Dust loadings were highest in the moist monsoon air and the observations are consistent with dust uplift by the nocturnal monsoon winds. There is some evidence that cold pools within the monsoon flow contributed to the dust uplift: regions of elevated dust, water vapor, and ozone within the monsoon air are consistent with precipitation cooling and moistening air from upper levels and the resultant dusty cold pools propagating northward. However, only southward propagating cold pool outflows could be observed in satellite imagery. Using European Centre for Medium‐Range Weather Forecasts analyses and satellite data, it is shown that the asymmetry in the seasonal dust cycle is closely related to the downdraft convective available potential energy (DCAPE) from convective storms. There is both more dust and more DCAPE during monsoon onset than during retreat. The larger DCAPE values during monsoon onset, as well as the stronger nocturnal monsoon flow and the stronger heat trough circulation, are expected to contribute to the higher dust loadings at this time. Both the monsoon flow and cold pool outflows within it result in dust uplift in the western Sahara during the monsoon onset, which is when the maximum dust uplift occurs. For dust modeling, this shows the importance of accurately modeling not only the monsoon flow itself but also deep convection and cold pools.
Diatom‐based inference of variations in the strength of Asian winter monsoon winds between 17,500 and 6000 calendar years B.P.
Authors: Wang Luo , Lu Houyuan , Liu Jiaqi , Gu Zhaoyan , Mingram Jens , Chu Guoqiang , Li Jingjing , Rioual Patrick , Negendank Jörg F. W. , Han Jingtai , Liu Tungsheng
Published: November 2008

We present a continuous record of fossil diatoms from Huguang Maar Lake (HML) in southeastern China, spanning the time interval 17,500 to 6000 calendar years (cal years) B.P. The seasonal change in relative abundance of the dominant diatom taxa, Aulacoseira and Cyclotella species, can be used as a proxy of the strength of winter monsoon winds (WMW), which is supported by the results of a sediment trap experiment in HML and by an extensive review of the literature on the autoecologies of these species. In the sediment, high C. stelligera abundance and high‐diatom concentration, which indicate warm conditions and low wind‐driven turbulence of the water column, characterize an interval equivalent to the Greenland Interstadial 1. This is followed by an interval with low‐diatom concentration and with assemblages dominated by Aulacoseira species, which suggests high wind‐driven turbulence and therefore strong WMW. This interval corresponds with the Greenland Stadial 1. During the early and middle Holocene, another two episodes with strong WMW are evident from the data between 10,000 and 8500 and between 7000 and 6000 cal years B.P. The diatom record implies that strong winter monsoon episodes not only occurred during the last glacial‐Holocene transition but also during the Holocene “thermal maximum.”
Observations of Cl2, Br2, and I2 in coastal marine air
Authors: Finley B. D. , Saltzman E. S.
Published: November 2008

Cl2, Br2, and I2 were measured in coastal Pacific air from 2 to 29 January 2006. Air was sampled at 10 m over the sea surface near the end of Scripps Pier (La Jolla, California). The measurements were made using atmospheric pressure chemical ionization with tandem mass spectrometry (APCI/MS/MS). Over the course of this study, Cl2, Br2, and I2 levels ranged from below detection limits of 1.0, 0.5, and 0.2 ppt, respectively, to maxima of 26, 19, and 8 ppt, respectively. Mean dihalogen levels for the study period were 2.3 ± 1 ppt for Cl2, 2.3 ± 0.4 ppt for Br2, and 0.7 ± 0.1 ppt for I2 (expressed as geometric mean ±1 geometric standard error). The mixed dihalogens BrCl, ICl, and IBr had geometric mean levels below 0.3 ± 1 ppt and never exceeded their detection limits of 0.5 ppt. Consistent patterns of diurnal variability were observed for Cl2 and I2, with Cl2 maxima during daytime and I2 appearing almost exclusively at night. The detection of I2 appeared to be related to the passage of air over nearby kelp beds. The observed dihalogen levels suggest that (1) chlorine atom oxidation of hydrocarbons makes a significant contribution to the formation of ozone and (2) halogen atom oxidation of airborne mercury contributes to mercury deposition in polluted coastal air.
Evidence for anomalous cloud particles at the poles of Venus
Authors: Wilson C. F. , Guerlet S. , Irwin P. G. J. , Tsang C. C. C. , Taylor F. W. , Carlson R. W. , Drossart P. , Piccioni G.
Published: November 2008

An analysis of near‐infrared emissions on the nightside of Venus observed by the Visible and Infrared Thermal Imaging Spectrometer (VIRTIS) instrument on board Venus Express reveals anomalous cloud particles in the polar regions of Venus. These anomalous particles are found within the centers of polar vortices at both poles and are either larger or different in composition from those elsewhere in the planet. We find no persistent latitudinal variation in cloud properties at low to midlatitudes, nor do we find asymmetry between the southern and northern hemispheres. These findings arise from analysis of the relative brightness of 1.74 and 2.30 μm infrared radiation thermally emitted from the deep atmosphere of Venus. Larger cloud particles cause relatively more attenuation at 2.30 μm than at 1.74 μm, so we use a “size parameter,” m = (I1.74μm)/(I2.30μm)0.53, as a proxy for particle size. This methodology follows that of Carlson et al. (1993), supported by new radiative transfer modeling.
N2O emissions and carbon sequestration in a nitrogen‐fertilized Douglas fir stand
Authors: Jassal Rachhpal S. , Black T. Andrew , Chen Baozhang , Roy Real , Nesic Zoran , Spittlehouse D. L. , Trofymow J. A.
Published: November 2008

This study investigated how nitrogen (N) fertilization with 200 kg N ha−1 of a 58‐year‐old West Coast Douglas fir stand influenced its net greenhouse gas (GHG) global warming potential (GWP) in the first year after fertilization. Effects of fertilization on GHG GWP were calculated considering changes in soil N2O emissions, measured using the static chamber technique and the soil N2O gradient technique; eddy covariance (EC) measured net ecosystem productivity (NEP); and energy requirements of fertilizer production, transport, and its aerial spreading. We found significant N2O losses in fertilized plots compared to a small uptake in nonfertilized plots. Chamber‐measured N loss in the fertilized plots was about 16 kg N2O ha−1 in the first year, which is equivalent to 10 kg N ha−1 or 5% of the applied fertilizer N. Soil N2O emissions measured using the gradient technique, however, exceeded the chamber measurements by about 50%. We also compared a polymer‐coated slow‐release urea with regular urea and found that the former delayed N2O emissions but the year‐end total loss was about the same as that from regular urea. Change in NEP due to fertilization was determined by relating annual NEP for the nonfertilized stand to environmental controls using an empirical and a process‐based model. Annual NEP increased by 64%, from 326 g C m−2, calculated assuming that the stand was not fertilized, to the measured value of 535 g C m−2 with fertilization. At the end of the year, net change in GHG GWP was −2.28 t CO2 ha−1 compared to what it would have been without fertilization, thereby indicating favorable effect of fertilization even in the first year after fertilization with significant emissions of N2O.
Air entry–based characteristic length for estimation of permeability of variably compacted earth materials
Authors: Assouline S. , Or D.
Published: November 2008

The permeability k of a porous medium is a geometrical pore space attribute required for quantifying fluid flows and transport processes for hydrological, civil, agriculture, and petroleum engineering applications. Permeability is often expressed as proportional to a characteristic length squared and inversely proportional to factors accounting for porosity, pore shape, and tortuosity effects. Compaction and diagenesis reduce porosity, mean pore size, and connectivity, resulting in decrease in k. Permeability prediction relies on suitable selection of a characteristic length that may vary from simple hydraulic radius approximation of Kozeny‐Carman to more complex critical path analysis to identify flow‐limiting pore size. For porous media undergoing significant changes in pore space (e.g., compaction due to anthropogenic activities), the proper choice of a robust characteristic length is particularly challenging. We propose using the air entry pressure, a natural characteristic length that gauges the largest drainable pore size. This choice of a characteristic length is compatible with the Aissen formula that provides robust estimates of k for complex pore shapes. Additionally, the model considers geometrical (tortuosity) factors and links relative changes in porosity to concurrent changes in k. The model was tested against experimental data for sands, sandstones with different cementing agents, and unconsolidated soils. For unconsolidated sands and soils the model provides reasonable predictions of permeability for the entire range of porosities determined in laboratory or field experiments. However, for sandstones, and especially those containing cementing agents such as clay, the model is valid up to a critical porosity where hydraulic connectivity is lost, resulting in drastic reduction in k. The geometrical factor for soils was influenced by silt‐to‐clay ratio, while for sands, it was correlated with mean grain diameter. The model offers improvement in predicting k and provides a means for incorporating critical pore size and connectivity information in addition to porosity.
Electrical characterization of non‐Fickian transport in groundwater and hyporheic systems
Authors: Singha Kamini , Pidlisecky Adam , Day‐Lewis Frederick D. , Gooseff Michael N.
Published: November 2008

Recent work indicates that processes controlling solute mass transfer between mobile and less mobile domains in porous media may be quantified by combining electrical geophysical methods and electrically conductive tracers. Whereas direct geochemical measurements of solute preferentially sample the mobile domain, electrical geophysical methods are sensitive to changes in bulk electrical conductivity (bulk EC) and therefore sample EC in both the mobile and immobile domains. Consequently, the conductivity difference between direct geochemical samples and remotely sensed electrical geophysical measurements may provide an indication of mass transfer rates and mobile and immobile porosities in situ. Here we present (1) an overview of a theoretical framework for determining parameters controlling mass transfer with electrical resistivity in situ; (2) a review of a case study estimating mass transfer processes in a pilot‐scale aquifer storage recovery test; and (3) an example application of this method for estimating mass transfer in watershed settings between streams and the hyporheic corridor. We demonstrate that numerical simulations of electrical resistivity studies of the stream/hyporheic boundary can help constrain volumes and rates of mobile‐immobile mass transfer. We conclude with directions for future research applying electrical geophysics to understand field‐scale transport in aquifer and fluvial systems subject to rate‐limited mass transfer.
Return of Kosi river induced by Tibet earthquake
Authors: Mukherjee Saumitra
Published: November 2008

Seismotectonics and change in river courses were correlated. Following the elastic rebound theory before the occurrence of the earthquake the subsurface rocks accumulate the energy by the tectonic movement. The Kosi river barrage was broken due to the tectonic forces accumulation in the south of Tibet Himalayas. Kosi river originates from Tibetan Himalayas and any disturbance in Tibet plateau has the potential to change the river course.
Voicing a Vision of Translational Research
Authors: Stemple Joseph C. , Thomas Lisa B.
Published: November 2008

Translational research has been characterized as effective translation of new knowledge, mechanisms, and techniques generated by advances in basic science research into new approaches for prevention, diagnosis, and treatment of disease essential for improving health. Research in the area of normal and abnormal voice production has a rich history in both the clinical and basic sciences. This report provides an overview of basic science work in the field of voice and considers the implications and importance of translating this research to the clinical realm.
From Bench to Bedside: Translational Research on Vocal Fold Hydration
Authors: Sivasankar Mahalakshmi , Leydon Ciara
Published: November 2008

The importance of well-hydrated vocal folds in maintaining optimal voice function is widely acknowledged. In this article, we summarize findings from recent bench and bedside research and highlight how use of these experimental techniques has improved our understanding of the physiological mechanisms that regulate vocal fold hydration.
Rheometers, Bioreactors, and Vocalization Forces: Using Basic Science Investigations to Help the Voices of Teachers
Authors: Klemuk Sarah
Published: November 2008

Collaborative studies at the University of Iowa and the National Center for Voice and Speech aim to help the voices of teachers. Investigators study how cells and tissues respond to vibration doses simulating typical vocalization patterns of teachers. A commercially manufactured instrument is uniquely modified to support cell and tissue growth, to subject tissues to vocalization-like forces, and to measure viscoelastic properties of tissues. Through this basic science approach, steps toward safety limits for vocalization and habilitating rest periods for professional voice users will be achieved.
Bench to Bedside: Research Review in Vocal Fold Extracellular Matrix
Authors: Thibeault Susan L.
Published: November 2008

The vocal fold lamina propria is crucial for the production of the vocal fold mucosal wave and quality of voice. Basic science research in this area has increased over the past 10 years secondary to our understanding of this importance. The translational aspects of this research are far reaching as we begin to better understand the development, maintenance, and regeneration of this area. This article serves to present a review of the multi faceted work being completed.
Receptor Mediated Uptake of Pepsin: Significance in Otolaryngology
Authors: Johnston Nikki
Published: November 2008

Reflux of gastric contents into the laryngopharynx contributes to voice disorders, otolaryngological inflammatory disorders, and perhaps even neoplastic diseases of the laryngopharynx. Treatment is currently focuses on increasing the pH of the refluxate because it was thought that the refluxate would not cause injury/symptoms at higher pH. However, many patients with reflux-attributed laryngeal injury/disease have persistent symptoms despite aggressive acid supression therapy. Recent studies using combined multi-channel intraluminal impedance with pH montioring have shown a positive symptom association with non- and weakly-acidic reflux and an association between non-/weakly acidic reflux and refractory symptoms on proton pump inhibitor therapy. Thus, the role of acid alone in the development of reflux related laryngeal pathology has to be questioned and studies examining the effects of the other components of the refluxate are clearly needed. Our data, described herein, supports a role for pepsin in reflux-attributed laryngeal injury/disease independent of the pH of the refluxate and highlights potential novel drug targets.
Determination of thermal diffusion coefficient in equimolar n-alkane mixtures: Empirical correlations
Authors: Blanco Pablo , Mounir Bou-Ali M. , Platten J. Karl , Urteaga Pedro , Madariaga Jose A. , Santamaria Carlos
Published: November 2008

In this article we determined the thermal diffusion coefficient (DT) in equimolar mixtures of n-alkanes nCi–nC12 (i=5,6,7,8,9,17,18), nCi–nC10 (i=5,6,7,15,16,17,18), and nCi–nC6 (i=10,12,14,16,18) at 25°C and at atmospheric pressure using the thermogravitational technique. The results obtained from this study together with the previously published ones in the series of nCi–nC18 (i=5,6,7,8,9,10,11,12,13) show that the main parameter that determines DT in each series is in association with the molecular weights of the mixture’s components. However, an empirical quantitative correlation has been obtained between DT, the molecular weights of the components, the viscosity, and the thermal expansion coefficient of the mixtures. This is the first report of a closely accurate correlation for DT in liquid mixtures.
Anomalous impurity ion heating from Alfvénic cascade in the reversed field pinch
Authors: Tangri Varun , Terry P. W. , Fiksel Gennady
Published: November 2008

Anomalous ion and impurity heating in reversed field pinch plasmas is addressed. Previous work [N. Mattor et al., Comments Plasma Phys. Controlled Fusion 15, 65 (1992)], which calculated the heating of bulk ions by gyro and Landau resonances with turbulent fluctuations cascading from unstable tearing modes, is extended to impurity species measured in Madison symmetric torus (MST). The heavier mass of impurities allows gyro-resonant heating at lower frequencies where more energy is present in the fluctuations. A 0D transport model is used to examine heating rates under various time-dependent, experimental heating scenarios, such as a sawtooth crash. Impurity heating rates calculated for impurities found in MST are comparable to observed rates inferred in the impurity temperature rise during sawtooth events.
Comparison of Autler–Townes splitting based absolute measurements of the L7i2 A Σ1u+−X Σ1g+ electronic transition dipole moment with ab initio theory
Authors: Salihoglu O. , Qi P. , Ahmed E. H. , Kotochigova S. , Magnier S. , Lyyra A. M.
Published: November 2008

We report a comparison between experimental and theoretical electronic transition dipole moment values for the L7i2 A Σ1u+−X Σ1g+ system. The experimental results are based on measuring the absolute magnitude of the transition dipole matrix elements from Autler–Townes splitting of rovibrational transitions for different R-centroid values. The ab initio theoretical calculations of the transition dipole moment for the L7i2 A Σ1u+−X Σ1g+ system were performed using two different quantum-mechanical models: an all-electron valence bond self-consistent-field method and a pseudopotential molecular orbital method. As expected for the smallest molecule with core electrons, the agreement between experiment and theory is very good.
Homogeneous nucleation rate measurements in supersaturated water vapor
Authors: Brus David , Ždímal Vladimír , Smolík Jiří
Published: November 2008

The rate of homogeneous nucleation in supersaturated vapors of water was studied experimentally using a thermal diffusion cloud chamber. Helium was used as a carrier gas. Our study covers a range of nucleation rates from 3×10−1to3×102cm−3s−1 at four isotherms: 290, 300, 310, and 320K. The molecular content of critical clusters was estimated from the slopes of experimental data. The measured isothermal dependencies of nucleation rate of water on saturation ratio were compared with the prediction of the classical theory of homogeneous nucleation, the empirical prediction of Wölk et al. [J. Chem. Phys. 117, 10 (2002)], the scaled model of Hale [Phys. Rev. A 33, 4156 (1986)], and the former nucleation onset data.
Diffractive imaging of the dumbbell structure in silicon by spherical-aberration-corrected electron diffraction
Authors: Morishita Shigeyuki , Yamasaki Jun , Nakamura Keisuke , Kato Takeharu , Tanaka Nobuo
Published: November 2008

The dumbbell structure in crystalline silicon as known with the separation of 0.136 nm has been reconstructed clearly by diffractive imaging using an electron beam. The spatial resolution in the result is estimated at about 0.1 nm. By utilizing the selected area diffraction technique in a spherical-aberration-corrected transmission electron microscope, one can reconstruct nanostructures with atomic resolution, even if they are not surrounded by empty space such as localized structures embedded in thin film samples. This means that the present method has a unique potential to expand the versatility of diffractive imaging by electron beams drastically.
Photodetachment spectra of the PtX42− (X=F,Cl,Br) dianions and their Jahn–Teller distortions: A fully relativistic study
Authors: Pernpointner Markus , Rapps Thomas , Cederbaum Lorenz S.
Published: November 2008

In this work we calculate the photoelectron spectra of the PtX42− (X=F,Cl,Br) dianions by application of the third-order Dirac–Hartree–Fock one-particle propagator technique. Relativistic effects and electron correlation are hereby treated on a consistent theoretical basis, which is mandatory for systems containing heavy elements. An experimental PtF42− gas phase photoelectron (PE) spectrum is not available and our calculations confirm its instability against autodetachment. For PtCl42− potential curves for the two Jahn–Teller (JT), active modes were determined and the influence of spin-orbit splitting on the JT stabilization is discussed. The scalar relativistic and four-component potential energy curves hereby exhibit remarkable differences relevant for the correct interpretation of the spectra. A dissociation channel through the b2g vibrational mode was obtained for PtCl42− in the E2u final state. For all species electron correlation strongly decreases the ionization potentials and the inclusion of spin-orbit coupling leads to alterations in the level order, which have to be taken into account for a correct peak assignment. The metal d contribution to the valence orbitals steadily decreases from the PtF42− to the PtBr42− compound, which rules out a pure metal d-orbital-based interpretation of the valence PE spectrum.
Investigation of factors affecting crystallization of cyclopentane clathrate hydrate
Authors: Whitman Catherine A. , Mysyk Roman , White Mary Anne
Published: November 2008

We report the results of systematic investigations of the influence of thermal history and other factors on crystallization of a model clathrate hydrate (cyclopentane hydrate) studied as water-in-oil and oil-in-water emulsions to remove the nucleation influence of substrates other than ice and hydrates. Hydrate and ice seem to form simultaneously under the conditions of these experiments, with ice forming preferentially. Thermal treatment, melting the ice, and leaving only the hydrate, promotes further hydrate formation. Not all the hydrate formed can be accounted for by the recrystallization of water freed by melting ice.
Dynamic surface plasmon patterns generated by reconfigurable “cogwheel-shaped” beams
Authors: Hu Z. J. , Yuan X.-C. , Zhu S. W. , Yuan G. H. , Tan P. S. , Lin J. , Wang Q.
Published: November 2008

A method for generating and controlling dynamic surface plasmon patterns by highly focused “cogwheel-shaped” beams is studied theoretically and experimentally. The “cogwheel” beams are formed by collinear superposition of two Laguerre–Gaussian beams with equal but opposite topological charges. It is shown that the patterned surface plasmons can be reconfigured locally with advantages over patterned metallic islands.
Ladder-type magnetic structures in MnAs epitaxial films–measurements and micromagnetic simulations
Authors: Manago Takashi , Akinaga Hiro
Published: November 2008

The ladder-type magnetic structure and magnetization reversal process of MnAs films on GaAs(001) were investigated using magnetic force microscopy, Kerr microscopy, and micromagnetic simulations. Micromagnetic simulations provided good reproduction of the experimental results for the ladder-type structure of the MnAs films for remanent states and the magnetization reversal process. The simulated magnetization reversal process shows that magnetostatic interactions between ferromagnetic stripes play an important role to form this structure in the MnAs system. The dependence of the magnetic structure on the saturation magnetization and magnetic anisotropy indicates that uniaxial hard magnetic anisotropy along the strips, a large saturation magnetization, and a large magnetic anisotropy are necessary to obtain the ladder-type magnetic structure.
Biorthonormal eigenbasis of a Markovian master equation for the quantum Brownian motion
Authors: Tay B. A. , Petrosky T.
Published: November 2008

The solution to a quantum Markovian master equation of a harmonic oscillator weakly coupled to a thermal reservoir is investigated as a non-Hermitian eigenvalue problem in space coordinates. In terms of a pair of quantum action-angle variables, the equation becomes separable and a complete set of biorthogonal eigenfunctions can be constructed. Properties of quantum states, such as the change in the quantum coherence length, damping in the motion, and disappearance of the spatial interference pattern, can then be described as the decay of the nonequilibrium modes in the eigenbasis expansion. It is found that the process of gaining quantum coherence from the environment takes a longer time than the opposite process of losing quantum coherence to the environment. An estimate of the time scales of these processes is obtained.
Ultrafast electron thermalization in a magnetic layered Au/Co/Au film
Authors: Labourt-Ibarre A. , Voisin C. , Cassabois G. , Delalande C. , Flytzanis C. , Roussignol P. , Beauvillain P.
Published: November 2008

The ultrafast electron dynamics subsequent to a hundred femtoseconds photoexcitation is monitored in a few nanometers thick Au/Co/Au film by means of time-resolved transient spectroscopy. We show that the insertion of thin Co layer in Au film leads to a drastic modification in the scattering rates of the different thermalization regimes. The electron-electron interactions are dominated by the mobile sp-electrons scattering on the heavy d-electrons, which concomitantly enhances the electron-phonon interactions by up to a factor of 5. In the framework of ultrafast magnetization dynamics, this study provides important data on the electronic processes underlying the spin dynamics in a sample typically designed for magneto-optical applications.
Electrical rectification effect in single domain magnetic microstrips: A micromagnetics-based analysis
Authors: Thiaville André , Nakatani Yoshinobu
Published: November 2008

Upon passing an ac electrical current along magnetic micro- or nanostrips, the measurement of a dc voltage that depends sensitively on current frequency and applied field has been recently reported by Yamaguchi et al. [Appl. Phys. Lett. 90, 182507 (2007); e-print arXiv:0710.2172; Phys. Rev. B 78, 104401 (2008)]. It was attributed to the excitation of spin waves by the spin transfer torque, leading to a time-varying anisotropic magnetoresistance, and by mixing of ac current and resistance to a dc. voltage. We have performed a quantitative analysis by micromagnetics including the spin transfer torque terms considered usually of this situation. The signals found from the spin transfer torque effect are several orders of magnitude below the experimental values, even if a static inhomogeneity of magnetization (the so-called ripple) is taken into account. On the other hand, the presence of a small nonzero average Oersted field is shown to be consistent with the full set of experimental results, both qualitatively and quantitatively. We examine, quantitatively, several sources for this average field and point to the contacts of the sample as a likely origin.
Tuning of the magnetization dynamics in as-sputtered FeCoSiN thin films by various sputtering gas pressures
Authors: Xu Feng , Phuoc N. N. , Zhang Xiaoyu , Ma Yungui , Chen Xin , Ong C. K.
Published: November 2008

In this work, we investigate the influence of various sputtering gas pressures on the high-frequency magnetization dynamics in as-sputtered FeCoSiN granular thin films. The permeability spectra are measured with the shorted microstrip transmission-line perturbation method and analyzed with the Landau–Lifshitz–Gilbert equation. The dependence of the effective damping coefficient on the external fields is fitted with a power law. The measurement and fitting results show that both the effective and the intrinsic damping coefficients in the magnetization dynamics can be conveniently and effectively tuned by changing the sputtering gas pressure. The physical origin of the influences is suggested to be related to the stress in the films.
Interfacial structure and chemistry of epitaxial CoFe2O4 thin films on SrTiO3 and MgO substrates
Authors: Xie S. , Cheng J. , Wessels B. W. , Dravid V. P.
Published: November 2008

Interfacial structure and chemistry of epitaxial CoFe2O4 thin films on (001)_SrTiO3 and (001)_MgO substrates were investigated using high-angle-annular-dark-field imaging combined with electron-energy-loss-spectra (EELSs) analyses at a subnanometer scale. The results show that CoFe2O4/SrTiO3 interface is semicoherent with requisite dislocation density to accommodate ∼7% lattice mismatch, while the small (∼0.3%) lattice mismatch renders CoFe2O4/MgO interface coherent. EELS indicates that Fe valence is nominally +3, with no measurable change across the interfaces. Structural characterization corroborates with observed lower saturation magnetization of CoFe2O4 on MgO, which is a consequence of tensile stress built up in the ⟨100⟩-direction negative magnetostrictive CoFe2O4.
On the nature of transport in near-critical dissipative-trapped-electron-mode turbulence: Effect of a subdominant diffusive channel
Authors: Mier J. A. , Sánchez R. , García L. , Newman D. E. , Carreras B. A.
Published: November 2008

The change in nature of radial transport in numerical simulations of near-critical dissipative-trapped-electron-mode turbulence is characterized as the relative strength of an additional diffusive transport channel (subdominant to turbulence) is increased from zero. In its absence, radial transport exhibits the lack of spatial and temporal scales characteristic of self-organized-critical systems. This dynamical regime survives up to diffusivity values which, for the system investigated here, greatly exceeds the expected neoclassical value. These results, obtained using a novel Lagrangian method, complete and extend previous works based instead on the use of techniques imported from the study of cellular automata [J. A. Mier et al., Phys. Plasmas 13, 102308 (2006)]. They also shed further light on why some features of self-organized criticality seem to be observed in magnetically confined plasmas in spite of the presence of mechanisms which apparently violate the conditions needed for its establishment.
Instability of wave modes in a free-electron laser with a helical wiggler and ion-channel guiding
Authors: Mohsenpour T. , Maraghechi B.
Published: November 2008

The dispersion relation for a free-electron laser (FEL) with a one-dimensional helical wiggler and an ion channel, in the collective regime, is found with all relativistic effects on the space-charge wave and radiation included. This dispersion relation is solved numerically to study the unstable interaction among all wave modes. In group I orbits, coupling between the positive-energy space-charge wave and the left circularly polarized electromagnetic wave is found. This instability and the coupling between the negative and positive-energy space-charge wave are found in the group II orbits in the negative mass regime. In group II orbits, there is a coupling between the right and left circularly polarized electromagnetic waves, in the positive mass regime. These instabilities are found to be distinct from the main FEL resonance. Contrary to the main FEL resonance, the additional instabilities have a nonrelativistic nature and are made of strongly coupled modes.
Silicon photonic crystal nanostructures for refractive index sensing
Authors: Dorfner D. F. , Hürlimann T. , Zabel T. , Frandsen L. H. , Abstreiter G. , Finley J. J.
Published: November 2008

The authors present the fabrication and optical investigation of silicon on insulator photonic crystal drop filters for use as refractive index sensors. Two types of defect nanocavities (L3 and H1−r) are embedded between two W1 photonic crystal waveguides to evanescently route light at the cavity mode frequency between input and output waveguides. Optical characterization of the structures in air and various liquids demonstrates detectivities in excess of Δn/n=0.018 and Δn/n=0.006 for the H1−r and L3 cavities, respectively. The measured cavity frequencies and detector refractive index responsivities are in good agreement with simulations, demonstrating that the method provides a background free transducer signal with frequency selective addressing of a specific area of the sensor chip.
Fabrication of 10 nm diameter hydrocarbon nanopores
Authors: Radenovic Aleksandra , Trepagnier Eliane , Csencsits Roseann , Downing Kenneth H. , Liphardt Jan
Published: November 2008

The addition of carbon to samples, during transmission electron microscope imaging, presents a barrier to accurate analysis; the controlled deposition of hydrocarbons by a focused electron beam can be a useful technique for local nanometer-scale sculpting of material. Here we use hydrocarbon deposition to form nanopores from larger focused ion beam holes in silicon nitride membranes. Using this method, we close 100–200 nm diameter holes to diameters of 10 nm and below, with deposition rates of 0.6 nm/min. I-V characteristics of electrolytic flow through these nanopores agree quantitatively with a one dimensional model at all examined salt concentrations.
Plasma-driven self-organization of Ni nanodot arrays on Si(100)
Authors: Levchenko I. , Ostrikov K. , Diwan K. , Winkler K. , Mariotti D.
Published: November 2008

The results of the combined experimental and numerical study suggest that nonequilibrium plasma-driven self-organization leads to better size and positional uniformity of nickel nanodot arrays on a Si(100) surface compared with neutral gas-based processes under similar conditions. This phenomenon is explained by introducing the absorption zone patterns, whose areas relative to the small nanodot sizes become larger when the surface is charged. Our results suggest that strongly nonequilibrium and higher-complexity plasma systems can be used to improve ordering and size uniformity in nanodot arrays of various materials, a common and seemingly irresolvable problem in self-organized systems of small nanoparticles.
Imaging and alignment of nanoscale 180° stripe domains in ferroelectric thin films
Authors: Thompson Carol , Fong D. D. , Wang R. V. , Jiang F. , Streiffer S. K. , Latifi K. , Eastman J. A. , Fuoss P. H. , Stephenson G. B.
Published: November 2008

Nanometer-period ferroelectric 180° stripe domains are observed in epitaxial PbTiO3 films using atomic force microscopy. Stripe domains can be aligned with surface step edges or in preferred crystallographic directions. A stripe alignment map as a function of temperature and film thickness is determined using synchrotron x-ray scattering. Pinning by step edges permits control of stripe domain morphology, as demonstrated by a film grown on a vicinal surface.
Ultralow resistance in situ Ohmic contacts to InGaAs/InP
Authors: Singisetti Uttam , Wistey Mark A. , Zimmerman Jeramy D. , Thibeault Brian J. , Rodwell Mark J. W. , Gossard Arthur C. , Bank Seth R.
Published: November 2008

We report a sharp reduction in the resistivity of Ohmic contacts using in situ deposition of molybdenum (Mo) contacts onto n-type In0.53Ga0.47As grown on InP. The contacts were formed by evaporating Mo onto the wafer using an electron beam evaporator connected to a molecular beam epitaxy chamber under ultrahigh vacuum. Transmission line measurements showed specific contact resistivities of 0.5±0.3 Ω μm2 (2.90 Ω μm), 0.9±0.4 Ω μm2 (4.3 Ω μm), and 1.3±0.4 Ω μm2 (4.7 Ω μm) for Mo on abrupt InAs/InGaAs heterojunctions, graded InAs/InGaAs, and InGaAs films, respectively. These low resistances meet the requirements for terahertz transistors.
Magnetic domains in magnetostrictive Fe–Ga alloys
Authors: Xing Q. , Lograsso T. A.
Published: November 2008

Lorentz microscopy was applied to the observation of magnetic domains in iron-gallium (Fe–Ga) alloys. Results did not show any link between the magnetic domains and the magnetostriction enhancement by Ga addition, but did reveal that the drastic decrease in magnetostriction for Fe–31.2 at. % Ga was due to the presence of large scale precipitates. Magnetic domain features did not change in the alloys of A2, D03, A2+D03, A2+B2+D03, and A2+fine scale precipitates. Large scale precipitates within the slow-cooled Fe–31.2 at. % Ga affected both the distribution and wall motion of magnetic domains.
Electric field mediated droplet centering
Authors: Bei Z.-M. , Jones T. B. , Tucker-Schwartz A. , Harding D. R.
Published: November 2008

Double emulsion droplets subjected to a uniform ac electric field self-assemble into highly concentric structures via the dipole/dipole force if the outer droplet has a higher dielectric constant than the suspending liquid. The dielectric constant of the inner droplet has no influence. To minimize field-induced droplet distortion, the liquids must be density matched to ∼0.1%. Centering of ∼3 to 6 mm diameter droplets is achieved within ∼60 s for field strengths of ∼104 Vrms/m in liquids of viscosity ∼10 cP. Effective centering depends strongly on frequency if the outer shell is conductive.
Series array of incommensurate superconducting quantum interference devices from YBa2Cu3O7−δ ion damage Josephson junctions
Authors: Cybart Shane A. , Wu S. M. , Anton S. M. , Siddiqi I. , Clarke John , Dynes R. C.
Published: November 2008

We have fabricated a series array of 280 superconducting quantum interference devices (SQUIDs) using YBa2Cu3O7−δ thin film ion damage Josephson junctions. The SQUID loop areas were tapered exponentially so that the response of the current-biased array to magnetic field is a single voltage spike at zero field. We fitted the current-voltage characteristics of the array to a model in which we summed the voltages across the SQUIDs assuming a resistively shunted junction model with a normal distribution of SQUID critical currents. At 75 K the standard deviation of these critical currents was 12%.
Low-loss modes in hollow metallic terahertz waveguides with dielectric coatings
Authors: Bowden Bradley , Harrington James A. , Mitrofanov Oleg
Published: November 2008

Cylindrical hollow-core metallic waveguides with an inner coating of polystyrene (PS) deposited over silver have losses less than 1dB/m for terahertz waves propagating in the HE11 mode. The thickness of the PS film determines whether the hybrid HE11 mode or the transverse TE01 mode exhibits the lowest loss. The mode selection is confirmed by studying mode profiles and transmission losses at 2.5 THz in waveguides with the dielectric coating thickness ranging from 0 to the optimum value of approximately 10 μm.
Comparative electrical bistable characteristics of ferroelectric poly(vinylidene fluoride-trifluoroethylene) copolymer based nonvolatile memory device architectures
Authors: Choi Chang Woo , Prabu Arun Anand , Kim Yu Min , Yoon Sun , Kim Kap Jin , Park Cheolmin
Published: November 2008

We report the thermal and electrical bistable characteristics of ferroelectric poly(vinylidene fluoride-trifluoroethylene) [P(VDF-TrFE) (72∕28mol%)] thin films as a function of varying memory device architectures. Rectangular-shaped capacitance-voltage (C-V) hysteresis loops obtained using 100nm P(VDF-TrFE) films with a metal-ferroelectric-insulator-semiconductor (MFIS) diode architecture were more suitable for distinguishing the data-bit state compared with the symmetrical hysteresis observed using metal-ferroelectric-metal capacitors. Poly(4-vinyl phenol) used as a dielectric insulator in the MFIS prevented shifting of the C-V hysteresis curve toward the negative bias voltage.
The physical origin of open recoil loops in nanocrystalline permanent magnets
Authors: Zheng Bo , Zhang Hong-Wei , Zhao Su-fen , Chen Jing-lan , Wu Guang-heng
Published: November 2008

The numerical simulation of the open recoil loops has been carried out using micromagnetic finite element method. By giving an example for this issue, the magnetization behaviors during the recoil processes of nanocomposite Pr2Fe14B∕α-Fe magnets have been analyzed. It is the strong intergrain exchange coupling that results in the magnetization reversal in some hard grains during the recoil processes, which leads to the large opening of recoil loops. The magnetization reversal of α-Fe grain follows that of its neighboring hard grains. Consequently, the opening of recoil loops is enhanced due to the presence of α-Fe grains.
Modeling of amorphous InGaZnO thin-film transistors based on the density of states extracted from the optical response of capacitance-voltage characteristics
Authors: Jeon Kichan , Kim Changjung , Song Ihun , Park Jaechul , Kim Sunil , Kim Sangwook , Park Youngsoo , Park Jun-Hyun , Lee Sangwon , Kim Dong Myong , Kim Dae Hwan
Published: November 2008

In order to model dc characteristics of n-channel amorphous InGaZnO thin-film transistors from experimentally obtained density of states (DOS), the acceptorlike DOS is extracted from the optical response of capacitance-voltage characteristics and confirmed by the technology computer-aided design (TCAD) simulation comparing with the measured data. Extracted DOS is a linear superposition of two exponential functions (tail and deep states), and its incorporation into TCAD model reproduces well the experimental current-voltage characteristics over the wide range of the gate and drain voltages. The discrepancy at higher gate voltage is expected to be improved by incorporating a gate voltage-dependent mobility in the model.
Solution-processed trilayer inorganic dielectric for high performance flexible organic field effect transistors
Authors: Tan H. S. , Kulkarni S. R. , Cahyadi T. , Lee P. S. , Mhaisalkar S. G. , Kasim J. , Shen Z. X. , Zhu F. R.
Published: November 2008

High performance organic field effect transistors using a solution-processable processed trilayer sol-gel silica gate dielectric architecture fabricated on plastic substrates exhibited low driving voltages of −3.0V, high saturation mobilities of ∼3.5cm2∕Vs, and on-off current ratio of 105. The enhancement in field effect mobility is attributed to improved dielectric-semiconductor interfacial morphology and increased capacitance of the tristratal dielectric. The pentacene devices displayed no signs of electrical degradation upon bending through a bending radius of 24mm, 2.27% strain. The slight increase in the drain currents upon bending strain was investigated using Raman spectroscopy, which revealed enhanced in-phase intermolecular coupling.
Radio interferometry measures the black hole at the Milky Way’s center
Authors: Schwarzschild Bertram
Published: November 2008

Looking for structure at the galactic center on the size scale predicted by general relativity requires very-long-baseline interferometry at the shortest radio wavelengths.
Two models combined can forecast lava flow accurately and promptly
Authors: Miller Johanna
Published: November 2008

Changes in an erupting volcano can be monitored by satellite, but computing their consequences is a challenge.
Research needs for future internal combustion engines
Authors: Manley Dawn K. , McIlroy Andrew , Taatjes Craig A.
Published: November 2008

The challenges of internal combustion require a broad collection of research discoveries to make the transition from hardware-intensive, experience-based fuel development and engine design to simulation-intensive, science-based design.
Role for β-catenin and HOX transcription factors in
Caenorhabditis elegans
and mammalian host epithelial-pathogen interactions
Authors: Irazoqui Javier E. , Ng Aylwin , Xavier Ramnik J. , Ausubel Frederick M.
Published: November 2008

We used the model nematode
Caenorhabditis elegans
infected with the human pathogen
Staphylococcus aureus
to identify components of epithelial immunity. Transcriptional profiling and reverse genetic analysis revealed that mutation of the
C. elegans
β-catenin homolog
bar-1
or the downstream homeobox gene
egl-5
results in a defective response and hypersensitivity to
S. aureus
infection. Epistasis analysis showed that
bar-1
and
egl-5
function in parallel to previously described
C. elegans
immune-response pathways. Overexpression of human homologs of
egl-5
modulated NF-κB-dependent TLR2 signaling in epithelial cells. These data suggest that β-catenin and homeobox genes play an important and conserved role in innate immune defense.