bluuebunny/crossref_metadata_2025 huggingface dataset:
Unraveling the New England orocline, east Gondwana accretionary margin
Authors: Cawood P. A. , Pisarevsky S. A. , Leitch E. C.
Published: August 2011

The New England orocline lies within the Eastern Australian segment of the Terra Australis accretionary orogen and developed during the late Paleozoic to early Mesozoic Gondwanide Orogeny (310–230 Ma) that extended along the Pacific margin of the Gondwana supercontinent. The orocline deformed a pre‐Permian arc assemblage consisting of a western magmatic arc, an adjoining forearc basin and an eastern subduction complex. The orocline is doubly vergent with the southern and northern segments displaying counter‐clockwise and clockwise rotation, respectively, and this has led to contrasting models of formation. We resolve these conflicting models with one that involves buckling of the arc system about a vertical axis during progressive northward translation of the southern segment of the arc system against the northern segment, which is pinned relative to cratonic Gondwana. Paleomagnetic data are consistent with this model and show that an alternative model involving southward motion of the northern segment relative to the southern segment and cratonic Gondwana is not permissible. The timing of the final stage of orocline formation (∼270–265 Ma) overlaps with a major gap in magmatic activity along this segment of the Gondwana margin, suggesting that northward motion and orocline formation were driven by a change from orthogonal to oblique convergence and coupling between the Gondwana and Pacific plates.
Kinematics of back‐arc inversion of the Western Black Sea Basin
Authors: Munteanu I. , Matenco L. , Dinu C. , Cloetingh S.
Published: August 2011

Back‐arc basin evolution is driven by processes active at the main subduction zone typically assuming the transition from an extensional back‐arc, during the retreat of a mature slab, to a contractional basin, during high‐strain collisional processes. Such a transition is observed in the Black Sea, where the accurate quantification of shortening effects is hampered by the kinematically unclear geometries of Cenozoic inversion. By means of seismic profiles interpretation, quantified deformation features and associated syn‐tectonic geometries on the Romanian offshore, this study demonstrates that uplifted areas, observed by exploration studies, form a coherent thick‐skinned thrust system with N‐ward vergence. Thrusting inverted an existing geometry made up by successive grabens that were inherited from the Cretaceous extensional evolution. The shortening started during late Eocene times and gradually affected all areas of the Western Black Sea Basin during Oligocene and Miocene times, deformation being coherently correlated across its western margin. The mechanism of this generalized inversion is the transmission of stresses during the collision recorded in the Pontides‐Balkanides system. Syn‐tectonic sedimentation in the Western Black Sea demonstrates that this process was continuous and took place through the onset of gradual shortening migrating northward. Although the total amount of shortening is roughly constant in an E‐W direction, individual thrusts have variable offsets, deformation being transferred between structures located at distance across the strike of the system. The Black Sea example demonstrates that the vergence and offset of thrusts can change rapidly along the strike of such a compressional back‐arc system. This generates apparently contrasting geometries that accommodate the same orogenic shortening.
Crustal and lithospheric structure of the Alborz Mountains, Iran, and surrounding areas from integrated geophysical modeling
Authors: Motavalli‐Anbaran Seyed‐Hani , Zeyen Hermann , Brunet Marie‐Françoise , Ardestani Vahid Ebrahimzadeh
Published: August 2011

Using gravity, geoid, topography and surface heat flow data, we have modeled the density and temperature distribution in the lithosphere along three profiles crossing Iran in SW‐NE direction from the Arabian foreland in the SW to the South Caspian Basin and the Turan Platform to the NE. We find thin lithosphere (100–120 km) underneath central Iran, whereas thick lithosphere (up to 240 km) is found underneath Arabia, the South Caspian Basin and the Turan Platform. Crustal thickening is found under the Zagros and Alborz mountains (up to 60 km) and under the Kopet‐Dagh Mountains (48 km), whereas the thin crust under the southern Caspian Sea is either an oceanic crust or a highly thinned continental one. Below the South Caspian Sea, the shape of the crust‐mantle interface and the base of the lithosphere indicate a subduction of the South Caspian block toward the N‐NW. Further east, under the Kopet‐Dagh, no evidence for active subduction is visible. This can be explained by a rheologically very strong South Caspian block, surrounded by weaker continental lithosphere.
Effect of the submergence, the bed form geometry, and the speed of the surface water flow on the mitigation of pesticides in agricultural ditches
Authors: Boutron Olivier , Margoum Christelle , Chovelon Jean‐Marc , Guillemain Céline , Gouy Véronique
Published: August 2011

Pesticides, which have been extensively used in agriculture, have become a major environmental issue, especially regarding surface and groundwater contamination. Of particular importance are vegetated farm drainage ditches, which can play an important role in the mitigation of pesticide contamination by adsorption onto ditch bed substrates. This role is, however, poorly understood, especially regarding the influence of hydrodynamic parameters, which make it difficult to promote best management practice of these systems. We have assessed the influence of three of these parameters (speed of the surface water flow, submergence, and geometrical characteristics of the bed forms) on the transfer and adsorption of selected pesticides (isoproturon, diuron, tebuconazole, and azoxystrobin) into the bed substrate by performing experiments with a tilted experimental flume, using hemp fibers as a standard of natural organic substrates that are found at the bottom of agricultural ditches. Results show the transfer of pesticides from surface water flow into bed substrate is favored, both regarding the amounts transferred into the bed substrate and the kinetics of the transfer, when the surface water speed and the submergence increase and when the bed forms are made of rectangular shapes. Extrapolation of flume data over a distance of several hundred meters suggests that an interesting possibility for improving the mitigation of pesticides in ditches would be to increase the submergence and to favor bed forms that tend to enhance perturbations and subsequent infiltration of the surface water flow.
Combined estimation of effective electrical conductivity and permittivity for soil monitoring
Authors: Brovelli A. , Cassiani G.
Published: August 2011

The mapping of moisture content, composition, and texture of soils is attracting a growing interest, in particular with the goal of evaluating threats to soil quality, such as soil salinization. Fast noninvasive geophysical surveys are often used in this context. The aim of this work was to study constitutive models that can be used to parameterize electrical conductivity and permittivity starting from a unifying conceptual approach, and to evaluate whether the information carried by one measurement type can be used to identify soil parameters that are then used to predict the other geophysical quantity. To this end, a recently developed constitutive model was extended and modified to consider the grain surface conductivity, a critical component in most natural situations. The extended model was successfully tested against laboratory measurements. In addition, the new model was compared against five other equations that use similar soil parameterizations. It was concluded that only three out of the five selected models yield similar predictions, while the remaining two predict a different geophysical response for the same soil texture. Following this analysis, a methodology was developed to estimate soil salinity starting from the simultaneous measurements of bulk electrical conductivity and permittivity and validating this methodology against laboratory experiments. The method is valid in situations where the conductivity of the pore water remains approximately constant during the measurement period. Key features of the approach proposed to map soil salinization are (1) simplicity, (2) absence of fitting parameters, and (3) the fact that moisture content does not need to be measured or estimated independently. The methodology was tested on a large number of soil samples and proved robust and accurate.
Representative roughness height of submerged vegetation
Authors: Cheng Nian‐Sheng
Published: August 2011

Roughness length scale is important in the evaluation of resistance caused by submerged vegetation in open channel flows. By transforming the concept of hydraulic radius, a representative roughness height is proposed in this study for quantifying effect of submerged vegetation on flow resistance in the surface layer. The proposed roughness height is characterized by its proportionality to both stem diameter and vegetation concentration and performs better than other length scales in collapsing resistance data collected under a wide range of vegetation conditions. An approach is then developed for estimate of the average flow velocity and thus resistance coefficients for both cases of rigid and flexible vegetation. Comparisons are also made between the present study and other four formulas available in the literature. This study also shows that all the formulas, if simplified for some simple conditions, can be unified in a general form.
How many tracers do we need for end member mixing analysis (EMMA)? A sensitivity analysis
Authors: Barthold Frauke K. , Tyralla Christoph , Schneider Katrin , Vaché Kellie B. , Frede Hans‐Georg , Breuer Lutz
Published: August 2011

End member mixing analysis (EMMA) is a commonly applied method to identify and quantify the dominant runoff producing sources of water. It employs tracers to determine the dimensionality of the hydrologic system. Many EMMA studies have been conducted using two to six tracers, with some of the main tracers being Ca, Na, Cl−, water isotopes, and alkalinity. Few studies use larger tracer sets including minor trace elements such as Li, Rb, Sr, and Ba. None of the studies has addressed the question of the tracer set size and composition, despite the fact that these determine which and how many end members (EM) will be identified. We examine how tracer set size and composition affects the conceptual model that results from an EMMA. We developed an automatic procedure that conducts EMMA while iteratively changing tracer set size and composition. We used a set of 14 tracers and 9 EMs. The validity of the resulting conceptual models was investigated under the aspects of dimensionality, EM combinations, and contributions to stream water. From the 16,369 possibilities, 23 delivered plausible results. The resulting conceptual models are highly sensitive to the tracer set size and composition. The moderate reproducibility of EM contributions indicates a still missing EM. It also emphasizes that the major elements are not always the most useful tracers and that larger tracer sets have an enhanced capacity to avoid false conclusions about catchment functioning. The presented approach produces results that may not be apparent from the traditional approach and it is a first step to add the idea of statistical significance to the EMMA approach.
Evaluation of bedload transport predictions using flow resistance equations to account for macro‐roughness in steep mountain streams
Authors: Nitsche Manuel , Rickenmann Dieter , Turowski Jens M. , Badoux Alexandre , Kirchner James W.
Published: August 2011

Steep mountain streams typically feature macro‐roughness elements like boulders, step‐pool sequences, and a varying channel width. Flow resistance because of such roughness elements appears to be an important control on bedload transport rates. Many commonly used bedload transport equations overestimate the transport in steep streams by orders of magnitude. Few approaches take into account the typical macro‐roughness elements, and systematic tests of these models with field observations are lacking. In the present study several approaches were considered that allow calculating the contribution of macro‐roughness elements to flow resistance. These approaches were combined with bedload transport equations and the predictions were compared to field measurements of discharge, transported bedload volumes, and channel characteristics in 13 Swiss mountain streams. The streams have channel slopes ranging from 2% to 19%, and catchment areas of 0.5 to 170 km2. For six streams there were time series of sediment yields, mostly measured annually, and for the other seven streams sediment volume estimates were available for large flood events in 2000 and 2005. All tested equation combinations achieved an improvement in bedload prediction compared to a reference equation that was uncorrected for macro‐roughness. The prediction accuracy mainly depended on the size and density of the macro‐roughness and on flow conditions. The best performance overall was achieved by an empirical approach accounting for macro‐roughness, on the basis of an independent data set of flow resistance measurements.
Physicochemical controls on adsorbed water film thickness in unsaturated geological media
Authors: Tokunaga Tetsu K.
Published: August 2011

Adsorbed water films commonly coat mineral surfaces in unsaturated soils and rocks, reducing flow and transport rates. Therefore, it is important to understand how adsorbed film thickness depends on matric potential, surface chemistry, and solution chemistry. Here the problem of adsorbed water film thickness is examined by combining capillary scaling with the Derjaguin‐Landau‐Verwey‐Overbeek (DLVO) theory. Novel aspects of this analysis include determining capillary influences on film thicknesses and incorporating solution chemistry–dependent electrostatic potential at air‐water interfaces. Capillary analysis of monodisperse packings of spherical grains provided estimated ranges of matric potentials where adsorbed films are stable and showed that pendular rings within drained porous media retain most of the “residual” water except under very low matric potentials. Within drained pores, capillary contributions to thinning of adsorbed films on spherical grains are shown to be small, such that DLVO calculations for flat surfaces are suitable approximations. Hamaker constants of common soil minerals were obtained to determine ranges of the dispersion component to matric potential–dependent film thickness. The pressure component associated with electrical double‐layer forces was estimated using the compression and linear superposition approximations. The pH‐dependent electrical double‐layer pressure component is the dominant contribution to film thicknesses at intermediate values of matric potential, especially in lower ionic strength solutions (<10 mol m−3) on surfaces with higher‐magnitude electrostatic potentials (more negative than ≈−50 mV). Adsorbed water films are predicted to usually range in thickness from ≈1 to 20 nm in drained pores and fractures of unsaturated environments.
Hypermixing in linear shear flow
Authors: Bolster Diogo , Dentz Marco , Le Borgne Tanguy
Published: August 2011

In this technical note we study mixing in a two‐dimensional linear shear flow. We derive analytical expressions for the concentration field for an arbitrary initial condition in an unbounded two‐dimensional shear flow. We focus on the solution for a point initial condition and study the evolution of (1) the second centered moments as a measure for the plume dispersion, (2) the dilution index as a measure of the mixing state, and (3) the scalar dissipation rate as a measure for the rate of mixing. It has previously been shown that the solute spreading grows with the cube of time and thus is hyperdispersive. Herein we demonstrate that the dilution index increases quadratically with time in contrast to a homogeneous medium, for which it increases linearly. Similarly, the scalar dissipation rate decays as t−3, while for a homogeneous medium it decreases more slowly as t−2. Mixing is much stronger than in a homogeneous medium, and therefore we term the observed behavior hypermixing.
Changes in Antioxidant Enzymes Activity and Oxidative Damage in Four Argania spinosa Ecotypes Under Water Stress Conditions
Authors: Chakhchar Abdelghani , Ferradous Abderrahim , Lamaoui Mouna , Wahbi Said , El Modafar Cherkaoui
Published: August 2011

Argania spinosa L. Skell, a tree endemic of Morocco, grows in semiarid and arid areas. Biochemical response to drought in four ecotypes of the A. spinosa was compared. Choice of ecotypes was based on evident differences in geographical features in south-west Morocco: two coastal ecotypes (Essaouira and Agadir) and two paralittorale ecotypes (Aoulouz and Lakhssas). Lipid peroxidation (malonyldialdehyde (MDA)), content of endogenous hydrogen peroxide (H2O2) and antioxidant enzyme system (Catalase (CAT), Ascorbate peroxidase (APX), Total peroxidase (POD) and Polyphenoloxidase (PPO) were measured in control (100% relative humidity (RH) at field capacity (FC)) and water-stressed plants (50 and 25% RH at FC). For all ecotypes, drought stress significantly increased the contents of MDA and H2O2 and an ecotype effect was noted. According Two-way ANOVA analysis, the ecotype x watering regime interaction was highly significant. We found an increase in the activities of the four ROS-scavenging enzymes and an ecotype effect was noted. Ecotype x watering regime interaction shows that only the CAT and APX activities were significant. Highest values of POD and PPO activities were found in both paralittorale ecotypes. Increase in antioxidant enzyme activities appears to be an adaptive response to restore the reactive oxygen species in their homeostasis. The four study ecotypes were separated by two discriminant functions obtained by canonical discriminant analysis. Coastal ecotypes are separated from the paralittorale ecotypes mainly by POD and PPO activities and MDA content.
NMR and Electron Microscopy Studies of Soybean Seeds, Soybean Proteins, and Oil for Improved Utilization in Foods and Feeds
Authors: Costescu Doina , Baianu I.
Published: August 2011

NMR, NIR and EM techniques are suitable methods of measuring protein and oil content in soybeans. After completion of a measurement with NMR or NIR, a soybean sample could be either replanted or consummated. NMR techniques involved in the present work are based on the response of nuclei, as nuclear spin flips, when set in a 7.05T magnetic field and excited with rf pulses of 300 MHz. NIR spectroscopy is based on outer electron molecular vibrations, when excited with radiation of frequency 1012 -4 × 1014Hz, and =2.5Om-750 nm.TEM and ESEM techniques are bulk and surface analysis techniques, respectively, working with electron beams of 15KV, and image resolution in the range of nm’s. ESEM is based on the possibility of imaging with secondary emitted electrons from the samples, and TEM on the possibility to have image contrast based on the difference in electron transmission through elements of different atomic weight. Novel results are presented by NMR, FT-NIR spectroscopy and Electron Microscopy for intact, selected soybean seeds accessions, soybean oil and soybean proteins.
Expression of leucine-rich repeat kinase 2 (LRRK2) inhibits the processing of uMtCK to induce cell death in a cell culture model system
Authors: Cui Jie , Yu Mei , Niu Jingwen , Yue Zhenyu , Xu Zhiheng
Published: August 2011

PD (Parkinson's disease) is the most common neurodegenerative movement disorder. Mutations in LRRK2 (leucine-rich repeat kinase 2) gene are linked to the most common inherited and sporadic PD. Overexpression of LRRK2 and its mutants could induce mitochondrial-dependent neuronal apoptosis. However, the underlying mechanism remains elusive. We have identified several novel LRRK2 interacting proteins and showed that LRRK2 can interact with three components of the PTPC (permeability transition pore complex) including ANT (adenine nucleotide translocator), VDAC (voltage-dependent anion channel) and uMtCK [ubiquitous MtCK (mitochondrial creatine kinase)]. Those components have been reported to be involved in the permeability of mitochondrial membrane. We provide evidence that LRRK2 is likely to interact with uMtCK directly and expression of LRRK2 and its mutant form can suppress the processing of the immature form of uMtCK. LRRK2 expression keeps the uMtCK preprotein on the outer mitochondrial membrane instead of entering the mitochondria. In addition, the expression of both wild-type and mutant forms of LRRK2 promotes the interaction between ANT and VDAC, which plays a role in permeabilization transition pore opening. Finally, LRRK2-induced cell death can be suppressed by uMtCK. Our findings imply that LRRK2 can interact directly with uMtCK to block its entry into mitochondria and its subsequent processing, resulting in inhibition of mitochondrial energy channelling. Meanwhile, the decrease of uMtCK in mitochondria results in elevated interaction between ANT and VDAC and leads to neuronal apoptosis. Thus, our study provides the rational for clinical trials using creatine to treat PD and supports the notion of exploiting LRRK2 as a drug target for PD.
Self-similar nonlinear dynamical solutions for one-component nonneutral plasma in a time-dependent linear focusing field
Authors: Qin Hong , Davidson Ronald C.
Published: August 2011

In a linear trap confining a one-component nonneutral plasma, the external focusing force is a linear function of the configuration coordinates and/or the velocity coordinates. Linear traps include the classical Paul trap and the Penning trap, as well as the newly proposed rotating-radio-frequency traps and the Mobius accelerator. This paper describes a class of self-similar nonlinear solutions of nonneutral plasma in general time-dependent linear focusing devices, with self-consistent electrostatic field. This class of nonlinear solutions includes many known solutions as special cases.
Modeling of the steady state characteristics of large-area graphene field-effect transistors
Authors: Thiele S. , Schwierz F.
Published: August 2011

A model to calculate the DC characteristics of large-area graphene field-effect transistors is presented. It applies the carrier-density-dependent quantum capacitance to calculate the carrier density, uses a steady-state velocity-field characteristics with soft saturation to describe carrier transport, and takes the carrier density dependence of the saturation velocity into account. Different from previous approaches to model graphene transistors, here the DC characteristics are obtained by feeding a drain current into the device and calculating the drain voltage for a given gate bias. The modeling results are compared with experimental data and very good agreement is obtained.
Effects of grain size and boundary structure on the dynamic tensile response of copper
Authors: Escobedo J. P. , Dennis-Koller D. , Cerreta E. K. , Patterson B. M. , Bronkhorst C. A. , Hansen B. L. , Tonks D. , Lebensohn R. A.
Published: August 2011

Plate impact experiments have been carried out to examine the influence of grain boundary characteristics on the dynamic tensile response of Cu samples with grain sizes of 30, 60, 100, and 200 μm. The peak compressive stress is ∼1.50 GPa for all experiments, low enough to cause an early stage of incipient spall damage that is correlated to the surrounding microstructure in metallographic analysis. The experimental configuration used in this work permits real-time measurements of the sample free surface velocity histories, soft-recovery, and postimpact examination of the damaged microstructure. The resulting tensile damage in the recovered samples is examined using optical and electron microscopy along with micro x-ray tomography. The free surface velocity measurements are used to calculate spall strength values and show no significant effect of the grain size. However, differences are observed in the free surface velocity behavior after the pull-back minima, when reacceleration occurs. The magnitude of the spall peak and its acceleration rate are dependent upon the grain size. The quantitative, postimpact, metallographic analyses of recovered samples show that for the materials with grain sizes larger than 30 μm, the void volume fraction and the average void size increase with increasing grain size. In the 30 and 200 μm samples, void coalescence is observed to dominate the void growth behavior, whereas in 60 and 100 μm samples, void growth is dominated by the growth of isolated voids. Electron backscatter diffraction (EBSD) observations show that voids preferentially nucleate and grow at grain boundaries with high angle misorientation. However, special boundaries corresponding to Σl (low angle, < 5 °) and Σ3 (∼60 ° <111> misorientation) types are more resistant to void formation. Finally, micro x-ray tomography results show three dimensional (3D) views of the damage fields consistent with the two dimensional (2D) surface observations. Based on these findings, mechanisms for the void growth and coalescence are proposed.
Micro to nano scale thermal energy conduction in semiconductor thin films
Authors: Maldovan Martin
Published: August 2011

We study the effects of phonon boundary scattering on the transport of thermal energy in semiconductor thin films across multiple length scales and temperatures. We use a model based on the kinetic theory of transport processes that accurately calculates the reduction of the phonon mean free paths by including the effects of spatial location and propagation direction of phonons. We investigate how the effective phonon mean free paths and the resultant thermal conductivities are reduced by the film length scale and surface roughness. The thermal conductivities of silicon and germanium thin films are calculated for temperatures between 4 K and 500 K and thicknesses from nano to micro and good agreement is obtained with experimental measurements. The theoretical study in this paper helps to understand and quantitatively predict the transport of thermal energy in nanoscale materials, which can be used to improve the efficiency of optoelectronic devices and thermoelectric materials.
Large amplitude ion-acoustic solitons in dusty plasmas
Authors: Tiwari R. S. , Jain S. L. , Mishra M. K.
Published: August 2011

Characteristics of ion-acoustic soliton in dusty plasma, including the dynamics of heavily charged massive dust grains, are investigated following the Sagdeev Potential formalism. Retaining fourth order nonlinearities of electric potential in the expansion of the Sagdeev Potential in the energy equation for a pseudo particle and integrating the resulting energy equation, large amplitude soliton solution is determined. Variation of amplitude (A), half width (W) at half maxima and the product P = AW2 of the Korteweg-deVries (KdV), dressed and large amplitude soliton as a function of wide range of dust concentration are numerically studied for recently observed parameters of dusty plasmas. We have also presented the region of existence of large amplitude ion-acoustic soliton in the dusty plasma by analyzing the structure of the pseudo potential. It is found that in the presence of positively charged dust grains, system supports only compressive solitons, on the other hand, in the presence of negatively charged dust grains, the system supports compressive solitons up to certain critical concentration of dust grains and above this critical concentration, the system can support rarefactive solitons also. The effects of dust concentration, charge, and mass of the dust grains, on the characteristics of KdV, dressed and large amplitude the soliton, i.e., amplitude (A), half width at half maxima (W), and product of amplitude (A) and half width at half maxima (P = AW2), are discussed in detail
Bulk-trap modulated Maxwell-Wagner type interfacial carrier relaxation process in a fullerene/polyimide double-layer device investigated by time-resolved second harmonic generation
Authors: Zhang Le , Taguchi Dai , Manaka Takaaki , Iwamoto Mitsumasa
Published: August 2011

The voltage dependent Maxwell-Wagner (MW) type interfacial carrier relaxation process in a fullerene(C60)/polyimide double-layer device was studied by using time-resolved second harmonic generation technique (TR-SHG). The charging of the electrodes, carrier transport, interfacial charge accumulation, and relaxation processes were revealed individually by TR-SHG and analyzed on the basis of the MW model. However, it was found that the interfacial carrier relaxation process followed a stretched exponential law and had a higher order dependence on the applied voltage, which cannot be explained by the simple MW model and were attributed to the bulk traps distributed in the fullerene layer. By taking into account the effects of bulk traps, a bulk-trap modulated MW model was proposed. This model indicates that the interfacial carrier relaxation time (τMW) is not only voltage dependent, but also time dependent, especially within the time region comparable to the characteristic relaxation time of the bulk traps (τt). It is suggested that the two-variable dependent τMW(Vex,t) is responsible for the observed experiment results.
A novel nuclear pyrometry for the characterization of high-energy bremsstrahlung and electrons produced in relativistic laser-plasma interactions
Authors: Günther M. M. , Sonnabend K. , Brambrink E. , Vogt K. , Bagnoud V. , Harres K. , Roth M.
Published: August 2011

We present a novel nuclear activation-based method for the investigation of high-energy bremsstrahlung produced by electrons above 7 MeV generated by a high-power laser. The main component is a novel high-density activation target that is a pseudo alloy of several selected isotopes with different photo-disintegration reaction thresholds. The gamma spectrum emitted by the activated targets is used for the reconstruction of the bremsstrahlung spectrum using an analysis method based on Penfold and Leiss. This nuclear activation-based technique allows for the determination of the number of bremsstrahlung photons per energy bin in a wide range energy without any anticipated fit procedures. Furthermore, the analysis method also allows for the determination of the absolute yield, the energy distribution, and the temperature of high-energy electrons at the relativistic laser-plasma interaction region. The pyrometry is sensitive to energies above 7 MeV only, i.e., this diagnostic is insensitive to any low-energy processes.
The effect of surface roughness on the turbulence structure of a plane wall jet
Authors: Rostamy N. , Bergstrom D. J. , Sumner D. , Bugg J. D.
Published: August 2011

In this paper, an experimental investigation of the turbulence characteristics of a plane wall jet over smooth and rough surfaces, using laser Doppler anemometry (LDA), is reported. The Reynolds number based on the slot height and exit velocity of the jet was approximately Re = 7500. A 36-grit sheet was used as the rough surface, creating a transitionally rough flow regime (44<ks+<70). Both inner and outer scales were used to analyze the effects of surface roughness on the Reynolds stress profiles. Comparisons between the present results and other LDA and hot-wire anemometry studies for a smooth surface indicate a similar behavior for the Reynolds stress profiles. However, the magnitudes of the peak values of the Reynolds stress were higher than in most previous studies due to the lower slot Reynolds number. The present results indicate that surface roughness does not appear to significantly modify the Reynolds stress profiles in the outer region of the jet except for a reduction in the level. In contrast, surface roughness modifies both the shape and magnitudes of the Reynolds stress profiles in the inner layer. Due to the much higher friction velocity for a rough surface, the magnitudes of both the streamwise and wall-normal Reynolds stress decrease in the inner region when normalized using inner scales compared to the smooth-wall values.
On the importance of optical phonons to thermal conductivity in nanostructures
Authors: Tian Zhiting , Esfarjani Keivan , Shiomi Junichiro , Henry Asegun S. , Chen Gang
Published: August 2011

The contribution of optical phonons to thermal conductivity has typically been ignored. However, when the system size decreases to the nanoscale regime, optical phonons are no longer negligible. In this study, the contributions of different phonon polarizations to the thermal conductivity of silicon are discussed based on the phonon lifetimes extracted from a first principles approach. The results indicate that around room temperature, optical phonons can contribute over 20% to the thermal conductivity of nanostructures as compared to 5% in bulk materials. In addition, the temperature and size dependence of the contributions from acoustic and optical phonons are fully explored.
Vibronic coupling in quantum wires: Applications to polydiacetylene
Authors: Yamagata H. , Spano F. C.
Published: August 2011

A theory describing vibronic coupling in direct band gap, one-dimensional semiconductors is developed to account for the photophysical properties of isolated, defect-free conjugated polymers. A Holstein-like Hamiltonian represented in a multi-particle basis set is used to evaluate absorption and emission due to Wannier-Mott excitons. The photophysical properties of such quantum wires are shown to strongly resemble those of Frenkel exciton J-aggregates. The 11Bu exciton coherence length and effective mass are readily determined from the ratio of the 0–0 and 0–1 line strengths, I0 − 0/I0 − 1, in the photoluminescence spectrum. I0 − 0/I0 − 1 is shown to follow a T−1/2 dependence, in an excellent agreement with experiments on the red-phase of polydiacteylene.
Current-less solar wind driven dust acoustic instability in cometary plasma
Authors: Vranjes J.
Published: August 2011

A quantitative analysis is presented of the dust acoustic wave instability driven by the solar and stellar winds. This is a current-less kinetic instability which develops in permeating plasmas, i.e.., when one quasi-neutral electron-ion wind plasma in its propagation penetrates through another quasi-neutral plasma which contains dust, electrons, and ions.
Highly stable amorphous In-Ga-Zn-O thin-film transistors produced by eliminating deep subgap defects
Authors: Nomura Kenji , Kamiya Toshio , Hosono Hideo
Published: August 2011

Highly stable amorphous-In-Ga-Zn-O (a-IGZO) thin film transistors (TFTs) against constant current stress and negative bias light illumination stress were realized by forming a Y2O3 passivation layer. A recent photoemission study revealed that deep defects located above the valence band top are formed at a high density to a depth of ∼2 nm in the surface layer of the a-IGZO channel. Here, we present that these deep defects are responsible for the instability of a-IGZO TFTs, and the instability can be much improved by passivation with Y2O3, which effectively eliminates the deep subgap defects from the surface of a-IGZO.
The role of the electron convection term for the parallel electric field and electron acceleration in MHD simulations
Authors: Matsuda K. , Terada N. , Katoh Y. , Misawa H.
Published: August 2011

There has been a great concern about the origin of the parallel electric field in the frame of fluid equations in the auroral acceleration region. This paper proposes a new method to simulate magnetohydrodynamic (MHD) equations that include the electron convection term and shows its efficiency with simulation results in one dimension. We apply a third-order semi-discrete central scheme to investigate the characteristics of the electron convection term including its nonlinearity. At a steady state discontinuity, the sum of the ion and electron convection terms balances with the ion pressure gradient. We find that the electron convection term works like the gradient of the negative pressure and reduces the ion sound speed or amplifies the sound mode when parallel current flows. The electron convection term enables us to describe a situation in which a parallel electric field and parallel electron acceleration coexist, which is impossible for ideal or resistive MHD.
Restoration of bulk magnetic properties by strain engineering in epitaxial CoFe2O4 (001) ultrathin films
Authors: Matzen S. , Moussy J.-B. , Mattana R. , Petroff F. , Gatel C. , Warot-Fonrose B. , Cezar J. C. , Barbier A. , Arrio M.-A. , Sainctavit Ph.
Published: August 2011

We report on the significantly enhanced in-plane magnetic properties of CoFe2O4 (001) ultrathin layers (5 nm) grown on MgAl2O4 (001) in comparison to films deposited on MgO (001). The predicted inverse spinel structure is confirmed by x-ray magnetic circular dichroism measurements and transmission electronic microscopy studies reveal a significant in-plane compressive strain, responsible for the strong film anisotropy. These results show that strain engineering can be used to tailor the magnetic properties of oxide ultrathin films. A large compressive strain restores bulk magnetic properties for CoFe2O4 films at tunnel barrier thicknesses.
Interface thermal resistance and thermal rectification in hybrid graphene-graphane nanoribbons: A nonequilibrium molecular dynamics study
Authors: Rajabpour A. , Vaez Allaei S. M. , Kowsary F.
Published: August 2011

The thermal conductivity of hybrid graphene-graphane nanoribbons (GGNRs) have been investigated using nonequilibrium molecular dynamics simulations. The interface between graphene and graphane leads to a Kapitza resistance with strongly dependence on the imposed heat flux direction. We introduce GGNRs as promising thermal rectifiers at room temperature. By calculating phonon spectra, underlying mechanisms were investigated.
Electrical power dissipation in semiconducting carbon nanotubes on single crystal quartz and amorphous SiO2
Authors: Tsai Cheng-Lin , Liao Albert , Pop Eric , Shim Moonsub
Published: August 2011

Heat dissipation in electrically biased individual semiconducting carbon nanotubes (CNTs) on single crystal quartz and amorphous SiO2 is examined with temperature profiles obtained by spatially resolved Raman spectroscopy. Despite the differences in phonon velocities, thermal conductivity, and van der Waals interactions with CNTs, on average, heat dissipation into single crystal quartz and amorphous SiO2 is found to be similar. Large temperature gradients and local hot spots often observed underscore the complexity of CNT temperature profiles and may be accountable for the similarities observed.
Wall pressure fluctuations beneath supersonic turbulent boundary layers
Authors: Bernardini Matteo , Pirozzoli Sergio
Published: August 2011

The structure of the wall pressure field beneath supersonic adiabatic turbulent boundary layers is analyzed by means of direct numerical simulations at free-stream Mach number M∞ = 2, 3, 4, spanning a relatively large range of Reynolds numbers. The data reported in the paper, which include wall pressure fluctuations intensities, frequency spectra, space-time correlations, and convection velocities, show that when pressure is scaled by the wall shear stress, most statistics well conform to low-speed findings, contradicting the conclusions of previous experimental studies. Genuine compressibility effects are found to provide a small contribution to the magnitude of the wall pressure fluctuations, their influence being limited to the high-frequency end of the spectra, where a systematic increase with the Mach number is observed.
Two-dimensional infrared spectroscopy of azido-nicotinamide adenine dinucleotide in water
Authors: Dutta Samrat , Rock William , Cook Richard J. , Kohen Amnon , Cheatum Christopher M.
Published: August 2011

Mid-IR active analogs of enzyme cofactors have the potential to be important spectroscopic reporters of enzyme active site dynamics. Azido-nicotinamide adenine dinucleotide (NAD+), which has been recently synthesized in our laboratory, is a mid-IR active analog of NAD+, a ubiquitous redox cofactor in biology. In this study, we measure the frequency–frequency time correlation function for the antisymmetric stretching vibration of the azido group of azido-NAD+ in water. Our results are consistent with previous studies of pseudohalides in water. We conclude that azido-NAD+ is sensitive to local environmental fluctuations, which, in water, are dominated by hydrogen-bond dynamics of the water molecules around the probe. Our results demonstrate the potential of azido-NAD+ as a vibrational probe and illustrate the potential of substituted NAD+-analogs as reporters of local structural dynamics that could be used for studies of protein dynamics in NAD-dependent enzymes.
Electronic structures of Fe-terminated armchair boron nitride nanoribbons
Authors: Wang Yanli , Ding Yi , Ni Jun
Published: August 2011

Using first-principles calculations, we investigate the structural, electronic, and magnetic properties of Fe-terminated armchair boron nitride nanoribbons (Fe-ABNNRs). We find that Fe atoms can form a dimerized zigzag chain along the armchair edge. Different from the semiconducting H-terminated ABNNRs, the Fe-ABNNRs are antiferromagnetic metals. When one edge is terminated by Fe atoms and the other edge by H atoms, the ABNNRs become half-metals regardless of the ribbon width. Other transition-metal terminated nanoribbons are also examined, which are semiconductors or half-metals with diverse magnetic states depending on the types of metals.
Surface acoustic wave response to ambient humidity in graphite oxide structures
Authors: Rimeika R. , Barkauskas J. , Čiplys D.
Published: August 2011

The effect of ambient air humidity on surface acoustic waves (SAW) in graphite oxide-lithium niobate structures was investigated. The acoustic wave amplitude and phase strongly depended on the humidity level in structures with graphite oxide films deposited on the free substrate surface. These dependencies were significantly reduced in structures with graphite oxide films deposited on a metalized substrate surface. Fast (sub-second range) response in the acoustic amplitude and phase to step-like humidity changes was observed. Humidity-induced variations in the SAW amplitude and velocity are attributed to acoustoelectric interaction and mass loading due to moisture adsorption by graphite oxide layers.
Oxygen enhanced ferromagnetism in Cr-doped ZnO films
Authors: Xiong Ze , Liu Xue-Chao , Zhuo Shi-Yi , Yang Jian-Hua , Shi Er-Wei , Yan Wen-Sheng
Published: August 2011

Cr-doped ZnO films have been prepared by inductively coupled plasma enhanced physical vapor deposition, and an in-depth study is performed on the chromium doping and oxygen partial pressure dependence of ferromagnetism. The x-ray diffraction and photoluminescence results indicate that the moderate oxygen can relax the lattice strain thus enhancing ferromagnetism which, as confirmed by soft x-ray absorption spectroscopy, is mainly attributed to the Cr valence state transition from Cr3+ to Cr6+. However, excessive oxygen suppresses the oxygen vacancies and the ferromagnetic exchange. Furthermore, the parabola-like dependence of ferromagnetism on oxygen partial pressure is consistent with the bound magnetic polaron scenario.
Solid-state optimal phase-covariant quantum cloning machine
Authors: Pan Xin-Yu , Liu Gang-Qin , Yang Li-Li , Fan Heng
Published: August 2011

Here, we report an experimental realization of optimal phase-covariant quantum cloning machine with a single electron spin in solid state system at room temperature. The involved three states of two logic qubits are encoded physically in three levels of a single electron spin with two Zeeman sub-levels at a nitrogen-vacancy defect center in diamond. The preparation of input state and the phase-covariant quantum cloning transformation is controlled by two independent microwave fields. The average experimental fidelity reaches 85.2% which is very close to theoretical optimal fidelity 85.4% and is beyond the bound 83.3% of universal cloning.
A dietary sodium gluconate supplement improves growth performance and prebiotic activity in the small intestine of nursery pigs grown under tropical conditions
Authors: Poeikhampha T. , Bunchasak C.
Published: August 2011

This study was conducted to evaluate the effect of sodium gluconate (SG) supplementation in diets on growth performance, small intestinal morphology and short chain fatty acid concentration in the caecum of nursery pigs. One-hundred and forty-four piglets (bodyweight ~10.5 kg) were raised in conventional open housing and divided into four treatments with six replications. The pigs received diet supplemented without (control), or with SG at a level of 1000, 2500 or 5000 ppm for 6 weeks. The results indicated that increasing SG supplementation from 0 to 5000 ppm linearly improved final bodyweight, average daily gain, feed : gain ratio, caecal propionic acid and total short-chain fatty acid concentration (linear P < 0.05). Adding SG in diet tended to reduce Escherichia coli counts in the caecum (P = 0.09) and adding SG at 2500–5000 ppm significantly increased the villous height in the duodenum (linear, P < 0.01), whereas there were no increase in caecal acetic acid and lactic acid bacterial counts in the caecum and rectum, and E. coli counts in the rectum when compared with the control group. SG supplementation did not affect the pH values in gastrointestinal tract of nursery pigs. This study implied that SG supplementation improved growth rate and may be useful as a prebiotic to accomplish the maximum growth performances in nursery pigs.