bluuebunny/crossref_metadata_2025 huggingface dataset:
Pattern and kinematic polarity of late Mesozoic extension in continental NE Asia: Perspectives from metamorphic core complexes
Authors: Wang Tao , Zheng Yadong , Zhang Jinjiang , Zeng Lingsen , Donskaya Tatiana , Guo Lei , Li Jianbo
Published: August 2011

Late Mesozoic extension in NE Asia resulted in the development of a large extensional province. Metamorphic core complexes (MCCs) are the major features in this province and have 40Ar/39Ar ages of 130–110 Ma for the mylonites and U‐Pb zircon ages of 150–110 Ma for the integral granitic intrusions. Based on this and previous studies, this paper summarizes major characteristics of these MCCs and recognizes a regional kinematic shear sense. Most MCCs in the Transbaikalia region, Sino‐Mongolia border tract, and the northwest‐central portion of the North China craton (NCC) show a top‐to‐the‐southeast (SE) shear, whereas those in the eastern and southern NCC locally underwent top‐to‐the‐northwest (NW) shear. The three largest basins (Songliao, Huabei and Ordos) in North China are located in the transitional zone between domains of opposing shear sense. We interpret the extension in the Transbaikalia, Sino‐Mongolia tract and northwestern part of the NCC to reflect late‐orogenic collapse of thickened crust following Middle‐Late Jurassic collision along the Okhotsk suture. The southeastward extension is probably controlled by crustal‐scale top‐to‐the‐SE tangential shear. The transition from contraction to extension is marked by detachment faults that nucleated as extensional crenulation cleavage (ecc, i.e., C′) in sub‐horizontal ductile shear zones late in orogenic crustal thickening. The combined effect of gravitational loading and thermal‐uplifting is considered to be the origin of the late‐or post‐orogenic collapse. The top‐to‐the‐NW extension in the NE of the NCC might reflect antithetic sub‐extensional zones or Mesozoic back‐arc extension as a far‐field effect of Cretaceous Pacific plate subduction.
Restoration of Cenozoic deformation in Asia and the size of Greater India
Authors: van Hinsbergen Douwe J. J. , Kapp Paul , Dupont‐Nivet Guillaume , Lippert Peter C. , DeCelles Peter G. , Torsvik Trond H.
Published: August 2011

A long‐standing problem in the geological evolution of the India‐Asia collision zone is how and where convergence between India and Asia was accommodated since collision. Proposed collision ages vary from 65 to 35 Ma, although most data sets are consistent with collision being underway by 50 Ma. Plate reconstructions show that since 50 Ma ∼2400–3200 km (west to east) of India‐Asia convergence occurred, much more than the 450–900 km of documented Himalayan shortening. Current models therefore suggest that most post‐50 Ma convergence was accommodated north of the Indus‐Yarlung suture zone. We review kinematic data and construct an updated restoration of Cenozoic Asian deformation to test this assumption. We show that geologic studies have documented 600–750 km of N‐S Cenozoic shortening across, and north of, the Tibetan Plateau. The Pamir‐Hindu Kush region accommodated ∼1050 km of N‐S convergence. Geological evidence from Tibet is inconsistent with models that propose 750–1250 km of eastward extrusion of Indochina. Approximately 250 km of Indochinese extrusion from 30 to 20 Ma of Indochina suggested by SE Asia reconstructions can be reconciled by dextral transpression in eastern Tibet. We use our reconstruction to calculate the required size of Greater India as a function of collision age. Even with a 35 Ma collision age, the size of Greater India is 2–3 times larger than Himalayan shortening. For a 50 Ma collision, the size of Greater India from west to east is ∼1350–2600 km, consistent with robust paleomagnetic data from upper Cretaceous‐Paleocene Tethyan Himalayan strata. These estimates for the size of Greater India far exceed documented shortening in the Himalaya. We conclude that most of Greater India was consumed by subduction or underthrusting, without leaving a geological record that has been recognized at the surface.
Coseismic displacements and Holocene slip rates for two active thrust faults at the mountain front of the Andean Precordillera (∼33°S)
Authors: Schmidt Silke , Hetzel Ralf , Mingorance Francisco , Ramos Victor A.
Published: August 2011

During the last few hundred years several destructive earthquakes occurred along the eastern margin of the Andean Precordillera, where GPS data reveal a shortening rate of ∼4.5 mm/a. We use fault scarp profiles and age determinations of deformed terraces (T1–T4) to infer coseismic displacements and quantify slip rates for the Peñas and Cal thrust faults near Mendoza city. Scarps on the lowest terrace level T1reveal vertical offsets of 0.8–1.0 m for both faults, which are interpreted as coseismic displacements during the last earthquake. Together with the fault dip these offsets indicate that both faults are capable of producing magnitude MW∼6.9 earthquakes, which is corroborated by a magnitude MS= 7.0 event on the Cal fault that destroyed Mendoza in 1861. At the Peñas thrust fault, terrace T2has an age of ∼3.3 ka and is offset by ∼1.9 m, whereas the ∼12‐ka‐old terrace T3is displaced by ∼11 m. Combined with the fault dip of ∼25°, the age and offset of terrace T3define a shortening rate of ∼2.0 mm/a on the Peñas fault, i.e., about half of the present‐day shortening at the eastern margin of the Precordillera. At the Cal fault, terraces T2to T4have ages of ∼0.8 ka (OSL), ∼3.9 ka (14C), and ≤12 ka (10Be) and are vertically offset by ∼2.6, ∼3.6, and ∼7.0 m, respectively, which implies that slip on the fault has recently accelerated. Hence, the Cal fault poses a serious seismic hazard to the one million inhabitants of Mendoza.
Enzyme activities and glyphosate biodegradation in a riparian soil affected by simulated saltwater incursion
Authors: Yang Changming , Wang Mengmeng
Published: August 2011

Soil salinization due to saltwater incursion, is a major threat to biochemical activities and thus strongly alters biogeochemical processes in a freshwater riparian of coastal estuary region. A pot incubation experiment was conducted to investigate the effects of simulated saltwater incursion on some key enzymatic activities and biodegradation dynamics of herbicide glyphosate in a riparian soil in Chongming Island located in the Yangtze River estuary, China. The results showed that saltwater addition with 10% artificial seawater significantly increased the biodegradation efficiency of glyphosate with the lowest residual concentration among all the treatments. However, glyphosate degradation was markedly decreased in the riparian soil with high levels of saltwater treatment. As compared with no saltwater treatment, the half-lives for 20% and 50% seawater treatments were prolonged by 4.9% and 21.1%, respectively. Throughout the incubation period, saltwater addition with 10% seawater stimulated the enzymatic activities in the glyphosate-spiked riparian soil, as compared to the treatment with 0% seawater. Flourescein diacetate (FDA) hydrolysis rate, dehydrogenase activity (DHA), catalase activity, and alkaline phosphatase activity in the glyphosate-spiked riparian soil treated with 10% seawater were 68.5%, 49.2%, 38.7%, and 28.6% higher than those for no saltwater treatment, respectively. The effect of 20% seawater treatment on the glyphosate-spiked riparian soil enzymatic activities fluctuated between promotion and inhibition depending on the type of enzymes. Soil enzymatic activities were severely depressed by increasing salinity level with 50% seawater treatment significantly inhibited, relative to no saltwater treatment. Especially, FDA hydrolysis rate and DHA were decreased by 73.8% and 64.8%, respectively, as compared to no saltwater treatment. Glyphosate degradation percentages were strongly positively correlated to the FDA hydrolysis rate and DHA, indicating that as compared to the other enzymes, the two enzymes contributed more to the herbicide biodegradation in the salt-affected riparian soil.
Sidewall and thermal boundary condition effects on the evolution of longitudinal rolls in Rayleigh-Bénard-Poiseuille convection
Authors: Mergui S. , Nicolas X. , Hirata S.
Published: August 2011

Experimental and numerical studies of steady longitudinal convection rolls that develop in a Poiseuille air flow in a rectangular channel heated from below and cooled from the top are conducted in the range 3500 ≤ Ra ≤ 6000 and 20 ≤ Re ≤ 200. The effect of the lateral vertical walls on the onset and development of the convection cells is investigated by changing the transverse aspect ratio of the channel from 4.7 to 18.4. The influence of the entrance temperature and adiabatic or conductive thermal boundary conditions at the side and top walls of the channel is also investigated. The scenario of the roll formation is described in details. It results in a symmetric pattern in the form of steady longitudinal rolls with an even number of rolls that depends not only on the aspect ratio but possibly on the inlet temperature of the flow. It is shown that the fully developed pattern is determined by the two rolls nearby each vertical side wall that are triggered just at the entrance of the channel due to the presence of velocity boundary layers adjacent to the walls. It is also shown that the heat conduction in the top horizontal wall of the experimental channel must be taken into account in the numerical simulations so that the experimental wavenumber can be properly depicted.
Electromagnetically induced localized ignition in secondary high explosives: Experiments and numerical verification
Authors: Lee Perry W. , Gunderson Jake A. , Glover Brian B. , Dattelbaum Dana M.
Published: August 2011

In order to more fully understand the factors that influence the thermal “hot-spot” initiation of high explosives, we have chosen a model system for study that uses the internal and localized dissipation of long wavelength electromagnetic energy (microwaves). High purity organic crystals generally interact weakly with microwave energy. Therefore, the addition of electromagnetically absorbing inclusions of silicon carbide provides a tractable system for the study of hot-spot ignition phenomena. Previously, we developed a simple analytic model that illuminates the important physical factors. In this work, we verify the relationships of the analytic model using a series of experiments and a numerical model.
Optical properties of carbon nanotube gas sensor
Authors: Tooski S. B. , Godarzi A. , Solari M. Sh. , Ramyar M. , Roohforouz A.
Published: August 2011

A kinetic theory combined with an effective medium theory in a nonlinear basis is used to compute the effective dielectric of single-walled carbon nanotubes (SWNTs) in the presence of gas molecules. The effect of the change of SWNT volume fraction on the response to gas molecules is investigated to find the optimum SWNTs embedded in the system. The computational results obtained show that the effective dielectric of the system increases explicitly with increasing dielectric and volume fraction of SWNTs. The effects of molecular adsorption on the effective dielectric of the system are also examined. This investigation showed that the effective dielectric of the system increases with increasing collision frequency and decreases with increasing electron density. This work is helpful for designing SWNT gas sensors.
A high-energy-density, high-Mach number single jet experiment
Authors: Hansen J. F. , Dittrich T. R. , Elliott J. B. , Glendinning S. G. , Cotrell D. L.
Published: August 2011

A high-energy-density, x-ray-driven, high-Mach number (M ≥ 17) single jet experiment shows constant propagation speeds of the jet and its bowshock into the late time regime. The jet assumes a characteristic mushroom shape with a stalk and a head. The width of the head and the bowshock also grow linearly in time. The width of the stalk decreases exponentially toward an asymptotic value. In late time images, the stalk kinks and develops a filamentary nature, which is similar to experiments with applied magnetic fields. Numerical simulations match the experiment reasonably well, but “exterior” details of the laser target must be included to obtain a match at late times.
Whistler anisotropy instability at low electron β: Particle-in-cell simulations
Authors: Gary S. Peter , Liu Kaijun , Winske Dan
Published: August 2011

The whistler anisotropy instability is studied in a magnetized, homogeneous, collisionless plasma model. The electrons (denoted by subscript e) are represented initially with a single bi-Maxwellian velocity distribution with a temperature anisotropy T⊥e/T∥e>1, where ⊥ and ∥ denote directions perpendicular and parallel to the background magnetic field Bo, respectively. Kinetic linear dispersion theory predicts that, if the ratio of the electron plasma frequency ωe to the electron cyclotron frequency Ωe is greater than unity and β∥e≥0.025, the maximum growth rate of this instability is at parallel propagation, where the fluctuating fields are strictly electromagnetic. At smaller values of β∥e, however, the maximum growth rate shifts to propagation oblique to Bo and the fluctuating electric fields become predominantly electrostatic. Linear theory and two-dimensional particle-in-cell simulations are used to examine the consequences of this transition. Three simulations are carried out, with initial β∥e=0.10, 0.03, and 0.01. The fluctuating fields of the β∥e=0.10 run are predominantly electromagnetic, with nonlinear consequences similar to those of simulations already described in the literature. In contrast, the growth of fluctuations at oblique propagation in the low electron β runs leads to a significant δE∥, which heats the electrons leading to the formation of a substantial suprathermal component in the electron parallel velocity distribution.
Control of axisymmetric vortex breakdown in a constricted pipe: Nonlinear steady states and weakly nonlinear asymptotic expansions
Authors: Meliga Philippe , Gallaire François
Published: August 2011

The present paper investigates numerically and theoretically the axisymmetric vortex breakdown occurring in a constricted pipe of infinite extension, i.e., the transition from a smooth columnar state to a breakdown state exhibiting a recirculation bubble. Velocity distributions are prescribed at the pipe inlet under the form of Batchelor vortices with uniform axial velocity and variable levels of confinement. A numerical continuation technique is developed to follow the branches of nonlinear steady solutions when varying the swirl parameter. In the most general case, vortex breakdown occurs abruptly owing to a subcritical, global instability of the non-parallel, viscous columnar solution, and results in the coexistence of multiple stable solutions over a finite range of swirl. For highly confined vortices, a second scenario prevails, where the flow transitions smoothly from the columnar to the breakdown state without any instability. The effect of a low-flow rate jet positioned at the pipe wall is then characterized in the perspective of control. Its effectiveness is evaluated in light of several practically meaningful criteria, namely, the ability of the control to optimize either the stability domain or the topology of the columnar state and its ability to alleviate hysteresis. For each criterion, an optimal jet position is determined from nonlinear simulations, the results being in good agreement with that issuing from an asymptotic expansion of the Navier–Stokes equations. Finally, we illustrate the importance of physically motivated control strategies by demonstrating how the wall jet technique can be outdone by an appropriate manipulation of the axial velocity profile prescribed at the pipe inlet.
Seebeck and thermal conductivity analysis in amorphous/crystalline β-K2Bi8Se13 nanocomposite materials
Authors: Kyratsi Th. , Hatzikraniotis E. , Ioannou M. , Chung D. Y. , Tsiaoussis I.
Published: August 2011

In this work, ball milling is applied on β-K2Bi8Se13 compounds in order to explore the potential of the process for the fabrication of nano-based material. Polycrystalline β-K2Bi8Se13, synthesized from melt, was ball milled under inert atmosphere. Powder x-ray diffraction showed a significantly increased disorder with ball milling time. TEM studies confirmed the presence of nanocrystalline material in an amorphous matrix, suggesting the development of crystalline/amorphous β-K2Bi8Se13 nanocomposite material via ball milling process. Seebeck coefficient and thermal conductivity were analyzed based on the effective medium theory and show a significant contribution of a nanocrystalline phase.
Dust-ion-acoustic solitary waves in dusty plasma with arbitrarily charged dust and vortex-like electron distribution
Authors: Rahman O. , Mamun A. A.
Published: August 2011

The nonlinear propagation of dust-ion-acoustic (DIA) waves in a dusty plasma containing trapped electrons following vortex-like distribution, cold mobile ions, and arbitrarily charged static dust is theoretically investigated. The properties of small but finite amplitude DIA solitary waves (SWs) are studied by employing the reductive perturbation technique. It is found that owing to the departure from the Maxwellian electron distribution to a vortex-like one, the dynamics of such DIA SWs is governed by a modified Korteweg-de Vries equation. The basic features (amplitude, width, speed, etc.) of such DIA SWs, which are found to be significantly modified by the vortex-like electron distribution and dust polarity, are also examined. The implications of our results to space and laboratory dusty plasmas are briefly discussed.
Surface-anisotropy and training effects of exchange bias in nanoparticles with inverted ferromagnetic-antiferromagnetic core-shell morphology
Authors: Hu Yong , Du An
Published: August 2011

A modified Monte Carlo method using the Metropolis algorithm is performed to simulate the hysteresis behaviors of the nanoparticles with an inverted antiferromagnetic (core)/ferromagnetic (shell) morphology at low temperature after field cooling. We have examined the dependence of exchange bias on the hard ferromagnetic surface anisotropy and the training effect. Our simulations reveal that, besides the antiferromagnetic core, another pinning source, namely, the hard ferromagnetic surface, can also contribute to the exchange bias in such a special structure. Above a critical surface anisotropy, the exchange bias field has a steep increase by means of the change of the magnetization reversal mechanisms, which are affected by the surface anisotropy. During the consecutive hysteresis loops, the exchange bias field decreases gradually to a constant value. The phenomena have been interpreted well by considering the combination of locking, releasing, and stabilizing of the spins on the antiferromagnetic core surface and the energy competition between Zeeman and antiferromagnetic anisotropy. Our results are in good agreement with the experimental findings.
Ion velocity distributions in the sheath and presheath of a biased object in plasma
Authors: Miloch W. J. , Gulbrandsen N. , Mishra L. N. , Fredriksen Å.
Published: August 2011

Ion velocity distributions in the vicinity of a spherical object with a negative potential with respect to collisionless, source-free plasma are studied with three-dimensional numerical simulations. The ion dynamics around the object leads to distorted radial velocity distributions in the presheath and the sheath edge region. Far in the sheath, an increase in the thermal velocity in the radial direction is observed. Different potentials of the object, ion temperatures, and ion masses are considered, as well as the role of spatial and temporal resolutions in laboratory measurements of ion velocity distributions. The simulations are carried out with the DiP3D, a three-dimensional particle-in-cell numerical code.
Oscillating magnetocaloric effect
Authors: Reis M. S.
Published: August 2011

This Letter presents the oscillatory behavior found in the magnetic entropy change of diamagnetic materials. We show that this quantity depends on the oscillating term and, as a consequence, the magnetocaloric potential can be tuned as either inverse or normal, depending on the value of the magnetic field change. A quite small change (≈10−3 T) of the magnetic field change is able to invert the magnetic entropy change. These results open doors for applications at quite low temperatures and can be further developed to be incorporated into adiabatic demagnetization refrigerators, as well as sensible magnetic field sensors.
Fractional spin in reduced density-matrix functional theory
Authors: Helbig N. , Theodorakopoulos G. , Lathiotakis N. N.
Published: August 2011

We study the behavior of different functionals of the one-body reduced density matrix (1RDM) for systems with fractional z-component of the total spin. We define these systems as ensembles of integer spin states. It is shown that, similarly to density functional theory, the error in the dissociation of diatomic molecules is directly related to the deviation from constancy of the atomic total energies as functions of the fractional spin. However, several functionals of the 1RDM show a size inconsistency which leads to additional errors. We also investigate the difference between a direct evaluation of the energy of an ensemble of integer-spin systems and a direct minimization of the energy of a fractional-spin system.
Delocalized electronic behavior observed in transition metal oxide clusters under strong-field excitation
Authors: Sayres Scott G. , Ross Matt W. , Castleman A. W.
Published: August 2011

Heterogeneously composed clusters are exposed to intensity resolved, 100 fs laser pulses to reveal the energy requirements for the production of the high charge states of both metal and nonmetal ions. The ionization and fragmentation of group V transition metal oxide clusters are here examined with laser intensities ranging nearly four orders in magnitude (∼3 × 1011 W/cm2 to ∼2 × 1015 W/cm2) at 624 nm. The ionization potentials of the metal atoms are measured using both multiphoton ionization and tunneling ionization models. We demonstrate that the intensity selective scanning method can be utilized to measure the low ionization potentials of transition metals (∼7 eV). The high charge states demonstrate an enhancement in ionization that is three orders of magnitude lower in laser intensity than predicted for the atomic counterparts. Finally, the response from the various metals and the oxygen is compared to elucidate the mechanism of enhanced ionization that is observed. Specifically, the sequence of ion appearances demonstrates delocalized electron behavior over the entire cluster.
Slow magnetization dynamics and energy barriers near vortex state nucleation in circular permalloy dots
Authors: Kakazei G. N. , Ilyn M. , Chubykalo-Fesenko O. , Gonzalez J. , Serga A. A. , Chumak A. V. , Beck P. A. , Laegel B. , Hillebrands B. , Guslienko K. Y.
Published: August 2011

Time decay of the magnetization of the arrays of Permalloy circular dots of submicron sizes was measured on a long time scale (hours) near the vortex nucleation field. A considerable influence of external magnetic field and temperature on the slow magnetization dynamics was detected. The observed effects are explained by overcoming the field dependent energy barriers in the process of vortex nucleation. The magnetic viscosity and energy barriers were found from the magnetization time decay dependencies.
Particle simulation of a ka-band gyrotron traveling wave amplifier
Authors: Xu Shou-Xi , Liu Pu-Kun , Zhang Shi-Chang , Du Chao-Hai , Xue Qian-Zhong , Geng Zhi-Hui , Su Yi-Nong
Published: August 2011

The design of a ka-band gyrotron traveling wave (gyro-TWT) amplifier is presented. The gyro-TWT amplifier with a severed structure operates in the fundamental harmonic TE01 circular electric mode. The beam-wave interaction is studied by using a particle-in-cell (PIC) code. The simulations predict that the amplifier can produce an output peak power of over 155 kW, 22% efficiency, 23 dB gain, and a 3 dB bandwidth of 2 GHz for a 70 kV, 10 A electron beam with an axial velocity spread Δvz/vz=5%.
Relativistic contributions to single and double core electron ionization energies of noble gases
Authors: Niskanen J. , Norman P. , Aksela H. , Ågren H.
Published: August 2011

We have performed relativistic calculations of single and double core 1s hole states of the noble gas atoms in order to explore the relativistic corrections and their additivity to the ionization potentials. Our study unravels the interplay of progression of relaxation, dominating in the single and double ionization potentials of the light elements, versus relativistic one-electron effects and quantum electrodynamic effects, which dominate toward the heavy end. The degree of direct relative additivity of the relativistic corrections for the single electron ionization potentials to the double electron ionization potentials is found to gradually improve toward the heavy elements. The Dirac–Coulomb Hamiltonian is found to predict a scaling ratio of ∼4 for the relaxation induced relativistic energies between double and single ionization. Z-scaling of the computed quantities were obtained by fitting to power law. The effects of nuclear size and form were also investigated and found to be small. The results indicate that accurate predictions of double core hole ionization potentials can now be made for elements across the full periodic table.
Strong Faraday rotation in Ce and Bi comodified epitaxial iron garnet films: Valence control through strain engineering
Authors: Hwang Jae-Yeol , Morandotti Roberto , Pignolet Alain
Published: August 2011

The correlation between lattice-misfit strain and the valence change of cerium was investigated in cerium and bismuth comodified iron garnet epitaxial films. We demonstrated that the transition of the valence state from Ce4+ to Ce3+ is triggered by reducing the compressive lattice-misfit strain and that the increase in concentration of Ce3+ induces a red-shift of the optical bandgap as well as an enhancement of the Faraday rotation. An extraordinary Faraday rotation of 0.91 deg/μm at 1.55 μm was achieved in these films by maximizing the concentration of Ce3+ through strain engineering.
On inhibiting Auger intraband relaxation in InAs/GaAs quantum dot intermediate band solar cells
Authors: Tomić Stanko , Martí Antonio , Antolín Elisa , Luque Antonio
Published: August 2011

The operation of ideal quantum dot intermediate band solar cell requires the largest possible reduction of carrier relaxation from the conduction band to the intermediate band (intraband relaxation) so that it approaches the radiative limit. In this respect, we examine the contribution to this relaxation of Auger related electron cooling non-radiative mechanisms and suggest ways of suppressing them.
Controlling the function of carbon nanotube devices with re-writable charge patterns
Authors: Prisbrey Landon , DeBorde Tristan , Park Ji-Yong , Minot Ethan D.
Published: August 2011

We use atomic force microscopy lithography to write charge patterns in close proximity to carbon nanotube field-effect transistor devices. The silicon dioxide substrate retains the charge for days, allowing various charge configurations to be tested. We show that the written charge can move the Fermi level in the nanotube by 1 eV and we use this charge lithography to reconfigure a field-effect transistor into a pn junction. The substrate charge can be erased and rewritten, offering a new tool for prototyping nanodevices and optimizing electrostatic doping profiles.
Nuclear magnetic relaxation in water revisited
Authors: Hartwig Stefan , Voigt Jens , Scheer Hans-Jürgen , Albrecht Hans-Helge , Burghoff Martin , Trahms Lutz
Published: August 2011

In this study, we revisited nuclear magnetic relaxation of 1H in water at very low Larmor frequencies that has been studied intensively in earlier years. We make use of the recently developed superconducting quantum interference device based ultra-low field NMR technique, which enables much easier access to the longitudinal spin-lattice relaxation time T1 and the transversal spin-spin relaxation time T2 below several kHz than traditional field cycling methods. Our data reproduce and complement the earlier results, in that they corroborate the finding of an exchange process with a correlation time of about 0.34 ms at room temperature which can be attributed to the migration of hydronium and hydroxyl ions in neutral water via hydrogen bridges. The corresponding relaxation process is driven by the interaction of the protons with 17O and contributes to the T1 and the T2 relaxation rate by about 0.12 s−1. In addition, we found evidence of a very slow exchange process at about 100 Hz that has hitherto not been reported.
Orientation of organic molecules in a monolayer vis-à-vis their molecular orbitals and transport gap
Authors: Chakrabarti Sudipto , Dey Sukumar , Pal Amlan J.
Published: August 2011

We form a monolayer of magnetic organic molecules with its plane parallel or perpendicular to the substrate. The molecules in a monolayer are oriented with an external magnetic field followed by immobilization though an electrostatic binding. In this work, from scanning tunneling microscopy (STM) measurements, we show that conductivity, molecular orbitals, and transport gap of the molecules in a monolayer depend on its orientation. From measurements carried out with different tip-to-molecule distances, we observe that the STM tip also influences molecular orbitals and transport-gap of molecules.
Effective static and high-frequency viscosities of concentrated suspensions of soft particles
Authors: Mendoza Carlos I.
Published: August 2011

We obtain an analytic expression that allows to determine the static η and high-frequency η∞ viscosities as function of the volume fraction ϕ of a concentrated suspension of soft spherical particles in a liquid of viscosity η0. The particles consist of a hard core of radius a covered by a porous layer of thickness d. Suspensions of hard spheres and homogeneous porous particles are limiting cases of the model. The proposed expression incorporates the results for the intrinsic viscosity obtained on the basis of a cell model [H. Ohshima, Langmuir 26, 6287 (2010)]10.1021/la904121p into a recently obtained relation for the effective viscosity of concentrated colloidal suspensions [C. I. Mendoza and I. Santamaría-Holek, J. Chem. Phys. 130, 044904 (2009)10.1063/1.3063120; J. Colloid. Interface Sci. 346, 118 (2010)]10.1016/j.jcis.2010.02.033. In this model, the correlations between the particles due to crowding effects are introduced through an effective volume fraction ϕeff which is then used as integration variable in a differential effective medium procedure. The final expression is simple, accurate, and allows to collapse all the data in a universal master curve that is independent of the parameters characterizing the system. The only difference between the static and high-frequency cases is that in the later case ϕeff also incorporates hydrodynamic interactions arising from the so-called relaxation term. We have tested the accuracy of our model comparing with experimental results for spherical polymeric brushes and simulations for the high-frequency viscosity of homogeneous porous particles. In all cases the agreement with the data is extremely good.
Robustness of multidimensional Brownian ratchets as directed transport mechanisms
Authors: González-Candela Ernesto , Romero-Rochín Víctor , Del Río Fernando
Published: August 2011

Brownian ratchets have recently been considered as models to describe the ability of certain systems to locate very specific states in multidimensional configuration spaces. This directional process has particularly been proposed as an alternative explanation for the protein folding problem, in which the polypeptide is driven toward the native state by a multidimensional Brownian ratchet. Recognizing the relevance of robustness in biological systems, in this work we analyze such a property of Brownian ratchets by pushing to the limits all the properties considered essential to produce directed transport. Based on the results presented here, we can state that Brownian ratchets are able to deliver current and locate funnel structures under a wide range of conditions. As a result, they represent a simple model that solves the Levinthal's paradox with great robustness and flexibility and without requiring any ad hoc biased transition probability. The behavior of Brownian ratchets shown in this article considerably enhances the plausibility of the model for at least part of the structural mechanism behind protein folding process.
Dual-donor codoping approach to realize low-resistance n-type ZnS semiconductor
Authors: Li Dengfeng , Deng Bo , Xue Shuwen , Wang Zhiguo , Gao Fei
Published: August 2011

Based on first-principles calculations, we explored a good candidate for achieving low-resistance and high carrier concentration of n-type ZnS by a dual-donor codoping method, where the ionization energy was effectively reduced. We found that the SnZn-FS pair has a shallow donor level of 17.2 meV, a small formation energy of 1.27 eV and a high binding energy of 1.28 eV. The density of states analysis showed that the SnZn-FS pair induces the downward shift of the conduction band minimum by about 0.15 eV, while the basis electronic structure does not change. Thus, the SnZn-FS pair is likely to be a best n-type dopant for ZnS.
Influence of the local environment on Zn acceptors in the GaAs(110) surface
Authors: Lee D. H. , Santagata N. M. , Gupta J. A.
Published: August 2011

Individual Zn acceptors in the GaAs (110) surface layer are studied with a scanning tunneling microscope. Tunneling spectroscopy reveals a peak associated with a Zn acceptor state, whose linewidth and response to local band bending depend on proximity to neighboring subsurface Zn acceptors. Though identical in topographic images, surface-layer Zn with nearby subsurface neighbors exhibits a broad peak that is insensitive to band bending, while more isolated surface-layer Zn exhibit a narrow peak which is sensitive to band bending. These results are suggestive of a shallow-to-deep acceptor transition, driven by the random dopant distribution.
Comprehensive experimental analysis of nonlinear dynamics in an optically-injected semiconductor laser
Authors: Schires Kevin , Hurtado Antonio , Henning Ian D. , Adams Michael J.
Published: August 2011

We present the first comprehensive experimental study, to our knowledge, of the routes between nonlinear dynamics induced in a semiconductor laser under external optical injection based on an analysis of time-averaged measurements of the optical and RF spectra and phasors of real-time series of the laser output. The different means of analysis are compared for several types of routes and the benefits of each are discussed in terms of the identification and mapping of the nonlinear dynamics. Finally, the results are presented in a novel audio/video format that describes the evolution of the dynamics with the injection parameters.
Weather and pasture characteristics associated with outbreaks of perennial ryegrass toxicosis in southern Australia
Authors: Reed K. F. M. , Nie Z. N. , Walker L. V. , Mace W. J. , Clark S. G.
Published: August 2011

Severe outbreaks of toxicosis caused by the natural endophyte Neotyphodium lolii in perennial ryegrass (Lolium perenne L.) have occasionally resulted in heavy loss of livestock in Victoria and Tasmania. Meteorological records were examined from locations where acute toxicosis was recorded. High rainfall (>350 mm) in spring–summer was an obvious common feature; typically, it prolonged the period of high growth rate of pasture, increasing predicted spring–summer (September–March) growth (by ~36%) and increasing the predicted digestibility of organic matter of summer pasture (1 February) by 2.7% units (up to 55.6%). In years when severe toxicosis occurred, such rainfall was accompanied by dry, warm conditions in March and April, viz. mean maximum daily temperatures on the mainland of ≥21°C (March) and ≥18°C (April). During summer–autumn 2002, pastures from 10 Victorian farms on which acute perennial ryegrass toxicosis resulted in the loss of >7000 sheep/deer, were found to be dominated by perennial ryegrass. The ryegrass endophyte-produced toxins, ergovaline and lolitrem B, were detected in 74% and 100%, respectively, of composite faecal samples collected from acutely affected animals. The populations of perennial ryegrass all tested positive for Neotyphodium lolii endophyte, with a mean infection frequency of 90.5% (s.e.m. 1.81). The mean mycelial mass in basal tillers of perennial ryegrass was estimated at 66.00 (s.e.m. 3.40) from a sample of 20 plants, each of which was assessed on a scale of 1–5. Mycelial mass accounted for 19–20% of the variation in the concentration of ergovaline and lolitrem B in perennial ryegrass. Toxin concentrations in the plants where acute toxicosis was observed exceeded the tolerance levels for sheep (ergovaline 0.8 mg/kg; lolitrem B 1.8 mg/kg) in the minor (green) fraction of the plant in all but one affected pasture for ergovaline and all but two for lolitrem B. Maximum concentrations recorded were 4.3 and 4.6 mg/kg for ergovaline and lolitrem B respectively. Ergovaline increased in an asymptotic relationship with lolitrem B, which accounted for 45% of the variation in ergovaline. The concentrations of ergovaline and lolitrem B in the whole plant (green and dead fractions combined) were not greater than those recorded from randomly sampled pastures in earlier seasons, when only occasional mild cases of toxicosis were reported. Further examination of stored grass samples collected during the 2002 outbreak recently revealed unidentified peaks on the chromatograms for both ergovaline and lolitrem B; peaks that are not seen on chromatograms for toxic perennial ryegrass from New Zealand, where the expression of perennial ryegrass toxicosis is usually milder and rarely fatal.
Aptitude, age and cognitive development
Authors: Suárez Maria del Mar , Muñoz Carmen
Published: August 2011

In the validation studies of the Modern Language Aptitude Test-Elementary (MLAT-E) (Carroll & Sapon 1967) and its Spanish version, the MLAT-ES (Stansfield & Reed 2005), the total scores across grades increase unsteadily. At no point, though, has this increase been discussed. Similar results are found in the present study, which addresses this issue from two viewpoints, age and the supposed stability of language aptitude. The participants in this study are bilingual Catalan-Spanish children in grades from 3 to 7. 325 participants took the MLAT-ES and 304 participants took its Catalan version (MLAT-EC). The analyses of the children’s performance in both tests suggest that the higher the grade, the higher the final score. However, the difference between the means of the total score is consistently larger between grade 3 and 4 than between the other grades. Besides, this increase seems to plateau between grade 6 and 7. Results are discussed in relation to the influence that children’s age and cognitive development in middle childhood seem to have on children’s language aptitude development.
Guessing and risk attitude in L2 vocabulary tests
Authors: Thoma Dieter
Published: August 2011

Guessing the meaning of unknown words is an essential process in L2 comprehension. At the same time, guessing is considered a nuisance in L2 vocabulary tests. This raises the question of the nature and causes of guessing in L2 vocabulary tests. The traditional claims in language testing are that guessing is (1) a function of proficiency and (2) a function of the test taker’s risk attitude. To investigate these claims in the context of standardized vocabulary testing, 135 advanced EFL learners participated in a computer-based yes/no vocabulary test combined with a translation task and a risk test. Stepwise regression analyses suggest that about 60% of the variation in yes/no test guesses are attributable to inappropriate or lack of semantic word knowledge. However, there was no systematic effect of risk attitude and guessing was largely independent of general lexical proficiency level. Methodological and inferential consequences for L2 vocabulary testing are discussed.
L1/L2 parametric directionality matters
Authors: Judy Tiffany
Published: August 2011

Assuming transfer of the L1 grammar, in the present study the question of whether all parameters can be reset even with access to UG is examined in light of the subset/superset relationship. Specifically, the resetting of the Null Subject Parameter (NSP) in L2 learners of English (L1 Spanish) is investigated by means of examining the application of the Overt Pronoun Constraint (Montalbetti 1984), a property that clusters with the null subject setting only, as well as acceptance/rejection of null subjects in English. Since English does not syntactically license empty subjects, but Spanish does, the two languages are in a subset/superset relationship such that Spanish is the superset grammar. Therefore, the results stand to shed light on the validity of the Subset Principle (Berwick 1982; Manzini and Wexler 1987; Wexler and Manzini 1987) and its learnability constraints applied to second language acquisition (SLA) where transfer might impede convergence on the narrow syntactic property despite full access to Universal Grammar.
The syntax and interpretation of embedded null subjects in Chinese, and their acquisition by English-speaking learners
Authors: Zhao Lucy Xia
Published: August 2011

This article reports an investigation of embedded null subjects in both L1 and L2 Chinese. Chinese null embedded subjects can refer either to a matrix subject or to a discourse entity. In the Government-Binding (GB) framework, these two possibilities resulted from the null subject being either pro or a variable. Neither pro nor a variable is compatible with the assumptions of the more recent Minimalist Program, however. This article proposes an alternative account for null embedded subjects in Chinese that is consistent with the Minimalist Program: deletion of the anaphor ziji and deletion of a topic under identity with appropriate antecedents. It then reports a study of knowledge of such deletion in the Chinese of L2 speakers. Although the existing literature has found that embedded null subjects are allowed by L2 learners of Chinese at early stages of development, no research has investigated whether they are interpreted in a target-like way by L2 speakers. A picture judgment task and a written interpretation task showed that English-speaking learners of high-intermediate proficiency in Chinese allow an embedded null subject to refer to the matrix subject, but not to a discourse entity. It is only at advanced proficiency that L2 speakers allow co-reference with both a matrix subject and a discourse entity. The implications of these results are discussed.
Gradient competence at the Syntax-Discourse Interface
Authors: Slabakova Roumyana , Rothman Jason , Kempchinsky Paula
Published: August 2011

In this article, we present additional support of Duffield’s (2003, 2005) distinction between Underlying Competence and Surface Competence. Duffield argues that a more fine-grained distinction between levels of competence and performance is warranted and necessary. While underlying competence is categorical, surface competence is more probabilistic and gradient, being sensitive to lexical and constructional contingencies, including the contextual appropriateness of a given construction. We examine a subset of results from a study comparing native and learner competence of properties at the syntax-discourse interface. Specifically, we look at the acceptability of Clitic Right Dislocation in native and L2 Spanish, in discourse-appropriate context. We argue that Duffield’s distinction is a possible explanation of our results.
Decreolization as emergent grammar(s)
Authors: Lipski John M.
Published: August 2011

A restructured variety of Spanish spoken by small communities of Afro-descendents in Bolivia differs from modern Spanish in exhibiting no noun-adjective agreement for gender or number. Only a few individuals continue to speak this most basilectal variety; the majority of speakers exhibit at least some gender and number concord, in a fashion that proceeds generally rightward, from determiners and other prenominal modifiers to head nouns, postnominal modifiers, and predicate nominatives/adjectives. Number concord (plural marking) usually appears before gender concord in mesolectal varieties, and occurs at a higher rate than gender concord across the entire range of Afro-Bolivian speakers. A variationist analysis based on a corpus of recorded material suggests that this gradual emergence of (feminine) gender and plural marking represents a systematic form of decreolization governed largely by structural principles, namely the stepwise activation of agreement projections. Decreolization is represented as a series of nested intermediate grammars, each of which properly contains the preceding one(s).
Language form and language substance
Authors: Mühlhäusler Peter
Published: August 2011

This paper argues that creolistics has tended to overemphasize the formal and general properties of Creole languages to the neglect of their substantive and singular lexical properties. Rather than assuming that Creoles can express anything their speakers need or want to say as soon as they come into being, this paper shows, with data from a range of Creoles, that lexical adaptation to new natural environments is a prolonged gradual process. The perspective taken is ecolinguistic, i.e. it regards language as a management tool enabling its users to sustain functional links between themselves and their environment. Ecolinguistics judges the adequacy of the lexicon in terms of its ability to do this.
La dénotation spatiale des noms d’événements
Authors: Huyghe Richard
Published: August 2011

This paper deals with the spatial features of event-denoting nouns [EvNs], which are often overlooked in the linguistic literature on space. EvNs can refer to spatial entities, as they can be used as trajectors in localization sentences (Il y a une cérémonie dans l’église ‘There is a ceremony in the church’). Still, EvNs differ in several ways from nouns denoting prototypical spatial entities. They do not combine with complements denoting spatial extension (*une cérémonie de deux hectares ‘a four acres’ ceremony’), and they are associated with specific nouns and verbs of location (le lieu / *la place de la cérémonie ‘the location / the place of the ceremony’, Une cérémonie a lieu / *se trouve dans l’église ‘A ceremony takes place / is in the church’). It is assumed that the peculiarity of the spatial denotation of EvNs is due to their direct relation to time. The dependence between the spatial and temporal properties of EvNs shows when these nouns are used as landmarks (Pierre se rend à la cérémonie ‘Peter goes to the ceremony’). First, spatial eventive landmarks bear a temporal specification. Second, the temporal features of events determine their ability to be used as spatial landmarks.
Nonlinear analyses of self-paced reading
Authors: Wallot Sebastian , Van Orden Guy
Published: August 2011

Nonlinear methods of fractal analysis and recurrence quantification analysis are becoming more commonplace in the cognitive and behavioral sciences. These methods are illustrated here in a tutorial style using self-paced reading data. Self-paced reading was performed in which each spacebar press revealed a story word-by-word or else sentence-by-sentence. Participant readers were either Ph.D. candidates in English literature or undergraduates from an introductory psychology course and the same story was read by all, either one time only or reread another time on another occasion. The nonlinear analyses revealed crucial differences between the word unit and sentence unit conditions. Performance in the word unit condition was dominated by a task specific strategy, yielding data patterns more like those observed in tapping tasks. Nonlinear analyses of the sentence unit condition, however, discriminated between graduate and undergraduate readers, and first readings of the story from re-reading. From these analyses, the repeated reading of the same story reveals a kind of über-fluency, in a manner of speaking, of the Ph.D. candidates in English literature, whose performance stayed at or closer to a performance ceiling in both readings.