bluuebunny/crossref_metadata_2025 huggingface dataset:
Magnetic and structural properties of BiFeO3 thin films grown epitaxially on SrTiO3/Si substrates
Authors: Laughlin Ryan P. , Currie Daniel A. , Contreras-Guererro Rocio , Dedigama Aruna , Priyantha Weerasinghe , Droopad Ravindranath , Theodoropoulou Nikoleta , Gao Peng , Pan Xiaoqing
Published: April 2013

The integration of oxides with semiconductors is important for the technological advancement of the next generation electronics. Concomitant ferroelectric and antiferromagnetic (AF) behavior is demonstrated in single crystal BiFeO3 (BFO) films grown on 20 nm SrTiO3 (STO) virtual substrates on Si(100) using molecular beam epitaxy (MBE). STO thin films are grown in an oxide MBE chamber by co-deposition of Sr, Ti, and molecular O2. Careful control of the O2 during nucleation produced commensurate growth of STO on Si. The sequence of the steps allows for the suppression of an amorphous SiO2 layer. This STO(20 nm)/Si structure was used as a virtual substrate for MBE deposition of BFO on Si without breaking vacuum. BFO was deposited using Fe and O2 plasma with an overpressure of Bi flux, the growth rate was controlled by the incoming Fe flux. The reflection high energy electron diffraction image shows a 2-D growth front with a 6-fold surface reconstruction under optimized O2 pressure of 5 × 10−8 mbar. Cross-sectional transmission electron microscopy (TEM) confirms the high crystallinity of the films and shows sharp, atomically flat interfaces. The selected area diffraction pattern (SADP) reveals that BFO grows in a distorted rhombohedral crystal structure. X-ray diffraction does not show formation of second phases and is consistent with the TEM and SADP results. The BFO films show AF behavior with a Neel temperature that exceeds 350 K, as expected (TN = 673 K) and with a residual ferromagnetic behavior that decreases with film thickness and is consistent with the G-type AF due to the canted spins. The saturation magnetization per unit volume for a 40 nm thick film was 180 emu/cm3 at an in-plane magnetic field of 8 kOe. The ferroelectric behavior of the films was verified using piezoresponse force microscopy.
Influence of absorber layer dopants on performance of Ge/Si single photon avalanche diodes
Authors: Pilgrim Neil J. , Ikonic Zoran , Kelsall Robert W.
Published: April 2013

Monte Carlo electronic transport simulations are applied to investigate the influence of the Ge absorber layer on the performance of Ge/Si single photon avalanche diodes. Ge dopant type and concentration control the internal electric field gradients, which directly influence the probabilistic distribution of times from the point of charge photo-generation to that of transmission over the Ge/Si heterojunction. The electric field adjacent to the heterointerface is found to be the dominant factor in achieving rapid transmission, leading to a preference for p-type dopants in the Ge absorber. The contribution to jitter from the Ge layer is estimated and appears relatively independent of bias, though scales near-linearly with layer height.
Quasiparticle energies and lifetimes in a metallic chain model of a tunnel junction
Authors: Szepieniec Mark , Yeriskin Irene , Greer J. C.
Published: April 2013

As electronics devices scale to sub-10 nm lengths, the distinction between “device” and “electrodes” becomes blurred. Here, we study a simple model of a molecular tunnel junction, consisting of an atomic gold chain partitioned into left and right electrodes, and a central “molecule.” Using a complex absorbing potential, we are able to reproduce the single-particle energy levels of the device region including a description of the effects of the semi-infinite electrodes. We then use the method of configuration interaction to explore the effect of correlations on the system's quasiparticle peaks. We find that when excitations on the leads are excluded, the device's highest occupied molecular orbital and lowest unoccupied molecular orbital quasiparticle states when including correlation are bracketed by their respective values in the Hartree-Fock (Koopmans) and ΔSCF approximations. In contrast, when excitations on the leads are included, the bracketing property no longer holds, and both the positions and the lifetimes of the quasiparticle levels change considerably, indicating that the combined effect of coupling and correlation is to alter the quasiparticle spectrum significantly relative to an isolated molecule.
Structure control of poly(p-phenylene vinylene) in layer-by-layer films by deposition on a charged poly(o-methoxyaniline) cushion
Authors: Marletta Alexandre , Curcino da Silva Silésia de Fátima , Piovesan Erick , Campos K. R. , Santos Silva Hugo , de Souza N. C. , Letícia Vega Maria , Raposo Maria , Constantino Carlos J. L , Silva Raigna A. , Oliveira Osvaldo N.
Published: April 2013

In this paper, we demonstrate that the intrinsic electric field created by a poly(o-methoxyaniline) (POMA) cushion layer hinders the changes in molecular conformation of poly(p-phenylenevinylene) (PPV) in layer-by-layer with dodecylbenzene sulfonic acid (DBS). This was modeled with density functional theory (DFT) calculations where an energy barrier hampered molecular movements of PPV segments when they were subjected to an electric field comparable to that caused by a charged POMA layer. With restricted changes in molecular conformation, the PPV film exhibited Franck-Condon transitions and the photoexcitation spectra resembled the absorption spectra, in contrast to PPV/DBS films deposited directly on glass, with no POMA cushion. Other effects from the POMA cushion were the reduced number of structural defects, confirmed with Raman spectroscopy, and an enhanced PPV emission at high temperatures (300 K) in comparison with the films on bare glass. The positive effects from the POMA cushion may be exploited for enhanced opto-electronic devices, especially as the intrinsic electric field may assist in separating photoexcited electron-hole pairs in photovoltaic devices.
Vibrational ladder climbing in carboxy-hemoglobin: Effects of the protein environment
Authors: Falvo Cyril , Debnath Arunangshu , Meier Christoph
Published: April 2013

We present simulations on vibrational ladder climbing in carboxy-hemoglobin. Motivated by recent experiments, we study the influence of different realistic pump probe parameters. To allow for a direct comparison with experimental results, transient absorption spectra obtained by a weak probe pulse following the strong, shaped pump pulse are calculated. The influence of the protein fluctuations is taken into account using a recently developed microscopic model. This model consists of a quantum Hamiltonian describing the CO vibration in carboxy-hemoglobin, together with a fluctuating potential, which is obtained by electronic structure calculation based on a large number of protein configurations. Using realistic pulse parameters, vibrational excitations to very high-lying states are possible, in qualitative agreement with experimental observations.
Electron-ion hybrid instability experiment upgrades to the Auburn Linear Experiment for Instability Studies
Authors: DuBois A. M. , Arnold I. , Thomas E. , Tejero E. , Amatucci W. E.
Published: April 2013

The Auburn Linear EXperiment for Instability Studies (ALEXIS) is a laboratory plasma physics experiment used to study spatially inhomogeneous flows in a magnetized cylindrical plasma column that are driven by crossed electric (E) and magnetic (B) fields. ALEXIS was recently upgraded to include a small, secondary plasma source for a new dual source, interpenetrating plasma experiment. Using two plasma sources allows for highly localized electric fields to be made at the boundary of the two plasmas, inducing strong E × B velocity shear in the plasma, which can give rise to a regime of instabilities that have not previously been studied in ALEXIS. The dual plasma configuration makes it possible to have independent control over the velocity shear and the density gradient. This paper discusses the recent addition of the secondary plasma source to ALEXIS, as well as the plasma diagnostics used to measure electric fields and electron densities.
Geostrophic turbulence near rapid changes in stratification
Authors: Smith K. S. , Bernard E.
Published: April 2013

Geostrophic turbulence near horizontal surfaces on which the vertical velocity vanishes exhibits a forward cascade of buoyancy variance, characterized by a shallow energy spectrum, secondary roll-up of filaments, and a fat-tailed vorticity probability distribution. Such surfaces occur at rigid boundaries, but also at discontinuous jumps in stratification. Here we relax this mathematical idealization and investigate geostrophic turbulence near a rapid but smooth jump in stratification, modeled by N(z) = N0[1 + αtanh (z/h)]. The rapidity of change is controlled by the length scale h and the profile approaches a step function as h → 0. The approximated Green's function for the quasigeostrophic potential vorticity (PV) is used to predict the spectral PV-streamfunction relationship, under various assumptions about the distribution of the initial PV. Numerical simulations of freely-evolving quasigeostrophic turbulence in the presence of the model stratification support the predictions and reveal that the jump has two effects: it alters the Green's function in the region of the jump and it produces a peak in PV near the jump, approaching a Dirac delta-function as the jump scale h → 0. When the Green's function is integrated against this sharp PV distribution, contributions far from the jump (|z| ≫ h) are suppressed and the flow in a region |z| ≲ O(h) exhibits surface effects. This occurs for horizontal scales L ≳ N0h/f, the deformation scale associated with the jump. These results have implications for geostrophic turbulence near the tropopause in the atmosphere and the base of the mixed layer in the ocean.
Speeding chemical reactions by focusing
Authors: Lacasta A. M. , Ramírez–Piscina L. , Sancho J. M. , Lindenberg K.
Published: April 2013

We present numerical results for a chemical reaction of colloidal particles which are transported by a laminar fluid and are focused by periodic obstacles in such a way that the two components are well mixed and consequently the chemical reaction is speeded up. The roles of the various system parameters (diffusion coefficients, reaction rate, and obstacles sizes) are studied. We show that focusing speeds up the reaction from the diffusion limited rate ∼t−1/2 to very close to the perfect mixing rate, ∼t−1.
Effect of hydrodynamic correlations on the dynamics of polymers in dilute solution
Authors: Huang Chien-Cheng , Gompper Gerhard , Winkler Roland G.
Published: April 2013

We analyze the effect of time-dependent hydrodynamic interactions on the dynamics of flexible polymers in dilute solution. In analytical calculations, the fluctuating hydrodynamics approach is adopted to describe the fluid, and a Gaussian model to represented the polymer. Simulations are performed exploiting the multiparticle collision dynamics approach, a mesoscale hydrodynamic simulation technique, to explicitly describe the fluid. Polymer center-of-mass velocity correlation functions are calculated for various polymer lengths. Similarly, segment mean square displacements are discussed and polymer diffusion coefficients are determined. Particular attention is paid to the influence of sound propagation on the various properties. The simulations reveal a strong effect of hydrodynamic interactions. Specifically, the time dependence of the center-of-mass velocity correlation functions is determined by polymer properties over a length-dependent time window, but are asymptotically solely governed by fluid correlations, with a long-time tail decaying as t−3/2. The correlation functions are heavily influenced by sound modes for short polymers, an effect which gradually disappears with increasing polymer length. We find excellent agreement between analytical and simulation results. This allows us to provide a theory-based asymptotic value for the polymer diffusion coefficient in the limit of large system sizes, which is based on a single finite-system-size simulation.
Microstructure and magnetic properties of C/Co-P and Al2O3/Co-P composite particles prepared by electroless plating
Authors: Denisova E. A. , Chekanova L. A. , Iskhakov R. S. , Bondarenko G. N.
Published: April 2013

The electroless plating is used to synthesize two types of composite powder, such as the activated carbon with pores filled by Co100-XPX particles and the Al2O3 microgranular coated by the shell which consists of Co100-XPX particles with 4 < X < 18. The magnetic and structural properties of the composite particles are characterized by scanning electron microscopy, X-ray diffraction, and vibrating sample magnetometer. It is found that the average Co(P) particle size in composite powders decreases from 300 nm to 120 nm with an increase in P- content from 4 to 18 at. %. It causes a reduction in coercivity from 300 to 80 Oe for Al2O3/Co(P) powders and from 680 to 150 Oe for C/Co(P) powders. The effects of two methods of immobilization of Co(P) particles on magnetic properties are studied.
Lattice Boltzmann simulations of a single n-butanol drop rising in water
Authors: Komrakova A. E. , Eskin D. , Derksen J. J.
Published: April 2013

The motion of an n-butanol drop in water under the influence of gravity was numerically studied using a diffuse interface free energy lattice Boltzmann method. A pure two-liquid system without mass transfer between the phases was considered. A range of drop diameters of 1.0–4.0 mm covered the flow conditions. Most calculations were carried out in a moving reference frame. This allowed studying of long-term drop behavior in a relatively small computational domain. The capability of the method to capture the drop shape especially in the oscillating regime was demonstrated. For each drop diameter the evolution of the drop velocity in time, the terminal rise velocity and drop's shape were determined. The results were compared to experimental and numerical results and to semi-empirical correlations. The deviation of the simulated terminal velocity from other results is within 5% for smaller drops and up to 20% for large oscillating drops. It was shown that beyond the onset of shape oscillations the binary system converges towards a constant capillary number of 0.056.
Modeling of nanoscale devices with carriers obeying a three-dimensional density of states
Authors: Giusi Gino , Iannaccone Giuseppe
Published: April 2013

While aggressively nanoscale field-effect transistors commonly used in CMOS technology exhibit strong quantum confinement of charge carriers in one or two dimensions, few devices have been recently proposed whose operation reminds that of vacuum tube triodes and bipolar transistors, since charge carriers are ballistically injected into a three-dimensional k-space. In this work we derive, under the parabolic band approximation, the analytical expressions of the first three directed ballistic moments of the Boltzmann transport equation (current density, carrier density, and average kinetic energy), suitable to describe ballistic and quasi-ballistic transport in such devices. The proposed equations are applied, as an example, to describe the ballistic transport in graphene-based variable-barrier transistors.
Interlayer growth in Mo/B4C multilayered structures upon thermal annealing
Authors: Nyabero S. L. , van de Kruijs R. W. E. , Yakshin A. E. , Zoethout E. , von Blanckenhagen G. , Bosgra J. , Loch R. A. , Bijkerk F.
Published: April 2013

Both multilayer period thickness expansion and compaction were observed in Mo/B4C multilayers upon annealing, and the physical causes for this were explored in detail. Using in situ time-dependent grazing incidence X-ray reflectometry, period changes down to picometer-scale were resolved. It was shown that the changes depend on the thickness of the B4C layers, annealing temperature, and annealing time. Although strong stress relaxation during annealing was observed, it was excluded as a cause for period expansion. Auger electron spectroscopy and wide angle X-ray diffraction measurements revealed the growth of interlayers, with associated period changes influenced by the supply of B and C atoms to the growing compound interlayers. For multilayers with a Mo thickness of 3 nm, two regimes were recognized, depending on the deposited B4C thickness: in multilayers with B4C ≤ 1.5 nm, the supply of additional Mo into the already formed MoBxCy interlayer was dominant and led to densification, resulting in period compaction. For multilayers with B4C ≥ 2 nm, the B and C enrichment of interlayers formed low density compounds and yielded period expansion.
Group delay of single-photon transmission in a waveguide side coupled with a Jaynes-Cummings chain
Authors: Dong Guangda , Zhang Yongyou , Arshad Kamran Muhammad , Zou Bingsuo
Published: April 2013

Using a real-space model Hamiltonian, we have theoretically studied the single-photon transmission in a waveguide side coupled with a Jaynes-Cummings chain (JCC). The JCC can induce the photon group advancement (GA) and group delay (GD) in different frequency ranges determined by JCC eigenmodes. For GA and GD, there exist different optimal JCC lengths. At certain frequency, the GA's maximum value as usual increases with decreasing the cavity dissipation, whereas the GD's eventually reaches saturation. For a 1.55 -μm photon, our calculation indicates that the GD's maximum value is about 400 ps simultaneously with a large transmission.
Nonlinear temperature dependent nucleation field in perpendicular exchange spring typed magnetic tunnel junctions
Authors: Wang Yi , Le Roy D. , Jiang Jun , Yin Xiaolu , Wei H. X. , Liou S. H. , Han X. F.
Published: April 2013

The nonlinear temperature dependence of nucleation field (Hn) of [Co/Pt]n multilayer based perpendicular magnetic tunnel junction stacks with wedged Co60Fe20B20 insertion layers is reported. When temperature decreases, the tilted spins away from perpendicular direction near Co60Fe20B20/AlOx interface play dominating role to promote the nucleation process and lower Hn value and even change the sign of Hn. By taking advantage of high temperature annealing under high perpendicular magnetic field, this nonlinear behavior and sign of Hn could be manipulated. The understanding of temperature dependent properties in such system is important for spintronics applications, such as in memory and spin oscillators.
Exchange bias between multiferroic HoMnO3 and ferromagnetic SrRuO3 films
Authors: Han T. C. , Lin J. G.
Published: April 2013

Orthorhombic HoMnO3 (o-HMO) thin films with a-axis orientation are epitaxially grown on ferromagnetic (FM) SrRuO3 (SRO) layers by using pulsed laser deposition. The structural and magnetic properties of o-HMO/SRO heterostructures are measured. The magnetic hysteresis loops of o-HMO/SRO show exchange bias at temperatures below the antiferromagnetic transition temperature of o-HMO. Furthermore, the large exchange bias field up to 815 Oe is observed at 5 K. These results demonstrate that the exchange bias between a FM oxide and the multiferroic o-HMO could be useful for future applications on spintronic devices.
Magnetoresistive properties of the “small disk on a big disk” nanostructure
Authors: Stebliy Maxim E. , Ognev Alexey V. , Samardak Alexander S. , Chebotkevich Ludmila A.
Published: April 2013

Magnetotransport properties of three-dimensional (3D) nano-sized structure with “small disk on a big disk” architecture are represented in this paper. We demonstrate an approach to analyze the spin configuration formed in the disks using magnetoresistance measurement. The behavior of magnetoresistance depends on the orientation of the applied magnetic field with respect to an axis connecting the centers of disks. This is explained by field dependent magnetic vortex nucleation and movement processes in the big disk. The experimental results are confirmed by the micromagnetic simulation of magnetoresistance loops.
Band offset measurements and magneto-transport properties of epitaxial TiO2−x (x = 0.05)/La0.7Sr0.3MnO3 heterostructure
Authors: Choudhary R. J. , Bapna Komal , Phase D. M.
Published: April 2013

We have studied the electronic transport behaviour and band offset properties of the epitaxial TiO2−x (x = 0.05)/La0.7Sr0.3MnO3 hetero-structure. The bilayer shows non-linear I-V characteristics at different temperatures as well as negative magneto-resistance with the application of magnetic field. Valence band offset (VBO) was measured using photoelectron spectroscopy and consequently the conduction band offset (CBO) was determined. It is found that type-I alignment takes place at the interface. The value for CBO (1.1 eV) is much lower than VBO (2.3 eV), suggesting that transport is mainly dominated by electrons. Observed negative magneto-resistance in such bilayer is explained with the help of band structure of La0.7Sr0.3MnO3.
Investigations on electrocaloric properties of ferroelectric Pb(Mg0.067Nb0.133Zr0.8)O3
Authors: Hamad Mahmoud A.
Published: April 2013

In this letter, ferroelectric Pb(Mg0.067Nb0.133Zr0.8)O3 (PMNZ) shows an electrocaloric effect at high temperature. This work is based on a phenomenological model of the electrocaloric effect in PMNZ using experimental data of polarization versus electric field and temperature. It is showed that the cooling ΔT per unit field MV m−1 in PMNZ is significantly larger and is comparable with value of the famous lead-containing bulk ceramics such as PbMg1/3Nb2/3O3 and PMN–PT (Pb(Mg1/3Nb2/3)O3–PbTiO3). This sample is consequently very interesting material in the framework of electrocaloric refrigeration devices for automotive, aerospace, or food industries.
Poly(ethylene glycol) modified [60]fullerene as electron buffer layer for high-performance polymer solar cells
Authors: Zhang Zhi-Guo , Li Hui , Qi Zhe , Jin Zhiwen , Liu Guo , Hou Jianhui , Li Yongfang , Wang Jizheng
Published: April 2013

A poly(ethylene glycol) end caped fullerene derivative, PEGN-C60, is used as electron buffer layer (EBL) in polymer solar cells (PSCs). Three donor:acceptor blends, namely P3HT:PCBM, PBDTTT-C:PC70BM, and PBDTTT-C-T:PC70BM, are employed to test the behavior of PEGN-C60 as EBL. The optimized power conversion efficiencies of the three systems reach 3.84%, 6.22%, 7.45%, respectively, which are slightly higher than that of their corresponding devices with metal Ca as EBL and much higher than that of their devices without any EBLs. Our results indicate that exploring EBLs based on fullerene derivatives might be an efficient way in finding functional solution-processable EBLs for high-performance PSCs.
Spin-based resonant effect and focusing lens of light by dielectric nanoparticles
Authors: Liu Yineng , Zhang Xiangdong
Published: April 2013

Spin-based resonant effect in the cluster of dielectric nanoparticles has been investigated using rigorous multiple scattering method. Two kinds of polarization-sensitive focusing based on single scattering resonance and collective resonance excitation of nanoparticles have been demonstrated. The corresponding focusing lens of light has been designed. The physical origin of phenomena, which is attributed to the presence of a geometric phase arising from the interaction of light with inhomogeneous cluster structures, has been analyzed.
High-responsivity GeSn short-wave infrared p-i-n photodetectors
Authors: Zhang Dongliang , Xue Chunlai , Cheng Buwen , Su Shaojian , Liu Zhi , Zhang Xu , Zhang Guangze , Li Chuanbo , Wang Qiming
Published: April 2013

Surface-illuminated GeSn p-i-n photodetectors (PDs) with Ge0.964Sn0.036 active layer on Ge substrate were fabricated. Photodetection up to 1.95 μm is achieved with a responsivity of 0.13 A/W. High responsivities of 0.56 and 0.71 A/W were achieved under a reverse bias voltage of 3 V at 1640 and 1790 nm, respectively. A low dark current of 1.08 μA was obtained at a reverse bias of 1 V with a diameter of 150 μm, which corresponds to a current density of 6.1 mA/cm2. This value is among the lowest dark current densities reported among GeSn PDs.
High-quality epitaxial NbN/AlN/NbN tunnel junctions with a wide range of current density
Authors: Wang Z. , Terai H. , Qiu W. , Makise K. , Uzawa Y. , Kimoto K. , Nakamura Y.
Published: April 2013

We have developed high-quality epitaxial NbN/AlN/NbN Josephson tunnel junctions with a wide range of current density Jc. The junctions show excellent tunneling properties with a large gap voltage of 5.6 mV and a large IcRN product of 3.5 mV. The quality factor Rsg/RN is about 60 for the junctions with a Jc of 2.2 A/cm2, and above 10 for the junctions with a Jc of 25 kA/cm2. The crystal structures across the junction barrier are investigated using x-ray diffraction and cross-sectional scanning transmission electron microscopy, and demonstrate epitaxial growth of the NbN/AlN/NbN trilayers for the wide range of Jc.
Importance of getting the numbers right: quantifying the rapid and substantial decline of an abundant marsupial, Bettongia penicillata
Authors: Wayne A. F. , Maxwell M. A. , Ward C. G. , Vellios C. V. , Ward B. G. , Liddelow G. L. , Wilson I. , Wayne J. C. , Williams M. R.
Published: April 2013

Context
A reliable measure of population size is fundamental to ecology and conservation but is often difficult to obtain. The woylie, Bettongia penicillata, provides an example where ‘getting the numbers right’ has important implications in verifying and quantifying the recent unexpected, rapid and substantial declines across much of its range. Initial estimates prompted a conservation-status upgrade for the species to Endangered by the Australian Government. The present paper constitutes the foundational paper addressing the first steps of a decline diagnosis framework intended to identify the causes of the recent declines.

Aims
To verify whether the declines in woylie trap-capture rates are representative of population change; better quantify the size of the largest woylie populations; and review what is understood about the ecology of the woylie and identify key knowledge gaps that may be relevant to identifying the causes of the recent declines.

Methods
Monitoring data from live-cage trapping (transects and grids), sandpads, woylie diggings and nest-density surveys and spotlighting were collated. Population measures derived from trapping data included capture rates, number of individuals, abundance estimates based on capture–mark–recapture modelling and density using spatially explicit capture–recapture models (SECR).

Key results
The declines in woylie trap-capture rates were verified as real population declines and corresponded closely with other measures of abundance derived from the same trapping data as well as with independent measures. A 95% decline occurred in the largest extant woylie populations (in the Upper Warren region, Western Australia) between 2002 and 2008. At a species level, woylies declined ~90% (1999–2006), from a peak of ~200 000 individuals in 1999.

Conclusions
An accurate formal conservation status is an important factor in promoting the conservation of a species. It is recommended that the woylie be considered for Critically Endangered status under the Australian EPBC Act.

Implications
Adequate and effective monitoring of species is critical to detecting and quantifying population changes in a timely manner. Having an accurate measure of population size can have a significant impact on the effectiveness of conservation and management efforts.
La dislocación a la derecha en el español escrito
Authors: Sedano Mercedes
Published: April 2013

Se estudia una estructura del español conocida como Dislocación a la Derecha (LA conozco yo, esa pieza
), formada por una cláusula/comentario (La conozco yo) y un constituyente TÓPICO situado a su derecha (
esa pieza
). En la cláusula/comentario hay un elemento correferencial con el tópico (La), denominado copia. En la investigación, basada en un corpus del español literario, se describen: (i) las características de la copia; (ii) las características del tópico; (iii) el funcionamiento de la Dislocación a la Derecha en el discurso. Los resultados indican lo siguiente: (i) la copia es un elemento catafórico anunciador del tópico; ambos constituyentes ofrecen las mismas marcas funcionales; (ii) lo más frecuente, por un lado, es que la copia sea un clítico que funciona como complemento directo y, por el otro, que el tópico sea una frase nominal léxica que transmite información evocada; (iii) la Dislocación a la Derecha parece cumplir tres funciones discursivas: esclarecedora (la más importante), indicadora del tópico del discurso y evaluativa.
Out-of-class interaction during study abroad
Authors: Shively Rachel L.
Published: April 2013

This study provides an in-depth examination of the opportunities for social interaction and second language (L2) use in service encounters recorded in situ by study abroad students in Toledo, Spain. The participants in the study were seven university students from the U.S. who recorded 113 naturally-occurring service encounters over the course of one semester studying abroad. An analysis of the corpus and of students’ journals and interviews indicated that while many of the encounters were brief, students did use the L2 to meet their needs as consumers and attended to language form while speaking the L2. In small talk episodes, there were opportunities for brief conversations and instances of orientation by participants to language and culture learning. Thus, the results suggest that although service encounters are typically brief, they can contribute to the immersion experience of study abroad.
Leo Valiani and Enrico Cuccia: Iran in the 1950s
Authors: Coltorti Fulvio
Published: April 2013

This essay details Leo Valiani's mission to Iran in 1952–53 on behalf of Mediobanca, in order to identify opportunities to promote investments for the development of both the country itself and Italian exports. The events are reconstructed through Valiani's correspondence with Enrico Cuccia (Mediobanca's CEO). A new picture of Valiani as banker emerges, effective on the ground, but also a subtle observer of local situations and prospects. The documents discussed herein highlight certain weaknesses in Mosaddeq's policies, mainly the weak relationship with the heads of finance. The oil dispute between Mosaddeq and the British and the coup orchestrated by the latter in collaboration with the Americans in order to bring down Mosaddeq's government complicated the picture so that every form of co-operation had to be postponed.
Reimbursement and Practice Policies among Providers of Buprenorphine-Naloxone Treatment
Authors: Wisniewski Angela M. , Dlugosz Michael R. , Blondell Richard D.
Published: April 2013

Background: Physician acceptance of cash payment and low adherence to practice guidelines may contribute to buprenorphine-naloxone diversion. The purpose of this study was to investigate the clinical practice policies of physicians who provide office-based treatment for opioid dependence with buprenorphine-naloxone. Methods: Data were obtained from 31 of 71 practices surveyed (response rate 43.7%) that provided answers to at least some of the survey questions. Results: Of these practices, 28 (90.3%) accepted cash as payment and 6 (19.4%) accepted only cash for treatment services. Analysis of open-ended responses to questions about office policies revealed wide variation among practices and overall suboptimal adherence to recommended treatment guidelines. Conclusions: These results underscore the need for continuing education for physicians who prescribe buprenorphine-naloxone.
Psychotic Symptoms of Cocaine Self-Injectors in a Harm Reduction Program
Authors: Roncero Carlos , Martínez-Luna Nieves , Daigre Constanza , Grau-López Lara , Gonzalvo Begoña , Pérez-Pazos Jesús , Casas Miguel
Published: April 2013

Background: Psychotic symptoms are common among cocaine users. Methods: An observational naturalistic study on the effects and events of intravenous cocaine use in a drug consumption room was carried out; the patients were diagnosed of cocaine dependence (according to the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition, Text Revision). Results: Twenty-one patients, 81% men self-injected cocaine 375 times. Psychotic symptoms were observed in 62% of the patients and 21% of the self-injections; delusions were observed in 9.3%, psychotic self-reference with insight in 9.1%, illusions in 6.4%, and hallucinations in 5.3%. A higher presence of psychotic symptoms was noted with cannabis used in the previous month (76.9% versus 44.4%; P = .001) (no psychotic symptoms group); also, a greater use of benzodiazepines was observed: 75.6% versus 63.6% ( P = .046). Lower use of methadone in the group with psychosis was observed: 75.6% versus 97.3% ( P = .001). Motor alterations were tremor 58%, stereotyped movements 24%, and behaviour alteration 6%, significantly more frequent in the psychotic group. Conclusions: Thus, there was a high frequency of psychotic symptoms after intravenous cocaine use; patients with psychotic symptoms reported higher use of cannabis and benzodiazepines in the previous month and lower use of methadone. More tremors and stereotyped movements were observed in the group with psychotic symptoms. It is necessary to give a special approach to cocaine intravenous users.
The Hardest Butter to Button: Immediate Context Effects in Spoken Word Identification
Authors: Brock Jon , Nation Kate
Published: April 2013

According to some theories, the context in which a spoken word is heard has no impact on the earliest stages of word identification. This view has been challenged by recent studies indicating an interactive effect of context and acoustic similarity on language-mediated eye movements. However, an alternative explanation for these results is that participants looked less at acoustically similar objects in constraining contexts simply because they were looking more at other objects that were cued by the context. The current study addressed this concern whilst providing a much finer grained analysis of the temporal evolution of context effects. Thirty-two adults listened to sentences while viewing a computer display showing four objects. As expected, shortly after the onset of a target word (e.g., “button”) in a neutral context, participants saccaded preferentially towards a cohort competitor of the word (e.g., butter). This effect was significantly reduced when the preceding verb made the competitor an unlikely referent (e.g., “Sam fastened the button”), even though there were no other contextually congruent objects in the display. Moreover, the time-course of these two effects was identical to within approximately 30 ms, indicating that certain forms of contextual information can have a near-immediate effect on word identification.
Mutation of SIMPLE in Charcot–Marie–Tooth 1C alters production of exosomes
Authors: Zhu Hong , Guariglia Sara , Yu Raymond Y. L. , Li Wenjing , Brancho Deborah , Peinado Hector , Lyden David , Salzer James , Bennett Craig , Chow Chi-Wing
Published: April 2013

Charcot–Marie–Tooth (CMT) disease is an inherited neurological disorder. Mutations in the small integral membrane protein of the lysosome/late endosome (SIMPLE) account for the rare autosomal-dominant demyelination in CMT1C patients. Understanding the molecular basis of CMT1C pathogenesis is impeded, in part, by perplexity about the role of SIMPLE, which is expressed in multiple cell types. Here we show that SIMPLE resides within the intraluminal vesicles of multivesicular bodies (MVBs) and inside exosomes, which are nanovesicles secreted extracellularly. Targeting of SIMPLE to exosomes is modulated by positive and negative regulatory motifs. We also find that expression of SIMPLE increases the number of exosomes and secretion of exosome proteins. We engineer a point mutation on the SIMPLE allele and generate a physiological mouse model that expresses CMT1C-mutated SIMPLE at the endogenous level. We find that CMT1C mouse primary embryonic fibroblasts show decreased number of exosomes and reduced secretion of exosome proteins, in part due to improper formation of MVBs. CMT1C patient B cells and CMT1C mouse primary Schwann cells show similar defects. Together the data indicate that SIMPLE regulates the production of exosomes by modulating the formation of MVBs. Dysregulated endosomal trafficking and changes in the landscape of exosome-mediated intercellular communications may place an overwhelming burden on the nervous system and account for CMT1C molecular pathogenesis.
Take advantage of time in your experiments: a guide to simple, informative kinetics assays
Authors: Pollard Thomas D. , De La Cruz Enrique M.
Published: April 2013

Understanding virtually any process in cellular and molecular biology depends on knowledge of the rates of the biochemical reactions, so it is regrettable that few cellular and molecular biologists take advantage of kinetics experiments in their work. Fortunately, the kinetics experiments that are most useful for understanding cellular systems are within reach for everyone whose research would benefit from this information. This essay describes simple methods to measure the valuable kinetic parameters that characterize the dynamics of life processes. These “transient-state” methods not only differ in concept from traditional approaches used to analyze enzyme reactions at steady state, but they are also applicable to learning about the dynamics of any biological process.
Spatial telomere organization and clustering in yeast Saccharomyces cerevisiae nucleus is generated by a random dynamics of aggregation–dissociation
Authors: Hozé Nathanaël , Ruault Myriam , Amoruso Carlo , Taddei Angela , Holcman David
Published: April 2013

Spatial and temporal behavior of chromosomes and their regulatory proteins is a key control mechanism in genomic function. This is exemplified by the clustering of the 32 budding yeast telomeres that form foci in which silencing factors concentrate. To uncover the determinants of telomere distribution, we compare live-cell imaging with a stochastic model of telomere dynamics that we developed. We show that random encounters alone are inadequate to produce the clustering observed in vivo. In contrast, telomere dynamics observed in vivo in both haploid and diploid cells follows a process of dissociation–aggregation. We determine the time that two telomeres spend in the same cluster for the telomere distribution observed in cells expressing different levels of the silencing factor Sir3 protein, limiting for telomere clustering. We conclude that telomere clusters, their dynamics, and their nuclear distribution result from random motion, aggregation, and dissociation of telomeric regions, specifically determined by the amount of Sir3.
DP2: Distributed 3D image segmentation using micro-labor workforce
Authors: Giuly Richard J. , Kim Keun-Young , Ellisman Mark H.
Published: April 2013

Summary: This application note describes a new scalable semi-automatic approach, the Dual Point Decision Process, for segmentation of 3D structures contained in 3D microscopy. The segmentation problem is distributed to many individual workers such that each receives only simple questions regarding whether two points in an image are placed on the same object. A large pool of micro-labor workers available through Amazon’s Mechanical Turk system provides the labor in a scalable manner.

Availability and implementation: Python-based code for non-commercial use and test data are available in the source archive at https://sites.google.com/site/imagecrowdseg/.

Contact:  rgiuly@ucsd.edu

Supplementary information:  Supplementary data are available at Bioinformatics online.
Biographer: web-based editing and rendering of SBGN compliant biochemical networks
Authors: Krause Falko , Schulz Marvin , Ripkens Ben , Flöttmann Max , Krantz Marcus , Klipp Edda , Handorf Thomas
Published: April 2013

Motivation: The rapid accumulation of knowledge in the field of Systems Biology during the past years requires advanced, but simple-to-use, methods for the visualization of information in a structured and easily comprehensible manner.

Results: We have developed biographer, a web-based renderer and editor for reaction networks, which can be integrated as a library into tools dealing with network-related information. Our software enables visualizations based on the emerging standard Systems Biology Graphical Notation. It is able to import networks encoded in various formats such as SBML, SBGN-ML and jSBGN, a custom lightweight exchange format. The core package is implemented in HTML5, CSS and JavaScript and can be used within any kind of web-based project. It features interactive graph-editing tools and automatic graph layout algorithms. In addition, we provide a standalone graph editor and a web server, which contains enhanced features like web services for the import and export of models and visualizations in different formats.

Availability: The biographer tool can be used at and downloaded from the web page http://biographer.biologie.hu-berlin.de/. The different software packages, including a server-indepenent version as well as a web server for Windows and Linux based systems, are available at http://code.google.com/p/biographer/ under the open-source license LGPL.

Contact:  edda.klipp@biologie.hu-berlin.de or handorf@physik.hu-berlin.de
The red blazar PMN J2345−1555 becomes blue
Authors: Ghisellini G. , Tavecchio F. , Foschini L. , Bonnoli G. , Tagliaferri G.
Published: April 2013

The flat spectrum radio quasar PMN J2345−1555 is a bright γ-ray source, that recently underwent a flaring episode in the infrared (IR), ultraviolet (UV) and γ-ray bands. The flux changed quasi-simultaneously at different frequencies, suggesting that it was produced by a single population of emitting particles, hence by a single and well-localized region of the jet. While the overall spectral energy distribution (SED) before the flare was typical of powerful blazars (namely two broad humps peaking in the far-IR and below 100 MeV bands, respectively), during the flare the peaks moved to the optical–UV and to energies larger than 1 GeV, to resemble low power BL Lac objects, even if the observed bolometric luminosity increased by more than one order of magnitude. We interpret this behaviour as due to a change of the location of the emission region in the jet, from within the broad-line region, to just outside. The corresponding decrease of the radiation energy density as seen in the comoving frame of the jet allowed the relativistic electrons to be accelerated to higher energies, and thus produce a ‘bluer’ SED.
Multiple roles of Activin/Nodal, bone morphogenetic protein, fibroblast growth factor and Wnt/β-catenin signalling in the anterior neural patterning of adherent human embryonic stem cell cultures
Authors: Lupo Giuseppe , Novorol Claire , Smith Joseph R. , Vallier Ludovic , Miranda Elena , Alexander Morgan , Biagioni Stefano , Pedersen Roger A. , Harris William A.
Published: April 2013

Several studies have successfully produced a variety of neural cell types from human embryonic stem cells (hESCs), but there has been limited systematic analysis of how different regional identities are established using well-defined differentiation conditions. We have used adherent, chemically defined cultures to analyse the roles of Activin/Nodal, bone morphogenetic protein (BMP), fibroblast growth factor (FGF) and Wnt/β-catenin signalling in neural induction, anteroposterior patterning and eye field specification in hESCs. We show that either BMP inhibition or activation of FGF signalling is required for effective neural induction, but these two pathways have distinct outcomes on rostrocaudal patterning. While BMP inhibition leads to specification of forebrain/midbrain positional identities, FGF-dependent neural induction is associated with strong posteriorization towards hindbrain/spinal cord fates. We also demonstrate that Wnt/β-catenin signalling is activated during neural induction and promotes acquisition of neural fates posterior to forebrain. Therefore, inhibition of this pathway is needed for efficient forebrain specification. Finally, we provide evidence that the levels of Activin/Nodal and BMP signalling have a marked influence on further forebrain patterning and that constitutive inhibition of these pathways represses expression of eye field genes. These results show that the key mechanisms controlling neural patterning in model vertebrate species are preserved in adherent, chemically defined hESC cultures and reveal new insights into the signals regulating eye field specification.
Food availability affects onset of reproduction in a long-lived seabird
Authors: Vincenzi Simone , Hatch Scott , Mangel Marc , Kitaysky Alexander
Published: April 2013

Life-history theory predicts that suboptimal developmental conditions may lead to faster life histories (younger age at recruitment and higher reproductive investment), but experimental testing of this prediction is still scarce in long-lived species. We report the effects of an experimental manipulation of food availability during early development and at recruitment on the onset of reproduction and reproductive performance (productivity at first breeding) in a long-lived seabird, the black-legged kittiwakeRissa tridactyla, breeding on Middleton Island, Alaska. Birds were born and raised in nests with supplemented food (‘fed’) or unsupplemented control nests (‘unfed’), and later recruited into either fed or unfed nests. Fed chicks grew faster than unfed chicks, and males grew faster than females. Birds were more likely to reproduce at younger ages when recruiting into fed nests. Faster growth during development tended to increase age at recruitment in all individuals. Social rank of individuals also affected age at recruitment: B-chicks recruited earlier than A-chicks and singletons recruited later than A- and B-chicks. Productivity increased with the age at recruitment and growth rate as chick, but much of the variability remained unexplained. We conclude that results of this study at least partially support predictions of life-history theory: younger age at first breeding for kittiwakes that experienced suboptimal natal conditions, as well as greater productivity of early recruiting kittiwakes that grew in control nests compared with those that grew in food-supplemented nests.
Identification of Novel Loci Regulating Interspecific Variation in Root Morphology and Cellular Development in Tomato
Authors: Ron Mily , Dorrity Michael W. , de Lucas Miguel , Toal Ted , Hernandez R. Ivan , Little Stefan A. , Maloof Julin N. , Kliebenstein Daniel J. , Brady Siobhan M.
Published: April 2013

While the Arabidopsis (Arabidopsis thaliana) root has been elegantly characterized with respect to specification of cell identity, its development is missing a number of cellular features present in other species. We have characterized the root development of a wild and a domesticated tomato species, Solanum pennellii and Solanum lycopersicum ‘M82.’ We found extensive differences between these species for root morphology and cellular development including root length, a novel gravity set point angle, differences in cortical cell layer patterning, stem cell niche structure, and radial cell division. Using an introgression line population between these two species, we identified numerous loci that regulate these distinct aspects of development. Specifically we comprehensively identified loci that regulate (1) root length by distinct mechanisms including regulation of cell production within the meristem and the balance between cell division and expansion, (2) the gravity set point angle, and (3) radial cell division or expansion either in specific cell types or generally across multiple cell types. Our findings provide a novel perspective on the regulation of root growth and development between species. These loci have exciting implications with respect to regulation of drought resistance or salinity tolerance and regulation of root development in a family that has undergone domestication.