bluuebunny/crossref_metadata_2025 huggingface dataset:
Dynamics of a broad-area diode laser with lateral-mode-selected long-cavity feedback
Authors: Chi Mingjun , Petersen Paul Michael
Published: September 2014

The temporal dynamics of a broad-area diode laser with lateral-mode-selected long-cavity feedback is studied experimentally. Different dynamics are observed when different lateral modes are selected. When the feedback mirror is aligned perfectly and high-order modes are selected, in most of the cases, the output of the laser shows a periodic oscillation corresponding to a single roundtrip external-cavity loop, but the dynamic behavior disappears in some case; when the zero-order lateral-mode is selected, periodic oscillation corresponding to a double roundtrip external-cavity loop is observed. When the feedback mirror is aligned non-perfectly, pulse-package oscillation is observed, for the first time to our knowledge, in a diode laser with long-cavity feedback.
Impact of GaN cap on charges in Al2O3/(GaN/)AlGaN/GaN metal-oxide-semiconductor heterostructures analyzed by means of capacitance measurements and simulations
Authors: Ťapajna M. , Jurkovič M. , Válik L. , Haščík Š. , Gregušová D. , Brunner F. , Cho E.-M. , Hashizume T. , Kuzmík J.
Published: September 2014

Oxide/semiconductor interface trap density (Dit) and net charge of Al2O3/(GaN)/AlGaN/GaN metal-oxide-semiconductor high-electron mobility transistor (MOS-HEMT) structures with and without GaN cap were comparatively analyzed using comprehensive capacitance measurements and simulations. Dit distribution was determined in full band gap of the barrier using combination of three complementary capacitance techniques. A remarkably higher Dit (∼5–8 × 1012 eV−1 cm−2) was found at trap energies ranging from EC-0.5 to 1 eV for structure with GaN cap compared to that (Dit ∼ 2–3 × 1012 eV−1 cm−2) where the GaN cap was selectively etched away. Dit distributions were then used for simulation of capacitance-voltage characteristics. A good agreement between experimental and simulated capacitance-voltage characteristics affected by interface traps suggests (i) that very high Dit (>1013 eV−1 cm−2) close to the barrier conduction band edge hampers accumulation of free electron in the barrier layer and (ii) the higher Dit centered about EC-0.6 eV can solely account for the increased C-V hysteresis observed for MOS-HEMT structure with GaN cap. Analysis of the threshold voltage dependence on Al2O3 thickness for both MOS-HEMT structures suggests that (i) positive charge, which compensates the surface polarization, is not necessarily formed during the growth of III-N heterostructure, and (ii) its density is similar to the total surface polarization charge of the GaN/AlGaN barrier, rather than surface polarization of the top GaN layer only. Some constraints for the positive surface compensating charge are discussed.
Magnetic and transport properties of cobalt doped La0.7Sr0.3MnO3
Authors: Chen X. G. , Fu J. B. , Yun C. , Zhao H. , Yang Y. B. , Du H. L. , Han J. Z. , Wang C. S. , Liu S. Q. , Zhang Y. , Yang Y. C. , Yang J. B.
Published: September 2014

The magnetic and transport properties of La0.7Sr0.3Mn1−xCoxO3 (0 ≤ x ≤ 1) samples were systematically studied. A magnetic phase diagram was constructed according to the observed results. At the two ends (x ≤ 0.3 and x > 0.9), the samples exhibit the conventional ferromagnetism with the metallic conducting behavior, which can be interpreted in terms of the double exchange coupling between Mn (Co) ions. As for the intermediate Co-doping region (0.3 < x ≤ 0.9), the samples enter a mixed magnetic phase state, which displays the characteristics of the glassy states. According to the frequency-dependent results from the ac susceptibility, a representative frequency sensitivity factor K was calculated to be ∼0.1 for the typical La0.7Sr0.3Mn0.6Co0.4O3 sample, corresponding to the coexistence of superparamagnetic-like free spins and the reentrant spin glass. The results of the Curie-Weiss fitting of the dc magnetization suggest that the Co3+ ions are in the intermediate spin state with the increase of Co-doping level (x ≥ 0.3), while the Co4+ ions show the spin state transition from the high spin state to the intermediate spin state at x = 0.6. The temperature dependence of resistivity shows a metal-insulator transition character for the intermediate Co-doping samples, which can be well fitted by the three dimensional variable-range-hopping model in the whole temperature range. These facts suggest that the double exchange interaction in the perovskite La0.7Sr0.3MnO3 is destroyed by the B site doping, due to the strong competition between the double exchange and superexchange interactions in Co/Mn ions as well as the frustration of spins in the system.
Ab initio potential energy curves of the valence, Rydberg, and ion-pair states of iodine monochloride, ICl
Authors: Kalemos Apostolos , Prosmiti Rita
Published: September 2014

We present for the first time a coherent ab initio study of 39 states of valence, Rydberg, and ion-pair character of the diatomic interhalogen ICl species through large scale multireference variational methods including spin-orbit effects coupled with quantitative basis sets. Various avoided crossings are responsible for a non-adiabatic behaviour creating a wonderful vista for its theoretical description. Our molecular constants are compared with all available experimental data with the aim to assist experimentalists especially in the high energy regime of up to ∼95 000 cm−1.
Effect of bound state of water on hydronium ion mobility in hydrated Nafion using molecular dynamics simulations
Authors: Mabuchi Takuya , Tokumasu Takashi
Published: September 2014

We have performed a detailed analysis of the structural properties of the sulfonate groups in terms of isolated and overlapped solvation shells in the nanostructure of hydrated Nafion membrane using classical molecular dynamics simulations. Our simulations have demonstrated the correlation between the two different areas in bound water region, i.e., the first solvation shell, and the vehicular transport of hydronium ions at different water contents. We have employed a model of the Nafion membrane using the improved force field, which is newly modified and validated by comparing the density and water diffusivity with those obtained experimentally. The first solvation shells were classified into the two types, the isolated area and the overlapped area. The mean residence times of solvent molecules explicitly showed the different behaviors in each of those areas in terms of the vehicular transport of protons: the diffusivity of classical hydronium ions in the overlapped area dominates their total diffusion at lower water contents while that in the isolated area dominates for their diffusion at higher water contents. The results provided insights into the importance role of those areas in the solvation shells for the diffusivity of vehicular transport of hydronium ions in hydrated Nafion membrane.
Direct measurement of sub-wavelength interference using thermal light and photon-number-resolved detection
Authors: Zhai Yanhua , Becerra Francisco E. , Fan Jingyun , Migdall Alan
Published: September 2014

We examine thermal light diffracted through a double slit using photon-number-resolved detection to directly measure high-order spatial correlations, and we see sinusoidal modulations of those correlations. The fringe width can, in principal, be made arbitrarily small, and we have experimentally obtained fringe widths as small as 30 nm with 800 nm wavelength light. This extreme sub-wavelength resolution, along with this direct detection technique, offers potential for high precision measurement applications.
The control of oscillation mode in silicon microbeams using silicon nitride anchor
Authors: Baek In-Bok , Lee Bong Kuk , Kim Yarkyeon , Ahn Chang-Geun , Kim Young Jun , Yoon Yong Sun , Jang Won Ik , Kim Hakseong , Lee Sang Wook , Lee Seongjae , Yu Han Young
Published: September 2014

We designed and fabricated gravimetric sensors composed of silicon (Si) microbeams surrounded by silicon nitride (SiN) anchors. The oscillation properties of the fabricated devices show that a single oscillation mode originating from quasi-one-dimensional microbeams appears at an applied alternating electric field, which motion is well matched to the theoretical predictions and is much different from the dimensionally mixed oscillation modes in normal non-anchored devices. In addition, in order to elucidate the possibilities of the devices for mass sensing applications, we measured the frequency shift as a function of mass loading in a self-assembled monolayer of 3-aminopropyltrimethoxysilane and Au nanoparticles. The resulting limit of detection was 1.05 × 10−18 g/Hz, which is an extremely high value for micro electromechanical system gravimetric sensors relative to the normal ones.
Dependence of e31,f on polar axis texture for tetragonal Pb(Zrx,Ti1−x)O3 thin films
Authors: Yeager Charles B. , Ehara Yoshitaka , Oshima Naoya , Funakubo Hiroshi , Trolier-McKinstry Susan
Published: September 2014

It was shown by Ouyang et al. [Appl. Phys. Lett. 86, 152901 (2005)] that the piezoelectric e31,f coefficient is largest parallel to the spontaneous polarization in tetragonal PbZrxTi1−xO3 (PZT) films. However, the expected piezoelectric data are typically calculated from phenomenological constants derived from data on ceramic PZT. In this work, the dependence of e31,f on c-axis texture fraction, f001, for {001}PZT thin films was measured by growing films with systematically changed f001 using CaF2, MgO, SrTiO3, and Si substrates. An approximately linear increase in e31,f with f001 was observed for compositions up to 43 mol. % Zr, and 100% c-domain properties were extrapolated. It was demonstrated that c-axis PZT films can achieve e31,f exceeding −12 C/m2 for many tetragonal compositions. The energy harvesting figure of merit, e31,f2/εr, for c-axis PZT films surpassed 0.8 C2/m4. This is larger than the figure of merit of gradient-free PZT films grown on Si substrates by a factor of four.
Novel spherical hohlraum with cylindrical laser entrance holes and shields
Authors: Lan Ke , Zheng Wudi
Published: September 2014

Our recent works [K. Lan et al., Phys. Plasmas 21, 010704 (2014); K. Lan et al., Phys. Plasmas 21, 052704 (2014)] have shown that the octahedral spherical hohlraums are superior to the cylindrical hohlraums in both higher symmetry during the capsule implosion and lower backscatter without supplementary technology. However, both the coupling efficiency from the drive laser energy to the capsule and the capsule symmetry decrease remarkably when larger laser entrance holes (LEHs) are used. In addition, the laser beams injected at angles > 45° transport close to the hohlraum wall, thus the wall blowoff causes the LEH to close faster and results in strong laser plasma interactions inside the spherical hohlraums. In this letter, we propose a novel octahedral hohlraum with LEH shields and cylindrical LEHs to alleviate these problems. From our theoretical study, with the LEH shields, the laser coupling efficiency is significantly increased and the capsule symmetry is remarkably improved in the spherical hohlraums. The cylindrical LEHs take advantage of the cylindrical hohlraum near the LEH and mitigate the influence of the blowoff on laser transport inside a spherical hohlraum. The cylindrical LEHs can also be applied to the rugby and elliptical hohlraums.
Near-interface charged dislocations in AlGaN/GaN bilayer heterostructures
Authors: Sangghaleh A. , Pan E. , Han X.
Published: September 2014

Understanding the behavior of semiconductor dislocation defects in AlGaN/GaN heterostructures is necessary in order to produce powerful and efficient transistors. This letter presents a straightforward technique to characterize dislocation defects with charges along their loops in a bilayer system. This is important regarding the behavior of near-interface dislocations in order to obtain an insight of the mechanical and physical responses. We characterize piezoelectric polarization and emphasize on the importance of dislocation-core electric charge. The results elaborate the variations of the dislocation force by the accumulation of charge and provide an explanation for the dominant dislocation types in nitride semiconductors.
Large-grain SiGe-on-insulator with uniform Si concentration by segregation-free rapid-melting growth
Authors: Matsumura Ryo , Kato Ryusuke , Sadoh Taizoh , Miyao Masanobu
Published: September 2014

Large-grain SiGe-crystal-on-insulator is essential for fabrication of devices such as advanced thin film transistors and/or photosensors. For these purposes, rapid-melting growth of amorphous SiGe stripes (7%–20% Si concentration) on insulating substrates is investigated over a wide range of cooling rates (from 2 to 17 °C/s). The growth features of SiGe change dynamically, depending on the cooling rate. A low cooling rate produces large crystals with laterally graded Si concentration profiles caused by significant Si segregation during solidification. In contrast, a high cooling rate suppresses the Si segregation, but small grains form because of high spontaneous nucleation under super-cooling conditions. By tuning of the cooling rate, moderate super-cooling conditions are obtained as a function of the Si concentration. This controls both the Si segregation and the spontaneous nucleation, and produces large SiGe crystals (∼400 μm length, 7%–20% Si concentration) with three-dimensionally uniform Si profiles.
Macrospin modeling of sub-ns pulse switching of perpendicularly magnetized free layer via spin-orbit torques for cryogenic memory applications
Authors: Park Junbo , Rowlands G. E. , Lee O. J. , Ralph D. C. , Buhrman R. A.
Published: September 2014

We model, using the macrospin approximation, the magnetic reversal of a perpendicularly magnetized nanostructured free layer formed on a normal, heavy-metal nanostrip, subjected to spin-orbit torques (SOTs) generated by short (≤0.5 ns) current pulses applied to the nanostrip, to examine the potential for SOT-based fast, efficient cryogenic memory. Due to thermal fluctuations, if solely an anti-damping torque is applied, then, for a device with sufficiently low anisotropy (Hanis0 ∼ 1 kOe) suitable for application in cryogenic memory, a high magnetic damping parameter (α∼0.1−0.2) is required for reliable switching over a significant variation of pulse current. The additional presence of a substantial field-like torque improves switching reliability even for low damping (α≤0.03).
Electrically controlling the polarizing direction of a graphene polarizer
Authors: Zhu Z. H. , Guo C. C. , Liu K. , Zhang J. F. , Ye W. M. , Yuan X. D. , Qin S. Q.
Published: September 2014

We theoretically demonstrate a polarizer with an electrically controllable polarizing direction in the far infrared range using two orthogonal periodic arrays of graphene ribbons, which have different widths and are supported on a dielectric film placed on a thick piece of metal. The operation mechanism originates from the polarization-dependent resonant absorption of the two orthogonal graphene ribbons, which can be respectively controlled with different external bias voltages. The operation wavelength can be expanded to terahertz (THz) radiation.
High frequency magneto-dielectric effects in self-assembled ferrite-ferroelectric core-shell nanoparticles
Authors: Popov M. , Sreenivasulu G. , Petrov V. M. , Chavez F. A. , Srinivasan G.
Published: September 2014

Magneto-dielectric effects in self-assembled core-shell nanoparticles of nickel ferrite (NFO) and barium titanate (BTO) have been investigated in the millimeter wave frequencies. The core-shell nano-composites were synthesized by coating 100 nm nickel ferrite and 50 nm barium titanate nanoparticles with complementary coupling groups and allowing them to self-assemble in the presence of a catalyst forming heterogeneous nanocomposites. Magneto-electric (ME) characterization of as-assembled particles has been carried out by measurements of the relative permittivity ɛr as a function of frequency f under an applied static magnetic field H over 16–24 GHz. Measurements show an H-induced decrease in ɛr of 1 to 1.5%. But a giant magneto-dielectric effect with an H-induced change in permittivity as high as 28% is measured under dielectric resonance in the samples. A strong ME coupling was also evident from H-tuning of dielectric resonance in the composites. A theory for the high frequency magneto-dielectric effect has been developed and consists of the following steps. First the Bruggeman model is used to estimate the effective dielectric constant for the shell consisting of the BTO particles and voids considered as spherical air-pores. Then the permittivity for the core and shell is estimated taking into consideration the sample porosity. Finally the H-dependence of the permittivity due to ME interactions is calculated from the free energy considerations. Estimated ɛr vs. H and dielectric resonance frequency vs. H characteristics are in general agreement with the data.
Frequency selective microwave absorption induced by controlled orientation of graphene-like nanoplatelets in thin polymer films
Authors: Mesfin Henok Mebratie , Baudouin A. C. , Hermans Sophie , Delcorte Arnaud , Huynen Isabelle , Bailly Christian
Published: September 2014

Highly ordered polycarbonate films containing parallel graphite nanoplatelets have been produced by squeezing the corresponding random nanocomposites in the melt. Orientation of the conductive fillers is observed in the plane of the film, i.e., perpendicular to the squeezing direction. It only appears above a critical concentration of 15 wt. % and results from a confinement effect. Oriented samples show a resonance-like sharp increase of the conductivity at a given frequency in the microwave region, with the possibility to control the value of this frequency and the resulting absorption by changing the nanoplatelets concentration. Above this frequency, the oriented polymer nanocomposites show a high level of electromagnetic absorption, which opens the possibility to tailor materials with effective electromagnetic interference shielding by absorption in selected frequency ranges. The in-plane stacking of conductive nanoplatelets separated by insulating polymer induces their strong capacitive coupling to the signal propagating in the plane of the polymer film. As a result, the equivalent circuit of this propagation becomes a resonant system composed of capacitors, inductors, and resistors, which agrees well with the experimental results.
The Possibilities of Tolerance: Intercultural Dialogue in a Multicultural Europe
Authors: Wilson Helen F
Published: September 2014

Tolerance is everywhere. The Council of Europe endeavours to build it, schools are required to teach it, and neighbours are asked to extend it. It features in citizenship ceremonies, city-marketing campaigns, and religious texts and is attached to a variety of different objects, people, and behaviours. Yet despite its ubiquitous circulation as a moral good, critiques of tolerance as a way of relating have called for its rejection in favour of alternative projects such as respect and equality. In this paper I contextualise recent critiques and ask what possibilities remain for a politics of tolerance in multicultural Europe. In so doing, I argue that critiques are insufficiently attuned to the different contexts in which tolerance becomes productive and offer a starting point for further empirical research on its embodied practice. Using an example of dialogue, I argue that tolerance can be intrinsic to the development of alternative relations when positioned as part of an ongoing struggle to multiply ways of thinking and acting. I finish by reflecting on the relationship between tolerance, agonism, and dialogue, to outline a more pragmatic politics of difference, arguing that it is not enough to call for alternative projects without attending to the difficult and incremental learning that such projects demand.
Effects of whole-body heat on male germ cell development and sperm motility in the laboratory mouse
Authors: Wechalekar H. , Setchell B. P. , Pilkington K. R. , Leigh C. , Breed W. G. , Peirce E.
Published: September 2014

This study investigated the effects of high temperatures on male germ cell development and epididymal sperm motility of laboratory mice. In Experiment 1, adult males (n = 16) were exposed to whole-body heat of 37–38°C for 8 h day–1 for 3 consecutive days, whereas controls (n = 4) were left at 23–24°C. In Experiment 2, adult mice (n = 6) were exposed to 37–38°C for a single 8-h period with controls (n = 6) left at 23–24°C. Experiment 2 was conducted as a continuation of previous study that showed changes in spermatozoa 16 h after exposure to heat of 37–38°C for 8 h day–1 for 3 consecutive days. In the present study, in Experiment 1, high temperature reduced testes weights 16 h and 14 days after exposure, whereas by Day 21 testes weights were similar to those in the control group (P = 0.18). At 16 h, 7 and 14 days after exposure, an increase in germ cell apoptosis was noticeable in early and late stages (I–VI and XI–XII) of the cycle of the seminiferous epithelium. However, apoptosis in intermediate stages (VII–X) was evident 16 h after heat exposure (P < 0.05), without any change at other time periods. By 21 days, there were no significant differences between heat-treated groups and controls. Considerably more caspase-3-positive germ cells occurred in heat-treated mice 16 h after heat exposure compared with the control group (P < 0.0001), whereas 8 h after heat in Experiment 2, sperm motility was reduced with a higher percentage of spermatozoa showing membrane damage. In conclusion, the present study shows that whole-body heat of 37–38°C induces stage-specific germ cell apoptosis and membrane changes in spermatozoa; this may result in reduced fertility at particular times of exposure after heating.
Epigenetic processes in the male germline
Authors: O'Doherty Alan M. , McGettigan Paul A.
Published: September 2014

Sperm undergo some of the most extensive chromatin modifications seen in mammalian biology. During male germline development, paternal DNA methylation marks are erased and established on a global scale through waves of demethylation and de novo methylation. As spermatogenesis progresses, the majority of the histones are removed and replaced by protamines, enabling a tighter packaging of the DNA and transcriptional shutdown. Following fertilisation, the paternal genome is rapidly reactivated, actively demethylated, the protamines are replaced with histones and the embryonic genome is activated. The development of new assays, made possible by high-throughput sequencing technology, has resulted in the revisiting of what was considered settled science regarding the state of DNA packaging in mammalian spermatozoa. Researchers have discovered that not all histones are replaced by protamines and, in certain experiments, various species of RNA have been detected in what was previously considered transcriptionally quiescent spermatozoa. Most controversially, several groups have suggested that environmental modifications of the epigenetic state of spermatozoa may operate as a non-DNA-based form of inheritance, a process known as ‘transgenerational epigenetic inheritance’. Other developments in the field include the increased focus on the involvement of short RNAs, such as microRNAs, long non-coding RNAs and piwi-interacting RNAs. There has also been an accumulation of evidence illustrating associations between defects in sperm DNA packaging and disease and fertility. In this paper we review the literature, recent findings and areas of controversy associated with epigenetic processes in the male germline, focusing on DNA methylation dynamics, non-coding RNAs, the biology of sperm chromatin packaging and transgenerational inheritance.
Vaccination against oncogenic human papillomavirus infection in HIV-infected populations: review of current status and future perspectives
Authors: Toft Lars , Tolstrup Martin , Storgaard Merete , Østergaard Lars , Søgaard Ole S.
Published: September 2014

Background
Men and women with HIV infection are at increased risk of developing cancers associated with human papillomavirus (HPV). The two licensed prophylactic HPV vaccines protect against de novo infection with HPV-16 and HPV-18, which cause the majority of HPV-associated cancers. Currently, no vaccine efficacy data are available for persons with HIV infection. Nevertheless, some countries have implemented specific HPV vaccination recommendations for HIV-positive populations. To specifically recommend prophylactic HPV vaccination in people with HIV, the vaccines must be safe and immunogenic in immunosuppressed people at a high risk of HPV infection. This review aims to summarise the current knowledge from published HPV vaccine trials in HIV-infected populations, to compile scheduled and ongoing HPV vaccine trials with HIV-positive study populations and to extrapolate the relevant knowledge about HPV vaccine efficacy in HIV-negative populations to an HIV context. Methods: The databases PubMed, Scopus and ClinicalTrials.gov were searched for peer-reviewed articles and scheduled or ongoing clinical HPV vaccine trials enrolling HIV-positive persons. Results: Current data indicate that prophylactic HPV vaccines are safe and immunogenic in different HIV-positive populations (children, female adolescents, adults). Increased immunogenicity has been reported in persons on antiretroviral therapy compared with antiretroviral-naïve persons, whereas no clear association has been found between CD4+ cell count at immunisation and vaccine response. Several scheduled and ongoing HPV vaccine trials aim to determine vaccine efficacy against disease endpoints in HIV-infected study populations. Conclusion: Prophylactic HPV vaccination appears safe, immunogenic and, by extrapolation, likely to reduce HPV-associated cancer development among persons with HIV infection.
Tuberculosis (TB)-associated immune reconstitution inflammatory syndrome in TB-HIV co-infected patients in Malaysia: prevalence, risk factors, and treatment outcomes
Authors: Tan Hong Yien , Yong Yean Kong , Lim Sin How , Ponnampalavanar Sasheela , Omar Sharifah F. S. , Pang Yong Kek , Kamarulzaman Adeeba , Price Patricia , Crowe Suzanne M. , French Martyn A.
Published: September 2014

Background Tuberculosis-associated immune reconstitution inflammatory syndrome (TB-IRIS) is an important early complication of antiretroviral therapy (ART) in countries with high rates of endemic TB, but data from South-East Asia are incomplete. Identification of prevalence, risk factors and treatment outcomes of TB-IRIS in Malaysia was sought. Methods: A 3-year retrospective study was conducted among TB-HIV co-infected patients treated at the University of Malaya Medical Centre. Simple and adjusted logistic regressions were used to identify the predictors for TB-IRIS while Cox regression was used to assess the influence of TB-IRIS on long-term CD4 T-cell recovery. Results: One hundred and fifty-three TB-HIV patients were enrolled, of whom 106 had received both anti-TB treatment (ATT) and ART. The median (IQR) baseline CD4 T-cell count was 52 cells μL–1 (13–130 cells μL–1). Nine of 96 patients (9.4%) developed paradoxical TB-IRIS and eight developed unmasking TB-IRIS, at a median (IQR) time of 27 (12–64) and 19 (14–65) days, respectively. In adjusted logistic regression analysis, only disseminated TB was predictive of TB-IRIS [OR: 10.7 (95% CI: 1.2–94.3), P = 0.032]. Mortality rates were similar for TB-IRIS (n = 1, 5.9%) and non-TB-IRIS (n = 5, 5.7%) patients and CD4 T-cell recovery post-ART was not different between the two groups (P = 0.363). Conclusion: Disseminated TB was a strong independent predictor of TB-IRIS in Malaysian HIV-TB patients after commencing ART. This finding underscores the role of a high pathogen load in the pathogenesis of TB-IRIS; so interventions that reduce pathogen load before ART may benefit HIV patients with disseminated TB.
A language-familiarity effect for speaker discrimination without comprehension
Authors: Fleming David , Giordano Bruno L. , Caldara Roberto , Belin Pascal
Published: September 2014

Significance

A recent report [Perrachione TK, Del Tufo SN, Gabrieli JDE (2011)
Science
333(6042):595] shows that dyslexic individuals do not show an advantage in the recognition of speakers of their own language compared with speakers of a foreign language (the well established “language-familiarity” effect) as typical subjects do, a finding that Perrachione et al. interpreted as evidence that “Human voice recognition depends on language ability.” Here, we refine this notion by providing, to our knowledge, the first evidence of a language-familiarity effect in adult cross-cultural listeners with speech rendered unintelligible by time reversal. This result shows that the phonological aspects of language ability only, even without comprehension, can influence speaker discrimination.
Global market integration increases likelihood that a future African Green Revolution could increase crop land use and CO
2
emissions
Authors: Hertel Thomas W. , Ramankutty Navin , Baldos Uris Lantz C.
Published: September 2014

Significance

Agriculture is a key driver of tropical deforestation, and there is heated debate about whether productivity-enhancing crop innovations can slow such environmental degradation. For fixed food demand, globally higher yields will reduce cropland and hence deforestation. However, regional innovations often boost agricultural profitability and lower prices, thereby leading to cropland expansion in the innovating region. This paper develops a framework for understanding the impact of regional innovations on global land use and the environment. Although the historical Green Revolution in Asia, Latin America, and the Middle East is shown to have been land sparing, a future Green Revolution in Africa could lead to global cropland expansion in the context of a more fully integrated global agricultural economy.
Polarized gene conversion at the
bz
locus of maize
Authors: Dooner Hugo K. , He Limei
Published: September 2014

Significance

Meiotic recombination between homologous paternal and maternal chromosomes allows the shuffling of genes that otherwise would be coinherited and originates at nonrandom sites termed hotspots. In maize, an organism with >90% repetitive DNA, recombination hotspots correspond to genes. Gene conversion is a nonreciprocal form of recombination that leads to an aberrant allelic segregation ratio. In most higher organisms, gene conversions can be identified as intragenic recombinants having a parental arrangement of flanking markers. Here, we show that in maize heterozygotes where most recombinants can be attributed to gene conversion, mutant sites at either end of the gene convert to WT more frequently than those in the middle, arguing for a polarized distribution of recombination initiation sites within the gene.
Structural analysis and modeling reveals new mechanisms governing ESCRT-III spiral filament assembly
Authors: Shen Qing-Tao , Schuh Amber L. , Zheng Yuqing , Quinney Kyle , Wang Lei , Hanna Michael , Mitchell Julie C. , Otegui Marisa S. , Ahlquist Paul , Cui Qiang , Audhya Anjon
Published: September 2014

The scission of biological membranes is facilitated by a variety of protein complexes that bind and manipulate lipid bilayers. ESCRT-III (endosomal sorting complex required for transport III) filaments mediate membrane scission during the ostensibly disparate processes of multivesicular endosome biogenesis, cytokinesis, and retroviral budding. However, mechanisms by which ESCRT-III subunits assemble into a polymer remain unknown. Using cryogenic electron microscopy (cryo-EM), we found that the full-length ESCRT-III subunit Vps32/CHMP4B spontaneously forms single-stranded spiral filaments. The resolution afforded by two-dimensional cryo-EM combined with molecular dynamics simulations revealed that individual Vps32/CHMP4B monomers within a filament are flexible and able to accommodate a range of bending angles. In contrast, the interface between monomers is stable and refractory to changes in conformation. We additionally found that the carboxyl terminus of Vps32/CHMP4B plays a key role in restricting the lateral association of filaments. Our findings highlight new mechanisms by which ESCRT-III filaments assemble to generate a unique polymer capable of membrane remodeling in multiple cellular contexts.
Self-assisted GaAs nanowires with selectable number density on Silicon without oxide layer
Authors: Bietti S , Somaschini C , Frigeri C , Fedorov A , Esposito L , Geelhaar L , Sanguinetti S
Published: September 2014

We present the growth of self-assisted GaAs nanowires (NWs) with selectable number density on bare Si(1 1 1), not covered by the silicon oxide. We determine the number density of the NWs by initially self-assembling GaAs islands on whose top a single NW is nucleated. The number density of the initial GaAs base islands can be tuned by droplet epitaxy and the same degree of control is then transferred to the NWs. This procedure is completely performed during a single growth in an ultra-high vacuum environment and requires neither an oxide layer covering the substrate, nor any pre-patterning technique.
Understanding doping at the nanoscale: the case of codoped Si and Ge nanowires
Authors: Amato Michele , Rurali Riccardo , Palummo Maurizia , Ossicini Stefano
Published: September 2014

Results of first-principles DFT calculations of the structural and electronic properties of B–P codoped Si and Ge NWs are presented and discussed. We find that, according to experiments, for both Si and Ge NWs, impurities tend to get closer together and to occupy edge positions, as a result of minor structural relaxation and hence lower formation energy. The study of the electronic structure shows that the simultaneous addition of B and P only slightly modifies the energy band gap value with respect to the pure wire, and is strongly dependent on the particular codoping configuration considered.
Influence of strain and polycrystalline ordering on magnetic properties of high moment rare earth metals and alloys
Authors: Scheunert G , Ward C , Hendren W R , Lapicki A A , Hardeman R , Mooney M , Gubbins M , Bowman R M
Published: September 2014

Despite being the most suitable candidates for solenoid pole pieces in state-of-the-art superconductor-based electromagnets, the intrinsic magnetic properties of heavy rare earth metals and their alloys have gained comparatively little attention. With the potential of integration in micro and nanoscale devices, thin films of Gd, Dy, Tb, DyGd and DyTb were plasma-sputtered and investigated for their in-plane magnetic properties, with an emphasis on magnetization versus temperature profiles. Based on crystal structure analysis of the polycrystalline rare earth films, which consist of a low magnetic moment fcc layer at the seed interface topped with a higher moment hcp layer, an experimental protocol is introduced which allows the direct magnetic analysis of the individual layers. In line with the general trend of heavy lanthanides, the saturation magnetization was found to drop with increasing unit cell size. In situ annealed rare earth films exceeded the saturation magnetization of a high-moment Fe65Co35 reference film in the cryogenic temperature regime, proving their potential for pole piece applications; however as-deposited rare earth films were found completely unsuitable. In agreement with theoretical predictions, sufficiently strained crystal phases of Tb and Dy did not exhibit an incommensurate magnetic order, unlike their single-crystal counterparts which have a helical phase. DyGd and DyTb alloys followed the trends of the elemental rare earth metals in terms of crystal structure and magnetic properties. Inter-rare-earth alloys hence present a desirable blend of saturation magnetization and operating temperature.
Planar heterojunction organic photovoltaic cells based on tetramethyl substituted copper(II) phthalocyanine treated with thermal annealing
Authors: Qu Dalong , Guo Runda , Yue Shouzhen , Wu Yukun , Yan Pingrui , Cheng Gang
Published: September 2014

The fabrication of planar heterojunction (PHJ) organic photovoltaic (OPV) cells using tetramethyl substituted copper(II) phthalocyanine (CuMePc) as an electron donor and C60 as an acceptor is described. The impact of post-fabrication thermal annealing upon the performance of these cells has been examined. Atomic force microscopy (AFM) images and UV–visible absorption spectra of CuMePc thin films revealed crystallization of CuMePc induced by thermal annealing at 190 °C. The crystallized CuMePc films accounted for improved hole mobility, broadened absorption spectrum, and increased donor/acceptor interface in the as-fabricated cells after thermal annealing. AFM images also revealed that the surface of MoO3 film was smooth and close-packed after thermal annealing, which efficiently blocked the leakage current in the annealed cells, leading to dramatic improvement of performance for the PHJ cells using CuMePc as the electron donor and MoO3 or V2O5 as the anode buffer layer. The power conversion efficiency of the thermal-annealed PHJ cell with a configuration of ITO/MoO3/CuMePc/C60/Bathocuproine/Al was higher than that of the bulk heterojunction (BHJ) cell fabricated by co-depositing CuMePc and C60. It was mainly because the isolated clusters of CuMePc and/or C60 molecules formed during the fabrication of the BHJ cell was avoided in the PHJ cell.
The influence of the tube diameter on the properties of an atmospheric pressure He micro-plasma jet
Authors: Jõgi Indrek , Talviste Rasmus , Raud Jüri , Piip Kaarel , Paris Peeter
Published: September 2014

In the present study, a single electrode micro-plasma jet working in helium flow was investigated. The aim of our study was to clarify the influence of the tube diameter on the discharge ignition and sustaining voltage, as well as on nitrogen rotational temperature, helium excitation temperature and electron density. The diameter of the micro-tubes was varied in the range of 80–500 µm. A sinusoidal voltage with a frequency of 6 kHz was applied to ignite and sustain the plasma jet. Both the ignition and sustaining voltage monotonically increased with the decreasing diameter of the tube. The gas temperature of the plasma in the capillary tube estimated by the rotational temperature of the N2 second positive system remained below 500 K and depended weakly on tube diameter, while the excitation temperature of He and electron density, n
e, increased as the tube diameter decreased.
Self-association of the APC tumor suppressor is required for the assembly, stability, and activity of the Wnt signaling destruction complex
Authors: Kunttas-Tatli Ezgi , Roberts David M. , McCartney Brooke M.
Published: September 2014

The tumor suppressor adenomatous polyposis coli (APC) is an essential negative regulator of Wnt signaling through its activity in the destruction complex with Axin, GSK3β, and CK1 that targets β-catenin/Armadillo (β-cat/Arm) for proteosomal degradation. The destruction complex forms macromolecular particles we termed the destructosome. Whereas APC functions in the complex through its ability to bind both β-cat and Axin, we hypothesize that APC proteins play an additional role in destructosome assembly through self-association. Here we show that a novel N-terminal coil, the APC self-association domain (ASAD), found in vertebrate and invertebrate APCs, directly mediates self-association of Drosophila APC2 and plays an essential role in the assembly and stability of the destructosome that regulates β-cat degradation in Drosophila and human cells. Consistent with this, removal of the ASAD from the Drosophila embryo results in β-cat/Arm accumulation and aberrant Wnt pathway activation. These results suggest that APC proteins are required not only for the activity of the destructosome, but also for the assembly and stability of this macromolecular machine.
The RNA-binding protein Staufen1 impairs myogenic differentiation via a c-myc–dependent mechanism
Authors: Ravel-Chapuis Aymeric , Crawford Tara E. , Blais-Crépeau Marie-Laure , Bélanger Guy , Richer Chase T. , Jasmin Bernard J.
Published: September 2014

Recent work has shown that Staufen1 plays key roles in skeletal muscle, yet little is known about its pattern of expression during embryonic and postnatal development. Here we first show that Staufen1 levels are abundant in mouse embryonic muscles and that its expression decreases thereafter, reaching low levels in mature muscles. A similar pattern of expression is seen as cultured myoblasts differentiate into myotubes. Muscle degeneration/regeneration experiments revealed that Staufen1 increases after cardiotoxin injection before returning to the low levels seen in mature muscles. We next prevented the decrease in Staufen1 during differentiation by generating stable C2C12 muscle cell lines overexpressing Staufen1. Cells overexpressing Staufen1 differentiated poorly, as evidenced by reductions in the differentiation and fusion indices and decreases in MyoD, myogenin, MEF2A, and MEF2C, independently of Staufen-mediated mRNA decay. However, levels of c-myc, a factor known to inhibit differentiation, were increased in C2C12 cells overexpressing Staufen1 through enhanced translation. By contrast, the knockdown of Staufen1 decreased c-myc levels in myoblasts. Collectively our results show that Staufen1 is highly expressed during early stages of differentiation/development and that it can impair differentiation by regulating c-myc, thereby highlighting the multifunctional role of Staufen1 in skeletal muscle cells.
The Impact of AD HOC Disaster and Crop Insurance Programs on the Use of Risk‐Reducing Conservation Tillage Practices
Authors: Schoengold Karina , Ding Ya , Headlee Russell
Published: September 2014

The paper estimates the impacts of risk‐reducing government programs on the use of conservation tillage (no‐till and other conservation tillage) practices in agriculture. Conservation tillage can be used to reduce production risk from weather shocks. However, subsidized crop insurance and disaster payments also reduce risk through financial assistance. The paper examines the extent to which risk‐reducing tillage practices and government programs are substitutes for each other. The economic model shows that a decline in average weather conditions increases the use of conservation tillage. The economic model also shows that the impact of weather risk and risk aversion on risk‐reducing practices like conservation tillage are ambiguous. The effect depends on the degree that losses are offset by government payments. The paper uses county‐level tillage practice data from the Conservation Tillage Information Center for the three‐state region of Iowa, Nebraska, and South Dakota. Results are estimated using instrumental variables and spatial panel data techniques. Instruments for the program participation and payment data include political variables and weather data. The empirical analysis shows that recent disaster and indemnity payments are associated with an increase in the use of no‐till and a decrease in the use of other conservation till. Results also show that producers in counties with recent drought and flood events are more likely to use other conservation tillage. The results imply that there may be unintended impacts of changes to agricultural policies like disaster payments and crop insurance on the use of on‐farm conservation practices.
The methyltransferase domain of dengue virus protein NS5 ensures efficient RNA synthesis initiation and elongation by the polymerase domain
Authors: Potisopon Supanee , Priet Stéphane , Collet Axelle , Decroly Etienne , Canard Bruno , Selisko Barbara
Published: September 2014

Viral RNA-dependent RNA polymerases (RdRps) responsible for the replication of single-strand RNA virus genomes exert their function in the context of complex replication machineries. Within these replication complexes the polymerase activity is often highly regulated by RNA elements, proteins or other domains of multi-domain polymerases. Here, we present data of the influence of the methyltransferase domain (NS5-MTase) of dengue virus (DENV) protein NS5 on the RdRp activity of the polymerase domain (NS5-Pol). The steady-state polymerase activities of DENV-2 recombinant NS5 and NS5-Pol are compared using different biochemical assays allowing the dissection of the de novo initiation, transition and elongation steps of RNA synthesis. We show that NS5-MTase ensures efficient RdRp activity by stimulating the de novo initiation and the elongation phase. This stimulation is related to a higher affinity of NS5 toward the single-strand RNA template indicating NS5-MTase either completes a high-affinity RNA binding site and/or promotes the correct formation of the template tunnel. Furthermore, the NS5-MTase increases the affinity of the priming nucleotide ATP upon de novo initiation and causes a higher catalytic efficiency of the polymerase upon elongation. The complex stimulation pattern is discussed under the perspective that NS5 adopts several conformations during RNA synthesis.
Clinical Utility of Indium 111–Labeled White Blood Cell Scintigraphy for Evaluation of Suspected Infection
Authors: Lewis Sarah S. , Cox Gary M. , Stout Jason E.
Published: September 2014

Background.  We sought to characterize the clinical utility of indium 111 (111In)–labeled white blood cell (WBC) scans by indication, to identify patient populations who might benefit most from this imaging modality.

Methods.  Medical records for all patients who underwent 111In-labeled WBC scans at our tertiary referral center from 2005 to 2011 were reviewed. Scan indication, results, and final diagnosis were assessed independently by 2 infectious disease physicians. Reviewers also categorized the clinical utility of each scan as helpful vs not helpful with diagnosis and/or management according to prespecified criteria. Cases for which clinical utility could not be determined were excluded from the utility assessment.

Results.  One hundred thirty-seven scans were included in this analysis; clinical utility could be determined in 132 (96%) cases. The annual number of scans decreased throughout the study period, from 26 in 2005 to 13 in 2011. Forty-one (30%) scans were positive, and 85 (62%) patients were ultimately determined to have an infection. Of the evaluable scans, 63 (48%) scans were deemed clinically useful. Clinical utility varied by scan indication: 111In-labeled WBC scans were more helpful for indications of osteomyelitis (35/50, 70% useful) or vascular access infection (10/15, 67% useful), and less helpful for evaluation of fever of unknown origin (12/35, 34% useful).

Conclusions.  111In-labeled WBC scans were useful for patient care less than half of the time at our center. Targeted ordering of these scans for indications in which they have greater utility, such as suspected osteomyelitis and vascular access infections, may optimize test utilization.