bluuebunny/crossref_metadata_2025 huggingface dataset:
Analysis of microstructure-dependent shock dissipation and hot-spot formation in granular metalized explosive
Authors: Chakravarthy Sunada , Gonthier Keith A.
Published: July 2016

Variations in the microstructure of granular explosives (i.e., particle packing density, size, shape, and composition) can affect their shock sensitivity by altering thermomechanical fields at the particle-scale during pore collapse within shocks. If the deformation rate is fast, hot-spots can form, ignite, and interact, resulting in burn at the macro-scale. In this study, a two-dimensional finite and discrete element technique is used to simulate and examine shock-induced dissipation and hot-spot formation within low density explosives (68%–84% theoretical maximum density (TMD)) consisting of large ensembles of HMX (C4H8N8O8) and aluminum (Al) particles (size ∼60–360 μm). Emphasis is placed on identifying how the inclusion of Al influences effective shock dissipation and hot-spot fields relative to equivalent ensembles of neat/pure HMX for shocks that are sufficiently strong to eliminate porosity. Spatially distributed hot-spot fields are characterized by their number density and area fraction enabling their dynamics to be described in terms of nucleation, growth, and agglomeration-dominated phases with increasing shock strength. For fixed shock particle speed, predictions indicate that decreasing packing density enhances shock dissipation and hot-spot formation, and that the inclusion of Al increases dissipation relative to neat HMX by pressure enhanced compaction resulting in fewer but larger HMX hot-spots. Ensembles having bimodal particle sizes are shown to significantly affect hot-spot dynamics by altering the spatial distribution of hot-spots behind shocks.
Mode splitting effect in FEMs with oversized Bragg resonators
Authors: Peskov N. Yu. , Kaminsky A. K. , Kuzikov S. V. , Perelstein E. A. , Sedykh S. N. , Sergeev A. S.
Published: July 2016

Splitting of the fundamental mode in an oversized Bragg resonator with a step of the corrugation phase, which operates over the feedback loop involving the waveguide waves of different transverse structures, was found to be the result of mutual influence of the neighboring zones of the Bragg scattering. Theoretical description of this effect was developed within the framework of the advanced (four-wave) coupled-wave approach. It is shown that mode splitting reduces the selective properties, restricts the output power, and decreases the stability of the narrow-band operating regime in the free-electron maser (FEM) oscillators based on such resonators. The results of the theoretical analysis were confirmed by 3D simulations and “cold” microwave tests. Experimental data on Bragg resonators with different parameters in a 30-GHz FEM are presented. The possibility of reducing the mode splitting by profiling the corrugation parameters is shown. The use of the mode splitting effect for the output power enhancement by passive compression of the double-frequency pulse generated in the FEM with such a resonator is discussed.
Propagation of arbitrary amplitude dust-ion acoustic waves in the collisional magnetized dusty plasma in the presence of non-thermal electrons
Authors: Sayyar M. , Zahed H. , Pestehe S. J. , Sobhanian S.
Published: July 2016

Using the Sagdeev pseudo-potential method, the oblique propagation of dust-ion acoustic solitary waves is studied in a magnetized dusty plasma. By considering non-thermal distribution of electrons, the related pseudo-potential is obtained using the Poisson equation. The behavior of the wave is investigated for some ranges of parameters. It is demonstrated that the increase in ion density, lz, β, and also δ1 can lead to the increases in the width and amplitude of the pseudo-potential, while any increase of a2, the coefficient that describes the first nonlinear term in the G(ϕ), increases the amplitude of the V(ϕ).
High energy photon emission from wakefields
Authors: Farinella D. M. , Lau C. K. , Zhang X. M. , Koga J. K. , Taimourzadeh S. , Hwang Y. , Abazajian K. , Canac N. , Ebisuzaki T. , Taborek P. , Tajima T.
Published: July 2016

Experimental evidence has accumulated to indicate that wakefield acceleration (WFA) accompanies intense and sometimes coherent emission of radiation such as from betatron radiation. The investigation of this issue has additional impetus nowadays because we are learning (1) there is an additional acceleration process of the ponderomotive acceleration; (2) WFA may become relevant in much higher density regimes; (3) WFA has been proposed as the mechanism for extreme high energy cosmic ray acceleration and gamma ray bursts for active galactic nuclei. These require us to closely examine the radiative mechanisms in WFA anew. We report studies of radiation from wakefield (self-injected betatron) and ponderomotive (laser field) mechanisms in scalings of the frequency and intensity of the driver, as well as the plasma density.
Self-limiting and complete oxidation of silicon nanostructures produced by laser ablation in water
Authors: Vaccaro L. , Popescu R. , Messina F. , Camarda P. , Schneider R. , Gerthsen D. , Gelardi F. M. , Cannas M.
Published: July 2016

Oxidized Silicon nanomaterials produced by 1064 nm pulsed laser ablation in deionized water are investigated. High-resolution transmission electron microscopy coupled with energy dispersive X-ray spectroscopy allows to characterize the structural and chemical properties at a sub-nanometric scale. This analysis clarifies that laser ablation induces both self-limiting and complete oxidation processes which produce polycrystalline Si surrounded by a layer of SiO2 and amorphous fully oxidized SiO2, respectively. These nanostructures exhibit a composite luminescence spectrum which is investigated by time-resolved spectroscopy with a tunable laser excitation. The origin of the observed luminescence bands agrees with the two structural typologies: Si nanocrystals emit a μs-decaying red band; defects of SiO2 give rise to a ns-decaying UV band and two overlapping blue bands with lifetime in the ns and ms timescale.
Output characteristics of a 0.14 THz dual sheet beam backward wave oscillator based on a hole-grating slow wave structure
Authors: Tang Xiaopin , Yang Ziqiang , Shi Zongjun , Lan Feng , Zeng Hongxin , Zhang Ting
Published: July 2016

A novel backward wave oscillator (BWO) based on a hole-grating slow wave structure is proposed as a dual sheet beam millimeter wave radiation source. In this paper, we focus on the output characteristics of a 0.14 THz hole-grating BWO. The output characteristics of the hole-grating BWO, the conventional single-beam grating BWO, and the dual-beam grating BWO are contrasted in detail. 3-D particle-in-cell results indicate that the hole-grating slow wave structure can help to increase the maximum output power as well as lower the operating current density. Meanwhile, the hole-grating BWO shows good insensitivity to the differences between two sheet electron beams. These characteristics make the hole-grating BWO feasible to be a stable millimeter wave radiation source with higher output power.
Multiple surface plasmons in an unbounded quantum plasma half-space
Authors: Palade D. I.
Published: July 2016

The propagation of surface plasmons on a quantum plasma half-space in the absence of any external confinement is investigated. By means of the Quantum Hydrodynamic Model in the electrostatic limit, it is found that the equilibrium density profile is a smooth continuous function which, in the linear regime, supports multiple non-normal surface modes. Defining a spectrum function and using a cutting condition, the dispersion relations of these modes and their relevance for realistic dynamics are computed. It is found that the multiple surface plasmons present a significant red-shift with respect to the case of fully bounded quantum plasmas.
A theoretical model for the Lorentz force particle analyzer
Authors: Moreau René , Tao Zhen , Wang Xiaodong
Published: July 2016

In a previous paper [X. Wang et al., J. Appl. Phys. 120, 014903 (2016)], several experimental devices have been presented, which demonstrate the efficiency of electromagnetic techniques for detecting and sizing electrically insulating particles entrained in the flow of a molten metal. In each case, a non-uniform magnetic field is applied across the flow of the electrically conducting liquid, thereby generating a braking Lorentz force on this moving medium and a reaction force on the magnet, which tends to be entrained in the flow direction. The purpose of this letter is to derive scaling laws for this Lorentz force from an elementary theoretical model. For simplicity, as in the experiments, the flowing liquid is modeled as a solid body moving with a uniform velocity U. The eddy currents in the moving domain are derived from the classic induction equation and Ohm's law, and expressions for the Lorentz force density j×B and for its integral over the entire moving domain follow. The insulating particles that are eventually present and entrained with this body are then treated as small disturbances in a classic perturbation analysis, thereby leading to scaling laws for the pulses they generate in the Lorentz force. The purpose of this letter is both to illustrate the eddy currents without and with insulating particles in the electrically conducting liquid and to derive a key relation between the pulses in the Lorentz force and the main parameters (particle volume and dimensions of the region subjected to the magnetic field).
Luminescent GdVO4:Sm3+ quantum dots enhance power conversion efficiency of bulk heterojunction polymer solar cells by Förster resonance energy transfer
Authors: Bishnoi Swati , Gupta Vinay , Sharma Chhavi , Haranath D. , Naqvi Sheerin , Kumar Mahesh , Sharma Gauri D. , Chand Suresh
Published: July 2016

In this work, we report enhanced power conversion efficiency (PCE) of bulk heterojunction polymer solar cells by Förster resonance energy transfer (FRET) from samarium-doped luminescent gadolinium orthovanadate (GdVO4:Sm3+) quantum dots (QDs) to polythieno[3,4-b]-thiophene-co-benzodithiophene (PTB7) polymer. The photoluminescence emission spectrum of GdVO4:Sm3+ QDs overlaps with the absorption spectrum of PTB7, leading to FRET from GdVO4:Sm3+ to PTB7, and significant enhancements in the charge-carrier density of excited and polaronic states of PTB7 are observed. This was confirmed by means of femtosecond transient absorption spectroscopy. The FRET from GdVO4:Sm3+ QDs to PTB7 led to a remarkable increase in the power conversion efficiency (PCE) of PTB7:GdVO4:Sm3+:PC71BM ([6,6]-phenyl-C71-butyric acid methyl ester) polymer solar cells. The PCE in optimized ternary blend PTB7:GdVO4:Sm3+:PC71BM (1:0.1:1.5) is increased to 8.8% from 7.2% in PTB7:PC71BM. This work demonstrates the potential of rare-earth based luminescent QDs in enhancing the PCE of polymer solar cells.
Low-power four-wave mixing in porous silicon microring resonators
Authors: Simbula A. , Rodriguez G. A. , Menotti M. , De Pace S. , Weiss S. M. , Galli M. , Liscidini M. , Bajoni D.
Published: July 2016

We report the measurement of low-power continuous-wave four-wave mixing in porous silicon microring resonators operating in the 1550 nm telecom band. Resonantly enhanced stimulated four-wave mixing has been measured in rings with 25 μm radius and quality factor around 5000 for pump powers as low as a few hundreds of microwatts. A waveguide nonlinear parameter γ = 20 W–1 m−1 has been determined. These results suggest further research on porous silicon for low-power nonlinear optics, possibly taking advantage of its tunable porosity.
A magnetic source imaging camera
Authors: Dolgovskiy V. , Fescenko I. , Sekiguchi N. , Colombo S. , Lebedev V. , Zhang J. , Weis A.
Published: July 2016

We describe a magnetic source imaging camera (MSIC) allowing a direct dynamic visualization of the two-dimensional spatial distribution of the individual components Bx(x,y), By(x,y) and Bz(x,y) of a magnetic field. The field patterns allow—in principle—a reconstruction of the distribution of sources that produce the field B→ by inverse problem analysis. We compare experimentally recorded point-spread functions, i.e., field patterns produced by point-like magnetic dipoles of different orientations with anticipated field patterns. Currently, the MSIC can resolve fields of ≈10 pT (1 s measurement time) range in a field of view up to ∼20 × 20 mm2. The device has a large range of possible applications. As an example, we demonstrate the MSIC's use for recording the spatially resolved Néel magnetorelaxation of blocked magnetic nanoparticles.
Prediction of spin-dependent electronic structure in 3d-transition-metal doped antimonene
Authors: Yang L. F. , Song Y. , Mi W. B. , Wang X. C.
Published: July 2016

We investigate the geometric structure and electronic and magnetic properties of 3d-transition-metal atom doped antimonene using spin-polarized first-principles calculations. Strong orbital hybridization exhibits between 3d-transition-metal and Sb atoms, where covalent bonds form in antimonene. A spin-polarized semiconducting state appears in Cr-doped antimonene, while half-metallic states appear by doping Ti, V, and Mn. These findings indicate that once combined with doping states, the bands of antimonene systems offer a variety of features. Specific dopants lead to half-metallic characters with high spin polarization that has potential application in spintronics.
On the origin of the spatial inhomogeneity of photoluminescence in thin-film CIGS solar devices
Authors: El-Hajje Gilbert , Ory Daniel , Guillemoles Jean-François , Lombez Laurent
Published: July 2016

In this letter, we investigate the origin of the spatial inhomogeneity of the photoluminescence (PL) intensity maps obtained on thin-film solar cells. Based on a hyperspectral imager setup, we record an absolute map of the quasi-Fermi level splitting Δμ by applying the generalized Planck's law. Then, using scanning confocal microscopy, we perform spatially and time-resolved photoluminescence measurements. This allowed us to quantify and map the micrometric fluctuations of the trapping defect density within these solar cells. Finally, we demonstrate the existence of a direct correlation between the spatial fluctuations of the quasi-Fermi level splitting and the trapping defect density. The latter was found to be correlated with the frequently reported spatially inhomogeneous PL maps of thin-film solar cells. Based on the observed correlation, we can quantify the local losses in quasi-Fermi level splitting induced by the spatial distribution of the trapping defects.
Photoexcited ZnO nanoparticles with controlled defects as a highly sensitive oxygen sensor
Authors: Goto Taku , Shimizu Yoshiki , Yasuda Hidehiro , Ito Tsuyohito
Published: July 2016

Conductance of photoexcited ZnO nanoparticles with various defects has been investigated in oxygen. ZnO nanoparticles, which show strong photoluminescence peaks originating from interstitial zinc atom (Zni) and singly charged oxygen vacancy (VO+), show oxygen-pressure-dependent conductance changes caused by photoexcitation. Herein, a model is proposed to simulate the conductance changes.
Numerical and experimental investigation of nonlinear ultrasonic Lamb waves at low frequency
Authors: Zuo Peng , Zhou Yu , Fan Zheng
Published: July 2016

Nonlinear ultrasonic Lamb waves are popular to characterize the nonlinearity of materials. However, the widely used nonlinear Lamb mode suffers from two associated complications: inherent dispersive and multimode natures. To overcome these, the symmetric Lamb mode (S0) at low frequency region is explored. At the low frequency region, the S0 mode is little dispersive and easy to generate. However, the secondary mode still exists, and increases linearly for significant distance. Numerical simulations and experiments are used to validate the nonlinear features and therefore demonstrate an easy alternative for nonlinear Lamb wave applications.
Advanced optical modelling of dynamically deposited silicon nitride layers
Authors: Borojevic N. , Hameiri Z. , Winderbaum S.
Published: July 2016

Dynamic deposition of silicon nitrides using in-line plasma enhanced chemical vapor deposition systems results in non-uniform structure of the dielectric layer. Appropriate analysis of such layers requires the optical characterization to be performed as a function of the layer's depth. This work presents a method to characterize dynamically deposited silicon nitride layers. The method is based on the fitting of experimental spectroscopic ellipsometry data via grading of Tauc–Lorentz optical parameters through the depth of the layer. When compared with the standard Tauc–Lorentz fitting procedure, used in previous studies, the improved method is demonstrating better quality fits to the experimental data and revealing more accurate optical properties of the dielectric layers. The most significant advantage of the method is the ability to extract the depth profile of the optical properties along the direction of the layer normal. This is enabling a better understanding of layers deposited using dynamic plasma enhanced chemical vapor deposition systems frequently used in the photovoltaic industry.
Mid-wavelength infrared heterojunction phototransistors based on type-II InAs/AlSb/GaSb superlattices
Authors: Haddadi A. , Adhikary S. , Dehzangi A. , Razeghi M.
Published: July 2016

A mid-wavelength infrared heterojunction phototransistor based on type-II InAs/AlSb/GaSb superlattices on GaSb substrate has been demonstrated. Near a wavelength of 4 μm saturated optical gains of 668 and 639 at 77 and 150 K, respectively, are demonstrated over a wide dynamic range. At 150 K, the unity optical gain collector dark current density and DC current gain are 1 × 10−3 A/cm2 and 3710, respectively. This demonstrates the potential for use in high-speed applications. In addition, the phototransistor exhibits a specific detectivity value that is four times higher compared with a state-of-the-art type-II superlattice-based photodiode with a similar cut-off wavelength at 150 K.
Inverse bilayer magnetoelectric thin film sensor
Authors: Yarar E. , Salzer S. , Hrkac V. , Piorra A. , Höft M. , Knöchel R. , Kienle L. , Quandt E.
Published: July 2016

Prior investigations on magnetoelectric (ME) thin film sensors using amorphous FeCoSiB as a magnetostrictive layer and AlN as a piezoelectric layer revealed a limit of detection (LOD) in the range of a few pT/Hz1/2 in the mechanical resonance. These sensors are comprised of a Si/SiO2/Pt/AlN/FeCoSiB layer stack, as dictated by the temperatures required for the deposition of the layers. A low temperature deposition route of very high quality AlN allows the reversal of the deposition sequence, thus allowing the amorphous FeCoSiB to be deposited on the very smooth Si substrate. As a consequence, the LOD could be enhanced by almost an order of magnitude reaching 400 fT/Hz1/2 at the mechanical resonance of the sensor. Giant ME coefficients (αME) as high as 5 kV/cm Oe were measured. Transmission electron microscopy investigations revealed highly c-axis oriented growth of the AlN starting from the Pt-AlN interface with local epitaxy.
High-Q lattice mode matched structural resonances in terahertz metasurfaces
Authors: Xu Ningning , Singh Ranjan , Zhang Weili
Published: July 2016

The quality (Q) factor of metamaterial resonances is limited by the radiative and non-radiative losses. At terahertz frequencies, the dominant loss channel is radiative in nature since the non-radiative losses are low due to high conductivity of metals. Radiative losses could be suppressed by engineering the meta-atom structure. However, such suppression usually occurs at the fundamental resonance mode which is typically a closed mode resonance such as an inductive-capacitive resonance or a Fano resonance. Here, we report an order of magnitude enhancement in Q factor of all the structural eigenresonances of a split-ring resonator fueled by the lattice mode matching. We match the fundamental order diffractive mode to each of the odd and even eigenresonances, thus leading to a tremendous line-narrowing of all the resonances. Such precise tailoring and control of the structural resonances in a metasurface lattice could have potential applications in low-loss devices, sensing, and design of high-Q metamaterial cavities.
Physical implication of transition voltage in organic nano-floating-gate nonvolatile memories
Authors: Wang Shun , Gao Xu , Zhong Ya-Nan , Zhang Zhong-Da , Xu Jian-Long , Wang Sui-Dong
Published: July 2016

High-performance pentacene-based organic field-effect transistor nonvolatile memories, using polystyrene as a tunneling dielectric and Au nanoparticles as a nano-floating-gate, show parallelogram-like transfer characteristics with a featured transition point. The transition voltage at the transition point corresponds to a threshold electric field in the tunneling dielectric, over which stored electrons in the nano-floating-gate will start to leak out. The transition voltage can be modulated depending on the bias configuration and device structure. For p-type active layers, optimized transition voltage should be on the negative side of but close to the reading voltage, which can simultaneously achieve a high ON/OFF ratio and good memory retention.
Distant and wide range wireless power transfer from metamedia
Authors: Zhu Lin , Luo Xudong , Ma Hongru
Published: July 2016

Based on electromagnetic scattering theory, a model of superscatterer enhanced distant wireless power transfer (WPT) device has designed and analyzed with the concept of transformation optics. The numerical results obtained through a series expansion method reveal that a properly designed ss-WPT has high efficiency for long transfer distances as well as a wide transfer range. The transfer distance can be further enlarged by fine tuning of the design. These effects can be explained qualitatively through the study of magnetic flux.
The study of three-dimensional temperature field distribution reconstruction using ultrasonic thermometry
Authors: Jia Ruixi , Xiong Qingyu , Wang Kai , Wang Lijie , Xu Guangyu , Liang Shan
Published: July 2016

As an efficient technique, microwave heating is applied for various thermal processes in recent years. Information of temperature field distribution is important to security and stability in the process of microwave heating. In this paper, we investigate a three-dimensional temperature field distribution reconstruction algorithm using ultrasonic thermometry. Four three-dimensional temperature field distribution models with different complex levels are used in the simulation experiments. The error analysis between the temperature field distribution models and the reconstructed ones indicates that the proposed reconstruction algorithm possesses high reconstruction precision.
Hay quality and intake by dairy cows. 2. Predicting feed intake with consumer-demand models
Authors: Sadler R. J. , Purser D. B. , Baker S. K.
Published: July 2016

Daily food intake is the single most important factor affecting milk production by dairy cows. However, an animal’s choice of food depends not only on the nutritional characteristics of the food in question, but also on the nutritional characteristics of other available foods. Any prediction of intake should be based on the nutritional characteristics of all foods on offer. However, when the initial food-preference experiment possesses a control-specific design (i.e. experiments that include only a limited number of control foods for comparison) it is apparent that the prediction of future food choices must include the same controls as the initial experiment underpinning the prediction model. This requirement is clearly impractical. By drawing an analogy between animal food preference and economic choice, the total and relative dry matter intake of two oaten hays was modelled on their nutritive characteristics by estimating a consumer-demand model (here a generalised additive model representation of a direct bundle good model) from experimental data offering hays to lactating cows (adj-R2 > 80%; where adj-R2 is the value adjusted for the number of predictor terms in the model). To negate the problem of control-specificity, a simplex interpolation was developed to construct and test predictions of hay intake for a second food-preference experiment (adj-R2 > 53%; correlation between predictions and actual intakes = 76%). To improve prediction accuracy and avoid control-specificity, it is recommended that future preference experiments be designed to exclude control-specificity by mimicking fractional factorial designs, supported by a two-stage approach to select a cost-effective number of comparisons. Our approach to predicting food intake may be extended to a choice between more than two foods, and to combinations of foods other than oaten hays.
Anionic Ring Opening Polymerization of ε-Caprolactone Initiated by Lithium Silanolates
Authors: Satti Angel J. , G. O. de Freitas Augusto , Marani M. Loreta Sena , Villar Marcelo A. , Vallés Enrique M. , Giacomelli Cristiano , Ciolino Andrés E.
Published: July 2016

Ring-opening homo- and co-polymerization reactions of ϵ-caprolactone were performed by employing anionic polymerization (high vacuum techniques) and lithium silanolates (LS) as initiators. LS were obtained by reaction between hexamethyl(cyclotrisiloxane) and sec-Bu–Li+, or from living poly(dimethylsiloxanyl)lithium chains. The results indicated that LS are efficient initiators for the ring-opening polymerization of ϵ-caprolactone, providing the respective homogeneous polymers in good yields.
Insights into natural organic matter and pesticide characterisation and distribution in the Rhone River
Authors: Slomberg Danielle L. , Ollivier Patrick , Radakovitch Olivier , Baran Nicole , Sani-Kast Nicole , Bruchet Auguste , Scheringer Martin , Labille Jérôme
Published: July 2016

Environmental contextNatural organic matter in surface waters is a transport vector for environmental pollutants with both its concentration and composition influencing pollutant fate. Characterisation of organic matter in surface waters, crucial to understanding pollutant transport, should also account for spatial variation along the water source. The present work characterises the natural organic matter in the Rhone River and describes the distributions of various pesticides and metabolites along the river. AbstractThorough characterisation of natural organic matter (NOM) in natural surface waters remains vital for evaluating pollutant dynamics and interactions with NOM under realistic environmental conditions. Here, we present the characterisation of NOM and pesticide compositions for nine sampling sites over the length of the Rhone River, also evaluating the advantages and limitations of different analytical techniques to determine how they complement one another. Together with dissolved and particulate organic carbon analyses, the dissolved organic matter (DOM, <0.8μm) or NOM (unfiltered organic matter) was characterised with gel permeation chromatography, the polarity rapid-assessment method, excitation–emission matrix fluorescence, and pyrolysis–gas chromatography–mass spectrometry to evaluate both composition and distribution. An additional objective was the determination of the NOM degradation state (i.e. constantly produced autochthonous or weakly degraded allochthonous species), an important factor in assessing potential NOM–pollutant interactions. The NOM compositions (i.e. proteins, polyhydroxy aromatics, polysaccharides, amino sugars) and proportions were similar between sites, but variations were observed in the relative proportions of autochthonous and allochthonous material from north to south. Anionic proteins and polyhydroxy aromatics in a molecular weight range of ~1000–1200 Da comprised the majority of the DOM. As a pollutant case study, five pesticides (glyphosate, metalochlor, chlortoluron, isoproturon, propyzamide) and some of their metabolites (aminomethylphosphonic acid, metolachlor ethanesulfonic acid and metolachlor oxanilic acid) were measured. Several exhibited trends with the NOM, particulate organic carbon and suspended particulate matter distributions in the Rhone waters, suggesting a significant influence on pesticide fate and transport in the river.
Persistence, loss and appearance of bacteria upstream and downstream of a river system
Authors: Dann Lisa M. , Smith Renee J. , Jeffries Thomas C. , McKerral Jody C. , Fairweather Peter G. , Oliver Rod L. , Mitchell James G.
Published: July 2016

Bacterial taxa shape microbial community composition and influence aquatic ecosystem dynamics. Studies on bacterial persistence in rivers have primarily focussed on microbial-source tracking as an indicator for faecal-source contamination, whereas archetypal freshwater species have received minimal attention. The present study describes the river microbial communities upstream and 3.3km downstream of a small rural town. By 16S rDNA sequencing, we report three patterns in microbial community composition, namely, persistence, loss and appearance. Persistence was observed as 46% inter-site similarity, perhaps owing to generalists that have information lengths that exceed 3.3km and are capable of adapting to system fluctuations. Loss was observed as 10% site exclusivity upstream, perhaps owing to removal processes such as predation and lysis during transport downstream. Last, appearance was observed as 44% site exclusivity downstream, indicating potential anthropogenic impacts from land run-off on bacterial community composition. High multivariate dispersion among downstream samples, as well as overall sample dissimilarity, present as microscale hotspots of discrete Firmicutes and Cyanobacteria species, indicated higher heterogeneity downstream, and therefore increased patchiness from downstream transport and inputs of bacterial genotypes. These findings suggest relativities among three fates for bacterial species of fluvial systems, persistence, loss and appearance, with each having different effects on system dynamics.
Left cortical specialization for visual letter strings predicts rudimentary knowledge of letter-sound association in preschoolers
Authors: Lochy Aliette , Van Reybroeck Marie , Rossion Bruno
Published: July 2016

Significance

This study reports a robust and specific marker of sensitivity to print in 5-y-old prereaders, in the form of an electrophysiological response recorded over visual areas of the left hemisphere in only 2 min. The significant correlation with rudimentary letter knowledge in preschoolers, a behavioral measure taken independently, suggests rapid domain-specific specialization of neuronal circuits, beyond mere visual familiarity. These findings also highlight the potential of an objective and highly sensitive behavior-free approach to assess letter knowledge, a precursor of reading ability, in developmental populations.
Disruptions of network connectivity predict impairment in multiple behavioral domains after stroke
Authors: Siegel Joshua Sarfaty , Ramsey Lenny E. , Snyder Abraham Z. , Metcalf Nicholas V. , Chacko Ravi V. , Weinberger Kilian , Baldassarre Antonello , Hacker Carl D. , Shulman Gordon L. , Corbetta Maurizio
Published: July 2016

Significance

Since the early days of neuroscience, the relative merit of structural vs. functional network accounts in explaining neurological deficits has been intensely debated. Using a large stroke cohort and a machine-learning approach, we show that visual memory and verbal memory deficits are better predicted by functional connectivity than by lesion location, and visual and motor deficits are better predicted by lesion location than functional connectivity. In addition, we show that disruption to a subset of cortical areas predicts general cognitive deficit (spanning multiple behavior domains). These results shed light on the complementary value of structural vs. functional accounts of stroke, and provide a physiological mechanism for general multidomain deficits seen after stroke.
Decreased function of survival motor neuron protein impairs endocytic pathways
Authors: Dimitriadi Maria , Derdowski Aaron , Kalloo Geetika , Maginnis Melissa S. , O’Hern Patrick , Bliska Bryn , Sorkaç Altar , Nguyen Ken C. Q. , Cook Steven J. , Poulogiannis George , Atwood Walter J. , Hall David H. , Hart Anne C.
Published: July 2016

Significance

Spinal muscular atrophy (SMA) is a devastating motor neuron disease, caused by decreased levels of the ubiquitous survival motor neuron (SMN) protein. Despite the well-characterized role of SMN in pre-mRNA splicing, it remains unclear why SMA has a high carrier frequency (∼1:50 Caucasians) and why diminished SMN affects synaptic function. Here, we demonstrate for the first time, to our knowledge, that SMN depletion causes defects in endosomal trafficking that impair synaptic function. Additionally, diminished SMN in human cells reduced endocytosis-dependent viral infection. It is possible that decreased SMN function may increase resistance to infection. Our findings point to endocytic trafficking as a major player in SMA pathogenesis.
Genetic evidence for natural selection in humans in the contemporary United States
Authors: Beauchamp Jonathan P.
Published: July 2016

Significance

I leverage recent advances in molecular genetics to test directly whether genetic variants associated with a number of phenotypes have been under natural selection in the contemporary United States. My finding that natural selection has been slowly occurring for genetic variants associated with educational attainment and (suggestively, in females) for variants associated with age at menarche provides additional evidence that humans are still evolving—albeit slowly and at a rate that cannot account for more than a small fraction of the large changes that have occurred over the past few generations.
Psychological resilience and the gene regulatory impact of posttraumatic stress in Nepali child soldiers
Authors: Kohrt Brandon A. , Worthman Carol M. , Adhikari Ramesh P. , Luitel Nagendra P. , Arevalo Jesusa M. G. , Ma Jeffrey , McCreath Heather , Seeman Teresa E. , Crimmins Eileen M. , Cole Steven W.
Published: July 2016

Significance

Adverse life conditions are linked to increased expression of proinflammatory genes and reduced expression of antiviral genes. However, these findings have come from Western, educated, industrialized, rich, and democratic (WEIRD) societies. Therefore, we evaluated adversity-related gene regulation among former child soldiers in Nepal—a non-WEIRD population. We found that posttraumatic stress disorder (PTSD) and resilience were inversely and independently associated with gene regulation among a population exposed to war during childhood. The results suggest that gene regulation responses to adversity are not restricted to WEIRD contexts and they underscore the role of psychological resilience in determining the molecular impact of traumatic experiences. Promoting resilience, even in the absence of PTSD symptom reduction, may have benefits for physical and mental health.
How van der Waals interactions determine the unique properties of water
Authors: Morawietz Tobias , Singraber Andreas , Dellago Christoph , Behler Jörg
Published: July 2016

Significance

Despite its simple chemical formula, H
2
O, water is a complex substance with a variety of unusual properties resulting from its ability to form hydrogen bonds. A famous example for the anomalous behavior of water is the fact that it exhibits a density maximum at 4 °C. Here, we unravel the density anomaly of water on the molecular level using a powerful ab initio-based simulation technique. We show that weak van der Waals forces crucially modulate the flexibility of the hydrogen bond network, giving rise to the density maximum in water and causing ice to be less dense than the liquid.
Delayed mortality effects cut the malaria transmission potential of insecticide-resistant mosquitoes
Authors: Viana Mafalda , Hughes Angela , Matthiopoulos Jason , Ranson Hilary , Ferguson Heather M.
Published: July 2016

Significance

Insecticide resistance poses one of the greatest challenges to the control of malaria and other vector-borne diseases. Quantifying the magnitude of its impact is essential to ensure the sustainability of future control programs. Mosquito vectors are defined as “resistant” when insecticides are no longer able to kill them on contact. However, they may suffer longer-term impairment following insecticide exposure that reduces their ability to transmit disease. We show that even highly resistant strains of the major malaria vector
Anopheles gambiae
have their life span cut by ∼50% after exposure to long-lasting insecticidal nets (LLINs). These delayed effects are sufficient to reduce their malaria transmission potential by two-thirds and could partially explain why insecticide resistance is not inextricably associated with LLIN failure.
Unfolding the mechanism of the AAA+ unfoldase VAT by a combined cryo-EM, solution NMR study
Authors: Huang Rui , Ripstein Zev A. , Augustyniak Rafal , Lazniewski Michal , Ginalski Krzysztof , Kay Lewis E. , Rubinstein John L.
Published: July 2016

Significance

Cellular function is tightly regulated by large molecular assemblies such as the proteasome, which is involved in the removal of damaged or misfolded proteins. Proteasome substrates are unfolded by complexes such as valosin-containing protein-like ATPase of
Thermoplasma acidophilum
(VAT) via a process that is coupled to ATP hydrolysis. We used a combined electron cryomicroscopy (cryo-EM) and NMR analysis to show that VAT undergoes large, previously unidentified, conformational changes that are essential for substrate unfolding and to suggest a model by which the energy released upon ATP hydrolysis can be coupled to the unfolding process. Our approach demonstrates that cryo-EM/NMR studies offer the exciting potential of obtaining both structural and dynamic information that, together, can provide a detailed understanding of how molecular machines function.
Assignment of function to a domain of unknown function: DUF1537 is a new kinase family in catabolic pathways for acid sugars
Authors: Zhang Xinshuai , Carter Michael S. , Vetting Matthew W. , San Francisco Brian , Zhao Suwen , Al-Obaidi Nawar F. , Solbiati Jose O. , Thiaville Jennifer J. , de Crécy-Lagard Valérie , Jacobson Matthew P. , Almo Steven C. , Gerlt John A.
Published: July 2016

Significance

Domain of unknown function (DUF) families constitute 3,892 of the 16,295 families in the Pfam database (release 29.0). Given their biological importance, large-scale strategies are required to accomplish their functional assignments. Here, we illustrate an integrated “genomic enzymology” strategy to identify diverse functions within the DUF1537 family (PF07005). We combined high-throughput ligand screening results for transport system solute binding proteins with the synergetic analysis of sequence similarity networks and genome neighborhood networks to establish that the members of the DUF1537 family are novel ATP-dependent four-carbon sugar kinases. This study illustrates the utility of this strategy and enhances our knowledge of bacterial carbohydrate catabolism.
FoxO3 regulates neuronal reprogramming of cells from postnatal and aging mice
Authors: Ahlenius Henrik , Chanda Soham , Webb Ashley E. , Yousif Issa , Karmazin Jesse , Prusiner Stanley B. , Brunet Anne , Südhof Thomas C. , Wernig Marius
Published: July 2016

Significance

Direct reprogramming of nonneuronal cells into induced neuronal (iN) cells has been of great interest for its potential applications in neurological disease modeling. Although this approach is well-established using cells from embryonic and neonatal animals, its applicability for cells from adult and aged animals has remained unexplored. This study demonstrates that iN cells can be efficiently generated from aging animals, but that age-dependent roadblocks which depend on the transcription factor FoxO3 affect the reprogramming efficiency and functional maturation of iN cell properties. Eliminating these roadblocks may be useful for modeling age-related neurological disorders using iN cells.
Growing timescales and lengthscales characterizing vibrations of amorphous solids
Authors: Berthier Ludovic , Charbonneau Patrick , Jin Yuliang , Parisi Giorgio , Seoane Beatriz , Zamponi Francesco
Published: July 2016

Significance

Amorphous solids constitute most of solid matter but remain poorly understood. The recent solution of the mean-field hard-sphere glass former provides, however, deep insights into their material properties. In particular, this solution predicts a Gardner transition below which the energy landscape of glasses becomes fractal and the solid is marginally stable. Here we provide, to our knowledge, the first direct evidence for the relevance of a Gardner transition in physical systems. This result thus opens the way toward a unified understanding of the low-temperature anomalies of amorphous solids.
Mitotic protein kinase CDK1 phosphorylation of mRNA translation regulator 4E-BP1 Ser83 may contribute to cell transformation
Authors: Velásquez Celestino , Cheng Erdong , Shuda Masahiro , Lee-Oesterreich Paula J. , Pogge von Strandmann Lisa , Gritsenko Marina A. , Jacobs Jon M. , Moore Patrick S. , Chang Yuan
Published: July 2016

Significance

Eukaryotic translation initiation factor 4E-binding protein 1 (4E-BP1) hyperphosphorylation is implicated in various cancers. Mammalian target of rapamycin (mTOR) targeting of canonical sites—Thr37, Thr46, Ser65, and Thr70—inhibits 4E-BP1 translation repression activity and promotes protein synthesis, which in turn leads to overexpression of several cellular oncoproteins. In addition to the canonical sites, cyclin-dependent kinase 1 (CDK1) phosphorylates 4E-BP1 at Ser83 during mitosis, which interestingly does not affect translation. Rather, this phosphorylation site is permissive for Merkel cell polyomavirus small T viral oncoprotein-induced cell transformation. These findings shed light on a previously unidentified role for mitotic 4E-BP1 in cancer cell growth.
p53-Dependent DNA damage response sensitive to editing-defective tRNA synthetase in zebrafish
Authors: Song Youngzee , Shi Yi , Carland Tristan M. , Lian Shanshan , Sasaki Tomoyuki , Schork Nicholas J. , Head Steven R. , Kishi Shuji , Schimmel Paul
Published: July 2016

Significance

Although DNA damage is a well-known cause of disease, its connection, if any, to mistranslation is unclear. Here, we used an editing-defective tRNA synthetase to show how an editing defect in zebrafish leads to severe consequences during development and to a shortened overall life span of adult fish. These effects were p53-dependent and reflect a strong connection of mistranslation to the DNA damage response. In addition, deep sequencing of genomic DNA revealed that expression of the editing-defective tRNA synthetase was mutagenic. We suggest that the p53-dependent DNA damage response links translational and genomic fidelity to promote vertebrate homeostasis.
Multicellularity makes somatic differentiation evolutionarily stable
Authors: Wahl Mary E. , Murray Andrew W.
Published: July 2016

Significance

Unicellular species lack the nonreproductive somatic cell types that characterize complex multicellular organisms. We consider two alternative explanations: first, that the costs of lost reproductive potential never exceed the benefits of somatic cells in unicellular organisms; and second, that somatic cells may profit a unicellular population but leave it vulnerable to invasion by common mutants. We test these hypotheses using engineered yeast strains that permit direct comparisons of fitness and evolutionary stability between lifestyles. We find that the benefits of somatic cell production can exceed the costs in unicellular strains. Multicellular, soma-producing strains resist invasion by nondifferentiating mutants that overtake unicellular populations, supporting the theory that somatic differentiation is stabilized by population structure imposed by multicellularity.
Maintenance of normal blood pressure is dependent on IP3R1-mediated regulation of eNOS
Authors: Yuan Qi , Yang Jingyi , Santulli Gaetano , Reiken Steven R. , Wronska Anetta , Kim Mindy M. , Osborne Brent W. , Lacampagne Alain , Yin Yuxin , Marks Andrew R.
Published: July 2016

Significance

In this study, we demonstrate that type 1 inositol 1,4,5-trisphosphate receptor channels are critically involved in the activation of the calcineurin/nuclear factor of activated T cells (NFAT)/endothelial nitric oxide synthase signaling pathway in endothelial cells. This pathway plays an essential role in the maintenance of normal blood pressure, with important implications in the clinical scenario.
Effects of weaving laser on scanning laser-MAG hybrid welding characteristics of high-strength steel
Authors: Cai C. , Li L. , Tao W. , Chen X.
Published: July 2016

Scanning laser-MAG hybrid welding with weaving laser was developed for the bead-on-plate welding of high-strength steel. Weaving laser exerted little effect on the droplet transfer behaviour during the scanning laser-MAG hybrid welding process. In order to achieve the keyhole mode of laser welding, the weaving amplitude should be no more than 2 mm. The weld penetration decreased with the increasing weaving frequency. Compared to laser-MAG hybrid weld, the ratio of arc zone width to laser zone width decreased significantly. Scanning laser-MAG hybrid welding could suppress the porosity defects of weld efficiently. The optimal weaving frequency for the porosity defects suppression was 20 Hz. However, the porosity defects increased sharply with the weaving frequency of laser over 40 Hz. The impact-absorbed energy value of specimen fabricated by scanning laser-MAG hybrid welding was about 46 J, increased by about 31.4% compared to about 35 J of laser-MAG hybrid welding.
Labour force and unemployment in Arab countries: selected indicators
Authors: El-Khoury Gabi
Published: July 2016

This statistical file is concerned with the latest available data that might be useful in dealing with the issue of the labour force and unemployment in Arab countries and worldwide. Table 1 introduces data on the working-age populations, while Table 2 shows figures on the labour force participation rates. Table 3 provides statements on the percentage of children (between 5 and 14 years) who are working in Arab countries, while Table 4 presents figures on the labour force distribution by sector. Table 5 is concerned with data on the employment rates, while Table 6 presents data on labour distribution by level of education in selected Arab countries. Data on education outputs and labour market needs in selected Arab countries and on the perceptions of work and the labour market are shown in Tables 7 and 8 respectively.
Discrete somatic niches coordinate proliferation and migration of primordial germ cells via Wnt signaling
Authors: Cantú Andrea V. , Altshuler-Keylin Svetlana , Laird Diana J.
Published: July 2016

Inheritance depends on the expansion of a small number of primordial germ cells (PGCs) in the early embryo. Proliferation of mammalian PGCs is concurrent with their movement through changing microenvironments; however, mechanisms coordinating these conflicting processes remain unclear. Here, we find that PGC proliferation varies by location rather than embryonic age. Ror2 and Wnt5a mutants with mislocalized PGCs corroborate the microenvironmental regulation of the cell cycle, except in the hindgut, where Wnt5a is highly expressed. Molecular and genetic evidence suggests that Wnt5a acts via Ror2 to suppress β-catenin–dependent Wnt signaling in PGCs and limit their proliferation in specific locations, which we validate by overactivating β-catenin in PGCs. Our results suggest that the balance between expansion and movement of migratory PGCs is fine-tuned in different niches by the opposing β-catenin–dependent and Ror2-mediated pathways through Wnt5a. This could serve as a selective mechanism to favor early and efficient migrators with clonal dominance in the ensuing germ cell pool while penalizing stragglers.