bluuebunny/crossref_metadata_2025 huggingface dataset:
Temporal evolution of vorticity staircases in randomly strained two-dimensional vortices
Authors: Turner M. R.
Published: November 2014

The evolution of a Gaussian vortex subject to a weak-external-random n-fold multipolar strain field is examined using fully nonlinear simulations. The simulations show that at large Reynolds numbers, fine scale steps form at the periphery of the vortex, before merging, generally leaving one large step, which acts as a barrier between the vorticity within the coherent core and the surrounding, well mixed, “surf zone.” It is shown for n = 2 that the width and the number of fine scale steps which initially form at the periphery of the vortex is dependent on the strain parameters, but that the range of radial values for which steps initially occur is only dependent on n and the amplitude of the strain field. A criteria is developed which can predict this range of radial values using the linear stability results of Le Dizès [“Non-axisymmetric vortices in two-dimensional flows,” J. Fluid Mech. 406, 175 (2000)]. This criteria is based upon the perturbation vorticity needing to be larger than some fraction of the vorticity gradient to flatten the vortex profile. For n = 3 and 4, the radial step range is again predicted, and it is observed that for these higher wavenumbers the long lasting steps are narrower than the n = 2 case. For n = 4 the steps which form are so narrow that they do not persist very long before they are destroyed by the strain field and viscosity.
The laminar wake behind a 6:1 prolate spheroid at 45° incidence angle
Authors: Jiang Fengjian , Gallardo José P. , Andersson Helge I.
Published: November 2014

The wake behind a 6:1 prolate spheroid at 45° angle of attack has been studied. The three-dimensional unsteady Navier-Stokes equations have been solved numerically for Reynolds numbers Re = 50, 200, and 1000, where Re is based on the inflow velocity U0 and the minor axis D of the spheroid. The wake at the two lowest Reynolds numbers is steady and symmetric about the meridional plane. Even at Re = 1000 the near-wake, which is dominated by vortex sheets separated from the spheroid, is still steady and symmetric except in a very limited region of size 0.2D near the tip of the spheroid. However, the intermediate wake, which extends from 4D downstream of the spheroid, is distinctly asymmetric and exhibits local oscillations with an amplitude below 1% of U0. The intermediate part of the wake consists of a pair of counter-rotating vortices and the wake is deflected to the side of the strongest vortex, whereas the other vortex is partially wrapped around. It is conjectured that the wake at this particular Reynolds number is on the verge of becoming unsteady. Nevertheless, the forces and torques on the prolate spheroid show no sign whatsoever of asymmetry or unsteadiness. The resulting drag coefficients compare to within 30% with the Hölzer-Sommerfeld correlation.
Asymptotic state discrimination and a strict hierarchy in distinguishability norms
Authors: Chitambar Eric , Hsieh Min-Hsiu
Published: November 2014

In this paper, we consider the problem of discriminating quantum states by local operations and classical communication (LOCC) when an arbitrarily small amount of error is permitted. This paradigm is known as asymptotic state discrimination, and we derive necessary conditions for when two multipartite states of any size can be discriminated perfectly by asymptotic LOCC. We use this new criterion to prove a gap in the LOCC and separable distinguishability norms. We then turn to the operational advantage of using two-way classical communication over one-way communication in LOCC processing. With a simple two-qubit product state ensemble, we demonstrate a strict majorization of the two-way LOCC norm over the one-way norm.
Structure and effective interactions of comb polymer nanocomposite melts
Authors: Xu Qinzhi , Xu Mengjin , Feng Yancong , Chen Lan
Published: November 2014

In this work, the structure and effective interactions of branched comb polymer nanocomposite (PNC) melts are investigated by using the polymer reference interaction site model (PRISM) integral equation theory. It is observed that the nanoparticle contact (bridging) aggregation is formed when the nanoparticle-monomer attraction strength is relatively weak (large) in comb PNCs. The organization states of aggregation for the moderate nanoparticle-monomer attraction strength can be well suppressed by the comb polymer architecture, while the bridging structure for relatively large attraction is obviously promoted. With the increase of the particle volume fraction, the organization states of bridging-type structure become stronger and tighter; however, this effect is weaker than that of the nanoparticle-monomer attraction strength. When the particle volume fraction and moderate nanoparticle-monomer attraction strength are fixed, the effects of degree of polymerization, side chain number, side chain length, and nanoparticle-monomer size ratio on the organization states of PNC melts are not prominent and the nanoparticles can well disperse in comb polymer. All the observations indicate that the present PRISM theory can give a detailed description of the comb PNC melts and assist in future design control of new nanomaterials.
Manipulation of elastic waves by zero index metamaterials
Authors: Wang Ziyu , Wei Wei , Hu Ni , Min Rui , Pei Ling , Chen Yiwan , Liu Fengming , Liu Zhengyou
Published: November 2014

In this work, we investigated anti-plane transverse elastic waves transmission through a zero index metamaterials (ZIM) waveguide embedded with defect. Theoretical analysis and numerical simulations show that total transmission and total reflection of the impinging transverse elastic waves can be achieved by simply adjusting the parameters of the defect, and a ZIM waveguide embedded with a free-wall hole can be utilized as an elastic waves cloaking. Moreover, we present a two-dimensional (2D) phononic crystal (PC) to exhibit Dirac-like cones dispersion at the zone center. Effective medium theory finds that such PC can have effectively zero reciprocal of shear modulus and zero mass density, thus zero refractive index. Numerical simulations show that the PC system would be a good experimental candidate to achieve the intriguing transmission properties of the ZIM waveguide structure.
Electrical detection of ferromagnetic resonance in ferromagnet/n-GaAs heterostructures by tunneling anisotropic magnetoresistance
Authors: Liu C. , Boyko Y. , Geppert C. C. , Christie K. D. , Stecklein G. , Patel S. J. , Palmstrøm C. J. , Crowell P. A.
Published: November 2014

We observe a dc voltage peak at ferromagnetic resonance (FMR) in samples consisting of a single ferromagnetic (FM) layer grown epitaxially on the n-GaAs (001) surface. The FMR peak is detected as an interfacial voltage with a symmetric line shape and is present in samples based on various FM/n-GaAs heterostructures, including Co2MnSi/n-GaAs, Co2FeSi/n-GaAs, and Fe/n-GaAs. We show that the interface bias voltage dependence of the FMR signal is identical to that of the tunneling anisotropic magnetoresistance (TAMR) over most of the bias range. Furthermore, we show how the precessing magnetization yields a dc FMR signal through the TAMR effect and how the TAMR phenomenon can be used to predict the angular dependence of the FMR signal. This TAMR-induced FMR peak can be observed under conditions where no spin accumulation is present and no spin-polarized current flows in the semiconductor.
Contributed Review: Nuclear magnetic resonance core analysis at 0.3 T
Authors: Mitchell Jonathan , Fordham Edmund J.
Published: November 2014

Nuclear magnetic resonance (NMR) provides a powerful toolbox for petrophysical characterization of reservoir core plugs and fluids in the laboratory. Previously, there has been considerable focus on low field magnet technology for well log calibration. Now there is renewed interest in the study of reservoir samples using stronger magnets to complement these standard NMR measurements. Here, the capabilities of an imaging magnet with a field strength of 0.3 T (corresponding to 12.9 MHz for proton) are reviewed in the context of reservoir core analysis. Quantitative estimates of porosity (saturation) and pore size distributions are obtained under favorable conditions (e.g., in carbonates), with the added advantage of multidimensional imaging, detection of lower gyromagnetic ratio nuclei, and short probe recovery times that make the system suitable for shale studies. Intermediate field instruments provide quantitative porosity maps of rock plugs that cannot be obtained using high field medical scanners due to the field-dependent susceptibility contrast in the porous medium. Example data are presented that highlight the potential applications of an intermediate field imaging instrument as a complement to low field instruments in core analysis and for materials science studies in general.
Magnetic control of magnetohydrodynamic instabilities in tokamaks
Authors: Strait E. J.
Published: November 2014

Externally applied, non-axisymmetric magnetic fields form the basis of several relatively simple and direct methods to control magnetohydrodynamic (MHD) instabilities in a tokamak, and most present and planned tokamaks now include a set of non-axisymmetric control coils for application of fields with low toroidal mode numbers. Non-axisymmetric applied fields are routinely used to compensate small asymmetries (δB/B∼10−3 to 10−4) of the nominally axisymmetric field, which otherwise can lead to instabilities through braking of plasma rotation and through direct stimulus of tearing modes or kink modes. This compensation may be feedback-controlled, based on the magnetic response of the plasma to the external fields. Non-axisymmetric fields are used for direct magnetic stabilization of the resistive wall mode—a kink instability with a growth rate slow enough that feedback control is practical. Saturated magnetic islands are also manipulated directly with non-axisymmetric fields, in order to unlock them from the wall and spin them to aid stabilization, or position them for suppression by localized current drive. Several recent scientific advances form the foundation of these developments in the control of instabilities. Most fundamental is the understanding that stable kink modes play a crucial role in the coupling of non-axisymmetric fields to the plasma, determining which field configurations couple most strongly, how the coupling depends on plasma conditions, and whether external asymmetries are amplified by the plasma. A major advance for the physics of high-beta plasmas (β = plasma pressure/magnetic field pressure) has been the understanding that drift-kinetic resonances can stabilize the resistive wall mode at pressures well above the ideal-MHD stability limit, but also that such discharges can be very sensitive to external asymmetries. The common physics of stable kink modes has brought significant unification to the topics of static error fields at low beta and resistive wall modes at high beta. These and other scientific advances, and their application to control of MHD instabilities, will be reviewed with emphasis on the most recent results and their applicability to ITER.
Dry-mass sensing for microfluidics
Authors: Müller T. , White D. A. , Knowles T. P. J.
Published: November 2014

We present an approach for interfacing an electromechanical sensor with a microfluidic device for the accurate quantification of the dry mass of analytes within microchannels. We show that depositing solutes onto the active surface of a quartz crystal microbalance by means of an on-chip microfluidic spray nozzle and subsequent solvent removal provides the basis for the real-time determination of dry solute mass. Moreover, this detection scheme does not suffer from the decrease in the sensor's quality factor and the viscous drag present if the measurement is performed in a liquid environment, yet allows solutions to be analysed. We demonstrate the sensitivity and reliability of our approach by controlled deposition of nanogram levels of salt and protein from a micrometer-sized channel.
InGaAs/GaAsP superlattice solar cells with reduced carbon impurity grown by low-temperature metal-organic vapor phase epitaxy using triethylgallium
Authors: Fujii Hiromasa , Toprasertpong Kasidit , Sodabanlu Hassanet , Watanabe Kentaroh , Sugiyama Masakazu , Nakano Yoshiaki
Published: November 2014

In this paper, we investigated the effects of carbon incorporation on photovoltaic performance of InGaAs/GaAsP superlattice (SL) solar cells grown by low-temperature MOVPE (LT-MOVPE), which is required for stable SL growth on vicinal substrates. Using trimethylgallium (TMGa) as the gallium precursor, methyl radicals formed by its pyrolysis tend to be absorbed on the surface at low temperature, causing severe carbon incorporation and p-type background doping. High background carrier concentration flattens the band-lineup of the intrinsic region and blocks the carrier transport across the SLs, and resulted in serious degradation of photocurrent. Intentional sulfur doping to cancel out the background doping and hence to recover the built-in field greatly improved the cell performance, but was found to require very precise control of doping level to achieve an exact compensation doping condition. Use of triethylgallium (TEGa) instead of TMGa much reduced the carbon incorporation at low temperature and significantly enhanced the photocurrent extraction without sulfur doping treatment. By thinning GaAsP barriers to 3 nm to facilitate efficient tunneling transport, a 50-period SL cell with bandgap of 1.22 eV grown on 6°-miscut substrates achieved 1.13 times higher efficiency with 31% current enhancement as middle cell performance than a GaAs reference cell.
Backward Raman amplification in the Langmuir wavebreaking regime
Authors: Toroker Z. , Malkin V. M. , Fisch N. J.
Published: November 2014

In plasma-based backward Raman amplifiers, the output pulse intensity increases with the input pump pulse intensity, as long as the Langmuir wave mediating energy transfer from the pump to the seed pulse remains intact. However, at high pump intensity, the Langmuir wave breaks, at which point the amplification efficiency may no longer increase with the pump intensity. Numerical simulations presented here, employing a one-dimensional Vlasov-Maxwell code, show that, although the amplification efficiency remains high when the pump only mildly exceeds the wavebreaking threshold, the efficiency drops precipitously at larger pump intensities.
Unexpected structural softening of interstitial boron solid solution WB3+x
Authors: Wu Hao , Sun Hong , Chen Changfeng
Published: November 2014

Using first-principles calculations, we reveal an unexpected structural softening in a recently proposed WB3+x structural model that tries to explain the X-ray diffraction, high resolution TEM, pressure dependence of the normalized lattice c/a ratio, and hardness experimental results of the synthesized tungsten boride compounds with a nominal composition WB4. We show that the interstitial boron in WB3+x, which was proposed to strengthen the covalent bonding network, unexpectedly weakens the atomic bonding, resulting in a large reduction of its indentation strength to well below that of WB3. This is in direct contradiction to the experimental results showing that synthesized WB4 is harder than WB3. The unusual structural softening is attributed to the unique three-center covalent bonding formed by the interstitial boron atoms that can easily deform under indentation. Our results show that the proposed interstitial boron solid solution WB3+x structure is incompatible with experimental results, which calls for further investigations to determine the crystal structure of the synthesized WB4.
Comment on “Effect of particle size and strain on phase stability of (Li0.06Na0.94)NbO3” [J. Appl. Phys. 115, 174104 (2014)]
Authors: Nalbandyan V. B.
Published: November 2014

It is shown that the powder XRD pattern attributed to the new “post perovskite” phase of the title niobate prepared by ball-milling actually corresponds to the cubic yttria stabilized zirconia, material of the milling balls.
Bolometric detection of magnetoplasma resonances in microwave absorption by two-dimensional electron systems based on doping layer conductivity measurements in GaAs/AlGaAs heterostructures
Authors: Dorozhkin S. I. , Sychev D. V. , Kapustin A. A.
Published: November 2014

We have implemented a new bolometric method to detect resonances in magneto-absorption of microwave radiation by two-dimensional electron systems (2DES) in selectively doped GaAs/AlGaAs heterostructures. Radiation is absorbed by the 2DES and the thermally activated conductivity of the doping layer supplying electrons to the 2DES serves as a thermometer. The resonant absorption brought about by excitation of the confined magnetoplasma modes appears as peaks in the magnetic field dependence of the low-frequency impedance measured between the Schottky gate and 2DES.
Electron and hole photoemission detection for band offset determination of tunnel field-effect transistor heterojunctions
Authors: Li Wei , Zhang Qin , Bijesh R. , Kirillov Oleg A. , Liang Yiran , Levin Igor , Peng Lian-Mao , Richter Curt A. , Liang Xuelei , Datta S. , Gundlach David J. , Nguyen N. V.
Published: November 2014

We report experimental methods to ascertain a complete energy band alignment of a broken-gap tunnel field-effect transistor based on an InAs/GaSb hetero-junction. By using graphene as an optically transparent electrode, both the electron and hole barrier heights at the InAs/GaSb interface can be quantified. For a Al2O3/InAs/GaSb layer structure, the barrier height from the top of the InAs and GaSb valence bands to the bottom of the Al2O3 conduction band is inferred from electron emission whereas hole emissions reveal the barrier height from the top of the Al2O3 valence band to the bottom of the InAs and GaSb conduction bands. Subsequently, the offset parameter at the broken gap InAs/GaSb interface is extracted and thus can be used to facilitate the development of predicted models of electron quantum tunneling efficiency and transistor performance.
Bi-induced band gap reduction in epitaxial InSbBi alloys
Authors: Rajpalke M. K. , Linhart W. M. , Yu K. M. , Birkett M. , Alaria J. , Bomphrey J. J. , Sallis S. , Piper L. F. J. , Jones T. S. , Ashwin M. J. , Veal T. D.
Published: November 2014

The properties of molecular beam epitaxy-grown InSb1−xBix alloys are investigated. Rutherford backscattering spectrometry shows that the Bi content increases from 0.6% for growth at 350 °C to 2.4% at 200 °C. X-ray diffraction indicates Bi-induced lattice dilation and suggests a zinc-blende InBi lattice parameter of 6.626 Å. Scanning electron microscopy reveals surface InSbBi nanostructures on the InSbBi films for the lowest growth temperatures, Bi droplets at intermediate temperatures, and smooth surfaces for the highest temperature. The room temperature optical absorption edge was found to change from 172 meV (7.2 μm) for InSb to ∼88 meV (14.1 μm) for InSb0.976Bi0.024, a reduction of ∼35 meV/%Bi.
Reduced electrical impedance of SiO2, deposited through focused ion beam based systems, due to impurity percolation
Authors: Faraby H. , DiBattista M. , Bandaru P. R.
Published: November 2014

The electrical impedance (both the resistive and capacitive aspects) of focused ion beam (FIB) deposited SiO2 has been correlated to the specific composition of the ion beam, in Ga- and Xe-based FIB systems. The presence of electrically percolating Ga in concert with carbon (inevitably found as the product of the hydrocarbon precursor decomposition) has been isolated as a major cause for the observed decrease in the resistivity of the deposited SiO2. Concomitant with the decreased resistivity, an increased capacitance and effective dielectric constant was observed. Our study would be useful to understand the constraints to the deposition of high quality insulator films through FIB based methodologies.
The realization of ferro-ferrimagnetic transition and half-metallicity in half-Heusler CoMnGa alloy
Authors: Wang L. Y. , Dai X. F. , Wang X. T. , Liu X. F. , Li P. P. , Cui Y. T. , Liu E. K. , Wang W. H. , Wu G. H. , Liu G. D.
Published: November 2014

We theoretically predicted that half-Heusler CoMnGa alloy to be half-metallic ferrimagnet at the equilibrium lattice parameter. With the lattice expansion, a local energy minimum occurs at a larger lattice parameter where CoMnGa alloy is in a metastable ferromagnetic state. However, a ferro-ferrimagnetic transition (Fo-Fi-T) is not observed in experiment. We found the Co-Mn antisites can induce the Fo-Fi-T by adjusting the driving force of magnetic transition and the energy barrier. The antisites are sensitive to the preparation methods and annealing temperatures. The highly ordered CoMnGa is achieved by annealing at 1073 K. The Fo-Fi-T occurs in a sample annealed at 1083 K.
Phase-space jets drive transport and anomalous resistivity
Authors: Lesur M. , Diamond P. H. , Kosuga Y.
Published: November 2014

In the presence of wave dissipation, phase-space structures spontaneously emerge in nonlinear Vlasov dynamics. These structures include not only well-known self-trapped vortices (holes) but also elongated filaments, resembling jets, as reported in this work. These jets are formed by straining due to interacting holes. Jets are highly anisotropic, and connect low and high velocity regions over a range larger than the electron thermal velocity. Jets survive long enough for particles to scatter between low and high phase-space density regions. Jets are found to contribute significantly to electron redistribution, velocity-space transport, and anomalous resistivity.
Electrowetting on dielectric device with crescent electrodes for reliable and low-voltage droplet manipulation
Authors: Xu Xiaowei , Sun Lining , Chen Liguo , Zhou Zhaozhong , Xiao Junjian , Zhang Yuliang
Published: November 2014

Digital microfluidics based on electrowetting on dielectric is an emerging popular technology that manipulates single droplets at the microliter or even the nanoliter level. It has the unique advantages of rapid response, low reagent consumption, and high integration and is mainly applied in the field of biochemical analysis. However, currently, this technology still has a few problems, such as high control voltage, low droplet velocity, and continuity in flow, limiting its application. In this paper, through theoretical analysis and numerical simulation, it is deduced that a drive electrode with a crescent configuration can reduce the driving voltage. The experimental results not only validate this deduction but also indicate that crescent electrode can improve the droplet motion continuity and the success in split rate.
Fabrication of triangular nanobeam waveguide networks in bulk diamond using single-crystal silicon hard masks
Authors: Bayn I. , Mouradian S. , Li L. , Goldstein J. A. , Schröder T. , Zheng J. , Chen E. H. , Gaathon O. , Lu M. , Stein A. , Ruggiero C. A. , Salzman J. , Kalish R. , Englund Dirk
Published: November 2014

A scalable approach for integrated photonic networks in single-crystal diamond using triangular etching of bulk samples is presented. We describe designs of high quality factor (Q = 2.51 × 106) photonic crystal cavities with low mode volume (Vm = 1.062 × (λ/n)3), which are connected via waveguides supported by suspension structures with predicted transmission loss of only 0.05 dB. We demonstrate the fabrication of these structures using transferred single-crystal silicon hard masks and angular dry etching, yielding photonic crystal cavities in the visible spectrum with measured quality factors in excess of Q = 3 × 103.
Side-to-side alignment of gold nanorods with polarization-free characteristic for highly reproducible surface enhanced Raman scattering
Authors: Dai Zhigao , Xiao Xiangheng , Wu Wei , Liao Lei , Mei Fei , Yu Xuefeng , Guo Shishang , Ying Jianjian , Ren Feng , Jiang Changzhong
Published: November 2014

A large-batch method for fabricating large-area, low-cost, and flexible surface enhanced Raman scattering (SERS) arrays with Au nanorods (NRs) using an inkjet printing technique was presented. The Raman mapping results of 441 points reveal clearly that the Au NRs arrays are a well reproducible SERS substrate for the detection of various chemicals. The neighbouring Au NRs aligned side-to-side nanoclusters were formed on printer paper as a highly reproducible SERS platform due to its polarization-free properties which were further confirmed by theoretical calculations of the electric field enhancement change about only two. Therefore, the SERS signals can be more evenly enhanced.
Enhanced thermal stability of Ag nanorods through capping
Authors: Bachenheimer Lou , Elliott Paul , Stagon Stephen , Huang Hanchen
Published: November 2014

Ag nanorods may serve as sensors in the detection of trace amounts of chemical agents, even single molecules, through surface enhanced Raman spectroscopy (SERS). However, thermal coarsening of Ag nanorods near room temperature limits their applications. This letter proposes the use of a thin oxide capping layer to enhance the thermal stability of Ag nanorods beyond 100 °C. Using electron microscopy characterization and SERS tests, the authors show that the proposed method is effective in stabilizing both morphology and sensitivity of Ag nanorods. The results of this work extend the applicability of Ag nanorods as chemical sensors to higher temperatures.
Optimization and simulation of MEMS rectilinear ion trap
Authors: Gang Huang , Yi Chen , Fei Tang , Li-Tao Liu , Xiaohao Wang
Published: November 2014

In this paper, the design of a MEMS rectilinear ion trap was optimized under simulated conditions. The size range of the MEMS rectilinear ion trap’s electrodes studied in this paper is measured at micron scale. SIMION software was used to simulate the MEMS rectilinear ion trap with different sizes and different radio-frequency signals. The ion-trapping efficiencies of the ion trap under these different simulation conditions were obtained. The ion-trapping efficiencies were compared to determine the performance of the MEMS rectilinear ion trap in different conditions and to find the optimum conditions. The simulation results show that for the ion trap at micron scale or smaller, the optimized length–width ratio was 0.8, and a higher frequency of radio-frequency signal is necessary to obtain a higher ion-trapping efficiency. These results have a guiding role in the process of developing MEMS rectilinear ion traps, and great application prospects in the research fields of the MEMS rectilinear ion trap and the MEMS mass spectrometer.
Two-dimensional electron gas in monolayer InN quantum wells
Authors: Pan W. , Dimakis E. , Wang G. T. , Moustakas T. D. , Tsui D. C.
Published: November 2014

We report in this letter experimental results that confirm the two-dimensional nature of the electron systems in a superlattice structure of 40 InN quantum wells consisting of one monolayer of InN embedded between 10 nm GaN barriers. The electron density and mobility of the two-dimensional electron system (2DES) in these InN quantum wells are 5 × 1015 cm−2 (or 1.25 × 1014 cm−2 per InN quantum well, assuming all the quantum wells are connected by diffused indium contacts) and 420 cm2/Vs, respectively. Moreover, the diagonal resistance of the 2DES shows virtually no temperature dependence in a wide temperature range, indicating the topological nature of the 2DES.
Multi-particle trapping and manipulation by a high-frequency array transducer
Authors: Yoon Changhan , Kang Bong Jin , Lee Changyang , Kim Hyung Ham , Shung K. Kirk
Published: November 2014

We report the multiple micro-particle trapping and manipulation by a single-beam acoustic tweezer using a high-frequency array transducer. A single acoustic beam generated by a 30 MHz ultrasonic linear array transducer can entrap and transport multiple micro-particles located at the main lobe and the grating lobes. The distance between trapped particles can be adjusted by changing the transmit arrangement of array-based acoustic tweezers and subsequently the location of grating lobes. The experiment results showed that the proposed method can trap and manipulate multiple particles within a range of hundreds of micrometers. Due to its simplicity and low acoustic power, which is critical to protect cells from any thermal and mechanical damages, the technique may be used for transportation of cells in cell biology, biosensors, and tissue engineering.
Image-based estimation of oat panicle development using local texture patterns
Authors: Boyle Roger , Corke Fiona , Howarth Catherine
Published: November 2014

Flowering time varies between and within species, profoundly influencing reproductive fitness in wild plants and productivity in crop plants. The time of flowering, therefore, is an important statistic that is regularly collected as part of breeding programs and phenotyping experiments to facilitate comparison of genotypes and treatments. Its automatic detection would be highly desirable. We present significant progress on an approach to this problem in oats (Avena sativa L.), an underdeveloped cereal crop of increasing importance. Making use of the many thousands of images of oat plants we have available, spanning different genotypes and treatments, we observe that during flowering, panicles (the flowering structures) betray particular intensity patterns that give an identifiable texture that is distinctive and discriminatory with respect to the main plant body and can be used to determine the time of flowering. This texture can be located by a filter, trained as a form of local pattern. This training phase identifies the best parameters of such a filter, which usefully discovers the scale of the panicle spikelets. The results demonstrate the success of the filter. We proceed to suggest and evaluate an approach to using the filter as a growth stage detector. Preliminary results show very good correspondence with hand-measured ground truth, and are amenable to improvement in several ways. Future work will build on this initial success and will go on to locate fully mature panicles, which have a different appearance, and assess whether this approach can be extended to a broader range of plants.
Spatial and temporal patterns in the distribution of large bivalves in a permanently open temperate estuary: implications for management
Authors: Kendrick Alan J. , Rule Michael J. , Lavery Paul S. , Hyndes Glenn A.
Published: November 2014

To inform management, baseline ecological studies in estuaries must be implemented at spatial scales that accommodate both environmental gradients and likely anthropogenic pressures. We describe fine-scale spatial patterns in the abundances and size structure of large infaunal bivalves inhabiting shallow sand habitats in the lower reaches of a relatively undisturbed, permanently open, temperate estuary. Sampling over 3 years at 19 sites during the autumn, when freshwater influence was minimal, revealed that Soletellina alba, Wallucina assimilis and Paphies elongata were consistently the most abundant of nine species present. Although most abundant near the ocean entrance, S. alba was distributed widely and shells of differing lengths, and presumably ages, were present at most sites, suggesting that this species recruited continuously throughout the study area when conditions were appropriate. In contrast, W. assimilis and P. elongata occurred only near or in the entrance channel of the Nornalup Inlet in areas where seagrass rhizomes may grow and where oceanic influences caused relatively turbulent conditions, respectively. Sediment structure appeared to exert only a moderate and intermittent influence on the bivalve assemblage at some sites where particularly large grain sizes occurred. This study provides important baseline information on the distribution and abundance of large bivalves in this estuary. These species are likely to be important in the trophic ecology of this system and are potential indicators of disturbance and ecosystem health.
Long-term dynamics of the zooplankton community during large salinity fluctuations in a coastal lagoon
Authors: Araújo Luciana Rabelo , Lopes Paloma Marinho , Santangelo Jayme Magalhães , Esteves Francisco de Assis , Bozelli Reinaldo Luiz
Published: November 2014

Aquatic coastal systems are affected by high fluctuations in salinity and the zooplankton may rely on dispersal or dormancy to recolonise these environments. Here, we analysed the long-term dynamics of the zooplankton community over 6 years during large salinity fluctuations in a coastal lagoon (Garças Lagoon, Brazil) and the effect of salinity on the hatching patterns of the resting egg bank. We hypothesised that salinity is the main driving factor of the zooplankton community structure, and that increases in salinity reduce the species richness and the abundance of hatchlings. Multiple regression analysis showed that salinity was associated negatively with species richness in the open water, whereas total phosphorus and chlorophyll-a concentrations were negatively and positively related to abundance respectively. Redundancy analysis demonstrated that temporally structured environmental variables (total phosphorus and salinity) were important for zooplankton composition. Periods of low salinity allowed the presence of freshwater organisms, changing the zooplankton composition over the years. However, our hatchling experiment showed a depauperate resting egg bank. Overall, our results showed a strong influence of salinity on the structure and dynamics of the zooplankton at Garças Lagoon, and that the resting egg bank likely plays a minor role in the zooplankton colonisation during low-salinity periods.
Oscillatory AAA
+
ATPase Knk1 constitutes a novel morphogenetic pathway in fission yeast
Authors: Scheffler Kathleen , Recouvreux Pierre , Paoletti Anne , Tran Phong T.
Published: November 2014

Significance

We describe a novel pathway controlling fission yeast cell morphogenesis depending on Knk1, a member of the conserved ATPases associated with various cellular activities (AAA
+
) family regulating important cellular processes in all organisms and often functioning in unfolding, degradation, or dissociation of multimeric complexes. Deletion of
knk1
(kink, encoded by SPBC947.01/alf1) founds a new class of morphogenesis mutants exhibiting sudden changes in directional growth. Knk1 performs oscillations between the two cell ends at a periodicity different from the reported cell division cycle 42 oscillations. We conclude that at least two oscillatory systems may coexist in fission yeast to control cell morphogenesis. We speculate that oscillatory properties could represent a key feature of morphogenetic factors to control the growth machinery in a dynamic manner and achieve an accurate definition of cell shape.
Silk-based resorbable electronic devices for remotely controlled therapy and in vivo infection abatement
Authors: Tao Hu , Hwang Suk-Won , Marelli Benedetto , An Bo , Moreau Jodie E. , Yang Miaomiao , Brenckle Mark A. , Kim Stanley , Kaplan David L. , Rogers John A. , Omenetto Fiorenzo G.
Published: November 2014

Significance

We present the demonstration of in vivo operation of a subcutaneously implanted, resorbable electronic device. The remotely controlled device was wirelessly activated after implantation, successfully eliminating infection, and subsequently dissolving in the surrounding tissue. This approach is a first step for the development of a class of implantable, technological, biomedical devices that resorb harmlessly, eliminating the need for retrieval after use.
Electrostatic transition state stabilization rather than reactant destabilization provides the chemical basis for efficient chorismate mutase catalysis
Authors: Burschowsky Daniel , van Eerde André , Ökvist Mats , Kienhöfer Alexander , Kast Peter , Hilvert Donald , Krengel Ute
Published: November 2014

Significance

Chorismate mutase (CM) is a textbook model for enzyme catalysis. Although it promotes a simple unimolecular reaction, the origins of its 2-million–fold rate acceleration have been debated for decades. The relative importance of electrostatic transition state stabilization versus ground state destabilization has been a particularly contentious issue. High-resolution crystallographic snapshots of an engineered CM variant and its complexes with substrate, transition state analog, and product now provide strong experimental evidence that properly positioned active-site charges are essential in this system and that preorganization of the substrate in a reactive conformation contributes relatively little to catalysis. A proper understanding of the role of electrostatics in this and other enzymes is important for ongoing efforts to design new enzymes de novo.
UbcH7 regulates 53BP1 stability and DSB repair
Authors: Han Xiangzi , Zhang Lei , Chung Jinsil , Mayca Pozo Franklin , Tran Amanda , Seachrist Darcie D. , Jacobberger James W. , Keri Ruth A. , Gilmore Hannah , Zhang Youwei
Published: November 2014

Significance

Double-strand break (DSB) repair sits at the core of genome stability maintenance. Abnormalities in the repair pathway often lead to the development of cancers and resistance to anticancer therapies. Tumor suppressor p53-binding protein 1 (53BP1), a protein critical in regulating DSB repair, is reduced in advanced breast tumors. Furthermore, low levels of 53BP1 correlated with poor prognosis and resistance to chemotherapy. Thus, the protein level of 53BP1 is important for therapeutic response. However, mechanisms regulating 53BP1 protein levels are poorly understood. Here we report a previously unidentified mechanism regulating the protein level of 53BP1, specifically, ubiquitin-conjugating enzyme H7 (UbcH7)-dependent ubiquitination and proteasome-dependent degradation. We further propose an innovative hypothesis that increasing the protein level of 53BP1 enhances the effect of radiotherapy or chemotherapy through suppressing faithful DSB repair.
Collapse of cooperation in evolving games
Authors: Stewart Alexander J. , Plotkin Joshua B.
Published: November 2014

Significance

This study offers a new perspective on an age-old question: When does cooperation emerge in populations? Two-player games used to study this question produce an array of counterintuitive results. And yet a consensus has emerged that, in an evolving population, cooperation tends to triumph over cheating––through reciprocity and generosity. But, what happens when players can influence not only their tendencies to cooperate, but also the rewards they reap for cooperation? We analyze coevolution of strategies and payoffs and find that, as individuals maximize the benefits of cooperation, they often pave the way for its collapse. Our analysis provides a framework for studying the coevolution of games and strategies, and suggests that maintaining cooperation may be more difficult than previously thought.
MACROD2
overexpression mediates estrogen independent growth and tamoxifen resistance in breast cancers
Authors: Mohseni Morassa , Cidado Justin , Croessmann Sarah , Cravero Karen , Cimino-Mathews Ashley , Wong Hong Yuen , Scharpf Rob , Zabransky Daniel J. , Abukhdeir Abde M. , Garay Joseph P. , Wang Grace M. , Beaver Julia A. , Cochran Rory L. , Blair Brian G. , Rosen D. Marc , Erlanger Bracha , Argani Pedram , Hurley Paula J. , Lauring Josh , Park Ben Ho
Published: November 2014

Significance

Despite the widespread use and success of tamoxifen for treating ER-positive breast cancers, overcoming resistance to this drug remains an unmet need in clinical breast oncology. The results presented in this study demonstrate that overexpression of a novel gene,
MACROD2
, can mediate tamoxifen resistance and estrogen independent growth in human breast cancers, and that amplification of
MACROD2
in primary breast tumors is associated with worse overall survival.
Early social exposure in wild chimpanzees: Mothers with sons are more gregarious than mothers with daughters
Authors: Murray Carson M. , Lonsdorf Elizabeth V. , Stanton Margaret A. , Wellens Kaitlin R. , Miller Jordan A. , Goodall Jane , Pusey Anne E.
Published: November 2014

Significance

Early social experience is critical to developing appropriate adult behavior. Mothers are particularly important social partners but may also facilitate or restrict access to others. Studies investigating human parental facilitation are limited and confounded by culture. Comparative studies therefore provide invaluable insight into how parents provide social opportunities for offspring. We investigated maternal subgrouping patterns by infant sex in one of our closest relatives, chimpanzees, and found that mothers with sons were more gregarious. Infants themselves may influence patterns later in infancy, but differences were apparent early in life, when mothers and infants are in almost constant contact. Furthermore, mothers with sons associated more with adult males, potential behavioral models, early in life. These differences foreshadow sex-typical adult social behavior.
Acquisition of an immunosuppressive protumorigenic macrophage phenotype depending on c-Jun phosphorylation
Authors: Hefetz-Sela Simona , Stein Ilan , Klieger Yair , Porat Rinnat , Sade-Feldman Moshe , Zreik Farid , Nagler Arnon , Pappo Orit , Quagliata Luca , Dazert Eva , Eferl Robert , Terracciano Luigi , Wagner Erwin F. , Ben-Neriah Yinon , Baniyash Michal , Pikarsky Eli
Published: November 2014

Significance

Tumor-associated macrophages are often associated with poor prognosis, but the molecular cues that impart the change in macrophage phenotypes are mostly unclear. Our findings identify c-Jun N-terminal phosphorylation as a key mediator of macrophage education and point to a recruitment of immunosuppressive regulatory T cells as a possible effector protumorigenic mechanism. This cross-talk between adaptive and innate immune responses occurs before overt tumorigenesis, reversing the classic paradigm of initiation and promotion. Our findings raise the possibility that targeting immune checkpoints could be effective for tumor prevention in chronic inflammatory diseases.
A common brain network links development, aging, and vulnerability to disease
Authors: Douaud Gwenaëlle , Groves Adrian R. , Tamnes Christian K. , Westlye Lars Tjelta , Duff Eugene P. , Engvig Andreas , Walhovd Kristine B. , James Anthony , Gass Achim , Monsch Andreas U. , Matthews Paul M. , Fjell Anders M. , Smith Stephen M. , Johansen-Berg Heidi
Published: November 2014

Significance

Many evolutionary–developmental models have attempted to relate development and aging, with one popular hypothesis proposing that healthy age-related brain decline mirrors developmental maturation. But this elegant hypothesis has so far lacked clear and direct data to support it. Here, we describe intrinsic, entirely data-driven evidence that healthy brain degeneration and developmental process mirror one another in certain brain regions. Specifically, a data-driven decomposition of structural brain images in 484 healthy participants reveals a network of mainly higher-order regions that develop relatively late during adolescence, demonstrate accelerated degeneration in old age, and show heightened vulnerability to disorders that impact on brain structure during adolescence and aging. These results provide a fundamental link between development, aging, and disease processes in the brain.
Catecholamine-induced lipolysis causes mTOR complex dissociation and inhibits glucose uptake in adipocytes
Authors: Mullins Garrett R. , Wang Lifu , Raje Vidisha , Sherwood Samantha G. , Grande Rebecca C. , Boroda Salome , Eaton James M. , Blancquaert Sara , Roger Pierre P. , Leitinger Norbert , Harris Thurl E.
Published: November 2014

Significance

Adipose tissue maintains metabolic homeostasis during fasting and fed conditions. When nutrients are plentiful, anabolic signaling is mediated by insulin, stimulating adipocytes to take up glucose for energy storage. In the absence of nutrients, catabolic signaling initiates lipolysis, or the release of lipids for energy use, and is mediated by catecholamines. These opposing pathways are evolutionarily conserved and prevent futile cycling, but can lead to metabolic disorders such as insulin resistance if not properly regulated. Here we define a novel mechanism whereby lipolysis inhibits insulin-stimulated glucose uptake in adipocytes. This signaling mechanism likely contributes to insulin resistance when lipolysis is active, such as during high stress or obesity, and this new understanding may lead to novel treatment approaches for hyperglycemia.
Anomalously large isotope effect in the glass transition of water
Authors: Gainaru Catalin , Agapov Alexander L. , Fuentes-Landete Violeta , Amann-Winkel Katrin , Nelson Helge , Köster Karsten W. , Kolesnikov Alexander I. , Novikov Vladimir N. , Richert Ranko , Böhmer Roland , Loerting Thomas , Sokolov Alexei P.
Published: November 2014

Significance

Water is by far the most important and intriguing liquid. Despite the relative simplicity of its chemical structure there are many puzzling properties of water that remain the focus of active discussions. Our studies revealed an unusually strong isotope effect and an extraordinarily slow temperature variation of the structural relaxation of water at low temperatures. We show that the anomalous behavior of deeply supercooled water is affected by quantum effects, usually considered negligible for the glass transition. However, in water they are significant owing to the small mass of the molecule. The presented results might considerably change our understanding of water dynamics at low temperatures.
Early Holocene chicken domestication in northern China
Authors: Xiang Hai , Gao Jianqiang , Yu Baoquan , Zhou Hui , Cai Dawei , Zhang Youwen , Chen Xiaoyong , Wang Xi , Hofreiter Michael , Zhao Xingbo
Published: November 2014

Significance

Ancient DNA analysis is a powerful tool to reveal the geographical origins of domesticated species. Here we obtained ancient mtDNA sequences from the earliest archaeological chicken bones from northern China as early as 10,000 y ago. Combined analyses of our ancient sequences with a large dataset of published modern and ancient chicken mtDNA sequences suggest that northern China was likely one of several regions of chicken domestication and provide further insights into the process of human-mediated spread of chickens across the globe. Our results not only suggest that the oldest archaeological chicken bones recovered so far are indeed from ancestors of domestic chickens, but also provide further evidence for one of the earliest, mixed agricultural complexes in the world.
Osteoinductivity of engineered cartilaginous templates devitalized by inducible apoptosis
Authors: Bourgine Paul E. , Scotti Celeste , Pigeot Sebastien , Tchang Laurent A. , Todorov Atanas , Martin Ivan
Published: November 2014

Significance

It has been previously reported that hypertrophic cartilage tissues engineered from human mesenchymal stromal cells can efficiently remodel in vivo into bone organs, recapitulating developmental steps of endochondral ossification. We have here demonstrated that the extracellular matrix (ECM) of such engineered cartilage, even in the absence of a living cell component, retains frankly osteoinductive properties. The use of an apoptosis-driven devitalization technique revealed the importance of preserving the ECM integrity and, in particular, the embedded factors to trigger the regenerative process. Although exemplified in a skeletal context, our work outlines the general paradigm of cell-based but cell-free off-the-shelf materials capable of activating endogenous cells toward the formation of specific tissues.
Structure-guided U2AF
65
variant improves recognition and splicing of a defective pre-mRNA
Authors: Agrawal Anant A. , McLaughlin Krystle J. , Jenkins Jermaine L. , Kielkopf Clara L.
Published: November 2014

Significance

The essential U2AF
65
protein recognizes a splice site signal that is frequently mutated in inherited human diseases. Herein we show that reduced U2AF
65
binding is a molecular consequence of splice site mutations that commonly underlie human genetic disease. We demonstrate for a proof-of-principle case that structure-guided U2AF
65
variants are a feasible tool to evoke disease-relevant changes in pre-mRNA splicing.