bluuebunny/crossref_metadata_2025 huggingface dataset:
The d 3Π state of LiRb
Authors: Stevenson I. C. , Blasing D. B. , Altaf A. , Chen Y. P. , Elliott D. S.
Published: December 2016

We report our spectroscopic studies of the d 3Π state of ultra-cold 7Li85Rb using resonantly enhanced multi-photon ionization and depletion spectroscopy with bound-to-bound transitions originating from the metastable a 3Σ+ state. We evaluate the potential of this state for use as the intermediate state in a stimulated-Raman-adiabatic-passage transfer scheme from triplet Feshbach LiRb molecules to the X 1Σ+ ground state and find that the lowest several vibrational levels possess the requisite overlap with initial and final states, as well as convenient energies. Using depletion measurements, we measured the well depth and spin-orbit splitting. We suggest possible pathways for short-range photoassociation using deeply bound vibrational levels of this electronic state.
Potential energy landscape of the apparent first-order phase transition between low-density and high-density amorphous ice
Authors: Giovambattista Nicolas , Sciortino Francesco , Starr Francis W. , Poole Peter H.
Published: December 2016

The potential energy landscape (PEL) formalism is a valuable approach within statistical mechanics to describe supercooled liquids and glasses. Here we use the PEL formalism and computer simulations to study the pressure-induced transformations between low-density amorphous ice (LDA) and high-density amorphous ice (HDA) at different temperatures. We employ the ST2 water model for which the LDA-HDA transformations are remarkably sharp, similar to what is observed in experiments, and reminiscent of a first-order phase transition. Our results are consistent with the view that LDA and HDA configurations are associated with two distinct regions (megabasins) of the PEL that are separated by a potential energy barrier. At higher temperature, we find that low-density liquid (LDL) configurations are located in the same megabasin as LDA, and that high-density liquid (HDL) configurations are located in the same megabasin as HDA. We show that the pressure-induced LDL-HDL and LDA-HDA transformations occur along paths that interconnect these two megabasins, but that the path followed by the liquid is different from the path followed by the amorphous solid. At higher pressure, we also study the liquid-to-ice-VII first-order phase transition, and find that the behavior of the PEL properties across this transition is qualitatively similar to the changes found during the LDA-HDA transformation. This similarity supports the interpretation that the LDA-HDA transformation is a first-order phase transition between out-of-equilibrium states. Finally, we compare the PEL properties explored during the LDA-HDA transformations in ST2 water with those reported previously for SPC/E water, for which the LDA-HDA transformations are rather smooth. This comparison illuminates the previous work showing that, at accessible computer times scales, a liquid-liquid phase transition occurs in the case of ST2 water, but not for SPC/E water.
A sparsity-based iterative algorithm for reconstruction of micro-CT images from highly undersampled projection datasets obtained with a synchrotron X-ray source
Authors: Melli S. Ali , Wahid Khan A. , Babyn Paul , Cooper David M. L. , Gopi Varun P.
Published: December 2016

Synchrotron X-ray Micro Computed Tomography (Micro-CT) is an imaging technique which is increasingly used for non-invasive in vivo preclinical imaging. However, it often requires a large number of projections from many different angles to reconstruct high-quality images leading to significantly high radiation doses and long scan times. To utilize this imaging technique further for in vivo imaging, we need to design reconstruction algorithms that reduce the radiation dose and scan time without reduction of reconstructed image quality. This research is focused on using a combination of gradient-based Douglas-Rachford splitting and discrete wavelet packet shrinkage image denoising methods to design an algorithm for reconstruction of large-scale reduced-view synchrotron Micro-CT images with acceptable quality metrics. These quality metrics are computed by comparing the reconstructed images with a high-dose reference image reconstructed from 1800 equally spaced projections spanning 180°. Visual and quantitative-based performance assessment of a synthetic head phantom and a femoral cortical bone sample imaged in the biomedical imaging and therapy bending magnet beamline at the Canadian Light Source demonstrates that the proposed algorithm is superior to the existing reconstruction algorithms. Using the proposed reconstruction algorithm to reduce the number of projections in synchrotron Micro-CT is an effective way to reduce the overall radiation dose and scan time which improves in vivo imaging protocols.
Interaction dynamics of gap flow with vortex-induced vibration in side-by-side cylinder arrangement
Authors: Liu Bin , Jaiman Rajeev K.
Published: December 2016

A numerical investigation of the vortex-induced vibration (VIV) in a side-by-side circular cylinder arrangement has been performed in a two-dimensional laminar flow environment. One of the cylinders is elastically mounted and only vibrates in the transverse direction, while its counterpart remains stationary in a uniform flow stream. When the gap ratio is sufficiently small, the flip-flopping phenomenon of the gap flow can be an additional time-dependent interference to the flow field. This phenomenon was reported in the experimental work of Bearman and Wadcock [“The interaction between a pair of circular cylinders normal to a stream,” J. Fluid Mech. 61(3), 499–511 (1973)] in a side-by-side circular cylinder arrangement, in which the gap flow deflects toward one of the cylinders and switched its sides intermittently. Albeit one of the two cylinders is free to vibrate, the flip-flop of a gap flow during VIV dynamics can still be observed outside the lock-in region. The exact moments of the flip-flop phenomenon due to spontaneous symmetry breaking are observed in this numerical study. The significant characteristic vortex modes in the near-wake region are extracted via dynamic modal analysis and the interference between the gap flow and VIV is found to be mutual. In a vibrating side-by-side arrangement, the lock-in region with respect to reduced velocity becomes narrower due to the interference from its stationary counterpart. The frequency lock-in occurs and ends earlier than that of an isolated vibrating circular cylinder subjected to an identical flow environment. Similar to a tandem cylinder arrangement, in the post-lock-in region, the maximum vibration amplitudes are escalated compared with those of an isolated circular cylinder configuration. On the other hand, subjected to the influence from VIV, the biased gap flow deflects toward the vibrating cylinder quasi-stably during the frequency lock-in process. This behavior is different from the reported bi-stable regime in a stationary side-by-side arrangement. The analyses show that the flip-flop is associated with a characteristic low flip-flopping frequency, which is dependent upon the values of gap ratio, Reynolds number and the symmetry of the gap flow strength in a time-averaged sense. The disappearance of the flip-flop during the frequency lock-in of vibrating side-by-side arrangements is further investigated through a critical-point concept and a critical vortex merging distance.
Non-isothermal extrudate swell
Authors: Konaganti Vinod Kumar , Derakhshandeh Maziar , Ebrahimi Marzieh , Mitsoulis Evan , Hatzikiriakos Savvas G.
Published: December 2016

The non-isothermal extrudate swell of a high molecular weight high-density polyethylene (HDPE) in long capillary and slit dies is studied numerically (ANSYS POLYFLOW®) using an integral K-BKZ constitutive model including crystallization kinetics, determined experimentally. The Nakamura model is used for crystallization of the HDPE, where the crystallization rate parameter is evaluated by using the well-known Ziabicki equation. This non-isothermal extrudate swell phenomenon is simulated using the pseudo-time integral K-BKZ model with the Wagner damping function along with the differential form of the Nakamura model to account for the crystallization of the extrudate. The swell measurements were carried out under non-isothermal conditions by extruding the polymer melt at 200 °C through long capillary and slit dies to ambient air at 25 °C, 110 °C, and 200 °C. The numerical results are found to be in excellent agreement with experimental observations.
Seeking maximum linearity of transfer functions
Authors: Silva Filipi N. , Comin Cesar H. , Costa Luciano da F.
Published: December 2016

Linearity is an important and frequently sought property in electronics and instrumentation. Here, we report a method capable of, given a transfer function (theoretical or derived from some real system), identifying the respective most linear region of operation with a fixed width. This methodology, which is based on least squares regression and systematic consideration of all possible regions, has been illustrated with respect to both an analytical (sigmoid transfer function) and a simple situation involving experimental data of a low-power, one-stage class A transistor current amplifier. Such an approach, which has been addressed in terms of transfer functions derived from experimentally obtained characteristic surface, also yielded contributions such as the estimation of local constants of the device, as opposed to typically considered average values. The reported method and results pave the way to several further applications in other types of devices and systems, intelligent control operation, and other areas such as identifying regions of power law behavior.
Effect of restricted geometry on the superconducting properties of low-melting metals (Review Article)
Authors: Kumzerov Yu. A. , Naberezhnov A. A.
Published: December 2016

This is a review of results from studies of the effect of artificially restricted geometry (the size effect) on the superconducting properties of nanoparticles of low-melting metals (Hg, Pb, Sn, In). Restricted geometrical conditions are created by embedding molten metals under high pressure into nanoporous matrices of two types: channel structures based on chrysotile asbestos and porous alkali-borosilicate glasses. Chrysotile asbestos is a system of parallel nanotubes with channel diameters ranging from 2 to 20 nm and an aspect ratio (channel length to diameter) of up to 107. The glasses are a random dendritic three-dimensional system of interconnected channels with a technologically controllable mean diameter of 2–30 nm. Temperature dependences of the resistance and heat capacity in the region of the superconducting transition and the dependences of the critical temperature on the mean pore diameter are obtained. The critical magnetic fields are also determined.
Metal-insulator transitions and magnetic susceptibility in doped cuprate compounds
Authors: Dzhumanov S. , Kurbanov U. T. , Khudayberdiev Z. S. , Hafizov A. R.
Published: December 2016

Results are presented from a theoretical study of the possibility of hole carrier localization and metal-insulator transitions which show up in the temperature dependences of the magnetic susceptibility χ(T) of doped copper-oxide (cuprate) compounds. The criteria for metal-insulator transitions owing to strong hole-lattice interactions and the formation of very narrow polaron bands in these materials with reduced doping level x are analyzed. It is shown that these kinds of metal-insulator transitions occur in underdoped La2-xSrxCuO4 and YBa2Cu3O6+x cuprates (i.e., for x ranging from 0.04 to 0.12). The characteristic temperature dependences χ(T) of the HTSC cuprates are found for different doping levels. These results are in good agreement with experimental data on metal-insulator transitions and the magnetic susceptibility of the HTSC cuprates.
Phase behavior of decorated soft disks in two dimensions
Authors: Borówko M. , Rżysko W. , Sokołowski S. , Staszewski T.
Published: December 2016

Molecular dynamics simulations are used to investigate the phase behavior of disks decorated with small ligands in two-dimensional films. We consider disks with four ligands, which are fixed at vertices of a square or slide over the circle delimiting the core. For selected model systems, phase diagrams are evaluated and discussed. We show that ligand mobility can change the topology of phase diagrams. In particular, it can affect fluid-solid transitions, changing the solid phase symmetry. Moreover, the mobility of ligands can either hamper or facilitate crystallization.
A DFT+U study of the structural, electronic, magnetic, and mechanical properties of cubic and orthorhombic SmCoO3
Authors: Olsson Emilia , Aparicio-Anglès Xavier , de Leeuw Nora H.
Published: December 2016

SmCoO3 is a perovskite material that has gained attention as a potential substitute for La1−xSrxMnO3−d as a solid oxide fuel cell cathode. However, a number of properties have remained unknown due to the complexity of the material. For example, we know from experimental evidence that this perovskite exists in two different crystal structures, cubic and orthorhombic, and that the cobalt ion changes its spin state at high temperatures, leading to a semiconductor-to-metal transition. However, little is known about the precise magnetic structure that causes the metallic behavior or the spin state of the Co centers at high temperature. Here, we therefore present a systematic DFT+U study of the magnetic properties of SmCoO3 in order to determine what magnetic ordering is the one exhibited by the metallic phase at different temperatures. Similarly, mechanical properties are difficult to measure experimentally, which is why there is a lack of data for the two different phases of SmCoO3. Taking advantage of our DFT calculations, we have determined the mechanical properties from our calculated elastic constants, finding that both polymorphs exhibit similar ductility and brittleness, but that the cubic structure is harder than the orthorhombic phase.
Water dynamics in rigid ionomer networks
Authors: Osti N. C. , Etampawala T. N. , Shrestha U. M. , Aryal D. , Tyagi M. , Diallo S. O. , Mamontov E. , Cornelius C. J. , Perahia D.
Published: December 2016

The dynamics of water within ionic polymer networks formed by sulfonated poly(phenylene) (SPP), as revealed by quasi-elastic neutron scattering (QENS), is presented. These polymers are distinguished from other ionic macromolecules by their rigidity and therefore in their network structure. QENS measurements as a function of temperature as the fraction of ionic groups and humidity were varied have shown that the polymer molecules are immobile while absorbed water molecules remain dynamic. The water molecules occupy multiple sites, either bound or loosely constrained, and bounce between the two. With increasing temperature and hydration levels, the system becomes more dynamic. Water molecules remain mobile even at subzero temperatures, illustrating the applicability of the SPP membrane for selective transport over a broad temperature range.
Quantum electron-vibrational dynamics at finite temperature: Thermo field dynamics approach
Authors: Borrelli Raffaele , Gelin Maxim F.
Published: December 2016

Quantum electron-vibrational dynamics in molecular systems at finite temperature is described using an approach based on the thermo field dynamics theory. This formulation treats temperature effects in the Hilbert space without introducing the Liouville space. A comparison with the theoretically equivalent density matrix formulation shows the key numerical advantages of the present approach. The solution of thermo field dynamics equations with a novel technique for the propagation of tensor trains (matrix product states) is discussed. Numerical applications to model spin-boson systems show that the present approach is a promising tool for the description of quantum dynamics of complex molecular systems at finite temperature.
The angularly resolved O 1s ion-yield spectrum of O2 revisited
Authors: Püttner R. , Ueda K.
Published: December 2016

The high-resolution photoabsorption spectrum of O2 below the O 1sσ−1 ionization threshold has been reanalyzed by using a sophisticated fit approach. For the vibrational substates of the O 1sσu−1(4∑u−)3sσg(3∑u−) Rydberg state Fano lineshapes are observed indicating an interaction with the O 1sσg−1(4∑g−)3σu∗(3∑u−) core-to-valence excited state. In the angularly resolved ion-yield spectrum recorded at 90° relative to the polarization direction of the synchrotron radiation clear evidence for the O 1sσg−1(2∑g−)3σu∗(3∑u−) and the O 1sσu−1(2∑u−)3sσg(3∑u−) state was found. This observation clearly suggests thatΛ, the projection of total orbital angular momentum on the molecular axis, is not well separated in the angularly resolved ion-yield spectrum due to a partial breakdown of the axial-recoil approximation for these transitions.
Mass, momentum, and energy flux conservation for nonlinear wave-wave interaction
Authors: Liu Zhen , Lin Zhiliang , Tao Longbin
Published: December 2016

A fully nonlinear solution for bi-chromatic progressive waves in water of finite depth in the framework of the homotopy analysis method (HAM) is derived. The bi-chromatic wave field is assumed to be obtained by the nonlinear interaction of two monochromatic wave trains that propagate independently in the same direction before encountering. The equations for the mass, momentum, and energy fluxes based on the accurate high-order homotopy series solutions are obtained using a discrete integration and a Fourier series-based fitting. The conservation equations for the mean rates of the mass, momentum, and energy fluxes before and after the interaction of the two nonlinear monochromatic wave trains are proposed to establish the relationship between the steady-state bi-chromatic wave field and the two nonlinear monochromatic wave trains. The parametric analysis on ε1 and ε2, representing the nonlinearity of the bi-chromatic wave field, is performed to obtain a sufficiently small standard deviation Sd, which is applied to describe the deviation from the conservation state (Sd = 0) in terms of the mean rates of the mass, momentum, and energy fluxes before and after the interaction. It is demonstrated that very small standard deviation from the conservation state can be achieved. After the interaction, the amplitude of the primary wave with a lower circular frequency is found to decrease; while the one with a higher circular frequency is found to increase. Moreover, the highest horizontal velocity of the water particles underneath the largest wave crest, which is obtained by the nonlinear interaction between the two monochromatic waves, is found to be significantly higher than the linear superposition value of the corresponding velocity of the two monochromatic waves. The present study is helpful to enrich and deepen the understanding with insight to steady-state wave-wave interactions.
Infrared laser ablation of polymeric nanocomposites: A study of surface structure and plume formation
Authors: Bartolucci S. F. , Miller M. J. , Warrender J. M.
Published: December 2016

The behavior of carbon nanotube composites subjected to laser pulse heating with a 1070 nm variable pulse duration laser has been studied. Previous work has shown that carbon nanotube composites form a protective network on the surface of a composite, which reduces heat input to the underlying polymer and slows mass loss. In this work, we have studied the interaction between the incident laser and the plume formed above the composite. We have correlated these interactions with features observed in the time-resolved mass loss data and confirmed them with observations using high-speed video of the laser irradiations. Beam interactions were studied as a function of laser irradiance and nanotube content. It is shown that beam-plume interactions occur for the carbon nanotube composites and that the interactions occur at shorter pulse durations for increased nanotube content and laser irradiance. When we eliminate beam-plume interaction through alteration of the sample orientation relative to the incident beam, we are able to elucidate the individual contributions of the carbon nanotube surface network and the plume to the observed decrease in mass loss after laser irradiation. We examine the plume content using microscopy and Raman spectroscopy and show that greater beam absorption occurs when there is a higher graphitic content in the plume.
Modulation axis performs circular motion in a 45° dual-drive symmetric photoelastic modulator
Authors: Li K. W. , Wang L. M. , Zhang R. , Wang Z. B.
Published: December 2016

A 45° dual-drive symmetric photoelastic modulator is demonstrated. Two piezoelectric actuators are connected to a symmetric photoelastic crystal at an angle of 45°. When the amplitudes of the stress standing waves induced by the two piezoelectric actuators are equal and the phase difference between the two stress standing waves is π2, the modulation axis performs circular motion with a frequency of half of the photoelastic modulator’s resonant frequency, while the retardation remains a constant that is determined at the driving voltage amplitudes. This reveals a new polarization modulation method. We have theoretically analyzed and experimentally observed the new polarization modulation, and the retardation calibration is also reported.
High-speed switching of biphoton delays through electro-optic pump frequency modulation
Authors: Odele Ogaga D. , Lukens Joseph M. , Jaramillo-Villegas Jose A. , Imany Poolad , Langrock Carsten , Fejer Martin M. , Leaird Daniel E. , Weiner Andrew M.
Published: December 2016

The realization of high-speed tunable delay control has received significant attention in the scene of classical photonics. In quantum optics, however, such rapid delay control systems for entangled photons have remained undeveloped. Here for the first time, we demonstrate rapid (2.5 MHz) modulation of signal-idler arrival times through electro-optic pump frequency modulation. Our technique applies the quantum phenomenon of nonlocal dispersion cancellation along with pump frequency tuning to control the relative delay between photon pairs. Chirped fiber Bragg gratings are employed to provide large amounts of dispersion which result in biphoton delays exceeding 30 ns. This rapid delay modulation scheme could be useful for on-demand single-photon distribution in addition to quantum versions of pulse position modulation.
Retarding field analyzer for the EAST plasma boundary
Authors: Li Y. L. , Xu G. S. , Xiao C. , Wang H. Q. , Yan N. , Wan B. N. , Chen L. , Liu Y. L. , Zhang H. , Zhang W. , Wang L. , Hu G. H. , Chen R. , Xu J. C. , Ye Y. , Li J.
Published: December 2016

A novel bi-directional Retarding Field Analyzer (RFA) probe has been installed on a fast reciprocating drive system on the Experimental Advanced Superconducting Tokamak (EAST) to measure the ion temperature and fast electron fluxes. A Langmuir probe assembly was added on the top of the RFA head to control the RFA position relative to the last closed flux surface and to have a possibility to measure the electron density and temperature as well. Except the ion temperature, the fast electron fluxes from both ion and electron drift sides have been measured during lower hybrid current drive. The RFA probe has been also used to measure the fast electrons associated with edge localized modes (ELMs), indicating their substantial presence in the scrape-off-layer plasma of EAST.
Cherenkov terahertz surface plasmon excitation by an electron beam over an ultrathin metal film
Authors: Kumar Pawan , Kumar Rajeev , Rajouria Satish Kumar
Published: December 2016

The mechanism of Cherenkov excitation of terahertz (THz) surface plasma wave (SPW), by a relativistic electron beam propagating over an ultrathin metal film deposited on glass, is investigated. The SPW field falls off exponentially in vacuum as well as glass, while the surface plasmon resonant frequency is lowered by the reduction of film thickness. The SPW field causes density bunching of the beam leading to current modulation and generation of THz radiation via the Cherenkov interaction. The frequency of the THz decreases with the energy of the beam, whereas the growth rate increases.
Controlling third harmonic generation with gammadion-shaped chiral metamaterials
Authors: Zhang Chi , Li Zhi-Qin , Yang Xin , Chen Zhuo , Wang Zhenlin
Published: December 2016

We theoretically investigated third harmonic generation (THG) from planar chiral metamaterials consisting of a square array of gammadion-shaped metal-insulator-metal multilayered nanostructures. We show that there exists strong circular dichroism (CD) for THG on the proposed chiral metamaterials. We also demonstrate that geometrically mirroring the gammadion -shaped meta-atoms can result in reversal of the THG-CD effect. Based on these CD effects in the optical nonlinear regime, we propose a design of a Fresnel zone plate (FZP) for intense focusing of the THG signals, in which adjacent zones of the FZP consist of gammadions with mirror symmetry and generate circularly polarized THG with opposite handedness. Furthermore, we demonstrate that the relative phase of the THG can be continuously changed by rotating the gammadion around its rotational axis, which could be used in the FZP to control the polarization of the output THG signals.
Dynamics of bow-tie shaped bursting: Forced pendulum with dynamic feedback
Authors: Hongray Thotreithem , Balakrishnan Janaki
Published: December 2016

A detailed study is performed on the parameter space of the mechanical system of a driven pendulum with damping and constant torque under feedback control. We report an interesting bow-tie shaped bursting oscillatory behaviour, which is exhibited for small driving frequencies, in a certain parameter regime, which has not been reported earlier in this forced system with dynamic feedback. We show that the bursting oscillations are caused because of a transition of the quiescent state to the spiking state by a saddle-focus bifurcation, and because of another saddle-focus bifurcation, which leads to cessation of spiking, bringing the system back to the quiescent state. The resting period between two successive bursts (Trest) is estimated analytically.
Single snapshot multiple frequency modulated imaging of subsurface optical properties of turbid media with structured light
Authors: Xu M. , Cao Zili , Lin Weihao , Chen Xinlin , Zheng Longfei , Zeng Bixin
Published: December 2016

We report a novel demodulation method that enables single snapshot wide field imaging of optical properties of turbid media in the Spatial Frequency Domain (SFD). This Single Snapshot Multiple frequency Demodulation (SSMD) method makes use of the orthogonality of harmonic functions to extract the modulation transfer function (MTF) at multiple modulation frequencies simultaneously from a single structured-illuminated image at once. The orientation, frequency, and amplitude of each modulation can be set arbitrarily subject to the limitation of the implementation device. We first validate and compare SSMD to the existing demodulation methods by numerical simulations. The performance of SSMD is then demonstrated with experiments on both tissue mimicking phantoms and in vivo for recovering optical properties by comparing to the standard three-phase demodulation approach. The results show that SSMD increases significantly the data acquisition speed and reduces motion artefacts. SSMD exhibits excellent noise suppression in imaging as well at the rate proportional to the square root of the number of pixels contained in its kernel. SSMD is ideal in the implementation of a real-time spatial frequency domain imaging platform and will open up SFDI for vast applications in imaging and monitoring dynamic turbid medium and processes.
On the generation of magnetic field enhanced microwave plasma line
Authors: Chen Longwei , Zhao Ying , Wu Kenan , Wang Qi , Meng Yuedong , Ren Zhaoxing
Published: December 2016

Microwave linear plasmas sustained by surface waves have attracted much attention due to the potential abilities to generate large-scale and uniform non-equilibrium plasmas. An external magnetic field was generally applied to enhance and stabilize plasma sources because the magnetic field decreased the electron losses on the wall. The effects of magnetic field on the generation and propagation mechanisms of the microwave plasma were tentatively investigated based on a 2-D numerical model combining a coupled system of Maxwell's equations and continuity equations. The mobility of electrons and effective electric conductivity of the plasma were considered as a full tensor in the presence of magnetic field. Numerical results indicate that both cases of magnetic field in the axial-direction and radial-direction benefit the generation of a high-density plasma; the former one allows the microwave to propagate longer in the axis direction compared to the latter one. The time-averaged power flow density and the amplitude of the electric field on the inner rod of coaxial waveguide attenuate with the propagation of the microwave for both cases of with and without external magnetic field. The attenuation becomes smaller in the presence of appropriately higher axial-direction magnetic field, which allows more microwave energies to transmit along the axial direction. Meanwhile, the anisotropic properties of the plasma, like electron mobility, in the presence of the magnetic field confine more charged particles in the direction of the magnetic field line.
Diagnostics of laser-produced plasmas based on the analysis of intensity ratios of He-like ions X-ray emission
Authors: Ryazantsev S. N. , Skobelev I. Yu. , Faenov A. Ya. , Pikuz T. A. , Higginson D. P. , Chen S. N. , Revet G. , Béard J. , Portugall O. , Soloviev A. A. , Grum-Grzhimailo A. N. , Fuchs J. , Pikuz S. A.
Published: December 2016

In this paper, we detail the diagnostic technique used to infer the spatially resolved electron temperatures and densities in experiments dedicated to investigate the generation of magnetically collimated plasma jets. It is shown that the relative intensities of the resonance transitions in emitting He-like ions can be used to measure the temperature in such recombining plasmas. The intensities of these transitions are sensitive to the plasma density in the range of 1016–1020 cm−3 and to plasma temperature ranges from 10 to 100 eV for ions with a nuclear charge Zn ∼ 10. We show how detailed calculations of the emissivity of F VIII ions allow to determine the parameters of the plasma jets that were created using ELFIE ns laser facility (Ecole Polytechnique, France). The diagnostic and analysis technique detailed here can be applied in a broader context than the one of this study, i.e., to diagnose any recombining plasma containing He-like fluorine ions.
A spherical hohlraum design with tetrahedral 4 laser entrance holes and high radiation performance
Authors: Jiang Shaoen , Jing Longfei , Huang Yunbao , Li Haiyan , Huang Tianxuan , Ding Yongkun
Published: December 2016

As usual cylindrical hohlraum with double laser ring cones may lead to serious laser-plasma interaction, such as the simulated Raman scatter and cross-beam energy transfer effect, spherical hohlraum with octahedral 6 Laser Entrance Holes (LEHs) and single cone laser beams, was investigated and reported to have a consistent high radiation symmetry during the whole implosion process. However, it has several potential challenges such as the smaller space left for diagnosis and the assembly of centrally located capsule. In this paper, based on the view-factor model, we investigate the radiation symmetry and the drive temperature on the capsule located in the spherical hohlraum with tetrahedral 4 LEHs and single cone laser beams, since there is more available space for laser disposition and diagnosis. Then, such target is optimized on the laser beam pointing direction to achieve a high radiation performance, i.e., the radiation symmetry and drive temperature on the capsule. Finally, an optimal spherical hohlraum with optimal laser beam pointing has been demonstrated and compared with the spherical hohlraum with octahedral 6 LEHs. The resulting radiation symmetry and the drive temperature shows that it has almost a similar radiation symmetry (the radiation asymmetry variation is no more than 0.2%), and higher drive temperature (the temperature has been increased by 1.73%, and an additional 133 kJ energy of 2 MJ energy for fusion can be saved).
Experimental demonstration of performance of a vertical axis marine current turbine in a river
Authors: Lundin Staffan , Forslund Johan , Goude Anders , Grabbe Mårten , Yuen Katarina , Leijon Mats
Published: December 2016

An experimental station for marine current power has been installed in a river. The station comprises a vertical axis turbine with a direct-driven permanent magnet synchronous generator. In measurements of steady-state operation in varying flow conditions, performance comparable to that of turbines designed for significantly higher flow speeds is achieved, demonstrating the viability of electricity generation in low speed (below 1.5 m/s) marine currents.
Unraveling the strain state of GaN down to single nanowires
Authors: Auzelle Thomas , Biquard Xavier , Bellet-Amalric Edith , Fang Zhihua , Roussel Hervé , Cros Ana , Daudin Bruno
Published: December 2016

GaN nanowires (NWs) grown by molecular beam epitaxy are usually assumed free of strain in spite of different individual luminescence signatures. To ascertain this usual assumption, the c/a of a GaN NW assembly has been characterized using both X-ray diffraction and Raman spectroscopy, with scaling the measurement down to the single NW. Free-standing single NWs have been observed free of strain—defined as [c/a−(c/a)o]/(c/a)o—within the experimental accuracy amounting to 1.25 × 10−4. However, in the general case, a significant portion of the NWs is coalesced, generating an average tensile strain that can be partly released by detaching the NWs from their substrates. It is concluded that at the scale of the single NW, the free surface and the residual doping do not generate a significant strain and only coalescence does.
Chimera states in a network-organized public goods game with destructive agents
Authors: Kouvaris Nikos E. , Requejo Rubén J. , Hizanidis Johanne , Díaz-Guilera Albert
Published: December 2016

We found that a network-organized metapopulation of cooperators, defectors, and destructive agents playing the public goods game with mutations can collectively reach global synchronization or chimera states. Global synchronization is accompanied by a collective periodic burst of cooperation, whereas chimera states reflect the tendency of the networked metapopulation to be fragmented in clusters of synchronous and incoherent bursts of cooperation. Numerical simulations have shown that the system's dynamics switches between these two steady states through a first order transition. Depending on the parameters determining the dynamical and topological properties, chimera states with different numbers of coherent and incoherent clusters are observed. Our results present the first systematic study of chimera states and their characterization in the context of evolutionary game theory. This provides a valuable insight into the details of their occurrence, extending the relevance of such states to natural and social systems.
Universality in freezing of an asymmetric drop
Authors: Ismail Md Farhad , Waghmare Prashant R.
Published: December 2016

We present the evidence of universality in conical tip formation during the freezing of arbitrary-shaped sessile droplets. The focus is to demonstrate the relationship between this universality and the liquid drop shape. We observe that, in the case of asymmetric drops, this universal shape is achieved when the tip reconfigures by changing its location, which subsequently alters the frozen drop shape. The proposed “two-triangle” model quantifies the change in the tip configuration as a function of the asymmetry of the drop that shows a good agreement with the experimental evidence. Finally, based on the experimental and theoretical exercise, we propose the scaling dependence between the variations in the tip configuration and the asymmetry of the drop.
Communication: Length-dependent thermopower of single-molecule junctions
Authors: Zimbovskaya Natalya A.
Published: December 2016

In the present work, we theoretically study the length dependence of thermopower of a single-molecule junction with a chain-like molecular bridge of an arbitrary length using a tight-binding model. We analyze conditions bringing a nonlinear growth of the thermopower accompanying the extension of the bridge length. Also, we show that the thermopower may decrease with increasing molecular length provided that the molecular bridge is sufficiently long.
The physics mechanisms of the weakly coherent mode in the Alcator C-Mod Tokamak
Authors: Liu Z. X. , Xu X. Q. , Gao X. , Hubbard A. E. , Hughes J. W. , Walk J. R. , Theiler C. , Xia T. Y. , Baek S. G. , Golfinopoulos T. , Whyte D. , Zhang T. , Li J. G.
Published: December 2016

The weakly coherent mode (WCM) in I-mode has been studied by a six-field two-fluid model based on the Braginskii equations under the BOUT++ framework for the first time. The calculations indicate that a tokamak pedestal exhibiting a WCM is linearly unstable to drift Alfven wave (DAW) instabilities and the resistive ballooning mode. The nonlinear simulation shows promising agreement with the experimental measurements of the WCM. The shape of the density spectral and location of the spectral peak of the dominant toroidal number mode n = 20 agrees with the experimental data from reflectometry. The simulated mode propagates in electron diamagnetic direction is consistent with the results from the magnetic probes in the laboratory frame, a large ratio of particle to heat diffusivity is consistent with the distinctive experimental feature of I-mode, and the value of the simulated χe at the edge is in the range of experimental errors of χeff from the experiment. The prediction of the WCM shows that free energy is mainly provided by the electron pressure gradient, which gives guidance for pursuing future I-mode studies.
Gamma motor neurons survive and exacerbate alpha motor neuron degeneration in ALS
Authors: Lalancette-Hebert Melanie , Sharma Aarti , Lyashchenko Alexander K. , Shneider Neil A.
Published: December 2016

Significance

Clinical and pathological hallmarks shared by various familial and sporadic forms of amyotrophic lateral sclerosis (ALS) suggest common underlying mechanisms of disease. Using a series of ALS mouse models, we demonstrate that one shared feature of ALS is the selective sparing of gamma motor neurons (γ-MNs), which innervate muscle spindles and regulate primary proprioceptive afferent (I
A
) feedback on alpha motor neurons (α-MNs). Genetic evidence presented here implicates this major excitatory input in the selective degeneration of α-MNs in ALS. Functional elimination of I
A
inputs or partial elimination of γ-MNs is protective in superoxide dismutase-1 (SOD1) mutant mice, suggesting that surviving γ-MNs contribute to α-MN loss by increasing muscle afferent-mediated excitation. This study highlights the role of synaptic connectivity and circuit function in motor neuron disease.
Understanding the nature of atmospheric acid processing of mineral dusts in supplying bioavailable phosphorus to the oceans
Authors: Stockdale Anthony , Krom Michael D. , Mortimer Robert J. G. , Benning Liane G. , Carslaw Kenneth S. , Herbert Ross J. , Shi Zongbo , Myriokefalitakis Stelios , Kanakidou Maria , Nenes Athanasios
Published: December 2016

Significance

Mineral dust is the most important external source of phosphorus (P), a key nutrient controlling phytoplankton productivity and carbon uptake, to the offshore ocean. The bioavailable P in dust exhibits considerable and poorly understood variability. Detailed laboratory experiments elucidate and quantify the major processes controlling P dissolution in the atmosphere. Dust exposure to acids is the main driver of P mineral transformations, and a simple direct proportionality is found between the amount of bioavailable P dissolved from the dust and acid exposure. Simulations suggest that dust acidification increases leachable P over large areas of the globe and explains much of its variability in important oceanic areas where primary productivity is limited by this nutrient (e.g., North Central Atlantic, Mediterranean).
Measuring spectroscopy and magnetism of extracted and intracellular magnetosomes using soft X-ray ptychography
Authors: Zhu Xiaohui , Hitchcock Adam P. , Bazylinski Dennis A. , Denes Peter , Joseph John , Lins Ulysses , Marchesini Stefano , Shiu Hung-Wei , Tyliszczak Tolek , Shapiro David A.
Published: December 2016

Significance

Magnetotactic bacteria are one of the simplest systems that perform biomineralization: organisms that create inorganic materials using biochemistry under genetic control. They synthesize magnetosomes, which are intracellular, membrane-bound nanoscale single crystals of magnetite, a magnetic iron oxide. We studied the magnetism of individual magnetosomes inside individual cells with spectro-ptychography, a new technique of high-resolution X-ray microscopy. Our results help us to understand how the cells biomineralize magnetosomes and their function in the cell ecophysiology. In addition to demonstrating a large improvement in spatial resolution relative to earlier nonptychography studies, the results presented provide insights into magnetosome biomineralization.
Light affects salt stress-induced transcriptional memory of
P5CS1
in
Arabidopsis
Authors: Feng Xuan Jun , Li Jing Rui , Qi Shi Lian , Lin Qing Fang , Jin Jing Bo , Hua Xue Jun
Published: December 2016

Significance

Light, a prevailing environmental factor, plays important roles in various processes during plant development and stress response. Whether light could also regulate stress-induced transcriptional memory, however, is not clear. Herein we reported that light signal is positively involved in salt-induced transcriptional memory of Δ
1
-pyrroline-5-carboxylate synthetase 1 (
P5CS1
) and subsequent proline accumulation. Furthermore, HY5-dependent light signaling is required for the maintenance of salt-induced H3K4me3 in
P5CS1
during the recovery stage. This mechanism is likely operating during other stress as well, and could shed light on future research into the concerted effects of different environmental factors on plant response to stresses.
Sox2+ progenitors in sharks link taste development with the evolution of regenerative teeth from denticles
Authors: Martin Kyle J. , Rasch Liam J. , Cooper Rory L. , Metscher Brian D. , Johanson Zerina , Fraser Gareth J.
Published: December 2016

Significance

Oral teeth and skin denticles share a deep, 450-million-year-old, evolutionary relationship among vertebrates. We investigate how teeth evolved from simpler denticles using sharks as an evolutionary developmental model. The striking ability of shark teeth to regenerate rapidly and continuously is not shared by denticles, and we suggest that this difference is related to the tooth-specific expression of the stem cell factor sox2. We show that epithelial progenitors of the shark dentition share a remarkable developmental relationship with taste buds. We suggest that teeth arose by combining the gene regulatory network for producing simple denticles with that for producing the highly regenerative taste buds in the oral cavity.
Janus effect of antifreeze proteins on ice nucleation
Authors: Liu Kai , Wang Chunlei , Ma Ji , Shi Guosheng , Yao Xi , Fang Haiping , Song Yanlin , Wang Jianjun
Published: December 2016

Significance

In the past decades, a vast body of experimental and theoretical work has been undertaken to investigate the molecular level mechanism underlying heterogeneous ice nucleation. However, understanding of heterogeneous ice nucleation is still far from satisfactory. Antifreeze proteins (AFPs) are endowed with the unique ability to control freezing. Our research reveals the exact effect of AFPs on ice nucleation at the molecular level, which correlates ice nucleation with the surface chemistry and topography of different faces of AFPs. We also emphasize a critical role for the non–ice-binding face of AFPs and discover that the proper function of AFPs is realized only by synergistic effects of the non–ice-binding face and the ice-binding face.
Dopamine release from the locus coeruleus to the dorsal hippocampus promotes spatial learning and memory
Authors: Kempadoo Kimberly A. , Mosharov Eugene V. , Choi Se Joon , Sulzer David , Kandel Eric R.
Published: December 2016

Significance

Successful completion of daily activities relies on the ability to select the relevant features of the environment to pay attention to and remember. Disruptions of these processes can lead to disorders, such as attention-deficit hyperactivity disorder and age-related memory loss. To devise therapeutic strategies, we must understand the neural circuits underlying normal cognition. One important pathway is the signaling of dopamine, a reinforcement-related neurotransmitter, in the hippocampus, a spatial learning and memory center. Surprisingly, the brain region supplying dopamine to the dorsal hippocampus is unclear. This study provides direct evidence that the noradrenergic locus coeruleus coreleases dopamine in the dorsal hippocampus and provides insight into dopamine function in selective attention and spatial learning and memory.
Estimating uncertainty in respondent-driven sampling using a tree bootstrap method
Authors: Baraff Aaron J. , McCormick Tyler H. , Raftery Adrian E.
Published: December 2016

Significance

Some hidden or hard-to-reach populations of interest to researchers are difficult to study with standard statistical methods because there is not a reliable list of members from which samples can be drawn. Respondent-driven sampling (RDS) is a common way to reach members of these populations by allowing a small number of respondents to recruit further respondents in the target population from their personal contacts. However, estimates derived from RDS are known to have a high degree of uncertainty, for which current methods do not fully account. We present a method that overcomes this problem and allows for better statistical inference from RDS data.
Genetic, immunological, and clinical features of patients with bacterial and fungal infections due to inherited IL-17RA deficiency
Authors: Lévy Romain , Okada Satoshi , Béziat Vivien , Moriya Kunihiko , Liu Caini , Chai Louis Yi Ann , Migaud Mélanie , Hauck Fabian , Al Ali Amein , Cyrus Cyril , Vatte Chittibabu , Patiroglu Turkan , Unal Ekrem , Ferneiny Marie , Hyakuna Nobuyuki , Nepesov Serdar , Oleastro Matias , Ikinciogullari Aydan , Dogu Figen , Asano Takaki , Ohara Osamu , Yun Ling , Della Mina Erika , Bronnimann Didier , Itan Yuval , Gothe Florian , Bustamante Jacinta , Boisson-Dupuis Stéphanie , Tahuil Natalia , Aytekin Caner , Salhi Aicha , Al Muhsen Saleh , Kobayashi Masao , Toubiana Julie , Abel Laurent , Li Xiaoxia , Camcioglu Yildiz , Celmeli Fatih , Klein Christoph , AlKhater Suzan A. , Casanova Jean-Laurent , Puel Anne
Published: December 2016

Significance

Chronic mucocutaneous candidiasis (CMC) is defined as persistent or recurrent infections of the skin and/or mucosae by commensal fungi of the
Candida
genus. It is often seen in patients with T-cell deficiencies, whether inherited or acquired, who typically suffer from multiple infectious diseases. Rare patients are otherwise healthy and display isolated CMC, which often segregates as a Mendelian trait. In 2011, we described the first genetic cause of isolated CMC, with autosomal recessive (AR), complete IL-17 receptor A (IL-17RA) deficiency, in a single patient. We report here 21 patients from 12 unrelated kindreds, homozygous for 12 different mutant alleles that underlie AR IL-17RA deficiency. All patients have isolated CMC and their cells do not respond to IL-17A, -17F, and -17E/IL-25.