bluuebunny/crossref_metadata_2025 huggingface dataset:
A strain-controlled RheoSANS instrument for the measurement of the microstructural, electrical, and mechanical properties of soft materials
Authors: Richards Jeffrey J. , Wagner Norman J. , Butler Paul D.
Published: October 2017

In situ measurements are an increasingly important tool to inform the complex relationship between nanoscale properties and macroscopic material measurements. Knowledge of these phenomena can be used to develop new materials to meet the performance demands of next generation technologies. Conductive complex fluids have emerged as an area of research where the electrical and mechanical properties are key design parameters. To study the relationship between microstructure, conductivity, and rheology, we have developed a small angle neutron scattering (SANS) compatible Couette rheological geometry capable of making impedance spectroscopy measurements under continuous shear. We have also mounted this geometry on a commercial strain controlled rheometer with a modified forced convection oven. In this manuscript, we introduce the simultaneous measurement of impedance spectroscopy, rheological properties and SANS data. We describe the validation of this dielectric RheoSANS instrument and demonstrate its operation using two systems—an ion gel comprising Pluronic® surfactant and ionic liquid, ethyl-ammonium nitrate, and poly(3-hexylthiophene) organogel prepared in a mixture of hexadecane and dichlorobenzene. In both systems, we use this new measurement capability to study the microstructural state of these materials under two different protocols. By monitoring their dielectric rheology at the same time as the SANS measurement, we demonstrate the capacity to directly probe structure-property relationships inherent to the macroscopic material response.
Note: Large active area solid state photon counter with 20 ps timing resolution and 60 fs detection delay stability
Authors: Prochazka Ivan , Kodet Jan , Eckl Johann , Blazej Josef
Published: October 2017

We are reporting on the design, construction, and performance of a photon counting detector system, which is based on single photon avalanche diode detector technology. This photon counting device has been optimized for very high timing resolution and stability of its detection delay. The foreseen application of this detector is laser ranging of space objects, laser time transfer ground to space and fundamental metrology. The single photon avalanche diode structure, manufactured on silicon using K14 technology, is used as a sensor. The active area of the sensor is circular with 200 μm diameter. Its photon detection probability exceeds 40% in the wavelength range spanning from 500 to 800 nm. The sensor is operated in active quenching and gating mode. A new control circuit was optimized to maintain high timing resolution and detection delay stability. In connection to this circuit, timing resolution of the detector is reaching 20 ps FWHM. In addition, the temperature change of the detection delay is as low as 70 fs/K. As a result, the detection delay stability of the device is exceptional: expressed in the form of time deviation, detection delay stability of better than 60 fs has been achieved. Considering the large active area aperture of the detector, this is, to our knowledge, the best timing performance reported for a solid state photon counting detector so far.
Fabrication of high edge-definition steel-tape gratings for optical encoders
Authors: Ye Guoyong , Liu Hongzhong , Yan Jiawei , Ban Yaowen , Fan Shanjin , Shi Yongsheng , Yin Lei
Published: October 2017

High edge definition of a scale grating is the basic prerequisite for high measurement accuracy of optical encoders. This paper presents a novel fabrication method of steel tape gratings using graphene oxide nanoparticles as anti-reflective grating strips. Roll-to-roll nanoimprint lithography is adopted to manufacture the steel tape with hydrophobic and hydrophilic pattern arrays. Self-assembly technology is employed to obtain anti-reflective grating strips by depositing the graphene oxide nanoparticles on hydrophobic regions. A thin SiO2 coating is deposited on the grating to protect the grating strips. Experimental results confirm that the proposed fabrication process enables a higher edge definition in making steel-tape gratings, and the new steel tape gratings offer better performance than conventional gratings.
Objective quantification of mode competition in THz BWO optimization
Authors: Bao Rong , Wang Hongguang , Zhang Ruxia , Li Yongdong , Liu Chunliang
Published: October 2017

The corrugated rectangular waveguide slow-wave structure (CRWSWS) terahertz (THz) backward wave oscillator (BWO) is suitable for many applications because of its compactness and portability. An analytical model is proposed for calculating the cold and hot parameters of a CRWSWS THz BWO. Two forms of mode competition are quantified using the analytical model. The quantifications are used as objectives when optimizing the CRWSWS THz BWO. The optimization is performed based on the analytical model and a local search algorithm. The optimization results are verified using CST Microwave Studio and Particle Studio. The influence of one of the quantifications on the convergence of the optimization algorithm is also investigated.
Annealing induced semiconductor-metal transition in Ge+ITO film
Authors: Car T. , Šantić A. , Ray N. , Nekić N. , Salamon K. , Bernstorff S. , Buljan M.
Published: October 2017

We report significant changes in the electrical properties of a thin film consisting of closely packed Ge quantum dots formed in an ITO matrix by magnetron sputtering, upon annealing. Prior to the treatment, the system shows semiconducting behavior where the carrier density can be easily modulated with a gate. After heating, a huge change in the resistivity of more than seven orders of magnitude is observed, and the system now shows metallic behavior as evidenced by the temperature dependence of the resistivity. The arrangement and size properties of the quantum dots remain the same before and after annealing, and the determined electrical properties are then attributed to the changes in the crystalline structure of the system.
Influence of quantum confined Stark effect and carrier localization effect on modulation bandwidth for GaN-based LEDs
Authors: Zhu Shichao , Lin Shan , Li Jing , Yu Zhiguo , Cao Haicheng , Yang Chao , Li Jinmin , Zhao Lixia
Published: October 2017

We have fabricated GaN-based light-emitting diodes (LEDs) with different quantum well (QW) thicknesses to investigate the influence of the quantum confined Stark effect (QCSE) and carrier localization effect on the carrier recombination processes under both direct current (DC) and alternating current (AC) biases. At low current density, QCSE dominates the carrier recombination and decreases the radiative recombination rate. With increasing the current density, QCSE will be screened by injected carriers, and both optical power and modulation bandwidth can be increased. When the polarization field is completely compensated, the carrier localization effect starts to dominate. By reducing the influence of the QCSE and carrier localization effect, a high modulation bandwidth of ∼700 MHz was achieved at a low current density of 425 A/cm2 for the LED with 5 nm QW. Our findings will pave an alternative solution for co-optimization of the modulation bandwidth and efficiency for LEDs at a relatively low current density for visible light communications.
Sb-induced strain fluctuations in a strained layer superlattice of InAs/InAsSb
Authors: Kim Honggyu , Meng Yifei , Klem John F. , Hawkins Samuel D. , Kim Jin K. , Zuo Jian-Min
Published: October 2017

We show that Sb substitution for As in a MBE grown InAs/InAsSb strained layer superlattice (SLS) is accompanied by significant strain fluctuations. The SLS was observed using scanning transmission electron microscopy along the [100] zone axis where the cation and anion atomic columns are separately resolved. Strain analysis based on atomic column positions reveals asymmetrical transitions in the strain profile across the SLS interfaces. The averaged strain profile is quantitatively fitted to the segregation model, which yields a distribution of Sb in agreement with the scanning tunneling microscopy result. The subtraction of the calculated strain reveals an increase in strain fluctuations with the Sb concentration, as well as isolated regions with large strain deviations extending spatially over ∼1 nm, which suggest the presence of point defects.
Theoretical study on the influence of photon reabsorption on spatially resolved photocarrier radiometric imaging of silicon wafers
Authors: Wang Qian , Liu Weiguo
Published: October 2017

The influence of reabsorption of spontaneously emitted photons within silicon wafers on spatially resolved steady-state photocarrier radiometric (PCR) imaging is theoretically analyzed. A new PCR model with photon reabsorption, in which both band-to-band absorption and free carrier absorption are taken into account, is introduced. It is shown that the influences strongly depend on both the excess carrier density and its distribution, which are sensitive to the doping level, electronic transport properties, sample thickness, and surface topography. If photon reabsorption is ignored in the determination of the electronic transport parameters for high-doping double polished silicon wafers via multi-parameter fitting, the relative errors of the fitted minority carrier lifetime, diffusion coefficient, and front surface recombination velocity could reach 38%, 9.5%, and 24%, respectively.
Perturbed angular correlations at ISOLDE: A 40 years young technique
Authors: Schell Juliana , Schaaf Peter , Lupascu Doru C.
Published: October 2017

The idea that “new-is-small” is a paradigm propelling industries and research: new materials for new applications and new technologies. Precise and efficient characterization techniques are, therefore, required to make the “new” and the “small”, understandable, applicable, and reliable. Within this concept, Time Differential Perturbed Angular Correlations, TDPAC, appears as one of the most exotic and efficient techniques to characterize materials and is celebrating 40 years at ISOLDE, CERN. In this overview we explore the TDPAC measurement possibilities at ISOLDE-CERN for solid state physics research with a rich potential due to the wide number of available radioactive probe elements, delivered with great purity and high yield.
The effect of electron processes on metal walls in magnetized microdischarges
Authors: Levko Dmitry , Raja Laxminarayan L.
Published: October 2017

The influence of the electron reflection and secondary electron emission due to electron impact on a microdischarge with magnetized electrons and unmagnetized ions is analyzed using a one-dimensional Particle-in-Cell Monte Carlo collision model. For low gas pressure (below 10 Torr), the accounting for the electron processes on the walls results in a significant decrease of the breakdown voltage and allows one to increase both the plasma density and the discharge current. The generation of much denser plasma shrinks the cathode sheath to such an extent that the Larmor radius of emitted electrons becomes a few times larger than the sheath thickness. This leads to the expansion of the region of dense plasma toward the anode, which decreases the frequency of the ionization instability and decreases the number of striations obtained in the cathode-anode gap.
Speckle-tracking X-ray phase-contrast imaging for samples with obvious edge-enhancement effect
Authors: Wang Feixiang , Wang Yudan , Wei Gongxiang , Du Guohao , Xue Yanling , Hu Tao , Li Ke , Deng Biao , Xie Honglan , Xiao Tiqiao
Published: October 2017

Compared to the grating or crystal-based X-ray phase contrast imaging, the speckle-tracking method has the advantages of a simple setup and two-dimensional imaging. However, the edge-enhancement effect prevents the application of the speckle-tracking imaging to a large variety of samples. In this letter, an image reconstruction method is proposed to solve this problem. The experimental results from phantom, a biomedical sample, and a sample with a speckle-resembling structure demonstrated that the proposed method is efficacious in eliminating the effect of edge enhancement. The proposed method may greatly expand the application of the speckle-tracking method to most biomedical and material samples.
Polarization controlled hybrid line shape and switching of noise correlation via Autler-Town splitting
Authors: Li Changbiao , Ahmed Irfan , Khan Ghulam A. , Zhang Da , Xu Mingyu , Wang Ruimin , Zhang Yanpeng
Published: October 2017

We report the experimental observations of the second- and third-order hybrid intensity noise correlation and intensity difference squeezing among two different multi-order nonlinear fluorescence (FL) and two FL signals as well as one of pair of phase conjugate four-wave mixing in a Pr3+:Y2SiO5 crystal, respectively. The degrees of the correlation and squeezing as well as the sharp and broad peaks are studied by changing the polarization of laser fields and gate position in Λ-type three-level systems. We observed the multi-channel hybrid intensities' correlation among the composite and coexisting signals, which turn out to be positive and negative for the cases without and with Autler-Town splitting of FL, respectively. A wide broad peak and a high sharp peak are observed with respect to the degrees of correlation and polarization state controlled by wave plates. Such results may find potential applications in optical transistor and optical hybrid communications.
Vector electric field measurement via position-modulated Kelvin probe force microscopy
Authors: Dwyer Ryan P. , Smieska Louisa M. , Tirmzi Ali Moeed , Marohn John A.
Published: October 2017

High-quality spatially resolved measurements of electric fields are critical to understanding charge injection, charge transport, and charge trapping in semiconducting materials. Here, we report a variation of frequency-modulated Kelvin probe force microscopy that enables spatially resolved measurements of the electric field. We measure electric field components along multiple directions simultaneously by employing position modulation and lock-in detection in addition to numeric differentiation of the surface potential. We demonstrate the technique by recording linescans of the in-plane electric field vector in the vicinity of a patch of trapped charge in a 2,7-diphenyl[1]benzothieno[3,2-b][1]benzothiophene (DPh-BTBT) organic field-effect transistor. This technique is simple to implement and should be especially useful for studying electric fields in spatially inhomogeneous samples like organic transistors and photovoltaic blends.
Mechanisms for plasma cryogenic etching of porous materials
Authors: Zhang Quan-Zhi , Tinck Stefan , de Marneffe Jean-François , Zhang Liping , Bogaerts Annemie
Published: October 2017

Porous materials are commonly used in microelectronics, as they can meet the demand for continuously shrinking electronic feature dimensions. However, they are facing severe challenges in plasma etching, due to plasma induced damage. In this paper, we present both the plasma characteristics and surface processing during the etching of porous materials. We explain how the damage occurs in the porous material during plasma etching for a wide range of chuck temperatures and the responsible mechanism for plasma damage-free etching at cryogenic temperature, by a combination of experiments and numerical modeling.
Vlasov simulations of electron acceleration by radio frequency heating near the upper hybrid layer
Authors: Najmi A. , Eliasson B. , Shao X. , Milikh G. , Sharma A. S. , Papadopoulos K.
Published: October 2017

It is shown by using a combination of Vlasov and test particles simulations that the electron distribution function resulting from energization due to Upper Hybrid (UH) plasma turbulence depends critically on the closeness of the pump wave to the double resonance, defined as ω ≈ ωUH ≈ nωce, where n is an integer. For pump frequencies, away from the double resonance, the electron distribution function is very close to Maxwellian, while as the pump frequency approaches the double resonance, it develops a high energy tail. The simulations show turbulence involving coupling between Lower Hybrid (LH) and UH waves, followed by excitation of Electron Bernstein (EB) modes. For the particular case of a pump with frequency between n = 3 and n = 4, the EB modes cover the range from the first to the 5th mode. The simulations show that when the injected wave frequency is between the 3rd and 4th harmonics of the electron cyclotron frequency, bulk electron heating occurs due to the interaction between the electrons and large amplitude EB waves, primarily on the first EB branch leading to an essentially thermal distribution. On the other hand, when the frequency is slightly above the 4th electron cyclotron harmonic, the resonant interaction is predominantly due to the UH branch and leads to a further acceleration of high-velocity electrons and a distribution function with a suprathermal tail of energetic electrons. The results are consistent with ionospheric experiments and relevant to the production of Artificial Ionospheric Plasma Layers.
Spin wave modes of width modulated Ni80Fe20/Pt nanostrip detected by spin-orbit torque induced ferromagnetic resonance
Authors: Tang Wei , Zhou Zhen-wei , Nie Yao-zhuang , Xia Qing-lin , Zeng Zhong-ming , Guo Guang-hua
Published: October 2017

We study magnetic dynamics of Ni80Fe20/Pt magnonic crystals made of width periodically varied nanostrips using the spin-torque induced ferromagnetic resonance technique. DC voltage signals are detected when nanostrip magnonic crystals (MCs) are driven resonantly. The DC voltage originates dominantly from the spin rectification effect due to the coupling between the AC electrical current and the oscillated anisotropic magnetoresistance. In addition to uniform magnetization precession across the MC, localized spin wave modes are also observed. Their evolution with the strength and direction of the magnetic field are studied. Micromagnetic simulations are performed to illustrate the experimental results.
Silicon nanowires to enhance the performance of self-powered near-infrared photodetectors with asymmetrical Schottky contacts
Authors: Nusir Ahmad I. , Bauman Stephen J. , Marie Mohammed S. , Herzog Joseph B. , Manasreh M. Omar
Published: October 2017

Silicon nanowires were etched vertically in the channel between asymmetrical interdigital electrodes. The self-powered near-infrared photodetector consists of a planar structure of Au-vertically aligned Si nanowire-Ti. The devices were characterized by measuring the current-voltage characteristics, the external quantum efficiency (EQE), and the spectral response. An enhancement of 32% in the short-circuit current was achieved after applying the Si nanowires. The EQE of the device with Si nanowires consists of a strong peak covering the near-infrared spectral range with a maximum EQE of 10.3% at 965 nm and 0 V. Furthermore, the spectral response measurements showed enhancement and broadening in the spectrum of devices with Si nanowires.
The role of electronic donor moieties in porphyrin dye sensitizers for solar cells: Electronic structures and excitation related properties
Authors: Li Shuai-Hu , Zhang Cai-Rong , Yuan Li-Hua , Zhang Mei-Ling , Chen Yu-Hong , Liu Zi-Jiang , Chen Hong-Shan
Published: October 2017

The development and synthesis of novel dye sensitizers are important for improving the power conversion efficiency of dye-sensitized solar cells (DSSCs) in terms of the role of dye sensitizers in photon to electricity energy conversion processes. How the different moieties tune the electronic structures and related properties is the fundamental issue in designing dye sensitizers. Here, the geometries, electronic structures, excitation properties, and free energy variations for electron injection (EI) and dye regeneration (DR) of porphyrin dye sensitizers SM315, GY50, FA, and KS, containing bulky bis(2′,4′-bis(hexyloxy)-[1,1′-biphenyl]-4-yl)amine, diarylamino group with two hexyl chains, quinolizinoacridine, and triazatruxene as electron donors, respectively, were investigated. The Q bands absorption spectra of FA and KS exhibit a blue-shift relative to those of SM315 and GY50, resulting from weak conjugation effects. The transition configurations and molecular orbital analysis suggest that the electron donors in these dyes are effective chromophores for photon-induced EI in DSSCs. The torsion angle between the electron-donor and the conjugation-bridge has significant effects on electronic structures, excited states, charge transfer (CT) properties, and free energy variations for EI and DR. The transferred charges and CT distances demonstrate that quinolizinoacridine in FA is the most prominent electron donor moiety among these porphyrin dyes.
Spin Seebeck effect in the antiferromagnet nickel oxide at room temperature
Authors: Holanda J. , Maior D. S. , Alves Santos O. , Vilela-Leão L. H. , Mendes J. B. S. , Azevedo A. , Rodríguez-Suárez R. L. , Rezende S. M.
Published: October 2017

The generation of spin currents by thermal gradients applied to a magnetic film is known as the spin Seebeck effect (SSE). The SSE is usually detected by an electric voltage generated in a metallic layer in contact with the magnetic film produced by the spin to charge current conversion through the inverse spin Hall effect (ISHE). The SSE has been widely studied in bilayers made of the insulating ferrimagnet yttrium iron garnet (YIG) and metals with large spin orbit coupling, such as platinum. Recently, the SSE has been observed in bilayers made of the antiferromagnets MnF2 and Cr2O3 with Pt at low temperatures and high magnetic fields. Here, we report measurements of the SSE at room temperature and low magnetic fields in bilayers made of well textured films of antiferromagnetic NiO with several metals. The detection of the spin current generated by the thermal gradient in the NiO layer is made by means of the ISHE in the nonmagnetic metals Pt and Ta, in the AF metal IrMn, and in the ferromagnetic metal Ni81Fe19 (permalloy). The measured spin Seebeck effect in NiO/Pt has the same sign and is about one order of magnitude smaller than in YIG/Pt.
Surface cleaning and pure nitridation of GaSb by in-situ plasma processing
Authors: Gotow Takahiro , Fujikawa Sachie , Fujishiro Hiroki I. , Ogura Mutsuo , Chang Wen Hsin , Yasuda Tetsuji , Maeda Tatsuro
Published: October 2017

A clean and flat GaSb surface without native oxides has been attained by H2 plasma cleaning and subsequent in-situ N2 plasma nitridation process at 300 oC. The mechanisms of thermal desorption behavior of native oxides on GaSb have been studied by thermal desorption spectroscopy (TDS) analysis. The suitable heat treatment process window for preparing a clean GaSb surface is given. Auger electron spectroscopy (AES) analysis indicates that native oxides were completely removed on the GaSb surface after H2 plasma exposure and the pure nitridation of the clean GaSb surface was obtained at a relatively low temperature of 300 °C. This pure nitridation of GaSb have a possibility to be used as a passivation layer for high quality GaSb MOS devices.
Ponderomotive beatwave ion acceleration using twisted light
Authors: Saberi Hossein , Vieira Jorge , Silva Luis O
Published: October 2017

An all-optical mechanism of ion acceleration in vacuum with two counter-propagating plane waves has been proposed by F. Peano et al., IEEE Trans Plasma Sci. 36, 1857 (2008). A suitable frequency chirping of lasers drives a beat wave with variable phase velocity that traps particles and accelerates them longitudinally. In this paper, direct ion acceleration by two counter-propagating focused laser beams with variable frequencies is considered, and the multi-dimensional effects associated with the finite transverse dimension of lasers are investigated. It is shown that the Gaussian laser beams provide a defocusing transverse force that stops the acceleration process as ions propagate towards regions of smaller laser fields. On the other hand, the Laguerre-Gaussian laser beams with identical orbital angular momentum can confine the off-axis ions radially as they accelerate to high energies. It is shown that the orbital angular momentum of the Laguerre-Gaussian lasers can be used to control the angular momentum of the accelerated ion beam.
Effect of thermal annealing on structural properties of GeSn thin films grown by molecular beam epitaxy
Authors: Zhang Z. P. , Song Y. X. , Li Y. Y. , Wu X. Y. , Zhu Z. Y. S. , Han Y. , Zhang L. Y. , Huang H. , Wang S. M.
Published: October 2017

GeSn alloy with 7.68% Sn concentration grown by molecular beam epitaxy has been rapidly annealed at different temperatures from 300°C to 800°C. Surface morphology and roughness annealed below or equal to 500°C for 1 min have no obvious changes, while the strain relaxation rate increasing. When the annealing temperature is above or equal to 600°C, significant changes occur in surface morphology and roughness, and Sn precipitation is observed at 700°C. The structural properties are analyzed by reciprocal space mapping in the symmetric (004) and asymmetric (224) planes by high resolution X-ray diffraction. The lateral correlation length and the mosaic spread are extracted for the epi-layer peaks in the asymmetric (224) diffraction. The most suitable annealing temperature to improve both the GeSn lattice quality and relaxation rate is about 500°C.
Event-based simulation of networks with pulse delayed coupling
Authors: Klinshov Vladimir , Nekorkin Vladimir
Published: October 2017

Pulse-mediated interactions are common in networks of different nature. Here we develop a general framework for simulation of networks with pulse delayed coupling. We introduce the discrete map governing the dynamics of such networks and describe the computation algorithm for its numerical simulation.
Mean, covariance, and effective dimension of stochastic distributed delay dynamics
Authors: René Alexandre , Longtin André
Published: October 2017

Dynamical models are often required to incorporate both delays and noise. However, the inherently infinite-dimensional nature of delay equations makes formal solutions to stochastic delay differential equations (SDDEs) challenging. Here, we present an approach, similar in spirit to the analysis of functional differential equations, but based on finite-dimensional matrix operators. This results in a method for obtaining both transient and stationary solutions that is directly amenable to computation, and applicable to first order differential systems with either discrete or distributed delays. With fewer assumptions on the system's parameters than other current solution methods and no need to be near a bifurcation, we decompose the solution to a linear SDDE with arbitrary distributed delays into natural modes, in effect the eigenfunctions of the differential operator, and show that relatively few modes can suffice to approximate the probability density of solutions. Thus, we are led to conclude that noise makes these SDDEs effectively low dimensional, which opens the possibility of practical definitions of probability densities over their solution space.
Effects of gas temperature, pressure, and discharge power on nucleation time of nano-particles in low pressure C2H2/Ar RF plasmas
Authors: Lin Jiashu , Orazbayev Sagi , Hénault Marie , Lecas Thomas , Takahashi Kazuo , Boufendi Laïfa
Published: October 2017

The formation of dust particles in low-pressure plasmas is a 3-step process. The first one corresponds to nucleation and growth of nanoparticles by chain reactions between ions and gas molecules, the second one is agglomeration of the nanoparticles to form larger particles, and finally, the particles grow by radical deposition on their surfaces. In this work, the nucleation time for carbon dust particles was studied in low pressure acetylene/argon radio frequency (RF) plasmas. Since the self-bias voltage on a powered electrode was drastically affected by the transition from the nucleation to the agglomeration phases, the nucleation time was measured by observing the self-bias voltage time evolution. The nucleation time increases with the gas temperature and decreases when the gas pressure and the RF power are increased. A kinetic model, involving balance between diffusion and charging times of the nanoparticles as well as the chain reactions, is used to explain the exponential dependence of the nucleation time on the gas temperature. The balance between the times was especially indispensable to get good agreement between the model and the experimental results.
Direct measurement of the mechanism by which magnesium specifically modifies the mechanical properties of DNA
Authors: Montasser I. , Coleman A. W. , Tauran Y. , Perret G. , Jalabert L. , Collard D. , Kim B. J. , Tarhan M. C.
Published: October 2017

We examine the effect of physiological cations Na+, K+, Mg2+, and Ca2+ on the mechanical properties of bundles of λ-phage DNA using silicon nanotweezers (SNTs). Integrating SNTs with a microfluidic device allows us to perform titration experiments while measuring the effect in real-time. The results show that only for Mg2+ and in particular, at the intra-nuclear concentration (100 mM), the interaction occurs.
Marangoni flow traveling with reaction fronts: Eikonal approximation
Authors: Guzman Roberto , Vasquez Desiderio A.
Published: October 2017

Chemical reaction fronts traveling in liquids generate gradients of surface tension leading to fluid motion. This surface tension driven flow, known as Marangoni flow, modifies the shape and the speed of the reaction front. We model the front propagation using the Eikonal relation between curvature and normal speed of the front, resulting in a front evolution equation that couples to the fluid velocity. The sharp discontinuity between the reactants and products leads to a surface tension gradient proportional to a delta function. The Stokes equations with the surface tension gradient as part of the boundary conditions provide the corresponding fluid velocity field. Considering stress free boundaries at the bottom of the liquid layer, we find an analytical solution for the fluid vorticity leading to the velocity field. Solving numerically the appropriate no-slip boundary condition, we gain insights into the role of the boundary condition at the bottom layer. We compare our results with results from two other models for front propagation: the deterministic Kardar-Parisi-Zhang equation and a reaction-diffusion equation with cubic autocatalysis, finding good agreement for small differences in surface tension.
Impact of collisions on the dust wake potential with Maxwellian and non-Maxwellian ions
Authors: Sundar Sita , Kählert Hanno , Joost Jan-Philip , Ludwig Patrick , Bonitz Michael
Published: October 2017

This work examines the formation of wake fields caused by ions streaming around a charged dust particle, using three-dimensional particle-in-cell simulations with charge-neutral collisions included. The influence of an external driving electric field, which leads to a non-Maxwellian distribution of ions, is investigated in detail. The wake features formed for non-Maxwellian ions exhibit significant deviations from those observed within the model of a shifted Maxwellian distribution. The dependence of the peak amplitude and position of the wake potential upon the degree of collisionality is analyzed for a wide range of streaming velocities (Mach numbers). In contrast to a shifted Maxwellian distribution of ions, the drift-driven non-Maxwellian distribution exhibits an increase in the wake amplitude of the first attractive peak with an increase in collisionality for high streaming velocities. At very low Mach numbers, collision-induced amplification is observed for Maxwellian and non-Maxwellian distributions.
Regioselective Synthesis of 2,5-Disubstituted Pyrroles via Stepwise Iododesilylation and Coupling Reactions
Authors: Yu Qixin , Li Xiaoyu , Wang Xinyue , Liu Jianhui
Published: October 2017

A new protocol has been developed for the regioselective preparation of 2,5-disubstituted pyrroles. This approach is based on a stepwise iododesilylation and a subsequent coupling reaction, involving a 6-step pathway starting from the simplest pyrrole. A variety of 2,5-disubstituted pyrrole derivatives are accessible in moderate to good yields. In this study, the protection group for the pyrrole nitrogen is carefully chosen and N,N-dimethylaminosulfonyl is the final choice, which facilitates the subsequent double lithiation and makes the pyrrole moiety more stable. However, the attempted removal of this group fails under several different conditions. Instead, unexpected dimethylaminosulfonyl migration to the β-position of the pyrrole ring in the presence of tetrabutylammonium fluoride is observed.
Relationships and phylogenetic revision of Filistatinella spiders (Araneae : Filistatidae)
Authors: Magalhaes Ivan L. F. , Ramírez Martín J.
Published: October 2017

Filistatids represent an antique lineage of araneomorph spiders which are most diverse in arid and semiarid regions of the globe. Phylogenetic relationships among its genera are still largely unexplored, and previous studies disagree on the position of the North American Filistatinella Gertsch & Ivie, 1936, which could either be the sister group of all other Prithinae, or deeply nested in the subfamily. We present a new phylogenetic hypothesis based on morphological data, which supports the position of Filistatinella at the base of Prithinae. We also argue that the central Asian Pholcoides Roewer, 1960, hitherto considered incertae sedis in the subfamily, represents the putative sister group of Filistatinella. The latter genus is revised, and we describe its fine morphology in detail using optical and scanning electron microscopy. We redescribe the three previously known species, F. crassipalpis (Gertsch, 1935), F. domestica Desales-Lara, 2012 and F. palaciosi Jiménez & Palacios-Cardiel, 2012. Seven new species are named: F. kahloae, sp. nov. and F. chilindrina, sp. nov. from Mexico; F. pistrix, sp. nov., F. tohono, sp. nov., F. howdyall, sp. nov. and F. hermosa, sp. nov. from south-western USA; and F. spatulata, sp. nov. from the border between the two countries. The phylogenetic relationships among these 10 species are assessed, revealing the monophyly of the genus.
http://zoobank.org/urn:lsid:zoobank.org:pub:71820858-545C-43EC-98E1-F9BF490AA3F1
Topsoil removal and carbon addition for weed control and native grass recruitment in a temperate-derived grassland in northern New South Wales
Authors: Brown Sharon L. , Reid Nick , Reid Jackie , Smith Rhiannon , Whalley R. D. B. (Wal) , Carr David
Published: October 2017

Restoring the grassy understorey to temperate woodlands in south-eastern Australia is often disregarded due to a poor understanding of the techniques involved. The natural recruitment of native grasses is uncommon in the remnants of some of these woodlands, so the restoration of the grass layer is often dependent on interventions to overcome restoration barriers. Soil enrichment from agricultural fertilisers favours the invasion of exotic broadleaf weeds and grasses, and is one of the primary barriers to the successful recruitment and establishment of native grasses, which dominated before agricultural development. This study on the Northern Tablelands of New South Wales investigated the effects of different weed control treatments – scalping, glyphosate (Roundup®) herbicide, and combinations of glyphosate with carbon (sugar and sawdust) addition and a control (nil treatment) recruitment of native grasses and weed emergence after broadcast seeding. The experimental site was a mown grass lawn consisting of fescue (Festuca arundinacea Shreb.), cocksfoot (Dactylis glomerata L.) and paspalum (Paspalum dilatatum Poir). Native grass recruitment varied significantly between treatments. The maximum number of recruits in scalped plots was 29 recruits m–2 compared with an average of <2 recruits m–2 for the glyphosate and glyphosate carbon combinations. Scalping reduced soil nitrogen from 0.6% in non-scalped plots to 0.1% and phosphorus from 191.6 ppm to 40.3 ppm. Maximum weed cover occurred in the glyphosate herbicide treatment (45%), whereas combinations of glyphosate plus either sugar or sawdust maintained weed cover at 13%. The present study suggests that scalping may be a successful intervention strategy because it has the potential to significantly improve native grass recruitment compared with other restoration methods used in this study. Scalping allows more time for native grasses to germinate and establish in the absence of competitive fast-growing exotic weeds.
Fabric of soil derived from parna and the riddle of transported pellets
Authors: Cattle Stephen R. , Smith Carol M. S.
Published: October 2017

It is generally accepted that large areas of southern New South Wales (NSW) and northern Victoria are mantled by soils derived from clayey loess deposits called parna. These parna deposits are believed to have formed during arid phases of the Pleistocene and the mineral constituents are assumed to have been transported as silt- and fine sand-sized pellets of calcareous clay, with some companion quartz grains of a similar size. A common property of parna-derived soils is subplasticity, where the apparent field texture grade becomes more clayey with increasing mechanical working of the bolus. This propensity for subplastic behaviour suggests that parna-derived soils contain stable silt- and fine sand-sized pellets of clay, yet there has been little direct micromorphological evidence of these pellets ever published. In the present study, thin section samples from several parna type-sites in southern NSW were examined micromorphologically to reveal the presence of very well size-sorted quartz grain populations (companion grains) and identifiable prolate clay aggregations of a similar silt to fine sand size. These prolate pellets, comprised of quartz, illite, kaolinite and chlorite, have a very distinctive mosaic-speckled b-fabric and are more widely distributed throughout the soil than the similarly sized and shaped faunal faecal pellets. Where these pelletal aggregations are not evident, such as in the deeper parna deposits, abundant illuviation features suggest that clay particles deposited within the parna, whether as pellets or coatings on grains, have subsequently undergone considerable weathering and a range of pedogenic processes.
Supply and demand drive a critical transition to dysfunctional fisheries
Authors: Fryxell John M. , Hilborn Ray , Bieg Carling , Turgeon Katrine , Caskenette Amanda , McCann Kevin S.
Published: October 2017

Significance

Recent years have witnessed strenuous ongoing debate about the sustainability of many commercial fisheries. Here we apply commonly accepted principles of fishery science to consider the impact of price flexibility on long-term fishery sustainability in an era of increasing demand due to population increase and rising economic expectations. We apply this model to two commercial oceanic fisheries (cod and pollock) to demonstrate that harvest and price statistics that are commonly available for commercial fisheries can be used to diagnose the degree to which a given fishery has been overharvested. More importantly, the same heuristic can also be used to identify plausible targets for fishery rehabilitation and evaluate the effectiveness of alternative policy options to achieve those goals.
Rise and fall of elites: professionals as movers?
Authors: Gulbrandsen Trygve
Published: October 2017

A significant topic within elite research deserving more attention is the issue of the “rise and fall of elites”. This subject addresses changes in the composition of elites, the emergence of new elites and the decline of established ones, and covers questions like: In what ways do particular groups climb to elite power and status? What may explain the rise of new elite groups? In this paper, the focus is upon the role of professionals in the processes of elite ascent (and descent). Most holders of elite positions are professionals. This fact invites to draw on approaches within the professions literature to explain the rise of elites. This paper presents three empirical cases of elite ascent in Norway – the rise of economists, communication practitioners and public accountants. The three historical cases demonstrate that the professionals themselves actively sought to promote their expertise, and to expand their occupational territory. Nonetheless, the professionals’ own efforts to obtain collective advancement contributed to a lesser degree to their elite ascent than more fundamental economic and political changes in the Norwegian society.
Cyclin B1 is essential for mitosis in mouse embryos, and its nuclear export sets the time for mitosis
Authors: Strauss Bernhard , Harrison Andrew , Coelho Paula Almeida , Yata Keiko , Zernicka-Goetz Magdalena , Pines Jonathon
Published: October 2017

There is remarkable redundancy between the Cyclin–Cdk complexes that comprise the cell cycle machinery. None of the mammalian A-, D-, or E-type cyclins are required in development until implantation, and only Cdk1 is essential for early cell divisions. Cyclin B1 is essential for development, but whether it is required for cell division is contentious. Here, we used a novel imaging approach to analyze Cyclin B1–null embryos from fertilization onward. We show that Cyclin B1−/− embryos arrest in G2 phase after just two divisions. This is the earliest arrest of any Cyclin known and places Cyclin B1 with cdk1 as the essential regulators of the cell cycle. We reintroduced mutant proteins into this genetically null background to determine why Cyclin B1 is constantly exported from the nucleus. We found that Cyclin B1 must be exported from the nucleus for the cell to prevent premature entry to mitosis, and retaining Cyclin B1–Cdk1 at the plasma membrane precludes entry to mitosis.
Regulation of reproduction and longevity by nutrient-sensing pathways
Authors: Templeman Nicole M. , Murphy Coleen T.
Published: October 2017

Nutrients are necessary for life, as they are a crucial requirement for biological processes including reproduction, somatic growth, and tissue maintenance. Therefore, signaling systems involved in detecting and interpreting nutrient or energy levels—most notably, the insulin/insulin-like growth factor 1 (IGF-1) signaling pathway, mechanistic target of rapamycin (mTOR), and adenosine monophosphate-activated protein kinase (AMPK)—play important roles in regulating physiological decisions to reproduce, grow, and age. In this review, we discuss the connections between reproductive senescence and somatic aging and give an overview of the involvement of nutrient-sensing pathways in controlling both reproductive function and lifespan. Although the molecular mechanisms that affect these processes can be influenced by distinct tissue-, temporal-, and pathway-specific signaling events, the progression of reproductive aging and somatic aging is systemically coordinated by integrated nutrient-sensing signaling pathways regulating somatic tissue maintenance in conjunction with reproductive capacity.
Image-based drug screen identifies HDAC inhibitors as novel Golgi disruptors synergizing with JQ1
Authors: Gendarme Mathieu , Baumann Jan , Ignashkova Tatiana I. , Lindemann Ralph K. , Reiling Jan H.
Published: October 2017

The Golgi apparatus is increasingly recognized as a major hub for cellular signaling and is involved in numerous pathologies, including neurodegenerative diseases and cancer. The study of Golgi stress-induced signaling pathways relies on the selectivity of the available tool compounds of which currently only a few are known. To discover novel Golgi-fragmenting agents, transcriptomic profiles of cells treated with brefeldin A, golgicide A, or monensin were generated and compared with a database of gene expression profiles from cells treated with other bioactive small molecules. In parallel, a phenotypic screen was performed for compounds that alter normal Golgi structure. Histone deacetylase (HDAC) inhibitors and DNA-damaging agents were identified as novel Golgi disruptors. Further analysis identified HDAC1/HDAC9 as well as BRD8 and DNA-PK as important regulators of Golgi breakdown mediated by HDAC inhibition. We provide evidence that combinatorial HDACi/(+)-JQ1 treatment spurs synergistic Golgi dispersal in several cancer cell lines, pinpointing a possible link between drug-induced toxicity and Golgi morphology alterations.
Actomyosin contractility regulators stabilize the cytoplasmic bridge between the two primordial germ cells duringCaenorhabditis elegansembryogenesis
Authors: Goupil Eugénie , Amini Rana , Hall David H. , Labbé Jean-Claude
Published: October 2017

Stable cytoplasmic bridges arise from failed cytokinesis, the last step of cell division, and are a key feature of syncytial architectures in the germline of most metazoans. Whereas the Caenorhabditis elegans germline is syncytial, its formation remains poorly understood. We found that the germline precursor blastomere, P4, fails cytokinesis, leaving a stable cytoplasmic bridge between the two daughter cells, Z2and Z3. Depletion of several regulators of actomyosin contractility resulted in a regression of the membrane partition between Z2and Z3, indicating that they are required to stabilize the cytoplasmic bridge. Epistatic analysis revealed a pathway in which Rho regulators promote accumulation of the noncannonical anillin ANI-2 at the stable cytoplasmic bridge, which in turns promotes the accumulation of the nonmuscle myosin II NMY-2 and the midbody component CYK-7 at the bridge, in part by limiting the accumulation of canonical anillin ANI-1. Our results uncover key steps in C. elegans germline formation and define a set of conserved regulators that are enriched at the primordial germ cell cytoplasmic bridge to ensure its stability during embryonic development.
3D-MICE: integration of cross-sectional and longitudinal imputation for multi-analyte longitudinal clinical data
Authors: Luo Yuan , Szolovits Peter , Dighe Anand S , Baron Jason M
Published: October 2017

Objective

A key challenge in clinical data mining is that most clinical datasets contain missing data. Since many commonly used machine learning algorithms require complete datasets (no missing data), clinical analytic approaches often entail an imputation procedure to “fill in” missing data. However, although most clinical datasets contain a temporal component, most commonly used imputation methods do not adequately accommodate longitudinal time-based data. We sought to develop a new imputation algorithm, 3-dimensional multiple imputation with chained equations (3D-MICE), that can perform accurate imputation of missing clinical time series data.

Methods

We extracted clinical laboratory test results for 13 commonly measured analytes (clinical laboratory tests). We imputed missing test results for the 13 analytes using 3 imputation methods: multiple imputation with chained equations (MICE), Gaussian process (GP), and 3D-MICE. 3D-MICE utilizes both MICE and GP imputation to integrate cross-sectional and longitudinal information. To evaluate imputation method performance, we randomly masked selected test results and imputed these masked results alongside results missing from our original data. We compared predicted results to measured results for masked data points.

Results

3D-MICE performed significantly better than MICE and GP-based imputation in a composite of all 13 analytes, predicting missing results with a normalized root-mean-square error of 0.342, compared to 0.373 for MICE alone and 0.358 for GP alone.

Conclusions

3D-MICE offers a novel and practical approach to imputing clinical laboratory time series data. 3D-MICE may provide an additional tool for use as a foundation in clinical predictive analytics and intelligent clinical decision support.