bluuebunny/crossref_metadata_2025 huggingface dataset:
The Variable Emergence of the Infrapatellar Branch of the Saphenous Nerve
Authors: Henry Brandon , Pękala Przemysław , Ramakrishnan Piravin , Taterra Dominik , Saganiak Karolina , Mizia Ewa , Walocha Jerzy , Tomaszewski Krzysztof
Published: November 2016

The infrapatellar branch of the saphenous nerve (IPBSN) is a cutaneous nerve of the lower limb, which arises distal to the adductor canal. High variability in the emergence, course, branching, termination, and morphometrics of the IPBSN poses an increased risk of injury to the nerve during surgical interventions on the anteromedial aspect of the knee. The aim of this study was to describe the anatomical characteristics of the IPBSN. This study utilized cadaveric (n = 100) and ultrasonography (n = 30) assessments, and meta-analysis. In the cadaveric study, the presence of IPBSN and its emergence mode in relation to the sartorius muscle (SaM) was determined (type A-anterior; type B-posterior; type C-penetrating the SaM). Ultrasonography examinations were conducted on healthy volunteers to determine the presence and mode of the emergence of the nerve. Finally, from electronic databases searching, all studies reporting the IPBSN emergence data were pooled into a meta-analysis. The mean distance between the medial border of the patellar ligament (MBPL) and the IPBSN at the level of the patellar apex (PA) was also analyzed in the cadaveric, ultrasonography, and meta-analysis portions of the study. Six studies (n = 336 limbs), including the present cadaveric study, were pooled into the meta-analysis of emergence. The most prevalent IPBSN emergence mode was type C (42.9%) followed by type B (41.9%) and type A (15.4%). In the ultrasonography assessment, type A was found to be the most common (82.8%). The mean distance between the MBPL and the IPBSN at the level of the PA was 4.89 ± 0.22 cm, and 5.57 ± 0.91 cm, for the cadaveric and meta-analysis studies combined, and the ultrasonography assessment, respectively. This multimodality study shows that the most common type of IPBSN emergence is type C. The horizontal distance between the MBPL and the IPBSN at the level of the PA is usually between 4.5 and 5.6 cm. Understanding the anatomy of IPBSN emergence is crucial for orthopedic surgeons to minimize the risks of iatrogenic nerve injury during surgical procedures in the region.
Modeling Verwey transition temperature of Fe3O4 nanocrystals
Authors: Jiang Xiao bao , Xiao Bei bei , Yang Hong yu , Gu Xiao yan , Sheng Hong chao , Zhang Xing hua
Published: November 2016

The Verwey transition in nanoscale is an important physical property for Fe3O4 nanocrystals and has attracted extensive attention in recent years. In this work, an analytic thermodynamic model without any adjusting parameters is developed to estimate the size and shape effects on modulating the Verwey transition temperature of Fe3O4 nanocrystals. The results show that the Verwey transition temperature reduces with increasing shape parameter λ or decreasing size D. A good agreement between the prediction and the experimental data verified our physical insight that the Verwey transition of Fe3O4 can be directly related to the atomic thermal vibration. The results presented in this work will be of benefit to the understanding of the microscopic mechanism of the Verwey transition and the design of future generation switching and memory devices.
Remote detection of hyperpolarized 129Xe resonances via multiple distant dipolar field interactions with 1H
Authors: Zhang Le , Antonacci Michael , Burant Alex , Koshlap Karl M. , Branca Rosa Tamara
Published: November 2016

A remote detection scheme utilizing the distant dipolar field interaction between two different spin species was proposed by Granwehr et al. [J. Magn. Reson. 176(2), 125 (2005)]. In that sequence 1H spins were detected indirectly via their dipolar field interaction with 129Xe spins, which served as the sensing spins. Here we propose a modification of the proposed detection scheme that takes advantage of the longer T1 relaxation time of xenon to create a long lasting dipolar field with which the fast relaxing 1H spins are allowed to interact many times during a single acquisition. This new acquisition scheme improves detection sensitivity, but it also presents some challenges.
Synchronization and local convergence analysis of networks with dynamic diffusive coupling
Authors: Burbano Lombana Daniel Alberto , di Bernardo Mario
Published: November 2016

In this paper, we address the problem of achieving synchronization in networks of nonlinear units coupled by dynamic diffusive terms. We present two types of couplings consisting of a static linear term, corresponding to the diffusive coupling, and a dynamic term which can be either the integral or the derivative of the sum of the mismatches between the states of neighbouring agents. The resulting dynamic coupling strategy is a distributed proportional-integral (PI) or a proportional-derivative (PD) law that is shown to be effective in improving the network synchronization performance, for example, when the dynamics at nodes are nonidentical. We assess the stability of the network by extending the classical Master Stability Function approach to the case where the links are dynamic ones of PI/PD type. We validate our approach via a set of representative examples including networks of chaotic Lorenz and networks of nonlinear mechanical systems.
A multidisciplinary approach to study the functional properties of neuron-like cell models constituting a living bio-hybrid system: SH-SY5Y cells adhering to PANI substrate
Authors: Caponi S. , Mattana S. , Ricci M. , Sagini K. , Juarez-Hernandez L. J. , Jimenez-Garduño A. M. , Cornella N. , Pasquardini L. , Urbanelli L. , Sassi P. , Morresi A. , Emiliani C. , Fioretto D. , Dalla Serra M. , Pederzolli C. , Iannotta S. , Macchi P. , Musio C.
Published: November 2016

A living bio-hybrid system has been successfully implemented. It is constituted by neuroblastic cells, the SH-SY5Y human neuroblastoma cells, adhering to a poly-anyline (PANI) a semiconductor polymer with memristive properties. By a multidisciplinary approach, the biocompatibility of the substrate has been analyzed and the functionality of the adhering cells has been investigated. We found that the PANI films can support the cell adhesion. Moreover, the SH-SY5Y cells were successfully differentiated into neuron-like cells for in vitro applications demonstrating that PANI can also promote cell differentiation. In order to deeply characterize the modifications of the bio-functionality induced by the cell-substrate interaction, the functional properties of the cells have been characterized by electrophysiology and Raman spectroscopy. Our results confirm that the PANI films do not strongly affect the general properties of the cells, ensuring their viability without toxic effects on their physiology. Ascribed to the adhesion process, however, a slight increase of the markers of the cell suffering has been evidenced by Raman spectroscopy and accordingly the electrophysiology shows a reduction at positive stimulations in the cells excitability.
Unified analysis of transient and steady-state electrophosphorescence using exciton and polaron dynamics modeling
Authors: Hershey Kyle W. , Holmes Russell J.
Published: November 2016

Phosphorescent organic light-emitting devices (OLEDs) can suffer a significant reduction in device efficiency under high current density excitation. This steady-state efficiency roll-off is frequently modeled by including losses from exciton-exciton and exciton-polaron quenching. Despite success in modeling the steady-state efficiency roll-off, the corresponding transient electroluminescence behavior has not been modeled as effectively using the same quenching processes. In this work, both the steady-state and transient electroluminescence behavior of phosphorescent OLEDs based on tris[2-phenylpyridinato-C2,N]Iridium(III) (Ir(ppy)3) are successfully reproduced by considering a dynamic polaron population. Within this model, polarons are able to either form excitons or leak through the device emissive layer, reducing the overall efficiency. This formalism permits a natural and rigorous connection between exciton and polaron dynamics and device charge balance, with the charge balance cast as the efficiency of exciton formation. The full dynamics model reproduces both the rise and decay of transient electroluminescence, as well as the full dependence of the external quantum efficiency on current density. Fit parameters are independently verified using separate studies of transient and steady-state photoluminescence. The model provides a complete picture for the dynamics present during the electrical operation of phosphorescent OLEDs, while also offering a direct route to elucidate exciton formation.
The phase behavior study of human antibody solution using multi-scale modeling
Authors: Sun Gang , Wang Ying , Lomakin Aleksey , Benedek George B. , Stanley H. Eugene , Xu Limei , Buldyrev Sergey V.
Published: November 2016

Phase transformation in antibody solutions is of growing interest in both academia and the pharmaceutical industry. Recent experimental studies have shown that, as in near-spherical proteins, antibodies can undergo a liquid-liquid phase separation under conditions metastable with respect to crystallization. However, the phase diagram of the Y-shaped antibodies exhibits unique features that differ substantially from those of spherical proteins. Specifically, antibody solutions have an exceptionally low critical volume fraction (CVF) and a broader and more asymmetric liquid-liquid coexistence curve than those of spherical proteins. Using molecular dynamics simulation on a series of trimetric Y-shaped coarse-grained models, we investigate the phase behavior of antibody solutions and compare the results with the experimental phase diagram of human immunoglobulin G (IgG), one of the most common Y-shape typical of antibody molecules. With the fitted size of spheres, our simulation reproduces both the low CVF and the asymmetric shape of the experimental coexistence curve of IgG antibodies. The broadness of the coexistence curve can be attributed to the anisotropic nature of the inter-protein interaction. In addition, the repulsion between the inner parts of the spherical domains of IgG dramatically expands the coexistence region in the scaled phase diagram, while the hinge length has only a minor effect on the CVF and the overall shape of the coexistence curve. We thus propose a seven-site model with empirical parameters characterizing the exclusion volume and the hinge length of the IgG molecules, which provides a base for simulation studies of the phase behavior of IgG antibodies.
Salting-out effects by pressure-corrected 3D-RISM
Authors: Misin Maksim , Vainikka Petteri A. , Fedorov Maxim V. , Palmer David S.
Published: November 2016

We demonstrate that using a pressure corrected three-dimensional reference interaction site model one can accurately predict salting-out (Setschenow’s) constants for a wide range of organic compounds in aqueous solutions of NaCl. The approach, based on classical molecular force fields, offers an alternative to more heavily parametrized methods.
Transition to turbulence by interaction of free-stream and discrete mode perturbations
Authors: Bose Rikhi , Durbin Paul A.
Published: November 2016

Mixed mode transition is studied by direct numerical simulation. Low frequency streaks are induced within the boundary layer by free-stream turbulence and an Orr-Sommerfeld discrete mode eigenfunction is introduced at the inlet. Amplitudes are selected such that the interaction of these modes can cause transition. Aside from the highest amplitude of free-stream turbulence, neither disturbance alone is sufficient to cause transition within the flow domain. Results are classified into three routes to transition, depending upon the 2D Tollmien-Schlichting (TS) mode strength and free-stream turbulence intensity. (1) At low turbulence intensities, secondary instabilities instigate transition. On a strong TS mode, Λ vortices develop, but they are neither H nor K type. The pattern and spanwise size of Λ vortices depend upon the frequency and spanwise width of Klebanoff streaks by which they are generated. (2) When the TS mode amplitude is low, transition is via streak breakdown. The streaks are induced by the free-stream turbulence, but this case differs from conventional bypass transition in the mechanism of inception of turbulent spots. Three dimensional visualizations of the perturbation flow field show growing, helical undulations similar to n = 1 instability modes observed in axisymmetric jets and wakes. (3) At high turbulence intensities, the flow undergoes bypass transition. The TS wave has a small effect, but its influence is seen at the larger of the two amplitudes studied.
Commercial counterboard for 10 ns software correlator for photon and fluorescence correlation spectroscopy
Authors: Molteni Matteo , Ferri Fabio
Published: November 2016

A 10 ns time resolution, multi-tau software correlator, capable of computing simultaneous autocorrelation (A-A, B-B) and cross (A-B) correlation functions at count rates up to ∼10 MHz, with no data loss, has been developed in LabVIEW and C++ by using the National Instrument timer/counterboard (NI PCIe-6612) and a fast Personal Computer (PC) (Intel Core i7-4790 Processor 3.60 GHz ). The correlator works by using two algorithms: for large lag times (τ ≳ 1 μs), a classical time-mode scheme, based on the measure of the number of pulses per time interval, is used; differently, for τ ≲ 1 μs a photon-mode (PM) scheme is adopted and the correlation function is retrieved from the sequence of the photon arrival times. Single auto- and cross-correlation functions can be processed online in full real time up to count rates of ∼1.8 MHz and ∼1.2 MHz, respectively. Two autocorrelation (A-A, B-B) and a cross correlation (A-B) functions can be simultaneously processed in full real time only up to count rates of ∼750 kHz. At higher count rates, the online processing takes place in a delayed modality, but with no data loss. When tested with simulated correlation data and latex spheres solutions, the overall performances of the correlator appear to be comparable with those of commercial hardware correlators, but with several nontrivial advantages related to its flexibility, low cost, and easy adaptability to future developments of PC and data acquisition technology.
Molecular weight effects on interfacial properties of linear and ring polymer melts: A molecular dynamics study
Authors: Meddah Chahrazed , Milchev Andrey , Sabeur Sid Ahmed , Skvortsov Alexander M.
Published: November 2016

Using molecular dynamics simulations, we study and compare the pressure, P, and the surface tension, γ, of linear chains and of ring polymers at the hard walls confining both melts into a slit. We examine the dependence of P and γ on the length (i.e., molecular weight) N of the macromolecules. For linear chains, we find that both pressure and surface tension are inversely proportional to the chain length, P(N)−P(N→∞)∝N−1,γ(N)−γ(N→∞)∝N−1, irrespective of whether the confining planes attract or repel the monomers. In contrast, for melts comprised of cyclic (ring) polymers, neither the pressure nor the surface tension is found to depend on molecular weight N for both kinds of wall-monomer interactions. While other structural properties as, e.g., the probability distributions of trains and loops at impenetrable walls appear quantitatively indistinguishable, we observe an amazing dissimilarity in the probability to find a chain end or a tagged monomer of a ring at a given distance from the wall in both kinds of polymeric melts. In particular, we demonstrate that the conformational equivalence of linear chains in a confined melt to a single chain under conditions of critical adsorption to a planar surface, established two decades ago, does also hold for ring polymers in a melt of linear chains. This analogy does not hold, however, for linear and ring chains in a confined melt of ring chains.
Near-field radiative heat transfer between doped-Si parallel plates separated by a spacing down to 200 nm
Authors: Watjen Jesse I. , Zhao Bo , Zhang Zhuomin M.
Published: November 2016

Heat transfer between two objects separated by a nanoscale vacuum gap holds great promise especially in energy harvesting applications such as near-field thermophotovoltaic systems. However, experimental validation of nanoscale radiative heat transfer has been largely limited to tip-plate configurations due to challenges of maintaining small gap spacing over a relatively large area. Here, we report measurements of heat transfer near room temperature between two 1 cm by 1 cm doped-Si parallel plates, separated by a vacuum gap from about 200 nm to 780 nm. The measured strong near-field radiative transfer is in quantitative agreement with the theoretical prediction based on fluctuational electrodynamics. The largest measured radiative heat flux is 11 times as high as the blackbody limit for the same hot and cold surface temperatures. Our experiments have produced the highest radiative heat transfer rate observed to date across submicron distances between objects near room temperature.
Measured electrical charge of SiO2 in polar and nonpolar media
Authors: Kokot G. , Bespalova M. I. , Krishnan M.
Published: November 2016

We present measurements of the net electrical surface charge of silicon dioxide (SiO2) in contact with solvents of dielectric constants between 5 and 80. Our experimental approach relies on observing the thermal motion of single silica particles confined in an electrostatic fluidic trap created by SiO2 surfaces. We compare the experimentally measured functional form of the trapping potential with that from free energy calculations and thereby determine the net surface charge in the system. Our findings clearly demonstrate that contrary to popular perception, even in the absence of surfactants, the net electrical charge of ionizable surfaces in contact with apolar solvents can be large enough to lead to significant repulsive forces. A charge regulation model for SiO2 surfaces with a single tunable parameter explains our measurements. This model may find general applicability in estimating the net charge of ionizable surfaces, given system parameters such as the dissociation or association constants of the ionizable groups and the pH, ionic strength, and dielectric constant of the solvent phase.
On the feasibility of designing hyperalkali cations using superalkali clusters as ligands
Authors: Sun Wei-Ming , Li Xiang-Hui , Li Ying , Liu Jia-Yuan , Wu Di , Li Chun-Yan , Ni Bi-Lian , Li Zhi-Ru
Published: November 2016

The possibility of using superalkali clusters instead of alkali atoms as ligands to design a class of cationic compounds, referred to as hyperalkali cations, has been examined by using gradient-corrected density functional theory. By taking typical superalkalis (FLi2, OLi3, and NLi4) as examples, a series of hyperalkali cations ML2+ [M = (super)halogen; L = superalkali] have been constructed and investigated. Calculational results show that all the superalkali moieties preserve their geometric and electronic integrity in these proposed cations. The stability of these studied cations is guaranteed by the strong ionic bonds between superalkali ligand and (super)halogen core, as well as their large highest occupied molecular orbital–lowest unoccupied molecular orbital gaps and positive dissociation energies. In particular, all these proposed cations possess lower vertical electron affinities (2.36–3.56 eV) than those of their corresponding cationic superalkali ligands, verifying their hyperalkali nature. We, therefore, hope that this study will provide an approach to obtain new species with excellent reducing capability by utilizing various superalkalis as building blocks.
48-channel coincidence counting system for multiphoton experiment
Authors: Zhang Chen , Li Wei , Hu Yi , Yang Tao , Jin Ge , Jiang Xiao
Published: November 2016

In this paper, we demonstrate a coincidence counting system with 48 input channels which is aimed to count all coincidence events, up to 531 441 kinds, in a multiphoton experiment. Using the dynamic delay adjusting inside the Field Programmable Gate Array, the alignment of photon signals of 48 channels is achieved. After the alignment, clock phase shifting is used to sample signal pulses. Logic constraints are used to stabilize the pulse width. The coincidence counting data stored in a 1G bit external random access memory will be sent to the computer to analyze the amount of 2-, 3-, 4-, 5-, and 6-fold coincidence events. This system is designed for multiphoton entanglement experiments with multiple degrees of freedom of photons.
Design and characterization of a linear Hencken-type burner
Authors: Campbell M. F. , Bohlin G. A. , Schrader P. E. , Bambha R. P. , Kliewer C. J. , Johansson K. O. , Michelsen H. A.
Published: November 2016

We have designed and constructed a Hencken-type burner that produces a 38-mm-long linear laminar partially premixed co-flow diffusion flame. This burner was designed to produce a linear flame for studies of soot chemistry, combining the benefit of the conventional Hencken burner’s laminar flames with the advantage of the slot burner’s geometry for optical measurements requiring a long interaction distance. It is suitable for measurements using optical imaging diagnostics, line-of-sight optical techniques, or off-axis optical-scattering methods requiring either a long or short path length through the flame. This paper presents details of the design and operation of this new burner. We also provide characterization information for flames produced by this burner, including relative flow-field velocities obtained using hot-wire anemometry, temperatures along the centerline extracted using direct one-dimensional coherent Raman imaging, soot volume fractions along the centerline obtained using laser-induced incandescence and laser extinction, and transmission electron microscopy images of soot thermophoretically sampled from the flame.
Airfoil-based electromagnetic energy harvester containing parallel array motion between moving coil and multi-pole magnets towards enhanced power density
Authors: Leung Chung Ming , Wang Ya , Chen Wusi
Published: November 2016

In this letter, the airfoil-based electromagnetic energy harvester containing parallel array motion between moving coil and trajectory matching multi-pole magnets was investigated. The magnets were aligned in an alternatively magnetized formation of 6 magnets to explore enhanced power density. In particular, the magnet array was positioned in parallel to the trajectory of the tip coil within its tip deflection span. The finite element simulations of the magnetic flux density and induced voltages at an open circuit condition were studied to find the maximum number of alternatively magnetized magnets that was required for the proposed energy harvester. Experimental results showed that the energy harvester with a pair of 6 alternatively magnetized linear magnet arrays was able to generate an induced voltage (Vo) of 20 V, with an open circuit condition, and 475 mW, under a 30 Ω optimal resistance load operating with the wind speed (U) at 7 m/s and a natural bending frequency of 3.54 Hz. Compared to the traditional electromagnetic energy harvester with a single magnet moving through a coil, the proposed energy harvester, containing multi-pole magnets and parallel array motion, enables the moving coil to accumulate a stronger magnetic flux in each period of the swinging motion. In addition to the comparison made with the airfoil-based piezoelectric energy harvester of the same size, our proposed electromagnetic energy harvester generates 11 times more power output, which is more suitable for high-power-density energy harvesting applications at regions with low environmental frequency.
Highly sensitive superconducting circuits at ∼700 kHz with tunable quality factors for image-current detection of single trapped antiprotons
Authors: Nagahama H. , Schneider G. , Mooser A. , Smorra C. , Sellner S. , Harrington J. , Higuchi T. , Borchert M. , Tanaka T. , Besirli M. , Blaum K. , Matsuda Y. , Ospelkaus C. , Quint W. , Walz J. , Yamazaki Y. , Ulmer S.
Published: November 2016

We developed highly sensitive image-current detection systems based on superconducting toroidal coils and ultra-low noise amplifiers for non-destructive measurements of the axial frequencies (550–800 kHz) of single antiprotons stored in a cryogenic multi-Penning-trap system. The unloaded superconducting tuned circuits show quality factors of up to 500 000, which corresponds to a factor of 10 improvement compared to our previously used solenoidal designs. Connected to ultra-low noise amplifiers and the trap system, signal-to-noise-ratios of 30 dB at quality factors of >20 000 are achieved. In addition, we have developed a superconducting switch which allows continuous tuning of the detector’s quality factor and to sensitively tune the particle-detector interaction. This allowed us to improve frequency resolution at constant averaging time, which is crucial for single antiproton spin-transition spectroscopy experiments, as well as improved measurements of the proton-to-antiproton charge-to-mass ratio.
Laser-induced asymmetric faceting and growth of a nano-protrusion on a tungsten tip
Authors: Yanagisawa Hirofumi , Zadin Vahur , Kunze Karsten , Hafner Christian , Aabloo Alvo , Kim Dong Eon , Kling Matthias F. , Djurabekova Flyura , Osterwalder Jürg , Wuensch Walter
Published: November 2016

Irradiation of a sharp tungsten tip by a femtosecond laser and exposed to a strong DC electric field led to reproducible surface modifications. By a combination of field emission microscopy and scanning electron microscopy, we observed asymmetric surface faceting with sub-ten nanometer high steps. The presence of faceted features mainly on the laser-exposed side implies that the surface modification was driven by a laser-induced transient temperature rise on a scale of a couple of picoseconds in the tungsten tip apex. Moreover, we identified the formation of a nano-tip a few nanometers high located at one of the corners of a faceted plateau. The results of simulations emulating the experimental conditions are consistent with the experimental observations. The presented technique would be a new method to fabricate a nano-tip especially for generating coherent electron pulses. The features may also help to explain the origin of enhanced field emission, which leads to vacuum arcs, in high electric field devices such as radio-frequency particle accelerators.
Melting along the Hugoniot and solid phase transition for Sn via sound velocity measurements
Authors: Song Ping , Cai Ling-cang , Tao Tian-jiong , Yuan Shuai , Chen Hong , Huang Jin , Zhao Xin-wen , Wang Xue-jun
Published: November 2016

It is very important to determine the phase boundaries for materials with complex crystalline phase structures to construct their corresponding multi-phase equation of state. By measuring the sound velocity of Sn with different porosities, different shock-induced melting pressures along the solid-liquid phase boundary could be obtained. The incipient shock-induced melting of porous Sn samples with two different porosities occurred at a pressure of about 49.1 GPa for a porosity of 1.01 and 45.6 GPa for a porosity of 1.02, based on measurements of the sound velocity. The incipient shock-induced melting pressure of solid Sn was revised to 58.1 GPa using supplemental measurements of the sound velocity. Trivially, pores in Sn decreased the shock-induced melting pressure. Based on the measured longitudinal sound velocity data, a refined solid phase transition and the Hugoniot temperature-pressure curve's trend are discussed. No bcc phase transition occurs along the Hugoniot for porous Sn; further investigation is required to understand the implications of this finding.
Liquid-phase catalytic reactor combined with measurement of hot electron flux and chemiluminescence
Authors: Nedrygailov Ievgen I. , Lee Changhwan , Moon Song Yi , Lee Hyosun , Park Jeong Young
Published: November 2016

Understanding the role of electronically nonadiabatic interactions during chemical reactions on metal surfaces in liquid media is of great importance for a variety of applications including catalysis, electrochemistry, and environmental science. Here, we report the design of an experimental apparatus for detection of the highly excited (hot) electrons created as a result of nonadiabatic energy transfer during the catalytic decomposition of hydrogen peroxide on thin-film metal–semiconductor nanodiodes. The apparatus enables the measurement of hot electron flows and related phenomena (e.g., surface chemiluminescence) as well as the corresponding reaction rates at different temperatures. The products of the chemical reaction can be characterized in the gaseous phase by means of gas chromatography. The combined measurement of hot electron flux, catalytic activity, and light emission can lead to a fundamental understanding of the elementary processes occurring during the heterogeneous catalytic reaction.
Effects of Taylor-Görtler vortices on turbulent flows in a spanwise-rotating channel
Authors: Dai Yi-Jun , Huang Wei-Xi , Xu Chun-Xiao
Published: November 2016

Fully developed turbulent channel flow with system rotation in the spanwise direction has been studied by direct numerical simulation at Rem = 2800 and 7000 with 0 ≤ Rom ≤ 0.5. The width of the computational domain is adjusted for each case to contain two pairs of Taylor-Görtler (TG) vortices. Under a relatively low rotation rate, the turbulent vortical structures are strongly influenced by the TG vortices. A conditional average method is employed to investigate the effects of these TG vortices on turbulence. In the upwash region where the fluid is pumped away from the pressure wall by the TG vortices, turbulence is found to be enhanced, while the opposite scenario occurs in the downwash region where the fluid is shifted toward the pressure wall. The statistics along the centerlines of the two regions of a TG vortex are presented in detail. Through the budget analysis of the transport equation of vorticity fluctuations, we found that the wall-normal stretching term caused by the TG vortices plays an important role in initiating the differences of turbulence intensities between the two regions, which are further augmented by the Coriolis force term in the streamwise direction. Meanwhile, the shear stress on the suction wall is observed to fluctuate in a quasi-periodic manner at Rem = 7000 and Rom = 0.3, which is also revealed to be induced by the TG vortices. Such quasi-periodicity is not found at Rem = 2800 and Rom = 0.3, where turbulence on the suction side is strongly suppressed by rotation.
A micro-nano-rheometer for the mechanics of soft matter at interfaces
Authors: Garcia Léo , Barraud Chloé , Picard Cyril , Giraud Jérôme , Charlaix Elisabeth , Cross Benjamin
Published: November 2016

We present a nano-rheometer based on the dynamic drainage flow between a sphere and a plane from bulk regime to highly confined regime. The instrument gives absolute measurements of the viscosity of simple liquids in both regimes. For complex fluids, the measurements involve the viscosity and the elastic modulus. The device operates on distances ranging over four orders of magnitude from 1 nm to 10 μm, bridging rheological properties from the macroscopic to the molecular scale. This allows to measure an hydrodynamic or visco-elastic boundary condition and to explore the causes of the boundary condition at the microscopic level.
The linear stability of swirling vortex rings
Authors: Gargan-Shingles C. , Rudman M. , Ryan K.
Published: November 2016

The stability of vortex rings with an azimuthal component of velocity is investigated numerically for various combinations of ring wavenumber and swirl magnitude. The vortex rings are equilibrated from an initially Gaussian distribution of azimuthal vorticity and azimuthal velocity, at a circulation-based Reynolds number of 10 000, to a state in which the vortex core is qualitatively identical to that of the piston generated vortex rings. The instability modes of these rings can be characterised as Kelvin instability modes, analogous to instability modes observed for Gaussian and Batchelor vortex pairs. The shape of an amplified mode typically depends only on the azimuthal wavenumber at the centre of the vortex core and the magnitude of the corresponding velocity component. The wavenumber of a particular sinuous instability varies with radius from the vortex ring centre for rings of finite aspect ratio. Thicker rings spread the amplification over a wider range of wavenumbers for a particular resonant mode pair, while the growth rate and the azimuthal wavenumber corresponding to the peak growth both vary as a function of the wavenumber variation. Normalisation of the wavenumber and the growth rate by a measure of the wavenumber variation allows a coherent description of stability modes to be proposed, across the parameter space. These results provide a framework for predicting the development of resonant Kelvin instabilities on vortex rings with an induced component of swirling velocity.
A viable non-axisymmetric non-force-free field to represent solar active regions
Authors: Prasad A. , Bhattacharyya R.
Published: November 2016

A combination of analytical calculations and vectormagnetogram data is utilized to develop a non-axisymmetric non-force-free magnetic field and assess its viability in describing solar active regions. For that purpose, we construct a local spherical shell where a planar surface, tangential to the inner sphere, represents a Cartesian cutout of an active region. The magnetic field defined on the surface is then correlated with magnetograms. The analysis finds that the non-axisymmetric non-force-free magnetic field, obtained by a superposition of two linear-force-free fields, correlates reasonably well with magnetograms.
Spin effects on the EM wave modes in magnetized plasmas
Authors: Hu Qiang-Lin , Zhou Shen-Lin , Yu Xiao-Guang , Xiao Gui-Lan , Luo Xiao-Bing , Cao Ren-Ping
Published: November 2016

The spin effects on the electromagnetic (EM) wave propagating in arbitrary direction in magnetized plasma are considered. The dispersion relations for EM propagating parallel and perpendicular to the external magnetic field are obtained. It is shown that the spin effects have significant influence on the low frequency modes. New wave modes appear both in left-hand polarized waves propagating parallel to the external magnetic field and in the traditional ordinary waves propagating perpendicular to the external magnetic field. Particularly, the new modes of the latter may exist even in moderate-density magnetized plasmas.
Region of validity of the Thomas–Fermi model with corrections
Authors: Dyachkov Sergey , Levashov Pavel , Minakov Dmitry
Published: November 2016

A new method to calculate thermodynamically consistent shell corrections in a wide range of parameters is used to predict the region of validity of the Thomas-Fermi approach. The method is applicable both at low and high density. Thermodynamic functions of electrons calculated by the Thomas–Fermi model are compared with quantum, exchange, and shell corrections. The corrections become quite big at moderate and low densities and low temperatures in the region of strongly coupled plasma.
Comment on “The universal instability in general geometry” [Phys. Plasmas 22, 090706 (2015)]
Authors: Smolyakov A. I. , Yagi M. , Kishimoto Y.
Published: November 2016

It is pointed out that the destabilization mechanism recently discussed by Helander and Plunk in relation to the universal instability was studied previously by Smolyakov et al. [Phys. Rev. Lett. 89, 125005 (2002)]. Moreover, the contribution of the trapped particles as discussed by Helander and Plunk is closely related to the mechanism of the ubiquitous instability previously studied by Coppi and Pegoraro [Nucl. Fusion 17, 969 (1977)].
Communication: “Position” does matter: The photofragmentation of the nitroimidazole isomers
Authors: Bolognesi P. , Casavola A. R. , Cartoni A. , Richter R. , Markus P. , Borocci S. , Chiarinelli J. , Tošić S. , Sa’adeh H. , Masič M. , Marinković B.P. , Prince K.C. , Avaldi L.
Published: November 2016

A combined experimental and theoretical approach has been used to disentangle the fundamental mechanisms of the fragmentation of the three isomers of nitroimidazole induced by vacuum ultra-violet (VUV) radiation, namely, 4-, 5-, and 2-nitroimidazole. The results of mass spectrometry as well as photoelectron–photoion coincidence spectroscopy display striking differences in the radiation-induced decomposition of the different nitroimidazole radical cations. Based on density functional theory (DFT) calculations, a model is proposed which fully explains such differences, and reveals the subtle fragmentation mechanisms leading to the release of neutral species like NO, CO, and HCN. Such species have a profound impact in biological media and may play a fundamental role in radiosensitising mechanisms during radiotherapy.
Communication: Cargo towing by artificial swimmers
Authors: Debnath Debajyoti , Ghosh Pulak K. , Li Yunyun , Marchesoni Fabio , Li Baowen
Published: November 2016

An active swimmer can tow a passive cargo by binding it to form a self-propelling dimer. The orientation of the cargo relative to the axis of the active dimer’s head is determined by the hydrodynamic interactions associated with the propulsion mechanism of the latter. We show how the tower-cargo angular configuration greatly influences the dimer’s diffusivity and, therefore, the efficiency of the active swimmer as a micro-towing motor.
Acoustic imaging and mirage effects with high transmittance in a periodically perforated metal slab
Authors: Zhao Sheng-Dong , Wang Yue-Sheng , Zhang Chuanzeng
Published: November 2016

In this paper, we present a high-quality superlens to focus acoustic waves using a periodically perforated metallic structure which is made of zinc and immersed in water. By changing a geometrical parameter gradually, a kind of gradient-index phononic crystal lens is designed to attain the mirage effects. The acoustic waves can propagate along an arc-shaped trajectory which is precisely controlled by the angle and frequency of the incident waves. The negative refraction imaging effect depends delicately on the transmittance of the solid structure. The acoustic impedance matching between the solid and the liquid proposed in this article, which is determined by the effective density and group velocity of the unit-cell, is significant for overcoming the inefficiency problem of acoustic devices. This study focuses on how to obtain the high transmittance imaging and mirage effects based on the adequate material selection and geometrical design.
The dynamics of copper intercalated molybdenum ditelluride
Authors: Onofrio Nicolas , Guzman David , Strachan Alejandro
Published: November 2016

Layered transition metal dichalcogenides are emerging as key materials in nanoelectronics and energy applications. Predictive models to understand their growth, thermomechanical properties, and interaction with metals are needed in order to accelerate their incorporation into commercial products. Interatomic potentials enable large-scale atomistic simulations connecting first principle methods and devices. We present a ReaxFF reactive force field to describe molybdenum ditelluride and its interactions with copper. We optimized the force field parameters to describe the energetics, atomic charges, and mechanical properties of (i) layered MoTe2, Mo, and Cu in various phases, (ii) the intercalation of Cu atoms and small clusters within the van der Waals gap of MoTe2, and (iii) bond dissociation curves. The training set consists of an extensive set of first principles calculations computed using density functional theory (DFT). We validate the force field via the prediction of the adhesion of a single layer MoTe2 on a Cu(111) surface and find good agreement with DFT results not used in the training set. We characterized the mobility of the Cu ions intercalated into MoTe2 under the presence of an external electric field via finite temperature molecular dynamics simulations. The results show a significant increase in drift velocity for electric fields of approximately 0.4 V/Å  and that mobility increases with Cu ion concentration.
Electronic ground state of Ni2+
Authors: Zamudio-Bayer V. , Lindblad R. , Bülow C. , Leistner G. , Terasaki A. , v. Issendorff B. , Lau J. T.
Published: November 2016

The Φ9/24 ground state of the Ni2+ diatomic molecular cation is determined experimentally from temperature and magnetic-field-dependent x-ray magnetic circular dichroism spectroscopy in a cryogenic ion trap, where an electronic and rotational temperature of 7.4±0.2 K was reached by buffer gas cooling of the molecular ion. The contribution of the spin dipole operator to the x-ray magnetic circular dichroism spin sum rule amounts to 7Tz=0.17±0.06μB per atom, approximately 11% of the spin magnetic moment. We find that, in general, homonuclear diatomic molecular cations of 3d transition metals seem to adopt maximum spin magnetic moments in their electronic ground states.
A numerical study of shock waves generated through laser ablation of explosives
Authors: Bai Wenyu , Diebold Gerald J. , Wynn Charles M. , Haupt Robert W. , Doherty John H.
Published: November 2016

Shock waves resulting from irradiation of energetic materials with a pulsed ultraviolet laser source have been shown to be an effective indicator for explosives detection. Here, the features of shock wave propagation are explored theoretically. The initial stage of the shock motion is simulated as a one-dimensional process. As the nonlinear wave expands to form a blast wave, a system of conservation equations, simplified to the Euler equations, is employed to model wave propagation. The Euler equations are solved numerically by the 5th order weighted essentially non-oscillatory finite difference scheme with the time integration carried out using the 3rd order total variation diminishing Runge Kutta method. The numerical results for the shock wave evolution are compared with those obtained from experiments with a meltcast 2,6-dinitrotoluene sample. The calculations lay a theoretical foundation for a recently investigated technique for photoacoustically sensing explosives using a vibrometer.
Above room temperature continuous wave operation of a broad-area quantum-cascade laser
Authors: Semtsiv M. P. , Masselink W. T.
Published: November 2016

We describe the design and implementation of a broad-area (w ≈ 30 μm) quantum-cascade laser operating in a continuous wave mode up to heat-sink temperatures beyond +100 °C. The room-temperature emission wavelength is 4.6 μm. The temperature gradient in the active region of such a wide laser stripe is essentially perpendicular to the epitaxial layers and the resulting steady-state active region temperature offset scales approximately with the square of the number of cascades. With only 10 cascades in the active region, the threshold electrical power density in the current quantum-cascade laser in the continuous-wave mode is as low as Vth × Ith = 3.8 V × 0.9 kA/cm2 = 3.4 kW/cm2 at room temperature for 2 mm-long two-side high-reflectivity coated laser stripe. A 4 mm-long one-side high-reflectivity coated laser stripe delivers in continuous-wave mode above 0.6 W at +20 °C and above 1.3 W at −27 °C (cooled with a single-stage Peltier element). A 2 mm-long two-side high-reflectivity coated laser stripe demonstrates continuous-wave lasing up to at least +102 °C (375 K). The thermal conductance, Gth, ranges between 235 W/K cm2 and 140 W/K cm2 for temperatures between −33 °C and +102 °C. This demonstration opens the route for continuous-wave power scaling of quantum-cascade lasers via broad-area laser ridges.
Sub-milliwatt AlGaN nanowire tunnel junction deep ultraviolet light emitting diodes on silicon operating at 242 nm
Authors: Zhao S. , Sadaf S. M. , Vanka S. , Wang Y. , Rashid R. , Mi Z.
Published: November 2016

We report AlGaN nanowire light emitting diodes (LEDs) operating in the ultraviolet-C band. The LED structures are grown by molecular beam epitaxy on Si substrate. It is found that with the use of the n+-GaN/Al/p+-AlGaN tunnel junction (TJ), the device resistance is reduced by one order of magnitude, and the light output power is increased by two orders of magnitude, compared to AlGaN nanowire LEDs without TJ. For unpackaged TJ ultraviolet LEDs emitting at 242 nm, a maximum output power of 0.37 mW is measured, with a peak external quantum efficiency up to 0.012%.
Growth and characterization of TbAs films
Authors: Bomberger Cory C. , Tew Bo E. , Lewis Matthew R. , Zide Joshua M. O.
Published: November 2016

We report on the molecular beam epitaxy growth and characterization of TbAs films. In situ reflection high energy electron diffraction and ex situ high resolution X-ray diffraction, reciprocal space mapping, and both scanning and transmission electron microscopy are used to confirm the complete film growth and study the films' morphology. Spectrophotometry measurements provide the energy of optical transitions, revealing a red shift in optical band gap with increasing thickness. The Hall effect measurements show temperature insensitive carrier concentrations, resistivities, and mobilities. The carrier concentration decreases and resistivity increases with increasing film thickness; mobility appears thickness independent. The films' reflectivity, obtained via Fourier transform infrared spectroscopy, shows a possible Drude edge that differs from the trend of other lanthanide monopnictides. These measurements show that TbAs is a degenerately doped semiconductor with a combination of electronic and optical properties that is dissimilar to other lanthanide monopnictides.
Spin-torque ferromagnetic resonance measurements utilizing spin Hall magnetoresistance in W/Co40Fe40B20/MgO structures
Authors: He Congli , Navabi Aryan , Shao Qiming , Yu Guoqiang , Wu Di , Zhu Weihua , Zheng Cheng , Li Xiang , He Qing Lin , Razavi Seyed Armin , Wong Kin L. , Zhang Zongzhi , Amiri Pedram Khalili , Wang Kang L.
Published: November 2016

We study the magnetic properties of W/Co40Fe40B20 (CoFeB)/MgO films using the spin-torque ferromagnetic resonance (ST-FMR) technique. This study takes the advantage of the spin Hall magnetoresistance (SMR) for generating an oscillating resistance, which is one of the necessary requirements for obtaining mixing voltage in the ST-FMR technique. We have measured both the as-grown and the annealed samples with different CoFeB layer thicknesses, which include the in-plane and out-of-plane magnetic anisotropies. The spectra for these two types of anisotropies show distinct signatures. By analyzing the ST-FMR spectra, we extract the effective anisotropy field for both types of samples. In addition, we investigate the influence of CoFeB thickness and annealing on the Gilbert damping constant. Our experiments show that by taking advantage of SMR, the ST-FMR measurement acts as an effective tool with high sensitivity for studying the magnetic properties of ultrathin magnetic films.