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https://www.readbyqxmd.com/read/28737402/ultrafast-hot-carrier-dynamics-in-gan-and-its-impact-on-the-efficiency-droop
#1
Vatsal Jhalani, Jin-Jian Zhou, Marco Bernardi
GaN is a key material for lighting technology. Yet, the carrier transport and ultrafast dynamics that are central in GaN light emitting devices are not completely understood. We present first-principles calculations of carrier dynamics in GaN, focusing on electron-phonon (e-ph) scattering and the cooling and nanoscale dynamics of hot carriers. We find that e-ph scattering is significantly faster for holes compared to electrons, and that for hot carriers with an initial 0.5 - 1 eV excess energy, holes take a significantly shorter time (~0...
July 24, 2017: Nano Letters
https://www.readbyqxmd.com/read/28735546/room-temperature-quantum-ballistic-transport-in-monolithic-ultrascaled-al-ge-al-nanowire-heterostructures
#2
Masiar Sistani, Philipp Staudinger, Johannes Greil, Martin Holzbauer, Hermann Detz, Emmerich Bertagnolli, Alois Lugstein
Conductance quantization at room temperature is a key requirement to utilize ballistic transport for e.g. high performance, low power dissipating transistors operating at the upper limit of ON-state conductance or multi-valued logic gates. So far, studying conductance quantization has been restricted to high mobility materials at ultralow temperatures and requires sophisticated nanostructure formation techniques and precise lithography for contact formation. Utilizing a thermally induced exchange reaction between single-crystalline Ge nanowires (NWs) and Al pads, we achieved monolithic Al-Ge-Al NW heterostructures with ultrasmall Ge segments contacted by self-aligned quasi one-dimensional crystalline Al (c-Al) leads...
July 22, 2017: Nano Letters
https://www.readbyqxmd.com/read/28733638/quantum-thermalization-and-the-expansion-of-atomic-clouds
#3
Louk Rademaker, Jan Zaanen
The ultimate consequence of quantum many-body physics is that even the air we breathe is governed by strictly unitary time evolution. The reason that we perceive it nonetheless as a completely classical high temperature gas is due to the incapacity of our measurement machines to keep track of the dense many-body entanglement of the gas molecules. The question thus arises whether there are instances where the quantum time evolution of a macroscopic system is qualitatively different from the equivalent classical system? Here we study this question through the expansion of noninteracting atomic clouds...
July 21, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28732167/quantum-transport-and-subband-structure-of-modulation-doped-gaas-alas-core-superlattice-nanowires
#4
Dominik Irber, Jakob Seidl, Damon James Carrad, Jonathan Becker, Nari Jeon, Bernhard Loitsch, Julia Winnerl, Sonja Matich, Markus Döblinger, Yang Tang, Stefanie Morkötter, Gerhard Abstreiter, Jonathan J Finley, M Grayson, Lincoln Lauhon, Gregor Koblmueller
Modulation-doped III-V semiconductor nanowire (NW) heterostructures have recently emerged as promising candidates to host high-mobility electron channels for future high-frequency, low-energy transistor technologies. The one-dimensional geometry of NWs also makes them attractive for studying quantum confinement effects. Here, we report correlated investigations into the discrete electronic sub-band structure of confined electrons in the channel of Si delta-doped GaAs/AlAs core-superlattice NW heterostructures and the associated signatures in low-temperature transport...
July 21, 2017: Nano Letters
https://www.readbyqxmd.com/read/28731774/femtosecond-spin-current-pulses-generated-by-the-nonthermal-spin-dependent-seebeck-effect-and-interacting-with-ferromagnets-in-spin-valves
#5
Alexandr Alekhin, Ilya Razdolski, Nikita Ilin, Jan P Meyburg, Detlef Diesing, Vladimir Roddatis, Ivan Rungger, Maria Stamenova, Stefano Sanvito, Uwe Bovensiepen, Alexey Melnikov
Using the sensitivity of optical second harmonic generation to currents, we demonstrate the generation of 250-fs long spin current pulses in Fe/Au/Fe/MgO(001) spin valves. The temporal profile of these pulses indicates ballistic transport of hot electrons across a sub-100 nm Au layer. The pulse duration is primarily determined by the thermalization time of laser-excited hot carriers in Fe. Considering the calculated spin-dependent Fe/Au interface transmittance we conclude that a nonthermal spin-dependent Seebeck effect is responsible for the generation of ultrashort spin current pulses...
July 7, 2017: Physical Review Letters
https://www.readbyqxmd.com/read/28727920/ballistic-penetration-of-highly-charged-nanoaerosol-particles-through-a-lipid-monolayer
#6
Victor N Morozov, Yuri M Shlyapnikov, Igor L Kanev, Elena Andreevna Shlyapnikova
To be used as a drug, inhaled nanoaerosol particles (NAPs) must first penetrate the lipid layer on top of the lung fluid before they will be able to reach the lung epithelium. We investigated how the penetration of NAPs through a model lipid monolayer (LM) depends upon their charging level and size. It was shown that deposition of NAPs 20-200 nm in diameter and charged to the Rayleigh limit gradually increased the surface tension of a dipalmitoylphosphatidylcholine monolayer (DPPC), indicating a loss of lipid molecules from the monolayer...
July 20, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
https://www.readbyqxmd.com/read/28721724/addressing-the-environment-electrostatic-effect-on-ballistic-electron-transport-in-large-systems-a-qm-mm-negf-approach
#7
Gustavo T Feliciano, Carlos Sanz-Navarro, Mauricio Domingues Coutinho-Neto, Pablo Ordejón, Ralph H Scheicher, Alexandre Reily Rocha
The effects of the environment in nanoscopic materials can play a crucial role in device design. Particularly in biosensors, where the system is usually embedded in a solution, water and ions have to be taken into consideration in atomistic simulations of electronic transport for a realistic description of the system. In this work, we present a methodology that combines quantum mechanics/molecular mechanics methods (QM/MM) with the nonequilibrium Green's function framework to simulate the electronic transport properties of nanoscopic devices in the presence of solvents...
July 19, 2017: Journal of Physical Chemistry. B
https://www.readbyqxmd.com/read/28720003/current-trends-in-the-management-of-ballistic-fractures-of-the-hand-and-wrist-experiences-of-a-high-volume-level-i-trauma-center
#8
Paul A Ghareeb, Charles Daly, Albert Liao, Diane Payne
BACKGROUND: Ballistic fractures of the carpus and hand are routinely treated in large urban centers. These injuries can be challenging due to many factors. Various treatment options exist for these complicated injuries, but there are limited data available. This report analyzes patient demographics, treatments, and outcomes at a large urban trauma center. METHODS: All ballistic fractures of the hand and wrist of the patients who presented to a single center from 2011 to 2014 were retrospectively reviewed...
March 1, 2017: Hand: Official Journal of the American Association for Hand Surgery
https://www.readbyqxmd.com/read/28719843/atomic-scale-modeling-of-electrically-doped-p-i-n-fet-from-adenine-based-single-wall-nanotube
#9
Debarati Dey, Pradipta Roy, Debashis De
The Field Effect Transistor (FET) characteristics has been observed from a single-walled Adenine nanotube device using Density Functional Theory associated with Non Equilibrium Green's Function based First Principle approach. This device is electrically doped which shows both n and p channel characteristics of a p-i-n FET. This device is designed and originated from a single-walled biomolecular nanotube structure. The p and n regions have been induced at the two ends of the device using electrical doping process...
July 10, 2017: Journal of Molecular Graphics & Modelling
https://www.readbyqxmd.com/read/28713458/trunk-strength-characteristics-of-elite-alpine-skiers-a-comparison-with-physically-active-controls
#10
Carolin Hildebrandt, Lisa Müller, Christian Heisse, Christian Raschner
Core muscle imbalances and weak trunk strength are relevant for injury prevention and performance. Information regarding core strength requirements and ideal flexion/extension ratios in alpine skiing is limited. We aimed to compare trunk strength capacities in elite alpine skiers with those of a matched control group. The concentric maximal trunk flexion and extension of 109 elite skiers and 47 active controls were measured at 150°/s in a ballistic mode using the CON-TREX® TP 1000 test system. The relative flexion peak torque was higher in male ski racers (p = 0...
June 2017: Journal of Human Kinetics
https://www.readbyqxmd.com/read/28709315/heat-perturbation-spreading-in-the-fermi-pasta-ulam-%C3%AE-system-with-next-nearest-neighbor-coupling-competition-between-phonon-dispersion-and-nonlinearity
#11
Daxing Xiong
We employ the heat perturbation correlation function to study thermal transport in the one-dimensional Fermi-Pasta-Ulam-β lattice with both nearest-neighbor and next-nearest-neighbor couplings. We find that such a system bears a peculiar phonon dispersion relation, and thus there exists a competition between phonon dispersion and nonlinearity that can strongly affect the heat correlation function's shape and scaling property. Specifically, for small and large anharmoncities, the scaling laws are ballistic and superdiffusive types, respectively, which are in good agreement with the recent theoretical predictions; whereas in the intermediate range of the nonlinearity, we observe an unusual multiscaling property characterized by a nonmonotonic delocalization process of the central peak of the heat correlation function...
June 2017: Physical Review. E
https://www.readbyqxmd.com/read/28703138/spin-diffusion-from-an-inhomogeneous-quench-in-an-integrable-system
#12
Marko Ljubotina, Marko Žnidarič, Tomaž Prosen
Generalized hydrodynamics predicts universal ballistic transport in integrable lattice systems when prepared in generic inhomogeneous initial states. However, the ballistic contribution to transport can vanish in systems with additional discrete symmetries. Here we perform large scale numerical simulations of spin dynamics in the anisotropic Heisenberg XXZ spin 1/2 chain starting from an inhomogeneous mixed initial state which is symmetric with respect to a combination of spin reversal and spatial reflection...
July 13, 2017: Nature Communications
https://www.readbyqxmd.com/read/28703121/quasiballistic-quantum-transport-through-ge-si-core-shell-nanowires
#13
Dharmraj Kotekar-Patil, Binh-Minh Nguyen, Jinkyoung Yoo, Shadi A Dayeh, Sergey M Frolov
We study signatures of ballistic quantum transport of holes through Ge/Si core/shell nanowires at low temperatures. We observe Fabry-Perot interference patterns as well as conductance plateaus at integer multiples of 2e^2/h at zero magnetic field. Magnetic field evolution of these plateaus reveals relatively large effective Lande g-factors. Ballistic effects are observed in nanowires with silicon shell thicknesses of 1 - 3 nm, but not in bare germanium wires. These findings inform the future development of spin and topological quantum devices which rely on ballistic subband-resolved transport...
July 13, 2017: Nanotechnology
https://www.readbyqxmd.com/read/28702804/the-dft-negf-scrutiny-of-doped-fullerene-junctions
#14
Milanpreet Kaur, Ravinder Singh Sawhney, Derick Engles
Using the smallest non-classical fullerene, we investigate the impact of doping at the molecule-electrode interface on the electron transport of molecular junctions. This is accomplished by employing the density functional theory combined with the non-equilibrium Green's function. We contemplate different electronic parameters, namely, density of states, transmission coefficient, energy levels, molecular orbitals, conduction gaps, electron density, and their charge transfer. The relevance of these physical parameters is obtained to calculate their electrical parameters, current, and conductance, computed from Landauer-Büttiker formalism...
August 2017: Journal of Molecular Modeling
https://www.readbyqxmd.com/read/28702697/the-acute-effect-of-strength-exercises-at-different-intensities-on-intraocular-pressure
#15
Jesús Vera, Amador García-Ramos, Raimundo Jiménez, David Cárdenas
BACKGROUND: This study aimed to determine the effect of two basic strength exercises with progressive loads on intraocular pressure (IOP). METHODS: Seventeen (out of 20 recruited) physically active male military officers (46 ± 4.77 years) performed the jump squat and the ballistic bench press exercises, in counterbalanced order, with four and five progressive loads, respectively. IOP was measured with a rebound tonometer before and after each of the corresponding loads...
July 12, 2017: Graefe's Archive for Clinical and Experimental Ophthalmology
https://www.readbyqxmd.com/read/28701719/dynamic-gene-expression-response-to-altered-gravity-in-human-t-cells
#16
Cora S Thiel, Swantje Hauschild, Andreas Huge, Svantje Tauber, Beatrice A Lauber, Jennifer Polzer, Katrin Paulsen, Hartwin Lier, Frank Engelmann, Burkhard Schmitz, Andreas Schütte, Liliana E Layer, Oliver Ullrich
We investigated the dynamics of immediate and initial gene expression response to different gravitational environments in human Jurkat T lymphocytic cells and compared expression profiles to identify potential gravity-regulated genes and adaptation processes. We used the Affymetrix GeneChip® Human Transcriptome Array 2.0 containing 44,699 protein coding genes and 22,829 non-protein coding genes and performed the experiments during a parabolic flight and a suborbital ballistic rocket mission to cross-validate gravity-regulated gene expression through independent research platforms and different sets of control experiments to exclude other factors than alteration of gravity...
July 12, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28701531/differential-contributions-to-the-interception-of-occluded-ballistic-trajectories-by-the-temporoparietal-junction-area-hmt-v5-and-the-intraparietal-cortex
#17
Sergio Delle Monache, Francesco Lacquaniti, Gianfranco Bosco
The ability to catch objects when transiently occluded from view suggests their motion can be extrapolated. Intraparietal cortex (IPS) plays a major role in this process along with other brain structures, depending on the task. For example, interception of objects under Earth's gravity effects may depend on time-to-contact predictions derived from integration of visual signals processed by hMT/V5+ with a-priori knowledge of gravity residing in the temporoparietal junction (TPJ). To investigate this issue further, we disrupted TPJ, hMT/V5+ and IPS activities with Transcranial Magnetic Stimulation (TMS) while subjects intercepted computer-simulated projectile trajectories perturbed randomly with either hypo- or hypergravity effects...
July 12, 2017: Journal of Neurophysiology
https://www.readbyqxmd.com/read/28692265/understanding-divergent-thermal-conductivity-in-single-polythiophene-chains-using-green-kubo-modal-analysis-and-sonification
#18
Wei Lv, Michael Winters, Freddy DeAngelis, Gil Weinberg, Asegun Henry
We used molecular dynamics simulations, the Green-Kubo Modal Analysis (GKMA) method as well as sonification to study the modal contributions to thermal conductivity in individual polythiophene chains. The simulations suggest that it is possible to achieve divergent thermal conductivity in individual polythiophene chains of certain lengths, with periodic boundary conditions. Application of the GKMA method further allowed for exact pinpointing of the modes responsible for the anomalous behavior. The analysis showed that transverse vibrations in the plane of the aromatic rings at low frequencies ~ 0...
July 10, 2017: Journal of Physical Chemistry. A
https://www.readbyqxmd.com/read/28689045/estimation-of-changes-in-breech-face-and-firing-pin-marks-over-consecutive-discharges-and-its-impact-on-an-ibis-%C3%A2-heritage%C3%A2-system
#19
Justin N Kirk, Eric F Law, Keith B Morris
When a firearm is discharged, the individual marks of the breech face and firing pin are imprinted onto the primer of the cartridge case. These individual marks are reproducible between shots; however, over a large number of consecutive shots, it has been observed that minute changes in these individual marks may occur. Changes in individual marks may affect an examiner in their ability to identify or eliminate and may change the magnitude of a likelihood ratio, depending on the system used by the laboratory, but the effect that these changes have on the Integrated Ballistic Identification System (IBIS(®)) is largely unknown...
June 29, 2017: Forensic Science International
https://www.readbyqxmd.com/read/28688435/influence-of-long-range-coulomb-interaction-in-velocity-map-imaging
#20
T Barillot, R Brédy, G Celep, S Cohen, I Compagnon, B Concina, E Constant, S Danakas, P Kalaitzis, G Karras, F Lépine, V Loriot, A Marciniak, G Predelus-Renois, B Schindler, C Bordas
The standard velocity-map imaging (VMI) analysis relies on the simple approximation that the residual Coulomb field experienced by the photoelectron ejected from a neutral or ion system may be neglected. Under this almost universal approximation, the photoelectrons follow ballistic (parabolic) trajectories in the externally applied electric field, and the recorded image may be considered as a 2D projection of the initial photoelectron velocity distribution. There are, however, several circumstances where this approximation is not justified and the influence of long-range forces must absolutely be taken into account for the interpretation and analysis of the recorded images...
July 7, 2017: Journal of Chemical Physics
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