216 research outputs found
Electron Density Dependence of in-plane Spin Relaxation Anisotropy in GaAs/AlGaAs Two-Dimensional Electron Gas
We investigated the spin dynamics of two-dimensional electrons in (001)
GaAs/AlGaAs heterostructure using the time resolved Kerr rotation technique
under a transverse magnetic field. The in-plane spin lifetime is found to be
anisotropic below 150k due to the interference of Rashba and Dresselhaus
spin-orbit coupling and D'yakonov-Perel' spin relaxation. The ratio of in-plane
spin lifetimes is measured directly as a function of temperature and pump
power, showing that the electron density in 2DEG channel strongly affects the
Rashba spin-orbit coupling.Comment: 3 pages, 2 figure
Effects of Pilot Injection Timing and EGR on a Modern V6 Common Rail Direct Injection Diesel Engine
Nitric oxide and smoke emissions in diesel engine can be controlled by optimising the air/fuel mixture and combustion temperature. Early in-cylinder diesel injection that produces premixed charge can simultaneously reduce NOx and smoke emissions. However, there could be an increase in hydrocarbons and CO emissions due to fuel impinged to the cylinder wall. The focus of the present work is on the effects of a variation of pilot injection timing with EGR to NOx and smoke level of a modern V6 common rail direct injection. This study is carried out at two different engine load conditions of 30 Nm and 55 Nm, at constant engine speed of 2000 rpm. Emissions of NOx are measured from the exhaust sample line by an exhaust gas analyzer (Horiba MEXA-7100EGR). Smoke level is measured by using an AVL 415S smoke meter which provides results directly as a Filter Smoke Number (FSN) unit. The results show that the early pilot injection timing contributed to the lower smoke level and higher NOx emissions. The higher level of NOx is due to higher combustion temperatures resulting from the complete combustion. Meanwhile, the lower smoke level is due to complete fuel combustion and soot oxidation. The early pilot injection timing produces an intermediate main ignition delay which also contributed to complete combustion. The formation of smoke is higher at a high engine load compared with low engine load is due to the higher amount of fuel being injected, resulting in higher smoke formatio
Dual Spin Filter Effect in a Zigzag Graphene Nanoribbon
By first principle calculations, a dual spin filter effect under finite bias
voltages is demonstrated in an antiferromagnetic junction of symmetric zigzag
graphene nanoribbon (ZGNR). Unlike conventional spin filter devices using half
metallic materials, the up- and down-spin electrons are unidirectionally
filtered in the counter direction of the bias voltage, making the junction a
dual spin filter. On the contrary, asymmetric ZGNRs do not exhibit such a spin
filter effect. By analyzing Wannier functions and a tight-binding model, we
clarify that an interplay between the spin polarized band structure of
and states near the Fermi level and decoupling of the interband hopping
of the two states, arising from the symmetry of the wave functions, plays a
crucial role in the effect.Comment: 15 pages, 4 figure
Barrier-to-autointegration factor 1 protects against a basal cGAS-STING response
Although the pathogen recognition receptor pathways that activate cell-intrinsic antiviral responses are well delineated, less is known about how the host regulates this response to prevent sustained signaling and possible immune-mediated damage. Using a genome-wide CRISPR-Cas9 screening approach to identify host factors that modulate interferon-stimulated gene (ISG) expression, we identified the DNA binding protein Barrier-to-autointegration factor 1 (Banf1), a previously described inhibitor of retrovirus integration, as a modulator of basal cell-intrinsic immunity. Ablation of Banf1 by gene editing resulted in chromatin activation near host defense genes with associated increased expression of ISGs, includin
A New Task: Deriving Semantic Class Targets for the Physical Sciences
We define deriving semantic class targets as a novel multi-modal task. By
doing so, we aim to improve classification schemes in the physical sciences
which can be severely abstracted and obfuscating. We address this task for
upcoming radio astronomy surveys and present the derived semantic radio galaxy
morphology class targets.Comment: 6 pages, 1 figure, Accepted at Fifth Workshop on Machine Learning and
the Physical Sciences (NeurIPS 2022), Neural Information Processing Systems
202
Flat optical conductivity in topological kagome magnet TbMnSn
Kagome magnet TbMnSn is a new type of topological material that is
known to support exotic quantum magnetic states. Experimental work has
identified that TbMnSn hosts Dirac electronic states that could lead to
topological and Chern quantum phases, but the optical response of the Dirac
fermions of TbMnSn and its properties remain to be explored. Here, we
perform optical spectroscopy measurement combined with first-principles
calculations on single-crystal sample of TbMnSn to investigate the
associated exotic phenomena. TbMnSn exhibits a frequency-independent
optical conductivity spectra in a broad range from 1800 to 3000 cm
(220-370 meV) in experiments. The theoretical band structures and optical
conductivity spectra are calculated with several shifted Fermi energy to
compare with the experiment. The theoretical spectra with 0.56 eV shift for
Fermi energy are well consistent with our experimental results. Besides, the
massive quasi-two-dimensional (quasi-2D) Dirac bands, which have linear band
dispersion in - plane and no band dispersion along the
direction, exist close to the shifted Fermi energy. According to tight-bond
model analysis, we find that quasi-2D Dirac bands give rise to a flat optical
conductivity, while its value is smaller than the result by calculations and
experiments. It indicates that the other trivial bands also contribute to the
flat optical conductivity
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