2,561 research outputs found
A slip model for micro/nano gas flows induced by body forces
A slip model for gas flows in micro/nano-channels induced by external body
forces is derived based on Maxwell's collision theory between gas molecules and
the wall. The model modifies the relationship between slip velocity and
velocity gradient at the walls by introducing a new parameter in addition to
the classic Tangential Momentum Accommodation Coefficient. Three-dimensional
Molecular Dynamics simulations of helium gas flows under uniform body force
field between copper flat walls with different channel height are used to
validate the model and to determine this new parameter
Relay selection for efficient HARQ-IR protocols in relay-assisted multisource multicast networks
This paper investigates relay selection for reliable data transmission in relay-assisted multisource multicast networks (RMMNs) where multiple source nodes distribute information to a set of destination nodes with the assistance of multiple relay nodes. Hybrid automatic repeat request with incremental redundancy (HARQ-IR) is used and supported by either a physical-layer network coding (PNC) or an analog network coding (ANC) technique employed at the relays. By deriving efficiency metrics of the HARQ-IR protocols, we propose relay selection schemes for RMMNs to minimize the transmission delay and energy consumption. Simulation results are provided to analyse each relay selection scheme
Hybridized magnonic materials for THz frequency applications
The capability of magnons to hybridize and strongly couple with diverse
excitations offers a promising avenue for realizing and controlling emergent
properties that hold significant potential for applications in devices,
circuits, and information processing. In this letter, we present recent
theoretical and experimental developments in magnon-based hybrid systems,
focusing on the combination of magnon excitation in an antiferromagnet with
other excitations, namely plasmons in a topological insulator, phonons in a 2D
AFM, and photons. The existence of THz frequency magnons, plasmons, and phonons
makes magnon-based hybrid systems particularly appealing for
high-operating-speed devices. In this context, we explore several directions to
advance magnon hybrid systems, including strong coupling between a surface
plasmon and magnon polariton in a TI/AFM bilayer, a giant spin Nernst effect
induced by magnon phonon coupling in 2D AFMs, and control of magnon-photon
coupling using spin torque
Unconventional anomalous Hall effect in 3d/5d multilayers mediated by the nonlocal spin-conductivity
We evidenced unconventionnal Anomalous Hall Effects (AHE) in 3d/5d
(Co0.2nm/Ni0.6nm)N multilayers grown on a thin Pt layer or thin Au:W alloy. The
inversion observed on AHE originates from the opposite sign of the spin-orbit
coupling of Pt compared to Ni. Via advanced simulations methods for the
description of the spin-current profiles based on the spin-dependent Boltzmann
formalism, we extracted the spin Hall angle (SHA) of Pt and (Co/Ni) as well as
the relevant transport parameters. The extracted SHA for Pt, +20%, is opposite
to the one of (Co/Ni), giving rise to an effective AHE inversion for thin
(Co/Ni) multilayers (N < 17). The spin Hall angle in Pt is found to be larger
than the one previously measured in combined spin-pumping inverse spin-Hall
effect experiments in a geometry of current perpendicular to plane. Whereas
magnetic proximity effects cannot explain the effect, spin-current leakage and
anisotropic electron scattering at Pt/(Co,Ni) interfaces fit the experiments.Comment: 7 pages, 2 figure
The impact of cataract surgey on vision-related quality of life for bilateral cataract patients in Ho Chi Minh City, Vietnam: a prospective study
BACKGROUND: To determine the impact of cataract surgery on vision-related quality of life (VRQOL) and examine the association between objective visual measures and change in VRQOL after surgery among bilateral cataract patients in Ho Chi Minh City, Vietnam. METHODS: A cohort of older patients with bilateral cataract was assessed one week before and one to three months after first eye or both eye cataract surgery. Visual measures including visual acuity, contrast sensitivity and stereopsis were obtained. Vision-related quality of life was assessed using the NEI VFQ-25. Descriptive analyses and a generalized linear estimating equation (GEE) analysis were undertaken to measure change in VRQOL after surgery. RESULTS: Four hundred and thirteen patients were assessed before cataract surgery and 247 completed the follow-up assessment one to three months after first or both eye cataract surgery. Overall, VRQOL significantly improved after cataract surgery (p < 0.001) particularly after both eye surgeries. Binocular contrast sensitivity (p < 0.001) and stereopsis (p < 0.001) were also associated with change in VRQOL after cataract surgery. Visual acuity was not associated with VRQOL. CONCLUSIONS: Cataract surgery significantly improved VRQOL among bilateral cataract patients in Vietnam. Contrast sensitivity as well as stereopsis, rather than visual acuity significantly affected VRQOL after cataract surgery
Multi-field Inflation with a Random Potential
Motivated by the possibility of inflation in the cosmic landscape, which may
be approximated by a complicated potential, we study the density perturbations
in multi-field inflation with a random potential. The random potential causes
the inflaton to undergo a Brownian motion with a drift in the D-dimensional
field space. To quantify such an effect, we employ a stochastic approach to
evaluate the two-point and three-point functions of primordial perturbations.
We find that in the weakly random scenario the resulting power spectrum
resembles that of the single field slow-roll case, with up to 2% more red tilt.
The strongly random scenario, leads to rich phenomenologies, such as primordial
fluctuations in the power spectrum on all angular scales. Such features may
already be hiding in the error bars of observed CMB TT (as well as TE and EE)
power spectrum and can be detected or falsified with more data coming in the
future. The tensor power spectrum itself is free of fluctuations and the tensor
to scalar ratio is enhanced. In addition a large negative running of the power
spectral index is possible. Non-Gaussianity is generically suppressed by the
growth of adiabatic perturbations on super-horizon scales, but can possibly be
enhanced by resonant effects or arise from the entropic perturbations during
the onset of (p)reheating. The formalism developed in this paper can be applied
to a wide class of multi-field inflation models including, e.g. the N-flation
scenario.Comment: More clarifications and references adde
Multi-field Inflation with a Random Potential
Motivated by the possibility of inflation in the cosmic landscape, which may
be approximated by a complicated potential, we study the density perturbations
in multi-field inflation with a random potential. The random potential causes
the inflaton to undergo a Brownian motion with a drift in the D-dimensional
field space. To quantify such an effect, we employ a stochastic approach to
evaluate the two-point and three-point functions of primordial perturbations.
We find that in the weakly random scenario the resulting power spectrum
resembles that of the single field slow-roll case, with up to 2% more red tilt.
The strongly random scenario, leads to rich phenomenologies, such as primordial
fluctuations in the power spectrum on all angular scales. Such features may
already be hiding in the error bars of observed CMB TT (as well as TE and EE)
power spectrum and can be detected or falsified with more data coming in the
future. The tensor power spectrum itself is free of fluctuations and the tensor
to scalar ratio is enhanced. In addition a large negative running of the power
spectral index is possible. Non-Gaussianity is generically suppressed by the
growth of adiabatic perturbations on super-horizon scales, but can possibly be
enhanced by resonant effects or arise from the entropic perturbations during
the onset of (p)reheating. The formalism developed in this paper can be applied
to a wide class of multi-field inflation models including, e.g. the N-flation
scenario.Comment: More clarifications and references adde
POLLUTION OF GROUNDWATER BY LEACHATE FROM DONG THANH LANDFILL DISPOSAL SITE
Joint Research on Environmental Science and Technology for the Eart
Predatory Bacteria: A Potential Ally against Multidrug-Resistant Gram-Negative Pathogens
Multidrug-resistant (MDR) Gram-negative bacteria have emerged as a serious threat to human and animal health. Bdellovibrio spp. and Micavibrio spp. are Gram-negative bacteria that prey on other Gram-negative bacteria. In this study, the ability of Bdellovibrio bacteriovorus and Micavibrio aeruginosavorus to prey on MDR Gram-negative clinical strains was examined. Although the potential use of predatory bacteria to attack MDR pathogens has been suggested, the data supporting these claims is lacking. By conducting predation experiments we have established that predatory bacteria have the capacity to attack clinical strains of a variety of ß-lactamase-producing, MDR Gram-negative bacteria. Our observations indicate that predatory bacteria maintained their ability to prey on MDR bacteria regardless of their antimicrobial resistance, hence, might be used as therapeutic agents where other antimicrobial drugs fail. © 2013 Kadouri et al
Chinese journals: a guide for epidemiologists.
Chinese journals in epidemiology, preventive medicine and public health contain much that is of potential international interest. However, few non-Chinese speakers are acquainted with this literature. This article therefore provides an overview of the contemporary scene in Chinese biomedical journal publication, Chinese bibliographic databases and Chinese journals in epidemiology, preventive medicine and public health. The challenge of switching to English as the medium of publication, the development of publishing bibliometric data from Chinese databases, the prospect of an Open Access publication model in China, the issue of language bias in literature reviews and the quality of Chinese journals are discussed. Epidemiologists are encouraged to search the Chinese bibliographic databases for Chinese journal articles.Published versio
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