4,245 research outputs found
Study of intermixing in a GaAs/AlGaAs quantum-well structure using doped spin-on silica layers
The effect of two different dopants, P and Ga, in spin-on glass (SOG) films on impurity-free vacancy disordering (IFVD) in GaAs/AlGaAs quantum-well structures has been investigated. It is observed that by varying the annealing and baking temperatures, P-doped SOG films created a similar amount of intermixing as the undoped SOG films. This is different from the results of other studies of P-doped SiO₂ and is ascribed to the low doping concentration of P, indicating that the doping concentration of P in the SiO₂ layer is one of the key parameters that may control intermixing. On the other hand, for all the samples encapsulated with Ga-doped SOG layers, significant suppression of the intermixing was observed, making them very promising candidates with which to achieve the selective-area defect engineering that is required for any successful application of IFVD.One of the authors (H.H.T.) acknowledges a fellowship
awarded to him by the Australian Research Council
Alpha-nucleus potential for alpha-decay and sub-barrier fusion
The set of parameters for alpha-nucleus potential is derived by using the
data for both the alpha-decay half-lives and the fusion cross-sections around
the barrier for reactions alpha+40Ca, alpha+59Co, alpha+208Pb. The alpha-decay
half-lives are obtained in the framework of a cluster model using the WKB
approximation. The evaluated alpha-decay half-lives and the fusion
cross-sections agreed well with the data. Fusion reactions between
alpha-particle and heavy nuclei can be used for both the formation of very
heavy nuclei and spectroscopic studies of the formed compound nuclei.Comment: 10 pages, 5 figure
Type-1.5 Superconductors
We demonstrate the existence of a novel superconducting state in high quality
two-component MgB2 single crystalline superconductors where a unique
combination of both type-1 (kappa_1 0.707)
superconductor conditions is realized for the two components of the order
parameter. This condition leads to a vortex-vortex interaction attractive at
long distances and repulsive at short distances, which stabilizes
unconventional stripe- and gossamer-like vortex patterns that we have
visualized in this type-1.5 superconductor using Bitter decoration and also
reproduced in numerical simulations.Comment: accepted in Phys. Rev. Let
Pair formation and collapse in imbalanced Fermion populations with unequal masses
We present an exact Quantum Monte Carlo study of the effect of unequal masses
on pair formation in Fermionic systems with population imbalance loaded into
optical lattices. We have considered three forms of the attractive interaction
and find in all cases that the system is unstable and collapses as the mass
difference increases and that the ground state becomes an inhomogeneous
collapsed state. We also address the question of canonical vs grand canonical
ensemble and its role, if any, in stabilizing certain phases
Optothermotronic effect as an ultrasensitive thermal sensing technology for solid-state electronics
The thermal excitation, regulation, and detection of charge carriers in solid-state electronics have attracted great attention toward high-performance sensing applications but still face major challenges. Manipulating thermal excitation and transport of charge carriers in nanoheterostructures, we report a giant temperature sensing effect in semiconductor nanofilms via optoelectronic coupling, termed optothermotronics. A gradient of charge carriers in the nanofilms under nonuniform light illumination is coupled with an electric tuning current to enhance the performance of the thermal sensing effect. As a proof of concept, we used silicon carbide (SiC) nanofilms that form nanoheterostructures on silicon (Si). The sensing performance based on the thermal excitation of charge carriers in SiC is enhanced by at least 100 times through photon excitation, with a giant temperature coefficient of resistance (TCR) of up to −50%/K. Our findings could be used to substantially enhance the thermal sensing performance of solid-state electronics beyond the present sensing technologies
Assessing Spatiotemporal Drought Dynamics and Its Related Environmental Issues in the Mekong River Delta
Drought is a major natural disaster that creates a negative impact on socio-economic development and environment. Drought indices are typically applied to characterize drought events in a meaningful way. This study aims at examining variations in agricultural drought severity based on the relationship between standardized ratio of actual and potential evapotranspiration (ET and PET), enhanced vegetation index (EVI), and land surface temperature (LST) derived from the Moderate Resolution Imaging Spectroradiometer (MODIS) platform. A new drought index, called the enhanced drought severity index (EDSI), was developed by applying spatiotemporal regression methods and time-series biophysical data derived from remote sensing. In addition, time-series trend analysis in the 2001–2018 period, along with the Mann–Kendal (MK) significance test and the Theil Sen (TS) slope, were used to examine the spatiotemporal dynamics of environmental parameters (i.e., LST, EVI, ET, and PET), and geographically weighted regression (GWR) was subsequently applied in order to analyze the local correlations among them. Results showed that a significant correlation was discovered among LST, EVI, ET, and PET, as well as their standardized ratios (|r| > 0.8, p 0.7 and a statistical significance p < 0.01. Besides, it was found that the temporal tendency of this phenomenon was the increase in intensity of drought, and that coastal areas in the study area were more vulnerable to this phenomenon. This study demonstrates the effectiveness of EDSI and the potential application of integrating spatial regression and time-series data for assessing regional drought conditions
CMBR Constraint on a Modified Chaplygin Gas Model
In this paper, a modified Chaplygin gas model of unifying dark energy and
dark matter with exotic equation of state
which can also explain the recent accelerated expansion of the universe is
investigated by the means of constraining the location of the peak of the CMBR
spectrum. We find that the result of CMBR measurements does not exclude the
nonzero value of parameter , but allows it in the range .Comment: 4 pages, 3 figure
ЧАСТОТНЫЕ ХАРАКТЕРИСТИКИ ИНТЕГРАЛЬНЫХ ДАТЧИКОВ ХОЛЛА
The results of device-technological and schematic simulation of the silicon Hall sensor with the purpose of determine its dynamic characteristics are presented. The influence of the dimensions of the active region is investigated, the theoretical and actual values of the upper limit of the bandwidth of the Hall sensor are determined, taking into account the internal parasitic capacitance, and the presence and absence of a capacitive load. The characteristics of the Hall sensor combined on a single crystal with a differential amplifier are simulated.Представлены результаты приборно-технологического и схемотехнического моделирования кремниевого датчика Холла с целью определения его динамических характеристик. Исследовано влияние размеров активной области, определены теоретическое и фактическое значения верхнего предела полосы пропускания датчика Холла с учетом внутренней паразитной емкости, а также при наличии и отсутствии емкостной нагрузки. Промоделированы характеристики датчика Холла, совмещенного на одном кристалле с дифференциальным усилителем
Reproductive Safety of Trazodone After Maternal Exposure in Early Pregnancy: A Comparative ENTIS Cohort Study.
Trazodone is indicated for the treatment of major depressive disorder, but more frequently prescribed off-label at lower doses for insomnia in women of childbearing age. The aim of this study was to assess the risks linked to trazodone exposure during pregnancy for which limited safety data are available.
This multicenter, observational prospective cohort study compared pregnancy outcomes in women exposed to trazodone in early pregnancy against those in a reference group of women exposed to a selective serotonin reuptake inhibitors (SSRIs) between 1996 and 2021.
The sample included 221 trazodone and 869 SSRI-exposed pregnancies. Exposure to trazodone in the first trimester was not associated with a significant difference in the risk of major congenital anomalies (trazodone [1/169, 0.6%]; SSRI [19/730, 2.6%]; adjusted odds ratio, 0.2; 95% confidence interval, 0.03-1.77). The cumulative incidences of live birth were 61% and 73% in the trazodone and reference group, respectively (25% vs 18% for pregnancy loss and 14% vs 10% for pregnancy termination). Trazodone exposure was not associated with a significantly increased risk of pregnancy termination and pregnancy loss. The rate of small for gestational age infants did not differ between the groups.
This study did not reveal a significant difference in the risk of major congenital anomalies after first trimester exposure to trazodone, compared with SSRI exposure. Although this study is the largest so far, these results call for confirmation through further studies
Entanglement Entropy in Quantum Gravity and the Plateau Problem
In a quantum gravity theory the entropy of entanglement between the
fundamental degrees of freedom spatially divided by a surface is discussed. The
classical gravity is considered as an emergent phenomenon and arguments are
presented that: 1) is a macroscopical quantity which can be determined
without knowing a real microscopical content of the fundamental theory; 2)
is given by the Bekenstein-Hawking formula in terms of the area of a
co-dimension 2 hypesurface ; 3) in static space-times can be
defined as a minimal hypersurface of a least volume separating the system in a
constant time slice. It is shown that properties of are in agreement with
basic properties of the von Neumann entropy. Explicit variational formulae for
in different physical examples are considered.Comment: 24 pages, 10 figure
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