441 research outputs found
3,3′-Dibromo-1,1′-[ethylenedioxybis(nitrilomethylidyne)]dibenzene
In the centrosymmetric title compound, C16H14Br2N2O2, the intramolecular interplanar distance between the parallel benzene rings is 1.305 (3) Å, while the intermolecular interplanar distance (between neighbouring molecules) is 3.463 (3) Å, exhibiting obvious strong intermolecular π–π stacking interactions
Pulse control of sudden transition for two qubits in XY spin baths and quantum phase transition
We study the dynamics of two initially correlated qubits coupled to their own
separate spin baths modeled by a XY spin chain and find the explicit expression
of the quantum discord for the system. A sudden transition is found to exist
between classical and quantum decoherence by choosing certain initial states.
We show that the sudden transition happens near the critical point, which
provides a new way to characterize the quantum phase transition. Furthermore,
we propose a scheme to prolong the transition time of the quantum discord by
applying the bang-bang pulses.Comment: 5 pages, 6 figure
Evolutionary Stages and Disk Properties of Young Stellar Objects in the Perseus Cloud
We investigated the evolutionary stages and disk properties of 211 Young
stellar objects (YSOs) across the Perseus cloud by modeling the broadband
optical to mid-infrared (IR) spectral energy distribution (SED). By exploring
the relationships among the turnoff wave bands lambda_turnoff (longward of
which significant IR excesses above the stellar photosphere are observed), the
excess spectral index alpha_excess at lambda <~ 24 microns, and the disk inner
radius R_in (from SED modeling) for YSOs of different evolutionary stages, we
found that the median and standard deviation of alpha_excess of YSOs with
optically thick disks tend to increase with lambda_turnoff, especially at
lambda_turnoff >= 5.8 microns, whereas the median fractional dust luminosities
L_dust/L_star tend to decrease with lambda_turnoff. This points to an
inside-out disk clearing of small dust grains. Moreover, a positive correlation
between alpha_excess and R_in was found at alpha_excess > ~0 and R_in > ~10
the dust sublimation radius R_sub, irrespective of lambda_turnoff,
L_dust/L_star and disk flaring. This suggests that the outer disk flaring
either does not evolve synchronously with the inside-out disk clearing or has
little influence on alpha_excess shortward of 24 microns. About 23% of our YSO
disks are classified as transitional disks, which have lambda_turnoff >= 5.8
microns and L_dust/L_star >10^(-3). The transitional disks and full disks
occupy distinctly different regions on the L_dust/L_star vs. alpha_excess
diagram. Taking L_dust/L_star as an approximate discriminator of disks with
(>0.1) and without (<0.1) considerable accretion activity, we found that 65%
and 35% of the transitional disks may be consistent with being dominantly
cleared by photoevaporation and dynamical interaction respectively. [abridged]Comment: 31 pages, 13 figures, 2 tables. To appear in a special issue of RAA
on LAMOST science
Salicylic acid alleviates decreases in photosynthesis under heat stress and accelerates recovery in grapevine leaves
Probing Dark force at BES-III/BEPCII
We study an experimental search of a GeV scale vector boson at
BES-III/BEPCII. It is responsible for mediating a new U(1) interaction, as
recently exploited in the context of weakly interacting massive particle dark
matter. At low energy colliders this dark state can be efficiently
probed. We discuss the direct productions of this light vector boson and
the decay of this state with BES-III data and its foreseen larger data. In
particular, we show that Higgs' strahlung in the dark sector can lead to
multilepton signatures, which probe the physics range for kinetic mixing
parameter over a large portion of the
parameter space.Comment: 8 pages and 4 figures, version to appear in Phys. Lett.
Reservoir landslide monitoring and mechanism analysis based on UAV photogrammetry and sub-pixel offset tracking: a case study of Wulipo landslide
Introduction: Reservoir landslides undergo large deformations during the early stages of impoundment and maintain long-term persistent deformations during the operational period of the reservoir. The management of reservoir landslides mostly focuses on the early identification, risk assessment during the large deformations, and long-sequence monitoring during long-term persistent deformations, which requires sufficient continuity and integrity of the landslide monitoring data.Methods: Taking the Wulipo (WLP) landslide in Baihetan Reservoir as example, this paper proposes a reservoir landslide monitoring method that integrates field survey, unmanned aerial vehicle (UAV) photogrammetry and global navigation satellite system (GNSS) monitoring, which can effectively eliminate the practical monitoring gaps between multiple monitoring methods and improve the continuity and completeness of monitoring data.Results and discussion: First, this study determined the initiation time of the landslide through the field investigation and collected five period of UAV data to analyze the overall displacement vector of the WLP landslide using sub-pixel offset tracking (SPOT). On the basis of the above data, we compensated for the missing data in GNSS system due to the practical monitoring vacancies by combining the field survey and the landslide-water level relationship. Based on these monitoring data, this paper points out that the WLP landslide is a buoyancy-driven landslide, and whether or not accelerated deformation will occur is related to the maximum reservoir water level. Finally, this study analyzed and discussed the applicability of UAV photogrammetry for reservoir landslide monitoring in the absence of ground control points (GCPs), and concluded that this method can be quickly and flexibly applied to the stage of large deformation of reservoir landslides
Optimization of the seed medium of Lactobacillus casei GJ00412 isolated from soy whey
Soy whey (SW) is generated as a process waste during soy isolate protein preparation. SW has low content of soluble sugar and high content of oligosaccharide, which is suitable for the growth of lactic acid bacteria (LAB). In this study, a strain of Lactobacillus casei GJ00412 (by 16S rRNA genesequencing and identification) was isolated from soy whey. In order to reduce the cost of culture medium, improve its biomass, and facilitate the next utilization, Response surface methodology (RSM) was employed to optimize the composition of seed medium of Lactobacillus casei By Plackett-Burman design, sucrose, yeast power, MgSO4, Tween80 and pH value were found to have significant effects on biomass, and were further analyzed by Box-behnken design, an application of response surface. The optimized medium was as follows (w/v): 2.5% sucrose, 1.8% soy peptone, 0.4% yeast powder, 0.08% MgSO4, 0.04% MnSO4, 0.08% Tween80, pH 7.17. The results showed that the cost of the optimized medium was decreased and the biomass of Lactobacillus casei has no significant difference when compared with MRS medium
- …