3,043 research outputs found
Study of TMDs nanosheets based saturable absorber used for Q-switching and mode lock laser system
Pulse width of pulsed laser determinates their applications. For the long pulse laser with µs or ns pulse width, it can be used for telecommunication, remote sensing and medical surgery. For the ultrashort pulse laser with ps or fs pulse width, it can be used for eye-surgery, precise micro- or even nano-machining on transparent material and novel 3D hologram formation. The saturable absorber (SA) is the crucial optical component that switch the laser operation from CW mode to pulse mode passively. Therefore it attract s great research interests from the laser photonic community.
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Bis[μ-2-(2-naphthoxy)acetato]bis{aqua[2-(2-naphthoxy)acetato]zinc(II)}
The title binuclear ZnII compound, [Zn2(C12H9O3)4(H2O)2], is centrosymmetric. Each Zn atom is coordinated by two bridging 2-naphthoxyacetate anions, one terminal 2-naphthoxyacetate anion and one water molecule in a distorted ZnO4 tetrahedral geometry. The naphthalene system of the bridging ligand is nearly perpendicular to the naphthalene of the terminal ligand, with a dihedral angle of 78.26 (6)°. Within the binuclear molecule the Zn⋯Zn separation is 3.815 (5) Å. In the crystal structure, intermolecular O—H⋯O hydrogen bonding between the water molecule and carboxylate groups helps to stabilize the crystal structure
Effects of the Interception of Litterfall by the Understory on Carbon Cycling in Eucalyptus Plantations of South China
For the purposes of forest restoration, carbon (C) fixation, and economic improvement, eucalyptus (Eucalyptus urophylla) has been widely planted in South China. The understory of eucalyptus plantations is often occupied by a dense community of the fern Dicranopteris dichotoma, which intercepts tree canopy leaf litter before it reaches the ground. To understand the effects of this interception of litterfall on C cycling in eucalyptus plantations, we quantified the mass of intercepted litter and the influences of litterfall interception on litter decomposition and soil respiration. The total mass of E. urophylla litterfall collected on the understory was similar to that collected by the traditional litter trap method. All of the eucalyptus litterfall is intercepted by the D. dichotoma canopy. Of the litterfall that was intercepted by D. dichotoma, 20–40% and 60–80% was intercepted by the top (50–100 cm) and bottom (0–50 cm) of the understory canopy, respectively. Intercepted litterfall decomposed faster at the bottom of understory canopy (at the base of the plants) than at the top, and decomposition was slower on the soil surface in the absence of understory than on any location in the understory canopy. Soil respiration was highest when both the understory and litter were present and was lowest when both the understory and litter were absent. These results indicate that litterfall interception changed carbon flow between aboveground and belowground through litter decomposition and soil respiration, which changed carbon cycling in eucalyptus plantations. The effects of the understory on litter decomposition and soil respiration should be considered in ecosystem carbon models
Form Factors from QCD Light-Cone Sum Rules
In this work, we calculate the transition form factors of
decaying into within the framework of light-cone sum rules with the
distribution amplitudes (DAs) of -baryon. In the hadronic
representation of the correlation function, we have isolated both the
and the states so that the form factors can be obtained without ambiguity. We investigate the
P-type and A-type current to interpolate the light baryons for a comparison
since the interpolation current for the baryon state is not unique. We also
employ three parametrization models for DAs of in the numerical
calculation. We present the numerical predictions on the form factors and the branching fractions, the averaged
forward-backward asymmetry , the averaged final hadron polarization and the
averaged lepton polarization of the decays,
as well as the ratio of branching ratios , and the predicted
can be consistent with the LHCb data.Comment: 22 pages, 2figur
Propagation characteristics and identification of type I cracks by the extended finite element method combined with modal analysis
Extended finite element frame based on Abaqus is applied to research the crack propagation problem of two-dimensional long rectangular thin plate. Presuppose type I crack with different horizontal locations and longitudinal dimensions, the propagation characteristics of the edge crack is discussed with the objects of structural flexibility of the thin plate, crack propagation length and plastic zone of crack tip etc. The results indicate that the horizontal location of the initial crack has a small influence on the crack propagation characteristics, and it only affects the local flexibility of the thin plate as well as the dimension and shape of plastic zone of crack tip. The longitudinal dimension of the initial crack obviously nonlinear influence on various parameters of the crack propagation characteristics. In view of the disastrous consequence of crack propagation, the vibration characteristics of the thin plate with different crack dimensions and crack locations are discussed based on the experiment and simulation modal analysis on the thin plate, thus providing basis for prior estimation and control for crack generation and propagation
Multimodal Recommendation Dialog with Subjective Preference: A New Challenge and Benchmark
Existing multimodal task-oriented dialog data fails to demonstrate the
diverse expressions of user subjective preferences and recommendation acts in
the real-life shopping scenario. This paper introduces a new dataset SURE
(Multimodal Recommendation Dialog with SUbjective PREference), which contains
12K shopping dialogs in complex store scenes. The data is built in two phases
with human annotations to ensure quality and diversity. SURE is well-annotated
with subjective preferences and recommendation acts proposed by sales experts.
A comprehensive analysis is given to reveal the distinguishing features of
SURE. Three benchmark tasks are then proposed on the data to evaluate the
capability of multimodal recommendation agents. Based on the SURE, we propose a
baseline model, powered by a state-of-the-art multimodal model, for these
tasks.Comment: ACL 202
Cosmological Time Crystals From Einstein-Cubic Gravities
By including appropriate Riemman cubic invariants, we find that the dynamics
of classical time crystals can be straightforwardly realized in Einstein
gravity on the FLRW metric. The time reflection symmetry is spontaneously
broken in the two vacua with the same scale factor , but opposite .
The tunneling from one vacuum to the other provides a robust mechanism for
bounce universes; it always occurs for systems with positive energy density.
For suitable matter energy-momentum tensor we also construct cyclic universes.
Cosmological solutions that resemble the classical time crystals can be
constructed in massive gravity.Comment: Latex, 11 page
Observation of the chiral anomaly induced negative magneto-resistance in 3D Weyl semi-metal TaAs
Weyl semi-metal is the three dimensional analog of graphene. According to the
quantum field theory, the appearance of Weyl points near the Fermi level will
cause novel transport phenomena related to chiral anomaly. In the present
paper, we report the first experimental evidence for the long-anticipated
negative magneto-resistance generated by the chiral anomaly in a newly
predicted time-reversal invariant Weyl semi-metal material TaAs. Clear
Shubnikov de Haas oscillations (SdH) have been detected starting from very weak
magnetic field. Analysis of the SdH peaks gives the Berry phase accumulated
along the cyclotron orbits to be {\pi}, indicating the existence of Weyl
points.Comment: Submitted in February'1
Serum selenium concentration is associated with metabolic factors in the elderly: a cross-sectional study
<p>Abstract</p> <p>Background</p> <p>Selenium is an essential micronutrient known for its antioxidant function. However, the association of serum selenium with lipid profiles and fasting glucose are inconsistent in populations with average intake of selenium. Furthermore, there were few studies conducted specifically for the elderly. This study examined the relationship of serum selenium concentration with serum lipids and fasting glucose in the Taiwanese elderly population.</p> <p>Methods</p> <p>This was a cross-sectional study of 200 males and females aged 65-85 years (mean 71.5 ± 4.6 years) from Taipei, Taiwan. Serum selenium was measured by inductively coupled plasma-mass spectrometer. The association between serum selenium and metabolic factors was examined using a multivariate linear regression analysis after controlling several confounders.</p> <p>Results</p> <p>The mean serum selenium concentration was 1.14 μmol/L, without significant difference between sexes. Total cholesterol, triglycerides, and LDL cholesterol increased significantly with serum selenium concentration (<it>P </it>< 0.001, <it>P </it>< 0.05 and <it>P </it>< 0.001, respectively) after adjusting for age, gender, anthropometric indices, lifestyle factors, and cardio-vascular risk factors in several linear regression models. Furthermore, there was a significantly positive association between serum selenium and serum fasting glucose concentrations (<it>P </it>< 0.05).</p> <p>Conclusions</p> <p>Total cholesterol, triglycerides, and LDL cholesterol, and fasting serum glucose concentrations increased significantly with serum selenium concentration in the Taiwanese elderly. The underlying mechanism warrants further research.</p
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