1,161 research outputs found
On low temperature kinetic theory; spin diffusion, Bose Einstein condensates, anyons
The paper considers some typical problems for kinetic models evolving through
pair-collisions at temperatures not far from absolute zero, which illustrate
specific quantum behaviours. Based on these examples, a number of differences
between quantum and classical Boltzmann theory is then discussed in more
general terms.Comment: 25 pages, minor updates of previous versio
Les analysis on cylinder cascade flow based on energy ratio coefficient
The flow field around the cylinder cascade is widely used to
analyze the interaction of vortex shedding and the information
on heat transfer. Large eddy simulation (LES) can be used to
get the turbulent flow information in detail. The resolved largescale
structures are determined by the size of the grid, and the
turbulent vortex dissipation is modeled with a subgrid scale
model. Whereas there is no accurate criterion to provide the
subgrid scale with the physical meaning. Based on turbulent
energy ratio coefficient and numerical simulation results with
turbulent model, the subgrid was generated for the
incompressible fluid flowing around a column of cylinder
cascade with a gap-to-diameter ratio of 2. Smagorinsky-Lily
(SM) model was applied to LES analysis. The turbulent flow
information was compared with the experimental data by PIV.
Two cases with different Reynolds numbers were studied.
When the turbulent energy ratio coefficient reached to 30%-
40%, the turbulent dissipation could be captured by LES
method with less grid number. The large scale vortex
interaction behind the cylinder cascade was analyzed further. It
is verified that LES method can be used for engineering based
on the turbulent energy ratio coefficient with acceptable
computational cost.papers presented to the 12th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Costa de Sol, Spain on 11-13 July 2016
Type IIB Solutions with Interpolating Supersymmetries
We study type IIB supergravity solutions with four supersymmetries that
interpolate between two types widely considered in the literature: the dual of
Becker and Becker's compactifications of M-theory to 3 dimensions and the dual
of Strominger's torsion compactifications of heterotic theory to 4 dimensions.
We find that for all intermediate solutions the internal manifold is not
Calabi-Yau, but has SU(3) holonomy in a connection with a torsion given by the
3-form flux. All 3-form and 5-form fluxes, as well as the dilaton, depend on
one function appearing in the supersymmetry spinor, which satisfies a nonlinear
differential equation. We check that the fields corresponding to a flat bound
state of D3/D5-branes lie in our class of solutions. The relations among
supergravity fields that we derive should be useful in studying new gravity
duals of gauge theories, as well as possibly compactifications.Comment: 27pp, v2 REVTeX4, typographical fixes and minor clarifications, v3
added ref, modified discussion of RR axion slightl
Charmonium states in QCD-inspired quark potential model using Gaussian expansion method
We investigate the mass spectrum and electromagnetic processes of charmonium
system with the nonperturbative treatment for the spin-dependent potentials,
comparing the pure scalar and scalar-vector mixing linear confining potentials.
It is revealed that the scalar-vector mixing confinement would be important for
reproducing the mass spectrum and decay widths, and therein the vector
component is predicted to be around 22%. With the state wave functions obtained
via the full-potential Hamiltonian, the long-standing discrepancy in M1
radiative transitions of and are alleviated
spontaneously. This work also intends to provide an inspection and suggestion
for the possible among the copious higher charmonium-like states.
Particularly, the newly observed X(4160) and X(4350) are found in the
charmonium family mass spectrum as MeV and MeV, which strongly favor the assignments
respectively. The corresponding radiative transitions, leptonic and two-photon
decay widths have been also predicted theoretically for the further
experimental search.Comment: 16 pages,3 figure
Association of jasmonic acid priming with multiple defense mechanisms in wheat plants under high salt stress
Salinity is a global conundrum that negatively affects various biometrics of agricultural crops. Jasmonic acid (JA) is a phytohormone that reinforces multilayered defense strategies against abiotic stress, including salinity. This study investigated the effect of JA (60 μM) on two wheat cultivars, namely ZM9 and YM25, exposed to NaCl (14.50 dSm−1) during two consecutive growing seasons. Morphologically, plants primed with JA enhanced the vegetative growth and yield components. The improvement of growth by JA priming is associated with increased photosynthetic pigments, stomatal conductance, intercellular CO2, maximal photosystem II efficiency, and transpiration rate of the stressed plants. Furthermore, wheat cultivars primed with JA showed a reduction in the swelling of the chloroplast, recovery of the disintegrated thylakoids grana, and increased plastoglobuli numbers compared to saline-treated plants. JA prevented dehydration of leaves by increasing relative water content and water use efficiency via reducing water and osmotic potential using proline as an osmoticum. There was a reduction in sodium (Na+) and increased potassium (K+) contents, indicating a significant role of JA priming in ionic homeostasis, which was associated with induction of the transporters, viz., SOS1, NHX2, and HVP1. Exogenously applied JA mitigated the inhibitory effect of salt stress in plants by increasing the endogenous levels of cytokinins and indole acetic acid, and reducing the abscisic acid (ABA) contents. In addition, the oxidative stress caused by increasing hydrogen peroxide in salt-stressed plants was restrained by JA, which was associated with increased α-tocopherol, phenolics, and flavonoids levels and triggered the activities of superoxide dismutase and ascorbate peroxidase activity. This increase in phenolics and flavonoids could be explained by the induction of phenylalanine ammonia-lyase activity. The results suggest that JA plays a key role at the morphological, biochemical, and genetic levels of stressed and non-stressed wheat plants which is reflected in yield attributes. Hierarchical cluster analysis and principal component analyses showed that salt sensitivity was associated with the increments of Na+, hydrogen peroxide, and ABA contents. The regulatory role of JA under salinity stress was interlinked with increased JA level which consequentially improved ion transporting, osmoregulation, and antioxidant defense
Stellar dynamics in young clusters: the formation of massive runaways and very massive runaway mergers
In the present paper we combine an N-body code that simulates the dynamics of
young dense stellar systems with a massive star evolution handler that accounts
in a realistic way for the effects of stellar wind mass loss. We discuss two
topics:
1. The formation and the evolution of very massive stars (with a mass >120
Mo) is followed in detail. These very massive stars are formed in the cluster
core as a consequence of the successive (physical) collison of 10-20 most
massive stars of the cluster (the process is known as runaway merging). The
further evolution is governed by stellar wind mass loss during core hydrogen
burning and during core helium burning (the WR phase of very massive stars).
Our simulations reveal that as a consequence of runaway merging in clusters
with solar and supersolar values, massive black holes can be formed but with a
maximum mass of 70 Mo. In small metallicity clusters however, it cannot be
excluded that the runaway merging process is responsible for pair instability
supernovae or for the formation of intermediate mass black holes with a mass of
several 100 Mo.
2. Massive runaways can be formed via the supernova explosion of one of the
components in a binary (the Blaauw scenario) or via dynamical interaction of a
single star and a binary or between two binaries in a star cluster. We explore
the possibility that the most massive runaways (e.g., zeta Pup, lambda Cep,
BD+433654) are the product of the collision and merger of 2 or 3 massive stars.Comment: Updated and final versio
Deactivation of a single-site gold-on-carbon acetylene hydrochlorination catalyst: An X-ray absorption and inelastic neutron scattering study
Single-site Au species supported on carbon have been shown to be the active sites for acetylene hydrochlorination. The evolution of these single-site species has been monitored by Au L3 X-ray Absorption Spectroscopy (XAS). Alternating between a standard reaction mixture of HCl/C2H2 and the single reactants, has provided insights into the reaction mechanism and catalyst deactivation processes. We demonstrate that oxidative addition of HCl across an Au(I) chloride species requires concerted addition with C2H2, in accordance with both the XAS measurements of Au oxidation state and the reaction kinetics being 1st order with respect to each reactant. The addition of excess C2H2 changes the Au speciation and results in the formation of oligomeric acetylene species which were detected by inelastic neutron scattering. Catalyst deactivation at extended reaction times can be correlated with the formation of metallic Au particles. The presence of this Au(0) species generated during the sequential gas experiments or after prolonged reaction times, results in the analysis of the normalised near edge white line intensity of the Au L3 X-ray absorption spectrum alone becoming an unsuitable guide for identifying the active Au species, affecting the strong correlation between normalized white line height and VCM productivity usually observed in the active catalyst. Thus, a combination of scanning transmission electron microscopy and detailed modelling of whole XAS spectrum was required to distinguish active Au(I) and Au(III) species from the spectator Au(0) component
Measurement of the B0-anti-B0-Oscillation Frequency with Inclusive Dilepton Events
The - oscillation frequency has been measured with a sample of
23 million \B\bar B pairs collected with the BABAR detector at the PEP-II
asymmetric B Factory at SLAC. In this sample, we select events in which both B
mesons decay semileptonically and use the charge of the leptons to identify the
flavor of each B meson. A simultaneous fit to the decay time difference
distributions for opposite- and same-sign dilepton events gives ps.Comment: 7 pages, 1 figure, submitted to Physical Review Letter
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