4,151 research outputs found
Top Quark Loop Corrections to the Neutral Higgs Boson Production at the Fermilab Tevatron
We calculate the corrections arising from diagrams
involving the top-quark loops to the light neutral Higgs boson production via
at the Fermilab Tevatron in both the standard model and the
minimal supersymmetric model. In contrast to the QCD correction which increases
the tree-level cross section, the corrections imply a few percent reduction in
the production cross section relative to the tree-leve results.Comment: Some misprints are corrected, numerical results and conclusions are
unchanged. To appear in PL
Observational Determination of the Turbulent Ambipolar Diffusion Scale and Magnetic Field Strength in Molecular Clouds
We study the correlation of the velocity dispersion of the coexisting
molecules H13CN and H13CO+ and the turbulent energy dissipation scale in the
DR21(OH) star-forming region. The down-shift of the H13CO+ spectrum relative to
H13CN is consistent with the presence of ambipolar diffusion at dissipation
length scales that helps the process of turbulent energy dissipation, but at a
different cut-off for ions compared to the neutrals. We use our observational
data to calculate a turbulent ambipolar diffusion length scale L'\simeq17 mpc
and a strength of B_{pos}\simeq1.7 mG for the plane of the sky component of the
magnetic field in DR21(OH)
Gold as hydrogen: Structural and electronic properties and chemical bonding in Si3Au3+/0/- and comparisons to Si3H3+/0/-
A single Au atom has been shown to behave like H in its bonding to Si in several mono- and disilicon gold clusters. In the current work, we investigate the Au∕H analogy in trisilicon gold clusters, Si3Au+∕0∕−3. Photoelectron spectroscopy and density functional calculations are combined to examine the geometric and electronic structure of Si3Au−3. We find that there are three isomers competing for the ground state of Si3Au−3 as is the case for Si3H−3. Extensive structural searches show that the potential energy surfaces of the trisilicon gold clusters (Si3Au−3, Si3Au3, and Si3Au+3) are similar to those of the corresponding silicon hydrides. The lowest energy isomers for Si3Au−3 and Si3Au3 are structurally similar to a Si3Au four-membered ring serving as a common structural motif. For Si3Au+3, the 2π aromatic cyclotrisilenylium auride ion, analogous to the aromatic cyclotrisilenylium ion (Si3H+3), is the most stable species. Comparison of the structures and chemical bonding between Si3Au+∕0∕−3 and the corresponding silicon hydrides further extends the isolobal analogy between Au and H
Offline-Online Associated Camera-Aware Proxies for Unsupervised Person Re-identification
Recently, unsupervised person re-identification (Re-ID) has received
increasing research attention due to its potential for label-free applications.
A promising way to address unsupervised Re-ID is clustering-based, which
generates pseudo labels by clustering and uses the pseudo labels to train a
Re-ID model iteratively. However, most clustering-based methods take each
cluster as a pseudo identity class, neglecting the intra-cluster variance
mainly caused by the change of cameras. To address this issue, we propose to
split each single cluster into multiple proxies according to camera views. The
camera-aware proxies explicitly capture local structures within clusters, by
which the intra-ID variance and inter-ID similarity can be better tackled.
Assisted with the camera-aware proxies, we design two proxy-level contrastive
learning losses that are, respectively, based on offline and online association
results. The offline association directly associates proxies according to the
clustering and splitting results, while the online strategy dynamically
associates proxies in terms of up-to-date features to reduce the noise caused
by the delayed update of pseudo labels. The combination of two losses enables
us to train a desirable Re-ID model. Extensive experiments on three person
Re-ID datasets and one vehicle Re-ID dataset show that our proposed approach
demonstrates competitive performance with state-of-the-art methods. Code will
be available at: https://github.com/Terminator8758/O2CAP.Comment: Accepted to TI
Negative and Positive Lateral Shift of a Light Beam Reflected from a Grounded Slab
We consider the lateral shift of a light beam reflecting from a dielectric
slab backed by a metal. It is found that the lateral shift of the reflected
beam can be negative while the intensity of reflected beam is almost equal to
the incident one under a certain condition. The explanation for the negativity
of the lateral shift is given in terms of the interference of the reflected
waves from the two interfaces. It is also shown that the lateral shift can be
enhanced or suppressed under some other conditions. The numerical calculation
on the lateral shift for a realistic Gaussian-shaped beam confirms our
theoretical prediction.Comment: 8pages,4 figure
Magnetic properties of undoped Cu2O fine powders with magnetic impurities and/or cation vacancies
Fine powders of micron- and submicron-sized particles of undoped Cu2O
semiconductor, with three different sizes and morphologies have been
synthesized by different chemical processes. These samples include nanospheres
200 nm in diameter, octahedra of size 1 micron, and polyhedra of size 800 nm.
They exhibit a wide spectrum of magnetic properties. At low temperature, T = 5
K, the octahedron sample is diamagnetic. The nanosphere is paramagnetic. The
other two polyhedron samples synthesized in different runs by the same process
are found to show different magnetic properties. One of them exhibits weak
ferromagnetism with T_C = 455 K and saturation magnetization, M_S = 0.19 emu/g
at T = 5 K, while the other is paramagnetic. The total magnetic moment
estimated from the detected impurity concentration of Fe, Co, and Ni, is too
small to account for the observed magnetism by one to two orders of magnitude.
Calculations by the density functional theory (DFT) reveal that cation
vacancies in the Cu2O lattice are one of the possible causes of induced
magnetic moments. The results further predict that the defect-induced magnetic
moments favour a ferromagnetically coupled ground state if the local
concentration of cation vacancies, n_C, exceeds 12.5%. This offers a possible
scenario to explain the observed magnetic properties. The limitations of the
investigations in the present work, in particular in the theoretical
calculations, are discussed and possible areas for further study are suggested.Comment: 20 pages, 5 figures 2 tables, submitted to J Phys Condense Matte
MiR-1254 inhibits proliferation, migration and invasion of human brain tumour cell lines
Purpose: To investigate the expression of miR-1254 in 5 astrocytoma cell lines, and the mechanism involved.Methods: Total RNA was isolated by RNeasy RNA isolation kit while cDNA was prepared by RevertAid cDNA synthesis kit. The transcripts were analysed by real-time polymerase chain reaction (RT-PCR). Transfection of miR-1254 was carried out using FuGENE HD (Promega). Apoptosis was determined by DAPI, acridine orange (AO)/ethidium bromide (EB) and annexin V/PI double staining. Cell migration and invasion were investigated by wound healing and Martigel invasion assays, respectively. Protein expression was measured by western blotting.Results: Expression of miR-1254 was significantly down-regulated in the astrocytoma cell lines when compared to normal astrocyte cells (p < 0.05). Ectopic expression of miR-1254 in astrocytoma SW 1088 cells inhibited cell proliferation via initiation of apoptosis and cell cycle arrest. Over-expression of miR- 1254 also led to significant decrease in cell migration and invasion of SW 1088 astrocytoma cells (p < 0.05).Conclusion: The results show that the expression of miR-1254 is down-regulated in astrocytoma cell lines, but over-expression of miR-1254 inhibits proliferation of the cell lines via cell cycle arrest and apoptosis. Thus, miR-1254 has promising potential for use in the treatment of brain tumour.Keywords: Brain tumour, Astrocytoma, miR-1254, Apoptosis, Cell migratio
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