A mutual GrabCut method to solve co-segmentation

Extent: 11 p.Co-segmentation aims at segmenting common objects from a group of images. Markov random field (MRF) has been widely used to solve co-segmentation, which introduces a global constraint to make the foreground similar to each other. However, it is difficult to minimize the new model. In this paper, we propose a new Markov random field-based co-segmentation model to solve co-segmentation problem without minimization problem. In our model, foreground similarity constraint is added into the unary term of MRF model rather than the global term, which can be minimized by graph cut method. In the model, a new energy function is designed by considering both the foreground similarity and the background consistency. Then, a mutual optimization approach is used to minimize the energy function. We test the proposed method on many pairs of images. The experimental results demonstrate the effectiveness of the proposed method.Zhisheng Gao, Peng Shi, Hamid Reza Karimi and Zheng Pe

Polarized positron beams via intense two-color laser pulses

Generation of ultrarelativistic polarized positrons during interaction of an ultrarelativistic electron beam with a counterpropagating two-color petawatt laser pulse is investigated theoretically. Our Monte Carlo simulation based on a semi-classical model, incorporates photon emissions and pair productions, using spin-resolved quantum probabilities in the local constant field approximation, and describes the polarization of electrons and positrons for the pair production and photon emission processes, as well as the classical spin precession in-between. The main reason of the polarization is shown to be the spin-asymmetry of the pair production process in strong external fields, combined with the asymmetry of the two-color laser field. Employing a feasible scenario, we show that highly polarized positron beams, with a polarization degree of $\zeta\approx 60\%$, can be produced in a femtosecond time scale, with a small angular divergence, $\sim 74$ mrad, and high density $\sim 10^{14}$ cm$^{-3}$. The laser-driven positron source, along with laser wakefield acceleration, may pave the way to small scale facilities for high energy physics studies

Melatonin protects against focal cerebral ischemia in rats via inhibition of ischemia-induced overproduction of nitric oxide

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Deficiency of COX-1 gene expression in mice reduces the infarction volume in a 24-hour permanent focal cerebral ischemia model

Inflammatory reactions have an important role in the ischemic pathophysiology. Cyclooxygenase (COX) is the key enzyme in converting arachidonic acid to prostanoids that, in turn, are the major contributors to the intrinsic inflammatory response. In this study, we used COX-1-null mice to investigate the role of COX-1 gene expression in a permanent focal cerebral ischemia model. Adult littermates (wild type +/+, heterozygous +/-, and homozygous -/-), were used. Genetic status was determined using a PCR analysis. The mice were anesthetized with chloral hydrate (350 mg/kg, IP). Right femoral artery was cannulated for monitoring of arterial blood pressure and heart rate. Rectal temperature was kept normal throughout anesthesia. Cerebral blood flow was monitored by Laser-Doppler Flowmetry. Permanent focal cerebral ischemia was achieved by passing a monofilament suture via the right external and internal carotid arteries to occlude the right middle cerebral artery (MCA) at its origin. Mice were killed by decapitation at 24 hours after MCA occlusion. The brains were cut into 2-mm coronal slices for staining with 2% tetrazolium chloride to reveal the infarct. The infarction volume was quantified using computer-assisted image analysis. Relative infarction volumes were, in mean ?SEM, 42.67 ?3.72% (n=6) in COX-1 +/+ mice, 25.97 ?8.48% (n=6) in COX-1 +/- mice, and 28.13 ?6.22% (n=6) in COX-1 -/- mice, respectively. There was no significant difference in physiological parameters and cerebral perfusion among the groups. Our results demonstrated that lack of COX-1 gene expression might reduce infarction volume in a 24-hour permanent MCA occlusion model in mice.published_or_final_versio

Superfluid and magnetic states of an ultracold Bose gas with synthetic three-dimensional spin-orbit coupling in an optical lattice

We study ultracold bosonic atoms with the synthetic three-dimensional spin-orbit (SO) coupling in a cubic optical lattice. In the superfluidity phase, the lowest energy band exhibits one, two or four pairs of degenerate single-particle ground states depending on the SO-coupling strengths, which can give rise to the condensate states with spin-stripes for the weak atomic interactions. In the deep Mott-insulator regime, the effective spin Hamiltonian of the system combines three-dimensional Heisenberg exchange interactions, anisotropy interactions and Dzyaloshinskii-Moriya interactions. Based on Monte Carlo simulations, we numerically demonstrate that the resulting Hamiltonian with an additional Zeeman field has a rich phase diagram with spiral, stripe, vortex crystal, and especially Skyrmion crystal spin-textures in each xy-plane layer. The obtained Skyrmion crystals can be tunable with square and hexagonal symmetries in a columnar manner along the z axis, and moreover are stable against the inter-layer spin-spin interactions in a large parameter region.Comment: 9 pages, 4 figures; title modified, references and discussions added; accepted by PR