13,656 research outputs found

    Can the Bump be Observed in the Early Afterglow of GRBS with X-Ray Line Emission Features?

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    Extremely powerful emission lines are observed in the X-ray afterglow of several GRBs. The energy contained in the illuminating continuum which is responsible for the line production exceeds 1051^{51} erg, much higher than that of the collimated GRBs. It constrains the models which explain the production of X-ray emission lines. In this paper, We argue that this energy can come from a continuous postburst outflow. Focusing on a central engine of highly magnetized millisecond pulsar or magnetar we find that afterglow can be affected by the illuminating continuum, and therefore a distinct achromatic bump may be observed in the early afterglow lightcurves. With the luminosity of the continuous outflow which produces the line emission, we define the upper limit of the time when the bump feature appears. We argue that the reason why the achromatic bumps have not been detected so far is that the bumps should appear at the time too early to be observed.Comment: 13 pags, 2 tables, appear in v603 n1 pt1 ApJ March 1, 2004 issu

    Realizing quantum controlled phase-flip gate through quantum dot in silicon slow-light photonic crystal waveguide

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    We propose a scheme to realize controlled phase gate between two single photons through a single quantum dot in slow-light silicon photonic crystal waveguide. Enhanced Purcell factor and beta factor lead to high gate fidelity over broadband frequencies compared to cavity-assisted system. The excellent physical integration of this silicon photonic crystal waveguide system provides tremendous potential for large-scale quantum information processing.Comment: 9 pages, 3 figure

    Fourth ABC Index and Fifth GA Index of Certain Special Molecular Graphs

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    Several chemical indices have been introduced in theoretical chemistry to measure the properties of molecular structures, such as atom bond connectivity index and geometric-arithmetic index. In this paper, we present the fourth atom bond connectivity index and fifth geometric-arithmetic index of fan molecular graph, wheel molecular graph, gear fan molecular graph, gear wheel molecular graph, and their r-corona molecular graphs

    Longitudinal Study of the Emerging Functional Connectivity Asymmetry of Primary Language Regions during Infancy

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    Asymmetry in the form of left-hemisphere lateralization is a striking characteristic of the cerebral regions involved in the adult language network. In this study, we leverage a large sample of typically developing human infants with longitudinal resting-state functional magnetic resonance imaging scans to delineate the trajectory of interhemispheric functional asymmetry in language-related regions during the first 2 years of life. We derived the trajectory of interhemispheric functional symmetry of the inferior frontal gyrus (IFG) and superior temporal gyrus (STG), the sensory and visual cortices, and two higher-order regions within the intraparietal sulcus and dorsolateral prefrontal cortex. Longitudinal models revealed a best fit with quadratic age terms and showed significant estimated coefficients of determination for both the IFG (r2 = 0.261, p < 0.001) and the STG (r2 = 0.142, p < 0.001) regions while all other regions were best modeled by log-linear increases. These inverse-U-shaped functions of the language regions peaked at ∼11.5 months of age, indicating that a transition toward asymmetry began in the second year. This shift was accompanied by an increase in the functional connectivity of these regions within the left hemisphere. Finally, we detected an association between the trajectory of the IFG and language outcomes at 4 years of age (χ2 = 10.986, p = 0.011). Our results capture the developmental timeline of the transition toward interhemispheric functional asymmetry during the first 2 years of life. More generally, our findings suggest that increasing interhemispheric functional symmetry in the first year might be a general principle of the developing brain, governing different functional systems, including those that will eventually become lateralized in adulthood

    The superheated Melting of Grain Boundary

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    Based on a model of the melting of Grain Boundary (GB), we discuss the possibility of the existence of superheated GB state. A Molecular Dynamics simulation presented here shows that the superheated GB state can realized in the high symmetric tilt GB. Whether the sizes of liquid nuclei exceed a critical size determined the superheating grain boundary melting or not. Our results also indicate that the increase of melting point due to pressure is smaller than the superheating due to nucleation mechanism.Comment: Accepted by PRB, 7 pages and 5 figure

    On local existence and blow-up of solution for the higher-order nonlinear Kirchhoff-type equation with nonlinear strongly damped terms

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    In this paper ,we deal with the initial boundary value problems for higher -order kirchhoff-type equation with nonlinear strongly dissipation:At first ,we prove the local existence and uniqueness of the solution by Galerkin methodthen and contracting mapping principle .Furthermore,we prove the global existence of solution , At last,we consider that blow up of solution in finite time under suitable condition

    Soil Microbial Diversity of an Artificial \u3cem\u3eCaragana Korshinskii\u3c/em\u3e Plantation on the Loess Plateau of China

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    Peashrub (Caragana korshinskii) is an important dune-fixation plant on the loess plateau of China and is valuable in ecological environment construction of North-western China. For determining relationships between peashrub and soil microbes, three clone libraries of 16S rDNA from rhizoplane, rhizosphere and bulk soil communities of peashrub were constructed with a culture-independent approach. The data obtained from three clone libraries were used to investigate the magnitude of vegetative changes in the microbial community, and to search for general ecological relationships
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