573 research outputs found

    Sub-additive ergodic theorems for countable amenable groups

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    In this paper we generalize Kingman's sub-additive ergodic theorem to a large class of infinite countable discrete amenable group actions.Comment: Journal of Functional Analysi

    Oriented growth during recrystallization revisited in three dimensions

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    International audienceThe two surfaces of a 40% cold-rolled tricrystal of aluminium were scratched to stimulate recrystallization nucleation. Serial sectioning combined with electron backscatter diffraction was used to characterize the nuclei in three dimensions. It was found that the largest nuclei have a 40 degrees relationship to the matrix, but there are also many nuclei of this orientation relationship which do not grow to large sizes. It is shown that local variations in the deformation microstructure determine where preferential growth occurs. (C) 2013 The Authors. Published by Elsevier Ltd. on behalf of Acta Materialia Inc. All rights reserved

    Data Mining: Concept, Aplications and Techniques

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    Dynamic binding of Ku80, Ku70 and NF90 to the IL-2 promoter in vivo in activated T-cells

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    IL-2 gene expression in activated T-cells is initiated by chromatin remodeling at the IL-2 proximal promoter and conversion of a transcriptional repressor into a potent transcriptional activator. A purine-box regulator complex was purified from activated Jurkat T-cell nuclei based on sequence-specific DNA binding to the antigen receptor response element (ARRE)/nuclear factor of activated T-cells (NF-AT) target DNA sequence in the proximal IL-2 promoter. ARRE DNA-binding subunits were identified as NF90, NF45 and systemic lupus erythematosis autoantigens, Ku80 and Ku70. Monoclonal antibodies to Ku80, Ku70 and NF90 specifically inhibit constitutive and inducible ARRE DNA-binding activity in Jurkat T-cells. Ku80, Ku70 and NF90 bind specifically to the IL-2 gene promoter in vivo, as demonstrated by chromatin immunoprecipitation. Activation of Jurkat T-cells and mouse primary spleen cells induces binding of Ku80 and NF90 to the IL-2 promoter in vivo, and decreases binding of Ku70 to the IL-2 promoter in vivo, and these dynamic changes are inhibited by immunosuppressants cyclosporin A and triptolide. Dynamic changes in binding of Ku80, Ku70 and NF90 to the IL-2 proximal promoter in vivo correlate with chromatin remodeling and transcriptional initiation in activated T-cells

    Magnetoresistance of high mobility HgTe quantum dot films with controlled charging

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    Funding: We thank Christopher Melnychuk for very useful discussions. This work was supported by the National Natural Science Foundation of China under grant number 62105022, the University of Chicago Materials Research Science and Engineering Center, which was funded by the National Science Foundation under award number DMR1420709, and by the Department of Defense (DOD) Air Force Office of Scientific Research under grant number FA9550-18-1-0099.The magnetoresistance of HgTe quantum dot films, exhibiting a well-defined 1Se state charging and a relatively high mobility (1-10 cm2 Vāˆ’1 sāˆ’1), is measured as a function of temperature down to 10 K and controlled occupation of the first electronic state. There is a positive-quadratic magnetoresistance which can be several 100% at low temperature and scales like x(1 āˆ’ x) where x is the filling fraction of the lowest quantum dot state in the conduction band, 1Se. This positive magnetoresistance is orders of magnitude larger than the effect estimated from mobile carriers and it is attributed to the increased confinement induced by the magnetic field. There is also a negative magnetoresistance of 1-20% from 300 K to 10 K which is rather independent of the fractional occupation, and which follows a negative exponential dependence with the magnetic field. It can be empirically fit with an effective g-factor of āˆ¼55 and it is tentatively attributed to the reduction of barrier heights by the Zeeman splitting of the 1Se state.Peer reviewe

    Engineering Colloidal Metal-Semiconductor Nanorods Hybrid Nanostructures for Photocatalysis

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    Comprehensive Summary Emerging engineering strategies of colloidal metal-semiconductor nanorod hybrid nanostructures spanning from type, size, dimension, and location of both metal nanoparticles and semiconductors, co-catalyst, band gap structure, surface ligand to hole scavenger are elaborated symmetrically to rationalize the design of this type of intriguing materials for efficient photocatalytic applications. This article is protected by copyright. All rights reserved

    Unravelling the Interfacial Dynamics of Bandgap Funneling in Bismuth-Based Halide Perovskites

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    An environmentally friendly mixed-halide perovskite MA3Bi2Cl9āˆ’xIx with a bandgap funnel structure has been developed. However, the dynamic interfacial interactions of bandgap funneling in MA3Bi2Cl9āˆ’xIx perovskites in the photoelectrochemical (PEC) system remain ambiguous. In light of this, single- and mixed-halide lead-free bismuth-based hybrid perovskitesā€”MA3Bi2Cl9āˆ’yIy and MA3Bi2I9 (named MBCl-I and MBI)ā€”in the presence and absence of the bandgap funnel structure, respectively, are prepared. Using temperature-dependent transient photoluminescence and electrochemical voltammetric techniques, the photophysical and (photo)electrochemical phenomena of solidā€“solid and solidā€“liquid interfaces for MBCl-I and MBI halide perovskites are therefore confirmed. Concerning the mixed-halide hybrid perovskites MBCl-I with a bandgap funnel structure, stronger electronic coupling arising from an enhanced overlap of electronic wavefunctions results in more efficient exciton transport. Besides, MBCl-I's effective diffusion coefficient and electron-transfer rate demonstrate efficient heterogeneous charge transfer at the solidā€“liquid interface, generating improved photoelectrochemical hydrogen production. Consequently, this combination of photophysical and electrochemical techniques opens up an avenue to explore the intrinsic and interfacial properties of semiconductor materials for elucidating the correlation between material characterization and device performance
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