120 research outputs found

    A Search for non-Newtonian force in a precision measurement of the scattering of slow neutrons in Xenon gas

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    An experimental search for non-newtonian, gravity-like force in a precision measurement of the scattering of slow neutrons in Xenon gas is proposed. A preliminary experiment with small statistics of 25 hours irradiation time was performed and the observed scattering distribution is consistent with the expectation with no additional forces. A 95% CL limit on the coupling strength for a hypothetical force of 1 nm interaction range was evaluated to be 2*10^-15. The expected sensitivity for a planned high statistics runs is discussed.Comment: 5pages, 3 figure

    Carbon Nanotube/Nanofibers and Graphite Hybrids for Li-Ion Battery Application

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    To improve the electrical conductivity of negative electrodes of lithium ion batteries, we applied a direct CVD synthesis of carbon nanomaterials on the surface of graphite particles. To prepare a catalyst, two alternative approaches were utilized: colloidal nanoparticles (NPs) and metal (Ni and Co) nitrate salt precursors deposited on the graphite surface. Both colloidal and precursor systems allowed us to produce carbon nanofibers (CNFs) on the graphite surface with high coverage under the optimum CVD conditions. Electrical measurements revealed that the resistivity of the actual electrodes fabricated from CNFs coated graphite particles was about 40% lower compared to the original pristine graphite electrodes.Peer reviewe

    Effects of Bepridil on Spiral Reentry

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    Bepridil is effective for conversion of atrial fibrillation to sinus rhythm and in the treatment of drug-refractory ventricular tachyarrhythmias. We investigated the effects of bepridil on electrophysiological properties and spiral-wave (SW) reentry in a 2-dimensional ventricular muscle layer of isolated rabbit hearts by optical mapping. Ventricular tachycardia (VT) induced in the presence of bepridil (1 μM) terminated earlier than in the control. Bepridil increased action potential duration (APD) by 5% – 8% under constant pacing and significantly increased the space constant. There was a linear relationship between the wavefront curvature (κ) and local conduction velocity: LCV = LCV0 − D·κ (D, diffusion coefficient; LCV0, LCV at κ = 0). Bepridil significantly increased D and LCV0. The regression lines with and without bepridil crossed at κ = 20 – 40 cm−1, resulting in a paradoxical decrease of LCV at κ > 40 cm−1. Dye transfer assay in cultured rat cardiomyocytes confirmed that bepridil increased intercellular coupling. SW reentry in the presence of bepridil was characterized by decremental conduction near the rotation center, prominent drift, and self-termination by collision with boundaries. These results indicate that bepridil causes an increase of intercellular coupling and a moderate APD prolongation, and this combination compromises wavefront propagation near the rotation center of SW reentry, leading to its drift and early termination

    IKs Block and Spiral-Wave Reentry

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    We tested a hypothesis that an enhancement of IKs may play a pivotal role in ventricular proarrhythmia under high sympathetic activity. A 2-dimensional ventricular muscle layer was prepared in rabbit hearts, and action potential signals were analyzed by optical mapping. During constant stimulation, isoproterenol (ISP, 0.1 μM) significantly shortened action potential duration (APD); chromanol 293B (30 μM), a selective IKs-blocker, reversed the APD shortening. VTs induced in the presence of ISP lasted longer than in the control, and this was reversed by 293B. E-4031 (0.1 μM), a selective IKr-blocker, did not cause such reversal. Spiral-wave (SW) reentry with ISP was characterized by more stable rotation around a shorter functional block line (FBL) than in the control. After application of 293B, SW reentry was destabilized, and rotation around a longer FBL with prominent drift reappeared. The APD abbreviation by ISP close to the rotation center was more pronounced than in the periphery, leading to an opposite APD gradient (center < periphery) compared with controls. This effect was also reversed by 293B. In conclusion, β-adrenergic stimulation stabilizes SW reentry most likely though an enhancement of IKs. Blockade of IKs may be a promising therapeutic modality in prevention of ventricular tachyarrhythmias under high sympathetic activity
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