11,486 research outputs found
Optimal parameters of leader development in lightning
The dependences between the different parameters of a leader in lightning are obtained theoretically. The physical mechanism of the instability leading to the formation of the streamer zone is proposed. The instability has the wave nature and is caused by the self-influence effects of the space charge. Using a stability condition of the leader propagation, a dependence is obtained between the current across the leader head and its velocity of motion. The dependence of the streamer zone length on the gap length is also obtained. It is shown that the streamer zone length is saturated with the increasing of the gap length. A comparison between the obtained dependences and the experimental data is presented
Novel mechanism for temperature-independent transitions in flexible molecules: role of thermodynamic fluctuations
Novel physical mechanism is proposed for explanation of
temperature-independent transition reactions in molecular systems. The
mechanism becomes effective in the case of conformation transitions between
quasi-isoenergetic molecular states. It is shown that at room temperatures,
stochastic broadening of molecular energy levels predominates the energy of low
frequency vibrations accompanying the transition. This leads to a cancellation
of temperature dependence in the stochastically averaged rate constants. As an
example, physical interpretation of temperature-independent onset of P2X_3
receptor desensitization in neuronal membranes is provided.Comment: 4 pages, 1 figur
Heavy Quark Lifetimes, Mixing and CP Violation
This paper emphasizes four topics that represent some of the year's
highlights in heavy quark physics. First of all, a review is given of charm
lifetime measurements and how they lead to better understanding of the
mechanisms of charm decay. Secondly, the CLEO collaboration's new search for
charm mixing is reported, which significantly extends the search for new
physics in that sector. Thirdly, important updates in Bs mixing are summarized,
which result in a new limit on the mass difference, and which further constrain
the unitarity triangle. Finally, the first efforts to measure CP violation in
the B system are discussed. Results are shown for the CDF and ALEPH
measurements of sin(2beta), as well as the CLEO branching fraction measurements
of B-->Kpi,pipi, which have implications for future measurements of alpha.Comment: 25 pages, 15 figures. Talk given at the XIX International Symposium
on Lepton and Photon Interactions, Stanford University, August 9-14, 199
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