Results 1 - 10 of 5025
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[en] The volume of recorded underdense meteor echoes is determined by transmitted power, treshold sensitivity of the receiver, antenna gain including its directivity and by the range of reflecting point on the meteor trail. These parameters must be considered when mass distribution index is evaluated. (author). 1 fig., 5 refs
[en] The radar observations of the Lyrid meteor stream at the Odrejov Observatory in 1980 to 1985 are analyzed and discussed from the viewpoint of determining the mass distribution exponent for overdense echoes in the range of 0.4 to 50 s. The mass exponent proved to be almost constant over the whole range of echo durations with s ∼1.58. The contribution of larger particles, as compared with other meteor streams was found to be more significant for the Lyrids. The almost constant value of s indicates a still active contribution of fresh cometary material to the stream. (author). 2 figs., 1 tab., 12 refs
[en] Double and multistation data on meteors from photographic and television records are used, to derive relative and absolute numbers of sporadic meteoroids coming to the Earth's vicinity and their mass accession. Seven different meteoroid populations are dealt with separately inside a mass interval of 2x107 g to 2x10-5 g and their cumulative numbers with decreasing mass determined. The paper is an abstract of a more extensive paper, which will be published in Bull. Astron. Inst. Czechosl. in 1988. (author). 2 figs., 3 tabs., 20 refs
[en] The density distribution near the boundary of a nucleus is computed in the effective-surface approximation and used to determine the radial dependence of the dynamical density component for resonance density oscillations. The results of the simple calculations are in good agreement with the results obtained in detailed microscopic computations
[en] A brief review of the experimental situation concerning the electrically charged charmoniumlike meson candidates, Z-, is presented. The Belle Collaboration reported peaks in the ψ(prime)π- and χc1π- invariant mass distributions in B → ψ(prime)π-K and B → χc1π-K, respectively. If these peaks are meson resonances, they would have a minimal quark substructure of c(bar c)d(bar u) and be unmistakeably exotic. However, even though the Belle signals have more than 5σ statistical significance, the experimental situation remains uncertain in that none of these peaks have yet been confirmed by other experiments. An analysis by the BABAR Collaboration of B → ψ(prime)π-K neither confirms nor contradicts the Belle claim for the Z(4430)- → ψ(prime)π-. In the BABAR analysis, B → J/ψπ-K decays were also studied, and no evidence for Z(4430)- → J/ψπ- was found. In this paper, we review and compare Belle and BABAR results on searches for charged charmonium-like states.
[en] The quality of the description of measured masses by theoretical models is studied. Much attention is given to the dependence of the quality of a given model on the region of nuclei for which the masses are calculated. Twelve models (among them, very recent ones) of various kinds are used in the study. Experimental masses evaluated recently (2011) are taken for the tests of the quality. A quite strong dependence of the quality of a given model on the region of nuclei, taken for the study, is found. (paper)
[en] Superheavy elements are created in the laboratory by the fusion of two heavy nuclei. The large Coulomb repulsion that makes superheavy elements decay also makes the fusion process that forms them very unlikely. Instead, after sticking together for a short time, the two nuclei usually come apart, in a process called quasifission. Mass-angle distributions give the most direct information on the characteristics and time scales of quasifission. A systematic study of carefully chosen mass-angle distributions has provided information on the global trends of quasifission. Large deviations from these systematics reveal the major role played by the nuclear structure of the two colliding nuclei in determining the reaction outcome, and thus implicitly in hindering or favouring superheavy element production.
[en] Evidence is provided to support the hypothesis that, because of the particular frequency separations of the solar g modes, resonant three-wave interactions stimulate only a selected few g modes. A resonant count diagram was obtained by plotting the total number of possible resonant three-wave interactions or a given beat frequency against the inverse of the beat frequency (the beat period), within a given frequency tolerance. The 1 = 1, 2, 3, 4 g modes calculated by Christensen-Dalsgaard, Gough and Morgan (1979) for a standard model of the Sun were used. The diagram has a significant peak at 160 minutes as well as other peaks at longer periods. The g modes that Delache and Scherrer (1983) tentatively identified from the Crimea-Stanford data were also plotted. These modes were found to correspond with the other peaks in the diagram. This coincidence between the observed g modes and the peaks in the resonant count diagram suggest that the observed g modes do owe their observability to resonant three-wave interactions
[en] Consideration is given to some theoretical issues in the problem of matter clustering in a neutrino-dominated universe. Among the topics discussed are: the role of right-handedness and left-handedness in neutrino interactions; Jeans instability; and Jeans coupling in a two-component field of massive neutrinos. On the basis of the theoretical discussion, a quantitative analysis is presented of the collapsing stage of clustering in an overdense region with a spherically symmetrical configuration