4,181 research outputs found
New Outlook on the Possible Existence of Superheavy Elements in Nature
A consistent interpretation is given to some previously unexplained phenomena
seen in nature in terms of the recently discovered long-lived high spin super-
and hyper-deformed isomeric states. The Po halos seen in mica are interpreted
as due to the existence of such isomeric states in corresponding Po or nearby
nuclei which eventually decay by gamma- or beta-decay to the ground states of
210Po, 214Po and 218Po nuclei. The low-energy 4.5 MeV alpha-particle group
observed in several minerals is interpreted as due to a very enhanced alpha
transition from the third minimum of the potential-energy surface in a
superheavy nucleus with atomic number Z=108 (Hs) and atomic mass number around
271 to the corresponding minimum in the daughter.Comment: 8 pages, 8 figures, 5 tables. Paper presented at VII Int.
School-Seminar on Heavy Ion Physics, May 27 - June 1, 2002, Dubna, Russi
An Event-based Simulation Model for Analysing the Utilization Levels of a Railway Line in Urban Area
This paper offers a simulation model for analyzing the utilization levels of a railway line between Edinburgh Waverley and Glasgow Queen Street. Specifically, a segment of this line has been simulated using Simul8 to study the impacts of freight trains on passenger trains. The utilisation levels of this segment have been observed in three scenarios: utilisation existing state where all scheduled passenger trains and a few freight trains are observed; utilisation in future state where more freight trains are input in available time gaps running at their actual speed; and utilisation future state where freight trains are input in available time gaps running at speed equivalent to a passenger train. A decomposition approach is implemented. The results suggest that extra freight trains can be input into the current timetables without impeding the current scenario, allowing a reasonable increase in utilisation of the rail line
Multi-particle Production and Thermalization in High-Energy QCD
We argue that multi-particle production in high energy hadron and nuclear
collisions can be considered as proceeding through the production of gluons in
the background classical field. In this approach we derive the gluon spectrum
immediately after the collision and find that at high energies it is
parametrically enhanced by ln(1/x) with respect to the quasi-classical result
(x is the Bjorken variable). We show that the produced gluon spectrum becomes
thermal (in three dimensions) with an effective temperature determined by the
saturation momentum Qs, T= c Qs/2pi during the time ~1/T; we estimate
c=sqrt{2pi}/2 ~ 1.2. Although this result by itself does not imply that the
gluon spectrum will remain thermal at later times, it has an interesting
applications to heavy ion collisions. In particular, we discuss the possibility
of Bose-Einstein condensation of the produced gluon pairs and estimate the
viscosity of the produced gluon system.Comment: 25 pages, 4 figures; typos fixed; discussions expanded; we added a
new section IV in which we argue that at high energies the production
mechanism discussed in the paper is parametrically enhanced by ln(1/x) with
respect to the quasi-classical resul
Exact Evolution Operator on Non-compact Group Manifolds
Free quantal motion on group manifolds is considered. The Hamiltonian is
given by the Laplace -- Beltrami operator on the group manifold, and the
purpose is to get the (Feynman's) evolution kernel. The spectral expansion,
which produced a series of the representation characters for the evolution
kernel in the compact case, does not exist for non-compact group, where the
spectrum is not bounded. In this work real analytical groups are investigated,
some of which are of interest for physics. An integral representation for the
evolution operator is obtained in terms of the Green function, i.e. the
solution to the Helmholz equation on the group manifold. The alternative series
expressions for the evolution operator are reconstructed from the same integral
representation, the spectral expansion (when exists) and the sum over classical
paths. For non-compact groups, the latter can be interpreted as the (exact)
semi-classical approximation, like in the compact case. The explicit form of
the evolution operator is obtained for a number of non-compact groups.Comment: 32 pages, 5 postscript figures, LaTe
Super- and Hyperdeformed Isomeric States and Long-Lived Superheavy Elements
The recent discoveries of the long-lived high spin super- and hyperdeformed
isomeric states and their unusual radioactive decay properties are described.
Based on their existence a consistent interpretation is given to the production
of the long-lived superheavy element with Z = 112, via secondary reactions in
CERN W targets, and to the low energy and very enhanced alpha-particle groups
seen in various actinide fractions separated from the same W target. In
addition, consistent interpretations are suggested for previously unexplained
phenomena seen in nature. These are the Po halos, the low-energy enhanced 4.5
MeV alpha-particle group proposed to be due to an isotope of a superheavy
element with Z = 108, and the giant halos.Comment: 4 pages. Contribution to the 2nd Int. Conf. on the Chemistry and
Physics of the Transactinide Elements (TAN 03) Napa California, November 200
Pair creation in transport equations using the equal-time Wigner function
Based on the equal-time Wigner function for the Klein-Gordon field, we
discuss analytically the mechanism of pair creation in a classical
electromagnetic field including back-reaction. It is shown that the equations
of motion for the Wigner function can be reduced to a variable-frequency
oscillator. The pair-creation rate results then from a calculation analogous to
barrier penetration in nonrelativistic quantum mechanics. The Wigner function
allows one to utilize this treatment for the formulation of an effective
transport theory for the back-reaction problem with a pair-creation source term
including Bose enhancement.Comment: 19 pages, LaTeX, UFTP 316/199
INTRAMURAL VESSELS, ACID MUCOPOLYSACCHARIDES AND LIPIDES IN THE WALL OF AORTA ABDOMINALIS AND ITS VISCERAL BRANCHES
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