6,683 research outputs found
Comment on "Observation of neutronless fusion reactions in picosecond laser plasmas"
The paper by Belyaev et al. [Phys. Rev. E {\bf 72}, 026406 (2005)] reported
the first experimental observation of alpha particles produced in the
thermonuclear reaction B()Be induced by
laser-irradiation on a B polyethylene (CH) composite target. The
laser used in the experiment is characterized by a picosecond pulse duration
and a peak of intensity of 2 W/cm. We suggest that both the
background-reduction method adopted in their detection system and the choice of
the detection energy region of the reaction products are possibly inadequate.
Consequently the total yield reported underestimates the true yield. Based on
their observation, we give an estimation of the total yield to be higher than
their conclusion, i.e., of the order of 10 per shot.Comment: 3 figures, accepted for publication in the Comment section of
Physical Review
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E-Process - Its Components And Their Neutron Excesses
NSF GP-18335, GP-32051NASA NGR-44-006-159Astronom
E-Process - Its Components And Their Neutron Excesses
NSF GP-18335, GP-32051NASA NGR-44-006-159Astronom
Vector field mediated models of dynamical light velocity
A vector-tensor theory of gravity that was introduced in an earlier
publication is analyzed in detail and its consequences for early universe
cosmology are examined. The multiple light cone structure of the theory
generates different speeds of gravitational and matter wave fronts, and the
contraction of these light cones produces acausal, superluminary inflation that
can resolve the initial value problems of cosmology.Comment: 16 pages, uses amsar
Fluctuation Spectrum from a Scalar-Tensor Bimetric Gravity Theory
Predictions of the CMB spectrum from a bimetric gravity theory
(gr-qc/0101126) are presented. The initial inflationary period in BGT is driven
by a vanishingly small speed of gravitational waves v_g in the very early
universe. This initial inflationary period is insensitive to the choice of
scalar field potential and initial values of the scalar field. After this
initial period of inflation, v_g will increase rapidly and the effects of a
potential will become important. We show that a quadratic potential introduced
into BGT yields an approximately flat spectrum with inflation parameters:
n_s=0.98, n_t=-0.027, alpha_s=-3.2e-4 and alpha_t=-5.0e-4, with r >= 0.014.Comment: 14 pages, uses amsmath, amssym
Tomographic Image of the Southern California Mantle
P wave teleseismic travel time delays recorded by the Southern California Array are inverted by the method of backprojection tomography to obtain images of variations in the P wave velocity structure to a depth of 750 km. Two major upper mantle features arc resolved: one beneath the Transverse Ranges region and another beneath the Salton Trough region. The Transverse Ranges feature appears as a curtainlike, east trending, high-velocity anomaly. This feature is ∼60 km thick, extends most deeply on its eastern end (to ∼250 km), and attains a maximum velocity −3% greater than average southern California mantle of the same depth. The Salton Trough feature, which is not as well resolved as the Transverse Ranges feature, is composed of low velocities in the upper 70–100 km. These P wave velocities arc depressed 3–4% compared to average southern California mantle. Tests of the inversion indicate the major aspects of the imaged structure are authentic
Unstable Hadrons in Hot Hadron Gas in Laboratory and in the Early Universe
We study kinetic master equations for chemical reactions involving the
formation and the natural decay of unstable particles in a thermal bath. We
consider the decay channel of one into two particles, and the inverse process,
fusion of two thermal particles into one. We present the master equations the
evolution of the density of the unstable particles in the early Universe. We
obtain the thermal invariant reaction rate using as an input the free space
(vacuum) decay time and show the medium quantum effects on reaction relaxation time. As another laboratory example
we describe the process in thermal hadronic gas in
heavy-ion collisions. A particularly interesting application of our formalism
is the process in the early Universe.
We also explore the physics of and freeze-out in the
Universe.Comment: 13 pages, 9 figures, published in Physical Review
Radioactivity in Supernova Remnants
We calculate implications of the idea developed by Burbidge et al. that the nearly exponential decrease after the (irst 100 days of the light-curves of Type i supernovae is due to nuclear energy released by the spontaneous fission of Cf354. Uncertainty of the correctness of the Cf-hypothesis qualifies any interpretation of (1) supernovae light-curves, (2) the location and mechanism of heavy-element nucleosynthesis by rapid neutron captures, and (3) the present-day energy balance in supernova remnants We demonstrate that, if the Cf-hypothesis is correct, the Crab Nebula presently has a radioactive energy input of 1 2 X 1030 ergs/sec, of which amount 92 per cent is in the form of kinetic energy of heavy ions (5-6-MeV alphaparticles and 60-140-MeV fission fragments). That much energy would be significantly related to observed properties of the nebula. An experimental test of the Cf-hypothesis may be made by searching for gamma-ray lines associated with transbismuth radioactivity The anticipated line spectrum is complex The strongest line flux is 9 7 X 10-0 from the Crab for the 390-keV line of Cf140. Good angular and energy resolution will be required to resolve the lines from the sky backgiound
Integral throat entrance development, qualification and production for the Antares 3 nozzle
Although design analyses of a G-90 graphite integral throat entrance for the Antares 3 solid rocket motor nozzle indicated acceptable margins of safety, the nozzle throat insert suffered a thermostructural failure during the first development firing. Subsequent re-analysis using properties measured on material from the same billet as the nozzle throat insert showed negative margins. Carbon-carbon was investigated and found to result in large positive margins of safety. The G-90 graphite was replaced by SAI fast processed 4-D material which uses Hercules HM 10000 fiber as the reinforcement. Its construction allows powder filling of the interstices after preform fabrication which accelerates the densification process. Allied 15V coal tar pitch is then used to complete densification. The properties were extensively characterized on this material and six nozzles were subjected to demonstration, development and qualification firings
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