17,796 research outputs found
An Alternative Parameterization of R-matrix Theory
An alternative parameterization of R-matrix theory is presented which is
mathematically equivalent to the standard approach, but possesses features
which simplify the fitting of experimental data. In particular there are no
level shifts and no boundary-condition constants which allows the positions and
partial widths of an arbitrary number levels to be easily fixed in an analysis.
These alternative parameters can be converted to standard R-matrix parameters
by a straightforward matrix diagonalization procedure. In addition it is
possible to express the collision matrix directly in terms of the alternative
parameters.Comment: 8 pages; accepted for publication in Phys. Rev. C; expanded Sec. IV,
added Sec. VI, added Appendix, corrected typo
How Well Do We Know the Beta-Decay of 16N and Oxygen Formation in Helium Burning
We review the status of the 12C(a,g)16O reaction rate, of importance for
stellar processes in a progenitor star prior to a super-nova collapse. Several
attempts to constrain the p-wave S-factor of the 12C(a,g)16O reaction at Helium
burning temperatures (200 MK) using the beta-delayed alpha-particle emission of
16N have been made, and it is claimed that this S-factor is known, as quoted by
the TRIUMF collaboration. In contrast reanalyses (by G.M. hale) of all thus far
available data (including the 16N data) does not rule out a small S-factor
solution. Furthermore, we improved our previous Yale-UConn study of the beta-
delayed alpha-particle emission of \n16 by improving our statistical sample (by
more than a factor of 5), improving the energy resolution of the experiment (by
20%), and in understanding our line shape, deduced from measured quantities.
Our newly measured spectrum of the beta-delayed alpha-particle emission of 16N
is not consistent with the TRIUMF('94) data, but is consistent with the
Seattle('95) data, as well as the earlier (unaltered !) data of Mainz('71). The
implication of this discrepancies for the extracted astrophysical p-wave
s-factor is briefly discussed.Comment: 6 pages, 4 figures, Invited Talk, Physics With Radioactive Beams,
Puri, India, Jan. 12-17, 1998, Work Supported by USDOE Grant No.
DE-FG02-94ER4087
Testing collapse models with levitated nanoparticles: the detection challenge
We consider a nanoparticle levitated in a Paul trap in ultrahigh cryogenic
vacuum, and look for the conditions which allow for a stringent
noninterferometric test of spontaneous collapse models. In particular we
compare different possible techniques to detect the particle motion. Key
conditions which need to be achieved are extremely low residual pressure and
the ability to detect the particle at ultralow power. We compare three
different detection approaches based respectively on a optical cavity, optical
tweezer and a electrical readout, and for each one we assess advantages,
drawbacks and technical challenges
Subharmonics and Aperiodicity in Hysteresis Loops
We show that it is possible to have hysteretic behavior for magnets that does
not form simple closed loops in steady state, but must cycle multiple times
before returning to its initial state. We show this by studying the
zero-temperature dynamics of the 3d Edwards Anderson spin glass. The specific
multiple varies from system to system and is often quite large and increases
with system size. The last result suggests that the magnetization could be
aperiodic in the large system limit for some realizations of randomness. It
should be possible to observe this phenomena in low-temperature experiments.Comment: 4 pages, 3 figure
The 13N(d,n)14O Reaction and the Astrophysical 13N(p,g)14O Reaction Rate
N()O is one of the key reactions in the hot CNO cycle
which occurs at stellar temperatures around 0.1. Up to now, some
uncertainties still exist for the direct capture component in this reaction,
thus an independent measurement is of importance. In present work, the angular
distribution of the N()O reaction at = 8.9
MeV has been measured in inverse kinematics, for the first time. Based on the
distorted wave Born approximation (DWBA) analysis, the nuclear asymptotic
normalization coefficient (ANC), , for the ground state of
O N + is derived to be fm. The
N()O reaction is analyzed with the R-matrix approach,
its astrophysical S-factors and reaction rates at energies of astrophysical
relevance are then determined with the ANC. The implications of the present
reaction rates on the evolution of novae are then discussed with the reaction
network calculations.Comment: 17 pages and 8 figure
A Review of Internet Resources Related to Spoken Language Intervention for Spanish-Speaking Parents of Children who are Deaf or Hard of Hearing
Objective: The purpose of this study was to identify website information related to hearing loss, hearing technology, and spoken language development available to Spanish-speaking parents of children who are deaf or hard of hearing (DHH).
Design: An exploratory, descriptive design was used to determine the presence or absence of parent education information on a variety of websites.
Study Sample: The study explored Internet resources provided by national, state, and parent support organizations in the United States.
Results: A total of 53 organization websites were identified that had information for parents of DHH children learning spoken language, eight of which were international. Fifteen content areas were reviewed for each website. Of the 53 websites, 25 had information in Spanish.
Conclusions: Results of the current study revealed website resources are often fragmented and less in depth for Spanish speaking parents with children who are DHH learning spoken language
Chromosomal Assignment of a Family of Human Oncogenes
A family of human transforming genes, previously shown to share homology with the ras family of viral oncogenes, maps to three different human chromosomes. A well-characterized mouse-human hybrid cell panel, combined with Southern blotting, was used in this study. The transforming gene of the T24 bladder carcinoma cell line maps to human chromosome 11. An oncogene isolated from the lung carcinoma cell line SK-Calu-1 maps to human chromosome 12. The third ras-related gene, cloned from SK-N-SH, a neuroblastoma cell line, maps to human chromosome 1
Structure Effects on Coulomb Dissociation of B
Coulomb Dissociation provides an alternative method for determining the
radiative capture cross sections at astrophysically relevant low relative
energies. For the breakup of B on Ni, we calculate the total Coulomb
Dissociation cross section and the angular distribution for E1, E2 and M1. Our
calculations are performed first within the standard first order semiclassical
theory of Coulomb Excitation, including the correct three body kinematics, and
later including the projectile-target nuclear interactions.Comment: 6 pages, proceedings from International Workshop on RNB, Puri, India,
January 1998 - to be published in J. Phys.
The Question of Low-Lying Intruder States in and Neighboring Nuclei
The presence of not yet detected intruder states in e.g. a
intruder at 9 excitation would affect the shape of the -delayed alpha spectra of and . In order to test the
plausibility of this assumption, shell model calculations with up to excitations in (and up to excitations in
) were performed. With the above restrictions on the model spaces, the
calculations did not yield any low-lying intruder state in . Another
approach -the simple deformed oscillator model with self-consistent frequencies
and volume conservation gives an intruder state in which is lower in
energy than the above shell model results, but its energy is still considerably
higher than 9 .Comment: 16 pages (RevTeX), 1 PS figure. To appear in Phys. Rev.
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