170 research outputs found
Q-Value for the Fermi Beta-Decay of 46V
By comparing the Q-values for the 46Ti(3He,t)46V and 47Ti(3He,t)47}V
reactions to the isobaric analog states the Q-value for the superallowed
Fermi-decay of 46V has been determined as Q_{EC}(46V)=(7052.11+/-0.27) keV. The
result is compatible with the values from two recent direct mass measurements
but is at variance with the previously most precise reaction Q-value. As
additional input quantity we have determined the neutron separation energy
S_n(47Ti)=(8880.51+/-0.25) keV
Level density of Fe and low-energy enhancement of -strength function
The MnFe differential cross section is measured at
MeV\@. The Fe level density obtained from neutron evaporation spectra is
compared to the level density extracted from the
FeHe,Fe reaction by the Oslo-type technique.
Good agreement is found between the level densities determined by the two
methods. With the level density function obtained from the neutron evaporation
spectra, the Fe -strength function is also determined from the
first-generation matrix of the Oslo experiment. The good agreement
between the past and present results for the -strength function
supports the validity of both methods and is consistent with the low-energy
enhancement of the strength below MeV first discovered by the
Oslo method in iron and molybdenum isotopes.Comment: 7 pages, 5 figure
Combinatorial nuclear level density by a Monte Carlo method
We present a new combinatorial method for the calculation of the nuclear
level density. It is based on a Monte Carlo technique, in order to avoid a
direct counting procedure which is generally impracticable for high-A nuclei.
The Monte Carlo simulation, making use of the Metropolis sampling scheme,
allows a computationally fast estimate of the level density for many fermion
systems in large shell model spaces. We emphasize the advantages of this Monte
Carlo approach, particularly concerning the prediction of the spin and parity
distributions of the excited states, and compare our results with those derived
from a traditional combinatorial or a statistical method. Such a Monte Carlo
technique seems very promising to determine accurate level densities in a large
energy range for nuclear reaction calculations.Comment: 30 pages, LaTex, 7 figures (6 Postscript figures included). Fig. 6
upon request to the autho
Study of the nucleon-induced preequilibrium reactions in terms of the Quantum Molecular Dynamics
The preequilibrium (nucleon-in, nucleon-out) angular distributions of
Al, Ni and Zr have been analyzed in the energy region from
90 to 200 MeV in terms of the Quantum Moleculear Dynamics (QMD) theory. First,
we show that the present approach can reproduce the measured (p,xp') and (p,xn)
angular distributions leading to continuous final states without adjusing any
parameters. Second, we show the results of the detailed study of the
preequilibrium reaction processes; the step-wise contribution to the angular
distribution, comparison with the quantum-mechanical Feshbach-Kerman-Koonin
theory, the effects of momentum distribution and surface refraction/reflection
to the quasifree scattering. Finally, the present method was used to assess the
importance of multiple preequilibrium particle emission as a function of
projectile energy up to 1 GeV.Comment: 22pages, Revex is used, 10 Postscript figures are available by
request from [email protected]
Endothelial-Mesenchymal Transition of Brain Endothelial Cells: Possible Role during Metastatic Extravasation
Cancer progression towards metastasis follows a defined sequence of events described as the metastatic cascade. For extravasation and transendothelial migration metastatic cells interact first with endothelial cells. Yet the role of endothelial cells during the process of metastasis formation and extravasation is still unclear, and the interaction between metastatic and endothelial cells during transendothelial migration is poorly understood. Since tumor cells are well known to express TGF-beta, and the compact endothelial layer undergoes a series of changes during metastatic extravasation (cell contact disruption, cytoskeletal reorganization, enhanced contractility), we hypothesized that an EndMT may be necessary for metastatic extravasation. We demonstrate that primary cultured rat brain endothelial cells (BEC) undergo EndMT upon TGF-beta 1 treatment, characterized by the loss of tight and adherens junction proteins, expression of fibronectin, beta 1-integrin, calponin and a-smooth muscle actin (SMA). B16/F10 cell line conditioned and activated medium (ACM) had similar effects: claudin-5 down-regulation, fibronectin and SMA expression. Inhibition of TGF-beta signaling during B16/F10 ACM stimulation using SB-431542 maintained claudin-5 levels and mitigated fibronectin and SMA expression. B16/F10 ACM stimulation of BECs led to phosphorylation of Smad2 and Smad3. SB-431542 prevented SMA up-regulation upon stimulation of BECs with A2058, MCF-7 and MDA-MB231 ACM as well. Moreover, B16/F10 ACM caused a reduction in trans-endothelial electrical resistance, enhanced the number of melanoma cells adhering to and transmigrating through the endothelial layer, in a TGF-beta-dependent manner. These effects were not confined to BECs: HUVECs showed TGF-beta-dependent SMA expression when stimulated with breast cancer cell line ACM. Our results indicate that an EndMT may be necessary for metastatic transendothelial migration, and this transition may be one of the potential mechanisms occurring during the complex phenomenon known as metastatic extravasation
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User's manual for the code STAPRE as implemented at Lawrence Livermore National Laboratory
This report gives a detailed description of the input and output of the statistical model code STAPRE for compound-nucleus reactions including a special section on the various level density options of the code. It is to be used in conjunction with the report IRK 76/01 + Add 76 + Add 78 by B. Strohmaier and M. Uhl which describes in detail the physical models on which the code is based and its general organization and structure
Evaluation of the angle integrated neutron emission cross sections from the interactions of 14 MeV neutrons with medium and heavy nuclei
Evaluations of the fast neutron cross sections of sup 2 sup 8 Si including complete covariance information
A new evaluation of all important neutron cross sections of sup 2 sup 8 Si was performed in the neutron energy range 1.75 - 20 MeV, that is for the whole energy range above the resonance region. The evaluation combines the results of nuclear model calculations and the complete existing experimental data base in order to obtain the most accurate description of the cross sections possible within our present knowledge. The evaluation was performed in the following way: The cross sections from the EFF - 2 file (results of model calculations) and their estimated covariances are used as prior information which is successively improved by adding experimental data and by applying Bayes' theorem to obtain the posterior information. For this process the code GLUCS was used. For some cross sections, not covered in EFF - 2, priors were taken from BROND and recent nuclear model calculations. As results we obtained evaluated cross sections and their covariances for a chosen set of 15 independent cross sections in a group structure of 31 neutron energy groups 0.2 - 1 MeV wide. The evaluated cross sections thus are the average cross sections over the respective energy group. Thus before use as evaluated data file, fine structure of the various cross sections has to be added whenever such fine structure has been established with sufficient accuracy. A final coupled set of evaluated cross sections and covariances was obtained by a last GLUCS run including the experimental data for 'redundant' cross sections, that is all cross sections which can be expressed as sum or difference of the basic cross sections chosen for the evaluation. The results of our new evaluation agree with ENDF/B-VI and EFF - 2 within the uncertainties of these evaluations. Most of the uncertainties of our evaluated cross sections, however, are considerably smaller than those of ENDF/B-VI and the estimated uncertainties of EFF - 2
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