5,218 research outputs found
The Pueblo Crisis and Public Opinion
The capture of the U.S.S. Pueblo by a third-rate power provoked an internal conflict between the forces of domestic public opinion and the U.S. Navy
The Future of Animal Agriculture in North America
Livestock Production/Industries, Q18,
Microscopic Enhancement of Heavy-Element Production
Realistic fusion barriers are calculated in a macroscopic-microscopic model
for several soft-fusion heavy-ion reactions leading to heavy and superheavy
elements. The results obtained in such a realistic picture are very different
from those obtained in a purely macroscopic model. For reactions on 208:Pb
targets, shell effects in the entrance channel result in fusion-barrier
energies at the touching point that are only a few MeV higher than the ground
state for compound systems near Z = 110. The entrance-channel fragment-shell
effects remain far inside the touching point, almost to configurations only
slightly more elongated than the ground-state configuration, where the fusion
barrier has risen to about 10 MeV above the ground-state energy. Calculated
single-particle level diagrams show that few level crossings occur until the
peak in the fusion barrier very close to the ground-state shape is reached,
which indicates that dissipation is negligible until very late in the fusion
process. Whereas the fission valley in a macroscopic picture is several tens of
MeV lower in energy than is the fusion valley, we find in the
macroscopic-microscopic picture that the fission valley is only about 5 MeV
lower than the fusion valley for soft-fusion reactions leading to compound
systems near Z = 110. These results show that no significant
``extra-extra-push'' energy is needed to bring the system inside the fission
saddle point and that the typical reaction energies for maximum cross section
in heavy-element synthesis correspond to only a few MeV above the maximum in
the fusion barrier.Comment: 7 pages. LaTeX. Submitted to Zeitschrift fur Physik A. 5 figures not
included here. Complete preprint, including device-independent (dvi),
PostScript, and LaTeX versions of the text, plus PostScript files of the
figures, available at http://t2.lanl.gov/publications/publications.html or at
ftp://t2.lanl.gov/pub/publications/mehe
A Self Triggered Amplifier/Digitizer Chip for CBM
The development of front-end electronics for the planned CBM experiment at FAIR/GSI is in full progress. For charge readout of the various sub-detectors a new self-triggered amplification and digitization chip is being designed and tested. The mixed signal readout chip will have 32-64 channels each containing a low-power/low-noise preamplifier/shaper front-end, an 8-9 bit ADC and a digital post-processing based on a FIR/IIR-filter. The ADC has a pipeline architecture that uses a novel current-mode storage cell as a basic building block. The current prototype provides 26 different parametrized preamplifier/shaper/discriminator channels, 8 pipeline ADCs, a readout shift register matrix and a synthesized redundant signed binary (RSD) decoder
Modelling sulphate stream concentrations in the Black Forest catchments Schluchsee and Villingen
International audienceThe sulphate (SO4) released by mineralisation and desorption from soil can play an important role in determining concentrations of SO4 in streams. The MAGIC model was calibrated for two catchments in the Black Forest, Germany (Schluchsee and Villingen) and SO4 concentrations in the streams for the years 2016 and 2030 were predicted. Special emphasis was placed on the dynamics of soil sulphur (S) pools. At Schluchsee, 90% of soil S is stored in the organic S (Sorg) pool, whereas at Villingen, 54% is in the inorganic (Sinorg) pool. The Villingen stream chemistry was modelled successfully by measured Langmuir isotherm parameters (LIPs) for Sinorg. Schluchsee data could not be modelled satisfactorily using measured or freely adapted LIPs only, as the Sinorg pool would have to be more than five times larger than what was measured. With 60.5 mmolc SO4 m-2 yr-1 as internal soil source by mineralisation and the measured LIPs, stream data was modelled successfully. The modelling shows that in these two catchments pre-industrial concentrations of SO4 in runoff can be reached in the next two decades if S deposition decreases as intended under currently agreed national and international legislation. Sorg is the most likely dominant source of SO4 released at Schluchsee. Mineralization from the Sorg pool must be included when modelling SO4 concentrations in the stream. As the dynamics and the controlling factors of S release by mineralisation are not yet clear, this process remains a source of uncertainty for predictions of SO4 concentrations in streams. Future research should concentrate on dynamics of S mineralisation in the field, such that mathematical descriptions of long-term S-mineralisation can be incorporated into biogeochemical models. Keywords: sulphate release, organic S, mineralisation, acidification, recovery, modelling, MAGIC, catchments, predictions, Germany, fores
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Sex Role Segregation and Mixing among Men Who Have Sex with Men: Implications for Biomedical HIV Prevention Interventions
Objective: Men who have sex with men (MSM) practice role segregation â insertive or receptive only sex positions instead of a versatile role - in several international settings where candidate biomedical HIV prevention interventions (e.g., circumcision, anal microbicide) will be tested. The effects of these position-specific interventions on HIV incidence are modeled.Materials and Methods: We developed a deterministic compartmental model to predict HIV incidence among Indian MSM using data from 2003â2010. The modelâs sex mixing matrix was derived from network data of Indian MSM (nâ=â4604). Our model captures changing distribution of sex roles over time. We modeled microbicide and circumcision efficacy on trials with heterosexuals.Results: Increasing numbers of versatile MSM resulted in little change in HIV incidence over 20 years. Anal microbicides and circumcision would decrease the HIV prevalence at 10 years from 15.6% to 12.9% and 12.7% respectively. Anal microbicides would provide similar protection to circumcision at the population level despite lower modeled efficacy (54% and 60% risk reduction, respectively). Combination of the interventions were additive: in 5 years, the reduction in HIV prevalence of the combination (â3.2%) is almost the sum of their individual reductions in HIV prevalence (â1.8% and â1.7%).Conclusions: MSM sex role segregation and mixing, unlike changes in the sex role distribution, may be important for evaluating HIV prevention interventions in international settings. Synergies between some position-specific prevention interventions such as circumcision and anal microbicides warrant further study.</p
RĂ©solution en temps d'un circuit de coĂŻncidences particule gamma
Des détecteurs à barriÚre de surface ont été utilisés dans un circuit de coïncidences rapides particule-gamma en vue de mesurer des vies moyennes de noyaux dans des états excités. L'influence sur la résolution en temps de différents facteurs (résistivité, tension de polarisation, etc.) a été étudiée
Isotopic and velocity distributions of Bi produced in charge-pickup reactions of 208Pb at 1 A GeV
Isotopically resolved cross sections and velocity distributions have been
measured in charge-pickup reactions of 1 A GeV 208Pb with proton, deuterium and
titanium target. The total and partial charge-pickup cross sections in the
reactions 208Pb + 1H and 208Pb + 2H are measured to be the same in the limits
of the error bars. A weak increase in the total charge-pickup cross section is
seen in the reaction of 208Pb with the titanium target. The measured velocity
distributions show different contributions - quasi-elastic scattering and
Delta-resonance excitation - to the charge-pickup production. Data on total and
partial charge-pickup cross sections from these three reactions are compared
with other existing data and also with model calculations based on the coupling
of different intra-nuclear cascade codes and an evaporation code.Comment: 20 pages, 12 figures, background information on
http://www-w2k.gsi.de/kschmidt
Skyrme Hartree-Fock Calculations for the Alpha Decay Q Values of Super-Heavy Nuclei
Hartree-Fock calculations with the SKX Skyrme interaction are carried out to
obtain alpha-decay Q values for deformed nuclei above Pb assuming axial
symmetry. The results for even-even nuclei are compared with experiment and
with previous calculations. Predictions are made for alpha-decay Q values and
half-lives of even-even super-heavy nuclei. The results are also compared for
the recently discovered odd-even chain starting at Z=112 and N=165.Comment: 17 pages, 8 figures, 1 tabl
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