Fission-Fragment Mass Distribution and Particle Evaporation at low Energies

Fusion-fission dynamics is investigated with a special emphasis on fusion reactions at low energy for which shell effects and pairing correlations can play a crucial role leading in particular to multi-modal fission. To follow the dynamical evolution of an excited and rotating nucleus we solve a 2-dimensional Langevin equation taking explicitly light-particle evaporation into account. The confrontation theory-experiment is demonstrated to give interesting information on the model presented, its qualities as well as its shortcomings.Comment: 19 pages, latex, 24 eps-figure

Miniature fibre optic ultrasonic probe

We investigate the feasibility of using optical fiber Bragg gratings for the sensing of ultrasonic fields for medical applications. In preliminary experimental investigations, ultrasonic waves with a frequency of 950 kHz have been detected with a noise limited pressure resolution of approximately 10-2 atmospheres in a 3 KHz measurement bandwidth

Light-particle emission from the fissioning nuclei 126Ba, 188Pt and (266,272,278)/110: theoretical predictions and experimental results

We present a comparison of our model treating fission dynamics in conjunction with light-particle (n, p, alpha) evaporation with the available experimental data for the nuclei 126Ba, 188Pt and three isotopes of the element Z=110. The dynamics of the symmetric fission process is described through the solution of a classical Langevin equation for a single collective variable characterizing the nuclear deformation along the fission path. A microscopic approach is used to evaluate the emission rates for pre-fission light particles. Entrance-channel effects are taken into account by generating an initial spin distribution of the compound nucleus formed by the fusion of two deformed nuclei with different relative orientations

A Measurement of the Coulomb Dissociation of 8B at 254 MeV/nucleon and the 8B Solar Neutrino Flux

We have measured the Coulomb dissociation of 8B into 7Be and proton at 254 MeV/nucleon using a large-acceptance focusing spectrometer. The astrophysical S17 factor for the 7Be(p,gamma)8B reaction at E{c.m.} = 0.25-2.78 MeV is deduced yielding S17(0)=20.6 \pm 1.2 (exp.) \pm 1.0 (theo.) eV-b. This result agrees with the presently adopted zero-energy S17 factor obtained in direct-reaction measurements and with the results of other Coulomb-dissociation studies performed at 46.5 and 51.2 MeV/nucleon.Comment: paper to be published in Phys. Rev. Lett. 3 figures. New Version fixes formatting problems with the figures only. There are no other change

Coulomb fragmentation and Coulomb fission of relativistic heavy-ions and related nuclear structure aspects

The Coulomb excitation of 208Pb projectiles has been studied at an energy of 640 A MeV. Cross sections for the excitation of the two-phonon giant dipole resonance were measured for different targets, and show clear evidence for a two-step electromagnetic excitation mechanism. The experimental cross sections exceed those calculated in the harmonic oscillator approximation by a factor of 1.33 ± 0.16. The deduced 27-decay probability is consistent with the expectation in the harmonic limit. Finally, the excitation of the two-phonon giant dipole resonance in the deformed and fissile nucleus 238U is discussed

Rapid detection of peptide markers for authentication purposes in raw and cooked meat using ambient liquid extraction surface analysis mass spectrometry

In this paper, our previously developed ambient LESA-MS methodology is implemented to analyze five types of thermally treated meat species, namely beef, pork, horse, chicken, and turkey meat, in order to select and identify heat-stable and species-specific peptide markers. In-solution tryptic digests of cooked meats were deposited onto a polymer surface, followed by LESA-MS analysis and evaluation using multivariate data analysis and tandem electrospray MS. The five types of cooked meat were clearly discriminated using principal component analysis and orthogonal partial least squares discriminant analysis. A number of 23 heat stable peptide markers unique to species and muscle protein were identified following data-dependent tandem LESA-MS analysis. Surface extraction and direct ambient MS analysis of mixtures of cooked meat species was performed for the first time and enabled detection of 10% (w/w) of pork, horse, and turkey meat, and 5% (w/w) of chicken meat in beef, using the developed LESA-MS/MS analysis. The study shows, for the first time, that ambient LESA-MS methodology displays specificity sufficient to be implemented effectively for the analysis of processed and complex peptide digests. The proposed approach is much faster and simpler than other measurement tools for meat speciation; it has potential for application in other areas of meat science or food production

Poland's 2011 Online Election Campaign: New Tools, New Professionalism, New Ways to Win Votes

This article analyzes the use of the online environment within the context of the Polish parliamentary election of 2011. Using traditional methods of content analysis, we find that parties tend to adhere to a professionalized model of campaigning, and adapting online tools to suit the objectives of the campaign. There also appears to be a recognition that their most likely visitors to these online presences would be converts, and so they attempt to mobilize supporters rather than convert browsers. New parties and candidates are more likely to target browsers, with the latter offering a more personalized experience to online visitors. Importantly, when analyzing the outcome of the contest, we find that being online matters for candidates when controlling for all other variables. Equally, the reach the candidate has, which may well influence their vote share, is dependent on offering a more personalized, representational image and having a frequently updated online presence that should encourage repeat visits. Cumulatively, we suggest the future of online campaigning must not only focus on having a presence, but on using it in a way that appeals to a range of visitors, encouraging repeat visits, and that this strategy could have a positive impact on election outcomes. © Taylor & Francis Group, LLC

Invariant-mass and [gamma]-ray spectroscopy using secondary, radioactive ion beams

Coulomb excitation of secondary beams (5 < Z < 20) at energies around 250 .1 MeV was explored at GSI. For low-lying states, 7-ray spectroscopy was utilized, while high-lying excitations were investigated by means of invariant-mass spectroscopy

Next Generation Extractants for Cesium Separation from High-Level Waste: From Fundamental Concepts to Site Implementation

This project unites expertise at Oak Ridge National Laboratory (ORNL) and Texas Tech University (TTU, Prof. Richard A. Bartsch) to answer fundamental questions addressing the problem of cesium removal from high-level tank waste. Efforts focus on novel solvent-extraction systems containing calixcrown extractants designed for enhanced cesium binding and release. Exciting results are being obtained in three areas: (1) a new lipophilic cesium extractant with a high solubility in the solvent; (2) new proton-ionizable calixcrowns that both strongly extract cesium and "switch off" when protonated; and (3) an improved solvent system that may be stripped with more than 100-fold greater efficiency. Scientific questions primarily concern how to more effectively reverse extraction, focusing on the use of amino groups and proton-ionizable groups to enable pH-switching. Synthesis is being performed at ORNL (amino calixcrowns) and TTU (proton-ionizable calixcrowns). At ORNL, the extraction behavior is being surveyed to assess the effectiveness of candidate solvent systems, and systematic distribution measurements are under way to obtain a thermodynamic understanding of partitioning and complexation equilibria. Crystal structures obtained at ORNL are revealing the structural details of cesium binding. The overall objective is a significant advance in the predictability and efficiency of cesium extraction from high-level waste in support of potential implementation at U. S. Department of Energy (USDOE) sites