19,288 research outputs found
Analysis of plasmas generated by fission fragments
A kinetic model is developed for a plasma generated by fission fragments and the results are employed to study helium plasma generated in a tube coated with fissionable material. Because both the heavy particles and electrons play important roles in creating the plasma, their effects are considered simultaneously. The calculations are carried out for a range of neutron fluxes and pressures. In general, the predictions of the theory are in good agreement with available intensity measurements. Moreover, the theory predicts the experimentally measured inversions. However, the calculated gain coefficients are such that lasing is not expected to take place in a helium plasma generated by fission fragments. The effects of an externally applied electric field are also considered
Thermodynamic properties of UF6 at high temperatures
The equilibrium composition and the thermodynamic properties of the mixture resulting from the decomposition of uranium hexafluoride is calculated for temperatures ranging from 600 K to 4000 K at pressures from 0.01 atmospheres to 10 atmospheres
The electron Boltzmann equation in a plasma generated by fission fragments
A Boltzmann equation formulation is presented for the determination of the electron distribution function in a plasma generated by fission fragments. The formulation takes into consideration ambipolar diffusion, elastic and inelastic collisions, recombination and ionization, and allows for the fact that the primary electrons are not monoenergetic. Calculations for He in a tube coated with fissionable material show that, over a wide pressure and neutron flux range, the distribution function is non-Maxwellian, but the electrons are essentially thermal. Moreover, about a third of the energy of the primary electrons is transferred into the inelastic levels of He. This fraction of energy transfer is almost independent of pressure and neutron flux but increases sharply in the presence of a sustainer electric field
Missing energies at pair creation
Wilson cloud chamber measurements of the separated spectra of positrons and electrons produced by gamma quanta of 6.14 MeV differ considerably from the theoretically predicted spectra by BETHE and HEITLER, but are in good agreement with those of a modified theory of pair creation
Purification of genuine multipartite entanglement
In tasks, where multipartite entanglement plays a central role, state
purification is, due to inevitable noise, a crucial part of the procedure. We
consider a scenario exploiting the multipartite entanglement in a
straightforward multipartite purification algorithm and compare it to bipartite
purification procedures combined with state teleportation. While complete
purification requires an infinite amount of input states in both cases, we show
that for an imperfect output fidelity the multipartite procedure exhibits a
major advantage in terms of input states used.Comment: 5 pages, 2 figure
Evaluation of Mineral Element and Sugar Contents of Soft Drinks in Nigeria
This research work analyzed and evaluated the sugar and mineral elements contents of soft drinks consumed daily in Nigeria using standard methods. The sugar content and mineral element were determined. The sugar content varies from 22.8.4mg/L to 274.4mg/l and means sugar level varies from 30.4mg/l to 271.07mg/l. The mineral elements analyzed were Na, K, Ca, Mg, Ni, Fe, Cu, Zn, Cr, Pb and Cd. From the results it can be seen that the macro element (Na and Ca) which are essential mineral reduces rapidly in all the samples of soft drink after 4 weeks. Results of one way ANOVA above indicates that there was a significant difference in the sugar test between sample 1 to sample 7 at p<0.05. (F= 1104.637, p= 0.000).Keywords: Soft drinks, mineral elements, sugar content, ANOV
Cosmological solutions of massive gravity on de Sitter
In the framework of the recently proposed models of massive gravity, defined
with respect to a de Sitter reference metric, we obtain new homogeneous and
isotropic solutions for arbitrary cosmological matter and arbitrary spatial
curvature. These solutions can be classified into three branches. In the first
two, the massive gravity terms behave like a cosmological constant. In the
third branch, the massive gravity effects can be described by a time evolving
effective fluid with rather remarkable features, including the property to
behave as a cosmological constant at late time.Comment: 6 pages, 1 figure; discussion extended, a few references added,
improved analysis in Section
Crossover from Endogenous to Exogenous Activity in Open-Source Software Development
We have investigated the origin of fluctuations in the aggregated behaviour
of an open-source software community. In a recent series of papers, de Menezes
and co-workers have shown how to separate internal dynamics from external
fluctuations by capturing the simultaneous activity of many system's
components. In spite of software development being a planned activity, the
analysis of fluctuations reveals how external driving forces can be only
observed at weekly and higher time scales. Hourly and higher change frequencies
mostly relate to internal maintenance activities. There is a crossover from
endogenous to exogenous activity depending on the average number of file
changes. This new evidence suggests that software development is a
non-homogeneous design activity where stronger efforts focus in a few project
files. The crossover can be explained with a Langevin equation associated to
the cascading process, where changes to any file trigger additional changes to
its neighbours in the software network. In addition, analysis of fluctuations
enables us to detect whether a software system can be decomposed in several
subsystems with different development dynamics.Comment: 7 pages, 4 figures, submitted to Europhysics Letter
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