Break-up mechanisms in heavy ion collisions at low energies

We investigate reaction mechanisms occurring in heavy ion collisions at low energy (around 20 MeV/u). In particular, we focus on the competition between fusion and break-up processes (Deep-Inelastic and fragmentation) in semi-peripheral collisions, where the formation of excited systems in various conditions of shape and angular momentum is observed. Adopting a Langevin treatment for the dynamical evolution of the system configuration, described in terms of shape observables such as quadrupole and octupole moments, we derive fusion/fission probabilities, from which one can finally evaluate the corresponding fusion and break-up cross sections. The dependence of the results on shape, angular momentum and excitation energy is discussed.Comment: submitted to Physical Review

Multiphotons and Photon-Jets

We discuss an extension of the Standard Model with a new vector-boson decaying predominantly into a multi-photon final state through intermediate light degrees of freedom. The model has a distinctive phase in which the photons are collimated. As such, they would fail the isolation requirements of standard multi-photon searches, but group naturally into a novel object, the photon-jet. Once defined, the photon-jet object facilitates more inclusive searches for similar phenomena. We present a concrete model, discuss photon-jets more generally, and outline some strategies that may prove useful when searching for such objects.Comment: 4 pages, 2 figure

Fast inactivation in Shaker K+ channels. Properties of ionic and gating currents.

Fast inactivating Shaker H4 potassium channels and nonconducting pore mutant Shaker H4 W434F channels have been used to correlate the installation and recovery of the fast inactivation of ionic current with changes in the kinetics of gating current known as "charge immobilization" (Armstrong, C.M., and F. Bezanilla. 1977. J. Gen. Physiol. 70:567-590.). Shaker H4 W434F gating currents are very similar to those of the conducting clone recorded in potassium-free solutions. This mutant channel allows the recording of the total gating charge return, even when returning from potentials that would largely inactivate conducting channels. As the depolarizing potential increased, the OFF gating currents decay phase at -90 mV return potential changed from a single fast component to at least two components, the slower requiring approximately 200 ms for a full charge return. The charge immobilization onset and the ionic current decay have an identical time course. The recoveries of gating current (Shaker H4 W434F) and ionic current (Shaker H4) in 2 mM external potassium have at least two components. Both recoveries are similar at -120 and -90 mV. In contrast, at higher potentials (-70 and -50 mV), the gating charge recovers significantly more slowly than the ionic current. A model with a single inactivated state cannot account for all our data, which strongly support the existence of "parallel" inactivated states. In this model, a fraction of the charge can be recovered upon repolarization while the channel pore is occupied by the NH2-terminus region

Effectiveness of environmental impact statement methods: A Colombian case study

Funding for open access charge: Universidad de Granada/CBUA. The authors also appreciate the support of the research group TEP-968 (Technologies for Circular Economy) of the University of Granada (Spain) .The effectiveness of impact assessment (IA) methods has been a neglected topic in procedural effectiveness research, which has placed higher relevance on the quality of Environmental Impact Statements (EISs) and the environment impact assessment (EIA) process in general. This study analysed the effectiveness of methods used in IA in Colombia to demonstrate that they have been used in compliance with the Terms of Reference (ToR) but did not analyse their effectiveness. A total of 131 EIS were analysed using a revised version of the Effectiveness Index for Environmental Impact Assessment Methods (EIM) proposed by Caro and Toro (2016). It is concluded that, even if the environmental authority has accepted the EIS as a requirement for obtaining an environmental license, most of the methods that have been used in these technical documents, obtained a medium or low degree of effectiveness. The parameters regulated for the law have a higher percentage of compliance. The analysis suggests that the guidelines provided for the law, related to the design and implementation of the methods, should be improved to develop an effective EIA.Universidad de Granada/CBUAUniversity of Granada (Spain) TEP-96

Fluidized bed as a solid precursor delivery system in a chemical vapor deposition reactor

Chemical vapor deposition (CVD) using precursors that are solids at operating temperatures and pressures, presents challenges due to their relatively low vapor pressures. In addition, the sublimation rates of solid state precursors in fixed bed reactors vary with particle and bed morphology. In a recent patent application, the use of fluidized bed (FB) technology has been proposed to provide high, reliable, and reproducible flux of such precursors in CVD processes. In the present contribution, we first focus on the reactor design which must satisfy fluidization,sublimation and CVD reactor feeding constraints. Then, we report masstransport results on the sublimation of aluminium acetylacetonate, a common precursor for the CVD of alumina films. Finally, we discuss the efficiency of the precursor feeding rate, we address advantages and drawbacks of the invention and we propose design modifications in order to meet the process requirements