A study of stopping power in nuclear reactions at intermediate energies

We show a systematic experimental study based on INDRA data of the stopping power in central symmetric nuclear reactions. Total mass of the systems goes from 80 to 400 nucleons while the incident energy range is from 12 AMeV to 100 AMeV. The role of isospin diffusion at 32 and 45 MeV/nucleon with 124,136Xe projectiles on 112,124Sn targets performed at GANIL is also discussed. Results suggest a strong memory of the entrance channel above 20 AMeV/A (nuclear transparency) and, as such, constitute valuable tests of the microscopic transport models.Comment: 7 pages, 3 figures, Proceedings of International Workshop on Multifragmentation and Related Topics (IWM 2009), Catania, Italy, 4 Nov-7 Nov 200

Precision measurements in nuclear {\beta}-decay with LPCTrap

The experimental achievements and the current program with the LPCTrap device installed at the LIRAT beam line of the SPIRAL1-GANIL facility are presented. The device is dedicated to the study of the weak interaction at low energy by means of precise measurements of the {\beta}-{\nu} angular correlation parameter. Technical aspects as well as the main results are reviewed. The future program with new available beams is briefly discussed.Comment: Annalen der Physik (2013

Activity analysis of coffee growers in complex agroforestry systems, understanding the farmers' pratices

In coffee based agroforestry systems, biodiversity management by farmers is a promising lever for innovation to promote system sustainability and increase income. We hypothesized that the co-design of agroforestry cropping systems based on ecological process, and on implementation of innovative practices have to take into account the reality of the technical work as well as the farmer concerns and the knowledge leading to the actual plot management. The aim of this study is to examine how coffee farmers understand the diversity of their agroforestry systems and how do they manage it through their practices. We have developed an original methodology based on the activity analysis applied to the study of the shade trees regulation practices in the agroforestry coffee plot by coffee growers. The activity analysis is interested in human activity with a view to transforming and designing work situations. According to Theureau (2010), considering enaction paradigm, activity is considered as a dynamic of asymmetrical interaction between an actor and his environment1. Thus, human action is not considered to the actual achievement of a predetermined program resulting from the application of decision rules2. First, semi-structured interviews were conducted to understand the systems and the cropping practices drivers. Then, practices were studied in real situation, through participant observation and the use of methods of verbalization during practice, of self-confrontation and farmer-guided practice1. This study took place in Costa Rica (Turrialba). Agroforestry systems consists of coffee (Coffea arabica) and various types of shade tree species. Our results highlight each action carried out by the coffee grower, associated with farmers indicators, considered as the factors that farmer take into account in the agroforestry environment against the background of his concerns, knowledge or habits. These indicators inform about complexity of interactions between the coffee grower and his environment. This interaction occurred at several levels: for a systemic management (to favor the ecological processes like disease regulation), for an ergonomic management (to favor movements, or reduce risk of injury), for a personal management (based on an affective relation with the biotope). In that respect, shade tree regulation is not only intended to increase the incident light energy received by coffee, but also driven by other motivations. The re-design of innovative and sustainable cropping systems has to take into account the interaction between diversity of human situations and the agroforestry system complexity. In this context, how can practices be transformed? How can we support farmers to think about their own practices and initiate changes specific to them? The activity analysis is an efficient framework to nourish the thinking on current management practices and a promising way to support their progressive transformation in complex agroforestry systems

The aquatic biota of the now extinct lacustrine complex of the Mexico basin

The commonest organisms of the original Mexico lake complex are listed, including those that exist today in the Lago Viejo. In addition, a brief hydraulic history of this endorheic basin is given

Chiral aspects of hadron structure

Chiral loop corrections for hadronic properties are considered in a constituent quark model. It is emphasized that the correct implementation of such corrections requires a sum over intermediate hadronic states. The leading non-analytic corrections are very important for baryon magnetic moments and explain the failure of the sum rule $(\mu_{\Sigma^{+}}+2\mu_{\Sigma^{-}})/\mu_{\Lambda}=-1$ predicted by the constituent quark model.Comment: 10 pages, latex, 2 ps figures, to appear in Phys. Lett.

Sudden To Adiabatic Transition in Beta Decay

We discuss effects in beta decays at very low beta energies, of the order of the kinetic energies of atomic electrons. As the beta energy is lowered the atomic response changes from sudden to adiabatic. As a consequence, the beta decay rate increases slightly and the ejection of atomic electrons (shake off) and subsequent production of X rays is turned off. We estimate the transition energy and the change in decay rate. The rate increase is largest in heavy atoms, which have a small Q value in their decay. The X ray switch-off is independent of Q value.Comment: 6 pages LaTe

Analytic evaluation of two-loop renormalization constants of enhanced electroweak strength in the Higgs sector of the Standard Model

We calculate renormalization constants Z_H, Z_w, the Higgs and W-boson mass and tadpole counterterms in the on-mass-shell renormalization scheme to two loops in the heavy-Higgs-boson limit m_H >> M_W. Explicit analytic formulae are presented for the two-loop integrals with masses, which are not known in the literature. As an application, the analytic expression for the two-loop leading correction to the fermionic Higgs boson width is obtained.Comment: 8 pages, 3 Postscript figures, uses epsfig.st