Memory effects on descent from nuclear fission barrier

Non-Markovian transport equations for nuclear large amplitude motion are derived from the collisional kinetic equation. The memory effects are caused by the Fermi surface distortions and depend on the relaxation time. It is shown that the nuclear collective motion and the nuclear fission are influenced strongly by the memory effects at the relaxation time $\tau \geq 5\cdot 10^{-23}{\rm s}$. In particular, the descent of the nucleus from the fission barrier is accompanied by characteristic shape oscillations. The eigenfrequency and the damping of the shape oscillations depend on the contribution of the memory integral in the equations of motion. The shape oscillations disappear at the short relaxation time regime at $\tau \to 0$, which corresponds to the usual Markovian motion in the presence of friction forces. We show that the elastic forces produced by the memory integral lead to a significant delay for the descent of the nucleus from the barrier. Numerical calculations for the nucleus $^{236}$U shows that due to the memory effect the saddle-to-scission time grows by a factor of about 3 with respect to the corresponding saddle-to-scission time obtained in liquid drop model calculations with friction forces.Comment: 22 pages, 8 figures, submitted to Phys. Rev.

The Use of Social Media by Alleged Members of Mexican Cartels and Affiliated Drug Trafficking Organizations

Focusing on Mexican cartels and affiliated drug trafficking organizations, this article examines how self-proclaimed cartel members use social media to further the criminal activities of their organizations. Employing an opensource, intelligence-driven methodology, the authors identified, followed, and mapped the connections between and among 75 alleged cartel members over a period of 4 months. Results indicated that cartel members actively use Facebook to plan, organize, and communicate in real-time. These findings provide tentative validation to the utility of using open-source social media platforms to study the social structure and operations of Mexican drug cartels. Implications for law enforcement, homeland security, and the intelligence enterprise are discussed

Hemophagocytic Macrophages Harbor Salmonella enterica during Persistent Infection

Salmonella enterica subspecies can establish persistent, systemic infections in mammals, including human typhoid fever. Persistent S. enterica disease is characterized by an initial acute infection that develops into an asymptomatic chronic infection. During both the acute and persistent stages, the bacteria generally reside within professional phagocytes, usually macrophages. It is unclear how salmonellae can survive within macrophages, cells that evolved, in part, to destroy pathogens. Evidence is presented that during the establishment of persistent murine infection, macrophages that contain S. enterica serotype Typhimurium are hemophagocytic. Hemophagocytic macrophages are characterized by the ingestion of non-apoptotic cells of the hematopoietic lineage and are a clinical marker of typhoid fever as well as certain other infectious and genetic diseases. Cell culture assays were developed to evaluate bacterial survival in hemophagocytic macrophages. S. Typhimurium preferentially replicated in macrophages that pre-phagocytosed viable cells, but the bacteria were killed in macrophages that pre-phagocytosed beads or dead cells. These data suggest that during persistent infection hemophagocytic macrophages may provide S. Typhimurium with a survival niche

Parents d'enfants hospitalisés dans une unité de soins intensifs: une étude exploratoire de leur vécu.

Le travail présenté ici repose sur une recherche qualitative effectuée par l'Institut universitaire de médecine sociale et préventive de Lausanne (IUMSP), sur l'initiative de l'unité des soins intensifs médico-chirurgicaux de pédiatrie (SIP) du Centre hospitalier universitaire vaudois (CHUV). Cette étude détaille le vécu de parents dont l'enfant a été hospitalisé dans une unité de soins intensifs. Il a paru essentiel aux initiateurs du projet d'imaginer offrir un accompagnement et une aide de type préventif aux personnes concernées par la maladie ou l'accident de leur enfant. Toutefois, avant de procéder à ce dispositif, il convenait de savoir plus précisément: 1. Ce que les parents vivaient durant l'hospitalisation de leur enfant; 2. Quels étaient leurs besoins et leurs attentes (à l'égard de l'unité, à l'égard des soignants) en pareilles circonstances

Low density instability in a nuclear Fermi liquid drop

The instability of a Fermi-liquid drop with respect to bulk density distortions is considered. It is shown that the presence of the surface strongly reduces the growth rate of the bulk instability of the finite Fermi-liquid drop because of the anomalous dispersion term in the dispersion relation. The instability growth rate is reduced due to the Fermi surface distortions and the relaxation processes. The dependence of the bulk instability on the multipolarity of the particle density fluctuations is demonstrated for two nuclei $^{40}Ca$ and $^{208}Pb$.Comment: 12 pages, latex, 3 ps-figures, submitted to Phys. Rev.

Evaluating Housing Health Hazards: Prevalence, Practices and Priorities in Delhi's Informal Settlements

Housing quality is crucially linked to health and sustainability goals, yet there is limited research on informal housing and settlements where housing quality is poor, and the health risks are expected to be greatest. This paper describes the investigation of housing conditions in a low-income resettlement colony in Delhi. A novel transdisciplinary methodology to evaluate multiple housing health hazards and establish intervention priorities in participation with the community was developed. Findings from housing surveys and indoor environmental monitoring were contrasted with a participatory self-assessment—revealing the widespread prevalence of hazards and suboptimal housing conditions as well as substantial differences in priorities, and thus perspectives, between participants and researchers. Focus group discussions explored the findings and built consensus on priorities. Our findings uncovered how poor housing conditions affect daily practices and thus are likely to adversely affect socio-economic development and gender equality. We highlight limitations in current frameworks to assess housing hazards and argue that a transdisciplinary approach is vital to provide a holistic understanding and to develop effective interventions. These insights are crucial to inform inclusive solutions for adequate housing and human settlements that can support improved health and help achieve the sustainable development goals

Genetic algorithm dynamics on a rugged landscape

The genetic algorithm is an optimization procedure motivated by biological evolution and is successfully applied to optimization problems in different areas. A statistical mechanics model for its dynamics is proposed based on the parent-child fitness correlation of the genetic operators, making it applicable to general fitness landscapes. It is compared to a recent model based on a maximum entropy ansatz. Finally it is applied to modeling the dynamics of a genetic algorithm on the rugged fitness landscape of the NK model.Comment: 10 pages RevTeX, 4 figures PostScrip

The Counterpart Principle of Analogical Support by Structural Similarity

We propose and investigate an Analogy Principle in the context of Unary Inductive Logic based on a notion of support by structural similarity which is often employed to motivate scientific conjectures

Climate change reduces resilience to fire in subalpine rainforests

Climate change is affecting the distribution of species and the functioning of ecosystems. For species that are slow growing and poorly dispersed, climate change can force a lag between the distributions of species and the geographic distributions of their climatic envelopes, exposing species to the risk of extinction. Climate also governs the resilience of species and ecosystems to disturbance, such as wildfire. Here we use species distribution modelling and palaeoecology to assess and test the impact of vegetation–climate disequilibrium on the resilience of an endangered fire‐sensitive rainforest community to fires. First, we modelled the probability of occurrence of Athrotaxis spp. and Nothofagus gunnii rainforest in Tasmania (hereon “montane rainforest”) as a function of climate. We then analysed three pollen and charcoal records spanning the last 7,500 cal year BP from within both high (n = 1) and low (n = 2) probability of occurrence areas. Our study indicates that climatic change between 3,000 and 4,000 cal year BP induced a disequilibrium between montane rainforests and climate that drove a loss of resilience of these communities. Current and future climate change are likely to shift the geographic distribution of the climatic envelopes of this plant community further, suggesting that current high‐resilience locations will face a reduction in resilience. Coupled with the forecast of increasing fire activity in southern temperate regions, this heralds a significant threat to this and other slow growing, poorly dispersed and fire sensitive forest systems that are common in the southern mid to high latitudes

Characterization of Landau-Zener Transitions in Systems with Complex Spectra

This paper is concerned with the study of one-body dissipation effects in idealized models resembling a nucleus. In particular, we study the quantum mechanics of a free particle that collides elastically with the slowly moving walls of a Bunimovich stadium billiard. Our results are twofold. First, we develop a method to solve in a simple way the quantum mechanical evolution of planar billiards with moving walls. The formalism is based on the {\it scaling method} \cite{ver} which enables the resolution of the problem in terms of quantities defined over the boundary of the billiard. The second result is related to the quantum aspects of dissipation in systems with complex spectra. We conclude that in a slowly varying evolution the energy is transferred from the boundary to the particle through Landau$-$Zener transitions.Comment: 24 pages (including 7 postcript figures), Revtex. Submitted to PR