Closed-cycle gas dynamic laser design investigation

A conceptual design study was made of a closed cycle gas-dynamic laser to provide definition of the major components in the laser loop. The system potential application is for long range power transmission by way of high power laser beams to provide satellite propulsion energy for orbit changing or station keeping. A parametric cycle optimization was conducted to establish the thermodynamic requirements for the system components. A conceptual design was conducted of the closed cycle system and the individual components to define physical characteristics and establish the system size and weight. Technology confirmation experimental demonstration programs were outlined to develop, evaluate, and demonstrate the technology base needed for this closed cycle GDL system

Using C. elegans as a Model Organism to Study Genes linked to Alzheimer’s

Alzheimer’s is a neurodegenerative disease that affects millions of people the world over. This is a growing problem, especially in developed countries where people are living longer. Over time, more and more young people will be tasked with taking care of their elderly family members, who can no longer take care of themselves. The causes leading up to the disease are still poorly understood, but by looking at certain genes that are associated with Alzheimer’s, we can gain a better understanding of the disease and the pathways that lead to it. Luckily, humans share lots of their genes with other animals, including about 50% with Caenorhabditis elegans, a type of nematode. We can easily do experiments on C. elegans that would be impossible in humans. In my research, I am using RNA interference to knock out 4 genes associated with Alzheimer’s in the worms; abt-2, abt-4, abt-5, and sel-12. There has been little or no research done on these genes. By observing the worms under these conditions, we can make inferences on the function of the genes that were knocked down, and deduce their function in humans, including where they fit in the Alzheimer\u27s pathway. Gaining a better understanding of the pathway in worms and humans will allow us to better focus future research, possibly finding areas to be targeted by drugs, or even discovering a cure

Implementing Welfare-to-Work Services: A Study of Staff Decision-Making

Copyright 2006 Alliance for Children and FamiliesIn the post-welfare reform era, increased discretion has been given to frontline staff for day-today welfare policy implementation. To determine how frontline staff address the complex needs of welfare program participants in this new policy environment, the decision-making processes of welfare staff (N = 52) in 11 San Francisco Bay Area county social service agencies were assessed through a case vignette using a Web-based survey design. We examined staff decision making in four areas: problem recognition, goal formulation, information search processes, and evaluation. The results suggest that the high level o f staff discretion apparent in the day-to-day implementation of welfare policy may have important implications for participants. Several recommendations for policy, practice, and future research are presented

A Man with Labile Blood Pressure

Ronald Ma and colleagues discuss the differential diagnosis and management of a patient who presented with recurrent episodes of chest discomfort, palpitations, and labile blood pressure

Intestinal Perforations in Behçet’s Disease

Behçet’s disease accompanied by intestinal involvement is called intestinal Behçet’s disease. The intestinal ulcers of Behçet’s disease are usually multiple and scattered and tend to perforate easily, so that many patients require emergency operation. The aim of this study is to determine the extent of surgical resection necessary to prevent reperforation and to point out the findings of concurrent oral and genital ulcers and multiple intestinal perforations in all patients of our series. During a 25-year study period, information of 125 Behçet’s disease cases was gathered. Among the 82 patients who were diagnosed with intestinal Behçet’s disease, 22 cases had intestinal perforations needing emergency laparotomy. We investigated and analyzed these cases according to the patients’ demographic characteristics, clinical presentations, laboratory data, and surgical outcome. There were 14 men and 8 women ranging from 22 to 65 years of age. Nine cases were diagnosed preoperatively, and the diagnoses were confirmed in all 22 cases during the surgical intervention. Surgical resection was performed in every patient, with right hemicolectomy and ileocecal resection in 11 cases, partial ileum resection in 8 cases with two reperforations, and ileocecal resection in 3 cases with one reperforation

Modeling the Afferent Dynamics of the Baroreflex Control System

In this study we develop a modeling framework for predicting baroreceptor firing rate as a function of blood pressure. We test models within this framework both quantitatively and qualitatively using data from rats. The models describe three components: arterial wall deformation, stimulation of mechanoreceptors located in the BR nerve-endings, and modulation of the action potential frequency. The three sub-systems are modeled individually following well-established biological principles. The first submodel, predicting arterial wall deformation, uses blood pressure as an input and outputs circumferential strain. The mechanoreceptor stimulation model, uses circumferential strain as an input, predicting receptor deformation as an output. Finally, the neural model takes receptor deformation as an input predicting the BR firing rate as an output. Our results show that nonlinear dependence of firing rate on pressure can be accounted for by taking into account the nonlinear elastic properties of the artery wall. This was observed when testing the models using multiple experiments with a single set of parameters. We find that to model the response to a square pressure stimulus, giving rise to post-excitatory depression, it is necessary to include an integrate-and-fire model, which allows the firing rate to cease when the stimulus falls below a given threshold. We show that our modeling framework in combination with sensitivity analysis and parameter estimation can be used to test and compare models. Finally, we demonstrate that our preferred model can exhibit all known dynamics and that it is advantageous to combine qualitative and quantitative analysis methods

Possible mineral contributions to the diet and health of wild chimpanzees in three East African forests

For financial support, the authors acknowledge the Mohamed bin Zayed Species Conservation Fund grant numbers 0925272, 10251055, 11252562, 12254904, the Royal Zoological Society of Scotland, the Leverhulme Trust grant number ECF‐2013‐507, and the Boise Fund.We present new data on the ingestion of minerals from termite mound soil by East African chimpanzees (Pan troglodytes schweinfurthii) living in the Budongo Forest Reserve, Uganda, the Gombe National Park and the Mahale Mountains National Park, Tanzania. Termite mound soil is here shown to be a rich source of minerals, containing high concentrations of iron and aluminum. Termite mound soil is not, however, a source of sodium. The concentrations of iron and aluminum are the highest yet found in any of the mineral sources consumed. Levels of manganese and copper, though not so high as for iron and aluminum, are also higher than in other dietary sources. We focus on the contribution of termite mound soil to other known sources of mineral elements consumed by these apes, and compare the mineral content of termite soil with that of control forest soil, decaying wood, clay, and the normal plant‐based chimpanzee diet at Budongo. Samples obtained from Mahale Mountains National Park and Gombe National Park, both in Tanzania, show similar mineral distribution across sources. We suggest three distinct but related mechanisms by which minerals may come to be concentrated in the above‐mentioned sources, serving as potentially important sources of essential minerals in the chimpanzee diet.PostprintPeer reviewe