Simulation and experimental evaluation of a flexible time triggered ethernet architecture applied in satellite nano/micro launchers

The success of small satellites has led to the study of new technologies for the realization of Nano and Micro Launch Vehicle (NMLV) in order to make competitive launch costs. The paper has the objective to define and experimentally investigate the performance of a communication system for NMLV interconnecting the End Systems as On-Board Computer (OBC), telemetry apparatus, Navigation Unit...we propose a low cost Ethernet-based solution able to provide the devices with high interconnection bandwidth. To guarantee hard delays to the Guide, Navigation and Control applications we propose some architectural changes of the traditional Ethernet network with the introduction of a layer implemented in the End Systems and allow for the lack of any contention on the network links. We show how the proposed solution has comparable performance to the one of TTEthernet standard that is a very expensive solution. An experimental test-bed equipped with Ethernet switches and Hercules boards by Texas Instruments is also provided to prove the feasibility of the proposed solution

Understanding patient acceptance and refusal of HIV testing in the emergency department

<p>ABSTRACT</p> <p>Background</p> <p>Despite high rates of patient satisfaction with emergency department (ED) HIV testing, acceptance varies widely. It is thought that patients who decline may be at higher risk for HIV infection, thus we sought to better understand patient acceptance and refusal of ED HIV testing.</p> <p>Methods</p> <p>In-depth interviews with fifty ED patients (28 accepters and 22 decliners of HIV testing) in three ED HIV testing programs that serve vulnerable urban populations in northern California.</p> <p>Results</p> <p>Many factors influenced the decision to accept ED HIV testing, including curiosity, reassurance of negative status, convenience, and opportunity. Similarly, a number of factors influenced the decision to decline HIV testing, including having been tested recently, the perception of being at low risk for HIV infection due to monogamy, abstinence or condom use, and wanting to focus on the medical reason for the ED visit. Both accepters and decliners viewed ED HIV testing favorably and nearly all participants felt comfortable with the testing experience, including the absence of counseling. While many participants who declined an ED HIV test had logical reasons, some participants also made clear that they would prefer not to know their HIV status rather than face psychosocial consequences such as loss of trust in a relationship or disclosure of status in hospital or public health records.</p> <p>Conclusions</p> <p>Testing for HIV in the ED as for any other health problem reduces barriers to testing for some but not all patients. Patients who decline ED HIV testing may have rational reasons, but there are some patients who avoid HIV testing because of psychosocial ramifications. While ED HIV testing is generally acceptable, more targeted approaches to testing are necessary for this subgroup.</p

Factors Associated with Refusal of Rapid HIV Testing in an Emergency Department

HIV screening studies in the emergency department (ED) have demonstrated rates of HIV test refusal ranging from 40–67%. This study aimed to determine the factors associated with refusal to undergo routine rapid HIV testing in an academic ED in Boston. HIV counselors offered routine testing to 1,959 patients; almost one-third of patients (29%) refused. Data from a self-administered survey were used to determine independent correlates of HIV testing refusal. In multivariate analysis, women and patients with annual household incomes of $50,000 or more were more likely to refuse testing, as were those who reported not engaging in HIV risk behaviors, those previously HIV tested and those who did not perceive a need for testing. Enrollment during morning hours was also associated with an increased risk of refusal. Increased educational efforts to convey the rationale and benefits of universal screening may improve testing uptake among these groups

Resource Utilization and Cost-Effectiveness of Counselor- vs. Provider-Based Rapid Point-of-Care HIV Screening in the Emergency Department

Routine HIV screening in emergency department (ED) settings may require dedicated personnel. We evaluated the outcomes, costs and cost-effectiveness of HIV screening when offered by either a member of the ED staff or by an HIV counselor.We employed a mathematical model to extend data obtained from a randomized clinical trial of provider- vs. counselor-based HIV screening in the ED. We compared the downstream survival, costs, and cost-effectiveness of three HIV screening modalities: 1) no screening program; 2) an ED provider-based program; and 3) an HIV counselor-based program. Trial arm-specific data were used for test offer and acceptance rates (provider offer 36%, acceptance 75%; counselor offer 80%, acceptance 71%). Undiagnosed HIV prevalence (0.4%) and linkage to care rates (80%) were assumed to be equal between the screening modalities. Personnel costs were derived from trial-based resource utilization data. We examined the generalizability of results by conducting sensitivity analyses on offer and acceptance rates, undetected HIV prevalence, and costs.Estimated HIV screening costs in the provider and counselor arms averaged $8.10 and$31.00 per result received. The Provider strategy (compared to no screening) had an incremental cost-effectiveness ratio of $58,700/quality-adjusted life year (QALY) and the Counselor strategy (compared to the Provider strategy) had an incremental cost-effectiveness ratio of$64,500/QALY. Results were sensitive to the relative offer and acceptance rates by strategy and the capacity of providers to target-screen, but were robust to changes in undiagnosed HIV prevalence and programmatic costs.The cost-effectiveness of provider-based HIV screening in an emergency department setting compares favorably to other US screening programs. Despite its additional cost, counselor-based screening delivers just as much return on investment as provider based-screening. Investment in dedicated HIV screening personnel is justified in situations where ED staff resources may be insufficient to provide comprehensive, sustainable screening services

A HYBRID FORMULATION FOR MODELLING MULTIBODY SPACECRAFT

In order to simulate the behavior of a space multibody system, the paper shows the possibility of shifting from a Newton Euler (NE) multibody approach to an Euler Lagrange (EL) formulation of the equations of motion. The NE is convenient to understand and to write down the mechanics equations of the system, but the EL equations of motion have a minimum mathematical complexity and a minimum number of equations in a minimum number of variables. The proposed procedure also allows to turn back to the NE formulation to calculate the reaction forces and torques among the bodies. The overall revised hybrid formulation, built by mixing both NE and EL approaches, is applied for simulating the deploying phase of spacecraft solar panels

Control parameters transition during deploying operations of a space flexible structure via multi-body approach

The need to model very complex spacecraft has induced many researchers to develop different methodologies for their study, depending on the type of analysis to be performed. In the ease of structural analysis a classical finite element approach is used to describe in detail each component. In the case of flight mechanics a simple rigid spacecraft can be used for studying guidance, navigation and control laws. On the contrary for studying deploying mechanisms it is necessary to define models of joints and actuators. The necessity to reduce time and cost of the development of new space platforms requires the integration of these different design models and processes. In recent years new methodologies, based on the so-called multibody approach, have been introduced for modeling mechanical systems. Complex space structures are divided into sub-elements (rigid or flexible) connected to each other through joints. With this approach, a very detailed multibody model of a spacecraft can be easily adapted to face different disciplines. Unfortunately, when dealing with elastic bodies the number of degrees of freedom (DOFs) drastically increases. The approach here suggested to keep the number of DOF low is to employ a hybrid approach where a limited number of bodies is chosen, depending on the values of their inertial and elastic properties. In the present work a very large flexible satellite is modeled via multibody technique. In particular the deployable solar arrays and the bus are represented with only three elastic bodies. The deployment phase of the solar panels is simulated through a time sequence of panels models with different geometries. For each configuration the inertial and modal properties are evaluated, and eventually these parameters are interpolated in order to determine their values when a continuous movement of the panels is simulated. On account of the geometry variation we can observe not only a variation on the values of the natural frequencies, but also an exchange on the ranking of the relevant modal shapes and hence on the relevant modal participation factors. A re-ordering of the modal shapes is mandatory before doing any interpolation. A robust and easy to implement re-ordering criteria is presented in the paper together with a number of numerical simulations showing that the proposed hybrid approach can be considered as a valid alternative to simulate a deployable structure with a reduced number of elements and hence of a reduced computational cost. Copyright © (2012) by the International Astronautical Federation

Serum (1→3)-β-d-Glucan Levels in Primary Infection and Pulmonary Colonization with Pneumocystis jirovecii▿

This article describes positive (1→3)-β-d-glucan levels in serum from infants with primary Pneumocystis infection and from immunosuppressed patients with Pneumocystis pneumonia (PCP) and negative levels in serum from patients colonized by Pneumocystis jirovecii. Glucan detection is a complementary tool for the diagnosis of the diverse clinical presentations of P. jirovecii infection