Tracking system study

A digital computer program was generated which mathematically describes an optimal estimator-controller technique as applied to the control of antenna tracking systems used by NASA. Simulation studies utilizing this program were conducted using the IBM 360/91 computer. The basic ideas of applying optimal estimator-controller techniques to antenna tracking systems are discussed. A survey of existing tracking methods is given along with shortcomings and inherent errors. It is explained how these errors can be considerably reduced if optimal estimation and control are used. The modified programs generated in this project are described and the simulation results are summarized. The new algorithms for direct synthesis and stabilization of the systems including nonlinearities, are presented

FOOD HABITS OF COYOTES (CANIS LATRANS) IN THE VALLES CALDERA NATIONAL PRESERVE, NEW MEXICO

Wildlife managers needed to understand coyote (Canis latrans) ecology in order to develop management plans on the nascent Valles Caldera National Preserve in northern New Mexico. Managers concerned about low elk (Cervus elaphus) recruitment had observed an increase in sightings of coyotes and observations of coyote predation on elk calves. Our objective was to identify and quantify coyote diet, and assess the temporal variation in coyote diet on the Valles Caldera National Preserve, particularly as related to elk calf consumption. We examined coyote food habits using 1,385 scats analyzed monthly from May 2005 to November 2008. The most frequent taxa were rodents (predominantly voles from the genus Microtus, and northern pocket gophers, Thomomys talpoides), elk, insects from the orders Orthoptera (grasshoppers and crickets) and Coleoptera (beetles), mountain cottontail rabbit (Sylvilagus nuttallii), and plant material (mainly grass). We detected rodent and elk in scats during all months of the study and were each present in 54% of scats overall. We identified elk remains in 43% of spring scats, 72% of winter scats, and 56% of fall scats. During summers, we could distinguish calf from adult elk hair: 8% of summer the scats contained adult elk hair and 39% contained calf elk hair. The frequency of prey items varied significantly over most seasons and years, with notable exceptions being that elk did not vary among summers and winters, and rabbits were a consistent diet item through all seasons. The high frequency of elk in the coyote diet bears further study on the density of elk calves, the vulnerability of elk to predation, the nutritional impacts from the quality of forage available to elk, and the role of hunting and other mammalian predators in providing carcasses

Space use and social ecology of coyotes (\u3ci\u3eCanis latrans\u3c/i\u3e) in a high-elevation ecosystem: relative stability in a changing environment

Coyote (Canis latrans) spatial and social ecology are variable, but have been little studied in high-elevation environments. In these temperate ecosystems, large ungulates are prevalent and coyote pack size may be large in order for them to scavenge and defend ungulate carcasses from conspecifics in neighboring packs. We initiated a study to understand the spatial and social ecology of coyotes on the Valles Caldera National Preserve, a high-elevation (2450–3400 m) protected area in northern New Mexico. Our objectives were to (1) describe the home range size and habitat use of coyotes in the preserve, (2) describe coyote movements within and outside of packs, and (3) to evaluate the relationship between coyote social cohesion and the amount of elk (Cervus elaphus) in the coyote diet. We acquired global positioning system and telemetry locations from 33 coyotes from August 2005 to July 2009. We classified 23 coyotes (70 % of individuals) as residents (i.e., territorial) during at least part of the study and ten coyotes (30 %) as transients. Overall mean home range size of resident packs was 10.6 ± 2.2 (SD) km2. Home range size varied between packs, but did not vary by season or year. Coyotes used dry and wet meadow habitats as expected based on availability; coyotes used riparian habitat more than expected, and forests less than expected. Social cohesion did not vary among biological seasons. Alpha coyotes were more socially cohesive with each other than with other pack members, and a transient exhibited temporal–spatial avoidance of pack members while inside the pack’s territory followed by integration into the pack. Contrary to expectations, we found no relationship between coyote social cohesion and the proportion of elk in coyote diets. We concluded that coyote space use and sociality on the preserve were relatively stable year-round despite changes in biological needs, snow depth, and utilization of variously sized prey

How to Resolve an Ethical Dilemma Concerning Randomized Clinical Trials

An apparent ethical dilemma arises when physicians consider enrolling their patients in randomized clinical trials. Suppose that a randomized clinical trial comparing two treatments is in progress, and a physician has an opinion about which treatment is better. The physician has a duty to promote the patient's best medical interests and therefore seems to be obliged to advise the patient to receive the treatment that the physician prefers. This duty creates a barrier to the enrollment of patients in randomized clinical trials.1-10 Two strategies are often used to resolve the dilemma in favor of enrolling patients in clinical trials

Ovonic nickel metal hydride batteries for space applications

Ovonic nickel-metal hydride (NiMH) rechargeable batteries are easily adaptable to a variety of applications. Small consumer NiMH cells were developed and are now being manufactured by licensees throughout the world. This technology was successfully scaled up in larger prismatic cells aimed at electric vehicle applications. Sealed cells aimed at satellite power applications were also built and cycle tested by OBC and other outside agencies. Prototype batteries with high specific energy (over 80 Wh/kg), high energy density (245 Wh/L), and excellent power capability (400 W/kg) were produced. Ovonic NiMH batteries demonstrated an excellent cycle life of over 10,000 cycles at 30 percent DOD. Presently, Ovonic Battery Company is working on an advanced version of this battery for space applications as part of an SBIR contract from NASA

The temporal nature of social context: Insights from the daily lives of patients with HIV

BACKGROUND: Patients\u27 life contexts are increasingly recognized as important, as evidenced by growing attention to the Social Determinants of Health (SDoH). This attention may be particularly valuable for patients with complex needs, like those with HIV, who are more likely to experience age-related comorbidities, mental health or substance use issues. Understanding patient perceptions of their life context can advance SDoH approaches. OBJECTIVES: We sought to understand how aging patients with HIV think about their life context and explored if and how their reported context was documented in their electronic medical records (EMRs). DESIGN: We combined life story interviews and EMR data to understand the health-related daily life experiences of patients with HIV. Patients over 50 were recruited from two US Department of Veterans Affairs HIV clinics. Narrative analysis was used to organize data by life events and health-related metrics. KEY RESULTS: EMRs of 15 participants documented an average of 19 diagnoses and 10 medications but generally failed to include social contexts salient to patients. In interviews, HIV was discussed primarily in response to direct interviewer questions. Instead, participants raised past trauma, current social engagement, and concern about future health with varying salience. This led us to organize the narratives temporally according to past-, present-, or future-orientation. Past-focused narratives dwelled on unresolved experiences with social institutions like the school system, military or marriage. Present-focused narratives emphasized daily life challenges, like social isolation. Future-focused narratives were dominated by concerns that aging would limit activities. CONCLUSIONS: A temporally informed understanding of patients\u27 life circumstances that are the foundation of their individualized SDoH could better focus care plans by addressing contextual concerns salient to patients. Trust-building may be a critical first step in caring for past-focused patients. Present-focused patients may benefit from support groups. Future-focused patients may desire discussing long term care options

Recent Accumulation Variability in Northwest Greenland from Ground-Penetrating Radar and Shallow Cores along the Greenland Inland Traverse

Accumulation is a key parameter governing the mass balance of the Greenland ice sheet. Several studies have documented the spatial variability of accumulation over wide spatial scales, primarily using point data, remote sensing or modeling. Direct measurements of spatially extensive, detailed profiles of accumulation in Greenland, however, are rare. We used 400 MHz ground-penetrating radar along the 1009 km route of the Greenland Inland Traverse from Thule to Summit during April and May of 2011, to image continuous internal reflecting horizons. We dated these horizons using ice-core chemistry at each end of the traverse. Using density profiles measured along the traverse, we determined the depth to the horizons and the corresponding water-equivalent accumulation rates. The measured accumulation rates vary from ~0.1 m w.e. a–1 in the interior to ~0.7 m w.e. a–1 near the coast, and correspond broadly with existing published model results, though there are some excursions. Comparison of our recent accumulation rates with those collected along a similar route in the 1950s shows a ~10% increase in accumulation rates over the past 52 years along most of the traverse route. This implies that the increased water vapor capacity of warmer air is increasing accumulation in the interior of Greenland

Neural Circuitry of Novelty Salience Processing in Psychosis Risk: Association With Clinical Outcome

Psychosis has been proposed to develop from dysfunction in a hippocampal-striatal-midbrain circuit, leading to aberrant salience processing. Here, we used functional magnetic resonance imaging (fMRI) during novelty salience processing to investigate this model in people at clinical high risk (CHR) for psychosis according to their subsequent clinical outcomes. Seventy-six CHR participants as defined using the Comprehensive Assessment of At-Risk Mental States (CAARMS) and 31 healthy controls (HC) were studied while performing a novelty salience fMRI task that engaged an a priori hippocampal-striatal-midbrain circuit of interest. The CHR sample was then followed clinically for a mean of 59.7 months (~5 y), when clinical outcomes were assessed in terms of transition (CHR-T) or non-transition (CHR-NT) to psychosis (CAARMS criteria): during this period, 13 individuals (17%) developed a psychotic disorder (CHR-T) and 63 did not. Functional activation and effective connectivity within a hippocampal-striatal-midbrain circuit were compared between groups. In CHR individuals compared to HC, hippocampal response to novel stimuli was significantly attenuated (P = .041 family-wise error corrected). Dynamic Causal Modelling revealed that stimulus novelty modulated effective connectivity from the hippocampus to the striatum, and from the midbrain to the hippocampus, significantly more in CHR participants than in HC. Conversely, stimulus novelty modulated connectivity from the midbrain to the striatum significantly less in CHR participants than in HC, and less in CHR participants who subsequently developed psychosis than in CHR individuals who did not become psychotic. Our findings are consistent with preclinical evidence implicating hippocampal-striatal-midbrain circuit dysfunction in altered salience processing and the onset of psychosis

Vortex lattice stability and phase coherence in three-dimensional rapidly rotating Bose condensates

We establish the general equations of motion for the modes of a vortex lattice in a rapidly rotating Bose-Einstein condensate in three dimensions, taking into account the elastic energy of the lattice and the vortex line bending energy. As in two dimensions, the vortex lattice supports Tkachenko and gapped sound modes. In contrast, in three dimensions the Tkachenko mode frequency at long wavelengths becomes linear in the wavevector for any propagation direction out of the transverse plane. We compute the correlation functions of the vortex displacements and the superfluid order parameter for a homogeneous Bose gas of bounded extent in the axial direction. At zero temperature the vortex displacement correlations are convergent at large separation, but at finite temperatures, they grow with separation. The growth of the vortex displacements should lead to observable melting of vortex lattices at higher temperatures and somewhat lower particle number and faster rotation than in current experiments. At zero temperature a system of large extent in the axial direction maintains long range order-parameter correlations for large separation, but at finite temperatures the correlations decay with separation.Comment: 10 pages, 2 figures, Changes include the addition of the particle density - vortex density coupling and the correct value of the shear modulu