3,128 research outputs found
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
Photosynthetic Acclimation in Pea and Soybean to High Atmospheric CO2 Partial Pressure
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
The calibrated population resistance tool: standardized genotypic estimation of transmitted HIV-1 drug resistance
Summary: The calibrated population resistance (CPR) tool is a web-accessible program for performing standardized genotypic estimation of transmitted HIV-1 drug resistance. The program is linked to the Stanford HIV drug resistance database and can additionally perform viral genotyping and algorithmic estimation of resistance to specific antiretroviral drugs
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
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
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
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