2,450 research outputs found
Development of a Ground-Based Aerial-Tracking Instrument for Open-Path Spectroscopy to Monitor Atmospheric Constituents
A ground-based aerial-tracking instrument, known as the Ground Tracker, designed to provide spectral data to quantify greenhouse gases is under development. The Ground Tracker includes an Optical System including a high power rifle scope, video camera, and spectrometer used to locate an active light source from the Emitter, and collect spectral data by utilizing an actuating mirror. The implementation of this instrument could be made low cost by utilizing existing weather balloon infrastructure to allow the Emitter to be placed into the lower stratosphere. The recovery of the emitter will be possible by tracking the GPS coordinates. Weather balloon instrument packages contain shipping instructions and postage for those packages that go beyond GPS range or are lost. The Ground Tracker and Emitter Gimbal, while not ready for implementation, demonstrate the feasibility of a spectroscopy system that could provide important data for climate observation and modeling at temporal and spatial resolutions not currently available to state-of-the-art satellites
Analysis of signal to noise enhancement using a highly selective modulation tracking filter
Experiments are reported which utilize photodielectric effects in semiconductor loaded superconducting resonant circuits for suppressing noise in RF communication systems. The superconducting tunable cavity acts as a narrow band tracking filter for detecting conventional RF signals. Analytical techniques were developed which lead to prediction of signal-to-noise improvements. Progress is reported in optimization of the experimental variables. These include improved Q, new semiconductors, improved optics, and simplification of the electronics. Information bearing signals were passed through the system, and noise was introduced into the computer model
Inhibition of pituitary-adrenal secretion by a corticotropin releasing hormone antagonist in humans.
Corticotropin releasing hormone (CRH) is the primary modulator of ACTH release from the pituitary, and a neuromodulator in limbic and autonomic brain regions. Dysfunction of CRH-mediated neurotransmission is emerging as a critical mechanism in several disorders. Therefore, modulation of CRH availability at receptor sites is a potentially powerful therapeutic tool. Inhibitory analogues of CRH have been tested in rodents and primates, but their safety and hormonal effects in humans are unknown. We administered a CRH-antagonist, alpha-helical-CRH-(9-41) to six individuals. Each received two intravenous infusions: 50 micrograms kg-1 on day 1, and 100 micrograms kg-1 on the following morning. These doses block both endocrine and central effects of CRH in experimental animals. ACTH, cortisol, electrolytes, glucose and autonomic parameters were monitored in comparison with control values. Infusion of CRH antagonist did not alter heart rate, blood pressure, temperature or plasma electrolytes and glucose. Pre-infusion plasma ACTH levels averaged 26.8 +/- 6.7 pg ml-1 on day 1, and 29.0 +/- 5.8 pg ml-1 on day 2. Post-infusion values were 11.8 +/- 2 and 11.5 +/- 2.4 pg ml-1, significantly lower than pre-infusion levels. Plasma cortisol levels, which averaged 21.4 +/- 4 micrograms dl-1 on the first morning and 22.9 +/- 4.2 on the second, also decreased significantly after CRH antagonist infusions (to 14.0 +/- 2.9 micrograms dl-1 on day 1, and 13.9 +/- 3.0 micrograms dl-1 on day 2). Hormonal changes were transient, and circadian rhythm was not affected. Though not measured formally, euphoria, anxiety or somnolence were not observed. In conclusion, CRH antagonist administration to adults reduces hormonal secretion by pituitary corticotrophs, with resulting decrease in plasma ACTH and cortisol
Assessing the Value of Coordinated Sire Genetics in a Synchronized AI Program
Synchronized artificial insemination was used to inseminate cows using different types of sire genetics, including low-accuracy, calving-ease, and high-accuracy. These three calf sire groups were compared to calves born to cows bred using natural service. We found substantial production efficiency grains, carcass merit improvement, and economic value to calves born to cows following a synchronized artificial insemination program with high-accuracy semen included. The economic advantage to the high-accuracy calf sire group was computed to be in the neighborhood of 80/head, relative to the natural service calf sire group.artificial insemination, beef, cow, carcass, feed-out, genetics, pre-conditioning, sire synchronization., Agricultural Finance,
Infantile spasms: hypothesis-driven therapy and pilot human infant experiments using corticotropin-releasing hormone receptor antagonists.
Background and rationaleInfantile spasms (IS) are an age-specific seizure disorder occurring in 1:2,000 infants and associated with mental retardation in approximately 90% of affected individuals. The costs of IS in terms of loss of lifetime productivity and emotional and financial burdens on families are enormous. It is generally agreed that the seizures associated with IS respond poorly to most conventional anticonvulsants. In addition, in the majority of patients, a treatment course with high-dose corticotropin (ACTH) arrests the seizures completely within days, often without recurrence on discontinuation of the hormone. However, the severe side effects of ACTH require development of better treatments for IS. Based on the rapid, all-or-none and irreversible effects of ACTH and on the established physiological actions of this hormone, it was hypothesized that ACTH eliminated IS via an established neuroendocrine feedback mechanism involving suppression of the age-specific endogenous convulsant neuropeptide corticotropin-releasing hormone (CRH). Indeed, IS typically occur in the setting of injury or insult that activate the CNS stress system, of which CRH is a major component. CRH levels may be elevated in the IS brain, and the neuropeptide is known to cause seizures in infant rats, as well as neuronal death in brain regions involved in learning and memory. If 'excess' CRH is involved in the pathogenesis of IS, then blocking CRH receptors should eliminate both seizures and the excitotoxicity of CRH-receptor-rich neurons subserving learning and memory.Patients and methodsWith FDA approval, alpha-helical CRH, a competitive antagonist of the peptide, was given as a phase I trial to 6 infants with IS who have either failed conventional treatment or who have suffered a recurrence. The study was performed at the Clinical Research Center of the Childrens Hospital, Los Angeles. The effects of alpha-helical CRH on autonomic parameters (blood pressure, pulse, temperature, respiration) were determined. In addition, immediate and short-term effects on ACTH and cortisol and on electrolytes and glucose were examined. The potential efficacy of alpha-helical CRH for IS was studied, using clinical diaries and video EEG.Resultsalpha-Helical CRH, a peptide, did not alter autonomic or biochemical parameters. Blocking peripheral CRH receptors was evident from a transient reduction in plasma ACTH and cortisol. No evidence for the compound's penetration of the blood-brain barrier was found, since no central effects on arousal, activity or seizures and EEG patterns were observed. In addition, a striking resistance of the patients' plasma ACTH to the second infusion of alpha-helical CRH was noted.ConclusionsPeptide analogs of CRH do not cross the blood-brain barrier, and their effects on peripheral stress hormones are transient and benign. Nonpeptide compouds that reach CNS receptors are required to test the hypothesis that blocking CRH receptors may ameliorate IS and its cognitive consequences
Perceptions and responses to climate policy risks among California farmers
This paper considers how farmers perceive and respond to climate change policy risks, and suggests that understanding these risk responses is as important as understanding responses to biophysical climate change impacts. Based on a survey of 162 farmers in California, we test three hypotheses regarding climate policy risk: (1) that perceived climate change risks will have a direct impact on farmer\u27s responses to climate policy risks, (2) that previous climate change experiences will influence farmer\u27s climate change perceptions and climate policy risk responses, and (3) that past experiences with environmental policies will more strongly affect a farmer\u27s climate change beliefs, risks, and climate policy risk responses. Using a structural equation model we find support for all three hypotheses and furthermore show that farmers’ negative past policy experiences do not make them less likely to respond to climate policy risks through participation in a government incentive program. We discuss how future research and climate policies can be structured to garner greater agricultural participation. This work highlights that understanding climate policy risk responses and other social, economic and policy perspectives is a vital component of understanding climate change beliefs, risks and behaviors and should be more thoroughly considered in future work
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