1,003 research outputs found
Pressurant requirements for discharge of liquid methane from a 1.52-meter-(5-ft-) diameter spherical tank under both static and slosh conditions
Pressurized expulsion tests were conducted to determine the effect of various physical parameters on the pressurant gas (methane, helium, hydrogen, and nitrogen) requirements during the expulsion of liquid methane from a 1.52-meter-(5-ft-) diameter spherical tank and to compare results with those predicted by an analytical program. Also studied were the effects on methane, helium, and hydrogen pressurant requirements of various slosh excitation frequencies and amplitudes, both with and without slosh suppressing baffles in the tank. The experimental results when using gaseous methane, helium, and hydrogen show that the predictions of the analytical program agreed well with the actual pressurant requirements for static tank expulsions. The analytical program could not be used for gaseous nitrogen expulsions because of the large quantities of nitrogen which can dissolve in liquid methane. Under slosh conditions, a pronounced increase in gaseous methane requirements was observed relative to results obtained for the static tank expulsions. Slight decreases in the helium and hydrogen requirements were noted under similar test conditions
Recommended from our members
Teaching students with Autism Spectrum Disorder to Mand Within the Inclusive Classroom
Recent federal legislation mandate that students with autism (ASD) be educated within the general education environment and held to high standards of achievement. Many interventions exist to teach language skills to children with ASD. Most have been developed in clinics or segregated settings, and have not been demonstrated as effective within general education classrooms. This research assessed the effectiveness of an intervention to teach two students with ASD to mand (request) within the general education classroom. Generalization and maintenance of independent manding (requesting) skills will be assessed. Both students learned to mand within the natural environment and demonstrated maintenance and generalization of the skill
Shear stress induced stimulation of mammalian cell metabolism
A flow apparatus was developed for the study of the metabolic response of anchorage dependent cells to a wide range of steady and pulsatile shear stresses under well controlled conditions. Human umbilical vein endothelial cell monolayers were subjected to steady shear stresses of up to 24 dynes/sq cm, and the production of prostacyclin was determined. The onset of flow led to a burst in prostacyclin production which decayed to a long term steady state rate (SSR). The SSR of cells exposed to flow was greater than the basal release level, and increased linearly with increasing shear stress. It is demonstrated that shear stresses in certain ranges may not be detrimental to mammalian cell metabolism. In fact, throughout the range of shear stresses studied, metabolite production is maximized by maximizing shear stress
NASA airborne satellite instrumentation calibrator (NASIC) technical reference
The NASA Satellite Instrumentation Calibrator (NASIC) is a visible and near-infrared spectrometer used to calibrate various satellite instruments by underflying those instruments in a NASA ER-2 aircraft. The calibration instrument's hardware and software are documented. The design, operation, and function of an Ebert-Fastie monochronomator, which by means of a moveable diffraction grating, becomes a visible and near-infrared spectrometer used to calibrate satellite-borne instruments by high altitude underflights in the NASA ER-2
Mental Health Needs Among Minority Aviation Students
Higher education, including science, technology, engineering, and mathematics (STEM) education, benefit our society and economic growth. However, overcoming gender disparity and increasing the retention of underrepresented minorities within these programs is challenging. Mental health across higher education has shown to be on the rise, and when it comes to the mental health needs of aviation students, research shows that underrepresented minorities experience unique challenges in achieving academic success. This paper focused on identifying aviation minority students\u27 unique challenges in a small STEM university. This mixed-methods action research study collected quantitative data using an adapted version of the Counseling Center Assessment of Psychological Symptoms-62 (CCAPS-62) and qualitative in-person focus groups. Essential elements evaluated were social support, psychological distress, and psychological well-being needed to thrive in the academic environment. The findings provide educational leaders with research-based strategies to meet the needs of underrepresented minority students and increase their retention in aviation education
Human visual performance during deployment of ALSEP in a lunar visual environment
The purpose of this investigation is to analyze the light reflected from the lunar surface, the light reflected from ALSEP, the contrast between the luminance of ALSEP and the lunar surface, the absence of scattered light, the capabilities of the astronaut, and effect on human visual performance when operating in this lunar visual environment.prepared by W. L. McIntire
Using an Augmented Reality App for Flight Training
As the global demand for aviation pilots continues to drastically increase, flight schools are experiencing a large influx of ab-initio flight students. Such flight training programs are seeking innovative, cutting-edge technologies to support these students and expedite their flight training. The ARAir app, a custom app developed by our team, was designed for ab-initio pilots training at the Embry-Riddle Prescott campus. The initial implementation in Spring 2021 included phonetic alphabet practice and strategic radiotelephony that allows students to practice in a self-paced environment with immediate corrective feedback at various levels of complexity. Students can compete against themselves to improve phonetic alphabet knowledge, create initial radio transmissions, read back ATC instructions, and manipulate an aircraft to the correct intended location at the KPRC airport. Based on the survey and interview feedback collected after the initial implementation, additional support for checklist memorization using the Augmented Reality (AR) feature was added to the ARAir app. This presentation will report students’ learning experience with the improved ARAir in the second implementation in Spring 2022
Acyclovir suppression to prevent recurrent genital herpes at delivery.
OBJECTIVE: To determine if suppressive acyclovir near term decreased the frequency of clinical recurrences at delivery in women with recurrent genital herpes simplex virus (HSV) infection. METHODS: We conducted a prospective, double-blind, randomized trial in 234 women with recurrent genital herpes. Women with genital infection of any frequency were enrolled. Patients received either suppressive oral acyclovir 400 mg three times daily or an identical placebo after 36 weeks' gestation. Clinical lesions were identified, and HSV cultures were obtained at delivery. The frequencies of clinical and subclinical HSV recurrences at delivery were evaluated. RESULTS: Six percent of patients treated with acyclovir, and 14% of patients treated with placebo had clinical HSV at delivery (p = 0.046). No patients in the acyclovir group had positive HSV cultures, compared with 6% of placebo-treated patients (p = 0.029). There was no significant difference in subclinical HSV shedding in the acyclovir group (0%) compared with the placebo-treated group (3%) (p = 0.102). CONCLUSIONS: Suppressive acyclovir therapy significantly decreased the incidence of clinical genital herpes and the overall incidence of HSV excretion at delivery in patients with previous herpes infection
On-farm Experiments with Millet in Niger: Crop Establishment, Yield Loss Factors and Economic Analysis
Results of farm-level experiments with pearl millet are reported from four villages in semi-arid Niger in 1982 and 1983. Crop establishment, yield loss factors (insects, diseases, striga) and economics of new practices were studied in a randomized design which included density, fertility, cultivar, and intercropping with cowpea as treatments. Improved cultivars did not establish significantly better than local ones, but fertilizer occasionally improved establishment. Incidence of yield loss factors was low, and only small effects of cultivar and fertilizer were seen. Fertilizer increased grain yields of the local cultivar by as much as 153%. The use of fertilizer and improved cultivars increased grain yields by as much as 171% over an unfertilized local millet. Even without government subsidies, fertilizer use was profitable for 56% of farmers on all cultivars. In general, fertilizers and improved cultivars had a small positive impact on profitability, with little adverse impact on grain yield variability, so that they could be recommended to farmers with some prospect of success. The intercropping treatment failed in both years, and would have to be modified before extensio
An electrostatic mechanism for Ca(2+)-mediated regulation of gap junction channels.
Gap junction channels mediate intercellular signalling that is crucial in tissue development, homeostasis and pathologic states such as cardiac arrhythmias, cancer and trauma. To explore the mechanism by which Ca(2+) blocks intercellular communication during tissue injury, we determined the X-ray crystal structures of the human Cx26 gap junction channel with and without bound Ca(2+). The two structures were nearly identical, ruling out both a large-scale structural change and a local steric constriction of the pore. Ca(2+) coordination sites reside at the interfaces between adjacent subunits, near the entrance to the extracellular gap, where local, side chain conformational rearrangements enable Ca(2+)chelation. Computational analysis revealed that Ca(2+)-binding generates a positive electrostatic barrier that substantially inhibits permeation of cations such as K(+) into the pore. Our results provide structural evidence for a unique mechanism of channel regulation: ionic conduction block via an electrostatic barrier rather than steric occlusion of the channel pore
- …