7,160 research outputs found
Transonic wind-tunnel investigation of the effects of taper ratio, body indentation, fixed transition, and afterbody shape on the aerodynamic characteristics of a 45 degree sweptback wing-body combination
Antiproton-Hydrogen annihilation at sub-kelvin temperatures
The main properties of the interaction of ultra low-energy antiprotons ( a.u.) with atomic hydrogen are established. They include the
elastic and inelastic cross sections and Protonium (Pn) formation spectrum. The
inverse Auger process () is taken into account in the
framework of an unitary coupled-channels model. The annihilation cross-section
is found to be several times smaller than the predictions made by the black
sphere absorption models. A family of nearthreshold metastable
states is predicited. The dependence of Protonium formation probability on the
position of such nearthreshold S-matrix singularities is analysed. An
estimation for the annihilation cross section is obtained.Comment: latex.tar.gz file, 22 pages, 9 figure
A Preliminary Report on Unique Hail and Tornadic Storm Observations in Central Illinois and Eastern Indiana on 3 April 1974
published or submitted for publicationis peer reviewedOpe
An Investigation of the Stream-tube Power Losses and an Improvement of the Diffuser-entrance Nose in the Langley 8-foot Transonic Tunnel
Effect of Compressibility and Camber as Determined from an Investigation of the NACA 4-(3)(08)-03 and 4-(5)(08)-03 Two-blade Propellers up to Forward Mach Numbers of 0.925
Program on Earth Observation Data Management Systems (EODMS)
An assessment was made of the needs of a group of potential users of satellite remotely sensed data (state, regional, and local agencies) involved in natural resources management in five states, and alternative data management systems to satisfy these needs are outlined. Tasks described include: (1) a comprehensive data needs analysis of state and local users; (2) the design of remote sensing-derivable information products that serve priority state and local data needs; (3) a cost and performance analysis of alternative processing centers for producing these products; (4) an assessment of the impacts of policy, regulation and government structure on implementing large-scale use of remote sensing technology in this community of users; and (5) the elaboration of alternative institutional arrangements for operational Earth Observation Data Management Systems (EODMS). It is concluded that an operational EODMS will be of most use to state, regional, and local agencies if it provides a full range of information services -- from raw data acquisition to interpretation and dissemination of final information products
Spectroscopy of Infrared Flares from the Microquasar GRS 1915+105
We present near-infrared medium-resolution () spectra of the
microquasar GRS 1915+105 on 1997 August 13-15 UTC from the Hale 200-inch
telescope. The spectra showed broad emission lines of He I (2.058 m) and H
I (2.166 m - Br), consistent with previous work. On August 14 UTC,
we took spectra with -minute time resolution during infrared flaring
events similar to those reported in Eikenberry et al. (1998a), which appear to
reveal plasma ejection from the system. During the flares, the emission line
fluxes varied in approximately linear proportionality to the IR continuum flux,
implying that the lines are radiatively pumped by the flares. We also detected
a weak He II (2.189 m) emission line on August 14 UTC. The nature of the
line variability and the presence of the He II feature indicate that the
emission lines in GRS 1915+105 arise in an accretion disk around the compact
object, rather than in the circumstellar disk of a proposed Oe/Be companion.
The radiative line pumping also implies that the flare emission originates from
ejecta which have moved out of the accretion disk plane.Comment: 13 pages plus 4 figures, to appear in ApJ Letter
A Leptin-regulated Circuit Controls Glucose Mobilization During Noxious Stimuli
Adipocytes secrete the hormone leptin to signal the sufficiency of energy stores. Reductions in circulating leptin concentrations reflect a negative energy balance, which augments sympathetic nervous system (SNS) activation in response to metabolically demanding emergencies. This process ensures adequate glucose mobilization despite low energy stores. We report that leptin receptor–expressing neurons (LepRb neurons) in the periaqueductal gray (PAG), the largest population of LepRb neurons in the brain stem, mediate this process. Application of noxious stimuli, which often signal the need to mobilize glucose to support an appropriate response, activated PAG LepRb neurons, which project to and activate parabrachial nucleus (PBN) neurons that control SNS activation and glucose mobilization. Furthermore, activating PAG LepRb neurons increased SNS activity and blood glucose concentrations, while ablating LepRb in PAG neurons augmented glucose mobilization in response to noxious stimuli. Thus, decreased leptin action on PAG LepRb neurons augments the autonomic response to noxious stimuli, ensuring sufficient glucose mobilization during periods of acute demand in the face of diminished energy stores
Shock tunnel studies of scramjet phenomena, supplement 7
Reports by the staff of the University of Queensland on various research studies related to the advancement of scramjet technology are presented. These reports document the tests conducted in the reflected shock tunnel T4 and supporting research facilities that have been used to study the injection, mixing, and combustion of hydrogen fuel in generic scramjets at flow conditions typical of hypersonic flight. In addition, topics include the development of instrumentation and measurement technology, such as combustor wall shear and stream composition in pulse facilities, and numerical studies and analyses of the scramjet combustor process and the test facility operation. This research activity is Supplement 7 under NASA Grant NAGW-674
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