558 research outputs found
Mars riometer system
A riometer (relative ionospheric opacity meter) measures
the intensity of cosmic radio noise at the surface of a planet.
When an electromagnetic wave passes through the
ionosphere collisions between charged particles (usually
electrons) and neutral gases remove energy from the wave.
By measuring the received signal intensity at the planet's
surface and comparing it to the expected value (the quietday
curve) a riometer can deduce the absorption
(attenuation) of the trans-ionospheric signal. Thus the
absorption measurements provide an indication of ionisation
changes occurring in the ionosphere.
To avoid the need for orbiting sounders riometers use the
cosmic noise background as a signal source. Earth-based
systems are not subject to the challenging power, volume
and mass restriction that would apply to a riometer for
Mars. Some Earth-based riometers utilise phased-array
antennas in order to provide an imaging capability.UnpublishedVienna - Austria3.9. Fisica della magnetosfera, ionosfera e meteorologia spazialeope
The atmospheric implications of radiation belt remediation
High altitude nuclear explosions (HANEs) and geomagnetic storms can produce large scale injections of relativistic particles into the inner radiation belts. It is recognised that these large increases in >1 MeV trapped electron fluxes can shorten the operational lifetime of low Earth orbiting satellites, threatening a large, valuable population. Therefore, studies are being undertaken to bring about practical human control of the radiation belts, termed "Radiation Belt Remediation" (RBR). Here we consider the upper atmospheric consequences of an RBR system operating over either 1 or 10 days. The RBR-forced neutral chemistry changes, leading to NOx enhancements and Ox depletions, are significant during the timescale of the precipitation but are generally not long-lasting. The magnitudes, time-scales, and altitudes of these changes are no more significant than those observed during large solar proton events. In contrast, RBR-operation will lead to unusually intense HF blackouts for about the first half of the operation time, producing large scale disruptions to radio communication and navigation systems. While the neutral atmosphere changes are not particularly important, HF disruptions could be an important area for policy makers to consider, particularly for the remediation of natural injections
Promjena pulsa kod kratkotrajnih mentalnih radova
Veränderungen der Pulsfrequenz bei einfachen kurzzeittigen Konzen-trationsleitungen wurden an 15 Mädchen, 15 Jungen und 15 Erwachsenen in insgesamt 90 Einzelversuchen untersucht. Die Beobachtung anderer Autoren über eine Pulsbeschleunigung bei einfach strukturierter geistiger\u27 Arbeit konnte bestätigt werden.Na 15 mladića, 15 djevojaka i 15 odraslih mjerili su autori promjene pulsa do kojih dolazi u toku kratkotrajnog računanja. Potvrdili su opažanja nekih drugih autora, da u toku takvog rada dolazi do ubrzanja pulsa. Ako se u toku rada uvedu kratke pauze, to dovodi do izvjesnog fiziološkog oporavka, ali u radnom učinku nisu opažene promjene. Izvjesne razlike opažene su među dječacima i djevojčicama, kao i između mladih i starijih ispitanika. Nije nađena nikakva zavisnost između radnog pulsa i radnog učinka u računanju
The intratracheal administration of endotoxin: X. Dexamethasone downregulates neutrophil emigration and cytokine expression in vivo
Intratracheal instillation of endotoxin (LPS) causes acute pulmonary inflammation characterized by the accumulation of plasma proteins and leukocytes within the pulmonary airways. The synthetic glucocorticoid dexamethasone 1) inhibits the LPS-initiated vascular leak of plasma proteins into the airspace, 2) inhibits the LPS-initiated emigration of neutrophils and lymphocytes into the airspace in a dose-dependent fashion, and 3) inhibits LPS-initiated mRNA and/or bronchoalveolar lavage protein expression of cytokines (TNF, IL-1 and IL-6) and chemokines (MIP-l α , MIP-2 and MCP-1). In conclusion, dexamethasone inhibits both the vascular and cellular aspects of acute inflammation by downregulation of a broad spectrum of inflammatory cytokines and chemokines.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/44515/1/10753_2005_Article_BF01487403.pd
Absolute calibration and beam reconstruction of MITO (a ground-based instrument in the millimetric region)
An efficient sky data reconstruction derives from a precise characterization
of the observing instrument. Here we describe the reconstruction of
performances of a single-pixel 4-band photometer installed at MITO (Millimeter
and Infrared Testagrigia Observatory) focal plane. The strategy of differential
sky observations at millimeter wavelengths, by scanning the field of view at
constant elevation wobbling the subreflector, induces a good knowledge of beam
profile and beam-throw amplitude, allowing efficient data recovery. The
problems that arise estimating the detectors throughput by drift scanning on
planets are shown. Atmospheric transmission, monitored by skydip technique, is
considered for deriving final responsivities for the 4 channels using planets
as primary calibrators.Comment: 14 pages, 6 fiugres, accepted for pubblication by New Astronomy (25
March
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