496 research outputs found
Long-term observations of Uranus and Neptune at 90 GHz with the IRAM 30m telescope - (1985 -- 2005)
The planets Uranus and Neptune with small apparent diameters are primary
calibration standards. We investigate their variability at ~90 GHz using
archived data taken at the IRAM 30m telescope during the 20 years period 1985
to 2005. We calibrate the planetary observations against non-variable secondary
standards (NGC7027, NGC7538, W3OH, K3-50A) observed almost simultaneously.
Between 1985 and 2005, the viewing angle of Uranus changed from south-pole to
equatorial. We find that the disk brightness temperature declines by almost 10%
(~2sigma) over this time span indicating that the south-pole region is
significantly brighter than average. Our finding is consistent with recent
long-term radio observations at 8.6 GHz by Klein & Hofstadter (2006). Both data
sets do moreover show a rapid decrease of the Uranus brightness temperature
during the year 1993, indicating a temporal, planetary scale change. We do not
find indications for a variation of Neptune's brightness temperature at the 8%
level. If Uranus is to be used as calibration source, and if accuracies better
than 10% are required, the Uranus sub-earth point latitude needs to be taken
into account.Comment: accepted for publication in A&
Comparison between manual scaling and Autoscala automatic scaling applied to SodankylÀ Geophysical Observatory ionograms
This paper presents a comparison between standard ionospheric parameters manually and automatically scaled from ionograms recorded at the high-latitude SodankylĂ€ Geophysical Observatory (SGO, ionosonde SO166, 64.1° geomagnetic latitude), located in the vicinity of the auroral oval. The study is based on 2610 ionograms recorded during the period JuneâDecember 2013. The automatic scaling was made by means of the Autoscala software. A few typical examples are shown to outline the method, and statistics
are presented regarding the differences between manually and automatically scaled values of F2, F1, E and sporadic E (Es) layer parameters. We draw the conclusions that:
1. The F2 parameters scaled by Autoscala, foF2 and M(3000)F2, are reliable.
2. F1 is identified by Autoscala in significantly fewer cases (about 50 %) than in the manual routine, but if identified
the values of foF1 are reliable.
3. Autoscala frequently (30% of the cases) detects an E layer when the manual scaling process does not. When identified by both methods, the Autoscala E-layer parameters
are close to those manually scaled, foE agreeing to within 0.4 MHz.
4. Es and parameters of Es identified by Autoscala are in many cases different from those of the manual scaling. Scaling of Es at auroral latitudes is often a difficult task
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
An Absolute Flux Density Measurement of the Supernova Remnant Casseopia A at 32 GHz
We report 32 GHz absolute flux density measurements of the supernova remnant
Cas A, with an accuracy of 2.5%. The measurements were made with the 1.5-meter
telescope at the Owens Valley Radio Observatory. The antenna gain had been
measured by NIST in May 1990 to be .
Our observations of Cas A in May 1998 yield . We also report absolute flux density measurements of 3C48, 3C147, 3C286,
Jupiter, Saturn and Mars.Comment: 30 pages, 4 figures; accepted for publication by AJ. Revised
systematic error budget, corrected typos, and added reference
Rotational spectra of isotopic species of methyl cyanide, CHCN, in their ground vibrational states up to terahertz frequencies
Methyl cyanide is an important trace molecule in star-forming regions. It is
one of the more common molecules used to derive kinetic temperatures in such
sources. As preparatory work for Herschel, SOFIA, and in particular ALMA we
want to improve the rest frequencies of the main as well as minor isotopologs
of methyl cyanide. The laboratory rotational spectrum of methyl cyanide in
natural isotopic composition has been recorded up to 1.63 THz. Transitions with
good signal-to-noise ratio could be identified for CHCN, CHCN,
CHCN, CHCN, CHDCN, and CHCN in their
ground vibrational states up to about 1.2 THz. The main isotopic species could
be identified even in the highest frequency spectral recordings around 1.6 THz.
The highest quantum numbers included in the fit are 64 for
CHCN and 89 for the main isotopic species. Greatly improved
spectroscopic parameters have been obtained by fitting the present data
together with previously reported transition frequencies. The present data will
be helpful to identify isotopologs of methyl cyanide in the higher frequency
bands of instruments such as the recently launched Herschel satellite, the
upcoming airplane mission SOFIA or the radio telescope array ALMA.Comment: 13 pages, 2 figures, article appeared; CDMS links update
Ground-based estimates of outer radiation belt energetic electron precipitation fluxes into the atmosphere
AARDDVARK data from a radio wave receiver in Sodankyla, Finland have been used to monitor transmissions across the auroral oval and just into the polar cap from the very low frequency communications transmitter, call sign NAA (24.0 kHz, 44 degrees N, 67 degrees W, L = 2.9), in Maine, USA, since 2004. The transmissions are influenced by outer radiation belt (L = 3-7) energetic electron precipitation. In this study, we have been able to show that the observed transmission amplitude variations can be used to determine routinely the flux of energetic electrons entering the upper atmosphere along the total path and between 30 and 90 km. Our analysis of the NAA observations shows that electron precipitation fluxes can vary by 3 orders of magnitude during geomagnetic storms. Typically when averaging over L = 3-7 we find that the >100 keV POES "trapped" fluxes peak at about 10(6) el. cm(-2) s(-1) sr(-1) during geomagnetic storms, with the DEMETER >100 keV drift loss cone showing peak fluxes of 105 el. cm(-2) s(-1) sr(-1), and both the POES >100 keV "loss" fluxes and the NAA ground-based >100 keV precipitation fluxes showing peaks of similar to 10(4) el. cm(-2) s(-1) sr(-1). During a geomagnetic storm in July 2005, there were systematic MLT variations in the fluxes observed: electron precipitation flux in the midnight sector (22-06 MLT) exceeded the fluxes from the morning side (0330-1130 MLT) and also from the afternoon sector (1130-1930 MLT). The analysis of NAA amplitude variability has the potential of providing a detailed, near real-time, picture of energetic electron precipitation fluxes from the outer radiation belts
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