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On applique le modele deja decrit (ibid., 405) au nuage de poussiere sombre L183 (L134N). Ce nuage presente des similitudes avec TMC-1 en ce qui concerne la densite, la temperature et l'extinction mais plusieurs especes moleculaires, dont les cyanopolyynes ont des abondances moindres

On decrit un modele visant a la comprehension des processus chimiques qui se produisent dans les nuages interstellaires sombres, froids et on l'applique a TMC-1

The problem of phase calibration between polarization channels of an imaging radar is studied. The causes of various types of phase errors due to the radar system architecture and system imperfections are examined. A simple model is introduced to explain the spatial variation in phase error as being due to a displacement between the phase centers of the vertical and horizontal antennas. It is also shown that channel leakage can cause a spatial variation in phase error. Phase calibration using both point and distributed ground targets is discussed and a method for calibrating phase using only distributed target is verified, subject to certain constraints. Experimental measurements using the NADC/ERIM P-3 synthetic-aperture radar (SAR) system and NASA/JPL DC-8 SAR, which operates at C-, L-, and P-bands, are presented. Both of these systems are multifrequency, polarimetric, airborne, SAR systems. >

The synthetic aperture radar (SAR) is an imaging system that achieves high azimuthal resolution by tracking individual point scatterers using their phase histories, with the expected phase history of a particular point scatterer being derived from the assumed motion of the airborne SAR platform. Normally, it is assumed that the platform travels along a straight line path and that the radar pulses are emitted at equal spatial intervals. However, the aircraft carrying the SAR will be susceptible to extraneous across tracl motions and errors in the pulse spacing also may occur. These errors manifest themselves. as two forms of image degradation in the final image. Firstly, the image will be defocused due to an error in the expected quadratic phase history, and secondly, the image will contain geometric distortions due to an error in the linear phase history. An autofocus technique can be used to focus the image and produce a measure of the quadratic phase error that in turn can be used to estimate the geometric distortions that will be present in the final image. These distortions can be independently measured by direct comparison with a map of the imaged area. This paper describes the application of these methods to some real SAR data and discusses the results of the comparison of the measurements of autofocus and geometric distortions in terms of both the likely platform motions present and the viability of predicting geometric distortion using the autofocus measurements.

This report reviews and updates the evidence from the Roman temple site of Pagans Hill, Chew Stoke, North Somerset, which was partly excavated between 1949 and 1953. This includes a revised terminus post quem for the initial building of the temple complex of c. A.D. 262 and an emphasis of the importance of the location of the well on the axis of a planned layout. This is accompanied by a resume of a reassessment by George Boon of the sculpture of the torso of a dog found in the well in 1951; this was formerly dated to the sixteenth century, but is now redated to the Roman period, and assigned to a group of temple sculpture. This has also stimulated discussion about the dedication of the temple, possibly to Apollo Cunomaglus. There is also a new review by Professor Vera Evison of the Anglo-Saxon glass jar from the temple well and other comparable vessels.A further excavation in 1986 clarified certain ambiguous points in the earlier work, and added some new data, notably of prehistoric (Neolithic/Early Bron...

Uncorrected across-track motions of a synthetic aperture radar (SAR) platform can cause both a severe loss of azimuthal positioning accuracy in, and defocusing of, the resultant SAR image. It is shown how the results of an autofocus procedure can be incorporated in the azimuth processing to produce a fully focused image that is geometrically accurate in azimuth. Range positioning accuracy is also discussed, leading to a comprehensive treatment of all aspects of geometric accuracy. The system considered is an X-band SAR. >

The Taurus molecular cloud 1 (TMC-1) is an interstellar gas cloud which contains a remarkable variety of complex molecules, including members of the cyanopolyyne group [HCzn, n=3,5,7,9] and other, possibly related, species, including C4H, C3H4 and C3N. The cyanopolyynes, which are found in several, different interstellar environments, have a notably high abundance in TMC-1 for such a small cloud and their method of formation has been a considerable problem in gas-phase chemistry. Several authors1–3 have presented schemes for the production of the cyanopolyynes but all these schemes break down under the weight of observational and experimental evidence4. We have reinvestigated the mode of cyanopolyyne formation hi TMC-1 and find that their absolute abundance may be reproduced to within a factor of 3 by a model which uses gas-phase reactions of atomic nitrogen with hydrocarbons to produce them. The observed, spatial displacement of the cyanopolyyne and ammonia peaks5 is readily understood in this model and the abundances of many other molecules are found to be in excellent agreement with observations.

Imaging radar offers potential for regular monitoring of changes in this region. In particular, the JERS-1 satellite carries an L-band HH SAR system which, via an on-board type recorder, can collect data from almost anywhere on the globe, at any time of year. The authors show how JERS-1 radar images can be used to accurately classify different forest types (i.e. flood plain vs. upland forest) and river courses in the Amazon basin. JERS-1 data has also shown significant differences between data obtained during the dry season and the wet season, indicating a strong potential for monitoring seasonal change. The algorithms used to classify JERS-1 data is a standard maximum-likelihood classifier, using the radar image local mean and standard deviation of texture as input. Rivers are detected using an edge detection and edge-following algorithm. This work was performed by the Jet Propulsion Laboratory, California Institute of Technology, under contract from NASA. >

The SIR-C/X-SAR imaging radar took its first flight on the Space Shuttle Endeavour in April 1994. This multi-frequency radar has fully polarimetric capability- at L- and C-band, and a single polarization at X-band (X-SAR). Calibration of polarimetric L- and C-band data for all the different modes SIR-C offers is an especially complicated problem. The solution involves extensive analysis of pre-flight test data to come up with a model of the system, analysis of in-flight test data to determine the actual antenna pattern and gains of the system during operation, and analysis of data from over ten calibration sites distributed around the SIR-C/X SAR orbit track. The SIR-C mission is the first time a multi-frequency polarimetric imaging radar employing phased array antenna has been flown in space. The effort put into the calibration of SIR-C data products has been considerable and is also unique in that this is the first time anyone has attempted to calibrate a spaceborne radar of this complexity. This work was performed by the let Propulsion Laboratory, California Institute of Technology, under contract from the National Aeronautics and Space Administration. >

A joint calibration experiment between the synthetic aperture radars (SAR) onboard NASA/JPL's AIRSAR and Japan's NASDA J-ERS-1 satellite was performed by cotemporally imaging Manu National Park in Peru on June 7, 1993. The data from both instruments were subsequently processed and calibrated at their respective institutions. In situ data at the site in Peru consisting of ground and aerial photographs, GPS coordinates, dielectric measurements, ecological characterization, rainforest structural parameters, and vegetation species identification were collected in early September 1993. Some of the objectives of this experiment were to quantify the relative calibration of AIRSAR and J-ERS-1 data, identify ecological habitats from radar backscatter, and to classify backscatter response due to structural characteristics of the rainforest. Since temporal, global coverage of the J-ERS-1 L-band HH polarization SAR exists, data from this instrument may provide a means for both remote ecological habitat identification and the ability to monitor the extent and conversion of rainforests as man encroaches on ever more remote regions of the world. This paper includes a discussion of the calibration of the SAR instruments. >

Background Initial reports have described the poor outcome of unexpected cardiac arrest (CA) in intensive care unit (ICU) among COVID-19 patients in China and the USA. However, there are scarce data on characteristics and outcomes of such CA patients in Europe. Methods Prospective registry in 35 French ICUs, including all in-ICU CA in COVID-19 adult patients with cardiopulmonary resuscitation (CPR) attempt. Favorable outcome was defined as modified Rankin scale ranging from 0 to 3 at day 90 after CA. Results Among the 2425 COVID-19 patients admitted to ICU from March to June 2020, 186 (8%) experienced in-ICU CA, of whom 146/186 (78%) received CPR. Among these 146 patients, 117 (80%) had sustained return of spontaneous circulation, 102 (70%) died in the ICU, including 48 dying within the first day after CA occurrence and 21 after withdrawal of life-sustaining therapy. Most of CA were non-shockable rhythm (90%). At CA occurrence, 132 patients (90%) were mechanically ventilated, 83 (57%) received vasopressors and 75 (51%) had almost three organ failures. Thirty patients (21%) had a favorable outcome. Sepsis-related organ failure assessment score > 9 before CA occurrence was the single parameter constantly associated with unfavorable outcome in multivariate analysis. Conclusions In-ICU CA incidence remains high among a large multicenter cohort of French critically ill adults with COVID-19. However, 21% of patients with CPR attempt remained alive at 3 months with good functional status. This contrasts with other recent reports showing poor outcome in such patients. Trial registration: This study was retrospectively registered in ClinicalTrials.gov (NTC04373759) in April 2020 (https://www.clinicaltrials.gov/ct2/show/NCT04373759?term=acicovid&draw=2&rank=1).