A 492 GHz cooled Schottky receiver for radio-astronomy

We developed a 492 GHz cooled GaAs Schottky receiver driven by a solid state local oscillator with a DSB noise temperature of 550 K measured at the telescope. The receiver-bandwidth is approx. equal to 1.0 GHz. Quasi-optical mirrors focus the sky and local oscillator radiation into the mixer. Stability analysis via the Allan variance method shows that the total system including a 1 GHz bandwidth acousto-optical spectrometer built in Cologne allows integration times up to 100 sec per half switching cycle. We successfully used the receiver at the KOSMA 3 m telescope on Gornergrat (3150m) located in the central Swiss Alps near Zermatt during January-February 1992 for observations of the 492 GHz, (CI) (3)P1 to (3)P0 fine structure line in several galactic sources. These observations confirm that Gornergrat is an excellent winter submillimeter site in accordance with previous predictions based on the atmospheric opacity from KOSMA 345 GHz measurements

On the dynamics of nitrite, nitrate and other biomarkers of nitric oxide production in inflammatory bowel disease

Nitrite and nitrate are frequently used surrogate markers of nitric oxide (NO) production. Using rat models of acute and chronic DSS-induced colitis we examined the applicability of these and other NO-related metabolites, in tissues and blood, for the characterization of inflammatory bowel disease. Global NO dynamics were assessed by simultaneous quantification of nitrite, nitrate, nitroso and nitrosyl species over time in multiple compartments. NO metabolite levels were compared to a composite disease activity index (DAI) and contrasted with measurements of platelet aggregability, ascorbate redox status and the effects of 5-aminosalicylic acid (5-ASA). Nitroso products in the colon and in other organs responded in a manner consistent with the DAI. In contrast, nitrite and nitrate, in both intra- and extravascular compartments, exhibited variations that were not always in step with the DAI. Extravascular nitrite, in particular, demonstrated significant temporal instabilities, ranging from systemic drops to marked increases. The latter was particularly evident after cessation of the inflammatory stimulus and accompanied by profound ascorbate oxidation. Treatment with 5-ASA effectively reversed these fluctuations and the associated oxidative and nitrosative stress. Platelet activation was enhanced in both the acute and chronic model. Our results offer a first glimpse into the systemic nature of DSS-induced inflammation and reveal a greater complexity of NO metabolism than previously envisioned, with a clear dissociation of nitrite from other markers of NO production. The remarkable effectiveness of 5-ASA to abrogate the observed pattern of nitrite instability suggests a hitherto unrecognized role of this molecule in either development or resolution of inflammation. Its possible link to tissue oxygen consumption and the hypoxia that tends to accompany the inflammatory process warrants further investigation

First observations with CONDOR, a 1.5 THz heterodyne receiver

The THz atmospheric windows centered at roughly 1.3 and 1.5~THz, contain numerous spectral lines of astronomical importance, including three high-J CO lines, the N+ line at 205 microns, and the ground transition of para-H2D+. The CO lines are tracers of hot (several 100K), dense gas; N+ is a cooling line of diffuse, ionized gas; the H2D+ line is a non-depleting tracer of cold (~20K), dense gas. As the THz lines benefit the study of diverse phenomena (from high-mass star-forming regions to the WIM to cold prestellar cores), we have built the CO N+ Deuterium Observations Receiver (CONDOR) to further explore the THz windows by ground-based observations. CONDOR was designed to be used at the Atacama Pathfinder EXperiment (APEX) and Stratospheric Observatory For Infrared Astronomy (SOFIA). CONDOR was installed at the APEX telescope and test observations were made to characterize the instrument. The combination of CONDOR on APEX successfully detected THz radiation from astronomical sources. CONDOR operated with typical Trec=1600K and spectral Allan variance times of 30s. CONDOR's first light observations of CO 13-12 emission from the hot core Orion FIR4 (= OMC1 South) revealed a narrow line with T(MB) = 210K and delta(V)=5.4km/s. A search for N+ emission from the ionization front of the Orion Bar resulted in a non-detection. The successful deployment of CONDOR at APEX demonstrates the potential for making observations at THz frequencies from ground-based facilities.Comment: 4 pages + list of objects, 3 figures, to be published in A&A special APEX issu

The Use of Spinning-Disk Confocal Microscopy for the Intravital Analysis of Platelet Dynamics in Response to Systemic and Local Inflammation

Platelets are central players in inflammation and are an important component of the innate immune response. The ability to visualize platelets within the live host is essential to understanding their role in these processes. Past approaches have involved adoptive transfer of labelled platelets, non-specific dyes, or the use of fluorescent antibodies to tag platelets in vivo. Often, these techniques result in either the activation of the platelet, or blockade of specific platelet receptors. In this report, we describe two new methods for intravital visualization of platelet biology, intravenous administration of labelled anti-CD49b, which labels all platelets, and CD41-YFP transgenic mice, in which a percentage of platelets express YFP. Both approaches label endogenous platelets and allow for their visualization using spinning-disk confocal fluorescent microscopy. Following LPS-induced inflammation, we were able to measure a significant increase in both the number and size of platelet aggregates observed within the vasculature of a number of different tissues. Real-time observation of these platelet aggregates reveals them to be large, dynamic structures that are continually expanding and sloughing-off into circulation. Using these techniques, we describe for the first time, platelet recruitment to, and behaviour within numerous tissues of the mouse, both under control conditions and following LPS induced inflammation

Correlation Reflectometry at TEXTOR

In high temperature fusion plasmas the transport of energy and particles is commonly believed to be driven by turbulence. Turbulence quantities as correlation length and decorrelation time are important for the confinement properties of a plasma. Besides other diagnostics, correlation reflectometry has proven to be a suitable tool for the measurement of turbulence properties. At the medium sized Toroidal EXperiment for Technical Oriented Research (TEXTOR) the existing correlation reflectometry has been recently upgraded. A new reflectometer based on a microwave synthesizer has been developed and installed for the investigation of turbulence properties in a fusion plasma. Together with the existing reflectometer the measurement of radial correlation length and decorrelation time becomes available. Both reflectometers are computer controlled and allow to program individual frequency sequences and the duration of each frequency step. With the existing poloidal antenna array at θ=0° and on top of the vacuum vessel, the system allows the measurement of radial correlation and poloidal correlations at the same time. First experiments have been performed and the results on the radial correlation length of density fluctuations in a fusion plasma are presented

A New Passive Microwave Linescanner for Airborne Measurements of Maritime Oil Pollutions.

A new passive microwave linescanner has been developed that will be used for airborne operational measurements of maritime oil pollutions. The system consists of two offset rotating parabolic mirrors and two radiometer sets, where each set contains three radiometers at 18.7, 36.5 and 89 GHz center frequency. A further 89 GHz radiometer is used for the measurement of the average radiometricsky temperature. The system is continuously calibrated by use of a hot load at ambient temperature and a Peltier cooled cold load. A computer system allows real time data reduction for the estimation of the amount of oil on the sea surface

Entwicklung eines 600 GHz-Empfaengers Schlussbericht

Receivers with cryogenic Schottky-mixers have been developed in the framework of a technology program for the ESA satellite project FIRST and the american - german airborne observatory project SOFIA. Three receivers have been built for the frequency ranges 330-345 GHz, 460/492 GHz and 660 GHz. The achieved DSB-receiver noise temperatures are 350 K (330-345 GHz), 550 K (460/492 GHz) and around 5000 K (660 GHz, uncooled). Especially the results of the first two receivers are internationally the best values for cryogenic Schottky-receivers. However, in the meantime better results have been achieved with superconducting (SIS) mixers, with the disadvantage of more complicated cryosystems (cryogenic cooling to 4 K instead of 20 K for Schottky-mixers). In the framework of the project, quasi-optic components, Gunn-oscillators and frequency multipliers have been developed. The combination Gunn-oscillator -multiplier generates the necessary pump power to drive the mixers. This type of pump sources is appropriate for space applications, because they are very compact and have a low power consumption. (orig.)Im Rahmen der Vorentwicklung fuer das Satelliten-Projekt FIRST (ESA) und dem amerikanisch-deutschen Flugzeugprojekt SOFIA wurden Empfaenger mit gekuehlten Schottky-Mischern entwickelt. Es wurden insgesamt drei Empfaenger aufgebaut und zwar fuer den Frequenzbereich 330-345 GHz, 460/492 GHz und 660 GHz. Die erreichten DSB-Empfaengerrauschtemperaturen liegen bei 350 K (330-345 GHz), 550 K (460/492 GHz) und um 5000 K (660 GHz, ungekuehlt). Insbesondere die Werte fuer die ersten beiden Empfaenger sind die international besten fuer gekuehlte Schottky-Empfaenger. Mit supraleitenden (SIS) Mischern werden jedoch inzwischen bessere Rauschwerte erreicht, allerdings mit dem Nachteil eines groesseren Aufwandes fuer die Kuehltechnik (Kuehlung auf ca. 4 K gegenueber 20 K bei Schottky-Mischern). Im Rahmen des Projektes wurden weiterhin quasi-optische Komponenten, Gunn-Oszillatoren und Frequenzvervielfacher entwickelt. Die Kombination Gunn-Oszillator-Frequenzvervielfacher liefert die erforderliche Pumpleistung fuer den Betrieb der Schottky-Mischer. Insbesondere bei Raumfahrtanwendungen sind diese Art von Pumpquellen sehr geeignet, da sie sehr kompakt sind und einem geringen elektrischen Leistungsbedarf haben. (orig.)SIGLEAvailable from TIB Hannover: F96B203+a / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekBundesministerium fuer Bildung, Wissenschaft, Forschung und Technologie, Bonn (Germany); Deutsche Agentur fuer Raumfahrtangelegenheiten (DARA) GmbH, Bonn (Germany)DEGerman