Mission Concept for the Single Aperture Far-Infrared (SAFIR) Observatory

The Single Aperture Far-InfraRed (SAFIR) Observatory's science goals are driven by the fact that the earliest stages of almost all phenomena in the universe are shrouded in absorption by and emission from cool dust and gas that emits strongly in the far-infrared and submillimeter. Over the past several years, there has been an increasing recognition of the critical importance of this spectral region to addressing fundamental astrophysical problems, ranging from cosmological questions to understanding how our own Solar System came into being. The development of large, far-infrared telescopes in space has become more feasible with the combination of developments for the James Webb Space Telescope and of enabling breakthroughs in detector technology. We have developed a preliminary but comprehensive mission concept for SAFIR, as a 10 m-class far-infrared and submillimeter observatory that would begin development later in this decade to meet the needs outlined above. Its operating temperature (<4K) and instrument complement would be optimized to reach the natural sky confusion limit in the far-infrared with diffraction-limited peformance down to at least 40 microns. This would provide a point source sensitivity improvement of several orders of magnitude over that of Spitzer or Herschel, with finer angular resolution, enabling imaging and spectroscopic studies of individual galaxies in the early universe. We have considered many aspects of the SAFIR mission, including the telescope technology, detector needs and technologies, cooling method and required technology developments, attitude and pointing, power systems, launch vehicle, and mission operations. The most challenging requirements for this mission are operating temperature and aperture size of the telescope, and the development of detector arrays.Comment: 36 page

Dynamic Contrast-enhanced MR Imaging of Carotid Atherosclerotic Plaque: Model Selection, Reproducibility, and Validation.

Purpose: compare four known pharmacokinetic models for their ability to describe dynamic contrast material-enhanced magnetic resonance (MR) imaging of carotid atherosclerotic plaques, to determine reproducibility, and to validate the results with histologic findings. Materials and Methods: The study was approved by the institutional medical ethics committee. Written informed consent was obtained from all patients. Forty-five patients with 30%-99% carotid stenosis underwent dynamic contrast-enhanced MR imaging. Plaque enhancement was measured at 16 time points at approximately 25-second image intervals by using a gadolinium-based contrast material. Pharmacokinetic parameters (volume transfer constant, Ktrans; extracellular extravascular volume fraction, v e; and blood plasma fraction, v p) were determined by fitting a two-compartment model to plaque and blood gadolinium concentration curves. The relative fit errors and parameter uncertainties were determined to find the most suitable model. Sixteen patients underwent imaging twice to determine reproducibility. Carotid endarterectomy specimens from 16 patients who were scheduled for surgery were collected for histologic validation. Parameter uncertainties were compared with the Wilcoxon signed rank test. Reproducibility was assessed by using the coefficient of variation. Correlation with histologic findings was evaluated with the Pearson correlation coefficient. Results: The mean relative fit uncertainty (+/- standard error) for Ktrans was 10% +/- 1 with the Patlak model, which was significantly lower than that with the Tofts (20% +/- 1), extended Tofts (33% +/- 3), and extended graphical (29% +/- 3) models (P <.001). The relative uncertainty for v p was 20% 6 2 with the Patlak model and was significantly higher with the extended Tofts (46% +/- 9) and extended graphical (35% +/- 5) models (P <.001). The reproducibility (coefficient of variation) for the Patlak model was 16% for Ktrans and 26% for v p. Significant positive correlations were found between Ktrans and the endothelial microvessel content determined on histologic slices (Pearson r = 0.72, P = .005). Conclusion: The Patlak model is most suited for describing carotid plaque enhancement. Correlation with histologic findings validated Ktrans as an indicator of plaque microvasculature, and the reproducibility of Ktrans was good. (C)RSNA, 201

Experimental Results from Tests in the DNW-LLF on the ALVAST Model in Take-Off Configuration with Turbofan Simulators

Engine-airframe interference investigations require a very high degree of accuracy. Previous experiments showed inacceptable agreement of balance measurements when results of different test campaigns are compared. A new test campaign was agreed by DLR, NLR and DNW including a new simulator calibration. Before this test, DLR checked model details and DNW improved their balance and airbridge situation. The results of the new test are satisfying and fulfill the requirements

Applications of PIV in the Large Low Speed Facility of DNW

A Particle Image Velocimetry (PIV) system has been successfully applied in the large low-speed wind tunnel (LLF) of the German Dutch Wind Tunnels (DNW). The described system was developed for the DNW by German Aerospace Research Establishment (DLR). The system equipment and the measurement results of a wake vortex investigation behind an Airbus half-model in the DNW are presented in this paper. The PIV-data were compared with five-hole probe data, which were measured at the same downstream location. The comparison of data and the demonstration show that industrial PIV measurements will be possible in large low-speed wind tunnels in the near futur

TPS calibration procedures

Communication to : International Forum on Turbine Powered Simulation, DNW Emmeloord (The Netherlands), May 16-17, 1995Available at INIST (FR), Document Supply Service, under shelf-number : 22419, issue : a.1995 n.88 / INIST-CNRS - Institut de l'Information Scientifique et TechniqueSIGLEFRFranc