Suppression of star formation in the galaxy NGC 253 by a starburst-driven molecular wind.

The under-abundance of very massive galaxies in the Universe is frequently attributed to the effect of galactic winds. Although ionized galactic winds are readily observable, most of the expelled mass (that is, the total mass flowing out from the nuclear region) is likely to be in atomic and molecular phases that are cooler than the ionized phases. Expanding molecular shells observed in starburst systems such as NGC 253 (ref. 12) and M 82 (refs 13, 14) may facilitate the entrainment of molecular gas in the wind. Although shell properties are well constrained, determining the amount of outflowing gas emerging from such shells and the connection between this gas and the ionized wind requires spatial resolution better than 100 parsecs coupled with sensitivity to a wide range of spatial scales, a combination hitherto not available. Here we report observations of NGC 253, a nearby starburst galaxy (distance ∼ 3.4 megaparsecs) known to possess a wind, that trace the cool molecular wind at 50-parsec resolution. At this resolution, the extraplanar molecular gas closely tracks the Hα filaments, and it appears to be connected to expanding molecular shells located in the starburst region. These observations allow us to determine that the molecular outflow rate is greater than 3 solar masses per year and probably about 9 solar masses per year. This implies a ratio of mass-outflow rate to star-formation rate of at least 1, and probably ∼3, indicating that the starburst-driven wind limits the star-formation activity and the final stellar content.

[CO2 angiography of transplanted kidneys]. / CO2-Angiographie von Transplantatnierenarterien.

PURPOSE: To compare image quality and diagnostic accuracy of carbon dioxide (CO2) and iodinated contrast medium as a contast medium in renal transplant artery angiography. MATERIAL AND METHODS: In this prospective, non-randomized, intra-individual study, we examined 17 patients. Digital subtraction angiography (DSA) was performed first with CO2 to find the optimal projection. Then at least one confirming run was performed with CM ("gold standard"). The quality of the angiographic studies with CO2 and CM and their diagnostic accuracy were compared. Blood creatinine levels were monitored during three days after angiography. RESULTS: Three of four renal transplant artery stenoses were diagnosed correctly with CO2. The false-negative CO2 angiography was due to poor contrast. There were no false-positive results with CO2. Regardless the inferior image quality of CO2 angiography, its positive predictive value was 100%. Renal function was not compromised. CONCLUSION: The primary use of CO2 as a contrast medium for the angiographic evaluation of renal transplant arteries is feasible and practical. It reduces the amount of CM needed. However, in order to confirm the diagnosis, at least one additional series with CM should be performed.

Efficacy of permanent and retrievable vena cava filters: experimental studies and evaluation of a new device.

PURPOSE: To evaluate the efficacy of vena cava filters and to compare them with the new TrapEase filter. METHODS: Thrombus capture rates of 10 permanent and retrievable vena cava filters were tested in vitro in vertical and horizontal positions with thrombus diameters of 3 and 5 mm (length 30 mm) and tube diameters of 21 and 28 mm. Testing included the new TrapEase filter. Results compared statistically using Fisher's exact test (capture rates) and the Kruskal-Wallis test (construction). RESULTS: Best-ranked filters were the Bird's Nest, the TrapEase and the Simon Nitinol filters. The Tempofilter, the Greenfield and the Keeper filter performed worst. Thrombus capture rates were significantly higher in the vertical position and also higher for large thrombi and in the small cava diameter. Conical filters performed worse than filters with two or more filtration levels. CONCLUSION: Filters with two or more filtration levels show the highest filtration efficiency in vitro and can be recommended, especially for the critically ill who will probably not tolerate even small emboli. The TrapEase filter is a promising device and should be evaluated clinically.