Swedish Defence Research Agency

About: Swedish Defence Research Agency is a government organization based out in Stockholm, Sweden. It is known for research contribution in the topics: Radar & Synthetic aperture radar. The organization has 1413 authors who have published 2731 publications receiving 56083 citations. The organization is also known as: Totalförsvarets forskningsinstitut.

Characterization and Ignition of ADN-Based Liquid Monopropellants

Abstract: Monopropellant propulsion systems for space applications have relied almost exclusively on hydrazine. Hydrazine is however highly toxic, volatile and carcinogenic, and thus costly safety measures are required. In the last few years there has been considerable interest in Europe and in the USA in finding a possible substitute, since a non-toxic monopropellant would offer substantial cost savings. ADN-based liquid monopropellants seem to be a promising alternative to hydrazine, being substantially easier to handle and having a 10% higher specific impulse, and up to 60% higher density-impulse, than hydrazine. To be able to replace hydrazine, ADN-based monopropellants must be as easy to ignite. Hydrazine and ADN-based liquid propellants are very different, and thus new ignition methods must be developed. This paper presents the results from a characterization of ADN-based liquid propellants, as well as the results from electrical ignition experiments in which the propellant was resistively heated to its ignition temperature. It was found that substantially less electric energy was needed than expected. This is due to local phenomena close to, or on the surface of, the electrodes. Very fast ignition was obtained, in most cases below 2 ms.

Deep‐level transient spectroscopy and photoluminescence studies of electron‐irradiated Czochralski silicon

Abstract: Isothermal annealing of electron‐irradiated Czochralski silicon samples (n‐type) has been performed at 335 °C. The annealing process was studied using deep‐level transient spectroscopy (DLTS) and photoluminescence (PL). The dominating level in the DLTS spectra directly after irradiation is located ∼0.18 eV below the conduction band and has previously been assigned to a vacancy‐oxygen center by other authors. During the anneal the concentration of vacancy‐oxygen centers decreases, and simultaneously a new level, ∼0.20 eV below the conduction band, grows up. It is shown that the defect giving rise to this new level may be vacancy related. The PL spectra directly after irradiation are dominated by the G line (969 meV) and the C line (790 meV). The G line disappears rapidly, while the C line is still present after 320 min at 335 °C. During the heat treatment some new lines appear, e.g., the P line (767 meV) and a line at 950 meV. Based on the annealing kinetics, it is speculated that the 950‐meV defect may be vacancy related.

The type IV pilin, PilA, is required for full virulence of Francisella tularensis subspecies tularensis.

Abstract: Background All four Francisella tularensis subspecies possess gene clusters with potential to express type IV pili (Tfp). These clusters include putative pilin genes, as well as pilB, pilC and pilQ, required for secretion and assembly of Tfp. A hallmark of Tfp is the ability to retract the pilus upon surface contact, a property mediated by the ATPase PilT. Interestingly, out of the two major human pathogenic subspecies only the highly virulent type A strains have a functional pilT gene.