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.

Advanced short-wavelength infrared range-gated imaging for ground applications in monostatic and bistatic configurations

Abstract: Some advanced concepts for gated viewing are presented, including spectral diversity illumination techniques, non-line-of-sight imaging, indirect scene illumination, and in particular setups in bistatic configurations. By using a multiple-wavelength illumination source target speckles could be substantially reduced, leading to an improved image quality and enhanced range accuracy. In non-line-of-sight imaging experiments we observed the scenery through the reflections in a window plane. The scene was illuminated indirectly as well by a diffuse reflection of the laser beam at different nearby objects. In this setup several targets could be spotted, which, e.g., offers the capability to look around the corner in urban situations. In the presented measuring campaigns the advantages of bistatic setups in comparison with common monostatic configurations are discussed. The appearance of shadows or local contrast enhancements as well as the mitigation of retroreflections supports the human observer in interpreting the scene. Furthermore a bistatic configuration contributes to a reduced dazzling risk and to observer convertness.

Reintroduction of Two Deleted Virulence Loci Restores Full Virulence to the Live Vaccine Strain of Francisella tularensis

Abstract: A disadvantage of several old vaccines is that the genetic events resulting in the attenuation are often largely unknown and reversion to virulence cannot be excluded. In the 1950s, a live vaccine strain, LVS, was developed from a type B strain of Francisella tularensis, the causative agent of tularemia. LVS, which is highly attenuated for humans but still virulent for mice by some infection routes, has been extensively studied and found to protect staff from laboratory-acquired tularemia. The efforts to improve biopreparedness have identified a demand for a vaccine against tularemia. Recently the rapid progress in genomics of different Francisella strains has led to identification of several regions of differences (RDs). Two genes carried within RDs, pilA, encoding a putative type IV pilin, and FTT0918, encoding an outer membrane protein, have been linked to virulence. Interestingly, LVS has lost these two genes via direct repeat-mediated deletions. Here we show that reintroduction of the two deleted regions restores virulence of LVS in a mouse infection model to a level indistinguishable from that of virulent type B strains. The identification of the two attenuating deletion events could facilitate the licensing of LVS for use in humans.

On the justification and extension of mixed models in LES

Abstract: A reformulation of the large eddy simulation (LES) equations is presented, based on an alternative decomposition of the subgrid stress tensor leading to modified Leonard, cross, and Reynolds terms, which are all individually frame indifferent. The new Leonard tensor, identical to the scale similarity model proposed by Bardina et al(J. Bardina, J. H. Ferziger and W. C. Reynolds, 1980, AIAA Paper 80-1357), is computable and thus becomes an integral part of the LES equations, so this formulation clearly emphasizes the difference between Reynolds averaged Navier–Stokes (RANS) and LES. The remaining modified cross and Reynolds terms can be regrouped further into a reconstructable part and a true subgrid component, where we here use an approximate deconvolution model and a subgrid viscosity model for the respective parts. This structure justifies the use of a dissipative model term in mixed models based on, e.g., the scale similarity model. The reformulated LES model is tested on two basic flows, the Taylor Gre...