Motivic classes of some classifying stacks

We prove that the class of the classifying stack $B PGL_n$ is the multiplicative inverse of the class of the projective linear group $PGL_n$ in the Grothendieck ring of stacks for $n = 2$ and $n = 3$ under mild conditions on the base field $k$. In particular, although it is known that the multiplicativity relation $\{T\} = \{S\}\cdot\{PGL_n\}$ does not hold for all $PGL_n$-torsors $T \to S$, it holds for the universal $PGL_n$-torsors for said $n$.Comment: 25 pages. Final versio

Weak factorization and the Grothendieck group of Deligne-Mumford stacks

We construct a presentation for the Grothendieck group of Deligne-Mumford stacks over a field of characteristic zero. The generators for this presentation are smooth, proper Deligne-Mumford stacks and the relations are expressed in terms of stacky blow-ups. In the process we prove a version of the weak factorization theorem for Deligne-Mumford stacks.Comment: Final versio

Conservative descent for semi-orthogonal decompositions

Motivated by the local flavor of several well-known semi-orthogonal decompositions in algebraic geometry, we introduce a technique called conservative descent, which shows that it is enough to establish these decompositions locally. The decompositions we have in mind are those for projectivized vector bundles and blow-ups, due to Orlov, and root stacks, due to Ishii and Ueda. Our technique simplifies the proofs of these decompositions and establishes them in greater generality for arbitrary algebraic stacks.Comment: Final versio

Solidarity in the neighbourhood, social support at work and psychosomatic health problems

Aims: The aim of this study was to analyse the link between psychosocial factors in the neighbourhood and work environments, and psychosomatic health problems. Methods: The data were collected in the survey 'Life and Health', which was conducted in 2000 in six Swedish county councils. A total of 71,580 questionnaires were distributed to randomly selected individuals aged 18-79. A total of 46,636 respondents completed the questionnaire. This gives a response rate of around 65%. For the purpose of this study only gainfully employed individuals aged 18-64 are included, which gives a total of 22,164 individuals: 11,247 (50.7%) women and 10,917 (49.3%) men. Two scales were used to measure the psychosocial environments in the neighbourhood and at work. The link between these scales and psychosomatic health problems was analysed by using multinomial logistic regression. Results: The results show that both 'Psychosocial Neighbourhood Environment' (PNE) and 'Psychosocial Working Environment' (PWE), independently, are related to psychosomatic health problems. Hence, the health effects of social relations in the neighbourhood were not modified by the quality of social relations at work, or vice versa. The levels of psychosomatic health problems are highest for people experiencing a low degree of social solidarity in the neighbourhood and for those experiencing low degrees of supportive work relationships. Conclusion: The strong, but independent, effects of social factors related to the neighbourhood and to the workplace on psychosomatic health problems point to the importance of simultaneously considering social relations in different arenas in order to increase the knowledge of the connection between social relations and health

Porcine CD18 mediates Actinobacillus pleuropneumoniae ApxIII species-specific toxicity

Actinobacillus pleuropneumoniae, the causative agent of porcine pleuropneumonia, produces Apx toxins that are recognized as major virulence factors. Recently, we showed that ApxIIIA-cytotoxic activity specifically targets Sus scrofa leukocytes. Since both LtxA from Aggregatibacter actinomycetemcomitans (aggressive periodontitis in humans) and LktA from Mannheimia haemolytica (pneumonia in ruminants) share this characteristic, respectively towards human and ruminant leukocytes, and because both use the CD18 subunit to interact with their respective LFA-1, we hypothesized that ApxIIIA was likely to bind porcine CD18 to exercise its deleterious effects on pig leukocytes. A β 2−integrin-deficient ApxIIIA-resistant human erythroleukemic cell line was transfected either with homologous or heterologous CD11a/CD18 heterodimers using a set of plasmids coding for human (ApxIIIA-resistant), bovine (-resistant) and porcine (-susceptible) CD11a and CD18 subunits. Cell preparations that switched from ApxIIIA-resistance to -susceptibility were then sought to identify the LFA-1 subunit involved. The results showed that the ApxIIIA-resistant recipient cell line was rendered susceptible only if the CD18 partner within the LFA-1 heterodimer was that of the pig. It is concluded that porcine CD18 is necessary to mediate A. pleuropneumoniae ApxIIIA toxin-induced leukolysis