Physical Processes in Star Formation

© 2020 Springer-Verlag. The final publication is available at Springer via https://doi.org/10.1007/s11214-020-00693-8.Star formation is a complex multi-scale phenomenon that is of significant importance for astrophysics in general. Stars and star formation are key pillars in observational astronomy from local star forming regions in the Milky Way up to high-redshift galaxies. From a theoretical perspective, star formation and feedback processes (radiation, winds, and supernovae) play a pivotal role in advancing our understanding of the physical processes at work, both individually and of their interactions. In this review we will give an overview of the main processes that are important for the understanding of star formation. We start with an observationally motivated view on star formation from a global perspective and outline the general paradigm of the life-cycle of molecular clouds, in which star formation is the key process to close the cycle. After that we focus on the thermal and chemical aspects in star forming regions, discuss turbulence and magnetic fields as well as gravitational forces. Finally, we review the most important stellar feedback mechanisms.Peer reviewedFinal Accepted Versio

First measurement of Ωc0 production in pp collisions at s=13 TeV

The inclusive production of the charm–strange baryon 0 c is measured for the first time via its hadronic √ decay into −π+ at midrapidity (|y| <0.5) in proton–proton (pp) collisions at the centre-of-mass energy s =13 TeV with the ALICE detector at the LHC. The transverse momentum (pT) differential cross section multiplied by the branching ratio is presented in the interval 2 < pT < 12 GeV/c. The pT dependence of the 0 c-baryon production relative to the prompt D0-meson and to the prompt 0 c-baryon production is compared to various models that take different hadronisation mechanisms into consideration. In the measured pT interval, the ratio of the pT-integrated cross sections of 0 c and prompt + c baryons multiplied by the −π+ branching ratio is found to be larger by a factor of about 20 with a significance of about 4σ when compared to e+e− collisions

Efficacy of probiotic Bacillus licheniformis

The aim of this study was to evaluate the impact of a probiotic Bacillus licheniformis strain (DSM 28710; B-Act®) on growth performance and its capacity to mitigate necrotic enteritis (NE; induced via a Clostridium perfringens challenge) in poultry. A broiler trial was conducted, examining three treatments for 42 days under an induced NE challenge; a negative control (basal diet only); an antibiotic treated group (oxytetracycline hydrochloride (OXT), therapeutic dose of 105 mg OXT/litre in drinking water, for three days after C. perfringens challenge); and a B-Act group (500 g B-Act/tonne of feed, equalling 1.6×1012 colony forming units B. licheniformis DSM 28710/tonne of feed, supplemented from start until finish). Despite the induced NE challenge, weight gains of the B-Act and OXT groups were similar to each other but significantly higher compared to the control at the end of the study (P<0.05). Weight gain of the B-Act group was already significantly higher compared to the control on day 21 (P<0.05), indicating a potential benefit of the probiotic even before clinical establishment of NE. Feed conversion ratio (FCR) values followed a similar pattern throughout the study, with a significantly lower overall FCR for the B-Act and OXT groups compared to the control (P<0.05; d0-42). Birds fed B-Act had significantly (P<0.05) lower NE lesions compared to the control and OXT group on day 21, although OXT was not supplemented to the animals at this stage yet. Both B-Act and OXT groups had significantly (P<0.05) lower NE scores than the control on day 28, demonstrating the effectiveness of the antibiotic treatment and the mitigating effect of B-Act on the effects of a Clostridium perfringens induced NE challenge