A timeline for massive star-forming regions via combined observation of o-H2_2D+^+ and N2_2D+^+

Context: In cold and dense gas prior to the formation of young stellar objects, heavy molecular species (including CO) are accreted onto dust grains. Under these conditions H$_3^+$ and its deuterated isotopologues become more abundant, enhancing the deuterium fraction of molecules such as N$_2$H$^+$ that are formed via ion-neutral reactions. Because this process is extremely temperature sensitive, the abundance of these species is likely linked to the evolutionary stage of the source. Aims: We investigate how the abundances of o-H$_2$D$^+$ and N$_2$D$^+$ vary with evolution in high-mass clumps. Methods: We observed with APEX the ground-state transitions of o-H$_2$D$^+$ near 372 GHz, and N$_2$D$^+$(3-2) near 231 GHz for three massive clumps in different evolutionary stages. The sources were selected within the G351.77-0.51 complex to minimise the variation of initial chemical conditions, and to remove distance effects. We modelled their dust continuum emission to estimate their physical properties, and also modelled their spectra under the assumption of local thermodynamic equilibrium to calculate beam-averaged abundances. Results: We find an anticorrelation between the abundance of o-H$_2$D$^+$ and that of N$_2$D$^+$, with the former decreasing and the latter increasing with evolution. With the new observations we are also able to provide a qualitative upper limit to the age of the youngest clump of about 10$^5$ yr, comparable to its current free-fall time. Conclusions: We can explain the evolution of the two tracers with simple considerations on the chemical formation paths, depletion of heavy elements, and evaporation from the grains. We therefore propose that the joint observation and the relative abundance of o-H$_2$D$^+$ and N$_2$D$^+$ can act as an efficient tracer of the evolutionary stages of the star-formation process

Can Deuteration be Used as A Chemical Clock in Protostellar Cores

Measuring deuteration fraction in protostellar cores is considered as an important method for age determinations of protostellar cores, and the high deuteration fraction of up to 10% has been considered as evidence for high ages and strong support via magnetic field. In this talk, I will present 3D magneto-hydrodynamical simulations including the deuteration chemistry to explore how the deuteration fraction depends on the dynamical and chemical conditions. I will show that high deuteration fractions can be obtained under a large set of different conditions

Improving compliance with isolation measures in the operating room: a prospective simulation study comparing the effectiveness and costs of simulation-based training vs video-based training

Background: Different isolation measures are required according to the routes of transmission of pathogens. Few studies have compared different forms of hygiene training in terms of efficiency and/or improvement of perception towards hygiene measures. This study aimed to evaluate the benefits of different forms of isolation training in the operating room, and their respective effects on the perception of hygiene measures by comparing simulation training with video-based training. Methods: This multi-centre, prospective, randomized, controlled trial compared hygiene knowledge, psychological safety and perception of training among healthcare workers after in-centre simulation training and conventional video-based training. Results: Neither type of training led to a significant improvement in knowledge or perceived psychological safety (F=0.235, P=0.629, η2=0.003). Participants in the simulation group reported higher levels of willingness to speak up in the depicted scenario compared with participants who received video-based training. Participants perceived the simulation-based training significantly more positively than the video-based training. Conclusion: Clear definition of the goals of training based on the pre-existing level of knowledge of the participants is crucial. For future studies, it would be interesting to investigate the long-term effect and continuing benefits concerning the implementation of hygiene regulations after different types of training