Ionizing Radiation in Smoothed Particle Hydrodynamics

A new method for the inclusion of ionizing radiation from uniform radiation fields into 3D Smoothed Particle Hydrodynamics (SPHI) simulations is presented. We calculate the optical depth for the Lyman continuum radiation from the source towards the SPHI particles by ray-tracing integration. The time-dependent ionization rate equation is then solved locally for the particles within the ionizing radiation field. Using test calculations, we explore the numerical behaviour of the code with respect to the implementation of the time-dependent ionization rate equation. We also test the coupling of the heating caused by the ionization to the hydrodynamical part of the SPHI code.Comment: 9 pages, 9 figures. accepted by MNRA

Quantum storage on subradiant states in an extended atomic ensemble

A scheme for coherent manipulation of collective atomic states is developed such that total subradiant states, in which spontaneous emission is suppressed into all directions due to destructive interference between neighbor atoms, can be created in an extended atomic ensemble. The optimal conditions for creation of such states and suitability of them for quantum storage are discussed. It is shown that in order to achieve the maximum signal-to-noise ratio the shape of a light pulse to be stored and reconstructed using a homogeneously broadened absorbtion line of an atomic system should be a time-reversed regular part of the response function of the system. In the limit of high optical density, such pulses allow one to prepare collective subradiant atomic states with near flat spatial distribution of the atomic excitation in the medium.Comment: V2: considerably revised (title, text). V3: minor changes - final version as published in PR

Radiation Driven Implosion of Molecular Cloud Cores

We present the first three-dimensional calculations of Radiation Driven Implosion of Molecular Clouds including self-gravity and ionization. We discuss the effects of initial density perturbations on the dynamics of ionizing globules and show that the onset of gravitational collapse can be significantly delayed for a multiple of the implosion timescale. We demonstrate that Radiation Driven Implosion could be an efficient process for injecting disordered kinetic energy into molecular clouds in the vicinity of massive stars

Accretion Signatures from Massive Young Stellar Objects

High resolution (lambda / Delta-lambda = 50,000) K-band spectra of massive, embedded, young stellar objects are presented. The present sample consists of four massive young stars located in nascent clusters powering Galactic giant H II regions. Emission in the 2.3 micron 2--0 vibrational--rotational bandhead of CO is observed. A range of velocity broadened profiles seen in three of the objects is consistent with the emission arising from a circumstellar disk seen at various inclination angles. Br gamma spectra of the same spectral and spatial resolution are also presented which support an accretion disk or torus model for massive stars. In the fourth object, Br emission suggesting a rotating torus is observed, but the CO profile is narrow, indicating that there may be different CO emission mechanisms in massive stars and this is consistent with earlier observations of the BN object and MWC 349. To--date, only young massive stars of late O or early B types have been identified with clear accretion disk signatures in such embedded clusters. Often such stars are found in the presence of other more massive stars which are revealed by their photospheric spectra but which exhibit no disk signatures. This suggests the timescale for dissipating their disks is much faster than the less massive OB stars or that the most massive stars do not form with accretion disks.Comment: 28 pages, 10 Figures, accepted for publication in the Astrophysical Journa

Anti-intruder port protection “MAC (Magnetic ACoustic) System”: advances in the magnetic component performance

In the following, we report the advances made in the development of a magnetic component for peripheral monitoring of port environments for anti-intruder systems. The project was initiated by the Office of Research and Development, COMFORDRAG, Italian Navy, in 2004, with the aim of improving the detection performance of current acoustic-based anti-intruder systems, in the vicinity of quays or the seabed or in acoustic-shadow zones behind natural or artificial objects. In the five-year period from 2004 to 2008, the system has been subjected to detection-performance tests in experiments involving divers equipped with air tanks and rebreather kits in real port environments and, at the same time, the associated signal processing has been subjected to development, to enhance detection performance. In tests involving simulated diver attacks against a vessel moored alongside a quay in the port of La Spezia, the system has been proved particularly effective by detecting 9 divers out of 9. The processing of the magnetic signal has been enhanced by implementing an amplitude threshold, as a means of filtering the passive energy components, termed Passive Energy Cutting (PEC), that is, the elimination of components that comprise no useful information regarding diver transits. The use of PEC boosts the reliability of the system in terms of detection versus false alarm rate, as evidenced by the comparison of the ROC curves for the system with and without PEC

Tobacco dependence treatment for special populations: challenges and opportunities

Although smoking rates have declined in most of the countries in the world, there are population groups within these countries whose smoking rates remain significantly higher than the general population. These ‘‘forgotten groups’’ who have not been receiving the needed attention in tobacco control policies and tobacco cessation efforts include people with serious mental illness, substance use disorders, tuberculosis, people living with human immunodeficiency virus (HIV), lesbian-gaybisexual-transgender-queer people, and pregnant women. A number of steps are needed at the national level in countries where these disparities exist, including modifications to national smoking cessation treatment guidelines that address the special needs of these populations, as well as targeted smoking cessation research, since these populations are often not included in clinical trials. Because of the higher smoking prevalence in these populations, as well as their lower smoking cessation treatment success rates than the general population, more resources are needed if we are to reduce health disparities in these vulnerable populations. Additionally, we believe that more effort should be focused on integrating smoking cessation treatment in the specialized care settings frequented by these subpopulations

Profiling the vendors of COVID‐19 related product on the Darknet: An observational study

Background In a time of unprecedented global change, the COVID-19 pandemic has led to a surge in demand of COVID-19 vaccines and related certifications. Mainly due to supply shortages, counterfeit vaccines, fake documentation, and alleged cures to illegal portfolios, have been offered on darkweb marketplaces (DWMs) with important public health consequences. We aimed to profile key DWMs and vendors by presenting some in-depth case studies. Methods A non-systematic search for COVID-19 products was performed across 118 DWMs. Levels of activity, credibility, content, COVID-19 product listings, privacy protocols were among the features retrieved. Open web fora and other open web sources were also considered for further analysis of both functional and non functional DWMs. Collected data refers to the period between January 2020 and October 2021. Results A total of 42 relevant listings sold by 24 vendors across eight DWMs were identified. Four of these markets were active and well-established at the time of the study with good levels of credibility. COVID-19 products were listed alongside other marketplace content. Vendors had a trusted profile, communicated in English language and accepted payments in cryptocurrencies (Monero or Bitcoin). Their geographical location included the USA, Asia and Europe. While COVID-19 related goods were mostly available for regional supply, other listings were also shipped worldwide. Interpretation Findings emerging from this study rise important questions about the health safety of certain DWMs activities and encourage the development of targeted interventions to overcome such new and rapidly expanding public health threats. Funding CovSaf, National Research centre on Privacy, Harm Reduction and Adversarial Influence Online (REPHRAIN), Commonwealth Fund

Risky business for a juvenile marine predator? Testing the influence of foraging strategies on size and growth rate under natural conditions

Mechanisms driving selection of body size and growth rate in wild marine vertebrates are poorly understood, thus limiting knowledge of their fitness costs at ecological, physiological and genetic scales. Here, we indirectly tested whether selection for size-related traits of juvenile sharks that inhabit a nursery hosting two dichotomous habitats, protected mangroves (low predation risk) and exposed seagrass beds (high predation risk), is influenced by their foraging behaviour. Juvenile sharks displayed a continuum of foraging strategies between mangrove and seagrass areas, with some individuals preferentially feeding in one habitat over another. Foraging habitat was correlated with growth rate, whereby slower growing, smaller individuals fed predominantly in sheltered mangroves, whereas larger, faster growing animals fed over exposed seagrass. Concomitantly, tracked juveniles undertook variable movement behaviours across both the low and high predation risk habitat. These data provide supporting evidence for the hypothesis that directional selection favouring smaller size and slower growth rate, both heritable traits in this shark population, may be driven by variability in foraging behaviour and predation risk. Such evolutionary pathways may be critical to adaptation within predator-driven marine ecosystems