Measurement of XeI and XeII velocity in the near exit plane of a low-power Hall effect thruster by light induced fluorescence spectroscopy

Near exit plane non-resonant light induced fluorescence spectroscopy is performed in a Hall effect low-power Xenon thruster at discharge voltage of 250V and anode flow rate of 0.7mg/sec. Measurement of the axial and radial velocity components are performed, exciting the 6s[3/2]_2-->6p[3/2]_2 transition at 823.16nm in XeI and the 5d[4]_(7/2)-->6p[3]_(5/2) transition at 834.724nm in XeII. No significant deviation from the thermal velocity is observed for XeI. Two most probable ion velocities are registered at a given position with respect to the thruster axis, which are mainly attributed to different areas of creation of ions inside the acceleration channel. The spatial resolution of the set-up is limited by the laser beam size (radius of the order of 0.5mm) and the fluorescence collection optics, which have a view spot diameter of 8mm.Comment: 6 pages, 8 figure

Access to particle-particle emitting sources at intermediate energies

The study of nuclear matter under extreme conditions is a very active area in nuclear physics. This study may improve our understanding of the equation of states and liquid-gas phase transitions in nuclear matter as well as the spectroscopic and dynamic characterization of exotic nuclear systems and reactions. A clear characterization of nuclear interacting systems requires probing the spacetime properties of various particle-emitting sources and the knowledge of the reaction mechanism. Particle-particle correlations represent a very powerful technique to study emitting sources produced during a reaction. In this work two-proton correlation functions measured in Xe+Au at E = 50MeV/nucleon have been studied. By using angle-averaged two-proton correlation functions and imaging techniques we have estimated some of the basic proprieties, such as the size and the relative contributions provided by two-particle–emitting sources produced in semi-central collisions and characterized by different emission time-scales

The blue sky of GJ3470b: the atmosphere of a low-mass planet unveiled by ground-based photometry

GJ3470b is a rare example of a "hot Uranus" transiting exoplanet orbiting a nearby M1.5 dwarf. It is of crucial interest for atmospheric studies because it is one of the most inflated low-mass planets known, bridging the boundary between "super-Earths" and Neptunian planets. We present two new ground-based light curves of GJ3470b gathered by the LBC camera at the Large Binocular Telescope. Simultaneous photometry in the ultraviolet (lambda_c = 357.5 nm) and optical infrared (lambda_c = 963.5 nm) allowed us to detect a significant change of the effective radius of GJ3470b as a function of wavelength. This can be interpreted as a signature of scattering processes occurring in the planetary atmosphere, which should be cloud-free and with a low mean molecular weight. The unprecedented accuracy of our measurements demonstrates that the photometric detection of Earth-sized planets around M dwarfs is achievable using 8-10m size ground-based telescopes. We provide updated planetary parameters, and a greatly improved orbital ephemeris for any forthcoming study of this planet.Comment: 8 pages, 6 figures, 1 table; accepted for publication in A&

Pulse shape discrimination of plastic scintillator EJ 299-33 with radioactive sources

The present study has been carried out in order to investigate about the possibility of using EJ 299-33 scintillator in a multi-detector array to detect neutrons along with light charged particles. In a reaction induced by stable and exotic heavy-ions beams, where copious production of neutrons and other light charged particles occurs, discrimination with low identification threshold of these particles are of great importance. In view of this, EJ 299-33 scintillator having dimension of 3 cm × 3 cm × 3 cm backed by a photomultiplier tube was tested and used under vacuum to detect neutrons, gamma-rays and alpha particles emitted by radioactive sources. Anode pulses from the photomultiplier tube were digitized through GET electronics, recorded and stored in a data acquisition system for the purpose of an off-line analysis. The measurements, under vacuum and low background conditions, show good pulse shape discrimination properties characterized by low identification threshold for neutrons, gamma-rays and alpha particles. The Figures of Merit for neutron-gamma and alpha particles-gamma discriminations have been evaluated together with the energy resolution for gamma-ray and alpha particles

A Gaussian approximation of the distributed computing process

The authors propose a refinement of the stochastic model describing the dynamics of the Desktop Grid (DG) project with many hosts and many workunits to be performed, originally proposed by Morozov et al. in 2017. The target performance measure is the mean duration of the runtime of the project. To this end, the authors derive an asymptotic expression for the amount of the accumulated work to be done by means of limit theorems for superposed on-off sources that lead to a Gaussian approximation. In more detail, depending on the distribution of active and idle periods, Brownian or fractional Brownian processes are obtained. The authors present the analytic results related to the hitting time of the considered processes (including the case in which the overall amount of work is only known in a probabilistic way), and highlight how the runtime tail distribution could be estimated by simulation. Taking advantage of the properties of Gaussian processes and the Conditional Monte-Carlo (CMC) approach, the authors present a theoretical framework for evaluating the runtime tail distribution

“Using digital media or sleeping … that is the question”. A meta-analysis on digital media use and unhealthy sleep in adolescence

This systematic review with meta-analysis aims to examine the relation between different aspects of digital media use and sleep health patterns. Eligible studies had to be longitudinal and with adolescents' sample. Multiple search strategies were applied until January 28, 2023 in order to identify relevant research published in peer-reviewed journal articles or available grey literature. A final set of 23 studies (N = 116,431; 53.2% female; Mage at baseline = 13.4 years) were included. The quality of the studies, assessed with an adapted version of the Newcastle-Ottawa Scale, was high with a consequent low risk of bias. Meta-analytic results showed that tradi-tional media use (r =-0.33 [-0.44;-0.22]), social media use (r =-0.12 [-0.22;-0.01]), prolonged use (r = -0.06 [-0.11;-0.01]), and dysfunctional use (r =-0.19 [-0.29;-0.09]) are negatively related to adolescents' sleep health at a later time point. Conversely, sleep patterns were not related to social media use (r =-.05 [-0.10; 0.00]) and utilization time (r =-0.13 [-0.30; 0.04]), but they were related to dysfunctional use of media (r = -0.22 [-0.33; -0.10]). Overall, this review highlights the presence of a vicious cycle between digital media use and sleep health in adolescence

Seeking Alpha: Excess Risk Taking and Competition for Managerial Talent

We present a model of labor market equilibrium in which managers are risk- averse, managerial talent (\alpha") is scarce, and rms seek alpha, that is, compete for this talent. Firms provide ecient long-term compensation, which allows for learning about managerial talent and assigning of managers to tasks based on their talent, when managers are not mobile across rms. In this case, rms can insure low-quality managers since high-quality managers have limited outside options. In contrast, when managers can move across rms, high-quality managers can fully extract ex post the rents due to their skill, which prevents rms from providing co-insurance among their employees. In anticipation, risk-averse managers may churn across firms before their perfor- mance is fully learnt and thereby prevent their efficient assignment to tasks. The result is excessive risk-taking with pay for short-term performance and build up of long-term risks. As the model is suited for the financial sector, we conclude with analysis of policies to address the externality in compensation among financial firms

Queue normalization methods in systems GI/GI/1/m with infinite variance of service time

Queuing systems with an infinite variance of service time are considered. The average waiting time in such systems is equal to infinity at a stationary regime. We analyze the efficiency of introducing of absolute priorities with infinite number of priority classes determined by the special axis marking on intervals for possible values of service time. It is stated that queues in systems become normalized, i.e. the average queue length become finite, when using regular marking. Furthermore, request loss probabilities radically decrease when buffer size is finite. More efficient marking - exponential marking - is proposed for practical purposes in networks with fractal traffic. The optimization problems of regular and exponential markings are solved