2,454 research outputs found
Effective potential at finite temperature in a constant hypermagnetic field: Ring diagrams in the Standard Model
We study the symmetry breaking phenomenon in the standard model during the
electroweak phase transition in the presence of a constant hypermagnetic field.
We compute the finite temperature effective potential up to the contribution of
ring diagrams in the weak field, high temperature limit and show that under
these conditions, the phase transition becomes stronger first order.Comment: 15 pages, 8 Postscript figure
Effective potential at finite temperature in a constant magnetic field I: Ring diagrams in a scalar theory
We study symmetry restoration at finite temperature in the theory of a
charged scalar field interacting with a constant, external magnetic field. We
compute the finite temperature effective potential including the contribution
from ring diagrams. We show that in the weak field case, the presence of the
field produces a stronger first order phase transition and that the temperature
for the onset of the transition is lower, as compared to the case without
magnetic field.Comment: Expanded comments, 4 figures added. Conclusions unchanged. Version to
match published pape
A stochastic framework for uncertainty analysis in electric power transmission systems with wind generation
International audienceThe purpose of this work is the analysis of the uncertainties affecting an electric transmission network with wind power generation and their impact on its reliability. A stochastic model was developed to simulate the operations and the line disconnection and reconnection events of the electric network due to overloads beyond the rated capacity. We represent and propagate the uncertainties related to consumption variability, ambient temperature variability, wind speed variability and wind power generation variability. The model is applied to a case study of literature. Conclusions are drawn on the impact that different sources of variability have on the reliability of the network and on the seamless electric power supply. Finally, the analysis enables identifying possible system states, in terms of power request and supply, that are critical for network vulnerability and may induce a cascade of line disconnections leading to massive network blackout
Improving Rigid 3-D Calibration for Robotic Surgery
Autonomy is the next frontier of research in robotic surgery and its aim is to improve the quality of surgical procedures in the next future. One fundamental requirement for autonomy is advanced perception capability through vision sensors. In this article, we propose a novel calibration technique for a surgical scenario with a da Vinci Research Kit (dVRK) robot. Camera and robotic arms calibration are necessary to precise position and emulate expert surgeon. The novel calibration technique is tailored for RGB-D cameras. Different tests performed on relevant use cases prove that we significantly improve precision and accuracy with respect to state of the art solutions for similar devices on a surgical-size setups. Moreover, our calibration method can be easily extended to standard surgical endoscope used in real surgical scenario
Fermion scattering off electroweak phase transition kink walls with hypermagnetic fields
We study the scattering of fermions off a finite width kink wall during the
electroweak phase transition in the presence of a background hypermagnetic
field. We derive and solve the Dirac equation for such fermions and compute the
reflection and transmission coefficients for the case when the fermions move
from the symmetric to the broken symmetry phase. We show that the chiral nature
of the fermion coupling with the background field in the symmetric phase
generates an axial asymmetry in the scattering processes. We discuss possible
implications of such axial charge segregation for baryon number generation.Comment: 9 pages, 3 Postscript figures, uses RevTeX4. Expanded discussion,
published versio
Could Dietary Goals and Climate Change Mitigation Be Achieved Through Optimized Diet? The Experience of Modeling the National Food Consumption Data in Italy
Objective: The aim of this study is to define a healthy and sustainable diet model with low GHGE, fulfilling dietary requirements, and considering current Italian food consumption patterns. Design: A duly designed database was developed, linking food nutritional composition and GHGE based on 921 food items consumed in Italy according to the last national food consumption survey (INRAN-SCAI 2005–2006). Linear programming was used to develop new diet plans separately for males and females, aged 18–60 years (n = 2,098 subjects), in order to minimize GHGE. The program is based on dietary goals and acceptability constraints as well as on 13 nutrient requirement constraints aiming to reach a healthy and acceptable diet for the Italian population. Results: Diet optimization resulted in a nutritionally adequate pattern minimizing GHGE values (4.0 vs. 1.9 kg CO2e/day for males and 3.2 vs. 1.6 kg CO2e/day for females). In both sexes, the nutrient intake of the optimized diet was at the established lower bound for cholesterol and calcium and at the established upper bound for free sugar and fiber. In males, intake of zinc was at the established lower bound whereas iron was at the established upper bound. Consumption of red meat and fruit and vegetables was at the established lower and upper bound, respectively, in both males and females. Despite the decrease in meat consumption, especially red meat, in the optimized diet with respect to the observed diet, levels of iron intake in females increased by 10% (10.3 vs. 11.3 mg/day) but remained below the adequate intake established in Italian national DRIs. Conclusions: An attainable healthy dietary pattern was developed that would lead to the reduction of GHGE by 48% for males and by 50% for females with respect to current food consumption in the Italian adult population. Health-promoting dietary patterns can substantially contribute to achieve related Sustainable Development Goals
Measurements of ZnWO anisotropic response to nuclear recoils for the ADAMO project
Anisotropic scintillators can offer a unique possibility to exploit the
so-called directionality approach in order to investigate the presence of those
Dark Matter (DM) candidates inducing nuclear recoils. In fact, their use can
overcome the difficulty of detecting extremely short nuclear recoil traces. In
this paper we present recent measurements performed on the anisotropic response
of a ZnWO crystal scintillator to nuclear recoils, in the framework of the
ADAMO project. The anisotropic features of the ZnWO crystal scintillators
were initially measured with particles; those results have been also
confirmed by the additional measurements presented here. The experimental
nuclear recoil data were obtained by using a neutron generator at ENEA-CASACCIA
and neutron detectors to tag the scattered neutrons; in particular, the
quenching factor values for nuclear recoils along different crystallographic
axes have been determined for three different neutron scattering angles (i.e.
nuclear recoils energies). From these measurements, the anisotropy of the light
response for nuclear recoils in the ZnWO crystal scintillator has been
determined at 5.4 standard deviations.Comment: 22 pages; 12 figures. In press on Eur. Phys. J.
Developments and improvements of radiopure ZnWO anisotropic scintillators
The ZnWO is an anisotropic crystal scintillator; for its peculiar
characteristics, it is a very promising detector to exploit the so-called
directionality approach in the investigation of those Dark Matter (DM)
candidates inducing nuclear recoils. Recently, in the framework of the ADAMO
project, an R\&D to develop high quality and ultra-radiopure ZnWO crystal
scintillators has been carried out. In the present paper the measurements to
study the anisotropic response of a ZnWO to particles and to
nuclear recoils induced by neutron scattering are reported. Monochromatic
neutrons have been produced by a neutron generator at ENEA-CASACCIA. The
quenching factor values for nuclear recoils along different crystallographic
axes have been determined for three different nuclear recoils energies. These
results open the possibility to realize a pioneer experiment to investigate the
above mentioned DM candidates by means of the directionality.Comment: Proceedings of the IPRD 2019 Conference, 10 pages, 7 figures,
accepted for publication in JINS
Cross-sectional survey of users of internet depression communities
Background: Internet-based depression communities provide a forum for individuals to
communicate and share information and ideas. There has been little research into the health status
and other characteristics of users of these communities.
Methods: Online cross-sectional survey of Internet depression communities to identify depressive
morbidity among users of Internet depression communities in six European countries; to
investigate whether users were in contact with health services and receiving treatment; and to
identify user perceived effects of the communities.
Results: Major depression was highly prevalent among respondents (varying by country from 40%
to 64%). Forty-nine percent of users meeting criteria for major depression were not receiving
treatment, and 35% had no consultation with health services in the previous year. Thirty-six
percent of repeat community users who had consulted a health professional in the previous year
felt that the Internet community had been an important factor in deciding to seek professional help.
Conclusions: There are high levels of untreated and undiagnosed depression in users of Internet
depression communities. This group represents a target for intervention. Internet communities can
provide information and support for stigmatizing conditions that inhibit more traditional modes of
information seeking
Baryogenesis and CP-Violating Domain Walls in the Background of a Magnetic Field
Within the domain wall-mediated electroweak baryogenesis, we study fermion
scattering off a CP-violating wall in the background of an uniform magnetic
field. In particular, we calculate the asymmetry between the reflection
coefficients for right-handed and left-handed chiral fermions, \Delta R = R_{R
\to L} - R_{L \to R}, which is of relevance to non local baryogenesis
mechanisms.Comment: replaced with revised conclusion version, to be published in JCA
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