205 research outputs found
Binding of magnetic monopoles and atomic nuclei
Abstract We discuss the possibility that magnetic monopoles bind to atomic nuclei. We estimate the binding energy of these systems to be in the range 10â100 keV and the formation cross section to be Ï for âł 10 â28 cm 2 . We find that most likely monopoles reaching Earth are bound to a proton and present bounds on the monopole flux
Helioseismology and screening of nuclear reactions in the Sun
We show that models for screening of nuclear reactions in the Sun can be tested by means of helioseismology. As well known, solar models using the weak screening factors are in agreement with data. We find that the solar model calculated with the anti screening factors of Tsytovitch is not consistent with helioseismology, both for the sound speed profile and for the depth of the convective envelope. Moreover, the difference between the no-screening and weak screening model is significant in comparison with helioseismic uncertainty. In other words, the existence of screening can be proved by means of helioseismology
Interactions of Magnetic Monopoles With Nuclei and Atoms: Formation of Bound States and Phenomenological Consequences
Abstract We discuss the binding of magnetic monopoles to nuclear and atomic systems. The energy spectrum is calculated, by assuming an interaction with a hard core. The formation process of monopole-nucleus bound states is analysed and it is shown that monopoles reaching Earth are most likely bound to a proton. We also discuss phenomenological implications of the existence of bound states in connection with the monopole catalysis of proton decay
Geo-Neutrinos: from Theory to the KamLAND Results
Earth shines in antineutrinos produced from long-lived radioactive elements: detection of this signal can provide a direct test of the Bulk Silicate Earth (BSE) model and fix the radiogenic contribution to the terrestrial heat flow. In this paper we present a systematic approach to geo-neutrino production based on global mass balance, supplemented by a detailed geochemical and geophysical study of the region near the detector, in order to build theoretical constraints on the expected signal. We show that the prediction is weakly dependent on mantle modeling while it requires a good description of the crust composition in the region of the detector site. In 2005 the KamLAND experiment proved that the technique for exploiting geo-neutrinos in the investigation of the Earth's interior is now available. After performing an analysis of KamLAND data which includes recent high precision measurements of the 13C(α, n)16O cross section, we discuss the potential of future experiments for assessing the amount of uranium and thorium in different reservoirs (crust, mantle and core) of the Earth
Helioseismic constraints to the central solar temperature and neutrino fluxes
The central solar temperature T and its uncertainties are calculated in helioseismologically-constrained solar models. From the best fit to the convective radius, density at the convective radius and seismically determined helium abundance the central temperature is found to be T=1.58x10^7 K, in excellent agreement with Standard Solar Models. Conservatively, we estimate that the accuracy of this determination is Delta T/T=1.4 %, better than that in SSM. Neutrino fluxes are calculated. The lower limit to the boron neutrino flux, obtained with maximum reduction factors from all sources of uncertainties, is 2 sigma higher than the flux measured recently by SuperKamiokande
Proposte per una revisione del finanziamento e dellâofferta dei servizi odontoiatrici in Italia. Lâintervento pubblico e i fondi integrativi.
Le cure odontoiatriche sono una componente di rilievo in un servizio sanitario ispirato al principio della globalitĂ assistenziale. Tuttavia, i volumi di prestazioni odontoiatriche erogate dal servizio sanitario sono relativamente modesti e il 90% della spesa odontoiatrica privata Ăš costituita da pagamenti diretti interamente a carico dei pazienti. Vi sono quindi problemi di disuguaglianza nellâaccesso alle cure odontoiatriche. Dal lato dellâofferta le strutture sono parcellizzate con prevalenza di studi con pochi professionisti. Lâentrata di nuovi soggetti imprenditoriali dallâestero e il fenomeno del turismo odontoiatrico sembrano introdurre incentivi a ridurre la frammentazione e ad adottare nuovi modelli organizzativi. La ricerca intende approfondire le possibilitĂ di unâestensione dellâaccesso alle cure odontoiatriche favorendo una riorganizzazione della domanda, modificando la regolamentazione dellâofferta e incentivando i meccanismi di finanziamento integrativi alle disponibilitĂ del servizio sanitario pubblico. Infine, vengono analizzati diversi modelli di fondi integrativi aperti e la loro efficacia nellâampliare il grado di copertura complessivo del rischio odontoiatrico.assistenza odontoiatrica; fondi integrativi; Lea odontoiatrici; fondi aperti; incentivi fiscali
Are bad health and pain making us grumpy? An empirical evaluation of reporting heterogeneity in rating health system responsiveness
This paper considers the influence of patientsâ characteristics on their evaluation of a health systemâs responsiveness, that is, a systemâs ability to respond to the legitimate expectations of potential users regarding non-health enhancing aspects of care (Valentine et al. 2003a). Since responsiveness is evaluated by patients on a categorical scale, their selfevaluation can be affected by the phenomenon of reporting heterogeneity (Rice et al. 2012).
A few studies have investigated how standard socio-demographic characteristics influence the reporting style of health care users with regard to the question of the health systemâs responsiveness (Sirven et al. 2012, Rice et al. 2012). However, we are not aware of any studies that focus explicitly on the influence that both the patientsâ state of health and their experiencing of pain have on the way in which they report on system responsiveness. This
paper tries to bridge this gap by using data regarding a sample of patients hospitalized in four Local Health Authorities (LHA) in Italyâs Emilia-Romagna region between 2010 and 2012.
These patients have evaluated 27 different aspects of the quality of care, concerning five domains of responsiveness (communication, social support, privacy, dignity and quality of facilities). Data have been stratified into five sub-samples, according to these domains. We estimate a generalized ordered probit model (Terza, 1985), an extension of the standard ordered probit model which permits the reporting behaviour of respondents to be modelled as a function of certain respondentsâ characteristics, which in our analysis are represented by the variables âstate of healthâ and âpainâ. Our results suggest that unhealthier patients are more likely to report a lower level of responsiveness, all other things being equal, while patients experiencing pain are more likely to make use of the extreme categories of responsiveness,
that is, to choose the category âcompletely dissatisfiedâ or the category âcompletely satisfiedâ. These results hold across all five domains of responsiveness
Building of a molecular beam epitaxy system
Orientadores: Marco Antonio Robert Alves, Gilberto Medeiros RibeiroDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Eletrica e de ComputaçãoResumo: O crescimento epitaxial de nanoestruturas semicondutoras e metĂĄlicas Ă© algo de grande interesse atualmente em ciĂȘncia e tecnologia devido Ă s propriedades singulares apresentadas pela matĂ©ria na escala nanomĂ©trica. Esta dissertação teve como objetivo principal a construção de um sistema de crescimento epitaxial baseado na tĂ©cnica de epitaxia por feixe molecular (MBE, do inglĂȘs Molecular Beam Epitaxy). Inicialmente, aspectos bĂĄsicos sobre a fĂsica e a tecnologia envolvidas em um sistema de MBE foram analisados. O que Ă© MBE e quais sĂŁo os princĂpios que governam seu funcionamento sĂŁo perguntas intrigantes a um aluno do curso de engenharia elĂ©trica. No decorrer do trabalho, todo o complexo sistema vĂĄcuo (bombeamento e monitoramento) teve de ser cuidadosamente montado e ajustado atĂ© que se obtivesse as condiçÔes Ăłtimas de trabalho dados os componentes disponĂveis bem como suas caracterĂsticas e limitaçÔes. Conceitos teĂłricos e prĂĄticos foram aplicados de forma a tornar o sistema o mais simples, eficiente e amigĂĄvel possĂvel. As evaporadoras por feixe de elĂ©trons foram montadas, testadas e ajustadas atĂ© que se pudesse alcançar os parĂąmetros de funcionamento desejados para estes dispositivos tĂŁo importantes dentro de um sistema de MBE. Toda a instrumentação envolvida no acionamento e no monitoramento destas fontes foi desenvolvido com base em conceitos simples de eletrĂŽnica analĂłgica e, em alguns momentos, digital, alĂ©m de soluçÔes de software, sempre usando LabView. Os resultados do trabalho de construção do sistema puderam ser caracterizados posteriormente de maneira a aferir a confiabilidade dos parĂąmetros utilizados e das amostras crescidas. Estes resultados foram baseados em tĂ©cnicas de microscopia de varredura por pontas (SPM, do inglĂȘs Scanning Probe Microscopy), as quais forneceram informaçÔes detalhadas sobre as nanoestruturas formadas e as superfĂcies dos substratos, dados estes muito importantes e que podem ser utilizados como indicadores das codiçÔes de funcionamento do sistema de crescimentoAbstract: The epitaxial growth of semiconductor and metallic nanostructures is a target of great interest nowadays in science and technology due to the unique properties presented by the matter at the nanometer scale. This dissertation had as the main goal the construction of a system for epitaxial growth based on the Molecular Beam Epitaxy (MBE) technique. First of all, basic aspects about the physics and the technology involved in a MBE system were analyzed. What is MBE and what are the principles that govern its operation are intriguing questions for an electrical engineering student. During this work, the entire complex vacuum system (pumping and monitoring) had to be carefully mounted and adjusted until the optimum conditions were obtained for the available components as well as their characteristics and limitations. Theoretical and practical concepts were applied so that the system become as simple, efficient and friendly as possible. The electron beam evaporation sources were mounted, tested and adjusted until the desired working parameters for these important devices were achieved. The whole instrumentation involved in the driving and in the monitoring of these sources was developed based on simple concepts of analog and, in some cases, digital electronics, besides software solutions, always using LabView. The performance of the system was evaluated by structural characterization using scanning probe microscopy techniques (SPM), which gave detailed information about the formed nanostructures and the substrates surfaces. These data can be used as indicators of the growth system operation conditionsMestradoEletrĂŽnica, MicroeletrĂŽnica e OptoeletrĂŽnicaMestre em Engenharia ElĂ©tric
The optimal resolution level of a protein is an emergent property of its structure and dynamics
Molecular dynamics simulations provide a wealth of data whose in-depth
analysis can be computationally demanding and, sometimes, even unnecessary.
Dimensionality reduction techniques are thus routinely employed to simplify and
improve the interpretation of trajectories focusing on specific subsets of the
system's atoms; a still open problem, in this context, is to determine the
optimal resolution level of the molecule, i.e. the smallest number of atoms
needed to preserve the largest information content from the full atomistic
trajectory. Here, we introduce the protein optimal resolution identification
method (PROPRE), an unsupervised approach built on information theory
principles that determines the smallest number of atoms that need to be
retained in order to attain a synthetic yet informative description of a
protein. By applying the method to a protein dataset and two particular case
studies, we show that this number is typically between 1.5 and 2 times the
amount of residues in a protein; furthermore, the degree of structural
variability of the system influences the optimal resolution level importantly,
in that a broader range of large-scale conformations correlates with fewer
retained sites. The PROPRE method is implemented in efficient and user-friendly
python scripts, which are made available for download on a github repository
Universal divergenceless scaling between structural relaxation and caged dynamics in glass-forming systems
On approaching the glass transition, the microscopic kinetic unit spends
increasing time rattling in the cage of the first neighbours whereas its
average escape time, the structural relaxation time , increases
from a few picoseconds up to thousands of seconds. A thorough study of the
correlation between and the rattling amplitude, expressed by the
Debye-Waller factor (DW), was carried out. Molecular-dynamics (MD) simulations
of both a model polymer system and a binary mixture were performed by varying
the temperature, the density , the potential and the polymer length to
consider the structural relaxation as well as both the rotational and the
translation diffusion. The simulations evidence the scaling between the
and the Debye-Waller factor. An analytic model of the master
curve is developed in terms of two characteristic length scales pertaining to
the distance to be covered by the kinetic unit to reach a transition state. The
model does not imply divergences. The comparison with the
experiments supports the numerical evidence over a range of relaxation times as
wide as about eighteen orders of magnitude. A comparison with other scaling and
correlation procedures is presented. The study suggests that the equilibrium
and the moderately supercooled states of the glassformers possess key
information on the huge slowing-down of their relaxation close to the glass
transition. The latter, according to the present simulations, exhibits features
consistent with the Lindemann melting criterion and the free-volume model.Comment: 8 pages, 11 figure
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