1,143 research outputs found

    Extra dimensions, orthopositronium decay, and stellar cooling

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    In a class of extra dimensional models with a warped metric and a single brane the photon can be localized on the brane by gravity only. An intriguing feature of these models is the possibility of the photon escaping into the extra dimensions. The search for this effect has motivated the present round of precision orthopositronium decay experiments. We point out that in this framework a photon in plasma should be metastable. We consider the astrophysical consequences of this observation, in particular, what it implies for the plasmon decay rate in globular cluster stars and for the core-collapse supernova cooling rate. The resulting bounds on the model parameter exceed the possible reach of orthopositronium experiments by many orders of magnitude.Comment: 13 pages, no figure

    Use of the Natural Circulation Flow Map for Natural Circulation Systems Evaluation

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    The aim of this paper is to collect and resume the work done to build and develop, at the University of Pisa, an engineering tool related to the natural circulation. After a brief description of the different loop flow regimes in single phase and two phase, the derivation of a suitable tool to judge the NC performance in a generic system is presented. Finally, an extensive comparison among the NC performance of various nuclear power plants having different design is done to show a practical application of the NC flow map

    LIMB BODY WALL COMPLEX IN TWO HETEROZYGOTIC TWINS: A CASE REPORT

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    Introdution. Limb-Body Wall Complex (LBWC) is a congenital defect which includes at least two of the following characteristics: abdominal and/or thoracic body wall defects, exencephaly or encephalocoele with or without craniofacial defects (56%) and spinal defects associated with marked vertebral or sacral defects (95%). Case Report. We present a case report of an infant with LBWC, borned by diamniotic twin pregnancy. A prenatal ultrasound reported an healthy fetus and a fetus with multiple malformations. At birth we found a big abdominal wall defect, absence of scrotal sac and testicles, asymmetric chest and no major deformities in craniofacial region. At 2 hours of life, we removed the amniotic sac, we put the stomach and the spleen in the abdominal cavity, which is virtual, and positioned a spring-loaded silo. At 15th day of life we had complete reduction of the intestinal loops and liver and we closed the wall defect with a prosthesis and a cryopreserved skin. The general conditions of the patient, very severe since birth, became progressively worse and he died in the 21st day of life. Discussion. Once the diagnosis is done the physician should offer the parents a therapeutic abortion, and above all, in case they want to carry the pregnancy to term, we need to prepare them to the severity of the malformation and the high probability of death

    A compact city for the wealthy? Employment accessibility inequalities between occupational classes in the London metropolitan region 2011

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    The prevalence of gentrification and housing marketisation processes in many cities points to increasingly wealthy inner-city areas and potentially greater population segregation by income. It is plausible that these trends are contributing to regional accessibility inequalities, though quantitative research testing this link is limited. This paper examines differences in employment accessibility between Standard Occupational Classification groups in the London Metropolitan Region for 2011 for car, transit, bus only and walking modes. Additionally, changes in occupational class populations 2006–2016 are considered, revealing continuing inner-city gentrification. Employment accessibility is calculated using cumulative measures, based on travel times from multi-modal network modelling. The results show that while car accessibility is relatively equal between occupational classes, public transport, bus and walk accessibility have significant inequalities favouring professional classes. Low income groups have lower accessibility for the most affordable bus and walk modes, and inequalities are greater for residents in the wider metropolitan region. Furthermore, professional groups combine accessibility advantages with the highest rates of owner occupation, maximising housing wealth benefits. Lower income groups are exposed to rent increases, though this is offset by social housing, which remains the most prevalent tenure in Inner London for low income classes

    MOBILITY ATLAS BOOKLET: AN URBAN DASHBOARD DESIGN AND IMPLEMENTATION

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    Abstract. The new data sources give the possibility to answer analytically the questions that arise from mobility manager. The process of transforming raw data into knowledge is very complex, and it is necessary to provide metaphors of visualizations that are understandable to decision makers. Here, we propose an analytical platform that extracts information on the mobility of individuals from mobile phone by applying Data Mining methodologies. The main results highlighted here are both technical and methodological. First, communicating information through visual analytics techniques facilitates understanding of information to those who have no specific technical or domain knowledge. Secondly, the API system guarantees the ability to export aggregates according to the granularity required, enabling other actors to produce new services based on the extracted models. For the future, we expect to extend the platform by inserting other layers. For example, a layer for measuring the sustainability index of a territory, such as the ability of public transport to attract private mobility or the index that measures how many private vehicle trips can be converted into electrical mobility.</p

    New constraints for heavy axion-like particles from supernovae

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    We derive new constraints on the coupling of heavy pseudoscalar (axion-like) particles to photons, based on the gamma ray flux expected from the decay of these particles into photons. After being produced in the supernova core, these heavy axion-like particles would escape and a fraction of them would decay into photons before reaching the Earth. We have calculated the expected flux on Earth of these photons from the supernovae SN 1987A and Cassiopeia A and compared our results to data from the Fermi Large Area Telescope. This analysis provides strong constraints on the parameter space for axion-like particles. For a particle mass of 100 MeV, we find that the Peccei-Quinn constant, f_a, must be greater than about 10^{15} GeV. Alternatively, for fa=10^{12} GeV, we exclude the mass region between approximately 100 eV and 1 GeV.Comment: 14 pages, 4 figures. Version published in JCAP. Major changes in the exposition. Added a figure. Added appendix. Minor changes in the results. Some changes in the bibliograph
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