2,863 research outputs found
Unparticle contribution to the hydrogen atom ground state energy
In the present work we study the effect of unparticle modified static
potentials on the energy levels of the hydrogen atom. By using
Rayleigh-Schr\"odinger perturbation theory, we obtain the energy shift of the
ground state and we compare it with experimental data. Bounds on the unparticle
energy scale as a function of the scaling dimension
and the coupling constant are derived. We show that
there exists a parameter region where bounds on are
stringent, signalling that unparticles could be tested in atomic physics
experiments.Comment: 11 pages, 3 figure
Minimal Scales from an Extended Hilbert Space
We consider an extension of the conventional quantum Heisenberg algebra,
assuming that coordinates as well as momenta fulfil nontrivial commutation
relations. As a consequence, a minimal length and a minimal mass scale are
implemented. Our commutators do not depend on positions and momenta and we
provide an extension of the coordinate coherent state approach to
Noncommutative Geometry. We explore, as toy model, the corresponding quantum
field theory in a (2+1)-dimensional spacetime. Then we investigate the more
realistic case of a (3+1)-dimensional spacetime, foliated into noncommutative
planes. As a result, we obtain propagators, which are finite in the ultraviolet
as well as the infrared regime.Comment: 16 pages, version which matches that published on CQ
Inclusive Safety at School: How to Train Teachers
The paper presents the activities proposed last year during the first edition of the course \u201cSafety at school\u201d, organized by the University of Macerata and S.E.T.A. (Safety Education Training Agency) Association. Six workshops held by uni\uadversity professors and other experts, focused on the topic of inclusive safety both at school and in the city in order to provide the opportunity of exchanging ideas and field experiences. The idea of the course came up after the earthquakes that stroke the cent\uadral Italy, to offer new conceptual and practical instruments to face the topic of safety at school. As a conclusion, the first edition of the course was a satisfying pilot to move forward to the next step. The exit questionnaire showed a high level of satisfaction from participants
Spinning Loop Black Holes
In this paper we construct four Kerr-like spacetimes starting from the loop
black hole Schwarzschild solutions (LBH) and applying the Newman-Janis
transformation. In previous papers the Schwarzschild LBH was obtained replacing
the Ashtekar connection with holonomies on a particular graph in a
minisuperspace approximation which describes the black hole interior. Starting
from this solution, we use a Newman-Janis transformation and we specialize to
two different and natural complexifications inspired from the complexifications
of the Schwarzschild and Reissner-Nordstrom metrics. We show explicitly that
the space-times obtained in this way are singularity free and thus there are no
naked singularities. We show that the transformation move, if any, the
causality violating regions of the Kerr metric far from r=0. We study the
space-time structure with particular attention to the horizons shape. We
conclude the paper with a discussion on a regular Reissner-Nordstrom black hole
derived from the Schwarzschild LBH and then applying again the Newmann-Janis
transformation.Comment: 18 pages, 18 figure
Diagnosing numerical Cherenkov instabilities in relativistic plasma simulations based on general meshes
Numerical Cherenkov radiation (NCR) or instability is a detrimental effect
frequently found in electromagnetic particle-in-cell (EM-PIC) simulations
involving relativistic plasma beams. NCR is caused by spurious coupling between
electromagnetic-field modes and multiple beam resonances. This coupling may
result from the slow down of poorly-resolved waves due to numerical (grid)
dispersion and from aliasing mechanisms. NCR has been studied in the past for
finite-difference-based EM-PIC algorithms on regular (structured) meshes with
rectangular elements. In this work, we extend the analysis of NCR to
finite-element-based EM-PIC algorithms implemented on unstructured meshes. The
influence of different mesh element shapes and mesh layouts on NCR is studied.
Analytic predictions are compared against results from finite-element-based
EM-PIC simulations of relativistic plasma beams on various mesh types.Comment: 31 pages, 20 figure
Alternatives to Transplantation in the Treatment of Heart Failure: New Diagnostic and Therapeutic Insights
none4siThe aim of our current special issue was to present a series of original researches and reviews on recent advances in the diagnosis, medical therapy, and surgical approaches of heart failure.
As reported in the introductive review of Agnetti et al., cardiovascular disease is the leading cause of mortality in the US and in westernized countries with ischemic heart disease accounting for the majority of these deaths. Paradoxically, the improvements in the medical and surgical treatments of acute coronary syndromes are leading to an increasing number of “survivors” who are then developing heart failure. Despite considerable advances in its management, the gold standard for the treatment of end-stage heart failure patients remains heart transplantation. Nevertheless, this procedure can be o ered only to a small percentage of patients who could bene t from a new heart due to the limited availability of donor organs. e authors reported in this comprehensive review the evaluation of the safety and e cacy of innovative approaches in the diagnosis and treatment of patients refrac- tory to standard medical therapy and excluded from cardiac transplantation lists.mixedNicolini, Francesco; Piepoli, Massimo F.; Agnetti, Giulio; Siniscalchi, GiuseppeNicolini, Francesco; Piepoli, Massimo F.; Agnetti, Giulio; Siniscalchi, Giusepp
New Insights in the Diagnosis and Treatment of Heart Failure
Cardiovascular disease is the leading cause of mortality in the US and in westernized countries with ischemic heart disease accounting for the majority of these deaths. Paradoxically, the improvements in the medical and surgical treatments of acute coronary syndrome are leading to an increasing number of "survivors" who are then developing heart failure. Despite considerable advances in its management, the gold standard for the treatment of end-stage heart failure patients remains heart transplantation. Nevertheless, this procedure can be offered only to a small percentage of patients who could benefit from a new heart due to the limited availability of donor organs. The aim of this review is to evaluate the safety and efficacy of innovative approaches in the diagnosis and treatment of patients refractory to standard medical therapy and excluded from cardiac transplantation lists
A criterion for optimal management of water distribution networks
The management of water supply systems is based on fundamental principles, set
by international and national legislations; the general target for water utilities is
to offer a reliable and effective service following efficiency criteria. In this
context, losses in distribution networks are one of the main problems to tackle:
their reduction implies a general decrease in operational costs and in the need for
a limited resource such as water. Numerous solutions have been proposed to
reduce non revenue water, from simple leak detection to structural interventions
on distribution systems, based on new design criteria which favour district-based
networks over redundant ones. The present work proposes a new procedure to
restructure a water supply network starting from its hydraulic model, comparing
different types of intervention and evaluating their feasibility, limits and
effectiveness in terms of the global system efficiency, as measured by the
infrastructure leakage index (ILI). The possibility to use excessive pressure in
specific parts of a network for the production of electricity is also examined, as it
offers an additional resource to improve the system performance. The procedure
has been tested for the water network in the municipalities of Tarcento and
Magnano in Riviera, near Udine in Italy. Thanks to a specific hydraulic model,
simulations were performed to identify the optimal interventions on the system
aimed at reducing water losses and improving performances and efficiency
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