2,513 research outputs found
Einstein-Cartan theory as a theory of defects in space-time
The Einstein-Cartan theory of gravitation and the classical theory of defects
in an elastic medium are presented and compared. The former is an extension of
general relativity and refers to four-dimensional space-time, while we
introduce the latter as a description of the equilibrium state of a
three-dimensional continuum. Despite these important differences, an analogy is
built on their common geometrical foundations, and it is shown that a
space-time with curvature and torsion can be considered as a state of a
four-dimensional continuum containing defects. This formal analogy is useful
for illustrating the geometrical concept of torsion by applying it to concrete
physical problems. Moreover, the presentation of these theories using a common
geometrical basis allows a deeper understanding of their foundations.Comment: 18 pages, 7 EPS figures, RevTeX4, to appear in the American Journal
of Physics, revised version with typos correcte
Fiber R and D for the CMS HCAL
This paper documents the fiber R and D for the CMS hadron barrel calorimeter
(HCAL). The R and D includes measurements of fiber flexibility, splicing,
mirror reflectivity, relative light yield, attenuation length, radiation
effects, absolute light yield, and transverse tile uniformity. Schematics of
the hardware for each measurement are shown. These studies are done for
different diameters and kinds of multiclad fiber.Comment: 23 pages, 30 Figures 89 pages, 41 figures, corresponding author: H.
Budd, [email protected]
Light-cone fluctuations and the renormalized stress tensor of a massless scalar field
We investigate the effects of light-cone fluctuations over the renormalized
vacuum expectation value of the stress-energy tensor of a real massless
minimally coupled scalar field defined in a ()-dimensional flat space-time
with topology . For modeling the influence of
light-cone fluctuations over the quantum field, we consider a random
Klein-Gordon equation. We study the case of centered Gaussian processes. After
taking into account all the realizations of the random processes, we present
the correction caused by random fluctuations. The averaged renormalized vacuum
expectation value of the stress-energy associated with the scalar field is
presented
Inhomogeneous Superconductivity in Comb-Shaped Josephson Junction Networks
We show that some of the Josephson couplings of junctions arranged to form an
inhomogeneous network undergo a non-perturbative renormalization provided that
the network's connectivity is pertinently chosen. As a result, the zero-voltage
Josephson critical currents turn out to be enhanced along directions
selected by the network's topology. This renormalization effect is possible
only on graphs whose adjacency matrix admits an hidden spectrum (i.e. a set of
localized states disappearing in the thermodynamic limit). We provide a
theoretical and experimental study of this effect by comparing the
superconducting behavior of a comb-shaped Josephson junction network and a
linear chain made with the same junctions: we show that the Josephson critical
currents of the junctions located on the comb's backbone are bigger than the
ones of the junctions located on the chain. Our theoretical analysis, based on
a discrete version of the Bogoliubov-de Gennes equation, leads to results which
are in good quantitative agreement with experimental results.Comment: 4 pages, 2 figures, revte
COVID-19 Vaccines and Atrial Fibrillation: Analysis of the Post-Marketing Pharmacovigilance European Database
Atrial fibrillation (AF) has been described in COVID-19 patients. Recently, some case reports and US pharmacovigilance analyses described AF onset as a rare adverse event following COVID-19 vaccination. The possible correlation is unclear. We systematically analyzed the reports of AF related to COVID-19 vaccines collected in the European pharmacovigilance database, EudraVigilance (EV), from 2020 to November 2022. We carried out descriptive and disproportionality analyses. Moreover, we performed a sensitivity analysis, excluding the reports describing other possible alternative AF causes (pericarditis, myocarditis, COVID-19, or other drugs that may cause/exacerbate AF). Overall, we retrieved 6226 reports, which represented only 0.3% of all those related to COVID-19 vaccines collected in EV during our study period. AF reports mainly referred to adults (in particular, >65 years old), with an equal distribution in sex. Reports were mainly related to tozinameran (54.04%), elasomeran (28.3%), and ChAdOx1-S (14.32%). The reported AF required patient hospitalization in 35% of cases and resulted in a life-threatening condition in 10% of cases. The AF duration (when reported) was highly variable, but the majority of the events had a short duration (moda = 24 h). Although an increased frequency of AF reporting with mRNA vaccines emerges from our study, other investigations are required to investigate the possible correlation between COVID-19 vaccination and the rare AF occurrence
Stochastic collective dynamics of charged--particle beams in the stability regime
We introduce a description of the collective transverse dynamics of charged
(proton) beams in the stability regime by suitable classical stochastic
fluctuations. In this scheme, the collective beam dynamics is described by
time--reversal invariant diffusion processes deduced by stochastic variational
principles (Nelson processes). By general arguments, we show that the diffusion
coefficient, expressed in units of length, is given by ,
where is the number of particles in the beam and the Compton
wavelength of a single constituent. This diffusion coefficient represents an
effective unit of beam emittance. The hydrodynamic equations of the stochastic
dynamics can be easily recast in the form of a Schr\"odinger equation, with the
unit of emittance replacing the Planck action constant. This fact provides a
natural connection to the so--called ``quantum--like approaches'' to beam
dynamics. The transition probabilities associated to Nelson processes can be
exploited to model evolutions suitable to control the transverse beam dynamics.
In particular we show how to control, in the quadrupole approximation to the
beam--field interaction, both the focusing and the transverse oscillations of
the beam, either together or independently.Comment: 15 pages, 9 figure
Avaliação do desenvolvimento de maracujá-doce (Passiflora alata Dryander) propagado por estaquia e por semente em condições de pomar comercial.
O trabalho foi realizado na Área de Propagação de Fruteiras do Departamento de Produção Vegetal da Faculdade de Ciências Agrárias e Veterinárias, Universidade Estadual Paulista (FCAV/UNESP), Jaboticabal-SP, e em área de produtor, no município de Araguari-MG, com o objetivo de verificar o potencial de crescimento vegetativo (diâmetro do caule, altura de plantas e número de folhas) de plantas de maracujá-doce (Passiflora alata Dryander), obtidas por estaquia e por semente, comparando o desenvolvimento inicial de plantas no campo. O experimento foi conduzido no período de janeiro de 2002 a fevereiro de 2003. A formação de mudas por semente foi realizada em casa de vegetação e, por estaca, em câmara de nebulização intermitente, sob condições de telado. As estacas e sementes foram coletadas de plantas adultas, oriundas do Banco de Germoplasma Ativo (BAG) do Departamento de Produção Vegetal da FCAV/UNESP. Para as estacas, utilizou-se a parte intermediária de ramos em estádio de crescimento vegetativo. As sementes, para a obtenção das plântulas, foram semeadas em bandejas plásticas. Efetuou-se o transplantio de estacas e de plântulas, para sacos de polietileno, mantido sob telado e irrigado diariamente por aspersão, para aclimatação e plantio no campo, após 60 dias. O diâmetro do caule, a altura e o número de folhas de plantas obtidas por estaca foram maiores do que nas obtidas por semente, em Jaboticabal-SP. Já em Araguari-MG, o diâmetro do caule foi maior naquelas oriundas de semente, enquanto a altura e o número de folhas foram maiores nas plantas propagadas por estacas
Enraizamento de estacas herbáceas de diferentes espécies de maracujazeiro.
O trabalho foi realizado na Área de Propagação de Fruteiras do Departamento de Produção Vegetal da Faculdade de Ciências Agrárias e Veterinárias, Universidade Estadual Paulista (FCAV/UNESP), em Jaboticabal-SP, com o objetivo de verificar a possibilidade de obtenção de mudas por estaquia de maracujá (Passiflora spp.), nas espécies comerciais P. edulis Sims f. flavicarpa Degener e P. alata Dryander, e nos porta-enxertos P. giberti N.E.Brown, P. nitida H.B.K. e P. setacea D.C. O experimento foi realizado no período de junho de 2000 a junho de 2001, em câmara de nebulização intermitente, em condições de telado (50% de sombreamento). As estacas foram coletadas de plantas adultas, oriundas do Banco de Germoplasma Ativo (BAG) do Departamento de Produção Vegetal da FCAV/UNESP e de pomares comerciais, no caso a espécie P. edulis f. flavicarpa, coletando-se a parte intermediária de ramos em estádio de crescimento vegetativo, preparando-se estacas herbáceas com, aproximadamente, 15cm de comprimento, três nós e duas folhas reduzidas ao meio, coletadas em junho e outubro de 2000, e abril de 2001. As estacas foram tratadas com ácido indolbutírico (IBA) nas concentrações de 500; 1.000 e 2.000mg.L-1, por cinco segundos, e sem tratamento (testemunha), e plantadas em bandejas plásticas (40x30x10cm), com vermiculita de textura média, por 60 dias. A percentagem de enraizamento foi maior na espécie P. edulis f. flavicarpa (76,7%), na primavera. A P. giberti e a P. nitida enraizaram na primavera e no inverno, e a P. alata em todas as épocas estudadas. A P. setacea não enraizou. A sobrevivência, o número e o comprimento de raízes foram maiores na primavera
Multi-disciplinary analysis of light shelves application within a student dormitory refurbishment
The achievement of sustainable cities and communities is closely linked to an accurate design of the buildings. In this context, the transparent elements of the building envelope have a crucial role since, on one hand, they are a bottleneck in regards to heat and mass transfers and sound propagation, while, on the other hand, they must allow daylight penetration. Thus, they are responsible for occupants' thermal and visual comfort and their health. Considering passive solutions for windows, the light shelves can improve natural light penetration, reducing the lights' electricity demand and controlling windows' related thermal aspects. The scientific literature is characterized by several studies that analyze this topic, which, however, focus only on the daylight field and sometimes the energy saving for lights. Moreover, they often refer to fixed sky type for the simulations. The aim of the present study is to analyze the application of the light shelves with a multi-disciplinary approach, by means of dynamic simulations, in the EnergyPlus engine, for a whole year. A new methodological approach is presented in order to investigate the technology under different fields of interest: daylight, lighting energy, cooling and heating needs, and thermo-hygrometric comfort. The case study chosen is an existing building, a student dormitory belonging to the University of Athens. It is subject to a deep energy renovation to conform to the "nearly Zero Energy Building" target, in the frame of a European research project called Pro-GET-onE (G.A No. 723747). By means of the calibrated numerical model of this HVAC-building system, ten different configurations of light shelves have been investigated. The best solution is given by the application of an internal horizontal light shelf placed at 50 cm from the top of the window with a depth of 90 or 60 cm. It has been found that despite the reduction in electricity demand for lighting, the variation in heating and cooling needs does not always lead to a benefit
The 1980 earthquake in southern Italy: rescue of trapped victims and mortality.
A retrospective survey was undertaken on the health effects of the 1980 earthquake in southern Italy. The study population included 3619 people living in 7 villages situated near the epicentre of the disaster. The overall casualty rate (dead and injured) was 19.7%. Nearly all the deaths (192/202) occurred among trapped people who died before they could be rescued. Eighty per cent of all the trapped people were extricated within 2 days, mostly without the use of sophisticated means. The probability of survival decreased sharply, the longer the time before extrication. The crude mortality during the 18 months following the earthquake was 19.0 per thousand among the injured people who received treatment, and 14.1 per thousand among non-injured people. After age standardization, there was no significant difference between these two figures and the expected mortality figures for the Italian population in normal times (14.4 per thousand). These results stress the importance of providing rescue activities in the first 48 hours after the impact. Strengthening the self-reliance of the community in disaster preparedness is suggested as the best way to improve the effectiveness of relief operations. In disaster-prone areas, training and education in methods of rescue should be an integral part of any primary health care programme
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