1,721,798 research outputs found
Weak gravitational lensing in fourth order gravity
No full textFor a general class of analytic functions f(R,R αÎ2RαÎ2,R αÎ2Î3Î ́RαÎ2Î3Î ́) we discuss the gravitational lensing in the Newtonian limit of theory. From the properties of the Gauss-Bonnet invariant it is enough to consider only one curvature invariant between the Ricci tensor and the Riemann tensor. Then, we analyze the dynamics of a photon embedded in a gravitational field of a generic f(R,R αÎ2RαÎ2) gravity. The metric is time independent and spherically symmetric. The metric potentials are Schwarzschild-like, but there are two additional Yukawa terms linked to derivatives of f with respect to two curvature invariants. Considering first the case of a pointlike lens, and after the one of a generic matter distribution of the lens, we study the deflection angle and the angular position of images. Though the additional Yukawa terms in the gravitational potential modifies dynamics with respect to general relativity, the geodesic trajectory of the photon is unaffected by the modification if we consider only f(R) gravity. We find different results (deflection angle smaller than the angle of general relativity) only due to the introduction of a generic function of the Ricci tensor square. Finally, we can affirm that the lensing phenomena for all f(R) gravities are equal to the ones known for general relativity. We conclude the paper by showing and comparing the deflection angle and position of images for f(R,R αÎ2RαÎ2) gravity with respect to the gravitational lensing of general relativity. © 2012 American Physical Society
Veni, vidi, ICI. Esiste un trade-off tra pianificazione urbanistica e finanza locale?
No full textL’imposta sugli immobili in Italia è da tempo al centro del dibattito politico elettoralistico. L’introduzione dell’ICI prima e dell’IMU poi ha sviluppato anche un dibattito scientifico che, però, si è prevalentemente focalizzato sugli aspetti equitativi e distributivi dell’imposta o sugli effetti di competizione territoriale. Nessuno studio, invece, ha testato l’impatto dell’imposta sull’offerta e/o domanda di abitazioni. A vent’anni dall’introduzione dell’ICI, il presente lavoro intende avviare una riflessione sul tema. In particolare, seguendo un impianto metodologico consolidato in letteratura, esso mira a verificare se l’introduzione dell’ICI abbia o meno avuto un impatto sull’elasticità dell’offerta di nuovi fabbricati e se, paradossalmente, la sua introduzione non abbia favorito, piuttosto che ostacolato, il consumo di suolo in Italia. In altre parole, partendo da un’ipotesi di lavoro ben definita, la ricerca vuole verificare se una delle conseguenze, non prevista, della decentralizzazione fiscale in Italia sia stata la creazione di una perversa alleanza tra controllati e controllori, il cui risultato è stato una velocizzazione del cambio di destinazione d’uso dei suoli e, quindi, della loro impermeabilizzazione
The Effect of Growth and Corruption on Soil Sealing in Italy: A Regional Environmental Kuznets Curve Analysis
No full textThis paper analyses and looks more closely at the empirical debate regarding the Income Elasticity Hypothesis postulated in relation to the Environmental Kuznets Curve, and the impact of corruption on the relationship between growth and environmental impact, measured in terms of soil sealing, as proxied by the number of Building Permits issued by public authorities. It postulates that when current private rent is high compared to perceived social costs and a large enough minority benefits from the rules, the EKC does not emerge and public intervention fails to perceive social optimality. To validate this hypothesis, we run a panel data regression model based on data from all Italian regions. Results confirmed the hypothesis evidencing a U-shaped relationship, i.e. a detrimental relationship between income and environmental impact/quality. It also demonstrated that this is contingent on the level of corruption. The latter affects the position and the shape of the inverted EKC, speeding up the exploitation process. It shows that the higher the income, the higher the effect of corruption on the environment. Therefore, it advocates caution against any simplistic inference from EKC
Spherical symmetry in f(R)-gravity
No full textSpherical symmetry in f(R)-gravity is discussed in detail considering also the relations to the weak field limit. Exact solutions are obtained for constant Ricci curvature scalar and for Ricci scalar depending on the radial coordinate. In particular, we discuss how to obtain results which can be consistently compared with general relativity giving the well known post-Newtonian and post-Minkowskian limits. Furthermore, we implement a perturbation approach to obtain solutions up to the first order starting from spherically symmetric backgrounds. Exact solutions are given for several classes of f(R)-theories in both R= constant and R = R(r). © 2008 IOP Publishing Ltd
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Design and Testing of a Demonstrator Electric-Pump Feed System for Liquid Propellant Rocket Engines
No full textThe construction of an experimental test rig of an electric-pump feed system for liquid-propellant rocket engines is discussed, focusing in particular on the choice of the different components, and the evaluation of their suitability. Most components are chosen off-the-shelf, yet they are proven to result in an efficient, lightweight design. However, the propellant pumps are found to require instead a customized design for actual inflight applications. Unlike other components, the injection plate is designed and machined ad hoc for the present test bench. It features a single pentad injector to accomodate for the widely different flowrates of oxidizer and fuel. Hydraulic oil is used instead of the actual propellants due to restrictions deriving from adopting off-the-shelf pumps, which however is likely to entail limitations not greater than those associated with standard water testing of liquid-propellant rocket injection plates. The five jets are found to intersect positively. The characteristic curves and relationships of the oxidizer and fuel hydraulic circuits are also shown and discussed
Linezolid in bolus vs linezolid in continous infusion. The host response in patients with severe sepsis.
No full textINTRODUCTION AND AIMS: Severe sepsis by gram positive pathogens is commonly associated with high morbidity and mortalità in every ICU. During the sepsis the coagulation cascade, the complement system and the activation system are activated, in different moments, and this contributes to the development of multiple organ failure. This activation involves all system specially in late sepsis and contributes to the development of multiple organ failure associated with high mortality rate.
Linezolid ia a one of a new class of antimicrobials (oxazolidinones) for the treatment of gram positive infection such as nosocomial pneumonia (including MRSA), community acquired pneumonia, complicate and uncomplicated skin infection and vancomycin resistant Enterococcus Faecium infection. In the study we propose to compare the clinical efficacy of Linezolid in bolus vs Linezolid in continuous infusion in patients with severe sepsis and septic shock (outcome) and to analyse whether significant differences are registered in the coagulation, inflammatory and complement response between the two group of patients.
METHODS: A prospective, randomized comparative trial involved not neutropenic patients admitted in ICU from January until March 2004. The 15 patients involved were those with severe sepsis or septic shock with a positive colture for gram positive and/or nosocomial pneumonia and/or complicated infection. 8 patients received iv Linezolid 600 mg q 12 h for 14 days (Group A), 7 patients iv Linezolid 600 mg as a loading dose and 1200 mg/24h as a mainteinance for 14 days. We monitored AT III, PC, via functional (activity), immunological (antigen) and ELISA. The C1-inhibitor was measured by a chromogenic functional assay.
DISCUSSION AND CONCLUSION: There is not difference significant, about mortality, between the patients of Group A and Group B. The markers levels show the same trend in each group. It’s to notice the different response registered in Survivors and No Survivors group. This preliminary data confirm the important role of coagulation and complement inhibitor in the modulation of host response in septic patient
Ipotesi di valutazione dei disturbi da reazione nevrotica, ai fini previdenziali e per l'invalidità civile
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