200 research outputs found
Preliminary Numerical Analysis of the Response of Base-Isolated SDOF Systems Constrained by Two Deformable Devices Under Seismic Excitations
No full textSeismic isolation is a passive control methodology widely used for the mitigation of the dynamic response of structures. However, significant seismic actions can induce considerable displacements in these structures, which in turn can cause damage to the isolation system or impacts against adjacent structures in the event of insufficient seismic gap.
A technique to prevent the occurrence of these negative phenomena can be obtained by interposing dissipative and deformable devices, called bumpers between the structure and the adjacent ones. Therefore, in this work the response, from a numerical point of view, of single-degree-of-freedom, SDOF, system isolated at the base subjected to known seismic actions and whose displacements are limited by bumpers has been studied. The system was designed according to an optimality relationship that relates the mechanical parameters of the isolator with those of the bumper, and is independent of the gap.
The SDOF system investigated is representative of a typical base-isolated structure, therefore, the system exhibits a damping ratio ξ = 10% and a system natural period Tn = 3.00s. The dynamic response of the system obtained by impact with an appropriately designed bumper is compared with the response of the same system obtained without the impact and with an impact whit rigid bumper. Finally, the influence of the stiffness of the bumper, designed with the optimality relationship, and the gap is evaluated.
The results show a considerable reduction in displacements compared to a modest increase in accelerations with respect to the no-impact condition, evidence that highlights the effectiveness of the optimality relationship used
Understanding Emergent Urbanism The Case of Tirana, Albania
No full texthe canonical architectural studies have handed us the idea that city is the result of a series of top-down procedures - and related documentary materials - which depict a rigid and hardly con- testable direction of development of our urban tissues. Looking at the different regulatory plans throughout which contempo- rary cities have been developed, it is quite difficult to perceive the human component of such spaces, leaving us to wander in a series of linear relations where the final form is predetermined by external judging eyes. But if we look at the city as a living being, characterized from the different complex entities that in- habit it and interact among each others, is it possible to bring the real city - or as the author underlines, the city of everyday life - close to conventional planning? [...
GIS data for Bracciano Smart Lake Initiatives
No full textGis Data relative to lake of bracciano ( RM) supporting Bracciano SmartLake initiative managed by Emanuele Perugini & Guido Tocco.
Author: Alfonso Crisci IBIMET CNR and & Massimo Perna Consorzio LaMMA
Data: Perimetral ISTAT administrative boundaries of Bracciano's Area, Bracciano Lake Catchment basin and 5 meter DEM of area ( digital elevation model) obtained troughout TIN interpolation by using elevation data ( CTR5K) retrieved from OpenData Lazio WEB Portal
Evaluación de macro, meso y microplásticos en mejillones Perna perna silvestres y cultivados (Mollusca: Bivalvia)
No full textMicroplastics have drawn significant interest within the scientific community due to their environmental impact. In marine ecosystems, these particles readily absorb toxic substances and, because of their microscopic size, are consumed by various organisms that are eventually incorporated into the human food chain. Several studies emphasize this unintentional transfer to human foods. To investigate microplastic contamination in Perna perna mussels sold commercially, wild (harvested from the coastal environment) and farm-raised (cultivated) samples were purchased from local markets in Niterói, RJ, Brazil. One kilogram of each type was processed through digestion in an NaOH 5% solution and then analysed to assess the quantity and types of microplastics present. Both wild and cultivated mussels contained microplastic film and fibres, with 145 items (0.145 items g⁻¹) identified in wild specimens [67% nylon (polyamide) and 33% polyethylene] and 120 items (0.120 items g⁻¹) in cultivated mussels (100% polyamide). The microplastics varied in size, ranging from 0.45 μm to 28 mm, with the most common colours being black, blue and transparent. These findings highlight the potential risks of consuming these organisms regardless of their source and the need for further investigation into the effects of these pollutants on human health.Los microplásticos han despertado un gran interés dentro de la comunidad científica debido a su impacto medioambiental. En los ecosistemas marinos, estas partículas absorben fácilmente sustancias tóxicas y, debido a su tamaño microscópico, son consumidas por diversos organismos que eventualmente se incorporan a la cadena alimentaria humana. Varios estudios enfatizan esta transferencia involuntaria a los alimentos humanos. Para investigar la contaminación por microplásticos en los mejillones Perna perna vendidos comercialmente, se compraron muestras silvestres (cosechadas del ambiente costero) y criadas en granjas (cultivadas) en los mercados locales de Niterói, RJ, Brasil. Se procesó un kilogramo de cada tipo mediante digestión en una solución de NaOH al 5% y luego se analizó para evaluar la cantidad y los tipos de microplásticos presentes. Tanto los mejillones silvestres como los cultivados contenían películas y fibras microplásticas, con 145 artículos (0,145 artículos g⁻¹) identificados en especímenes silvestres (67% nailon (PA) y 33% polietileno (PE)) y 120 artículos (0,120 artículos g⁻¹) en mejillones de cultivo (100% PA). Los microplásticos variaban en tamaño, desde 0,45 μm hasta 28 mm, siendo los colores más comunes el negro, el azul y el transparente. Estos hallazgos resaltan los riesgos potenciales de consumir estos organismos independientemente de su fuente y la necesidad de realizar más investigaciones sobre los efectos de estos contaminantes en la salud humana
Low hydrogen sulphide and chronic kidney disease: A dangerous liaison
No full textHydrogen sulphide, H(2)S, is a gaseous compound involved in a number of biological responses, e.g. blood pressure, vascular function and energy metabolism. In particular, H(2)S is able to lower blood pressure, protect from injury in models of ischaemia-reperfusion and induce a hypometabolic state. In chronic kidney disease (CKD), low plasma hydrogen sulphide levels have been established in humans and in animal models. The enzymes involved in its production are cystathionine β-synthase, cystathionine γ-lyase and 3-mercaptopyruvate sulphurtransferase. The mechanisms for H(2)S decrease in CKD are related to the reduced gene expression (demonstrated in uraemic patient blood cells) and decreased protein levels (in tissues such as liver, kidney, brain in a CKD rat model). In the present Nephrol Dial Transplant issue, in fact, Aminzadeh and Vaziri document that the alterations in this pathway complicate the uraemic state and are linked to CKD progression. They furnish a time frame in CKD and record enzyme tissue distribution. It remains to be established if low H(2)S is causally linked to CKD progression and if interventions aimed to restore the status quo ante are able to modify this picture.Hydrogen sulphide, H2S, is a gaseous compound involved in a number of biological responses, e.g. blood pressure, vascular function and energy metabolism. In particular, H2S is able to lower blood pressure, protect from injury in models of ischaemia-reperfusion and induce a hypometabolic state. In chronic kidney disease (CKD), low plasma hydrogen sulphide levels have been established in humans and in animal models. The enzymes involved in its production are cystathionine β-synthase, cystathionine γ-lyase and 3-mercaptopyruvate sulphurtransferase. The mechanisms for H2S decrease in CKD are related to the reduced gene expression (demonstrated in uraemic patient blood cells) and decreased protein levels (in tissues such as liver, kidney, brain in a CKD rat model). In the present Nephrol Dial Transplant issue, in fact, Aminzadeh and Vaziri document that the alterations in this pathway complicate the uraemic state and are linked to CKD progression. They furnish a time frame in CKD and record enzyme tissue distribution. It remains to be established if low H2S is causally linked to CKD progression and if interventions aimed to restore the status quo ante are able to modify this picture. © 2011 The Author
Street-level workers, managers and institutional tensions: a comparative ethnography of healthcare practices of in/exclusion in three Italian public organisations
No full textEste artículo está sujeto a una licencia CC BY 4.0Public organisations are fundamental actors in migrant incorporation processes, as they are in charge of assessing migrants’ entitlement and providing access to welfare services. While a lot has been written on the individual determinants of street-level decisions, the role of organisational and institutional factors in shaping implementation practices has received little attention so far. By linking the street-level bureaucracy approach and the neo-institutionalist perspective in organisational analysis, this article investigates how public organisations mediate migrant incorporation processes in the field of healthcare. Drawing on a comparative ethnographic study of three public health organisations in an Italian region, the paper suggests that, in times of institutional tensions, managers’ priorities and framings of the issue, the ways they respond to decision-makers’ goals and allocate resources for implementing them, orient - and lead to variation in - street-level healthcare practices of in/exclusion for migrants with irregular status.The author acknowledges support of the publication fee by Erasmus University and the CSIC Open Access Publication Support Initiative through its Unit of Information Resources for Research (URICI)Peer reviewe
Aortic dilatation in patients with bicuspid aortic valve
No full textThe association of a bicuspid aortic valve (BAV) with abnormalities of the proximal thoracic aorta, including dilatation, aneurysm and dissection, has been previously described, leading to the hypothesis of a common underlying developmental defect involving the aortic valve and the aortic wall. Consequently, any patient with BAV should receive a careful assessment not only of the valve function, but also of the aortic root and the ascending aorta. Dilatation of the proximal thoracic aorta is a common finding in patients with BAV and is believed to be related to aortic rupture and dissection. Because progressive dilatation can occur, careful long-term surveillance of the aortic dimensions is required. Prophylactic surgical repair of the dilated aorta should be recommended more aggressively for patients with BAV than for those with a tricuspid aortic valve. However, the optimal timing of aortic surgery in BAV patients remains uncertain because of the limited data available on the natural history of asymptomatic aortic dilatation. © 2006 Italian Federation of Cardiology
MPM hydro-mechanical modelling of flows impacting rigid walls
No full textThe study on impact mechanisms of flow-like landslides against structures is still an open issue in the scientific literature. Many researchers have employed so far either experiments or numerical methods, but the evaluation of the impact forces on mitigation obstacles remains difficult especially if the solid-fluid interaction within the flow is considered. This study shows how advanced numerical tools, such as Material Point Method, may be used in simulating those complex processes. The simulations are carried out for two well documented laboratory tests: a dry granular flow impacting a rigid wall under different geometries and testing conditions in a small-scaled flume and a saturated flow with complex propagation pattern in a centrifuge apparatus. The numerical modelling is validated against the observations and then used to explore the response of different flows impacting rigid structures in other conditions than in the experiments. The soil-fluid interaction influences the type of impact mechanism, the kinematics of the flow, and the space-time trend of the impact pressure against the structure.The presentation of the authors' names and (or) special characters in the title of the pdf file of the accepted manuscript may differ slightly from what is displayed on the item page. The information in the pdf file of the accepted manuscript reflects the original submission by the author
How rapidly do neutron stars spin at birth? Constaints from archival X-ray observations of extragalactic supernovae
No full textTraditionally, studies aimed at inferring the distribution of birth periods of neutron stars are based on radio surveys. Here we propose an independent method to constrain the pulsar spin periods at birth based on their X-ray luminosities. In particular, the observed luminosity distribution of supernovae (SNe) poses a constraint on the initial rotational energy of the embedded pulsars, via the correlation found for radio pulsars, and under the assumption that this relation continues to hold beyond the observed range. We have extracted X-ray luminosities (or limits) for a large sample of historical SNe observed with Chandra, XMM and Swift, which have been firmly classified as core-collapse SNe. We have then compared these observational limits with the results of Monte Carlo simulations of the pulsar X-ray luminosity distribution for a range of values of the birth parameters. We find that a pulsar population dominated by millisecond periods at birth is ruled out by the data
Paleokarstic fills in Iglesiente (Sardinia Italy) sedimentary processes and age
No full textThe Mount S. Giovanni caves developed mostly during Paleozoic and Mesozoic in Cambrian limestones (Gonnesa formation) locally mineralized. Their infilling, of economic interest, took place during or nearly after the volcanic Cenozoic phase. The material derives from the removal of important pedogenetic cover, with episodes of clays masses redeposition and phases of wall collapses and of concretioning. -from Author
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