Leaf closures of Riemannian foliations: a survey on topological and geometric aspects of Killing foliations

A smooth foliation is Riemannian when its leaves are locally equidistant. The closures of the leaves of a Riemannian foliation on a simply connected manifold, or more generally of a Killing foliation, are described by flows of transverse Killing vector fields. This offers significant technical advantages in the study of this class of foliations, which nonetheless includes other important classes, such as those given by the orbits of isometric Lie group actions. Aiming at a broad audience, in this survey we introduce Killing foliations from the very basics, starting with a brief revision of the main objects appearing in this theory, such as pseudogroups, sheaves, holonomy and basic cohomology. We then review Molino's structural theory for Riemannian foliations and present its transverse counterpart in the theory of complete pseudogroups of isometries, emphasizing the connections between these topics. We also survey some classical results and recent developments in the theory of Killing foliations. Finally, we review some topics in the theory of singular Riemannian foliations and discuss singular Killing foliations, also proposing a new approach to them via holonomy metric pseudogroups and the theory of blow-ups, which possibly opens up a new area of interest.Comment: 45 pages, 9 figures. Small corrections and addition

Thermal hydraulic analysis of Alfred bayonet tube steam generator

The paper analyzes the performance of ALFRED steam generator from the thermal-hydraulic point of view highlighting the effect of some design features. The parameters object of the study are the regenerative heat transfer, the dimension of the inner tube and the length of the bayonet. The system code RELAP5-3D/2.4.2 has been chosen for the analysis. Sensitivities analysis allowed the determination of the different design parameters influence, here briefly summarized. The increase of regenerative heat transfer affects the efficiency of the steam generator through a degradation of the outlet steam quality: the number of bayonet tubes required to remove the nominal power increases with the increase of the global heat transfer coefficient of the inner tube. A higher inner diameter results in a larger surface area for the regenerative heat transfer and in a higher heat transfer coefficient in the annular region because of the reduction of the cross section. The result is an improvement of the performances of the steam generator thanks to the dimension reduction of the annular gap. Finally, if the height of the bayonet tube is reduced by 1 meter, the number of bayonet tubes required to remove the nominal power increases up to 20%

Evaluación de los efectos del herbicida glifosato en el pez Prochilodus lineatus a través del test de aberración cromosómica.

The widespread use of glyphosate has been subject of numerous controversies since the prolonged exposure to low concentrations of this substance could lead to toxic effects. Then, the appearance of pathologies in medium and long term progressively will increase because of the exposure of people and animals through the consumption of contaminated water or food. Considering this, the aim of this study was to evaluate the potential mutagenicity of glyphosate herbicide in fish (Prochilodus lineatus) using the test of chromosome aberrations. The fish were exposed to 0,1 ug/l of glyphosate for 70 days. After this period, samples of the anterior portion of the kidney were extracted for chromosomal aberrations (CAs) analysis. A greater number of CAs (gaps, breaks, stickiness, endomitosis, fragmentations, and pulverizations) were observed in individuals exposed to the pesticide. The statistical analysis of the data showed significant differences between the control and treated groups. In this way, the results suggested the existence of a genetic response as a consequence of pesticide exposure in fish.El uso generalizado del glifosato ha sido objeto de numerosas controversias, ya que la exposición prolongada a bajas concentraciones de este agroquímico podría dar lugar a efectos no deseados o nocivos. Ello favorecería la aparición de patologías en el mediano y largo plazo, lo que aumenta progresivamente el riesgo de exposición en seres humanos y animales, a través del consumo de agua y alimentos contaminados. Teniendo en cuenta esta premisa, el objetivo del trabajo fue evaluar el posible efecto mutagénico del herbicida a través de la prueba de aberraciones cromosómicas en peces de la especie Prochilodus lineatus. Los peces fueron expuestos a 0,1 ug/l de glifosato durante 70 días. Después de este período una muestra de la porción anterior del riñón fue extraída para el análisis de aberraciones cromosómicas (AC). En los individuos expuestos al pesticida se registró mayor número de AC. El análisis estadístico de los datos mostró diferencias significativas entre los grupos control y tratado. Los resultados sugieren la existencia de una respuesta genética causada por la exposición y el contacto de los especímenes con el herbicida

Questões ambientais : em busca de perspectivas para a compreensão da complexidade

A urgência de discussões sobre as questões ambientais no ambiente escolar tem motivado muitas propostas, com diversidade de temas e enfoques. Compartilhando a perspectiva de uma educação ambiental crítica, investiga-se, nesse trabalho, a preocupação com enfoques que privilegiem a ciência como conhecimento aberto, acentuando as questões da complexidade. Para isso, são discutidas algumas ênfases, do ponto de vista do conhecimento físico, a serem privilegiadas. Essas ênfases se traduzem por abordagens com predominância de análises dinâmicas de processos, aspectos entrópicos inerentes às transformações, dimensões e considerações temporais dos fenômenos, além da diversidade de inter-relações entre fenômenos e níveis hierárquicos. Para concretizar tais discussões são utilizados exemplos relacionados ao ciclo da água e às questões relacionadas aos seus usos

Post-Test Analysis of SIRIO Facility Data by System Thermal-Hydraulic Codes for LFR Application

As part of the R&D activities supporting Generation IV innovative nuclear technologies, an experimental facility named SIRIO has been designed and constructed to test and validate a new concept of Decay Heat Removal system at a relevant scale for Gen-IV Lead-cooled Fast Reactor (LFR), in particular for the DEMO LFR ALFRED. This innovative system provides a safe long-term cooling condition of the reactor coolant system with no need of external action or energy supply, and claims capability to passively control the heat removed by the ultimate heat sink thanks to non-condensable gases. This new concept is attractive for LFRs because it can prevent the early freezing of lead, which is a concern after the proper intervention of the DHRs. In addition, for water cooled reactors, passive control of heat transfer capability reduces the thermal stresses on the materials, smoothing the fluid internal thermal gradients and the depressurization rate. In this work, SIRIO facility is described, along with the numerical model developed using the RELAP5/Mod3.3 thermal-hydraulic system code. Part of the efforts in the experimental campaign within the EU project PIACE aims at reproducing the conditions of ALFRED in Stage 2 configuration (i.e., loop and gas pressure set at 180 and 110 bar, respectively). The experimental outcomes are compared with those obtained with RELAP5 code to validate the numerical tool for LFRs applications and to assess the code capability in reproducing two-phase natural circulation conditions with noncondensable gases and the system response during accidental scenarios

Periodontitis como factor de riesgo de enfermedades cardiovasculares

Las enfermedades cardiovasculares representan una de las principales causas de muerte en las sociedades desarrolladas. Estas enfermedades no sólo son importantes por la mortalidad que generan, sino por la gran cantidad de individuos afectados y en tratamiento que han de soportar los sistemas de salud de los distintos países. De ahí que la detección precoz de los factores de riesgo conducentes a desencadenar estas enfermedades haya sido vista como el mecanismo más eficaz para prevenirlas. En los últimos tiempos se viene relacionando de una manera más o menos directa a la patología periodontal con el padecimiento de enfermedades cardiovasculares. Este hecho podría tener una gran relevancia clínica y probablemente epidemiológica, debido a la considerable prevalencia actual de las enfermedades periodontales. En la presente revisión se analizan los factores clínicos y fisiopatológicos que dan soporte científico a esta asociación, llegándose a la conclusión de que hacen falta más estudios, para tener la evidencia de que dicha asociación, representa un factor de riesgo determinante para el padecimiento de las enfermedades cardiovasculares.

Is physician assessment of alcohol consumption useful in predicting risk of severe liver disease among people with HIV and HIV/HCV co-infection?

Background Alcohol consumption is a known risk factor for liver disease in HIV-infected populations. Therefore, knowledge of alcohol consumption behaviour and risk of disease progression associated with hazardous drinking are important in the overall management of HIV disease. We aimed at assessing the usefulness of routine data collected on alcohol consumption in predicting risk of severe liver disease (SLD) among people living with HIV (PLWHIV) with or without hepatitis C infection seen for routine clinical care in Italy. Methods We included PLWHIV from two observational cohorts in Italy (ICONA and HepaICONA). Alcohol consumption was assessed by physician interview and categorized according to the National Institute for Food and Nutrition Italian guidelines into four categories: abstainer; moderate; hazardous and unknown. SLD was defined as presence of FIB4 > 3.25 or a clinical diagnosis of liver disease or liver-related death. Cox regression analysis was used to evaluate the association between level of alcohol consumption at baseline and risk of SLD. Results Among 9542 included PLWHIV the distribution of alcohol consumption categories was: abstainers 3422 (36%), moderate drinkers 2279 (23%), hazardous drinkers 637 (7%) and unknown 3204 (34%). Compared to moderate drinkers, hazardous drinking was associated with higher risk of SLD (adjusted hazard ratio, aHR = 1.45; 95% CI: 1.03–2.03). After additionally controlling for mode of HIV transmission, HCV infection and smoking, the association was attenuated (aHR = 1.32; 95% CI: 0.94–1.85). There was no evidence that the association was stronger when restricting to the HIV/HCV co-infected population. Conclusions Using a brief physician interview, we found evidence for an association between hazardous alcohol consumption and subsequent risk of SLD among PLWHIV, but this was not independent of HIV mode of transmission, HCV-infection and smoking. More efforts should be made to improve quality and validity of data on alcohol consumption in cohorts of HIV/HCV-infected individuals