1,722,108 research outputs found
On the relationship between the planetary radius and the equilibrium temperature for transiting exoplanets
No full textScaling laws have always played an important role in astronomy. They can give a general qualitative overview of common behaviors of many astrophysical objects, helping to understand the occurring physical processes. In the context of exoplanets, we study the possible correlation between (i) the planetary radius and the equilibrium temperature, Rp - Teq, and (ii) the planetary radius and the parent-star metallicity, Rp - [Fe/H]. We considered a sample of transiting planets, for which their mass radius and equilibrium temperature are accurately determined. While we do not see any notable evidence of a correlation between Rp and [Fe/H], the existence of a relationship between Rp and Teq is almost clear. We sub-divided our sample in different groups, based on their mass, and performed a least-squares regression of Rp on Teq for each sub-sample of planets. We found that the Rp - Teq relation results very tight for two groups of intermediate-massive gas planets (i.e. for Mp in the range between 0.5-1.0MJup and 1.0-1.5MJup) and that the slope of the best-fitting line gradually increases from the group of very massive to those of less massive planets, up to reverse in the Neptunian-Super-Earth regime, which has a negative correlation
Gravitational lensing by the supermassive black hole in the center of the Andromeda Galaxy
No full textWe examine the possibility of observing gravitational lensing in the weak deflection regime by the supermassive black hole in the center of the galaxy M31. This black hole is significantly more massive than the black hole in the center of our Galaxy qualifying itself as a more effective lens. However, it is also more distant and the candidate stellar sources appear consequently fainter. As potential sources we separately consider stars belonging to the bulge, to the disk, to the triple nucleus formed by P1+P2 and by the recently discovered inner cluster P3. We calculate the number of simultaneously lensed stars at a given time as a function of the threshold magnitude required for the secondary image. For observations in the K-band we find 1.4 expected stars having secondary images brighter than K=24 and 182 brighter than K=30. For observations in the V-band we expect 1.3 secondary images brighter than V=27 and 271 brighter than V=33. The bulge stars have the highest chance to be lensed by the supermassive black hole, whereas the disk and the composite nucleus stars contribute by 10% each. The typical angular separation of the secondary images from the black hole range from 1 mas to 0.1''. For each population we also show the distribution of the lensed sources as a function of their distance and absolute magnitude, the expected angular positions and velocities of the generated secondary images, the rate and the typical duration of the lensing events
Conventional, Organic and Polycultural Farming Practices: Material Intensity of Italian Crops and Foodstuffs
No full textFood system sustainability is a major issue of concern for policy makers. Feeding an increasing world population without compromising the endowment of natural resources or worsening the environmental crisis is, indeed, a major challenge. The need to boost sustainable and productive farming systems and enhance resource efficiency has been acknowledged by European Union policy in its 2020 Strategy. This study assesses the impact of some Italian foodstuffs and agricultural products in terms of material requirement, using the Material Input Per Service unit (MIPS) indicator. The conventional, organic and post-organic agricultural practice called Ma-Pi polyculture is investigated. Results show that, in spite of higher yields obtained by conventional agriculture, material efficiency of organic crops and foodstuffs is generally higher. Moreover, a drastic enhancement of material efficiency is achievable using agronomic practices that minimize the employment of external inputs. As a tool for evaluating the environmental sustainability of agricultural products, MIPS allows focusing on a priority policy area, i.e., resource efficiency, which could be easily employed for driving agricultural systems towards a sustainable intensification. Data quality and availability of Material Input (MI) factors remains, however, a constraining issue for the applicability of the indicator
Microlensing towards the LMC revisited by adopting a non Gaussian velocity distribution for the sources
No full textAims: We discuss whether the Gaussian is a reasonable approximation of the velocity distribution of stellar systems that are not spherically distributed. <BR />Methods: By using a non-Gaussian velocity distribution to describe the sources in the Large Magellanic Cloud (LMC), we reinvestigate the expected microlensing parameters of a lens population isotropically distributed either in the Milky Way halo or in the LMC (self lensing). We compare our estimates with the experimental results of the MACHO collaboration. <BR />Results: An interesting result that emerges from our analysis is that, moving from the Gaussian to the non-Gaussian case, we do not observe any change in the form of the distribution curves describing the rate of microlensing events for lenses in the Galactic halo. The corresponding expected timescales and number of expected events also do not vary. Conversely, with respect to the self-lensing case, we observe a moderate increase in the rate and number of expected events. We conclude that the error in the estimate of the most likely value for the MACHO mass and the Galactic halo fraction in form of MACHOs, calculated with a Gaussian velocity distribution for the LMC sources, is not higher than 2%
Black flies (Diptera, Simuliidae) as ecological indicators of stream ecosystem health in an urbanizing area (Rome, Italy)
No full textIntroduction. The effectiveness of Simuliidae (Diptera. Nematocera) as indicators of stream health was tested in the urbanizing area of Rome, Central Italy. Methods. 108 sampling sites were investigated in the spring to acquire data on environmental variables and black fly species. Results and discussion. The comparison of sampling and literature data highlighted the disappearance of some species (Simulium reptans, S. vernum, S. liriense), possibly due to water pollution and land use changes. Correspondence analysis confirms altitude as the main factor influencing black fly species' distribution. However, water quality becomes predominant when considering exclusively plain sites: "ornatum" and "equinum" species groups show the greatest tolerance to chemical pollution. The high course of the Aniene river and its tributaries were sampled bimonthly, confirming the spatial- Temporal black fly successions previously observed in central Apennines. The results also indicate that S. omatum may supplant all other species in areas where the rural use is substituted by urban landscape. Conclusion. In conclusion, black flies can be considered good environmental indicators to assess ecological health of both watercourses and surrounding landscapes
Regolazione della potenza per sistemi eolici a passo fisso mediante gestione integrata della turbina e del generatore
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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
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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