1,720,964 research outputs found
Accidents in nuclear-powered submarines and their effect on environmental marine pollution
No full textSince 1953, hundreds of nuclear-powered submarines (NPS) have been produced all over the world. Nowadays, about 160 nuclear submarines are in operation. In particular, USSR (then Russia) built 248 NPS between in the last 50 years. Most of them are now not operating anymore and have been dismantled only partially. Nowadays, Russia and USA have 75 and 52 operating NPS, while UK has 16, France has 10, and China has 6. Naval reactors have been in most cases pressurised water types, which differ from commercial reactors producing electricity (PWR) in that: - they deliver a lot of power from a very small volume and therefore run on highly-enriched uranium (>20% U-235, originally 93% but apparently now 20-25% in western vessels, and up to 45% in later Russian ones). This nuclear material has also proliferation problems. - the fuel is not UO2 but a U-Zr or U-Al alloy or a metal-ceramic. - they have long core lives, so that refuelling is needed only after 10 or more years, and new cores are designed to last 50 years in carriers and 30-40 years in submarines Decommissioning nuclear-powered submarines has become a major task for US and Russian navies. After defuelling, normal practice is to cut the reactor section from the vessel for disposal in shallow land burial as low-level waste. In Russia the whole vessels, or the sealed reactor sections, sometimes remain stored afloat indefinitely. Environmental consequences of such procedures may be very dangerous. Incidents and emergencies in atomic submarine fleet of USSR / RUSSIA have been many during their 50 years operational period of NPS: twelve nuclear and more 100 radiation emergencies have taken place. A nuclear emergency is such kind of emergency that concerns with the damage of fuel elements exceeding the established limits of safe operation, and/or irradiation of staff exceeding the permissible level for normal operation, caused by violation of control and managing of a chain nuclear reaction of fission in the reactor core, creation of a critical mass during reload, transportation and storage of fuel elements, or violation of heat elimination from fuel elements. Most of the emergencies were accompanied by serious radiological and ecological consequences. A relatively frequent event is the release of radioactive pollutants to the marine environment. In the Mediterranean sea, the effects of environmental marine pollution due to the presence of nuclear submarines has been recently studied. In particular, the most recent studies originated from the accident to the nuclear submarine "Hartford" that took place in 2003 close to the "La Maddalena" submarines base in Sardinia island (Italy). However it is not demonstrated that environmental release took place during the accident, findings about the presence of plutonium traces in certain types of algae close to the site have put into evidence the presence of artificial radioactive pollutants in that marine environment, a natural area of great ecological importance, designated by the Italian government as a natural marine park
Radon Flux Variations as Earthquake Precursors
No full textScientific research leading to the successful prediction of large earthquakes, sufficiently in advance, has great significance to mankind. Unfortunately, to this date, no reliable method has been developed for the successful application of earthquake prediction based on a geological scale, when applied to a human scale; the latter requires precise timing, location and intensity, factors not easily defined geologically. Major, erratic changes in Radon concentration have been observed in many earthquake-prone zones a few months/days before, during and after a large earthquake. It is tempting to consider a sudden erratic fluctuation in Radon concentration as a potential signal for an earthquake. Here, a refinement of the Radon precursor method is proposed, based on results from a network of twelve multiple, synchronous underground monitoring station
Nuclear Powered Submarines as Hazards For The Marine Environment
No full textHundreds of nuclear-powered submarines (NPS) have been manufactured since 1953; some 160 are still in operation. Decommissioning NPS is a major, delicate and costly task. There have been many incidents with NPS during their 50 years operational period: Most of these emergencies resulted in serious radiological and ecological consequences. In the Mediterranean, the effects of marine pollution due to NPS have been under recent investigation following the October 2003 accident to the US nuclear submarine Hartford in Sardinia (Italy). Preliminary studies indicated that no apparent environmental release had taken place as a direct result of the accident. However, further analyses detected traces of Pu-239 in several of the algal species, indicative of anthropogenic pollutants. Furthermore, several samples showed concentrations of radially distributed alpha tracks (forming "hot spots") emanating from micron-sized point sources. The concentrated, extremely localized occurrence of these nuclides cannot be explained in terms of left-over worldwide nuclear pollution. A local source seems more plausible. Our ongoing sampling programme has revealed that: some of the high alpha/hot spot levels measured in February 2004 have decreased markedly during subsequent months, others have decreased only slightly, and others still have remained unchanged: a clear indication that different nuclides are present. We are now analyzing 2005 sample
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
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
- …
