1,721,241 research outputs found
An Aerial Gamma Ray Survey of Torness Nuclear Power Station on 27-30 March 1994
Full text link<p>An aerial gamma-ray survey of the environment of Torness Nuclear Power Station was commissioned by Scottish Nuclear Limited, and conducted by the Scottish Universities Research and Reactor Centre. The area surveyed encloses a 31km square, with Torness Nuclear Power Station at the centre, flown with a line spacing of 500m. A secondary area, in closer proximity to the nuclear site, was flown with 250m spacing.</p>
<p>Over 6000 gamma ray spectra were recorded with a high volume spectrometer operated from a helicopter over a three day period in March 1994. Spectral data were recorded together with satellite navigation (GPS) and radar altimetry data. The results provide a comprehensive record of the radiation environment around Torness and have been used to map the distribution of natural and man-made radionuclides, forming a baseline to enable future environmental changes may be assessed.</p>
<p>The natural radionuclides 40K, 214Bi and 208Tl are highly correlated with each other and show a distribution which reflects both the underlying geological and geomorphological features of the area. The main structural boundaries of the Dunbar-Gifford and Lammermuir faults can be partly discerned in the maps, as can some igneous intrusions. Areas with peat or alluvium cover appear as negative features in the radiometric maps.</p>
<p>Radiocaesium 137Cs levels range from below 4 kBq m-2 to over 20 kBq m-2. Upland areas near Coldingham Common, Black Castle Hill and Dunbar Common show the highest values, similar in deposition pattern and level to Chernobyl activity observed in the West of Scotland and elsewhere. Published national maps derived from meteorological and ground sampling data predicted much lower levels for these locations. However core samples taken after the survey have confirmed the presence of the activity, and the attribution to Chernobyl. This finding demonstrates both the effectiveness of the method for rapid location of radioactive deposition, and the need for baseline studies to determine present levels. Count rates from a spectral window corresponding to 60Co were also mapped. The results are close to detection limits and show a slight correlation with natural sources. Therefore they are more probably due to residuals remaining after separation of spectral interferences than to low level 60Co contamination.</p>
<p>Gamma ray dose rates range from approximately 0.1 to 0.6 mGy a-1 with a mean value of 0.34 mGy a-1, and are derived mainly from natural sources. Ground level measurements were taken at nine district monitoring points within the area using a 3x3" NaI spectrometer and a survey meter (Series 6/80) used routinely by SNL. Both ground based data sets were in good agreement with each other and with the aerial survey after accounting for instrumental and cosmic ray background contributions.</p>
<p>There is no evidence that Torness Power Station has affected the surrounding radiation environment, within the operational and sensitivity limits of the aerial survey.</p>
<p>The longer term impact of the site can be assessed by future surveys. Moreover under emergency conditions it would be possible to utilise this method for rapid mapping of the area on a timescale which cannot be matched using alternative approaches. </p>
An Airborne Gamma Ray Survey of Parts of SW Scotland in February 1993. Final Report
Full text linkAn airborne gamma ray survey was conducted for the Scottish Office Environment Department of coastal and inland parts of SW Scotland to define existing background levels, to locate features worthy of further attention, and to demonstrate the emergency response capabilities of radiometric methods. Coastal areas were surveyed with 500 m line spacing. Inland areas were specified to 2 km line spacing, however it was possible to achieve 1 km line spacing in the majority of the inland zone.
Fieldwork was conducted between the 1st and 16th February 1993. A total of over 17,000 gamma ray spectra were recorded, using a 16 litre NaI spectrometer mounted in a helicopter flying at 50-75m ground clearance and 120kph. A total area of 3650 km2 was surveyed in 41.6 flying hours, from roughly 4370 line kilometres. The data were reduced in the field using standard SURRC procedures for background subtraction, stripping of spectral interferences, altitude correction, and calibration. Preliminary maps of the distribution of 137Cs, 40K, 214Bi, 208Tl, and estimated ground level gamma dose rate were produced during the fieldwork period using working calibration values derived from previous surveys. A set of core samples was collected from Wigtown Merse, Longbridgemuir and Caerlaverock merse for calibration purposes, and aerial observations were performed at these sites.
Further soil sampling and ground level in-situ gamma spectrometry was performed in the summer of 1993 to investigate the applicability of the calibration to a range of upland soil types and topographical environments. These locations received peak deposition from the Chernobyl accident, are vulnerable to wet deposition, and are difficult to monitor rapidly using ground based methods. A total of 76 soil cores, subdivided into 168 separate samples was thus collected for high resolution gamma spectrometry in the laboratory. This was conducted from April to November 1993.
For the terrestrial sites the aerial survey estimates based on the working calibration, were in good agreement with both in-situ gamma spectrometry and the results of core analysis. This validates the preliminary maps in these contexts, and confirms that a general calibration is sufficient for fallout mapping under emergency response conditions. On coastal salt marsh sites (merse), where aged deposits of Sellafield derived activity have accumulated, subsurface activity profiles for 137Cs and 241Am and the presence of superficial levels of 134Cs were observed from the soil cores. Similar features have been observed in previous surveys. In these cases the effects of source burial must be taken into account to avoid underestimation of activity levels by both ground-based and aerial gamma spectrometry. A separate set of detailed maps for the principal merse sites was therefore prepared using a calibration factor derived from the soil cores from this context. There are prospects for developing spectral analysis procedures to account for source depth in aerial surveys. Source burial on the merse also has implications for sampling techniques, and for dose rate measurement, which would merit further consideration.
The radiometric maps show clearly the distributions of each individual nuclide and indicate the contribution which individual localised features make to the overall gamma ray dose rate. Naturally occurring nuclides reflect the underlying geological and geomorphological contexts of the landscape. The main granite intrusions, most notably at Cairnsmore of Fleet, the Loch Doon Granodiorite, Glencairn of Carsphairn, the Dalbeattie granite, and Criffel Pluton are readily visible in 40K, 214Bi and 208Tl maps, and control their local radiation environments. A number of areas of enhanced 214Bi, which may reflect radon potential, were noted. A transient radon associated 214Bi signal was observed on the west of the Wigtown peninsular during the survey. Examination of spectral data in the vicinity of Dundrennan has confirmed that there is no evidence of widespread terrestrial contamination arising from the use of depleted uranium projectiles on the range.
The 137Cs map indicates the environmental distribution of this nuclide in considerable detail. Levels of 137Cs range from approximately 2 kBq m-2, a level consistent with global weapons’ testing fallout, from 2-40kBq m-2 on terrestrial sites affected by deposition from the Chernobyl accident, and from 40 kBq m-2 to over 200 kBq m-2 on tide washed pastures which have accumulated marine sediments from the Irish Sea. All three levels are represented within the survey zone, in a manner which is consistent with the findings of previous aerial surveys in adjacent areas, and with ground based studies.
The main Chernobyl deposition in Dumfries and Galloway appears to have occurred between an area just east of the Nith, and Glenluce. The northern limit has not yet been defined, and there may be grounds for considering extension of the northern and particularly eastern limits of the inland survey zone. Within the survey zone the deposition pattern is complex, including both upland and lowland components. The plume trajectories for deposition inferred from these observations are oriented northwards rather than in the NW directions predicted by meteorological derived estimates. This may explain the contradiction between results from the Central Highlands and the estimated fallout patterns. The data presented here both add to previous knowledge, and serve as a baseline against which any future changes can be measured.
The survey provides systematic coverage of the sedimentary and terrestrial coastal system for the first time, and has identified a number of merse sites which have accumulated radioactivity from past marine discharges from Sellafield, and which are not routinely monitored under existing Scottish Office arrangements. Some of these locations are extensive and fall within SSI’s; furthermore they are key sites for studying future deposition trends. It would seem prudent to review radiological assessments in the light of this work to ensure that the patterns of occupancy and sensitive ecologies of the merse are taken fully into account.
The emergency response potential of aerial radiometrics has been clearly demonstrated in this project. It provides the only practical means of providing comprehensive environmental measurements of remote and upland landscapes on a short time scale, with an effective area sampling density some 106-107 times greater than soil sampling. Results are compatible with ground based approaches, and could focus ground based efforts effectively under emergency conditions. Modern approaches to data recording and analysis are able to produce maps during the survey period. National baseline mapping in Scotland, at 1 km resolution, would require less than 800 flying hours; 20 km line spacing would take roughly 40 hours of flight time. A long term programme of high resolution national baseline mapping, coupled to an emergency response standby arrangement, would provide an extremely cost effective way of preserving the capability developed since the Chernobyl accident, while producing high quality environmental data for research purpos
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
- …
