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Raccolta dati sulla presenza di radionuclidi naturali ed artificiali nell'area Bosco Negri - 2: Risultati delle indagini Radiometiche su campioni delle indagini, serie 238U e 232Th; 40K e 137Cs
No full textIn the second part of this research we have studied the natural and artifi cial radioactivity in the soils of the Siro Negri forest.
The analysis with high resolution gamma spectrometry have allowed the determination of specific activity of the radionuclides of the two natural series of the Uranium (234Th, 234mPa, 214Pb and 214Bi) and of the Thorium (228Ac and 212Pb) from which we have calculated the specifi c activity of the 238U, in the fi rst case, and of the 232Th,
in the second case, at the different depth in the three sampling stations; also we have verifi ed the secular equilibrium,
demonstration that the soil profi le is undisturbed; specific activity of the 40K, an other primordial radionuclide; specific activity of the 137Cs, the only artifi cial radionuclide, introduced in the environment from the accident in the nuclear power reactor at Chernobyl, in the 1986.
The secular equilibrium for the Uranium series has been verifi ed through the calculation of some parameters (relationship of mean
activities of 214Bi and 234Th, correlation between 234Th – 214Pb and 234Th – 214Bi, presence of the peak at 1001 keV of the 234mPa). The mean activity for the gamma decay products (214Pb and 214Bi) is about 4.0÷6.0 Bq. In the third station, located in South West part of the forest (station C), we have found the inferior value, only 3.0 Bq, at 45 cm depth (layer S). The mean specifi c activity of the 238U are comprised between about 20 and 60 Bq kg-1 with more signifi cant variation in the south pedological profi le of the forest; moreover we have found that the distribution of the activity of 238U, in the forest soil’s, depend from the texture (in particular, from the percentage of clay and silt) and the cation exchange capacity values.
Also the secular equilibrium for the Thorium series have been verifi ed using the comparison of mean activities of the daughters, 228Ac and 212Pb (relationship and correlation coeffi cient); the decay products activity is comprised between 4,0÷6,0 Bq, with minimum
value about 3.0 Bq, in station C, at the depth of the S layer. The mean specifi c activity of 232Th (calculated from the activity of the
228Ac) is comprised between 30 and 50 Bq/kg for stations A, B and between 20 and 60 for the station C. Also the specific activity of this radioisotope depend of the chemical and physical characteristics of soil, in particular we have determined that depends from the distribution of clay and silt and from the cation exchange capacity values. Percentage of water in soil solution (humidity %) is other
important characteristic of soils that infl uences the specific activity of the 232Th.
The results of the 40K have been obtained using a characteristic peak of this radionuclide for gamma spectrometry (at 1460 keV
energy). The mean specifi c activity, of this radionuclide, is about 683 Bq kg-1 in the station A, 656 Bq kg-1 for the station B and 720 Bq/kg in the station C. Also, the migration and distribution of this radioisotope is infl uenced from the presence of river’s water and
for this reason the specifi c activity in the station located in the North East part of the forest (A) and in the South West part of the forest (C) is the highest. In the pedological profi le of the three stations the lowest concentration measured is 600 Bq kg-1 (at 70 cm depth, in the layer S, for the station B) and the highest is 900 Bq kg-1 (at 90 cm depth in station C). We have found that also the distribution of the 40K, in soil layer, is infl uenced from the humidity and cation exchange capacity. For this reason we assert that the distribution and migration of natural radionuclide (238U and his decay products, 232Th and his products and 40K) varies in function of two soils characteristics: the water content (humidity) and cation exchange capacity value, in the soil profi le.
The measurements of the activity for the 137Cs have been carried out using the characteristic gamma peak of this radionuclide, at 661,7 keV. The maximum of the activity for this radionuclide is localized in upper layer between 10 and 15 cm depth and the specifi c activity
in this layer is 22 Bq kg-1 for station A and about 17 Bq kg-1 for station B and C while the other depths the specifi c activity, in each stations, is less than 1 Bq kg-1.
It depends on the fact that in the superfi cial soil layers of the forest there’s the highest contents of organic matter (3%) and acid pH.
Caesium adsorption on soil and soil constituents is an ion exchange phenomenon that it can be modifi ed if the soil’s organic matter is associated with clay minerals. The acid reaction of soils is an important parameter to be observed: in fact, acid pH favours the
development of fungi, accumulators of 137Cs. Also, some species of fungi not only accumulate radiocaesium effi ciently but also have slow turnover rate for this element, thus forming the major rediocaesium pool in the soil
Presenza di radionuclidi naturali ed artificiali nell’area Bosco Negri - 1: Caratteristiche Chimico-Fisiche del suolo
Full text linkSiro Negri forest, extends for 11 ha on the Ticino river right side at 10 km from Pavia (North of Italy), it is the best example of the
ancient alluvial forest of the Po plain. It was declared a Fully Protected Nature Reserve in the 1967. In the fi rst part of this research have been studied the chemical and physical characteristics of soils collected in this site, for evaluating the relation between soils
properties and distribution of natural and artifi cial radionuclides in pedological profi le. This work is the fi rst step in investigating of
environmental radioactivity in this natural area. For this purpose samples of soil was collected in three different points and at different depth, inside this area, to investigate the vertical and horizontal migration of natural (the two series 238U, 232Th and 40K) and artificial (137Cs) radioisotopes in the soils profile.
Uranium and Thorium are found in the upper layer of the earth. They exist only as unstable, radioactive isotopes which undergo a long chain of radioactive decays to end fi nally with stable isotopes of the Pb (lead). Due to their short half – lives, these decay products
are present in the environment only in small quantities but their activity concentration can modify the environmental radioactivity. In addition, these radioactive products of decay of the two series 238U, 232Th and the radioisotopes 40K, 137Cs are carried from river and deposited into the forest soils.
In the fi rst area, located in the North East part of the forest (named station A), have been collected seven soil profi les at 10, 25, 40, 55, 70, 85 and 110 cm depth; in the second station, located in the central part of the forest (named station B), have been collected eight samples at 10, 25, 40, 55, 70, 85, 110 and 125 cm depth; in the third station, located in the South West part of the forest (named station C), have been collected eight samples at 15, 30,45, 60, 75, 90, 105 and 125 cm depth.
In this part of the work we show the results related to texture, density, humidity, pH, cationic exchange capacity, organic Carbon
and soils organic matter. For every analytical determination the soil samples were dried at 40°C and sieved at 2 mm. In the texture
determination soils are sieved in different sieves with automatic sieve (2 mm, 200 mm, 50 mm and 20 mm) and with Laser Diffraction System (particle size comprised between 0,2 and 44 mm). The texture of the soil describe the contents of sand, silt and clay in
pedological profi le. In this area there is sandy soils with greater percentage at different soil depth in the three stations (station A: 55 cm depth – 88% sand; station B: 70 cm depth – 96% sand; station C: 45cm depth – 94% sand); this depth have been named layer S.
Density are typical of inorganic components of the soil (2,4 and 2,9 g/cm3). Soil water content (Humidity percentage) is very small,
greater in superfi cial layer (station A: 1,6% at 10 cm depth; station B: 1,2% at 10 cm depth; station C: 1,4% at 15 cm depth) but small in profound pedological profi le. Minimum for this property correspond at layer S (station A: 0,4%; station B: 0,4%; station C: 0,2%).
Soil’s pH was determined potentiometrically in water and KCl 1M. Every investigated soil is acid in superfi cial layer (pH units:
4,4÷5) and moderately acid or neutral, at greater depth (pH units: 6÷7).
The Cation Exchange Capacity (CEC or CSC) is a very important parameter because the adsorption of some radionuclides on soils
and on clays particles is a cation exchange phenomenon. Greater CEC have been determined in superfi cial layer of the station A (27,3 cmol kg-1) more small, but the same order of magnitude, for the others two stations (station B: 23,7 cmol kg-1; station C: 22,6 cmol kg-1).
At the layer S depth the CEC is very low but it increased at greater depth (CEC of layer S – station A: 7,8 cmol kg-1; station B: 4,8 cmol kg-1; station C: 5,1 cmol kg-1).
The organic matter may make a signifi cant contribution to the CEC of the soil and it can have an indirect effect on radioisotopes
adsorption on clay minerals. The organic Carbon were measured using Walkley-Black method and the conversion factor used were
calculated like if 58% of the elemental composition of organic matter is constituted by organic Carbon. The organic matter amount in the pedological profile of the soil is elevated in the superficial part greater in station B but the same order of magnitude for station A and C (about 15 g kg-1 of organic Carbon and about 25 g kg-1of organic matter). Also, in all three stations, minimum value for this parameter correspond to layer S
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
La Certosa di Pavia: valutazione del degrado dei marmi della facciata e implicazioni per li studi di provenienza dei materiali.
No full textLa Certosa di Pavia è una magnifica struttura monastica, chiesa e monastero, costruita alla fine del Medioevo. Campioni di marmo bianco sono stati raccolti dalla facciata e sottoposti ad Analisi per Attivazione Neutronica per la determinazione di Ca e di elementi minori e in tracce.
Per determinare e verificare la provenienza dei marmi è stata utilizzata una banca-dati sulla composizione dei marmi bianchi delle principali cave del bacino del Mediterraneo, alcuni parametri basati sugli elementi delle terre rare (REE) e l'analisi statistica rmiltivariata. Nonostante l'alterazione della composizione, fortemente indotta dalle attività antropiche, i parametri delle terre rare (REE) e l'analisi discriminante forniscono una indicazione dì provenienza coincidente con quella tornita dai documenti storici
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
Ossidiana del Monte Arci: nuovi dati sulla composizione delle diverse fonti.
No full textLa caratterizzazione degli affioramenti di ossidiana nel Monte Arci (Sardegna, Italia) è quanto mai importante per la identificazione e classificazione di tutte le potenziali fonti. Ciò rende possibile, ai fini archeometrici, la attribuzione di provenienza dei manufatti di ossidiana ritrovati negli insediamenti preistorici. Nel Convegno Internazionale di Oristano-Pau del 2002 erano stati presentati i dati relativi alla composizione in elementi in traccia di alcuni campioni di ossidiana provenienti dalle tre aree SA, SB e SC. Al fine di avere una più ampia casistica di campioni analizzali e disporre di risultati maggiormente rappresentativi sotto il profilo statistico si è proceduto ad una nuova e più estesa campionatura presso gli affioramenti delle tre fonti note e nelle prossime aree di deposizione secondaria. Sono stati inoltre campionati blocchi di ossidiana ritrovali anche a notevole distanza dagli affioramenti primari, in terrazzi alluvionali antichi del territorio compreso nel Comune di San Nicolò Arridano (OR). La composizione in elementi in traccia è stata ottenuta mediante analisi per attivazione neutronica strumentale utilizzando il reattore nucleare di ricerca TRICA Mark II dell'Università di Pavia. I dati analitici dei nuovi campioni rientrano nell'intervallo di concentrazione stabilito precedentemente per le tre fonti. L'appartenenza dei campioni alle diverse fonti è inoltre confermata da alcuni parametri basati sugli elementi delle terre rare e sulla loro distribuzione, nonché dai trattamenti di analisi statistica multivariata. Inoltre è stato possibile confermare l'attribuzione iniziale di provenienza per i campioni ritrovati a distanza rispetto agli affioramenti primari, basata sull'analisi visuale dei caratteri macroscopici nonché sulla formazione geologica dell'area di reperimento, ipotizzandone il trascinamento a valle a causa di eventi alluvionali. Da questi dati potrebbero derivare importanti implicazioni sulle strategie di acquisizione dell'ossidiana nei territori circostanti il Monte Arci e sulla diffusione della materia prima nell'ambito del sistema di produzione litica in Sardegna, particolarmente durante le fasi neolitiche
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