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Trace organic compounds in speleothems as a pioneering approach to high-resolution paleofire reconstructrion
No full textA paper-based screen-printed electrochemical sensor combined with a 3D printed extracting cartridge for analysis of phosphorus in Antarctic lacustrine sediments
Full text linkHere, we present a novel fully printed electrochemical sensing tool for determining phosphorus levels in sediment samples. The integrated electrochemical device is composed of an office paper-based sensor combined with a customized 3D printing cube-shaped holder used for the extraction of phosphorus from sediment samples. The extracted phosphorus was trapped on a filter pad placed over the sensor and preloaded with acidic ammonium molybdate, allowing for the formation of the phosphomolybdate complex, which is electroactive. The use of carbon black as a nanomodifier of office paper-based electrode together with square wave voltammetry enabled the detection of phosphorus with a detection limit of 0.011 ppm within a broad linear range of 0.039-20 ppm. Furthermore, this sensor demonstrated excellent selectivity towards phosphate ions among the several ions studied, namely NO3-, NO2-, F-, SO42-, CH3COO-, Cl-, CO23-, Mg2+, K+, Zn2+, Ca2+, Na+, Cu2+, and Ni2+. The precision of the analytical platform was evaluated using eight distinct sensors, yielding a relative standard deviation below 5 %. The reliability of the paper-based integrated sensor was assessed by determining phosphorus levels in sediment samples obtained from various seasonal shallow coastal lakes situated in Northern Victoria Land, Antarctica, by comparing the data obtained with both the novel printed integrated device and the colorimetric reference method. The agreement of the data with a coefficient of correlation equal to 0.86 (r = 0.86) demonstrated the great potential of the developed sensing tool for use in real-world applications
Millennial-Scale Climate and Human Drivers of Environmental Change and Fire Activity in a Dry, Mixed-Conifer Forest of Northwestern Montana
No full textWarm summer temperatures and longer fire seasons are promoting larger, and in some cases, more fires that are severe in low- and mid-elevation, dry mixed-conifer forests of the Northern Rocky Mountains (NRM). Long-term historical fire conditions and human influence on past fire activity are not well understood for these topographically and biophysically heterogeneous forests. We developed reconstructions of millennial-scale fire activity, vegetation change, and human presence at Black Lake, a small closed-basin lake on the Flathead Indian Reservation in the Mission Valley, Northwestern Montana, United States. Fossil pollen, charcoal, and biomarkers associated with human presence were used to evaluate the interaction between climate variability, fire activity, vegetation change and human activity for the past 7000 years. Comparisons among multiple proxies suggest climate variability acted as the primary control on fire activity and vegetation change from the early Holocene until the late Holocene when records suggest fire activity and climate variability decoupled. Specific biomarkers (5 beta-stanols including coprostanol and epi-coprostanol) associated with human presence indicate humans were present within the Black Lake watershed for thousands of years, although the inferred intensity of human presence is highly variable. A strong relationship between climate variability and fire activity during the early and mid-Holocene weakens during the last few thousand years, suggesting possible increased influence of humans in mediating fire activity in recent millennia, and/or a shift in the interaction between the distribution and abundance of woody fuel and fire severity. Human-set fires during the cooler and wetter late Holocene may have been aimed at maintaining important cultural resources associated with the heterogeneous mosaic of mixed conifer forests within the Black Lake watershed. The paleoenvironmental reconstruction at Black Lake corroborates archeological records that show humans were present within the Black Lake watershed for over 7000 years. Further research is needed to evaluate the evidence for this continuous presence and the possible role that people played in shaping fire regimes and vegetation within low- to mid-elevation mixed-conifer ecosystems of the NRM
A 2000-year record of fecal biomarkers reveals past herbivore presence and impacts in a catchment in northern Yellowstone National Park, USA
No full textMolecular biomarkers preserved in lake sediments are increasingly used to develop records of past organism occurrence. When linked with traditional paleoecological methods, analysis of molecular biomarkers can yield new insights into the roles of herbivores and other animals in long-term ecosystem dynamics. We sought to determine whether fecal steroids in lake sediments could be used to reconstruct past ungulate use and dominant taxa in a small catchment in northern Yellowstone National Park. To do so, we characterized the fecal steroid profiles of a selection of North American ungulates historically present in the Yellowstone region (bison, elk, moose, mule deer, and pronghorn) and compared them with those of sediments from a small lake in the Yellowstone Northern Range. Analysis of a set of fecal steroids from herbivore dung (Δ5-sterols, 5α-stanols, 5β-stanols, epi5β-stanols, stanones, and bile acids) differentiated moose, pronghorn, and mule deer, whereas bison and elk were partially differentiated. Our results show that bison and/or elk were the primary ungulates in the watershed over the past c. 2300 years. Fecal steroid influxes reached historically unprecedented levels during the early and middle 20th century, possibly indicating high local use by ungulates. Comparison of fecal steroid influxes with pollen and diatom data suggests that elevated ungulate presence may have contributed to decreased forage taxa (Poaceae, Artemisia, and Salix), relative to long-term averages, and possibly increased lake production. Our results reflect past change within a single watershed, and extending this approach to a network of sites could provide much-needed information on past herbivore communities, use, and environmental influences in Yellowstone National Park and elsewhere
Fecal biomarkers in Italian anthropogenic soil horizons and deposits from Middle Ages and bronze age
Full text linkArchaeological excavations in urban and rural contexts often uncover dark homogeneous anthropogenic deposits, soils and soil horizons, known as Dark Earths, Cultural Layers and Anthrosols. Major scientific questions arise about the processes that lead to the formation of these soils and deposits, as they are often related to a complex combination of environmental, climatic, and anthropogenic factors. Many studies focused on the morphological and physical-chemical investigation of the archaeological remains found as well as the inorganic constituent of the soil. The organic fraction has been only roughly investigated and studies carried out on a molecular level are very limited. However, a more refined investigation of the chemical constituents of these soils can potentially reveal pivotal insights on the archaeological context such as past domestic habits and/or urban organization. It has been demonstrated that, among organic matter constituents, fecal steroids are promising biomarkers to track fecal input in many environmental matrixes such as water, soils, and sediments. In this paper we determine the fecal sterols and stanols content in dark homogeneous anthropogenic deposits and soils found in seven archaeological sites in Italy (from Verona, Como, Florence, Mel and Conegliano) dated from the Late Bronze Age and the Medieval Period, aiming to assess the major contribution of the fecal input using diagnostic fecal indexes obtained from specific fecal sterol proportions. To this purpose, a baseline was established by identifying the fecal fingerprint of domestic herbivores (caprids, ovines, equines and bovines) and omnivores (pigs). Based on their fecal fingerprint, we classified the deposits of seven studied sites into four distinct categories: i) the medieval sites of Verona, presented a strong mixed fecal input from both herbivores and humans; ii) the medieval sites of Como and Florence which showed a similar pattern, with a predominance of human fecal input over livestock; iii) the late medieval soils of Mel and the late bronze age Cultural Layers of Castellar di Leppia (Verona) which exhibited a generally scarce fecal contamination while iv) the final bronze age site of Conegliano (Treviso), a strong fecal contamination from herbivores was detected. These results thus demonstrate that for the Medieval Dark Earth the socio-cultural processes leading to the formation of the Dark Earth differ in terms of sewage and waste management and/or in animal husbandry practices
Fecal biomarkers in Italian anthropogenic soil horizons and deposits from Middle Ages and bronze age
No full textArchaeological excavations in urban and rural contexts often uncover dark homogeneous anthropogenic deposits, soils and soil horizons, known as Dark Earths, Cultural Layers and Anthrosols. Major scientific questions arise about the processes that lead to the formation of these soils and deposits, as they are often related to a complex combination of environmental, climatic, and anthropogenic factors. Many studies focused on the morphological and physical-chemical investigation of the archaeological remains found as well as the inorganic constituent of the soil. The organic fraction has been only roughly investigated and studies carried out on a molecular level are very limited. However, a more refined investigation of the chemical constituents of these soils can potentially reveal pivotal insights on the archaeological context such as past domestic habits and/or urban organization. It has been demonstrated that, among organic matter constituents, fecal steroids are promising biomarkers to track fecal input in many environmental matrixes such as water, soils, and sediments. In this paper we determine the fecal sterols and stanols content in dark homogeneous anthropogenic deposits and soils found in seven archaeological sites in Italy (from Verona, Como, Florence, Mel and Conegliano) dated from the Late Bronze Age and the Medieval Period, aiming to assess the major contribution of the fecal input using diagnostic fecal indexes obtained from specific fecal sterol proportions. To this purpose, a baseline was established by identifying the fecal fingerprint of domestic herbivores (caprids, ovines, equines and bovines) and omnivores (pigs). Based on their fecal fingerprint, we classified the deposits of seven studied sites into four distinct categories: i) the medieval sites of Verona, presented a strong mixed fecal input from both herbivores and humans; ii) the medieval sites of Como and Florence which showed a similar pattern, with a predominance of human fecal input over livestock; iii) the late medieval soils of Mel and the late bronze age Cultural Layers of Castellar di Leppia (Verona) which exhibited a generally scarce fecal contamination while iv) the final bronze age site of Conegliano (Treviso), a strong fecal contamination from herbivores was detected. These results thus demonstrate that for the Medieval Dark Earth the socio-cultural processes leading to the formation of the Dark Earth differ in terms of sewage and waste management and/or in animal husbandry practices
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
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