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STRUCTURAL AND SPECTROSCOPIC ANALYSIS OFBALTIC AMBER
No full textAmber is a fossilized tree resin appreciated since antiquity for its unique aesthetic qualities in the production of small decorative objects. Its chemical composition is strongly related to the origin of the resin, but Baltic amber is synonymous with the chemical name butanedioic acid (C4H6O4), more commonly known as succinic acid (Beck, 1986). C4H6O4 is also a natural constituent of plant and animal tissues which has been used in Europe as a natural antibiotic and general curative for centuries. It has been stated, for example, that succinic acid isolated from Baltic amber can stimulate human and plant organisms, and can contribute to an increase in the yield of some cultivated plants (Matuszewska and John, 2004). In the literature it was reported that not all Baltic ambers contain succinic acid (Matuszewska and John, 2004).
The primary goal of this study was to characterize succinite, a Baltic amber characterized by levels of succinic acid ranging from 3 to 8%. The selected succinite samples - (Palmnicken, Baltic Coast, and Prussia amber) consisted of opaque pale brown to nearly dark red-brown rounded masses of this amber variety. For comparative purposes, our tests were also carried out on a number of reference materials, including amber from Danzig Region, Poland, and commercial specimens. Standard gemological methods were used to document the samples’ colour, hardness, refractive indices, fluorescence to long and short-wave ultraviolet radiation, and inclusions. X-ray powders patterns were collected before and after adsorption on a Bruker D8 Advance diffractometer equipped with SOL-X detector. Thermal analyses (TG and DTA) were performed in air up to 900°C at 10°C min-1. According to Shashoua et al. (2006), IR techniques have been shown to identify the provenance of the amber beyond the basic Baltic/ non-Baltic distinction. In this study, infrared spectra collected on a Thermo Electron Corporation FT Nicolet 5700 Spectrometer FTIR spectra revealed characteristic spectral differences that make it possible to positively identify Baltic amber.
Beck C. W. (1986). Spectroscopic Investigations of Amber. Applied Spectroscopy Reviews, 22, 57-110.
Matuszewska A., Shashoua J. A. (2004). Some possibilities of thin layer chromatographic analysis of the molecular phase of Baltic amber and other natural resins. Acta Chromatographica, 14, 82-91.
Shashoua Y., Degn Berthelsen M.-B. L. & Nielsen O. F. (2006). Raman and ATR-FTIR spectroscopies applied to the conservation of archaeological Baltic amber. Journal of Raman Spectroscopy, 37, 1221–1227
Temperature-Induced Structural Changes in Acidic L-Zeolite: An In Situ Synchrotron Time-Resolved Powder Diffraction Study
No full textZeolite L (K6Na3Al9Si27O72 & BULL;21H(2)O, the synthetic counterpartofthe mineral perlialite) has important catalytic properties, the efficiencyof which derives from the high acidity due to the presence of Bronstedsites (BAS), enhanced by the synergistic activity with Lewis sites(LAS) with increasing temperature. In this work, we carried out adetailed structural characterization of the acid form of this zeolite(H-LTL) by in situ time-resolved synchrotron X-raydiffraction from room temperature up to 800 & DEG;C on a powderedsample in order to obtain the structural response to heating. Despitethe fact that the crystallinity is maintained when the maximum temperatureis reached, thermal pathways show significant distortions of channelaperture as well as differences in host-guest interactions.The distortion of the T2 polyhedron and the progressive widening ofthe O3-T2-O5 angle suggest the formation of a Lewisacid site from the progressive conversion of BAS on O5 at 550 & DEG;Cduring heating. The in situ synchrotron X-ray diffractiondata provided reliable evidence of the high thermal stability of theacidic L-zeolite and the adaptable behavior of the framework duringthe evolution of the BAS to LAS
Soil Organic Carbon Depletion in Managed Temperate Forests: Two Case Studies from the Apennine Chain in the Emilia-Romagna Region (Northern Italy)
No full textForest soils contain a large amount of organic carbon (OC); therefore, small changes in these ecosystems have effects on climate. In this study, variation in the quantity of C pools that occurred in one year in the soil of temperate forests managed by two farms in the Apennine chain (Emilia-Romagna Region) was investigated using elemental and isotopic C analyses of soil samples collected in 2020 and 2021. In one year, soil from the Branchicciolo (BRA) farm lost organic matter as shown by the decrease in C contents and the less negative C isotopic signatures (13C/12C), whereas the C contents and C isotopic signatures remained almost stable during time in the soil from the Beghelli (BEG) farm. This cannot be related to thinning interventions, as much more forest material was removed from the BEG forest than from the BRA forest (60% and 25%, respectively). Therefore, other causes should be considered. The BRA forest was at a lower altitude than the BEG forest; thus,
it was more affected by C depletion due to the warmer temperature. Moreover, the sandy soil in the BRA forest was less prone to sequestering organic matter than the soil in the BEG forest, which was characterized by phyllosilicates (including vermiculite) and zeolites (clinoptinolite) having high C sequestration capacity. This work showed the different impacts of the pedo-climatic conditions in two nearby farms, which should be considered in planning appropriate silvicultural management for OC sequestration
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
High-silica zeolites as sorbent media for adsorption and pre-concentration of pharmaceuticals in aqueous solutions
No full textThe present work focused on the use of high-silica commercial zeolites as sorbent media for pharmaceuticals in an aqueous matrix. As drug probes, ketoprofen, hydrochlorothiazide, and atenolol were selected, because of their occurrence in surface waters and effluents fromwastewater treatment plants. Pharmaceuticals adsorption was evaluated for two Faujasite topology zeolites with Silica/Alumina Ratio 30 and 200. The selected zeolites were demonstrated to be efficient sorbents towards all investigated pharmaceuticals, thanks to their high saturation capacities (from 12 to 32% w/w) and binding constants. These results were corroborated by thermal and structural analyses, which revealed that adsorption occurred inside zeolite's porosities, causing lattice modifications. Finally, zeolites have been tested as a pre-concentration media in the dispersive-solid phase extraction procedure. Recoveries higher than 95% were gained for ketoprofen and hydrochlorothiazide and approximately 85% for atenolol, at conditions that promoted the dissolution of the neutral solute into a phase mainly organic. The results were obtained by using a short contact time (5 min) and reduced volume of extraction (500 μL), without halogenated solvents. These appealing features make the proposed procedure a cost and time saving method for sample enrichment as well as for the regeneration of exhausted sorbent, rather than the more energetically expensive thermal treatment
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
Carbon and sulphur isotopic composition of Vardar ophiolite of North Macedonia: implications for volatiles cycling in subduction zones
No full textThe North Macedonia is part of the Dinaric-Hellenic belt, an Alpine collisional belt extending from Slovenia to Greece. It resulted from the Mesozoic-Cenozoic convergence between Eurasia and Adria, ophiolite obduction, and continental collision after the closure of the Tethys Ocean. In this work we investigated the subvolcanic and volcanic rocks of the Vardar ophiolites of the North Macedonia, which represent the remnants of the Mesozoic Tethyan oceanic lithosphere formed in supra-subduction zone tectonic setting. Samples were collected at Lipkovo and Demir Kapija localities, in the northern and southern part of North Macedonia, respectively. Based on whole-rock major and trace element composition, two main groups of rocks can be distinguished: i) Group 1 rocks, which are subalkaline basalts showing backarc affinity and ii) Group 2 rocks, which are calc-alkaline basalts showing arc affinity. Petrogenetic modelling, based on trace and REE, indicates that Group 1 mantle sources were affected by limited metasomatic processes by slab-released components, in particular aqueous fluids and sediment melts, whereas the Group 2 mantle sources were strongly metasomatized by sediment melts and/or adakitic melts. In addition to this, the isotopic ratios of volatiles such as carbon (C) and sulphur (S) were also investigated to better constrain the nature and composition of the slab-components responsible for the metasomatism. In fact, volatiles are commonly transferred into the mantle from subduction of oceanic lithosphere and overlying sediments, whose C and S isotopic composition is well distinguishable from that of the mantle. The Group 1 rocks exhibit C-enriched and S-depleted signatures slightly different from those typical for the mantle, indicating a minor involvement of melts from the subducting sediments in the backarc basin settings. On the contrary, the C-depleted and S-enriched isotopic signatures of the Group 2 rocks suggest a major involvement of melts derived from the subducting sediments rich in organic matter and sulphate phases. Therefore, both geochemical and isotopic data of the North Macedonia ophiolites indicate that the sub-arc mantle sources are more affected by slab-released fluids than those of the backarc basin, which are more distal from the trench. This approach may be useful to better constrain the composition of the metasomatic agents, as well as to understand the origin and the fate of volatiles near subduction zones
F/OH ratio in a rare fluorine-poor blue topaz from Padre Paraíso (Minas Gerais, Brazil) to unravel topaz’s ambient of formation
No full textTopaz [Al2SiO4(F,OH)2] is one of the main fluorine-bearing silicates occurring in environments where variably acidic (F)/aqueous (OH) fluids saturate the silicate system. In this work we fully characterized blue topaz from Padre Paraíso (Minas Gerais, Brazil) by means of in situ synchrotron X-Ray and neutron powder diffraction measurements (temperature range 298–1273 K) combined with EDS microanalyses. Understanding the role of OH/F substitution in topaz is important in order to determine the hydrophilicity and the exchange reactions of fluorine by hydroxyl groups, and ultimately to characterize the environmental redox conditions (H2O/F) required for mineral formation. The fluorine content estimated from neutron diffraction data is ~ 1.03 a.f.u (10.34 wt%), in agreement with the chemical data (on average 10.0 wt%). The XOH [OH/(OH + F)] (0.484) is close to the maximum XOH value (0.5), and represents the OH- richest topaz composition so far analysed in the Minas Gerais district. Topaz crystallinity and fluorine content sharply decrease at 1170 K, while mullite phase starts growing. On the basis of this behaviour, we suggest that this temperature may represent the potential initial topaz’s crystallization temperature from supercritical fluids in a pegmatite system. The log(fH2O/fHF)fluid (1.27 (0.06)) is coherent with the fluorine activity calculated for hydrothermal fluids (pegmatitic stage) in equilibrium with the forming mineral (log(fH2O/fHF)fluid = 1.2–6.5) and clearly different from pure magmatic (granitic) residual melts [log(fH2O/fHF)fluid < 1]. The modelled H2O saturated fluids with the F content not exceeding 1 wt% may represent an anomalous water-dominant / fluorine-poor pegmatite lens of the Padre Paraíso Pegmatite Field
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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