124,672 research outputs found
Photodegradation of rhodamine 6G dimers in silica sol–gel films
No full textThe process of dimerization of rhodamine 6G at high concentrations in solution and when incorporated in a solid state matrix is well known but the dimer response to photodegration is still not well understood. Silica sol–gel films have been doped with rhodamine 6G with a concentration up to 10−1 M to form large amounts of dimers within the matrix. Fluorescence and UV absorption spectra have shown that both not-fluorescent H-dimers and fluorescent J-dimers together with the monomer form of rhodamine 6G are present in the matrix. Upon exposure up to 11 h to UV light a selective photodegradation of the different species has been finally observed. Analysis of the absorption spectra has shown that the H-type dimers are more resistant to photodegradation with respect to the J-type dimers
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe 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
Dispelling the Myths Behind First-author Citation Counts
No full textWe 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
XRF investigation on skeletal remains from King Peter III of Aragon (1239-1285 A.D.) and Queen Blanche of Anjou (1280-1310 A.D.)
No full textWe conducted an X-Ray Fluorescence investigation on bone fragments belonging to King Peter III of Aragon and Queen Blanche of Anjou. The spectroscopic analysis was carried out in selected points of the bone fragments. Several transitional elements normally unexpected in the bone composition have been found at varying level of concentration. The presence of these elements was interpreted in relation to chemical treatments for mummification of bodies as well as to dietary habits, including tools used for cooking and for the consumption of food
Co-precipitation synthesis of neodymium-doped yttrium aluminium oxides nanopowders: Quantitative phase investigation as a function of joint isothermal treatment conditions and neodymium content
No full textCo-precipitation synthesis of neodymium-doped yttrium aluminium oxides nanopowders: quantitative phase investigation as a function of joint isothermal treatment conditions and neodymium content.
No full textNeodymium-doped yttrium aluminium nanopowders with nominal Nd:Y:Al ratio equal to X:3-X:5 (where X = 0, 0.006, 0.012, 0.024, 0.048, 0.081, 0.096, 0.171, 0.192, 0.384, 0.540 and 0.720) were prepared by the co-precipitation method and subjected to five cumulative stages of isothermal treatment in the temperature range from 900 to 1050 °C. The phase evolution of the oxides were investigated quantitatively by the X-ray powder diffraction approach using the Rietveld method of analysis. An almost single phase cubic garnet structure was attained at temperatures as low as 900 °C for specimens with neodymium loading less than ca. 6 at.% with respect to total (Nd + Y) atoms. Isothermal treatments of the powders up to 1050 °C remove the hexagonal YAlO3 metastable phase and maximize the amount of the garnet phase. However, for neodymium loading higher than ca. 6 at.%, the garnet structure remains substantially affected by the presence of monoclinic Y4Al2O9 and orthorhombic distorted perovskite-like YAlO3 phases
Magnetic core-shell nanoparticles coated with a molecularly imprinted organogel for organophosphate hydrolysis
No full textIndentation strain rate sensitivity of ball-milled spark-plasma sintered Cu-C metal matrix composite
No full textBulk ultrafine grained metal matrix composites (MMC) have attracted much attention of many researchers due to their potential in terms of excellent mechanical properties for engineering applications, such as high strength, which can be two or more times of that of their coarse grained counterpart. Bulk ultrafine grained Cu-3wt.%C MMC samples were produced by Ball-Milling (BM) followed by Spark Plasma Sintering (SPS), at a temperature of 900 °C. The Cu-C MMC was compacted progressively by repeating the BM + SPS procedure without changing the weight ratio between Cu and graphite. The room temperature creep behavior, and the strain rate sensitivity (SRS) were inspected by using nanoindentation measurements. Strain rate ranged 0.0025-to-0.5 s−1, and the contact dwelling times ranged 5-to-300 s. A secondary steady-state regime was reached starting from a dwelling time of 120 s irrespective of the strain rate and Cu-C compaction level. A negative trend of the SRS exponent with Cu-C compaction was obtained, with creep stress exponent as high as 28. These results were discussed according to the microstructure features that differentiated the Cu-3wt.%C MMC obtained by the progressive BM + SPS compaction levels
New data on the presence of celestite into fossil bones from the uppermost Cretaceous Molí del Baró-1 site (Spain) and an alternative hypothesis on its origin
No full textThe Molí del Barò-1 site is located in south-central Pyrenees (Spain) and is dated to about 66.5 Ma (latest
Cretaceous), just before the end Cretaceous mass extinction that wiped out most dinosaurs and many other
groups of organisms. The site has yielded one of the richest fossil assemblages of the continental upper
Maastrichtian from western Europe. A combined investigation by X-ray fluorescence (XRF), Fourier Transform
Infrared spectroscopy attenuated total reflectance (FTIR-ATR) and powder X-ray diffraction (XRD), supplemented
with the Rietveld analysis, was conducted on twenty-seven fossil bone samples from Molí del Baró-1
vertebrate-bearing fossil site to investigate taphonomy and diagenetic processes in terms of physico-chemical
properties.
The XRD analysis confirms the unusual presence of celestite and other rare sulphates in the bone structure. Previous
explanations of the presence and sometimes abundance of celestite in the fossil bones from this site were
based on the supposed total absence of marine water in the original depositionary environment. New geological
information suggesting the possibility of marine influence allows formulating an alternative hypothesis focused
on the peculiar environment of deposition of Molí del Baró-1 site
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