1,720,979 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
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 text
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
Engineering the surface of hybrid organic-inorganic films with orthogonal grafting of oxide nanoparticles
No full textSuperparamagnetic iron oxide nanoparticles
of magnetite have been grafted on the surface of a
hybrid organic–inorganic film prepared using an
organically modified alkoxide, 3-glycidoxypropyltrimethoxysilane,
as precursor. A solventless synthesis
of the hybrid films at high pH has been employed and
the surface chemistry of the deposited films has been
processed by controlling the aging time of the sol. The
films have been characterized by FTIR, Raman and
UV spectroscopy and grazing incidence X-ray diffraction.
Films prepared with fresh sols have shown a
mixed presence of epoxides and hydroxyls on the
surface, which enabled the successful grafting of the
iron oxide nanoparticles. Films from aged sols, which
contain only hydroxyls, have failed to bind the iron
particles but have instead shown the capability of
grafting ceria nanoparticles. This method has,
therefore, allowed a direct grafting of nanoparticles
on the hybrid surface without any post-synthetic
functionalization step. Moreover, the phase transition
induced in iron oxide nanoparticles by means of a laser
beam has been exploited to pattern the film surface
creating different domains of magnetite and hematite
Elemental investigation on Spanish dinosaur bones by x-ray fluorescence
No full textIn this paper we examine the chemical composition results obtained on a collection of 18 dinosaur fossil bones from Spain studied using a portable x-ray fluorescence spectrometer together with a reverse Monte Carlo numerical technique of data analysis. This approach is applied to the hypothesis of arbitrarily rough surfaces in order to account for the influence of the surface state of specimens on the chemical content evaluation. It is confirmed that the chemical content of elements is essential for understanding the changes brought about by diagenetic and taphonomic processes. However, for precise knowledge of what changes fossil bones have undergone after animal life and burial, it is necessary to use a multi-technique approach making use of other instruments like x-ray diffraction in order to describe accurately the transformations undergone by the mineralogical and bioinorganic phases and the properties of specific molecular groups
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