1,720,980 research outputs found
Atomic resolution studies detect new biologic evidences on the Turin Shroud
No full textWe performed reproducible atomic resolution Transmission Electron Microscopy and Wide Angle X-ray Scanning Microscopy experiments studying for the first time the nanoscale properties of a pristine fiber taken from the Turin Shroud. We found evidence of biologic nanoparticles of creatinine bounded with small nanoparticles of iron oxide. The kind, size and distribution of the iron oxide nanoparticles cannot be dye for painting but are ferrihydrate cores of ferritin. The consistent bound of ferritin iron to creatinine occurs in human organism in case of a severe polytrauma. Our results point out that at the nanoscale a scenario of violence is recorded in the funeral fabric and suggest an explanation for some contradictory results so far published
Changes in Physiological and Agronomical Parameters of Barley (Hordeum vulgare) Exposed to Cerium and Titanium Dioxide Nanoparticles
Full text linkThe aims of our experiment were to evaluate the uptake and translocation of cerium and titaniumoxide nanoparticles and to verify their effects on the growth cycle of barley (Hordeum vulgare L.). Barley plants were grown to physiological maturity in soil enriched with either 0, 500 or 1000 mg kg1 cerium oxide nanoparticles (nCeO2) or titanium oxide nanoparticles (nTiO2) and their combination. The growth cycle of nCeO2 and nTiO2 treated plants was about 10 days longer than the controls. In nCeO2 treated plants the number of tillers, leaf area and the number of spikes per plant were reduced respectively by 35.5%, 28.3% and 30% (p ¤ 0.05). nTiO2 stimulated plant growth and compensated for the adverse effects of nCeO2. Concentrations of Ce and Ti in aboveground plant fractions were minute. The fate of nanomaterials within the plant tissues was different. Crystalline nTiO2 aggregates were detected within the leaf tissues of barley, whereas nCeO2 was not present in the form of nanoclusters
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
Advances in Transmission Electron Microscopy for the Study of Soft and Hard Matter
Full text linkThis book provides readers with some examples of advanced applications of electron microscopy on organic and inorganic specimens, highlighting out how new original approaches could provide a deeper understanding of the properties of matter and how a transmission electron microscope is not only a microscope but also a flexible tool for tailoring experiments, properly suited, to the issue of interest
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
Magnetic circular dichroism in the transmission electron microscope
Full text linkDichroism is the property of certain materials that their photon absorption spectrum depends on the polarization of the incident radiation. In the case of X-Ray Magnetic Circular Dichroism (XMCD) the absorption cross section of a ferromagnet or a paramagnet in a magnetic field changes when the helicity of a circularly polarized probing photon is reversed relative to the magnetization. Although the similarities between X-ray absorption (XAS) and electron energy loss spectra (EELS) in the Transmission Electron Microscope (TEM) have long been recognized, it was presumed that extending such equivalence to circular dichroism would require a beam of spin polarized electrons. Recently, it was argued on theoretical grounds that this is probably wrong.In this Thesis I report the first direct experimental proof of magnetic circular dichroism in the TEM by comparing what has been named electron Energy-loss Magnetic Chiral Dichroism (EMCD) with XMCD spectra from the same specimen together with theoretical calculations. The experiment shows that chiral atomic transitions in a specimen are accessible with inelastic electron scattering under particular scattering conditions.The specimen itself is used as beam splitter and phase locker to obtain the equivalent of circularly polarized photons in the TEM.A broad range of experimental conditions is explored and the effect of several experimental parameters is studied and compared with ab initio simulations. A few alternative scattering conditions are detailed, together with their advantages and disadvantages, and demonstrated on simple systems (Fe, Co and Ni single crystals).A theoretical justification of the effect is provided within the Bloch theory framework with the use of the Mixed Dynamical Form Factors.This result bears dramatic consequences for the study of magnetism at high resolution. Whereas circular dichroism of many magnetic materials has been studied with synchrotron radiation since twenty years, there is a number of technical limitations related to the spatial resolution and the signal depth with this technique. Circular dichroic experiments in the TEM, on the other hand, offer the potential of spatial resolutions down to the nanometre scale and provide depth information.<br /
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