1,720,970 research outputs found
Componenti ottici negli ambienti spaziali: fabbricazione, caratterizzazione e degrado delle prestazioni
Get PDFThe objectives of the next-generation space missions lead the development of increasingly innovative instrumentation able to visit unexplored areas of the solar system, and to operate in relative increasing harsh environments. All the instrumental sub-systems, included optical components will have to be able to withstand extreme operational environments, characterized by high thermal gradients, electromagnetic irradiation, particulate and high and low energy particles/ions irradiation. In particular, recently, it was demonstrated that low energy particles could compromise the performances of optical coatings, leading a potential failure of a space instrument.
Accelerators are commonly used to reproduce the particles irradiation on components. By selecting ions energies and mission lifetime equivalent fluences it is in principle possible to replicate the effects induced by the space environment, although accelerators flux rates are higher of orders of magnitude with respect to the real space conditions. For this reason, it is arduous to be sure that ground tests are effectively representative of what occurs in space, making a crucial issue the definition of the experimental irradiation parameters like the ion flux. Moreover, the knowledge of the environmental agents of a specific space environment is still limited, and only in few cases in-situ measurements were performed. In order to overcome this lack, scaling models based on data collected at 1 A.U. can be used to estimate environment parameters of an unexplored space location.
The impact on the optical components of the space environment is the main topic of this research project. In particular, a systematic investigation devoted to define clear and reliable testing procedures for optical coatings were performed. Such systematic studies started with Monte Carlo simulations to evaluate the penetration depth of a specific ion specie or particle within an optical element, determining the energy range where the ions highly interact with the coating. After that, in order to perform a systematic investigation of the damage mechanisms that a coating can undergo, many implantation experiments were carried out by using accelerators facilities. We observed that, depending on the coating structure and the ion energy, different potential damages can occur, such as changes of the optical properties of the materials, inter-diffusion at the interfaces due to elastic scattering interactions between the incident ions and the target atoms, delamination of some layers or a full detachment of the coating or part of it
In vitro Assessment of Solar Filters for Erythropoietic Protoporphyria in the Action Spectrum of Protoporphyrin IX
Get PDFIntroduction: Subjects with erythropoietic protoporphyria rely on broad-spectrum sunscreens with high sun protection factor, which is not informative on efficacy in the absorption spectrum of protoporphyrin IX, spanning visible radiation and peaking around 408 nm. Photoactivation of protoporphyrin IX is responsible for painful skin photosensitivity in erythropoietic protoporphyria. The authors assessed the protective efficacy of six sunscreens in vitro in the absorption spectrum of protoporphyrin IX. Method: Transmittance measurements were performed in the 300-850 nm wavelengths on samples of six photoprotective products applied to polymethyl methacrylate plates. Porphyrin protection factor was calculated in the 300-700 nm region to provide a measurement for the efficacy of each product based on the action spectrum of protoporphyrin IX. Results: Product A showed the highest porphyrin protection factor among tested products with a median value of 4.22. Product A is a sunscreen containing organic filters, titanium dioxide and synthetic iron oxides, pigmentary grade active ingredients that absorb visible radiation. Other products showed inefficient protection in the visible, with transmittance between 75 and 95% at 500 nm. The low porphyrin protection factor of inorganic filter product B was attributed to particle micronization, as declared by the manufacturer. Conclusion: Adding porphyrin protection factor to sunscreen labeling could help patients with erythropoietic protoporphyria and other photosensitivity disorders identify products tailored on their specific needs. The development of sunscreens providing protection from visible radiation and excellent cosmetical tolerability could improve the lifestyle of patients with erythropoietic protoporphyria
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Systematic investigation of the optical coatings damages induced in harsh space environment
No full textThe scientific goals required to the next-generation space missions lead the development of innovative instrumentation, conceived to operate in increasingly harsh environments. Optical coatings are among the sub-systems which can highly suffer the agents in such environments. In particular, as recently demonstrated, the accelerated ions and particles can potentially jeopardize the coatings optical performances, with a consequent degradation of the overall functionality of an instrument. Despite its importance, this issue is still poorly investigated. In fact, the fragmentary knowledge of the space environments and the low number of previous ground testing experiments complicates the definition of clear procedures to investigate the behavior of the optical coatings in space. A systematic approach devoted to identify a methodology for the validation of optical coatings under ions irradiation is presented. Monte Carlo simulations are used to evaluate the effects induced by different ion species and energies on both layers and multilayers of different materials, getting an accurate overview of the main criticalities. Such results are then used to plan representative irradiation experiments and the subsequent analysis procedures needed for a proper characterization of the exposed samples. In this paper, a summary of the experiments performed so far is presented. Thanks to these studies we have identified three main damage mechanisms which can be used to explain most of the degradation effects observed when an optical coating is irradiated with low energy particles. A brief discussion of such mechanisms is reported
Variations on the Author
Get PDF“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
Get PDFWe 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
Get PDFWe 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
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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