1,721,022 research outputs found
Modeling stray field distribution generated by domain-walls in rare-earth substituted iron garnets
No full textRare heart substituted iron garnets (REIGs) are interesting material which may present large in-plane magnetization. In correspondence of defects, domain walls (DWs) undergo nucleation, segmentation and pinning. In such cases, the Néel spike domain structure may appear, and its DWs can produce not negligible stray fields above the REIG. Experimental characterization through quantitative magneto-optical imaging with an indicator film showed that stray fields are detectable above the surface of (Lu, Bi) substituted iron garnets in correspondence of DWs delimiting a Néel spike that is generated by a micro-crack. These DWs are interesting both for fundamental studies and for innovative applications, and therefore performing a quantitative analysis is crucial. To understand how the externally detected stray fields are correlated to the pattern of the internal magnetization, here we propose 2D and 3D models based on FEM developed through the COMSOL Multiphysics® software. These models consider the in-plane magnetization of the REIG and the magnetic microstructure of the Néel spike. They provide a good reproduction of the magnetic fields and allows to describe the corresponding magnetic microstructure. It turns out that the results are both in agreement with experiments
Multiphysics Simulation of a Superconducting Neutron Detector
No full textThe detection of neutrons is crucial for both the operation of nuclear devices and the development of advanced imaging techniques. Recently, a hybrid superconducting niobium-boron sensor on a Si/SiO2 substrate has been developed, aiming for high pulse shape discrimination and controllability of the relaxation time. This device detects thermal neutrons by leveraging the 10B(n,α)7Li reaction in the B layer and the interaction of the charged products with the Nb strip. To critically assess the operation of the Nb-B thermal neutron detector, a multiphysicsmodeling approach is presented here. The software COMSOL Multiphysics is used to provide thermal and electrical responses of this device during the transition-to-normal state and its recovery phase. The study takes into account the impact of the thermal irradiation of the cryostat lid and the joule heating on the operating conditions of the Nb strip. Moreover, a pulsed heat load is introduced in the model to simulate the energy released by either the α or the Li reaction products in the current-biased Nb strip. The SRIM software is used to obtain the deposited power density profiles and theirmean volume of interaction within the sample. For simplicity, the reaction is assumed to take place at the half-thickness of the B layer and the particles propagate perpendicularly to the sample surface. Finally, an iterative procedure was applied to find themost favorable conditions to employ the device in a self-recovering mode by varying both the bias current and the cold finger temperature. This study presents a comprehensive understanding of the working mechanism of the Nb-B thermal neutron detector and proposes a computational approach to find the optimal working point of superconducting neutron detectors
Melt-derived copper-doped ferrimagnetic glass-ceramic for tumor treatment
Full text linkCopper-containing ferrimagnetic glass-ceramic with the following composition: 24.7% SiO2-8.5% CaO-13.5% Na2O-3.3% P2O5-31% Fe2O3-14% FeO–5CuO (wt%) was synthesized by means melt and quenching process both in powder and bulk form. The obtained samples were characterized and compared by means morphological, compositional and structural analyses. The magnetic properties and the ability to release heat were also investigated together with the antimicrobial properties towards S. aureus strain. The obtained results showed that copper introduction and the annealing process influenced the nucleation of crystalline phases; in particular the samples produced in powder form evidenced a low amount of magnetite and thus a reduced hysteresis area and ability to produce heat when exposed to an alternating magnetic field. While Cu-containing samples in the bulk form maintained the magnetic and calorimetric properties of pristine glass-ceramic. Preliminary evaluation of antibacterial properties demonstrated Cu-doped samples were not able to reduce the bacterial proliferation and thus the need to optimize the copper introduction process
Synthesis and characterization of magnetic and antibacterial nanoparticles as filler in acrylic cements for bone cancer and comorbidities therapy
Full text linkIn this work an innovative formulation of bone cement for the treatment of bone tumor and its associated complications has been designed by preparing a new class of Fe3O4–Ag nanostructures, using gallic acid as a reducing agent. The obtained nanoparticles have been introduced in polymethyl methacrylate (PMMA)-based composite cement evaluating the insertion of different amounts and the use of different mixing methods. The morphology, the composition and the antibacterial effect of Fe3O4–Ag nanostructures have been investigated together with the morphology, the composition, the mechanical properties of the nanoparticles-containing composite cements as well as their antibacterial effect. The obtained results revealed a good antimicrobial effect of Fe3O4–Ag nanostructures, a significant influence of their amount and of the used mixing method on the particles dispersion and agglomeration in the PMMA matrix and, as a result, on the mechanical properties. In particular, a better dispersion of nanoparticles was obtained by using the mechanical mixing, reducing the tendency to agglomerate. The increase of nanoparticles amount induced a slight decrease of the mechanical properties; however, the introduction of 10% w/w of Fe3O4–Ag allowed to improve the composites ability to reduce the bacteria adhesion
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
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
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