1,720,968 research outputs found
Analysis of the capability of HREM applied to quantum heterostructures
No full textThis work analyzes the possibilities offered by HREM for the observation of quantum heterostructures. Multilayers of Cu/Pd, Fe/Ag and Ag/Si are constructed by using a molecular dynamics simulation method and the configuration of the electronic charge at the interfaces is obtained from a Hartree-Fock calculation of the type extended Debye-Hueckel approximation. The HREM image of the multilayers is calculated by using a standard dynamical diffraction method. MD simulations show that in all cases good epitaxis can be achieved. However the interfacial regions have a complex structural and electronic configuration which is significantly different from the bulk reference state. As these regions span few monolayers across their observation is extremely critical. The HREM image of the films is clear. The interfaces and defective epitaxial growth can be observed. An interesting possibility for future developments appears to be offered by the availability of the interfacial potential obtained from the HREM image intensity
Multiple cascades regime in fcc metals. Molecular dynamics simulations and calculated HREM imaging
No full textThis study presents a simulation method which consists of three parts. The first one is classic molecular dynamics and is used to evaluate disordered atomic configurations. The second one is an evaluation of the electronic charge configuration of the type extended Debye-Hueckel. The third one calculates the HREM image of the lattice structure obtained from molecular dynamics. The simulation method is applied to collective motions of PKAs displaced in a fee lattice with energies near the displacement threshold. These conditions, which represent in a simplified manner e(-) irradiation, are aimed at investigating whether the defect growth kinetics shows ordering phenomena similar to the ones studied in phase transition. Embryonic forms of ordered interstitial agglomeration and unusual oscillatory behaviours of recrystallization are observed. The HREM calculations show that disorder is visible during its entire evolution
Interleukin 7 production by bone marrow-derived stromal cells in HIV-1-infected patients during highly active antiretroviral therapy.
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IN-VIVO ULTRASONIC PARAMETRIC IMAGING OF CAROTID ATHEROSCLEROTIC PLAQUE BY VIDEODENSITOMETRIC TECHNIQUE
No full textExtensive experimental and clinical data show that the ultrasonic image conveys information on the biochemical composition of the atherosclerotic plaque, ie, the relative content of lipids (hypoechoic), fibrous tissue (hyperechoic), and calcific deposits (very echogenic with shadowing). A more dishomogeneous echo structure of the plaque is also more often associated with clinically complicated carotid plaques. To date, however, the assessment of plaque density and homogeneity by transcutaneous B-mode imaging remains subjective and qualitative. The aim of this study was to assess whether plaque echodensity and homogeneity might be established on a more objective and quantitative basis by description of the spatial distribution of echo amplitude (referred to as tissue texture) applied to digitized images, obtained with commercially available B-mode transcutaneous imaging systems. A total of 47 B-mode images derived from echotomographic studies in 10 patients were digitized off line. For each region of interest, a set of first-order (mean gray level, standard deviation, skewness, kurtosis: mathematical descriptors of the shape of the frequency distribution of gray-level histogram) and of second-order (entropy, angular moment: mathematical descriptors of the spatial distribution of gray levels within the region of interest) textural parameters were evaluated. The visual, concordant reading by two independent, experienced observers assigned the plaques on the basis of qualitatively assessed echodensity to three groups: ''soft'' (n = 18), ''fibrotic'' (n = 20), ''calcific'' (n = 9). Regarding spatial gray-level distribution, 46 plaques would be separated into ''homogeneous'' (n = 17) and ''dishomogeneous'' (n = 29). On digitized images, the normalized mean gray level was the most effective first-order textural parameter for distinguishing soft (24.2 +/- 12.4 arbitrary units in a zero to 255 scale) from fibrotic (64.5 +/- 16.4) and calcific plaques (125.3 +/- 24.5), P < 0.01 for all intergroup differences. ''Homogeneous'' plaques were separated from ''heterogeneous'' ones on the basis of entropy (5 +/- 1 vs 7.9 +/- 9.7; P < 0.01), whereas the values of angular second moment overlapped (1.542E-3 + 1.334E-3 vs 5.181E-4 +/-2.5615E-4, P = ns). In conclusion, quantitative texture analysis of ultrasonic images derived from transcutaneous, high-resolution, commercially available B-scan systems is feasible in man and provides a quantitative operator-independent assessment of plaque echodensity and homogeneity
The role of oxidative imbalance in progression to AIDS: effect of the thiol supplier N-acetylcysteine.
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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
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