1,720,975 research outputs found
Atomic force microscopy observations of acyl chains in phospholipids
No full textThe potential use of atomic force microscopy (AFM) to image the mode of assembly and to measure the corresponding lattice parameters of model systems consisting of ordered aggregates of cardiolipin molecules has been investigated. An unprecedented resolution of about 0.2 nm has been achieved on suitably prepared specimens. This enables the orientational order and the positional correlations of the individual molecules in the lattice to be defined, and submolecular details, such as the acyl chains and the polar groups, to be imaged. The structural parameters derived from AFM have been compared with those obtained by transmission electron diffraction of the same specimen and found to be in excellent agreement. AFM turns out to be a powerful, and probably a unique tool to reveal local phase variations in systems, such as biological membranes, that have non-homogeneous composition and organization
"Stabilità strutturale e primi stadi di cristallizzazione di leghe amorfe Ni-P depositate da diversi tipi di bagno"
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Correlation between electric force microscopy and scanning electron microscopy for the characterization of percolative conduction in electronic devices
No full textThe correlation betweem electric force microscopy (EFM) and scanning electron microscopy (SEM)techniques provide interpretation of the contrast features of electric force images and gave an insight into the two-dimensional (2D) electrical transport properties of RuO2-based thick film resisitors (TFRs). From the comparison between EFM. tapping mode-atomic force microscopy, SEM (secondary electrons, specimen current and X-ray energy-dispersive spectroscopy) of TFRs on the same specimen area, it turned out that the conduction mechanism was related to the grain size and to how RuO2 crystals were distributed in the glassy matrix. Dark area in EFM images corresponded to conductive-insulating interfaces. In SEM the same areas were the interfaces between the Ru=2 crystals and the insulating matrix. The 2D percolative path of the electrical current near the surface was observed in connection with the net of RuO2 grains not homogeneously dispersed in the insulating matrix
A preliminary study of human pineal gland concretions: structural and chemical analysis.
No full textAcervuli and fragments of pineal gland obtained from 33 subjects of both sexes and age ranging from 1 to 87 years, (30 autopsy and 3 biopsy specimens) were analyzed by light microscopy, transmission and scanning electron microscopy, X-ray diffraction and X-ray energy dispersive microanalysis. It was found that primary mineralization occurs in an organic matrix formed by pinealocytes and that hydroxyapatite also takes place in mineral deposition. From our analysis, the formation of acervuli appears to be age and sex independent and can be possibly related to the secretory activity of the gland
Correlation between electric force spectroscopy and scanning electron microscopy for the characterization of percolative conduction in electronic devices
No full textThe correlation between electron force microscopy (EFM) and SEM techniques provided interpretation of the contrast features of electron force images and gave an insight into the two-dimensional (2D) electron transport properties of RuO2-based thick film resistors (TFRs). From the comparison between EFM, tapping-mode atomic force microscopy, SEM (secondary electrons, specimen current and x-ray energy-dispersive spectroscopy) of TFRs on the same specimen area, the conduction mechanism was related to the grain size and to how RuO2 crystals were distributed in the glassy matrix. Dark areas in EFM images corresponded to conductive-insulating interfaces. In SEM the same areas were the interfaces between the RuO2 crystals and the insulating matrix. The 2-dimensional percolative path of the electron current near the surface was observed in connection with the net of RuO2 grains not homogeneously dispersed in the insulating matrix
Electric force microscopy investigation of the microstructure of thick film resistors
No full textMaps of the electric field distribution on the surface of thick film resistors (TFRs) have been acquired by using electric force microscopy (EFM). TFRs based on various types of conducting phases (Bi-ruthenate, Pb-ruthenate, or RuO2) and with different volume fractions in the glassy matrix have been examined. Scanning electron microscopy, x-ray energy dispersive spectroscopy and x-ray diffraction have been used to correlate the EFM results to the morphological, microchemical, and structural characteristics of the samples. The evolution of the TFRs microstructure and the segregation characteristic with the firing conditions have been investigated. The results showed that the concentration of the electric field around the conductive grains is a general feature of all the films, independently of the resistor composition, and a meander-like path of charge carriers on a microscopic scale has been assessed. The observations also indicated that at high firing temperatures the segregated structure did not disappear, but on the contrary was enhanced. All the results are critically discussed in relation to the electrical and piezoresistive properties of the TFRs and suggestions for new models to correlate the microstructure and the electric properties are presented
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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