1,720,985 research outputs found
Large equilibrium clusters in low-density aqueous suspensions of polyelectrolyte-liposome complexes: A phenomenological model
No full textIn this paper, we revisit some of our previous results together with further experimental evidences for the existence of large equilibrium clusters in low-density aqueous colloidal suspensions, resulting from the screening of charged spherical macroions by oppositely charged linear polyelectrolytes. The aggregation process is described by a simple phenomenological model where aggregates interact via a long-range repulsion Yukawa potential and some supports to the equilibrium properties of the resulting aggregates, on the basis of dynamic light scattering, zeta potential, and transmission electron microscopy techniques, have been provided
The neurotoxicity of native metastable prefibrillar oligomers from salmon Calcitonin: an innovative amyloid-induced excitotoxicity paradigm
Get PDFProtein misfolding is implicated in different severe amyloid-related neurodegenerative diseases, like Alzheimer's, Parkinson’s and Creutzfeldt-Jacob’s. This process results in the aggregation of toxic small soluble prefibrillar oligomers (PFOs), almost ineffective proto-fibrils (PFs) and mature fibres (MFs). Many efforts are pointing to clarify PFOs structures and cytotoxicity. However, since their metastability, oligomers change their conformation along with the experiments leading to inconsistency in comparing data from different groups. Salmon Calcitonin (sCT), is a 32 amino acid polypeptide hormone displaying the tendency to self-assemble in the amyloid pattern, with a very low aggregation rate. This appealing feature allows investigating the effects of native PFOs in the early stages of neurotoxicity, without any chemical stabilization. We purified sCT PFOs enriched fractions by means of size exclusion chromatography (SEC) aiming to find who is the most toxic species, among sCT PFOs, comparing the biologic effects of native PFOs enriched fraction respect to sCT monomers. The intracellular Ca2+ rise plays a fundamental role in amyloid protein-induced neurodegenerations. According to what we found in literature, two paradigms have been explored: i) the “membrane permeabilization” due to the formation of amyloid pores or other types of membrane damage; ii) “receptor-mediated” modulation of Ca2+ channels. Therefore, we tested the effects of native sCT PFOs or monomers in differentiated neurons, employing Ca2+imaging, cellular viability, Long-Term Potentiation (LTP), post-synaptic densities protein expression, excised patch-clamp recordings, and miniature-Excitatory Post-Synaptic Currents (mEPSC). Results indicated that PFOs-, but not Monomer-enriched solutions, induced abnormal permeability to Ca2+, not fully explained by N-methyl-D-aspartate receptors (NMDARs) activation. We also found that the formation of small amyloid pores was consistent with an increased quantal release of neurotransmitters, able to drive a receptor-mediated response, per se. Thus, we propose an innovative neurotoxicity mechanism for amyloid proteins where the “membrane permeabilization” and “receptor-mediated” paradigms coexist
Metallic oxide microphases in fly ashes: An ultrastructural investigation
No full textFly ashes from fuel oil combustion consist almost entirely of hollow, spheroidal formations, cenospheres, with sizes ranging from about 10 to 100 mu m. These particles, produced during microdrop fuel oil combustion, look like droplet skeletons with numerous holes irregularly distributed on their surface. Heavy metals are present in fly ashes mostly like crystalline sulphate or oxide phases located into the cenosphere hollow. In this paper oxide phases were studied. They turned out to be prevalently composed of small particles with irregular shapes and sizes ranging from less than 0.1 mu m to about 1 mu m. Oxide microparticles were classified by cluster analysis; the atomic percentages of eight metallic elements-Fe, Ni, V, Al Cr, Mg, Zn, Ti, that represent virtually all the cations revealed in the composition of the oxides-were used to evaluate the ''degree of similarity''. On the basis of the obtained chemical, compositional and morphological data the structure of the major metallic oxide phases was defined
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
Electrical properties by volt-amperometric and impedance spectroscopy of -Fe2O3 ceramic humidity sensor.
No full textVariations 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
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