Search results for " Fisica"

Electroluminescence and transport properties in amorphous silicon nanostructures

2006

We report the results of a detailed study on the structural, electrical and optical properties of light emitting devices based on amorphous Si nanostructures. Amorphous nanostructures may constitute an interesting system for the monolithic integration of optical and electrical functions in Si ULSI technology. In fact, they exhibit an intense room temperature electroluminescence (EL), with the advantage of being formed at a temperature of 900 °C, while at least 1100 °C is needed for the formation of Si nanocrystals. Optical and electrical properties of amorphous Si nanocluster devices have been studied in the temperature range between 30 and 300 K. The EL is seen to have a bell-shaped trend …

Cholesterol facilitates interactions between α‐synuclein oligomers and charge‐neutral membranes

2015

AbstractOligomeric species formed during α-synuclein fibrillation are suggested to be membrane-disrupting agents, and have been associated with cytotoxicity in Parkinson’s disease. The majority of studies, however, have revealed that the effect of α-synuclein oligomers is only noticeable on systems composed of anionic lipids, while the more physiologically relevant zwitterionic lipids remain intact. We present experimental evidence for significant morphological changes in zwitterionic membranes containing cholesterol, induced by α-synuclein oligomers. Depending on the lipid composition, model membranes are either unperturbed, disrupt, or undergo dramatic morphological changes and segregate …

Secondary nucleation and accessible surface in insulin amyloid fibril formation.

2008

At low pH insulin is highly prone to self-assembly into amyloid fibrils. The process has been proposed to be affected by the existence of secondary nucleation pathways, in which already formed fibrils are able to catalyze the formation of new fibrils. In this work, we studied the fibrillation process of human insulin in a wide range of protein concentrations. Thioflavin T fluorescence was used for its ability to selectively detect amyloid fibrils, by mechanisms that involve the interaction between the dye and the accessible surface of the fibrils. Our results show that the rate of fibrillation and the Thioflavin T fluorescence intensity saturate at high protein concentration and that, surpr…

Multiple aggregation mechanism in Abeta(1-40) fibril formation

2011

A general characteristic of aggregation is the multiple interaction and cross-feedback among distinct mechanisms occurring at different hierarchical levels. The comprehension of the different species interconversion during aggregation is very important since emerging evidences indicate intermediate oligomeric aggregates as primary toxic species. In this context, Aβ amyloid peptide provides a challenging model for studying aggregation phenomena both for the complexity of its association process and for the direct implications in Alzheimer’s Disease. Indeed, aggregates growth conditions strongly affect their final morphology and their molecular structure as well as the time evolution of aggre…

Corrigendum to “Polysorbate 80 controls Morphology, structure and stability of human insulin Amyloid-Like spherulites” [J. Colloid Interface Sci. 606…

2023

Bollettino di Matematica Pura e Applicata

2008

K-means Clustering to Study How Student Reasoning Lines Can Be Modified by a Learning Activity Based on Feynman’s Unifying Approach

2017

Background:Research in Science Education has shown that often students need to learn how to identify differences and similarities between descriptive and explicative models. The development and use of explicative skills in the field of thermal science has always been a difficult objective to reach. A way to develop analogical reasoning is to use in Science Education unifying conceptual frameworks.Material and methods:A questionnaire containing six open-ended questions on thermally activated phenomena was administered to the students before instruction. A second one, similar but focused on different physical content was administered after instruction. Responses were analysed using k-means Cl…

Electrochemical pH Control at Gold Nanowires

2018

In this work, interdigitated arrays of nanowire electrodes are used with one array acting as the working electrode while the other is used to generate the required protons. Finite element simulations of the pH control electrodes were performed to provide insight on the generation and subsequent diffusion of protons. This informed the inter-tine spacing of the electrodes used.. This electrochemical pH control method was then used to enable the detection of analytes of interest.

Graphene and ionic liquids new gel paste electrodes for caffeic acid quantification

2015

Abstract Graphene/ionic liquids nanocomposite gels were synthesized by an electrochemical etching approach and fully characterized under a morphological and structural point of view. For this purpose, several analytical techniques were applied, as HR-TEM/EDX (High Resolution-Transmission Electron Microscopy/Energy Dispersive X-Ray Analysis); FE-SEM/EDX (Field Emission-Scanning Electron Microscopy/Energy Dispersive X-Ray Analysis); XPS (X-Ray Photoelectron Spectroscopy); FT-IR (Fourier Transform-Infrared Spectroscopy) and electrochemical techniques. After the characterization study, nanocomposite-gel paste electrodes were assembled, exhibiting a selective and specific detection toward the ca…

Phase formation in mixed TiO2-ZrO2 oxides prepared by sol-gel method

2011

Pure titania, zirconia, and mixed oxides (3—37 mol.% of ZrO2) are prepared using the sol-gel method and calcined at different temperatures. The calcined samples are characterized by Raman spectroscopy, X-ray powder diffraction, scanning electron microscopy, transmission electron microscopy, and nitrogen adsorption porosimetry. Measurements reveal a thermal stability of the titania anatase phase that slightly increases in the presence of 3—13 mol.% of zirconia. Practically, the titania anatase-rutile phase transformation is hindered during the temperature increase above 700 C. The mixed oxide with 37 mol.% of ZrO2 treated at 550 C shows a new single amorphous phase with a surface area of the…