Search results for "Microscopy"
showing 10 items of 3390 documents
Inter-observer variability of central corneal thickness measurements using non-contact specular microscopy after laser in situ keratomileusis.
2003
BACKGROUND The aim of this study was to investigate the inter-observer variability of central corneal thickness measurements carried out with a non-contact specular microscope in patients who had undergone myopic laser in situ keratomileusis. METHODS Twenty-six eyes of 26 subjects who had undergone myopic laser in situ keratomileusis were studied with the Topcon SP-2000P non-contact specular microscope (Topcon Corp, Tokyo, Japan). The mean of three consecutive measurements of the central corneal thickness was recorded by two investigators prior to and one month after myopic laser in situ keratomileusis. Results obtained by each of the two physicians were compared. RESULTS Prior to surgery t…
Self-Organization Pathways and Spatial Heterogeneity in Insulin Amyloid Fibril Formation
2009
At high temperature and low pH, the protein hormone insulin is highly prone to form amyloid fibrils, and for this reason it is widely used as a model system to study fibril formation mechanisms. In this work, we focused on insulin aggregation mechanisms occurring in HCl solutions (pH 1.6) at 60 degrees C. By means of in situ Thioflavin T (ThT) staining, the kinetics profiles were characterized as a function of the protein concentration, and two concurrent aggregation pathways were pointed out, being concentration dependent. In correspondence to these pathways, different morphologies of self-assembled protein molecules were detected by atomic force microscopy images also evidencing the prese…
Elasticity and yield strength of pentagonal silver nanowires: In situ bending tests
2014
This paper reports in situ mechanical characterization of silver nanowires (Ag NWs) inside a scanning electron microscope using a cantilevered beam bending technique. Measurements consisted in controlled bending of a cantilevered NW by the tip of an atomic force microscope glued to the force sensor. Relatively high degree of elasticity followed by either plastic deformation or fracture was observed in bending experiments. Experimental data were numerically fitted into the model based on the elastic beam theory and values of Young modulus and yield strength were extracted. Measurements were performed on twenty Ag NWs with diameters from 76 nm to 211 nm. Average Young modulus and yield streng…
The effects of sodium alginate and calcium levels on pea proteins cold-set gelation
2013
Abstract A multi-scale investigation of pea proteins – alginate cold-set gels was proposed in this study. The gel preparation followed a two-steps procedure. Globular pea proteins were first denatured and aggregated by a pre-heating step. Sodium alginate was then added at different concentrations. Thereafter the in situ gelation process was induced at 20 °C using glucono-δ-lactone (GDL) and two calcium carbonate (CC) levels; calcium cations were released as the pH decreased. Small-amplitude rheology measurements (storage modulus G′) showed that stronger mixed gels were obtained than single-biopolymer solutions. Confocal laser scanning microscopy (CLSM) revealed phase-separating microstructu…
Incorporation of membrane proteins into lipid surface monolayers: Characterization by fluorescence and electron microscopies
2007
The preparation of oriented protein samples is an attractive goal, e.g., to gain more detailed information from spectroscopic experiments. Our approach towards this aim was to prepare monolayers of phospholipids at the air-water interface and to incorporate the proteins into these ordered structures. Subsequently, we used the Langmuir-Boldgett (LB) transfer technique to obtain samples of oriented proteins on solid supports. — Incorporation was achieved by spreading the proteins from a detergent solution onto a prespread lipid monolayer on the water surface. We characterized successful incorporation by in situ fluoresence microscopy and by electron microscopy, and investigated the topology o…
Affinity scale between a carrier and a drug in DPI studied by atomic force microscopy.
2002
The dry powder inhalers (DPIs) consist, in the most cases, of ordered mixture where the particles adhesion results of interactions between the drug and the carrier. Generally, one step of production process is the micronization of the drug particles in order to reduce the size for ordered mixing optimization. But this operation is known to partially create an amorphous surface. In this case, surrounding storage conditions, like relative humidity (RH), are able to modify the percentage of amorphous drug surface. The aim of this study was to investigate surface reactivity, surface energy and direct force measurements by atomic force microscopy (AFM) between lactose (carrier) and zanamivir (dr…
In situ structural analysis of SARS-CoV-2 spike reveals flexibility mediated by three hinges
2020
Flexible spikes The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) spike protein enables viral entry into host cells by binding to the angiotensin-converting enzyme 2 (ACE2) receptor and is a major target for neutralizing antibodies. About 20 to 40 spikes decorate the surface of virions. Turoňová et al. now show that the spike is flexibly connected to the viral surface by three hinges that are well protected by glycosylation sites. The flexibility imparted by these hinges may explain how multiple spikes act in concert to engage onto the flat surface of a host cell. Science, this issue p. 203
Determination ofHER2amplification in primary breast cancer using dual-colour chromogenicin situhybridization is comparable to fluorescencein situhybr…
2010
García-Caballero T, Grabau D, Green A R, Gregory J, Schad A, Kohlwes E, Ellis I O, Watts S & Mollerup J (2010) Histopathology56, 472–480 Determination of HER2 amplification in primary breast cancer using dual-colour chromogenic in situ hybridization is comparable to fluorescence in situ hybridization: a European multicentre study involving 168 specimens Aims: Fluorescence in situ hybridization (FISH) can be used to reveal several genomic imbalances relevant to proper cancer diagnosis and to the correct treatment regime. However, FISH requires expensive and advanced fluorescence microscopes in addition to expertise in fluorescence microscopy. To determine whether a newly developed dual-colou…
In situ study of the sintering of a lead phosphovanadate in an Environmental Scanning Electron Microscope
2011
cited By 3; International audience; The in situ sintering of a powder of Pb3(VO4) 1.6(PO4)0.4 composition was performed in an Environmental Scanning Electron Microscope. The electric current induced by the electron beam was found to reduce the effective temperature of sintering as well as to accelerate the kinetics of shrinkage of a cluster composed of sub-micrometric grains of material. The presence of the residual current flow in the cluster during observation for in situ experiments helps to reduce the apparent sintering temperatures from 50 to 150 °C compared to conventional heating conditions without current. © 2011 Elsevier B.V. All rights reserved.
Tribological Aspects of In Situ Manipulation of Nanostructures Inside Scanning Electron Microscope
2014
This chapter is dedicated to manipulation of nanostructures inside a scanning electron (SEM) microscope employed for real-time tribological measurements. Different approaches to force registration and calculation of static and kinetic friction are described. Application of the considered methodology to Au and Ag nanoparticles, as well as ZnO and CuO nanowires, is demonstrated. Advantages and limitations of the methodology in comparison to traditional AFM-based manipulation techniques are discussed.