1,720,963 research outputs found
Fabrication and characterization of spiral phase masks for super-resolution
Full text linkConfocal microscopy, with both high lateral and axial resolution, has enabled the observation of the inner workings of cells and tissues with great detail. Strong scattering and absorption of light, though, strongly limit the depth at which samples can be imaged, and resolution is limited to a wavelength-wide area in the focal plane by diffraction. Sample penetration of hundreds of µm can be reached by nonlinear microscopy, based on the interaction between the tissue and multiple infrared photons, that undergo much less scattering and absorption. Resolutions of just tens of nanometers can also be reached with STED microscopy, an upgrade to the confocal architecture. Two-photon excitation STED (TPE-STED) microscopes have been invented in the last decade to combine the two properties, with resolution gains up to 4-5 times the diffraction-limited systems, at depths of tens of microns. Still, scattering and absorption of the depletion beam limit the observation of super-resolved features in the 100 µm regions. The aim of this thesis was the development of the first TPE-STED microscope working with excitation wavelengths in the [1000−1500] nm range and depletion wavelengths near 800 nm, capable of surpassing the depth limit of current STED microscopes. Suitable fluorophores must be used in this regime, so we tested the depletion performance of ATTO 594, ATTO 647N and mGarnet2. In parallel, we used the dual-beam nature of the platform to provide simultaneous nonlinear imaging with both degenerate and nondegenerate absorption of photons at the different wavelengths. A consistent part of the thesis work was also centered on the development of a protocol of fabrication and characterization optical elements for the manipulation of the STED beam. This was done in order to be able to freely couple every selected fluorophore with its most efficient depletion wavelength, without the need for long waiting times of commercial applications
Fabrication and characterization of high-quality spiral phase plates for optical applications
No full textA perspective on NETosis in diabetes and cardiometabolic disorders
No full textAims: To review the significance of a new type of neutrophil cell death (NETosis) in diabetes and cardiometabolic diseases.
Data synthesis: Diabetes and the metabolic syndrome are characterized by activation of the innate immune system. In this framework, neutrophils are front line defences against infections, but can also turn deleterious if abnormally stimulated. NETosis refers to a type of cell death whereby neutrophils release nuclear material and granule enzymes that together form the NETs (neutrophil extracellular traps). As NETs entrap bacteria, NETosis is instrumental to the clearance of microorganisms, but an exaggerated NETosis response can also lead to tissue damage in several pathological conditions. In diabetes, the finely tuned balance of NETosis required to protect the human body from microorganisms yet avoiding self-damage seems to be lost. In fact, in vitro induction of NETosis and circulating concentrations of NET-associated proteins appear to be enhanced in diabetic patients. Furthermore, NETs contribute to endothelial damage, thrombosis, and ischemia/reperfusion injury, making it a novel player in the pathobiology of cardiovascular disease. Though the cellular events taking place during NETosis have been described and directly visualized, its molecular machinery is still incompletely understood. Protein kinase C (PKC) and NADPH oxidase (NOX) are two important targets to counter NETosis in the setting of diabetes.
Conclusions: NETosis appears to be part of an abnormal response to damage in diabetes that, in turn, can promote or aggravate end-organ complications. We suggest that this will be a hot topic of investigation in diabetology in the near futur
Multimodal label-free ex vivo imaging using a dual-wavelength microscope with axial chromatic aberration compensation
Full text linkLabel-free microscopy is a very powerful technique that can be applied to study samples with no need for exogenous fluorescent probes, keeping the main benefits of multiphoton microscopy, such as longer penetration depths and intrinsic optical sectioning while enabling serial multitechniques examinations on the same specimen. Among the many label-free microscopy methods, harmonic generation (HG) is one of the most intriguing methods due to its generally low photo-toxicity and relative ease of implementation. Today, HG and common two-photon microscopy (TPM) are well-established techniques, and are routinely used in several research fields. However, they require a significant amount of fine-tuning to be fully exploited, making them quite difficult to perform in parallel. Here, we present our designed multimodal microscope, capable of performing simultaneously TPM and HG without any kind of compromise thanks to two, separate, individually optimized laser sources with axial chromatic aberration compensation. We also apply our setup to the examination of a plethora of ex vivo samples to prove its capabilities and the significant advantages of a multimodal approach
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
Generation and exploitation of high-order oam beams for anti-counterfeiting applications
No full textAppropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe 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
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
- …
