Search results for "Contrast"
showing 10 items of 1162 documents
Robust association between vascular habitats and patient prognosis in glioblastoma: An international multicenter study
2019
Background Glioblastoma (GBM) is the most aggressive primary brain tumor, characterized by a heterogeneous and abnormal vascularity. Subtypes of vascular habitats within the tumor and edema can be distinguished: high angiogenic tumor (HAT), low angiogenic tumor (LAT), infiltrated peripheral edema (IPE), and vasogenic peripheral edema (VPE). Purpose To validate the association between hemodynamic markers from vascular habitats and overall survival (OS) in glioblastoma patients, considering the intercenter variability of acquisition protocols. Study Type Multicenter retrospective study. Population In all, 184 glioblastoma patients from seven European centers participating in the NCT03439332 c…
Rectal cancer: Assessment of response to neoadjuvant chemoradiation by dynamic contrast-enhanced MRI
2012
Purpose To assess pretreatment functional and morphological tumor characteristics with magnetic resonance imaging (MRI) in advanced rectal carcinoma and to identify factors predicting response to neoadjuvant chemoradiation. Materials and Methods In a prospective study, 95 patients with rectal carcinoma underwent dynamic contrast-enhanced MRI before and after chemoradiation. Quantitative parameters were derived from a pharmacokinetic two-compartment model. Tumors were also characterized with regard to mucinous status at pretreatment high-resolution MRI as nonmucinous or mucinous. Response to treatment was defined as a downshift in the local tumor stage. Results The parameter k21 (contrast me…
Optical Imaging and Spectroscopy of Atomically Precise Armchair Graphene Nanoribbons
2019
We report the optical imaging and absorption spectroscopy on atomically precise armchair graphene nanoribbons (GNRs) on insulating fused silica substrates. This is achieved by controlling light polarization on macroscopically aligned GNRs which greatly enhances the optical contrast of the submonolayer GNRs on the insulating substrates. We measure the linear absorption spectra of 7-armchair and 9-armchair GNRs in this study, and the experimental data agree qualitatively with ab inito calculation results. The polarization spectroscopy technique enables an unambiguous optical identification of GNRs and provides a rapid tool to characterize the transferred film over a large area.
Improvement of two-dimensional structured illumination microscopy with an incoherent illumination pattern of tunable frequency.
2018
In two-dimensional structured illumination microscopy (2D-SIM), high-resolution images with optimal optical sectioning (OS) cannot be obtained simultaneously. This tradeoff can be overcome by using a tunable-frequency 2D-SIM system and a proper reconstruction method. The goal of this work is twofold. First, we present a computational approach to reconstruct optical-sectioned images with super-resolution enhancement (OS-SR) by using a tunable SIM system. Second, we propose an incoherent tunable-frequency 2D-SIM system based on a Fresnel biprism implementation. Integration of the proposed computational method with this tunable structured illumination (SI) system results in a new 2D-SIM system…
A comparison of different optimization algorithms for retrieving aerosol optical depths from satellite data: an example of using a dual-angle algorit…
2011
Optimization techniques are often used in remote sensing retrieval of surface or atmospheric parameters. Nevertheless, different algorithms may exhibit different performances for the same optimization problem. Comparison of some classic optimization approaches in this article aims to select the best method for retrieving aerosol opacity, or even for other parameters, from remotely sensed data. Eight frequently used optimization algorithms were evaluated using both simulated data and actual AATSR advanced along track scanning radiometer data. Several typical land cover types and aerosol opacity levels were also considered in the simulations to make the tests more representative. It was obser…
Comparison of Numerical Methods in the Contrast Imaging Problem in NMR
2013
International audience; In this article, the contrast imaging problem in nuclear magnetic resonance is modeled as a Mayer problem in optimal control. A first synthesis of locally optimal solutions is given in the single-input case using geometric methods based on Pontryagin's maximum principle. We then compare these results using direct methods and a moment-based approach, and make a first step towards global optimality. Finally, some preliminary results are given in the bi-input case.
Zilo gaismu bloķējošo lēcu ietekme uz kontrastjutību
2018
Bakalaura darbs ir 21 lappaspusi garš, satur 9. attēlus, 1. tabulu un 39. literatūras atsauces. Darba mērķis ir novērtēt zilo gaismu bloķējošo lēcu ietekmi uz kontrastjutību. Mērījumi tika veikti, izmantojot Pelli-Robsona testu, kurš tika rādīts iPad telefonā. Mērījumā piedalījās 55 dalībnieki. Mērījumi tika veikti ar briļļu lēcām, kurām bija zilo gaismu bloķējošais klājums, kā arī ar lēcām, kurām bija tradicionālais pretatspīdumu klājums. Kontrastjutība bija labāka ar zilo gaismu bloķējošām lēcām nekā ar lēcām, kurām bija tradicionālais pretatspīdumu klājums (p<0.001). Dalībniekiem ar sūdzībām par žilbšanu kontrastjutības uzlabojums ar zilo gaismu bloķējošām lēcām bija lielāks nekā dalībni…
Engaging in upward and downward comparisons as a determinant of relative deprivation at work
2003
A longitudinal study was conducted among 93 nurses to determine the role of comparing one's performance with that of one's colleagues in the increase versus decrease of perceived relative deprivation at work over a period of one year. Relative deprivation at T2 had increased particularly among those high in social comparison orientation (Gibbons & Buunk, 1999) who at T1 (1) more frequently engaged in upward comparisons; (2) more frequently derived positive as well as negative feelings from such comparisons; and (3) more frequently derived negative feelings from downward comparison. Moreover, engaging in downward comparison also led to an increase in perceived relative deprivation at T2.…
Knowledge and management of temporomandibular joint disorders by general dentists in Spain
2019
Background Given the importance of temporomandibular disorders (TMD), we tried to assess general dentists’ knowledge regarding etiology, diagnosis, and treatment in order to understand their attitude. Material and Methods A sample of 130 general dentists answered a 16-item questionnaire on three areas – etiology, diagnosis, and management of common temporomandibular disorders – as well as a question on the need for continuous education regarding TMD management in common clinical practice in Spain. Given that the descriptive statistics achieved reflect significantly different values among means in each area, a variance analysis for repeated measurements was applied in order to contrast diffe…
School Teaching in Germany Between Tradition and Innovation: The Concept of the Outdoor School
2019
It is a well known fact that school is seen as having a spatial characteristic, being associated to indoor learning. The aim of this chapter is to underlined the idea that learning and educational processes can take place in different settings, and to offer other experiences that the traditional classroom with its specific conditions largely neglected. The dimensions of space, time, and body are re-evaluated from the perspective of outdoor education which faces children (and teachers) with new, sometimes challenging, and adventurous experiences that contrast with an everyday routine of school instruction.