Search results for "Contrast"
showing 10 items of 1162 documents
Locally weighted minimum contrast estimation for spatio-temporal log-Gaussian Cox processes
2023
A local version of spatio-temporal log-Gaussian Cox processes is proposed by using Local Indicators of Spatio-Temporal Association (LISTA) functions plugged into the minimum contrast procedure, to obtain space as well as time-varying parameters. The new procedure resorts to the joint minimum contrast fitting method to estimate the set of second-order parameters. This approach has the advantage of being suitable in both separable and non-separable parametric specifications of the correlation function of the underlying Gaussian Random Field. Simulation studies to assess the performance of the proposed fitting procedure are presented, and an application to seismic spatio-temporal point pattern…
Confronto tra mezzi di contrasto con differente concentrazione iodica nell’imaging di placca coronarica mediante Tomografia Computerizzata Multistrat…
2012
Influenza della concentrazione iodica dei mezzi di contrasto sulla caratterizzazione della placca aterosclerotica coronarica valutata mediante TC Mul…
2010
Desktop X-ray tomography for low contrast samples
2013
Abstract Based on the experience in the use of polycapillary optical systems, recently XLab Frascati LNF and IM CNR have been strongly involved in studying the techniques for high resolution X-ray Imaging and micro-tomography that intends in the development of a new imaging instrument to examine low contrast samples complicated by fast developing processes. In order to get the reliable signal to noise ratio, typically available via synchrotron radiation (SR) dedicated X-ray optical devices, for the desktop solutions we have to increase the radiation fluxes from conventional sources. As known, manipulated through polycapillary optics beams result in getting higher fluxes with respect to a pi…
Choosing among alternative technological strategies: an empirical analysis of formal sources of innovation
2003
Abstract This work aims to offer a detailed conceptual and empirical analysis of the inter-firm differences in deciding the composition of their technological efforts. Using data for Spanish firms in the period 1990–1996, the study begins with the standard analysis of the determinants of innovative investment, then moves on to the less analysed question of the determinants of the generate versus import alternative and ends with a novel analysis of the characteristics which lead firms to organise research internally as compared to the possibility of contracting R&D services externally. In contrast to standard practice, the econometric approach takes into account the existence of non-linearit…
A multiscale X-ray phase-contrast tomography dataset of whole human left lung
2021
ABSTRACTTechnological advancements in X-ray imaging using bright and coherent synchrotron sources now allows to decouple sample size and resolution, while maintaining high sensitivity to the microstructure of soft, partially dehydrated tissues. The recently developed imaging technique, hierarchical phase-contrast tomography, is a comprehensive approach to address the challenge of organ-scale (up to tens of centimeters) soft tissue imaging with resolution and sensitivity down to the cellular level. Using this technique, we imaged ex vivo an entire human left lung at an isotropic voxel size of 25.08 μm along with local zooms down to 6.05 - 6.5 μm and 2.45 - 2.5 μm in voxel size. The high tiss…
PCA-based source-space contrast maps reveal psychologically meaningful individual differences in continuous MEG activity
2019
AbstractWithin the field of neuroimaging, there has been an increasing trend towards studying brain activity in naturalistic conditions, and it is possible to robustly estimate networks of on-going oscillatory activity in the brain. However, not many studies have focused on differences between individuals in on-going brain activity that would be associable to psychological or behavioral characteristics. Existing standard methods can perform well at single-participant level, but generalizing the methodology across many participants is challenging due to individual differences of brains. As an example of a clinically relevant, naturalistic condition we consider here mindfulness. Trait mindful…
Accommodation-related changes in monochromatic aberrations of the human eye as a function of age.
2008
PURPOSE. To investigate the relationship between accommodation and the optical aberrations of the whole human eye, as a function of age. METHODS. Sixty healthy subjects with spherical ametropia in the range 3 D, astigmatism less than 1 D, corrected visual acuity of 20/18 or better, and normal findings in an ophthalmic examination were enrolled. Subjects were divided into four groups, with age ranges of 19 to 29, 30 to 39, 40 to 49, and 50 to 60 years. Monochromatic optical aberrations and pupil size were measured with a Hartmann-Shack wavefront sensor under monocular viewing conditions, without pharmacological dilation or cycloplegia. Stimulus vergences were in the range of 0 to 5 D, with a…
Retinal straylight in patients with monofocal and multifocal intraocular lenses
2007
Purpose To determine the differences in retinal straylight perceived by patients with monofocal intraocular lenses (IOLs) and patients with multifocal IOLs. Setting Vissum-Instituto de Oftalmologico de Alicante, Alicante, Spain. Methods In this prospective study, contrast sensitivity and retinal straylight were measured prospectively 6 months postoperatively in 67 eyes of 40 patients with a monofocal or multifocal IOL. In the monofocal group, a ThinOptX IOL (ThinOptX, Inc.) was implanted in 12 eyes and an Acri.Smart 48 S IOL (Acri.Tec) in 20 eyes. In the multifocal IOL group, a ReZoom IOL (Advanced Medical Optics) was implanted in 13 eyes and a ReSTOR IOL (Alcon Laboratories) in 22 eyes. Re…
Magneto-optical nanomaterials: a SPIO–phthalocyanine scaffold built step-by-step towards bimodal imaging
2013
A SPIO-phthalocyanine nanohybrid is developed as a bimodal contrast agent for Optical and Magnetic Resonance Imaging. The organic coating was covalently attached onto SPIO in a step-by-step approach. Each coated-SPIO was thoroughly characterized. The hydrodynamic size of the SPIO-Pc is ca. 60 nm with a coverage of ca. 690 Pc/SPIO.