Search results for "Filter"

Facepiece filtering respirators with exhalation valve should not be used in the community to limit SARS-CoV-2 diffusion.

2020

Shaded-mask filtering: novel strategy for improvement of resolution in radial-polarization scanning microscopy

2006

Radially polarized illumination produces, in combination with annular pupil filtering, the sharpest focal spot. However, the enhanced sidelobes produce an effective deterioration of spatial resolution. This study shows that if one substitutes the annular filter by one, adequately designed, shaded-mask filter, the sidelobes' strength is strongly reduced, and an important, effective improvement of resolution is achieved.

Microscope system with on axis programmable Fourier transform filtering

2017

Abstract We propose an on-axis microscope optical system to implement programmable optical Fourier transform image processing operations, taking advantage of phase and polarization modulation of a liquid crystal on silicon (LCOS) display. We use a Hamamatsu spatial light modulator (SLM), free of flickering, which therefore can be tuned to fully eliminate the zero order component of the encoded diffractive filter. This allows the realization of filtering operation on axis (as opposed to other systems in the literature that require operating off axis), therefore making use of the full space bandwidth provided by the SLM. The system is first demonstrated by implementing different optical proce…

Analytical design of 160 Gbits/s densely dispersion-managed optical fiber transmission systems using Gaussian and raised cosine RZ ansätze

2004

We present an easy and efficient analytical method to design 160 Gbits/s densely dispersion-managed optical fiber transmission systems using Gaussian and raised cosine RZ ansatze.

LabVIEW modeling and simulation, of the low-pass and high-pass analog filters

2015

Some programs for simulating different types of filters are developed using LabView software. Implementing a simulation program of an analog filter requires the prior establishment of mathematical model. As a general purpose programming environment, LabVIEW offers possibility of achieving some user programs for plotting frequency characteristics of passive and active analog filters, if established beforehand mathematical models that characterize their behavior. The scientific objectives of this paper are: -the analysis of the possibilities of using virtual instrumentation in the study of electrical filters; -implementation of virtual instruments for analysis and simulation of analog filters…

Comparison of the decameric structure of peroxiredoxin-II by transmission electron microscopy and X-ray crystallography

2001

Abstract The decameric human erythrocyte protein torin is identical to the thiol-specific antioxidant protein-II (TSA-II), also termed peroxiredoxin-II (Prx-II). Single particle analysis from electron micrographs of Prx-II molecules homogeneously orientated across holes in the presence of a thin film of ammonium molybdate and trehalose has facilitated the production of a ≥20 A 3-D reconstruction by angular reconstitution that emphasises the D5 symmetry of the ring-like decamer. The X-ray structure for Prx-II was fitted into the transmission electron microscopic reconstruction by molecular replacement. The surface-rendered transmission electron microscopy (TEM) reconstruction correlates well…

Isolation of the left atrial surface from cardiac multi-detector CT images based on marker controlled watershed segmentation

2006

The delineation of left atrium (LA) and pulmonary veins (PVs) anatomy from high resolution images holds importance for atrial fibrillation (AF) investigation and treatment. In this study, a semiautomatic segmentation procedure for LA and PVs inner surface from contrast enhanced CT data was developed. The procedure consists of a three dimensional marker controlled watershed segmentation applied to the external morphological gradient, followed by variable threshold surface extraction from the original intensity image. A preliminary anisotropic non-linear filtering was implemented to improve the S/N ratio of CT images. The performance of segmentation was evaluated on cardiac CT scans of 12 AF …

Motion analysis using the novelty filter

1991

Abstract An original approach to the motion analysis, based on the novelty filter, is proposed. The novelty filter stresses the novelties occurring in a pattern representing an image of the scene under consideration with respect to patterns representing previous images of the same scene, so that visual information about the motion of the objects is obtained. The novelty filter may be implemented by a neural network architecture, taking advantage of the capabilities of massive parallelism, adaptive learning and noise robustness. The novelty filter may learn the entire trajectory of an object, through an incremental learning of a sequence of images capturing the scene, thus emphasizing if the…

Automatic detection and analysis of cell motility in phase-contrast time-lapse images using a combination of maximally stable extremal regions and Ka…

2013

Phase-contrast illumination is simple and most commonly used microscopic method to observe nonstained living cells. Automatic cell segmentation and motion analysis provide tools to analyze single cell motility in large cell populations. However, the challenge is to find a sophisticated method that is sufficiently accurate to generate reliable results, robust to function under the wide range of illumination conditions encountered in phase-contrast microscopy, and also computationally light for efficient analysis of large number of cells and image frames. To develop better automatic tools for analysis of low magnification phase-contrast images in time-lapse cell migration movies, we investiga…

A fiber-based limiter at 170 Gbit/s for all-optical regeneration

2009

We report the numerical and experimental studies of a spectrally filtered fiber-based optical limiter at 170 Gbit/s. The device, including less than 1 km-long of highly nonlinear optical fiber and a 3 nm-width filter, exhibits good performance at an average input power of 14.5 dBm. No power penalty has been observed and a strong robustness against optical noise has been demonstrated.