Search results for " Emission"
showing 10 items of 1496 documents
Imaging techniques in inflammatory bowel disease: recent trends, questions and answers
2009
Summary Imaging techniques have undergone substantial progress in recent years and contribute significantly in the diagnosis of inflammatory bowel diseases in conjunction with patient history, clinical and laboratory examination. Modern cross-sectional imaging modalities such as computed tomography and magnetic resonance imaging allow an evaluation not only of the complete bowel wall of the small intestine, but also of extraluminal structures. They constitute a major diagnostic component in the initial workup, in stricturing or fistulizing disease and in suspected abscess. Transabdominal ultrasonography has been re-appreciated in these settings as an easy- and ready-to-use tool yielding rea…
An unusual case of chronic diarrhea: a case report
2022
Gastroenteropancreatic-neuroendocrine neoplasms or tumors (GEP-NEN or NETs) are rare tumors arising from the diffuse neuroendocrine system. This clinical case highlights the complexity of the diagnostic process and the difficulties in interpreting the examinations for this type of tumor, showing how the negativity of firstlevel examinations did not prevent from performing further investigations, in the presence of a suggestive clinical presentation. The search of similar cases in the published literature suggests that this represents an unusual presentation of a NET.
Diffractive optics for spectral tuning of second harmonic and supercontinuum generated in nonlinear crystals
2011
It is shown that diffractive lenses can tune the spectrum of femtosecond pulses after nonlinear optical processes. We focus on spectra of second-order pulses generated in birefringent crystals and supercontinuum in sapphire crystals. The tunability is achieved by changing the relative distance between the nonlinear crystal and the diffractive lens.
Crystalline microstructure of sepiolite influenced by grinding
2005
The crystalline microstructure of ground sepiolite has been investigated. A reference sample of sepiolite and products of its comminution by dry grinding were studied through X-ray diffraction pattern analysis, specific surface measurements by nitrogen adsorption and complementary analysis of field emission scanning electron microscope images. A statistical model of polycrystals was applied to describe and determine the crystalline microstructure of the studied specimens. The model parameters characterizing the microstructure were prevalent crystallite shape, volume-weighted crystallite size distribution and second-order crystalline lattice strain distribution, and they were determined for …
Artificially inscribed defects in opal photonic crystals
2005
Opals are three-dimensional photonic crystals, self-assembled from dielectric spherical beads into a face-centered cubic lattice. By introducing intentional defects in the crystal lattice, one modifies features such as spontaneous emission and the directionality of diffracted light. We here present a method for the artificial introduction of a lattice of such intentional defects in self-assembled poly(methyl methacrylate) (PMMA) photonic crystals by means of electron beam lithography. The inscribed defects are of the size of an individual bead, providing a broad spectral range between adjacent resonance peaks. This opens for devices with single line transmission in the photonic band gap, as…
<title>Forward diffracted parametric X radiation from a thick Tungsten single crystal at 855 MeV electron energy</title>
2007
Features of forward diffracted Parametric X-Radiation (PXR) were investigated at experiments with the 855 MeV electron beam of the Mainz Microtron MAMI employing a 410 micrometer thick tungsten single crystal. Virtual photons from the electron field are diffracted by the (10-1) plane at a Bragg angle of 3.977 degree. Forward emitted radiation was analyzed at an energy of 40 keV with the (111) lattice planes of a flat silicon single crystal in Bragg geometry. Clear peak structures were observed in an angular scan of the tungsten single crystal. The results were analyzed with a model which describes forward diffracted PXR under real experimental conditions. The experiments show that forward d…
Effect of gamma radiation on thermostimulated exoelectron emission from Gd2O3 films
2020
Abstract The effect of gamma irradiation on Gd2O3 films was studied using the thermostimulated exoelectron emission (TSEE) technique. The films were deposited on a glass and Si/SiO2 substrates using an extraction-pyrolytic method. Crystalline structure, chemical composition, film thickness and surface morphology were characterized by means of X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and atomic force microscopy (AFM). The films were irradiated by 10 MeV gamma photons and TSEE was measured from the irradiated films. It was found that gamma irradiation decreases TSEE intensity and the area below TSEE spectral curves. A linear correlati…
Mechanism of photoluminescence in intrinsically disordered CaZrO3 crystals: First principles modeling of the excited electronic states
2017
Abstract CaZrO3 (CZO) powders obtained by the polymeric precursor method at 400 °C, and then, the samples were annealed at different temperatures (400, 600, 800, and 1000 °C) and characterized by X-ray diffraction, Raman and ultraviolet–visible spectroscopic methods, along with photoluminescence (PL) emissions. First principle calculations based on the density functional theory (DFT), using a periodic cell models, provide a theoretical framework for understanding the PL spectra based on the localization and characterization of the ground and electronic excited states. Fundamental (singlet, s ) and excited (singlet, s* , and triplet, t* ) electronic states were localized and characterized us…
Impacts of roundabouts in suburban areas on congestion-specific vehicle speed profiles, pollutant and noise emissions: an empirical analysis
2019
Abstract Increasing concern about global warming and air quality has meant an increasing use of energetic and environmental indicators in roundabout design. This research compares different suburban roundabouts in terms of traffic performance, pollutant and noise emissions through an integrated empirical assessment. Field measurements were carried out with a light duty vehicle in single-lane (SL), compact two-lane (CTL) and multi-lane (ML) roundabouts using Portable Emission Measurements Systems, On-Board Diagnostic scan tool and Sound Level Meter, to measure real-world exhaust emissions, engine activity and acoustic data, respectively. Afterwards, predictive discrete choice models that cor…
Application of wavelet analysis to acoustic emission pulses generated by partial discharges
2004
The subject matter of this paper refers to the improvement of the acoustic emission (AE) method when used for detection, measurement and location of partial discharges (PDs) in oil insulation systems of power appliances. The detailed subject matter refers to the issues connected with the application of modern methods of digital processing of signals obtained during technical high-power measurements. The paper presents the results of measurements and analyses of the AE pulses generated in setups making the modeling of basic PD forms that can occur in oil insulations possible. The research concentrated mainly on the following types of PDs: point-plane, multipoint-plane, multipoint-plane with …