19 research outputs found
On the interaction of Mg with the (111) and (110) surfaces of ceria
The catalytic activity of cerium dioxide can be modified by deposition of alkaline earth oxide layers or nanoparticles or by substitutional doping of metal cations at the Ce site in ceria. In order to understand the effect of Mg oxide deposition and doping, a combination of experiment and first principles simulations is a powerful tool. In this paper, we examine the interaction of Mg with the ceria (111) surface using both angle resolved X-ray (ARXPS) and resonant (RPES) photoelectron spectroscopy measurements and density functional theory (DFT) corrected for on-site Coulomb interactions (DFT + U). With DFT + U, we also examine the interaction of Mg with the ceria (110) surface. The experiments show that upon deposition of Mg, Ce ions are reduced to Ce3+, while Mg is oxidised. When Mg is incorporated into ceria, no reduced Ce3+ ions are found and oxygen vacancies are present. The DFT + U simulations show that each Mg that is introduced leads to formation of two reduced Ce3+ ions. When Mg is incorporated at a Ce site in the (111) surface, one oxygen vacancy is formed for each Mg to compensate the different valencies, so that all Ce ions are oxidised. The behaviour of Mg upon interaction with the (110) surface is the same as with the (111) surface. The combined results provide a basis for deeper insights into the catalytic behaviour of ceria-based mixed oxide catalysts
Measurement campaign on the JRC Ispra decommissioning site
The purpose of this document is to describe the measurement campaign with the Free Release Measurement Facility (FRMF) at building 41m âInterim Storage Facilityâ (ISF) of material clearable according to existing licenses as part of the collaborative research project MetroDecom.
The description of the measurement campaign includes the technical requirements and safety implementations necessary for carrying out this project.
The Free Release Measurement Facility (FRMF) was designed as a state of the art facility for measurement of low gamma-ray activity waste packages. Gamma spectrometric method for free release measurment was developed. The complemented with passive neutron counting method. The both methods are used for different nuclide contents in the waste and are complementary.
For this purpose the instrument incorporates:
â Three passive neutron counters (design of JRC)
â A gamma-ray detection system HPGe Interchangeable Detector Module IDM-200-V (ORTEC)
â NuDET Plastic Scintillation Detectors (design of NUVIA)
Decommissioning unit delivered seventy containers with material clearable according to existing JRC licenses. JRC G.II.7 performed the testing of the free release measurement system. The document contains the overview of that measurement campaign. The detailed measurement protocols, spectra generated by FRMF software are shared with MetroDecom Partners.JRC.G.II.7-Nuclear securit
X-ray microscopy of living multicellular organisms with the Prague Asterix Iodine Laser System
Soft X-ray contact microscopy (SXCM) experiments have been performed
using the Prague Asterix Iodine Laser System (PALS). Laser wavelength
and pulse duration were λ = 1.314 ÎŒm and Ï (FWHM) = 450 ps,
respectively. Pulsed X rays were generated using teflon, gold, and
molybdenum targets with laser intensities I â„
1014 W/cm2. Experiments have been performed
on the nematodes Caenorhabditis elegans. Images were recorded
on PMMA photo resists and analyzed using an atomic force microscope
operating in contact mode. Our preliminary results indicate the
suitability of the SXCM for multicellular specimens
Density, porosity, mineralogy, and internal structure of cosmic dust and alteration of its properties during high velocity atmospheric entry
X-ray microtomography (XMT), X-ray diffraction (XRD) and magnetic hysteresis measurements were used to determine micrometeorite internal structure, mineralogy, crystallography, and physical properties at ~Όm resolution. The study samples include unmelted, partially melted (scoriaceous) and completely melted (cosmic spherules) micrometeorites. This variety not only allows comparison of the mineralogy and porosity of these three micrometeorite types, but also reveals changes in meteoroid properties during atmospheric entry at various velocities. At low entry velocities, meteoroids do not melt, and their physical properties do not change. The porosity of unmelted micrometeorites varies considerably (0-12%) with one friable example having porosity around 50%. At higher velocities, the range of meteoroid porosity narrows, but average porosity increases (to 16-27%) due to volatile evaporation and partial melting (scoriaceous phase). Metal distribution seems to be mostly unaffected at this stage. At even higher entry velocities, complete melting follows the scoriaceous phase. Complete melting is accompanied by metal oxidation and redistribution, loss of porosity (1 ± 1%), and narrowing of the bulk (3.2 ± 0.5 g/cm3) and grain (3.3 ± 0.5 g/cm3) density range. Melted cosmic spherules with a barred olivine structure show an oriented crystallographic structure, whereas other subtypes do not.Peer reviewe
Shock pressure induced by 0.44 [mu]m laser radiation on aluminum targets
Shock pressure generated in aluminum targets due to the interaction
of 0.44 ÎŒm (3 Ï of iodine laser) laser radiation has been
studied. The laser intensity profile was smoothed using phase zone
plates. Aluminum step targets were irradiated at an intensity
I â 1014 W/cm2. Shock velocity in
the aluminum target was estimated by detecting the shock luminosity
from the target rear using a streak camera to infer the shock pressure.
Experimental results show a good agreement with the theoretical model
based on the delocalized laser absorption approximation. In the present
report, we explicitly discuss the importance of target thickness on the
shock pressure scaling
A Survey of Methods for 3D Model Feature Extraction, Bulletin of IV. Seminar "Geometry and Graphics in Teaching Contemporary Engineer
Abstract. This paper deals with problems that are related to a feature extraction from 3D objects. The main aim of the feature extraction is to describe a shape of 3D object by a feature vector. Then the elements of this feature vector characterize the shape of the own 3D objects and they can serve as a key in searching for similar models. In this paper are introduced current methods for the feature extraction of 3D models and their classification. These methods are based on different mathematical background and according to that they are separated into several groups. Key words: feature extraction, retrieval system 1
Clinical utility of intracardiac echocardiography in transvenous lead extraction
The epidemics of heart failure and an aging population resulted in an exponential rise in the use of cardiac implantable devices (CIEDs) in developed countries. This is paralleled by the increased rate of complications such as system infection or malfunction. The higher number of complications, and longer patient life expectancies, are followed by an increase in the need for lead extractions. 
On the interaction of Mg with the (111) and (110) surfaces of ceria
The catalytic activity of cerium dioxide can be modified by deposition of alkaline earth oxide layers or nanoparticles or by substitutional doping of metal cations at the Ce site in ceria. In order to understand the effect of Mg oxide deposition and doping, a combination of experiment and first principles simulations is a powerful tool. In this paper, we examine the interaction of Mg with the ceria (111) surface using both angle resolved X-ray (ARXPS) and resonant (RPES) photoelectron spectroscopy measurements and density functional theory (DFT) corrected for on-site Coulomb interactions (DFT + U). With DFT + U, we also examine the interaction of Mg with the ceria (110) surface. The experiments show that upon deposition of Mg, Ce ions are reduced to Ce3+, while Mg is oxidised. When Mg is incorporated into ceria, no reduced Ce3+ ions are found and oxygen vacancies are present. The DFT + U simulations show that each Mg that is introduced leads to formation of two reduced Ce3+ ions. When Mg is incorporated at a Ce site in the (111) surface, one oxygen vacancy is formed for each Mg to compensate the different valencies, so that all Ce ions are oxidised. The behaviour of Mg upon interaction with the (110) surface is the same as with the (111) surface. The combined results provide a basis for deeper insights into the catalytic behaviour of ceria-based mixed oxide catalysts
Substrate- to Laterally-Driven Self-Assembly Steered by Cu Nanoclusters: The Case of FePcs on an Ultrathin Alumina Film
We show that, for the formation of a metallorganic monolayer, it is possible to artificially divert from substrate- to laterally-driven self-assembly mechanisms by properly tailoring the corrugation of the potential energy surface of the growth template. By exploiting the capability of an ultrathin alumina film to host metallic nanoparticle seeds, we tune the symmetry of a iron phthalocyanine (FePc) two-dimensional crystal, thus showing that it is possible to switch from trans to lateral dominating interactions in the controlled growth of an organic/inorganic heterostack. Finally, by selecting the size of the metallic clusters, we can also control the FePc 12metal interaction strength