Search results for "interaction [electron p]"
showing 10 items of 282 documents
Resonance interaction energy between two accelerated identical atoms in a coaccelerated frame and the Unruh effect
2016
We investigate the resonance interaction energy between two uniformly accelerated identical atoms, interacting with the scalar field or the electromagnetic field in the vacuum state, in the reference frame coaccelerating with the atoms. We assume that one atom is excited and the other in the ground state, and that they are prepared in their correlated symmetric or antisymmetric state. Using perturbation theory, we separate, at the second order in the atom-field coupling, the contributions of vacuum fluctuations and radiation reaction field to the energy shift of the interacting system. We show that only the radiation reaction term contributes to the resonance interaction between the two ato…
Resonance energy transfer between two atoms in a conducting cylindrical waveguide
2018
We consider the energy transfer process between two identical atoms placed inside a perfectly conducting cylindrical waveguide. We first introduce a general analytical expression of the energy transfer amplitude in terms of the electromagnetic Green's tensor; we then evaluate it in the case of a cylindrical waveguide made of a perfect conductor, for which analytical forms of the Green's tensor exist. We numerically analyse the energy transfer amplitude when the radius of the waveguide is such that the transition frequency of both atoms is below the lower cutoff frequency of the waveguide, so that the resonant photon exchange is strongly suppressed. We consider both cases of atomic dipoles p…
Coarse grained and fine dynamics in trapped ion Raman schemes
2004
A novel result concerning Raman coupling schemes in the context of trapped ions is obtained. By means of an operator perturbative approach, it is shown that the complete time evolution of these systems (in the interaction picture) can be expressed, with a high degree of accuracy, as the product of two unitary evolutions. The first one describes the time evolution related to an effective coarse grained dynamics. The second is a suitable correction restoring the {\em fine} dynamics suppressed by the coarse graining performed to adiabatically eliminate the nonresonantly coupled atomic level.
Development of a High Precision Axial 3-D PET for Brain Imaging
2009
We describe a PET device based on a novel method to extract the coordinates of the interaction point of the 511keV γ rays from 100 mm long and thin LYSO (Lutetium Yttrium OxyorthoSilicate) scintillator bars, positioned axially in the tomograph. The coordinate along the hit crystal is measured by using a hodoscope of Wave Length Shifting (WLS) plastic strips mounted perpendicularly to each plane of scintillators. As photodetectors, new Geiger mode Avalanche PhotoDetectors (G-APDs) with integrated electronics are being used to detect both the hit crystal in a block (x and y coordinates) and the interaction point in the crystal (z coordinate) through the light escaping from the crystal and tra…
Master equation for cascade quantum channels: a collisional approach
2012
It has been recently shown that collisional models can be used to derive a general form for the master equations which describe the reduced time evolution of a composite multipartite quantum system, whose components "propagate" in an environmental medium which induces correlations among them via a cascade mechanism. Here we analyze the fundamental assumptions of this approach showing how some of them can be lifted when passing into a proper interaction picture representation.
Towards an Experimental Determination of the Transition Strength Between the Ground States of $^{20}$F and $^{20}$Ne
2017
Electron capture on $^{20}$Ne is thought to play a crucial role in the final evolution of electron-degenerate ONe stellar cores. Recent calculations suggest that the capture process is dominated by the second-forbidden transition between the ground states of $^{20}$Ne and $^{20}$F, making an experimental determination of this transition strength highly desirable. To accomplish this task we are refurbishing an intermediate-image magnetic spectrometer capable of focusing 7 MeV electrons, and designing a scintillator detector surrounded by an active cosmic-ray veto shield, which will serve as an energy-dispersive device at the focal plane.
Phospholipid monolayers at water∣oil interfaces: theoretical modelling of surface pressure–molecular area isotherms
1998
Abstract The phospholipid adsorption and surface pressure–molecular area isotherms at interfaces are interpreted theoretically from two-dimensional (2D) lattice and real gas models that incorporate a minimum number of adjustable parameters. The first model is based on the lattice statistics of binary solutions and the molecular parameters introduced are the energy changes involved in the mixing process of the phospholipid and organic solvent molecules and the effective phospholipid head area. The surface pressure is interpreted in terms of the difference between the two liquid surface tensions. The second model makes use of (i) a non-localised adsorption model with a square-well potential e…
A measurement of material in the ATLAS tracker using secondary hadronic interactions in 7 TeV pp collisions
2016
Knowledge of the material in the ATLAS inner tracking detector is crucial in understanding the reconstruction of charged-particle tracks, the performance of algorithms that identify jets containing b-hadrons and is also essential to reduce background in searches for exotic particles that can decay within the inner detector volume. Interactions of primary hadrons produced in pp collisions with the material in the inner detector are used to map the location and amount of this material. The hadronic interactions of primary particles may result in secondary vertices, which in this analysis are reconstructed by an inclusive vertex-finding algorithm. Data were collected using minimum-bias trigger…
Characterization of trophic links in an agrosystem : weed seed predation by carabid beetles
2012
Agroecology gives evidence of new perspectives in agriculture, and open doors for alternative weed management approaches through different regulation mechanisms. Seed predation is one of them, and the interest is growing to deepen knowledge, relative to this process. This Phd work aims (i) to describe weed seed predation, the dominant carabid predators and the available resource at a local scale in a common crop (winter wheat); (ii) to study predation profiles of main predators, and the pair-wise correlations between the biological components of the system; (iii) to bring new insights regarding potential regulation of weed communities, through seed predation by carabid beetles. Complementar…
Changes in the proteome of sea urchin Paracentrotus lividus coelomocytes in response to LPS injection into the body cavity.
2020
Background The immune system of echinoderm sea urchins is characterised by a high degree of complexity that is not completely understood. The Mediterranean sea urchin Paracentrotus lividus coelomocytes mediate immune responses through phagocytosis, encapsulation of non-self particles, and production of diffusible factors including antimicrobial molecules. Details of these processes, and molecular pathways driving these mechanisms, are still to be fully elucidated. Principal findings In the present study we treated the sea urchin P. lividus with the bacterial lipopolysaccharide (LPS) and collected coelomocytes at different time-points (1, 3, 6 and 24 hours). We have shown, using label-free q…