Plasmon excitations in graphitic carbon spheres

©1998 The American Physical Society. The electronic version of this article is the complete one and can be found online at: http://link.aps.org/doi/10.1103/PhysRevB.57.15599DOI: 10.1103/PhysRevB.57.15599Electron energy loss spectroscopy in a high-resolution transmission electron microscope has recently been used with success to characterize the electronic properties of closed cage nanometer-size graphitic particles. In the plasmon region, the experimental data reveal interesting size-dependent variations, which are not yet fully understood. The difficulties encountered in the interpretation of the spectra are principally due to the lack of a complete theoretical treatment of the anisotropic dielectric response in nanometer-size particles. In order to obtain a better understanding of the experimental data we propose a model based on nonrelativistic local dielectric response theory for electrons penetrating through a nested concentric-shell fullerene or the so-called ‘‘carbon onion.’’ The anisotropy of the electronic properties of the sphere is taken into account via the frequency-dependent dielectric tensor of graphite. The model can be applied to simulate electron energy loss spectra as well as line scans through energy filtered images and allows thus a direct comparison to experimental data

Collective oscillations in a single-wall carbon nanotube excited by fast electrons

©2001 The American Physical Society. The electronic version of this article is the complete one and can be found online at: http://link.aps.org/doi/10.1103/PhysRevB.64.115424DOI: 10.1103/PhysRevB.64.115424Electron energy loss spectroscopy is a well adapted tool for the investigation of the valence excitations of individual nanometer-size particles. The interpretation of the loss spectra of such small particles, however, relies in most cases on a quantitative comparison with simulated excitation probabilities. Here we present a formalism developed for the interpretation of the energy loss data of single-wall carbon nanotubes based on the hydrodynamic theory of plasmon excitations by high-energy electrons. The nanotubes are modeled as a two-dimensional electron gas confined on the circumference of a cylinder. The plasmon excitation probabilities, directly comparable to measurements, are discussed for various parameters

Plasmon excitations in carbon onions: Model vs. measurements

©1998 American Institute of PhysicsNon-relativistic local dielectric response theory has proven successful in the interpretation of Electron Energy Loss data of nanometer-size isotropic particles of different geometries. In previous work, we have adapted this model to take into account anisotropy as encountered in the case of carbon onions. We have shown that this anisotropy needs to be taken into account since important deviations with respect to an isotropic model can be observed. In this contribution, we report on the first energy filtered images of carbon onions and compare intensity profiles across the spheres to our calculations

Functional Impact of Sydenham’s Chorea: A Case Report

Background: Sydenham's chorea (SC) is the most common type of acquired chorea in childhood. In some cases, symptoms (most commonly described in terms of neurological signs) last up to 2 years, and many cases relapse. This report describes the clinical course in terms of functional abilities following diagnosis of SC. Case report: Standardized assessments across the domains of activity and participation were administered following diagnosis, prior to and following treatment with haloperidol to measure treatment response and identify occupational therapy intervention needs. SC was observed to significantly reduce the child's participation and independence in activities of daily living. In this case, the standardized assessments administered highlighted difficulties with both motor and process skills. At 1 week after commencing haloperidol, both motor and process skills had improved. Clinically significant changes in self-care and mobility were noted with less improvement with handwriting. At 9 weeks, most symptoms and functional difficulties had resolved. Discussion: Given the process difficulties detected in this case, and the possibility of enduring symptoms, the use of functional assessments is advocated in the routine management of SC. These findings illustrate the potential for motor and non-motor sequelae in acute childhood movement disorders and related functional disabling consequences

Improving the Numerical Performance of Static and Dynamic Aggregate Discrete Choice Random Coefficients Demand Estimation

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/93649/1/ECTA8585.pd

Reinforcement Learning Algorithm for Mixed Mean Field Control Games

We present a new combined \textit{mean field control game} (MFCG) problem which can be interpreted as a competitive game between collaborating groups and its solution as a Nash equilibrium between groups. Players coordinate their strategies within each group. An example is a modification of the classical trader's problem. Groups of traders maximize their wealth. They face cost for their transactions, for their own terminal positions, and for the average holding within their group. The asset price is impacted by the trades of all agents. We propose a three-timescale reinforcement learning algorithm to approximate the solution of such MFCG problems. We test the algorithm on benchmark linear-quadratic specifications for which we provide analytic solutions