Idealized Slab Plasma approach for the study of Warm Dense Matter

Recently, warm dense matter (WDM) has emerged as an interdisciplinary field that draws increasing interest in plasma physics, condensed matter physics, high pressure science, astrophysics, inertial confinement fusion, as well as materials science under extreme conditions. To allow the study of well-defined WDM states, we have introduced the concept of idealized-slab plasmas that can be realized in the laboratory via (i) the isochoric heating of a solid and (ii) the propagation of a shock wave in a solid. The application of this concept provides new means for probing the dynamic conductivity, equation of state, ionization and opacity. These approaches are presented here using results derived from first-principles (density-functional type) theory, Thomas-Fermi type theory, and numerical simulations.Comment: 37 pages, 21 figures, available, pdf file only. To appear in: Laser and Particle beams. To appear more or less in this form in Laser and Particle beam

Dielectric spectroscopy study of thermally-aged extruded model power cables

“Model” extruded power cables, having a much reduced geometry but using the same extrusion techniques and materials as full-sized cables, have been examined using dielectric spectroscopy techniques to study their thermal ageing effects. Cables insulated with homo-polymer XLPE and co-polymer of XLPE with micron-sized ethylene-butyl-acrylate (EBA) islands were studied by both frequency-domain and time-domain dielectric spectroscopy techniques after accelerated thermal ageing under 135°C for 60 days. In the frequency domain, a frequency response analyzer (FRA) was used to measure the frequency range from 10-4Hz to 1Hz at temperatures from 20°C to 80°C. In the time domain, a special charging/discharging current measurement system was developed to measure the frequencies from 10-1Hz to 102Hz. These techniques were chosen to cope with the extremely low dielectric losses of the model cables. The results are compared with those from new model power cables that were degassed at 80°C for 5 days. Thermal ageing was found to increase the low-frequency conductivity, permittivity and the discharging current. Both homo- and co-polymer cables have substantial increase of dielectric loss after ageing

Structure of the Local-field factor of the 2-D electron fluid. Possible evidence for correlated scattering of electron pairs

The static local-field factor (LFF) of the 2-D electron fluid is calculated {\it nonperturbatively} using a mapping to a classical Coulomb fluid $\lbrack$Phys. Rev. Lett., {\bf 87}, 206$\rbrack$. The LFF for the paramagnetic fluid {\it differs markedly} from perturbation theory where a maximum near 2$k_F$ is expected. Our LFF has a quasi-linear small-k region leading to a maximum close to 3$k_F$, in agreent with currently available quantum Monte Carlo data. The structure in the LFF and its dependence on the density and temperature are interpretted as a signature of correlated scattering of electron pairs of opposite spin.The lack of structure at $2k_F$ implies weakened Friedel oscillations, Kohn anomalies etc.Comment: 4 pages, 3 figures, version 2 of condmat/0304034, see http://nrcphy1.phy.nrc.ca/ims/qp/chandre/chnc/ Changs in the text, figure 2 and updated reference

Quantum Brayton cycle with coupled systems as working substance

We explore the quantum version of Brayton cycle with a composite system as the working substance. The actual Brayton cycle consists of two adiabatic and two isobaric processes. Two pressures can be defined in our isobaric process, one corresponds to the external magnetic field (characterized by $F_x$) exerted on the system, while the other corresponds to the coupling constant between the subsystems (characterized by $F_y$). As a consequence, we can define two types of quantum Brayton cycle for the composite system. We find that the subsystem experiences a quantum Brayton cycle in one quantum Brayton cycle (characterized by $F_x$), whereas the subsystem's cycle is of quantum Otto in another Brayton cycle (characterized by $F_y$). The efficiency for the composite system equals to that for the subsystem in both cases, but the work done by the total system are usually larger than the sum of work done by the two subsystems. The other interesting finding is that for the cycle characterized by $F_y$, the subsystem can be a refrigerator while the total system is a heat engine. The result in the paper can be generalized to a quantum Brayton cycle with a general coupled system as the working substance.Comment: 7 pages, 3 figures, accepted by Phys. Rev.

Early improvement of respiratory function after surgical plication for unilateral diaphragmatic paralysis

We reported an unusual case of symptomatic diaphragmatic paralysis in an elderly patient with progressive respiratory-dependent limitation of her daily activities. Surgical plication of the affected hemidiaphragm resulted in early clinical and physiological improvement

Du tâtonnement ethnographique au discernement de sens : enquêtes participatives en boucherie et dans la zone d'attente des mineurs isolés étrangers

Partant d’univers de recherche a priori éloignés – la boucherie et la zone d’attente des mineurs isolés étrangers – cet article repose sur une affirmation commune : pour rendre compte des catégories mobilisées par les enquêtés, il faut se mettre en situation de les percevoir. En ce qu’elle rend observable et descriptible le recours à des catégories in situ, l’ethnographie est apparue comme un moyen d’accéder à ce qui est constitutif des expériences de travail. L’enrôlement dans les actions en cours s’est réalisé selon des conditions d’entrée et des modalités distinctes : stagiaire volontaire et experte involontaire. En examinant les configurations d’enquête, l’article montre comment la modulation de la présence participative peut induire le déplacement de la problématique de recherche

Cosmic-ray propagation properties for an origin in SNRs

We have studied the impact of cosmic-ray acceleration in SNR on the spectra of cosmic-ray nuclei in the Galaxy using a series expansion of the propagation equation, which allows us to use analytical solutions for part of the problem and an efficient numerical treatment of the remaining equations and thus accurately describes the cosmic-ray propagation on small scales around their sources in three spatial dimensions and time. We found strong variations of the cosmic-ray nuclei flux by typically 20% with occasional spikes of much higher amplitude, but only minor changes in the spectral distribution. The locally measured spectra of primary cosmic rays fit well into the obtained range of possible spectra. We further showed that the spectra of the secondary element Boron show almost no variations, so that the above findings also imply significant fluctuations of the Boron-to-Carbon ratio. Therefore the commonly used method of determining CR propagation parameters by fitting secondary-to-primary ratios appears flawed on account of the variations that these ratios would show throughout the Galaxy.Comment: Accepted for publication in Ap

Manufacturing cement-based materials and building products via extrusion: From laboratory to factory

Manufacturing is critical to the economies of the UK and many other countries in the rest of the world. However, manufacturing of cement-based materials and building products predominantly remains based on old batch processing such as casting and pressing technologies and this may limit the applications and performance of the materials and products formed. In this paper, research is reported on transforming manufacturing of precast cement-based materials and building products from in batches to continuous processes via extrusion. Techniques used for producing plastic products are transferred into manufacturing cement-based building products like flat and corrugated sheet tiles, down pipes, door/window frames, door panels, solid wall/facade panels, honeycomb wall/facade panels etc. at laboratory and factory scales. In combination with sustainable cementitious materials with low carbon and low energy as matrix, this enables sustainable building products with key characteristics required by the 21st century can be manufactured via extrusion. The cement-based building products extrusion technique has been successfully transferred to industry. For instance, fibre reinforced cement-based partition wall panels, with a honeycomb cross section as large as 600 mm wide and 90 mm high, have been produced by a continuous extrusion process in a precast concrete products factory in Hangzhou, China.European Commission Seventh Framework Programme, (grant agreement no. 262954) and from the Hong Kong Research Grants Council through grants 6091/00E, 6226/01E, 6273/03E and 6167/06