Low Temperature Physics at the Laboratoire National des Champs Magnétiques Pulsés in Toulouse

An overview over past and present activities and future developments at the Toulouse pulsed magnetic field facility is given, both as far as technical developments of the infrastructure, as well as low temperature physics performed at the LNCMP are concerned.     

Crystallization study of chemically vapour-deposited amorphous silicon films by in situ x-ray diffraction

The solid phase crystallization kinetics of chemically vapour-deposited amorphous silicon films were studied by in situ X-ray diffraction. We determined the crystalline volume directly from the Bragg peak intensities at various times during isothermal annealing in the temperature range 578 °C < T < 658 °C. From these experiments we deduced that the crystallization was due to nucleation predominantly at the substrate-film interface followed by crystal growth perpendicular to this interface. The crystal growth rate was thermally activated with an activation energy E_v of 3.1 eV. A strong 〈111〉 preferred orientation of the growing polycrystal was observed and the grain size remained constant at about 60 nm. Evidence of stresses at the amorphous-crystalline interface during the early stages of crystallization was observed. A comparison with previous conductivity measurements is also carried out.     

Study of potential leakage on several stressed fittings for hydrogen pressures up to 700 bar

In order to improve risk analyses and influence the design of the future H₂ systems, an experimental study on “real” leaks qualification and quantification was performed. In H₂ energy applications, fittings appeared as a significant leakage potential and subsequently explosion and flame hazards. Thus, as a part of the “Horizon Hydrogène Energie” French program, four kinds of commercial fittings usually employed on H₂ systems were tested thanks to a new high pressure test bench – designed, setup and operated by INERIS – allowing experiments to be led for H₂ pressures until 700 bar. The fittings underwent defined stresses representative of H₂ systems lifetime and beyond. The associated leaks – when existing – are characterized in terms of flow rate.     

Human biological reactions at the interface between bone tissue and polymethylmethacrylate cement

This study investigated cytotoxicity of cement fragments harvested from two prosthesis revisions by the MTT test using L929 fibroblasts and human osteoblasts. The results did not show any toxicity of the extracts prepared after 48 and 78 months implantation. We consider that no MMA monomer has been released from the cement fragments. Histological studies on undecalcified samples harvested around revising prosthesis from 11 patients were used to evaluate tissue reactions at the bone–cement interface after 2–168 months implantation. Cement and prosthesis particles (5–35 m) either dispersed or forming a layer were observed. A fibrous tissue layer, osteolysis, and osteonecrosis areas were observed at the interface. Besides, fibroblasts, macrophages, and multinucleated giant cells were also observed. New bone formation with osteoid, osteoblasts, and endochondral ossification with fibrocartilaginous tissue has been observed. The tissue reactions seemed to decrease with time. However, osseous trabeculae fractures were observed in the samples after 19 months. Although we consider that monomer toxicity, exothermic reaction, and particles formation may cause short-term prosthesis loosening; the trabeculae fractures may be due to prosthesis and bone cement micromovements. This fractures and particles formation may cause long-term prosthesis loosening.     

Physical activity and aging

About a third of the initial muscle volume is lost during human life. This decline in muscle mass is responsible for impaired muscle strength, physical frailty, falls, impaired mobility, and functional decline. The age-related loss in muscle mass accounts for the age-associated decreases in basal metabolic rate, oxygen consumption, glucose utilisation, and bone density. Several of the anatomical and physiological changes in sedentary people, commonly attributed to primary aging processes, are in fact the consequence of lack of exercise. Recent studies show that strategies to maintain muscle strength and mass among the elderly (like regular exercise training) are most important for their functional independence.     

Dense ceramics of BaTiO3 produced from powders prepared by a chemical process

A sintering optimization of barium titanate ceramics from fine-grained and homogeneous reproducible powders obtained by the citric process is presented. Different sintering parameters are studied: heating rates, final temperature, dwelling times at this final temperature, and influence of the powder deagglomeration step. The sintering is followed by dilatometric measurements. The ceramics obtained by sintering at 1230 or 1300 °C are free of barium carbonate, the residual carbon content being estimated at about 400 ppm in the surface layer. They exhibit a grain size close to 1 μm, a structure in which the cubic and tetragonal phases coexist, and a density of about 96% of the theoretical density. Their permittivity and loss factor are respectively about 5000 and 2.5 × 10⁻² at 25 °C.     

Sir Colin MacKenzie and the Institute of Anatomy

Implant therapy can be used to build permanent restorations when there is loss of osseous and dental structures. In diffuse sclerosing osteomyelitis, permanent restorations utilizing implants could improve masticatory function. However, because of the probability of bone separation, the presence of an inadequate blood supply and the possibility of exacerbating the disease, implant therapy should be used with caution in the majority of patients. Certainly the operative sites should not be placed in the midst of these lesions. Questions exist as to their placement in unaffected portions of the jaws.     

ITU-T G.729.1 Scalable Codec for New Wideband Services

G.729.1 is a scalable codec for narrowband and wideband conversational applications standardized by ITU-T Study Group 16. The motivation for the standardization work was to meet the new challenges of VoIP in terms of quality of service and efficiency in networks, in particular regarding the strategic rollout of wideband service. G.729.1 was designed to allow smooth transition from narrowband (300-3400 Hz) PSTN to high-quality wideband (50-7000 Hz) telephony by preserving backward compatibility with the widely deployed G.729 codec. The scalable structure allows gradual quality increase with bit rate. A low-delay mode makes the coder especially suitable for high-quality speech communication. The article presents the standardization goals and process, an overview of the coding algorithm, and the codec performance in various conditions.     

Convergence of the Enhancement of the Effective Mass Under Pressure and Magnetic Field in Heavy-Fermion Compounds: CeRu2Si2, CeRh2Si2, and CeIn3

Emphasis is given on the observation of a convergence to a critical value of the effective mass of a heavy fermion compound by tuning it through a quantum instability either by applying pressure or magnetic field from an antiferromagnetic (AF) to a paramagnetic (PM) ground state. Macroscopic and microscopic results are discussed and the main message is to rush to the discovery of an ideal material whose Fermi surface could be fully observed on both sides of each quantum phase transition.