Chez les patients porteurs d’une bronchopneumopathie chronique obstructive, le risque de morbi-mortalité est inversement corrélé au niveau d’activité physique. Par ailleurs, la pratique d’une activité physique par ces patients permet d’obtenir des bénéfices sur le plan psychologique, d’améliorer la capacité inspiratoire, d’améliorer la tolérance à la dyspnée, d’améliorer la tolérance musculaire à l’exercice, de réduire le nombre d’exacerbations et d’améliorer la qualité de vie. Les recommandations d’activité physique spécifient que le réentraînement en endurance au seuil de dyspnée et durant 30 à 45 minutes est la modalité d’exercice musculaire la plus utilisée en réhabilitation respiratoire, que le réentraînement intermittent peut aussi être proposé, que les exercices en résistance peuvent être utiles (en particulier chez les patients présentant une diminution de la masse musculaire), et que le réentraînement des muscles inspiratoires devrait être proposé de même que l’électrostimulation musculaire.In chronic obstructive bronchopulmonary disease patients, the risk of morbidity and mortality is inversely correlated with the level of physical activity. In addition, when these patients take part in a physical activity they benefit on a psychological level ; improve their inspiratory capacity, tolerance to dyspnea, and muscular tolerance to exercise ; reduce the number of exacerbations ; and improve their quality of life. The recommendations for physical activity specify that endurance training to the dyspnea threshold lasting 30–45 minutes is the most frequently used muscular exercise modality in pulmonary rehabilitation, that intermittent training can also be proposed, that resistance exercises can be useful (particularly in patients presenting a reduction in muscle mass), and that training inspiratory muscles should be proposed as well as muscular electrostimulation.

L'ajout de certains oxydes dans un verre initialement homogene peut entrainer des cristallisations plus ou moins importantes du melange lors de son refroidissement. Parmi les oxydes connus pour induire de tels phenomenes dans des verres de silicates, se trouvent l'oxyde de molybdene MoO 3 et l'oxyde de phosphore P 2 O 5 . Les materiaux etudies ici sont des verres silico-sodo-calciques auxquels ont ete ajoutes MoO 3 et P 2 O 5 en quantite variable, ce qui provoque des cristallisations importantes. L'identification et la quantification des phases cristallines en presence par MEB et methode Rietveld a partir des diffractogrammes permettent de comprendre les roles respectifs du molybdene et du phosphore dans les phenomenes de cristallisation intervenant dans ces verres.

Silicate glasses with high molybdenum and phosphorus concentrations are partially crystalline. Their microstructure reveals the contribution of phase separation and crystallisation phenomena (luring cooling. We investigated these phenomena in three soda-lime-silica glasses containing phosphorus oxide and/or molybdenum oxide. Specimens were submitted to isothermal heat treatments at various temperatures, then characterised mainly by scanning electron microscopy (SEM) and x-ray diffraction (XRD) to determine their microstructure. These observations made it possible to determine the chronology of the phenomena occurring (luring cooling: first, a liquid/liquid phase separation occurs, followed by crystallisation of phosphates (it the border of the droplets; then molybdates crystallise inside the droplets.

The aim of this work was to get a better understanding of the O 1s binding energies Eb(O1s) in complex glasses of interest in nuclear waste storage in relationship with the mean charge on the oxygen atoms, relevant to acidic/basic properties of the glass. Three different glasses were considered: an aluminum borosilicate, a lanthanum aluminosilicate and a calcium aluminosilicate. The O1s binding energies were measured for each glass, along with individual simple oxides. The oxygen charges were estimated by an empirical method based on the electronegativity equalization principle. We show that for the first two glasses, the O 1s binding energy shift is driven by the changes in the oxygen charge induced by mixing the oxides to obtain the glass For the latter glass however, Madelung effects are of prime importance and the Eb(O1s) value of the glass cannot be predicted from the values in the individual oxides.

Reflection electron energy loss experiments were carried out on monocrystalline (101̄0) and (0001) quartz samples. Five bulk single loss structures appear at 10.5, 12.5, 14.3, 17.9 and 21.3 eV. The 10.5 eV peak is due to the SiO2 exciton, the 21.3 eV peak to the SiO2 plasmon, and the three other transitions are interband transitions, as confirmed by the calculated JDOS. Our experiments show that two electronic transitions at 5.1 and 7.2 eV appear in the gap of α-quartz under several excitations: by phonon excitation (UHV heating), by atomic excitation (collision between the 7 keV ions and the nuclei of the surface and near-surface atoms), and by electronic excitation (interaction with the 350 eV electron beam). The defects responsible for these structures are located at the surface and related to the neutral oxygen vacancy that is the precursor of the E$́centre.

The positive surface charge induced by the photoelectron emission is a major problem in the XPS study of insulating materials. This paper is devoted to the definition of an XPS experimental procedure for the analysis of large gap oxides, three of which are considered: sapphire, quartz and yttria-doped-zirconia, their gap widths being respectively about 8.5, 9 and 5.5 eV. The influence of the substrate temperature on the charge is first described. The charge compensation is then studied using low energy electron bombardment (flood gun), which was calibrated prior to the experiments; the reliability and reproducibility of the XPS results (peak energy positions, FWHM and intensity) are discussed. The question of the Fermi edge and energy referencing for insulating materials, as well as the role of the surface potential on the neutralization conditions and its possible use in the analysis of insulating material are outlined. The last section establishes a set of technical recommendations for the analysis of insulators, pointing out the criteria to be chosen for optimizing the flood gun settings.

This paper presents a low energy electron diffraction study of the α-SiO2(0001) surface structure modifications induced by thermal treatments under air. A reconstruction was observed as soon as the air heating temperature was greater than 600°C. The reconstructed mesh area is 84 times greater than the initial one. A preliminary interpretation in relation with the α-β transition phase of quartz occurring at 573°C is suggested. In particular, the observed rotation angle (11°) between the initial and the reconstructed surface lattices would be possibly related to the orientation of the triangular Dauphiné domains observed near the transition temperature.

Monocrystalline (0001) quartz surfaces may present two kinds of imperfections point defects (surface oxygen vacancies) and tridimensional disorder (superficial amorphization). The point defects are studied thanks to Reflection Electron Energy Loss Spectroscopy experiments, which show that electronic transitions (5.1 and 7.2 eV) associated with surface oxygen vacancies appear in the gap of alpha-quartz under ion or electron bombardment and 900-degrees-C vacuum heating. The defects responsible for these structures are located in the first nm under the surface. X-ray Absorption Near Edge experiments (XANES) at the O K-edge show that the 900-degrees-C vacuum heating leads moreover to the destruction of the surface crystallinity (almost-equal-to 5 nm), as proved by the modification of the multiple scattering structures.

Reflection electron energy loss experiments were carried out on monocrystalline (1010BAR) and (0001) quartz samples. Five bulk single loss structures appear at 10.5, 12.5, 14.3, 17.9 and 21.3 eV. The 10.5 eV peak is due to the SiO2 exciton, the 21.3 eV peak to the SiO2 plasmon, and the three other transitions are interband transitions, as confirmed by the calculated JDOS. Our experiments show that two electronic transitions at 5.1 and 7.2 eV appear in the gap of alpha-quartz under several excitations: by phonon excitation (UHV heating), by atomic excitation (collision between the 7 keV ions and the nuclei of the surface and near-surface atoms), and by electronic excitation (interaction with the 350 eV electron beam). The defects responsible for these structures are located at the surface and related to the neutral oxygen vacancy that is the precursor of the E' centre.

X-ray absorption spectra of alpha-quartz in the XANES region are presented both at oxygen and silicon K edges. The consequences of the electric dichroism of the samples on XANES structures are investigated. Polarization effects are detected when the electric field of the incident beam is parallel or perpendicular to the crystallographic c-axis. The structures after the absorption edges are discussed both in the frame of the Natoli's rule and from a density of states point of view.

We studied the structure of the (0110BAR) alpha-quartz surface after different treatments (900-degrees-C vacuum or air heating and ion bombardment). The long-range order was investigated by low-energy electron diffraction (LEED), the mean-range order by X-ray absorption spectroscopy at the oxygen K edge (XANES) and the electronic structure of the surface band gap by low-energy electron loss spectroscopy (ELS). The (1 x 1) structure is obtained only after a slight chemical etching in HF. A 900-degrees-C air-annealed sample exhibits a (3 x 1) or (1 X 3) LEED pattern associated with reconstructed surface regions, which structure is either related to the bulk alpha --> beta transition phase occurring at 573-degrees-C, or to a new SiO2 phase present only at the surface (tridymite). Finally, a 900-degrees-C heating in vacuum provides a glassy surface, also containing oxygen vacancies. These three structures lead to different surface electronic properties: the reconstructed surface presents a larger surface band gap than the (1 X 1) (9.5 instead of 8.6 eV). The disordered surface shows an 8.8 eV wide surface band gap, containing two electronic levels associated with surface oxygen vacancies.

We studied the structure of the (011̄0) α-quartz surface after different treatments (900°C vacuum or air heating and ion bombardment). The long-range order was investigated by low-energy electron diffraction (LEED), the mean-range order by X-ray absorption spectroscopy at the oxygen K edge (XANES) and the electronic structure of the surface band gap by low-energy electron loss spectroscopy (ELS). The (1 × 1) structure is obtained only after a slight chemical etching in HF. A 900°C air-annealed sample exhibits a (3 × 1) or (1 × 3) LEED pattern associated with reconstructed surface regions, which structure is either related to the bulk α → β transition phase occurring at 573°C, or to a new SiO2 phase present only at the surface (tridymite). Finally, a 900°C heating in vacuum provides a glassy surface, also containing oxygen vacancies. These three structures lead to different surface electronic properties: the reconstructed surface presents a larger surface band gap than the (1 × 1) (9.5 instead of 8.6 eV). The disordered surface shows an 8.8 eV wide surface band gap, containing two electronic levels associated with surface oxygen vacancies.