Direct imaging of p-n junction in core-shell GaN wires.

While core-shell wire-based devices offer a promising path toward improved optoelectronic applications, their development is hampered by the present uncertainty about essential semiconductor properties along the three-dimensional (3D) buried p-n junction. Thanks to a cross-sectional approach, scanning electron beam probing techniques were employed here to obtain a nanoscale spatially resolved analysis of GaN core-shell wire p-n junctions grown by catalyst-free metal-organic vapor phase epitaxy on GaN and Si substrates. Both electron beam induced current (EBIC) and secondary electron voltage constrast (VC) were demonstrated to delineate the radial and axial junction existing in the 3D structure. The Mg dopant activation process in p-GaN shell was dynamically controlled by the ebeam exposure conditions and visualized thanks to EBIC mapping. EBIC measurements were shown to yield local minority carrier/exciton diffusion lengths on the p-side (∼57 nm) and the n-side (∼15 nm) as well as depletion width in the range 40-50 nm. Under reverse bias conditions, VC imaging provided electrostatic potential maps in the vicinity of the 3D junction from which acceptor Na and donor Nd doping levels were locally determined to be Na = 3 × 10(18) cm(-3) and Nd = 3.5 × 10(18) cm(-3) in both the axial and the radial junction. Results from EBIC and VC are in good agreement. This nanoscale approach provides essential guidance to the further development of core-shell wire devices.

Hydrogen-induced passivation of boron acceptors in monocrystalline and polycrystalline diamond.

This paper presents a review of the properties induced by the presence of hydrogen in monocrystalline boron-doped diamond (BDD) and proposes a comparison with results obtained on polycrystalline materials. Hydrogen diffusion, luminescence and electrical properties show the passivation of boron acceptors in diamond by the formation of (B,H) complexes, in both monocrystalline and polycrystalline forms, but at a different level. This behaviour raises open questions concerning the role of structural defects in the passivation of boron impurities by hydrogenation. Based on the assessment of the high thermal stability of (B,H) complexes, this approach leads to a route to provide patterned diamond conductive structures for micro as well as for nanotechnology applications.

[Physical activity and pulmonary rehabilitation]. / Activités physiques et réadaptation respiratoire.

INTRODUCTION: Physical activity in daily life (PA) in patients with chronic respiratory disease is reduced. Inactivity is associated with an increased risk of hospitalisation and mortality. Even though pulmonary rehabilitation (PR) is associated with improved quality of life (fewer symptoms, greater exercise capacity…), its benefits with regard to PA remain unclear. STATE OF THE ART: For each patient, it is important during a respiratory rehabilitation (RR) programme to evaluate PA and its determinants. Only programs aimed at improved self-management and including educational therapy (ETP) have shown a short-term increase of PA following PR. Several studies have reported better long-term adherence when professionals help the patient to construct a personalised PA project, with regular follow-up and an array of activities (local facilities, urban walking…) chosen by the patient and adapted to the environment. PERSPECTIVES: The ongoing SARS-CoV2 pandemic has highlighted the importance of human interaction, even at a distance using information and communication technologies, as a means of sustaining patient motivation. Future controlled and randomized studies should focus on the long-term impact on PA of innovative strategies in patients with chronic respiratory diseases. Moreover, it would be interesting to quantify the socioeconomic impact as well as the sustainable health benefits of the different strategies outlined in this review. CONCLUSION: It is not possible to offer a single solution likely to maintain RR benefits over an extended lapse of time. However, follow-up with an ETP and/or regular and customized support during the post-training period facilitates the long-term adoption of active behavior.

[COLIBRI: Improving clinical practice and producing relevant scientific data]. / COLIBRI : optimiser la pratique clinique et produire des données scientifiques pertinentes.

COLIBRI-COPD is a francophone consultation web portal accessible to pulmonologists in the hospital and in the community. We present this observation which describes the phenotype of COPD patients entered (anthropometry, exposures, addictions, functional impairments, questionnaires: MRC, DIRECT, CAT, HAD, Epworth, co-morbidities, incidence of exacerbations, drug treatment or other treatments). The results of the first 1079 patients show a high level of completeness for the main data items. A comparison of patients seen in outpatient consultations shows significant variability between patients with the same GOLD stage, regarding the incidence of exacerbations, signs of anxiety-depression, of diabetes mellitus, or the prescriptions of anticholinergics and inhaled corticosteroids. These initial results suggest that data collection in real life gives a reliable database to obtain longitudinal data on various aspects of COPD. The data quality (completeness, reliability) is partly related to the usability of the web tool and to the possibility of doing self-assessment of practitioners' own recorded data.

[Pituitary metastasis revealing a lung cancer]. / Métastase hypophysaire symptomatique révélant un cancer bronchique.

INTRODUCTION: Pituitary metastases are rare and difficult to diagnose. Their optimal approach and management remains to be defined. CASE REPORT: We report the case of a 56-year-old patient suffering from squamous cell lung carcinoma who developed pituitary metastasis with secondary hypopituitarism, the symptoms of which were initially attributed to depression. CONCLUSION: Pituitary metastases can be difficult to diagnose, which may lead to delays in care, which can be fatal.

Spectroscopic XPEEM of highly conductive SI-doped GaN wires.

Using soft X-ray photoelectron emission microscopy (XPEEM), complemented by scanning Auger microscopy (SAM) and scanning capacitance microscopy, we have quantitatively studied the incorporation of silicon and band bending at the surface (m-facet) of an individual, highly conductive Si-doped GaN micro-wires (Tchoulfian et al., Applied Physics Letters 102 (12), 2013). Electrically active n-dopants Si atoms in Ga interstitial sites are detected as nitride bonding states in the high-resolution Si2p core level spectra, and represent only a small fraction (<10%) of the overall Si surface concentration measured by SAM. The derived carrier concentration of 2×10(21) at cm(-3) is in reasonable agreement with electrical measurements. A consistent surface band bending of ~1 eV is directly evidenced by surface photo-voltage measurements. Such an approach combining different surface-sensitive microscopies is of interest for studying other heavily doped semiconducting wires.

[Problems posed by professional rehabilitation of cardiac patients]. / Problèmes posés par l'insertion professionnelle des cardiaques

The authors have followed up children with cardiac defects over almost a twenty year period. During the 1960's most of their patients had come of age, and they conclude that despite the enthusiasm of these young people and their potential, they have the greatest difficulties in finding work. This seems regrettable from the human as well as the socio-economic point of view. They propose that the law should be changed as, indeed, should the spirit of the law, so that; a subject with heart disease should no longer be considered as incapable of useful work, and that each person should be assessed according to his potential. They envisage the setting up of medico-administrative cardiological centres. Thus, in addition to the purely medical cardiological consultation, three additional persons would add their expertise: a social worker, an industrial medicine inspector, and an employment officer. These centres could be instituted easily, without making the existing system too unworkable.

[Long-term results of palliative operations and complete cure of tetralogy of Fallot]. / Résultats à long terme des interventions palliatives et de la cure complète dans la tétralogie de Fallot.

714 cases of Fallot's tetralogy have been encountered over the last thirty years. A closed heart operation was undertaken in 472 patients. The mean age at operation was 5,1 years. In 87% of cases, a Blalock-Taussig anastomosis was carried out. The operative mortality was of the order of 3%. The operative risk was almost three times as large before the age of two years as after. The patients benefit by a demonstrable improvement of function after this operation, but it does not protect them from the complications of the condition (cervica abscess, Osler's disease, cerebro-vascular accidents) or from death. Open heart surgery was carried out in 403 patients. 161 as a primary procedure, and 242 after an initial palliative operation. The mean age at operation was 13.3 years. The operative mortality was 15%. The functional improvement was striking, and the patients appeared to be protected from the usual sequelae of the condition. On the other hand they cannot always be considered as cured: 16 died some time after the operation; 37% had pulmonary incompetence; 15% had a residual BSD; 8% had a block of both bundles, and 3% had a definitive atrio-ventricular block.

[Study of variations of osteocalcin concentrations in function of collection, assay method and its nyctohemeral rhythm]. / Etude des variations de concentrations de l'ostéocalcine en fonction du mode de prélèvement, de la méthode de dosage et de son cycle nycthéméral.

Osteocalcin or bone GLA protein (BGP) can be used as well as a peripheral marker of the action of hormones on osteoblast. In the present study, we report our clinical and biological results in three different conditions: the kits used for determination, the time and the hour of withdrawal. We used 4 different radioimmunoassay kits: two kits (Elsa-os-nat (cis), Osca-test (Henning)) detect intact osteocalcin molecules only and the two others (Elsa-osteo(cis), Ostk-PR(cis)) detect intact osteocalcin molecules and osteocalcin fragments. Time between collection and assay is important: we observed a diminution of osteocalcin level which can be due to the degradation of intact molecules, of 25% to 49% (depending on the kit used). The clinical profile was studied with circadian rhythm. We observed a variation of osteocalcin level in 30% of circadian rhythm according to the hour of collection sample. In conclusion, we have seen two differents situations at risk of wrong interpretation due to low level BGP: inadequate serum collection or single blood collection instead of circadian cycle.

Main parameters involved in microencapsulation by in situ polycondensation.

The influences of 11 factors are studied. Molecular weight of the emulsifier, amount of wall material and amount of core material were found to be the most influential factors.

Optimization of microencapsulation of acrylic adhesives.

The preparation of microcapsules of an acrylic adhesive in a solvent medium with reticulated walls of melamine-formaldehyde was studied. In order to obtain the best experimental conditions for this process, the methodology of factorial design was used. It was found that, among the 11 tested parameters, four had an important effect on the microencapsulation: amount of wall polymer, amount and nature of the copolymer, GANTREZ, and amount of adhesive in the core. The process was optimized using a surface response methodology. A layer of microcapsules deposited on paper gave, after manual breakage, very good adhesive properties.

Influence of experimental parameters on the microencapsulation of a photopolymerizable phase.

Conditions of microencapsulation by in situ polycondensation, using melamine-formaldehyde as wall material, are influenced by the chemical nature of the core to encapsulate. In our study concerning the encapsulation of a photopolymerizable phase containing an electrically charged compound, it was necessary to modify the experimental process to obtain capsules of good quality. We used the factorial design method of screening by utilization of an asymmetric matrix, according to the collapsing principle of Addleman. The advantage of this method is that it allows determination of the simultaneous influences of the 11 experimental parameters involved in this preparation. The calculation method can be applied to more than two levels for some of the factors. The continuously varying parameters were altered between two extreme levels, chosen to allow encapsulation. For discontinuous factors, such as the molecular weight of the modifying system or nature of the aminoplast, we used the commercially available compounds, respectively three and four kinds. The results of the obtained capsules were determined by comparing microphotographic pictures. With 16 experiments we found four more factors influencing quality of capsules. We also determined the most favourable levels for the other seven parameters. The results allowed us to find optimal conditions in the experimental field. We obtained capsules of a satisfactory quality for this purpose, using only minimum experimentation.