Quantitative evaluation of microtwins and antiphase defects in GaP/Si nanolayers for a III-V photonics platform on silicon using a laboratory X-ray diffraction setup

A laboratory X-ray diffraction setup is reported, which allows quantitative characterization of the microtwin and antiphase domain densities in epitaxial GaP/Si thin layers.

This study is carried out in the context of III–V semiconductor monolithic integration on silicon for optoelectronic device applications. X-ray diffraction is combined with atomic force microscopy and scanning transmission electron microscopy for structural characterization of GaP nanolayers grown on Si. GaP has been chosen as the interfacial layer, owing to its low lattice mismatch with Si. But, microtwins and antiphase boundaries are still difficult to avoid in this system. Absolute quantification of the microtwin volume fraction is used for optimization of the growth procedure in order to eliminate these defects. Lateral correlation lengths associated with mean antiphase boundary distances are then evaluated. Finally, optimized growth conditions lead to the annihilation of antiphase domains within the first 10 nm.

Interdependency of subsurface carbon distribution and graphene-catalyst interaction

The dynamics of the graphene-catalyst interaction during chemical vapor deposition are investigated using in situ, time- and depth-resolved X-ray photoelectron spectroscopy, and complementary grand canonical Monte Carlo simulations coupled to a tight-binding model. We thereby reveal the interdependency of the distribution of carbon close to the catalyst surface and the strength of the graphene-catalyst interaction. The strong interaction of epitaxial graphene with Ni(111) causes a depletion of dissolved carbon close to the catalyst surface, which prevents additional layer formation leading to a self-limiting graphene growth behavior for low exposure pressures (10(-6)-10(-3) mbar). A further hydrocarbon pressure increase (to ∼10(-1) mbar) leads to weakening of the graphene-Ni(111) interaction accompanied by additional graphene layer formation, mediated by an increased concentration of near-surface dissolved carbon. We show that growth of more weakly adhered, rotated graphene on Ni(111) is linked to an initially higher level of near-surface carbon compared to the case of epitaxial graphene growth. The key implications of these results for graphene growth control and their relevance to carbon nanotube growth are highlighted in the context of existing literature.

[Rare cause of pulmonary embolism in a child]

Cardiac hydaticyst is a rare condition and accounts for only 0.5 to 2% of all visceral locations of hydatid disease. The objective of this study was to point out the main clinical, radiological, and disease-course characteristics of this rare and serious pathology. We report a 13-year-old patient with a hydatid pulmonary embolism caused by a hydatid cyst of the interauricular septum. The diagnosis was established by transthoracic echocardiography, thoracic CT scan, and hydatid serology. Surgery was performed without delay and the outcome was good after 15 months of follow-up. This case underlines the need for rapid diagnosis and surgery before complications of cardiac hydatid cyst.

Reactivity of the NO dimer: on the role of the triplet electronic states

We performed ab initio calculations to investigate the lowest triplet and singlet electronic states of the NO dimer and their mutual spin-orbit couplings. The electronic structure calculations are done using multiconfigurational approaches and a large diffuse basis set. A high density of electronic states is found favoring their mutual interactions by vibronic and spin-orbit couplings. We used our potential curves and spin-orbit couplings to discuss the mechanisms for the IR dissociation and the UV photodissociation of the NO dimer and the electronic de-excitation of NO (A(2)Sigma(+)) after collision with NO (X(2)Pi). For these reactions, multistep pathways, which involve the long-range and the molecular regions of the potential energy surfaces of the triplet and singlet electronic states of N(2)O(2), are suggested. A qualitative agreement between our findings and previous experimental assumptions is found.

[Elastofibroma: imaging features]

Elastofibroma dorsi is a rare benign and slow growing fibro-proliferative lesion of unknown pathogenesis. It has a characteristic location (periscapular region) and a specific imaging appearance (songraphy, CT, MRI) allowing accurate prospective diagnosis. The recognition of this benign lesion avoids unnecessary biopsy and/or surgery. We report three cases of elastofibroma dorsi illustrating the characteristic features on sonography, CT and MRI. Involvement was bilateral in two cases.

[Tuberculous sacro-iliitis: a series of twenty-two cases]

BACKGROUND

Despite their relative rarity, increased awareness of tuberculous sacro-iliitis is necessary. Indeed, diagnosis is usually delayed, because of the non specific clinical features and the difficulty to explore the sacro-iliac joint.

OBJECTIVE

To study the characteristics of sacro-iliac joint tuberculosis.

MATERIALS AND METHODS

A retrospective study of 22 cases of tuberculous sacro-iliitis collected between 1987 and 2003 in four university hospital centres. All our patients were explored clinically and radiologically. Microbiology, biochemical and serologic tests were also performed.

RESULTS

13 cases were confirmed bacteriologically or histologically and for the remaining nine cases evidence of tuberculous sacroiliitis was based on clinical, biological, radiological features and outcome on treatment. Inflammatory pain was present in almost all cases, and a collected abscess in 11 cases. Standard radiographs were also in all cases and ultrasound and CT scan showed an abscess in 8 patients. The average duration of treatment was nine months. The outcome was excellent in the majority of cases.

CONCLUSION

Sacro-iliac joint is difficult to explore and has recently beneficiated of technical improvement in imaging and diagnostic. Medical treatment of tuberculosis sacro-iliitis is often sufficient.

Kyste hydatique des tissus mous : apport de l’IRM (À propos de trois observations)

Three cases of hydatid disease of the soft tissues are reported. All presented as soft tissue lesions in the neck and lower extremities. All three cases were studied with ultrasound (US) and magnetic resonance (MR) imaging techniques. Two patients presented with multivesicular lesions, which were considered diagnostic for hydatid disease. The third showed a lesion with hypoechoic solid and lobulated pattern mimicking lymph node. MR outlined the cystic pattern with intense peripheral enhancement and was suggestive of an infected cystic lesion. Surgery was performed in all three cases. Hydatid disease presenting in the soft tissues can be diagnosed with confidence, when US and/or MR shows multivesicular lesions. MR appears to be the most useful imaging technique when a complex or solid pattern is present. Enhancement of the peri-cystic soft tissues can be considered as a suggestive MR feature of soft tissue hydatid disease.