Characterization of nanostructured GaSb: comparison between large-area optical and local direct microscopic techniques.

Low energy ion-beam sputtering of GaSb results in self-organized nanostructures with the potential of structuring large surface areas. Characterization of such nanostructures by optical methods is studied and compared to direct (local) microscopic methods. The samples consist of densely packed GaSb cones on bulk GaSb, approximately 30, 50, and 300 nm in height, prepared by sputtering at normal incidence. The optical properties are studied by spectroscopic ellipsometry, in the range 0.6-6.5 eV, and with Mueller matrix ellipsometry in the visible range, 1.46-2.88 eV. The optical measurements are compared to direct topography measurements obtained by scanning electron microscopy, high resolution transmission electron microscopy, and atomic force microscopy. Good agreement is achieved between the two classes of methods when the experimental optical response of the short cones (<55 nm) is inverted with respect to topological surface information, via a graded anisotropic effective medium model. The main topological parameter measured was the average cone height. Optical methods are shown to represent a valuable characterization tool of nanostructured surfaces, in particular when a large coverage area is desirable. Because of the fast and nondestructive properties of optical techniques, they may readily be adapted to in situ configurations.

InnOscent system: Advancing flavor analysis using an original gas chromatographic analytical device.

Despite continuous advances in analytical and physiological knowledge, the comprehension of an aroma is still a challenge. Gas chromatography coupled to olfactometry (GC-O) is an efficient method to identify and estimate individual potential of odorants, but there is a gap between this individual characterization and the effective contribution of compounds in the mixture, which is due to complex chemical and perceptual interactions. Therefore, recombination and omission experiments are often performed to achieve an understanding of food aromas. In this study, a chromatographic device, developed to facilitate aroma analysis, is presented. It was configured to perform both (1) conventional analyses by GC coupled with a mass spectrometer, olfactometric port(s), and a flame ionization detector (FID), and (2) omission or recombination experiments. This dual capability is due to the singular configuration of the system using an ingenious combination of splitter and Deans switch microfluidics transfer modules, and the existence of multiple outlets. The operational status of the system was tested using a purposely simple mixture of compounds. The similarity of retention times (RT) and FID peak areas obtained for each outlet demonstrates that the multiple outlets of the system are equivalent. The reproducibility of retention times (RT) and FID peak areas obtained in switching and non-switching conditions, also demonstrates the efficiency of switching operations. The validation of the system enables multiple detectors to be connected to the outlets and complementary information can be obtained from the eluate. The connection of recovery disposals to the outlets provides fraction collection and recombination possibilities, which contribute much to the understanding of aroma-aroma interactions. As an illustration of the InnOscent system relevance for the comprehension of more complex aromas, the device was used to study the aroma of a wine made from Cabernet Franc grape variety. An olfactometric profile was efficiently produced with the device configured as a GC-MS coupled to a dual olfactometric port. The main odorant active compounds were identified. The omission approach, carried out with the system on isopropyl- and isobutyl-methoxypyrazines, demonstrates the significant contribution of these compounds to the aroma of the wine studied, despite an individual perception among the weakest of the aromagram. A similar approach can be used to evaluate the contribution of any compound to any aroma. This approach overcomes constraints of current methodologies associated to reconstituted model solutions and paves the way for a better understanding of aroma construction.

[False anastomotic iliac aneurysms. How to detect them?]. / Les faux anévrismes anastomotiques iliaques. Comment les dépister?

We report about 5 iliac anastomotic false aneurysms that occurred in 4 patients 8 to 21 years (average 15.5 years) after aortoiliac prosthetic reconstruction. The diagnosis was not established at once because of atypical clinical signs, in spite of the constant presence of an abdominal pulsating mass. All patients were operated by portal excision and graft replacement. One patient, who had presented with a hypovolemic collapse due to an acute rupture, died. The incidence of iliac false aneurysms after aortoiliac reconstructions is underestimated because the clinical surveillance is not reliable. The analysis of the explorations that were proposed led to prefer computed tomography to ultrasonography and angiography. The period of occurrence of iliac false aneurysms ranges between 6 to 10 years in average after the first operation. We therefore propose to perform a systematic follow-up CT examination on the 5th postoperative year, then every 5 years, and to operate the iliac false aneurysms as soon as their diagnosis is made.

Determination of aspirin and salicylic acid in transdermal perfusates.

A high-performance liquid chromatographic (HPLC) method has been developed for the simultaneous determination of aspirin and salicylic acid in transdermal perfusates. The compounds were separated on a C8 Nucleosil column (5 microm, 250x4.6 mm) using a mobile phase containing a mixture of water-acetonitrile-orthophosphoric acid (650:350:2, v/v/v) and a flow-rate of 1 ml/min. The transdermal samples were in phosphate-buffered saline (PBS) and could be injected directly onto the HPLC system. The method was reproducible with inter-day R.S.D. values of no greater than 3.46 and 2.60% for aspirin and salicylic acid, respectively. The method was linear over the concentration range 0.2-5.0 microg/ml and had a limit of detection of 0.05 microg/ml for both compounds. For certain samples, it was necessary to ensure that no transmembrane leakage of the aspirin prodrugs had occurred. In these cases, a gradient was introduced by increasing the acetonitrile content of the mobile phase after the salicylic acid had eluted. The method has been applied to the determination of aspirin and salicylic acid in PBS following in vitro application of the compounds to mouse skin samples.