Comparison of cryogenic and differential flow (forward and reverse fill/flush) modulators and applications to the analysis of heavy petroleum cuts by high-temperature comprehensive gas chromatography.

The development of new efficient conversion processes to transform heavy petroleum fractions into valuable products, such as diesel, requires improved chemical knowledge of the latter. High-temperature comprehensive gas chromatography (HT-GC × GC) has proven to be a powerful technique for characterizing such complex samples. This paper reports on an evaluation of the performances of four different differential flow modulators, including two original ones that have not been previously described in the literature, in terms of dispersion, peak intensity, peak capacity and overloading.

Assessment of the calf vein cross section change during stand-test after a 90 day bed rest by echography.

Objective: To evaluate the contribution of the calf veins distension during stand test to orthostatic intolerance (OI).

Method: The population consisted of a control group (Co, n=9) and an exercise (Fly-Wheel) counter-measure group (CM, n=9). Calf vein cross section area was assessed by echography during pre and post HDT stand-tests.

Calf venous volume during stand-test after a 90-day bed-rest study with or without exercise countermeasure.

The objectives to determine both the contribution to orthostatic intolerance (OI) of calf venous volume during a stand-test, and the effects of a combined eccentric-concentric resistance exercise countermeasure on both vein response to orthostatic test and OI, after 90-day head-down tilt bed-rest (HDT). The subjects consisted of a control group (Co-gr, n = 9) and an exercise countermeasure group (CM-gr, n = 9). Calf volume and vein cross-sectional area (CSA) were assessed by plethysmography and echography during pre- and post-HDT stand-tests.

Gas chromatography-combustion-isotope ratio mass spectrometry analysis of 19-norsteroids: application to the detection of a nandrolone metabolite in urine.

Determination of whether the major metabolite of nandrolone in urine, 19-norandrosterone (19-NA), is exogenous or endogenous in origin is one of the most exciting challenges for antidoping laboratories. Gas chromatography-combustion-isotope ratio mass spectrometry (GC-C-IRMS) can be used to differentiate these two origins by carbon isotopic ratio analysis. A complete method for purification of 19-NA in urine has been established.