Magnetic resonance imaging of the neuroprotective effect of xaliproden in rats

RATIONALE AND OBJECTIVES: The neurotrophic effect of Xaliproden has been followed using sequential cerebral magnetic resonance imaging (MRI) in rats with vincristine-induced brain lesion as a model of Alzheimer disease. METHODS: Nineteen rats received an intraseptal injection of vincristine on day 0, followed by a daily gavage with either the vehicle (Tween-20 1%) (n = 10) or Xaliproden (10 mg/kg) (n = 9). Eight sham-operated controls received a daily gavage with either the vehicle (n = 4) or Xaliproden (n = 4). Brain MR imaging was performed at 4.7 T on a Biospec 47/30 MR system before surgery then 3, 7, 10, and 14 days after surgery. RESULTS: At day 3 following vincristine injection, an increase in MR signal intensity in the septum was observed on T2-weighted images. This increase was maximal at day 10, and remained stable until day 14. Daily treatment with Xaliproden delayed the appearance of hypersignals until day 7 and reduced by Ca. 50% the magnitude of the increase in signal intensity from day 10. No changes were observed in the hippocampus. CONCLUSION: Quantitative MRI objectifies noninvasively the neuroprotective effect of Xaliproden on rat brain anatomy

Nurses' perceptions of aids and obstacles to the provision of optimal end of life care in ICU

Contains fulltext : 172380.pdf (publisher's version ) (Open Access

Compendio de física médica

Na port.: Ilustrado con 475 figuras intercaladas en el text

A specialized database manager for interpretation of NMR spectra of synthetic glucides: JPD

The current communication presents a program, written specifically to create and handle a specialized database, containing NMR spectral patterns of various monosaccharidic units. The program's database format is compatible with that of the Aurelia/Amix Bruker software package. The software facilitates the search for J patterns included in the database and their comparison with an experimental spectrum, in order to identify the components of the studied system, including the contaminants

Silicon speciation by gas chromatography coupled to mass spectrometry in gasolines

cited By 14International audienceA method for the speciation of silicon compounds in petroleum products was developed using gas chromatography coupled to mass spectrometry (GC-MS). Prior to analysis, several precautions about storage and conservation were applied for all samples. In spiked gasoline samples, limits of detection between 24 and 69μgkg -1 for cyclic siloxanes (D 4-D 6) and between 1 and 7μgkg -1 for other species were obtained. In this study, cyclic siloxanes (D n) and one ethoxysilane were quantified for the first time in petroleum products by a specific method based on response factor calculation to an internal standard. This method was applied to four samples of naphthas and gasolines obtained from a steam cracking process. Cyclic siloxanes were predominant in four investigated samples with concentrations ranging between 101 and 2204μgkg -1. Cyclic siloxane content decreased with an increase in their degree of polymerization. During a steam cracking process, silicon concentrations determined by GC-MS SIM (single ion monitoring) significantly increase. This trend was confirmed by ICP-OES (inductively coupled plasma optical emission spectroscopy) measurements but a difference on the total silicon content was observed, certainly highlighting the presence of unknown silicon species. GC-MS SIM method gives access to the chemical nature of the silicon species, which is crucial for the understanding of hydrotreatment catalyst poisoning in the oil and gas industry. © 2011 Elsevier B.V

Combining fourier transform-ion cyclotron resonance/mass spectrometry analysis and kendrick plots for silicon speciation and molecular characterization in petroleum products at trace levels

cited By 13International audienceA new method combining FT-ICR/MS analysis and Kendrick plots for the characterization of silicon species at trace levels in light petroleum products is presented. The method provides efficient instrumental detection limits ranging from 80 ng/kg to 5 μg/kg and reliable mass accuracy lower than 0.50 ppm for model silicon molecules in spiked gasoline. More than 3000 peaks could be detected in the m/z 50-500 range depending on the nature of the gasoline sample analyzed. An in-house software program was used to calculate Kendrick plots. Then, an algorithm searched, selected, and represented silicon species classes (O 2Si, O 3Si, and O 4Si classes) in Kendrick plots by incorporating model molecules' information (i.e., exact mass and intensity). This procedure allowed the complete characterization of more than 50 new silicon species with different degrees of unsaturation in petroleum products. © 2012 American Chemical Society

Detailed characterization of coal-derived liquids from direct coal liquefaction on supported catalysts

RAFFINAGE+JST:CLO:CGECoal liquids from Direct Coal Liquefaction (DCL) are one of the possible substitutes of conventional hydrocarbons resources. However the primary liquids obtained from DCL (i.e. outflow liquids of the first reactor in a two stages liquefaction process) do not meet the product specifications and need to be upgraded via downstream catalytic hydrotreatment processes. The in depth knowledge of the feed of this upgrading step is of key importance to design better catalysts. In this study, we applied new cutting-edge techniques to improve the characterization of a coal derived liquid obtained from a liquefaction step starting from Scottish bituminous coal. For this purpose, bidimensional chromatography (GC xGC), and C-13 nuclear magnetic resonance (NMR) were used to analyze four cuts of the coal liquid with the following boiling points intervals: heavy naphtha (initial boiling point: IBP-215 degrees C), gas oil (215-343 degrees C), vacuum gas oil (343-524 degrees C) and vacuum residue (524(+) degrees C). The analyses showed high aromaticity of all four cuts. The weight content of aromatics in the gas oil fraction, was 75%, with a majority of two rings aromatics and the remainder consisting mostly of normal paraffins. In the vacuum gas oil cut, which contains mostly four aromatic rings, we found 11 wt% of asphaltenes (compounds in n-heptane), an unexpected high amount comparing to petroleum VGO fractions. The amount of heptane-insoluble (asphaltenes, pre-asphaltenes and sediments) is as high as 80% in the vacuum residue fraction (524(+) degrees C). Aromaticity given by C-13 NMR in this cut is as high as the level observed in petroleum asphaltenes (C-aro = 53 wt%). High content of heteroelements, which highly increase the polarity of the molecules, in the coal liquid and especially in the vacuum residue can explain the enhanced amount of n-heptane-insoluble compounds. (C) 2011 Elsevier Ltd. All rights reserved

Development of heart-cutting multidimensional gas chromatography coupled to time of flight mass spectrometry for silicon speciation at trace levels in gasoline samples

cited By 8International audienceTo improve the understanding of hydrotreatment (HDT) catalyst poisoning by silicon species, these molecules must be characterized in petroleum products using powerful analytical systems. Heart-cutting gas chromatography coupled to time of flight mass spectrometry (GC-GC/TOFMS) method equipped with a Deans switch (DS) system was developed for the direct characterization of target silicon compounds at trace level (μgkg-1) in gasoline samples. This method was performed to identify silicon compounds never characterized before. After the selection of the second dimension column using GC-GC-FID, GC-GC/TOFMS was performed. The calibration curves obtained by the GC-GC/TOFMS method were linear up to 1000μgkg-1. Limits of detection (LOD) were ranging from 5 to 33μgkg-1 in spiked gasoline. The method provided sufficient selectivity and sensitivity to characterize known silicon compounds thanks to their specific ions and their retention times. The analysis of a naphtha sample by GC-GC/TOFMS has shown the presence of cyclic siloxanes (Dn) as major compounds of PDMS thermal degradation with the occurrence of linear siloxanes, especially hexamethyldisiloxane (L2), which was never characterized in petroleum products but already known as severe poison for catalyst. © 2012 Elsevier B.V