Etude par spectroscopie de photoelectrons (XPS) de la surface de profiles a base de PVC

Variations of the surface composition (over a thickness of 50 Å) of stabilized and rigid PVC for outdoor applications and of pure moulded PVC resin have been investigated by photoelectron spectroscopy (ESCA or XPS) after extrusion, outdoor and accelerated ageing and photooxidation. Extrusion is accompanied by a pronounced migration of lead thermal stabilizers and of calcium stearate, used as an external lubricant, towards the outer surface. This treatment however, induces neither significant oxidation nor formation of a great quantity of ionic chloride. Natural and accelerated weathering were compared and were characterized by a large decrease in the lead surface concentration. The surface of this material is unaffected when exposed to air in a closed vessel and protected from external radiations. Finally, surface photooxidation by u.v. exposure has been evaluated and compared for the stabilized material and for the pure resin. This treatment involves formation of carbonyl and carboxylic groups. ESCA spectroscopy, a speedy and non-destructive surface analytical method, is well suited for study migration of stabilizers and lubricants.     

Displacement Uncertainty Quantifications in T3-Stereocorrelation

Background Uncertainty quantifications are required for any measurement result to be meaningful.

Objective The present work aims at deriving and comparing a priori estimates of displacement uncertainties in T3-stereocorrelation for a setup to perform high temperature tests.

Methods Images acquired prior to the actual experiment (i.e.,at room temperature) were registered using 3-noded triangular elements (T3-stereocorrelation) to determine displacement uncertainties for different positions of the experimental setup.

Results The displacement uncertainties were then compared to their a priori estimates.

Conclusions For the analyzed experiment, it is shown that noise floor estimates only differed by a factor 2 when compared to a posteriori measurements of standard displacement uncertainties.

     

GC-MS-based urine metabolic profiling of autism spectrum disorders

Autism spectrum disorders (ASD) are a group of neurodevelopmental disorders resulting from multiple factors. Diagnosis is based on behavioural and developmental signs detected before 3 years of age, and there is no reliable biological marker. The purpose of this study was to evaluate the value of gas chromatography combined with mass spectroscopy (GC-MS) associated with multivariate statistical modeling to capture the global biochemical signature of autistic individuals. GC-MS urinary metabolic profiles of 26 autistic and 24 healthy children were obtained by liq/liq extraction, and were or were not subjected to an oximation step, and then were subjected to a persilylation step. These metabolic profiles were then processed by multivariate analysis, in particular orthogonal partial least-squares discriminant analysis (OPLS-DA, R ²Y(cum) = 0.97, Q ²(cum) = 0.88). Discriminating metabolites were identified. The relative concentrations of the succinate and glycolate were higher for autistic than healthy children, whereas those of hippurate, 3-hydroxyphenylacetate, vanillylhydracrylate, 3-hydroxyhippurate, 4-hydroxyphenyl-2-hydroxyacetate, 1H-indole-3-acetate, phosphate, palmitate, stearate, and 3-methyladipate were lower. Eight other metabolites, which were not identified but characterized by a retention time plus a quantifier and its qualifier ion masses, were found to differ between the two groups. Comparison of statistical models leads to the conclusion that the combination of data obtained from both derivatization techniques leads to the model best discriminating between autistic and healthy groups of children.     

ESCA surface study of metal borides

To investigate metal-boron bonding, a number of typical transition metal borides have been studied using ESCA; for the sake of comparison, spectra have been obtained as well on aluminium borides as on other boron compounds. Spectra are very sensitive to surface oxidation and give a semi-quantitative appreciation of the relative oxidability of boron and metal (or metals when dealing with binary metal borides). Relevant features are discussed herein.     

Synthesis of new 2-aryl-3,3a-dihydro-4-oxo-5H-pyrazolo-[1,5-d][1,2,4]triazines and some of their derivatives

The preparation of new dihydropyrazolo[1,5-d][1,2,4]triazinones involved the formation of carboxylic acid hydrazides via the appropriate ethyl aroylacrylates, followed by condensation with an orthoester. The synthesis of some derivatives substituted on the nitrogen atom in the 5-position of the triazine ring was reported and their anticonvulsant activity was evaluated.     

Nucleophilic fluorination of alkynyliodonium salts by alkali metal fluorides: access to fluorovinylic compounds

Fluorovinylic compounds were synthesized by a one-pot procedure from the corresponding alkynyliodonium salts and alkali metal fluorides. Different reaction parameters, such as the temperature, the solvent and the reaction time were examined, and interestingly CsF was chosen for regio- and stereo-selective reactions leading to different alkenyliodonium salts in good yields. Their reduction using NaBH₄ provided the corresponding 2-fluorovinylic products quantitatively.     

Etude de la Basicite de Composes Organophosphores Typiques dans Leurs Complexes de Lewis Avec le Trifluorure de Bore

Various complexes of boron trifluoride and typical organo-phosphours compounds have been investigated using proton and fluorine resonance (at variable temperature) and boron and phosphorus resonance. In BF₃, boron resonance is insensitive to the complex strength, but fluorine resonance suggests the possibility of various types of complexes on the phosphorus group or, additionally on the heteroatoms (e.g. oxygen, nitrogen) of the molecule. These complexes are probably σ type. Proton chemical shifts in the organo-phosphorus compounds follow the same trends as in similar complexes of amines, esters etc.; these perturbations may be mainly due to magnetic anisotropy effects; proton-phosphorus couplings conversely follow changes in phosphorus electronegativity.