Cyclisations par l'intermédiaire de fonctions phénylthioet phénoxy-carbamyle. I. Diphényl-1,2-alcoyl-5-dioxo-3,6-hexahydro-triazines-1,2,4

The N-(p-nitrophenoxy-carbonyl) and N-(phenylthio-carbonyl) derivatives of α-amino-acyl-hydrazides cyclize in presence of diazomethane, yielding hexahydro-1, 2, 4-triazines with simultaneous formation of p-nitro-anisole or thio-anisole respectively. The molecules with a phenoxycarbonyl function such as N-(phenoxycarbonyl)-glycyl-(N, N′-diphenylhydrazide) give the corresponding ring products and anisole only in solvents with high dielectric constant (e.g. nitromethane). The phenylthio-carbonyl derivatives give the same ring products in presence of lead acetate by the intervention of HO^?. The p-nitrophenoxycarbonyl derivatives give rise to the same cyclisations in the presence of pyridine by the intermediate of carbamyle-pyridinium ion acting as electrophile. These different types of intramolecular reactions are illustrated by the formation of 1, 2-diphenyl-5-alcoyl-3, 6-dioxo-1, 2, 4-hexahydro-triazines.     

Colour formation in poly(ethylene terephthalate) during melt processing

The discolouration, that occurs in virgin poly(ethylene terephthalate) - PET during melt processing, was studied using various bulk and surface analytical techniques. Proton nuclear magnetic resonance (¹H NMR) was used to study the bulk chemical changes occurring in the polymer during thermo-oxidative degradation. Chemical derivatisation with trifluoroacetic anhydride (TFAA) was used to label the hydroxyl groups introduced on the polymer surface by thermal oxidation.From the surface analysis studies using photoacoustic Fourier transform infrared spectroscopy (PA/FT-IR), diffuse reflectance infrared Fourier transform spectroscopy (DRIFT) and X-ray photoelectron spectroscopy (XPS) it was evident that colour formation starts initially with the hydroxylation of the terephthalic ring. Further, the formation of additional carbonyl functionalities and conjugated chromophoric systems complete the colour formation process.     

Surface influence on the rotational and translational dynamics of molecules confined inside a mesoporous carbon xerogel

Low-field nuclear magnetic resonance techniques are employed to extract information about the effects introduced by the interaction with the surface on the rotational and translational dynamics of molecules confined inside a mesoporous carbon xerogel. The molecules under study were water, cyclohexane, and hexane. They were chosen due to their different interaction strength with the carbonaceous matrix. Frequency dependent longitudinal relaxation measurements, using the fast field cycling technique, allowed extraction of the fractal dimension of the carbon xerogel surface. It was observed that the measured value is influenced by the molecule affinity to the surface. Diffusion measurements, using the pulse field gradient technique, have revealed that the stronger interaction with the surface of cyclohexane and hexane molecules leads to an increased diffusive tortuosity, as compared with water.     

Reliability and performances of a high-purity gamma spectrometry system used for environmental measurements

Proficiency testing is among the most methods to assess the accuracy of the analytical data produced by laboratories. The results presented in this paper show the performance of the laboratory for three intercomparisons organized by Radionuclide Metrology Laboratory (RML) and by IAEA, in which SALMROM laboratory have participated in three consecutive years. The feedbacks from the final reports from RML and IAEA demonstrate the performance of the laboratory where 34 out of 39 pass all acceptance criteria of the test. The rest of five results which failed served to improve the laboratory analysis and to optimize accuracy measurements. The overall results of the proficiency tests point out the reliability and traceability of the gamma spectrometry system used for environmental measurements.     

Dynamics of the thermocline in the equatorial region of the Pacific ocean

This paper is devoted to the subsurface current dynamics in equatorial regions, where the hallmark of a strong stratification is a sharp interface (thermocline), separating two layers of different density, and whose depth is dependent upon the strength of the winds above the ocean's surface. We give here a few monotonicity results concerning the dynamics of the thermocline in the equatorial region. The most important one asserts that the level of the thermocline decreases as the strength of the wind at ten meters above the ocean surface, denoted |U_w|, increases. Moreover, the strength of the current at the thermocline decreases as |U_w| increases.     

Epoxy-functionalized large-pore SBA-15 and KIT-6 as affinity chromatography supports

Mesoporous silica supports are proposed as an alternative to polymeric stationary phases for fast affinity chromatography due to their better mechanical strength compared to polymers. Ideal supports should combine high surface area and large pore size to allow a high loading capacity of large molecules, such as proteins, and favor their accessibility. Increasing the pore size of large-surface area micelle-templated silicas (SBA-15, KIT-6) has been achieved by swelling the micelles by the addition of organic molecules and increasing synthesis time and temperature. The pore size of hexagonal silica mesostructured SBA-15 has been increased up to 35 nm. These materials could find therefore application as affinity chromatography for immunoextraction.     

Pricing a stochastic car value depreciation deal

This paper deals with pricing a contract under which a dealer buys back a car from a client, for a cash amount contained in a given depreciation table. The value of the car is supposed to depreciate according to a stochastic model with random repairs modeled by a Poisson process. Copyright © 2013 John Wiley & Sons, Ltd.