Application of 13C nmr spectroscopy to the elucidation of the electrochemical oxidation mechanism of the l-ascorbic and d-araboascorbic acids

The previously proposed electrochemical oxidation mechanism of the l-ascorbic and d-araboascorbic acids in basic medium must be rejected because of the variation in the carbon chemical shifts and coupling constants with the pH, which shows that the supposed rupture of the furanose rings at pH ～ 9 does not occur. Electrolysis in basic medium yields the same products as those obtained when the pH of the products of the electrolysis in acid medium are raised to pH ～ 11. This suggests that the oxidation mechanisms in acid and basic media are similar. The assigned carbon chemical shifts of the oxidation products in acid medium $\text{3}$ (or $\text{4}$) and in basic medium $\text{5}$ (or $\text{6}$) and $\text{7}$ (or $\text{8}$) are reported.     

Formula zero: Development and kart’s competition driven by PEM fuel cell

Formula Zero (FZ) is an European project that promotes a zero emissions karts championship based on fuel cell (FC) technology. The project’s objectives are: first, to compete at FZ championship with own FC vehicle, second, to demonstrate that sustainable mobility is possible having zero emissions transports, and third, to take out all the knowledge gained during the development of this project for implanting it in future projects with FC automotive applications. The team has designed and built a kart powered by a stack of PEM 1.2 kW at a first prototype and another prototype powered by a 8 kW stack in a second stage. The goal of the project is to confirm that karts powered by hydrogen and FC are able to compete at velocity races, getting same performance as conventional karts. The difference is that the FC kart is an electric vehicle, with no emissions, no noise, and no vibrations.     

Ca and K decorated germanene as hydrogen storage: An ab initio study

The hydrogen storage capacity and performance of Ca and K decorated germanene were studied using density functional theory calculation. The Ca and K adatoms were found to be sufficiently bonded to the germanene without clustering at the hollow site. Further investigation has shown an ionic bonding is apparent based on the charge density difference and Bader charge analysis. Upon adsorption of H₂ on the decorated germanene, it was found that the Ca and K decorated systems could adsorb 8 and 9 H₂ molecules, respectively. The adsorption energies of H₂ molecules were within the Van der Waals energy (400–435 meV), suggesting weak physisorption. The charge density profile revealed that the electron of H₂ moved toward the adatom decoration without leaving the local region of H₂. This suggests that a dipole-dipole interaction was apparent and consistent with the energy range found. Finally, the gravimetric density obtained from the adsorption of H₂ on the decorated germanene shows that this material is a potential for H₂ storage media.     

Correction of photoresponse nonuniformity for matrix detectors based on prior compensation for their nonlinear behavior

What we believe to be a novel procedure to correct the nonuniformity that is inherent in all matrix detectors has been developed and experimentally validated. This correction method, unlike other nonuniformity-correction algorithms, consists of two steps that separate two of the usual problems that affect characterization of matrix detectors, i.e., nonlinearity and the relative variation of the pixels' responsivity across the array. The correction of the nonlinear behavior remains valid for any illumination wavelength employed, as long as the nonlinearity is not due to power dependence of the internal quantum efficiency. This method of correction of nonuniformity permits the immediate calculation of the correction factor for any given power level and for any illuminant that has a known spectral content once the nonuniform behavior has been characterized for a sufficient number of wavelengths. This procedure has a significant advantage compared with other traditional calibration-based methods, which require that a full characterization be carried out for each spectral distribution pattern of the incident optical radiation. The experimental application of this novel method has achieved a 20-fold increase in the uniformity of a CCD array for response levels close to saturation.     

A Reinterpretation of Beall’s ‘Off-Topic’ Semantics

Journal of Logic, Language and Information - Jc Beall’s off-topic interpretation of Weak Kleene logic offers a logic of ‘true-and-topic’ preservation. However, Nissim Francez has...     

Automatic correction of background phase offset in 4D-flow of great vessels and of the heart in MRI using a third-order surface model

Magnetic Resonance Materials in Physics, Biology and Medicine - To evaluate an automatic correction method for velocity offset errors in cardiac 4D-flow acquisitions. Velocity offset correction was...     

Microstructure and Mechanical Properties of Silicon Nitride Materials Fabricated from SHS Powders

Two different silicon nitride powders, one produced by self-propagating high-temperature synthesis (SHS) and one commercial, have been equally processed to obtain dense materials. Y₂O₃ powders as a sintering aid and hot-pressing techniques were used to process the materials. The fracture toughness and strength of the materials prepared have been evaluated and the results comparatively discussed as a function of the microstructure, with special emphasis on the characteristics of the initial powders.     

Absorption and effects of 3-(N-phenylamino)-1,2-propanediol esters in relation to toxic oil syndrome

Toxic Oil Syndrome (TOS) was an epidemic disease related to the consumption of rapeseed oil denatured with aniline that made its sudden appearance in Spain in 1981. The fatty acid esters of 3-(N-phenylamino)-1,2-propanediol (PAP), which is a chemical class of by-products resulting from the reaction of aniline with oil components, have shown a strong association with TOS-related oils. These compounds also show some structural similarities to platelet-activating factor (PAF). In search of a toxic agent that could explain the widespread systemic effects observed in TOS patients, we investigated the intestinal absorption and biotransformation of the different PAP esters found in TOS-related oil samples and the possible pathophysiological effect of these mediators and their metabolic products if acting as PAF analogs. Results indicate that PAP esters are absorbed in the gastrointestinal tract and are distributed and stored in different organs, particularly in the liver and brown adipose tissue. PAP in these organs showed different patterns of fatty acids, indicating the ability of the gastrointestinal tract to modify the fatty acid composition of the parent PAP. Thus, the fatty acid profile of the PAP esters found in intestine appears to be related to the type of oil used as vehicle. Some of these PAP esters, when a long acyl chain was present in the sn-1 position of the molecule, showed an inhibitory effect on the PAF synthesis. This is an important observation in line with the systemic nature of the disease.     

Etude du diagramme de phases et cristallogenese des phosphovanadates de plomb

The phase diagram of lead phosphovanadate Pb₃(P_xV_1?xO₄)₂ for 0.5 ≤ x ≤ 1 has been investigated. Liquidus and solidus have been determined by means of differential thermal analysis and X-ray techniques. These results are confirmed through a molecular absorption spectrophotometry analysis of phosphor and vanadium, by comparing the compositions of lead phosphovanadate single crystals, grown by Czochralski pulling, with that of the starting melts. Good optical and crystallographic quality crystals of large size are obtained for x = 0 and x = 0.5, while for other compositions, they are still suitable for physical measurements. A definite, congruently melting compound with trigonal symmetry at room temperature is found for x = 0.5.