General Inhomogeneous Discrete Linear Partial Differential Equations with Constant Coefficients on the Whole Spaces

In this paper we shall introduce new constructions of approximate solutions of general linear partial differential equations with constant coefficients on the whole spaces, and establish fundamental estimates of the solutions depending on the inhomogeneous terms. This will be done by combining general ideas of the Tikhonov regularization and discretization of bounded linear operator equations on reproducing kernel Hilbert spaces. Furthermore, we will provide approximate solutions for the related inverse source problems.     

Stable regimes for hard disks in a channel with twisting walls

We study a gas of N hard disks in a box with semi-periodic boundary conditions. The unperturbed gas is hyperbolic and ergodic (these facts are proved for N=2 and expected to be true for all N≥2). We study various perturbations by twisting the outgoing velocity at collisions with the walls. We show that the dynamics tends to collapse to various stable regimes, however we define the perturbations, and however small they are.     

LC-DAD/ESI-MS/MS study of phenolic compounds in ash (Fraxinus excelsior L. and F. americana L.) heartwood. Effect of toasting intensity at cooperage

The phenolic composition of heartwood extracts from Fraxinus excelsior L. and F. americana L., both before and after toasting in cooperage, was studied using LC-DAD/ESI-MS/MS. Low-molecular weight (LMW) phenolic compounds, secoiridoids, phenylethanoid glycosides, dilignols and oligolignols compounds were detected, and 48 were identified, or tentatively characterized, on the basis of their retention time, UV/Vis and MS spectra, and MS fragmentation patterns. Some LMW phenolic compounds like protocatechuic acid and aldehyde, hydroxytyrosol and tyrosol, were unlike to those for oak wood, while ellagic and gallic acid were not found. The toasting of wood resulted in a progressive increase in lignin degradation products with regard to toasting intensity. The levels of some of these compounds in medium-toasted ash woods were much higher than those normally detected in toasted oak, highlighting vanillin levels, thus a more pronounced vanilla character can be expected when using toasted ash wood in the aging wines. Moreover, in seasoned wood, we found a great variety of phenolic compounds which had not been found in oak wood, especially oleuropein, ligstroside and olivil, along with verbascoside and isoverbascoside in F. excelsior, and oleoside in F. americana. Toasting mainly provoked their degradation, thus in medium-toasted wood, only four of them were detected. This resulted in a minor differentiation between toasted ash and oak woods. The absence of tannins in ash wood, which are very important in oak wood, is another peculiar characteristic that should be taken into account when considering its use in cooperage.     

Gel permeation chromatographic study of the molecular weight distribution of tannins in the wood,bark and leaves ofEucalyptus spp.

Summary The molecular weight distribution of tannins from the wood, bark and leaves ofEucalyptus camaldulensis, E. globulus andE. rudis from two different Spanish provenances has been studied by high performance gel permeation chromatography, using the compounds' acetylated derivatives. The MW distribution profiles showed important variability depending on the type of vegetal tissue, the species and, in some cases, on the geographical provenance of the samples. Bark was the vegetal tissue that yielded tannins with the highest molecular weight, followed by wood and leaves. Tannins from wood and bark ofE. camaldulensis were of higher molecular size than those fromE. globulus andE. rudis; those in the leaves ofE. globulus andE. camaldulensis were similar in molecular size and larger than those in the leaves ofE. rudis.     

Gamma activation analysis of marine sediments at Havana Bay, Cuba

Summary Twenty six elements was studied preliminary in the superficial sediments of Havana Bay using gamma activation analysis by the electron accelerator microtron MT-25 at the Flerov Laboratory of Nuclear Reactions, JINR. Samples from five zones of Havana Bay including the three coves were analyzed. The obtained results show a close relation between the concentration levels of the studied elements and the pollution sources. Some elements (As, Ba, Ni, Pb, Cu, Zn, Fe, Cr, Mn) have high concentration levels compared to the values for other environmental marine sediments reported in the literature.     

Gradient flow titration for the determination of fluoride ion in natural waters

The determination of fluoride ions in water samples was accomplished by using a gradient flow titration. A standard commercial combined electrode is used in a cell configuration that combines the gradient chamber and the electrode in a single unit. The methodology developed gives results with a relative standard deviation of about 3%. The average recoveries after spiking natural samples with fluoride are in the range 100–102%. The method was used successful in determining the fluoride concentration in water samples.     

Flavonoid separation by capillary electrophoresis. Effect of temperature and pH

Summary The use of capillary electrophoresis for the analysis of selected flavonols present in fruit juices and wines (kaempferol-3- rutinoside, rutin, avicularin, quercitrin, isoquercitrin, isorhamnetin, kaempferol and quercetin) was explored, and the effect of pH and temperature on the separation studied. The method had good reproducibility and analyses were carried out in less than 10 minutes.     

Asymmetric syntheses of 1-deoxy-6,8a-di-epi-castanospermine and 1-deoxy-6-epi-castanospermine

Asymmetric syntheses of both 1-deoxy-6,8a-di-epi-castanospermine and 1-deoxy-6-epi-castanospermine, polyhydroxylated indolizidine alkaloids that act as selective glycosidase inhibitors, have been accomplished in seven steps. The key feature of our unique syntheses includes the stereoselective introduction of the C-3 and C-4 hydroxyl groups utilizing the aza-Claisen rearrangement-induced ring expansion of 1-acyl-2-alkoxyvinyl pyrrolidine and a substrate-controlled stereoselective transannulation of the resulting azoninone intermediate.