Homogenization for conductive thin layers of pre-fractal type

The aim of this work is to obtain convergence results for the solutions of transmission problems across highly conductive layers of pre-fractal type from the point of view of homogenization. We prove the M-convergence of the energy functionals to an energy functional which incorporates a singular term, supported within the layer. From the convergence of the energy functionals we deduce the convergence of the approximating solutions to the limit solution in a suitable sense.     

New chiral imino- and amino-sulfoxides as activators of allyl trichlorosilane in the asymmetric allylation of aldehydes

Chiral 2-methylsulfinyl benzaldehyde proved to be a valuable starting material for a convenient approach towards a variety of imino- and amino-sulfoxides. The catalytic properties of these new ligands, as potential activators of allyl trichlorosilane, have been exploited in new catalytic procedures for the synthesis of enantioenriched homoallylic alcohols.     

Spiroketals of monosaccharides by dye-sensitized photooxygenation of furyl ketoses

[4+2] Cycloaddition of singlet oxygen to suitably substituted furans followed by reduction of the corresponding endoperoxides afforded functionalized enediones which quickly cyclized into the titled spiroketals. The reported method represents a green synthetic one-pot procedure for novel [6,6]-, [5,6]-, and [5,5]-spiroketals of sugars.     

Dye-sensitized photooxygenation of sugar furans: novel bis-epoxide and spirocyclic C-nucleosides

Dye-sensitized photooxygenation of 2-methyl 5-(2,3,5-tri-O-acetyl-β-d-ribofuranosyl)furoate leads to (1S,4R)-endo-peroxide, highlighting a high facial diastereoselectivity. This endo-peroxide rearranges into syn-(1R,2R:3S,4R)-diepoxide C-nucleoside, while by Et₂S-reduction followed by NEt₃ catalysis affords a spirocyclic C-nucleoside.     

Physico-chemical characterization of protein-pigment interactions in tempera paint reconstructions: casein/cinnabar and albumin/cinnabar

In this work, we characterized paint reconstructions using ovalbumin and casein as binders, and cinnabar (HgS) as a pigment, before and after artificial ageing. Egg and casein are common paint binders that were used historically in the technique of tempera painting. Despite extensive research on the identification of proteinaceous binders in paintings, there is a substantial lack of knowledge regarding the ageing pathway of their protein content, and their chemical interaction with inorganic pigments. Thermogravimetric analysis, infrared spectroscopy and size-exclusion chromatography (SEC) were used to reveal the physico-chemical processes involved in the ageing of proteins in paintings. Taken together, the three techniques highlighted that proteins are subject to both cross-linking and hydrolysis upon ageing, and to a lesser extent, to oxidation of the side chains. Mercury–protein interactions were also revealed using a cold vapour generation atomic fluorescence spectrometer mercury-specific detector coupled to SEC. The study clearly showed that HgS forms stable complexes with proteins and acts as a sensitizer in cross-linking, hydrolysis and oxidation.     

Quantitative and physical evaluation of patchouli essential oils obtained from different sources of Pogostemon cablin

Patchouli essential oil can be obtained from fresh, dried and fermented plant material. It is a highly valuable product in the fragrance industry and its quality changes depending upon raw material age and oil storage. In this work, patchouli essential oils derived from different treatments have been subjected to GC-FID quantitative analysis using an internal standard (ISTD) method with response factors (RF). Samples were obtained from i) fresh plants; ii) hydrodistillation of one year mature and fermented plants; iii) hydrodistillation of one year mature plants; iv) commercial products from Indonesia and Malaysia. Linear Retention Indices (LRI) for both polar and non-polar GC-MS analyses were also measured as a tool for qualitative analysis towards a homologous series of C7-C30 n-alkanes. The results obtained confirmed that, in all samples, patchouli alcohol was the main volatile constituent, with higher amount in lab-scale produced oils, compared with commercial samples. Other major compounds, in lab oils and commercial samples respectively, were: delta-guaiene, alpha-guaiene, pogostol, seychellene and alpha-patchoulene. Another 36 compounds were also found.     

Cationic porphyrins are reversible proteasome inhibitors

The aim of this study is to verify if water-soluble porphyrins can be used as proteasome inhibitors. We have found that cationic porphyrins inhibit proteasome peptidase activities much more effectively than the corresponding anionic derivatives. The relevance of electrostatics in driving porphyin-proteasome interactions has been confirmed by the observation that the inhibitory efficiency of the cationic macrocycles decreases with the number of positive substituents. We have also investigated various metalloporphyrins, which differ due to the different propension of the central metal ion toward axial coordination. Our experimental results indicate that the naked cationic porphyrins are the most active in reversibly inhibiting the three main protease activities of the proteasome in the micromolar range. A spectroscopic characterization of porphyrin-proteasome interactions by UV-vis spectra parallels the results of inhibition assays: the higher the inhibitory effect the stronger the spectroscopic variations are. To interpret the action of porphyrins at a molecular level, we have performed calculations evidencing that cationic porphyrins may hinder the access to the canonical proteolytic site on the proteasome β5 subunit. In particular, an inspection of the top-scoring docking modes shows that the tetracationic porphyrin blocks the catalytic pocket, close to the N termini of the β5 proteasome subunit, more efficiently than its anionic counterpart. Proteasome inhibition activity of porphyrins unites their known anticancer properties making them suitable as a scaffold for the design of novel multitargeted molecules.     

A GCV based Arnoldi-Tikhonov regularization method

For the solution of linear discrete ill-posed problems, in this paper we consider the Arnoldi-Tikhonov method coupled with the Generalized Cross Validation for the computation of the regularization parameter at each iteration. We study the convergence behavior of the Arnoldi method and its properties for the approximation of the (generalized) singular values, under the hypothesis that Picard condition is satisfied. Numerical experiments on classical test problems and on image restoration are presented.