A dual finite element complex on the barycentric refinement

A simplicial mesh on an oriented two-dimensional surface gives rise to a complex $X^{?}$ of finite element spaces centered on divergence conforming Raviart–Thomas vector fields and naturally isomorphic to the simplicial cochain complex. On the barycentric refinement of such a mesh, we construct finite element spaces forming a complex $Y^{?}$, centered around curl conforming vector fields, naturally isomorphic to the simplicial chain complex on the original mesh and such that $Y^{2?i}$ is in ${\mathrm{L}}^2$ duality with $X^i$. In terms of differential forms this provides a finite element analogue of Hodge duality. To cite this article: A. Buffa, S.H. Christiansen, C. R. Acad. Sci. Paris, Ser. I 340 (2005).     

Point defect dynamics and evolution of chemical reactions in alanates by anelastic spectroscopy

We report the first measurements of elastic modulus and energy dissipation in Ti-doped and undoped sodium aluminum hydride. It is shown that the chemical reactions that occur by varying the sample temperatures or by aging most sensitively affect the elastic constants, such that the modulus variations allow the time and temperature evolution of decomposition to be monitored. After a well-defined thermal treatment at 436 K, a thermally activated relaxation process appears at 70 K in the kilohertz range, denoting the existence of a new species, likely involving hydrogen, having a very high mobility, that is, 10(3) jumps/s at the peak temperature corresponding to a relaxation rate of about 10(11) s(-1) at room temperature. The activation energy of the process is 0.126 eV and the preexponential factor 7 x 10(-14) s, which is typical of point defect relaxation. The peak is very broad with respect to a single Debye process, indicating strong interaction or/and multiple jumping type of the mobile entity. The present data suggest that the models aiming at interpreting the decomposition reactions and kinetics should take into account the indicated point-defect dynamics and stoichiometry defects.     

Alcune questioni intorno alle ultraestensioni di strutture relazionali

Riassunto Si introduce il concetto di ultrafiltro debolmente uniforme di un'algebra di Boole completa e si dà un teorema sulla cardinalità di una ultraestensione rispetto a un tale ultrafiltro. Si mettono in evidenza proprietà di ultrafiltri in particolari algebre di Boole.

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Summary The notion of a “weakly uniform ultrafilter? of a complete Boolean Algebra is introduced and a theorem on the cardinality of an ultraextension with respect to such an ultrafilter is given. Some properties of ultrafilters of particular Boolean algebras are emphasized.

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Lavaro eseguito nell'ambito dell'attività del Comitato per le Scienze Matematiche del C.N.R. per l'anno 1969 contratto n. 15218205174.     

Improved Schemes for Visual Cryptography

A (k,n)-threshold visual cryptography scheme ((k,n)-threshold VCS, for short) is a method to encode a secret image SI into n shadow images called shares such that any k or more shares enable the visual recovery of the secret image, but by inspecting less than k shares one cannot gain any information on the secret image. The visual recovery consists of xeroxing the shares onto transparencies, and then stacking them. Any k shares will reveal the secret image without any cryptographic computation.In this paper we analyze visual cryptography schemes in which the reconstruction of black pixels is perfect, that is, all the subpixels associated to a black pixel are black. For any value of k and n, where 2 k n, we give a construction for (k,n)-threshold VCS which improves on the best previously known constructions with respect to the pixel expansion (i.e., the number of subpixels each pixel of the original image is encoded into). We also provide a construction for coloured (2,n)-threshold VCS and for coloured (n,n)-threshold VCS. Both constructions improve on the best previously known constructions with respect to the pixel expansion.     

Flavonoid distribution in tissues of Phillyrea latifolia L. leaves as estimated by microspectrofluorometry and multispectral fluorescence microimaging

A new method for detecting the tissue-specific distribution of flavonoids has been developed by coupling microspectrofluorometry and multispectral fluorescence microimaging techniques. Fluorescence responses of cross sections taken from 1 year old Phillyrea latifolia leaves exposed to full (sun leaves) or 15% (shade leaves) solar radiation in a coastal area of Southern Tuscany were analyzed. Fluorescence spectra of different tissue layers, each normalized at its fluorescence maximum, that were stained or not stained with Naturstoff reagent A (in ethanol), under excitation with UV light (lambdaexc = 365 nm) or blue light (lambdaexc = 436 nm) were recorded. The shape of the fluorescence spectra of tissue layers from shade and sun leaves differed only under UV excitation. The fluorescence of stained cross sections from sun and shade leaves as well as from different layers of sun leaves received a markedly different contribution from the blue (470 nm) and the yellow-red (580 nm) wavebands. Such changes in tissue fluorescence signatures were related to light-induced changes of extractable caffeic acid derivatives and flavonoid glycosides, namely quercetin 3-O-rutinoside and luteolin 7-O-glucoside. Wall-bound phenolics, i.e. hydroxycinnamic acids (p-coumaric, ferulic and caffeic acid) and flavonoids (apigenin and luteolin derivatives), did not substantially differ between sun and shade leaves. A Gaussian deconvolution analysis of fluorescence spectra was subsequently performed to estimate the contribution of flavonoids (emitting at 600 nm, F600 [red fluorescence contribution = signal integrated over a Gaussian band centered at about 600 nm]) relative to the tissue fluorescence (Ftot [total fluorescence = signal integrated over the whole fluorescence spectrum]). The F600/ Ftot ratios sharply differed between analogous tissues of sun and shade leaves, as well as among tissue layers within each leaf type. A highly resolved picture of the tissue flavonoid distribution was finally provided through a fluorescence microimaging technique by acquiring fluorescence images at the blue (fluorescence at about 470 nm [F470]) and yellow-red (fluorescence at about 580 nm [F580]) wavelengths and correcting the F580 image for the contribution of nonflavonoids to the fluorescence at 580 nm. Monochrome images were elaborated by adequate computing functions to visualize the exclusive accumulation of flavonoids in different layers of P. latifolia leaves. Our data show that in shade leaves flavonoids almost exclusively occurred in the adaxial epidermal layer. In sun leaves flavonoids largely accumulated in the adaxial epidermal and subepidermal cells and followed a steep gradient passing from the adaxial epidermis to the inner spongy layers. Flavonoids also largely occurred in the abaxial epidermal cells and constituted the exclusive class of phenylpropanoids synthesized by the cells of glandular trichomes. The proposed method also allowed for the discrimination of the relative abundance of hydroxycinnamic derivatives and flavonoids in different layers of the P. latifolia leaves.     

Ecological assessment of Santa Giusta Lagoon (Sardinia,Italy)

The general environmental conditions of Santa Giusta Lagoon, an important Sardinian coastal lagoon often affected by dystrophic crises, are examined. The study considers both the monitoring data collected over the past ten years on the relevant water quality parameters and the preliminary results on the structure and heavy metal content of the surface sediments of the lagoon. These data emphasised its elevated trophic level, due to the excessive presence of plant nutrients in water, and a relative low level of heavy metal contamination. At the moment, the eutrophy--brought about the urban and industrial wastes from Oristano and Santa Giusta--can be considered the main environmental issue of the lagoon.     

Structure–Activity Relationship Study of a Potent α-Thrombin Binding Aptamer Incorporating Hexitol Nucleotides

The replacement of one or more nucleotide residues in the potent α-thrombin-binding aptamer NU172 with hexitol-based nucleotides has been devised to study the effect of these substitutions on the physicochemical and functional properties of the anticoagulant agent. The incorporation of single hexitol nucleotides at the T9 and G18 positions of NU172 substantially retained the physicochemical features of the parent oligonucleotide, as a result of the biomimetic properties of the hexitol backbone. Importantly, the NU172- T ^H9 mutant exhibited a higher binding affinity toward human α-thrombin than the native aptamer and an improved stability even after 24 h in 90 % human serum, with a significant increase in the estimated half-life. The anticoagulant activity of the modified oligonucleotide was also found to be slightly preferable to NU172. Overall, these results confirm the potential of hexitol nucleotides as biomimetic agents, while laying the foundations for the development of NU172-inspired α-thrombin-binding aptamers.     

Trace metal concentration in wild avian species from Campania,Italy

This study was conducted to determine heavy metals concentrations in tissues of 94 birds belonging to different species from coastal areas of Naples and Salerno (Southern Italy) in order to provide baseline data concerning trace element levels in wild birds living in or close to an area characterized by high anthropogenic impact. Additional aim of this study was to verify if diet influenced metal accumulation, so birds were classified as birds of prey, fish eating birds and insectivorous birds.     

Design and synthesis of novel polycycles based on the 3H‐pyrrolo/6,7‐dihydropyrido[1,2‐a]indole scaffold as templates for pharmaceutical development

In the course of our work aimed at developing novel heterocycles of pharmaceutical interest, we designed and synthesized several polycyclic templates as potential substrates to be used in drug design. We obtained a set of condensed ring systems as versatile structural platforms to generate potential DNA‐interactive agents and/or reversible inhibitors of enzymes such as topoisomerases, poly(ADP‐ribose) polymerase‐1 (PARP‐1), telomerase, and, in particular, cyclin dependent kinases. Herein, we report the design, synthesis, structural investigation, and preliminary DNA‐binding affinity of these heteroaromatic systems. J. Heterocyclic Chem., (2011).