Dielectric Shielding of Ionic Charges in Aqueous Solutions of Different Ionic Strength

The thermodynamic functions of the proton transfer H₂tn²⁺+tn → 2 Htn⁺ (tn = 1,3-diaminopropane) have been determined in aqueous solutions containing different amounts of KCl (0.05 ? μ ? 3.01). The free energy (?ΔG) of the process decreases, whereas the enthalpy (-ΔH) increases with μ. There is reason to believe that the reaction is entirely controlled by the Coulomb forces between the two protonic charges. The electrostatic energy involved can be described in terms of a model incorporating an effective dielectric constant εe, such that δε_e/δμ and δ²ε_e/δμδT are both positive. The polarisation of pure water is produced by orientation of hydrogen-bonded dipole molecules H₂O, whereas the electrolyte solution is polarised in addition by dislocation of the ions K⁺ and Cl^?. Our results demonstrate that the former type of polarisation is much more temperature dependent than the latter.     

Inorganic coordination polymers. XIV. Chromium(III) phosphinate perfluorocarboxylate polymers

A series of polymers, {Cr(OH)(OPRR′O)[OOC(CF₂)_nCF(CF₃)₂]}_x has been prepared and studied. The polymers with R = R′ = C₆H₅ are soluble in CCl₂FCClF₂, whereas those with R = CH₃ and R′ = C₆H₅ and with R = R′ = C₈H₁₇ are insoluble in all solvents. Attempts to prepare similar materials without hydroxyl groups gave the polymers {Cr(OH)_r(OPRR′O)_p[OOC(CF₂)_nCF(CF₃)₂]_q}_x with 0 < r < 1. The latter polymers are much more tractable than the former; however they are also less thermally stable. The perfluoro-carboxylate groups in these materials can either be chelating or bridging, depending on the other ligands present.     

The chemistry and the stereochemistry of poly(N-alkyliminoalanes) : V. The preparation and crystal structure of the pentamer [(HalN-i-Pr)2(H2AlNH-i-Pr)3]

The compound [(HAlN-i-Pr)₂(H₂AlNH-i-Pr)₃] has been prepared and the crystal and molecular structure determined by an X-ray analysis, carried out with three-dimensional data collected on a diffractometer. The molecule is made up of a cyclohexane-type ring, [(HAlN-i-Pr)₂(H₂AlNH-i-Pr)], in skewboat conformation, on each side of which is bonded an -H₂AlNH-i-Pr- bridging unit between a nitrogen atom and an aluminum atom of the ring. The molecule lies on a binary axis of the crystal, but this symmetry is fulfilled only by a statistical orientation of the asymmetric molecular units (the statistical model is not however completely defined). The AlN bond lengths range from 1.901 to 1.985 Å; the average NC bond length is 1.527(9) Å. Main crystal data are: monoclinic space group C2/c; a = 10.15(2), b = 21.64(3), c = 12.84(2) Å, β = 111.9(5)°; Z = 4; calculated density 1.095 g/cm³. The structure was solved by direct methods and block-matrix least-squares converged to an R value of 5.6%.     

Non-destructive in situ determination of pigments in 15th century wall paintings by Raman microscopy

Raman microscopy has been applied to the study of 15th century wall paintings in a chapel of St. Orso Priory palace (Aosta, Italy) in view of their restoration. The use of a transportable instrument has made it possible to work non-destructively in situ without sampling. The main inorganic pigments used by the unknown artist, namely mercury sulphide, azurite, white lead, red and yellow ochre, carbon black and lead tin yellow type I have been identified, and the presence of organic substances and of some decay products (calcium sulphate and oxalate) has been observed.     

The chemistry and the stereochemistry of poly(n-alkyliminoalanes) : III. The crystal and molecular structure of the adduct (HalN-i-Pr)6AlH3

The crystal and molecular structure of the adduct (HAlN-i-Pr)₆AlH₃ has been determined from single-crystal and three dimensional X-ray diffraction data collected by counter methods. The cage-type molecular structure consists of two six-membered rings, (AlN)₃, joined together by four adjacent transverse AlN bonds; the loss of two of these bonds allows the complexation of one alane molecule, with five-coordination of the aluminum (trigonal bipyramidal geometry), through two AlN bonds and two AlHAl bridge bonds. The AlN bond lengths range from 1.873 to 1.959 Å; the average AlH bond length is 1.50(1) Å for the four-coordinated aluminum atoms; the average distance of the two apical hydrogens from the five-coordinated aluminum atom is 1.92(5) Å. Colourless prismatic crystals of the compound have the following crystal data: triclinic space group P$\text{1}$; a = 17.13(2); b = 10.78(2); c = 10.20(2) Å; α = 124.3(4), β = 92.0(4), γ = 92.1(5); Z = 2; calculated density 1.157 g/cm³. The structure has been refined by block-matrix, least-squares methods using 4358 independent reflections to a standard unweighted R factor of 4.9%.     

Reaction of thiete 1,1-dioxide with α-chlorobenzalphenylhydrazine and methyl phenylhydrazonochloroacetate

Thiete 1,1-dioxide reacts with 2 moles of α-chlorobenzalphenylhydrazine and methyl phenylhydrazonochloroacetate in the presence of triethylamine leading to the pyrazole derivatives 6 and 7 whose structure and mechanism of formation are discussed.     

The chemistry and the stereochemistry of poly(N-alkyliminoalanes) : XV. The crystal and molecular structure of the compounds [((THF)Mg)(HA1N-t-Bu)3] and [((THF)3Ca)(HA1N-t-Bu)3] · THF

The compounds [((THF)Mg)(HA1N-t-Bu)₃] (I) and [((THF)₃Ca)(HA1N-t-Bu)₃] · THF (II) have been structurally characterized from single-crystal diffraction data. The molecular structures are based on an (A1N)₄ “cubane” type framework in which an aluminum is replaced by an alkaline earth metal. According to the size and the coordination of the “foreign” atom (four for Mg, six for Ca) the cubic geometry of the cage is increasingly distorted. Coordination is completed by one molecule of THF to the Mg atom and three molecules to the Ca atom; in II a molecule of THF crystallizes with a cage molecule. Mean MgN and CaN bond distances are 2.090(4) and 2.490(2) Å. Crystal data: I, orthorombic, space group Pbca, a 17.107(2), b 17.305(4) and c 20.220(5) Å, Z = 8, calculated density 1.031 g/cm³; II, orthorombic, space group Pbca, a 20.48(1), b 20.38(1), c 20.51(1), Z = 8, calculated density 1.081 g/cm³.     

A nonlinear hyperbolic problem arising from a question of nonlinear optics, Part II

A modified analytical and numerical method is presented for a preliminary study of the problem of Graffi-Cesari in Nonlinear Optics [1, 12]. This problem concerns electromagnetic laser wave propagation in a nonlinear (quartz) crystal slab embedded between two linear media, and is a suitably simplified version of the experimental situation of Franken, Ward and co-workers (1961). A new version of an existence and uniqueness theorem is proved in a functional class which is chosen following Cesari's works on quasilinear hyperbolic systems in the Schauder canonic form, under a set of restrictions upon the admissible slab widtha of the crystal. The present method consists essentially in centering the relevant functional ball at the linear solution, and yields numerical values fora of the order of 2 mm, with a good agreement with values of quartz crystal widths used in experiments.     

A nonlinear hyperbolic problem arising from a question of nonlinear optics,part I

Summary Analytical and numerical results are given for the problem of Graffi, recently proposed by D. Graffi in order to give a rigorous mathematical theory of the experiments carried out by Franken, Ward and coworkers (1961) in Nonlinear Optics, following the theoretical scheme developed by L. Cesari in some recent papers concerning boundary value problems for quasilinear hyperbolic systems in the Schauder canonic forms.Numerical results refer to the estimate by defect of the maximal slab widtha of the nonlinear medium (a quartz crystal slab), under which the relevant existence and uniqueness theorem holds, in a suitable functional class which is chosen following Cesari's works and is well-suited for applications to Mathematical Physics.

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Riassunto Si presentano risultati analitici e numerici relativi al problema di Graffi, recentemente proposto da D. Graffi per una teoria matematica degli esperimenti di Franken, Ward et al. (1961) in Ottica Non Lineare, seguendo lo schema teorico elaborato da L. Cesari in alcuni recentissimi lavori su certi problemi ai limiti per sistemi iperbolici quasi lineari nella forma canonica di Schauder.I risultati numerici si riferiscono alla stima per difetto del massimo spessore del mezzo non lineare (lamina di cristallo di quarzo) per cui restano validi teoremi di esistenza, unicità e dipendenza continua dall'onda (laser) incidente, in una opportuna classe funzionale, scelta seguendo i lavori citati di Cesari.

     

The Potential of Lamiaceae Herbs for Mitigation of Overweight,Obesity, and Fatty Liver: Studies and Perspectives

Numerous plants, plant extracts, and plant-derived compounds are being explored for their beneficial effects against overweight and liver diseases. Obesity is associated with the increased prevalence of non-alcoholic fatty liver disease (NAFLD), becoming the most common liver disease in Western countries. Obesity and NAFLD are closely associated with many other metabolic alternations such as insulin resistance, diabetes mellitus, and cardiovascular diseases. Many herbs of the Lamiaceae family are widely employed as food and spices in the Mediterranean area, but also in folk medicine, and their use for the management of metabolic disorders is well documented. Hereby, we summarized the scientific results of the medicinal and nutraceutical potential of plants from the Lamiaceae family for prevention and mitigation of overweight and fatty liver. The evidence indicates that Lamiaceae plants may be a cost-effective source of nutraceuticals and/or phytochemicals to be used in the management of metabolic-related conditions such as obesity and NAFLD. PubMed, Google Scholar, Scopus, and SciFinder were accessed to collect data on traditional medicinal plants, compounds derived from plants, their reported anti-obesity mechanisms, and therapeutic targets.