Evaluation of the Ti diffusion process during fabrication of Ti:LiNbO3 optical waveguides

The Ti oxidation and the formation of a surface Ti-Nb-O compound occurring during Ti diffusion process in LiNbO₃ for fabricating optical waveguides have been analysed using backscattering spectrometry and glancing-angle X-ray diffraction. Results show that Ti oxidation partially occurs owing to Ti reaction with oxygen atoms of the substrate and that the Ti-Nb-O compound grows epitaxially and behaves as a real source for Ti diffusion.     

Total synthesis of tetracyclic kynurenic acid analogues isolated from chestnut honey

A short and efficient synthesis of novel tetracyclic Kynurenic acid analogues, isolated from chestnut honey, is described. The crucial step of the strategy was a MW-assisted cyclization of enamines of ethyl dioxohexahydropyrrolizine and 2,3-dioxooctahydroindolizine carboxylates to obtain 2,3,6,11b-tetrahydro-1H-pyrrolizino[2,1-b]quinoline-5,11-dione and 5,8,91,011,11a-hexahydroindolizino[2,1-b]quinoline-6,12-dione, respectively. Because of its modular nature, the synthetic strategy can have value as a general method for the preparation of compounds containing these new heterocyclic scaffolds.     

The influence of Cu(2+) on the unfolding and refolding of intact and proteolytically processed beta(2)-microglobulin

Human beta(2)-microglobulin (beta(2)m) is an amyloidogenic protein in patients suffering from chronic kidney disease and especially in those patients that need intermittent hemodialysis for longer periods, e.g., when awaiting transplantation. While many in vitro conditions induce beta(2)m-amyloid formation from wild-type (wt) beta(2)m and while a number of structurally altered beta(2)m molecules are known to be conformationally unstable and amyloidogenic on their own, it is not known why beta(2)m-amyloid is generated in some dialysis patients. For many amyloid proteins it is known that divalent metal ions, especially Cu(2+), display strong binding and distinct destabilizing effects on protein conformation. The present study uses CE to assess conformational states of wt and cleaved beta(2)m (dK58-beta(2)m, beta(2)m cleaved at lysine-58, a modification found in the circulation of hemodialysis patients) in the presence of divalent metal ions. The experiments provide both qualitative and quantitative data showing the specific destabilizing effects of Cu(2+)-ions on the folding of wt beta(2)m. Both refolding after acid denaturation and solution structure of beta(2)m under otherwise native conditions are severely influenced by Cu(2+). An increased unfolding, aggregation, and induction of Congo red-reactive molecular species in Cu(2+)-incubated wt-beta(2)m could be demonstrated while the refolding kinetics of dK58-beta(2)m, already slower than the wt molecule, appeared not to be further decreased by Cu(2+). Given the interest in the actions of metal ions in other types of amyloidosis, including, e.g., Alzheimer's disease and the prion encephalopathies, the use of microelectrophoretic methods to monitor unfolding and refolding of biomolecules available in scarce amounts as shown in this study is an attractive option.     

A game theoretical analysis of the impact of income inequality and ethnic diversity on fiscal corruption

In this paper, we construct a theoretical game model with incomplete information to analyze the tax revenues of a multiethnic country, when fiscal corruption is widespread. Our proposal is that income inequality between ethnic groups causes differences leading to prejudice and discrimination among ethnic groups themselves and, as a consequence, this affects the control of corruption and evasion. Hence, the amount of tax revenues is proven to be dependent on the relevance of the income distribution between the ethnic groups.     

An unprecedented Pd-catalyzed, water-promoted sequential oxidative aminocarbonylation-cyclocarbonylation process leading to 2-oxazolidinones

An unprecedented, PdI2-catalyzed, sequential oxidative aminocarbonylation-cyclocarbonylation process, leading to 2-oxazolidinone derivatives 3 in good to excellent yields starting from readily available alpha,alpha-disubstituted 2-ynylamines 1 and secondary amines 2, is reported. In the case of an alpha-monosubstituted substrate, the initially formed 2-oxazolidinone derivative underwent shift of the double bond to give a 3H-oxazol-2-one derivative in excellent isolated yield.     

Morse index for solutions of the nonlinear Schrödinger equation in a degenerate setting

In this paper, we study the Morse index of the single-peak solutions concentrating at a point P∊ ℝ ^N of the problem

New insight into the reaction of singlet oxygen with sulfur-containing cyclic alkenes: dye-sensitized photooxygenation of 5,6-dihydro-1,4-dithiins

The reaction of 3-methyl-5,6-dihydro-1,4-dithiins with singlet oxygen affords dicarbonyl compounds and/or ring-contracted ketosulfoxides, the latter regio- and stereoselectively, depending on the nature of the substituent at C-2 and on the reaction conditions. In competition with normal fragmentation, the intermediate dioxetanes, derived from [2 + 2] cycloaddition of singlet oxygen to the double bond, undergo an intramolecular oxygen transfer to the sulfur-1 atom, leading to labile epoxide intermediates. The latter convert to cis- and trans-ketosulfoxides through a non-concerted S-4 migration. This pathway is promoted by the electron-withdrawing group at C-2 and, for monosubstituted amide, by the solvent basicity. S-Oxidation of dithiins is insignificant, except for the monosubstituted amide derivative or in the presence of protic species, and occurs selectively at the S-1 atom.