Gas-phase reactivity of silver and copper coordinated monosaccharide cations studied by electrospray ionization and tandem mass spectrometry

The analytical distinction of the most common isomeric underivatized hexoses was investigated by means of mass spectrometry experiments. Electrospray ionization and tandem mass spectrometry were used in the analysis of silver and copper-coordinated monosaccharides (D-glucose, D-galactose, D-fructose, O-methyl-alpha-D-glucose and O-methyl-beta-D-glucose). The results show that cationization by Ag(+) allows the differentiation of the three first monosaccharides while the complexes formed by association of Cu(+) with these three monosacharides display a similar reactivity that prevents stereoisomer distinction. Unlike copper, silver adduct-ions of both alpha and beta anomeric O-methyl-D-glucoses exhibit specific decomposition patterns (i.e. a loss of methanol for the alpha-anomer and a loss of silver hydride for the beta-anomer), which allow an easy characterization. A theoretical survey of selected complexes, based on the use of DFT calculations were carried out on both anomers in order to rationalize the experimental findings.     

Universal Components of Random Nodal Sets

We give, as L grows to infinity, an explicit lower bound of order \({L^{\frac{n}{m}}}\) for the expected Betti numbers of the vanishing locus of a random linear combination of eigenvectors of P with eigenvalues below L. Here, P denotes an elliptic self-adjoint pseudo-differential operator of order \({m > 0}\), bounded from below and acting on the sections of a Riemannian line bundle over a smooth closed n-dimensional manifold M equipped with some Lebesgue measure. In fact, for every closed hypersurface \({\Sigma}\) of \({\mathbb{R}^n}\), we prove that there exists a positive constant \({p_\Sigma}\) depending only on \({\Sigma}\), such that for every large enough L and every \({x \in M}\), a component diffeomorphic to \({\Sigma}\) appears with probability at least \({p_\Sigma}\) in the vanishing locus of a random section and in the ball of radius \({L^{-\frac{1}{m}}}\) centered at x. These results apply in particular to Laplace–Beltrami and Dirichlet-to-Neumann operators.     

Criterion for identification of ferroelectric domains in TGS crystals from AFM images

Criteria for identification of actual (dynamic) domains and morphologically similar domain “memory” regions are proposed based on the study of various types of contrast of topographic atomic-force microscopy images of lenslike regions on the polar surface of TGS crystals. Inaccuracy in identification may result in further errors in estimating the parameters of the domain structure. The images of ferroelectric domains in the spreading-resistance mode that indicate directly the presence of conductive properties of the domain walls have been obtained for the first time.     

硫氰酸铵树脂相分光光度法同时测定天然水中微量铁和钴

研究了在Ｔｗｅｅｎ－８０存在的酸性介质中，Ｆｅ（Ⅲ）和Ｃｏ（Ⅱ）与ＳＣＮ＾－形成稳定的有色络阴离子与阴树脂交换吸附，有色络合物富集显色于树脂组上，进行树脂组分光光度集显色于树脂相上，进行树脂相分光光度法同时测定铁和钴的实验条件，Ｆｅ（Ⅲ）和Ｃｏ（Ⅱ）树脂具有色络合物最大吸收波长λｍａｘ分别为４９０ｎｍ和６３０ｎｍ，摩尔吸光系数，ε为２．４×１０＾５Ｌ．ｍｏｌ＾－１．ｃｍ＾－１和２．１×１０＾５Ｌ．     

Anomalous isotopic effect in multibubble sonoluminescence of aqueous solutions of terbium chloride

An anomalously low isotope effect has been discovered in 20-kHz sonoluminescence of terbium chloride solutions in H₂O-D₂O mixtures. The intensity of luminescence in the characteristic 488-and 545-nm lines of the Tb³⁺ ion, which are observed against the solvent continuum (230–700 nm), increases with the content of D₂O to a maximum value of 4.0 ± 0.4, whereas the isotope effect in photoluminescence of the same solutions reaches 10 ± 1.0. The result is explained using the model of nonexponential decay of sonoluminescence of Tb³⁺ ions. These ions, which are formed in an excited state in cavitation bubbles, first undergo radiative and radiationless deactivation in the gas phase. However, some excited ions enter the solution bulk, because the excitation lifetime is longer than the average bubble lifetime. At the first stage, the isotope effect is small, because the density of the gas phase is low and quenching by solvent molecules is weak. At the second stage, the isotope effect coincides with the effect in usual photoluminescence in the solution. The total decrease in the effect in sonoluminescence depends on the weight of the “gas” stage of deactivation of excited Tb³⁺ ions.     

Inexistence de structures affines sur les fibrés de Seifert

Sans résumé

---

     

Entropy in nuclear collisions

Data on the multiplicity of pions produced in nucleon-nucleon interactions and central collisions of identical nuclei are discussed using a statistical approach. It is argued that the suppression of the pion production observed at low energies (p _LAB <15>c per nucleon) is due to entropy transfer to baryons. The enhancement of the entropy production in central S+S collisions at 200 GeV/c per nucleon may be interpreted as manifestation of the increase, by a factor of about 3, of the effective number of degrees of freedom in the early stage of the collision.     

Synthesis of benzo analogs of oxoarcyriaflavins and caulersine

In the course of a program aimed at designing new antitumor agents, we were interested in the synthesis of mixed structures of maleimidophenyl carbazoles and natural product caulersine as potential CDK inhibitors. This was performed through an efficient four-step sequence starting from indole or 3-formyl-N-Boc indole. 5H-Benzocycloheptaindol-6-one derivatives equipped with a fused maleimide (oxophenylarcyriaflavins) or a methyl ester (benzo analog of caulersine) on the central tropone ring were thus obtained.