Synthesis of H (type 4) trisaccharide,key structural fragment of globo-H and fucosyl-GM1 cancer-associated antigens

A convenient synthesis of Fucα1-2Galβ1-3GalNAcβ-OCH₂CH₂CH₂NH₂ (trisaccharide H type 4) is described. This glycan is the terminal part of glycosphingolipids globo-H and fucosyl-GM1 known as cancer-associated carbohydrate antigens.     

Design of pincer complexes based on (methylsulfanyl)acetic/propionic acid amides with ancillary S‐ and N‐donors as potential catalysts and cytotoxic agents

Pincer complexes featuring readily tunable tridentate ligand frameworks comprise one of the most actively studied classes of organometallic and metal–organic compounds and find extensive use in catalysis, organic synthesis, materials science, and other fields of chemistry and allied disciplines. Currently growing attention is devoted to non‐classical ligand scaffolds, such as functionalized carboxamides, which offer multiple options for directed structural modifications. In this study, the reactions of (methylsulfanyl)acetyl and propanoyl chlorides with 2‐(aminomethyl)pyridine, 2‐(2‐aminoethyl)pyridine, 8‐aminoquinoline and 2‐(diphenylthiophosphoryl)aniline afford a series of new pincer‐type ligands based on functionalized carboxamides. The ligands obtained readily undergo direct cyclopalladation under the action of PdCl₂(NCPh)₂ in dichloromethane at room temperature, resulting in Pd(II) pincer complexes with N,N,S‐ and S,N,S‐donor sets. Importantly, some of the cyclopalladated derivatives can also be produced efficiently under solvent‐free conditions according to the approach recently developed by our group. The complexes obtained have been tested for cytotoxicity against several human cancer cell lines and catalytic activity in the model Suzuki reaction. The results have been compared to those for the related Pd(II) pincer complexes to define the main structure–activity relationships and to outline the most promising structures for further investigations.     

The influence of compression conditions on the peculiarities of self-propagating exothermal reaction in Al–Ni powder reactive materials

The paper deals with the effect of the compression conditions on the propagation front velocity of exothermal reaction and the specific heat release in Al–Ni powder reactive materials with mean particle sizes of 70–110 nm. It was shown that the velocity increases from 2.7 to 8 cm s^?1 and comes to saturation with the lowering of the porosity (η) from 0.91 to 0.34, while the dependence of the specific heat release has its maximum for η?=?0.5. The results of the X-ray diffraction analysis obtained in situ during the sample heating suggest that the sequence of phase transformations in the system does not depend on the porosity. In all cases, first in the temperature range of ~?500–540 °C the NiAl compound is formed. With the further heating up to ~?640 °C, the Ni₃Al, Ni₂Al₃ and NiAl₃ compounds are additionally formed. The calculation of kinetic parameters was performed using the obtained curves of the differential scanning calorimetry: activation energy, pre-exponential factor and reaction model. The comparison of the calculated results and the scanning electron microscopy data has shown that such behavior of the Al–Ni system with the porosity lowering occurs due to the growth of the transformation degree and is associated with the presence in the final powder mixture of mutually non-contacting Al and Ni agglomerates with the dimensions of over 10 μm.     

Electrochemical properties of outer-sphere associates of bipyridyl and sepulchrate metal complexes with (thia)calix[4]arenes

The electrochemical one-electron reduction (oxidation) of bipyridyl metal complexes ([Co(bipy)₃]³⁺, [Cr(bipy)₃]³⁺, [Fe(bipy)₃]²⁺, [Ru(bipy)₃]²⁺ (as well as Co(III) sepulcrate)) with water-soluble (thia)calix[4]arenes has been studied by means of cyclic voltammetry. It has been shown that [M(bipy)₃]^3+/2+ bind to (thia)calix[4]arenes via sulfonate groups of the upper rim. Oxidized forms bind stronger than reduced ones leading to reduction (oxidation) of half-wave cathodic shift. The effect of predominant stabilization of oxidized forms of metal complexes for carboxylated calix[4]arene is stronger than for thiacalix[4]arene (ΔΔG₀?=???7.8?÷???12.5 and ??3.7 kJ/mol, respectively). The redox-switchable outer-sphere binding of Co(III) sepulchrate via lower rim of carboxylated calix[4]arene has been revealed using cyclic voltammetry. The binding constants of outer-sphere associates based on calix[4]arenes and unstable metal complexes ([Co(sep)]²⁺, [Ru(bipy)₃]³⁺, [Co(bipy)₃]²⁺) have been calculated for the first time using ¹H NMR titration and cyclic voltammetry data.

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Application of the fractional factorial design in multiple W/O/W emulsions

In presented research, multiple W/O/W emulsions were developed by using experimental design method. A 24-1 fractional factorial design was performed by varying the following input parameters: primary polymeric emulsifier (PEG 30-dipolyhydroxystearate) concentration (0.8% and 2.4%), secondary polymeric emulsifier (Poloxamer 407) concentration (0.8% and 1.2%), electrolyte magnesium sulfate heptahydrate (0.08% and 0.4%) and electrolyte sodium chloride (0.08% and 0.4%). Multiple emulsions were prepared by a two-step emulsification process. Obtained emulsions were characterized with rheological measurements, conductivity and centrifugation tests. Factorial analysis revealed that the concentration of the primary emulsifier was the predominant factor influencing the phase separation, conductivity and maximal apparent viscosity. Additionally, electrolyte magnesium sulfate heptahydrate was more efficient in stabilizing these systems, compared to sodium chloride. The applied fractional factorial design method enabled determination of the optimal concentrations of the primary and secondary emulsifier, as well as the concentration of electrolytes, in order to obtain W/O/W emulsions with desired maximal apparent viscosities, low values of conductivity and without phase separation after centrifugation.     

Aza-substitution,benzo-annulation effects and catalytic activity of <Emphasis Type="Italic">β</Emphasis>-octaphenyl-substituted tetrapyrrolic macroheterocyclic cobalt complexes. I. heterogeneous catalysis

The influence of the size of conjugated π-system on catalytic activity of cobalt complex with β-octaphenylporphyrin and its tetraaza-, tetrabenzo and tetrabenzotetraaza derivatives was studied in present work. It is found that catalytic activity for oxidation of sulfur-containing compounds increases under extension of conjugated macrocycle system according to the following series CoP < CoBP ≤ CoPz < CoPPz ? CoPc.     

The Fried Average Entropy and Slow Entropy for Actions of Higher Rank Abelian Groups

We consider two numerical entropy-type invariants for actions of \({\mathbb{Z}^k}\) , invariant under a choice of generators and well-adapted for smooth actions whose individual elements have positive entropy. We concentrate on the maximal rank case, i.e. \({\mathbb{Z}^k,\,k \geq 2}\) actions on k + 1-dimensional manifolds. In this case we show that for a fixed dimension (or, equivalently, rank) each of the invariants determines the other and their values are closely related to regulators in algebraic number fields. In particular, in contrast with the classical case of \({{\mathbb Z}}\) actions the entropies of ergodic maximal rank actions take only countably many values. Our main result is the dichotomy that is best expressed under the assumption of weak mixing or, equivalently, no periodic factors: either both invariants vanish, or their values are bounded away from zero by universal constants. Furthermore, the lower bounds grow with dimension: for the first invariant (the Fried average entropy) exponentially, and for the second (the slow entropy) linearly.     

Heegner points,cycles and Maass forms

We derive for Hecke-Maass cusp forms on the full modular group a relation between the sum of the form at Heegner points (and integrals over Heegner cycles) and the product of two Fourier coefficients of a corresponding form of half-integral weight. Specializing to certain cycles we obtain the nonnegativity of theL-function of such a form at the center of the critical strip. These results generalize similar formulae known for holomorphic forms. Partially supported by NSF grant # DMS-9096262. Partially supported by NSF grant # DMS-9102082.     

Efficient algorithms for the recognition of topologically conjugate gradient-like diffeomorhisms

It is well known that the topological classification of structurally stable flows on surfaces as well as the topological classification of some multidimensional gradient-like systems can be reduced to a combinatorial problem of distinguishing graphs up to isomorphism. The isomorphism problem of general graphs obviously can be solved by a standard enumeration algorithm. However, an efficient algorithm (i. e., polynomial in the number of vertices) has not yet been developed for it, and the problem has not been proved to be intractable (i. e., NPcomplete). We give polynomial-time algorithms for recognition of the corresponding graphs for two gradient-like systems. Moreover, we present efficient algorithms for determining the orientability and the genus of the ambient surface. This result, in particular, sheds light on the classification of configurations that arise from simple, point-source potential-field models in efforts to determine the nature of the quiet-Sun magnetic field.