Preparative production and separation of 2-acetamido-2-deoxymannopyranoside-containing saccharides using borate-saturated polyolic exclusion gels

A new separation method based on the combination of exclusion and ion exchange chromatography in borate buffer was developed. It allows semi-preparatory and preparatory separation of isobaric N-acylhexosamines (C-2 epimers) and corresponding methyl glycosides (anomers and tautomers). Three types of polyolic gels were tested for these separations. Ion-exchange HPLC was used as a rapid and reliable method for the quantification of the respective analytes. NMR studies of the interactions of N-acetylhexosamines with borate confirmed the importance of a proper stereochemical arrangement of acetamido sugars for their interactions with borate anions.     

Evidence of the photonic gap contribution to the guiding mechanism for strongly confined modes in the refractivelike domain

The group index dispersion and birefringence of guided modes supported by straight photonic crystal (PhC) waveguides are theoretically and experimentally investigated as a function of the waveguide width within various reduced frequency domains. Within the photonic gap and far from the Brillouin zone edges, strongly confined modes supported by narrow PhC guides exhibit both a group index and a birefringence larger than those of a deep ridge. These two results evidence the contribution of the photonic gap to the guiding mechanism in the refractivelike domain.     

Travel groupoids

In this paper, by a travel groupoid is meant an ordered pair (V, *) such that V is a nonempty set and * is a binary operation on V satisfying the following two conditions for all u, v ∈ V:

Quasicontinuous functions,minimal usco maps and topology of pointwise convergence

In [HOLá, Ľ.—HOLY, D.: Pointwise convergence of quasicontinuous mappings and Baire spaces, Rocky Mountain J. Math.] a complete answer is given, for a Baire space X, to the question of when the pointwise limit of a sequence of real-valued quasicontinuous functions defined on X is quasicontinuous. In [HOLá, Ľ.—HOLY, D.: Minimal USCO maps, densely continuous forms and upper semicontinuous functions, Rocky Mountain J. Math. 39 (2009), 545–562], a characterization of minimal USCO maps by quasicontinuous and subcontinuous selections is proved. Continuing these results, we study closed and compact subsets of the space of quasicontinuous functions and minimal USCO maps equipped with the topology of pointwise convergence. We also study conditions under which the closure of the graph of a set-valued mapping which is the pointwise limit of a net of set-valued mappings, is a minimal USCO map.     

Precovers

Let be an abstract class (closed under isomorpic copies) of left R-modules. In the first part of the paper some sufficient conditions under which is a precover class are given. The next section studies the -precovers which are -covers. In the final part the results obtained are applied to the hereditary torsion theories on the category on left R-modules. Especially, several sufficient conditions for the existence of -torsionfree and -torsionfree -injective covers are presented.     

On the Existence of Relative Injective Covers

Let be a hereditary torsion theory for the category -mod of unital left -modules over an associative ring with an identity element. The purpose of this note is to prove that if the associated Gabriel filter consists of finitely presented left ideals, then every module has a -injective cover and if contains a cofinal subset of finitely presented left ideals, then every module has a -torsionfree -injective cover. The methods used working with pure submodules contained in ``large" submodules also allow to unify the proofs of some previously known results.     

Kinetical systems—local analysis

The paper gives the answer to the question of the number and qualitative character of stationary points of an autonomous detailed balanced kinetical system.     

Wilson Quotients for Composite Moduli

An analogue for composite moduli of the Wilson quotient is studied. Various congruences are derived, and the question of when these quotients are divisible by is investigated; such an will be called a ``Wilson number". It is shown that numbers in certain infinite classes cannot be Wilson numbers. Eight new Wilson numbers up to 500 million were found.

     

Strong regular varieties of partial algebras

Presented by H. P. Gumm.     

Improved synthesis of 1,4-dideoxy-1,4-imino-d-galactitol, an inhibitor of E. coli K12 UDP-Gal mutase and mycobacterial galactan biosynthesis

The E. Coli K12 UDP-Gal mutase inhibitor 1 was prepared from d-glucose in 5 steps (42% overall yield). The 4-azido galactose derivative 11, leading to 1, was formed by treatment of galactose dithioacetal 7 with mercuric oxide and mercuric chloride in acetone. To obtain 7, acetal 3 was tosylated or triflated and treated with NaN₃.