In situ formation of N-trifluoroacetoxy succinimide (TFA-NHS): one-pot formation of succinimidyl esters, N-trifluoroacetyl amino acid succinimidyl esters, and N-maleoyl amino acid succinimidyl esters

A method for the in situ formation of N-trifluoroacetoxy succinimide (TFA-NHS) and its application in the formation of succinimidyl esters is presented. The developed method provides N-trifluoroacetyl and N-maleoyl amino acid succinimidyl esters from a variety of amino acids using a one-pot, high-yielding protocol. Investigations into the formation of an N-maleoyl amino acid succinimidyl ester supported the proposal of a revised reaction mechanism, and contributed to the optimization of the reaction conditions.     

A new group of potential antituberculotics: <Emphasis Type="Italic">N</Emphasis>-(2-pyridylmethyl)salicylamides and <Emphasis Type="Italic">N</Emphasis>-(3-pyridylmethyl)salicylamides

As a part of our systematic study of antimycobacterially active derivatives of salicylamides, a series of nineteen derivatives of N-(2-pyridylmethyl)salicylamides and N-(3-pyridylmethyl)salicylamides was synthesised. The compounds exhibited in vitro activity against Mycobacterium tuberculosis and M. avium. Their lipophilicity, R _M, was measured by thin layer chromatography on silica gel impregnated with trioctadecylsilane and the logarithm of the partition coefficient (octanol-water), logP, was calculated. Both the parameters of lipophilicity correlated. The quantitative relationship between the structure and antimycobacterial activity was calculated. Antimycobacterial activity increased with an increase in lipophilicity. The N-(2-pyridylmethyl)salicylamide derivatives were more active than the derivatives of isomeric N-(3-pyridylmethyl)salicylamides. The geometry of compounds was calculated and the calculation was verified by measuring the length of the hydrogen bond between hydroxyl and carbonyl groups on the salicylic moiety.     

Instrumental HPTLC Determination of α-Solanine and α-Chaconine in Peeled Potato Tubers

JPC – Journal of Planar Chromatography – Modern TLC - An HPTLC method has been used for quantification of glycoalkaloids (α-solanine and α-chaconine) in peeled potato tubers....     

Revised Phase Diagram of the System NaF–NaBF4

Summary. The phase diagram of the binary system NaF–NaBF₄ was determined using the thermal analysis method. Subsequent coupled analysis of the thermodynamic and phase diagram data was carried out to calculate the thermodynamically consistent phase diagram. The system NaF–NaBF₄ forms a simple eutectic phase diagram with the calculated coordinates of the eutectic point: 8.1 mol% NaF, 91.9 mol% NaBF₄, and 385.7°C. The probable inaccuracy in the calculated binary phase diagram is 9°C.     

Adsorption and release of terbinafine hydrochloride: Effects of adsorbents, additives, pH, and temperature

The paper describes results obtained within the study of factors affecting the process of an antifungal drug — terbinafine hydrochloride adsorption on two different adsorbents — charcoal and silicagel. The effects of the adsorbent area, pH value, temperature and additives (polymers — methyl cellulose and hydroxypropyl cellulose) were analyzed and their impact on the adsorption of terbinafine was derived. The increase of pH and temperature, and the presence of additives decreased the amount of terbinafine adsorbed on the adsorbents. Terbinafine is currently applied both perorally and topically. Hydrogels, i.e. compositions of a drug, additives and water, are, due to their advantageous properties, preferred topical dosage forms. Mass fraction of additives of 1 % to 4 % were studied from the view point of drug release. This study shows that both the sort and the concentration of polymers influence the drug release from hydrogels significantly.     

Cultural and linguistic problems in the use of authentic textbooks when teaching mathematics in a foreign language

This paper is a part of a longitudinal study focusing on qualitative aspects of learning in a foreign language in the development of cognitive processes in mathematics. The aim of the paper is to present a more complex analysis of textbook-based obstacles to communication. These obstacles originate in the process of vocabulary and grammar acquisition within a particular multicultural and sociocultural context. The study was carried out using mathematics textbooks from English-speaking countries which are used when teaching mathematics in English to Czech students.     

On a characterization of lattices by the betweenness relation —on a problem of M. Kolibiar

Presented by R. Quackenbush.     

Optimal labelling of a product of two paths

If G is a graph with p vertices and at least one edge, we set φ (G) = m n max |f(u) ? f(v)|, where the maximum is taken over all edges uv and the minimum over all one-to-one mappings f : V(G) → {1, 2, …, p}: V(G) denotes the set of vertices of G.P_n will denote a path of length n whose vertices are integers 1, 2, …, n with i adjacent to j if and only if |i ? j| = 1. P_m × P_n will denote a graph whose vertices are elements of {1, 2, …, m} × {1, 2, …, n} and in which (i, j), (r, s) are adjacent whenever either i = r and |j ? s| = 1 or j = s and |i ? r| = 1.Theorem.If max(m, n) ? 2, thenφ(P_m × P_n) = min(m, n).