Saturating constructions for normed spaces

We prove several results of the following type: given finite dimensional normed space V there exists another space X with log dim X = O(log dim V) and such that every subspace (or quotient) of X, whose dimension is not too small, contains a further subspace isometric to V. This sheds new light on the structure of such large subspaces or quotients (resp. large sections or projections of convex bodies) and allows us to solve several problems stated in the 1980s by V. Milman.     

On the existence of an invariant measure for Markov-Feller operators

Let X be a Polish space and P a Markov operator acting on the space of Borel measures on X. We will prove the existence of an invariant measure with respect to P, provided that P satisfies some condition of a Prokhorov type and that the family of functions is equi-continuous with respect to the Prokhorov distance at some point of the space X. Moreover, we will construct a counterexample which show that the above equi-continuity condition cannot be dropped.     

3D MR imaging of dental cavities-an in vitro study

A 3D spin-echo (3D SE) pulse sequence was used on a 4.7 T research MRI system to produce images of extracted human first molar tooth placed in CuSO4 water solution. The maximal resolution achieved was 35 x 63 x 300 microm3 in read and two phase directions, respectively. The high-intensity signal from water in solution together with the lack of signal from mineralized tooth tissue produce very good contrast allowing to visualize topography of outer and inner surfaces of the tooth. The 3D MR data were median filtered, binarized and then divided into separate segments corresponding to the inner tooth cavities and the hard tooth tissue. The topography of the root canals was visualized and the canals volume was calculated. The presented technique may be used for quantitative analysis of the root canal cavities shape and volume. The results of such an analysis may be applied for estimation of the quality of the impressional mapping methods in restorative dentistry or as an alternative non-impressional 3D mapping method.     

Application of chemiluminescence for the detection of peroxy compounds in high-performance liquid chromatography

The possibility of applying post-column reaction and chemiluminescence to determine organic peroxy compounds by RP-HPLC was investigated. Conditions of qualitative and quantitative analyses have been established. The applicability of the method has been demonstrated for a series of compounds representative of the most important groups of peroxy-type compounds, that is, hydroperoxides, dialkyl peroxides, diacyl peroxides, peroxyesters, and peroxyacids.     

Reductive activation of mitomycin A by thiols

[reaction: see text]. Mitomycin C is unchanged upon exposure to thiols under physiological conditions. Its more toxic variant, mitomycin A (MA), undergoes elimination of methanol to give a variety of mitosene derivatives, diagnostic of its activation to a reactive electrophile. Evidence is presented for a novel reductive mechanism, characterized by the transient addition of a thiol to the quinone of MA, followed by intramolecular electron transfer, leading to reduced quinone and oxidized thiol.     

Experimental and computational study on the reactivity of 2,3-bis[(3-pyridylmethyl)amino]-2(Z)-butene-1,4-dinitrile, a key intermediate for the synthesis of tribenzoporphyrazine bearing peripheral methyl(3-pyridylmethyl)amino substituents

Abstract  

An earlier developed alkylating path leading to tetraalkylated diaminomaleonitrile derivatives was explored. Attempts to explain the reactivity of the representative dialkylated diaminomaleonitrile 2,3-bis[(3-pyridylmethyl)amino]-2(Z)-butene-1,4-dinitrile during the alkylation reaction were performed using X-ray and density functional theory (DFT) studies. The condensed Fukui functions accompanied by softness indices were found to be useful in explaining its reactivity observed during the reaction. The values of the Fukui functions and condensed softness for electrophilic attack calculated from Mulliken, L?wdin, and natural population analyses closely corresponded to the experimental observations. When 2,3-bis[(3-pyridylmethyl)amino]-2(Z)-butene-1,4-dinitrile disodium salt was treated with dimethyl sulfate at lower temperatures the alkylation reaction prevailed, whereas at higher temperatures the alkylating agent acted as a hydride anion acceptor, which favored the elimination reaction. The tetraalkylated dinitrile 2,3-bis[methyl(3-pyridylmethyl)amino]-2(Z)-butene-1,4-dinitrile was used in the synthesis of tribenzoporphyrazine bearing methyl(3-pyridylmethyl)amino groups, which was subsequently subjected to solvatochromic and metallation studies. The changes observed during metallation seem to result from the coordination of the 3-pyridyl group by a palladium ion. This could influence the configuration of the methyl(3-pyridylmethyl)amino moiety, causing more effective donation of a lone pair of electrons from peripheral nitrogen to the macrocyclic ring.     

Splittings in the variety of residuated lattices

It is shown that the only algebra that splits the lattice of subvarieties of the variety of residuated lattices is the two element boolean algebra. Received October 4, 1999; accepted in final form August 11, 2000.