Cyclic boronates in the mass spectrometry of ecdysteroids

For the structural elucidation of ecdysteroids a reaction with phenylboronic acid has been employed. This reaction takes place exclusively on the C20,C22 diol moiety, thus facilitating fast and easy detection of this moiety in the molecule od ecdysteroid. This derivatization also redirects fragmentation to C17/C20 bond cleavage with charge retention on both fragments enabling assessment of the structure both of the steroid nucleus and of the side-chain. Possible reaction of phenylboronic acid with the diol moiety of the glycosyl group of the glycoside od ecdysteroid, producing di-adduct, is demonstrated; participation of the 5β-hydroxy group of 5β,20-dihydroxyecdysone in the formation of such a di-adduct is discussed; and the role of theenol form of the 6-carbonyl group is proved.     

Nanocrystalline titanium carbide thin films deposited by reactive magnetron sputtering

We investigated the structure and composition of titanium carbide thin films deposited by the reactive magnetron sputter ion plating process as a function of deposition parameters. The films were sputtered onto unheated glass substrates by means of an unbalanced planar d.c. magnetron equipped with a titanium target using a mixture of argon and methane. The deposition parameters ranged from 0.05 Pa to 2 Pa for total working gas pressurep _T, from 10% to 60% (volume) for relative methane concentration in the working gas mixture, from 45 mm to 85 mm for the substrate-to-target distanced _s-t and from −50V to −800V for the substrate biasU _S. It was found that the crystallinity of the thin films strongly decreases with increasingp _T,d _s-t andU _S. The experiments described show the conditions necessary to obtain sputter-deposited nanocrystalline titanium carbide films. This work has been partially supported by the Grant Agency of the Czech Republic under Grant No. 106/96/K245 and by the Ministry of Education of the Czech Republic under Grant No. VS96 059.     

On quartic half-arc-transitive metacirculants

Following Alspach and Parsons, a metacirculant graph is a graph admitting a transitive group generated by two automorphisms ρ and σ, where ρ is (m,n)-semiregular for some integers m≥1, n≥2, and where σ normalizes ρ, cyclically permuting the orbits of ρ in such a way that σ ^m has at least one fixed vertex. A half-arc-transitive graph is a vertex- and edge- but not arc-transitive graph. In this article quartic half-arc-transitive metacirculants are explored and their connection to the so called tightly attached quartic half-arc-transitive graphs is explored. It is shown that there are three essentially different possibilities for a quartic half-arc-transitive metacirculant which is not tightly attached to exist. These graphs are extensively studied and some infinite families of such graphs are constructed. Both authors were supported in part by “ARRS – Agencija za znanost Republike Slovenije”, program no. P1-0285.     

Note on the QED corrections to leptonic decays of the neutral vector boson

An exact calculation of the lowest-order QED corrections to leptonic decay rates of the neutral vector boson is presented and the origin of a discrepancy between two recent results is explained.     

Surface states on the (100) plane of a sphalerite-type crystal

The surface states of an ideal (100) plane of a sphalerite-type crystal were studied in the one-electron approximation; both the plane formed by electronegative atoms (>0) and that consisting of electropositive atoms (<0) were investigated. The interpretation of surface states whose energy lies in the gap is the same as for the diamond-like lattice. The influence of electro-negativity or electropositivity of the surface on the position of these states in the gap was investigated and possible consequences of these states joining one of the energy bands of volume states were pointed out. The results of this paper can be used to discuss correlation effects on the (100) plane of a diamond-like crystal.     

Lumineszenz der Nacl-Ni-Kristalle

Ohne Zusammenfassung     

Strong homology of inverse systems of spaces. II

Recently the authors have defined a coherent prohomotopy category of topological spaces CPHTop [5]. In the present paper, which is a sequel to Part I [6], the authors define a strong homology functor H^s:CPHTop→Ab. The results of this paper are essential for the construction of a Steenrod-Sitnikov homology theory for arbitrary spaces.