Study on the Existence of Hydrogen Bonds in Ammonium Permanganate

The crystal structures of ammonium permanganate and ammonium perchlorate at 293 K were determined and compared. X‐ray and vibrational spectroscopic data confirmed the existence of weak hydrogen bonds in NH₄MnO₄. These hydrogen bonds proved to be slightly stronger than H‐bonds in ammonium perchlorate. Difference between the results of diffuse reflectance and KBr matrix pellet IR spectra of NH₄MnO₄ has been explained.     

Positive electrospray ion trap multistage mass spectrometric fragmentation of synthetic analogs of saccharide part of lipopolysaccharides of Vibrio cholerae O:1

Oligosaccharides (mono- to hexamers) that mimic the terminal epitopes of O-antigens of Vibrio cholerae O:1, serotypes Ogawa and Inaba, have been studied by electrospray ion trap (ESI IT) mass spectrometry. Sodium or potassium-cationized adducts are characteristic ions under the conditions of ESI-MS analysis. The tentative pathways of fragmentation have been proven by multistage ion trap MS (MS(n), n = 1-3). The predominant pathway of fragmentation of the oligomers is the neutral loss of monosaccharide residue shortening the length of the oligosaccharide. In this way, conversion of the Ogawa to Inaba fragments takes place under the conditions of measurement. ESI MS/MS provided sufficient information about molecular mass, the number of saccharide residues, and the structure of saccharides, about the C (4)-amide of 3-deoxy-L-glycero-tetronic acid (DGT) of the compounds investigated, and allows to distinguish between Ogawa and Inaba serotypes.     

AFM and TEM study of hydrogenated sputtered Si/Ge multilayers

Multilayers of hydrogenated ultrathin (3 nm) amorphous a-Si and a-Ge layers prepared by sputtering have been studied by atomic force microscopy (AFM) and transmission electron microscopy (TEM) to check the influence of annealing on their structural stability. The annealed multilayers exhibit surface and bulk degradation with formation of bumps and craters whose density and size increase with increasing hydrogen content and/or annealing temperature and time. Bumps are due to the formation of H₂ bubbles in the multilayer. The craters are bumps blown up very likely because of too high a gas pressure inside. The release of H from its bonds to Si and Ge occurs within cavities very likely present in the samples. The necessary energy is supplied by the heat treatment and by the recombination of thermally generated carriers. Results by energy filtered TEM on the interdiffusion of Si and Ge upon annealing are also presented.     

Uniqueness of embedding into a Gaussian semigroup on a nilpotent Lie group

This research was partially supported by the Hungarian Foundation for Scientific Researchers under grant number OTKA-T4047/1992.     

Parameter estimation of selfsimilarity exponents

The characteristic feature of operator selfsimilar stochastic processes is that a linear rescaling in time is equal in the sense of distributions to a linear operator rescaling in space, which in turn is characterized by the selfsimilarity exponent. The growth behaviour of such processes in any radial direction is determined by the real parts of the eigenvalues of the selfsimilarity exponent. We extend an estimation method of Meerschaert and Scheffler [M.M. Meerschaert, H.-P. Scheffler, Moment estimator for random vectors with heavy tails, J. Multivariate Anal. 71 (1999) 145-159, M.M. Meerschaert, H.-P. Scheffler, Portfolio modeling with heavy tailed random vectors, in: S.T. Rachev (Ed.), Handbook of Heavy Tailed Distributions in Finance, Elsevier Science B.V., Amsterdam, 2003, pp. 595-640] to be applicable for estimating the real parts of the eigenvalues of the selfsimilarity exponent and corresponding spectral directions given by the eigenvectors. More generally, the results are applied to operator semi-selfsimilar processes, which obey a weaker scaling property, and to certain Ornstein-Uhlenbeck type processes connected to operator semi-selfsimilar processes via Lamperti's transformation.     

Ozonation of 3β-acetoxy-5α-chloro-cholestane in solution. X-ray study of 3β-acetoxy-5α-chloro-14-cholestene-ozonide.

A selected saturated steroid derivative has been subjected to ozonation in solution. As the main reaction product 14,15-ozonide has been isolated in crystalline form whose structure has been unambiguously confirmed by the X-ray difraction method.     

Effect of Grain Boundary Segregation and Migration on Diffusion Profiles: Analysis and Experiments

In many experimental studies, curved penetration profiles are observed for grain boundary diffusion performed in the B kinetics regime in contrast to the shape expected from the solutions of the second Fick's equation. To explain these curvatures the effects of grain boundary structure, grain boundary migration, and grain boundary segregation have been successively proposed in the literature. Using previous data for Cu–Ag and Cu–Ni and new ones on Cu–Fe and Cu–Zn systems we will show how it is possible to separate all these possible contributions and how, knowing the true origin of the curvature, one can deduce much quantitative information impossible (or very difficult) to obtain by other techniques.     

Verallgemeinerung eines Satzes von Jentzsch

Ohne Zusammenfassung     

More line narrowing in TROSY by decoupling of long-range couplings: shift correlation and 1JNC' coupling constant measurements

Since the introduction of RDCs in high-resolution NMR studies of macromolecules, there is a growing interest in the development of accurate, and sensitive methods for determining coupling constants. Most methods for extracting these couplings are based on the measurement of the splitting between multiplet components in J-coupled spectra. However, these methods are often unreliable since undesired multiple-bond couplings can considerably broaden the multiplet components and consequently make accurate determination of their position difficult. To demonstrate one approach to this problem, G-BIRD((r)) decoupled TROSY sequences are proposed for the measurement of (1)J(NH) and (1)J(NC') coupling constants. Resolved or unresolved splittings due to remote protons are removed by a G-BIRD((r)) module employed during t(1) and as a result, spectra with narrow, well-resolved peaks are obtained from which heteronuclear one-bond couplings can be accurately measured. Moreover, introduction of a spin-state-selective alpha/beta-filter in the TROSY sequence allows the separation of the (1)J(NC') doublet components into two subspectra which contain the same number of peaks as the regular TROSY spectrum. The (1)J(NC') couplings are obtained from the displacement between the corresponding peaks in the subspectra.