Monitoring cyclodextrin-polyviologen pseudopolyrotaxanes with the Bradford assay

Self-assembled multivalent pseudopolyrotaxanes, composed of lactoside-bearing cyclodextrin (CD) rings threaded on linear polyviologen polymers, have been introduced recently as flexible and dynamic neoglycoconjugates. In the course of this research, it was found that polyviologens are responsive to the Bradford assay, which is traditionally highly selective for proteins. The response of the pseudopolyrotaxanes to the Bradford assay was dependant on, and thus indicative of, the degree of threading of the CD rings onto the polyelectrolyte. The assay was then used to report on the threading and dethreading of native and lactoside-bearing alpha-CD rings onto and off of polyviologen chains, a phenomenon which demonstrates the utility of biochemical assays to address problems unique to supramolecular chemistry.     

Resonant rayleigh scattering in semiconductor structures

Il Nuovo Cimento D - A detailed study of the relative role played by localized and/or propagating intermediate excitonic states in, resonant Rayleigh scattering (RRS) is presented for a large set...     

Anreicherung von Spuren Seltener Erden aus Mineralwässern durch Ionenaustausch

In the described analysis of mineral waters, after the throughflow of the sample through a column with Dowex 50 WX 12 in H⁺ form, the main cations are first eluted by 1.6 N HCl and then the rare earths by 6 N HCl. The latter are separated by ion-exchange chromatography on Dowex 50WX8 in NH₄ ⁺ form, the elution being performed with ammonium citrate pH 4.19. The presence of rare earths in the eluate was ascertained spectrophotometrically by means of their reaction with xylenol orange in the presence of cetylpyridinium bromide. In mineral waters from the West-Bohemian spa region it was possible to find traces of trivalent La, Ce, Pr, Nd, Sm + Gd, Y, Dy, Ho, Er, Tm, Yb and Lu.     

A stochastic model of deposition processes with nucleation

We study an interacting particle system on a one-dimensional infinite lattice and one-dimensional lattices with a periodic boundary. In this system, each site of the lattice may be either empty or occupied and initially all the lattice sites are empty. The evolution of the system is defined as follows: an empty site waits an exponential time with mean 1 and becomes occupied, and an occupied site becomes empty at a time which is distributed exponentially with mean _k, wherek is the number of occupied neighboring sites of this site in the current state of the system. We show that the mean number of the occupied sites of the lattice, considered as a function of time, may possess a convex part. A sufficient condition for this is that ₀ is large and _k,k1, are small. The studied system has been proposed recently as a mathematical model of certain deposition processes, in particular those which exhibit nucleation caused by lateral attractive interaction between the deposited molecules. Our research was motivated by the observation that the density of deposited molecules contains a convex part, over some time interval, if the attractive forces are strong, while this density is a concave function of time if these forces are weak or absent. Our result agrees with this observation.     

Analytische Aspekte der Oxydation organischer Stickstoffverbindungen mit Chromsäure. IV

Zusammenfassung Die schon früher vorgeschlagene Halbmikromethode zur Bestimmung der N-N-Gruppierung wurde an einer Reihe aromatischer Azoverbindungen erprobt. Sie beruht auf der Oxydation der Substanz mit einem Chromsäure-Schwefelsäure-Gemisch in einer geschlossenen Apparatur. Die Azogruppen werden als elementarer Stickstoff abgespalten, der im Azotometer gesammelt und gemessen wird. Durch die Rücktitration der unverbrauchten Chromsäure kann außerdem die Oxydationszahl der untersuchten Substanz bestimmt werden.

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Summary The semimicro method previously suggested for the determination of the N-N-grouping was tested on a number of aromatic azo compounds. It is based on oxidation of the sample with a chromic-sulfuric acid mixture in a closed apparatus. The azo groups are split off as elementary nitrogen which is collected in an azotometer and measured. In addition the oxidation number of the material being studied can be found by backtitration of the unconsumed chromic acid.

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Résumé On a mis à l'épreuve la semimicrométhode déjà préconisée auparavant, pour le dosage du groupe N-N, sur une série de composés azo-aromatiques. Elle repose sur l'oxydation de la substance par un mélange d'acide chromique et d'acide sulfurique, en système clos. Les groupes azoïques se trouvent dissociés à l'état d'azote élémentaire que l'on récupère et que l'on dose dans l'azotomètre. On peut déterminer, de plus, l'indice d'oxydation de la substance étudiée par titrage en retour de l'acide chromique non consommé.

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III. Mitteilung siehe 1.     

Uniqueness of Gibbs State for Non-Ideal Gas in ℝd: The Case of Multibody Interaction

We study the question of existence and uniqueness of non-ideal gas in ^d with multi-body interactions among its particles. For each k-tuple of the gas particles, 2km ₀<, their interaction is represented by a potential function _k of a finite range. We introduce a stabilizing potential function , such that (x ₁,..., ) grows sufficiently fast, when diam{x ₁,..., } shrinks to 0. Our results hold under the assumption that at least one of the potential functions is stabilizing, which causes a sufficiently strong repulsive force. We prove that (i) for any temperature there exists at least one Gibbs field, and (ii) there exists exactly one Gibbs field at sufficiently high temperature, such that for any >0, C(V ₀)< for all volumes V smaller than a certain fixed finite volume V ₀. The proofs use the criterion of the uniqueness of Gibbs field in non-compact case developed in ref. 4, and the technique employed in ref. 1 for studying a gas with pair interaction.     

Gamma-ray bursts from evaporating primordial black holes

It is believed that the detection of gamma-ray bursts from evaporating primordial black holes is highly improbable in the near future since the expected photon flux, consisting mainly of photons with energies ? GeV, is too low. Contrary to this point of view, we show that a large fraction of the black hole power at the final stage of evaporation (the last 10³ s) can be liberated as a burst of soft γ-ray emission of duration 10^?1–10³ s and luminosity 10²⁸–10³¹ erg/s in the energy range 0.1–1 MeV. According to our calculations of the black hole evaporation rate (within the Standard Model of elementary particles), when the black hole temperature exceeds approximately 10 GeV, the charged particle outflow from a black hole forms a well-defined plasma and can be described in the hydrodynamic approximation. In this case more than half of the rest energy of a black hole can be converted into soft gamma-rays due to the presence of the magnetic field with energy density comparable to that of charged particles. We consider various mechanisms leading to such transformation and estimate their efficiency. It is shown that, at least, some of the gamma-ray bursts detected by BATSE can be associated with evaporating black holes.