Showing papers by "Jagiellonian University published in 1984"

Local structure of ternary semiconducting random solid solutions: Extended x-ray-absorption fine structure of Cd 1-x Mn x Te

Abstract: The nearest-neighbor distances around Te atoms in the random semiconducting alloy Cd1-xMnxTe have been determined by the extended x-ray-absorption fine-structure technique. The distribution of the anion-cation distances is bimodal. A model of the microscopic structure of the zinc-blende-type A1-xBxC ternary alloys based on a random distribution of cations has been developed. The model describes the bimodal distribution of nearest-neighbor distances in terms of distortion of the anion sublattice, using only the lattice constant of the alloy and the bond-stretching constants of each binary component. Within the framework of this model we consider also the problem of the structural stability of Cd1-xMnxTe.

Evidence for the Electromagnetic Production of the A1

Abstract: Using data on the coherent production of ${\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}$ systems in ${\ensuremath{\pi}}^{+}$ collisions with nuclei, we have extracted an estimate for the radiative partial width of the ${A}_{1}$. The rate for ${{A}_{1}}^{+}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{+}\ensuremath{\gamma}$ is 640\ifmmode\pm\else\textpm\fi{}246 keV, which is a factor of about 2-3 below the value expected on the basis of predictions from quark models and from vector dominance ideas.

Vibronic coupling effects in magnetic vibrational circular dichroism. A model formalism for doubly degenerate states

Abstract: A formalism for magnetic vibrational circular dichroism (MVCD) of a model system is developed by considering vibronic coupling effects between a nondegenerate ground state and a degenerate excited state. Only one degenerate vibrational coordinate and one degenerate electronic excited state are considered in the model. A diabatic basis set representation was used for the vibronic functions paralleling previous Jahn–Teller effect formalisms. The parametrized model which results is shown to give MVCD A and B terms of a magnitude comparable to those previously observed for substituted benzenes. These model studies are suggestive that vibronic coupling effects are important for complete interpretation of MVCD spectra.

Emission of large hydrocarbons from frozen CH 4 by keV proton irradiation

Abstract: Ever since the first description of the synthesis of molecules by impinging protons on ices1, the possibility of formation of various molecules on cold surfaces by particle radiation has been widely discussed2–5. Because fluxes of light ions with energies of ∼1 keV AMU−1 exist in a wide variety of astrophysical sites6 there has been a dispute over whether molecules in space are formed by such a process or by gaseous reactions7. We have recently studied sputtering of species by bombarding simple frozen gases such as water, carbon monoxide and ammonia with light ions2. With these substances, only rather simple molecules were found. However, when bombarding methane, we detected much larger molecules in the sputtered beam—hydrocarbons containing up to at least 13 atoms. We propose, therefore, that bombardment of frozen methane by keV protons may produce large molecules in the Solar system.

Primakoff production of the b+ (1235) meson

Abstract: We have measured the coherent nuclear production of ${\ensuremath{\pi}}^{+}\ensuremath{\omega}$ systems at 202.5 GeV. This final state is dominated by the ${B}^{+}(1235)$ meson with a measured mass and full width of 1.271 \ifmmode\pm\else\textpm\fi{} 0.011 GeV and 0.232 \ifmmode\pm\else\textpm\fi{} 0.029 GeV, respectively. A radiative width of 230 \ifmmode\pm\else\textpm\fi{} 60 keV was extracted for the process ${B}^{+}(1235)\ensuremath{\rightarrow}{\ensuremath{\pi}}^{+}\ensuremath{\gamma}$.

Flavin-Mediated Weak-Light Chloroplast Movement in Mougeotia

Abstract: In Mougeotia the two types of chloroplast movement depend in a different way on the wavelength of the orienting light: The high-fluence-rate response (face-to-profile orientation) can be induced exclusively by blue light, and this is an effect of an interaction of phytochrome and a blue-light-absorbing pigment (cf. [10]). In contrast, the low- fluence-rate response (profile-to-face orientation) has its maximum in red light with a typical red/far-red reversibility; thus, phytochrome has been accepted as the main photoreceptor pigment involved ([4], cf. also [5]). There was, however, some controversy, whether or not the lower effect of the blue light region could be explained on the basis of phytochrome alone (e.g. [3], cf. also [5]). Only recently a strong argument in favor of a separate blue-light photoreceptor pigment has been derived from a new experimental approach [2]. These results will be summarized briefly, and additional experiments will be reported.

Partial-wave analysis of coherent 3. pi. production on nuclei at 200 GeV

Abstract: We have carried out a partial-wave analysis (PWA) of three-pion systems produced in the coherent dissociation of ${\ensuremath{\pi}}^{+}$ mesons on nuclear targets. The data have been analyzed for copper and lead targets at an incident ${\ensuremath{\pi}}^{+}$ energy of 202.5 GeV. This PWA provides further evidence for resonant contributions to ${J}^{P}={1}^{+} \mathrm{and} {0}^{\ensuremath{-}}$ waves at $3\ensuremath{\pi}$ masses below 1.5 GeV, which can be plausibly identified with ${A}_{1}$ and ${\ensuremath{\pi}}^{\ensuremath{'}}$ mesons. The contribution from electromagnetic production of the ${A}_{2}$ has also been extracted, and an estimate for Coulomb production and radiative width of the ${A}_{1}$ has been obtained.

Preliminary Studies on the Growth and Movements of the Yellow-bellied Toad, Bombina variegata (Anura: Discoglossidae)

Abstract: Yellow-bellied toads were studied in their natural environment in a mountain locality in south-eastern Poland. In June 1981, 353 specimens were captured in a small area, marked by yellow skin autografts, and released. 49 individuals were recaptured in July 1982 in the same area, and 17 animals were recaptured at other places 200-1200 m away. Movements were carried out mainly by juveniles. Large increases in body length of young individuals, probably yearlings, and small growth rates in older individuals, were generally found.

Pyrylium-mediated transformations of natural products. Part 2. Reaction of 4-(4-methoxy-3-sulphophenyl)-2,6-bis-(4-sulphophenyl)pyrylium perchlorate with primary amines

Abstract: The title pyrylium cation reacts with amines in aqueous solution to give mixtures of divinylogous amide and pseudobase. The two products are formed by kinetic control in quantities which then slowly come to equilibrium. Further pyridinium ion is formed slowly from pseudobase. The divinylogous amide cyclises to pyridinium ion. Kinetic rate constants are described for reactions with lysine and other typical primary amines. With s-butylamine appreciable quantities of the 2H-pyran are formed.

Crystallization of amorphous alloys ― determination of activation energies from electrical resistivity measurements

Abstract: The paper presents a review of various methods used to determine the activation energy for crystallization of amorphous alloys from their electrical resistivity data. Both isothermal and constant heating rate approaches are discussed. The method of employing first or higher order derivatives have been presented

Complexation between quaternary ammonium salts and high molecular weight poly(ethylene oxide)

Abstract: Complexation between tetrabutylammonium bromide, or oligomeric tetramethyl-2,6-ionene bromide (1), and high molecular weight poly(ethylene oxide) (PEO) was studied viscometrically, using the following media as solvents: water; 0,1 M aq. KCl; 2 M aq. KCl and 0,1 M aq. HCl. It was found that tetrabutylammonium bromide as well as the ionene 1 convert the initially linear ηred vs. cPOE relationships into bent and hunchbacked curves, thus suggesting the formation of water soluble complexes. In aqueous KCl and HCl solutions these complexes behave as typical polyelectrolytes. Contrary to cations of alkali metals, however, protons do not influence the linear ηred vs. cPOE relation, so that it is possible to determine intrinsic viscosities by use of 0,1 M aq. HCl as solvent. These viscosities are rising if the complexation between POE and ammonium salt is accomplished by the polyfunctional ionene. The increase of [η] depends on the unit mole ratio (u.m.r.) of the ionene to POE. With increasing unit mole ratio from 0 to 7 [η] increases from 9 up to 21 dl · g−1. In water the complexation between one unit mole of POE and two unit moles of ionene 1 causes an increase of the reduced viscosity ηred from 11,2 up to 80,2 dl · g−1.

Eolian processes in alpine belts of the high Tatra mountains, Poland

Abstract: Eolian processes were the subject of detailed studies in the high-mountain area of the Tatra Mts. The field investigations in 1975–80 attempted to determine the amount of deflation and eolian deposition and to improve understanding of their mechanism. The net rates of these processes were determined from repeated survey of deflational forms and of eolian deposits. Observations of the mechanism of material displacement were based on field experiments carried out during strong winds. All the investigations were conducted using simple methods and traps. Relationships between the course and intensity of processes and wind conditions and soil properties were obtained.

Potential-ph diagrams for the silver-water-ammonia-sulphuric acid system at elevated temperatures

Abstract: Potential-pH diagrams were constructed for the Ag-H 2 O-NH 3 -H 2 SO 4 system at temperatures of 298, 333, 373 and 423 K. The thermodynamic calculations used to derive these diagrams are based largely on the correspondence principle proposed by Criss and Cobble.