Effect of Zn2+ and Cu2+ on free radical properties of melanin fromCladosporium cladosporioides

Effect of metal ions on free radical properties of natural melanin produced by soil fungiCladosporium cladosporioides was studied. The electron paramagnetic resonance (EPR) spectrum of the studied melanin consists mainly of a single line of eumelanin, and only a very weak signal of pheomelanin was observed. o-Semiquinone free radicals form paramagnetic centers in melanin. Diamagnetic Zn²⁺ ions produce an increase in the free radical concentration in melanin. Quenching of melanin EPR lines was obtained for melanin and paramagnetic Cu²⁺ ion complexes. Slow spin-lattice relaxation processes are characteristic for the free radicals in melanin samples and fast spin-lattice relaxation was observed for Cu²⁺ ions. The EPR lines of copper ions saturate at higher microwave powers than the EPR lines of melanin.     

Universal relation between hall conductivity and the damping constant of edge magnetoplasma resonances

The spectra of edge magnetoplasma excitations in two-dimensional (2D) electron disks have been analyzed by the method of optical detection of resonant microwave absorption. The magnetic dispersion of an edge magnetoplasmon in samples with a high 2D electron density is found to be poorly reproduced by existing theoretical models. Analysis of the magnetic-field dependence of the linewidth of resonant microwave absorption for samples with various 2D electron densities shows that the inverse width of the main mode of resonant microwave absorption is universally proportional to the Hall resistance of 2D electrons.     

Time-resolved streak camera system with solid state laser and optical parametric generator in different spectroscopic applications

Apparatus to study time-evolution of emission spectra over very wide time and spectral range is described. Excitation part of the equipment consists of solid state Nd:YAG laser and optical parametric generator. The heart of the detection system consists of spectrograph and streak camera. The significance of optics and electronics built in the system for proper, fast and convenient measurements is underlined. The results of donor-acceptor energy transfer in a rigid polyvinyl alcohol matrix serve here as an example of application our equipment to study complex systems.     

Synthesis of lysine derivatives containing aza-crown ethers and a chromophore unit

The synthesis of a lysine-like chromo-ionophore and its derivatives, useful in peptide chemistry, is described. The influence of the peptide framework on the anthraquinone properties is examined with spectroscopic and electrochemical methods.     

Studies of the out-of-plane emission of pions in symmetric heavy-ion collisions

Triple differential cross-sections of midrapidity pions from ²⁰⁹Bi+²⁰⁹Bi collisions were measured with the Kaon Spectrometer at SIS at incident energies of 400, 700 and 1000 AMeV. The azimuthal emission pattern of the pions has been investigated in dependence of beam energy and impact parameter. An enhanced emission of pions perpendicular to the reaction plane is observed. The strength of the anisotropy increases with beam energy and pion transverse momentum. In contrast to the nucleons the anisotropy varies only little with the impact parameter. No difference in the behaviour of positive and negative pions is observed.     

Low temperature ESR spectra of nickel — doped NaCl crystals

Paramagnetic resonance of Bridgman-grown NaCl crystals nominally doped with divalent nickel was studied over the temperature range from 4 K to 300 K. The broad isotropic EPR line with g = 2.12 ÷ 2.23 and ΔH _pp = 280 ÷ 780 G was detected at temperatures higher than 130 K for samples of various thermal history. The origin of these spectra was attributed to aggregated and precipitated Ni²⁺ ions. At temperatures lower than 40 K another ESR signal was registered. It was an anisotropic one, the intensity of which strongly depends upon the temperature. This spectrum results from substitutional Ni⁺ ions with tetragonally distorted surrounding along a S100T direction. The angular dependence of the ESR line positions was fitted to an appropriate spin-Hamiltonian with the g-factor components g _∥ and g _⊥ equal to 2.86 and 2.10, respectively. The temperature-dependence of the signal intensity at temperatures between 4 and 110 K has been interpreted in terms of a transition from the static to dynamic Jahn-Teller effect.     

On stationary flow of asymmetric fluids with diffusion

We prove existence and uniqueness theorems for weak solutions of equations describing stationary isothermic motion of a mixture of two viscous incompressible fluids with asymmetric stress tensor, in a bounded subset of ?³. The model of the flow we consider here assumes that some of coefficients characterizing isotropic properties of the fluid equal zero.     

Experimental confirmation by galvanomagnetic methods of a complex transport model in In0.53Ga0.47As layers deposited by MBE on SI-InP

At low temperatures In_0.53Ga_0.47As samples show an increase of carrier concentration, which can be explained in terms of a two carriers transport model. This type of problem exists since the beginning of the semiconductor era, dating back to monocrystalline germanium.We propose that in all the investigated layers, there are X atoms or charged dislocations in the region of the first monolayers, which are built in during epitaxial growth. The layers were intentionally undoped. They form an impurity band in which low mobility carriers dominate over the localised electron scattering due to the s-d exchange interaction. These carriers do not freeze out at liquid helium temperature and give rise to two transport media for electrons; a conduction band at higher temperatures and an impurity band at lower temperatures. The electron which fall down onto the previously ionised X atoms, then move by thermally activated hopping. We show that the two carriers model for In_0.53Ga_0.47As epitaxial layers are confirmed by the carrier concentration-temperature, carrier concentration-magnetic field, resistivity-magnetic field behaviour, and also by YKA theory also. The differences between the two transport models are so distinctive that observed phenomena may exist. This paper presents experimental results, which constitute comprehensive evidence for the complicated structure of the semiconductor epitaxial layers on the sample of n-type In_0.53Ga_0.47As/InP layer with n=2.2×10¹⁵/cm³.     

Non-homeomorphic density topologies

In [ANISZCZYK, B.-FRANKIEWICZ, R.: Non homeomorphic density topologies, Bull. Polish Acad. Sci. Math. 34 (1986), 211–213] the authors constructed 2^c non-homeomorphic density topologies tied to the concept of measure. In [WROŃSKI, S.: The number of non-homeomorphic I-density topologies. Institute of Mathematics of Polish Academy of Sciences. Preprint 482, December 1990, XXXIV Semester in Banach Center, Theory of Real Functions] an analogous construction has been given for topologies tied to the concept of category. Here we present a generalization containing both the results mentioned above. This generalization based only on the topological ideas is independent of the concept of measure or category. Communicated by L’ubica Holá