Leszek Sirko

Biochemical analysis of transgenic tobacco lines producing bacterial serine acetyltransferase

Abstract The preliminary biochemical analysis of the selected lines of transgenic tobacco producing Escherichia coli serine acetyltransferase (SAT, EC 2.3.1.30) targeted either to the chloroplasts or to the cytosol was performed. The selected enzymatic activities and chemical composition of the leaf tissues collected from the plants cultivated in vivo were examined and statistically evaluated. In all SAT-over-producers increased level of non-protein thiols in comparison with the controls was detected and a higher resistance of the leaf tissue to the oxidative stress generated by hydrogen peroxide was observed. These two factors were significantly positively correlated only in plants producing bacterial SAT in the cytosol. Moreover, in the ‘cytosolic’ but not ‘chloroplastic’ groups, a strong negative correlation between glutathione and sulfate levels was seen. The leaves of most SAT-over-producers contained more protein, sulfur, calcium and iron (but less phosphorus, potassium and sodium) than the leaves of control plants. The vast majority of transgenics had higher glutathione S -transferase activity. All plants producing foreign SAT in the cytosol had an elevated activity of O -acetyl-serine (thiol) lyase, while in most plants from ‘chloroplastic’ groups, this activity remained closed to the control level.

Experimental investigation of Wigner's reaction matrix for irregular graphs with absorption

We use tetrahedral microwave networks consisting of coaxial cables and attenuators connected by T-joints to make an experimental study of Wigners reaction K matrix for irregular graphs in the presence of absorption. From measurements of the scattering matrix S for each realization of the microwave network, we obtain distributions of the imaginary and real parts of K. Our experimental results are in good agreement with theoretical predictions.

Ray-Splitting Billiards

Ray splitting is a universal phenomenon that occurs with appreciable amplitude in all wave systems when the properties of the system change on a scale smaller than the wave length. We study the quantum implications of ray splitting theoretically and experimentally with the help of ray-splitting billiards in one and two dimensions. We show that Gutzwillers trace formula works even in the context of ray-splitting systems provided reflection and transmission of waves at ray-splitting boundaries is properly included.

Observation of dynamical localization in a rough microwave cavity

Abstract We measure the angular momentum content of modes in a flat, near-circular microwave cavity with a rough perimeter and demonstrate localization in angular momentum space. Because Schrodingers wave mechanics and Maxwells electrodynamics are equivalent for a 2d cavity, we compare our experimental results directly with the quantum theory of rough 2d cavities [K.M. Frahm and D.L. Shepelyansky, Phys. Rev. Lett. 78 (1997) 1440]. Introducing the concept of effective roughness we find good qualitative agreement.

Power Spectrum Analysis and Missing Level Statistics of Microwave Graphs with Violated Time Reversal Invariance

We present experimental studies of the power spectrum and other fluctuation properties in the spectra of microwave networks simulating chaotic quantum graphs with violated time reversal invariance. On the basis of our data sets, we demonstrate that the power spectrum in combination with other long-range and also short-range spectral fluctuations provides a powerful tool for the identification of the symmetries and the determination of the fraction of missing levels. Such a procedure is indispensable for the evaluation of the fluctuation properties in the spectra of real physical systems like, e.g., nuclei or molecules, where one has to deal with the problem of missing levels.

Experimental investigation of properties of hexagon networks with and without time reversal symmetry

We present the results of experimental study of the distribution P(R) of the reflection coefficient R and the distributions of Wigners reaction K matrix for irregular hexagon fully connected microwave networks simulating quantum graphs with time reversal symmetry (TRS) in the presence of absorption. The distributions of the reflection coefficient R and the real and imaginary parts of K matrix were obtained from the measurements of the scattering matrix S of the microwave networks. Furthermore, we show that the microwave networks with microwave circulators can be used to study systems with broken TRS. Properties of such networks are investigated using the cross-correlation function c12(ν) and the integrated nearest-neighbor spacing distribution I(s).

Experimental investigation of microwave networks simulating quantum chaotic systems: the role of direct processes

The influence of direct processes on the cross-correlation function c12(ν) and the elastic enhancement factor WS, β was studied experimentally using microwave networks in the presence of absorption. Microwave networks simulate quantum graphs with and without time-reversal symmetry. Direct processes exist because, for example, of non-perfect coupling between a studied system and a measuring device. We show that direct processes strongly influence the cross-correlation function c12(ν) in contrast to the enhancement factor WS, β, which is not sensitive to these processes. It makes the enhancement factor WS, β an important measure of the chaoticity of a quantum system.

Experimental investigation of the enhancement factor and the cross-correlation function for graphs with and without time-reversal symmetry: the open system case

We present the results of an experimental study of the enhancement factor WS,? of the two-port scattering matrix and the cross-correlation function c12(?) for microwave irregular networks simulating quantum graphs with time-reversal symmetry (TRS), symmetry index ?=1, and without TRS, ?=2, in the presence of absorption. We show that even for systems with notable losses the elastic enhancement factor WS,? remains a statistical measure that allows the determination of a symmetry class of the chaotic quantum systems under investigation. Therefore, the enhancement factor WS,? may be contrasted with many others statistical measures such as, for example, the nearest neighbor spacing distribution or the spectral rigidity, which are not directly applicable in the presence of strong absorption. The quantum graphs with TRS were simulated by the microwave networks built of coaxial cables connected by joints and attenuators, which allowed us to control absorption. The microwave circulators were added to the networks to simulate graphs with broken TRS. The experimental results are compared to the ones obtained within the framework of random matrix theory.

Essential features of the bleached silver halide holographic materials

Abstract Commercial holographic plates of the type Kodak 649-F, Agfa-Gevaert 8E75 and 10E75 are exposed and then bleached in direct or reverse process. Main optical properties of the bleached emulsions are determined. The experimental procedure is described and the data are given on phase retardation per unit density difference as a function of spatial frequency and on intensity transmittance as a function of the initial optical density.

Nonuniversality in the spectral properties of time-reversal-invariant microwave networks and quantum graphs

We present experimental and numerical results for the long-range fluctuation properties in the spectra of quantum graphs with chaotic classical dynamics and preserved time-reversal invariance. Such systems are generally believed to provide an ideal basis for the experimental study of problems originating from the field of quantum chaos and random matrix theory. Our objective is to demonstrate that this is true only for short-range fluctuation properties in the spectra, whereas the observation of deviations in the long-range fluctuations is typical for quantum graphs. This may be attributed to the unavoidable occurrence of short periodic orbits, which explore only the individual bonds forming a graph and thus do not sense the chaoticity of its dynamics. In order to corroborate our supposition, we performed numerous experimental and corresponding numerical studies of long-range fluctuations in terms of the number variance and the power spectrum. Furthermore, we evaluated length spectra and compared them to semiclassical ones obtained from the exact trace formula for quantum graphs.