The possibilities of modeling developed neuronetwork dynamics are investigated by nonlinear coherent optical systems with a 2-D feedback. A comparative analysis of neuron-like systems of various physical nature has been made. The results of experimental investigations of nonlinear optical system dynamics with nonlocal connections are discussed.

Quantum description of the molecular dynamics under laser excitation of electronic transitions is reduced to an equivalent classical form. This classical treatment is applied to the molecular dynamics problem and some specific results for one-dimensional case are demonstrated. Absorption probability and laser induced quantum coordinate displacement spectra are calculated.

Since 1974 when first laser Doppler measurements were performed of the velocity of stationary cytoplasmic streaming in single living cells of algae,' much work has been done to develop the technique and to show its potentials to monitor nonstationary intracellular motility.2'° The best model for such measurements and studies of the ameboid type of cell motility is plasmodium of slime mold Physarum polycephalum (Fig. 1). It exhibits very pronounced shuttle streaming of endoplasm inside visco—elastic protoplasmic strands with velocities up to 1.5 mm/sec. The endoplasm is driven by oscillating intracellular pressure gradients generated in the course of cyclic contractions and relaxations of the plasmodium.

Physical effects which have been observed in molecular gases by time-domain coherent antistokes Raman spectroscopy are described. Namely the slowing down of molecular vibrations doppler dephasing under the gas pressure increase (Dicke''s effect) quantum beats collisional frequency exchange. Experimental data dealing with molecules of hydrogen nitrogen and ammonia are presented. The physical mechanisms and calculation methods of effects mentioned above are discussed. The influence of laser pulses incoherence on the time-domain CARS signal is considered.

The model of rotational instability of light field in 2_D feedback nonlinear optical systems is investigated. Typical theoretical and experimental results are presented.

Modern nonlinear and coherent optics provides a great variety of possibilities to create many types of spatially distributed neural network optical systems and uses them to simulate the collective behavior of dynamics systems with nonlocal interactions (e.g., analogs of advanced neural networks).' We can point out the following basic properties of these systems: — intrinsic N-shape nonlinearity (bistable or multistable optical response); — existence of the local excitation transfer mechanism (e.g., diffusion); — possible implementation of large scale (nonlocal) interactions; All these requirements can be fulfilled in nonlinear 2-D feedback optical systems: in various nonlinear resonators and interferometers.2 Complexity and variety of nonlinear dynamic modes (different selfoscillation and dissipative structures, optical turbulence) observed in neural network optical systems with the simplest nonlocal interconnectors promote the search for principal most important models of large scale interactions and corresponding nonlinear dynamic structures. One of these models is one-dimensional rotational instability occurring in a neural network system with rotated field.3 Rotating waves observed in this system have been analyzed in detail.4 Theoretical and experimental research of 2-D models of optical neural networks appears to be most interesting. Implementing any type of "pure" nonlocal interconnectors in an optical experiment is a rather complicated task. Optical aberrations and some other factors result in the fact that additional "spurious" interactions affecting dynamic structures being formed in the system seem to be superimposed on a given type of nonlocal interconnectors. The only possibility to examine multiple nonlinear structures corresponding to a certain type of large scale interactions appears to be a comparative analysis of optical and numerical experiments in which the interconnect topologies can be defined in a "pure" form. 2-D selfoscillation structures observed in a neural network with 2-D optical feedback and nonlocal interconnectors have been studied in this paper. The simplest types of topological transforms, i.e., lateral inversion and rotation, are realized in optical and numerical experiments.

A new approach is proposed for the description of a diffusional motion of rodlike macromolecules in semidilute solution. The approach is based on the model " polymer chain in the array of obstacles" and is alternative to a reptation theory. The result obtained within the model adopted (model of statistical reorientations) agree well with available data of real experiments as well as with computer experiments which were performed in the course of the present study.

The short review concerning the results on development of the new pico- and subpicosecond laser sources of high stability for ultrafa. st spectroscopy is presentedYassive mode-locked Y3A15015:Nd YA1O3:Nd Lo2Be2O5:Nd and Nd:glass lasers with negative feedback (NFB) are analysed in detail. Inserting NFB in flash pumped mode-locked solid state lasers ensured the energy and pulse width stability on the level of 1. Subpicosecond pulse as short as 600 fs width is generated in Nd:glass laser by NFB cOntrol for the first time. Possibility to reach 10 mJ level by regenerative amplification of stretched ultrashort pulses is demonstrated. Comparison of adequate amplification methods is carried out.

Laser-induced bulk gratings and temporal instabilities of nonlinear wave processes with different components of light polarization have been studied in the liquid crystals (LC). A mirrorless feedback arises because of the non-local nonlinear response of an anisotropic elastic medium on the external field. The multiplicative nature of the molecular fluctuations in the LC under external field are discussed and the light-induced reorientation effects in this medium can be considered as a noise-induced phase transition. . The quantum aspects of behavior of the radiation fluctuations for passing through the LC light are considered. A new method of formation of quantum states of the light in the linear system at dynamic diffraction is discussed for the first time. The squeezed states of the field and the photon superbunching are obtained for two geometries (Bragg and Laue) of diffraction in spatially periodic medium. The approach gives a new opportunities for a verification of quantum properties of the light in experiment.

The statement of a problem and the results of molecular dynamics computer simulations of the mobility of spin label (nitroxide radical) attached to model surface of protein globule are discussed. Various characteristics of spin label mobility obtained during computer experiment are presented. It is shown that Brownian diffusion is more preferable as a model of the process of label motion at short time intervals.

New possilities appeared in time-domain CARS of molecules due to the application of femtosecond lasers are analyzed. The most important one is that femtosecond pulses allow to control not only amplitude but also the phase of molecular vibrations.

Practically all laser studies of biological objects, irrespectively to their state are connected with the study of the spectroscopic features of the object on the one hand, and with the processing of its represention with the aim of visualizing the evolution processes in it, on the other hand.

Protein-lipid interactions play a decisive role in the architecture of the cell membrane structure. They can be used to explain molecular mechanisms of various membrane processes, such as energy transmission and conversion, mechanoreception, etc. The study of interactions of integral proteins with the lipid bilayer is of the special interest. Integral proteins, namely their hydrophobic parts, are immersed into the membrane. Due to differences in the length of the hydrophobic moieties of the proteins and the hydrocarbon chains of the lipids, as well as to the action of electrostatic and mechanical forces, regions of changed lipid bilayer structure arise in the environment of a protein. These areas may change upon conformational changes of a protein. A number of questions arise in studying protein-lipid systems, e.g., 1 . How do physical and structural characteristics of lipid bilayer change upon the incorporation of integral proteins and during conformational changes of the latters? 2. What are the dimensions of changed membrane structure regions in the environment of a protein? 3. How is the temporal stability of the structural changes? To approach the above problems, mechanical and thermodynamical characteristics of bilayer lipid membranes (BLM) and large unilamellar liposomes (LUV, diameter approx. 100 nm) with incorporated integral proteins (bacteriorhodopsin, BR, and hormonal receptors for insulin, HR) were studied. Also, mechanical characteristics of membrane were studied during conformational changes of BR (in the dark and induced by light) and HR (under the action of insulin and its antagonist glucagon). The electrostriction method of measurement of modulus of elasticity in the direction normal to the membrane plane, E was used together with differential scanning calorimetry (DSC)2 and differential ultrasonic velocimetry (DUV).3

Langmuir—Blodget (LB) films are thin or ultrathin molecular layer systems. They are good basis for the creation of molecular encembles with predetermined architecture including superlattices and quasi two-dimensional systems. This opens new possibilities for a detailed investigation of various intermolecular coupling. In this paper we present preliminary fluorescence hole burning data of metal-free tetra-4-terc-butyl phthalocyanine (H2TTBPc) in LB film.

On the basis of the metastable zone investigations the optimal conditions for adenine sulphate solution stability were found. These made it possible to apply the novel high rate growth technique developed for KDP-family crystals group to the nucleic acid base crystals. The optical quality of adenine sulphate crystals grown at the rate about five times higher than the traditional one thus reducing the growth period six or seven times is sufficient not only for Raman spectroscopy but even for the normal reflection one.

In this paper the lateral mobility of membrane components as well as the possibility of its measurement are discussed. The development of our own apparatus for fluorescence one-point microphotolysis is characterized. Also the results obtained in the course of determination of the lateral coefficient mobility for selected lipids and melittin are discussed.

The so called WTA ( " winner take all" ) model appears to be one of the most interesting models of artificial neural networks. '' In networks of this kind only one single neuron specified by maximum (or minimum) initial activity becomes active as a result of cooperative transient process. In this work the optical implementations of WTA neural network are presented. The example of WTA neural network demonstrates that due to the existence of strong NL competition the problem of global extremum search can actually be solved. It should be mentioned that this problem seems to be quite complicated for digital computers. It is worth adding that these neural networks have multiple applications.

Nonclassical light is now available in a number oflaboratories, being generated by Frank—Hertz experiment, optical parametric processes, four-wave mixing including optical fibres, by optical system with feedback, etc. Therefore it is senseful to reconsider various nonlinear optical interactions involving initially nonclassical light ,originally solved with coherent (laser) light. Adopting tools of quasidistributions related to antinormal ordering, the photocount distributions, its factorial moments and characteristics of squeezing of vacuum fluctuations can be investigated assuming initially nonclassical (squeezed) light in the framework of the Heisenberg—Langevin of Schrödinger approaches. Photon statistics of stimulated Raman scattering of squeezed light can be derived assuming phonon system in chaotic, coherent or squeezed states and including additive noise. The influence of nonlinear dynamics can be established on initially inclassical light and it can be shown that the initially nonclassical effects are encresed by the nonlinear dynamics provided that the Stokes mode is less amplified than the anti-Stokes mode is damped, whereas in the opposite case the nonclassical features are smoothed out. Also frequency detuning can be optimized to have maximum nonclassical effects, which are missing with increasing phonon number, even if the phonon system is squeezed. Small initial squeezing can by increased by the nonlinear dynamics, whereas strong squeezing can only be diminished.

The interactions between hematoporphyrin (HP) and artificial bilayer lipid membranes (BLM) has been studied. No influence of HP on the BLM conductivity has been observed at the HP concentrations from 1O_6 to 3 x iO M. The modulus of elasticity in the direction normal to the membrane plane (E1) and the dynamic viscosity coefficient (7)) have been measured both exhibiting the HP- induced decrease by 22 --31 in darkness. Under illumination by low-intensity HeNe laser () 632nm) the values of parameters E1 and ij of the Hp-modified membranes were found to increase by 41 66. When removing the HP from the solution by perfusion the irreversible changes in mechanical properties of the HP-modified membranes caused by the laser light were observed. This could be due to formation of the stable complexes of HP with lipid molecules.

Results of time-resolved fluorescence anisotropy decay kinetics measurements of hematoporphyrin (Hp) in liposomes are presented. The increase of average rotational correlation time with the increase of incubation time is an evidence of HP aggregation in lipid bilayer. Experiments were carried out with suspensions of monolayer liposomes from natural phosphatidyicholine (PC). The time-resolved polarized fluorescence spectroscopy with time-correlated single photon counting technique was used. The possibility of different types of aggregates formation in lipid bilayer is discussed.

Comparative analysis of main optical characteristics of KDP crystals grown by traditional technique at growth rates up to 1 mm/day and by rapid growth technique at growth rates ranging from 15 to 40 mm/day is carried out. The results on anomalous biaxiality absorption ard scattering of light effective nonlinear susceptibility and bulk laser damage threshold of crystals are given. It is shown that the increase of the crystal growth rate by more than one order does not deteriorate the crystal optical quality.

The optical methods for testing the structure of the randomly phased objects are based on the relationship between the statistical structure parameters of an object and the correlation parameters of the scattered radiation field. The randomly phased objects (RPO) can be classified into two groups, each requiring a specific approach to testing.

Create the pulse Nd:YAG laser system intend for measurements of lateral diffusion of biological membrane component and diffusion coefficient of molecule and molecular complex in liquid media by technique registration fluorescence recovery after photobleaching of microsample. The aggregation phenomenon of hematoporphyrin (Hp) and hematoporphyrin derivative (HpD) in various solutions are investigated by FRAP technique. Nonlinear photodestruction quantum efficiency and diffusion coefficient of dye molecular complexes and proteins is measured.

In this paper a short description of different Slovaklaboratories and institution dealing with fundamental research and application of laser is given. More detailed the research work on the biological implementation of laser is presented carried out at the Department of Biophysics at the Mathematics and Physics Faculty of Comenius University in Bratislava.

In order to study the dynamic characteristics of molecular components in biological and model membranes a highly automatized laser system has been elaborated performing on the basis of microphotolysis method1. The equipment works on the principle of fluorescence recovery after photobleaching.

Micelles are species of colloidal dimensions, which form in solutions as a result of the reversible aggregation of relatively small molecules of amphiphilic character, the monomers1. Molecular weights monomers do not usually exceed several hundreds, these of micelles are ranging from a few thousands to millions. Most amphiphilic solutes contain a hydrophobic flexible chain moiety and a polar group. The hydrocarbon chains form a liquid—like core, the polar groups are exposed to water at the surface. The small micelles are roughly spherical and can be looked upon as a monolayer curved on itself. For its characteristics micelles serve as models for many interfacial, colloidal and membrane—like systems. With increasing monomer concentration of an aqueous solution micelles start to form at so called critical micelle concentration (CMC) as a result of the three kinds of interactions: the hydrophobic interaction, the interaction between head groups and the interaction between head groups and the hydrocarbone core. The number of monomers per micelle i is called the aggregation number. The moderately sized micelles ( ranging from 50 to 1 40) do not increase in size much over considerable intervals of concentrations and exhibit a low degree of polydispersity. The total micelle concentration [M ] can.be related to the detergent (monomer) concentration ED] as EM]=flcmc).

Unique possibilities of the active influence of laser radiation light field on compounds, in particular, the use of different methods and approaches based on the nonlinear optical phenomena allow in a new fashion to come in the resolution of such important problems as isotope separation detection of single atoms and molecules, initiation and control of chemical reactions, selective photomodefication of biological molecules, etc. With the creation of powerful lasers it becomes possible to observe many nonlinear effects as a result of the interaction of intensive light field with substances. In the papers by G. A. Askarian,' F. V. Bunkin ei al.2 ithas been considered theoretically the possibilities and the conditions of multiquantum excitation of molecular oscillations and direct photodissociation. The creation of powerful CO2 lasers allows to realize experimentally multiquantum absorption by vibration-rotation states and to observe the decay of some simple molecule in gas phase.3 There are other mechanisms of photodecomposition of molecules in the case of the action of powerful visible and near IR lasers. In rather strong light fields, when the selection rules for vibration-rotation transitions are disturbed very interesting nonlinear effects are possible: absorption of laser photon and straight throw over some vibrational levels, the appearance of absorption lines of homopolar molecules in those sections of the spectrum, where these molecules do not show optical activity in the light field of small intensities and so on.1 At present there are only some papers concerning the given mechanism for the initiation of chemical reactions.4