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As in many transition countries, also in Georgia rural urban migration as well as migration from the agricultural sector takes place. This also applies to the Kazbegi district, a mountainous region in the Greater Caucasus of Georgia. The main activity in the district is subsistence farming, while only a few agricultural producers are commercially active. As the region offers beautiful nature, during the last decade tourism has been on the rise, while a dwindling interest in the agricultural sector can be observed. However, the growth in tourism also provides opportunities for small-scale agricultural producers to increase their income by marketing their surplus production to the local tourism sector and thereby improving their livelihoods. In turn, an increase in local agri-food products offered might have a positive effect on the tourism sector. Thus, establishing linkages of agricultural food production and rural tourism might contribute to the economic development of the district and even counteract migration to the capital and from the agricultural sector. Through a qualitative study, we aim at identifying local agri-food products suitable for being marketed to the tourism sector and efficient marketing options. In order to do so, we analyze local agri-food chains. Exploratory interviews, focus group discussions and expert interviews provide data for a qualitative content analysis. First results show that food products which require little technological equipment for processing and do not underlie strict food safety standards, like for example honey, seem to be adequate to tap marketing potentials with regard to rural tourism.

During the propagation of an optically smoothed laser beam through a warm plasma the speckle field pattern and the corresponding speckle intensity distribution are modified in time and along the laser propagation direction. It is shown here that the laser–plasma interaction can change the character of speckle statistics from an initially exponential-type limit law to a Weibull-type law. The Weibull distribution is characterized by a power-law-type behavior in a limited interval of the random variable, which is, in the present case, the speckle intensity. The properties of the speckle distributions are studied using methods of extremal and order statistics. The scattering instability process (here stimulated Brillouin forward scattering) causing the change in speckle statistics has an onset behavior associated with a “critical gain” value, as pointed out in work by Rose and DuBois (1993b). The saturation of the instability process as a function of intensity explains the limited interval of the Weibull-type speckle distribution. The differences in the type of the speckle statistics are analyzed by using “excess over threshold” methods relying on the generalized Pareto distribution, which clearly brings to evidence the transition from an exponential type distribution to the Weibull-type distribution as a function of the instability gain value, that is, from the regime below critical gain to values above the critical gain.

Ponderomotive profile steepening and resonance absorption of a flowing stratified laser produced plasma are investigated self‐consistently when both cases of linear polarization with respect to the plane of incidence (s and p polarization) are combined. This analysis enables a representation of ‘‘mixed’’ polarized light, desirable for application in advanced codes modeling laser plasmas. Profile steepening forms (i) a layer around the turning point of the light, and, embedded therein, (ii) a thinner sublayer at the critical surface, where plasma waves are excited. The structure and the density transition of both layers are determined as a function of dimensionless parameters, i.e., the angle of incidence and the light intensities corresponding to both polarizations (related to plasma temperature and light wavelength). The plasma flow changes from sub‐ to supersonic in the steepened region; the sound speed depends on the intensity of the longitudinal electric field. In contrast to the purely polarized case...

High-order harmonic radiation from a thin solid layer illuminated by a subpicosecond laser pulse is investigated. For laser intensities ${\mathit{I}}_{\mathit{L}}$ and wavelengths ${\ensuremath{\lambda}}_{\mathit{L}}$ with ${\mathit{I}}_{\mathit{L}}$${\ensuremath{\lambda}}_{\mathit{L}}^{2}$g${10}^{14}$ W \ensuremath{\mu}${\mathrm{m}}^{2}$/${\mathrm{cm}}^{2}$, free electrons oscillate with amplitudes \ensuremath{\delta} extending over many lattice periods ${\mathit{l}}_{\mathit{c}}$ of the solid and, due to interaction with the lattice, radiate a spectrum of harmonics with a sharp cutoff at ${\mathit{n}}_{\mathrm{max}}$\ensuremath{\simeq}2\ensuremath{\pi}\ensuremath{\delta}/${\mathit{l}}_{\mathit{c}}$. Laser pulses (of order 100 fs) shorter than the lattice disintegration time are required. The harmonics emission crucially depends on electron correlations. Competing spontaneous atomic radiation is discussed.

A series of hydrodynamic simulations is presented, related to laser compression of matter. In particular, low entropy compression of hydrogen is studied in order to reach the metallic phase transition. Anomalous hydrodynamic phenomena like shock splitting and rarefaction shocks occuring in the neighbourhood of the phase transition are investigated for a special configuration.

A new diagnostic method of the thermal transport zone of a laser‐created plasma at short wavelength (0.26 μm) is presented. This method uses soft x‐ray spectroscopy and allows one to deduce the temperature of the propagating thermal front during the laser interaction. Time‐resolved X–UV spectra of the rear side of thin plastic foils coated on their front side with a thin layer of gold of different thicknesses (50–300 A) are presented. The layers of gold must be sufficiently thin in order to avoid the fact that their spectrum perturbs the heating of the foil by radiative effects. The plastic thicknesses are chosen less or equal to the ablation thickness of the material for the laser illumination conditions, i.e., about 6 μm. The spectrum emitted by the gold layer plays the role of a backlighter that probes the plastic heated by the laser. Computer simulations including radiation (multi) confirm the weak effect of radiation heating particularly for the thinner layers of gold.

Stimulated Brillouin scattering (SBS) is investigated one dimensionally under conditions when the typical growth rate is comparable with the ion acoustic frequency. The equations for the three‐wave interaction are modified according to strong coupling. Studies of SBS in homogeneous plasma slabs exhibit the onset of steady‐state solutions. A reflecting rear boundary can cause the backscattering to show nonstationary behavior. In addition, inhomogeneous plasma profiles that include the critical density are studied using the electromagnetic wave equation together with a hydrodynamic approach for the ion fluid.

The influence of nonlinear ion acoustic waves on the stimulated Brillouin backscattering process is investigated with the help of the hydrodynamic description of the ion fluid. Numerical calculations were systematically performed for a wide range of relevant parameters in the presence of an ideal plasma. It is shown that the scaling of steady‐state solutions due to spatially amplified scattering deviates significantly from the theory where only linearized ion acoustic waves are considered. An analytic approach using harmonic expansion confirms the similarity parameters found numerically. The significance of kinetic effects, such as anomalous heat transport due to fast ions and ion trapping in the presence of weakly damped ion waves, is also studied using particle simulations.

By solving the Vlasov equation in the capacitor model approximation it is shown that the linear theory of resonance absorption yields the correct conversion factors for laser intensities at which the electron plasma wave is highly nonlinear or may even break. At Nd-laser wavelength and 1 keV plasma temperature the linear limit is exceeded at least by a factor of 200 in intensity. Over a wide range the structure of the nonlinear Langmuir wave is governed by a fluidlike behaviour on which strong nonlinear Landau damping is imposed.

We have studied plasma-induced smoothing due to stimulated Brillouin scattering (SBS) under the aspect of the extremal statistics of smoothed laser beams. As pointed out in the work by Rose and DuBois (1994 Phys. Rev. Lett. 72 2883), scattered light can be subject to uncontrolled (or even ‘explosive’) behaviour, associated with a critical gain value for SBS. In this work we show how this critical behaviour can be predicted on the basis of the order statistics of laser speckle fields, and we analyse the transition to uncontrolled behaviour of the laser beam due to the dominance of high intensity speckles.

In inhomogeneous density profiles electromagnetic light is partially absorbed and reflected at the critical surface. In those profiles where the reflection is non-negligible the counterpropagating electromagnetic waves cause standing ion density fluctuations which act as a source for backscattering. To study this effect a simplified model based on the usual three wave interaction as well as an extended model using the nonlinear hydrodynamic description of the ion fluid have been investigated. In certain parameter regions at which absorption and reflection at the critical surface are of comparable magnitude no steady state in the evolution of the back-scattered light can establish over long time intervals. The spectral composition of the backscattering signal shows a strong competition between the frequency shifted stimulated scattering (SBS) and the unshifted reflection process.

The transport coefficients of fully ionized plasmas under the influence of a high-frequency electric field are derived solving numerically the electron Fokker–Planck equation using a perturbation method, parametrized as a function of the electron mean-free-path λei compared to the spatial scales L. The isotropic and anisotropic contributions of the inverse bremsstrahlung heating are considered. Electron-electron collision terms are kept in the analysis, which allows us to consider with sufficient accuracy to describe plasmas with arbitrary atomic number Z. Practical numerical fits of the transport coefficients are proposed as functions of Z and the collisionality parameter λei∕L.