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The article focuses on comparison of discretizations of the Navier-Stokes equations using the nite element method. Several choices of nite element spaces are discussed. First, the conforming spaces (TH, SV) are used. Second, the nonconforming equal order choice of P1/P1 elements is made. For the latter case the discrete equations are solved by a pressure correction scheme for the Taylor-Hood and Scott-Vogelius elements, the arising system is solved by a direct solver. The numerical results are compared to experimental and reference data. Methods are applied for the flow over the backward-facing step and for the flow around the cylinder.

Net photosynthetic rate (PN), productivity and the first phases of the fluorescence induction curve were investigated in leaves of two potato cultivars exposed to water stress. Water stress applied to potato plants at the beginning of their development (planting-bud formation) increased productivity but decreased PN and variable fluorescence (Fv) of leaves. The short-term influence of water stress on the same plants also diminished the Fv.

Polystyrene, material frequently used for ELISA microtiter plates, was modified by gamma irradiation in order to enhance the passive absorption binding capacity of immunoglobuline E. The dependences of this capacity increase on dose and irradiation conditions (atmosphere, presence of water) permitted the optimization this treatment of plates up to the technological scale. However the increase of passive absorption in the case of low-molecular weight synthetic peptides, such as anti-EBNA, was not sufficient and the reason for this remains to be clarified. Radiation grafting made it possible to fix the hydrazide functional group onto the polysterene. It offers the possibility to of binding the proteins, via covalent linkage, with the carbonyl group formed by the oxidation of carbohydrates included in the protein molecule.

In a nonlinear vibration system with energy supply the lowest frequency mode may be coherently excited as was predicted by Frohlich. Computer simulation of nonlinear vibration systems reveals that even the higher frequency modes may be excited. The conditions for higher frequency modes excitation are specified. Coherent states may be excited in the time period less than about one hour after switching on the energy supply.

Coherent vibration systems are very likely composed of oscillating protein molecules located in the closed surface of the plasma membrane. Except short periods in the cell life, the distribution of the oscillating molecules corresponds to the condition of the minimum energy of the generated electromagnetic field. In this case the Raman scattering is hardly possible.

Absorption and circular dichroism spectra and steady state and time-resolved fluorescence of complexes of 5,10,15,20-tetrakis (4-carboxyphenyl)porphyrin with sequential helical polypeptides (L-Lys-L-Ala) n , (L-Lys-L-Ala-L-Ala) n , and (L-Lys-L-Ala-L-Ala-L-Ala) n are studied. Changes of electronic transition energies, induction of optical activity and two-component fluorescence decay with components t 1 = 2–3 ns and t 2 = 180 ps characterize the complexed pigment. Dependence of these changes on relative number of lysine amino acids in polypeptide primary structures was observed and is discussed in terms of perturbational influence of polypeptide molecular field on mixing of porphyrin electronic states.

The fast rise of Seebeck coefficient in CdTe with decreasing temperature found experimentally, has not been successfully explained theoretically for many years. It is shown that this effect can be realistically explained by a new theory (Yu. Gurevich et al, Phys. Rev., in press) which includes processes on the metal semiconductor interface. Also the influence of temperature gradient on the sensitivity of gamma detectors in CdTe is discussed.

The presented study is designed to evaluate the role of structure and conformation of pigment-protein complexes in the determination of the spectral properties of the complexed porphyrin. The protein environment is simulated by the well-defined polypeptides with variable primary structures. The discussed experimental results provide a basic insight into the physical mechanism of the porphyrin electronic structure alternation by protein in a pigment-protein complexes.

Site selection and hole burning spectroscopy are low temperature spectroscopic techniques based on the removal of the inhomogeneous broadening in optical spectra. These spectroscopic techniques, applied to photosynthetic systems, their subunits and models, represent powerful tools for studying pigment-pigment and pigment-matrix interactions, as well as energy transfer and electron transport. The digested information obtained from low temperature spectroscopy results on chlorophylls and photosynthetic systems can be found in |1|. Most important results are briefly mentioned below. Conventional low temperature spectra of chlorophylls in vitro have shown only broad bands in absorption and emission. The narrow red laser excitation enables to observe vibrationally resolved site selection spectra in solid solutions |2, 3| and in polymer foils |4|. The hole burning (HB) effects in absorption (A) and fluorescence excitation (E) spectra were measured in different matrices including the discussion of HB mechanisms |5, 6, 7|.

All the so far investigated theoretical models of the excitation energy transfer in the primary processes of photosynthesis have only limited range of validity. For this and other reasons we suggested a model of the transfer processes (1,2) which is quite general as far as the inter-molecular transfer it is concerned and allows to obtain the first principle answers to the following questions. 1) What are physical reasons of the high value of the quantum yield of the transfer to the charge transfer state of the reaction center? 2) What information of the intermolecular transfer may be obtained from the experimental observables? 3) What is the effect of a finite experimental resolution and other experimental conditions on the attainability of this information? 4) What is the mutual relation of the experimental observables? 5) What is the importance of different transfer regimes — coherent, intermediate and incoherent? In this contribution, some of the most important results in this respect are summarized.

The locality of underground water, contaminated with cyanides, has been successfully cleaned by using the hydraulic barrier method (assembly of pumped wells) since 1986. The average cyanide concentrations in the outflow exceeded 35 m per litre. Contamination had to be eliminated before the discharge into the sewer system. The radiation approach “in situ” i.e. decomposition of cyanides by barrier, was applied and is still being used today. The cyanide concentration was lowered more than one order of magnitude. This process was approved by the Czechoslovak radiation security authorities and further applications of “in Situ” regeneration of underground water contamination is anticipated.

–The absorption and fluorescence characteristics of subchloroplast particles highly enriched in P700 (1 P700 to 10–15 chlorophyll a molecules) and of two artificial systems are presented here. The fluorescence characteristics measured were excitation and emission spectra, and the degree of polarization of fluorescence. The model systems studied were chlorophyll a and pheophytin a in a polystyrene matrix, and a colloidal mixture of these two pigments with bovine serum albumin. Effects of 0.5% sodium dodecyl sulfate on the optical properties of the P700-enriched particles are also described. The importance of pigment-pigment and pigment-protein interactions in determining the fluorescence properties of these particles are discussed. The possible role of pheophytin in these preparations needs further investigation.

Temperature dependence of the electron-hole plasma (EHP) radiative recombination in TlBr crystals was measured in the bath temperature range 8.5–56 K. Strong phonon-assisted competition due to intervalley electron scattering between direct and indirect gaps EHP components was found. A kinetic model is presented which explains the main features of the experiment.

The Frohlich coherent polar vibrations may be a source of the cell-generated electromagnetic field. The cellular membrane is assumed to be the locus of the dipole vibrations. We adopt a model of the spherical dipole layer with both uniform and domain distributions of the dipole densities and of the dipole moments. Computer results indicate that the electromagnetic field of cellular origin may be significant within a distance of about 1–10 μm from the cell surface. The Schottky barrier might be used to determine the frequency and the intensity of the cell-generated field in the frequency range below 1 THz.

Electronic excitation energy transfer was studied for chlorophyll a in a solid solution of poly­styrene by measuring the concentration quenching of quantum yield, polarization, and lifetime of fluorescence. The concentration quenching of the experimental fluorescence quantum yield is adequately described by Kelly and Porter’s empirical formula (Proc. Roy. Soc., Lond. A 315, 149, 1970), and of polarization of fluorescence by the Jablonski theory (Acta Phys. Pol., 14, 295, 1955). With increasing concentration of chlorophyll a, the fluorescence peak at 672 nm (mainly monomer) is red-shifted, the intensity of the emission peak at ∼730 nm (mainly aggregate) relative to that at the shorter wavelength is increased. The R̅0 values, calculated by using total concentrations, for the emission at 672 nm and 730 nm are 73 ± 2 Å and 45 ±1 Å, respectively. This may suggest that the chlorophyll monomers have a greater efficiency of energy transfer than the aggregates, which fluoresce at ∼ 730 nm.

Fluorescence and fluorescence polarization spectra of chlorophyll a dissolved in ethanol, n-propanol, EM (ethanol-methanol, 4:1) and EPE (ether, n-pentane, ethanol, 5:5:2) were measured at 77 K. An emission band (‘shoulder’) between the two usual fluorescence bands appears in such spectra of dilute solutions (concentration ˜ 10-5M) of chlorophyll a (except in EPE). The position, intensity and half-width of this band were calculated using a computer. The correlation between electronic transitions of chlorophyll a and these emission bands is discussed.

Emission spectrum of pure AgCl crystals at room temperature after ruby laser excitation was measured. The emission consists of a continuous fluorescence band with the maximum at about 460 nm which is at sufficiently high excitation intensities covered with characteristic line structure emission. The appearance of continous emission at this temperature was in accordance with experimental results explained by the increase of the radiative transition probability in AgCl crystals.

Radiative and nonradiative processes were investigated in subchloroplast particles highly enriched in P-700 (1 P-700 to 10 chlorophyll molecules) according to the method of classical fluorescence and of photoacoustical spectroscopy. The envelope of fluorescence spectrum divided into three Gaussian bands and their quantum yields of fluorescence were calculated. Independently the quantum yield of fluorescence was determined from the spectral course of the photoacoustical signal. Finally, the estimate of the photochemical activity of P-700, based upon the measured fluorescence quantum yield and upon the measured nonradiative losses of excitation energy, was done.

Excitation and flourescence spectra of chlorophyll-a were studied in matrices of normal alkanes (C8H18, C12H26, C16H34) at low temperature (5–30 K). Narrow band excitation of fluorescence using a pulsed tunable dye laser was used for the site selection to eliminate ambiguities due to impurities and multiple sites. Fluorescence and excitation spectra show 0-0 quasi-lines on band background. The spectra and the frequencies of normal vibrations in the first excited electronic state are compared to those of chlorophyll in other solvents.

Luminescence of TlBr crystals highly excited by a nanosecond pulsed-dye laser (3.4 eV) at the bath temperature ∼ 8.5 K was studied. Two emission lines labeled A (∼ 2.98 eV) and B (∼ 2.62 eV) were found, which show typical behavior of the electron-hole plasma recombination radiation. The A-line is assigned to the recombination of e-h pairs in the direct gap ( X + 6 − X - 3 ) and the B-line to the simultaneous recombination in the indirect gap ( X + 6 − R - 6 ). Condensation of carriers into an electron-hole liquid was not observed.

Low temperature fluorescence spectra of chlorin-e6-trimethylester, 7-cyano-chlorin-e6-trimethylester, mesoisochlorin-e4-dimethylester, 13-acetyl-mesoisochlorin-e4-dimethylester and 20-chloro-mesoisochlorin-e4-dimethylester in Shpolskii n-octane and non-Shpolskii methanol + + dichloromethane matrices at 5 K are reported. The role of both laser and conventional excitation together with matrix-pigment interaction are discussed. Especially, Shpolskii and site-selection fluorescence spectra were measured and their vibrational analysis is presented yielding frequencies of normal vibrations in the ground and the first excited singlet state.

Luminescence spectra of AgBr at the temperature range 5–50 K and under pulse excitation intensity up to ∼ 0.7 MW cm −2 are investigated. Intensity and temperature dependences of biexciton emission line (2.67 eV) yield thermodynamic determination of biexciton binding energy in agreement with the spectroscopic value (6.7 meV). The behaviour of biexciton emission in the investigated temperature range is explained by the concept of “biexciton pocket”. Some questions of the electron-hole liquid recombination radiation (2.60 eV) are discussed as well.

— Low temperature (T= 10 K) site-selection fluorescence and excitation spectra of both isolated pheophorbide-a molecules (I PHEO) and pheophorbide covalently bonded to the synthetic l-lysyl-l-alanyl-l.-alanine polypeptide (B PHEO) were measured in dimethylformamide (DMF) matrices. The fluorescence spectra display sharp vibronic lines at different wavenumbers for different dye laser excitation wavelengths, superimposed on a broad band background. Spectral analysis provides frequencies of normal vibrations (FNV) and site distribution functions (SDF). The FNV and SDF of I PHEO in DMF have been found to show good agreement with other chlorophyll-like molecules. A covalent binding between the polypeptide and PHEO molecules produces only slight changes in FNV but significant broadenings and shifts to lower energies in SDF. The fluorescence spectra of I PHEO in a typical Shpolskii matrix (n-octane) were also measured and found to exhibit sharp non-shifting vibronic lines for all wavelengths and kinds of excitation. A general model explaining both site-selection and Shpolskii spectroscopy is presented.

Site-selection spectroscopy of carboxytrimethyl tetraphenylporphyrin and its phenylalanine complexes in n -octane at 10 K are reported. The frequencies of normal vibrations and the site distribution functions were determined from the fluorescence spectra. Pigment-pigment and pigment-short-chain-protein interactions are discussed.

The regeneration of biologically clogged water wells by radiation proved to be a successful and economically beneficial process among other promising applications of ionizing radiation in the water supply technology. The application conditions and experience are mentioned. The potential pathogenic Mycobacteria occuring in the warm washing and bathing water are resistant against usual chlorine and ozone concentrations. The radiation sensitivity of Mycobacteria allowed to suggest a device for their destroying by radiation. Some toxic substances in the underground water can be efficiently degraded by gamma radiation directly in the wells drilled as a hydraulic barrier surrounding the contaminated land area. Substantial decrease of CN- concentration and C.O.D. value was observed in water pumped from such well equipped with cobalt sources and charcoal. The removing of pathogenic contamination remains to be the main goal of radiation processing in the water purification technologies. The decrease of liquid sludge specific filter resistance and sedimentation acceleration by irradiation have a minor technological importance. The hygienization of sludge cake from the mechanical belt filter press by electron beam appears to be the optimum application in the Czechoslovak conditions. The potatoes and barley crop yields from experimental plots treated with sludge were higher in comparison with using the manure. Biological sludge from the municipal and food industry water purification plants contains nutritive components. The proper hygienization is a necessary condition for using them as a livestock feed supplement. Feeding experiments with broilers and pigs confirmed the possibility of partial (e.g. 50%) replacement of soya-, bone- or fish flour in feed mixtures by dried sludge hygienized either by heat or by the irradiation.

A new technique — the photoacoustic spectroscopy with microphone detection has been successfully applied to the studies of spectral sensitivity of silver halide emulsions. Regardless of the fact that the sensitivity of photographic emulsions is greater or comparable with the detectivity of real photoacoustic transducers (i.e. the photoacoustic cell with microphone or piezoelectric transducer), absorption-like spectra of strongly diffusive and nontransparent silver halide emulsions can be readily recorded. Applications of this new technique for the studies of silver halide emulsions bears full potential advantages of photoacoustic spectroscopy. Particularly we demonstrate priority of the new technique over the conventional photographic sensitometry or reflectance spectroscopy both in qualitative and quantitative manner. Photoacoustic measurements of photochemical decomposition rates are shown and suggestions for the measurements of excitation energy transfer efficiencies are given. The results clearly show a unique applicability of the technique in fundamental as well as industrial research and process control of the photographic emulsion production.

The decay of polyenyl macroradicals in irradiated poly(vinylidene flouride) and its dependence on radiation crosslinking was studied by the ESR method. The decay rate constants were found to decrease in the lower temperatures region but they show some anomaly at higher temperatures with respect to radiation dose. Temperature dependences of kinetic constants are correlated with thermodynamic parameters from DSC measurements and are interpreted as a result of the steric hindrances changes on molecular mobility due to structural changes caused by radiation crosslinkings and phase transition in a semicrystalline matrix.

The Frohlich kinetic equation (FKE) describes the coherent excitation in a band of polarization waves consisting of normal modes. The FKE involves the one and two quanta terms representing energy supply, energy losses and energy channeling between the modes with the help of the heat bath. The energy channeling between the vibration systems located at different positions and the channeling connected with multiple quanta processes without the help of the heat bath are analyzed. The additional terms of the FKE are derived. The multiple quanta processes may channel the energy from the coherently excited mode (or modes) to higher frequency ones.

The inactivation rate of cells induced by heat in biological systems exhibits significant variations. The Frohlich hypothesis of coherent vibrations is used to explain the observed differences between thermal sensitivities of malignant cells and their healthy counterparts. The resistance of the cellular membrane to the thermal fluctuations, pore creation, and membrane permeability increase may depend on the coherent state energy. A higher membrane permeability results in a lower cell survival rate when heated to the hyperthermic range.

Site selection fluorescence and excitation spectra of chlorophyll-a in n-alkanes (octane, dodecane, hexadecane, eicosane) and polystyrene matrices were measured at low temperatures (5-30 K), using a pulsed dye laser tuned in the range 605 nm - 660 nm. The vibrational analysis of fluorescence quasilines gives very similar results for chlorophyll-a in matrices with different molecular chain lengths.

Dependence of two-photon absorption (TPA) rate on the state of polarization of a laser beam is investigated in the low-temperature orthorhombic modification of Hg2Cl2 crystals. Theoretical calculations of the dependence of TPA rate on the direction of polarization vector of the beam are performed for centrosymmetric pointsγ, Y, Z, T, R andS of the Brillouin zone. The domain structure of real crystals is taken into consideration and it is shown that periodicity of the polarization dependence may indicate whether TPA is due to transitions either atγ, Y, Z, T orR, S points. The polarization dependence of TPA cannot, however, distinguish between points inside these two groups. Comparison of theory with a low-temperature (T ∼ 8·5 K) experimental curve of polarization dependence is discussed. It is shown that the experiment can be explained in main features by a model of noninteracting oriented linear dipoles. Further, on the basis of TPA measurements, a simple energy band structure of Hg2Cl2 is proposed regarding Hg2Cl2 crystal as a linear chain of molecules.

Excitation and fluorescence spectra of free base phthalocyanine were studied in matrices of normal alkanes (C8H18, C12H26, C16H34) at low temperatures (5 to 30 K). Narrow band excitation of fluorescence using a pulsed tunable dye laser was used for site selection to eliminate ambiguities due to impurities and multiple sites. Fluorescence and excitation spectra show quasiline structure. Multiplicity of 0-0 transitions depends on the chain length of normal alkanes. The spectra and frequencies of normal vibrations are compared with those of phthalocyanine in other n-alkanes (C9H20, C10H22) and noble gas matrices (Ar, Ne) under different excitation conditions.

The course of thermostimulated currents in AgCl crystals was measured in a temperature region between 200‡ and 300‡K. Maxima at 240‡, 275‡ and 290‡K were observed on the curves obtained.

An investigation is made of the electroluminescence excited by short electric field pulses in pure and doped (0.01 mol% TlCl or 0.01 mol% MnCl2) AgCl crystals. The majority of the results obtained (dependence of electroluminescence on voltage and pulse duration; threshold exciting voltage) are similar to electroluminescence phenomena in ZnS. Illumination of the electroluminescence cell by red light, and by UV light, respectively decreases and increases the electroluminescence brightness. Attempts to interpret the data in terms of a bipolar field emission model prove satisfactory under the assumption that the luminescence centres are cation vacancies. Durch kurze Spannungsimpulse angeregte Elektrolumineszenz wird in reinen und dotierten (0,01 mol% TlCl oder 0,01 mol% MnCl2) AgCl-Kristallen untersucht. Der groste Teil der erhaltenen Ergebnisse (Abhangigkeit der Elektrolumineszenz von der Spannung und der Impulslange, Schwellenwert der Anregungsspannung) ist den Elektrolumineszenz-erscheinungen in ZnS ahnlich. Bestrahlung der Elektrolumineszenzzellen mit rotem Licht und UV-Strahlung vermindert bzw. erhoht die Elektrolumineszenzhelligkeit. Unter der Annahme, das die Lumineszenzzentren Kationenlucken sind, erweisen sich Versuche, die Ergebnisse mit einem bipolaren Feldemissionsmodell zu deuten, als erfolgreich.

This paper summarizes and analyses our experimental results obtained on photoluminescence of AgCl crystals excited by ruby and u.v. laser in first part, and after and during deformation in second part. The influence of pressure on AgCl photoluminescence is explained by means of a qualitative model based on charged dislocations for both the elastic and plastic regions of the deformation curve.

The temperature dependence and the influence of pressure on band width of blue-green luminescence were measured in pure AgCl crystals. The comparison of results obtained with other published data support the existence of two luminescence centres (in the temperature ranges between 130–160°K and between 20–30°K).

Изучалось влияние да вления на так называе мые экситонные полос ы AgBr, Agcl и AgIпри температуре — 160°C.Под влиянием давления эти полосы у образцов AgBrи AgClрасшири лисъ и сместилисъ в длинноволновую сто рону спектра. Па образ цах AgIнаблюдалосъ усиление этих полос б ез смещения их положе ния.

From the effects of γ-radiation dose, scavenger concentration, photobleaching and temperature on the yield of electrons and radicals trapped in glassy 2-methyltetrahydrofuran (2-MTHF) irradiated at 77 K, the spatial distribution of trapped electrons and radicals is considered. At doses around 4 × 10 21 eV g −1 the electrons are scavenged efficiently by accumulated trapped radicals and ions. At higher doses newly formed radicals and ions react with remaining trapped electrons, the concentration of which thus tends to zero. The initial thermal decay of trapped electrons at 93 K is fast and its kinetics cannot be measured; this part of the electrons amounts to 30–60 per cent of all trapped electrons; the remainder of the trapped electrons decays at low doses (10 17 -10 19 eV g − ) by second-order kinetics, which changes to first order at higher doses (1·2−1·6 × 10 21 eV g −1 ); this is accounted for the change of a bimolecular reaction of electrons with radicals and ions to a pseudomonomolecular reaction due to the increase in trapped radical and ion concentrations. The electrons are not precursors of hydrogen; no protonated molecules or radicals are formed on irradiation. Hydrogen formation can be partly suppressed by scavengers of hydrogen atoms. The radiolysis mechanism is discussed.

Some new measurements of the luminescence of pure and doped AgCl crystals are dealt with and evaluated, in particular the shift of the blue-green emission band as a function of the doped ion and the temperature shift of this band. The concentration of luminescence centra in pure AgCl crystals and the creation ofX-ray luminescence in AgCl crystals at room temperature are briefly discussed in the two final remarks.

Измерялась люминесц енция монокристалло в AgCl разной толщины до и после деφормации при температуре −180°С. У деφормированных обр азцов было найдено ум еньшение интенсивности люмин есценции. В полосе изл учения упомянутых кр исталлов наблюдалась тонкая с труктура, для которой можно было применить правило серий (края серий:λ ∞ ′ =4640 A,λ ∞ ′ =5080 A). Наблюда емая люминесценция о бъяснена при помощи механизма экс итонов, предложенног о Матыашем, т. е. анниги ляцией локализирова нного экситона или на вакан сии из-под катиона или на такой же вакансии на пороге дислокации. Фотограφическим мет одом измерялся также выход люминесценции при −183°С, ϕ=1,6. 10−8%±10%.

The kinetics of luminescence decay of single crystal plates of AgCl was measured at the temperature of liquid nitrogen. Luminescence decay first takes place (fort≦2·5× ×10−3 sec) according to a hyperbole and then according to an exponential. The constantsa anda of the hyperbolic andt of the exponential dependence were measured for different intensity of the exciting radiation in normal and deformed samples and in samples irradiated withb-particles during measurement.

Emission spectra of chlorophyll a dissolved in non-polar and polar media were measured by different methods and with different excitation. The fluorescence excitation spectrum was compared with the absorption spectrum and good coincidence was found.

Изучалось влияние да вления на границу nогл ощения чиСтых монокр исталлов AgBr, AgClи AgI.Поглощение изме рялоСь при температу ре −180 °С. Обнаружено смеще ние границы поглощен ия в сторону ультраφиолетовой ча сти спектра. Смещение объясняется в соотно шении с работой Биллига [7],ра сширением запрещенн ой зоны вследствие умен ьшения постоянной ре шетки кристалла под влиянием давления.

Present article is devoted to the pursuit of excitation spectra and of thermal dependencies of emission spectra of photoluminescence of pure samples of AgCl during the preparation and/or annealing in argon, air, oxygen or HG1. Differences of luminescence properties of different samples are explained by the existence of different surface luminescence centres created during the preparation of samples.