Evolution of the electron Langmuir oscillations in an inhomogeneous magnetized plasma

The conditions under which the energy of the electron Langmuir oscillations can escape from the plasma into vacuum are determined in the simplest model of a plane slab of an inhomogeneous cold magnetized plasma in a uniform magnetic field.     

Excitation of Langmuir oscillations by a laser pulse in a semi-infinite dense plasma

A study is made of the nonlinear mechanism for the excitation of Langmuir waves in a dense plasma by an intense laser pulse with the frequency ω = ω_p/2 (where ω_p is the electron plasma frequency).     

Effect of power frequency harmonics on magnetic field measurements

This paper presents a study of the effect of harmonic frequencies on magnetic field measurements. We introduced magnetic field meters in a known magnetic field of different frequencies: power frequency (50 Hz) as well as 3rd (150 Hz) and 5th (250 Hz) harmonic frequencies. Two magnetic field levels (0.25 A and 2.5 A) were used. A Helmholtz coil was applied to generate an exact magnetic field. The difference between the measurement results at harmonic frequencies and at power frequency was analyzed using the t-test for matched pairs. The test results show significant differences (P≤0.01) for 13 out of 28 tests carried out, which is probably due to a curved frequency response near the power frequency. It is, therefore, essential to consider harmonic frequencies in magnetic field measurements in practice. Received: 12 January 1998 / Accepted in revised form: 1 October 1999     

Escape of electron Langmuir waves from a magnetized plasma

A study is made of electromagnetic oscillations of a plasma in open field line geometry (open magnetic devices). The oscillations that propagate from the critical surface and are originally of the nature of the electron Langmuir waves are shown to continuously change their nature and to escape from the plasma into vacuum in the form of electromagnetic waves. This phenomenon may give rise to wave energy losses from a thermodynamically nonequilibrium (unstable) plasma, e.g., a plasma penetrated by charged particle beams.     

Excitation of eosin when catalyzing electron transport in biochemical systems.

Phenols may participate in electron transport and, as such, catalyze the oxidation of NADH and of acetoacetate in the horseradish peroxidase/Mn²⁺/O₂ system. Eosin can be substituted for the phenol and, in this case, photon emission is observed. The spectrum is mainly eosin fluorescence in the case of NADH oxidation, whereas fluorescence and another emission—presumably phosphorescence—are observed during acetoacetate oxidation. This appears to be the first report of excitation of an electron carrier in biochemical systems.     

Generation of solar microwave bursts at the second harmonic of the plasma frequency

The nonlinear interaction between upper hybrid waves is simulated numerically for conditions corresponding to the sources of solar microwave bursts (at a frequency of about 5.7 GHz). The source of plasma waves is considered to be an electron beam with a loss-cone-type distribution. It is shown that, for a symmetric double-sided loss cone, the degree of polarization of the radiation generated in a direction transverse to the magnetic field can reach 100% and corresponds to an extraordinary wave. For a one-sided loss cone, in accordance with the previous results, the degree of polarization is found to be low. The efficiency of the plasma mechanism for the radiation generation is estimated.     

Nonlinear currents generated in plasma by a radiation pulse with a frequency exceeding the electron plasma frequency

It is shown that the nonlinear currents generated in plasma by a radiation pulse with a frequency exceeding the electron plasma frequency change substantially due to a reduction in the effective electron–ion collision frequency.     

Transient emission studies of electron injection in dye sensitised solar cells

Time resolved single photon counting is employed to monitor electron injection dynamics in dye sensitised solar cells. It is shown that, by the use of a non-injecting reference film and a simple stretched exponential fitting procedure with only two fitting parameters it is possible to resolve electron injection half-times down to 60 ps resolution. This provides a potentially cheaper and experimentally easier approach to monitor such dynamics compared to more widely used ultrafast pump/probe laser spectroscopy. Injection dynamics are observed for a range of different sensitiser dyes and redox electrolytes. As expected, the presence of a redox electrolyte results in a significant retardation of the injection half-times relative to an inert, aprotic solvent, with typical injection half-times being in the range 120-3000 ps depending upon sensitiser dye employed. In all cases, the injection dynamics fitted well to the stretched exponential function, consistent with a numerical model based upon inhomogeneous energetics of electron injection.     

Heme reduction by intramolecular electron transfer in cysteine mutant myoglobin under carbon monoxide atmosphere

Human myoglobin (Mb) possesses a unique cysteine (Cys110), whereas other mammalian Mbs do not. To investigate the effect of a cysteine residue on Mb, we introduced cysteine to various sites on the surface of sperm whale Mb (K56C, V66C, K96C, K102C, A125C, and A144C) by mutation. The cysteines were inserted near the end of alpha-helices, except for V66C, where the cysteine was introduced in the middle of an alpha-helix. Reduction of the heme was observed for each mutant metMb by incubation at 37 degrees C under carbon monoxide atmosphere, which was much faster than reduction of wild-type metMb under the same condition. Heme reduction did not occur significantly under nitrogen or oxygen atmospheres. The rate constant for heme reduction increased for higher mutant Mb concentration, whereas it did not change significantly when the CO concentration was reduced from 100% CO to 50% CO with 50% O(2). The similarity in the rate constants with different CO concentrations indicates that CO stabilizes the reduced heme by coordination to the heme iron. SDS-PAGE analysis showed that mutant Mb dimers were formed by incubation under CO atmosphere but not under air. These dimers were converted back to Mb monomers by an addition of 2-mercaptoethanol, which showed formation of a Mb dimer through a disulfide bond. The rate constant decreased in general as the heme-cysteine distance was increased, although V66C Mb exhibited a very small rate constant. Since V66 is placed in the middle of an alpha-helix, steric hindrance would occur and prevent formation of a dimer when the cysteine residues of two different V66C Mb molecules interact with each other. The rate constants also decreased for K56C and A144C Mbs presumably because of the electrostatic repulsion during dimer formation, since they are relatively charged around the inserted cysteine.     

Transverse and longitudinal permittivities of a gaseous plasma with an electron collision frequency proportional to the electron velocity

The transverse and longitudinal plasma permittivities, ?^tr and ? ^l , are analyzed for the case where the electron collision frequency in the Bhatnagar-Gross-Krook collision integral is proportional to the absolute value of the electron velocity. It is found that, in both the low-and high-frequency limits, the expressions for ?^tr and ? ^l derived for the case of a variable electron collision frequency coincide with the classical formulas obtained under the assumption of a constant collision frequency, whereas for frequencies close to the electron collision frequency, these expressions differ significantly from the classical ones.     

Excitation of growing wake waves by an electron bunch in a plasma in an intense pump wave

A study is made of the excitation of wake waves by a one-dimensional electron bunch in an electron plasma in the presence of an intense monochromatic pump wave with circular polarization. In the main state (in the absence of a bunch), the interaction between a pump wave and a plasma is described by Maxwell's equations and the nonlinear relativistic hydrodynamic equations for a cold plasma. The excitation of linear waves by a one-dimensional bunch is investigated against a cold plasma background. It is shown that, in a certain range of parameter values of the bunch, pump wave, and plasma, the excitation is resonant in character and the amplitude of the excited wake waves increases with distance from the bunch.     

An electron microscopic study of solar ganglia in piglets infected with Aujeszky's disease virus

Ten 2-day-old piglets were inoculated intranasally with Aujeszky's disease virus and their solar ganglia were examined by light and electron microscopy. The cytopathic change noticed was neuronal and glial cell degeneration. It was invariably associated with the virus replicated within the cells. All the main stages of virus development were observed in the degenerated ganglionic cells. Characteristically, plexiform vermicellar array and electron-dense tubular filaments were detected in a part of the nuclei of the infected neuron.     

Oxygen in the early atmosphere

Origins of Life and Evolution of Biospheres -     

Skin effect in a gaseous plasma with a collision frequency proportional to the electron velocity

An analytic solution to the problem of skin effect in plasma is found for the first time by using a kinetic equation in which the collision frequency is proportional to the absolute value of the electron velocity. Mirror reflection of electrons from the plasma boundary is used as a boundary condition. The calculated expression for the impedance is compared with the classical one.     

On measurements of the higher harmonics of transmembrane current

The higher harmonics of the current caused by an alternating voltage applied to bilayer lipid membranes made of diphytanoyl phosphatidylcholine (DPhPC) in decane and tetradecane were measured. A universal relation between the amplitudes of harmonics was proposed and experimentally verified. This allowed the coefficients of expansion of the capacitance in even powers of voltage to be calculated for the DPhPC membrane in tetradecane; it also permitted comparison of the inhomogeneity in the thickness of the DPhPC membranes in decane and tetradecane.     

Thermodynamic equilibrium of domains in a two-component Langmuir monolayer

This [corrected] article outlines the results from a combined experimental and theoretical study on the properties of circular domains in a mixed Langmuir monolayer at thermodynamic equilibrium. The mixed monolayer consisted of a binary mixture of dimyristoyl-phosphatidyl-choline and dihydrocholesterol. A long-term fluorescence microscopy study of these domains was carried out over the course of approximately 60 h. Image analysis of the domains over time revealed that the domains ripened slowly with an [corrected] increase in mean domain radius and a [corrected] decrease in domain number density. At the end of the measurement, the domains remained polydisperse, and true thermodynamic equilibrium was not reached. Theoretically, collective thermodynamic equilibrium properties such as mean domain size and size distribution were calculated by combining micelle self-assembly theory and the "equivalent dipole" model for the self-energy of two-dimensional domains. The calculations predicted existence of finite-sized circular domains at equilibrium. This suggests that equilibrium circular monolayer domains of single- or multicomponent lipids with a finite size distribution should form only at very limited experimental conditions. Both the predicted mean domain size and size distribution are strongly affected by line tension and dipole moment density difference. A comparison between the theoretical and experimental results is made.