Hydrogen photoproduction ofA. Variabilis incorporated in a photobioreactor

H₂ photoproduction and nitrogenase activities in two strains ofAnabaena variabilis marked wild type ATCC 29413 and mutant PK84 exposed to thermal stress (temperature higher than the normal incubation temperature of 30°C) were studied. Cultures of both strains collected from any interval of logarithmic growth phase exhibited high H₂ photoproduction and nitrogenase activities when exposed to limited time heat shock during the assay process. In contrast, the algal H₂ photoproduction rate of both strains fluctuated with long term thermal stress caused by increasing the growth temperature from 30°C to 36°C.

The changes of nitrogenase (the key H₂ photobiosynthetic enzyme) activities in the mutant PK84 showed variation tendency similar to that of H₂ photoproduction during exposure to thermal stress, indicating that fluctuation of H₂ photoproduction in the mutant was mainly due to the variation of nitrogenase activities. A temporary maximal H₂ photoproduction in the mutant PK84 (wild type ATCC29413) was observed when cells grew at 36°C for 14 (6) days. However, the responses of nitrogenase activities in the wild type to thermal stress were not completely similar to those in the mutant in spite of similar variations of H₂ photoproduction in both strains. The data obtained in these studies suggested that the activities of other enzymes (in the wild strain) involved in H₂ photoproduction were affected by thermal stress since H₂ photoproduction maximized or dropped to 0 without variation tendency similar to that of nitrogenase activities.

Furthermore, an enhancement of H₂ photoproduction speed of the mutant strain cultured in a 4.4 L laboratory photobioreactor was also observed when it was subjected to short time continuous charge of argon, and temperature rise.

All these results indicated that high temperature plays an important role in the photo-autotrophic H₂ photoproduction, and that long term thermal stress is unfavourable for net H₂ photoproduction in both strains ofA. variabilis though short-time heat shock is conducive to H₂ photoproduction.

     

Endogenic nature of variations in the bottom topography of the mid-ocean rift zones with intermediate spreading rates

Specific features of variations in the bottom topography of the mid-ocean rift zones with intermediate spreading rates are considered in this work. The rift zones with a transition morphology are analyzed, and the main features of the transition topography are distinguished. Several successive stages of topographic variations, each of which is characterized by a specific relative position of the topographic features of the rift zone cross section, have been distinguished based on an analysis of the character of rift zone topographic variations in going from axial rises to rift valleys. The specific features of variations in the structural segmentation of rift zones with intermediate spreading rates, depending on the morphological changes, have been established. The thermal models of the structure of the rift zone magmatic formations have been considered, and the geodynamic relations of the magmatic systems with the specific features of the morphology and the structural segmentation of the mid-ocean axial zones with the intermediate spreading rates have been discussed.     

A nonstationary model of the thermal regime of axial zones of mid-ocean ridges: Formation of crustal and mantle magma chambers

A nonstationary model of spreading with periodic intrusions of a molten material into an axial zone of a mid-ocean ridge (MOR) is applied to numerical analysis of the thermal state in MOR axial zones and the formation of crustal and mantle magma chambers in them. The model satisfactorily explains the positions, dimensions, and shapes of magma chambers, as well as variations in these parameters depending on the spreading rate, temperature, and composition of crustal and mantle rocks. The release and absorption of the latent heat of rock melting, hydrothermal heating of the crust, and variations in the solidus and liquidus temperatures of crustal and mantle rocks as a function of their composition are factors controlling the shape and position of crustal magma chambers.     

H2 PRODUCTION BY ANABAENA VARIABILIS MUTANT IN COMPUTER CONTROLLED TWO-STAGE AIR-LIFT TUBULAR PHOTOBIOREACTOR

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Thermal and rheological state of the lithosphere and specific features of structuring in the rift zone of the Reykjanes Ridge (from the results of numerical and experimental modeling)

Specific features of the bottom topography structure and the character of morphostructural segmentation of the rift zone of the Reykjanes Ridge change substantially along the ridge strike with increasing distance from Iceland’s hotspot. A clearly pronounced regularity of changes is observed in the rift zone’s morphology from the axial uplift (in the northern part of the ridge) to the rift valleys (in the southern part of the ridge) through an intermediate or transitional type of morphology. The results of numerical modeling showed that changes in the rift zone’s morphology along the Reykjanes Ridge strike are largely caused by changes in the degree of mantle heating and depend on the intensity of magma supply. It is shown that under conditions of ultraslow spreading, it is these parameters that control the presence or absence of crustal magma chambers, as well as the thickness of the effectively-elastic layer of the axial lithosphere. The experimental modeling of topography-forming deformations and structuring on the Reykjanes Ridge showed that under oblique extension, specific features of the formation of axial fractures and the character of their segmentation mainly depend on the thickness of the axial lithosphere, its heating zone width, and the kinematics of spreading. The experiments also showed that the tendency of fractures to develop obliquely to the extension axis is caused by the action of the inclined zone of the location of the deformation, and shear deformations play a substantial role in the lithosphere’s destruction as the inclination angle increases.     

Dynamical equinox and analytical theory of the Sun

A concept of the dynamical equinox and its relation to the analytical form of the adopted theory of the Sun is discussed. Connection between the FK4 equinox and the dynamical equinox is determined by comparing two analytical theories of the Sun (the adopted Newcomb's theory and a new one (AT-1) constructed at the Institute of Theoretical Astronomy) with solar meridian observations made at the U.S. Naval Observatory (1911–1971). Corrections to the FK4 right ascensions, ₀ to declinations and to the angle between the equator and the ecliptic are: Secular variations in and are negligible. Large secular variations of ₀ may be explained by improvement of observational conditions after the reconstruction of the telescope pavilion in the forties.Proceedings of the Conference on Analytical Methods and Ephemerides: Theory and Observations of the Moon and Planets. Facultés universitaires Notre Dame de la Paix Namur, Belgium, 28–31 July, 1980.     

The motion of major planets from observations 1769–1988 and some astronomical constants

Modern planetary theories may be considered as a realisation of a four-dimensional dynamical reference frame. The existence of secular trends between the dynamical system and the adopted system of the Fundamental Catalogue (as well as between time scales involved) has been studied by discussing planetary observations of different types and by comparison with a numerical theory constructed for the time span 1769–1988. Parameters of the theory were fitted to radar ranging data for 1961–1988 for inner planets and to meridian observations of 18^th–20^th centuries for outer planets. Then a set of the inner planet optical observations, which includes USNO meridian observations, transits through the solar disk and occultations of fundamental stars are discussed. The main results are the following:

1. Radar data were used to estimate the time derivative? of the gravitational constantG (in another interpretation, the secular trend between the atomic and dynamic time scales): $$\dot G/G = (0.37 \pm 0.45) \times 10^{ - 11} /y.$$ This estimation, being statistically insignificant, gives some physically meaningful restriction to?.
2. From the same data a new estimation of relativistic effects in the motion of Mercury was obtained, which has confirmed the Einstein value of the perihelion advance with the error 0″.06/cy. So in the frame of Einstein's theory the value of solar dynamic oblateness cannot be larger than 2×10^?6.
3. The analysis of time behavior of residuals in the inner planet longitudes shows secular trends. It is demonstrated that these trends may be explained by combined action of a linear trenddT of Brouwer's time scale (which is adopted as a standard for reduction of observations before 1959) and the error in Newcomb's value of the constant of precession. From USNO meridian observations fordT the following estimate was obtained:dT=?14.5±2.1 sec/cy with the corresponding correction,dp, to Newcomb's precessiondp=0″.46±0″.13/cy. The estimate ofdT is in good agreement with the value ofdT determined from transits of Mercury and Venus through the solar diskdT=?12.9±1.3 sec/cy which does not depend on any precession error.
4. As a by-product, new accurate ephemerides of the outer planets are obtained over the time interval 1769–1988, the average residuals being presented.