Tidal evolution in close binary systems,III

In this paper we shall investigate the energy of close binary systems of constant momentum takng into consideration the first-order effects of rotation and tidal attraction of the components of finite size. The equations for the momentum and the energy of the system will be set up in Section 2, making use of terms including the effects of finite size of the components of finite degree of central condensation. In Section 3 perturbation theory is applied to these equations using the results of Kopal (1972b) as our initial values. In Section 4 we shall compare our results with the initial values and then discuss variations in our constants and the application to various real systems.     

Suprathermal oxygen and hydrogen atoms in the upper Martian atmosphere

The processes of kinetics and transport of hot oxygen and hydrogen atoms in the transition (from the thermosphere to the exosphere) region of the upper Martian atmosphere are studied. The reaction of dissociative recombination of the principal ionospheric ion O ₂ ⁺ with thermal electrons in the ionosphere of Mars served as the source of hot oxygen atoms. The process of momentum and energy transfer in elastic collisions between hot oxygen atoms and atmospheric hydrogen atoms with thermal energies was regarded as the source of hot hydrogen atoms. The kinetic energy distribution functions are determined for suprathermal oxygen and hydrogen atoms. It is shown that the exosphere is populated with a significant number of suprathermal oxygen atoms with kinetic energies ranging up to the escape energy of 2 eV (i.e., the hot oxygen Martian corona is formed). The transfer of energy from hot oxygen atoms to thermal hydrogen atoms creates an additional nonthermal flux of atomic hydrogen escaping from the Martian atmosphere.     

Growth of multilayered polycrystalline reaction rims in the MgO–SiO<Subscript>2</Subscript> system,part II: modelling

Part I of this contribution (Gardés et al. in Contrib Mineral Petrol, 2010) reported time- and temperature-dependent experimental growth of polycrystalline forsterite-enstatite double layers between single crystals of periclase and quartz, and enstatite single layers between forsterite and quartz. Both double and single layers displayed growth rates decreasing with time and pronounced grain coarsening. Here, a model is presented for the growth of the layers that couples grain boundary diffusion and grain coarsening to interpret the drop of the growth rates. It results that the growth of the layers is such that (Δx)² ∝ t ^1−1/n , where Δx is the layer thickness and n the grain coarsening exponent, as experimentally observed. It is shown that component transport occurs mainly by grain boundary diffusion and that the contribution of volume diffusion is negligible. Assuming a value of 1 nm for the effective grain boundary width, the following Arrhenius laws for MgO grain boundary diffusion are derived: log D _gb,0^Fo (m²/s) = −2.71 ± 1.03 and E _gb^Fo = 329 ± 30 kJ/mol in forsterite and log D _gb,0^En (m²/s) = 0.13 ± 1.31 and E _gb^En = 417 ± 38 kJ/mol in enstatite. The different activation energies are responsible for the changes in the enstatite/forsterite thickness ratio with varying temperature. We show that significant biases are introduced if grain boundary diffusion-controlled rim growth is modelled assuming constant bulk diffusivities so that differences in activation energies of more than 100 kJ/mol may arise. It is thus important to consider grain coarsening when modelling layered reaction zones because they are usually polycrystalline and controlled by grain boundary transport.     

Deposition of finely disseminated gold mineralization in black shales: A hypothesis of microstructural control

The deposition of finely disseminated gold in the deposits hosted in black shales is considered. It is suggested that gold deposition is controlled by microstructure of pore space in host rocks. The pore space structure of tight shales indicates that most pore volume is occupied by nanopores with hundredths of micrometers in characteristic dimension. The balance calculations show that deposition of native gold in nanopore channels of filtration is hampered by shortage of number of atoms necessary to overcome a nucleation threshold of the future gold crystal in the pore volume. When ore-transporting solution meets on its way the cavities (pores, micro- and macrofractures), whose volume is sufficient to overcome the nucleation threshold, the excess content of ore component, which exceeds equilibrium concentration, is released with formation of crystallization centers and further precipitation of gold. The conditions of ore deposition are exemplified in the reference Sukhoi Log deposit hosted in black shales. On the basis on the PT conditions of ore deposition and physical features of fluid heat and mass transfer, it is suggested that ore disseminations were deposited at the early high-temperature stage under a fluid pressure close to lithostatic and at a host rock permeability markedly exceeding its present-day value.     

The fluvial and pyroclastic deposits of the Cagayan Basin, Northern Luzon, Philippines—an example of non-marine volcaniclastic sedimentation in an interarc basin

ABSTRACT The Cagayan basin of Northern Luzon, an interarc basin 250 km long and 80 km wide, contains a 900 m thick sequence of Plio-Pleistocene fluvial and pyroclastic deposits. These deposits are divided into two formations, the Ilagan and Awidon Mesa, and three lithofacies associations. The facies, which are interpreted as meandering stream, braided stream, lahar, and pyroclastic flow and fall deposits, occur in a coarsening upward sequence. Meandering stream deposits interbedded with tuffs are overlain by braided stream deposits interbedded with coarser pyroclastic deposits; lahars and ignimbrites. The coarsening upward volcaniclastic deposits reflect the tectonic and volcanic evolution of the adjacent Cordillera Central volcanic arc. Uplift of the arc resulted in the progradation of coarser clastics further into the basin, the development of an alluvial fan, and migration of the basin depocentre away from the arc. The coarsening of the pyroclastic deposits reflects the development of a more proximal calc-alkaline volcanic belt in the maturing volcanic arc. The Cagayan basin sediments serve as an example of the type and sequence of non marine volcaniclastic sediments that may form in other interarc basins. This is because the tectonic and volcanic processes which controlled sedimentation in the Cagayan basin also affect other arc systems and will therefore control or significantly influence volcaniclastic sedimentation in other interarc basins.     

Algorithm of Calculation of Lyapounov Coefficients for Analysis of Chemical Autooscillations, as Applied to Calcite Crystallization Model

The numerical algorithm of calculation of Lyapounov coefficients (L _k) of any order is developed. The apparatus of analytical calculations is not used in this algorithm. The proposed algorithm is of use for usual computer languages and allows us to find the numerical value of L _k for any k and to make complete qualitative analyses of dynamic models on the plane.     

震后快速钻探:历史、现状与未来

大地震发生后立即在断层带上进行钻探可以帮助我们获取更多的地震信息,尤其是可获得决定断层动态破裂的摩擦水平和强度,观测断层的愈合过程及可能触发余震的应力变化,并可获取控制破裂过程的重要的物理和化学属性。在2008年11月由国际大陆科学钻探项目（ICDP）和南加州地震中心（SCEC）联合在日本东京举办的为期3天的“震后快速钻探：历史、现状与未来”研讨会上,     

Analyse des Standards de L'U.S.G.S. : GXR-1 a GXR-6 par Activation Neutronique et Fluorescence X

Six roches standards de I'USGS : GXR-1 à GXR-6 ont été analysées par activation neutronique instrumentale (INAA) pour le dosage de 17 éléments traces et par fluorescence X (XRF) pour les autres éléments difficiles à doser par activation neutronique. Les travaux précédemment publiés par Gladney et al. ont été pris comme référence en particulier les valeurs recommandées (R.V.) qui sont généralement en bon accord avec nos résultats. Quelques remarques et corrections sont proposées pour expliquer certaines disparités.
Six United States Geological Survey's (USGS) Geochemical Exploration References Samples (GXR) have been analyzed by instrumental neutron activation analysis (INAA) for the determination of seventeen trace elements and by X-ray fluorescence spectrometry (XRFS) for other trace elements difficult to determine by INAA. Our results compare favourably with the values recommended by E.S. Gladney et al. Some suggestions and corrections are proposed to explain some discrepancies.     

Application of remote sensing technology for Impact Assessment of Watershed Development Programme

The current study was taken up to investigate the utility of remote sensing and GIS tools for evaluation of Integrated Wasteland Development Programme (IWDP) implemented during 1997–2001 in Katangidda Nala watershed, Chincholi taluk, Gulbarga district, Karnataka. The study was carried out using IRS 1C, LISS III data of December 11, 1997 (pre-treatment) and November 15, 2002 (post-treatment) covering the watershed to assess the changes in land use / land cover and biomass that have changed over a period of five years (1997–2002). The images were classified into different land use/land cover categories using supervised classification by maximum likelihood algorithm. They were also classified into different biomass levels using Normalized Difference Vegetation Index (NDVI) approach. The results indicated that the area under agriculture crops and forest land were increased by 671 ha (5.7%) and 1,414 ha (11.94%) respectively. This is due to the fact that parts of wastelands and fallow lands were brought into cultivation. This increase in the area may be attributed to better utilization of surface and ground waters, adoption of soil and water conservation practices and changes in cropping pattern. The area under waste lands and fallow lands decreased by 1,667 ha (14.07%) and 467 ha (3.94%), respectively. The vegetation vigour of the area was classified into three classes using NDVI. Substantial increase in the area under high and low biomass levels was observed (502 ha and 19 ha respectively). The benefit-cost analysis indicates that the use of remote sensing and GIS was 2.2 times cheaper than the conventional methods. Thus, the repetitive coverage of the satellite data provides an excellent opportunity to monitor the land resources and evaluate the land cover changes through comparison of images for the watershed at different periods.