The Catoca kimberlite pipe, Republic of Angola: A paleovolcanological model

The Catoca kimberlite pipe is among the world’s largest primary diamond deposits. The Catoca volcanic edifice is only slightly eroded. Kimberlitic rocks of various facies compose a crater of about 1 km in diameter and a diatreme. The structure of the pipe and mining conditions of the deposit are complicated by intense intrapipe tectonic processes related to large-amplitude subsidence. Based on geological data, we propose a structural model of the deposit and a paleovolcanological model of the Catoca pipe formed during a full cycle beginning with a stage of active volcanism and completed by stages of gradually waning volcanic activity and sedimentation. It is suggested that the banded tuffisitic kimberlite of the crater zone was deposited at the stage of active volcanic eruption from specific pyroclastic suspension as a low-viscosity mixture of crystals and aqueous sol rich in serpentine.     

On the Use of CloudSat and MODIS Data for Estimating Hurricane Intensity

This letter presents preliminary results concerning the use of new observations from the A-Train Constellation for testing a new technique of remotely sensing hurricane intensity from space based on modeling a hurricane as a balanced, convectively neutral vortex. The key observational requirements are simultaneous, accurate measurements of cloud-top height, cloudtop temperature, and cloud profiling information across the center of the storm, although there are ways to bypass the need for cloud-top temperature. In this letter, the Moderate Resolution Imaging Spectroradiometer onboard Aqua provides an estimation of the cloud-top temperature, and the near-simultaneous CloudSat observations provide the essential cloud-top height and cloud profiling information. Initial results indicate that the new technique is a promising method for estimating storm intensity when compared post facto to the best track database. Potential uncertainties and room for further refinement of the technique are discussed.     

Some properties of flows in unsaturated soils with an exponential dependence of the hydraulic conductivity upon the pressure head

A systematic development of the consequences of an exponential dependence of the hydraulic conductivity upon the pressure head is presented. Alternative expressions for the flux are discussed in detail. For steady flows, partial differential equations in terms of the matric flux potential, the pressure head, and the total head are derived. For steady, plane and axially symmetric flows, partial differential equations for the stream function are given. A theoretical basis for the construction of viscous flow analogs for steady, plane and axially symmetric flows is also presented.     

哈萨克斯坦共和国地震学数据库简介

建立哈萨克斯坦共和国地震学数据库是CASIN国际项目的一部分,应由中亚各国来共同完成。项目主要目的旨在建立地震学数据库,以作为今后减小哈萨克斯坦共和国地震危险性的工作基础。哈萨克斯坦共和国地震学数据库由下列子系统构成:1)文件输入子系统;2)信息检索和提交子系统;3)信息元数据存储子系统;4)档案库运行控制子系统;5)信息安全子系统。哈萨克斯坦共和国地震学数据库有以下功能:1)永久存储综合信息并上报和收集(记录)其他资料;2)存储数据和资料计算;3)电子文档的长期存储和管理;4)规定序号进行信息查询和文件的联机保证;5)信息统计和…     

Observations of polar patches generated by solar wind Alfvén wave coupling to the dayside magnetosphere

A long series of polar patches was observed by ionosondes and an all-sky imager during a disturbed period (K_p = 7- and IMF B_z <0). The ionosondes measured electron densities of up to 9 × 10¹¹ m⁻³ in the patch center, an increase above the density minimum between patches by a factor of ≈4.5. Bands of F-region irregularities generated at the equatorward edge of the patches were tracked by HF radars. The backscatter bands were swept northward and eastward across the polar cap in a fan-like formation as the afternoon convection cell expanded due to the IMF B_y > 0. Near the north magnetic pole, an all-sky imager observed the 630-nm emission patches of a distinctly band-like shape drifting northeastward to eastward. The 630-nm emission patches were associated with the density patches and backscatter bands. The patches originated in, or near, the cusp footprint where they were formed by convection bursts (flow channel events, FCEs) structuring the solar EUV-produced photoionization and the particle-produced auroral/cusp ionization by segmenting it into elongated patches. Just equatorward of the cusp footprint Pc5 field line resonances (FLRs) were observed by magnetometers, riometers and VHF/HF radars. The AC electric field associated with the FLRs resulted in a poleward-progressing zonal flow pattern and backscatter bands. The VHF radar Doppler spectra indicated the presence of steep electron density gradients which, through the gradient drift instability, can lead to the generation of the ionospheric irregularities found in patches. The FLRs and FCEs were associated with poleward-progressing DPY currents (Hall currents modulated by the IMF B_y) and riometer absorption enhancements. The temporal and spatial characteristics of the VHF backscatter and associated riometer absorptions closely resembled those of poleward moving auroral forms (PMAFs). In the solar wind, IMP 8 observed large amplitude Alfvén waves that were correlated with Pc5 pulsations observed by the ground magnetometers, riometers and radars. It is concluded that the FLRs and FCEs that produced patches were driven by solar wind Alfvén waves coupling to the dayside magnetosphere. During a period of southward IMF the dawn-dusk electric field associated with the Alfvén waves modulated the subsolar magnetic reconnection into pulses that resulted in convection flow bursts mapping to the ionospheric footprint of the cusp.     

Restrain of a seismically isolated bridge by external stoppers

The current design of seismically isolated bridges usually combines the use of bearings and stoppers, as a second line of defence. The stoppers allow the development of the in-service movements of the bridge deck, without transmitting significant loads to the piers and their foundations, while during earthquake they transmit the entire seismic action. Despite the fact that stoppers, which restrain the transverse seismic movements of the deck, are used frequently in seismically isolated bridges, the use of longitudinal stoppers is relatively rare, mainly due to the large in-service constraint movements of bridges. The present paper proposes a new type of external longitudinal stoppers, which are installed in stiff sub-structures-boundaries, aiming at limiting the bridge seismic movements. The parametric investigation, which was conducted in order to identify the seismic efficiency of the external stoppers, showed that the interaction of the bridge with the stiff boundaries can lead to significant reductions in the seismic movements of the bridge. Serviceability is appropriately arranged in the paper by expansion joints and approach slabs.     

A contribution to the theory of the equatorial noise generation in the Earth’s magnetosphere

This work is devoted to the study of the generation of the equatorial noise—electromagnetic emission below the LHR frequency observed near the equatorial plane of the magnetosphere at distances of ~4R_E. According to accepted views, the generation of the equatorial noise is related to the instability of ring current protons. In this work, a logarithmic distribution of energetic protons over the magnetic moment with an empty loss cone is proposed, and arguments for the formation of such a distribution are presented. The main result of the work is the calculation and analysis of the instability growth rate of waves forming the equatorial noise. The growth rate obtained in this work significantly differs from that encountered in the literature.     

Peculiarities of Water Circulation in the Southern Tatar Strait

Izvestiya, Atmospheric and Oceanic Physics - Satellite altimetry data have been used to study water circulation in the Tatar Strait region (the northern part of the Sea of Japan) for the time...     

Biogeochemical Modelling of a Seasonally Anoxic Lake: Calibration of Successive and Competitive Pathways and Processes in Lake Aydat,France

A reactive transport model was developed to describe seasonal variations of biogeochemical and physical processes in Lake Aydat. The model includes physical processes such as vertical mixing, sedimentation and advection related to inflows into the lake and biogeochemical conversion processes in the water column and in the sediment surface layer. The reactions described in the model include primary redox reactions such as primary production, aerobic and anaerobic respiration, methanogenesis and secondary reactions established between oxidants and reducers produced by the primary reactions. After adjusting various kinetic constants, the model reasonably reproduced the main features of seasonal variations of dissolved oxygen and nitrate depth profiles and pH. The reactive transport model was also used to quantify the relative importance of different biogeochemical pathways. For instance, ferrous denitrification seems to play an important role when stratification is increasing.