Exchange and correlation interactions in electron-positron plasma

The effect of particle-particle interaction on the adiabatic index γ for an electron-positron plasma is considered. An improved method for numerically calculating the Hartree-Fock exchange integral is presented and its relativistic asymptotics is determined. An approximation formula is derived for the correlation part of the interaction in the low-density limit. This formula includes degeneracy and the positron component.     

Statistics of the individual-pulse polarization based on propagation effects in the pulsar magnetosphere

Pulsar radio emission is modelled as a sum of two completely polarized non-orthogonal modes with the randomly varying Stokes parameters and intensity ratio. The modes are the result of polarization evolution of the original natural waves in the hot, magnetized, weakly inhomogeneous plasma of the pulsar magnetosphere. In the course of the wavemode coupling, the linearly polarized natural waves acquire purely orthogonal elliptical polarizations. Further on, as the waves pass through the cyclotron resonance, they become non-orthogonal. The pulse-to-pulse fluctuations of the final polarization characteristics and the intensity ratio of the modes are attributed to the temporal fluctuations in the plasma flow.
The model suggested allows one to reproduce the basic features of the one-dimensional distributions of the individual-pulse polarization characteristics. Besides that, the propagation origin of the pulsar polarization implies a certain correlation between the mode ellipticity and position angle. On a qualitative level, for different sets of parameters, the expected correlations appear compatible with the observed ones. Further theoretical studies are necessary to establish the quantitative correspondence of the model to the observational results and to develop a technique of diagnostics of the pulsar plasma on this basis.     

Fast neutral particles as probes of the extent of Io's exosphere

The spatial extent of ion cyclotron waves at Io has been interpreted as requiring a multistep acceleration and transport process: exospheric ions are accelerated outward (relative to Jupiter) due to the corotation electric field, neutralized due to charge exchange in the surrounding exosphere, and then reionized after traveling far across magnetic field lines, at which point they generate the waves. The trajectories of the particles away from Io are sensitive to the location of their initial ionization. This paper examines the spatial distributions of fast neutrals produced under varying conditions in order to provide constraints on the possible structure and nature of the Io exosphere. While a rapid onset of cyclotron waves at a specific location around Io can be modeled with a single, point-source region of ions, such as might occur over a volcano, the regional extent of the waves suggests multiple or distributed sources.     

Crustal and upper mantle structures of the brazilian coast

The Rayleigh wave phase and group velocities in the period range of 24–39 sec, obtained from two earthquakes which occurred in northeastern brazil and which were recorded by the Brazilian seismological station RDJ (Rio de Janeiro), have been used to study crustal and upper mantle structures of the Brazilian coastal region. Three crustal and upper mantle models have been tried out to explain crustal and upper mantle structures of the region. The upper crust has not been resolved, due basically to the narrow period range of the phase and group velocities data. The phase velocity inversions have exhibited good resolutions for both lower crust and upper mantle, with shear wave velocities characteristic of these regions. The group velocity data inversions for these models have showed good results only for the lower crust. The shear wave velocities of the lower crust (3.86 and 3.89 km/sec), obtained with phase velocity inversions, are similar to that (=3.89 km/sec) found byHwang (1985) to the eastern South American region, while group velocity inversions have presented shear velocity (=3.75 km/sec) similar to that (=3.78 km/sec) found byLazcano (1972) to the Brazilian shield. It was not possible to define sharply the crust-mantle transition, but an analysis of the phase and group velocity inversions results has indicated that the total thickness of the crust should be between 30 and 39 km. The crustal and upper mantle model, obtained with phase velocity inversion, can be used as a preliminary model for the Brazilian coast.     

Design of shallow foundations under tensile loading for transmission line towers: An overview

Tensioned foundations are common in civil engineering applications such as transmission towers, harbors, offshore structures, basement slabs under pressure, industrial equipment, etc. Procedures for the design of tensioned foundations are discussed in this paper, including specific recommendations for more common transmission tower foundations. Starting from a distinction between shallow and deep modes of failure, the paper presents the most common failure mechanisms for shallow failure in tension, including procedures for calculation of foundation tensile capacity under vertical and inclined loading. Emphasis is given to the influence of the strength of the compacted backfill compared to the strength of the natural soil, including presentation of results of full-scale loading tests.     

Phaeocystis globosa与Phaeocystis antarctica叶绿体psbA基因的比较

测定了2株球形棕囊藻Phaeocystis globosa P1、P2的psbA基因序列。发现得到的2个序列完全相同。以P2序列对比分析了P．globosa和P．antarctica的psbA基因在DNA序列、氮基酸序列和RNA二级结构上的差异性，发现2种棕囊藻psbA基因DNA序列和氨基酸序列非常保守，无插入／缺失，其核苷酸和氨基酸变异率分别为1．88％和1．13％。与核基因核苷酸的碱基替换不同，psbA基因核苷酸的碱基替换主要发生在密码子的第1位上。且不引起氨基酸的变化，引起氨基酸变化的碱基替换都发生在密码子的第2位和第3位上。在RNA二级结构上两序列的1～4茎环结构完全相同，表现出明显的棕囊藻属的特异性，其它结构区域差异较大。种间差异表现明显。由于psbA基因DNA序列和氨基酸序列非常保守，可能不适宜棕囊藻属的系统发育分析。但其RNA二级结构可能对于棕囊藻的分子分类有一定的参考价值。     

Internal generation of waves: Delta source function method and source term addition method

In this study, we investigate two internal wave generation methods in numerical modeling of time-dependent equations for water wave propagation, i.e., delta source function method and source term addition method, the latter of which has been called the line source method in literatures. We derive delta source functions for the Boussinesq-type equations and extended mild-slope equations. By applying the fractional step splitting method, we show that the delta source function method is equivalent to the source term addition method employing the energy velocity. This suggests that the energy velocity should be used rather than the phase velocity for the transport of incident wave energy in the source term addition method. Finally, the performance of the delta source function method is verified by accurately generating nonlinear cnoidal waves as well as linear waves for horizontally one-dimensional cases.