现今绝对板块运动

根据热点假设,热点对于中间层是固定的。相对热点的板块运动叫做绝对板块运动。绝对板块运动模型可以通过反演火山链传播的速率和走向数据以确定相对板块运动在角速度空间的原点来得到。利用一组近来（0～7．8Ma）全球分布的热点的迁移速率和走向数据,结合板块运动模型NNR—NUVELIA,已研制出一个叫做APM2的现今绝对板块运动模型。按照该模型,太平洋板块围绕60．063°S、102．210°E处的极以（0．8330°±0．0133°）／Ma的速率运动,非洲板块围绕46．849°N、44．372°W的极以（0．1015°±0．0134°）／Ma的速率运动,南极板块的运动则以46．871°N、146．942°E为极,速率为（0．0846°±0．0177°）／Ma,欧亚板块的运动更慢,极为27．291°N、171．925°W,速率为（0．0655°±0．0206°）／Ma。这一模型表明,岩石圈相对深部地幔有一个以49．423°S、90．625°E为极,速率为（0．1983°±0．0135°）／Ma的净旋转。表明太平洋热点同印度-大西洋热点不一致,显示太平洋热点的运动也不一致。为了分析和比较,还给出了仅用全球分布的热点的走向数据和仅用印度一大西洋热点的走向数据得到的板块绝对运动的角速度。     

Spectroscopy of Globular Clusters in the Spheroidal Dwarf Galaxy IKN

Astronomy Reports - Moderate resolution spectra of four globular clusters in the dwarf spheroidal galaxy IKN obtained with the 6-m telescope of the Special Astrophysical Observatory have been used...     

The Chemical Composition of Globular Clusters of Different Nature in Our Galaxy

A catalog of Galactic globular clusters has been compiled and used to analyze relations between the chemical and kinematic parameters of the clusters. The catalog contains positions, distances, luminosities, metallicites, and horizontal-branch morphology indices for 157 globular clusters, as well as space velocities for 72 globular clusters. For 69 globular clusters, these data are suppleented with the relative abundances of 28 chemical elements produced in various nuclear-synthesis processes, taken from 101 papers published between 1986 and 2018. The tendency for redder horizontal branches in lowmetallicity accreted globular clusters is discussed. The discrepancy between the criteria for cluster membership in the thick-disk and halo subsystems based on chemical and kinematic properties is considered. This is manifest through the fact that all metal-rich ([Fe/H] > ?1.0) clusters are located close to the center and plane of the Galaxy, regardless of their kinematic membership in particular Galaxy subsystems. An exception is three accreted clusters lost by a dwarf galaxy in Sagittarius. At the same time, the fraction of more distant clusters is high among metal-poorer clusters in any kinematically selected Galactic subsystem. In addition, all metal-rich clusters whose origins are related to the same protogalactic cloud are located in the [Fe/H]–[α/Fe] diagram considerably higher than the strip populated with field stars. All metal-poor clusters (most of them accreted) populate the entire width of the strip formed by high-velocity (i.e., presumably accreted) field stars. Stars of dwarf satellite galaxies (all of them being metal-poor) are located in this diagram much lower than accreted field stars. These facts suggest that all stellar objects in the accreted halo are remnants of galaxies with higher masses than those in the current environment of the Galaxy. Differences in the relative abundances of α-process elements among stellar objects of the Galaxy and surrounding dwarf satellite galaxies confirmthat the latter have left no appreciable stellar traces in the Galaxy, with the possible exception of the low-metallicity cluster Rup 106, which has low relative abundances of α-process elements.

     

Chemical Composition of Globular Clusters of Milky Way Subsystems from Gaia DR2 Data

Results of a study of the kinematic and chemical properties of globular clusters of the Milky Way based on data from the Gaia DR2 catalog and meaurements with the Hubble Space Telescope are presented. A new method for dividing globular clusters into Galatic subsystems based on the elements of their Galactic orbits is proposed. Samples of globular clusters belonging to the bar/bulge, thick disk, and halo of the Milky Way are obtained. The mean metallicities of the globular clusters in various subsystems are calculated. The mean metallicities of globular clusters of the thick disk and halo display statistically significant differences. At the same time, no statistically significant differences are present between the mean metallicities of halo globular clusters moving in the direction of rotation of the Galactic disk and those moving in the retrograde direction. This argues against the suggestion that retrograde and prograde globular clusters have different origins.

     

Galaxy Rotation Parameters from OB2 Stars with Proper Motions and Parallaxes from the Gaia EDR3 Catalog

Astronomy Reports - We have analyzed the kinematics of OB2 stars with proper motions and parallaxes selected by Xu et al. from the Gaia EDR3 catalog. The relative parallax errors for all the stars...     

Comparison of the Orbital Properties of the Milky Way Globular Clusters from the Data of the Gaia DR2 and EDR3 Catalogs

Astronomy Reports - We provide new values of the orbital parameters of 152 globular clusters, which are calculated using the new mean proper motions obtained from the Gaia EDR3 catalog data. The...     

Globular cluster subsystems in the galaxy

Data from the literature are used to construct a homogeneous catalog of fundamental astrophysical parameters for 145 globular clusters of the Milky Way Galaxy. The catalog is used to analyze the relationships between chemical composition, horizontal-branch morphology, spatial location, orbital elements, age, and other physical parameters of the clusters. The overall globular-cluster population is divided by a gap in the metallicity function at [Fe/H]=?1.0 into two discrete groups with well-defined maxima at [Fe/H]=?1.60±0.03 and ?0.60±0.04. The mean spatial-kinematic parameters and their dispersions change abruptly when the metallicity crosses this boundary. Metal-poor clusters occupy a more or less spherical region and are concentrated toward the Galactic center. Metal-rich clusters (the thick disk subsystem), which are far fewer in number, are concentrated toward both the Galactic center and the Galactic plane. This subsystem rotates with an average velocity of V _rot=165±28 km/s and has a very steep negative vertical metallicity gradient and a negligible radial gradient. It is, on average, the youngest group, and consists exclusively of clusters with extremely red horizontal branches. The population of spherical-subsystem clusters is also inhomogeneous and, in turn, breaks up into at least two groups according to horizontal-branch morphology. Clusters with extremely blue horizontal branches occupy a spherical volume of radius ～9 kpc, have high rotational velocities (V _rot=77±33 km/s), have substantial and equal negative radial and vertical metallicity gradients, and are, on average, the oldest group (the old-halo subsystem). The vast majority of clusters with intermediate-type horizontal branches occupy a more or less spherical volume ≈18 kpc in radius, which is slightly flattened perpendicular to the Z direction and makes an angle of ≈30° to the X-axis. On average, this population is somewhat younger than the old-halo clusters (the young-halo subsystem), and exhibits approximately the same metallicity gradients as the old halo. As a result, since their Galactocentric distance and distance from the Galactic plane are the same, the young-halo clusters have metallicities that are, on average, Δ[Fe/H] ≈0.3 higher than those for old-halo clusters. The young-halo subsystem, which apparently consists of objects captured by the Galaxy at various times, contains many clusters with retrograde orbits, so that its rotational velocity is low and has large errors, V _rot=?23±54 km/s. Typical parameters are derived for all the subsystems, and the mean characteristics of their member globular clusters are determined. The thick disk has a different nature than both the old and young halos. A scenario for Galactic evolution is proposed based on the assumption that only the thick-disk and old-halo subsystems are genetically associated with the Galaxy. The age distributions of these two subsystems do not overlap. It is argued that heavy-element enrichment and the collapse of the proto-Galactic medium occurred mainly in the period between the formation of the old-halo and thick-disk subsystems.     

球状晶质铀矿形成条件的模拟实验

球状晶质铀矿是我国主要的工业铀矿物之一,也是核工业的主要原料之一。因此研究球状晶质铀矿的形成条件、成矿机制有着重要意义。球状晶质铀矿的水热合成是进行上述研究的重要手段。人们已从不同的角度进行了大量实验,实验的数据曾为解决铀成矿     

The Stellar Population and Orbit of the Galactic Globular Cluster Palomar 3

Deep stellar photometry of one of the most distant Galactic globular clusters, Palomar 3, based on frames taken with the VLT in Johnson–Cousins broadband V and I filters is presented, together with medium-resolution stellar spectroscopy in the central region of the cluster obtained with the CARELEC spectrograph of the Observatoire de Haute Provence and measurements of the Lick spectral indices for the integrated spectrum. Computations of the orbital parameters of Palomar 3 and nine Galactic globular clusters with similar metallicities and ages are also presented. The orbital parameters, age, metallicity, and distance of Palomar 3 are estimated. The interstellar absorption is consistent with and supplements values fromthe literature. The need to obtainmore accurate data on the propermotions, ages, and chemical compositions of the cluster stars to elucidate the origin of this globular cluster is emphasized.     

Kinematics of the Eastern Mediterranean region and the WEGENER-MEDLAS project

The Eastern Mediterranean is a region of complex kinematic behaviour resulting from the collision of the African/Arabian and Eurasian plates. Neither the geodynamic processes nor the kinematic quantities involved in the deformations taking place are well understood and they are subject to several alternative interpretations. Different solutions presented in the literature are discussed as an introduction to the WEGENER-MEDLAS Project, by means of which geodetic data will be introduced in an attempt to help resolve the current pattern of kinematic changes. The manner of field observation and data reduction are discussed along with the practical experience obtained to date and a summary of the first years's field experience and the estimated accuracies of baseline results are presented.Mitteilung aus dem Institut für Angewandte Geodäsie, 6000 Frankfurt 70, FR Germany     

Kinematics of shear bands

Shear bands appear at limit states of soil bodies. They are analysed as thin zones of localised deformation that takes place as simple (i.e. dilatant) shear. It can be observed, however, that shear bands are discontinuous and also may be “reflected” at rigid boundaries. These phenomena appear as incompatible with the assumed shear deformation. The analysis in this paper reveals the kinematics of such “incompatibilities” in terms of continuous deformation fields.     

Kinematics of fault-bend folding

The concept of bed-duplication folding, a process of folding by stacking of duplicate beds above a thrust ramp, was introduced by John L. Rich in 1934, and such folding has been studied mechanically and geometrically during the last few years.

This paper introduces two kinematical models to bridge between geometrical and mechanical analyses, so results of the two methods of determining the deformations and geometry of bed-duplication folding can be compared. One kinematical model is required for early stages and the other for late stages of bed-duplication folding, but each involves a simple, domainal, velocity distribution. It is remarkable that such simple kinematical models can produce complex geometrical models. The kinematical models clearly produce the type of bed-duplication fold developed by graphical construction and termed “fault-bend fold”. The kinematical models provide new insights into the essence of the type.

The velocity distributions assumed in the kinematical models are similar to those predicted by a first-order, mechanical model for thrust ramps with low slopes (less than about 20 degrees) and zero drag. The fold forms computed from the two sets of models are also similar, so geometrical construction roughly reproduces a simple, low-amplitude bed-duplication fold.

The approximation is poorer for steeper thrust ramps. The upper limit of the kinematical fold. and geometrical construction is 30 degrees and, at that ramp angle, the dip of the distal limb of the fold is twice the dip of the thrust ramp. Results of the mechanical analysis of relatively steep ramps, carried to second-order accuracy, indicate that the 30-degree limit of the ramp angle is an artifact of the geometrical analysis and that the block being thrusted is subjected to general simple shearing. The simple shear is absent in the kinematical models and the geometrical construction. Nevertheless, both the kinematical and mechanical models predict asymmetry of fold limbs.     

Dynamics of the Formation of Globular Silica Particles according to Dynamic Light Scattering

For the first time, the dynamics of the origination and growth of monodispersion spherical silica particles is studied by dynamic light scattering in the real-time mode. Experimental changes in the particle size and intensity of scattering during their formation and growth indicate the hierarchical formation of silica globules under various mechanisms of aggregation of particles.     

Kinematics of the Gondwana basins of peninsular India

The Gondwana successions (1–4 km thick) of peninsular India accumulated in a number of discrete basins during Permo-Triassic period. The basins are typically bounded by faults that developed along Precambrian lineaments during deposition, as well as affected by intrabasinal faults indicating fault-controlled synsedimentary subsidence. The patterns of the intrabasinal faults and their relationships with the respective basin-bounding faults represent both extensional and strike-slip regimes. Field evidence suggests that preferential subsidence in locales of differently oriented discontinuities in the Precambrian basement led to development of Gondwana basins with varying, but mutually compatible, kinematics during a bulk motion, grossly along the present-day E–W direction. The kinematic disparity of the individual basins resulted due to different relative orientations of the basement discontinuities and is illustrated with the help of a simple sandbox model. The regional E–W motion was accommodated by strike-slip motion on the transcontinental fault in the north.     

Erratum to: Globular Cluster as Indicators of Galactic Evolution

Astronomy Reports - An Erratum to this paper has been published: https://doi.org/10.1134/S1063772922330010     

Testing the Response of Mycenaean Terracotta Figures and Vessels to Earthquake Ground Motions

In the late 1970s, the hypothesis originated that earthquakes played a decisive role in the decline of the Mycenaean civilization at the end of the Late Bronze Age. The late excavator of Tiryns in the Argolid/Greece, Klaus Kilian, presented evidence for earthquake‐related damage to Mycenaean structures and considered four terracotta figures and two ceramic vessels lying on a floor of a potential cult room (later 12th century B.C.) in the Lower Citadel as “earthquake victims.” The broken figures were confined to a small area on the cult room's floor in front of a bench. We assess the archaeological data and test the plausibility of earthquake‐induced toppling of the objects with engineering seismological models. Dimensions and physical properties of the models were taken from the originals. In our simulations the models are virtually placed on a bench, and are exposed to earthquake ground motions based on records from recent Greek earthquakes. We test the artifacts’ toppling behavior and compare the final position of the fallen objects with the original find spots. Statistical analysis of 74,250 model calculations with highly varied ground motion parameters and bench heights reveal only a small probability that the find situation of the objects was caused by an earthquake.     

Motions and oscillations in a filament preceding its eruption

The Doppler motions in a filament and the underlying photosphere over the several days before its eruption are analyzed. A large filament in the northern hemisphere near the central meridian observed from August 31-September 2, 2014 erupted on September 2, 2014. The filament lost the bulk of its mass as a result of its eruption, and the process of its reconstruction had begun a day later. Observations of this filament in a spectral range encompassing the Hβ λ 486.1 nm (chromospheric) and Fe I λ 485.9 nm (photospheric) lines were carried out on the Horizontal Solar Telescope of the Sayan Solar Observatory on August 31-September 2, 2014. Analysis of the Doppler motions in and beneath the filament yielded the following results. Strong rotational motions were present in the filament over a prolonged period (the entire three days of observations). The coincidence of the steady-state motions of the photosphere and filament was disrupted at the moment of destabilization of the filament by the emergence of new magnetic flux. Short-period (about five-minute) photospheric oscillationswith a train-like character arose in filament from time to time several hours before the eruption. Large segments underwent nearly vertical oscillations in the initial phase of the ascent of the filament.