Spatial orientation of the spin vectors of the disk galaxies in the Virgo cluster I. A catalogue of the disk galaxies in the Virgo cluster

Based on four UK Schmidt Telescope (UKST) IIIa-j direct plates which had been digitized by the Automated Plate Measuring System (APM), a detailed identification of the disk galaxies in the Virgo cluster has been carried out. The certain and possible member galaxies are mainly selected from the updated Catalogue of 2096 Galaxies in the Virgo Cluster Area (VCC). The area of this identification covers a 85 square degree region centered on this cluster. As a result, we compiled a new catalogue of 340 certain and possible member disk galaxies, including 85 lenticulars (SO), 136 spirals (S) and 119 irregulars (Irr), where the APM-measured values of the position angle (P.A.) and diameters of 299 disk galaxies are provided. For at least 149 galaxies, the values of the P.A. and diameters are published for the first time.Comparison between the APM-measured P.A. and diameters of galaxies and those given by the Uppsala General Catalog of Galaxies (UGC) demonstrates the reliability of our data. The statistical properties and completeness of this database are also discussed. Compared with the UGC-given P.A. and diameters which were determined by eyes, our data has no selection effect owing to the instrument measurements. Within our searching region, this might be the largest and relatively complete photometric database published so far for investigating the spatial orientation of the spin vectors of galaxies in the Virgo cluster.     

POPULATION EXPANSION IN CHINA''''S METROPOLISES AND ITS SCALE-CONTROL

Metropolises are centers of politics, economy, culture and information, and also economic growth poles in comparatively large areas. After 1949, China's urban structure have changed greatly, from original "pyramid" shape into "upside -down pyramid" shape, that is, more megalopolises and metropolises, fewer medium-sized and small cities. The most distinguishing feature of urban population growth was the remarkable increase of population in megalopolises and metropolises. The key reason for urban population expansion is to want to obtain the benefits of scale -agglomeration economy of metropolises. The number of urban functions directly determines the quality and quantity of urban population. Metropolises appeal not only agricultural population but also the population of medium-sized and small cities, which put much more population pressure on metropolises. The ideal goals of scale-control of metropolitan population are discussed in terms of economy, society and ecollogy. In order to control the metropoli     

Objective prism survey of qsos in the field centered at 10h40m + 00°00′

QSO objective prism survey was done for the field centered at 10^h40^m + 00°00. For the 348 objects selected, we present in this paper their positions,B _J magnitudes, spectra, and finding charts. Based on the sample containing 163 QSO candidates with higher reliabilities (F 3), the surface density of QSO candidates withB _J 20 is estimated to be about 4.5 per square degree.Work based on UKST plates.     

船式支护在基坑中的应用

在深厚软土地区的基坑,对基坑底软土进行搅拌加固形成强度较高的底板而保证坑底稳定,侧壁采用支护桩支护保证侧壁的稳定使其不倾倒,支护桩与加固底板两者共同作用形成的船状结构支护体系类似轮船的船侧壁及船底板,以保证基坑的稳定。结合具体的工程实例,介绍了船式支护的侧壁及底板的设计方法。工程案例成功实施,监测结果表明,船式支护既可避免支护桩嵌固深度过长,又利于软土的土方施工及工程桩的保护,是安全可靠的,对类似工程有一定的参考意义。     

Slip-weakening constitutive relation and the structure in the vicinity of a shear crack tip

Shear-crack model with a cohesive zone (or breakdown zone) is appropriate for the analysis of a fault surface in which slip distribution is strongly nonuniform. As the slipped portion advances, slip-weakening occurs over the so-called cohesive zone, a distance behind the fault tip. For a prescribed strength vs. displacement constitutive relation, however, the zone structure is difficult to determine by an analytical method except for some simple cases, thus it often requires a certain numerical procedure. This work proposes a numerical procedure to obtain approximated solutions of the problem by combining a series of elastic solutions derived bySmith (1974). The series is linearly combined and the unknown coefficients are determined by a nonlinear least square method. This method can fit a wide range of prescribed strength vs. displacement relations which may be simple algebraic relations or curves obtained by laboratory tests. By examining the residual errors and in comparison with a derived result in which linear stress is assumed within the zone, it could be concluded that the results provide good accuracy. Moreover, because the results are written in formulae, they can be easily referred to or used. By fitting constitutive curves in many different shapes, it is found that the stress distribution within the zone is more sensitive to the constitutive curve shape than the displacement. The most interesting fact is that the zone size is not sensitive to the curve shape, i.e., the zone size can be estimated by $$R = 3\mu \zeta \upsilon _c /\{ 2(1 - \upsilon )(\tau _c - \tau _f )\}$$ with ζ=1±0.11 for most cases.     

Strength and stability of frictional sliding of gabbro gouge at elevated temperatures

To investigate the strength of frictional sliding and stability of mafic lower crust, we conducted experiments on oven-dried gabbro gouge of 1 mm thick sandwiched between country rock pieces (with gouge inclined 35° to the sample axis) at slip rates of 1.22 × 10^− 3 mm/s and 1.22 × 10^− 4 mm/s and elevated temperatures up to 615 °C. Special attention has been paid to whether transition from velocity weakening to velocity strengthening occurs due to the elevation of temperature.Two series of experiments were conducted with normal stresses of 200 MPa and 300 MPa, respectively. For both normal stresses, the friction strengths are comparable at least up to 510 °C, with no significant weakening effect of increasing temperature. Comparison of our results with Byerlee's rule on a strike slip fault with a specific temperature profile in the Zhangbei region of North China shows that the strength given by experiments are around that given by Byerlee's rule and a little greater in the high temperature range.At 200 MPa normal stress, the steady-state rate dependence a − b shows only positive values, probably still in the “run-in” process where velocity strengthening is a common feature. With a normal stress of 300 MPa, the values of steady-state rate dependence decreases systematically with increasing temperature, and stick-slip occurred at 615 °C. Considering the limited displacement, limited normal stress applied and the effect of normal stress for the temperatures above 420 °C, it is inferred here that velocity weakening may be the typical behaviour at higher normal stress for temperature above 420 °C and at least up to 615 °C, which covers most of the temperature range in the lower crust of geologically stable continental interior. For a dry mafic lower crust in cool continental interiors where frictional sliding prevails over plastic flow, unstable slip nucleation may occur to generate earthquakes.     

Structural similarity and variety at the tips in a wide range of strike–slip faults: a review

Strike–slip faults are often accompanied by a variety of structures, particularly at their tips. The zones of additional fracturing are classified as tip‐damage zones. These zones can be subdivided into several different damage patterns based on the nature and orientation of faults and fractures developed. Damage zones at the ends of small strike–slip faults (mode II tips) develop wing cracks, horsetail splays, antithetic faults, synthetic branch faults and solution surfaces. Similar tip‐damage patterns are also commonly observed at larger (regional) scales, but with a dominance of faulting over tensile cracks and solution surfaces. Wing cracks and horsetail splays developed at small‐scale faults are replaced by normal faults in large‐scale faults. Antithetic faults and synthetic branch faults are observed at small and large scales. Thrust faults are developed at large scales, in a similar pattern to solution surfaces at a small scale. All these structures may show slightly different angular relationships to the master fault at small and large scale, but develop in response similar stress distribution and mechanics around the fault. Thus, mode II tip‐damage zones show similar patterns over a wide range of fault scales.     

Food Deserts in the Prairies? Supermarket Accessibility and Neighborhood Need in Edmonton,Canada*

The U.S. and U.K. literatures have discussed “food deserts,” reflecting populated, typically urban, low‐income areas with limited access to full‐service supermarkets. Less is known about supermarket accessibility within Canadian cities. This article uses the minimum distance and coverage methods to determine supermarket accessibility within the city of Edmonton, Canada, with a focus on high‐need and inner‐city neighborhoods. The results show that for 1999 both of these areas generally had higher accessibility than the remainder of the city, but six high‐need neighborhoods had poor supermarket accessibility. We conclude by examining potential reasons for differences in supermarket accessibility between Canadian, U.S., and U.K. cities.     

Dissolved trace elements in river water: spatial distribution and the influencing factor, a study for the Pearl River Delta Economic Zone, China

Twenty-nine water samples were collected from different river channels of the Pearl River Delta Economic Zone, China. An inductively coupled plasma-mass spectromonitor (ICP-MS) was used to measure concentrations of the trace elements in these samples. The results suggest that the average concentrations of rare earth elements in river water show an increasing trend from the West River, the North River, the rivers of the Pearl River Delta, and the Shenzhen River to the East River. Relatively high concentrations of heavy metals appear in the East River, the rivers of the Pearl River Delta and the Shenzhen River, while the West River and the North River have relatively low heavy metal concentrations. Trace element concentrations in samples collected near urban or industrial areas are much higher than those of samples collected from distant areas, away from urban and industrial areas. After natural conditions, human activities have significant influence on the trace element concentrations in river water. This trace element concentration’s spatial distribution in the river water from the Pearl River Delta Economic Zone is actually an integrated effect of natural conditions and human activity.