黄海冷水团演变过程及其与邻近水团关系的分析

黄海冷水团是出现在黄海的一种独特的水文现象.文中利用覆盖整个黄海的GDEM三维水温资料,结合近期一些大型调查所获得的有关观测研究结果,首先较系统地分析了黄海冷水团的形成和演变过程,并对冷水团3个冷中心的季节演变提出了一些与前不同的认识.同时,通过对黄海冷水团形成、发展和消亡与该海域温跃层演变关系的分析,进一步揭示了黄海冷水团演变的机理.然后,探讨了黄海冷水团演变过程中与青岛和仁川东南海域冷水团以及东海北部底层冷水的关系.分析表明,在黄海冷水团发展的鼎盛时期,青岛冷水团和仁川东南海域冷水团以及东海北部底层冷水皆包络其中.     

Mantle flow patterns at the Neyriz Paleo-spreading center, Iran

The mantle peridotites of Neyriz record two successive episodes of plastic deformations; the first one related to the igneous accretion of the lithosphere and the second one developed during the first stage of the emplacement of the peridotites. These two events have been distinguished on the basis of microstructural criteria. The diapiric pattern, particularly relevant to the mantle process beneath spreading ridges, features vertical flow lines and elliptic flow plane trajectories in a pipe and extends along the ridge axis about 5 km. These structures rotate to horizontal and diverge in every direction in a narrow transition zone, a few hundred meters thick, below the Moho discontinuity. Such a diapiric pattern has been recognized in a few places along the Neyriz paleo-ridge. A large amount of magma passed through these mantle diapirs that were probably the main zones feeding the overlying magma chamber. The most common pattern features very regular structures over several kilometers along the strike of the paleo-ridge: the flow plane dips away from the ridge axis, and the flow line is parallel to the spreading direction. This flow pattern is frozen during the gradual accretion of the lithospheric mantle away from the ridge in a steady-state spreading regime. A shear-sense inversion at just below the Moho is commonly observed, pointing to forced asthenospheric flow. The reconstructed orientation of the Neyriz paleo-spreading center is 105°, compatible with the geometry and orientation of harzburgite foliations and lineations and sheeted dikes.     

A rifted inside corner massif on the Mid-Atlantic Ridge at 5°S

The structure of the Mid-Atlantic Ridge at 5°S was investigated during a recent cruise with the FS Meteor. A major dextral transform fault (hereafter the 5°S FZ) offsets the ridge left-laterally by 80 km. Just south of the transform and to the west of the median valley, the inside corner (IC – the region bounded by the ridge and the active transform) is marked by a major massif, characterized by a corrugated upper surface. Fossil IC massifs can also be identified further to the west. Unusually, a massif almost as high as the IC massif also characterizes the outside corner (OC) south of the inactive fracture zone and to the east of the median valley. This OC massif has axis-parallel dimensions identical to the IC massif and both are bounded on their sides closest to the spreading axis by abrupt, steep slopes. An axial volcanic ridge is well developed in the median valley both south of the IC/OC massifs and in an abandoned rift valley to the east of the OC massif, but is absent along the new ridge-axis segment between the IC and OC massifs. Wide-angle seismic data show that between the massifs, the crust of the median valley thins markedly towards the FZ. These observations are consistent with the formation of the OC massif by the rifting of an IC core complex and the development of a new spreading centre between the IC and OC massifs. The split IC massif presents an opportunity to study the internal structure of the footwall of a detachment fault, from the corrugated fault surface to deeper beneath the fault, without recourse to drilling. Preliminary dredging recovered gabbros from the scarp slope of the rifted IC massif, and serpentinites and gabbros from the intersection of this scarp with the corrugated surface. This is compatible with a concentration of serpentinites along the detachment surface, even where the massif internally is largely plutonic in nature.     

Interpretation of charging on fracture or frictional slip surface of rocks

Fracturing and frictional sliding of quartz and granite under dry condition generates fractoluminescence, charged particle emission and electromagnetic radiation. Various kinds of experiments indicate that surface charge density on fracture or frictional slip surface of quartz and granite is 10⁻⁴ to 10⁻² C/m² which is larger than bound charges induced by the disappearance of piezoelectricity due to the release of stress. Hole and electron trapping centers, which is found in semiconductor devices with the Si–SiO₂ system, are causes of surface charging on fracture or frictional slip surface of quartz crystal. The quantity of the surface charge is enough to cause corona discharge that can generate earthquake lights. The mechanism considering the hole and electron trapping centers has a probability to explain why non-piezoelectric minerals or rocks generate electromagnetic phenomena. It can be one of origins of seismo-electromagnetic phenomena (SEP).     

Comparison between the Chile and Mexico triple junction areas substantiates slab window development beneath northwestern Mexico during the past 12-10 Myr

When combined with the Miocene-Recent volcanic record of Baja California, a parallel drawn between the Chile and Mexico triple junction areas substantiates slab window development beneath northwestern Mexico during the past 12-10 Myr. The slab-free zone manifestations challenge the notion that ridge subduction has not occurred beneath the southern Baja California peninsula. The geochemically distinctive rocks from the Santa Clara volcanic field of west-central Baja California, including coeval adakites and niobium-enriched basalt, are commonly inferred to signal partial melting of the subducting plate at shallow depths and relatively high temperatures, before slab dehydration occurs. Such PT conditions for slab melting have only been observed in association with spreading-ridge subduction. We propose that slab window development beneath southern Baja California and mainland Mexico (30° to 18°N) resulted from subduction of the East Pacific rise.     

Vibrant Centers as Locations for High-Growth Firms: An Analysis of Thirty U.S. Metropolitan Areas

What kinds of places have high entrepreneurial activities? There has been an emerging body of studies about so-called entrepreneurship ecosystems, but virtually all of the past studies have examined this question from a perspective of which metropolitan areas have higher entrepreneurial activities. In this article, we examine the intrametropolitan scale at the Census tract level. By analyzing thirty metropolitan areas to extend external validity, we demonstrate the concentration of high-growth firms in specific employment nodes in both urban and suburban parts of each metropolitan area. Significant correlations exist between place-based vibrancy indicators and high-growth firm concentrations.     

西北太平洋气候和海洋环境变化对柔鱼空间分布的影响

Ommastrephes bartramii is an ecologically dependent species and has great commercial values among the AsiaPacific countries. This squid widely inhabits the North Pacific, one of the most dynamic marine environments in the world, subjecting to multi-scale climatic events such as the Pacific Decadal Oscillation(PDO). Commercial fishery data from the Chinese squid-jigging fleets during 1995–2011 are used to evaluate the influences of climatic and oceanic environmental variations on the spatial distribution of O. bartramii. Significant interannual and seasonal variability are observed in the longitudinal and latitudinal gravity centers(LONG and LATG) of fishing ground of O. bartramii. The LATG mainly occurred in the waters with the suitable ranges of environmental variables estimated by the generalized additive model. The apparent north-south spatial shift in the annual LATG appeares to be associated with the PDO phenomenon and is closely related to the sea surface temperature(SST)and sea surface height(SSH) on the fishing ground, whereas the mixed layer depth(MLD) might contribute limited impacts to the distribution pattern of O. bartramii. The warm PDO regimes tend to yield cold SST and low SSH, resulting in a southward shift of LATG, while the cold PDO phases provid warm SST and elevated SSH,resulting in a northward shift of LATG. A regression model is developed to help understand and predict the fishing ground distributions of O. bartramii and improve the fishery management.     

ESR dating of fluvial quartz: Estimate of the minimal distance transport required for getting a maximum optical bleaching

An ESR experimental study of artificial optical bleaching of sedimentary quartz has shown that the aluminum center was maximally bleached after a 6-month illumination equivalent to natural light. This duration seems too long to apply in natural conditions. Nevertheless, the measurement of the ESR intensity of aluminum centers in quartz extracted from modern sediments and deposited in sandy bars shows that the maximum bleaching has effectively been reached.

In order to determine the relationship between the bleaching and the distance covered by a quartz grain in a river, samples were collected along the Creuse River (France) from its spring to about 170 km downstream, where maximum bleaching levels were observed in previous studies. The ESR intensities of the aluminum and titanium centers in quartz were measured, using X-band spectroscopy, before and after artificial bleaching. The difference measured between these sub-samples shows that the maximum bleaching level is obtained in the course of the first kilometer. Hence, the assumption that ESR dating of fluvial sediment is based on the optical bleaching was validated.     

Spatial dynamics of retail structure and the venerable retail hierarchy

The retail system is continuously adapting itself to changing demographic conditions, consumer behavior and economic conditions. Existing retail units, getting larger in order to achieve economics of scale, and new forms of large-scale retailing do not fit easily in the traditional spatial pattern of retail concentrations. Neverteless the spatial distribution of retailing in urban areas, as schematized by Berry thirty-five years ago, still has its value. Through an upward hierarchical movement the retail system has adapted itself to an inflexible spatial system, in which downtown has still a dominant position. Future developments, however, may weaken the position of central shopping areas in favour of peripheral locations. This revised version was published online in July 2006 with corrections to the Cover Date.     

INTERMODAL TRANSPORTATION IN NORTH AMERICA AND THE DEVELOPMENT OF INLAND LOAD CENTERS*

This paper analyzes the changes that are transforming intermodal transportation in the United States and Canada. Traffic is being concentrated at a relatively small number of inland load centers that serve as regional truck distribution points, and are linked by high volume dedicated train services. Both theoretical and practical implications of the changes are examined, and a range of research questions are presented.