Drift tube studies of bay-ocean water exchange and implications for larval dispersal     

Lisa Ann Levin 《Estuaries and Coasts》1983,6(4):364-371

Surface water transport and larval dispersal potential within Mission Bay, San Diego, California and along the southern California coast were studied with drift test tubes. Drift tubes, released once during each season at six sites inside Mission Bay, traveled up to 173 km north and 205 km south of Mission Bay at maximum rates of 36 cm per s (north) and 50 cm per s (south). These findings were used to estimate probability of larval transport out of Mission Bay for the intertidal spionid polychaete Pseudopolydora paucibranchiata (Okuda) which occurred in the back of the bay. Outer coast drift tube returns were used to determine potential for gene flow, via larval exchange, between populations in isolated bays along the California coast. Drift tube recoveries and larval abundances in the plankton indicate that few Pseudopolydora larvae leave Mission Bay, but that longshore currents can carry those which do to other suitable bay habitats.  相似文献   

Displacement of the earth’s inner core revisited (Comment on V.A. Antonov and B.P. Kondrat’ev’s paper “On the magnitude of the earth’s inner core displacement”)     

B. V. Levin  V. P. Pavlov 《Izvestiya Physics of the Solid Earth》2006,42(1):87-88

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On “Birthmarks” in rare-metal granites of the Losevka pluton,northern Kazakhstan     

F. A. Letnikov  A. V. Levin  A. F. Letnikova 《Geology of Ore Deposits》2007,49(8):663-668

The Losevka pluton of rare-metal albite granite, which was explored as a possible source of columbite-zircon-malacon ore, is composed of quartz, sodic plagioclase, potassium feldspar, annite, protolithionite, lepidomelane, and Li-muscovite. The average chemical composition of this rock is as follows, wt %: 74.14 SiO₂, 0.04 TiO₂, 14.07 Al₂O₃, 1.05 Fe₂O₃, 0.78 FeO, 0.15 MnO, 0.09 MgO, 0.47 CaO, 4.65 Na₂O, 4.11 K₂O, and 0.03 P₂O₅. The accessory minerals are zircon, malacon, and cyrtolite (874 ppm); apatite (18 ppm); ilmenite (114 ppm); xenotime and monazite (119 ppm); and Nb-columbite (463 ppm). The black inclusions up to 15 cm in size, which are observed in this granite and called “birthmarks” by local geologists, consist of the same rock-forming minerals as the surrounding granite, but are enriched in MnO, MgO, CaO, TiO₂, and F and depleted in SiO₂ relative to the light granite. The black granite is also distinguished by much higher Sr and Ba contents and lower La, Rb, Y, Nb, REE, Cs, Ta, Th, and U contents. The black color is caused by enrichment in manganese oxides, manganoilmenite, and Mn-annite. All rock-forming minerals are pervaded by thin veinlets of Mn-oxides. In addition, bastnaesite, Y-and Th-fluorides, zircon, and malacon have been identified. Aggregates of black-colored minerals are not the products of the fractionation of the initial magma or immiscibility effects, because the structure of the albite-potassium feldspar-quartz-mica matrix is the same both in black and light granites. The percolation of a deep-sourced fluid enriched in Mn and F into a granitic melt might be a more probable origin.  相似文献   

Particle motion in the vicinity of the protosun with variable luminosity     

B. J. Levin  A. N. Simonenko 《Earth, Moon, and Planets》1981,24(2):231-243

Variations of luminosity of the protosun during its Hayashi stage produced variations of its repulsive radiative action on small particles in its vicinity — or, in other words, variations of the effective mass of the protosun. Changes of the effective mass produced changes of size of orbits for particles circling around the protosun. When the luminosity increased, the effect of variable luminosity (EVL) diminished or overbalanced the Poynting-Robertson effect (PRE), hindering the small particles in their drift toward the protosun, and reinforced PRE when the luminosity decreased. An analysis of quasicircular motion of small uncharged particles moving in transparent circumsolar space under both effects — EVL and PRE — is given.  相似文献   

Predicted electrical conductivity between 0 and 80 km in the Venusian atmosphere     

W.J. Borucki  Z. Levin  R.C. Whitten  R.G. Keesee  L.A. Capone  O.B. Toon  J. Dubach 《Icarus》1982,51(2):302-321

Calculations of the space charge, ion density, and conductivity in the Venus atmosphere were made. The presence of the cloud particles on Venus causes a profound reduction in the calculated values of the ion density and conductivity compared to the values that are obtained without consideration of the cloud particles. When the cloud particles are included in the calculations, the results for the ion density and conductivity are approximately the same as those of the terrestrial atmosphere at the same pressure-altitude. Because the particles span such a large range of sizes and are abundant over a substantial range of pressure, the space charge varies strongly with altitude and particle size. Differential settling of the particles is expected to produce weak electric fields in the clouds.  相似文献   

Local Occurrence of the Relationship between Variations in the Earth’s Rotation Rate and the Dynamics of Seismicity: Case Study of Sakhalin     

Levin  B. W.  Sasorova  E. V.  Zakupin  A. S.  Kamenev  P. A. 《Doklady Earth Sciences》2018,483(2):1575-1578

Doklady Earth Sciences - On the basis of three methods, the current seismic situation in the zone of the Central Sakhalin Fault is assessed and the scenarios of its development are predicted. It is...  相似文献   

Finding of Re Sulfides in Copper-Sulfide Ores of the Maike Occurrence,Ulytau, Central Kazakhstan     

Levin  V. L.  Stepanets  V. G.  Li  E. S.  Bekenova  G. K.  Khakimdzhanov  M. S. 《Geology of Ore Deposits》2021,63(8):830-841

Geology of Ore Deposits - Microinclusions of Re-, Mo-, Cu-, Pb-, and Bi-bearing sulfides are found for the first time in Cu sulfide ores of the Maike occurrence, northern Ulytau. The...  相似文献   

Seismic response of floor-anchored nonstructural components fastened with yielding elements     

Tal Feinstein  Jack P. Moehle 《地震工程与结构动力学》2022,51(1):3-21

Failure of nonstructural components during an earthquake can lead to structure functionality loss, cause widespread property damage, and pose a life-safety threat to the occupants. Current code provisions for floor-anchored components aim to minimize the life safety threat by specifying lateral force demands and anchoring requirements. These code requirements are based on a simplified equation that does not fully consider the contribution of the attachment to the overall component dynamic response. Previous results from shaking-table tests of anchored components suggest that the component attachment is an important parameter that determines its dynamic properties. For this study, a nonstructural experimental model was attached via several attachment designs to a concrete slab and tested on a shaking table to evaluate this contribution. The attachments were dimensioned based on a capacity design approach, such that they would be the weakest element in the force path while providing a yielding mechanism. The attachment designs provide different plastic mechanisms that control the displacement ductility in the response of the component. This paper focuses on the contribution of the attachment to the dynamic response and seismic force demand on the component. The experimental results demonstrate that the selected attachment properties govern the boundary conditions of the nonstructural component and strongly influence its dynamic response. The more flexible attachments sustained large deformations, leading to tensile membrane action and enhanced tensile strength in the attachments. Consequently, the ductile attachments did not result in reduced seismic loads in the nonstructural components.  相似文献   

What is the Meaning of ‘Social Mix’? Shifting perspectives in planning and implementing public housing estate redevelopment     

Kathy Arthurson  Iris Levin  Anna Ziersch 《The Australian geographer》2015,46(4):491-505

This paper unravels a variety of perspectives about the concept of social mix, drawing on a case study of the implementation of a redevelopment project in Melbourne. The first part provides a theoretical overview of two internationally predominant academic debates around policy interpretations of this concept, namely social mix as a means for promotion of social inclusion; and as a state-led form of gentrification. These two arguments are usually presented as one, with social inclusion and reductions of concentrations of disadvantage one side of the ‘social mix policy’ coin, and state-led gentrification the other. This paper contributes to the national and international literature on public housing estate regeneration and social mix policies through exploring the question of whether these two ideas about social mix were shared by different stakeholders as the ‘messy’ process of redevelopment unfurled. Interviews were conducted with public tenants, homeowners and homebuyers, private renters and local service providers at the Carlton Housing Estate to explore the diverse perspectives of various stakeholder groups as estate design and implementation shifted. The study identified that as a result of the global financial crisis and the developers exerting pressure on government there was a gradual move away from perceiving social mix as a policy tool for encouraging social inclusion at Carlton, between public housing tenants and private residents, towards a different form of social mix and inclusion. Contrary to intentions, the revised form of social mix at Carlton was perceived as a means to harness market capital and attract higher income residents to the inner city.  相似文献   

Dead zone dilemma   总被引：2，自引：0，他引：2  

Robert J. Díaz  Rutger Rosenberg  Nancy N. Rabalais  Lisa A. Levin 《Marine pollution bulletin》2009,58(12):1767-1768

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