An electron microprobe study of P645/T390: Evidence for an Early Helladic III Lerna–Aegina connection     

Michael J. Dorais  Christine M. Shriner 《Geoarchaeology》2002,17(8):755-778

Middle Helladic Aeginetan Ware is widely distributed throughout the Aegean. It is characterized by a “gold mica or volcanic ash” fabric and is abundant at Lerna on the Argive plain, Greece, in the Middle Helladic and Late Helladic I periods. A group of Early Helladic III ceramics at Lerna includes P645/T390, which also has a volcanic fabric. We have sampled all the major rock types of the separate volcanic episodes on Aegina, Methana, and Poros and analyzed the constituent minerals with the electron microprobe. These analyses provide a reference standard against which the mineralogy of P645/T390 and other potential Aeginetan wares can be compared. The compositions of amphibole, clinopyroxene, plagioclase, and biotite in P645/T390 are identical to the same minerals in dacites on Aegina, suggesting an origin on that island. Compositional mismatches with the minerals of Methana and Poros indicated the ceramic was not manufactured at these locations. This narrow‐necked jar represents the earliest occurrence of Aeginetan Ware on mainland Greece that has been confirmed by a quantitative method. © 2002 Wiley Periodicals, Inc.  相似文献   

Magnetotail dipolarization fronts and particle acceleration: A review     

Fu  Huishan  Grigorenko  Elena E.  Gabrielse  Christine  Liu  Chengming  Lu  San  Hwang  K. J.  Zhou  Xuzhi  Wang  Zhe  Chen  Fang 《中国科学:地球科学(英文版)》2020,63(2):235-256

In this paper, the particle acceleration processes around magnetotail dipolarization fronts(DFs) were reviewed. We summarize the spacecraft observations(including Cluster, THEMIS, MMS) and numerical simulations(including MHD, testparticle, hybrid, LSK, PIC) of these processes. Specifically, we(1) introduce the properties of DFs at MHD scale, ion scale, and electron scale,(2) review the properties of suprathermal electrons with particular focus on the pitch-angle distributions,(3)define the particle-acceleration process and distinguish it from the particle-heating process,(4) identify the particle-acceleration process from spacecraft measurements of energy fluxes, and(5) quantify the acceleration efficiency and compare it with other processes in the magnetosphere(e.g., magnetic reconnection and radiation-belt acceleration processes). We focus on both the acceleration of electrons and ions(including light ions and heavy ions). Regarding electron acceleration, we introduce Fermi,betatron, and non-adiabatic acceleration mechanisms;regarding ion acceleration, we present Fermi, betatron, reflection, resonance, and non-adiabatic acceleration mechanisms. We also discuss the unsolved problems and open questions relevant to this topic, and suggest directions for future studies.  相似文献   

Wide Binaries among High-Velocity and Metal-Poor Stars     

Christine Allen  M.A. Herrera  A. Poveda 《Astrophysics and Space Science》1999,265(1-4):233-234

  相似文献   

A simple time-dependent solution of the geomagnetic ring-current problem     

Christine M. Davies 《Geophysical Journal International》1977,50(1):23-28

  相似文献   

Preliminary Results on the 3-dimensional Seismic Structure of the Lithosphere under the USGS Central California Seismic Array     

Eystein S. Husebye  ers Christoffersson  Keiiti Aki  Christine Powell 《Geophysical Journal International》1976,46(2):319-340

About 1500 readings of teleseismic P -time residuals obtained from the US Geological Survey seismograph network in central California have been used to obtain a three-dimensional image of seismic velocity anomalies for this area by the method of Aki, Christoffersson & Husebye We found that the California network is less suitable than the LASA and NORSAR arrays for this kind of studies because of its greater proportion of peripheral blocks in which the resolution is very poor for the stochastic inverse solution and the random error effect is severe for the generalized inverse solution. Nevertheless, the resultant velocity anomalies show a remarkable correlation with the San Andreas fault zone to a depth of 75 km. The anomaly pattern changes drastically as the depth exceeds 75 km, suggesting that the asthenosphere has been reached.  相似文献   

Aperture synthesis observations of individual molecular clouds in M33     

Christine D. Wilson  Nick Scoville 《Astrophysics and Space Science》1989,156(1-2):269-273

Aperture synthesis maps of six fields in the nearby spiral galaxy M33 have revealed the presence of a population of molecular clouds whose masses, sizes, velocity widths, and brightness temperatures are similar to Galactic giant molecular clouds. The masses of the clouds obtained from the virial theorem and from the integrated CO flux are in relatively good agreement, suggesting that the conversion factor from CO flux to molecular mass in M33 is unlikely to be much different from the value measured in our own Galaxy. The star formation properties of these regions are under study with deep optical CCD imaging and near-infrared data.  相似文献   

Environmental aspects of child growth and nutrition: A case study from Ibadan,Nigeria     

Christine E. Rossington Dr. 《GeoJournal》1981,5(4):347-356

Protein-energy malnutrition, especially among young children, is a major health problem in many developing areas. Its causes are complex and inadequately understood. The paper outlines a pilot survey designed to investigate the impact of economic, demographic and socio-cultural factors on growth and nutrition among a small group of children aged between one and five years from urban poor families living in Ibadan, Nigeria. Field surveys were undertaken between July 1971 and August 1972 using 51 children from the Oje area of the city who formed part of a larger longitudinal study of child growth and development. Records of child growth patterns were compiled from monthly anthropometric measurements and enquiries made into the socio-economic and demographic status of the sample families.Basic analysis identified periods of growth retardation and seasonal fluctuations in somatic attainments. Multiple correlation analyses attempted to define statistically some of the aspects of the environment which significantly influenced somatic achievements. Relatively low levels of explanation were obtained, emphasising data deficiencies and the complexity of the nutrition problem, but small groups of economic and demographic causative variables were isolated.The research for this paper was funded by the Social Science Research Council, when the author was a postgraduate student, Department of Geography, University of Liverpool.  相似文献   

Continental growth and volatile exchange during Earth''s evolution     

Siegfried Franck  Christine Bounama 《Physics of the Earth and Planetary Interiors》1997,100(1-4):189-196

We investigate the thermal and degassing history of the Earth with the help of a parameterized mantle convection model including the volatile exchange between mantle and surface reservoirs. The weakening of mantle silicates by dissolved volatiles is described by a functional relationship between creep rate and water fugacity. We use flow law parameters of diffusion creep in olivine under dry and wet conditions. The mantle degassing rate is considered as directly proportional to the seafloor spreading rate, which is also dependent on the mantle heat flow and the continental area. To calculate the spreading rate, we assume three different continental growth models: constant growth, delayed growth, and the one proposed by Reymer and Schubert (1984, Tectonics, 3: 63–77). The rate of regassing also depends on the seafloor spreading rate, as well as on other factors. Both mechanisms (degassing and regassing) are coupled self-consistently with the help of a parameterized convection model under implementation of a temperature and volatile-content dependent mantle viscosity. We calculate time series for the Earth's evolution over 4.6 Gyr for the average mantle temperature, the mantle heat flow, the mantle viscosity, the Rayleigh number, the Urey ratio, the volatile loss, and the seafloor spreading rate. In those numerical simulations with continental growth from the beginning and a high initial average mantle temperature water is outgassed rapidly. In the delayed continental growth model there is a very early outgassing event and the delayed continental growth has no remarkable influence on the thermal and outgassing history. A similar situation is found for the linear continental growth model but not for the Reymer and Schubert (1984) model.  相似文献   

Crustal structure, accretionary processes and rift propagation: a gravity study of the intermediate-spreading Valu Fa Ridge, Lau Basin     

Christine Peirce  Ian M. Turner  Martin C. Sinha 《Geophysical Journal International》2001,146(1):53-73

  相似文献   

Downstream migration of juvenile European sturgeonAcipenser sturio L. in the Gironde estuary     

Eric Rochard  Mario Lepage  Pierre Dumont  Serge Tremblay  Christine Gazeau 《Estuaries and Coasts》2001,24(1):108-115

The European sturgeon (Acipenser sturio) is an endangered diadromous fish species that spawns in the rivers in late spring and early summer. The juveniles spend their first years in the brackish waters (5‰ to 25‰) of the estuary zone before moving out to sea. This study describes the downstream migration pattern of juvenile sturgeon, belonging to the 1994 cohort, the only one born naturally in the Gironde basin, France since the end of the 1980s. During October 1994 to December 1996 the inland section of the Gironde estuary was sampled monthly by trawl (n=818 tows) and all European sturgeon caught (n=381) were marked and released. The first sturgeon of the 1994 cohort (TL=27 cm) were caught in early March 1995 in the zones furthest upstream. During their second fall of life, juveniles gradually acclimatized, and spread over a wide range of salinity conditions. A first incursion into marine water was also observed (at least for a few fish) by the end of the second winter. During this second period, sturgeon showed preference for two particular zones situated at 18 and 38 km, respectively, from the mouth of the estuary. These zones, belonging to two different salinity sectors of the estuary, did not appear to be any different to their neighbors with regards to depth and type of substrate. There were no significant size differences among estuarine zones. Seasonal movements of sturgeon seem to be motivated by a search for warmer temperatures. After a period of early acclimatization of 15 months, juvenile European sturgeon appear to be highly tolerant of salinity variations.  相似文献