A note on Einstein-Maxwell solutions and vacuum to electrovac solutions transforms     

Reinaldo J. Gleiser  Gabriela I. González  Jorge A. Pullin 《Astrophysics and Space Science》1988,149(2):369-373

We discuss a direct construction of solitonic solutions in the Einstein-Maxwell system and analyze the connection of these with vacuum to electrovac transforms of the usual Belinskii-Zakharov vacuum solutions in the static and Einstein-Rosen waves cases.It should be noted that the construction of Belinskii is the same as the one that appears in the Kaluza-Klein ansatz, although in his case there is no direct interpretation to the scalarg ₅₅ fieldSupported by a CONICET fellowship.  相似文献   

Petrology, geochemistry and mineralization of the Las Águilas and Virorco mafic–ultramafic bodies, San Luis Province, Argentina     

Gabriela Ferracutti  Ernesto Bjerg  Aberra Mogessie 《International Journal of Earth Sciences》2013,102(3):701-720

The layered mafic–ultramafic rocks in the Sierras de San Luis, Argentina (Las Águilas, Las Higueras and Virorco), constitute a 3–5-km-wide belt that extends over 100 km from NE to SW. They carry a sulphide mineralization consisting of pyrrhotite, pentlandite and chalcopyrite, in veins and as disseminated to massive ore. Disseminated spinels are frequently associated with the sulphide minerals as well as platinum group minerals. A strong correlation between S, Ni, Co, Cu, Cr, Pt and Pd indicates the presence of one to three levels of mineralization within the ultramafic units. The maximum concentration of these elements coincides with the units containing platinum group minerals (PGM) and spinel group minerals. This clear relationship constitutes a good prospecting guide in the search for layers with high-grade ore, probably associated with deeper stratigraphic levels where ultramafic rocks are dominant. The bulk rock chemistry and concentrations of metals and platinum group elements as well as textural evidence suggest that the parental magma was mafic with tholeiitic affinities and MgO rich. The Las Águilas layered mafic–ultramafic body and the remaining bodies in the area bear similar characteristics to well-known stratified complexes developed in extensional tectonic regimes, as it is the case of Jinchuan (China), Kabanga (Tanzania) and Fiambala (Argentina).  相似文献   

Frontiers in geoscience: A tribute to Prof. Xuanxue Mo-Preface     

Zengqian Hou  M.Santosh  Wenjiao Xiao  Yaoling Niu  Victor Mocanu 《地学前缘(英文版)》2018,9(5):1261-1264

正1.Introduction In response to the proposal by the Earth Science community of China,we are delighted to organize this special issue of Geoscience Frontiers(GSF)in honor of the work by Xuanxue Mo,Professor of Petrology and Geochemistry of China University of Geosciences(Beijing)and Academician of the Chinese Academy of Sciences,as a tribute to him on his 80th birthday.In his over 50 years of profes-  相似文献   

Historical intensity VIII earthquakes along the Rhone valley (Valais, Switzerland): primary and secondary effects     

Stefan Fritsche  Donat F?h  Gabriela Schwarz-Zanetti 《Swiss Journal of Geoscience》2012,105(1):1-18

In recent years the upper Rhone Valley has been one of the most intensively investigated regions by the Swiss Seismological Service. The high seismicity in the region encourages research in the seismological field and one main focus has been historical seismology. This report presents the state of the art of our historical investigations by giving an overview of the effects of four damaging earthquakes with intensity larger than VII, for which a fairly large number of documents could be found and analyzed. The overview includes the events of 1584 (Aigle, epicentral intensity VIII), 1755 (Brig, epicentral intensity VIII), 1855 (Visp, epicentral intensity VIII), and 1946 (Sierre, epicentral intensity VIII for the main shock and intensity VII for the largest aftershock). The paper focuses mainly on primary and secondary effects in the epicentral region, providing the key data and a general characterization of the event. Generally, primary effects such as the reaction of the population and impact on buildings took more focus in the past. Thus building damage is more frequently described in historic documents. However, we also found a number of sources describing secondary effects such as landslides, snow avalanches, and liquefaction. Since the sources may be useful, we include citations of these documents. The 1584 Aigle event, for example, produced exceptional movements in Lake Geneva, which can be explained by an expanded sub aquatic slide with resultant tsunami and seiche. The strongest of the aftershocks of the 1584 event triggered a destructive landslide covering the villages Corbeyrier and Yvorne, VD. All macroseismic data on the discussed events are accessible through the webpage of the Swiss Seismological Service (http://www.seismo.ethz.ch).  相似文献   

Coca’s haunting presence in the agrarian politics of the Bolivian lowlands     

Gabriela Valdivia 《GeoJournal》2012,77(5):615-631

This essay explores the role of the coca economy in the politics of basic foodstuff production in the lowlands department of Santa Cruz, Bolivia. Efforts throughout the 1980s and 1990s to diminish the coca economy in Santa Cruz have led to a significant decrease in the physical presence of coca in the region. This paper argues that while coca has been physically eradicated, the relationships and inequalities that characterized the coca economy at its height in the 1980s and 1990s continue to haunt present-day agrarian relations and decisions in the region. Using the framework of haunting and drawing on stories narrating the intersections between the livelihood challenges of rice farmers in the province of Ichilo, Santa Cruz, regional agrarian politics, and regional-state governance conflicts, I explore how the coca economy matters to the dynamics of principal agrarian foodstuff production. While coca cultivation in Ichilo is expressly assigned to the past and modern agrarian politics are explicitly articulated as “post-coca,” this paper offers a reminder about how the coca economy continues to shape present day agrarian politics, even as it is considered “successfully” eradicated.  相似文献   

Glutamate dehydrogenase and Na+-K+ ATPase expression and growth response of Litopenaeus vannamei to different salinities and dietary protein levels     

�����  ������ 《中国海洋湖沼学报》2011,29(2):343-349

Improvement in the osmoregulation capacity via nutritional supplies is vitally important in shrimp aquaculture.The effects of dietary protein levels on the osmoregulation capacity of the Pacific white shrimp(L.vannamei) were investigated.This involved an examination of growth performance,glutamate dehydrogenase(GDH) and Na+-K+ ATPase mRNA expression,,and GDH activity in muscles and gills.Three experimental diets were formulated,containing 25%,40%,and 50% dietary protein,and fed to the shrimp at a salinity of 25.After 20 days,no significant difference was observed in weight gain,though GDH and Na+-K+ ATPase gene expression and GDH activity increased with higher dietary protein levels.Subsequently,shrimp fed diets with 25% and 50% dietary protein were transferred into tanks with salinities of 38 and 5,respectively,and sampled at weeks 1 and 2.Shrimp fed with 40% protein at 25 in salinity(optimal conditions) were used as a control.Regardless of the salinities,shrimp fed with 50% dietary protein had significantly higher growth performance than other diets;no significant differences were found in comparison with the control.Shrimp fed with 25% dietary protein and maintained at salinities of 38 and 5 had significantly lower weight gain values after 2 weeks.Ambient salinity change also stimulated the hepatosomatic index,which increased in the first week and then recovered to a relatively normal level,as in the control,after 2 weeks.These findings indicate that in white shrimp,the specific protein nutrient and energy demands related to ambient salinity change are associated with protein metabolism.Increased dietary protein level could improve the osmoregulation capacity of L.vannamei with more energy resources allocated to GDH activity and expression.  相似文献   

The problem of phase mixed shear Alfvén waves in the solar corona revisited     

G. Mocanu  A. Marcu  I. Ballai  B. Orza 《Astronomische Nachrichten》2008,329(8):780-785

The problem of phase mixing of shear Alfvén waves is revisited taking into account dissipative phenomena specific for the solar corona. In regions of space plasmas where the dynamics is controlled by the magnetic field, transport coefficients become anisotropic with transport mechanism having different behavior and magnitude depending on the orientation with respect to the ambient magnetic field. Taking into account realistic values for dissipative coefficients we obtain that the previous results derived in context of torsional Alfvén wave phase mixing are actually heavily underestimated so phase mixing cannot be used to explain the damping of torsional Alfvén waves and heating of open coronal structures. The presented results indicate that in order for phase mixing to still be a viable mechanism to explain heating or wave damping unrealistic assumptions have to be made. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献