A simple and generalised <Emphasis Type="Italic">P–T–V</Emphasis> EoS for continuous phase transitions,implemented in EosFit and applied to quartz     

Ross?J.?AngelEmail authorView author&#;s OrcID profile  Matteo?Alvaro  Ronald?Miletich  Fabrizio?Nestola 《Contributions to Mineralogy and Petrology》2017,172(5):29

  相似文献   

Impact of tropical instability waves on nutrient and chlorophyll distributions in the equatorial Pacific     

Wiley Evans  Peter G. Strutton  Francisco P. Chavez 《Deep Sea Research Part I: Oceanographic Research Papers》2009,56(2):178-188

This work quantifies the role of tropical instability waves (TIWs) in modulating nutrient and chlorophyll distributions in the equatorial Pacific through an analysis of satellite data and a case study of in situ observations. A TIW index is constructed to differentiate periods of strong and weak TIW activity. TIW impacts are first examined in monthly averaged satellite SST and chlorophyll data for three distinct regions north of the equator where TIWs are most active. The chlorophyll data are high-pass filtered to preserve the seasonal cycle and remove long-term trends. Although SST follows a predictable relationship with the TIW index, chlorophyll concentrations do not. Periods of high TIW activity are characterized by cooler SSTs but consistently low chlorophyll. A case study of individual TIW vortices demonstrates that their impact on nutrients and chlorophyll is a function of intensity. Strong TIWs drive reductions in nutrients and chlorophyll due to the subduction of nutrient-replete water north of the equator and the advection of nutrient-poor water toward the equator from adjacent to the upwelling zone. Weak TIWs do not drive these advective processes to the same degree, so retain elevated nutrients that fuel chlorophyll increases. The most positive effect on nutrients and chlorophyll by TIWs was observed during boreal winter, likely owing to thermocline topography. A shallower thermocline in combination with weak TIWs results in elevated nutrients and chlorophyll north of the equator. Given the variability associated with TIW intensity and season, generalizing TIW effects has proven difficult, but targeted Lagrangian studies will better characterize these dynamic features and their impact on elemental fluxes.  相似文献   

Book reviews     

Howard T. Evans  Hernani A. F. Chavez 《Natural Resources Research》1998,7(2):157-158

  相似文献   

Laboratory simulation of interplanetary ultraviolet radiation (broad spectrum) and its effects on Deinococcus radiodurans     

Ivan Gláucio Paulino-Lima  Sérgio Pilling  Eduardo Janot-Pacheco  João Alexandre Ribeiro Gonçalves Barbosa  Alvaro Costa Leitão 《Planetary and Space Science》2010,58(10):1180-1040

The radiation-resistant bacterium Deinococcus radiodurans was exposed to a simulated interplanetary UV radiation at the Brazilian Synchrotron Light Laboratory (LNLS). Bacterial samples were irradiated on different substrates to investigate the influence of surface relief on cell survival. The effects of cell multi-layers were also investigated. The ratio of viable microorganisms remained virtually the same (average 2%) for integrated doses from 1.2 to 12 kJ m⁻², corresponding to 16 h of irradiation at most. The asymptotic profiles of the curves, clearly connected to a shielding effect provided by multi-layering cells on a cavitary substrate (carbon tape), means that the inactivation rate may not change significantly along extended periods of exposure to radiation. Such high survival rates reinforce the possibility of an interplanetary transfer of viable microbes.  相似文献   

The first description and confirmation of the Vista Alegre impact structure in the Paraná flood basalts of southern Brazil     

Alvaro P. CRÓSTA  Christian KOEBERL  Rafael A. FURUIE  Cesar KAZZUO‐VIEIRA 《Meteoritics & planetary science》2010,45(2):181-194

Abstract– The Vista Alegre structure, centered at 25°57′S and 52°41′W, has been recently proposed as a meteorite impact structure. The 9.5 km‐diameter structure is located in the Paraná state of southern Brazil, within the Paraná Basin, which contains one of the largest and most extensive flood basalt provinces on Earth. The Paraná flood basalts belong to the Serra Geral Formation and are temporally related to the opening of the South Atlantic Ocean, having been dated at about 133–132 Ma. Tholeiitic basalts dominate the western portion of Paraná state, with some minor rhyodacites. Morphologically, Vista Alegre has a prominent circular outline, in the form of an incomplete ring of escarpments, and an inner depression. The presence of a central uplift is not obvious, but it is inferred by the occurrence of deformed sandstone blocks near the center of the structure. These sandstones are possibly related to the Triassic Pirambóia Formation and/or to the Cretaceous Botucatu Formation. These units are normally at stratigraphic depths of about 700–800 m below the present surface in this portion of the Paraná Basin. The structure appears to be in an advanced erosion stage and its interior is occupied by a soil cover several meters thick, extensively used for agriculture. As a result there are limited outcrops in the interior of the structure, all of polymict breccias, some of them melt‐bearing. We report the extensive occurrence of shatter cones, in the form of fine‐grained rock clasts within the polymict breccias. The shatter cone‐bearing breccias occur at different locations within the structure, separated by several kilometers. The nested shatter cones range in size from about 0.5 to 20 cm for individual cones, and up to half a meter for complete assemblages. The shatter cones formed in fine‐grained Parana flood basalt and might be the first examples of shatter cones in such a rock type. In addition, planar deformation features (PDFs) were found in quartz grains within sedimentary rock clasts of the polymict breccia. These findings confirm the impact origin of the Vista Alegre structure.  相似文献   

The Colônia structure,São Paulo,Brazil     

Claudio RICCOMINI  Alvaro P. CRÓSTA  Renato L. PRADO  Marie‐Pierre LEDRU  Bruno J. TURCQ  Lucy G. SANT’ANNA  José A. FERRARI  W. Uwe REIMOLD 《Meteoritics & planetary science》2011,46(11):1630-1639

Abstract– The near‐circular Colônia structure, located in the southern suburbs of the mega‐city of São Paulo, Brazil, has attracted the attention of geoscientists for several decades due to its anomalous character and the complete absence of any plausible endogenous geologic explanation for its formation. Origin by impact cratering has been suggested repeatedly since the 1960s, but no direct evidence for this has been presented to date. New seismic data have been recently acquired at Colônia, providing new insights into the characteristics and possible layering of infill of the structure, as well as into the depth to the underlying basement. We review the current knowledge about the Colônia structure, present the new seismic data, and discuss the existing—as yet still indirect—evidence for a possible origin by an impact. The new data suggest the existence of a sedimentary fill of approximately 275 m thickness and also the presence of two intermediate zones between sediment and basement: an upper zone that is approximately 65 m thick and can be interpreted as a possible crater‐fill breccia, whereas the other zone possibly represents fractured/brecciated basement, with a thickness of approximately 50 m. Although this depth to basement seems to be inconsistent with the expected geometry of a simple, bowl‐shape impact structure of such diameter, there are a number of still unconstrained parameters that could explain this, such as projectile nature, size and velocity, impact angle, and particularly the current erosion depth.  相似文献   

The complex impact structure Serra da Cangalha,Tocantins State,Brazil     

Thomas KENKMANN  Marcos A. R. VASCONCELOS  Alvaro P. CRÓSTA  Wolf U. REIMOLD 《Meteoritics & planetary science》2011,46(6):875-889

Abstract– Serra da Cangalha is a complex impact structure with a crater diameter of 13,700 m and a central uplift diameter of 5800 m. New findings of shatter cones, planar fractures, feather features, and possible planar deformation features are presented. Several ring‐like features that are visible on remote sensing imagery are caused by selective erosion of tilted strata. The target at Serra da Cangalha is composed of Devonian to Permian sedimentary rocks, mainly sandstones that are interlayered with siltstone and claystones. NNE–SSW and WNW–ESE‐striking joint sets were present prior to the impact and also overprinted the structure after its formation. As preferred zones of weakness, these joint sets partly controlled the shape of the outer perimeter of the structure and, in particular, affected the deformation within the central uplift. Joints in radial orientation to the impact center did not undergo a change in orientation during tilting of strata when the central uplift was formed. These planes were used as major displacement zones. The asymmetry of the central uplift, with preferred overturning of strata in the northern to western sector, may suggest a moderately oblique impact from a southerly direction. Buckle folding of tilted strata, as well as strata overturning, indicates that the central uplift became gravitationally unstable at the end of crater formation.  相似文献   

El Niño along the west coast of North America     

Francisco P. Chavez  Curtis A. Collins  Adriana Huyer  David L. Mackas 《Progress in Oceanography》2002,54(1-4)

  相似文献   

Multi-platform remote sensing of new production in central California during the 1997–1998 El Niño     

R. M. Kudela  F. P. Chavez 《Progress in Oceanography》2002,54(1-4)

The effects of the 1997–1999 El Niño/La Nina event on new primary production are examined using a physiologically based algorithm of nitrate uptake by phytoplankton for the Monterey Bay, California region. Primary inputs for the model come from temperature and phytoplankton biomass (chlorophyll) using both moorings and satellite observations, providing estimates of new production with higher spatial and temporal resolution as compared to traditional shipboard measurements. We observed significant decrease in new production values during the El Niño event, and a corresponding enhancement during La Niña as compared to the values during the El Niño period. The observed interannual changes in new production varied as a function of distance from shore, consistent with the hypothesis that productivity offshore from the upwelling center was impacted because of the suppression of the thermocline and nitracline associated with the ENSO event. There was less evidence for a significant downstream trend in new production values, suggesting that distance from shore is the predominant variable in spatial estimates of new production.  相似文献   

Introduction to ‘The 1997–8 El Niño Atlas of oceanographic conditions along the west coast of North America (23°N–50°N)’     

C. G. Castro  T. R. Baumgartner  S. Bograd  R. Castro  F. P. Chavez  C. A. Collins  R. Durazo  J. García  G. Gaxiola-Castro  T. Hayward  A. Huyer  R. Lynn  A. S. Mascarenhas  M. R. D. Robert  R. L. Smith  P. A. Wheeler  F. A. Whitney 《Progress in Oceanography》2002,54(1-4)

Hydrographic data collected along the West Coast of North America between January 1997 and January 1999 have been compiled into a web-based Atlas of the 1997–8 El Niño event. This paper discusses the organization of the Atlas, describes the data that were incorporated into the Atlas and explains how vertical and horizontal distributions for the different properties were constructed. Examples of figures from the Atlas are shown.  相似文献