Dauphiné twinning and texture memory in polycrystalline quartz. Part 1: Experimental deformation of novaculite     

Hans-Rudolf Wenk  Erik Rybacki  Georg Dresen  Ivan Lonardelli  Nathan Barton  Hermann Franz  Gabriela Gonzalez 《Physics and Chemistry of Minerals》2006,33(10):667-676

Mechanical Dauphiné twinning in quartz has been of long-standing interest, both in single crystals and polycrystalline aggregates. This study investigates texture development in fine-grained quartz rock novaculite with no initial texture using compression experiments conducted in the Paterson gas apparatus to explore the influence of stress and temperature. Texture patterns are measured with time-of-flight neutron diffraction and hard synchrotron X-rays, analyzing diffraction data with the Rietveld method. Similar texture patterns are observed as described previously but the new results establish a profound influence of temperature and document that twinning initiates at stresses less than 50 MPa. Possibilities of using Dauphiné twinning as a paleopiezometer in quartz-bearing rocks are discussed.  相似文献   

Modern Diatom Assemblages in Surface Sediments from Estuarine Systemsin the Southeastern Buenos Aires Province, Argentina   总被引：1，自引：0，他引：1  

Gabriela S. Hassan  Marcela A. Espinosa  Federico I. Isla 《Journal of Paleolimnology》2006,35(1):39-53

Paleoecological reconstructions of Holocene sea-level changes in Argentinean coastal regions were based mainly on ecological data gathered from other regions, as there was a lack of information on modern estuarine diatom distributions. The aim of the present work was to assess the spatial variation of diatom assemblages in two representative estuaries of Argentina in order to gather ecological information for paleoecological reconstructions in the region. The two selected estuaries have different geomorphologic features and salinity regimes: Mar Chiquita Lagoon is shallow, which prevents the development of a stable salinity gradient as it occurs in the Quequén Grande River. Surface sediment samples were taken from selected stations representative of the environmental gradient from the inlet to the inner reaches of both estuaries. Cluster analysis defined three diatom zones at Mar Chiquita: marine/brackish assemblages dominate the inlet (zone I), where salinity, tidal range and current speed are higher. The brackish/freshwater tychoplankton Staurosira construens var. venter and Staurosirella pinnata dominate the inner lagoon (zone II), where environmental conditions are very variable and concentrations of suspended sediments are higher. Brackish/freshwater euryhaline diatoms dominate the headwaters (zone III). On the other hand, the Quequén Grande River was divided into three diatom zones: coastal taxa are distributed at the inlet (zone I), while the middle estuary (zone II) is dominated by brackish/freshwater euryhaline taxa. At the upper estuary region (zone III), freshwater diatoms dominate, and the halophobous Nitzschia denticula increased in abundance values. Diatom distributions were most closely related to the salinity gradient at Quequén Grande River than at Mar Chiquita Lagoon. Fossil data of a sequence from Mar Chiquita Lagoon (Las Gallinas Creek) were compared to the modern data set in order to search for analogies between fossil and modern diatom assemblages. DCA results showed that fossil diatom assemblages have modern counterparts. Most diatom assemblages of Las Gallinas Creek fall within Mar Chiquita zone III, representing a shallow brackish/freshwater environment, with low salinity fluctuations (~1–9‰) and no tidal influence. Therefore, our modern diatom data provide useful analogs to interpret paleoenvironments in the region.  相似文献   

Gendered production spaces and crop varietal selection: Case study in Yucatán, Mexico     

Diana Gabriela Lope-Alzina 《Singapore journal of tropical geography》2007,28(1):21-38

This paper examines the influence of gender relations and gendered domains on maize and squash varietal selection in a village in Yucatán State, southeast Mexico. Results of the exploratory study indicate that the traditional production spaces of homegardens and agricultural fields are complementary gendered domains of varietal maintenance for both crops although with different cropping patterns, while a 'new' space, of land allocated to some families for future residential construction ( terreno ) is in the meantime a jointly worked agricultural domain. Women's labour, knowledge and preferences predominate in post-harvest processes. Fieldwork revealed that neither men nor women are independent decision-makers, planning what to grow, where and in what amounts, but that in most aspects of farming the interests of both are accommodated within the household's production spaces.  相似文献   

Hydrogeochemical and Geophysical Evaluation of the Recharge Zone of Guarani Aquifer in Municipally of Candelária,Rio Grande do Sul,Brazil     

Moreno  Wilmer Emilio García  Soares  Gabriela Borges  Pires  Júlio César Gall  Sotelo  Daniela Govoni  Moura  Cássio Stein 《Geotechnical and Geological Engineering》2021,39(6):4593-4613

Geotechnical and Geological Engineering - A large part of the Guarani Aquifer is located in the state of Rio Grande do Sul (Brazil) and additionally possesses a recharge area located in its central...  相似文献   

Characterization of cholinesterase activity from different tissues of Nile tilapia (Oreochromis niloticus)     

Rodríguez-Fuentes G  Gold-Bouchot G 《Marine environmental research》2004,58(2-5):505-509

Cholinesterases (ChE) from brain, muscle and liver in Nile tilapia (Oreochromis niloticus) were characterized using three substrates: acetylthiocholine iodide, propionylthiocholine iodide, and butyrylthiocholine iodide. Eserine was used as a total ChE inhibitor; BW284c51 and iso-OMPA were used as selective inhibitors for acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE), respectively. The results indicate that AChE is the enzyme present in brain, whereas in both liver and muscle, the presence of atypical ChEs are suggested. These findings indicate that characterization of ChE is necessary prior to use in monitoring programs.  相似文献   

Flood hazard assessment and mapping in semi-arid piedmont areas: a case study in Beni Mellal,Morocco     

Gabriela Werren  Emmanuel Reynard  Stuart N. Lane  Daniela Balin 《Natural Hazards》2016,81(1):481-511

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Development of a drought vulnerability index using MCDM and GIS: study case in São Paulo and Ceará, Brazil     

de Azevedo Reis  Gabriela  de Souza Filho  Francisco Assis  Nelson  Donald Robert  Rocha  Renan Vieira  da Silva  Samiria Maria Oliveira 《Natural Hazards》2020,104(2):1781-1799

Natural Hazards - Although climate change vulnerability research in general has increased over the last decade, Latin American countries have more directed more limited efforts toward vulnerability...  相似文献   

Evolutionary convergence of the highly adapted desert rodent Tympanoctomys barrerae (Octodontidae)     

Ricardo A. Ojeda  Carlos E. Borghi  Gabriela B. Diaz  Stella M. Giannoni  Michael A. Mares  Janet K. Braun 《Journal of Arid Environments》1999,41(4):443

Octodontid rodents have a long evolutionary history in arid landscapes of South America. The red vizcacha rat, Tympanoctomys barrerae , is a monotypic, micro-endemic species that inhabits salt pan-sand dune habitats in west-central Argentina. Its natural history is almost unknown. We present an analysis of the ecology, morphology, behavior, and physiology of the red vizcacha rat and assess the overall degree of convergence of this species with rodents that inhabit similar habitats in different deserts. Our results show that Tympanoctomys barrerae is highly adapted to salt flat basin habitats. Its diet of halophytic vegetation with a high salt content, and physiological and anatomical traits related to salt consumption, are similar to those found in some members of the families Heteromyidae (Dipodomys microps) of North America, and Muridae (Psammomys obesus and Rhombomys opimus) of Africa and Asia. Similarities include feeding behavior, diet composition, kidney morphology, and urine concentration, among other traits. Tympanoctomys barrerae is more similar to these desert rodents than it is to confamilials that do not feed on halophytes.  相似文献   

Kidney structure and allometry of Argentine desert rodents     

Gabriela B. Diaz  Ricardo A. Ojeda 《Journal of Arid Environments》1999,41(4):453

Two large groups of rodents inhabit South America: the hystricognaths and the murids. It has been postulated that while the former show a high degree of specialization to desert habitats, the murids are not well adapted to xeric conditions. We studied the renal structure and function of selected desert-dwelling murid and octodontid (hystricognath) rodents from Argentina to evaluate levels of adaptation to aridity. Our results show that the murids Salinomys, Andalgalomys, Calomys and Eligmodontia have the highest renal indices and urine concentration among Argentine desert rodents. The octodontid Tympanoctomys barrerae shows higher renal indices and urine osmolarity than those of its close relativesOctomys mimax and Octodontomys gliroides . We compare the renal traits of the Argentine desert murids with those of other world-desert rodents such as North American heteromyid rodents. The results show that these Argentine murid rodents posses renal adaptations to conditions which are as impressive as those of both octodontids and the classic desert-adapted heteromyids.  相似文献   

The false Basel earthquake of May 12, 1021   总被引：1，自引：0，他引：1  

Gabriela Schwarz-Zanetti  Virgilio Masciadri  Donat Fäh  Philipp Kästli 《Journal of Seismology》2008,12(1):125-129

The Basel (CH) area is a place with an increased seismic hazard. Consequently, it is essential to scrutinize a famous statement by Stumpf (Gemeiner loblicher Eydgnoschafft Stetten, Landen und Völckeren Chronikwirdiger thaaten beschreybung. Durch Johann Stumpffen beschriben, 1548) that allegedly a large earthquake took place in Basel in 1021. This can be disproved unambiguously by applying historical and philosophical methods.  相似文献