Interplay between metamorphic strengthening and structural softening in inclusion‐bearing layered rocks     

Marta Adamuszek  Marcin Dabrowski  Daniel W. Schmid 《地学学报》2013,25(5):381-386

We employ numerical and analytical methods to investigate the effect of the presence of rigid porphyroblasts such as garnets on layer strengthening and the folding instability. We use a 50% fraction of non‐overlapping, circular‐shaped inclusions with a wide size distribution. These inclusions cause a fourfold effective viscosity increase and can significantly promote the folding instability. This is not only due to the increased viscosity but also due to the layer interface roughness generation driven by relative movement of inclusions. The increase in layer viscosity promotes strengthening of the whole system. However, with progressive fold development, the system undergoes an effective softening that may counteract the strengthening effect of the porphyroblast growth.  相似文献   

Sheath fold development in monoclinic shear zones          下载免费PDF全文

Marta Adamuszek  Marcin Dabrowski 《地学学报》2017,29(6):356-362

We use numerical simulations to investigate the evolution of sheath folds around slip surfaces in simple‐shear‐dominated monoclinic shear zones. A variety of sheath fold shapes develops under general shear, including tubular folds with low aspect ratio eye patterns and tongue‐like structures showing bivergent flanking structures in sections normal to the sheath elongation, which may potentially lead to confusing shear sense interpretations. Not all investigated monoclinic flow end‐members lead to the development of sheath folds sensu stricto (folds with apical angle <90°). The aspect ratio of the eye patterns, R_yz, correlates with the ratio between the principal strain in the Y‐direction and the smaller of the principal strains in the X–Z plane, and thus it could be used in strain analysis.  相似文献   

The global uranium rush and its Africa frontier. Effects,reactions and social movements in Namibia     

Marta Conde  Giorgos Kallis 《Global Environmental Change》2012,22(3):596-610

Uranium mines are the often forgotten source of nuclear power. This article studies impacts and social movements at a uranium mining frontier looking at the interaction between the global social metabolism, industrial dynamics and local ecologies of resistance. Namibia, the world's fourth largest producer of uranium, stands at the vanguard of the global uranium rush with 66 granted prospecting licenses and two operating mines. We focus on three generic attributes that help to explain the emergence and intensity of resistance by local communities to uranium mining: the ecology and geography of the resource; the degree and type of political and economic marginalisation of the community; and crucially, the connection and integration of local concerns with broader social movements and political demands. We show with the use of empirical material how these factors play out differently in five Namibian communities that have been, or stand to be, affected by uranium mining, and explain how local ecologies of resistance shape, or fail to shape, the global uranium rush. Our work offers an example of an integrative approach for the analysis of the global–local dynamics of environmental change in relation to the extraction and flow of the essential materials that fuel industrial economies.  相似文献   

Palaeoenvironments of early hominins in temperate and Mediterranean Eurasia: new palaeobotanical data from Palaeolithic key-sites and synchronous natural sequences     

Erwan Messager  Vincent Lebreton  Laurent Marquer  Elda Russo-Ermolli  Ronan Orain  Josette Renault-Miskovsky  David Lordkipanidze  Jackie Despriée  Carlo Peretto  Marta Arzarello 《Quaternary Science Reviews》2011,30(11-12):1439-1447

The present study focuses on new palaeobotanical data (pollen, phytoliths and fruits) from three of the oldest Early Palaeolithic sites in Eurasia (Dmanisi in Georgia, Ca’ Belvedere di Monte Poggiolo in Italy and Pont-de-Lavaud in France). The main aim is to examine the ecological factors associated with the first human dispersals out of Africa into Eurasia. The palaeoecological data are discussed with regards to chronology and geographical location of the settlements. The vegetation pattern of each site consists of temperate Eurasian and Mediterranean taxa, subtropical trees being more or less recorded depending on climatic and geographic features. The new palaeobotanical data show that different vegetation structures occurred between the first human dispersal in Caucasus and the later dispersals in western Eurasia. However, in all cases hominins seemed to be adapted to temperate ecosystems. In Caucasus, human occupation took place at 1.7 Ma in a forest-steppe environment, while at ca 1 Ma human populations occupied various settings such as open landscapes or dense forests. These data suggest that during the Early Pleistocene, human populations evolved and dispersed in western Eurasia, gradually increasing their degree of adaptation to diversified environments.  相似文献   

Search for radio pulsations in four anomalous X-ray pulsars and discovery of two new pulsars     

Marta Burgay  Nanda Rea  GianLuca Israel  Andrea Possenti  Luciano Burderi  Tiziana Di Salvo  Nichi D’Amico  Luigi Stella  Elisa Nichelli 《Astrophysics and Space Science》2007,308(1-4):531-534

We have performed deep searches for radio pulsations from four southern anomalous X-ray pulsars (AXPs) to investigate their physical nature in comparison with the rotation powered pulsars. The data were acquired using the Parkes radio telescope with the 1.4 GHz multibeam receiver. No pulsed emission with periodicity matching the X-ray ephemeris have been found in the observed targets down to a limit of ∼0.1 mJy. A blind search has also been performed on all the 13 beams of the multibeam receiver (the central beam being pointed on the target AXP), leading to the serendipitous discovery of two new radio pulsars and to the further detection of 18 pulsars. Also a search for single dispersed pulses has been performed in the aim to detect signals similar to those of the recently discovered rotating radio transients.   相似文献   

Chandra smells a RRAT     

Bryan M. Gaensler  Maura McLaughlin  Stephen Reynolds  Kazik Borkowski  Nanda Rea  Andrea Possenti  Gianluca Israel  Marta Burgay  Fernando Camilo  Shami Chatterjee  Michael Kramer  Andrew Lyne  Ingrid Stairs 《Astrophysics and Space Science》2007,308(1-4):95-99

“Rotating RAdio Transients” (RRATs) are a newly discovered astronomical phenomenon, characterised by occasional brief radio bursts, with average intervals between bursts ranging from minutes to hours. The burst spacings allow identification of periodicities, which fall in the range 0.4 to 7 seconds. The RRATs thus seem to be rotating neutron stars, albeit with properties very different from the rest of the population. We here present the serendipitous detection with the Chandra X-ray Observatory of a bright point-like X-ray source coincident with one of the RRATs. We discuss the temporal and spectral properties of this X-ray emission, consider counterparts in other wavebands, and interpret these results in the context of possible explanations for the RRAT population. B.M.G. acknowledges the support of NASA through LTSA grant NAG5-13023 and of an Alfred P. Sloan Fellowship.  相似文献   

Hydrometeorological dataset (2014–2019) from the high Arctic unglaciated catchment Fuglebekken (Svalbard)     

Tomasz Wawrzyniak  Marta Majerska  Marzena Osuch 《水文研究》2021,35(1):e13974

In this study, a hydrometeorological dataset of unglaciated High Arctic catchment is presented. The time series encompasses air temperature, precipitation, wind speed, relative humidity, and runoff data from 2014 to 2019. Meteorological data come from continuous meteorological monitoring carried out at the Hornsund station located in SW Spitsbergen. Flow in the Fuglebekken stream was measured using a portable flowmeter Nivus PCM-F with Active Doppler sensor. Continuous hydrometeorological monitoring in polar environments is crucial for the understanding processes controlling the water circulation in the catchments. Inter- and intra- annual variability of the provided variables gives an insight into river functioning. The data set is provided in an open-access PANGAEA repository (https://doi.pangaea.de/10.1594/PANGAEA.921921), in three time intervals (6, 12, and 24 hours). It may serve as the input to rainfall-runoff hydrological models, and allows multi-model parameter estimation and validation. It can be used in a variety of research topics, including streamflow projections, and more generally in examining Arctic ecosystems and climate change impact studies.  相似文献   

Markovian characteristics of dry spells over the Iberian Peninsula under present and future conditions using ESCENA ensemble of regional climate models     

Noelia López-Franca  Enrique Sánchez  Teresa Losada  Marta Domínguez  Raquel Romera  Miguel Ángel Gaertner 《Climate Dynamics》2015,45(3-4):661-677

  相似文献   

Last Glacial Maximum and the Gschnitz stadial in the Maritime Alps according to 10Be cosmogenic dating     

Paolo Roberto Federici  Darryl E. Granger  Adriano Ribolini  Matteo Spagnolo  Marta Pappalardo  Andrew J. Cyr 《Boreas: An International Journal of Quaternary Research》2012,41(2):277-291

  相似文献   

Development of mirrors made of chemically tempered glass foils for future X-ray telescopes     

Bianca Salmaso  Marta Civitani  Claudia Brizzolari  Stefano Basso  Mauro Ghigo  Giovanni Pareschi  Daniele Spiga  Laura Proserpio  Yves Suppiger 《Experimental Astronomy》2015,39(3):527-545

  相似文献