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131.
N. Thompson Hobbs Kathleen A. Galvin Chris J. Stokes Jill M. Lackett Andrew J. Ash Randall B. Boone Robin S. Reid Philip K. Thornton 《Global Environmental Change》2008,18(4):776
Fragmentation of the ecosystems of the earth into spatially isolated units has emerged as a primary component of global change. Often, fragmentation results from actions that are intended to enhance human livelihoods and well-being; however, there are often costs to ecosystems and human economies that are not considered. We describe the three general categories of processes causing fragmentation of rangelands worldwide: dissection, decoupling, and compression. We show that access to heterogeneity of landscapes is an important attribute of grazing ecosystems worldwide, and that fragmentation of these systems, even when it proceeds in the absence of habitat loss, can limit options of people and animals, options that are particularly important in temporally heterogeneous environments. We discuss the consequences of fragmentation for people, livestock, wildlife, and landscapes and describe potential adaptations that can mitigate its harmful outcomes. We close by reviewing policy options that promote re-aggregation of landscapes and adaptation to fragmentation. 相似文献
132.
Sonja Schuh Roberto Silvotti Ronny Lutz Björn Loeptien Elizabeth M. Green Roy H. Østensen Silvio Leccia Seung-Lee Kim Gilles Fontaine Stéphane Charpinet Myriam Francœur Suzanna Randall Cristina Rodríguez-López Valerie van Grootel Andrew P. Odell Margit Paparó Zsófia Bognár Péter Pápics Thorsten Nagel Benjamin Beeck Markus Hundertmark Thorsten Stahn Stefan Dreizler Frederic V. Hessman Massimo Dall’Ora Dario Mancini Fausto Cortecchia Serena Benatti Riccardo Claudi Rimvydas Janulis 《Astrophysics and Space Science》2010,329(1-2):231-242
In 2007, a companion with planetary mass was found around the pulsating subdwarf B star V391 Pegasi with the timing method, indicating that a previously undiscovered population of substellar companions to apparently single subdwarf B stars might exist. Following this serendipitous discovery, the EXOTIME (http://www.na.astro.it/~silvotti/exotime/) monitoring program has been set up to follow the pulsations of a number of selected rapidly pulsating subdwarf B stars on time scales of several years with two immediate observational goals:
- determine $\dot{P}$ of the pulsational periods P
- search for signatures of substellar companions in O–C residuals due to periodic light travel time variations, which would be tracking the central star’s companion-induced wobble around the centre of mass
133.
We present the first results of an observational campaign aimed at detecting rapid extreme horizontal branch (EHB) pulsators in globular clusters. So far, we have observed multi-frequency luminosity variations for three EHB stars in ω Cen, with typical periods in the 100–120 s range. This is towards the short end, but comparable to, the periodicities measured for rapidly pulsating subdwarf B (sdB) stars in the field. Given that the effective temperatures of the variables discovered seem to be compatible with the instability strip for fast sdB pulsators, we believe we have uncovered the first such variables in a globular cluster. 相似文献
134.
Water quality affects many aspects of water availability, from precluding use to societal perceptions of fit-for-purpose. Pathogen source and transport processes are drivers of water quality because they have been responsible for numerous outbreaks resulting in large economic losses due to illness and, in some cases, loss of life. Outbreaks result from very small exposure (e.g., less than 20 viruses) from very strong sources (e.g., trillions of viruses shed by a single infected individual). Thus, unlike solute contaminants, an acute exposure to a very small amount of contaminated water can cause immediate adverse health effects. Similarly, pathogens are larger than solutes. Thus, interactions with surfaces and settling become important even as processes important for solutes such as diffusion become less important. These differences are articulated in “Colloid Filtration Theory”, a separate branch of pore-scale transport. Consequently, understanding pathogen processes requires changes in how groundwater systems are typically characterized, where the focus is on the leading edges of plumes and preferential flow paths, even if such features move only a very small fraction of the aquifer flow. Moreover, the relatively short survival times of pathogens in the subsurface require greater attention to very fast (<10 year) flow paths. By better understanding the differences between pathogen and solute transport mechanisms discussed here, a more encompassing view of water quality and source water protection is attained. With this more holistic view and theoretical understanding, better evaluations can be made regarding drinking water vulnerability and the relation between groundwater and human health. 相似文献
135.
Yang Kun Davidson Rachel A. Vergara Humberto Kolar Randall L. Dresback Kendra M. Colle Brian A. Blanton Brian Wachtendorf Tricia Trivedi Jennifer Nozick Linda K. 《Natural Hazards》2019,96(2):857-878
Natural Hazards - Formal engineering hurricane evacuation studies have not typically considered inland flooding explicitly, though it has been shown repeatedly to be a major cause of damage and... 相似文献
136.
Randall Whitlock Charles F. Lewis James C. Clark Carleton B. Moore 《Meteoritics & planetary science》1991,26(2):169-170
Abstract— The Cerro los Calvos meteorite is a single stone of 68.5 g found in the Nuevo Mercurio strewn field of Zacatecas, Mexico (24°20′N, 102°8′W). It is an unusual H4 chondrite. Its olivine (Fa12.5) and orthopyroxene (Fs 11.7, Wo 0.8) are reduced relative to typical H chondrites. The La Banderia meteorite of 54.3 g from the same vicinity is an LL5 chondrite of shock classification e. 相似文献
137.
Gravel distributions within treethrow mounds and adjacent undisturbed soils in Wisconsin and Pennsylvania were examined to determine the pedoturbation effects of tree uprooting. Erosion of fine materials from the fresh root plate and subsequent treethrow mound leaves gravels as a lag deposit forming surface gravel armors. Continued slow erosion of remaining nongravelly materials diminishes topograhic expression of the mound. In time, gravel armors remain as the only evidence of past uprooting events. 相似文献
138.
Petrogenesis of group A eclogites and websterites: evidence from the Obnazhennaya kimberlite,Yakutia
Lawrence?A.?TaylorEmail author Gregory?A.?Snyder Randall?Keller David?A.?Remley Mahesh?Anand Rene?Wiesli John?Valley Nikolai?V.?Sobolev 《Contributions to Mineralogy and Petrology》2003,145(4):424-443
Mantle xenoliths from the Obnazhennaya kimberlite pipe, Yakutia, possess a large range of mineralogical and chemical compositions, from both group A and B eclogites. Major-element contents of the group A eclogites exhibit transitional features between the group B eclogites and peridotite. The Mg# of clinopyroxenes is 0.86–0.94, with 0.60–0.84 for garnets. Differences in concentration of LREEs exist between the Obnazhennaya group A and the well-studied group B eclogites from the Udachnaya kimberlite pipe. In general, garnets in the group A eclogites contain lower LREEs than those from the group B eclogites; however, the trend for clinopyroxene is reversed. High d 18O (5.46–7.81) values, and the positive Eu anomalies in the garnets and clinopyroxenes (Eu/Eu* 1.2–1.4) demonstrate the involvement of an oceanic crustal component in the formation of the group A eclogites. The group A eclogites formed between 21.0 and 37.6 kbar, and 711 and 923 °C, in a time interval of 1,071–1,237 Ma. An innovative model is proposed to explain the formation of the group A eclogites and websterites. It involves the reaction of a depleted mantle peridotite with TTG and carbonatite melts closely related to the subduction of oceanic crust. 相似文献
139.
Robust smooth magneto tell uric transfer functions 总被引:3,自引:0,他引:3
140.