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1.
Murray Close Phil Abraham Judith Webber Eliza Cowey Bronwyn Humphries Graham Fenwick Simon Howard Kimberly Huynh Travis Grace Pierre-Yves Dupont Louise Weaver 《Ground water》2020,58(6):901-912
The vast majority of microorganisms in aquifers live as biofilms on sediment surfaces, which presents significant challenges for sampling as only the suspended microbes will be sampled through normal pumping. The use of a down-well low frequency sonicator has been suggested as a method of detaching microbes from the biofilm and allowing rapid sampling of this community. We developed a portable, easy to use, low-frequency electric sonicator and evaluated its performance for a range of well depths (tested up to 42 m below ground level) and casing types. Three sonicators were characterized in laboratory experiments using a 1 m long tank filled with pea gravel. These included a commercially available pneumatic sonicator, a rotating flexible shaft sonicator, and the prototype electric sonicator. The electric sonicator detached between 56 and 74% of microbes grown on gravel-containing biobags at distances ranging between 2 and 50 cm from the sonicator. The field testing comprises of a total of 55 sampling events from 48 wells located in 4 regions throughout New Zealand. Pre- and post-sonication samples showed an average 33 times increase in bacterial counts. Microbial sequence data showed that the same classes are present in pre- and post-sonicated samples and only slight differences were seen in the proportions present. The sampling process was rapid and the significant increases in bacterial counts mean that microbial samples can be quickly obtained from wells, which permits more detailed analysis than previously possible. 相似文献
2.
Four co-ignimbrite plumes were generated along the flow path of the pyroclastic flow of 7 August 1980 at Mount St. Helens.
Three of the plumes were generated in discrete pulses which can be linked to changes in slope along the channel. One plume
was generated at the mouth of the channel where the flow decelerated markedly as it moved onto the lower slopes of the pumice
plain. Plume generation here may be triggered by enhanced mixing due to a hydraulic jump associated with an abrupt slope change.
Measurements of plume ascent velocity and width show that the co-ignimbrite plumes increased in velocity with height. The
plumes have initial velocities of 1–2 m/s. Two of the plumes reached a velocity maximum (4.6 and 8.8 m/s, respectively, at
heights of 270 and 315 m above the flow) and thereafter decelerated. The other plumes reached velocities of 6.2 and 13 m/s.
The four plumes become systematically less energetic downstream as measured by their ascent rates, which can be interpreted
as a consequence of decreasing interaction of the pyroclastic flow front with the atmosphere. Theoretical models of both co-ignimbrite
plumes and discrete co-ignimbrite clouds assume that there is no initial momentum, and both are able to predict the observed
acceleration stage. The rising plumes mix with and heat air and sediment out particles causing their buoyancy to increase.
Theoretical models agree well with observations and suggest that the initial motion of the ascending material is best described
as a discrete thermal cloud which expands as it entrains air, whereas the subsequent motion of the head may become influenced
by material supplied from the following plume. The models agree well with observations for an initial temperature of the ash
and air mixture in the range of 500–600 K, which is in turn consistent with the measured initial ash temperature of around
920 K. Ash masses of 3.4×105 to 1.8×106 kg are estimated.
Received: 11 January 1996 / Accepted: 7 October 1996 相似文献
3.
We use N-body experiments to study the survival of power-law density cusps in mergers of spherical galaxy models. Steep cusps (e.g.
ρ∝r
-2) are preserved during mergers of equal-mass models; this may be viewed as a general consequence of the incomplete violent
relaxation observed in such mergers. Progenitor profile has a strong effect on remnant shape; steep cusps produce oblate remnants.
If bright ellipticals form by hierarchical mergers of faint ones, the lack of steep cusps in these galaxies is somewhat surprising.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
4.
Hjalmar Laudon Eliza Maher Hasselquist Matthias Peichl Kim Lindgren Ryan Sponseller Fredrik Lidman Lenka Kuglerová Niles J. Hasselquist Kevin Bishop Mats B. Nilsson Anneli M. Ågren 《水文研究》2021,35(4):e14170
Improving our ability to detect changes in terrestrial and aquatic systems is a grand challenge in the environmental sciences. In a world experiencing increasingly rapid rates of climate change and ecosystem transformation, our ability to understand and predict how, when, where, and why changes occur is essential for adapting and mitigating human behaviours. In this context, long-term field research infrastructures have a fundamentally important role to play. For northern boreal landscapes, the Krycklan Catchment Study (KCS) has supported monitoring and research aimed at revealing these changes since it was initiated in 1980. Early studies focused on forest regeneration and microclimatic conditions, nutrient balances and forest hydrology, which included monitoring climate variables, water balance components, and stream water chemistry. The research infrastructure has expanded over the years to encompass a 6790 ha catchment, which currently includes 11 gauged streams, ca. 1000 soil lysimeters, 150 groundwater wells, >500 permanent forest inventory plots, and a 150 m tall tower (a combined ecosystem-atmosphere station of the ICOS, Integrated Carbon Observation System) for measurements of atmospheric gas concentrations and biosphere-atmosphere exchanges of carbon, water, and energy. In addition, the KCS has also been the focus of numerous high resolution multi-spectral LiDAR measurements and large scale experiments. This large collection of equipment and data generation supports a range of disciplinary studies, but more importantly fosters multi-, trans-, and interdisciplinary research opportunities. The KCS attracts a broad collection of scientists, including biogeochemists, ecologists, foresters, geologists, hydrologists, limnologists, soil scientists, and social scientists, all of whom bring their knowledge and experience to the site. The combination of long-term monitoring, shorter-term research projects, and large-scale experiments, including manipulations of climate and various forest management practices, has contributed much to our understanding of boreal landscape functioning, while also supporting the development of models and guidelines for research, policy, and management. 相似文献
5.
Melina Ey Jai Allison Susan Caves Eliza Crosbie Ainsley Hughes 《The Australian geographer》2020,51(3):283-305
ABSTRACT In neoliberalising universities, collegial and collective practices such as reading groups are often positioned by students, staff and managers as less important than meeting individual KPIs (such as producing research publications, seeking research grants, or meeting the increasing demands of producing quality teaching outcomes.) However, reading groups can be vital for cultivating caring collectives and spaces of collegiality. In this paper we use assemblage thinking to explore 25 years of a Geography reading group at the University of Newcastle. The paper addresses two questions: what does reading together do and make possible; and how might we think about the labours of reading together as a way of building caring collectives. The paper draws on reflections from 24 past and present members of reading group to explore how these kinds of academic practices nourish our working lives. 相似文献
6.
Metamorphic record of collision and collapse in the Ediacaran‐Cambrian Araçuaí orogen,SE‐Brazil: Insights from P–T pseudosections and monazite dating 
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下载免费PDF全文 The Araçuaí orogen is the Brazilian counterpart of the Araçuaí‐West Congo orogenic system (AWCO), a component of the Ediacaran‐Cambrian orogenic network formed during the amalgamation of West Gondwana. The northwestern portion of the Araçuaí orogen is dominated by a succession of metasedimentary rocks made up of Meso‐ to Neoproterozoic rift, passive margin and syn‐orogenic sequences, locally intruded by post‐collisional granites. These sequences are involved in three distinct tectonic units, which from west to east are: the southern Espinhaço fold‐thrust system (SE‐thrust system), the normal‐sense Chapada Acauã shear zone (CASZ) and the Salinas synclinorium. Three deformation phases were documented in the region. The first two phases (D1 and D2) are characterized by contractional structures and represent the collisional development stage of the orogen. The third phase (D3) is extensional and currently viewed as a manifestation of orogenic collapse of the system. The distribution of the metamorphic mineral assemblages in the region characterizes two metamorphic domains. The M‐Domain I on the west, encompassing the SE‐thrust system and the CASZ, is marked by a syn‐collisional (syn‐D1) Barrovian‐type metamorphism with P–T conditions increasing eastwards and reaching ~8.5 kbar at ~650°C between 575 and 565 Ma. The M‐Domain II comprises the Salinas synclinorium in the hangingwall of the CASZ, and besides the greenschist facies syn‐collisional metamorphism, records mainly a Buchan‐type metamorphic event, which took place under 3–5.5 kbar and up to 640°C at c. 530 Ma. The northwestern Araçuaí orogen exhibits, thus, a paired metamorphic pattern, in which the Barrovian and Buchan‐type metamorphic domains are juxtaposed by a normal‐sense shear zone. Lithospheric thinning during the extensional collapse of the orogen promoted ascent of the geotherms and melt generation. A large volume of granites was emplaced in the high grade and anatectic core of the orogen during this stage, and heat advected from these intrusions caused the development of Buchan facies series over a relatively large area. Renewed granite plutonism, hydrothermal activities followed by progressive cooling affected the system between 530 and 490 Ma. 相似文献
7.
Australian education policies advocate equal opportunities and non-discrimination through legislation that people with disabilities willing to attend ‘main-stream’ schools must be accommodated for. In this paper, people with mobility disabilities talk about their high school experiences in New South Wales, Australia. We are particularly interested in how these men and women talk about the affirmation of bodily differences within various high school spaces. Adopting narrative analysis and a feminist approach we understand identity as constructed spatially. Our interpretation is focused upon how school spaces helped to shape participants’ sense of self and in turn how participants shaped school spaces. We present a series of vignettes which illustrate how participants with mobility disabilities negotiated their bodily differences in and through school space. 相似文献
8.
Jessica L. Ball Eliza S. Calder Bernard E. Hubbard Marc L. Bernstein 《Bulletin of Volcanology》2013,75(1):1-18
A combination of field mapping, geochemistry, and remote sensing methods has been employed to determine the extent of hydrothermal alteration and assess the potential for failure at the Santiaguito lava dome complex, Guatemala. The 90-year-old complex of four lava domes has only experienced relatively small and infrequent dome collapses in the past, which were associated with lava extrusion. However, existing evidence of an active hydrothermal system coupled with intense seasonal precipitation also presents ideal conditions for instability related to weakened clay-rich edifice rocks. Mapping of the Santiaguito dome complex identified structural features related to dome growth dynamics, potential areas of weakness related to erosion, and locations of fumarole fields. X-ray diffraction and backscattered electron images taken with scanning electron microscopy of dacite and ash samples collected from around fumaroles revealed only minor clay films, and little evidence of alteration. Mineral mapping using ASTER and Hyperion satellite images, however, suggest low-temperature (<150 °C) silicic alteration on erosional surfaces of the domes, but not the type of pervasive acid-sulfate alteration implicated in collapses of other altered edifices. To evaluate the possibility of internal alteration, we re-examined existing aqueous geochemical data from dome-fed hot springs. The data indicate significant water–rock interaction, but the Na–Mg–K geoindicator suggests only a short water residence time, and δ18O/δD ratios show only minor shifts from the meteoric water line with little precipitation of secondary (alteration) minerals. Based on available data, hydrothermal alteration on the dome complex appears to be restricted to surficial deposits of hydrous silica, but the study has highlighted, importantly, that the 1902 eruption crater headwall of Santa María does show more advanced argillic alteration. We also cannot rule out the possibility of advanced alteration within the dome complex interior that is not accessible to the methods used here. It may therefore be prudent to employ geophysical methods to make further assessments in the future. 相似文献
9.
First identification and characterization of Borrobol‐type tephra in the Greenland ice cores: new deposits and improved age estimates 下载免费PDF全文
下载免费PDF全文 Eliza Cook Siwan M. Davies Esther R. Guðmundsdóttir Nicholas J. G. Pearce 《第四纪科学杂志》2018,33(2):212-224
Contiguous sampling of ice spanning key intervals of the deglaciation from the Greenland ice cores of NGRIP, GRIP and NEEM has revealed three new silicic cryptotephra deposits that are geochemically similar to the well‐known Borrobol Tephra (BT). The BT is complex and confounded by the younger closely timed and compositionally similar Penifiler Tephra (PT). Two of the deposits found in the ice are in Greenland Interstadial 1e (GI‐1e) and an older deposit is found in Greenland Stadial 2.1 (GS‐2.1). Until now, the BT was confined to GI‐1‐equivalent lacustrine sequences in the British Isles, Sweden and Germany, and our discovery in Greenland ice extends its distribution and geochemical composition. However, the two cryptotephras that fall within GI‐1e ice cannot be separated on the basis of geochemistry and are dated to 14358 ± 177 a b2k and 14252 ± 173 a b2k, just 106 ± 3 years apart. The older deposit is consistent with BT age estimates derived from Scottish sites, while the younger deposit overlaps with both BT and PT age estimates. We suggest that either the BT in Northern European terrestrial sequences represents an amalgamation of tephra from both of the GI‐1e events identified in the ice‐cores or that it relates to just one of the ice‐core events. A firm correlation cannot be established at present due to their strong geochemical similarities. The older tephra horizon, found within all three ice‐cores and dated to 17326 ± 319 a b2k, can be correlated to a known layer within marine sediment cores from the North Iceland Shelf (ca. 17179‐16754 cal a BP). Despite showing similarities to the BT, this deposit can be distinguished on the basis of lower CaO and TiO2 and is a valuable new tie‐point that could eventually be used in high‐resolution marine records to compare the climate signals from the ocean and atmosphere. 相似文献
10.
对于地震物理学和断裂运动研究而言,探索断裂带构造和地震行为之间的联系是至关重要的。地震代表滑动行为的一个极端;摩擦熔融和假玄武玻璃为动力破裂过程中的局部滑动提供了野外证据[1-3]。无震滑动则 相似文献