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51.
David A. Clague Alice S. Davis James L. Bischoff Jacqueline E. Dixon Renee Geyer 《Bulletin of Volcanology》2000,61(7):437-449
Glassy bubble-wall fragments, morphologically similar to littoral limu o Pele, have been found in volcanic sands erupted
on Lō'ihi Seamount and along the submarine east rift zone of Kīlauea Volcano. The limu o Pele fragments are undegassed with
respect to H2O and S and formed by mild steam explosions. Angular glass sand fragments apparently form at similar, and greater, depths
by cooling-contraction granulation. The limu o Pele fragments from Lō'ihi Seamount are dominantly tholeiitic basalt containing
6.25–7.25% MgO. None of the limu o Pele samples from Lō'ihi Seamount contains less than 5.57% MgO, suggesting that higher
viscosity magmas do not form lava bubbles. The dissolved CO2 and H2O contents of 7 of the limu o Pele fragments indicate eruption at 1200±300 m depth (120±30 bar). These pressures exceed that
generally thought to limit steam explosions. We conclude that hydrovolcanic eruptions are possible, with appropriate pre-mixing
conditions, at pressures as great as 120 bar.
Received: 22 December 1998 / Accepted: 16 July 1999 相似文献
52.
Alice Recanati Yves Missenard Rmi Leprêtre Ccile Gautheron Jocelyn Barbarand Fatiha Abbassene Nachida Abdallah Aziouz Ouabadi Mohamed El Messaoud Derder Claire Boukari Rosella Pinna‐Jamme Frdric Haurine 《地学学报》2019,31(1):39-48
In North Africa, the Algerian margin is made of basement blocks that drifted away from the European margin, namely the Kabylia, and docked to the African continental crust in the Early Miocene. This young margin is now inverted, as dated Miocene (17 Ma) granites outcrop alongshore, evidencing kilometre‐scale exhumation since their emplacement. Age of inversion is actually unknown, although Pliocene is often considered in the offshore domain. To decipher the exhumation history of the margin between 17 and 5 Ma, we performed a coupled apatite fission track (AFT) and (U–Th–Sm)/He (AHe) study in the Cap Bougaroun Miocene granite. AFT dates range between 7 ± 1 and 10 ± 1 Ma, and mean AHe dates between 8 ± 2 and 10 ± 1 Ma. These data evidence rapid and multi‐kilometre exhumation during Tortonian times. This event cannot be related to slab break‐off but instead to the onset of margin inversion that has since developed as an in‐sequence north‐verging deforming prism. 相似文献
53.
Peter S.K. Knappett Alice Layton Larry D. McKay Daniel Williams Brian J. Mailloux M.R. Huq M.J. Alam Kazi Matin Ahmed Yasuyuki Akita Marc L. Serre Gary S. Sayler Alexander van Geen 《Ground water》2011,49(1):53-65
The goal of this study was to test hollow‐fiber ultrafiltration as a method for concentrating in situ bacteria and viruses in groundwater samples. Water samples from nine wells tapping a shallow sandy aquifer in a densely populated village in Bangladesh were reduced in volume approximately 400‐fold using ultrafiltration. Culture‐based assays for total coliforms and Escherichia coli, as well as molecular‐based assays for E. coli, Bacteroides, and adenovirus, were used as microbial markers before and after ultrafiltration to evaluate performance. Ultrafiltration increased the concentration of the microbial markers in 99% of cases. However, concentration factors (CF = post‐filtration concentration/pre‐filtration concentration) for each marker calculated from geometric means ranged from 52 to 1018 compared to the expected value of 400. The efficiency was difficult to quantify because concentrations of some of the markers, especially E. coli and total coliforms, in the well water (WW) collected before ultrafiltration varied by several orders of magnitude during the period of sampling. The potential influence of colloidal iron oxide precipitates in the groundwater was tested by adding EDTA to the pre‐filtration water in half of the samples to prevent the formation of precipitates. The use of EDTA had no significant effect on the measurement of culturable or molecular markers across the 0.5 to 10 mg/L range of dissolved Fe2+ concentrations observed in the groundwater, indicating that colloidal iron did not hinder or enhance recovery or detection of the microbial markers. Ultrafiltration appears to be effective for concentrating microorganisms in environmental water samples, but additional research is needed to quantify losses during filtration. 相似文献
54.
Griselda Chaparro María Cristina Marinone Ruben J. Lombardo María Romina Schiaffino Alice de Souza Guimarães Inés O’Farrell 《Limnologica》2011,41(4):371-381
We examined the zooplankton abundance and composition of Laguna Grande, a floodplain wetland of the Lower Paraná Basin (Argentina), during an extraordinary drought–flood cycle that affected both the environment and the biological conditions of the lake. Low waters were characterised by remarkably high conductivities and pH values, and high phytoplankton and bacterioplankton abundances with cyanobacterial blooms, while high waters showed opposite features. In relation to zooplankton, the mean abundances of all the taxonomic groups (rotifers, cladocerans, copepods, ciliates, and heterotrophic nanoflagellates) were slightly higher at low waters. Major changes were observed in the specific composition of metazooplankton: the euryhaline species assemblage that dominated in the dry warm period was replaced by several oligohaline littoral and planktonic species characteristic of the Paraná River Basin, when the water level rose. Mean species richness values at high waters doubled those of low waters and were directly correlated to water depth. Most of the rotifers of the genus Brachionus and the cladoceran Moina micrura switched from parthenogenetic to sexual reproduction during low waters, as a response to a harsh environment and crowding. We suggest that the main changes in the environmental conditions in this eutrophic floodplain lake are driven by the hydrology, which regulates the zooplankton succession. The herein described shifts in the zooplankton structure and dynamics of Laguna Grande over an extraordinary drought–flood cycle contribute to the understanding of the processes that might occur under the scenarios predicted by climate change models. 相似文献
55.
Olaf Nehlich Benjamin T. Fuller Mandy Jay Alice Mora Colin I. Smith Michael P. Richards 《Geochimica et cosmochimica acta》2011,75(17):4963-4977
This study investigates the application of sulphur isotope ratios (δ34S) in combination with carbon (δ13C) and nitrogen (δ15N) ratios to understand the influence of environmental sulphur on the isotopic composition of archaeological human and faunal remains from Roman era sites in Oxfordshire, UK. Humans (n = 83), terrestrial animals (n = 11), and freshwater fish (n = 5) were analysed for their isotope values from four locations in the Thames River Valley, and a broad range of δ34S values were found. The δ34S values from the terrestrial animals were highly variable (−13.6‰ to +0.5‰), but the δ34S values of the fish were clustered and 34S-depleted (−20.9‰ to −17.3‰). The results of the faunal remains suggest that riverine sulphur influenced the terrestrial sulphur isotopic signatures. Terrestrial animals were possibly raised on the floodplains of the River Thames, where highly 34S-depleted sulphur influenced the soil. The humans show the largest range of δ34S values (−18.8‰ to +9.6‰) from any archaeological context to date. No differences in δ34S values were found between the males (−7.8 ± 6.0‰) and females (−5.3 ± 6.8‰), but the females had a linear correlation (R2 = 0.71; p < 0.0001) between their δ15N and δ34S compositions. These δ34S results suggest a greater dietary variability for the inhabitants of Roman Oxfordshire than previously thought, with some individuals eating solely terrestrial protein resources and others showing a diet almost exclusively based on freshwater protein such as fish. Such large dietary variability was not visible by analysing only the carbon and nitrogen isotope ratios, and this research represents the largest and most detailed application of δ34S analysis to examine dietary practices (including breastfeeding and weaning patterns) during the Romano-British Period. 相似文献
56.
Peter J. Brown Alice A. Breeveld Stephen Holland Paul Kuin Tyler Pritchard 《Astrophysics and Space Science》2014,353(1):89-96
This paper studies the motion of an infinitesimal mass in the framework of Robe’s circular restricted three-body problem in two cases; the first case is when the hydrostatic equilibrium figure of the first primary is an oblate spheroid, the shape of the second primary is considered as an oblate spheroid with oblateness coefficients up to the second zonal harmonic, while the first primary is a Roche ellipsoid in the second case and the full buoyancy of the fluid is taken into account. In case one; it is observed that there are two axial libration points on the line joining the centres of the primaries, points on the circle within the first primary are also libration points under certain conditions. It is further found that the first axial point is stable, while the second one is conditionally stable, and the circular points are unstable. It is found in case two that there is exist only one libration point (0,0,0) this point is stable. 相似文献
57.
For the first time, new material of one of the world's oldest known tetrapods, Acanthostega, has been studied in its sedimentological context. The reported evidence suggests that Acanthostega was primarily aquatic and inhabited active fluvial channels in fluvial-dominated environments. 相似文献
58.
Steven J Ostro Jon D Giorgini Alice A Hine Jean-Luc Margot Christian Veillet 《Icarus》2003,166(2):271-275
Radar echoes from Earth co-orbital Asteroid 2002 AA29 yield a total-power radar cross section of 2.9×10−5 km2 ±25%, a circular polarization ratio of SC/OC=0.26±0.07, and an echo bandwidth of at least 1.5 Hz. Combining these results with the estimate of its visual absolute magnitude, HV=25.23±0.24, from reported Spacewatch photometry indicates an effective diameter of 25±5 m, a rotation period no longer than 33 min, and an average surface bulk density no larger than 2.0 g cm−3; the asteroid is radar dark and optically bright, and its statistically most likely spectral class is S. The HV estimate from LINEAR photometry (23.58±0.38) is not compatible with either Spacewatch's HV or our radar results. If a bias this large were generally present in LINEAR's estimates of HV for asteroids it has discovered or observed, then estimates of the current completeness of the Spaceguard Survey would have to be revised downward. 相似文献
59.
Max Pettini Samantha A. Rix Chuck C. Steidel Matthew P. Hunt Alice E. Shapley Kurt L. Adelberger 《Astrophysics and Space Science》2002,281(1-2):461-466
Recent advances in instrumentation and observing techniques have made it possible to begin to study in detail the stellar
populations and the interstellar media of galaxies at redshift z = 3, when the universe was still in its ‘teen years’. I illustrate recent progress in this field with the latest observations
of the gravitationally lensed galaxy MS 1512- cB58.
This revised version was published online in September 2006 with corrections to the Cover Date. 相似文献
60.
Ronald R. Gutierrez Alice Lefebvre Francisco Núñez-González Humberto Avila 《地球表面变化过程与地形》2021,46(1):47-54
In recent years, open and data-driven science has fostered very important scientific breakthroughs. This study describes the challenges and opportunities for the scientific community devoted to bed form dynamics research in adopting such scientific paradigms through, for example, engineered data sharing, formal recognition of scientists who collect the data, and collaborative development of free accessible software. It highlights that once these actions are completed, the potential application of deep learning techniques could substantially improve bed form models and the scientific understanding of bed form dynamics. Likewise, it discusses the potential of Bedforms-ATM, a free available software, to standardize some bed form data analysis techniques. We propose that the technical challenges be tackled by following scholarly accepted/proposed standards (e.g. FAIR Guiding Principles, Geoscience Papers of the Future), using the body of knowledge being built on the matter by some institutions (e.g. Federation of Earth Science Information Partners), and through technical discussions at scientific meetings such as MARID. © 2020 John Wiley & Sons, Ltd. 相似文献