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1.
A. S. Lapukhov B. V. Guzman V. A. Gorev E. P. Solotchina A. V. Travin 《Journal of Volcanology and Seismology》2007,1(6):405-409
New data on the age of epithermal gold-silver mineralization of Asachinskoe Deposit (southern Kamchatka) are obtained by the 40Ar/39Ar method of stage heating involving preirradiation of samples for 48 hours by fast neutron currents in a cadmium-plated reactor channel. Correlation with the earlier data on integral K/Ar dating and a laser variant of the 40Ar/39Ar method has been carried out. According to the structural orderliness revealed by high resolution X-ray analysis and infrared spectroscopy, potassic feldspars found in veins have been identified as a continuous series: maximum microcline → intermediate microcline → intermediate orthoclase → extreme orthoclase. The age of quartz-orthoclase vein 1 is 3.2 ± 0.2 Ma (the Piacenzian). A younger age, about 1.1 ± 0.3 Ma (the Early Pleistocene) is determined for a quartz-microcline vein with post-mineralization brecciation and recrystallization related to the basalt dike magmatism of this age. 相似文献
2.
Claire E. Lazareth Nury Guzman Frederic Candaudap 《Geochimica et cosmochimica acta》2007,71(22):5369-5383
Mollusk shells are increasingly used as records of past environmental conditions, particularly for sea-surface temperature (SST) reconstructions. Many recent studies tackled SST (and/or sea-surface salinity) tracers through variations in the elementary (Mg and Sr) or stable isotope (δ18O) composition within mollusk shells. But such attempts, which sometimes include calibration studies on modern specimens, are not always conclusive. We present here a series of Mg and Sr analyses in the calcitic layer of Concholepas concholepas (Muricidae, Gastropoda) with a very high time-resolution on a time window covering about 1 and a half month of shell formation, performed by Laser Ablation Inductively-Coupled Plasma Mass Spectrometry (LA-ICP-MS) and electron probe micro-analysis (EPMA). The selected specimen of this common Chilean gastropod was grown under controlled environmental conditions and precise weekly time-marks were imprinted in the shell with calcein staining. Strontium variations in the shell are too limited to be interpreted in terms of environmental parameter changes. In contrast, Mg incorporation into the shell and growth rate appear to change systematically between night and day. During the day, Mg is incorporated at a higher rate than at night and this intake seems positively correlated with water temperature. The nightly reduced Mg incorporation is seemingly related to metabolically controlled processes, formation of organic-rich shell increments and nocturnal feeding activity of the animals. The nyctemeral Mg changes in the C. concholepas shell revealed in this study might explain at least part of the discrepancies observed in previous studies on the use of Mg as a SST proxy in mollusk shells. In the case of C. concholepas, Mg cannot be used straightforwardly as a SST proxy. 相似文献
3.
Chemical compositions of tetrahedrite—Ag-rich tetrahedrite—freibergite solid solutions (Ag-rich tetrahedritess) and homogenization temperatures of fluid inclusions in quartz and carbonates of seventeen samples from nine veins in the El Zancudo deposit, Antioquia, Colombia, were investigated to reveal the origin of silver in Ag-rich tetrahedritess, to derive their crystallization temperatures and to examine the relationship between chemical compositions of Ag-rich tetrahedritess and their crystallization temperatures. The ores consist of arsenopyrite, pyrite, sphalerite, Ag-rich tetrahedritess, galena, boulangerite, andorite, owyheeite, diaphorite, jamesonite, miargyrite, bournonite, chalcopyrite, and electrum. Ag-rich tetrahedritess forms about 10 volume % of the total ores and is one of the most common and widely distributed sulfosalts in this deposit. Ag-rich tetrahedritess is rich in Ag (1.13 to 31.02 wt%) and Sb (22.93 to 29.82 wt%), and poor in As (0.06 to 2.43 wt%), consistent with the reported incompatibilities of Ag and As in Ag-rich tetrahedritess. The Zn/(Zn + Fe)-, Ag/(Ag + Cu)- and Sb/(Sb + As + Bi)-atomic ratios exhibit some variations among the veins. Ag-rich tetrahedritess with higher Ag/(Ag + Cu) ratios coexist with diaphorite, whereas those with lower ratios are not associated with this sulfosalt. Ag-rich tetrahedritess in the assemblages of Ag-rich tetrahedritess+ sphalerite and of Ag-rich tetrahedritess+ bournonite + galena shows no Zn ↔ Fe and Cu ↔ Ag variations between core and rim, respectively, negating the possibility of solid state reaction during cooling. Ag-rich tetrahedritess is thus regarded as primary phase. Homogenization temperatures of primary fluid inclusions in quartz and carbonates co-existing with Ag-rich tetrahedritess define the mineralization temperatures of 134 to 263°C. Independent crystallization temperatures of Ag-rich tetrahedrite estimated based on Zn/(Zn + Fe) and Ag/(Ag + Cu) ratios of the Ag-rich tetrahedritess associated with silver minerals such as miargyrite, andorite and diaphorite using Sack's thermochemical database lie in a range between 170 and ∼250°C. Both results are thus in good agreement. 相似文献
4.
Emanuele Perinati Marco Barbera Sebastian Diebold Alejandro Guzman Andrea Santangelo Chris Tenzer 《Experimental Astronomy》2017,44(3):387-399
We present a preliminary assessment of the non-X-ray background for the WFI on board ATHENA conducted at IAAT in the context of the collaborative background and radiation damage working group activities. Our main result is that in the baseline configuration originally assumed for the camera the requirement on the level of non-X-ray background could not be met. In light of the results of Geant4 simulations we propose and discuss a possible optimization of the camera design and pinpoint some open issues to be addressed in the next phase of investigation. One of these concerns the possible contribution to the non-X-ray background from soft protons and ions funneled to the focal plane through the optics. This is not quantified at this stage, here we just briefly report on our ongoing activities aimed at validating the mechanisms of proton scattering at grazing incidence. 相似文献
5.
Distributed discharge and sediment concentration predictions in the sub‐humid Ethiopian highlands: the Debre Mawi watershed 
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下载免费PDF全文 Seifu A. Tilahun Christian D. Guzman Assefa D. Zegeye Dessalegn C. Dagnew Amy S. Collick Birru Yitaferu Tammo S. Steenhuis 《水文研究》2015,29(7):1817-1828
Experimental research in the Ethiopian highlands found that saturation excess induced runoff and erosion are common in the sub‐humid conditions. Because most erosion simulation models applied in the highlands are based on infiltration excess, we, as an alternative, developed the Parameter Efficient Distributed (PED) model, which can simulate water and sediment fluxes in landscapes with saturation excess runoff. The PED model has previously only been tested at the outlet of a watershed and not for distributed runoff and sediment concentration within the watershed. In this study, we compare the distributed storm runoff and sediment concentration of the PED model against collected data in the 95‐ha Debre Mawi watershed and three of its nested sub‐watersheds for the 2010 and 2011 rainy seasons. In the PED model framework, the hydrology of the watershed is divided between infiltrating and runoff zones, with erosion only taking place from two surface runoff zones. Daily storm runoff and sediment concentration values, ranging from 0.5 to over 30 mm and from 0.1 to 35 g l?1, respectively, were well simulated. The Nash Sutcliffe efficiency values for the daily storm runoff for outlet and sub‐watersheds ranged from 0.66 to 0.82, and the Nash–Sutcliffe efficiency for daily sediment concentrations were greater than 0.78. Furthermore, the model uses realistic fractional areas for surface and subsurface flow contributions, for example between saturated areas (15%), degraded areas (30%) and permeable areas (55%) at the main outlet, while close similarity was found for the remaining hydrology and erosion parameter values. One exception occurred for the distinctly greater transport limited parameter at the actively gullying lower part of the watershed. The results suggest that the model based on saturation excess provides a good representation of the observed spatially distributed runoff and sediment concentrations within a watershed by modelling the bottom lands (as opposed to the uplands) as the dominant contributor of the runoff and sediment load. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
6.
Addressing climate change requires the synergy of technological, behavioural and market mechanisms. This article proposes a policy framework that integrates the three, deploying personal carbon trading as a key element within a policy portfolio to reduce personal carbon footprints. It draws on policy and human motivation literatures that address the behavioural changes that may be needed in the context of a long-term threat such as climate change. This proposal builds on an analysis of the British Columbia carbon tax, international examples of carbon pricing instruments and strategies for behavioural change such as social networks, loyalty management, mobile apps and gamification. Interviews were conducted with experts in financial services, energy conservation and clean technology, as well as with specialists in climate, health and taxation policy. Their input, together with a review of the theoretical literature and practical case studies, informed the proposed design of a Carbon, Health and Saving System for promoting individual engagement and collective action by linking long-term climate mitigation measures with short-term personal and social goals, including health, recreation and social reinforcement.Policy RelevanceThis article identifies areas for climate policy innovation and recommends policies that can support, promote and enable personal carbon budgeting and collective action. Although this study is focused on British Columbia, both the input provided by key opinion leaders and the proposed framework are applicable to other jurisdictions.This policy proposal shows how personal carbon trading could work in the context of a Canadian province with an existing climate mitigation policy. It also specifies a minimum viable product approach to establishing the economic, social and technological foundations for personal carbon trading.The Carbon, Health and Saving System identifies the technologies and stakeholders needed to implement personal carbon trading, and offers the possibility of motivating a widespread conscious human response in the event that carbon taxation proves insufficient to generate economic adaptation in a changing climate. 相似文献
7.
U. Ott S. Merchel S. Herrmann S. Pavetich G. Rugel T. Faestermann L. Fimiani J. M. Gomez‐Guzman K. Hain G. Korschinek P. Ludwig M. D'Orazio L. Folco 《Meteoritics & planetary science》2014,49(8):1365-1374
Cosmogenic He, Ne, and Ar as well as the radionuclides 10Be, 26Al, 36Cl, 41Ca, 53Mn, and 60Fe have been determined on samples from the Gebel Kamil ungrouped Ni‐rich iron meteorite by noble gas mass spectrometry and accelerator mass spectrometry (AMS), respectively. The meteorite is associated with the Kamil crater in southern Egypt, which is about 45 m in diameter. Samples originate from an individual large fragment (“Individual”) as well as from shrapnel. Concentrations of all cosmogenic nuclides—stable and radioactive—are lower by a factor 3–4 in the shrapnel samples than in the Individual. Assuming negligible 36Cl decay during terrestrial residence (indicated by the young crater age <5000 years; Folco et al. 2011 ), data are consistent with a simple exposure history and a 36Cl‐36Ar cosmic ray exposure age (CRE) of approximately (366 ± 18) Ma (systematic errors not included). Both noble gases and radionuclides point to a pre‐atmospheric radius >85 cm, i.e., a pre‐atmospheric mass >20 tons, with a preferred radius of 115–120 cm (50–60 tons). The analyzed samples came from a depth of approximately 20 cm (Individual) and approximately 50–80 cm (shrapnel). The size of the Gebel Kamil meteoroid determined in this work is close to estimates based on impact cratering models combined with expectations for ablation during passage through the atmosphere (Folco et al. 2010 , 2011 ). 相似文献
8.
Ivan L. Guzman Magued Iskander Eduardo Suescun-Florez Mehdi Omidvar 《Acta Geotechnica》2014,9(2):187-206
This paper presents the geotechnical properties of a new family of synthetic transparent soils made of fused quartz, saturated with a matched refractive index water-based sucrose solution, suitable for modeling the behavior of sand in small-scale model tests. The dry density ranged between 1,134 and 1,358 kg/m3. The peak angle of friction was found to range from 46° to 57°. The average hydraulic conductivity was 1.7 × 10?5 cm/s. The compressibility index (C c) ranged from 0.34 to 0.57. The main advantage of fused quartz over available sand surrogates made of silica gel is that its solid structure better models the behavior of natural sand. The matching pore fluids are inert and non-toxic, which facilitates their use in educational settings. The availability of a safe and easy-to-use transparent sand permits measurement of three-dimensional deformation patterns and flow characteristics in controlled research experiments. The introduction of an aqueous solution permits the use of two immiscible pore fluids, one made of mineral oil and the other made of a sucrose solution, for modeling multiphase flow problems, as well as coupled flow-deformation problems. 相似文献
9.
Enrique Guzman 《Astrophysics and Space Science》1990,173(1):163-164
In this paper, we again discuss the new Brans-Dicke-Bianchi type-VII
h
perfect fluid solutions, first given by us (Guzman, 1989). It is shown that the objections presented by Lorenz-Petzold (1989) are misleading. The dust case =0 is discussed. 相似文献
10.
Enrique Guzman 《Astrophysics and Space Science》1993,199(2):289-292
We have found the most general solution for the Bianchi type-I equations in the Brans-Dicke theory (BDT) for the vacuum case. It is shown that forw > 500 the Universe will become isotropic for any amount of initial anisotropy, secondly it is shown that in the extended inflation scenario, the BDT-scalar field can avoid the inflation in one direction,R
3. In the other scale factorsR
1 andR
2 there is inflationary expansion. 相似文献