The Calcium Isotope Composition (δ44/40Ca) of NIST SRM 915b and NIST SRM 1486     

Alexander Heuser  Anton Eisenhauer 《Geostandards and Geoanalytical Research》2008,32(3):311-315

The calcium isotopic composition of NIST SRM 915b and 1486 provided by the National Institute of Standards and Technology was analysed. The δ^44/40Ca values of the two reference materials relative to NIST SRM 915a were: NIST SRM 915b =+0.72 ± 0.04‰ and NIST SRM 1486 =?1.01 ± 0.02‰. NIST SRM 1486 did not require any chemical separation prior to measurement.  相似文献   

Extension and inversion structures in the Tethys–Atlantic linkage zone,Algarve Basin,Portugal     

Adrià Ramos  Oscar Fernández  Pedro Terrinha  Josep Anton Muñoz 《International Journal of Earth Sciences》2016,105(5):1663-1679

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Design of Pressure Relief Valves for Protection of Steel-Lined Pressure Shafts and Tunnels Against Buckling During Emptying   总被引：1，自引：1，他引：0  

Anton J. Schleiss  Pedro A. Manso 《Rock Mechanics and Rock Engineering》2012,45(1):11-20

Using high-strength steels for pressure shafts and tunnel liners and taking into account significant rock mass participation allows the design of comparatively thin steel liners in hydropower projects. Nevertheless, during emptying of waterways, these steel linings may be endangered by buckling. Compared with traditional measures such as increased steel liner thickness and stiffeners, pressure relief valves are a very economical solution for protection of steel liners against critical external pressure and therefore buckling during emptying. A calculation procedure has been developed for the design of the required number and arrangement of pressure relief valves, and this has been used successfully in practice. Systematic model tests enabled the assumptions of the design method to be verified.  相似文献   

Exiting,enduring and innovating: Farm household adaptation to global zoonotic disease     

Colin Ray Anderson  Stéphane Marc McLachlan 《Global Environmental Change》2012,22(1):82-93

Bovine spongiform encephalopathy (BSE) has been found in 25 countries, costing billions of dollars in those affected economies, and has had profound social and environmental impacts at multiple scales of organization. As a global phenomenon, the impacts of BSE were mediated directly through the environment (animal and human health) but in Canada the indirect socioeconomic impacts of BSE were far more damaging, especially for farm households. Yet, very little research has been conducted on adaptation to the indirect impacts of global environmental change, such as those mediated through the market and governance. Our goal was to examine how farm households adapted to the Canadian BSE crisis in order to better understand rural adaptations to global zoonotic diseases and to agriculture-related global environmental change as a whole. We conducted our mixed methods research in 2004–2006. Data sources included 826 survey responses, 27 individual interviews and 12 group interviews with farmers and ranchers in western Canada. Factor analysis separated out responses into three general adaptation strategies: ‘innovating’ to pursue new opportunities; ‘enduring’ or adaptations that seek stability; and ‘exiting’ from beef production or agriculture altogether. Farm household and community level innovation was a crucial adaptive strategy in the absence of governmental and expert-based support. Enduring adaptations were important to farm household survival in the short term, yet “chronic enduring” can compromise long-term adaptive capacity. Farm exiting was highly problematic during the BSE crisis as these responses were largely unexpected and often left households more vulnerable. Government support at the farm level promoted stability, with little support provided for change-orientated adaptations. Effective farm adaptation will require support for all three types of adaptive strategies and ones that are both expert-based and grassroots in nature to enable farm households in their pursuit of pluriactive and multifunctional livelihood strategies.  相似文献   

Investigation of iron sulfide impact crater residues: A combined analysis by scanning and transmission electron microscopy     

Penelope J. WOZNIAKIEWICZ  Hope A. ISHII  Anton T. KEARSLEY  Mark J. BURCHELL  Philip A. BLAND  John P. BRADLEY  Zurong DAI  Nick TESLICH  Gareth S. COLLINS  Mike J. COLE  Sara S. RUSSELL 《Meteoritics & planetary science》2011,46(7):1007-1024

Abstract– Samples returned from comet 81P/Wild 2 by the Stardust mission provided an unequaled opportunity to compare previously available extraterrestrial samples against those from a known comet. Iron sulfides are a major constituent of cometary grains commonly identified within cometary interplanetary dust particles (IDPs) and Wild 2 samples. Chemical analyses indicate Wild 2 sulfides are fundamentally different from those in IDPs. However, as Wild 2 dust was collected via impact into capture media at approximately 6.1 km s^?1, it is unclear whether this is due to variation in preaccretional/parent body processes experienced by these materials or due to heating and alteration during collection. We investigated alteration in pyrrhotite and pentlandite impacted into Stardust flight spare Al foils under encounter conditions by comparing scanning and transmission electron microscope (SEM, TEM) analyses of preimpact and postimpact samples and calculating estimates of various impact parameters. SEM is the primary method of analysis during initial in situ examination of Stardust foils, and therefore, we also sought to evaluate the data obtained by SEM using insights provided by TEM. We find iron sulfides experience heating, melting, separation, and loss of S, and mixing with molten Al. These results are consistent with estimated peak pressures and temperatures experienced (approximately 85 GPa, approximately 2600 K) and relative melting temperatures. Unambiguous identification of preserved iron sulfides may be possible by TEM through the location of Al‐free regions. In most cases, the Ni:Fe ratio is preserved in both SEM and TEM analyses and may therefore also be used to predict original chemistry and estimate mineralogy.  相似文献   

Documentary proxies and interdisciplinary research on historic geomorphologic hazards: a discussion of the current state from a central European perspective     

Pavel Raška  Vilém Zábranský  Jakub Dubišar  Antonín Kadlec  Alena Hrbáčová  Tomáš Strnad 《Natural Hazards》2014,70(1):705-732

During the last two decades, documentary data (written and iconographic sources) have been increasingly employed in geomorphologic research aiming at reconstruction of territorial distribution, temporal occurrence and social and economic impacts of various geomorphologic hazards. The goal of this paper is to broaden the previous discussion (Glade et al. The use of historical data in natural hazard assessments. Kluwer, Dordrecht, 2001) of the methodological constraints on the use of documentary data for geomorphologic hazard research. Using the interdisciplinary approach of geomorphology, historiography and medial studies, we firstly summarise the major finding of papers that have employed various types of documentary data sources to study geomorphologic hazards in different regions. In the second section, we present case studies from the Czech Republic resulting from the ongoing research project that is devoted to the assessment of the potential of documentary data to reconstruct past occurrences of and mitigation strategies for geomorphologic hazards. Finally, we discuss three main methodological issues emerging from our research: (a) problems emerging from the positivist approach to documentary data sources and the necessity for critical analyses of documentary data sources based on modern historiographic approaches, (b) constraints arising from the combination of documentary data from different spatiotemporal scales and (c) lacks in the use of documentary data to study local-based adaptation strategies to cope with geomorphologic hazards.  相似文献   

Lateral variation in structural style of mountain building: controls of rheological and rift inheritance     

Suzon Jammes  Ritske S. Huismans  Josep Anton Muñoz 《地学学报》2014,26(3):201-207

Many mountain belts exhibit significant along‐strike variation in structural style with changes in the width of the orogen, the geometry and kinematics of the crustal‐scale thrust system, and the degree of partitioning between pro‐ and retro‐wedge deformations. Although the main factors controlling first‐order structural style are understood, the cause of these lateral variations remains to be resolved. Here we focus on the Pyrenees, characterized by significant lateral variation in structural style with a thrust system involving more and thinner thrust sheets in the eastern section than in the western part. Similarly, the prior Mesozoic rifting event was characterized by significant lateral variation in structure. We integrate available geological and geophysical data with forward lithospheric scale numerical models. We show that lateral variation in crustal strength attributed to inherited Variscan crustal composition accentuated during Mesozoic rifting explains the variation in structural style observed during Pyrenean mountain building.  相似文献   

Impact of isostatic land uplift and artificial drainage on oxidation of brackish-water sediments rich in metastable iron sulfide   总被引：1，自引：0，他引：1  

Anton Boman  Sören Fröjdö  Mats E. Åström 《Geochimica et cosmochimica acta》2010,74(4):1268-177

This study examines the dynamics of sulfur and trace elements (As, Co, Mo, Ni, Ti and Zn) when brackish-water sediments, unusually rich in metastable iron sulfide (probably a mixture of mackinawite and greigite), are brought into the oxidation zone by postglacial isostatic land uplift and farmland drainage. When subaqueous sediments approach the sea level, metastable iron sulfide is oxidized in the upmost layers and pyrite preserved and even accumulated concomitantly trapping Co, Ni and Zn but not As and Mo. When the land uplift has brought the sediments above sea level and natural drainage thus is initiated, the pyrite is oxidized and Co, Ni and Zn are released and transported down the profile. If this setting remained undisturbed, the slightly oxidized sediment (unripe soil) would become covered by peat and thus protected from further oxidation and metal translocation. Often these sediments are, however, artificially drained resulting in extensive oxidation and fast soil-profile development. The soil is an acid sulfate (AS) soil, characterized by low pH (<4), extensive leaching of metals and an abundance of disseminated brownish Fe(III) precipitates. We suggest that the fast soil development is due to initial oxidation of metastable iron sulfide, followed by pyrite oxidation. Drain bottom sediment, which in terms of chemistry and S-isotopes resembled that of the surfacing sea bottom strata, acted during the sampling period as a sink for metals. The abundant preservation of metastable iron sulfide below the groundwater table, even long periods after uplift above the sea level, is a puzzling feature. We suggest that it is the net result of sulfur starvation, an abundance of Fe(II) and strongly reducing conditions.  相似文献   

Eccentric Eclipsing Binary YY Sagittarii     

Marek Wolf  P. G. Niarchos  K. D. Gazeas  V. N. Manimanis  Lenka Kotková  Anton Paschke  Miloslav Zejda 《Astrophysics and Space Science》2006,304(1-4):181-183

Seven new precise times of minimum light have been gathered for the triple eccentric eclipsing binary YY Sgr (P = 2^d.63, e = 0.16). Its O--C diagram is presented and improved elements of the apsidal motion and the light-time effect are given. We found a new short period of the third body of about 18.5 years in an eccentric orbit (e ₃ ≃ 0.4).  相似文献   

Radio frequency interference measurements in Indonesia     

Taufiq Hidayat  Achmad Munir  Budi Dermawan  Anton Timur Jaelani  Stéphane Léon  Dading Hadi Nugroho  Andriyan Bayu Suksmono  Putra Mahasena  Premana Wardayanti Premadi  Dhani Herdiwijaya  Chatief Kunjaya  Zadrach Ledoufij Dupe  Budi Brahmantyo  Denny Mandey  Muhammad Yusuf  Hesti Retno Tri Wulandari  Falahuddin Arief  Muhammad Irfan  Agus Triono Puri Jatmiko  Evan Irawan Akbar  Hery Leo Sianturi  Jehunias Leonidas Tanesib  Ali Warsito  Judhistira Aria Utama 《Experimental Astronomy》2014,37(1):85-108

We report the first measurements of radio frequency spectrum occupancy performed at sites aimed to host the future radio astronomy observatory in Indonesia. The survey is intended to obtain the radio frequency interference (RFI) environment in a spectral range from low frequency 10 MHz up to 8 GHz. The measurements permit the identification of the spectral occupancy over those selected sites in reference to the allocated radio spectrum in Indonesia. The sites are in close proximity to Australia, the future host of Square Kilometre Array (SKA) at low frequency. Therefore, the survey was deliberately made to approximately adhere the SKA protocol for RFI measurements, but with lower sensitivity. The RFI environment at Bosscha Observatory in Lembang was also measured for comparison. Within the sensitivity limit of the measurement equipment, it is found that a location called Fatumonas in the surrounding of Mount Timau in West Timor has very low level of RFI, with a total spectrum occupancy in this measured frequency range being about 1 %, mostly found at low frequency below 20 MHz. More detailed measurements as well as a strategy for a radio quiet zone must be implemented in the near future.  相似文献