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211.
The use of multifunctionalism to conceptualise contemporary rural landscapes has focused attention on the increased extent and impact of non-farmers in traditionally agriculture-based rural communities. Typologies of rural landholders have been developed as part of that research effort. However, those typologies are not grounded in established theory, including collective identity theory that could provide an important foundation for the study of occupational identity. Indeed, most quantitative studies may be flawed in drawing on only one of the seven elements contributing to collective identity. This paper examines the efficacy of relying on self-declared occupational identity through the analysis of rural landholder survey data in an Australian region. Tests for expected relationships between self-declared identity of farmer/non-farmer and social and farming variables expected to be correlated with occupation, such as property size, profitability, hours worked on- and off-property, enterprise type and membership of farming-related local organisations found that the expected relationships existed. It seems that self-declared occupational identity is a valid and cost-effective way to explore occupational identity amongst rural landholders. Collective identity, however, is complex and it is unlikely that important research questions can be adequately explored without a more holistic approach to the study of farmer identity in multifunctional landscapes. The paper concludes with a discussion of the potential benefits of moving beyond self-declared occupation to include other elements in the collective identity construct. 相似文献
212.
A comparative study of melt-rock reactions in the mantle: laboratory dissolution experiments and geological field observations 总被引:2,自引:2,他引:0
Systematic variations in mineralogy and chemical composition across dunite-harzburgite (DH) and dunite-harzburgite-lherzolite
(DHL) sequences in the mantle sections of ophiolites have been widely observed. The compositional variations are due to melt-rock
reactions as basaltic melts travel through mantle peridotite, and may be key attributes to understanding melting and melt
transport processes in the mantle. In order to better understand melt-rock reactions in the mantle, we conducted laboratory
dissolution experiments by juxtaposing a spinel lherzolite against an alkali basalt or a mid-ocean ridge basalt. The charges
were run at 1 GPa and either 1,300°C or 1,320°C for 8–28 h. Afterward, the charges were slowly cooled to 1,200°C and 1 GPa,
which was maintained for at least 24 h to promote in situ crystallization of interstitial melts. Cooling allowed for better
characterization of the mineralogy and mineral compositional trends produced and observed from melt-rock reactions. Dissolution
of lherzolite in basaltic melts with cooling results in a clinopyroxene-bearing DHL sequence, in contrast to sequences observed
in previously reported isothermal-isobaric dissolution experiments, but similar to those observed in the mantle sections of
ophiolites. Compositional variations in minerals in the experimental charges follow similar melt-rock trends suggested by
the field observations, including traverses across DH and DHL sequences from mantle sections of ophiolites as well as clinopyroxene
and olivine from clinopyroxenite, dunite, and wehrlite dikes and xenoliths. These chemical variations are controlled by the
composition of reacting melt, mineralogy and composition of host peridotite, and grain-scale processes that occur at various
stages of melt-peridotite reaction. We suggest that laboratory dissolution experiments are a robust model to natural melt-rock
reaction processes and that clinopyroxene in replacive dunites in the mantle sections of ophiolites is genetically linked
to clinopyroxene in cumulate dunite and pyroxenites through melt transport and melt-rock reaction processes in the mantle. 相似文献
213.
Sheryl A. SINGERLING Aubrey L. MODI Blake MCFERRIN Emily A. WORSHAM Harry Y. MCSWEEN JR. Douglas RUMBLE III Ryoji TANAKA Lawrence A. TAYLOR 《Meteoritics & planetary science》2013,48(2):E1-E9
Abstract– This work describes two newly discovered eucrite breccias: three presumably paired meteorites, all named Northwest Africa (NWA) 6105, and NWA 6106. For each meteorite, major‐ and minor‐element compositions of minerals were determined using the electron microprobe. Pyroxene Fe‐Mn co‐variations and bulk‐rock oxygen isotope compositions confirm their classification as eucrites. Variations in mineral compositions and textures are attributed to differences in clast types present (i.e., basaltic or cumulate eucrite). The pyroxene compositions support the hypothesis that samples NWA 6105,1; 6105,2; and 6105,3 are paired polymict eucritic breccias, whereas sample NWA 6106 is a monomict basaltic eucritic breccia. Two‐pyroxene geothermometry yields temperatures too low for igneous crystallization. The variation in temperatures among samples suggests that metamorphism occurred prior to brecciation. 相似文献
214.
Kayvan Karimi Askarani Emily B. Stockwell Keith R. Piontek Tom C. Sale 《Ground Water Monitoring & Remediation》2018,38(3):43-52
Natural depletion of subsurface petroleum liquids releases energy in the form of heat. The rate of natural source zone depletion (NSZD) can be derived from subsurface temperature data. An energy balance is performed to resolve NSZD‐generated energy in terms of W/m2. Biodegradation rates are resolved by dividing the NSZD energy by the heat of reaction in joules/mol. Required temperature data are collected using data loggers, wireless connections, and automated data storage and analysis. Continuous thermal resolution of monthly NSZD rates at a field site indicates that apparent monthly NSZD rates vary through time, ranging from 10,000 to 77,000 L/ha/year. Temporal variations in observed apparent NSZD rates are attributed to processes governing the conversion of CH4 to CO2, as opposed to the actual rates of NSZD. Given a year or more of continuous NSZD rate data, it is anticipated that positive and negative biases in apparent NSZD rates will average out, and averaged apparent NSZD rates will converge to true NSZD rates. An 8.4% difference between average apparent NSZD rates over a 31‐month period using the thermal monitoring method and seven rounds of CO2 efflux measurements using CO2 traps supports the validity of both CO2 trap and thermal monitoring methods. A promising aspect of thermal monitoring methods is that continuous data provide a rigorous approach to resolving the true mean NSZD rates as compared to temporally sparse CO2 trap NSZD rate measurements. Overall, a vision is advanced of real‐time sensor‐based groundwater monitoring that can provide better data at lower costs and with greater safety, security, and sustainability. 相似文献
215.
The timing of seasonal snowmelt in high-latitude tundra has implications ranging from local biological productivity to global atmospheric circulation, yet remains difficult to quantify, particularly at large spatial scales. Snowmelt detection in such remote polar environments is possible using satellite-based microwave scatterometers, such as NASA’s QuikSCAT. QuikSCAT measured scattering in Ku-band, which is sensitive to snowmelt signals, from 1999 until the antenna failed in 2009. The Advanced Scatterometer (ASCAT) (2006–2021 (projected) operational), which operates at C-band, may be able to extend the QuikSCAT record, but existing techniques fail to adequately monitor tundra environments. Here, we designed a departure threshold algorithm to produce a consistent 15-year time series of melt onset for the tundra of the Alaskan North Slope, using the overlap period for the enhanced resolution datasets to calibrate the ASCAT melt detection record against QuikSCAT. We produced a time series of day of year of melt onset for 4.45 km x 4.45 km grid cells on the Alaskan North Slope from 2000–2014. Time series validation with in situ mean daily air temperature produced mean R2 values of 0.75 (QuikSCAT) and 0.72 (ASCAT). We qualitatively observed a difference between early-season melt, which occurred rapidly and was driven by strong wind events, and more typical melt, which occurred gradually along a latitudinal gradient. We speculate that future melt timing will have greater frequency of early-season onset as climate change destabilizes the high-latitude atmosphere. 相似文献
216.
Emily Bukowski 《Geographical review》2019,109(2):180-198
Prior to the arrival of Dutch elm disease to the United States in 1930, American elm (Ulmus americana) had become one of the most beloved and commonly planted urban trees throughout the country, especially in the Northeastern United States. The trees were revered for their beauty, hardiness, and the corridor‐like shade provided to city streets. Syracuse, NY stands as an example of this popularity: in 1951, when the disease first arrived in the city, over 50,000 elms grew in the city. But over the course of twenty years, nearly all elms in the city had become infected and succumbed to the disease. Although efforts to control the fungus in Syracuse ultimately failed to stop elm loss, the case study can be used to better inform contemporary urban forest management practices today by highlighting the effects of mixed property ownership in cities and its effects on pest management. 相似文献
217.
218.
Jenni E. Sherriff Keith N. Wilkinson Poppy Harding Hayley Hawkins Rhys G. O. Timms Daniel S. Adler Emily J. Beverly Simon P. E. Blockley Boris Gasparyan Christina J. Manning Darren Mark Samvel Nahapetyan Katie J. Preece 《第四纪科学杂志》2022,37(1):6-27
The significance of the southern Caucasus in understanding Pleistocene hominin expansions is well established. However, the palaeoenvironments in which Palaeolithic occupation of the region took place are presently poorly defined. The Hrazdan river valley, Armenian Highlands, contains a rich Palaeolithic record alongside Middle Pleistocene volcanic, fluvial and lacustrine strata, and thus offer exciting potential for palaeoenvironmental reconstruction. We present the first results of sedimentological, geochemical, tephrostratigraphical and biological (diatoms) study of the sequence of Bird Farm 1, located in the central part of the valley. These data show six phases of landscape development during the interval 440–200 ka. The sequence represents the first quantitative Pleistocene diatom record from the Armenian Highlands and the southern Caucasus, and indicates the persistence of a deep, stratified lacustrine system, with evidence for changing lake productivity that is tentatively linked to climate. Furthermore, major element chemical characterization of visible and crypto-tephra horizons in the sequence enables the first stages of the development of a regional tephrostratigraphy. Together, the evidence from Bird Farm 1 demonstrates the importance of lacustrine archives in the region for palaeoenvironmental reconstruction and highlights the potential for linkages between archives on both a local and regional scale. 相似文献
219.
Emily M. Chiappe Richard D. Ash Arto Luttinen Sari Lukkari Jukka Kuva Connor D. Hilton Richard J. Walker 《Meteoritics & planetary science》2023,58(12):1747-1759
The meteorite Lieksa was found in 2017 in Löpönvaara, Finland, and later donated to the Finnish Museum of Natural History. Here, we report siderophile element concentrations, genetic isotopic data, and a metal–silicate segregation age for the meteorite. The ~280 g Lieksa is ~80% metal and ~20% silicate and oxide inclusions by volume, with the inclusions consisting primarily of Fe-rich olivine. Due to Lieksa's silicate content, coupled with a texture characterized by metal enclosing the silicates, it has been classified as a pallasite. Lieksa's olivine and bulk chemical characteristics are distinct from those of the known pallasite and iron meteorite groups, consistent with its classification as ungrouped. The meteorite exhibits a flat, chondrite-normalized highly siderophile element pattern, consistent with an origin as an early crystallization product from a metallic melt with chondritic relative abundances. Molybdenum, Ru, and 183W isotopic data indicate that Lieksa formed in the non-carbonaceous (NC) domain of the solar nebula. Radiogenic 182W abundances for Lieksa yield a model metal–silicate segregation age of 1.5 ± 0.8 Myr after calcium-aluminum-rich inclusion formation, which is within the range established for other NC-type pallasite and iron meteorite parent bodies. 相似文献