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951.
Indian agriculture is trapped in a complex nexus of groundwater depletion and energy subsidies. This nexus is the product of past public policy choices that initially offered opportunities to India’s small-holder-based irrigation economy but has now generated in its wake myriad economic, social, and environmental distortions. Conventional ‘getting-the-price-right’ solutions to reduce these distortions have consistently been undermined by the invidious political economy that the nexus has created. The historical evolution of the nexus is outlined, the nature and scale of the distortions it has created are explored, and alternative approaches which Indian policy makers can use to limit, if not eliminate, the damaging impacts of the distortions, are analysed.  相似文献   
952.
The Miran oilfield is one of the new oil fields in Kurdistan region, northern Iraq, located in the Sulaimani Governorate. Twelve Cuttings samples from the Upper Jurassic Naokelekan and Barsarin formations in well Miran-2 were selected for detailed organic geochemical investigations. All the samples were subjected to bitumen extraction in order to study any biomarkers present using gas chromatography-mass spectrometry. The dominance of low-molecular-weight n-alkanes and other calculated parameters indicate a marine source for the organic matter derived from planktonic algal and bacterial precursors deposited under anoxic conditions. The isoprenoids/n-alkanes ratios indicate type II and mixed II/III kerogen for both formations. The type II/III kerogen is characteristic of transitional environment under anoxic to dysoxic conditions as also indicated by the homohopane index for studied samples. More argillaceous carbonate rocks were deposited when reducing conditions were prevalent. Medium to high gammacerane index values in the rock extracts probably indicate a stratified water column during deposition of both formations. The studied samples from both formations have entered peak oil window maturity as reflected from the biomarker ratios from both aliphatic and aromatic fractions of the extracts.  相似文献   
953.
A new ion exchange chromatography method is presented for the isolation of high field‐strength elements (HFSE) from freshwater and seawater samples that have undergone iron coprecipitation. Large volumes of water can be condensed through the application of iron coprecipitation, but clean separation of elements from the precipitate proves difficult. The technique described is a five‐column process designed to separate the HFSE, including rare earth elements such as neodymium and hafnium, before removing the iron and isolating uranium. Subsequent isolation of Nd and Hf was achieved using established ion exchange chromatography methods. The efficacy of our chemistry was verified by measurements of analytical reference materials – both reference solutions and seawater samples – subjected to the chemical separation methods described. Elution results indicate high yields (> 90%) determined by concentration measurements of a known reference material added to each column. Measurement results for isotopic compositions of seawater (U, Nd) and reference solutions (NIST SRM 960, U) were identical within uncertainty to previously published values. Compositions were identical between solutions (Spex CLMS3, Spex PLND2) that underwent different iron coprecipitation procedures. Isotopic determinations for reference materials JNdi‐1 and NIST SRM 960 measured with the mass spectrometers used in this study were in agreement with universally accepted values for these materials, and indicate high precision.  相似文献   
954.
The high-pressure behavior of Keokuk kaolinite has been studied to 9.5 GPa by infrared spectroscopy using synchrotron radiation. The kaolinite-I → kaolinite-II and kaolinite-II → kaolinite-III transformations have clear spectroscopic expression, with discontinuities coinciding with the transformation pressures bracketed by X-ray diffraction (Welch and Crichton in Am Mineral 95:651–654, 2010). The experimental spectra have been interpreted from band assignments derived from density functional theory for the structures of kaolinite-II and kaolinite-III, using as starting models the ab initio structures reported by Mercier and Le Page (Acta Crystallogr A B64:131–143, 2008, Mater Sci Technol 25:437–442, 2009) and unit-cell parameters from Welch and Crichton (Am Mineral 95:651–654, 2010). The relaxed theoretical structures are very similar to those reported by Mercier and Le Page (Acta Crystallogr A B64:131–143, 2008, Mater Sci Technol 25:437–442, 2009) in their theoretical investigation of kaolinite polytypes at high pressure. The vibrational spectra calculated from the quantum-mechanical analysis allow band assignments of the IR spectra to be made and provide insights into the behavior of different OH environments in the two high-pressure polytypes. The single perpendicular-interlayer OH group of kaolinite-III has a distinctive spectroscopic signature that is diagnostic of this polytype (ν = 3,595 cm−1 at 9.5 GPa) and is sensitive to the compression/expansion of the interlayer space. This OH group also has a distinctive signature in the calculated spectra. The spectra collected on decompression are those of kaolinite-III and persist largely unchanged to 4.6 GPa, except for a continuous blue shift of the 3,595 cm−1 band to 3,613 cm−1. Finally, kaolinite-I is recovered at 0.6 GPa, confirming the kaolinite-III → kaolinite-I transformation previously observed by X-ray diffraction, and the irreversibility of the kaolinite-II → kaolinite-III transformation. The ambient spectra collected at the start and finish of the experiment are those of kaolinite-I, and start/finish band frequencies agree to within 6 cm−1.  相似文献   
955.

There is a scarcity of long-term groundwater hydrographs from sub-Saharan Africa to investigate groundwater sustainability, processes and controls. This paper presents an analysis of 21 hydrographs from semi-arid South Africa. Hydrographs from 1980 to 2000 were converted to standardised groundwater level indices and rationalised into four types (C1–C4) using hierarchical cluster analysis. Mean hydrographs for each type were cross-correlated with standardised precipitation and streamflow indices. Relationships with the El Niño–Southern Oscillation (ENSO) were also investigated. The four hydrograph types show a transition of autocorrelation over increasing timescales and increasingly subdued responses to rainfall. Type C1 strongly relates to rainfall, responding in most years, whereas C4 notably responds to only a single extreme event in 2000 and has limited relationship with rainfall. Types C2, C3 and C4 have stronger statistical relationships with standardised streamflow than standardised rainfall. C3 and C4 changes are significantly (p <?0.05) correlated to the mean wet season ENSO anomaly, indicating a tendency for substantial or minimal recharge to occur during extreme negative and positive ENSO years, respectively. The range of different hydrograph types, sometimes within only a few kilometres of each other, appears to be a result of abstraction interference and cannot be confidently attributed to variations in climate or hydrogeological setting. It is possible that high groundwater abstraction near C3/C4 sites masks frequent small-scale recharge events observed at C1/C2 sites, resulting in extreme events associated with negative ENSO years being more visible in the time series.

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956.
957.
The crystallographic fabric of siderite in siderite concretions has been determined for upper Carboniferous (Westphalian‐A) non‐marine concretions and lower Jurassic (Pliensbachian) marine concretions. Compositional zoning indicates that individual siderite crystals grew over a period of changing pore water chemistry, consistent with the concretions being initially a diffuse patch of cement, which grew progressively. The siderite crystallographic fabric was analysed using the anisotropy of magnetic susceptibility, which is carried by paramagnetic siderite. The siderite concretions from marine and non‐marine formations exhibit differences in fabric style, although both display increases in the degree of preferred siderite c‐axis orientation towards the concretion margins. The Westphalian non‐marine siderites show a preferred orientation of siderite c‐axes in the bedding plane, whereas the Pliensbachian marine siderites have a preferred orientation of c‐axes perpendicular to the bedding. In addition, a single marine concretion shows evidence of earlier formed, inclined girdle‐type fabrics, which are intergrown with later formed vertical c‐axis siderite fabrics. The marine and non‐marine fabrics are both apparently controlled by substrate processes at the site of nucleation, which was probably clay mineral surfaces. Siderite nucleation processes on the substrate were most probably controlled by the (bio?) chemistry of the pore waters, which altered the morphology and crystallographic orientation of the forming carbonate. The preferred crystallographic orientation of siderite results from the orientation of the nucleation substrate. Fabric changes across the concretions partially mimic the progressive compaction‐induced alignment of the clay substrates, while the concretion grew during burial.  相似文献   
958.
The Christensen Mastodon Site, located in central Indiana, contains a rich assemblage of vertebrates (including mastodon, caribou, and giant beaver), invertebrates, and plant macrofossils in situ in lake and bog sediments of late-glacial age. Studies of pollen and plant macrofossils suggest the existence of open, white spruce-dominated boreal forests from >; 14,000 yr B.P. to ca. 13,000 yr B.P. The regional decline of spruce, local occurrence of black spruce, white spruce, and larch, immigration of many hardwood taxa (e.g., ash, oak, elm), and the initiation of bog development are recorded beginning about 13,000 yr B.P. Recent reconstructions of late-glacial and early postglacial vegetational changes provide a context for understanding the disappearance of mastodons. The dramatic and rapid restriction of boreal forests along the retreating ice margin from 11,000 to 9000 yr B.P. may have caused a substantial reduction of mastodon populations. A diminished population would be more susceptible to small-scale, stochastic events such as short-term extremes of weather, outbreaks of disease, or predation pressure from paleoindian hunters.  相似文献   
959.
Computer-controlled scanning electron microscopy is introduced as a faster, reliably and cost-reducing alternative to conventional electron microprobe analyses on kimberlite indicator minerals. The method is based on conventional scanning electron microscopy and energy dispersive X-ray spectrometry, but due to extended counting times, optimised settings and computer-controlled particle recognition valid data can be obtained on a low amount of operator and machine time. A comparison of the results between both methods yields that computer-controlled scanning electron microscopy is able to investigate major and minor element concentrations in indicator minerals with almost the same precision as the electron microprobe.  相似文献   
960.

Background  

The voluntary carbon market is a new and growing market that is increasingly important to consider in managing forestland. Monitoring, reporting, and verifying carbon stocks and fluxes at a project level is the single largest direct cost of a forest carbon offset project. There are now many methods for estimating forest stocks with high accuracy that use both Airborne Laser Scanning (ALS) and high-resolution optical remote sensing data. However, many of these methods are not appropriate for use under existing carbon offset standards and most have not been field tested.  相似文献   
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