196,692 research outputs found
Low resolution stable isotopes of ice core Taylor Dome
No full textThe delta 18O values were determined at the Quaternary Isotope Laboratory (M. Stuiver, Box 351360, University of Washington, Seattle WA 98195, USA). The time scale (st9507) was estimated from a correlation of delta 18O with the Vostok delta D record (Grootes et al. 1994; Steig, 1996). Between 0-340m the samples measured were of 1m cuts taken in the field. Each 1m core section was slabbed to provide a surface for ECM measurement; a thin slice was removed uniformly along the length for isotope analysis. From 340m to the bottom, sampling was done at the National Ice Core Lab at 0.5m lengths. Note that these core sections were shipped intact to NICL; they were not processed in the field
North Pacific response to millennial-scale changes in ocean circulation over the last 60 kyr
No full textPollen profile from exposure Fluderbach II, Samerberg
No full textZero at the base of the profile. A Picea trunk found at 2.26 m gave a radiometrical age of 72300 +4100/-2700 yrs BP, GrN-7225; Grootes, P.M. (1977). If autochthonous the wood dates the younger part of the spreading phase of Picea. A layer of sand and gravel between 4.465 m and 4.62 m divides the gyttja of the third interstadial into two parts
Transformation of organic matter in agricultural soils: radiocarbon concentration versus soil depth
No full textRadiocarbon measured by accelerator mass spectrometry (AMS) was used as a tracer to study the origin and fate of organic materials in soils. Fractionation methods used to separate the heterogeneous organic material into functionally defined pools of different stability included acid-alkali-acid extraction and density fractionation. C-14 values of the humin fraction, isolated from samples of different field trials at the agricultural station Rotthalmunster (Germany), yielded C-14 decreases of about 30% to 54% from the surface soil to ca. 65 cm depth. These results indicate a progressive enrichment of stable organic compounds with increasing soil depth. In contrast, a minor decline in 14C concentrations of the humic acid fraction, which mostly showed higher 14C values than the humin, reflect the translocation of modern organic carbon towards greater depth. Low radiocarbon levels of the light occluded particulate organic matter (14C results for density fractions from field trials located in a rural and an industrialized region reflect their susceptibility to contamination by fossil fuel-derived carbon and their heterogeneous composition. As a consequence individual short-chain phospholipid fatty acids (PLFA), as indicators for viable soil microbial biomass, were isolated by preparative capillary gas-chromatography. Compound-specific radiocarbon analysis of the isolated PLFAs revealed the assimilation of different substrates for their synthesis. C-14 concentrations of the monounsaturated PLFAs (n-C16:1, n-C17:1, and n-C18:1), which were close to the modern atmospheric C-14 level, suggest a high specificity to young carbon sources. The saturated PLFAs, isolated from the plough-horizon, were synthesized from sub-recent soil organic carbon (SOC) as shown by a higher contribution of bomb-C-14. A considerable 14C decrease from the surface to 30-45 cm soil depth of the saturated PLFAs indicates the incorporation of more stabilized SOC particularly in subsoil i/a-C15:0, n-C16:0, and 17C17:0 PLFAs. (c) 2004 Elsevier B.V. All rights reserved. [References: 48
Dr. Duane M. Jackson, Morehouse College, July 2011
No full textThis video is a conversation with Dr. Duane M. Jackson. Dr. Jackson talks about his paper, "Recall and the Serial Position Effect: The Role of Primacy and Recency on Accounting Students' Performance." Jackie Daniel, AUC Woodruff Library, is the interviewer
"Reflections on the subject of Emigration from Europe with a view to Settlement in the United States" By M. Carey.
No full text"Reflections on the subject of Emigration from Europe with a view to Settlement in the United States: containing bried sketches of the moral and political character of those states.
By M. Carey, member of the American philosophical, and of the American Antiquarian Society, and author of The Olive Branch, Cindiciae Hibernicae, essays on banking, on political economy, and on internal improvement.
To which are now added the English editor's comments on the subject; together with Important Advice to Emigrants, and Cautions Against Impositions Practiced in the Outports
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
Dr. Glendon Swarthout
No full textHosted by Roger M. Busfield, MSU Assistant Professor of Speech and Theater, Meet the Author is designed to introduce a general audience to a contemporary author and their work through in-depth interviews. This episode features a conversation between Dr. Glendon Swarthout, prolific author and English professor at MSU, and assistant professors Sam S. Baskett and Theodore B. Strandness
GISP2 Oxygen Isotope Data
No full textMeasured at University of Washingtons Quaternary Isotope Laboratory. Timescale (down to 2808 m) includes revisions by Meese as of Sept 1994. Depths below 167 m are D core; above 167 meters depths are B core+1.09 meters. Depth is top of interval
Storage and stability of organic matter and fossil carbon in a Luvisol and Phaeozem with continuous maize cropping: A synthesis
No full textQuantitative information about the amount and stability of organic carbon (OC) in different soil organic-matter (OM) fractions and in specific organic compounds and compound-classes is needed to improve our understanding of organic-matter sequestration in soils. In the present paper, we summarize and integrate results performed on two different arable soils with continuous maize cropping (a) Stagnic Luvisol with maize cropping for 24 y, b) Luvic Phaeozem with maize cropping for 39 y) to identify (1) the storage of OC in different soil organic-matter fractions, (2) the function of these fractions with respect to soil-OC stabilization, (3) the importance and partitioning of fossil-C deposits, and (4) the rates of soil-OC stabilization as assessed by compound-specific isotope analyses. The fractionation procedures included particle-size fractionation, density fractionation, aggregate fractionation, acid hydrolysis, different oxidation procedures, isolation of extractable lipids and phospholipid fatty acids, pyrolysis, and the determination of black C. Stability of OC was determined by 13C and 14C analyses. The main inputs of OC were plant litter (both sites) and deposition of fossil C likely from coal combustion and lignite dust (only Phaeozem).
Total soil OC stocks down to a depth of 65 cm (7.83 kg m–2 in the Luvisol and 9.66 kg m–2 in the Phaeozem) consisted mainly of mineral-bound OC (87% of total SOC in the Luvisol and 69% in the Phaeozem). In the Luvisol, free light particulate OM, OM associated with sand and coarse silt, and particulate OM occluded in macro-aggregates represented SOM fractions with mean turnover times shorter than that of the bulk soil OC (54 y). Additionally, the turnover of all individual compounds or compound classes (except for black carbon) was faster than that of bulk soil OC. These OM fractions that were less stable than the bulk soil OM made up 13% to 20% of the total OC. Organic matter in fine and medium silt and clay fractions, particulate OM occluded in micro-aggregates (53–250 lm) and OM resistant to acid hydrolysis had intermediate turnover times of about 50–100 y. These fractions with intermediate turnover times contributed 70%–80% to total soil OC. Passive OM with turnover times >200 y was isolated from the mineral-bound OM by different oxidation procedures (H2O2, Na2S2O8) and made up ≤10% of the total OC. The isotopic signature of PLFAs suggests an efficient recycling of OC derived from C3 substrate.
In the Phaeozem, partitioning of maize-derived C exhibited a pattern similar to the Luvisol, but turnover rates of vegetation-derived soil OC were lower, probably because of the considerably smaller input of plant residues. Fossil C contributed approx. 50% to the total OC and accumulated preferentially in the particulate OM occluded in aggregates and in the fine-sand and coarse-silt fractions. It formed a large stock of passive soil OM but a minor part also entered the microbial C cycle. The results show that the partitioning of OC derived from vegetation and deposition of fossil compounds among soil fractions differed mainly because of their different bioavailability and recalcitrance. There was no evidence for a high recalcitrance of individual plant compounds. Mineral-bound OM resistant to oxidation by H2O2 and Na2S2O8 represented highly stable OC pools in both soils
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