196,541 research outputs found
(Table 4) Age determination of wood and foraminiferal shells from sediment core MD98-2181
No full textFor data below 12.62 m see Broecker et al. (2004)
Saint-Lizier
No full textIdentifiant de l'opération archéologique : Date de l'opération : 1989 (SD) Inventeur(s) : Broecker Régine La dépose partielle du plancher du chœur durant sa restauration a donné l'occasion d'un sondage limité dans l'ancienne cathédrale établie dans la « Ville Basse », dont la nef a été explorée en 1958 par S. Stym-Popper (Gallia,1959 : 409). Cinq sépultures le plus souvent recoupées, incomplètes du fait de l'exiguïté du sondage (1,50 m2), ont été relevées sur une épaisseur de 1,50 m jusqu'au..
Accelerator radiocarbon ages on foraminifera separated form deep-sea sediments
No full textA first set of accelerator radiocarbon dates for foraminifera shells separated from a deep-sea core from the western equatorial Pacific is reported. While the ultimate objective of this work is to obtain evidence for changes in the rate of deep-sea ventilation over the last 20,000 years, this preliminary study concentrates on illuminating some of the possible biases which will surely complicate such studies. The results reveal that while whole shells and shell fragments of a single species give ages which agree within experimental error, there are significant differences among the ages for coexisting whole shells of different planktonic species. It is not possible as yet to pin down the source of these differences. Because of this, the finding that the benthic-planktonic age difference was greater 6000 to 12,000 years ago than over the last 5000 years does not necessarily mean that the ventilation rate for the deep sea was significantly slower during late glacial and early Holocene times than it is today. Other equally plausible explanations are possible. Much has yet to be learned about the origin and seafloor history of the material in deep-sea cores before any firm answers regarding paleocirculation rates can be obtained by this approach. Such studies should initially be concentrated on cores from areas of the seafloor characterized by a higher ratio of sedimentation rate to bioturbation depth than is found for typical open sea sediments
Saint-Lizier – Ancienne cathédrale
No full textIdentifiant de l'opération archéologique : Date de l'opération : 1989 (SD) Inventeur(s) : Broecker Régine La dépose partielle du plancher du chœur durant sa restauration a donné l'occasion d'un sondage limité dans l'ancienne cathédrale établie dans la « Ville Basse », dont la nef a été explorée en 1958 par S. Stym-Popper (Gallia,1959 : 409). Cinq sépultures le plus souvent recoupées, incomplètes du fait de l'exiguïté du sondage (1,50 m2), ont été relevées sur une épaisseur de 1,50 m jusqu'au..
Comment on “What do we know about the evolution of Mg to Ca ratios in seawater?” by Wally Broecker and Jimin Yu
No full textA record of the Mg/Ca ratio of ancient seawater is essential to understand variations in the major geological processes that control ocean chemistry and for estimating past ocean temperatures. A recent contribution by Broecker and Yu (2011) regarding past seawater Mg/Ca provides an unbalanced assessment of the uncertainties and key assumptions of the methodologies considered. It misrepresents aspects of a new method to estimate past ocean Mg/Ca proposed by Coggon et al. (2010); here we provide clarification of that approach. We estimate the accuracy and precision of seawater Mg/Ca estimates derived from planktonic foraminifera test calcite, the preferred approach of Broecker and Yu. These are shown to be consistent with other records that suggest major changes in seawater cation chemistry. An explanation of how major changes in the Mg/Ca of seawater might occur is beyond the scope of this comment
Constitutive activation of the G(s)alpha protein-adenylate cyclase pathway may not be sufficient to generate toxic thyroid adenomas
No full textIn toxic thyroid adenomas, mutations in the TSH receptor (TSH-R) gene or the gene encoding the alpha-subunit of the stimulatory guanine nucleotide-binding protein (G(s) alpha) have been demonstrated to constitutively activate the cAMP cascade, which subsequently stimulates the growth and function of these tumors. However, the widely varying thyroid phenotypes in patients with TSH-R germline mutations, ranging from only slightly enlarged diffuse to multinodular goiters, suggest that additional mechanisms may be effective in the pathogenesis of toxic adenomas. We have investigated the levels of stimulatory and inhibitory G protein alpha-subunits together with basal and TSH-stimulated adenylate cyclase (AC) activity in toxic adenomas with or without activating mutations and in nodular and extranodular tissues of a toxic goiter due to a germline mutation in the TSH-R gene. Augmented expression of G(s) alpha protein was detected in all toxic adenomas, independent of the presence of mutations, and in the nodular tissue of the toxic goiter, but not in the nonnodular hyperplastic tissue of the toxic goiter with the mutated TSH-R. Analogously, the expression of the alpha-subunit of the inhibitory G protein (G(i) alpha) was also increased in all adenomas and the nodular tissue of the goiter, but, again, not in the hyperplastic goiter tissue. Basal AC activity was high in all tissues with mutations, but was only slightly increased in adenomas without detected mutations. No correlation was detectable between basal or TSH-stimulated AC activity and the levels of G(s) alpha and G(i) alpha. Our data suggest that mutational activation of the cAMP cascade may not be sufficient to generate toxic nodules and adenomas, but far more complex mechanisms, including alterations of G protein signaling, may be effective in the pathogenesis of these tumors
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
(Table 1) Age determination of DSDP Hole 94-607 and sediment cores V30-101 and V23-81
No full textOxygen isotope measurements in Greenland ice demonstrate that a series of rapid warm-cold oscillations -called Dansgaard-Oeschger events- punctuated the last glaciation (Dansgard et al., 1993, doi:10.1038/364218a0). Here we present records of sea surface temperature from North Atlantic sediments spanning the past 90 kyr which contain a series of rapid temperature oscillations closely matching those in the ice-core record, confirming predictions that the ocean must bear the imprint of the Dansgaard–Oeschger events (Broecker et al., 1988, doi:10.1016/0033-5894(88)90082-8; 1990, doi:10.1029/PA005i004p00469). Moreover, we show that between 20 and 80 kyr ago, the shifts in ocean-atmosphere temperature are bundled into cooling cycles, lasting on average 10 to 15 kyr, with asymmetrical saw-tooth shapes. Each cycle culminated in an enormous discharge of icebergs into the North Atlantic (a 'Hein-rich event' (Bond et al., 1992, doi:10.1038/360245a0; Broecker et al., 1992, doi:10.1007/BF00193540), followed by an abrupt shift to a warmer climate. These cycles document a previously unrecognized link between ice sheet behaviour and ocean-atmosphere temperature changes. An important question that remains to be resolved is whether the cycles are driven by external factors, such as orbital forcing, or by inter-nal ice-sheet dynamics
"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
No full textWe 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
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