6 results
Global climate change and North American mammalian evolution
- John Alroy, Paul L. Koch, James C. Zachos
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- Journal:
- Paleobiology / Volume 26 / Issue S4 / 2000
- Published online by Cambridge University Press:
- 26 February 2019, pp. 259-288
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We compare refined data sets for Atlantic benthic foraminiferal oxygen isotope ratios and for North American mammalian diversity, faunal turnover, and body mass distributions. Each data set spans the late Paleocene through Pleistocene and has temporal resolution of 1.0 m.y.; the mammal data are restricted to western North America. We use the isotope data to compute five separate time series: oxygen isotope ratios at the midpoint of each 1.0-m.y. bin; changes in these ratios across bins; absolute values of these changes (= isotopic volatility); standard deviations of multiple isotope measurements within each bin; and standard deviations that have been detrended and corrected for serial correlation. For the mammals, we compute 12 different variables: standing diversity at the start of each bin; per-lineage origination and extinction rates; total turnover; net diversification; the absolute value of net diversification (= diversification volatility); change in proportional representation of major orders, as measured by a simple index and by a G-statistic; and the mean, standard deviation, skewness, and kurtosis of body mass. Simple and liberal statistical analyses fail to show any consistent relationship between any two isotope and mammalian time series, other than some unavoidable correlations between a few untransformed, highly autocorrelated time series like the raw isotope and mean body mass curves. Standard methods of detrending and differencing remove these correlations. Some of the major climate shifts indicated by oxygen isotope records do correspond to major ecological and evolutionary transitions in the mammalian biota, but the nature of these correspondences is unpredictable, and several other such transitions occur at times of relatively little global climate change. We conclude that given currently available climate records, we cannot show that the impact of climate change on the broad patterns of mammalian evolution involves linear forcings; instead, we see only the relatively unpredictable effects of a few major events. Over the scale of the whole Cenozoic, intrinsic, biotic factors like logistic diversity dynamics and within-lineage evolutionary trends seem to be far more important.
Accurate Nanoscale Crystallography in Real-Space Using Scanning Transmission Electron Microscopy
- J. Houston Dycus, Joshua S. Harris, Xiahan Sang, Chris M. Fancher, Scott D. Findlay, Adedapo A. Oni, Tsung-ta E. Chan, Carl C. Koch, Jacob L. Jones, Leslie J. Allen, Douglas L. Irving, James M. LeBeau
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- Journal:
- Microscopy and Microanalysis / Volume 21 / Issue 4 / August 2015
- Published online by Cambridge University Press:
- 14 July 2015, pp. 946-952
- Print publication:
- August 2015
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Here, we report reproducible and accurate measurement of crystallographic parameters using scanning transmission electron microscopy. This is made possible by removing drift and residual scan distortion. We demonstrate real-space lattice parameter measurements with <0.1% error for complex-layered chalcogenides Bi2Te3, Bi2Se3, and a Bi2Te2.7Se0.3 nanostructured alloy. Pairing the technique with atomic resolution spectroscopy, we connect local structure with chemistry and bonding. Combining these results with density functional theory, we show that the incorporation of Se into Bi2Te3 causes charge redistribution that anomalously increases the van der Waals gap between building blocks of the layered structure. The results show that atomic resolution imaging with electrons can accurately and robustly quantify crystallography at the nanoscale.
Contributors
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- By Basem Abdelmalak, Joseph Abdelmalak, Alaa A. Abd-Elsayed, David L. Adams, Eric E. Adelman, Maged Argalious, Endrit Bala, Gene H. Barnett, Sheron Beltran, Andrew Bielaczyc, William Bingaman, James M. Blum, Alina Bodas, Vera Borzova, Richard Bowers, Adam Brown, Chad M. Brummett, Alexandra S. Bullough, James F. Burke, Juan P. Cata, Neeraj Chaudhary, Michael J. Claybon, Miguel Cruz, Milind Deogaonkar, Vikram Dhawan, Thomas Didier, D. John Doyle, Zeyd Ebrahim, Hesham Elsharkawy, Wael Ali Sakr Esa, Ehab Farag, Ryen D. Fons, Joseph J. Gemmete, Matt Giles, Phil Gillen, Goodarz Golmirzaie, Marcos Gomes, Lisa Grilly, Maged Guirguis, David W. Healy, Heather Hervey-Jumper, Shawn L. Hervey-Jumper, Paul E. Hilliard, Samuel A. Irefin, George K. Istaphanous, Teresa L. Jacobs, Ellen Janke, Greta Jo, James W. Jones, Rami Karroum, Allen Keebler, Stephen J. Kimatian, Colleen G. Koch, Robert Scott Kriss, Andrea Kurz, Jia Lin, Michael D. Maile, Negmeldeen F. Mamoun, Mariel Manlapaz, Edward Manno, Donn Marciniak, Piyush Mathur, Nicholas F. Marko, Matthew Martin, George A. Mashour, Marco Maurtua, Scott T. McCardle, Julie McClelland, Uma Menon, Paul S. Moor, Laurel E. Moore, Ruairi Moulding, Dileep R. Nair, Todd Nelson, Julie Niezgoda, Edward Noguera, Jerome O’Hara, Aditya S. Pandey, Mauricio Perilla, Paul Picton, Marc J. Popovich, J. Javier Provencio, Venkatakrishna Rajajee, Mohit Rastogi, Stacy Ritzman, Lauryn R. Rochlen, Leif Saager, Vivek Sabharwal, Oren Sagher, Kenneth Saliba, Milad Sharifpour, Lesli E. Skolarus, Paul Smythe, Wolf H. Stapelfeldt, William R. Stetler, Peter Stiles, Vijay Tarnal, Khoi D. Than, B. Gregory Thompson, Alparslan Turan, Christopher R. Turner, Justin Upp, Sumeet Vadera, Jennifer Vance, Anthony C. Wang, Robert J. Weil, Marnie B. Welch, Karen K. Wilkins, Erin S. Williams, George N. Youssef, Asma Zakaria, Sherif S. Zaky, Andrew Zura
- Edited by George A. Mashour, Ehab Farag
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- Book:
- Case Studies in Neuroanesthesia and Neurocritical Care
- Published online:
- 03 May 2011
- Print publication:
- 03 February 2011, pp x-xvi
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Contributors
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- By Paul Appelbaum, Robert R. Bies, Kristin L. Bigos, Stanley N. Caroff, James J. Crowley, Sonia M. Davis, Vicki G. Davis, Donald C. Goff, Richard Kaczynski, Richard S. E. Keefe, Gary G. Koch, Douglas L. Leslie, Jeffrey A. Lieberman, Joseph P. McEvoy, Stephen R. Marder, Jonathan M. Meyer, Del D. Miller, John L. Olsen, Deborah A. Perlick, Bruce G. Pollock, Fred Reimherr, Sandra G. Resnick, Robert A. Rosenheck, T. Scott Stroup, Patrick F. Sullivan, Jeffrey Swanson, Marvin S. Swartz, Richard Van Dorn
- Edited by T. Scott Stroup, Columbia University, New York, Jeffrey A. Lieberman, Columbia University, New York
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- Book:
- Antipsychotic Trials in Schizophrenia
- Published online:
- 03 May 2010
- Print publication:
- 01 April 2010, pp ix-x
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Methanol, pectin and pectinesterase changes during soybean seed maturation
- James L. Koch, Marcin Horbowicz, Ralph L. Obendorf
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- Journal:
- Seed Science Research / Volume 9 / Issue 4 / April 1999
- Published online by Cambridge University Press:
- 22 February 2007, pp. 311-320
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Methanol accumulates in maturing seeds, correlating with preharvest deterioration. Since the source of methanol may be from pectin de-methylation, methanol, cell wall uronic acid, pectin methyl esterification, pectinesterase (PE; EC 3.1.1.11) activity, and neutral sugar composition and partitioning of cell wall polysaccharides were determined during soybean (Glycine max [L.] Merrill) seed development, maturation, and desiccation in planta. Axis cell wall polysaccharides were more easily solubilized, richer in uronic acid, rhamnose, and xylose, and less rich in galactose than cotyledon cell wall polysaccharides. Methanol accumulated to 9.7 μg per two cotyledons and 0.5 μg per axis; total methanol decreased to 3 μg per two cotyledons during loss of green color. Total uronic acid increased from 0.12 to 0.27 mg per axis and 0.9 to 4 mg per cotyledon between 24 and 50 days after flowering (DAF). After loss of green color, pectin methyl esterification in axes increased from 7 to 24 mole% between 50 and 60 DAF but decreased to 14 mole%by 62 DAF in latter stages of seed desiccation. In cotyledons, methyl esterification ranged from 25 to 40 mole% and was 31 mole% after desiccation. PE activity increased 100 fold in axes, including a 30-fold increase in activity after loss of green color at 46 DAF. Cotyledon PE activity was 40-fold higher than in axes at 24 DAF, declined 75% by 56 DAF, and then increased 5 fold during desiccation. Pectin methyl de-esterification by PE is sufficient to be the sole source for methanol accumulation in seed tissues during development and maturation.
Isotopic evidence for paleoclimatic and paleoatmospheric variations from the Paleogene Bighorn Basin sequence
- Paul L. Koch, David L. Dettman, James C. Zachos
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- Journal:
- The Paleontological Society Special Publications / Volume 6 / 1992
- Published online by Cambridge University Press:
- 26 July 2017, p. 170
- Print publication:
- 1992
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Land mammal faunas changed dramatically from the late Paleocene to the Eocene. This interval was marked by substantial paleoceanographic changes, including marine warming, and mass extinction of benthic foraminifera. Yet study of the impact of marine events on continental climates and faunas is problematic, due to imprecision in marine/continental correlation.
Oxygen isotope measurements of paleosol carbonates, mammals, and bivalves from the Paleogene Bighorn Basin can be used to estimate mean annual temperature (MAT). The δ18O of paleosol carbonate is controlled by two factors: the δ18O of the groundwater from which it crystallizes, and the temperature during crystallization. Because mammals and bivalves secrete mineral in a biologically-restricted range of temperatures, their isotopic compositions serve as proxy indicators of surface water δ18O. The difference in δ18O between these proxy indicators of water and paleosol carbonate is used to calculate MAT through application of standard oxygen isotope thermometry relationships. Calculated temperatures vary significantly throughout the interval, with high values (>20°) in the late Paleocene, lower values in the earliest Eocene (10–20°), and renewed warmth later in the Early Eocene.
In modern temperate regions, MAT and the δ18O of precipitation are closely correlated. Estimates for Paleocene/Eocene surface waters from tooth apatite and bivalves range from −8 to −12± (SMOW). Today, precipitation with values this low is usually found in cold regions (0–10°). These temperature estimates are too low in light of other isotopic and paleobotanical indicators, which suggest very warm temperatures in the Bighorn Basin during the Paleogene. We hypothesize that vapor transport to the region was substantially different than at present. A potential model may be Amazonia, where wet season air masses lose up to 80% of their water vapor as they move across the basin, resulting in 18O-depleted rainfall despite a warm climate.
Variations in δ13C provide a tool for marine/continental correlation. Carbon in tooth apatite and soil carbonate is derived from plants, which fix atmospheric CO2. Atmospheric CO2 is, in turn, in isotopic equilibrium with marine carbonate. Because of these links, marine carbonate, land plants, land mammals, and soil carbonate should exhibit coupled carbon isotope variations. In the Paleogene, when C3 plants dominated floras, isotopic variations due to shifting floral composition, such as those documented in the Miocene Siwalik Sequence, could not occur. Paleogene continental and marine carbon isotope records are tightly coupled. In particular, there is an unusual marine carbon isotope excursion immediately preceding the Paleocene/Eocene boundary, which corresponds precisely to the major paleoceanographic changes and the extinction of benthic foraminifera. Tooth apatite and soil carbonate from the Paleogene Bighorn Basin also record this excursion, which occurs at the base of the Wasatchian, where perrisodactyls, artiodactyls, and modern primates first appear. Carbon isotopes allow tight marine/continental correlation of the Paleocene/Eocene boundary, and demonstrate that major biologic and climatic events at this time were globally synchronous.