抗原变异可使得多种致病微生物易于逃避宿主免疫应答。表达在感染红细胞表面的恶性疟原虫红细胞表面蛋白1（PfPMP1）与感染红细胞、内皮细胞、树突状细胞以及胎盘的单个或多个受体作用，在黏附及免疫逃避中起关键的作用。每个单倍体基因组var基因家族编码约60种成员，通过启动转录不同的var基因变异体为抗原变异提供了分子基础。

疟原虫var基因转换速率变化导致抗原变异[英]／Paul H, Robert P, Christodoulou Z, et al//Proc Natl Acad Sci U S A

Additional co-authors: TJ Heaton, AG Hogg, KA Hughen, KF Kaiser, B Kromer, SW Manning, RW Reimer, DA Richards, JR Southon, S Talamo, CSM Turney, J van der Plicht, CE Weyhenmeyer

/pdf/intcal13-and-marine13-radiocarbon-age-calibration-curves-0-4f3vsbzfqx.pdf

IntCal13 and Marine13 radiocarbon age calibration curves 0-50,000 years cal BP

The recent completion of drilling at Vostok station in East Antarctica has allowed the extension of the ice record of atmospheric composition and climate to the past four glacial–interglacial cycles. The succession of changes through each climate cycle and termination was similar, and atmospheric and climate properties oscillated between stable bounds. Interglacial periods differed in temporal evolution and duration. Atmospheric concentrations of carbon dioxide and methane correlate well with Antarctic air-temperature throughout the record. Present-day atmospheric burdens of these two important greenhouse gases seem to have been unprecedented during the past 420,000 years.

Climate and atmospheric history of the past 420,000 years from the Vostok ice core, Antarctica

/pdf/climate-and-atmospheric-history-of-the-past-420-000-years-2jdtde1xna.pdf

Surface winds and surface ocean hydrography in the subpolar North Atlantic appear to have been influenced by variations in solar output through the entire Holocene. The evidence comes from a close correlation between inferred changes in production rates of the cosmogenic nuclides carbon-14 and beryllium-10 and centennial to millennial time scale changes in proxies of drift ice measured in deep-sea sediment cores. A solar forcing mechanism therefore may underlie at least the Holocene segment of the North Atlantic's "1500-year" cycle. The surface hydrographic changes may have affected production of North Atlantic Deep Water, potentially providing an additional mechanism for amplifying the solar signals and transmitting them globally.

http://science.sciencemag.org/content/sci/294/5549/2130.full.pdf

Persistent Solar Influence on North Atlantic Climate During the Holocene

10 Be and 26 Al in Greenland Cosmic Spherules; Evidence for Irradiation in Space as Small Objects and a Probable Cometary Origin

The Laschamp excursion is a period of reduced geomagnetic field intensity occurring 40.7 ± 1.0 kyr ago. As a consequence, cosmogenic isotope production increased dramatically and its sensitivity to solar activity was enhanced during this period. The latter occurs because a larger fraction of the lower-energy interstellar galactic cosmic-ray particles, normally excluded by the geomagnetic field, is able to reach Earth’s atmosphere. This produces a cosmogenic isotope production signal with a significant structure. As high-resolution 10 Be profiles from both Antarctica (EDC) and Greenland (NGRIP–GRIP) during this crucial period are now available, one can use them as input into a box carbon cycle model in order to predict atmospheric 14 C variations due to the Laschamp excursion. For this purpose, 10 Be data are converted into 14 C, using production calculations for the 10 Be- 14 C conversion, after correction for the estimated difference of sensitivity between polar and global 10 Be deposition. Several scenarios of carbon cycle state are simulated, from preindustrial to glacial conditions. Applying two recent cosmogenic isotope production calculations for the 10 Be to 14 C conversion, we found that the resulting atmospheric ∆ 14 C variations are very sensitive to which of these two are employed. For example, ∆ 14 C amplitude under glacial conditions varies from 260‰ (EDC) and 320‰ (Greenland) to 430‰ (EDC) and 510‰ (Greenland) depending on the formulation used for 10 Be- 14 C conversion. DOI:  10.2458/56.16478

/pdf/use-of-10be-to-predict-atmospheric-14c-variations-during-the-180tzkea5u.pdf

Use of 10Be to Predict Atmospheric 14C Variations during the Laschamp Excursion: High Sensitivity to Cosmogenic Isotope Production Calculations

https://horizon.documentation.ird.fr/exl-doc/pleins_textes/pleins_textes_5/b_fdi_30-30/31871.pdf

10 Be and natural isotopes of U and Th in a laterite cover from Cameroon

In order to account for geomagnetically-induced changes in cosmogenic nuclide production rates in situ, and thereby increase the potential accuracy of exposure age dating, we have developed a numerical model which generates geomagnetically-calibrated exposure ages. Currently accepted, model-age calculations are based on time-averaged production rates. Use of time-averaged production rates may introduce systematic errors >20% in exposure ages causing cosmogenically dated events to be correlated incorrectly with events dated by other means (Clark et al., Quat. Res., 44, Nov, 1995). Applying our model to existing nuclide abundance data generally increases calculated exposure ages (Fig. 1), supports the 10Be-based assertion of Gosse et al. (Geology, 23, p. 877-880, 1995) that a glacial advance in the Rocky Mountains may have occurred during Younger Dryas time, and most importantly, reconciles three apparently disparate production rate estimates for 26Al and 10Be. We have created a computer program (COSMO-CALIBRATE) which uses generally accepted geomagnetic paleointensity records (Meynadier et al., Earth & Planetary Science Letters, 114, 39-57, 1992; and McElhinny & Senanayake, J. of Geomagnetism & Geoelectricity, 34, 39-51, 1982) and empirical relationships to account for cosmogenic isotope production rate variations over the last 140 ky. Magnetic field strengths are converted to apparent paleolatitudes using the formulation of Nishiizumi et al. (JGR, 94, 17907-17915, 1989) after which instantaneous production rates are calculated using the third degree polynomial of Lal (Earth & Planetary Science Letters, 104, 424-439, 1991). Muon contribution is currently assumed to be minimal as suggested by Brown et al. (GRL, 22, 703-706, 1995). Samples exposed at lower latitudes and higher altitudes will have experienced greater production rate variation (Fig. 2). Our program calculates instantaneous 10Be and 26Al production rates at any given sample site (altitude and latitude) and outputs both geomagnetically-calibrated and uncalibrated exposure ages from sample isotopic abundance data. Calibration, such as we propose, will likely increase the accuracy of exposure ages and once verified by additional data, may allow for more robust cosmogenic dating and correlation of relatively brief geomorphic and climatic events. Our program (COSMO-CALIBRATE) is available as user-friendly, compiled Macintosh code by anonymous ftp from beluga.uvm.edu.

/pdf/direct-examination-of-terrestrial-cosmogenic-nuclide-2ji3tkzt0e.pdf

Direct examination of terrestrial cosmogenic nuclide production rates of (super 10) Be, (super 3) He and (super 3) H.

/pdf/segmentation-of-the-el-tigre-fault-zone-san-juan-province-1kg9bis8te.pdf

Grant M. Raisbeck

Papers

10 Be and 26 Al in Greenland Cosmic Spherules; Evidence for Irradiation in Space as Small Objects and a Probable Cometary Origin

Use of 10Be to Predict Atmospheric 14C Variations during the Laschamp Excursion: High Sensitivity to Cosmogenic Isotope Production Calculations

10 Be and natural isotopes of U and Th in a laterite cover from Cameroon

Direct examination of terrestrial cosmogenic nuclide production rates of (super 10) Be, (super 3) He and (super 3) H.

Segmentation of the El Tigre Fault zone, San Juan Province (Argentina) from spot images analysis