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

Recently reported radioisotopic dates and magnetic anomaly spacings have made it evident that modification is required for the age calibrations for the geomagnetic polarity timescale of Cande and Kent (1992) at the Cretaceous/Paleogene boundary and in the Pliocene. An adjusted geomagnetic reversal chronology for the Late Cretaceous and Cenozoic is presented that is consistent with astrochronology in the Pleistocene and Pliocene and with a new timescale for the Mesozoic. The age of 66 Ma for the Cretaceous/Paleogene (K/P) boundary used for calibration in the geomagnetic polarity timescale of Cande and Kent (1992) (hereinafter referred to as CK92) was supported by high precision laser fusion Ar/Ar sanidine single crystal dates from nonmarine strata in Montana. However, these age determinations are now

/pdf/revised-calibration-of-the-geomagnetic-polarity-timescale-3xg69p3ilk.pdf

Revised calibration of the geomagnetic polarity timescale for the Late Cretaceous and Cenozoic

Assembly, configuration, and break-up history of Rodinia: A synthesis

The Lu–Hf and Sm–Nd isotopic composition of CHUR: Constraints from unequilibrated chondrites and implications for the bulk composition of terrestrial planets

The revolution that wasn't: a new interpretation of the origin of modern human behavior.

Small gabbroic bodies intruding metagraywackes and cherts of the Late Mesozoic Franciscan Complex represent small-scale magmatic activity in a trench sedimentary environment or in the accretionary prism itself. At Leech Lake Mountain, located in the eastern Franciscan belt of northern California, interbedded radiolarian cherts and graywackes are locally intruded by Ti-rich alkalic diabase sills. The thicker sills are internally differentiated and display cumulate textures of olivine and augite. Although the diabases and surrounding graywackes were overprinted by blueschist metamorphism as indicated by jadeite-rich clinopyroxene and glaucophane, they show little deformation and good preservation of the mafic igneous minerals. The sills comprize alkali basaltic to hawaiitic compositions, all related by fractionation of olivine (Fo 8 4 ), augite, and titanomagnetite. The immobile trace elements Th, U, Nb, and the LREE (light Rare Earth Elements) are strongly enriched compared to MORB (Mid-Ocean Ridge Basalt), whereas Y and the HREE (heavy Rare Earth Elements) are depleted. Trace element modeling is consistent with either small degrees of melting of primitive mantle or with 6 to 8 percent of partial melting of depleted MORB mantle, which is enriched by up to 8 percent of a metasomatic melt. About 6 percent of garnet in the mantle source of the diabases can account for the observed HREE fractionation and suggests a depth of melting below the garnet-spinel transition zone at 60 to 80 km. This is in agreement with the reconstructed age and thickness of the oceanic plate the diabases intruded in the Early Cretaceous. Incompatible trace element ratios of the diabases are consistent with a HIMU (high μ)-type mantle source. The Early Cretaceous tectonic setting of the Leech Lake Mountain intrusive rocks along the California continental margin is dominated by rapid, highly oblique subduction. If melt is present beneath the oceanic lithosphere without a thermal anomaly, it may readily percolate upward through conduits opened by transtensional tectonics. Asthenospheric up-welling beneath a fracture zone that is migrating along the continental margin may be a viable alternative. 4 0 Ar/ 3 9 Ar dating of amphibole from a diabase olivine cumulate yields a plateau age of 119.0 ′ 0.4 Ma, which is the first reported igneous age for the northern California Franciscan Complex. This age implies rapid subduction and metamorphism a few million years after intrusion of the diabases similar to the southern California Ortigalita Peak intrusion. However, the Leech Lake Mountain intrusive rocks are 25 my older and demonstrate that correlations on the basis of similar lithologies and metamorphic grade are problematic.

/pdf/alkaline-intrusions-in-a-near-trench-setting-franciscan-4u6miyckbw.pdf

Alkaline Intrusions in a Near-Trench Setting, Franciscan Complex, California: Constraints from Geochemistry, Petrology, and 40AR/39AR Chronology

Late Miocene-Pliocene (8-3 Ma) olivine basalt lavas, dated in this study by the 40 Ar/ 39 Ar method, have been faulted and tilted on both the east and west sides of the Warner Range of NE California, which is itself a tilted block rising to 2960 m at its crest that is composed of Miocene-Oligocene lavas and volcaniclastic rocks. The late Miocene-Pliocene lavas, distinctively poor in K 2 O and rich in MgO, are called low-K olivine tholeiites and have a different mantle source region than that of the older subduction-related lavas of the main Warner Range. Hays Canyon Range (max. elev. 2400 m) lies to the east of the Wamer Range, and the broad Surprise Valley separates the two fault-bounded ranges. Middle Miocene (ca. 15 Ma) basic lavas, with a small easterly dip, cap the Hays Canyon Range and overlie Oligocene silicic ash-flow deposits and a basaltic andesite spatter volcano. Middle Miocene basic lavas also form the crest of the Warner Range and its westerly dip slope (-15°). Nearly horizontal basic lavas of the same age are also found on both sides of the Warner Range, and it is a plausible conclusion that these middle Miocene basalts were a contiguous group before faulting and uplift of the Warner Range. Derived estimates of uplift rates (∼1 mm/ yr) of the Warner Range indicate that uplift could have been initiated at ca. 4 Ma, a period of the most voluminous eruption of low-K olivine tholeiite lavas. If the slower Cretaceous exhumation rate of the Sierra Nevada (0.5-1.0 mm/yr) is applied to the total offset of the Warner Range (4270 m), and it did not vary with time, then the uplift of the Warner Range was initiated at ca. 8 Ma, which coincides with the age of the oldest low-K olivine tholeiite lava (8 Ma). Low-K olivine tholeiites require a hot shallow asthenospheric source, and it is the rise of this hot mantle that is presumed to have caused the uplift of the Warner Range. Whether or not the widespread eruption of small volumes of Pliocene low-K olivine tholeiites in central and eastern Oregon is associated with crustal uplift is unknown.

Faulted and tilted Pliocene olivine-tholeiite lavas near Alturas, NE California, and their bearing on the uplift of the Warner Range

The Permian-Triassic boundary & mass extinction in China

Paleoenvironmental and biostratigraphic significance of siliceous microfossils of the Permo-Triassic Redding Section, Eastern Klamath Mountains, California

Laser probe 40Ar/39Ar analyses of individual sanidine grains from four tuffs in the alluvial Late Cretaceous (Campanian) El Gallo Formation yield statistically distinct mean dates ranging from 74.87±0.05 Ma to 73.59±0.09 Ma. The exceptional precision of these dates permits calculation of statistically significant sediment accumulation rates that are much higher than passive sediment loading would cause, implying rapid tectonically induced subsidence. The dates bracket tightly the age of important dinosaur and mammalian faunas previously reported from the El Gallo Formation. The dates support an age less than 73 Ma for the Campanian/Maastrichtian stage boundary, younger than indicated by several currently used time scales. Further application of the single grain 40Ar/39Ar technique may be expected to greatly benefit stratigraphic studies of Mesozoic sedimentary basins and contribute to calibration of biostratigraphic and magnetostratigraphic time scales.

Paul R. Renne

Papers

Alkaline Intrusions in a Near-Trench Setting, Franciscan Complex, California: Constraints from Geochemistry, Petrology, and 40AR/39AR Chronology

Faulted and tilted Pliocene olivine-tholeiite lavas near Alturas, NE California, and their bearing on the uplift of the Warner Range

The Permian-Triassic boundary & mass extinction in China

Paleoenvironmental and biostratigraphic significance of siliceous microfossils of the Permo-Triassic Redding Section, Eastern Klamath Mountains, California

High resolution 40AR/39AR chronostratigraphy of the Late Cretaceous El Gallo Formation, Baja California del Norte, Mexico