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

Modified Gravity and Cosmology

The status of experimental tests of general relativity and of theoretical frameworks for analyzing them is reviewed and updated. Einstein’s equivalence principle (EEP) is well supported by experiments such as the Eotvos experiment, tests of local Lorentz invariance and clock experiments. Ongoing tests of EEP and of the inverse square law are searching for new interactions arising from unification or quantum gravity. Tests of general relativity at the post-Newtonian level have reached high precision, including the light deflection, the Shapiro time delay, the perihelion advance of Mercury, the Nordtvedt effect in lunar motion, and frame-dragging. Gravitational wave damping has been detected in an amount that agrees with general relativity to better than half a percent using the Hulse-Taylor binary pulsar, and a growing family of other binary pulsar systems is yielding new tests, especially of strong-field effects. Current and future tests of relativity will center on strong gravity and gravitational waves.

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The Confrontation Between General Relativity and Experiment

Advances in atomic physics, such as cooling and trapping of atoms and molecules and developments in frequency metrology, have added orders of magnitude to the precision of atom-based clocks and sensors. Applications extend beyond atomic physics and this article reviews using these new techniques to address important challenges in physics and to look for variations in the fundamental constants, search for interactions beyond the standard model of particle physics, and test the principles of general relativity.

Search for New Physics with Atoms and Molecules

One century after its formulation, Einstein's general relativity (GR) has made remarkable predictions and turned out to be compatible with all experimental tests. Most of these tests probe the theory in the weak-field regime, and there are theoretical and experimental reasons to believe that GR should be modified when gravitational fields are strong and spacetime curvature is large. The best astrophysical laboratories to probe strong-field gravity are black holes and neutron stars, whether isolated or in binary systems. We review the motivations to consider extensions of GR. We present a (necessarily incomplete) catalog of modified theories of gravity for which strong-field predictions have been computed and contrasted to Einstein's theory, and we summarize our current understanding of the structure and dynamics of compact objects in these theories. We discuss current bounds on modified gravity from binary pulsar and cosmological observations, and we highlight the potential of future gravitational wave measurements to inform us on the behavior of gravity in the strong-field regime.

/pdf/testing-general-relativity-with-present-and-future-3ik25z2kf9.pdf

Testing general relativity with present and future astrophysical observations

We used a continuously rotating torsion balance instrument to measure the acceleration difference of beryllium and titanium test bodies towards sources at a variety of distances. Our result Δa N,Be-Ti = (0.6 ± 3.1) X 10 -15 m/s 2 improves limits on equivalence-principle violations with ranges from 1 m to ∞ by an order of magnitude. The Eotvos parameter is η Earth,Be-Ti = (0.3 ± 1.8) X 10 -13 . By analyzing our data for accelerations towards the center of the Milky Way we find equal attractions of Be and Ti towards galactic dark matter, yielding η DM,Be-Ti = (∼4 ± 7) X 10 -5 . Space-fixed differential accelerations in any direction are limited to less than 8.8 X 10 -15 m/s 2 with 95% confidence.

Test of the Equivalence Principle Using a Rotating Torsion Balance

We briefly summarize motivations for testing the weak equivalence principle and then review recent torsion-balance results that compare the differential accelerations of beryllium–aluminum and beryllium–titanium test-body pairs with precisions at the part in 1013 level. We discuss some implications of these results for the gravitational properties of antimatter and dark matter and speculate about the prospects for further improvements in experimental sensitivity.

Torsion-balance tests of the weak equivalence principle

We briefly summarize motivations for testing the weak equivalence principle and then review recent torsion-balance results that compare the differential accelerations of beryllium-aluminum and beryllium-titanium test body pairs with precisions at the part in $10^{13}$ level. We discuss some implications of these results for the gravitational properties of antimatter and dark matter, and speculate about the prospects for further improvements in experimental sensitivity.

We show that a previous polarized $^{3}\mathrm{He}$ experiment at Princeton, plus E\"ot--Wash equivalence-principle tests, constrain exotic, long-ranged ($\ensuremath{\lambda}g0.15\text{ }\text{ }\mathrm{m}$) parity-violating interactions of neutrons at levels well below those inferred from a recent study of the parity-violating spin precession of neutrons transmitted through liquid $^{4}\mathrm{He}$. For $\ensuremath{\lambda}g{10}^{8}\text{ }\text{ }\mathrm{m}$ the bounds on ${g}_{A}{g}_{V}$ are improved by 11 orders of magnitude.

T. A. Wagner

Papers

Test of the Equivalence Principle Using a Rotating Torsion Balance

Torsion-balance tests of the weak equivalence principle

Torsion-balance tests of the weak equivalence principle

Improved limits on long-range parity-odd interactions of the neutron