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

This article reviews the current status of lattice-dynamical calculations in crystals, using density-functional perturbation theory, with emphasis on the plane-wave pseudopotential method. Several specialized topics are treated, including the implementation for metals, the calculation of the response to macroscopic electric fields and their relevance to long-wavelength vibrations in polar materials, the response to strain deformations, and higher-order responses. The success of this methodology is demonstrated with a number of applications existing in the literature.

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Phonons and related crystal properties from density-functional perturbation theory

The use of individual molecules as functional electronic devices was first proposed in the 1970s (ref 1) Since then, molecular electronics2,3 has attracted much interest, particularly because it could lead to conceptually new miniaturization strategies in the electronics and computer industry The realization of single-molecule devices has remained challenging, largely owing to difficulties in achieving electrical contact to individual molecules Recent advances in nanotechnology, however, have resulted in electrical measurements on single molecules4,5,6,7 Here we report the fabrication of a field-effect transistor—a three-terminal switching device—that consists of one semiconducting8,9,10 single-wall carbon nanotube11,12 connected to two metal electrodes By applying a voltage to a gate electrode, the nanotube can be switched from a conducting to an insulating state We have previously reported5 similar behaviour for a metallic single-wall carbon nanotube operated at extremely low temperatures The present device, in contrast, operates at room temperature, thereby meeting an important requirement for potential practical applications Electrical measurements on the nanotube transistor indicate that its operation characteristics can be qualitatively described by the semiclassical band-bending models currently used for traditional semiconductor devices The fabrication of the three-terminal switching device at the level of a single molecule represents an important step towards molecular electronics

Room-temperature transistor based on a single carbon nanotube

Ionization of highly compressed ammonia has previously been predicted by computation. Here, the authors provide experimental evidence for this autoionization process at high pressures, showing the transformation of molecular ammonia into ammonium amide.

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Ammonia as a case study for the spontaneous ionization of a simple hydrogen-bonded compound

A concise, self-contained introduction to solid polymers, the mechanics of their behavior and molecular and structural interpretations. This updated edition provides extended coverage of recent developments in rubber elasticity, relaxation transitions, non-linear viscoelastic behavior, anisotropic mechanical behavior, yield behavior of polymers, breaking phenomena, and other fields.

Mechanical properties of solid polymers

Solid hydrogen, an electrical insulator, is predicted to become an alkali metal under extreme compression, although controversy surrounds the pressure required to achieve this1,2,3. The electrical conductivity of hydrogen as a function of pressure and temperature is of both fundamental and practical interest—metallic hydrogen may be of relevance to planetary interiors4, and has been suggested as a potential high-temperature superconductor5. Calculations1,2 suggest that depairing (destruction of the molecular bond) should occur around 340 GPa, accompanied by the formation of an alkali metal at this pressure1, or at substantially higher pressures2,3. Here we report that solid hydrogen does not become an alkali metal at pressures of up to 342 ± 10 GPa, achieved using a diamond anvil cell. This pressure (which is almost comparable to that at the centre of the Earth) significantly exceeds those reached in earlier experiments—216 GPa (ref. 6) and 191 GPa (ref. 7)—at which hydrogen was found to be non-metallic. The failure of solid hydrogen to become an alkali metal at the extreme pressures reported here has implications for our current theoretical understanding of the solid-state phase.

Solid hydrogen at 342 GPa: no evidence for an alkali metal

Phase transitions in the group-IV transition-metal zirconium were studied by the energy-dispersive x-ray-diffraction technique with a synchrotron source to a pressure of 32 GPa. A first-order phase transition between an \ensuremath{\omega} phase and a bcc phase (isostructural with group-V transition elements) was observed during compression and decompression in a pressure range of 30\ifmmode\pm\else\textpm\fi{}2 GPa, which is in qualitative agreement with the recent first principles theoretical predictions. The observation of the bcc phase in Zr (a group-IV element) under pressure at room temperature signifies a pressure-induced electronic configuration similar to that of a group-V element.

New high-pressure phase transition in zirconium metal.

Energy‐dispersive x‐ray diffraction studies were carried out on the III‐V compound aluminum nitride to 65 GPa using a synchrotron x‐ray source. A pressure‐induced first‐order phase transition from a wurtzite structure to a rocksalt structure was observed. The first peaks of the high‐pressure phase appeared at 14 GPa. On further loading of the diamond anvil cell, the wurtzite peaks disappeared by 20 GPa. After unloading the cell to atmospheric pressure, the rocksalt structure persisted. The equilibrium transformation pressure lies on the interval 0–14 GPa.

Pressure‐induced rocksalt phase of aluminum nitride: A metastable structure at ambient condition

The crystal structure of ${\mathrm{CeO}}_{2}$ has been investigated to 70 GPa using energy dispersive x-ray diffraction in a diamond-anvil cell. At 31.5\ifmmode\pm\else\textpm\fi{}1.0 GPa the fluorite phase transforms, on loading, to an orthorhombic \ensuremath{\alpha}-${\mathrm{PbCl}}_{2}$-like structure of space group Pnam, with a 7.5%\ifmmode\pm\else\textpm\fi{}0.7% increase in density. The cubic fluorite phase has a bulk modulus ${B}_{0}$=230\ifmmode\pm\else\textpm\fi{}10 GPa with an assumed pressure derivative of ${B}_{0}^{\mathcal{'}}$=4.00. The \ensuremath{\alpha}-${\mathrm{PbCl}}_{2}$-type structure seems to be the stable high-pressure phase in the case of the group-IVB, lanthanide, and actinide fluorite-type dioxides, independent of metal-ion size, at reduced volumes less than 0.89\ifmmode\pm\else\textpm\fi{}0.01.

High-pressure x-ray diffraction study of CeO 2 to 70 GPa and pressure-induced phase transformation from the fluorite structure

High-pressure energy-dispersive x-ray-diffraction studies were carried out on the III-V compound gallium nitride to 70 GPa using a synchrotron x-ray source. A pressure-induced first-order phase transition from a wurtzite structure to a rocksalt structure was observed to begin at a pressure of 37 GPa.

Arthur L. Ruoff

Papers

Solid hydrogen at 342 GPa: no evidence for an alkali metal

New high-pressure phase transition in zirconium metal.

Pressure‐induced rocksalt phase of aluminum nitride: A metastable structure at ambient condition

High-pressure x-ray diffraction study of CeO 2 to 70 GPa and pressure-induced phase transformation from the fluorite structure

High-pressure structure of gallium nitride: Wurtzite-to-rocksalt phase transition.