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

Surface plasmons are waves that propagate along the surface of a conductor. By altering the structure of a metal's surface, the properties of surface plasmons--in particular their interaction with light--can be tailored, which offers the potential for developing new types of photonic device. This could lead to miniaturized photonic circuits with length scales that are much smaller than those currently achieved. Surface plasmons are being explored for their potential in subwavelength optics, data storage, light generation, microscopy and bio-photonics.

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Surface plasmon subwavelength optics

We present experimental scattering data at microwave frequencies on a structured metamaterial that exhibits a frequency band where the effective index of refraction (n) is negative. The material consists of a two-dimensional array of repeated unit cells of copper strips and split ring resonators on interlocking strips of standard circuit board material. By measuring the scattering angle of the transmitted beam through a prism fabricated from this material, we determine the effective n, appropriate to Snell's law. These experiments directly confirm the predictions of Maxwell's equations that n is given by the negative square root of epsilon.mu for the frequencies where both the permittivity (epsilon) and the permeability (mu) are negative. Configurations of geometrical optical designs are now possible that could not be realized by positive index materials.

/pdf/experimental-verification-of-a-negative-index-of-refraction-37hlxn3tta.pdf

Experimental Verification of a Negative Index of Refraction

We show that microstructures built from nonmagnetic conducting sheets exhibit an effective magnetic permeability /spl mu//sub eff/, which can be tuned to values not accessible in naturally occurring materials, including large imaginary components of /spl mu//sub eff/. The microstructure is on a scale much less than the wavelength of radiation, is not resolved by incident microwaves, and uses a very low density of metal so that structures can be extremely lightweight. Most of the structures are resonant due to internal capacitance and inductance, and resonant enhancement combined with compression of electrical energy into a very small volume greatly enhances the energy density at critical locations in the structure, easily by factors of a million and possibly by much more. Weakly nonlinear materials placed at these critical locations will show greatly enhanced effects raising the possibility of manufacturing active structures whose properties can be switched at will between many states.

/pdf/magnetism-from-conductors-and-enhanced-nonlinear-phenomena-2fpnoamwae.pdf

Magnetism from conductors and enhanced nonlinear phenomena

The emerging field of plasmonics has yielded methods for guiding and localizing light at the nanoscale, well below the scale of the wavelength of light in free space. Now plasmonics researchers are turning their attention to photovoltaics, where design approaches based on plasmonics can be used to improve absorption in photovoltaic devices, permitting a considerable reduction in the physical thickness of solar photovoltaic absorber layers, and yielding new options for solar-cell design. In this review, we survey recent advances at the intersection of plasmonics and photovoltaics and offer an outlook on the future of solar cells based on these principles.

Plasmonics for improved photovoltaic devices

In order to confine waves beyond the diffraction limit, advances in fabrication techniques have enabled subwavelength structuring of matter, achieving near-field control of light and other types of waves. The price is often expensive fabrication needs and the irreversibility of device functionality, as well as the introduction of impurities, a major contributor to losses. In this Letter, we propose temporal inhomogeneities, such as a periodic drive in the electromagnetic properties of a surface which supports guided modes, as an alternative route for the coupling of propagating waves to evanescent modes across the light line, thus circumventing the need for subwavelength fabrication, and achieving the temporal counterpart of the classical Wood anomaly. We show analytically and numerically how this concept is valid for any material platform and at any frequency, and propose and model a realistic experiment in graphene to couple terahertz radiation to plasmons with unit efficiency, demonstrating that time modulation of material properties could be a tunable, lower-loss and fast-switchable alternative to the subwavelength structuring of matter for near-field wave control.

Wood Anomalies and Surface-Wave Excitation with a Time Grating

Calculation of X-ray absorption near-edge structure, XANES

We analyze from a theoretical point of view the optical properties of arrays of carbon nanotubes filled with silver. Dependence of these properties on the different parameters involved is studied using a transfer matrix formalism able to work with tensorlike dielectric functions and including the full electromagnetic coupling between the nanotubes. We find that these structures exhibit very strong linear optical response and hence could be used as spectroscopic enhancers or chemical sensors in the visible range. Very localized surface plasmons, created by the electromagnetic interaction between the capped silver cylinders, are responsible for this enhancing ability. Enhancements of up to ${10}^{6}$ in the Raman signal of molecules absorbed on these arrays could be obtained.

Silver-filled carbon nanotubes used as spectroscopic enhancers

Matthias Kraft, Yu Luo, S. A. Maier, and J. B. Pendry Department of Physics, The Blackett Laboratory, Imperial College London, London SW7 2AZ, United Kingdom Centre for OptoElectronics and Biophotonics (OPTIMUS), School of Electrical and Electronic Engineering, Nanyang Technological University, Nanyang Avenue 639798, Singapore (Received 9 March 2015; revised manuscript received 2 July 2015; published 8 September 2015)

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Designing plasmonic gratings with transformation optics

The introduction of geometrical complexity into a dielectric structure radically alters the pattern of losses from a passing charged particle. Here we introduce an approach to the problem which is ideally suited to numerical work and to the treatment of complex geometry. We apply the method to losses in colloidal metallic systems where the local juxtaposition of surfaces produces a host of modes and consequent changes in the loss spectrum. We also calculate the ``Smith-Purcell effect,'' in which a particle passing over a grating may radiate energy into the vacuum. This method is powerful and flexible and will, we trust, open a class of materials to quantitative study.

John B. Pendry

Papers

Wood Anomalies and Surface-Wave Excitation with a Time Grating

Calculation of X-ray absorption near-edge structure, XANES

Silver-filled carbon nanotubes used as spectroscopic enhancers

Designing plasmonic gratings with transformation optics

Energy loss by charged particles in complex media.