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.

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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

Layer Korringa-Kohn-Rostoker electronic structure code for bulk and interface geometries

Artificial materials composed of either structured or random subunits far below the wavelength of light can be designed to display fascinating physical properties. Recent advances in fabrication technology have established the great potential of such metamaterials for applications.

Photonics: metamaterials in the sunshine.

Metallic structures with sharp corners harvest the energy of incident light through plasmonic resonances, concentrating it in the corners and greatly increasing the local energy density. Despite its wide array of applications, this effect is normally strongly dependent on how sharp the corners are, presenting problems for fabrication. In this Letter, an analytical approach is proposed, based on transformation optics, to investigate a general class of plasmonic nanostructures with blunt edges or corners. Comprehensive discussions are provided on how the geometry affects the local field enhancement as well as the frequency and energy of each plasmonic resonance. Remarkably, our results evidence the possibility of designing broadband light harvesting devices with an absorption property insensitive to the geometry bluntness.

/pdf/broadband-light-harvesting-nanostructures-robust-to-edge-1ehc5wmbb1.pdf

Broadband Light Harvesting Nanostructures Robust to Edge Bluntness

We apply the conformal transformation technique to study systematically a variety of singular plasmonic structures, including two-dimensional sharp edges, rough surfaces, and nanocrescents. These structures are shown to exhibit two distinct features. First, different from a planar metallic surface, the surface plasmon excitations on the examined structures have a lower bound cutoff at a finite frequency; second, the electric field diverges below a critical frequency even when metallic losses are considered. For rough surfaces and open-crescent nanostructures, the influence of the structure shapes on the absorbance characteristics is also discussed. Our analysis gives a unique insight into the light capture process on singular structures and holds the promise of detection of single molecules and greatly enhanced nonlinear effects.

/pdf/surface-plasmons-and-singularities-2hs104plkr.pdf

Surface plasmons and singularities.

Some time ago it was shown that a slab of material with e 1 =−1, μ 1 =−1 and suspended in vacuo has the ability to focus a perfect image: both the near-field and far-field components are delivered to the image plane with the correct amplitude and phase reproducing every detail in the original source [Phys. Rev. Lett. 85 (2000) 3966]. Real materials fall short of this ideal particularly with respect to losses which manifest themselves as imaginary components to e1 and μ1. In this talk we shall examine how to minimise the restrictions by structuring the lens into a series of thin slices. This results in a novel mapping onto an anisotropic system which behaves like an optical fibre bundle, but operating on the near field.

John B. Pendry

Papers

Layer Korringa-Kohn-Rostoker electronic structure code for bulk and interface geometries

Photonics: metamaterials in the sunshine.

Broadband Light Harvesting Nanostructures Robust to Edge Bluntness

Surface plasmons and singularities.

Refining the perfect lens