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

Various sensors and arrays of sensors that utilize nanostructures or carbon structures, such as nanotubes, nanotube meshes, or graphene sheets, are disclosed. In some arrangements, at least a pair of contacts are electrically coupled with a given nanostructure or carbon structure to sense a change.

Nanostructure sensors and sensing systems

Superlenses made of plasmonic materials and metamaterials have been exploited to image features of sub-diffractional scale. However, their intrinsic losses impose a serious restriction on the imaging resolution, which is a long-standing problem that has hindered wide-spread applications of superlenses. Optical waves of complex frequency exhibiting a temporally attenuating behavior have been proposed to offset the intrinsic losses in superlenses via virtual gain, but the experimental realization has been missing due to the challenge involved in preparing the illumination with temporal decay. Here, by employing multi-frequency measurement, we successfully implement a synthetic optical wave of complex frequency to experimentally observe deep-subwavelength superimaging patterns enabled by the virtual gain. Our work represents a practical approach to overcoming the intrinsic losses of plasmonic systems for imaging and sensing applications.

Overcoming losses in superlenses with synthetic waves of complex frequency

We present a novel computational approach for calculating spontaneous emission in the presence of a surface of a material slab. The only requirement on the material is that it should have periodicity parallel to the surface. The spontaneous emission rate is calculated using Fermi’s golden rule, which can be described in terms of the classical Density of States (DOS). The DOS can in turn be expressed in terms of the Green’s function. We calculate the Green’s function for light of a specific frequency and a specific incident direction and distance with respect to the surface and then integrate over all incident directions. The only information required from the material, is the reflection coefficients for plane waves at the surface. With our method we reproduce results of an analytical calculation for a semi-infinite homogeneous dielectric. We also present new results for a slab of cylindrical dielectric rods embedded in air on a square lattice.

Numerical method for calculating spontaneous emission rate near a surface using Green’s functions

New advances in theory and experiment have greatly increased our ability to study structure at surfaces. Not only can complex ordered structures of adsorbates be determined, but we can bring the same high precision techniques to disordered systems, and the methodology is available to find probability distributions of atoms, and hence dynamics of anharmonic vibrations and of diffusion. These advances are reminiscent of the contribution that protein crystallography has made to our understanding of complex biological systems, and of the impact that has had on the design of drugs by computer. Design of heterogeneous catalysts by computer remains a long term goal, but surface studies are on the move in that direction.

Structure and function at catalyst surfaces

Metamaterials ofier a huge range of new electromagnetic properties: negative re- fraction, spatial inhomogeneity to name only two. To exploit the possibilities ofiered in this new world we need a new design tool. Maxwell's equations are exact at the classical level but lack transparency; Snell's law is elegantly visual, an aid to the imagination, but fails to account for many vital aspects of electromagnetism. Transformation optics retains an intuitive appeal, replacing the rays of Snell's law with the fleld lines of Maxwell whose equations is represents exactly.

John B. Pendry

Papers

Nanostructure sensors and sensing systems

Overcoming losses in superlenses with synthetic waves of complex frequency

Numerical method for calculating spontaneous emission rate near a surface using Green’s functions

Structure and function at catalyst surfaces

Transformation Optics Shapes Metamaterials