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.

/pdf/surface-plasmon-subwavelength-optics-5e55p12p4o.pdf

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

Transformation optics (TO) is a new tool for controlling electromagnetic fields. In the context of metamaterial technology, it provides a direct link between a desired electromagnetic (EM) phenomenon and the material response required for its occurrence. Recently, this powerful framework has been successfully exploited to study surface plasmon assisted phenomena such as light harvesting. Here, we review the general strategy based on TO to design plasmonic devices capable of harvesting light over a broadband spectrum and achieving considerable field confinement and enhancement. The methodology starts with two-dimensional (2D) cases, such as 2D metal edges, crescent-shaped cylinders, nanowire dimers, and rough metal surfaces, and is well extended to fully-fledged three-dimensional (3D) situations. The largely analytic approach gives physical insights into the processes involved and suggests a way forward to study a wide variety of plasmonic nanostructures.

Harvesting light with transformation optics

The electronic states responsible for transport constitute a wildly fluctuating minority of the total number of states in a disordered system. These fluctuations are the essence of the problem and demand a rich and powerful formulation if they are to be described accurately. In this paper the author introduces a new formalism for treating transport in three-dimensional systems based on the transfer matrix. The method gains its power from the interplay of theory of the symmetric group, which enables irrelevant parts of the mathematics to be thrown out, leaving the essentials intact but simplified. Analogies with replica theory are drawn, and replica symmetry breaking discussed.

https://iopscience.iop.org/article/10.1088/0953-8984/2/14/012/pdf

Transfer matrices and conductivity in two- and three-dimensional systems. I. Formalism

Photoemission spectra for nickel are contrasted with those for copper. The differences noted are largely attributable to the short hole lifetimes in nickel-a consequence of the Fermi level falling within the band.

Photoemission from transition metal surfaces

The structure of c(2\ifmmode\times\else\texttimes\fi{}2)O on Cu(100) is investigated with a full multiple-scattering analysis of the near-edge x-ray-absorption fine structure (NEXAFS). Various adsorption sites and bond lengths are tested, with the oxygen overlayer found to occupy fourfold hollow sites 0.7 A\r{} above the Cu surface plane, in agreement with recent surface extended x-ray-absorption fine-structure (SEXAFS) work on the same sample. Our study provides the first demonstration that a quantitatively accurate NEXAFS analysis is attainable with low-noise high-resolution data, and opens up new possibilities for surface analysis for those cases where SEXAFS is not applicable.

Quantitative multiple-scattering analysis of near-edge x-ray-absorption fine structure: c(22)O on Cu(100).

Apparatus, methods, and systems provide emitting and negatively-refractive focusing of electromagnetic energy. In some approaches the negatively-refractive focusing includes negatively-refractive focusing from an interior field region with an axial magnification substantially less than one. In some approaches the negatively-refractive focusing includes negatively-refractive focusing with a transformation medium, where the transformation medium may include an artificially-structured material such as a metamaterial.

John B. Pendry

Papers

Harvesting light with transformation optics

Transfer matrices and conductivity in two- and three-dimensional systems. I. Formalism

Photoemission from transition metal surfaces

Quantitative multiple-scattering analysis of near-edge x-ray-absorption fine structure: c(22)O on Cu(100).

Emitting and negatively-refractive focusing apparatus, methods, and systems