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

The electronic response of a composite consisting of aligned metallic cylinders in vacuum is investigated on the basis of photonic band structure calculations. The effective long-wavelength dielectric response function is computed as a function of the filling fraction. A spectral representation of the effective response is considered and the surface mode strengths and positions are analyzed. The range of validity of a Maxwell-Garnett--like approach is discussed and the impact of our results on absorption spectra and electron energy-loss phenomena is addressed.

Effective electronic response of a system of metallic cylinders

X-ray absorption near-edge structure of adsorbate-induced reconstruction: (2x1)O on Cu(110)

We show how to calculate photonic band structures for idealized metals and other dispersive systems using an efficient order-N scheme. That is to say, we use a scheme where the calculation time scales linearly with the system size. The inverse dielectric function is treated as a simple pole. The method is applied to two simple periodic idealized metallic systems where it gives results in close agreement with calculations made with other techniques. Further, the approach demonstrates excellent numerical stability within the limits we give. By generalizing to an inverse dielectric function expanded as a series of poles, our method opens the way for efficient calculations on complex structures containing a whole different class of material.

https://arxiv.org/pdf/cond-mat/9807022.pdf

Order-N photonic band structures for metals and other dispersive materials

We show that metal nanoparticles can be used to improve the performance of super-resolution fluorescence nanoscopes based on stimulated-emission-depletion (STED). Compared with a standard STED nanoscope, we show theoretically a resolution improvement by more than an order of magnitude, or equivalently, depletion intensity reductions by more than 2 orders of magnitude and an even stronger photostabilization. Our scheme may allow improvement of existing STED nanoscopes and assist in the development of low-power, low-cost nanoscopes. This has the potential to increase the availability of STED nanoscopes and lead to a significant expansion of our understanding of biological and biochemical phenomena occurring on the nanoscale.

/pdf/nanoparticle-assisted-stimulated-emission-depletion-55dawficmw.pdf

Nanoparticle-Assisted Stimulated- Emission-Depletion Nanoscopy

We propose an explanation for the large negative heat of solution of helium in metals, in terms of the strong repulsive helium pseudopotential interacting with the metal conduction electrons. Calculations for helium in aluminium and magnesium show that this mechanism indeed generates the expected negative heats. We expect the helium atoms always to seek out the site of lowest charge density.

John B. Pendry

Papers

Effective electronic response of a system of metallic cylinders

X-ray absorption near-edge structure of adsorbate-induced reconstruction: (2x1)O on Cu(110)

Order-N photonic band structures for metals and other dispersive materials

Nanoparticle-Assisted Stimulated- Emission-Depletion Nanoscopy

Energy of helium dissolved in metals