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

Exemplary methods, systems and components enable an enhanced direct-viewing optical device to make customized adjustments that accommodate various optical aberrations of a current user. In some instances a real-time adjustment of the transformable optical elements is based on known corrective optical parameters associated with a current user. In some implementations a control module may process currently updated wavefront measurements as a basis for determining appropriate real-time adjustment of the transformable optical elements to produce a specified change in optical wavefront at an exit pupil of the direct-viewing device. Possible transformable optical elements may have refractive and/or reflective and/or diffractive and/or transmissive characteristics that are adjusted based on current performance viewing factors for a given field of view of the direct-viewing device. Some embodiments enable dynamic repositioning and/or transformation of corrective optical elements based on a detected shift of a tracked gaze direction of a current user of the direct-viewing device.

Adjustable optics for ongoing viewing correction

Calculation of photoelectron spectra from TiC(111) and WC(0001)

Abstract Negative refraction, an unnatural optical phenomenon in which the incident and the refracted waves reside on the same side of the surface normal, has been demonstrated with the invention of negative index media based on artificially engineered photonic structures called metamaterials. It has received wide attention due to its potential applications in imaging, nonlinear optics, and electromagnetic cloaking. However, it is highly challenging to realize negative refraction operating at all angles and with the perfect transmission. In this work, leveraging the recent development in topological photonics, we propose to realize reflectionless negative refraction for all incident angles with a topological metamaterial. The proposed metamaterial possesses two Weyl points of opposite topological charges. By interfacing the metamaterial with a perfect electric conductor (PEC) or a perfect magnetic conductor (PMC), the Fermi arc connecting the two Weyl points can take the form of a half-circle possessing a positive or a negative refractive index. Importantly, due to the topological protection, there is no reflection at the interface between the PEC and PMC covered areas, leading to the observation of all-angle negative refraction without reflection at the boundary. Our work provides a new platform for manipulating the propagation of surface waves, which may find applications in the construction of integrated photonic devices. 

/pdf/all-angle-reflectionless-negative-refraction-with-ideal-3tr6jg1e.pdf

All-angle reflectionless negative refraction with ideal photonic Weyl metamaterials

An imaging device arranged to image near field as well as far field components from an object comprises a stack of layers 8 spaced apart from each other, the layers having a negative real part of electrical permittivity or magnetic permeability in a direction normal to the layers, and being constructed from microstructured material comprising an array of elements spaced apart from each other by a distance less than the wavelength of radiation to be imaged. The layers may be spaced 9 by medium of positive real part of electrical permittivity or magnetic permeability, both the layer and the spacing being isotropic. In an alternative embodiment, the layers are in pairs in which the component of electrical permittivity or magnetic permeability in a direction normal to the layers is alternately negative and positive, while the electrical permittivity or magnetic permeability in a transverse direction is positive or negative, respectively. In an alternative embodiment, the magnitude of the component of the electrical permittivity or magnetic permeability is very large in a direction normal to the incident face. The device operates in the microwave and millimetre range.

Radio frequency imaging device

The authors discuss the formation of Rydberg states at surfaces, presenting models for the many-body effective potential outside a surface. In the light of these effects the binding energy and effective mass of electrons in these surface states is studied, as well as the many-body contributions to lifetimes. They speculate that the disagreement with experiment of some of the conclusions may be due to resolution problems.

http://iopscience.iop.org/article/10.1088/0022-3719/19/27/018/pdf

John B. Pendry

Papers

Adjustable optics for ongoing viewing correction

Calculation of photoelectron spectra from TiC(111) and WC(0001)

All-angle reflectionless negative refraction with ideal photonic Weyl metamaterials

Radio frequency imaging device

Plasmon effects on image states at metal surfaces