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

Plasmonic systems exhibit a host of intriguing optical properties. In this talk I shall assert that the underlying source of this diversity is geometry: that is to say the shape of a plasmonic particle or the structure of a particular surface. I shall show how geometric complexity can be generated starting from simple structures such as waveguides and transforming them into more complex structures, then turning to transformation optics to understand how the properties of the complex structure relate to the simple one. Particular attention will be paid to singular structures which are know to act as harvesters of light and are responsible for the enhanced spectroscopic response that occurs in SERS experiments.

Plasmonics and geometry (Conference Presentation)

Emanuele Galiffi, Yao-Ting Wang, Zhen Lim, J. B. Pendry, Andrea Al, and Paloma A. Huidobro The Blackett Laboratory, Imperial College London, SW7 2AZ, London, UK Department of Mathematics, Imperial College London, SW7 2AZ, London, UK Photonics Initiative, Advanced Science Research Center, City University of New York, New York, New York 10031, USA Instituto de Telecomunicações, Instituto Superior Tecnico-University of Lisbon, Portugal (Dated: April 21, 2020)

Temporal Wood Anomalies -- Smoothing the Path to the Near-Field

An Archimedes' Screw captures water, feeding energy into it by lifting it to a higher level. We introduce the first instance of an optical Archimedes' Screw, and demonstrate how this system is capable of capturing light, dragging it and amplifying it. We unveil new exact analytic solutions to Maxwell's Equations for a wide family of chiral space-time media, and show their potential to achieve chirally selective amplification within widely tunable parity-time-broken phases. Our work, which may be readily implemented via pump-probe experiments with circularly polarized beams, opens a new direction in the physics of time-varying media by merging the rising field of space-time metamaterials and that of chiral systems, and may form a new playground for topology and non-Hermitian physics, with potential applications to chiral spectroscopy and sensing.

/pdf/an-archimedes-screw-for-light-su2u0egybg.pdf

An Archimedes' Screw for Light

Scientists and novelists have been intrigued for centuries by the possibility of hiding an object so completely that neither trace of the object nor of its cloak is to be found. Recent theoretical developments show that cloaking is, in principle, possible for electromagnetic waves and to a limited extent for other types of wave, such as acoustic waves. An energetic program of experimental research has shown some of the schemes to be realizable in practice.

Trend: Taking the wraps off cloaking

Negative refractive index materials [1] have excited the optics community both through the intriguing possibilities they appear to offer, and the challenges they present to our understanding of the diffraction process. Most intriguing of all is the possibility of a lens whose resolution is limited not by wavelength, but only by the losses in the constituent materials. The resolution of this lens increases without limit as the losses tend to zero. However the lens is only one member of a whole category of systems, such as intersecting planes, which satisfy a generalized lens theorem [5]. We shall see that good use of coordinate transformations tackles geometries related to one another by mirror symmetry. In this pamphlet, we explore imaging effects through negative refraction in 1D Photonic Crystals. The tool of choice will be the generalised transfer matrix formalism. Our approach amounts to solving the Maxwell system by taking full account of the invariance of the structure in, say, x and y (using a Fourier Transform), and its periodicity in z (by means of Floquet-Bloch decomposition). We only assume that the electromagnetic field satisfies a prerequisite energy criterion of square integrability. We achieve a clean mathematical derivation which leads to an analytical expression for the field by means of the transfer matrix formalism which proved to be a fast and accurate algorithm in numerous studies on Photonic Band Gap structures through the past decade. Our meta-material requires of course some modifications with respect to the original algorithm (described for instance at length in [3,6,7]): we need now consider some loss in the layers with negative refractive index (for causality reasons). Further, we also introduce a periodic arrangement of line current sources oriented along the y -axis, which radiate in the overall periodic structure (see figure 1(a)).

https://www.piers.org/piers2k4Pisa/session_30a/30a_04.pdf

John B. Pendry

Papers

Plasmonics and geometry (Conference Presentation)

Temporal Wood Anomalies -- Smoothing the Path to the Near-Field

An Archimedes' Screw for Light

Trend: Taking the wraps off cloaking

'Short stories on line sources in meta-materials'