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

Time-dependent systems do not in general conserve energy, invalidating much of the theory developed for static systems and turning our intuition on its head. This is particularly acute in luminal space-time crystals, where the structure moves at or close to the velocity of light. Conventional Bloch wave theory no longer applies, energy grows exponentially with time, and a new perspective is required to understand the phenomenology. In this paper, we identify a new mechanism for amplification: the compression of lines of force that are nevertheless conserved in number.

Gain in time-dependent media—a new mechanism

A Comment on the Letter by Mark I. Stockman, Phys. Rev. Lett. 106, 156802 (2011). The author of the Letter offers a Reply.

Comment on “Spaser Action, Loss Compensation, and Stability in Plasmonic Systems with Gain”

A theoretical study of the structure and reactivity of carbon and graphite layers on nickel surfaces

Bound states and resonances of energy Ec in the atoms of a crystal severely distort the band structure of the crystal in a systematic fashion. The distortions extend throughout the energy range Ec to (c mod H0 mod c), though at the intermediate energies one must look far out into the complex k plane near ki approximately=(c mod H0 mod c)12/. The distortions are expected to be of importance in several surface phenomena.

https://iopscience.iop.org/article/10.1088/0022-3719/3/1/009/pdf

Complex band structure in the presence of bound states and resonances

A linear approximation to dynamical low-energy electron diffraction (LEED) is proposed, called linear LEED (LLEED). It may hold the key to the solution of complex surface structures with large atomic displacements, in a way complementary to tensor LEED. More ambitious possibilities also present themselves, based on direct inversion schemes and related in spirit to holographic ideas. Linear LEED relies on the approximate linear independence of diffracted amplitudes from subunits such as atoms or molecules, and reduces enormously the number of full dynamical LEED calculations needed in a structural search.

John B. Pendry

Papers

Gain in time-dependent media—a new mechanism

Comment on “Spaser Action, Loss Compensation, and Stability in Plasmonic Systems with Gain”

A theoretical study of the structure and reactivity of carbon and graphite layers on nickel surfaces

Complex band structure in the presence of bound states and resonances

Linear approximation to dynamical low-energy electron diffraction.