John B. Pendry

Bio: John B. Pendry is an academic researcher from Imperial College London. The author has contributed to research in topics: Metamaterial & Plasmon. The author has an hindex of 100, co-authored 536 publications receiving 88802 citations. Previous affiliations of John B. Pendry include University of California, San Diego & Duke University.

Saturable Time-Varying Mirror Based on an Epsilon-Near-Zero Material

Abstract: We report a switchable time-varying mirror, composed of an indium-tin-oxide--gold bilayer, displaying a tenfold modulation of reflectivity ($\mathrm{\ensuremath{\Delta}}R\ensuremath{\approx}0.6$), which saturates for a driving-pump intensity ${I}_{\mathrm{pump}}\ensuremath{\approx}100\phantom{\rule{0.2em}{0ex}}\mathrm{GW}/{\mathrm{cm}}^{2}$. Upon interacting with the saturated time-varying mirror, the frequency content of a reflected pulse is extended up to 31 THz, well beyond the pump spectral content (2.8 THz). We interpret the spectral broadening as a progressive shortening of the mirror rise time from 110 fs to below 30 fs with increasing pump power, which is confirmed by four-wave-mixing experiments and partially captured by a linear time-varying model of the mirror. A temporal response unbounded by the pump bandwidth enables applications for spectral manipulation from time-varying systems with impact for communication networks, optical switching, and computing.

Scanning-tunneling-microscopy investigation of the Ni(100)-p(2×2)C surface

Abstract: The scanning-tunneling-microscopy (STM) image of the Ni(100)-p(2×2)C surface has been investigated both experimentally and theoretically. The well-known p4g reconstruction of this surface could not be observed in the STM. Atomic resolution could be achieved only for positve or very small negative sample bias voltage, and even then the Ni atoms were not visible. Surprisingly, for a metallic surface, the corrugation could be observed for a bias voltage of up to +2 V. These observations are explained theoretically by the presence of a surface band gap above the Fermi energy, which causes the tip to come closer for positive voltage than for negative voltage

Disorder, symmetry, and electrons.

Abstract: Les concepts de la theorie de groupe sont utilises pour definir une matrice de transfert generalisee pour un materiau desordonne substitutionnellement. Des densites d'etats moyennes peuvent etre calculees pour des systemes infinis

Focussing RF flux

Abstract: A material having magnetic permeability at r.f. frequency, for example, a microstructured magnetic material has a magnetic permeability of negative value but unity magnitude over a particular r.f. frequency range. The singularity in the flux pattern has the result that magnetic resonant disturbances in a plane C,E normal to the line C,D are focussed into a plane D,F also normal to the line C,D, and vice versa. This is particularly applicable to magnetic resonance apparatus, since the material can be used to transfer the r.f. magnetic flux distribution in a target region in a patient, for example at C,E to D,F where the flux may be directly measured by receive coils. Equally, transmit coils may generate flux to be focussed into the target region by the material. Magnetic resonance apparatus may be constructed which does not require gradient coils, and r.f. hypothermia may be carried out in a focussed way, minimising damage to surrounding tissue.

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

Abstract: 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。

Surface plasmon subwavelength optics

Abstract: 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.

Experimental Verification of a Negative Index of Refraction

Abstract: 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.

Magnetism from conductors and enhanced nonlinear phenomena

Abstract: 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.

Plasmonics for improved photovoltaic devices

Abstract: 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.