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

Two-photon excitation provides a means of activating chemical or physical processes with high spatial resolution in three dimensions and has made possible the development of three-dimensional fluorescence imaging, optical data storage, and lithographic microfabrication. These applications take advantage of the fact that the two-photon absorption probability depends quadratically on intensity, so under tight-focusing conditions, the absorption is confined at the focus to a volume of order λ3 (where λ is the laser wavelength). Any subsequent process, such as fluorescence or a photoinduced chemical reaction, is also localized in this small volume. Although three-dimensional data storage and microfabrication have been illustrated using two-photon-initiated polymerization of resins incorporating conventional ultraviolet-absorbing initiators, such photopolymer systems exhibit low photosensitivity as the initiators have small two-photon absorption cross-sections (δ). Consequently, this approach requires high laser power, and its widespread use remains impractical. Here we report on a class of π;-conjugated compounds that exhibit large δ (as high as 1, 250 × 10−50 cm4 s per photon) and enhanced two-photon sensitivity relative to ultraviolet initiators. Two-photon excitable resins based on these new initiators have been developed and used to demonstrate a scheme for three-dimensional data storage which permits fluorescent and refractive read-out, and the fabrication of three-dimensional micro-optical and micromechanical structures, including photonic-bandgap-type structures.

Two-photon polymerization initiators for three-dimensional optical data storage and microfabrication

Photonic metamaterials are man-made structures composed of tailored micro- or nanostructured metallodielectric subwavelength building blocks. This deceptively simple yet powerful concept allows the realization of many new and unusual optical properties, such as magnetism at optical frequencies, negative refractive index, large positive refractive index, zero reflection through impedance matching, perfect absorption, giant circular dichroism and enhanced nonlinear optical properties. Possible applications of metamaterials include ultrahigh-resolution imaging systems, compact polarization optics and cloaking devices. This Review describes recent progress in the fabrication of three-dimensional metamaterial structures and discusses some of the remaining challenges.

Past achievements and future challenges in the development of three-dimensional photonic metamaterials

The detection and measurement of gas concentrations using the characteristic optical absorption of the gas species is important for both understanding and monitoring a variety of phenomena from industrial processes to environmental change. This study reviews the field, covering several individual gas detection techniques including non-dispersive infrared, spectrophotometry, tunable diode laser spectroscopy and photoacoustic spectroscopy. We present the basis for each technique, recent developments in methods and performance limitations. The technology available to support this field, in terms of key components such as light sources and gas cells, has advanced rapidly in recent years and we discuss these new developments. Finally, we present a performance comparison of different techniques, taking data reported over the preceding decade, and draw conclusions from this benchmarking.

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Optical gas sensing: a review

Colloidal synthesis offers a route to nanoparticles (NPs) with controlled composition and structural features. This Perspective describes the use of polyvinylpyrrolidone (PVP) to obtain such nanostructures. PVP can serve as a surface stabilizer, growth modifier, nanoparticle dispersant, and reducing agent. As shown with examples, its role depends on the synthetic conditions. This dependence arises from the amphiphilic nature of PVP along with the molecular weight of the selected PVP. These characteristics can affect nanoparticle growth and morphology by providing solubility in diverse solvents, selective surface stabilization, and even access to kinetically controlled growth conditions. This Perspective includes discussions of the properties of PVP-capped NPs for surface enhanced Raman spectroscopy (SERS), assembly, catalysis, and more. The contribution of PVP to these properties as well as its removal is considered. Ultimately, the NPs accessed through the use of PVP in colloidal syntheses are opening new applications, and the concluding guidelines provided herein should enable new nanostructures to be accessed facilely.

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Polyvinylpyrrolidone (PVP) in nanoparticle synthesis

A new optical concept for compact digital image acquisition devices with large field of view is developed and proofed experimentally. Archetypes for the imaging system are compound eyes of small insects and the Gabor-Superlens. A paraxial 3x3 matrix formalism is used to describe the telescope arrangement of three microlens arrays with different pitch to find first order parameters of the imaging system. A 2mm thin imaging system with 21x3 channels, 70 masculinex10 masculine field of view and 4.5mm x 0.5mm image size is optimized and analyzed using sequential and non-sequential raytracing and fabricated by microoptics technology. Anamorphic lenses, where the parameters are a function of the considered optical channel, are used to achieve a homogeneous optical performance over the whole field of view. Captured images are presented and compared to simulation results.

Microoptical telescope compound eye

Photonic Nanojets are highly localized wave fields emerging directly behind dielectric microspheres; if suitably illuminated. In this contribution we reveal how different illumination conditions can be used to engineer the photonic Nanojets by measuring them in amplitude and phase with a high resolution interference microscope. We investigate how the wavelength, the amplitude distribution of the illumination, its polarization, or a break in symmetry of the axial-symmetric structure and the illumination affect the position, the localization and the shape of the photonic Nanojets. Various fascinating properties are systematically revealed and their implications for possible applications are discussed.

Engineering photonic nanojets

Two different approaches for ultra flat image acquisition sensors on the basis of artificial compound eyes are examined. In apposition optics the image reconstruction is based on moire- or static sampling while the superposition eye approach produces an overall image. Both types of sensors are compared with respect to theoretical limitations of resolution, sensitivity and system thickness. Explicit design rules are given. A paraxial 3×3 matrix formalism is used to describe the arrangement of three microlens arrays with different pitches to find first order parameters of artificial superposition eyes. The model is validated by analysis of the system with raytracing software. Measurements of focal length of anamorphic reflow lenses, which are key components of the superposition approach, under oblique incidence are performed. For the second approach, the artificial apposition eye, a first demonstrator system is presented. The monolithic device consists of a UV-replicated reflow microlens array on a thin silica-substrate with a pinhole array in a metal layer on the backside. The pitch of the pinholes differs from the lens array pitch to enable an individual viewing angle for each channel. Imaged test patterns are presented and measurements of the angular sensitivity function are compared to calculations using commercial raytracing software.

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Artificial compound eyes: different concepts and their application for ultraflat image acquisition sensors

We propose an artificial three-dimensional material that exhibits a strong resonance in the effective permeability in the visible spectral domain. This material may be implemented in a two-step procedure. First, a metamaterial made of densely packed metallic nanoparticles is fabricated that shows a Lorentz-type resonance in the permittivity at the collective plasmon frequency. Second, spheres are formed out of this material and arranged in a cubic lattice. This meta-metamaterial exhibits a strong resonance in the permeability which is caused by a Mie resonance associated with the magnetic mode of a single metamaterial sphere. Realization of this material based on self-organization in liquid crystals and the limitations of the approach are discussed.

Design of an artificial three-dimensional composite metamaterial with magnetic resonances in the visible range of the electromagnetic spectrum.

Preface. 1 Polarized Light. 1.1 Introduction. 1.2 Concept of Light Polarization. 1.3 Description of The State of Polarization. 1.4 The Stokes Concept. 1.5 The Jones Concept. 1.6 Coherence and Polarized Light. References. 2 Electromagnetic Waves in Anisotropic Materials. 2.1 Introduction. 2.2 Analytical Background. 2.3 Time Harmonic Fields and Plane Waves. 2.4 Maxwell's Equations in Matrix Representation. 2.5 Separation of Polarizations for Inhomogeneous Problems. 2.6 Separation of Polarizations for Anisotropic Problems. 2.7 Dielectric Tensor and Index Ellipsoid. References. 3 Description of Light Propagation with Rays. 3.1 Introduction. 3.2 Light Rays and Wave Optics. 3.3 Light Propagation Through Interfaces (Fresnel Formula) . 3.4 Propagation Direction of Rays in Crystals. 3.5 Propagation Along A Principal Axis. 3.6 Rays at Isotropic-Anisotropic Interfaces. 3.7 Gaussian Beams. References. 4 Stratified Birefringent Media. 4.1 Maxwell Equations for Stratified Media. 4.2 Jones Formalism in Examples. 4.3 Extended Jones Matrix Method. 4.4 The 4x4 Berreman Method. 4.5 Analytical Solution for A Birefringent Slab. 4.6 Reflection and Transmission. References. 5 Space-Grid Time-Domain Techniques. 5.1 Introduction. 5.2 Description of the FDTD Method. 5.3 Implementation and Boundary Conditions. 5.4 Rigorous Optics for Liquid Crystals. References. 6 Organic Optical Materials. 6.1 Introduction. 6.2 Polymers for Optics. 6.3 Physical Properties of Polymers. 6.4 Optical Properties of Polymers. 6.5 Liquid Crystal Phases. 6.6 Liquid Crystal Polymers. 6.7 Birefringence in Isotropic Materials. 6.8 Form Birefringence. 6.9 Order-Induced Birefringence. 6.10 Optical Properties of Liquid Crystals and Oriented Polymers. References. 7 Practical Polarization Optics with the Microscope. 7.1 Introduction. 7.2 Microscope Characteristics. 7.3 Polarization Microscope. 7.4 Polarizers. 7.5 Polarization Colors. 7.6 Compensation and Retardation Measurement. 7.7 Conoscopy. 7.8 Local Polarization Mapping. References. 8 Optics of Liquid Crystal Textures. 8.1 Introduction. 8.2 Calculation of Liquid Crystal Director Distributions. 8.3 Optical Properties of Uniform Textures. 8.4 Optical Properties of Liquid Crystal Defects. 8.5 Surface Line Defects in Nematics. 8.6 Defects in Smectic Phases. 8.7 Confined Nematic Liquid Crystals. 8.8 Instabilities in Liquid Crystals. 8.9 Deformation of Liquid Crystal Directors by Fringing Fields. 8.10 Resolution Limit of Switchable Liquid Crystal Devices. 8.11 Switching in Layered Phases. References. 9 Refractive Birefringent Optics. 9.1 Birefringent Optical Elements. 9.2 Fabrication of Refractive Components. 9.3 Optical Properties of Modified Birefringent Components. 9.4 Liquid Crystal Phase Shifters. 9.5 Modal Control Elements. 9.6 Interferometers Based on Polarization Splitting. 9.7 Birefringent Microlenses. 9.8 Electrically Switchable Microlenses. References. 10 Diffractive Optics with Anisotropic Materials. 10.1 Introduction. 10.2 Principles of Fourier Optics. 10.3 Polarization Properties. 10.4 Diffraction at Binary Gratings. 10.5 Concepts and Fabrication. 10.6 Diffractive Elements Due to surface Modifications. 10.7 Electrically Switchable Gratings. 10.8 Switchable Diffractive Lenses. References. 11 Bragg Diffraction. 11.1 Reflection by Multilayer Structures. 11.2 Polymer Films. 11.3 Giant Polarization Optics. 11.4 Reflection by Cholesteric Liquid Crystals. 11.5 Color Properties of Cholesteric Bragg Reflectors. 11.6 Apodization of Cholesteric Bragg Filters. 11.7 Reflection by Dispersed Cholesteric Liquid Crystals. 11.8 Depolarization Effects by Polymer Dispersed Cholesteric Liquid Crystals. 11.9 Defect Structures in Cholesteric Bragg Reflectors. 11.10 Structured Cholesteric Bragg Filters. 11.11 Plane Wave Approach to the Optics of Blue Phases. References. Index.

Toralf Scharf

Papers

Microoptical telescope compound eye

Engineering photonic nanojets

Artificial compound eyes: different concepts and their application for ultraflat image acquisition sensors

Design of an artificial three-dimensional composite metamaterial with magnetic resonances in the visible range of the electromagnetic spectrum.

Polarized light in liquid crystals and polymers