There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

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

Recent years have witnessed many breakthroughs in research on graphene (the first two-dimensional atomic crystal) as well as a significant advance in the mass production of this material. This one-atom-thick fabric of carbon uniquely combines extreme mechanical strength, exceptionally high electronic and thermal conductivities, impermeability to gases, as well as many other supreme properties, all of which make it highly attractive for numerous applications. Here we review recent progress in graphene research and in the development of production methods, and critically analyse the feasibility of various graphene applications.

/pdf/a-roadmap-for-graphene-1nstzmbk5x.pdf

A roadmap for graphene

A fast-Fourier-transform method of topography and interferometry is proposed. By computer processing of a noncontour type of fringe pattern, automatic discrimination is achieved between elevation and depression of the object or wave-front form, which has not been possible by the fringe-contour-generation techniques. The method has advantages over moire topography and conventional fringe-contour interferometry in both accuracy and sensitivity. Unlike fringe-scanning techniques, the method is easy to apply because it uses no moving components.

Fourier-transform method of fringe-pattern analysis for computer-based topography and interferometry

A topical review of numerical and experimental studies of supercontinuum generation in photonic crystal fiber is presented over the full range of experimentally reported parameters, from the femtosecond to the continuous-wave regime. Results from numerical simulations are used to discuss the temporal and spectral characteristics of the supercontinuum, and to interpret the physics of the underlying spectral broadening processes. Particular attention is given to the case of supercontinuum generation seeded by femtosecond pulses in the anomalous group velocity dispersion regime of photonic crystal fiber, where the processes of soliton fission, stimulated Raman scattering, and dispersive wave generation are reviewed in detail. The corresponding intensity and phase stability properties of the supercontinuum spectra generated under different conditions are also discussed.

Supercontinuum generation in photonic crystal fiber

A new interferometric technique is demonstrated for measuring Coherent Anti-Stokes Raman Scattering (CARS) signals. Two forward-directed CARS signals are generated, one in each arm of an interferometer. The deterministic nature of the CARS process allows for these two signals, when spatially and temporally overlapped, to interfere with one another. Heterodyne detection can therefore be employed to increase the sensitivity in CARS signal detection. In addition, nonlinear CARS interferometry will facilitate the use of this spectroscopic technique for molecular contrast in Optical Coherence Tomography (OCT).

Coherent Anti-Stokes Raman Scattering Heterodyne Interferometry

Optical coherence tomography (OCT) uses low-coherence interferometry to perform optical ranging measurements within biological tissue. Recent advances in OCT technology have permitted high-speed imaging at 4-8 frames/s. In vivo catheter/endoscope-based OCT imaging has recently been performed in a rabbit. OCT has also shown a feasibility for surgical diagnostics and for assessing microsurgical repairs of vessels and nerves. In this study, we investigate the use of high-speed OCT as an interventional imaging modality for surgical guidance. OCT can provide continuous image-guidance for the precise delivery of high-power laser radiation and selective ablation of diseased tissue.

Interventional optical coherence tomography for surgical guidance

The brain is an especially active metabolic system, requiring a large supply of energy following neuronal activation. However, direct observation of cellular metabolic dynamics associated with neuronal activation is challenging with currently available imaging tools. In this study, an optical imaging approach combining imaging of calcium transients and the metabolic co-enzyme nicotinamide adenine dinucleotide (phosphate) (NAD(P)H) is utilized to track the metabolic dynamics in hippocampal neuron cultures. Results show distinct cellular components for the NAD(P)H response following neuronal activity, where notable differences in the NAD(P)H dynamics between neurons and astrocytes can be directly observed. Additionally, tracking of these responses across a large field of view is demonstrated for metabolic profiling of neuronal activation. Observation of neuronal dynamics using these methods allows for closer examination of the complex metabolic machinery of the brain, and may lead to a better understanding of the cellular metabolism of neuronal activation.

High-speed label-free two-photon fluorescence microscopy of metabolic transients during neuronal activity.

We demonstrate electrically-tunable femtosecond Cherenkov fiber laser output at the visible range Using an all-fiber, self-starting femtosecond Yb-doped fiber laser as the pump source and nonlinear photonic crystal fiber link as the wave-conversion medium, ultrafast, milliwatt-level, tunable and spectral isolated Cherenkov radiation at visible wavelengths are reported Such a femtosecond Cherenkov laser source is promising for practical biophotonics applications

Stephen A. Boppart

Papers

Coherent Anti-Stokes Raman Scattering Heterodyne Interferometry

Interventional optical coherence tomography for surgical guidance

High-speed label-free two-photon fluorescence microscopy of metabolic transients during neuronal activity.

Tunable femtosecond Cherenkov fiber laser

Microsphere contrast agents for OCT