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

Synthesis and surface engineering of iron oxide nanoparticles for biomedical applications

物件導向軟體之架構(Object-Oriented Software Construction)探討

Author(s): Vogel, Alfred; Venugopalan, Vasan | Abstract: The mechanisms of pulsed laser ablation of biological tissues were studied. The transiently empty space created between the fiber tip and the tissue surface improved the optical transmission to the target and thus increased the ablation efficiency. It was found that the structure and morphology also affect the energy transport among tissue constituents.

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Mechanisms of pulsed laser ablation of biological tissues.

A new fiber‐optic sensor system, comprised of an IR tunable diode lasersource and an unclad multimode IR fiber, is described. Design considerations, theoretical predictions, and experimental verification of the sensor performance are presented. This sensor has a relatively high sensitivity, and it will be very useful for monitoring and controlling i n s i t u and in real time, concentrations and chemical transformations of liquids and pastes.

Fiber‐optic‐based evanescent field chemical sensor using tunable diode lasers for the midinfrared spectral region

In order to increase the operating temperature of lasers emitting in the mid-IR, various lead chalcogenide diode lasers have been fabricated and examined: Pb 0.95 Sn 0.05 Se/PbSe and PbSe/PbS double heterostructure and funnel-type Pb 1-x Eu x Se lasers (the Eu content in the cladding layers increased steadily from x = 0.01 near the active layer up to x = 0.03 ). All the lasers were grown by molecular beam epitaxy on PbSe substrates. The p-n junctions were located not on the (lattice mismatched) interfaces, but at various distances (2000-6000 A) within the confinement layer. The highest operation temperatures (CW operation up to 165 K at 5.3 μm and pulsed operation up to 220 K at 4.4 μm) were attained by the PbSe/Pb 1-x Eu x Se funnel-type laser. The experimental results were compared to theoretical computer-assisted calculations, which accounted in a self-consistent way for the distributions of light, charge carriers, and temperature within the lasers. The agreement between theory and measurements for the temperature dependence of the threshold current and wavelength and for maximal operation temperatures was quite good. We found that the main contributions to the current come from interface recombination and from overbarrier leakage of nonconfined carriers (both minority and majority). Ways to improve the lasers are discussed.

On the performance of selenium rich lead-salt heterostructure lasers with remote p-n junction

Calculations of lifetime have been carried out for intervalley Auger processes in PbSnTe. The more generalized treatment, as compared to Emtage's earlier calculations, accounted for 1) nonparabolic dispersion laws, 2) arbitrary statistics, and 3) arbitrary injection level. The lifetime was found to be an order of magnitude larger than the value given by Emtage's formula. As a result, the predicted performance of PbSnTe lasers and infrared detectors may be much better than thought before.

Lifetime calculations for Auger recombination in lead-tin-telluride

The refractive indices of mixed AgClxBr1−x crystals, with x ranging from 0 to 1, are measured at three wavelengths: 0.6328, 2.94, and 10.6 μm. A nonlinear dependence of the refractive index on composition is observed and explained on the basis of a simple Lorentz–Lorenz classical approximation. The theoretical dependence of the static dielectric constant on composition is also calculated. The same calculation is applied to KClxBr1−x crystals, and, in both crystal systems, good agreement with experiment is obtained.

Dielectric properties of silver halide and potassium halide crystals.

Optical absorption edges of mixed AgClxBr1−x (0≤x≤1) crystals and polycrystalline fibers were investigated as a function of composition. Both visible edge, resulting from electronic transitions, and infrared edge due to multiphonon processes behave as the one‐mode (amalgamation) type of mixed crystals, shifting continuously with composition. Quantitative expressions were used to discuss the results. Polycrystalline extruded fibers preserve this spectral window of silver‐halide crystals, except for slight deviations which are explained by the small‐grain structure of the fibers.

Abraham Katzir

Papers

Fiber‐optic‐based evanescent field chemical sensor using tunable diode lasers for the midinfrared spectral region

On the performance of selenium rich lead-salt heterostructure lasers with remote p-n junction

Lifetime calculations for Auger recombination in lead-tin-telluride

Dielectric properties of silver halide and potassium halide crystals.

Absorption edges of mixed silver‐halide crystals and polycrystalline optical fibers