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.

/pdf/mechanisms-of-pulsed-laser-ablation-of-biological-tissues-58cltfa63z.pdf

Mechanisms of pulsed laser ablation of biological tissues.

Nitrate is a frequent water pollutant that results from human activities such as fertilizer over-application and agricultural runoff and improper disposal of human and animals waste. Excess levels of nitrate in watersheds can trigger harmful algal blooms (HABs) and biodiversity loss with consequences that affect the economy and pose a threat to human health. Municipal drinking water and wastewater treatment plants are therefore required to control nitrogen levels to ensure the safety of drinking water and the proper discharge of effluent. Nitrate exhibits distinct absorption bands in the infrared spectral range. While infrared radiation is strongly attenuated in water, implementation of fiber optic evanescent wave spectroscopy (FEWS) enables monitoring of water contaminants in real-time with high sensitivity. This work outlines the development of a non-dispersive infrared (NDIR) detector for the real-time monitoring of nitrate, nitrite and ammonia concentrations targeting implementation at municipal wastewater treatment plants (WWTPs) and onsite wastewater treatment systems (OWTS).

Non-dispersive infrared (NDIR) sensor for real-time nitrate monitoring in wastewater treatment

Lasers & optical fibers in medicine

The presented work demonstrates that powerful laser radiation causes changes in absorbance spectra of epoxy resin and polyethylene. Thin polymer films were located between IR AgBrCl optical fibres and exposed to the radiation of a CO2 laser. The output of the laser source was varied in the range 0-8.5 W. Absorbance spectra were measured by a Fourier transform IR spectrophotometer. It was revealed that characteristic absorbance peaks of polymers decay under the powerful IR light. The apparent dependence of peak magnitude on IR radiation power has been established. The mathematical theory of the observed effect was worked out. The authors suggest that the effect under discussion is caused by the oxygen-free thermal action of IR radiation on the chemical structure of polymer materials. The revealed effect could be effectively used for the lowering of losses in adhesive contacts of IR optic elements. The novelty of the proposed method lies in the fact that thermal treatment is localized strictly in the adhesive contact: optical elements to be contacted (fibres, lenses etc), which are highly transparent in the IR, do not experience the IR radiation, but the polymer adhesive is subjected to a temperature rise. The phenomenon could be effectively used for the lowering of losses in optical contacts and recording and storage of information in polymer films as well.

https://iopscience.iop.org/article/10.1088/1464-4258/2/5/104/pdf

Infrared laser radiation induced changes in the IR absorption spectra of thin polymer films

Modal filters are necessary to the proposed high-performance mid-infrared nulling interferometers, because they can help achieve deeper interferometric nulls Silver halide fibers of composition AgClxBr1-x (0<x<1) are leading candidates for these purposes, due to their high transparency in 4-20 µm spectral range We have fabricated silver halide fibers with small cores and small differences between the refractive indices of the core and the clad These operated as single mode fibers An outer absorbing layer was applied to strip off cladding modes and reduce the minimum fiber length needed for modal filtering Short sections of such fibers exhibited round and symmetrical optical field mode distributions with losses of 10-15dB/m at λ=106µm We have tested the modal filtering properties of such short fiber sections We found that the presence of unsuppressed cladding modes at the output is the main factor limiting the fiber’s performance as a modal filter This effect can be mitigated by appropriate aperturing of the output With a properly sized aperture, a 105 cm long fiber can suppress the power in nonfundamental modes by a factor larger than 17000 If an aperture is not used, the suppression is reduced by a factor of ~ 20

Silver halide single mode fibers for modal filtering in the middle infrared

We have developed a Scanning Near-field Infrared Microscope (SNIM) that is based on tapered fiber probes made of AgClBr. This microscope can be used for thermal imaging and spectral imaging in the middle infrared, in the spectral range of 5-15 mum, with a subwavelength spatial resolution. We have used the microscope for imaging of inorganic and organic samples that were either placed in air or immersed in water. We have already adapted the system for the study of living biological cells of sizes smaller than a wavelength. Such a study promises to be important both as a pure scientific tool in biology and as a diagnostic tool in medicine.

Abraham Katzir

Papers

Non-dispersive infrared (NDIR) sensor for real-time nitrate monitoring in wastewater treatment

Lasers & optical fibers in medicine

Infrared laser radiation induced changes in the IR absorption spectra of thin polymer films

Silver halide single mode fibers for modal filtering in the middle infrared

A Scanning Near-Field Infrared Microscope Based on AgClBr Fiber Probes