Improved performance of subcarrier multiplexed multichannel AM-VSBvideo signal transmission using Pr3+-doped fluoride fibreamplifier

The performance of 40 channel AM-VSB video signal transmission using a Pr³⁺-doped fluoride fibre amplifier (PDFA) was examined. The PDFA improves the loss budget by 10 dB for 52 dB CNR, and distortion levels almost satisfy the CATV trunk line specifications. The video quality degradation after PDFA amplification was `imperceptible' in subjective tests     

中国充电器标准化带来的变化

中国政府率先开始了手机充电器的标准化,其目的是让用户更换手机终端后可继续使用原来的充电器,从而通过削减废弃物达到保护环境的目的。     

Ultra light-weight and high-resolution X-ray mirrors using DRIE and X-ray LIGA techniques for space X-ray telescopes

We are developing novel ultra light-weight and high-resolution X-ray micro pore optics for space X-ray telescopes. In our method, curvilinear micro pore structures are firstly fabricated by silicon deep reactive ion etching (DRIE) or X-ray LIGA processes. Secondly, side walls of the micro structures are smoothed by magnetic field assisted finishing and/or hydrogen annealing techniques for high reflectivity mirrors. Thirdly, to focus parallel X-ray lights from astronomical objects, these structures are elastically or plastically bent into a spherical shape. Fourthly, the bent structures are stacked to form a multi-stage X-ray telescope. In this paper, we report on fabrication and X-ray reflection tests of silicon and nickel X-ray mirrors using the DRIE and LIGA processes, respectively. For the first time, X-ray reflections were confirmed on both of the mirrors. Estimated rms roughnesses were 5 nm and 3 nm for the silicon and nickel mirrors, respectively.     

Robust loss functions for boosting

Boosting is known as a gradient descent algorithm over loss functions. It is often pointed out that the typical boosting algorithm, Adaboost, is highly affected by outliers. In this letter, loss functions for robust boosting are studied. Based on the concept of robust statistics, we propose a transformation of loss functions that makes boosting algorithms robust against extreme outliers. Next, the truncation of loss functions is applied to contamination models that describe the occurrence of mislabels near decision boundaries. Numerical experiments illustrate that the proposed loss functions derived from the contamination models are useful for handling highly noisy data in comparison with other loss functions.     

Regulation of selectin binding activity by cyclization of sialic acid moiety of carbohydrate ligands on human leukocytes

We provide here evidence that supports the occurrence of a biologically dormant form of selectin ligand carbohydrate, the sialyl 6-sulfo Lewis X containing modified sialic acid, in human leukocytes. The modification of sialic acid involves first de-N-acetylation of sialic acid moiety through ubiquitous de-N-acetylation/re-N-acetylation cycle, followed by the dehydrative cyclization of de-N-acetyl sialic acid to form "cyclic sialic acid." The enzyme involved in the dehydration of de-N-acetyl sialic acid is a calcium-dependent enzyme having neutral-alkaline pH optimum. De-N-acetyl sialyl 6-sulfo Lewis X retained selectin binding activity as well as parental sialyl 6-sulfo Lewis X, but cyclic sialyl 6-sulfo Lewis X was devoid of selectin binding activity. Sialyl 6-sulfo Lewis X carrying the cyclic sialic acid is specifically recognized by the newly generated mAb, G159. The determinant was distributed widely among normal human leukocytes, especially on monocytes and subsets of lymphocytes including NK cells, helper memory T cells, Tcr-gammadelta T cells, and a part of B cells. The determinant was detected also on several cultured lymphocytic leukemia cell lines and O-tetradecanoylphorbol 13-acetate-activated lymphoid cells. Cyclic sialyl 6-sulfo Lewis X is efficiently formed by the action of the partly membrane-bound calcium-dependent enzyme, tentatively called "sialic acid cyclase," and a possible physiological significance of this reaction could be a rapid inactivation of selectin binding activity at the cell surface. Conversely, the accumulated intracellular cyclic sialyl 6-sulfo Lewis X determinant may function as a dormant pool of selectin ligands, which, on appropriate stimulation, is hydrolyzed and becomes active in selectin-dependent cell adhesion.     

Applications of highly nonlinear chalcogenide glass fibers inultrafast all-optical switches

Applications of chalcogenide glass fibers in ultrafast all-optical switches have been investigated. Ultrafast all-optical switching has been accomplished in an optical Kerr shutter configuration using As₂S₃-based glass fiber. The nonlinear refractive index of the As₂S₃-based glass is estimated to be n₂=4.0×10^-14 (cm²/W ), which is higher by two orders of magnitude than that of silica glass fiber. Nonlinear absorption due to two-photon absorption has been revealed to be negligible, and up to a 2π-phase shift has been obtained. Switching speed and switching power were investigated experimentally and through calculations. A switching time of 12 ps and a switching power of 5 W can be achieved using a 10-ps gate pulse and only a 1-m chalcogenide glass fiber. However, signal transformation due to cross-phase modulation and group velocity dispersion is not negligible for shorter gate pulses. Lower switching power is possible by reducing the transmission loss and the core area and by optimizing the driving conditions     

Methanol synthesis from CO2 over Cu/ZnO catalysts prepared from various coprecipitated precursors

Various precursors of Cu/ZnO catalysts were prepared by coprecipitation methods. By varying the conditions of coprecipitation, precursors having different structures (aurichalcite, malachite, hydrozincite, or their mixture) were obtained at given Cu/Zn ratios, ranging from 30/70 to 70/30. In a wide range of the Cu/Zn ratios, the catalysts derived from the precursors containing aurichalcite exhibited high performance in the methanol synthesis from CO₂.