Highly efficient configuration of a Pr3+-doped fluoridefiber amplifier module with an optical circulator

A highly efficient Pr³⁺-doped fluoride fiber amplifier configuration with an optical circulator, in which the input signal light is amplified both forward and backward through a Pr³⁺-doped fluoride fiber, is investigated with a view to decreasing the drive current and improving the reliability of pump laser diodes (LD's). With this double-path configuration, a 25-dB signal gain is achieved at an LD drive current of 110 mA. This LD drive current is about half that needed for a conventional single-path configuration. It is also found that this double-path configuration provides a double-gain coefficient, a slightly low saturation power, and a slightly narrow spectral gain width     

Noise characteristics of Er3+-doped fiber amplifierspumped by 0.98 and 1.48 μm laser diodes

Measured noise characteristics of Er³⁺-doped optical fiber amplifiers pumped by 0.98- and 1.48-μm laser diodes (LDs) are reported. The noise figures estimated from the beat noise between signal and spontaneous emission are 3.2 dB for pumping by 0.98-μm LD and 4.1 dB for pumping by 1.48-μm LD. The beat noise between spontaneous emission components and the spontaneous shot noise for the 0.98-μm pumping are lower than those for the 1.48-μm pumping     

2.5 Gb/s CPFSK coherent multichannel transmission experiment forhigh capacity trunk line system

A 2.5-Gb/s CPFSK four-channel FDM transmission experiment has been conducted with a 150-km-long nondispersion-shifted fiber. This system employed a wideband channel space controller, a common polarization control, and a channel identification function. These were indispensable for realizing a high-capacity, coherent FDM trunk line system. The results of the experiment confirm the feasibility of trunk line systems with over 160-Gb/s capacity     

Time division multiplexed OTDR system

A new technique to increase the effective sampling rate of an optical time-domain reflectometer using a time division multiplexing digital sampling averaging procedure is proposed. This permits an increase in distance measuring accuracy of an optical time-domain reflectometer.     

Novel repeated batch operation for flash fermentation system: Experimental data and mathematical modelling

A novel repeated batch operation mode was proposed for ethanol fermentation, where the fermenter beer was periodically exchanged between the fermenter with biomass recycle and the distillation unit, to promote the selective removal of ethanol. Using the mathematical model developed, as based on the experimental results, the optimal operation of the proposed method was shown to attain high performance, with a productivity of about 12 g dm⁻³ h⁻¹ and a product concentration of 400 g dm⁻³.     

Wave venation in downward gas-liquid two-phase flow (part I,time-spatial behavior chart of interface and analysis of main wave-vein)

Time-series information on both the cross-sectional mean liquid holdup along a tube axis and the gas-liquid phase distribution along a tube diameter was obtained by means of supermultiple cross-sectional mean liquid holdup probes (S-CHOP) and semi-supermultiple point-electrode probes (SS-PEP) for vertical downward gas-liquid two-phase flow. Typical time-spatial behavior charts of interface and gas-liquid interfacial profiles are presented. Close inspection of these results reveals that a huge wave and a disturbance wave appear in downward two-phase flow as well as upward flow. It was clarified that the huge wave flow region covers a wide range of superficial gas velocities. Wave velocity, wave width and maximum liquid holdup of individual waves were examined by wave-vein analysis. Histograms of these flow parameters were also studied. It was found that there exist distinct differences in wave width between the huge wave and the disturbance wave. © 1997 Scripta Technica, Inc. Heat Trans Jpn Res, 25(8): 499–510, 1996     

Characterization of neurons differentiated from mouse embryonic stem cells using conditioned medium of dorsal root ganglia

Mouse embryonic stem (ES) cells have the pluripotent ability to differentiate in vitro into various cell lineages, including neurons. Adding chick dorsal root ganglion (DRG) conditioned medium (CM) to the culture medium promotes the differentiation of ES cells into neurons. We determined the types of neurons that differentiate from ES cells. The addition of DRG-CM caused nearly half of all ES cells on the periphery of the colony sphere to differentiate into neurons. Immunofluorescence analysis showed that the neurons that differentiated from ES cells were mainly motor, GABAergic, serotonergic, and cholinergic neurons. Of particular note, flow cytometry showed that approximately 50% of betaIII-tubulin-positive neurons were motor neurons. This indicates that DRG-CM induces ES cells to differentiate into motor neurons as target of DRG neurons (sensory neurons).     

Positive-temperature-coefficient effect of electrical resistivity below melting point of poly(vinylidene fluoride) (PVDF) in Ni particle-dispersed PVDF composites

This paper discusses the positive-temperature-coefficient effects of resistivity in Ni particle-dispersed poly(vinylidene fluoride) (PVDF) composites based on experiment results from SEM, DSC, and pressure-volume-temperature (PVT) measurements. The melting points of composites with Ni content of 20, 30, 40, and 50vol.% were equal to that of pure PVDF. The PTC effects in composites with Ni content of 40 and 50vol.% occurred at temperatures near the melting point of the PVDF matrix, whereas those in composites with Ni content of 20 and 30vol.% occurred at temperatures below the melting point of the PVDF matrix. We found that the PTC effect occurs even without melting of the matrix polymer. Moreover, we determined that a slight increase in specific volume at temperatures below the melting point of the matrix polymer acts fully as a driving force for forming a gap between fillers. This suggestion was backed up by theoretical analyses using percolation theory and a thermal-fluctuation-induced tunneling model.