NRZ operation at 40 Gb/s of a compact module containing an MQW electroabsorption modulator integrated with a DFB laser

NRZ operation at 40 Gb/s has been successfully performed using a very compact module of a multiple-quantum-well (MQW) electroabsorption modulator integrated with a distributed-feedback (DFB) laser. While the DFB laser is injected with a constant current, the integrated MQW electroabsorption modulator is driven with a 10-Gb/s electrical NRZ signal. A clearly opened eye diagram has been observed in the modulated light from the modulator. And a receiver sensitivity of -27.2 dBm at 10/sup -9/ has been experimentally confirmed in the bit-error-rate (BER) performance.     

Glucose- and phorbol ester-induced insulin secretion in human insulinoma cells--association with protein kinase C activation

To investigate the incidence and demographics of gastric hypoacidity among persons infected with human immunodeficiency virus (HIV), 146 asymptomatic subjects were evaluated with use of a radiotelemetry device (Heidelberg capsule). Gastric hypoacidity (minimum gastric pH of > or = 3) occurred in 24 subjects (17%). Demographic characteristics, CD4 cell counts, and Helicobacter pylori serological status were evaluated for an association with gastric pH. Subjects with hypoacidity were more likely to have positive H. pylori serology than were subjects without hypoacidity (15 of 24 vs. 23 of 74, respectively; P = .004). Multivariate analysis indicated that a positive H. pylori serology was the most significant predictor of hypoacidity, accounting for an increase in gastric pH of 39%. A history of injection drug use, heterosexual transmission of HIV, and male gender were also associated with an elevated gastric pH. CD4 cell counts did not contribute to predictions of gastric pH. A history of H. pylori infection is relatively common in HIV-positive black and Hispanic populations and is a predictor of gastric pH.     

A narrow beam 1.3-μm-super luminescent diode integrated with aspot-size converter and a new type rear absorbing region

The device structure and performance of 1.3-μm narrow beam superluminescent diodes (NB-SLD's), which consist of a spot-size converter and a new type rear absorbing region, are reported. A butt-jointed selectively grown spot-size converter (SSC) is employed to realize the narrow beam characteristics. The rear absorbing region is designed as a taper structure with a part of the region is inclined from the active-stripe axes. In order to investigate the effects of both SSC length and active-region length on device performance, two types of NB-SLDs, whose SSC and active-region lengths differ, are fabricated. An electrode to sweep out photoexcited carriers in the absorption region is formed on one device. By comparing the characteristics of these devices, we clarify that a 500-μm-active-region device is suitable for high-output power operation, and a 400-μm-active-region device is suitable for realizing short coherent length. The light-output power is 13.9 mW at 200-mA-injection current for the former device, and the full-width at half-maximum (FWHM) of the spectrum is 62.6 nm (calculated coherence length is 26.5 μm) for the latter device. Very small spectral modulation index (0.015 at 5 mW-output power) is attained by grounding the absorption-region electrode. For the SSC length, a 300-μm SSC device shows very narrow far-field patterns (FFPs) and very good fiber-coupling characteristics. The FWHM of horizontal and vertical FFPs are 8.9 and 10.6°, respectively. Because of this narrow beam divergence, the coupling efficiency of -1.9 dB to a flat-end 4-μm spot-size fiber is obtained without lenses. The alignment tolerance of this device to the fiber for both horizontal and vertical direction is more than 3 μm at a loss of when -1 dB from the optimum coupling     

Retinal efferents from the pretectal area in the rat

Horseradish peroxidase (HRP) labeled neuronal somas were consistently found in the medial pretectal area after intraocular injection of HRP. The labeled cells represent the source of centrifugal fibers to the rat retina.     

Fabrication and lasing properties of mesa substrate buried heterostructure GaInAsP/InP lasers at 1.3 µm wavelength

Fabrication and lasing properties of novel GaInAsP/InP injection lasers at 1.3 μm, with buried heterostructure grown on mesa substrate and fabricated by single-step crystal growth are reported. In this mesa substrate buried heterostructure (MSB) laser, the GaInAsP active layer was grown separately on the top of a mesa structure formed along the surface of a     

1.5 μm transmission experiment with distributed feedback laser

The paper reports an experiment which demonstrates the possibility of error-free transmission over 100 km without repeater, by using a single-mode fiber and a laser diode with distributed feedback emitting a single longitudinal mode at the wavelength 1.5 μm.     

Direct modulation characteristics of GaInAsP/InP d.h. lasers with various stripe widths measured by sharp-pulse method

The direct modulation characteristics of GaInAsP/InP d.h. lasers emitting at 1.3 ?m with various stripe widths were measured by the proposed sharp-pulse method. As a result, a flat modulation frequency response up to 1.9 GHz was observed in a laser diode with 5 ?m stripe width.     

Fuel and emissions properties of Stirling engine operated with wood powder

From viewpoints of the environment and fuel cost reduction, small-scale biomass combined heat and power (CHP) plants are in demand, especially wood-waste fueled system, which are simple to operate and maintenance-free with high thermal efficiency similar to oil fired units. These are requested by wood and other industries located in mountainous region. To meet these requirements, a Stirling engine CHP system combined with simplified biomass combustion process with pulverized wood powder was developed.In an R&D project started in 2004 considering wood powder properties as a fuel, combustion performance and emissions in combustion flue gas were tested using combustion test apparatus with commercial size units. The wood powder combustion system was modified and optimized during the combustion test results, and the design of the demonstration plant combined with 55 kW_e Stirling engine power unit was considered. The demonstration plant was finally completed in March of 2006, and test operation has been progressed for the future commercial CHP system.In the wood powder combustion test, wood powder of less than 500 μm is mainly used, and a combustion chamber length of 3 m is applied. In these conditions, the air ratio can be reduced to 1.1 without increasing CO emission of less than 10 ppm and combustion efficiency of 99.9%. In the same conditions, NO_x emission is estimated to be less than 120 ppm (6% O₂ basis). Wood powder was confirmed to have excellent properties as a fuel for Stirling engine CHP system. This paper summarizes the wood powder combustion test, and presents the evaluation of the burner design parameters for the biomass Stirling engine system.     

Seasonal changes of arsenic speciation in lake waters in relation to eutrophication

In this study, the influence of eutrophication on arsenic speciation in lake waters was investigated. Surface water samples (n = 1-10) were collected from 18 lakes in Japan during July 2007 and February 2008. The lakes were classified into mesotrophic (7 lakes) and eutrophic (11 lakes) based on the total phosphate (T-P) and chlorophyll-a (Chl-a) concentrations in water column. Inorganic, methylated and ultraviolet-labile fractions of arsenic species were determined by combining hydride generation atomic absorption spectrometry with ultraviolet irradiation. Organoarsenicals (mainly methylated and ultraviolet-labile fractions) comprised 30-60% of the total arsenic in most lakes during summer. On the other hand, inorganic arsenic species (As(III + V)) dominates (about 60-85%) during winter. The occurrence of ultraviolet-labile fractions of arsenic was higher in eutrophic lakes than those in mesotrophic lakes in both seasons. The concentration of dimethyl arsenic (DMAA) was high in eutrophic lakes during winter; and in mesotrophic lakes during summer. The results suggest that the conversion of As(III + V) to more complicated organoarsenicals occurred frequently in eutrophic lakes compared to that in mesotrophic lakes, which is thought to be the influence of biological activity in the water column. The distribution of arsenic species were well correlated with phosphate concentrations than those of Chl-a. This might be due to the competitive uptake of As(V) and phosphate by phytoplankton. The organoarsenicals (OrgAs)/As(V) ratio was higher at low phosphate concentration indicating that conversion of As(V) to OrgAs species was more active in phosphate-exhausted lakes with high phytoplankton density.