Low-threshold operation of 1.5?m buried-heterostructure DFB lasers grown entirely by low-pressure MOVPE

Buried-heterostructure (BH) distributed feedback (DFB) lasers have been fabricated by a three-step low-pressure MOVPE process. The CW threshold currents were as low as 15mA and a high differential efficiency of 0.21 W/A was obtained. The laser operated in a stable single longitudinal mode over a wide range of driving currents and under highspeed direct modulation.     

Growth hormone-secreting pituitary adenoma associated with multiple bone cysts, skin pigmentation and aortitis syndrome

McCune-Albright syndrome (MAS) is clinically characterized by polyostotic fibrous dysplasia, cafe au lait pigmentation of the skin and multiple endocrinopathies. Recently activating mutations of codon 201 in the gene encoding Gs alpha have been found in affected tissues in MAS. Herein we report a case of acromegaly associated with multiple bone cysts and skin pigmentation in a 47-year-old women. She had suffered a history of aortitis syndrome. The DNA sequence indicated that a Cys201 for Arg201 substitution was found in the GH secreting pituitary adenoma tissue but not in peripheral mononuclear cells. We speculate that the patient has a possible variant from of MAS characterized by multiple bone lesions skin pigmentation and GH-secreting pituitary adenoma.     

Optical and structural properties of implanted silicon nanocrystals

A novel method for the fabrication of Si nanocrystals in an amorphous SiO₂ matrix by ion implantation is reported. Transmission electron microscopy indicates the formation and growth of Si nanocrystals on annealing at 1100°C which were not observed before annealing. After annealing, a photoluminescence band around 1.7 eV is observed. The shape of the emission spectrum of the photoluminescence is found to be independent of annealing time, while the intensity of the luminescence increases and then decreases as the annealing time increases. We also show direct evidence of widening of the band-gap energy of a few nanometer-sized Si particles by employing photoacoustic spectroscopy. These results indicate that the photons are absorbed by Si nanocrystals, for which the band-gap energy is modified by the quantum confinement effects, and the emission is not simply due to direct electron-hole recombination inside Si nanocrystals but is related to defects probably at the interface between Si nanocrystals and SiO₂.     

Development of a direct PCR assay for detection of the diphtheria toxin gene

PCR has proved to be a reliable tool for the detection of the diphtheria toxin gene, tox, and its use has allowed for the rapid differentiation between toxigenic and nontoxigenic strains. In this study, this PCR was further developed, evaluated, and standardized to detect this gene directly from clinical specimens. Optimal conditions for collection, transport, and storage of the clinical specimens and isolation and purification of DNA from the clinical specimens were defined. With two sets of primers that detect the A and B subunits of the diphtheria toxin gene, sensitivity levels of 50 and 500 CFU/PCR mixture, respectively, were achieved. This PCR was evaluated with 162 clinical samples collected from patients with diphtheria and other upper respiratory tract infections, as well as from healthy individuals.     

Prevalence and characterization of novel pANCA, antibodies to the high mobility group non-histone chromosomal proteins HMG1 and HMG2, in systemic rheumatic diseases

OBJECTIVE: To determine the immunodiagnostic value of antibodies to the high mobility group non-histone chromosomal proteins HMG1 and HMG2, which have been identified as novel target antigens of perinuclear antineutrophil cytoplasmic antibodies (pANCA), in sera from patients with systemic rheumatic diseases. METHODS: Anti-HMG1 or HMG2 antibody was assayed by ELISA and Western blotting in sera from patients with systemic rheumatic diseases. These antibodies were analyzed for the relationship with pANCA detected by indirect immunofluorescence in these diseases, and with clinical features in rheumatoid arthritis (RA) and systemic lupus erythematosus (SLE). RESULTS: Anti-HMG1 or HMG2 antibody was frequently detected in sera from patients with RA (48%), SLE (45%), Sj?gren's syndrome (SS) (44%), and systemic sclerosis (SSc) (41%). In these diseases, anti-HMG1 antibody was detected more frequently than anti-HMG2 antibody. In sera from patients with RA, the positivity for anti-HMG1 and HMG2 antibodies was significantly correlated with the positivity for pANCA (p < 0.0001). Anti-HMG1/HMG2 antibodies were associated with some disease activity variables, e.g., erythrocyte sedimentation rate, C-reactive protein, rheumatoid factor, joint score and hand grip strength in RA, and CH50, C3, C4, and IgG in SLE. CONCLUSION: Anti-HMG1/HMG2 antibodies are detected commonly in systemic rheumatic diseases, particularly in RA, SLE, SS, and SSc. HMGI and HMG2 seem to be the significant target antigens of pANCA in RA. These antibodies are significantly associated with disease activity indices in RA and SLE.     

Narrow linewidth and low chirping characteristics in high poweroperating butt-jointed DBR lasers grown by MOVPE

High power operation in 1.5 μm butt-jointed DBR lasers, made entirely by MOVPE is demonstrated. An output power of more than 30 mW and 60 mW is observed in the CW and pulsed condition, respectively. The minimum spectral linewidth achieved here is 2.1 MHz, at an output power of 12.5 mW and the wavelength chirping width under NRZ modulation is 60-70% of that of conventional DFB lasers     

A high-density data-path generator with stretchable cells

This paper describes a newly developed module generator for cell-based design which generates a data-path layout comparable to a handcrafted one both in speed and in transistor density. The chip designer enters his schematic data-path diagram using the configurable function block library provided. There is no constraint either in the number of function blocks used, or in how to interconnect them. The data-path generator generates the function blocks, which are components of the data-path, and automatically places and routes them. The configurable function blocks were developed in 0.8-μm double metal CMOS technology. A new cell structure suitable for over the cell routing, called “stretchable cell with access free terminals,” is adopted as a bit-slice element of the data-path generator. This removes the routing region outside the cell for the wiring between function blocks, and a high density layout can be obtained. Also because of the new cell structure, there is no upper limit on the number of tracks per bit. Using this data-path generator, several data-paths were generated with high density of more than 6k Trs./mm²     

Instability of the Characteristics of the Positive Temperature Coefficient of Resistivity in High-Curie-Point Barium-Lead Titanate Ceramics and Their Grain Structures

A significant isothermal increase in resistivity with time has been observed in high-Curie-point barium-lead titanate ceramics in the temperature region of the Curie points, giving rise to an instability of the characteristics of the positive temperature coefficient of resistivity (PTCR). The isothermal increase in resistivity (ρ) with time (t) observed at various temperatures can be expressed by the equation log ρ=A+B√t, where A and B are both temperature-dependent constants. The temperature dependence of A gave the usual PTCR characteristics because A is log ρ at t=0, while the temperature dependence of B was found to show a characteristic curve with a peak around the Curie point. Observation by SEM revealed a considerable difference between the grain structure of a sample showing a significant resistivity change and that of a sample showing little resistivity change.