Quantum-confined field-effect light emitters: device physics andexperiments

Extended experimental results on three-terminal quantum-confined field-effect light emitters with current injection and field control of luminescent characteristics in the quantum-well structure are reported. By incorporating superlattice buffer layers (SLBLs), the quantum efficiency of the device is dramatically improved and equivalently nonradiative recombination processes are sufficiently suppressed at room temperature. The red-shift of the emission spectra by the quantum-confined Stark effect assures that the electric field is effectively applied to the quantum well. The experimental data on the transient responses of emission intensity to input voltage pulses show fairly good correspondences with theoretical prediction and previous photoluminescence experiments. The authors discuss the ultimate capability of high-speed switching and point that an optical pulse with a duration as short as 30 ps and involving more than 100 photons can be generated by scaling down the size of the device with 1% external efficiency     

Mode characteristics of the multiple-stripe laser effects of the loss embedded in the outer unpumped region

The criteria for the mode selections in multiple-stripe lasers are presented. It is shown that the couplings of the higher-order modes of each stripe, which constitute the multiple-stripe laser, play important roles in the mode selections. Based on this analysis, a method for realizing 0° phase-shift mode oscillations is proposed. The method involves loss embedment in the outer unpumped region and the use of multiple stripes with fine center-to-center spacings. For the realization of this scheme, a grating-incorporated channeled-substrate planar (GICSP) laser is proposed and is fabricated. It is demonstrated that the 180° phase-shift mode is completely suppressed with this scheme. Single-longitudinal mode oscillations of well-defined index-guided 0° modes are observed for wide-channel CSP lasers.     

Sequence analysis of SRSV in fecal specimens from an epidemic of infantile gastroenteritis, October to December 1995, Japan

BACKGROUND AND HYPOTHESIS: Valvar pulmonary stenosis is a common congenital heart defect. Progression of stenosis over time, even when mild initially, has been shown by serial cardiac catheterization studies in children and adults. We studied the natural history of asymptomatic valvar pulmonary stenosis diagnosed in infancy with two-dimensional echocardiography and Doppler method. METHODS: Between November 1986 and March 1993, 51 infants in the Northeast Tennessee and Southwest Virginia region were clinically diagnosed to have isolated valvar pulmonary stenosis. In 40 patients, the diagnosis was confirmed by two-dimensional echocardiogram/Doppler and color-flow mapping study at the time of presentation, and only their course is reported. Of 40 infants, six asymptomatic infants (15%) showed rapid progression of pulmonary stenosis over a relatively short period of time. Within the first 6 months of life, three of the six infants showed worsening of the stenosis needing intervention (one had surgical valvectomy and the others had percutaneous balloon valvuloplasty). The three other infants showed a more gradual increase of pulmonary stenosis over the first 2 years of life. RESULTS: Pulmonary stenosis even when mild can worsen in infancy, and it is not possible to predict which patients will follow this course. In our group of asymptomatic infants with initial mild pulmonary stenosis, 15% developed significant stenosis that needed intervention. CONCLUSION: We recommend frequent follow-up of asymptomatic infants with mild pulmonary stenosis during the first 2 years of life to detect rapid progression that may need intervention.     

Determinants of collateral development in a canine model with repeated coronary occlusion

It is now accepted that repetitive 2-min coronary occlusion can develop collateral vessels to the area perfused by the occluded coronary artery. However, which factors influence collateral development has yet to be fully elucidated. The goal of the present study was to identify the determinants of the rate of coronary collateral development in dogs undergoing repeated coronary occlusion. The study was conducted in 19 conscious dogs instrumented for measurements of a subendocardial segment length in the area perfused by the left circumflex coronary artery (LCCA), LCCA flow, and left ventricular pressure. An externally inflatable pneumatic occluder was placed around the LCCA. After the recovery from surgery, 2-min LCCA occlusions were conducted eight times daily. Following 141 +/- 61 (SD) LCCA occlusions (20 +/- 7 days), an LCCA occlusion produced no reduction in segment shortening and negligible reactive hyperemia. The total number of LCCA occlusions needed for adequate collateral development (the rate of collateralization) correlated well with the severity of myocardial ischemia during the first occlusion, which was determined mainly by the extent of postsurgical initial collateral circulation. On the other hand, the response to the ischemic stimulus in the later stage of collateral development was independent of the extent of development of the initial postsurgical collaterals. It is concluded that the overall rate of collateral development is slower in dogs with initially poorer collaterals; however, the response of each dog to the ischemic stimulus in the later stage of collateral development was similar among dogs regardless of the extent of the initial collaterals.     

An in-frame deletion in peripheral myelin protein-22 gene causes hypomyelination and cell death of the Schwann cells in the new Trembler mutant mice

Cloning and sequencing of the peripheral myelin protein-22 cDNA and genomic DNA from newly found Trembler mice revealed an in-frame deletion including exon IV which codes for the second (TM2) and a part of third (TM3) transmembrane domain of peripheral myelin protein-22. This mutation was distinct from those in both other allelic Trembler and Trembler-J mice, which carry point mutations within the putative transmembrane spanning regions of peripheral myelin protein-22. Inheritance was autosomal dominant. The affected mice revealed an abnormal gait, which appeared at 15-20 days of age, followed by motor and sensory ataxia, which remained throughout life. Most of the affected mice could survive more than one year. One of the most notable pathological phenotypes was a giant vacuolar formation in the sciatic nerve of homozygotes. They vary in size within the cytoplasm of Schwann cells, which failed to assemble myelin at any ages studied. Heterozygotes showed normal myelination during the early postnatal stages, followed by a segmental demyelination at an advanced stage. Vacuolar formation was not so frequent as in the homozygotes. These results suggest that the missing of transmembrane spanning region (TM2 and TM3) of peripheral myelin protein-22 may disturb a dual biological function of peripheral myelin protein-22, leading to a dysmyelination of axons and to a vacuolar formation within the cytoplasm of the Schwann cells. The latter phenotype is discussed in conjunction with the disruption of an intracellular transport system and subsequent cell death.     

Gain-switching characteristics and fast transient response of three-terminal size-effect modulation laser

Gain-switching characteristics of the proposed size-effect modulation light sources are investigated. For realizing the laser operation, the consideration of the screening effect on the applied electric fields due to the high concentration of carriers is indispensable. In this respect, we propose a separate-confinement-hetero-multiple-quantum-well (SCH-MQW) structure as the most suitable one for gain switching. The key point of the structure is the sufficiently high heterobarriers at the clad-barrier interfaces to prevent carrier leakage. The examinations of the transient response clarify that they are principally photon-lifetime limited. Employing the three-terminal character of the proposed laser, the fast pulse modulation up to 12 Gbits/s, which is almost free from the relaxation oscillations and the pattern effects, is predicted.     

Stress induced urinary incontinence in patients with spinocerebellar degeneration

To better understand genetic alterations in atypical adenomatous hyperplasia (AAH) of the prostate, we examined the prevalence of allelic imbalance at 5 microsatellite polymorphic markers on chromosomes 7q31-35, 8p12-21, 8p22, 8q22.2, and 18q12.2 from 15 patients with AAH. DNA samples were obtained from formalin-fixed paraffin-embedded sections using tissue microdissection. We found allelic imbalance in 7 of 15 (47%) cases of AAH. Genetic changes that commonly occur in early prostatic carcinogenesis and prostate carcinoma are found in AAH. Current data provide evidence of a genetic link between some cases of AAH and carcinoma.