Pure strain effects in strained-layer multiple-quantum-well lasers

Pure effects of strain in strained-layer multiple-quantum-well (MQW) lasers are measured separately from quantum effects using Fabry-Perot (FP) lasers with the same well thicknesses but different strains. The differential gain and gain saturation coefficients and the K factors of the lasers are determined by measuring relative-intensity-noise (RIN) spectra with various bias conditions. The differential gain coefficient increases when the compressive strain increases. The gain saturation coefficient also increases with increasing compressive strain. The K factor increases slightly when the compressive strain increases because of the slight increase in the ratio of the gain saturation coefficient to the differential gain coefficient     

Pharmacotherapy in the elderly--pharmacokinetic and pharmacodynamic considerations]

OBJECTIVE: N-acetyl-aspartyl-glutamic acid (NAAGA) was effective in the treatment of allergic rhinitis, with an action on early allergen-induced nasal symptoms and mediator release. The aim of this study was to evaluate the clinical activity of NAAGA and its effects on the late antigen-induced reaction in the nose. METHODS: Ten patients with allergic seasonal rhinitis were included in this randomized double-blind crossover trial of a 6% wt/vol solution of NAAGA (daily dosage 84 mg) versus placebo (lactose). The drug and placebo were administered intranasally five times daily for 1 week, with a 2-week interval between treatments. RESULTS: Treatment with NAAGA, but not with placebo, significantly reduced the late antigen-induced nasal symptoms, mainly nasal obstruction. Eosinophil numbers in the nasal lavages collected 6 h and 24 h after challenge were significantly lower after NAAGA than after placebo. Active treatment also significantly reduced the neutrophil count 6 h after antigen challenge, and significantly lowered eosinophil cationic protein and myeloperoxidase levels in nasal lavages 6 h and 24 h after antigen challenge. CONCLUSION: These results indicate that treatment for 1 week with NAAGA can reduce the late antigen-induced reaction in the nose. This is accompanied by a reduction in eosinophil and neutrophil recruitment and release of eosinophil cationic protein and myeloperoxidase.     

Neurotoxicodynamics of the interaction between ciprofloxacin and foscarnet in mice

The potential for convulsions induced by the coadministration of ciprofloxacin (CPFX) and foscarnet (PFA) may be due not to a change in the distribution of CPFX to the brain but to a potential CPFX-induced inhibition of gamma-aminobutyric acid (GABA)-GABA(A) receptor binding in the presence of PFA.     

Lasing characteristics of low-threshold oxide confinementInGaAs-GaAlAs vertical-cavity surface-emitting lasers

Some lasing characteristics of index-guided InGaAs-GaAlAs vertical-cavity surface-emitting lasers (VCSEL's) with a native oxide confinement structure, which produced a low threshold current of 70 μA, are presented. It was found that nonradiative recombination was reduced and the estimated surface recombination velocity was almost negligible. The oxidation process was uniform to produce low threshold devices while the oxidation rate was dependent on the doping or composition of DBR's     

Excess intensity noise originated from polarization fluctuation invertical-cavity surface-emitting lasers

We have observed an excess-intensity noise that is attributed to polarization fluctuations of InGaAs-GaAs vertical-cavity surface-emitting lasers (VCSELs). It was observed, for the first time, that the intensity noise increased remarkably by the polarization fluctuation even when the single transverse mode operation was maintained. This result indicates that it is necessary to control the polarization state of VCSELs as well as control the transverse modes for low-noise operations     

Frequency chirping in external modulators

A general formula is given that expresses frequency chirping in some types of external intensity modulators, such as the loss modulator, directional-coupler-type modulator, Mach-Zehnder interferometry-type modulator, and total-internal-reflection-type modulator. The chirping phenomenon treated is caused by the phase modulation due to an accompanied refractive index change. It is uniquely expressed in terms of an α-parameter that contributes to frequency chirping in the same manner as in the direct modulation of a semiconductor laser. In addition, the transmission bandwidth of a single-mode fiber system using an external modulator is discussed and compared with the results obtained utilizing direct laser modulation     

Low-loss antiresonant reflecting optical waveguide on Si substrate in visible-wavelength region

A low-loss (0.3 dB/cm) antiresonant reflecting optical waveguide on an Si substrate was realised at 0.633 ?m wavelength by employing a TiO2/SiO2 interference reflector instead of an Si/SiO2 pair used in the long-wavelength range.     

Negative strand of hepatitis C virus RNA in the liver of patients with chronic hepatitis C after interferon treatment

In patients receiving interferon therapy for chronic hepatitis C, serum hepatitis C virus (HCV) RNA often reverts from an undetectable to a detectable form after completion of treatment. Detection of the negative strand of HCV-RNA in liver tissue is regarded as an index of viral proliferation. Therefore, we investigated changes in the hepatic negative-strand HCV-RNA following interferon therapy to determine whether this parameter could predict the long-term response to treatment. The subjects of this study were 27 patients with chronic active hepatitis C. Serum positive-strand and hepatic tissue negative-strand HCV-RNA were detected using polymerase chain reaction. At the completion of interferon treatment, serum HCV-RNA was not detected in 21 patients. One year following treatment it remained undetectable in 14 of these patients but it had reverted to a detectable form in seven. The 14 patients in whom hepatic negative-strand RNA was not detected between 2 weeks and 12 months after treatment, had not relapsed after another year. In the 13 remaining patients, negative-strand RNA was found in liver tissue and serum RNA either reverted to a detectable form or remained detectable throughout. From these findings, we conclude that the detection of negative-strand HCV-RNA in liver tissue 2 weeks after the completion of interferon therapy is useful for predicting the long-term effect of therapy.     

Anisotropy in ac losses near the irreversibility field of Bi2Sr2CaCu2O8

The ac susceptibility under a biased dc field near the irreversibility field (H _irr) of a Bi₂Sr₂CaCu₂O₈ single crystal has been measured. The frequency dependence, the ac-power dependence, and the nearly lossless character of the?″ vs.H _dc curve forH∥a-axis have been roughly explained from a reversible (elastic) fluxoid motion, while those forH∥ c-axis have been explained from a thermally assisted flux-flow (TAFF) model. The obtained parameters are discussed in relation to anisotropic flux-pinning mechanisms in the layered structure of this compound.