Progress of Aluminum Gallium Indium Phosphide Red Laser Diodes and Beyond

Abstract

High-quality aluminum gallium indium phosphide epitaxial layers for red laser diodes have been grown by the metal organic chemical vapor deposition method. The layers have some issues, such as narrowing of the band gap, low p-carrier concentration, difficulty in epitaxial growth for quantum well structures, and generating of high-density hillocks. The issues have been successfully solved by introducing (100) substrates with misorientaion toward the [011] direction. High performance transverse-mode stabilized lasers are achieved by introducing the substrates, novel strain-compensated multiple-quantum well structures, which can add large strain to the wells, and low-loss optical cavity. This article also describes their applications.     

Simulation of a ridge-type semiconductor laser for separate confinement of horizontal transverse modes and carriers

A ridge-type semiconductor laser with selectively proton-implanted cladding layers for separate confinement of horizontal transverse modes and carriers is proposed, and lasing characteristics are simulated. Light is confined by the proton-implanted n-cladding layer; carriers are confined by the proton-implanted p-cladding layer. It is found that light output operating in the fundamental transverse mode is enhanced and threshold current is decreased.     

Monitoring of extra-axial brain tumor response to radiotherapy using pseudo-continuous arterial spin labeling images: Preliminary results

IntroductionTechnological developments have increased the ease of performing perfusion MRI by arterial spin labeling (ASL) in clinical settings. The objective of this study was to evaluate the effects of radiotherapy on extra-axial brain tumors by using MR perfusion images obtained using the pseudo-continuous arterial spin labeling (pcASL) method.Materials and MethodsSix consecutive patients (nine lesions) with extra-axial brain tumors treated only with radiotherapy were enrolled in this study. MR examinations, including pcASL imaging, were performed before and after radiotherapy. Cerebral blood flow, maximum tumor blood flow (mTBF), tumor volume and the ratio of signal enhancement by contrast material (enhancement ratio) were evaluated in serial examinations during the course of radiotherapy. Both the percentage change in mTBF (mTBF ratio) and the percentage change in volume (volume ratio) were calculated using values obtained before and after radiotherapy. The correlation between the volume ratio and the mTBF ratio was assessed using linear regression analysis and Spearman’s rank correlation coefficient (r_s).ResultsA strong correlation was demonstrated between the tumor volume ratio and the mTBF ratio before and after radiotherapy (r_s= 0.93, P< .01). However, no significant correlation was identified between changes in enhancement and volume ratio (r_s= 0.20) or between changes in enhancement and mTBF ratio (r_s= 0.30) before and after radiotherapy.ConclusionThe mTBF measured using pcASL may serve as an additive index for tumor volume when determining tumor response to radiotherapy even in the absence of contrast material.     

Synthesis and Properties of Thieno[3,2‐b]thiophene Derivatives for Application of OFET Active Layer

A series of thieno[3,2‐b]thiophene derivatives having styryl groups were synthesized via short steps and characterized by UV–vis absorption spectra and cyclic voltammetry. Based on these results, we found that the introduction of long chain alkyl groups to the terminal styryl groups leads to narrower HOMO–LUMO gaps and higher HOMO energy levels than the unalkylated styryl substituted molecules. Organic field–effect transistor (OFET) devices using these derivatives as the active layer were fabricated by a vacuum deposition process. It was demonstrated that these devices showed a relatively high hole mobility up to 3.5 × 10⁻² cm²/Vs. These devices also showed a good stability, namely their mobilities did not decrease over 100 days in air. Therefore, these facts suggested that the introduction of long‐chain alkylated styryl groups is an effective way to improve the hole mobilities in OFETs. © 2012 Wiley Periodicals, Inc. Heteroatom Chem 24:25–35, 2013; View this article online at wileyonlinelibrary.com . DOI 10.1002/hc.21059     

Na‐site energy of P2‐type NaxM O2 (M = Mn and Co)

P2‐type Na_xM O₂ (M = Mn and Co) is a promising cathode material for low‐cost sodium ion secondary batteries. In this structure, there are two different crystallographic Nai (i = 1 and 2) sites with different Coulomb potential $ (\varphi _i)$ provided by M^4–x and O^2–. Here, we experimentally determine a difference ${(\rm \Delta }\varepsilon \equiv \varepsilon _1 - \varepsilon _2)$ of Na‐site energies ${(}\varepsilon _i \equiv e\varphi {\kern 1pt} _i)$ based on the temperature dependence of the site occupancies. We find that ${\rm \Delta }\varepsilon \;{=}\;56\;{K}$ for Na_0.52MnO₂ is significantly smaller than 190 K for Na_0.59CoO₂. We interpret the suppressed ${\rm \Delta }\varepsilon $ in Na_0.52MnO₂ in terms of the screening effect of the Na⁺ charge. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Hg(OTf)(2)-catalyzed direct vinylation of tryptamines and versatile applications for tandem reactions

We have developed a unique catalytic protocol for direct gem-vinylation of tryptamine derivatives employing Hg(OTf)(2) as the optimum catalyst. The intermolecular vinylations with a series of aromatic acetylenes proceeded under ambient temperature at the C2 positions of indoles with high functional group tolerance. Based on the mechanistic insights, we further developed the tandem reactions successfully constructing a quaternary center.     

Synthesis of nitrogen-bridged terthiophenes by tandem Buchwald-Hartwig coupling and their properties

The first synthesis of nitrogen-bridged terthiophenes (NBTTs) has been achieved by a tandem Buchwald-Hartwig coupling of 3,3',3",4'-tetrabromo-2,2':5',2"-terthiophene. Several NBTT derivatives bearing aryl or alkyl moieties on the N-atoms could be synthesized. Their fundamental electrochemical characteristics and HOMO-LUMO levels were found to be influenced by the substituents on the N-atoms.     

Kinetic resolution of secondary alcohols by the combination of a chiral Brønsted acid, DABCO, and acetyl chloride

An efficient and simple protocol for the kinetic resolution of secondary alcohols is presented. The new system is based on a combination of chiral Br?nsted acid, DABCO, and acetyl chloride and gives various enantioenriched alcohols with selectivity factors up to 105.     

Hg(OTf)2-catalyzed vinylogous semi-pinacol rearrangement leading to 1,4-dihydroquinolines

An efficient method for the construction of dihydroquinoline derivatives possessing a quaternary carbon center is developed by an application of Hg(OTf)(2)-catalyzed vinylogous semi-pinacol-type rearrangement. The reaction was found to be specifically catalyzed by mercury salt and to proceed via a bicyclic aminal.     

Potential clinical factors affecting hepatobiliary enhancement at Gd-EOB-DTPA-enhanced MR imaging

Objective

The objective was to clarify the clinical factors that might affect the degree of hepatic parenchymal enhancement at gadolinium ethoxybenzyl diethylenetriamine pentaacetic acid (Gd-EOB-DTPA)-enhanced magnetic resonance (MR) imaging.

Materials and Methods

A total of 84 patients with (n=63) and without chronic liver disease (n=21) underwent Gd-EOB-DTPA-enhanced MR imaging. Contrast-enhanced MR images of hepatobiliary phase (HP) were obtained at 20 min after Gd-EOB-DTPA administration. The relative enhancement (RE) of liver parenchyma at 20 min HP was calculated from region of interest measurements at each patient. Then, these results were correlated with various clinical parameters using Pearson correlation coefficient or Spearman rank correlation coefficient. Furthermore, the predictor of the degree of hepatic parenchymal enhancement was determined using multiple regression analysis.

Results

The presence or absence of chronic liver disease (P=.002), ascites (P=.005) and splenomegaly (P=.027), and the values of prothrombin activity (P=.008), total bilirubin (T-Bil) (P=.001), albumin (P=.001), aspartate aminotransferase (AST) (P=.002) and cholinesterase (P=.007) were significantly correlated with the RE of liver parenchyma at 20 min HP. Among these parameters, increases of T-Bil (P=.011 to .028) and AST (P=.018 to .049) were predictors of decreased hepatic parenchymal enhancement.

Conclusions

Hepatic parenchymal enhancement of Gd-EOB-DTPA was affected by various clinical parameters. Impaired hepatobiliary enhancement may be predicted by routine biochemical tests, such as T-Bil and AST.