Multi-Terabit Long-Haul Transmission System Utilizing Distributed Raman Amplification Technologies

Here we summarize multi-terabit long-haul transmission experiment and distributed Raman amplification (DRA) technologies. As well, we investigate the configuration of dispersion-managed fibers for the DRA-based system from the viewpoint of the fiber non-linear effect and required pumping power.     

Photoluminescence characteristics of nitrogen atomic-layer-doped GaAs grown by MOVPE

Nitrogen atomic-layer-doped and uniformly doped GaAs were grown by MOVPE using dimethylhydrazine on a (001) plane. They showed several sharp photoluminescence lines with a full width at half maximum less than 1 meV at 8 K. Compared with uniformly doped GaAs, the photoluminescence intensity of the nitrogen-related line at the longest wavelength is enhanced in nitrogen atomic-layer-doped GaAs, suggesting that it is easier to form nitrogen pairs during atomic layer doping. To investigate the sharp nitrogen-related lines, we also grew GaAs with double atomic-layer-doped planes and varied the distance between the two planes. When the two planes are brought close to 1 nm, two new lines, NN_C and NN_D, appear between the two nitrogen-related lines, NN_A and NN_B, observed in a single nitrogen atomic-layer-doped GaAs. The NN_C and NN_D lines are also observed in uniformly doped GaAs. Therefore, NN_A and NN_B originate from excitons bound to pairs of nitrogen atoms, both of which are in the (001) plane, while NN_C and NN_D originate from those bound to pairs of nitrogen atoms, of which pairing directions are not included in the (001) plane. From the photoluminescence characteristics, distances between nitrogen atoms of a pair are estimated for each line.     

Bayesian analysis of lymphatic spreading patterns in cancer of the thoracic esophagus

For the treatment of patients with cancer of the thoracic esophagus, lymphatic spreading is one important factor to infer how advanced their cancer is. We introduced a one-dimensional scale based on lymphatic spreading patterns, the stage of cancer, to express how advanced their cancer is, and we proposed a method to infer each patient's stage from his lymphatic spreading pattern by applying a Bayesian model. Our Bayesian model was built based on the assumption that lymphatic spreading in cancer could be explained as what was brought about by the advance of stage. In the modeling, we introduced the probability of what stage each patient was in as a prior distribution. We also introduced distribution functions of Weibull distributions to express the relation between the advance of stage and the increase of the probability of metastasis. Our model was applied to the data of nodal involvement obtained from 103 patients with cancer of the thoracic esophagus and the parameters were estimated with the maximum likelihood method. AIC was used to check that the data had enough information to be divided into the stages of a clinically reasonable number. With the estimated parameters, we inferred the probability of metastasis to each lymph node in each stage and calculated by Bayes' theorem with 31 new patients the probability of what stage they were in. The results well represented some characteristics of the lymphatic spreading and suggested the appropriateness of our approach.The present study was carried out under the ISM Cooperative Research Program (91-ISM·CRP-18).     

Stokes parameters measurement of light over a wide wavelength range by judicious choice of azimuthal settings of quarter-wave plate and linear polarizer

The Stokes parameters (S_p, S₁, S₂, S₃) of light are measured at an arbitrary wavelength over a wide wavelength range. The Stokes parameters S₁ and S₂ are easily obtained. But the Stokes parameter S₃ at the arbitrary wavelength is affected by the phase difference error Δ₁ of the quarter-wave plate mismatch and the Stokes parameters S₁ or S₂. Therefore, in this paper, S₃ is obtained from both the intensity measurements by the circular polarizer rotating the quarter-wave plate by 0° and 90°. Then, S₃ is obtained by considering only Δ₁, but is not affected by S₁ and S₂. Also, though Δ₁ is not accounted for, S₃ is measured more accurately.     

Poly(γ-alkyl L-glutamates). II. Optical rotatory dispersion studies in organic solvents

Conformations of a series of poly(γ-alkyl L -glutamates) (ethyl, n-propyl, n-butyl, isobutyl, and isoamyl) were studied by ORD and infrared absorption methods. All except the n-propyl ester were found to be in helical form in nonpolar non-aromatic solvents such as ethyl acetate, chloroform, ethylene dichloride, methylene chloride, carbon tetrachloride, 2-chloroethanol, dimethylformamide, and dioxane. In such cases, the Cotton effects due to the n–π* transition of peptide bonds occurred near 234 mμ and were of a magnitude similar to those found for poly(γ-benzyl L -glutamate) and poly-L -methionine in nonpolar non-aromatic organic solvents. These four polypeptides in aromatic nonpolar solvents, such as benzene, benzyl alcohol, pyridine, and m-cresol, were also found to be in helical form, although the ORD parameters differed considerably from the values in non-aromatic solvents. An essential cause seems to be the interaction of π electrons on peptide bonds with π electrons in the solvents. Helix-coil transitions of these esters in chloroform-dichloroacetic acid mixtures (dichloroacetic acid seems to be a random coil-forming solvent) were expressed by the Shechter-Blout formulation. This was not true, however, for helix–coil transitions in benzyl alcohol–dichloroacetic acid mixtures. The dependence of the helical stability of these polypeptides in chloroform solution upon the side-chain length and upon temperature is discussed.     

Biochemical preparations of both the enantiomers of methyl 3-hydroxypentanoate and their conversion to the enantiomers of 4-hexanolide,the pheromone of trogoderma glabrum1

Both the enantiomers of methyl 3-hydroxypentanoate were prepared by microbial asymmetric reduction of 3-oxopentanoic esters. Conversion of methyl 3-hydroxypentanoate to 4-hexanolide, the pheromone of Trogoderma glabrum, was achieved.