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The fabrication and the optical properties of ultrathin GaN quantum wells on AlN (0001) vicinal surfaces with macrosteps are studied. The employed growth condition spontaneously restricts the GaN thickness to one monolayer (ML) on a planar plane. However, because of a higher density of dangling bonds at macrosteps, 2 ML GaN can be stabilized only at step edges, which creates quantum‐wire‐like 1D nanostructures with a dimension of a few nanometers for the lateral confinement. Exciton (carrier) confinement within the 1D GaN nanostructure is predicted theoretically and is confirmed experimentally by strongly polarized photoluminescence with in‐plane twofold symmetry at a wavelength of ≈250 nm at room temperature. This study demonstrates one path to realize quantum confinement within a fine nanoarchitecture composed of nitride semiconductors and might provide clues to the future creation of novel low‐dimensional nanostructures for the UV–vis spectral range. [ABSTRACT FROM AUTHOR]

Herein, the wavelength dependence of the efficiency and the lifetime of far UV‐C light‐emitting diodes (LEDs) on a single‐crystal AlN substrate is systematically analyzed from experiments and simulations. A positive relation between efficiency and emission wavelength is observed. The wall‐plug efficiency reaches 0.47, 1.0, 2.1, and 2.4% at 227, 230, 233, and 235 nm wavelengths, respectively. The simulation results show that carrier injection plays a critical role in the efficiency change in the far UV‐C region rather than in the internal quantum or light extraction efficiency. The lifetime test clearly demonstrates a trade‐off between the L70 lifetime and the emission wavelength, although the initial optical power increases with the longer wavelength. The measurement results under various wavelengths and stress currents indicate that the carriers injected in quantum wells motivate power reduction during current stress. Moreover, the internal quantum efficiency affects the degradation rate because the influence of defects becomes stronger during stress. Finally, the reliability of a 231 nm LED is investigated at a reduced current of 35 mA. The projected L70 and L50 lifetimes are 11 000 and 28 000 h, respectively, from the fitting model based on the defect generation during aging. [ABSTRACT FROM AUTHOR]

We fabricated sub-230-nm (far UV-C) light emitting diodes (LEDs) on a single-crystal AlN substrate. With 20 quantum well cycles implemented to enhance carrier injection into the active layers, over 1-mW output power (1.4 and 3.1 mW for 226- and 229-nm LEDs, respectively) was obtained under 100-mA operation. The maximum output power reached 21.1 mW for the single-chip 229-nm LED operating at 700 mA, without significant drooping. The forward voltage for both sub-230-nm LEDs operating at 100 mA was low (5.9 V) due to their low resistances and ideal Ohmic contacts between metal and semiconductor components. Additionally, wall plug efficiencies were 0.24% and 0.53% for the 226- and 229-nm LEDs, respectively. The lifetime of the 226-nm LED while operating at 25 °C reached over 1500 h and did not show current leakage, even after 1524 h. This long lifetime will be achieved by improving carrier injection due to many quantum wells, using a high-quality AlN substrate and achieving high wall plug efficiency. [ABSTRACT FROM AUTHOR]

Abstract: Three new serinolipid derivatives, shishididemniols C (1), D (2), and E (3), were isolated as antibacterial constituents of a tunicate of the family Didemnidae. Their planar structures were elucidated by interpretation of NMR and MS data, whereas the absolute stereochemistry was determined by chemical conversions. Shishididemniols C (3), D (4), and E (5) exhibited antibacterial activity against the fish pathogenic bacterium Vibrio anguillarum. [Copyright &y& Elsevier]

Two new serinolipid derivatives, shishididemniols A (1) and B (2), were isolated as antibacterial constituents of a tunicate of the family Didemnidae. The structure of 1 was elucidated by interpretation of spectral data and the application of the modified Mosher method to 1 and its suitable degradation products. Compound 2 was the chiorohydrin of 1. Compounds 1 and 2 exhibited antibacterial activity against fish pathogenic bacterium Vibrio anguillarum. [ABSTRACT FROM AUTHOR]

Three new bromotyrosine derivatives, 11-N-methylmoloka'iamine (1), 11-N-cyano-11-N-methylmoloka'iamine (2), and kuchinoenamine (3), were isolated as antibacterial constituents from a marine sponge Hexadella sp. Their structures were elucidated on the basis of spectral and chemical methods. They exhibited moderate antibacterial activity against the fish pathogenic bacterium Aeromonas hydrophila. [ABSTRACT FROM AUTHOR]

Abstract: A new dimeric oroidin derivative, carteramine A (1), was isolated as a neutrophil chemotaxis inhibitor from the marine sponge Stylissa carteri. The structure of 1 was elucidated by the analysis of spectral data. [Copyright &y& Elsevier]

GaN/AlN ultrathin quantum wells (QWs) emitting in the deep UV spectral range are fabricated by metalorganic vapor phase epitaxy. The GaN thickness is automatically limited to the monolayer (ML) scale due to the balance between crystallization and evaporation of Ga adatoms. This growth characteristic facilitates the fabrication of highly reproducible GaN ML QWs. The strong quantum confinement within the GaN ML QWs achieves emissions below 250 nm. The photoluminescence intensity at room temperature with respect to that at low temperature, which is closely related to the emission internal quantum efficiency, is drastically improved from 0.1% for a conventional Al0.8Ga0.2N/AlN QWs to 5% for a 1 ML GaN/AlN (0001) QW and 50% for a 2 ML GaN/AlN (11¯02) QW under weak excitation conditions. These higher emission efficiencies are attributed to the suppressed nonradiative recombination in the GaN QWs and the enhanced radiative recombination in the (11¯02) QW. [ABSTRACT FROM AUTHOR]

Discusses a study on a hybrid-type superconducting magnetic bearing (SMB) system with nonlinear control. What the system consisted of; Investigation of the compliance for the bearings, displacements of the rotating rotor and energy levels for the system; Indication of the results.