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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]

Low-temperature photoluminescence spectroscopy is performed for unintentionally doped and silicon-doped aluminum nitride (AlN) films grown on AlN substrates. Considering the positive electron–hole exchange interaction constant substantially changes the neutral silicon-donor bound exciton binding energy from 28.5 to 15.3 meV. The silicon-donor binding energy is also experimentally deduced as 64.8 meV from a two-electron transition, which is justified by a theoretical calculation considering the crystal anisotropy and electron–phonon coupling. The estimated binding energies are discussed with a previous theoretical result within the effective mass approximation and the experimentally known binding energy of elementary four-particle (three-particle) systems. [ABSTRACT FROM AUTHOR]

The isolation, structure elucidation and antimicrobial activity of two new serinolipid derivatives, shishididemniols A and B is described, as antibacterial constituents of a tunicate of the family didemnidae. Shishididemniols, didemniserinolipids, and cyclodidemniserinol trisulfate, all possess [C.sub.28]-polyketide acid in the central part of the molecule.

A search for biologically active compounds found that the hydrophilic extract of a marine sponge Hexadella sp. collected in southern Japan exhibited moderate antibacterial activity against the bacterium Aeromonas hydrophila, which causes hemorrhagic septicemia in fish. Their structures were elucidated on the basis of spectral and chemical methods and they exhibited moderate antibacterial activity against the fish pathogenic bacterium Aeromonas hydrophila.

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.

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]

Eleven kinds of catechin metabolites produced from (-)-epigallocatechin (EGC) and (-)-epigallocatechin gallate (EGCg) by intestinal microbiota were evaluated for inhibitory activity on the proliferation of HeLa cells, which are human cervical cancer cells. Among the catechin metabolites, 1-(3,4,5-trihydroxyphenyl)-3-(2,4,6-trihydroxyphenyl)propan-2-ol (EGC-M2), 4-hydroxy-5-(3,4,5-trihydroxyphenyl)valeric acid (EGC-M7), and 5-(3,4,5-trihydroxyphenyl)valeric acid (EGC-M9) were found to show inhibitory activity on HeLa cell proliferation as compared with control. The results suggested that three adjacent hydroxyl groups in the phenyl moiety may play an important role in the inhibitory activity. In addition, the inhibitory activity was also examined with four (-)-epicatechin (EC) metabolites possessing two adjacent hydroxyl groups in the phenyl moiety. Only 5-(3,4-dihydroxyphenyl)valeric acid (EC-M9) showed inhibitory activity and therefore valeric acid moiety likely contributes to the inhibitory activity. EGC-M9 showed the strongest inhibitory activity with IC 50 of 5.58 µM. Thus, in this study it was found for the first time that several catechin metabolites derived from EGC, EGCg, and EC inhibit the proliferation of cervical cancer cells.

Aim: To elucidate the association between small bowel diseases (SBDs) and positive fecal occult blood test (FOBT) in patients with obscure gastrointestinal bleeding (OGIB)., Methods: Between February 2008 and August 2013, 202 patients with OGIB who performed both capsule endoscopy (CE) and FOBT were enrolled (mean age; 63.6 ± 14.0 years, 118 males, 96 previous overt bleeding, 106 with occult bleeding). All patients underwent immunochemical FOBTs twice prior to CE. Three experienced endoscopists independently reviewed CE videos. All reviews and consensus meeting were conducted without any information on FOBT results. The prevalence of SBDs was compared between patients with positive and negative FOBT., Results: CE revealed SBDs in 72 patients (36%). FOBT was positive in 100 patients (50%) and negative in 102 (50%). The prevalence of SBDs was significantly higher in patients with positive FOBT than those with negative FOBT (46% vs 25%, P = 0.002). In particular, among patients with occult OGIB, the prevalence of SBDs was higher in positive FOBT group than negative FOBT group (45% vs 18%, P = 0.002). On the other hand, among patients with previous overt OGIB, there was no significant difference in the prevalence of SBDs between positive and negative FOBT group (47% vs 33%, P = 0.18). In disease specific analysis among patients with occult OGIB, the prevalence of ulcer and tumor were higher in positive FOBT group than negative FOBT group. In multivariate analysis, only positive FOBT was a predictive factors of SBDs in patients with OGIB (OR = 2.5, 95%CI: 1.4-4.6, P = 0.003). Furthermore, the trend was evident among patients with occult OGIB who underwent FOBT on the same day or a day before CE. The prevalence of SBDs in positive vs negative FOBT group were 54% vs 13% in patients with occult OGIB who underwent FOBT on the same day or the day before CE (P = 0.001), while there was no significant difference between positive and negative FOBT group in those who underwent FOBT two or more days before CE (43% vs 25%, P = 0.20)., Conclusion: The present study suggests that positive FOBT may be useful for predicting SBDs in patients with occult OGIB. Positive FOBT indicates higher likelihood of ulcers or tumors in patients with occult OGIB. Undergoing CE within a day after FOBT achieved a higher diagnostic yield for patients with occult OGIB.

Merobatzelladines A (1) and B (2) have been isolated from a marine sponge Monanchora sp. as antibacterial constituents. Their structures including relative stereochemistry were determined by interpretation of spectral data. The absolute stereochemistry of merobatzelladine B (2) was elucidated after introduction of the fourth ring system preinstalled with a secondary hydroxyl group to which the modified Mosher method was applied. Merobatzelladines exhibit moderate anti-infective activity against a bacterium and protozoa.