Optimum Policies for a Standby System with Preventive Maintenance

Journal of the Operational Research Society - This paper considers preventive maintenance policies for a standby system where preventive maintenance for an operating unit is possible but corrective...     

Anomalous magnetization processes and non-symmetrical domain wall displacements in L10 FePt particulate films

Anomalous magnetization processes and non-symmetrical domain wall displacements in the minor loop of L1₀ FePt particulate films were investigated by magnetization measurements and in situ magnetic force microscopy. Magnetization (M) decreases dramatically on increasing the magnetic field to ∼3 kOe after which M becomes small and constant in the range of 5–20 kOe as observed in the successive measurement of minor loops. The domain wall displacement is non-symmetrical with respect to the field direction. The anomalous magnetization behavior was attributed to the non-symmetrical domain wall displacement and large magnetic field required for domain wall nucleation. Energy calculations from modeling suggest that non-symmetrical domain wall displacement is caused by the existence of metastable domains in which the domain edges are stuck to the particle boundaries.     

Synthesis and intramolecular pericyclization of 1-azulenyl thioketones

Several azulene-substituted thioketones, 1-thiobenzoylazulene (1a) and di(1-azulenyl) thioketone (2a) and their derivatives (1b and 2b-d) with alkyl substituents on each azulene ring, were prepared and their intramolecular pericyclization reaction was examined. The thioketones with a 3-alkyl substituent on each azulene ring exhibited the presumed pericyclization reaction under thermal and acid-catalyzed conditions, although the cases of the 1-azulenyl thioketones without the 3-alkyl substituents afforded a complex mixture under similar conditions. The intramolecular reaction following the intramolecular hydrogen transfer afforded the products 13b, 14b, and 14c. The products 13b and 14b were converted into the corresponding cations 18(+) and 19(+), which have structural similarity with that of the phenalenyl cation. These cations exhibited the expected two-step reduction waves upon CV, although the ESR analysis revealed that the neutral radical state did not have the presumed high stability.     

Vibronic structure in the S1-S0 transition of jet-cooled dibenzofuran

Fluorescence excitation spectra of dibenzofuran in a supersonic jet are observed and the vibronic structure is analyzed for the S(1) (1)A(1) (pipi) and S(0) states. An observation of the rotational envelopes reveals that the band is a B-type band. However, it is shown that most of the strong vibronic bands are A-type bands. The intensity arises from vibronic coupling with the S(2) (1)B(2) state. We find a broad emission in the dispersed fluorescence spectrum for the excitation of the high vibrational levels in the S(1) state. This indicates that intramolecular vibrational redistribution (IVR) occurs efficiently in the isolated dibenzofuran molecule.     

Fast scintillation detectors for high-energy X-ray region

We have developed fast scintillation detectors for nuclear resonant scattering experiments using synchrotron radiation and a nuclear excited level existing in >30?keV. A fast x-ray detector using an organic-inorganic perovskite scintillator of phenethylamine lead bromide (PhE-PbBr₄) had a dominant light emission with a fast decay time of 9.9?ns. An x-ray detector equipped with a 0.9-mm-thick PhE-PbBr₄ crystal (size: ～8 × 7?mm²) was used to detect nuclear resonant scattering in ⁶¹Ni (the first excited level: 67.41?keV; half-life: 5.3?ns). We could successfully record the decaying gamma rays emitted from ⁶¹Ni with a relatively high detection efficiency of 24%. A lead-doped plastic scintillator (NE142, Pb ～5?wt% doped) had been known to have a faster decay time of 1.7?ns. Following a test of a single NE142 detector, a four-channel NE142 detector was fabricated and successfully applied to the synchrotron-radiation based M?ssbauer spectroscopy experiment on ⁶¹Ni.     

Doppler-free two-photon excitation spectroscopy and the Zeeman effects. Perturbations in the 14(0)1 and 1(0)(1)14(0)1 bands of the S1 <-- S0 transition of C6D6

Doppler-free two-photon excitation spectra and the Zeeman effects for the 1 band of the S1 1B2u <-- S0 1A1g transition in gaseous benzene-d6 were measured. Although the spectral lines were strongly perturbed, almost all of the lines near the band origin could be assigned. From a deperturbation analysis, the perturbation near the band origin was identified as originating from an anharmonic resonance interaction. Perturbation centered at K = 28-29 in the 14(0)1 band was analyzed, and it was identified as originating from a perpendicular Coriolis interaction. The symmetry and the assignment of the perturbing state proposed by Schubert et al. (Schubert, U.; Riedle, E.; Neusser, H. J. J. Chem. Phys. 1989, 90, 5994.) were confirmed. No perturbation originating from an interaction with a triplet state was observed in both bands. From the Zeeman spectra and the analysis, it is demonstrated that rotationally resolved levels are not mixed with a triplet state. The intersystem mixing is not likely to occur at levels of low excess energy in the S1 state of an isolated benzene. Nonradiative decay of an isolated benzene in the low vibronic levels of the S1 state will occur through the internal mixing followed by the rotational and vibrational relaxation in the S0 state.     

Synthesis and antifungal activity of novel 14-membered benzomacrolides, as galbonolide analogues

Asymmetric total synthesis of benzene analogues of galbonolide, a 14-membered antifungal macrolide, possessing a benzene ring instead of a conjugated diene structure, was achieved starting from chiral 1-aryl-1-propanol obtained by enzyme-catalyzed kinetic resolution with high enantioselectivity. Representatively, a method for the introduction of a methylthio and chloride function at the vinyl position was also established. The resulting analogues unfortunately exhibited very little antifungal potency in comparison with galbonolide A.     

CP/MAS (13)C NMR study of cellulose and cellulose derivatives. 1. Complete assignment of the CP/MAS (13)C NMR spectrum of the native cellulose

The precise assignments of cross polarization/magic angle spinning (CP/MAS) (13)C NMR spectra of cellulose I(alpha) and I(beta) were performed by using (13)C labeled cellulose biosynthesized by Acetobacter xylinum (A. xylinum) ATCC10245 strain from culture medium containing D-[1,3-(13)C]glycerol or D-[2-(13)C]glucose as a carbon source. On the CP/MAS (13)C NMR spectrum of cellulose from D-[1,3-(13)C]glycerol, the introduced (13)C labeling were observed at C1, C3, C4, and C6 of the biosynthesized cellulose. In the case of cellulose biosynthesized from D-[2-(13)C]glucose, the transitions of (13)C labeling to C1, C3, and C5 from C2 were observed. With the quantitative analysis of the (13)C transition ratio and comparing the CP/MAS (13)C NMR spectrum of the Cladophora cellulose with those of the (13)C labeled celluloses, the assignments of the cluster of resonances which belong to C2, C3, and C5 of cellulose, which have not been assigned before, were performed. As a result, all carbons of cellulose I(alpha) and I(beta) except for C1 and C6 of cellulose I(alpha) and C2 of cellulose I(beta) were shown in equal intensity of doublet in the CP/MAS spectrum of the native cellulose, which suggests that two inequivalent glucopyranose residues were contained in the unit cells of both cellulose I(alpha) and I(beta) allomorphs.     

New molecular compound precursor for aluminum chemical vapor deposition

A new type of precursor for aluminum chemical vapor deposition (Al‐CVD) has been developed by mixing dimethylaluminum hydride (DMAH) and trimethylaluminum (TMA). The new precursor has proven itself to be effective for Al‐CVD, where a good selectivity between the Si and the SiO₂ mask, a 3.0 μΩ cm resistivity and a pure Al film with low C and O contamination levels (under 100 ppm) were achieved. Quadrupole mass and infrared absorption analysis have shown that the precursor contains a new molecular compound, consisting of a DMAH monomer and a TMA monomer. The mixture has lower viscosity than DMAH and can be easily bubbled for a stable precursor vapor supply. Copyright © 2000 John Wiley & Sons, Ltd.     

Kendarimide A, a novel peptide reversing P-glycoprotein-mediated multidrug resistance in tumor cells, from a marine sponge of Haliclona sp.

A novel modulator of multidrug resistance (MDR) in tumor cells, kendarimide A (1), was isolated from an Indonesian marine sponge of Haliclona sp. Compound 1 reversed MDR in KB-C2 cells mediated by P-glycoprotein (P-gp) at a 6 μM concentration, and the chemical structure of 1 was characterized to be a linear peptide composed of N-methylpyroglutamic acid (pyroMeGlu), N-methylated eight-membered cysteinyl-cysteine (ox-[MeCys-MeCys]) together with many N-methyl amino acid residues. The amino acid sequence of 1 was determined by 2D NMR and FAB MS analysis. The absolute configuration of the amino acid residues in 1 except for the MeCys part was determined to be l-form respectively, based on interpretation of the HPLC analysis of Marfey's derivatives of the hydrolysates of 1 and the synthetic method for the pyroMeGlu residue.