Structures of new ceramides from the fruit bodies of Grifola frondosa

Four new phytosphingosine-type ceramides, (2S,3S,4R)-2-[(2'R)-2'-hydroxydocosanoylamino]-1,3,4-octadecane triol (1), (2S,3S,4R)-2-[(2'R)-2'-hydroxytricosanoylamino]-1,3,4-octadecan etriol (2), (2S,3S,4R)-2-[(2'R)-2'-hydroxypentacosanoylamino]-1,3,4-octadec anetriol (3) and (2S,3S,4R)-2-[(2'R)-2'-hydroxyhexacosanoylamino]-1,3,4-octadeca netriol (4), have been isolated from the fruit bodies of Grifola frondosa. The structures of the new compounds were elucidated on the basis of their spectral data.     

Reactivities of cis- and trans-3-substituted acrylic acids on copolymerization with acrylamide

Several pairs of cis- and trans-3-substituted acrylic acids (3SAA) were copolymerized with acrylamide in order to determine the major factors affecting the relative reactivities of geometrical isomers of 1,2-disubstituted ethylenes (1,2-DE). The results were that the relative reactivity of cis isomer is larger than that of trans isomer when one substituent is electron-withdrawing and the other is electron-donating. The trans isomer is more reactive than the cis isomer when both substituents are electron-withdrawing. A new method of reactivity comparison of cis- and trans-1,2-DE is proposed in regard to the inductive substituent constant.     

Simultaneous measurement of amplitude and phase in surface second-harmonic generation

The intensity and the phase in surface second-harmonic generation were simultaneously measured by use of an ac optical balanced homodyne detection system. In this system the surface second-harmonic wave was superimposed upon a local oscillator wave generated by a barium borate nonlinear optical crystal and then detected as an interference signal. Extremely high sensitivity of 3 aW (6 photons/s) and high precision were achieved by use of a lock-in amplifier, in which an interference signal of fundamental waves was used as a reference signal. Simultaneous measurement of the intensity and the phase in surface second-harmonic waves generated from native-oxidized Si(111) surfaces is demonstrated.     

Optical isolators using Bi-substituted rare-earth iron garnet films

Using Bi-substituted rare-earth iron garnet film, (GdBi)₃ (FeAlGa)₅O₁₂ or (YbTbBi)₃ Fe₅O₁₂, grown by liquid phase epitaxy technique, we have fabricated a compact, low cost and high performance optical isolator for near-infrared wavelength region, in comparison with conventional isolator using yttrium iron garnet (YIG) single crystal as Faraday rotator. Typical insertion loss and isolation of developed isolators are 0.6 dB and 35 dB respectively at =1.31 m and the size is 6×6 mm. The isolators, which could be used in the wavelength range of 1.31 to 1.55 m, are also fabricated with insertion loss of less than 1.1 dB and isolation of more than 35 dB.     

Crystal and molecular structures of three ketoximes: (E)-O-hexanoyl phenyl 2-pyridyl ketone oxime (C18H20N2O2), (E)-O-octanoyl phenyl 2-pyridyl ketone oxime (C20H24N2O2), (E)-O-myristoyl phenyl 2-pyridyl ketone oxime (C26H38N2O2)

The crystal structures of the three title compounds have been determined by the X-ray structure analysis. The molecule of (E)-O-hexanoyl phenyl 2-pyridyl ketone oxime1 has an anti form at the N-O-C-C ester linkage, while the molecules of (E)-O-octanoyl phenyl 2-pyridyl ketone oxime2 and (E)-O-myristoyl phenyl 2-pyridyl ketone oxime 3 each have a syn form. Compounds2 and3 are crystallized in isomorphic bilayer structures, in which alkyl chains are packed in an antiparallel arrangement.     

Anomalous excimer formation of a pyrenyl derivative having a mesogen group of alkoxycyanobiphenyl in its smectic mesophase

The direct photolysis of 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonate) (ABTS) in aqueous solution was investigated under monochromatic ultraviolet (UV) irradiation at 254 nm. ABTS was found to be directly photolyzed by UV irradiation to yield the one-electron oxidized radical, ABTS⁺, which is a blue-green colored persistent radical species that has strong visible absorption bands. The photochemical production of ABTS⁺ was strongly dependent on the solution pH and the presence of dissolved oxygen. The presence of dissolved oxygen increased the quantum yields at pH 3, whereas it inhibited the production of ABTS⁺ at pH 6.5. Spectrophotometric and spectrofluorometric data indicated that ABTS photolysis may occur as a result of the transfer of one-electron between the singlet excited state and the ground state of ABTS. Observations made during UV/H₂O₂ experiments with ABTS suggested that the dependence of the photoloysis of ABTS on the solution pH and the presence of dissolved oxygen is related to the role of the hydroperoxyl/superoxide radical (HO₂/O₂⁻), which appears to be formed via a secondary reaction of the reduced intermediate of ABTS with dissolved oxygen. The proposed photolytic reactions were supported by the observed stoichiometry between the amount of ABTS⁺ radicals produced and the amount of ABTS molecules decomposed.     

Effects of capacitive coupling on the escape rate in intrinsic Josephson junction stacks

We formulate a macroscopic quantum theory that can describe the macroscopic quantum tunneling (MQT) in intrinsic Josephson junctions (IJJs). The capacitively coupled IJJ model is quantized in terms of the canonical quantization method. The multi-junction effect for the MQT to the first resistive branch is clarified. It is shown that the escape rate is greatly enhanced by the capacitive coupling between junctions.     

Field-angle-dependent specific heat measurements and gap determination of a heavy fermion superconductor URu2Si2

To identify the superconducting gap structure in URu2Si2, we perform field-angle-dependent specific heat measurements for the two principal orientations in addition to field rotations, and a theoretical analysis based on microscopic calculations. The Sommerfeld coefficient gamma(H)'s in the mixed state exhibit a distinctly different field dependence. This comes from point nodes and the substantial Pauli paramagnetic effect of URu2Si2. These two features combined give rise to a consistent picture of superconducting properties, including a possible first order transition of Hc2 at low temperatures.