Antioxidant activity of anacardic acids

Anacardic acids, 6-pentadec(en)ylsalicylic acids isolated from the cashew Anacardium occidentale L. (Anacardiaceae) nut and apple, were found to possess preventive antioxidant activity while salicylic acid did not show this activity. These anacardic acids prevent generation of superoxide radicals by inhibiting xanthine oxidase (EC 1.1.3.22, Grade IV) without radical-scavenging activity. Notably, the inhibition kinetics of anacardic acids do not follow hyperbolic dependence of enzyme inhibition on inhibitor contents (Michaelis–Menten equation) but follow the Hill equation instead. Anacardic acid (C_15:1) inhibited the soybean lipoxygenase-1 (EC 1.13.11.12, Type 1) catalyzed oxidation of linoleic acid with an IC₅₀ of 6.8 μM. The inhibition is a slow and reversible reaction without residual enzyme activity. The inhibition kinetics indicate that anacardic acid (C_15:1) is a competitive inhibitor and the inhibition constant, K_I, was 2.8 μM. Anacardic acids act as antioxidants in a variety ways, including inhibition of various prooxidant enzymes involved in the production of the reactive oxygen species and chelate divalent metal ions such as Fe²⁺ or Cu²⁺, but do not quench reactive oxygen species. The C₁₅-alkenyl side chain is largely associated with the activity.     

Reduction of higher harmonic sequences in terminal voltage of an AC exciting synchronous generator using magnetically anisotropic slot wedges

This paper describes relationships between characteristics of a magnetically anisotropic slot wedge and voltage higher harmonics in an ac exciting synchronous generator terminal due to permeance ripple caused by an open-slot-type rotor. From the relationships obtained, practical guidelines were formulated for machine designs applying the magnetically anisotropic slot wedge. The results are as follows.

• 1 (1) Equivalent permeability of the magnetically anisotropic slot wedge became isotropic wedge permeability for air-gap flux ripple.
• 2 (2) Two ways were identified to reduce voltage-higher harmonics by using the slot wedges.
• 3 (3) The level of leakage flux passing through the anisotropic slot wedge was determined only by its permeability in the width direction.
• 4 (4) Effectiveness of the magnetic anisotropic slot wedges inserted into the stator slots was verified from experimental results using a model machine of the open- slot-type rotor.

     

Exploring the role of the spacers and acceptors on the triphenylamine-based dyes for dye-sensitized solar cells

Six triphenylamine-based dyes were explored for their application in dye-sensitized solar cells (DSSCs). Dyes 1–3 and dyes 4–6 possess cyanoacrylic acid (C-acceptor) and rhodanine-3-acetic acid (R-acceptor), respectively. Stilbene (in dyes 2 and 5) and bis(styryl)benzene (in dyes 3 and 6) were used as π-spacers. There is no π-spacer in the dye 1 and 4. To elucidate the role of π-spacers, optical, electrochemical, and photovoltaic properties of the dyes were studied. Among C-acceptor dyes, dye 2 exhibits the highest light-to-electricity conversion efficiency of 4.45%, followed by dye 3 (4.16%). Similarly, among R-acceptor dyes, dye 5 is the best. These results indicate that stilbene is a better π-spacer over bis(styryl)benzene. Although bis(styryl)benzene could extend the light absorption range (in dye-adsorbed TiO₂ film), its tendency to promote intermolecular π-π stacking is possibly the reason for its poor performance in DSSCs. Furthermore, the conjugation break in the R-acceptor moiety attached to the TiO₂ surface limits the electron injection of R-acceptor dyes poorer than C-acceptor dyes. Density functional theory calculations were performed for the dye-(TiO₂)₈ cluster, assuming a bidentate chelation of a carboxylic acid group with Ti⁴⁺ of TiO₂ anatase. The natural bond orbital (NBO) analysis indicated relatively more electron-accepting ability of cyanoacrylic acid over rhodanine-3-acetic acid.     

Isotope 18O/16O ratio measurements of water vapor by use of the 950-nm wavelength region with cavity ring-down and photoacoustic spectroscopic techniques

Two optical methods, cavity ring-down spectroscopy and photoacoustic spectroscopy, are applied to the measurement of the isotope ratio 18O/16O in water-vapor samples with a Nd3+:YAG pumped-dye laser. The combination band of (2v1 + v3) in the 960-nm region of water molecules is investigated for two standard water samples, the Vienna Standard Mean Ocean Water and the Standard Light Antarctic Precipitation. The results demonstrate that the two methods have the potential of compact systems for in-situ measurements of H2O isotope ratio in the environment.     

Optical topography: practical problems and new applications

We will briefly review the present status of optical topography and then discuss the method of improving practicality, i.e., the signal-to-noise (S/N) ratio and the spatial resolution in observations of higher-order brain functions. The optimum wavelength pair improved the S/N ratio sixfold for deoxyhemoglobin, and new configurations of light irradiation and detection positions doubled the spatial resolution. We also report on developing application fields of optical topography. This modality will bridge the gap between natural sciences, neuroscience, and pedagogy, and show actual real-time brain activity.     

Near-net-shape forming of Al-Al3Ni functionally graded material over eutectic melting temperature

A possibility to make near-net-shape functionally graded material (FGM) products has been examined. The FGM billets having a graded volume fraction of Al₃Ni in thickness direction were machined from an Al-Al₃Ni FGM thick-walled tube manufactured by a vacuum centrifugal method. Billets, which were set in the container for the backward extruding, were heated to 650 °C to 680 °C, at which temperature the FGM becomes a mixture of molten aluminum eutectic and solid intermetallics. Then, billets were extruded successfully to FGM cups by a semisolid forming, except at 650 °C. Residual bulky Al₃Ni particles are found at higher temperature. Thus, an optimum operation temperature is found to be around 660 °C, because bulky Al₃Ni particles transform to fine spheroidal or fibrous shape after the forming. The volume fraction of intermetallics at the bottom region of the cup was condensed more than 60 vol pct in a proper billet setting.     

Novel π-conjugated organoboron polymers: Poly (ethynylene-phenylene-ethynylene-borane)s

Summary Novel poly(ethynylene-phenylene-ethynylene-borane)s were prepared by polycondensation between bifunctional lithium acetylide and aryldimethoxyborane. The polymers obtained are expected as a novel type of organoboron π-conjugated polymers via vacant p-orbital of boron atom. The polymerization between dilithium 2,5-didodecyloxybenzene- 1,4-diethynilide and tripyldimethoxyborane [tripyl=2,4,6-triisopropylphenyl] gave the corresponding polymer in 67% yield. From gel permeation chromatographic analysis (THF, PSt standards), the number-average molecular weight of the polymer was found to be 2700. In the UV-vis spectrum of the polymer (in chloroform at room temperature), an absorption maximum was observed at 397 nm. The fluorescence emission spectrum (in chloroform, room temperature, excitation wavelength at 400 nm) showed its λ_max at 456 nm in the visible blue region. The polymers obtained were very soluble in common organic solvents such as THF, chloroform and benzene. Received: 11 April 2000/Accepted: 22 April 2000     

Alternating boration copolymerization between diyne and bisallene

Summary Alternating boration copolymerization between 1,4-diallenylbenzene (2) and 2,7-diethynylfluorene (3) was examined using diphenylbromoborane (1) to give the corresponding copolymer (4). The organoboron copolymer obtained was characterized by ¹H-, ¹¹B-NMR, IR, and UV-vis absorption spectra. Received: 5 August 1999/Accepted: 31 August 1999     

Acetic Acid-Catalyzed Formation of N-Phenylphthalimide from Phthalanilic Acid: A Computational Study of the Mechanism

In glacial acetic acid, phthalanilic acid and its monosubstituents are known to be converted to the corresponding phthalimides in relatively good yields. In this study, we computationally investigated the experimentally proposed two-step (addition-elimination or cyclization-dehydration) mechanism at the second-order Møller-Plesset perturbation (MP2) level of theory for the unsubstituted phthalanilic acid, with an explicit acetic acid molecule included in the calculations. In the first step, a gem-diol tetrahedral intermediate is formed by the nucleophilic attack of the amide nitrogen. The second step is dehydration of the intermediate to give N-phenylphthalimide. In agreement with experimental findings, the second step has been shown to be rate-determining. Most importantly, both of the steps are catalyzed by an acetic acid molecule, which acts both as proton donor and acceptor. The present findings, along with those from our previous studies, suggest that acetic acid and other carboxylic acids (in their undissociated forms) can catalyze intramolecular nucleophilic attacks by amide nitrogens and breakdown of the resulting tetrahedral intermediates, acting simultaneously as proton donor and acceptor. In other words, double proton transfers involving a carboxylic acid molecule can be part of an extensive bond reorganization process from cyclic hydrogen-bonded complexes.