Evaluation of antioxidative activity of vegetable extracts in linoleic acid emulsion and phospholipid bilayers

The antioxidative effects of vegetable extracts were evaluated using linoleic acid emulsion and liposomal phospholipid suspension systems. First, the antioxidative activities of water, ethanol and 2% metaphosphoric acid extracts of the vegetables were investigated by measuring the rate of oxygen consumption in the peroxidation of linoleic acid initiated by a radical generator, 2,2′-azobis(2-amidinopropane) dihydrochloride (AAPH), with a Clark electrode in the absence of metal chelators. Ethanol extracts of moroheiya and perilla exhibited the highest antioxidative activities. Without metal chelators, 12 ethanol extracts and one water extract acted as prooxidants, and this phenomenon could be attributed to the prooxidant action of ascorbic acid in the presence of free transition metal ions. Next, peroxyl radical-scavenging activities of vegetable extracts were examined by adding a metal chelator, diethylenetriaminepentaacetic acid (DTPA), to the linoleic acid emulsion system. The results were compared with their antioxidative activities in phospholipid bilayers by measuring the inhibition of lipid peroxidation in large unilamellar vesicles composed of egg yolk phosphatidylcholine (PC). A good correlation was observed between the antioxidative activities obtained from these two systems. The antioxidative activities in the liposomal phospholipid suspension system correlated with total contents of ascorbic acid and polyphenols in vegetable extracts. © 1999 Society of Chemical Industry     

Single-molecule conductance of π-conjugated rotaxane: new method for measuring stipulated electric conductance of π-conjugated molecular wire using STM break junction

An electronic conductance with small fluctuations, which is stipulated in single-molecule junctions, is necessary for the precise control of single-molecule devices. However, the suppression of conductance fluctuations in conventional molecular junctions is intrinsically difficult because the fluctuations are related to the contact fluctuations and molecular motion. In the present study involving experimental and theoretical investigations, it is found that covering a single π-conjugated wire with an α-cyclodextrin molecule is a promising technique for suppressing conductance fluctuations. The conductance histogram of the covered molecular junction measured with the scanning tunneling microscope break-junction technique shows that the conductance peak for the covered junction is sharper than that of the uncovered junction. The covering technique thus has two prominent effects: the suppression of intramolecular motion, and the elimination of intermolecular interactions. Theoretical calculations of electronic conductance clearly support these experimental observations.     

Selective dissolution of nanolamellar Ti–41 at.% Al alloy single crystals

The selective dissolution behavior of Ti–41 at.% Al single crystals having a α₂/γ-lamellar structure with a lamellar thickness in the range 20 nm to 1 μm have been investigated in 0.5 M NaCl aqueous solution focusing on the effect of lamellar thickness on the dissolution of γ-lamellae. In the case where γ-lamellae were thicker than ～100 nm on average, γ-lamellae were selectively dissolved and, as a result, crevasses whose widths were close to the γ-lamellae thicknesses were formed. However, not all γ-lamellae were dissolved and the distribution of crevasses was much less uniform compared with that of the γ-lamellae. On the other hand, when the average γ-lamellae thickness was <100 nm relatively thick γ-lamellae were preferentially dissolved, but the distribution of the crevasses was relatively uniform compared with that obtained from the coarse lamellar structure. The reasons for this difference are discussed from the viewpoint of the absence of misfit dislocations in nanoscaled lamellae and the difference in ion transport through crevasses of different width formed by dissolution of γ-lamellae.     

Synthesis of New Superconducting Pb-Based 1222 Cuprates Containing Sulfur in the (Pb0.75S0.25)Sr2(Eu2.0−x Ce x )Cu2O z System

We have synthesized new Pb-based 1222 cuprates containing sulfur in the (Pb_0.75S_0.25)Sr₂(Eu_2.0?x Ce _x )Cu₂O _z system. X-ray diffraction study shows that almost the single 1222 phase samples can be obtained for a considerable wide area of 0.3≤x≤1.2 in the composition of (Pb_0.75S_0.25)Sr₂(Eu_2.0?x Ce _x )Cu₂O _z . Next, the sample with x=0.4 after annealing under high-pressure O₂ is discovered to show an onset of the resistivity drop at about 31 K and to show an onset of diamagnetic signal at about 29 K. These phenomena clearly indicate that the sample is a new superconductor.     

Cross-coupling reaction of alkyl halides with grignard reagents catalyzed by Ni, Pd, or Cu complexes with pi-carbon ligand(s)

Transition metal-catalyzed cross-coupling reactions of organic halides and pseudo-halides containing a C-X bond (X = I, Br, Cl, OTf, OTs, etc.) with organometallic reagents are among the most important transformations for carbon-carbon bond formation between a variety of sp, sp(2), and sp(3)-hybridized carbon atoms. In particular, researchers have widely employed Ni- and Pd-catalyzed cross-coupling to synthesize complex organic structures from readily available components. The catalytic cycle of this process comprises oxidative addition, transmetalation, and reductive elimination steps. In these reactions, various organometallic reagents could bear a variety of R groups (alkyl, vinyl, aryl, or allyl), but the coupling partner has been primarily limited to sp and sp(2) carbon compounds: alkynes, alkenes, and arenes. With alkyl coupling partners, these reactions typically run into two problems within the catalytic cycle. First, oxidative addition of alkyl halides to a metal catalyst is generally less efficient than that of aryl or alkenyl compounds. Second, the alkylmetal intermediates formed tend to undergo intramolecular beta-hydrogen elimination. In this Account, we describe our efforts to overcome these problems for Ni and Pd chemistry. We have developed new catalytic systems that do not involve M(0) species but proceed via an anionic complex as the key intermediate. For example, we developed a unique cross-coupling reaction of alkyl halides with organomagnesium or organozinc reagents catalyzed by using a 1,3-butadiene as the additive. This reaction follows a new catalytic pathway: the Ni or Pd catalyst reacts first with R-MgX to form an anionic complex, which then reacts with alkyl halides. Bis-dienes were also effective additives for the Ni-catalyzed cross-coupling reaction of organozinc reagents with alkyl halides. This catalytic system tolerates a wide variety of functional groups, including nitriles, ketones, amides, and esters. In addition, we have extended the utility of Cu-catalyzed cross-coupling reactions. With 1-phenylpropyne as an additive, Cu-catalyzed reactions of alkyl chlorides, fluorides, and mesylates with Grignard reagents proceed efficiently. These new catalytic reactions use pi-carbon ligands such as pi-allyl units or alkynes instead of heteroatom ligands such as phosphines or amines. Overall, these reactions provide new methodology for introducing alkyl moieties into organic molecules.     

Pulse Combustors—Performance and Control

Limited resources of fossil energy require the search for new energy conversion processes and the increase of the efficiency of power plants to ensure the energy household in the future. Basically, changing the combustion mode from steady to pulse combustion makes an enormous reduction of fuel consumption possible. Active control systems for pulse combustors installed into the inlet further improve the efficiency and extend the operating range considerably. The control algorithm including fuel rate - air rate - pressure characteristics and control strategies as well are presented.     

High-pressure studies on Tc and crystal structure of iron chalcogenide superconductors

The superconducting transition temperature, T_c, in iron-based solids can be enhanced by applied pressure: T_c increases from 8 to 37 K for the 11-type FeSe when the pressure is raised from 0 to 4 GPa. High-pressure studies can elucidate the mechanism of superconductivity in such novel materials. In this paper, we present a high-pressure study of Fe(Se_1−xTe_x) and Fe(Se_1−xS_x). In the case of Fe(Se_1−xTe_x), the maximum T_c under high pressure did not exceed the T_c of FeSe, which can be attributed to the structural transition to the monoclinic phase. For Fe(Se_1−xS_x) (0 < x < 0.3), T_c exhibited a significant increase with pressure; however, the maximum T_c under high pressure did not exceed the T_c of FeSe. This may be due to the disorder induced by substituting S for Se, which is similar to the pressure effect on T_c for the 1111-type superconductor Ca(Fe_1−xCo_x)AsF. The T_c of Fe(Se_1−xS_x) showed a complex behavior below 1 GPa, first decreasing and then increasing with increasing pressure. From high-pressure x-ray diffraction measurements, the T_c (P) curve was correlated with the local structural parameter.     

Dehydration ofn-butanol over highly dispersed heteropolyacid intercalation compounds

Heteropolyacid is introduced in an intercalation compound of zinc aluminum carbonate hydroxide by an anion-exchanging technique. The acid is probably present as H_2.1PW_9.2O^4.2– _33.3 and is shown to be highly dispersed. The compound catalyzes dehydration ofn-butanol with noticeably higher activity and selectivity to 1-butene than free Keggin type 12-heteropolyacid.     

Association study of a functional catechol-O-methyltransferase gene polymorphism in Japanese schizophrenics

Catechol-O-methyltransferase (COMT) is an enzyme which inactivates catecholamine neurotransmitters by methylation, and is considered a candidate for involvement in schizophrenia. A functional COMT gene polymorphism influencing the enzyme activities, the high activity (val-108) and the low activity allele (met-108), was recently confirmed. We investigated a genetic association between schizophrenia and the COMT gene polymorphism in 150 Japanese schizophrenics and controls. We detected the low activity met-108 allele more frequently in schizophrenics than in the controls, and found that subjects sharing the met-108 allele (val/met and met/met) are significantly more common in the patients than in the controls. The results suggest that the low activity met-108 allele may be involved in susceptibility for schizophrenia.     

Cerebral infarction associated with nephrotic syndrome in a young adult: a case report

We report a 19-year-old man who developed a cerebral infarction in the territory of the anterior choroidal artery and showed a hypercoagulable state and nephrotic syndrome after diarrhea and appetite loss. He had suffered from nephrotic syndrome from the age of three and had been treated for five years. MR-angiography showed an occlusion originating in the right internal carotid artery. The right anterior and middle cerebral arteries were imaged from the left internal carotid artery via the anterior communication artery. He showed symptoms of left hemiparesis, agnosia, loss of activity, anasarca and left hypacusis following his clinical course, but had recovered from all but left hemiparesis following medical treatments including steroid therapy. The histologic finding by a renal biopsy revealed focal glomerulosclerosis. In this case, we considered that when he was in a hypercoagulable state and had a second attack of nephrotic syndrome because of inflammation and dehydration due to diarrhea and appetite loss, his hypercoagulable state grew worse, and he then developed a cerebral infarction. When one see a patient with nephrotic syndrome, one should be attentive to the possibility of a complication of cerebral infarction.