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排序方式: 共有305条查询结果,搜索用时 15 毫秒
1.
Tetsuhiko Kobayashi Nolven Guilhaume Jun Miki Naoyuki Kitamura Masatake Haruta 《Catalysis Today》1996,32(1-4):171-175
In an attempt to develop new catalysts for the formation of formaldehyde from methane, the promotion effect of Fe on SiO2 and that of Sn on WO3 have been studied. The formation of formaldehyde on silica can be appreciably enhanced by the impregnation of Fe, as far as iron loadings are kept below 0.1 atom.% (Fe/Si × 100). In the case of Sn---W---Ox catalysts, both the addition of Sn to WO3, and that of W on SnO2 were effective to the selective formaldehyde formation. Absorption spectra (UV-Vis) and ESR measurements revealed that tetrahedrally coordinated Fe3+ in the silica network plays an important role in the formation of formaldehyde. A thin surface layer consisting of W and Sn oxides can account for the selective formaldehyde formation on the Sn---W---Ox catalysts. 相似文献
2.
Harumi Yokokawa Tatsuya Kawada Masayuki Dokiya 《Journal of the American Ceramic Society》1989,72(1):152-153
It has been found that the enthalpy of formation of perovskite compounds, Δf H° (ABO3 , B = transition metais), from binary oxides can be well characterized in terms the tolerance factor, t≡(rA + ro )√2 (rB + ro ), where rA and rB are the radii of A-site ions with 12-coordination and B-site ions with 6-coordination, respectively, and Δf H°=−168 + 270(1 − t) kJ·mol−1 for AI BV O3 , Δf H°=−125 + 1000(1 − t) kJ·mol−1 for AII BIV O3 , and Δf H°=− 90 + 720(1 − t) kJ·mol−1 for AIII BIII O3 . Although the thermodynamic data of K2 NiF4 compounds are not extensive, a similar regularity can be found when use is made of the radii of A-site ions with 9-coordination for the K2 NiF4 compounds. These correlations will be quite useful in predicting. 相似文献
3.
Beneficial effects of dietary phytic acid (myo-inositol hexaphosphate; IP6) have often been explained by its strong iron ion-chelating ability, which possibly suppresses iron ion-induced oxidative
damage in the gastrointestinal tract. Because phytic acid is hydrolyzed during digestion, this work aimed to know whether
its hydrolysis products (IP2′ IP3′, IP4′ and IP5) could still prevent iron ion-induced lipid peroxidation. Studies using liposomal membranes demonstrated that hydrolysis
products containing three or more phosphate groups are able to inhibit iron ion-induced lipid peroxidation although their
effectiveness decreased with dephosphorylation. Similarly, they also prevented iron ion-induced decomposition of phosphatidylcholine
hydroperoxide. These results demonstrate that intermediate products of phytic acid hydrolysis still possess iron ion-chelating
ability, and thus they can probably prevent iron ion-induced lipid peroxidation in biological systems. 相似文献
4.
K. Sato J. Yano I. Kawada M. Kawano F. Kaneko M. Suzuki 《Journal of the American Oil Chemists' Society》1997,74(9):1153-1159
Molecular properties of polymorphic forms of gondoic acid [cis-C20:1Δ11ω9 (GOA)] have been studied by X-ray diffraction (XRD), differential scanning calorimetry (DSC), optical microscopy, and
Raman scattering, in comparison to those of six principal unsaturated fatty acids: oleic acid [cis-C18:1Δ9ω9 (OA)], erucic acid [cis-C22:1Δ13ω9 (ERA)], petroselinic acid [cis-C18:1Δ6ω12 (PSA)], asclepic acid [cis-C18:1Δ11ω7 (APA)], palmitoleic acid [cis-C16:1Δ9ω7 (POA)], and elaidic acid [trans-C18:1Δ9ω9 (ELA)]. In addition, phase behavior of binary mixtures of GOA and APA and OA was examined by XRD and DSC. The polymorphic
structures of GOA are quite similar to those of APA, ERA, POA, and partly to OA. In particular, DSC and Raman scattering studies
have shown that gondoic acid exhibits conformational disordering on heating at the ω-chain, a chain segment between the double
bond and CH3 group, as a transition from all-trans (γ form) to gauche-rich (α form) conformations. A miscible mixing phase was observed in the mixture of GOA and APA, yet eutectic phases were
observed in the GOA and OA mixtures. This is a remarkable contrast because the binary mixture systems of varying combinations
of cis-unsaturated fatty acids examined so far exhibited either eutectic nature or molecular compound formation. It is expected
that specific molecular interactions between GOA and APA that originate from the equivalence of the length of the Δ-chain,
the chain segment between the cis-double bond and COOH group, and also from the presence of the γ-α order-disorder transformation would be operating to form
the miscible mixing phase. 相似文献
5.
Factors associated with serum magnesium and vascular stiffness in maintenance hemodialysis patients 下载免费PDF全文
Mai Yorifuji Takahiro Kuragano Sayuri Kawada Wataru Fukao Kazuhiro Toyoda Takeshi Nakanishi 《Hemodialysis international. International Symposium on Home Hemodialysis》2018,22(3):342-350
Introduction : We evaluated the associated factors of serum magnesium in patients on maintenance hemodialysis (MHD). Furthermore, we evaluated the relationship between low serum magnesium and arteriosclerosis in these patients. Methods : In 129 patients on MHD, we evaluated the blood levels of magnesium, brachial‐ankle pulse wave velocity (ba‐PWV), ankle‐brachial index (ABI), and intima‐media thickness of the common carotid artery (IMT). Findings : In MHD patients, the serum level of magnesium was significantly correlated with age, calcium, TNF‐α, albumin, and ba‐PWV but not with ABI or IMT. In the multiple regression analysis, albumin (P = 0.0001, β = 0.31) and calcium (P = 0.029, β = 0.18) were selected as significant predictors of the magnesium level in MHD patients. Furthermore, the serum level of magnesium, as well as systolic blood pressure (P = 0.0001, β = 0.32) and age (P = 0.005, β = 0.25), were selected as significant (P = 0.012, β = ?0.22) predictors of ba‐PWV in MHD patients. Discussion : In MHD patients, the serum magnesium level was associated with the serum levels of calcium and albumin. Furthermore, a low serum magnesium level in MHD patients was associated with the index of vascular stiffness. 相似文献
6.
7.
Shunjiro Ogawa Hideyo Suzuki Masatake Toyoda Yoshio Ito Masahiro Iwaida Hiroko Nonogi Tazu Fuke Kazuo Obara Tadao Adachi Koichi Fujita Makiko Ikuzawa Tetsuo Izumi Takashi Hamano Yukimasa Mitsuhashi Yukio Matsuki 《Zeitschrift für Lebensmitteluntersuchung und -Forschung A》1979,168(4):293-298
Summary Detection and determination of traces of sulphites in foods was attempted by use of the modified Rankine apparatus and pararosaniline colorimetry. Replacement of alkaline titration reported previously by pararosaniline colorimetry lowered the absolute detection limit from 30 g (titration method) to 2 g. In view of clean analysis, in the color developing system, 0.1 N-sodium hydroxide was used in place of mercuric chloride solution commonly used as an absorbant of sulphites. In order to prevent oxidative decomposition of sulphites during operation, nitrogen gas was used as carrier instead of air. Dimedone and sodium azide were used for the elimination of aldehydes and nitrites, respecitvely, in the sample, which will disturb the color development of sulphites with pararosaniline-formaldehyde reagents. With this improved method, it was possible to determine the residual sulphites in frozen peeled shrimps, sugared beans and other foods with low sulphite contents accurately.
Studies on the Analyses of Sulphites in Foods (IV) 相似文献
Colorimetrische Mikrobestimmung von Sulfiten in Lebensmitteln bei Anwendung der modifizierten IV. Rankine Apparatur
Zusammenfassung Geringe Sulfitmengen in Lebensmitteln (geschälte Garnelen, gezuckerte Bohnen) können colorimetrisch bestimmt werden. Die neuentwickelte Methode beruht auf einer Kombination von colorimetrischer Bestimmung mittels p-Rosanilin und der Bestimmungsmethode nach Rankine. Auf diese Weise lassen sich Gehalte von 2 g noch genau bestimmen. Bei der Farbentwicklung wurde das giftige Quecksilbertetrachlorid durch 0.1 n-NaOH ersetzt, anstelle von Luft Stickstoff als Trägergas verwendet und somit eine Oxydation des Sulfits während der Bestimmung vermieden. Da Nitrit und Aldehyde die Farbentwicklung stören, wurde ihr Einfluß durch Dimedon und Natriumazid ausgeschaltet.
Studies on the Analyses of Sulphites in Foods (IV) 相似文献
8.
9.
Masatake Ohnishi Atsuko Higuchi Setsuko Todoriki Keitaro Hiromi Wmikio Ohgushi Akiyoshi Wada 《Starch - St?rke》1990,42(7):273-276
Using the pH-jump (neutral to above 11) for Tyr-OH ionization as a probe, two glucoamylases from Rhizopus niveus and Rhizopus delemar were found to be caused the change in conformation, which is in a kinetically single step. The pH titration at pHs below 12 was carried out on a multidimensional correlation spectrophotometer. Correlations among the spectrophotometric properties: fluorescence, absorption and circular dichroism are almost identical for the two enzymes. These results suggest that conformational characteristics of the niveus enzyme is almost the same as that of the delemar one. 相似文献
10.
Based on the subsite structure of an α-amylase from Bacillus subtilis, production of glucose from a substrate maltohexaose in the amylase-catalyzed reaction was theoretically predicted as a function of time. The theoretical time course was found consistent with the experimental results, which were obtained by the determination of a product glucose with a commercial assay-kit. Hence, glucose, product from a substrate maltohexaose, will be a useful probe for the amylase-catalyzed reaction. 相似文献