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71.
Shuping Chen 《Applied Mathematics and Optimization》1992,26(1):95-110
Necessary and sufficient conditions are established in this paper for the existence of positive- and/or negative-definite solutions to the algebraic Riccati equation with indefinite coefficient. An iterative procedure is also given for computing such a solution.Project supported by the National Science Foundation of China and by the special program of the State Education Commission of China under grant 9033507. 相似文献
72.
Summary The photogalvanic effect of ferrousbis-(acetylacetonate) (Fe(II)(acac)2) and ferrousbis-(trifluoroacetylacetonate) (Fe(II)(tfac)2) complexes in aqueous acetonitrile thionine dye solutions has been studied in a photogalvanic cell of 70 cm3 capacity with identical platinum electrodes (area: 0.25 cm2) using visible light (80 mW/cm2) at 25°C. The theoretical Sunlight Engineering Efficiency (SEE) was determined for both complexes and it was found that the best SEE was obtained when Fe(II)(tfac)2 was used at a concentration of 1.5×10–4 mol/dm3 with a thionine concentration of 1×10–4 mol/dm3 atpH=4 in 40% aqueous acetonitrile. Effects of incident light intensity and temperature on the photogalvanic performance and the action spectrum of the present system were also investigated. A mechanism of the photoredox reaction between the Fe(II)-complex and the dye molecule is proposed.
Der photogalvanische Effekt von Fe(II)-w6rrm4v1937/xhuge946.gif" alt="beta" align="MIDDLE" BORDER="0">-Diketonat/Thionin-Systemen in wäßrigem Acetonitril
Zusammenfassung Der photogalvanische Effekt von Eisen(II)-bis-(acetonylacetonat) (Fe(II)(acac)2) und Eisen(II)-bis-(trifluoracetylacetonat) (Fe(II)(tfac)2 in wäßriger acetonitrilischer Thioninlösung wurde in einer photogalvanischen Zelle (70 cm3) mit identischen Platinelektroden (Fläche: 0.25 cm2) mit sichtbarem Licht (80 mW/cm2) bei 25°C untersucht. Für beide Komplexe wurde die theoretische Sunlight Engineering Efficiency (SEE) bestimmt; der beste SEE-Wert wurde für Fe(II)(tfac)2 bei einer Konzentration von 1.5×10–4 mol/dm3 beipH=4 in 40%igem Acetonitril gefunden (Thioninkonzentration: 1.0×10–4 mol/dm3). Effekte, die durch Änderung der Lichtintensität und der Temperatur hervorgerufen werden, werden diskutiert. Ein Mechanismus für die Photoredoxreaktion zwischen dem Fe(II)-Komplex und dem Farbstoffmolekül wird vorgeschlagen.相似文献
73.
A seven-step synthesis ofS-(+)-hydroprene (S-1) in w037843t2/xxlarge8764.gif" alt="sim" align="MIDDLE" BORDER="0">20 % overall yield starting fromS-(+)-3,7-dimethyl-1,6-octadiene (2) of 55+-10 % optical purity is described. The introduction of an optical enhancement step in the synthetic sequence at the stage ofS-(–)-3,7-dimethyl-1-octanol (9) raises the optical purity ofS-1 from w037843t2/xxlarge8764.gif" alt="sim" align="MIDDLE" BORDER="0">50 % to w037843t2/xxlarge8764.gif" alt="sim" align="MIDDLE" BORDER="0">80 %.For part 13, see. ref.1
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 342–348, February, 1993. 相似文献
74.
L. M. Pisarenko T. V. Maksimova Z. S. Kartasheva O. T. Kasaikina 《Russian Chemical Bulletin》2003,52(7):1500-1503
The temperature effect on the rate of the decomposition of hydroperoxides and the rate of the formation of free radicals in the oxidation of ethylbenzene with molecular oxygen in the presence of w831w203676825gu/xxlarge945.gif" alt="agr" align="BASELINE" BORDER="0">-phenylethyl hydroperoxide—cetyltrimethylammonium bromide (CTAB) as a catalytic system for free radical generation was studied by kinetic methods (from the oxygen consumption and hydroperoxide decomposition rates) and the inhibition method involving different acceptors of free radicals. 相似文献
75.
《Arabian Journal of Chemistry》2022,15(9):104037
This study aimed to investigate the beneficial role of Millettia ferruginea extract (MF) in preventing cisplatin (Cisp) induced nephrotoxicity in rats. A total of 55 metabolites were identified using LC-MS analysis. The in vivo results indicated that MF pretreatment for 4 weeks (20 mg/kg b.w.) remarkably attenuated the altered renal biomarkers by decreasing the levels of plasma creatinine, urea, and uric acid when compared to the Cisp-group. The nephroprotective capacity of MF was further strengthened by histopathological observations, where Cisp + MF treated rats showed lower number of inflammatory cells and tubular degenerative changes than the Cisp-group. The harmful effects of cisplatin on renal oxidative stress indicators (MDA, SOD, CAT, and GPx), were restored by the treatment of MF. In addition, the reduction of inflammatory markers (IL-6 and TNF-α), associated with alleviating DNA fragmentation, highlighted the preventive effect of MF in kidney tissue. Additionally, MF components presented lower binding energies when docked into the active site of TNF-α and IL-6. The present findings concluded that M. ferruginea extract exhibited nephroprotective potential, which may be attributed to its antioxidant and anti-inflammatory properties. Further work is recommended to confirm the current results, explore the involved mechanism of action, and determine the therapeutic doses and time. 相似文献
76.
In the framework of the Hückel MO approximation, the differences in total binding energy between a given molecule and the corresponding distorted Kekulé-type structure are calculated for a variety of benzenoid hydrocarbons. The total binding energy is assumed to be given by the sum of the w88j6287438g48/xxlarge960.gif" alt="pgr" align="BASELINE" BORDER="0">-electron and w88j6287438g48/xxlarge963.gif" alt="sgr" align="BASELINE" BORDER="0">-electron binding energies. It is shown that there is a good linear relationship between the calculated differences in total binding energy and the w88j6287438g48/xxlarge960.gif" alt="pgr" align="BASELINE" BORDER="0">-electron delocalization energies (DE) as obtained by using the simple Hückel MO method. This provides a physical basis for the use of the w88j6287438g48/xxlarge960.gif" alt="pgr" align="BASELINE" BORDER="0">-electron DE as a theoretical index to the empirical resonance energy (RE). Further, by examining the changes in w88j6287438g48/xxlarge960.gif" alt="pgr" align="BASELINE" BORDER="0">-electron binding energy between a given molecule and the corresponding distorted Kekulé-type structure, it is concluded that in benzenoid hydrocarbons the main contributor to the RE is not the w88j6287438g48/xxlarge960.gif" alt="pgr" align="BASELINE" BORDER="0">-electron DE but the compressional energy of w88j6287438g48/xxlarge963.gif" alt="sgr" align="BASELINE" BORDER="0"> bonds. 相似文献
77.
Keita Hamasaki Asao Nakamura Akihiko Ueno Fujio Toda 《Journal of inclusion phenomena and macrocyclic chemistry》1992,13(4):349-359
The effects of w380n14522661410/xxlarge946.gif" alt="beta" align="MIDDLE" BORDER="0">-cyclodextrin (w380n14522661410/xxlarge946.gif" alt="beta" align="MIDDLE" BORDER="0">-CyD), heptakis(2,6-di-O-methyl)-w380n14522661410/xxlarge946.gif" alt="beta" align="MIDDLE" BORDER="0">-cyclodextrin (DMw380n14522661410/xxlarge946.gif" alt="beta" align="MIDDLE" BORDER="0">CyD) and heptakis(2,3,6-tri-O-methyl)-w380n14522661410/xxlarge946.gif" alt="beta" align="MIDDLE" BORDER="0">-cyclodextrin (TMw380n14522661410/xxlarge946.gif" alt="beta" align="MIDDLE" BORDER="0">CyD) ontrans-cis photoisomerization of 1-ethyl-4-(4w380n14522661410/xxlarge8242.gif" alt="prime" align="BASELINE" BORDER="0">-hydroxystyryl)pyridinium (POH) have been studied in aqueous solutions. The ratio of [cis]/[trans] for POH in the photostationary state at pH 8.54 was remarkably reduced by the presence of w380n14522661410/xxlarge946.gif" alt="beta" align="MIDDLE" BORDER="0">CyD or DMw380n14522661410/xxlarge946.gif" alt="beta" align="MIDDLE" BORDER="0">CyD. The reduction of the [cis]/[trans] ratio in the photostationary state was explained in terms of the shift of the equilibrium of POH
+
trans
w380n14522661410/xxlarge8652.gif" alt="rlhar" align="MIDDLE" BORDER="0"> PO
trans
+ H– toward PO
trans
formation. The binding constants of w380n14522661410/xxlarge946.gif" alt="beta" align="MIDDLE" BORDER="0">CyD and DMw380n14522661410/xxlarge946.gif" alt="beta" align="MIDDLE" BORDER="0">CyD for PO
trans
were 2.00- and 1.36-fold larger than those for POH
+
trans
, respectively. The binding constants of TMw380n14522661410/xxlarge946.gif" alt="beta" align="MIDDLE" BORDER="0">CyD for both species are much smaller than those of w380n14522661410/xxlarge946.gif" alt="beta" align="MIDDLE" BORDER="0">CyD and DMw380n14522661410/xxlarge946.gif" alt="beta" align="MIDDLE" BORDER="0">CyD. This result indicates that PO
trans
, which has a betain structure, forms stable complexes with w380n14522661410/xxlarge946.gif" alt="beta" align="MIDDLE" BORDER="0">CyD and DMw380n14522661410/xxlarge946.gif" alt="beta" align="MIDDLE" BORDER="0">CyD with its hydrophobic parts inside and the charged parts outside the CyD cavities. 相似文献
78.
K. -H. Frömming V. Wedelich W. Mehnert 《Journal of inclusion phenomena and macrocyclic chemistry》1984,2(3-4):605-611
The World Health Organization issued a nitrosation procedure (NAP Test) which allows to carry out nitrosation under standard conditions. It has proved that the in vitro reaction rates of the fast nitrosatable drugs piperazine, cimetidine and ethambutol are not influenced by w503/xxlarge945.gif" alt="agr" align="BASELINE" BORDER="0">-, w503/xxlarge946.gif" alt="beta" align="MIDDLE" BORDER="0">- and w503/xxlarge947.gif" alt="gamma" align="MIDDLE" BORDER="0">-cyclodextrin. On the contrary, w503/xxlarge946.gif" alt="beta" align="MIDDLE" BORDER="0">-, w503/xxlarge947.gif" alt="gamma" align="MIDDLE" BORDER="0">-cyclodextrin and heptakis-2,6-di-O-methyl-w503/xxlarge946.gif" alt="beta" align="MIDDLE" BORDER="0">-cyclodextrin enhance the nitrosation of the slower nitrosatable 1-ephedrine and fencamfamine significantly. This possible reaction must be considered if nitrosatable drugs are formulated with cyclodextrins to be administered to human beings. 相似文献
79.
(+)-4w3/xxlarge945.gif" alt="agr" align="BASELINE" BORDER="0">-(1-Trimethylsilyloxyethen-1-yl)-2-carene was synthesized, and the products of its ozonization were identified.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1984–1987, October, 1995. 相似文献
80.
Abdel-Wahab M. Nourein 《BIT Numerical Mathematics》1976,16(3):291-297
In this paper we describe a new technique for generating iteration formulas — of arbitrary order — for determining a zero (assumed simple) of a functionf, assumed analytic in a region containing the zero. The 1/p Padé Approximant (pw832w32067v3/xxlarge8807.gif" alt="gE" align="MIDDLE" BORDER="0">0) to the functiong(t)w832w32067v3/xxlarge8801.gif" alt="equiv" align="MIDDLE" BORDER="0">f(z) is formed wherez=w+t, using the Taylor series forf at the pointw, an approxination to the zero off. The value oft for which the 1/p Padé Approximant vanishes provides the basis of iteration formulas of orderp+2.Some known iteration formulas, e.g., Newton-Raphson's, Halley's and Kiss's of order of convergence two, three and four, are directly obtained by settingp=0,1 and 2, respectively. 相似文献