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1.
Let ir(G) and γ(G) be the irredundance number and the domination number of a graph G, respectively. A graph G is called irredundance perfect if ir(H)=γ(H), for every induced subgraph H of G. In this article we present a result which immediately implies three known conjectures on irredundance perfect graphs. © 2002 Wiley Periodicals, Inc. J Graph Theory 41: 292–306, 2002 相似文献
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3.
D. Beese R. Steiner H. Scheer A. Angerhofer B. Robert M. Lutz 《Photochemistry and photobiology》1988,47(2):293-304
Abstract— Reaction centers from Rhodobacter sphaeroides have been modified by treatment with sodium borohydride similar to the original procedure [Ditson et al., Biochim. Biophys. Acta 766 , 623 (1984)], and investigated spectroscopically and by gel electrophoresis.
(1) Low temperature (1.2 K) absorption, fluorescence, absorption- and fluorescence-detected ODMR, and microwave-induced singlet-triplet absorption difference spectra (MIA) suggest that the treatment produces a spectroscopically homogeneous preparation with one of the 'additional' bacteriochlorophylls being removed. The modification does not alter the zero field splitting parameters of the primary donor triplet (T P870).
(2) From the circular dichroism and Raman resonance spectra in the1500–1800 cm-1 region, the removed pigment is assigned to BchlM , e.g. the "extra" Bchl on the "inactive" M-branch.
(3) A strong coupling among all pigment molecules is deduced from the circular dichroism spectra, because pronounced band-shifts and/or intensity changes occur in the spectral components assigned to all pigments. This is supported by distinct differences among the MIA spectra of untreated and modified reaction centers, as well as by Raman resonance.
(4) The modification is accompanied by partial proteolytic cleavage of the M-subunit. The preparation is thus spectroscopically homogeneous, but biochemically heterogenous. 相似文献
(1) Low temperature (1.2 K) absorption, fluorescence, absorption- and fluorescence-detected ODMR, and microwave-induced singlet-triplet absorption difference spectra (MIA) suggest that the treatment produces a spectroscopically homogeneous preparation with one of the 'additional' bacteriochlorophylls being removed. The modification does not alter the zero field splitting parameters of the primary donor triplet (
(2) From the circular dichroism and Raman resonance spectra in the1500–1800 cm
(3) A strong coupling among all pigment molecules is deduced from the circular dichroism spectra, because pronounced band-shifts and/or intensity changes occur in the spectral components assigned to all pigments. This is supported by distinct differences among the MIA spectra of untreated and modified reaction centers, as well as by Raman resonance.
(4) The modification is accompanied by partial proteolytic cleavage of the M-subunit. The preparation is thus spectroscopically homogeneous, but biochemically heterogenous. 相似文献
4.
Perfluoroalkyl iodine compounds: preparations and properties of CF3IO, CF3IOF2, and CF3IO2. The trifluoromethyl iodine compounds CF3IO, CF3IOF2, and CF3IO2 are formed from the reactions of CF3I, CF3IF2 or CF3IF4 with ozone or silicon dioxide respectively. Their preparartions, properties, 19F-nmr spectra, and ir spectra are described. 相似文献
5.
6.
In the case of the formation of thiospinels (MnCr2S4, ZnCr2S4 and CdCr2S4) a simple method for the determination of the activation energy of solid state reactions in polycrystalline samples by means of conductivity measurements is shown. The maxima and minima of conductivity (glow curve maxima and -minima) in the σ vs T-curves got by annealing with linearly increasing temperature are shifted towards higher temperatures with increasing rate of heating(q). By plotting ln (q/T) vs 1/Tσmax a straight line results. The activation energy of the reaction may be deduced from the slope of this straight line in analogy to the determination of the trap depth of electrons from glow curves observed in thermoluminescence. 相似文献
7.
The determination of yttrium in the presence of large amounts of the rare earths by the thermal neutron reaction (89)Y(n, gamma)(90)Y is complicated because of frequent problems of sample self-shielding from major constituents of the sample, and the difficulty of separating (90)Y, a pure beta-emitter, from other elements which are very similar chemically. A non-destructive photon activation analysis method has been developed for this determination. Bremsstrahlung from a 35-muA beam of 35-MeV electrons induces the photonuclear reaction (89)Y(gamma, n)(88)Y. Optimum sensitivity is obtained by coincidence counting of the 0.90 and 1.84 MeV gamma-rays associated with the decay of (88)Y. The detection limit is less than 1 mug of yttrium. 相似文献
8.
Robert E. Pratt William J. Welstead Robert E. Lutz 《Journal of heterocyclic chemistry》1970,7(5):1051-1055
Hydrazoic-sulfuric acid mixture converted cis-α-phenyl-β-benzoylchalcone (trans-dibenzoylstilbene, 4 ) into 2,3-diphenyl-4-benzoylquinoline ( 5 ) the structure of which was proved by debenzoylation to 2,3-diphenylquinoline. α,β-Diphenyl and cis-α,β-dibromochalcones similarly were converted respectively into 2,3,4-triphenylquinoline ( 19 ) and 2-phenyl-3,4-dibromoquinoline ( 20 ). The structure of 19 was shown by difference from the corresponding isoquinoline 21 (synthesized). Smith's mechanism for the analogous conversion of o-phenylbenzophenone into 9-phenylphenanthridine through the 9-fluorenol and the 9-hydroazide with loss of nitrogen and ring expansion, was supported by methyl label experiments using 2-(p-tolyl)benzophenone which gave a 53:47 mixture of 3- and 8-methyl-6-phenylphenanthridines. Applicability of the mechanism to the reactions with disubstituted cis-chalcones was shown by sulfuric acid conversions of two of these into indenol 22 and 2-bromo-3-phenylindenone ( 24 ), respectively. trans-Dibenzoylstilbene underwent resinification in sulfuric acid, giving the quinoline ( 5 ) only when hydrazoic acid was present. 相似文献
9.
Zusammenfassung Von den in der vorigen Mitteilung beschriebenen 3,4-Bis-(p-methoxyphenylhexandionen-(2,5) [meso undracem.] wurde diemeso-Verbindung durch Reduktion in zwei (der drei möglichen) entsprechende sekundäre Diole übergeführt und das höherschmelzende Diol durch Entmethylierung in ein 3,4-Bis-(p-hydroxyphenyl)-hexandiol-(2,5) (Dihydroxyhexoestrol) umgewandelt. Versuche, durch Reduktion eine Überführung in ein Hexoestrol zu erreichen und die sterische Anordnung festzulegen, schlugen sämtlich fehl.Eingehender wurde die Gewinnung homologer tertiärer Diole durch Umsetzung der beiden Hexandionderivate (meso undracem.) mit CH3MgX bearbeitet, wobei unter Ätherspaltung die beiden Bis-homologen-dihydroxy-hexoestrole resultierten. Ammesoiden Hexandionderivat wurde auch die Grignardreaktion allein (ohne Entmethylierung) durchgeführt.
6. Mitt.:H. Bretschneider undR. Lutz, Mh. Chem.95, 1702 (1964). 相似文献
Of the two (meso andracemic) 3,4-di(p-methoxyphenyl)-hexanediones-(2,5) described in the previous communication, themeso compound has been converted by reduction into two (of the three possible) corresponding secondary diols. Demethylation of the higher melting isomer yielded 3,4-di(p-hydroxyphenyl)-hexanediol-(2,5) (dihydroxyhexestrol). Attempts to obtain the corresponding hexestrol by reduction and hence to determine its configuration remained unsuccessful.The preparation of homologous tertiary diols by reaction of the two hexanedione derivatives (meso andracemic) with CH3MgX has been investigated more closely; on ether cleavage the two di-homologous dihydroxyhexestrols were formed. The Grignard reaction was also carried out on themeso hexanedione without subsequent demethylation.
6. Mitt.:H. Bretschneider undR. Lutz, Mh. Chem.95, 1702 (1964). 相似文献
10.
Using an adiabatic calorimeter, the heat of transition Sα ? Sβ, the heat of fusion of Sβ and the specific heat of the liquid had been determined on sulfur samples refined by zone melting and samples doped with chlorine, bromine and iodine. The data obtained from pure sulfur (heat of fusion: 1608 ± 8 J/Tom, specific heat of the liquid at 120°C: 29,4 J/Tom.°C) are about 10% lower than comparable values of other authors. Apparently they represent heat of fusion and specific heat of the pure cyclooctasulfur. The measurements on doped samples (δHS = 1736 ± 10 J/Tom) are in agreement with the data reported in literature and include a portion of enthalpy from the transition reaction of cycloocta-sulfur (Sλ) to catenaocta-sulfur (Sπ), requiring extremly long equilibrium times in pure sulfur. The influence of impurity on the caloric properties of the liquid sulfur is also indicated by the increasing width and decreasing highness of the Cp-maximum at 159°C with increasing amount of halogens. For the heat of transition Sα → Sβ, independent of the amount of impurity, the literature data could be confirmed. At the samples doped with iodine there was observed a previously unreported transition near 65,9°C. 相似文献