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991.
In order to determine the electronic factors that may affect the catalytic antioxidant activity of water-soluble metallocorroles a series of 10-aryl-5,15-pyridinium manganese(III) corroles was prepared. These complexes were examined regarding the effect of the C(10) substituent on the Mn(IV)/Mn(III) redox potentials, catalytic rate constants for decomposition of HOONO, prevention of tyrosine nitration, and superoxide dismutase activity. This structure-activity relationship investigation provides new insight regarding the mechanism by which manganese(III) corroles act as catalytic antioxidants. It also discloses the superiority of the C(10)-anysil-substituted complex in all examined aspects. 相似文献
992.
993.
Aleksandra Tyl El?bieta Che?mecka Magdalena Jab?ońska Maria Nowak Joachim Kusz Karol Pasterny Roman Wrzalik 《Structural chemistry》2012,23(2):325-332
The X-ray structure, synthesis, theoretical calculation and IR spectra of 1-naphthaleneacrylic acid are reported. The titled
compound crystallizes in the monoclinic C 2/c space group with unit cell parameters: a = 14.556(3), b = 5.1332(10), c = 26.832(5) ?, β = 97.02(3)°, V = 1989.8(7) ?3, Z = 8 and form typical centrosymmetric hydrogen-bonded dimers. Theoretical calculations of 1-naphthylacrylic acid isolated
molecule and hydrogen-bonded dimer have been carried out using density functional theory at the B3LYP level. For optimized
structures the vibrational spectra have been then calculated and compared with experimental IR spectrum. The assignment and
characterization of theoretical vibrational spectra were based on the potential energy distribution analysis. This comparison
has shown that the theoretical spectrum for the dimer structure is in good agreement with the experimental one. Structural
comparisons with naphthalene, and with some substituted 2-propenoic acids have shown influence of the substituent on conformation
of the naphthalene ring or 2-propenoic moiety. 相似文献
994.
We complete the classification of positive rank gradings on Lie algebras of simple algebraic groups over an algebraically closed field k whose characteristic is zero or not too small, and we determine the little Weyl groups in each case. We also classify the stable gradings and prove Popov’s conjecture on the existence of a Kostant section. 相似文献
995.
We study a system of partial differential equations describing the steady flow of a heat conducting incompressible fluid in a bounded three dimensional domain, where the right-hand side of the momentum equation includes the buoyancy force. In the present work we prove the existence of a weak solution under both the smallness and a sign condition on physical parameters α0 and α1 which appear on the right hand side. 相似文献
996.
997.
Bart Vermang Emanuele Cornagliotti Victor Prajapati Joachim John Jef Poortmans Robert Mertens 《固体物理学:研究快报》2012,6(6):259-261
This Letter discusses an important difference between positively charged SiO2 and negatively charged Al2O3 rear‐passivated p‐type Si solar cells: their illumination level dependency. For positively charged SiO2 rear‐passivated p‐type Si solar cells, a loss in short circuit current (JSC) and open circuit voltage (VOC) as a function of illumination level is mainly caused by parasitic shunting and a decrease in surface recombination, respectively. Hence, the relative loss in cell conversion efficiency, JSC, and VOC as a function of the illumination level for SiO2 compared to Al2O3 rear‐passivated p‐type Si solar cells has been measured and discussed. Subsequently, an exponential decay fit of the loss in cell efficiency is applied in order to estimate the difference in the energy output for both cell types in three different territories: Belgium (EU), Seattle and Austin (US). The observed trends in the difference in energy output between both cells, as a function of time of the year and region, are as expected and discussed. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
998.
Suppose thatX is a vector field on a manifoldM whose flow, exptX, exists for all time. If μ is a measure onM for which the induced measuresμ
t
≡(exptX)*
μ are absolutely continuous with respect to μ, it is of interest to establish bounds on theL
p
(μ) norm of the Radon-Nikodym derivativedμ
t
/dμ. We establish such bounds in terms of the divergence of the vector fieldX. We then specilizeM to be a complex manifold and derive reverse hypercontractivity bounds and reverse logarithmic Sololev inequalities in some
holomorphic function spaces. We give examples onC
m and on the Riemann surface forz
1/n
.
Research supported in part by CONACyT, Mexico, grant 32725-E.
Research supported in part by CONACyT, Mexico, grant 32146-E. 相似文献
999.
Yinsheng Wang John-Stephen Taylor Michael L. Gross 《Journal of the American Society for Mass Spectrometry》2001,12(11):1174-1179
We report the effect of metal-ion adduction on the fragmentation of oligodeoxynucleotides (ODNs) bearing DNA photoproducts. When protons on backbone phosphates of ODNs are completely replaced with metal ions, cleavages occur readily within the photoproduct moiety, whereas those cleavages do not occur in photomodified ODNs in which the phosphates are associated with protons. For example, thymine/adenine (TA*) photoproducts revert to their undamaged precursors upon collisional activation, the pyrimidine(6-4)pyrimidone product and its Dewar valence isomer show a characteristic neutral loss of C4H3NO3, and dimeric adenine photoproducts show a distinctive loss of NH2CN from the adenine six-membered ring. The product-ion mass spectra of photodamaged ODNs that are adducted to metal ions are complementary in terms of structure information to those spectra of ODNs in which the phosphates are associated with protons. The results also demonstrate that the energy required for strand cleavages is higher for ODNs adducted with metal ions than that for ODNs bound with protons. Furthermore, the loss of a pyrimidine is more favorable than the loss of a purine in the fragmentation of ODNs associated with metal ions. 相似文献
1000.
A series of selected bicyclic carbamates in which the range of accessible angles and distances between the carbonyl group and the proton removed in an alpha-lithiation reaction are structurally defined have been investigated. Oxazolidinones 7-10 undergo stereoselective lithiation-substitution reactions to provide cis-18-27 and cis-31-35 as the major diastereomers. Two series of competition experiments show that the conformationally restricted carbamates 7, 10, 11, and 15 undergo lithiation via complexes more efficiently than Boc amines 4-6. These results along with semiempirical calculations suggest that a small dihedral angle and a calculated distance of 2.78 A between the carbamate carbonyl oxygen and the proton to be removed are favorable for a carbamate-directed lithiation. A series of tin-lithium exchange experiments on cis- and trans-18 and (S)-39 indicate that the configurational stability of a carbamate-stabilized organolithium species may be enhanced by restrictive geometry. 相似文献