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排序方式: 共有146条查询结果,搜索用时 15 毫秒
31.
Stefano Pigola Marco Rigoli Alberto G. Setti 《Proceedings of the American Mathematical Society》2003,131(4):1283-1288
We prove that the stochastic completeness of a Riemannian manifold is equivalent to the validity of a weak form of the Omori-Yau maximum principle. Some geometric applications of this result are also presented.
32.
M. F. R. Fouda M. M. Abd-Elzaher M. M. E. Shakdofa F. A. El Saied M. I. Ayad A. S. El Tabl 《Transition Metal Chemistry》2008,33(2):219-228
A hydrazone ligand (HL) containing the thiophene moiety has been prepared via condensation of thiophene-2-carbohydrazide with
1,5-dimethyl-3-oxo-2-phenyl-2,3-dihydro-1H-pyrazole-4-carbaldehyde. The complexes of copper(II), nickel(II), cobalt(II), manganese(II),
zinc(II), palladium(II), iron(III), ruthenium(III), uranyl(VI), and titanium(IV) with the ligand were prepared in good yield
from the reaction of the ligand with the corresponding metal salts. The ligand and complexes were characterized using infrared,
mass spectra, nuclear magnetic resonance, electronic absorption spectra, electron spin resonance, and magnetic moment measurements
as well as elemental and thermal analyses. The results showed that the complexes are enolic by nature, whilst the ratio between
the metal ion and the ligand depends on the acidity of the metallic ions and their oxidation numbers. 相似文献
33.
Jumat Salimon Nadia Salih Emad Yousif Ayad Hameed Ayad Kreem 《Arabian Journal of Chemistry》2010,3(4):205-210
In the present study a new acridone derivatives were synthesized. The newly synthesized compounds were characterized by IR, NMR and C, H, N, S analyses. All newly synthesized compounds were screened for their antibacterial (Staphylococcus aureus, Streptococcus viridans and Escherichia coil) and antifungal (Gibberela, Cercospora arachidicola, Physolospora piricola and Fusarium oxysporum) studies. The results revealed that all synthesized compounds have a significant biological activity against the tested microorganisms. 相似文献
34.
Sébastien Prévost Sébastien Gauthier Maria Cristina Caño de Andrade Céline Mordant Ali Rhida Touati Philippe Lesot Philippe Savignac Tahar Ayad Phannarath Phansavath Virginie Ratovelomanana-Vidal Jean-Pierre Genêt 《Tetrahedron: Asymmetry》2010,21(11-12):1436-1446
The dynamic kinetic resolution (DKR) of racemic α-chloro β-ketoesters and α-chloro β-ketophosphonates through ruthenium-mediated asymmetric hydrogenation is reported. The corresponding α-chloro β-hydroxyesters and α-chloro β-hydroxyphosphonates were obtained in good to high enantio- and diastereomeric excesses using, in particular, the atropisomeric ligand DIFLUORPHOS. This methodology allowed an efficient preparation of the anti phenylisoserine side chain of Taxotere® which has been used for the hemisynthesis of the cancer therapeutic agent itself. In addition, 13C NMR in chiral oriented solvents was used to investigate the DKR effect. 相似文献
35.
Monosaccharide osazones are utilized in the spectrophotometric determination of their parent compounds through charge transfer complexes (CTC) formation with three-electron acceptor reagents. These acceptors indlude iodine (as -π-acceptor) and chloranil (tetrachloro P-benzoquinone) & TCNE (tetracyano ethylene) as π-acceptors. The presence of two phenylhydrazone moieties in the osazone molecule imparts electron-donating properties toward electron-accepting reagents, yielding spectrophotometrically measurable complexes. However, the reaction of osazone intermediates with TCNE reagent gave tricyanovinyl derivative rather than CTC formation. The above complexes together with their corresponding intermediates were subjected to structure elucidation studies to confirm the results and conclusions obtained. These studies include IR, Raman spectra, H1, C13-NMR, MS, ESR (electron spin resonance spectra) and microanalysis. 相似文献
36.
37.
Summary The electronic absorption spectra of someSchiff bases derived from 3-amino-1,2,4-triazole have been investigated in organic solvents of different polarities. Assignment of the absorption bands, solvent effects, and spectral structure correlations are considered. The fundamental IR bands and the main signals in the1H NMR spectra are assigned and discussed with respect to the effect of substituents on the phenyl ring. A change of the electrical conductance of the compounds with increasing temperature is observed for the solid samples.
Spektroskopische und konduktometrische Untersuchungen einigerSchiffscher Basen
Zusammenfassung Die UV/Vis-Spektren einiger von 3-Amino-1,2,4-triazol abgeleiteterSchiffscher Basen wurden in Lösungsmitteln unterschiedlicher Polarität bezüglich Zuordnung der Banden, Lösungsmitteleffekten und Spektrum-Struktur — Korrelationen untersucht. Die wesentlichen IR- und1H-NMR — Signale wurden zugeordnet und werden mit Substituenteneffekten in Beziehung gesetzt. Im Festzustand zeigen die Proben eine Änderung der elektrischen Leitfähigkeit mit steigender Temperatur.相似文献
38.
Al-Jibori Subhi A. Al-Nassiri Ilham N. Al-Hayaly Lamaan J. Jassim Ayad H. 《Transition Metal Chemistry》2002,27(2):191-195
Transition metal complexes containing two types of ligands: 5-phenyl-1,3,4-oxadiazole-2-thione ion (L) and tertiary phosphines, have been prepared. The complexes, [ML2A2] [M = Pd or Pt; A = PPh3 or Ph2PCH2CH2P(O)Ph2] and [ML2B] (M = Co, Ni, Pd or Pt; B = Ph2PCH2PPh2 or Ph2PCH2CH2PPh2), were characterized by elemental analysis, molar conductance, i.r., u.v.–vis., 31P-n.m.r., magnetic susceptibility measurements and mass spectra. 相似文献
39.
Anastassov A Duboscq JE Eckhart E Gan KK Gwon C Hart T Honscheid K Hufnagel D Kagan H Kass R Pedlar TK Schwarthoff H Thayer JB von Toerne E Zoeller MM Richichi SJ Severini H Skubic P Undrus A Chen S Fast J Hinson JW Lee J Miller DH Shibata EI Shipsey IP Pavlunin V Cronin-Hennessy D Lyon AL Thorndike EH Jessop CP Savinov V Coan TE Fadeyev V Maravin Y Narsky I Stroynowski R Ye J Wlodek T Artuso M Ayad R Boulahouache C Bukin K Dambasuren E Karamov S Majumder G Moneti GC Mountain R Schuh S 《Physical review letters》2001,86(20):4467-4471
The tau decays to six-pion final states have been studied with the CLEO detector at the Cornell Electron Storage Ring. The measured branching fractions are B(tau(-)-->2pi(-)pi(+)3pi(0)nu(tau)) = (2.2+/-0.3+/-0.4)x10(-4) and B(tau(-)-->3pi(-)2pi(+)pi(0)nu(tau)) = (1.7+/-0.2+/-0.2)x10(-4). A search for substructure in these decays shows that they are saturated by intermediate states with eta or omega mesons. We present the first observation of the decay tau(-)-->2pi(-)pi(+)omega(nu)tau and the branching fraction is measured to be (1.2+/-0.2+/-0.1)x10(-4). The measured branching fractions are in good agreement with the isospin expectations but somewhat below the conserved-vector-current predictions. 相似文献
40.
Alastair J. Florence Alan R. Kennedy Norman Shankland Elaine Wright Ayad Al‐Rubayi 《Acta Crystallographica. Section C, Structural Chemistry》2000,56(11):1372-1373
The antibiotic norfloxacin recrystallizes from acetonitrile as a dihydrate with the norfloxacin molecule in a zwitterionic form, i.e. 1‐ethyl‐6‐fluoro‐1,4‐dihydro‐4‐oxo‐7‐(1‐piperazin‐4‐io)‐3‐quinolinecarboxylate dihydrate, C16H18FN3O3·2H2O. 相似文献