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排序方式: 共有273条查询结果,搜索用时 15 毫秒
31.
32.
Riassunto Si dà una costruzione di un insieme minimale di generatori omogenei per l'ideale di una curva monomiale proiettiva e una limitazione
per il grado delle equazioni che la definiscono.
Summary A construction of a minimal system of homogeneous generators for the ideal of a monomial projective curve and a degree bound for its defining equations are given.相似文献
33.
Pia Nalli 《Annali di Matematica Pura ed Applicata》1938,17(1):193-202
Sunto I due problemi dei quali intendiamo occuparci sono i seguenti:integrazione delle equazioni differenziali di un moto rigido; costruzione di una curva, della quale siano assegnate la curvatura
e la torsione in funzione dell'arco. 相似文献
34.
Summary The1H nuclear magnetic resonance spectra of Os3(CO)8(Ph2C2)2 and Os3(CO)8[(p-ClC6H4)2C2]2 are described. In these metal cluster complexes theortho-metalation involves phenyl groups linked to a cyclopentadiene ring. 相似文献
35.
Solid-state sintering of a bcc structure of spherical particles has been studied numerically by use of simple shape parameters to describe the state of the unit cell. Both free and pressure-assisted sintering of particles of equal and different sizes for various ratios of boundary and surface diffusion have been considered. At low relative densities, the evolution of particle radius, interparticle junction radius and shrinkage predicted by the bcc model are rather similar to sintering of a simple row of particles. At higher densities, the porosity closes up; that is, the junctions start to interact, or the next-nearest neighbours in the particle structure attain contact. Quantative measures of the density at the transition from open pore space between the particles to closed porosity as well as the density at which the next-nearest neighbours start to touch are derived. Furthermore, different dihedral angles and the evolution of relative density and sintering stresses are studied. 相似文献
36.
Mathematical Programming - A classic result by Cook, Gerards, Schrijver, and Tardos provides an upper bound of $$n \Delta $$ on the proximity of optimal solutions of an Integer Linear Programming... 相似文献
37.
Dr. Aleksandra Markovic Luca Gerhards Dr. Pia Sander Dr. Carsten Dosche Prof. Dr. Thorsten Klüner Prof. Dr. Rüdiger Beckhaus Prof. Gunther Wittstock 《Chemphyschem》2020,21(22):2506-2514
Multinuclear transition metal complexes bridged by ligands with extended π-electronic systems show a variety of complex electronic transitions and electron transfer reactions. While a systematic understanding of the photochemistry and electrochemistry has been attained for binuclear complexes, much less is known about trinuclear complexes such as hexaphenyl-5,6,11,12,17,18-hexaazatrinaphthylene-tristitanocene [(Cp2Ti)3HATN(Ph)6]. The voltammogram of [(Cp2Ti)3HATN(Ph)6] shows six oxidation and three reduction waves. Solution spectra of [(Cp2Ti)3HATN(Ph)6] and of the electrochemically formed oxidation products show electronic transitions in the UV, visible and the NIR ranges. Density functional theory (DFT) and linear response time-dependent DFT show that the three formally titanium(II) centers transfer an electron to the HATN ligand in the ground state. The optically excited transitions occur exclusively between ligand-centered orbitals. The charged titanium centers only provide an electrostatic frame to the extended π-electronic system. Complete active self-consistent field (CASSCF) calculation on a structurally simplified model compound, which considers the multi-reference character imposed by the three titanium centers, can provide an interpretation of the experimentally observed temperature-dependent magnetic behavior of the different redox states of the title compound in full consistency with the interpretation of the electronic spectra. 相似文献
38.
Michele Iannone Anna Pia Dima Francesca Sciarra Francesco Botrè Andrea M. Isidori 《Biomedical chromatography : BMC》2022,36(5):e5344
We present a liquid chromatography tandem mass spectrometry method for the simultaneous analysis of 16 endogenous steroids (androgens, estrogens, glucocorticoids and progestogens) in human serum. Samples (250 μl of matrix) were extracted with t-butylmethyl ether prior to LC–MS/MS analysis. The chromatographic separation was achieved on a reversed-phase column using a methanol–water gradient. The HPLC was coupled to a triple quadrupole mass spectrometer equipped with an electrospray ionization source with acquisition in multiple reaction monitoring mode. The method was validated using surrogate matrices and human serum samples. The specificity of the method was confirmed for all of the considered steroids; linearity was also assessed (R2 > 0.99, lack-of-fit test) in the ranges of concentrations investigated. The lower limits of quantification were in the range 10–400 pg/ml depending on the target steroid. Accuracy was in the range 85–115% for all target steroids except for the lower limit of quantitation levels where it was 80–120%. The extraction recovery was always >65%. No significant matrix effects were observed. To test the reliability of the method, the analysis of serum samples collected from 10 healthy subjects (5 M/5F) was performed. The present method can be used to identify the trajectories of deviation from the concentration normality ranges applied to disorders of the gonadal and adrenal axes. 相似文献
39.
40.
Luca Giacomo Bettini Maria Vittoria Diamanti Maurizio Sansotera Maria Pia Pedeferri Walter Navarrini Paolo Milani 《Journal of nanoparticle research》2016,18(8):238
Anatase/rutile mixed-phase titanium dioxide (TiO2) photocatalysts in the form of nanostructured powders with different primary particle size, specific surface area, and rutile content were produced from the gas-phase by flame spray pyrolysis (FSP) starting from an organic solution containing titanium (IV) isopropoxide as Ti precursor. Flame spray-produced TiO2 powders were characterized by means of X-ray diffraction, Raman spectroscopy, and BET measurements. As-prepared powders were mainly composed of anatase crystallites with size ranging from 7 to 15 nm according to the synthesis conditions. TiO2 powders were embedded in a multilayered fluoropolymeric matrix to immobilize the nanoparticles into freestanding photocatalytic membranes. The photocatalytic activity of the TiO2-embedded membranes toward the abatement of hydrosoluble organic pollutants was evaluated employing the photodegradation of rhodamine B in aqueous solution as test reaction. The photoabatement rate of best performing membranes significantly overcomes that of membranes produced by the same method and incorporating commercial P25-TiO2. 相似文献