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141.
The ultrafast electron and spin dynamics of Co films was investigated using a femto-second pump-probe technique. The samples were magnetically characterized by means of magnetooptical Kerr effect and non-optical magnetometers, i.e. superconductive quantum interference device and alternating gradient field magnetometer. Time evolution of both, Kerr rotation and ellipticity, was measured at different points of the static hysteresis cycle. This allowed separating magnetic and non-magnetic contributions to the signal. The sample magnetization was found to drop within 200 fs, following the pulse cross-correlation trace, while the magnetization recovery time was found to last few picoseconds. 相似文献
142.
143.
Marco Andreatta Massimiliano Mella 《Transactions of the American Mathematical Society》1997,349(11):4669-4683
A complex manifold of dimension together with an ample vector bundle on it will be called a generalized polarized variety. The adjoint bundle of the pair is the line bundle . We study the positivity (the nefness or ampleness) of the adjoint bundle in the case . If this was previously done in a series of papers by Ye and Zhang, by Fujita, and by Andreatta, Ballico and Wisniewski.
If is nef then, by the Kawamata-Shokurov base point free theorem, it supports a contraction; i.e. a map from onto a normal projective variety with connected fiber and such that , for some ample line bundle on . We describe those contractions for which . We extend this result to the case in which has log terminal singularities. In particular this gives Mukai's conjecture 1 for singular varieties. We consider also the case in which for every fiber and is birational.
144.
Jeremy N. Harvey Massimiliano Aschi Helmut Schwarz Wolfram Koch 《Theoretical chemistry accounts》1998,99(2):95-99
The phenyl cation is known to have two low-energy minima, corresponding to 1
A
1 and 3
B
1 states, the first of which is more stable by ca. 25 kcal/mol. The minimum energy crossing point between these two surfaces,
located at various levels including a hybrid method first described here, lies just above the minimum of the triplet, 0.12
kcal/mol at the CCSD(T)/cc-pVDZ//B3LYP/SV level, and there is significant spin-orbit coupling between the surfaces at this
point. On the basis of these results, the lifetime of the triplet is expected to be very short.
Received: 24 October 1997 / Accepted: 25 November 1997 相似文献
145.
Carla Di Teodoro Massimiliano Aschi Andrea Amadei Danilo Roccatano Francesco Malatesta Luca Ottaviano 《Chemphyschem》2005,6(4):681-689
A theoretical study of the conformational properties of a small heme peptide in aqueous solution is carried out by classical, long-timescale molecular dynamics simulations. The electronic properties of this species, that is, the relative energies of its excited electronic states and the redox potential, are reproduced and related to the conformational behavior using the perturbed matrix method and basic statistical mechanics. Our results show an interesting coupling between the conformational transitions and the electronic properties. These investigations, beyond the biophysically relevant results addressing the long-standing question of the actual role of the enzyme structure on the enzyme activity, are also of some methodological interest since they offer a further computational perspective for including the electronic degrees of freedom into the modeling of rather complex molecular systems. 相似文献
146.
Monica Ermolli Anna Fantozzi Massimiliano Marini Domenico Scotti Branko Balla Sebastian Hoffmann Maddalena Querci Claudia Paoletti Guy Van den Eede 《Accreditation and quality assurance》2006,11(1-2):55-57
GMO protein content in maize flours or fresh crops can be easily assessed by the enzyme-linked immunosorbent assays (ELISA)
and immunochromatographic (lateral flow) strip tests commercially available. Therefore, ELISA can be seen as a useful tool
for screening, for control purposes and for traceability implementation. In order to highlight the importance of monitoring
GMO protein presence in food products and to investigate the performance of representative ELISA commercial kits, we evaluated
three commercial kits by measuring the amount of Cry1Ab/Cry1Ac in IRMM certified reference materials.
Presented at AOAC Europe/Eurachem Symposium March 2005, Brussels, Belgium 相似文献
147.
Frassanito R Cantonati M Tardìo M Mancini I Guella G 《Journal of chromatography. A》2005,1082(1):33-42
The analysis and identification of a wide range of secondary metabolites biosynthesized by different algal taxa and cyanobacteria has been performed through a selective and sensitive methodology, mainly based on reversed-phase HPLC coupled both to UV photodiode array detection and to atmospheric pressure mass spectrometric techniques (HPLC-DAD-APIMS). Results are reported here with special attention to the analyses carried out both on the natural phytoplankton (mixed populations) of Lake Tovel (Northern Italy, Brenta Dolomites) and on enclosure-produced biomass of the dinoflagellate Glenodinium sanguineum Marchesoni (1941). This analytical procedure might represent a powerful tool for the fast screening of the taxonomic composition (broad groups, e.g. divisions) of natural mixed populations of phytoplankton, by providing a reliable distribution of accessory pigments extracted from microalgae, such as carotenoids and chlorophyll derivatives. Furthermore, we showed that in the same chromatographic analysis other classes of natural products, such as galactolipids, alkaloids, sterols and mycosporine-like amino acids, can be detected by using combined optical and mass spectrometric techniques. These metabolites represent distinctive biochemical signatures, sometimes even at the species level. 相似文献
148.
The method is based on the separation of Tl(I) as Tl(2)HPMo(12)O(40), stripping of the molybdate, and measurement of the peak current in differential-pulse polarography of the molybdenum. The calibration graph is linear over the range 2-12 ppm of thallium. The relative standard deviation is 1.2% (7 replicates each containing 500 microg of thallium). The current due to reduction of the molybdenum is three times that for reduction of the equivalent amount of Tl(I) in the thallous phosphomolybdate precipitate, making the indirect approach more sensitive than direct polarographic determination of the Tl(I). 相似文献
149.
This tutorial review illustrates how work on the reversible interconversion between the colorless and colored forms of photochromic compounds can be exploited to modulate electron and energy transfer processes. Indeed, a photochrome can be designed to accept electrons or energy from a complementary donor in one of its two states only. Alternatively, the photoinduced transformations associated with a photochromic switch can be engineered to control the relative orientation and distance of donor-acceptor pairs. If either the donor or the acceptor is fluorescent, the photoregulated transfer of energy or electrons results in the modulation of the emission intensity. Thus, these fascinating molecular and supramolecular systems can advance the basic understanding of electron and energy transfer processes, while leading to viable operating principles to control light with light. 相似文献
150.
[reaction: see text] We have designed a chromogenic oxazine for the colorimetric detection of cyanide. Indeed, the [1,3]oxazine ring of our compound opens to form a 4-nitrophenylazophenolate chromophore in response to cyanide. This quantitative chromogenic transformation permits the detection of micromolar concentrations of cyanide in water. Furthermore, our chromogenic oxazine is insensitive to the presence of large concentrations of fluoride, chloride, bromide, or iodide anions, which are generally the principal interferents in the colorimetric detection of cyanide. 相似文献