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61.
Giovanna Gasparri Fava Marisa Belicchi Ferrari Giorgio Pelosi Franca Zanardi Giovanni Casiraghi Gloria Rassu 《Journal of chemical crystallography》1996,26(7):509-513
The structure of 2,3-dideoxy-4-thio-d-arabino-heptonic acid 1,4-lactone has been determined by X-ray diffraction. Crystals of the compound are orthorhombic, space groupP212121, with cell dimensionsa=11.555(5),b=10.451(5),c=9.604(5) Å, andZ=4. The diffraction experiment has allowed to assign the absolute configuration (4R, 5R, 6R) to the chiral centers of the molecule. 相似文献
62.
Sandor Divenyi Marcelo A. Savi Hans I. Weber Luiz Fernando P. Franca 《Chaos, solitons, and fractals》2008,38(3):685-695
Non-smooth characteristics are, in general, the source of difficulties for the modeling and simulation of natural systems. These characteristics are usually related to either the friction phenomenon or the discontinuous behavior as intermittent contacts. This article develops an experimental investigation concerning non-smooth systems with discontinuous support. An experimental apparatus is developed in order to analyze the nonlinear dynamics of a single-degree of freedom system with discontinuous support. The apparatus is composed by an oscillator constructed by a car, free to move over a rail, connected to an excitation system. The discontinuous support is constructed considering mass–spring systems separated by a gap to the car position. This apparatus is instrumented to obtain all the system state variables. System dynamical behavior shows a rich response, presenting dynamical jumps, bifurcations and chaos. Different configurations of the experimental set up are treated in order to evaluate the influence of the internal impact within the car and also support characteristics in the system dynamics. 相似文献
63.
de Pasquale F Testa C Soldaini R Casieri C Podo F De Luca F 《Magnetic resonance imaging》2005,23(4):577-584
We propose an application of a Bayesian methodology to dynamic MR images of protons J-coupled to 13C nuclei for monitoring the in vivo 13C-glucose uptake of mouse brain. The very low population of these protons and the random noise make the analysis of these images extremely difficult. The proposed method restores the images and provides an "activation" map of the mouse brain by means of a hypothesis testing procedure. The restoration step is performed in the Bayesian framework so that among the other advantages of a stochastic approach, it is possible to model spatial and temporal information about neighboring pixels. This leads to a restoration procedure able to reduce the noise level while preserving the information about the edges of signal areas. Based on the restored images, the testing procedure provides us with a reliable map of pixels characterized by the 13C-glucose uptake. 相似文献
64.
Franca Graiff 《Annali di Matematica Pura ed Applicata》1971,89(1):65-84
Sunto Dopo aver definito le coordinate intrinseche in una generica varietà riemanniana viene costruita una variazione del tensore
fondamentale che lascia invariate le coordinate stesse. Viene quindi dimostrato che la conoscenza di questa deformazione rende
possibile la costruzione di un tensore doppio simmetrico avente data divergenza: cioè fornisce un integrale particolare delle
equazioni della statica dei continui comunque curvi a due e tre dimensioni, in presenza di forze di campo.
Viene inoltre mostrato che tale integrale particolare serve per costruire l’integrale generale delle equazioni stesse, e delle
analoghe in assenza di forze di campo. Si può ottenere così anche l’integrale generale delle equazioni della dinamica dei
continui negli spazi-tempo della Relatività generale.
Entrata in Redazione il 19 aprile 1971. 相似文献
65.
Bruno Lunelli Gabriele Cazzoli Franca Lattanzi 《Journal of Molecular Spectroscopy》1983,100(1):174-181
Contour simulation of the gas phase infrared fundamental bands of AsCl3 led to estimated values for the first-order Coriolis constants, the vibrational frequencies, and the relative values of the vibrational transition moments. Improved values of the six independent force constants of a general quadratic force field were determined on the basis of the observed frequencies, mean amplitudes of vibration, and Coriolis and centrifugal distortion constants. The potential energy distribution over the normal modes is reported. 相似文献
66.
Franca Busulini 《Annali dell'Universita di Ferrara》1959,9(1):71-117
Riassunto In questo lavoro si studia la geometria sopra una retta con riferimento al gruppo delle congruenze, supposto non transitivo
e con diverse ipotesi di rigidità.
Si perviene a strutture algebriche di tipo generale, che suggeriscono varie operazioni di immersione e contrazione, e ciò
mantenendo sempre vivo il legame con una intuizione che sia la più generale possibile della realtà empirica.
Lavoro fatto nel gruppo di ricerca n. 25 del C.N.R.: ?Strutture algebriche e loro legami con la geometria moderna?. 相似文献
Résumé Dans cet travail on étudie la géométrie sur une droite par rapport au groupe des congruences, supposé non transitif et avec des diverses hypothèses de rigidité. On arrive à des structures algébriques d'un type général suggérant diverses opérations d'immersion et de contraction, et cela en maintenant toujours la liaison par une intuition qui soit la plus générale que possible de la réalité empirique.
Lavoro fatto nel gruppo di ricerca n. 25 del C.N.R.: ?Strutture algebriche e loro legami con la geometria moderna?. 相似文献
67.
Carru C Zinellu A Sotgia S Serra R Usai MF Pintus GF Pes GM Deiana L 《Biomedical chromatography : BMC》2004,18(6):360-366
Neopterin, a pyrazinopyrimidine compound, serves as a marker of cellular immune system activation, and it can be used as a prognostic predictor for certain types of diseases. We propose a new simple HPLC method to measure serum neopterin with highly sensitive fluorimetric detection. After TCA serum protein precipitation, the supernatant was diluted five times, injected into a C18 reversed-phase column and eluted at a flow rate of 1.5 mL/min by an isocratic water-acetonitrile (99:1) mobile phase. The natural fluorescence of the molecule was detected at excitation wavelength 353 nm and emission 438 nm. In these conditions the neopterin retention time was about 4 min. Our proposed method was compared with a validated chromatographic separation, and the obtained data of the serum neopterin from 35 healthy volunteers were analysed by Passing-Bablok regression and Bland-Altman test. Neopterin measurement in healthy subjects was also employed to investigate on its potential relationships with plasma thiols levels. 相似文献
68.
69.
Franca Marinone Albini Rita De Franco Tiziano Bandiera Pierluigi Caramella Antonino Corsaro Giancarlo Perrini 《Journal of heterocyclic chemistry》1989,26(3):757-761
Bisadducts of some aromatic nitrile oxides to pyridine are described. Crossed adducts are formed by exposure of pyridine to a couple of different nitrile oxides. 相似文献
70.
Antonino Corsaro Ugo Chiacchio Giancarlo Perrini Pierluigi Caramella Franca Marinone Albini 《Journal of heterocyclic chemistry》1989,26(6):1691-1699
A study on the acetylation and benzoylation of title compounds by quenching the corresponding 4-carbanions with acyl chlorides or esters is reported. The obtained ketones are formed as minor regioisomeric adducts in the cycloadditions of benzo and mesitonitrile oxide to methyl and phenyl vinyl ketone. The quenching with methyl chloroformate was also examined as a possible convenient route to 4-methoxycarbonyl-3-aryl-4,5-dihydroisoxazoles. 相似文献