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141.
The reagent obtained by mixing anhydrous FeCl3 and silica gel induced, in dry medium, dehydration and specific C4 → C5 ring enlargement of tertiary cyclobutanols, cyclization of olefinic alcohols and cleavage of tetrahydropyranyl ethers. 相似文献
142.
Several (diolefin)M(A) complexes (M = Rh, Ir) were prepared, where AH is 1-phenyl-3-methyl- 4-benzoylpyrazolone-5, a very stable asymmetric analogue of acetylacetone. In these complexes the diolefin could be replaced by one mole of (Ph2PCH2CH2)2, two of CO or of PPh3, or three of CNBut, while 1,10-phenanthroline displaced the chelating ligand to yield [(cyclooctadiene)Rh(phen)]+ (A)?. Some compounds X?Y (X?Y = iodine or MeI) added oxidatively yielding the corresponding trivalent species. Using 31P NMR spectra the presence of the expected steric isomers was detected in (Ph3P)(CO)Rh(A) and in (Ph3P) (CO)Rh(A)(X)(Y). 相似文献
143.
The fluoride interference on the molecular emission of boron in largely methanolic solutions introduced into flames is described. The magnitude of this influence depends on the methanol, boron and fluoride concentrations and on the apparent pH. The results are explained on the basis of gradual substitution of BO bonds by BF bonds. 相似文献
144.
Summary We consider structures (G,T,J) whereT is a tolerance (i.e. a reflexive and symmetric binary relation) on the setG (whose elements are called lines) andJ is 0271 0247 V 3 a family of sets of mutuallyT-related lines, called incidence structures with tolerance (briefly: ISTs).
We study certain operators between the tolerances on a setG and certain classes of ISTs defined onG.
Riassunto Una struttura d'incidenza con tolleranza (brevemente IST) è una terna (G,T,J) doveT è una tolleranza (cioè una relazione binaria che sia riflessiva e simmetrica) su un insieme non vuotoG (i cui elementi sono detti rette) eJ è una famiglia di insiemi 0271 0247 V 3 di rette in mutua relazioneT. In questa nota noi studiamo certi operatori tra le tolleranze su un insiemeJ e 0271 0247 V 2 certe classi di ISTs definite suG.相似文献
145.
Cleide M. F. Soares Onelia A. dos Santos Heizir F. de Castro Flavio F. de Moraes Gisella M. Zanin 《Applied biochemistry and biotechnology》2004,113(1-3):307-319
The hydrolysis of tetraethoxysilane using the sol-gel process was used to produce silica matrices, and these were tested for the immobilization of lipase from Candida rugosa by three methods: physical adsorption, covalent binding, and gel entrapment in the presence and absence of polyethylene glycol (PEG-1450). The silica matrices and their derivatives were characterized regarding particle size distribution, specific surface area, pore size distribution (Brunauer, Emmett, and Teller [B.E.T.] method), yield of grafting (thermogravimetric analyzer [TGA]), and chemical composition (Fourier transform infrared). Immobilization yields based on recovered lipase activity varied from 3.0 to 32.0%, and the highest efficiency was attained when lipase was encapsulated in the presence of PEG. 相似文献
146.
147.
The vibrational dephasing rate is calculated for H2-rare gas mixtures between 85 and 300 K. The semiclassical calculation which only considers unbounded trajectories is based on binary interaction of particles through a Lennard—Jones potential. A comparison is made with three-dimensional and with collinear results obtained when a purely repulsive potential is considered. It is shown that the temperature dependence of the vibrational dephasing rate increases monotonically as T rises. Experimental investigation of Q1 (1) Raman lines for n-H2 perturbed by neon, argon and krypton between 100 and 300 K has been realized. The comparison between calculated and measured linewidths suggests that bounded states have to be taken into account at the lowest temperatures considered here. 相似文献
148.
149.
Mikhail Agrachev Wenwen Fei Sabrina Antonello Sara Bonacchi Tiziano Dainese Alfonso Zoleo Marco Ruzzi Flavio Maran 《Chemical science》2020,11(13):3427
Singlet oxygen, 1O2, can be generated by molecules that upon photoexcitation enable the 3O2 → 1O2 transition. We used a series of atomically precise Au24M(SR)18 clusters, with different R groups and doping metal atoms M. Upon nanosecond photoexcitation of the cluster, 1O2 was efficiently generated. Detection was carried out by time-resolved electron paramagnetic resonance (TREPR) spectroscopy. The resulting TREPR transient yielded the 1O2 lifetime as a function of the nature of the cluster. We found that: these clusters indeed generate 1O2 by forming a triplet state; a more positive oxidation potential of the molecular cluster corresponds to a longer 1O2 lifetime; proper design of the cluster yields results analogous to those of a well-known reference photosensitizer, although more effectively. Comprehensive kinetic analysis provided important insights into the mechanism and driving-force dependence of the quenching of 1O2 by gold nanoclusters. Understanding on a molecular basis why these molecules may perform so well in 1O2 photosensitization is instrumental to controlling their performance.Atomically precise Au24M(SR)18 clusters were used as singlet-oxygen photosensitizers. Comprehensive kinetic analysis provided insights into the mechanism and driving-force dependence of the quenching of 1O2 by gold nanoclusters. 相似文献
150.
A number of 2-substituted-4-thiazolidinecarboxylic acid derivatives were synthesized by cyclocondensation of L-cysteine or its esters with various aldehydes, resulting from acids provided with antiinflammatory properties. In the cyclocondensation a new chiral center at C-2 position of thiazolidine ring is formed giving rise to a mixture of diastereoisomers which can be partially separated. These diastereoisomers show in solution a fast epimerisation at the same chiral center as evidenced by 1H-nmr studies. 相似文献