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961.
962.
Tino Rossi Daniele Andreotti Bruno Tamburini Carla Marchioro 《Journal of heterocyclic chemistry》1994,31(4):909-915
The synthesis of a series of 6,6-disubstituted penems starting from penicillanate 5a is described. These penems were isolated and characterized as their pivaloyloxy methyl ester. 相似文献
963.
Nelson Dur’an Adriane M. F. Mllagres Elisa Esposito Emilia Curotto Carolina Aguirre Maria Francisca S. Teixeira Sonia M. S. Carvalho Ormezinda C. C. Fernandes 《Applied biochemistry and biotechnology》1995,53(2):155-162
A plate-agar technique for fungal screening was applied to evaluate the xylanolytic activities of 18Penicillium janthinellum and 10Aspergillus sydowi species from the Amazon region. In order to compare these genera with those of other regions, oneAspergillus sp., one P.janthinellum, and 12 unknown genera from the southern region of Chile were studied. From these fungi strain,A. sydowi (56 strain) (25.2 IU/mL),P. janthinellum (671 strain) (47.3 IU/mL) from Amazonia,P. janthinellum (X4Z2 strain) (9.5 IU/mL), and anAspergillus sp. (X2M1 strain) (33.3 IU/mL) from the southern region of Chile were identified. 相似文献
964.
Elisa Guagenti Grandori 《Milan Journal of Mathematics》1982,52(1):283-297
In this paper three problems of seismic risk reduction are discussed. They pertain to three different temporal phases of intervention: the definition of design seismic coefficients (long term), the antiseismic strenghtening of existing constructions (medium term), the alarm for a possible forthcoming earthquake (short term). The characteristics of the stochastic models that can represent these seismic events are different in the three cases: the stochastic process is stationary in the first case, with memory in the second case, with memory and external information in the third case. If a renewal process is assumed in the second case, the other two processes are obtained by adding suitable hypoteses. Finally, it is examined how the stochastic hypotheses affect the evaluation of future damage. 相似文献
965.
966.
Elisa Perissutti Francesco Frecentese Ferdinando Fiorino Beatrice Severino Donatella Cirillo Vincenzo Santagada Giuseppe Caliendo 《Journal of heterocyclic chemistry》2007,44(4):815-819
967.
968.
The aim of this study was to prepare air-filled nanocapsules intended ultrasound contrast agents (UCAs) with a biodegradable polymeric shell composed of poly(d,l-lactide-co-glycolide) (PLGA). Because of their size, current commercial UCAs are not capable of penetrating the irregular vasculature that feeds growing tumors. The new generation of UCAs should be designed on the nanoscale to enhance tumor detection, in addition, the polymeric shell in contrast with monomolecular stabilized UCAs improves the mechanical properties against ultrasound pressure and lack of stability. The preparation method of air-filled nanocapsules was based on a modification of the double-emulsion solvent evaporation technique. Air-filled nanocapsules with a mean diameter of 370 ± 96 nm were obtained. Electronic microscopies revealed spherical-shaped particles with smooth surfaces and a capsular morphology, with a shell thickness of ∼50 nm. Air-filled nanocapsules showed echogenic power in vitro, providing an enhancement of up to 15 dB at a concentration of 0.045 mg/mL at a frequency of 10 MHz. Loss of signal for air-filled nanocapsules was 2 dB after 30 min, suggesting high stability. The prepared contrast agent in this work has the potential to be used in ultrasound imaging. 相似文献
969.
Caballero AB Rodríguez-Diéguez A Lezama L Barea E Salas JM 《Dalton transactions (Cambridge, England : 2003)》2011,40(19):5180-5187
Conventional reactions of the versatile multidentate ligand 5-methyl-1,2,4-triazolo[1,5-a]pyrimidin-7(4H)-one (HmtpO) with metallic(II) salts lead to three novel multidimensional complexes [Cu(HmtpO)(2)(H(2)O)(3)](ClO(4))(2)·H(2)O (1), {[Cu(HmtpO)(2)(H(2)O)(2)](ClO(4))(2)·2HmtpO}(n) (2) and {[Co(HmtpO)(H(2)O)(3)](ClO(4))(2)·2H(2)O}(n) (3). In each compound, the triazolopyrimidine ligand shows a different and unusual coordination mode, giving rise to structures with diverse topologies and dimensionality. Compound 1 is a monomeric complex, in which HmtpO shows both N3-monodentate and N1,O71-bidentate modes. 2 is a bidimensional framework with the ligand showing a N3,O71 bidentate-bridging mode. The structure of 3 consists of 1D chains, in which HmtpO displays a N1,N3,O71-tridentate-bridging mode. It should be noted that these coordination modes of the HmtpO ligand are unique in the case of compounds 2 and 3. On the other hand, the magnetic properties of the polynuclear complexes 2 and 3 have been studied showing weak ferromagnetic and antiferromagnetic behaviour, respectively. 相似文献
970.
de Araújo ME Contesini FJ Franco YE Sawaya AC Alberto TG Dalfré N Carvalho Pde O 《Molecules (Basel, Switzerland)》2011,16(8):7171-7182
Response surface methodology (RSM) based on a five-level, three-variable central composite design (CCD) was employed for modeling and optimizing the conversion yield of the enzymatic acylation of hesperidin with decanoic acid using immobilized Candida antarctica lipase B (CALB) in a two-phase system containing [bmim]BF(4). The three variables studied (molar ratio of hesperidin to decanoic acid, [bmim]BF(4)/acetone ratio and lipase concentration) significantly affected the conversion yield of acylated hesperidin derivative. Verification experiments confirmed the validity of the predicted model. The lipase showed higher conversion degree in a two-phase system using [bmim]BF(4) and acetone compared to that in pure acetone. Under the optimal reaction conditions carried out in a single-step biocatalytic process when the water content was kept lower than 200 ppm, the maximum acylation yield was 53.6%. 相似文献