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71.
Reina M González-Coloma A Domínguez-Díaz D Cabrera R Giménez Mariño C Rodríguez ML Villarroel L 《Natural product research》2006,20(1):13-19
A new bioactive eremophilanolide, 1alpha-tigloyloxy-8betaH,10betaH-eremophil-7(11)-en-8alpha,12-olide, was isolated from Senecio poepigii and its structure was elucidated by spectral analysis. 1alpha-Angeloyloxy-8beta-methoxy-10betaH-eremophil-7(11)-en-8alpha,12-olide was also isolated. Antifungal and insect antifeedant properties were evaluated. 相似文献
72.
Europium-doped aluminophosphate glasses prepared by the melt-quenching technique have been studied by photoluminescence (PL) and X-ray photoelectron spectroscopy (XPS). The effects of silver and tin doping, and of further thermal processing on Eu3+ ions luminescence have been assessed. For the glass system containing only europium, Eu3+ PL observed under UV excitation is suggested to occur through energy transfer from the excited glass host. After silver and tin doping, an enhanced UV excited Eu3+ PL has been indicated to occur essentially due to radiative energy transfer from isolated Ag+ ions and/or two fold-coordinated Sn centers. Since thermal processing of the material leads to a quenching effect on Eu3+ PL and Ag nanoparticles (NPs) formation due to reduction of silver ions by tin, XPS was employed in order to investigate the possibility for Eu3+→Eu2+ reduction during HT as a potential source of the PL decrease. The data points towards Ag NPs as main responsible for the observed weakening of Eu3+ PL. 相似文献
73.
Let A be an algebra whose multiplication algebra M(A) is semiprime. We prove that, except in an exceptional case, the proper closed prime ideals of A are the maximal closed ideals of A, for the closure operations π and ?. In fact, these sets agree for both closures. The same can be said in M(A) for the closure operations π and ?′. Moreover, we establish the relationships between the proper closed prime ideals of A and the ones of the algebras M(A),U and A/U, for a given ideal U of A. 相似文献
74.
75.
Jeon JY Kim YH Cabrera D Bassett J 《The Journal of the Acoustical Society of America》2008,123(6):4272-4282
Opera performance conveys both visual and auditory information to an audience, and so opera theaters should be evaluated in both domains. This study investigates the effect of static visual and auditory cues on seat preference in an opera theater. Acoustical parameters were measured and visibility was analyzed for nine seats. Subjective assessments for visual-only, auditory-only, and auditory-visual preferences for these seat positions were made through paired-comparison tests. In the cases of visual-only and auditory-only subjective evaluations, preference judgment tests on a rating scale were also employed. Visual stimuli were based on still photographs, and auditory stimuli were based on binaural impulse responses convolved with a solo tenor recording. For the visual-only experiment, preference is predicted well by measurements taken related to the angle of seats from the theater midline at the center of the stage, the size of the photographed stage view, the visual obstruction, and the distance from the stage. Sound pressure level was the dominant predictor of auditory preference in the auditory-only experiment. In the cross-modal experiments, both auditory and visual preferences were shown to contribute to overall impression, but auditory cues were more influential than the static visual cues. The results show that both a positive visual-only or a positive auditory-only evaluations positively contribute to the assessments of seat quality. 相似文献
76.
Cabrera Garcia M.; Moreno Galindo A.; Rodriguez Palacios A. 《Journal London Mathematical Society》1998,57(1):231-244
The following result is well known and easy to prove (see [14,Theorem 2.2.6]). Theorem 0. If A is a primitive associative Banach algebra, thenthere exists a Banach space X such that A can be seen as a subalgebraof the Banach algebra BL(X) of all bounded linear operatorson X in such a way that A acts irreducibly on X and the inclusionABL(X) is continuous. In fact, if X is any vector space on which the primitive Banachalgebra A acts faithfully and irreducibly, then X can be convertedin a Banach space in such a way that the requirements in Theorem0 are satisfied and even the inclusion ABL(X) is contractive. Roughly speaking, the aim of this paper is to prove the appropriateJordan variant of Theorem 0. 相似文献
77.
María I. Cabrera Patricia D. Zgolicz Ricardo J. Grau 《Reaction Kinetics and Catalysis Letters》2008,93(1):175-185
Homogeneous and biphasic hydrogenation of avermectins catalyzed by rhodium complexes in situ formed from [RhCl(COD)]2 and triphenylphosphine or sulphonated arylphosphines, respectively, was studied under mild reaction conditions. Effects of
adding TBAB and bis-QACs as phase transfer agents, Tween? 80 as non-ionic surfactant, β-cyclodextrin as inverse phase-transfer
agent, and triphenylphosphine as co-ligand, are reported for the biphasic system. 相似文献
78.
Vennapusa R Hunegnaw SM Cabrera RB Fernández-Lahore M 《Journal of chromatography. A》2008,1181(1-2):9-20
Biomass adhesion onto an adsorbent matrix or "interaction" as well as biological particle co-adhesion or "aggregation" can severely affect the overall performance of many direct-contact methods for downstream processing of bioproducts. Studies to quantitatively describe this biomass-adsorbent interaction were developed utilizing surface energetics. An indirect thermodynamic approach via contact angle and zeta potential measurements was utilized. Intact yeast cells, yeast homogenates, and disrupted bacterial paste were employed as model system. Various surfaces that are relevant to biochemical and environmental applications were characterized. The extended Derjaguin, Landau, Verwey, Overbeek (XDLVO) theory was found to appropriately predict biomass adhesion behaviour. It was observed that cell attachment onto anion-exchange supports is promoted by strong and close interaction within a secondary energy minimum followed by moderate multilayer cell aggregation. On the other hand, cell interaction with cation-exchange materials can take place within a reversible secondary energy minimum and at longer separation distance. The influence of particle charge and size, as well as the influence of the nature of the material under study were summarized in the form of energy vs. distance profiles. These investigations lead to many process-related conclusions: (a) process buffer conductivity windows can be recommended for anion-exchange chromatography (AEX) vs. cation-exchange chromatography (CEX) systems, (b) increased hydrodynamic shear is required to prevent biomass attachment onto AEX as compared to CEX, and (c) aggregation phenomena is a function of contact time and biomass concentration. Understanding biomass-adsorbent interaction at the particle (local) level is opening the pave for optimized operation of expanded bed adsorption methods at the process (macro) scale. A universal methodological approach is presented to guide both process and material design. 相似文献
79.
J. C. Maciel A. A. D. Mercês M. Cabrera W. T. Shigeyosi S. D. de Souza M. Olzon-Dionysio J. D. Fabris C. A. Cardoso D. F. M. Neri M. P. C. Silva L. B. CarvalhoJr. 《Hyperfine Interactions》2016,237(1):3
It is reported the synthesis of magnetic nanoparticles via the chemical co-precipitation of Fe 3+ ions and their preparation by coating them with polyaniline. The electronic micrograph analysis showed that the mean diameter for the nanoparticles is ~15 nm. FTIR, powder X-ray diffraction and Mössbauer spectroscopy were used to understand the chemical, crystallographic and 57Fe hyperfine structures for the two samples. The nanoparticles, which exhibited magnetic behavior with relatively high spontaneous magnetization at room temperature, were identified as being mainly formed by maghemite (γFe2O3). The coated magnetic nanoparticles (sample labeled “mPANI”) presented a real ability to bind biological molecules such as trypsin, forming the magnetic enzyme derivative (sample “mPANIG-Trypsin”). The amount of protein and specific activity of the immobilized trypsin were found to be 13±5 μg of protein/mg of mPANI (49.3 % of immobilized protein) and 24.1±0.7 U/mg of immobilized protein, respectively. After 48 days of storage at 4 °C, the activity of the immobilized trypsin was found to be 89 % of its initial activity. This simple, fast and low-cost procedure was revealed to be a promising way to prepare mPANI nanoparticles if technological applications addressed to covalently link biomolecules are envisaged. This route yields chemically stable derivatives, which can be easily recovered from the reaction mixture with a magnetic field and recyclable reused. 相似文献
80.
Protein separation during ion-exchange chromatography implies complex physicochemical events. This work has evaluated the chromatographic behaviour of a complex cell proteome on commercial agarose-based adsorbents. Various ligand types in the cation- and anion-exchange mode were studied. ANX-Sepharose, a weak anion exchanger, performed similarly to the strong anion exchanger-type materials. Proteomic tools were applied in order to understand protein separation. Experimental evidence showed a correlation between apparent isoelectric point distributions and the mobile phase conductivity. Molecular weight distributions were unaffected by the elution position. On the basis of two-dimensional electrophoresis, operational windows were described having typical minor contaminants. These could be annotated for future implementation of in silico downstream processing. 相似文献