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41.
42.
This review covers the literature on the chemically mediated ecology of cyanobacteria, including ultraviolet radiation protection, feeding-deterrence, allelopathy, resource competition, and signalling. To highlight the chemical and biological diversity of this group of organisms, evolutionary and chemotaxonomical studies are presented. Several technologically relevant aspects of cyanobacterial chemical ecology are also discussed. 相似文献
43.
Gouveia CA Oliveira A Pinho S Vasconcelos C Carvalho F Moreira RF Dinis-Oliveira RJ 《Biomedical chromatography : BMC》2012,26(8):1041-1047
The development of analytical techniques that enable the use of hair as an alternative matrix for the analysis of drugs of abuse is useful for confirming the exposure in a larger time window (weeks to months, depending on the length of the hair shaft). In the present study a methodology aimed at the simultaneous quantification of cocaine and morphine in human hair was developed and validated. After decontamination, hair samples (20?mg) were incubated with a mixture of methanol/hydrochloric acid (2:1) at 65?°C overnight (~16?h) in order to extract the drugs of the matrix. Purification was performed by solid-phase extraction using mixed-mode extraction cartridges. After derivatization with N-methyl-N-(trimethylsilyl) trifluoroacetamide, blank, standards and samples were analyzed by gas chromatography/electron impact-mass spectrometry (GC-EI/MS). The method proved to be selective, as there were no interferences of endogenous compounds with the same retention time as cocaine, morphine and ethylmorphine (internal standard). The regression analysis for both analytes showed linearity in the range 0.25-10.00?ng/mg with correlation coefficients ranging from 0.9989 to 0.9991. The coefficients of variation oscillated between 0.83 and 14.60%. The limits of detection were 0.01 and 0.02?ng/mg, and the limits of quantification were 0.03 and 0.06?ng/mg for cocaine and morphine, respectively. The proposed GC-EI/MS method provided an accurate and simple assay with adequate precision and recovery for the quantification of cocaine and morphine in hair samples. The proof of applicability was performed in hair samples obtained from drug addicts enrolled in a Regional Detoxification Treatment Center. The importance of hair samples is highlighted, since positives results were obtained when urine immunoassay analyses were negative. Copyright ? 2012 John Wiley & Sons, Ltd. 相似文献
44.
Daniela C.L. Vasconcelos Eduardo H.M. Nunes Wander L. Vasconcelos 《Journal of Non》2012,358(11):1374-1379
In this work we obtained sol–gel alumina coatings on AISI 304 stainless steel substrates. Alumina sols were prepared by using aluminum isopropoxide (AI) as precursor, acetic acid (HOAc) as catalyst, ethanol (C2H5OH) or isopropanol (C3H8O) as solvent, and water. The as-prepared solutions were deposited on stainless steel substrates by means of the dip-coating technique. The obtained composites were characterized by Fourier transform infrared spectroscopy (FTIR) and Auger electron spectroscopy (AES). We observed that the concentration of AlO type bonds in the obtained alumina coatings depends on the solvent type used, temperature and peptization state of the sol, withdrawal speed, and number of dipping cycles. AES experiments showed that the interface formed between the alumina coating and substrate surface is in general formed by several layers of different chemical compositions. 相似文献
45.
de Vasconcelos MA Cunha CO Arruda FV Carneiro VA Mercante FM do Nascimento Neto LG de Sousa GS Rocha BA Teixeira EH Cavada BS dos Santos RP 《Molecules (Basel, Switzerland)》2012,17(5):5244-5254
To study the interactions between a Rhizobium tropici strain and lectins isolated from the seeds of Canavalia ensiformis (ConA) and Canavalia brasiliensis (ConBr), a lectin fluorescence assay was performed. In addition, an experiment was designed to evaluate the effect of the two lectins on bacterial growth. Both lectins were found to bind to R. tropici cells, but the interactions were inhibited by D-mannose. Interestingly, only ConBr stimulated bacterial growth in proportion to the concentrations used (15.6-500 μg/mL), and the bacterial growth stimulation was inhibited by D-mannose as well. Structure/Function analyses by bioinformatics were carried out to evaluate the volume and carbohydrate recognition domain (CRD) configuration of ConA and ConBr. The difference of spatial arrangement and volume of CRD may indicate the variation between biological activities of both lectins. The results suggest that ConBr could be a promising tool for studies focusing on the interactions between rhizobia and host plants. 相似文献
46.
In this work we will address the problem of finding spectral values and bases for the corresponding spectral subspaces for a bounded operator on a Banach space. We will make a bridge between the spectral problem for the continuous operator and the computation of the eigenpairs of a matrix. This approximate problem results first from an approximation by a sequence of continuous operators with finite rank, followed by the reduction to a spectral problem for an operator whose domain as well as range are finite dimensional. Some discussion on defect correction procedures will be also presented. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
47.
The set of Hilbert functions of standard graded algebras is considered as a partially ordered set under numerical comparison. For the set of algebras H(d, e0), of a given dimension d and multiplicity e0, we describe the requirements its maximal elements must satisfy; under fairly general conditions, the extremal functions arise from Cohen-Macaulay algebras. We also examine the subset H(d, e0, e1), of those functions whose first two coefficients of their Hilbert polynomials are assigned. Finally, we show how these results and the use of certain extended multiplicities can be used to prove finiteness theorems for the number of corresponding functions. 相似文献
48.
Malucelli L. C. Carneiro J. Vasconcelos E. C. Magalhães W. L. E. Murakami F. S. Carvalho Filho M. A. S. 《Journal of Thermal Analysis and Calorimetry》2020,141(3):1149-1155
Journal of Thermal Analysis and Calorimetry - The use of biomass has been a recent trend as a potential feedstock for char generation with improved energetic value. In this work, agricultural... 相似文献
49.
The triglyceride profiles for corn, soybean, sunflower, grapestone, olive and olive husks oils were obtained by high temperature capillary gas chromatography on HT-FS capillary columns coated with OV-17-OH. The data were treated by methods of computerized pattern analysis, involving principal component analysis, discriminant analysis, and hierarchical clustering. A graphical representation of results as “star symbol plots” allows prompt visual recognition of the characteristic profiles and straightforward qualitative identification of unknowns as well as recognition of adulterations. 相似文献
50.
For a finitely generated moduleE over the Noetherian ringR we consider formulas for the Krull dimension of the symmetric algebraS(E). A result of Huneke and Rossi is re-proved and an effective formula is derived that reads the dimension ofS(E) from a presentation ofE. They provide a first line of obstructions forS(E) to be an integral domain. For algebras of codimension at most four we give methods, including computer-assisted ones, to ascertain whetherS(E) is a Cohen-Macaulay domain.AMS 1980 Mathematics Subject Classification (1985 Revision). Primary 13H10; Secondary 13-04, 13C05, 13C15Partially supported by CNPq, BrazilPartially supported by the NSF 相似文献