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It is shown that the set of timelike curves in a globally hyperbolic space-time manifold can be given the structure of a Hubert manifold under a suitable definition of timelike. The causal curves are the topological closure of this manifold. The Lorentzian energy (corresponding to Milnor's energy, except that the Lorentzian inner product is used) is shown to be a Morse function for the space of causal curves. A fixed end point index theorem is obtained in which a lower bound for the index of the Hessian of the Lorentzian energy is given in terms of the sum of the orders of the conjugate points between the end points. 相似文献
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Philip J. Everson Carl N. Morris 《Journal of computational and graphical statistics》2013,22(2):380-389
Abstract This article provides an efficient algorithm for generating a random matrix according to a Wishart distribution, but with eigenvalues constrained to be less than a given vector of positive values. The procedure of Odell and Feiveson provides a guide, but the modifications here ensure that the diagonal elements of a candidate matrix are less than the corresponding elements of the constraint vector, thus greatly improving the chances that the matrix will be acceptable. The Normal hierarchical model with vector outcomes and the multivariate random effects model provide motivating applications. 相似文献
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Ana Valria de Oliveira Braz Mariana Carvalho Rodrigues Philippe Alencar Araújo Maia Ana Paula Dantas Pereira Jussara de Lima Silva Francisco Antonio Vieira dos Santos Luiz Everson da Silva Wanderley do Amaral Maura Lins dos Santos Henrique Douglas Melo Coutinho Tomasz Baj Grayna Kowalska Radosaw Kowalski Edinardo Fagner Ferreira Matias 《Molecules (Basel, Switzerland)》2022,27(18)
Commercialized mouthwashes are generally expensive for the most financially vulnerable populations. Thus, several studies evaluate the antimicrobial potential of herbal products, such as essential oils, to reduce the activity of microorganisms in the mouth. The objective of this research was to carry out the chemical characterization and antibacterial activity of the essential oil of Piper mosenii (EOPm), providing data that enable the development of a low-cost mouthwash formulation aimed at vulnerable communities. The analysis of the antibacterial potential and modulator of bacterial resistance was verified by the microdilution method to determine the minimum inhibitory concentration-MIC. The chemical components were characterized by gas chromatography coupled to mass spectrometry, where 23 chemical constituents were detected, with α-pinene, being the major compound. The EOPm showed a MIC ≥ 1024 µg/mL for all bacterial strains used in the tests. When the EOPm modulating activity was evaluated together with chlorhexidine, mouthwash and antibiotics against bacterial resistance, the oil showed a significant synergistic effect, reducing the MIC of the products tested in combination, in percentages between 20.6% to 96.3%. Therefore, it is recommended to expand the tests with greater variation of EOPm concentration and the products used in this research, in addition to the evaluation of toxicity and in vivo tests, seeking the development of a possible formulation of mouthwash accessible to the vulnerable population. 相似文献
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Fontana Jose D. Beck Roland Baron Madalena de Almeida Eduardo R. A. Nogoceke Everson 《Applied biochemistry and biotechnology》1993,39(1):249-263
Applied Biochemistry and Biotechnology - Enzymatic coupling of aminopolyols and medium-chain length fatty acids was carried out via the reverse action of a fungal lipase. Model reactants and... 相似文献
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John R. Peterson Terrence P. Everson Robin D. Rogers 《Journal of chemical crystallography》1990,20(1):37-45
CompoundA is (1,2,4)-1,2-diacetoxy-4-(4-methoxyphenyl)-6-methoxy-l,2,3,4-tetrahydronaphthalene, C22H24O6,M
r=384.43, monoclinic, P21/n, witha=11.074(3),b=10.353(4),c=17.616(4)Å,=94.96(2)°,V=2012.1Å3,D
calc=1.27 g cm–3 and=0.55 cm–1 forZ=4. Least-squares refinement of 1371 observed [F
05 (F
0)] reflections led to the final agreement index ofR=0.052. A twofold disorder was observed for the 1-acetoxy group whereas the 2-acetoxy group was ordered. CompoundB, (1,2,4)-1,2-diacetoxy-4-(2-methoxyphenyl)-8-methoxy-l,2,3,4-tetrahydronaphthalene, C22H24O6,M
r=384.43, crystallizes in the monoclinic space group, P21/c, witha=16.209(2),b=10.076(1),c=13.357(4)Å,=111.41(2)°,V=2030.9Å3,D
calc=1.26 g cm–3 and=0.54 cm–1 forZ=4. A final agreement index ofR=0.045 was realized by least-squares refinement of 1486 observed [F
o5 (F
o)] reflections. Intermolecular interactions in the cell lattices of compoundsA andB are noted. The title compoundsA andB were prepared by manganese(III) acetate oxidative dimerization of two molecules of 4-methoxystyrene and 2-methoxystyrene, respectively. 相似文献
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Everson Kandare Baljinder K. Kandola Dennis Price Shonali Nazaré Richard A. Horrocks 《Polymer Degradation and Stability》2008,93(11):1996-2006
The thermal degradation behaviours of flame-retarded unsaturated polyester resin formulations containing ammonium polyphosphate (APP), Cloisite 25A nanoclay and zinc based smoke suppressants have been studied using thermogravimetric analysis (TGA) combined with infrared analysis of the evolved gases (EGA) and pyrolysis/gas chromatography-mass spectrometry (GC/MS). In TGA-EGA experiments, the mass loss as a function of temperature has been correlated with the evolution of carbon monoxide (CO) and carbon dioxide (CO2) and oxygen (O2) consumption as measured by an oxygen analyser. The effect of APP, Cloisite 25A and the smoke suppressants on the evolution of CO and CO2 has been examined. The decomposition behaviour of flame-retarded polyester resins under isothermal pyrolytic conditions was investigated and the evolved gaseous products were collected and qualitatively and semi-quantitatively analysed via GC/MS. The addition of APP does not yield many new gaseous products relative to the unmodified polyester resin neither does the presence of zinc borate (ZB) and zinc stannate (ZS) together with APP. Possible chemical interactions are discussed in an attempt to explain the observed results. 相似文献
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Reactions catalyzed by supported enzymes present important advantages when compared with those in aqueous media or organic
solvents: separation of enzymes from substrate is easily accomplished, enzyme stability may be improved, and control of the
reaction products is more accurate. We present the experimental results of the kinetic study of ethyl acetate hydrolysis in
gaseous phase catalyzed by a commercial immobilized lipase (Lipozyme IM; Novo Nordisk). The hydrolysis reaction was studied
as a function of ethyl ester and water partial pressure at a constant temperature of 318 K. The amount of biocatalyst used
was varied between 100 and 300 mg, and the reaction was studied in a flow-through glass microreactor. Under the conditions
used, water was an important parameter in the gas-phase reaction. Activation energy was 24.8 kJ/mol and the overall order
of reaction was one. Finally a Bi-Bi reaction mechanism is proposed. 相似文献