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排序方式: 共有134条查询结果,搜索用时 78 毫秒
11.
12.
Laura L. G. Fuentes Sarita C. Rabelo Rubens Maciel Filho Aline C. Costa 《Applied biochemistry and biotechnology》2011,163(5):612-625
The objective of this work was to determine the optimum conditions of sugarcane bagasse pretreatment with lime to increase
the enzymatic hydrolysis of the polysaccharide component and to study the delignification kinetics. The first stage was an
evaluation of the influence of temperature, reaction time, and lime concentration in the pretreatment performance measured
as glucose release after hydrolysis using a 23 central composite design and response surface methodology. The maximum glucose yield was 228.45 mg/g raw biomass, corresponding
to 409.9 mg/g raw biomass of total reducing sugars, with the pretreatment performed at 90°C, for 90 h, and with a lime loading
of 0.4 g/g dry biomass. The enzymes loading was 5.0 FPU/dry pretreated biomass of cellulase and 1.0 CBU/dry pretreated biomass
of β-glucosidase. Kinetic data of the pretreatment were evaluated at different temperatures (60°C, 70°C, 80°C, and 90°C),
and a kinetic model for bagasse delignification with lime as a function of temperature was determined. Bagasse composition
(cellulose, hemicellulose, and lignin) was measured, and the study has shown that 50% of the original material was solubilized,
lignin and hemicellulose were selectively removed, but cellulose was not affected by lime pretreatment in mild temperatures
(60–90°C). The delignification was highly dependent on temperature and duration of pretreatment. 相似文献
13.
A new, vectorial approach to fast correlation attacks on binary memoryless combiners is proposed. Instead of individual input sequences or their linear combinations, the new attack is targeting subsets of input sequences as a whole thus exploiting the full correlation between the chosen subset and the output sequence. In particular, the set of all the input sequences can be chosen as the target. The attack is based on a novel iterative probabilistic algorithm which is also applicable to general memoryless combiners over finite fields or finite rings. To illustrate the effectiveness of the introduced approach, experimental results obtained for random balanced combining functions are presentedMost of this work was done while he was with Rome CryptoDesign Center, Gemplus, Italy 相似文献
14.
The motion of a holonomic scleronomic non-conservative mechanicalsystem with minimal dissipation is considered. As applicationsof the theory several problems are studied in detail. 相似文献
15.
Rubens G. Lintz 《Annali di Matematica Pura ed Applicata》1966,72(1):45-57
Summary We study here conditions under which a homomorphism of Čech groups can be realized by generalized fonctions. 相似文献
16.
Rubens G. Lintz 《Annali di Matematica Pura ed Applicata》1966,72(1):97-103
Summary I give here a theorem of realization of homomorphism in Cech homology theory, which improves some previous results of mine. 相似文献
17.
Abstract The formation of protein aggregates after pressure treatment was investigated by Fourier Transform Infrared Spectroscopy (FTIR). The results show that the pressure unfolded protein ends in a conformation, after the release of the pressure, which has an increased tendency to aggregate, even at temperatures lower than the denaturation temperature of the untreated protein. After pressure pretreatment the infrared spectrum shows the same intermolecular antiparallel β-structure features as observed after a temperature treatment that gives rise to protein gelation. on the other hand, this structure can be destabilized by applying moderate pressures, which are significantly lower than the corresponding denaturation pressure. 相似文献
18.
da Silva Pedro Rafael Sena Laís Cristina Santana Silva Rubens Pedro Lorena de Santana Danielle Cristine Almeida Silva de Santana Fernando José Malagueño 《Analytical and bioanalytical chemistry》2019,411(16):3447-3461
Analytical and Bioanalytical Chemistry - This study aimed to determine simultaneously five major street cocaine adulterants (caffeine, lidocaine, phenacetin, diltiazem, and hydroxyzine) in human... 相似文献
19.
Summary A method for the quantitative determination of oxalic acid based onEegriwe's color test for glycolic acid is described. The principle of the method is the reduction of oxalic to glycolic acid by nascent hydrogen from magnesium powder and dilute sulfuric acid. By heating with a solution of 2,7-dihydroxynaphthalene in concentrated sulfuric acid formaldehyde splitt off from glycolic acid condensates with the reagent, tetrahydroxydinaphthylmethane forms and is oxidized to a deep colored dye-stuff by atmospheric oxygen.A study of interfering substances and the way of avoiding their influence was made.The color system, under the conditions of the method, follows theLambert-Beer's law. With the exception of a photoelectric colorimeter, no special equipment is required. The procedure is very simple, possesses great sensitivity, and may be applied with minor variations to a wide variety of materials.
Zusammenfassung Es wird ein Verfahren zur quantitativen Bestimmung der Oxalsäure beschrieben, das auf der Farbreaktion nachEegriwe für Glykolsäure beruht. Das Prinzip der Methode beruht auf der Reduktion der Oxalsäure zu Glykolsäure durch nascierenden Wasserstoff aus Magnesiumpulver und verd. Schwefelsäure. Durch Erhitzen mit einer Lösung von 2,7-Dioxynaphthalin in konz. Schwefelsäure wird der abgespaltene Formaldehyd mit dem Reagens kondensiert. Es bildet sich Tetraoxydinaphthylmethan, welches durch den Luftsauerstoff zu einem intensiv gefärbten Produkt oxydiert wird. Der Einfluß störender Substanzen und dessen Vermeidung werden untersucht. Die Farbreaktion folgt unter den geschilderten Versuchsbedingungen demLambert-Beerschen Gesetz. Mit Ausnahme eines photoelektrischen Kolorimeters ist kein besonderer Aufwand erforderlich. Die Methode ist sehr einfach und von großer Empfindlichkeit. Sie kann mit geringfügigen Abänderungen für verschiedenartiges Untersuchungsmaterial angewendet werden.
Résumé On décrit une méthode pour le dosage quantitatif de l'acide oxalique, basé sur le test coloré d'Eegriwe pour l'acide glycolique. Le principe de la méthode repose sur la réduction de l'acide oxalique en acide glycolique par l'hydrogène naissant produit avec le magnésium en poudre et l'acide sulfurique dilué. En chauffant avec une solution de dihydroxy-2,7 naphtalène dans l'acide sulfurique concentré, le formaldéhyde se libère du produit de condensation entre l'acide glycolique et le réactif; le tétrahydroxydinaphtylméthane se forme et s'oxyde en une matière colorante foncée sous l'action de l'oxygène atmosphérique.On a fait une étude des substances interférentes et de la manière d'éviter leur influence.Le système coloré, dans les conditions de la méthode, suit la loi deLambert-Beer. A l'exception d'un colorimètre photoélectrique, aucun équipement spécial n'est nécessaire. Le mode opératoire est très simple, possède une grande sensibilité et peut être appliqué avec de minimes variations à un grand nombre de substances.相似文献
20.
Eliton S. Medeiros Luiz H. C. Mattoso Rubens Bernardes-Filho Delilah F. Wood William J. Orts 《Colloid and polymer science》2008,286(11):1265-1272
Nanostructured films of poly(o-ethoxyaniline) (POEA) alternated with cellulose nanofibrils (CnF) were successfully produced
by self assembly (SA) at different pH values and investigated by atomic force microscopy and ultraviolet-visible spectroscopy.
Results show that it was possible to build up films by alternating POEA and CnF layers with relatively precise architectural
control by controlling the number of layers and pH. Film thickness had a dependence on pH which is a combination of the effects
of the deposited amount for each POEA layer and the pH at which the absorption of the cellulose nanofibrils was carried out.
Comparison of alternated layers of POEA and CnF with multi-immersions of POEA at different pH values, as measured by the ratio
between slopes of the straight lines of deposited amount of polymer versus the number of self-assembled layers, shows that
alternate deposition at pH 2 has a fourfold increase in the slope. Alternatively, at pH 5, there is no significant difference
whether the deposition is alternated (POEA–CnF) or not (POEA). 相似文献