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1.
Daniele Mazza Maria Lucco-Borlera Esterina Lepore Silvia Ronchetti 《Journal of Thermal Analysis and Calorimetry》1996,46(6):1625-1632
A calorimetric method is proposed to evaluate the catalytic activity of a solid catalyst with respect to the exothermic oxidation of Volatile Organic Compounds (VOC).This method employs a differential thermal analyzer in which an inert reference and a catalytically active sample are both fluxed at a constant rate with a reactive gaseous mixture composed of an inert gas (N2 90% vol.), oxygen and VOC, the last typically 900 to 5000 ppm. While the temperature is varied according to a predefined cycle, the output signal due to the exothermic reaction on the catalyst is continuously recorded. The design of the test chamber, the amount of catalyst, the shape of the holders and finally the flow rate and composition of the gaseous mixture should be carefully selected in order to achieve reproducible results. 相似文献
2.
This paper introduces a mathematical model which makes it possible both to determine the concentration of photosynthetic herbicides and to obtain a quantitative parameter in order to compare their activity using a previously described sensing system. The working principle involves the changes in absorption properties at 860 nm of the reaction centre (RC) isolated from the bacteria Rhodobacter sphaeroides when photosynthetic herbicides are present. The method has been used for the determination and activity comparison of five photosynthetic herbicides: diuron, atrazine, terbutryn, terbuthylazine and simazine. Detection limits obtained were 2.2, 0.75, 0.046, 0.25, and 1.4 μM, respectively. The resulting order for the different herbicides according to their action on RC was: terbutryn > terbuthylazine > atrazine > simazine > diuron. 相似文献
3.
Further exploration of the scope of our solid-phase method for the synthesis of 3-aminobenzisoxazoles (using the Kaiser oxime resin 1) is described. The effects of base, leaving group, and solvent on the nucleophilic aromatic substitution based resin-loading reaction are discussed. Representative aryloxime intermediates were subjected to a variety of acidic conditions commonly used in protecting group removal to establish the acid stability profile of this linker. Regioselectivity was evaluated with various di- and trifluorobenzonitriles, which gave single benzisoxazole products after loading and cyclorelease reactions. Substituent effects observed in the course of the acid stability and regioselectivity studies suggest that the nitrile plays a critical role in the oxime hydrolysis mechanism. Finally, to establish the compatibility of the aryloxime linker with a variety of useful on-resin synthetic transformations, functionalized substrates were loaded onto resin 1, and carbon-nitrogen, carbon-oxygen, and carbon-carbon bond-forming reactions were successfully executed. 相似文献
4.
The very important engineering problem of modeling the fluid-structure interaction occurring during the shedding of vortices has defied, and will probably continue to defy, a closed form exact solution for the foreseeable future. Therefore, an attempt must be made to extract relevant information about the process in order to be able to have a basic understanding of it for the purpose of analysis. A useful method involves the flow-oscillator concepts of Hartlen and Currie [1] redefined here for stochastic processes. The fluid-structure system is assumed to be governed by the cross-coupled equations where these equations govern the structure and fluid oscillators, respectively. The fluid damping is non-linear. These equations are taken as stochastic differential equations because of the many unpredictable, random effects that determine the loading and response. The lift coefficient C(t) is assumed to be a zero mean, narrow band process and the velocity V0, composed of a uniform, constant velocity current plus oscillating wave, a broad band process. The analysis is based on solving equation (i) for x(t) by using Duhamel's integral and substituting its derivative into equation (ii). This equation is then used to derive the Fokker-Planck equation for the process C(t). To obtain the Fokker-Planck equation, slowly varying variables are replaced by their long-time averages [2] and then the method of stochastic averaging is employed [3, 4]. The moment equation for the lift-oscillator process is derived from the Fokker-Planck equation and, as equation (ii) is non-linear, one finds the moment equation to be in terms of higher order moments. A truncation scheme [5] is used to derive the moment generating function. It is possible then to generate the first and second order statistics of the lift coefficient and the structure response in terms of the empirical parameters of fluid damping. This work was carried out in conjunction with an analysis of ocean wave-current forces with application to offshore fixed structures [6]. 相似文献
5.
6.
Animesh Roy Maximilian A. Silvestri Robert A. Hall Salvatore D. Lepore 《Tetrahedron letters》2017,58(1):106-108
In the attempt to synthesize substituted allenyl esters through a metathesis coupling of unsubstituted allenyl esters and alkenes using a variety of ruthenium catalysts, it was discovered that allenyl esters themselves cleanly arrested the activity of the catalysts. Further studies suggests possible utility of allene esters as general quenching agents for metathesis reactions. To explore this idea, several representative olefin metathesis reactions, including ring closing, were successfully terminated by the addition of simple allenyl esters for more convenient purification. 相似文献
7.
A second-order interferometric experiment in which de Broglie waves pass through a set of beamsplitters and progressively
lose intensity, leading to a decrease in the visibility, is presented. On the contrary, since the intensity reduction is the
same in the two overlapping waves, quantum mechanics predicts a constant visibility. 相似文献
8.
García-Domínguez P Lepore I Erb C Gronemeyer H Altucci L Álvarez R de Lera AR 《Organic & biomolecular chemistry》2011,9(20):6979-6987
The purported structures of the peyssonenynes A and B isolated from Peyssonnelia caulifera, and considered to be geometric isomers at the acetoxyenediyne moiety, have been synthesized. The E and Z geometries of the synthetic compounds were secured by the magnitude of the (3)J(H9-C7) values measured using the EXSIDE band-variant of the gradient HSQC pulse sequence and by the chemical shifts of C(6). Comparison of the NMR data of the synthetic and natural products revealed that only those of the Z isomers matched, which correspond to peyssonenyne A. Using HPLC analysis it was found that peyssonenyne B must correspond to the sn-2 positional isomer of the Z sn-1/3 counterpart. The four synthetic sn-1/3 diastereomers are roughly equipotent as DNMT1 inhibitors when evaluated on a radioactive methyl transfer enzymatic assay after immunoprecipitation from K562 human leukemia cells with anti-DNMT1 antibody. 相似文献
9.
Birarda Giovanni Delneri Ambra Lagatolla Cristina Parisse Pietro Cescutti Paola Vaccari Lisa Rizzo Roberto 《Analytical and bioanalytical chemistry》2019,411(27):7315-7325
Analytical and Bioanalytical Chemistry - Biofilms are communities of bacteria living embedded in a highly hydrated matrix composed of polysaccharides, proteins, and extracellular DNA. This life... 相似文献
10.
High performance ion chromatography of haloacetic acids on macrocyclic cryptand anion exchanger 总被引:1,自引:0,他引:1
Bruzzoniti MC De Carlo RM Horvath K Perrachon D Prelle A Tófalvi R Sarzanini C Hajós P 《Journal of chromatography. A》2008,1187(1-2):188-196
A new high performance ion chromatographic method has been developed for the separation of the nine chlorinated-brominated haloacetic acids (HAAs) that are the disinfection by-products of chlorination of drinking water, using a macrocycle-based adjustable-capacity anion-exchange separator column (IonPac Cryptand A1). A gradient method based on theoretical and experimental considerations has been optimized in which 10 mM NaOH-LiOH step gradient was performed at the third minute of the analysis. The optimized method allowed us to separate the nine HAAs and seven possibly interfering inorganic anions in less than 25 min with acceptable resolution. The minimum concentrations detectable for HAAs were between 8.0 (MBA) and 210 (TBA) microg L(-1), with linearity included between 0.9947 (TBA) and 0.9998 (MBA). To increase sensitivity, a 25-fold preconcentration step on a reversed phase substrate (LiChrolut EN) has been coupled. Application of this method to the analysis of haloacetic acids in real tap water samples is illustrated. 相似文献