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排序方式: 共有211条查询结果,搜索用时 361 毫秒
91.
Terry JM Mohr S Fielden PR Goddard NJ Barnett NW Olson DC Wolcott DK Francis PS 《Analytical and bioanalytical chemistry》2012,403(8):2353-2360
We have examined a range of new and previously described flow cells for chemiluminescence detection. The reactions of acidic potassium permanganate with morphine and amoxicillin were used as model systems representing the many fast chemiluminescence reactions between oxidising agents and organic analytes, and the preliminary partial reduction of the reagent was exploited to further increase the rates of reaction. The comparison was then extended to high-performance liquid chromatography separations of α- and β-adrenergic agonists, with permanganate chemiluminescence detection. Flow cells constructed by machining novel channel designs into white polymer materials (sealed with transparent films or plates) have enabled improvements in mixing efficiency and overall transmission of light to the photodetector. 相似文献
92.
Miroslav Mirchev Gregory S. Duane Wallace K.S. Tang 《Communications in Nonlinear Science & Numerical Simulation》2012,17(7):2741-2751
Most of the existing approaches for combining models representing a single real-world phenomenon into a multi-model ensemble combine the models a posteriori. Alternatively, in our method the models are coupled into a supermodel and continuously communicate during learning and prediction. The method learns a set of coupling coefficients from short past data in order to unite the different strengths of the models into a better representation of the observed phenomenon. The method is examined using the Lorenz oscillator, which is altered by introducing parameter and structural differences for creating imperfect models. The short past data is obtained by the standard oscillator, and different weight is assigned to each sample of the past data. The coupling coefficients are learned by using a quasi-Newton method and an evolutionary algorithm. We also introduce a way for reducing the supermodel, which is particularly useful for models of high complexity. The results reveal that the proposed supermodel gives a very good representation of the truth even for substantially imperfect models and short past data, which suggests that the super-modeling is promising in modeling real-world phenomena. 相似文献
93.
Gold nanoparticles have been precipitated on the surface of quartz slides covered with titanium (IV) butoxide. UV irradiation
of modified quartz slides immersed into water solutions of hydrogen tetrachloroaurate of different concentrations (2.5 × 10−4–1.0 × 10−2 M) has been used for this purpose. Properties of produced samples have been investigated by UV–Vis spectroscopy, IR spectroscopy,
SEM-EDX, TGA, and AFM. According to the obtained data, produced gold particles are distributed on modified quartz surface
very uniformly and the average size of gold particles is about 30–50 nm. 相似文献
94.
A formulation describing the rheology of crystallising polymers is discussed. For some semi-crystalline polymers where spherulites
form as part of the crystallisation process, the use of a suspension-type model is appropriate. Whilst it is possible to so
describe simple shearing and elongational rheology during on-going crystallisation with such models, the flow through a capillary
tube is much more complex and numerical solution is usually necessary. To give some insight into this complex flow, a ‘step
function’ or ‘amorphous-frozen’ model of the viscosity changes due to crystallisation has been devised so that a semi-analytical
approach is feasible. We use this simple model and compare the results with recently published experiments in tubes and channels
at high (O(103 s − 1)) shear rates using poly(butene-1). A direct correlation between simple shear and tube flow crystallisation onset times is
found. 相似文献
95.
Sven Mahnkopf Duane A. Louderback Dhiraj Kumar Peter S. Guilfoyle 《Optical and Quantum Electronics》2008,40(14-15):1205-1209
The effect of the mode order of a vertical cavity surface emitting laser on the surface normal coupling efficiency into a horizontal optical waveguide is discussed. The numerical results are compared with experimental observations. 相似文献
96.
James W. Favell Kerry L. Wilkinson Ieva Zigg Sarah M. Lyons Renata Ristic Carolyn J. Puglisi Eric Wilkes Randell Taylor Duane Kelly Greg Howell Marianne McKay Lucky Mokwena Tim Plozza Pei Zhang AnhDuyen Bui Ian Porter Orrin Frederick Jasha Karasek Colleen Szeto Bruce S. Pan Steve Tallman Beth Anne McClure Hui Feng Eric Herv Anita Oberholster Wesley F. Zandberg Matthew Noestheden 《Molecules (Basel, Switzerland)》2022,27(15)
Vineyard exposure to wildfire smoke can taint grapes and wine. To understand the impact of this taint, it is imperative that the analytical methods used are accurate and precise. This study compared the variance across nine commercial and research laboratories following quantitative analysis of the same set of smoke-tainted wines. In parallel, correlations between the interlaboratory consensus values for smoke-taint markers and sensory analyses of the same smoke-tainted wines were evaluated. For free guaiacol, the mean accuracy was 94 ± 11% in model wine, while the free cresols and 4-methylguaiacol showed a negative bias and/or decreased precision relative to guaiacol. Similar trends were observed in smoke-tainted wines, with the cresols and glycosidically bound markers demonstrating high variance. Collectively, the interlaboratory results show that data from a single laboratory can be used quantitatively to understand smoke-taint. Results from different laboratories, however, should not be directly compared due to the high variance between study participants. Correlations between consensus compositional data and sensory evaluations suggest the risk of perceivable smoke-taint can be predicted from free cresol concentrations, overcoming limitations associated with the occurrence of some volatile phenols, guaiacol in particular, as natural constituents of some grape cultivars and of the oak used for barrel maturation. 相似文献
97.
Birnbaum Duane T. Kosmala Jacqueline D. Brannon-Peppas Lisa 《Journal of nanoparticle research》2000,2(2):173-181
Microparticles and nanoparticles of poly(lactic acid-co-glycolic acid) (PLAGA) are excellent candidates for the controlled release of many pharmaceutical compounds because of their biodegradable nature. The preparation of submicron PLAGA particles poses serious challenges that are not necessarily present when preparing microparticles. We have evaluated several combinations of organic solvents and surfactants used in the formulation of PLAGA nanoparticles. Critical factors such as the ability to separate the nanoparticles from the surfactant, the ability to re-suspend the nanoparticles after freeze-drying, formulation yield and nanoparticle size were studied. The smallest particles were obtained using the surfactant/solvent combination of sodium dodecyl sulfate and ethyl acetate (65 nm) and the largest particles were obtained using poly(vinyl alcohol) and dichloromethane (466 nm). However, the optimal nanoparticles were produced using either acetone or ethyl acetate as the organic solvent and poly(vinyl alcohol) or human serum albumin as the surfactant. This is because the most critical measure of performance of these nanoparticles proved to be their ability to re-suspend after freeze-drying. 相似文献
98.
Joseph G. Cannon Teresa Lee James A. Beres H. Duane Goldman 《Journal of heterocyclic chemistry》1980,17(7):1633-1636
A synthetic sequence leading to the title compounds began with methyl 5,6-dimethoxy-2-tetralone-3-carboxylate and involved a multi-step construction of the heterocyclic ring. The trans-fused isomer was isolated from the cyclization step. However, the possibility of formation of some cis-fused isomer cannot be precluded. 相似文献
99.
100.
LetS be a convex compact set in a normed linear spaceX. For each cardinal numbern, defineS
n = {x X:x has exactlyn farthest points inS} andT
n =
kn
S
k. It is shown that ifX =E thenT
3 is countable andT
2 is contractible to a point. Properties of associated level curves are given. 相似文献