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排序方式: 共有197条查询结果,搜索用时 84 毫秒
41.
A. Dora R. Pontinha S. Carlos B. Oliveira Ana Maria Oliveira‐Brett 《Electroanalysis》2008,20(23):2531-2536
Metolazone is a diuretic agent used in patients with edematous states and/or hypertension. The electrochemical behavior of metolazone on a glassy carbon electrode was investigated using cyclic, differential pulse, and square‐wave voltammetry at different pHs. The pH dependent oxidation of metolazone occurs in two consecutive steps in a diffusion‐controlled mechanism and involves the formation of a main oxidation product. The first oxidation process is reversible, and involves two electrons and two protons corresponding to the oxidation of nitrogen in the sulfonamide moiety. The second oxidation process is irreversible, also occurs in the sulfonamide moiety, involves a one electron‐transfer, and is followed by deprotonation to produce a cation radical, which reacts with water and yields a hydroxylated product. The diffusion coefficient of metolazone was calculated to be 3.43×10?6 cm2 s?1 in pH 7.0 0.1 M phosphate buffer. 相似文献
42.
Pier Giovanni Baraldi Francesca Fruttarolo Mojgan Aghazadeh Tabrizi Romeo Romagnoli Delia Preti Ennio Ongini Hussein El‐Kashef María Dora Carrión Pier Andrea Borea 《Journal of heterocyclic chemistry》2007,44(2):355-361
43.
Fourteen collaborating laboratories assayed maleic hydrazide (MH), 6-hydroxypyridazin-3(2H)-one, in technical and formulated products by reversed-phase liquid chromatography (LC) with sulfanilic acid as an internal standard. The active MH in the samples (6 lots) ranged from 16% (expressed as the potassium salt) to 98% (MH in the technical). A small amount of 1 M KOH was added to the technical MH and analytical standards to create the potassium salt of the analyte which is soluble in water. Test samples and standards were extracted with water containing the internal standard before analysis by LC on a C8 column with an ion-pairing eluting solution and UV detection at 254 nm. The concentration of MH was calculated by comparing the peak area response ratios of the analyte and the internal standard with those in the analytical standard solution. Eleven laboratories weighed each test sample twice with single analysis. Three laboratories weighed each sample once and made duplicate injections on the LC system. The data were analyzed using the 11 laboratories' results. A second data analysis was done including all laboratory results using a Youden pair approach, selecting one of 2 duplicate assay values randomly for each laboratory and sample. In the first data analysis, the repeatability standard deviation ranged from 0.07 to 1.39%; reproducibility standard deviation ranged from 0.22 to 1.39%. In the second data analysis (using all laboratory data), repeatability standard deviation ranged from 0.09 to 0.86%; reproducibility standard deviation ranged from 0.22 to 1.31%. 相似文献
44.
Formation and evolution of a compressible vortex ring generated at the open end of a short driver section shock tube has been
simulated numerically for pressure ratios (PR) of 3 and 7 in the present study. Numerical study of compressible vortex rings
is essential to understand the complicated flow structure and acoustic characteristics of many high Mach number impulsive
jets where simultaneously velocity, density and pressure fields are needed. The flow development, incident shock formation,
shock diffraction, vortex ring formation and its evolution are simulated using the AUSM+ scheme. The main focus of the present
study is to evaluate the time resolved vorticity field of the vortex ring and the shock/expansion waves in the starting jet
for short driver section shock tubes—a scenario where little data are available in existing literature. An embedded shock
and a vortex induced shock are observed for PR = 7. However the vortex ring remains shock free, compact and unaffected by
the trailing jet for PR = 3. Numerical shadowgraph shows the evolution of embedded shock and shock/expansion waves along
with their interactions. The velocity and vorticity fields obtained from simulation are validated with the particle image
velocimetry results and these data match closely. The translational velocity of the vortex ring, velocity across the vortex
and the centre line velocity of the jet obtained from simulation also agree well with the experimental results. 相似文献
45.
46.
Andrea Gmez-Maqueo Dora Steurer Jorge Welti-Chanes M. Pilar Cano 《Molecules (Basel, Switzerland)》2021,26(17)
High hydrostatic pressure (HHP) is a commercial processing technology which can enhance the health potential of foods by improving the bioaccessibility of their bioactive compounds. Our aim was to study the bioaccessibility and digestive stability of phenolic compounds and betalains in prickly pear fruits (Opuntia ficus-indica L. Mill. var. Pelota and Sanguinos) treated with HHP (100, 350, and 600 MPa; come-up time and 5 min). The effects of HHP on pulps (edible fraction) and peels (sources of potential healthy ingredients) were assessed. In pulps, betanin bioaccessibility increased (+47% to +64%) when treated at 350 MPa/5 min. In HHP-treated pulps, increases in the bioaccessibility of piscidic acid (+67% to +176%) and 4-hydroxybenzoic acid glycoside (+126% to 136%) were also observed. Isorhamnetin glycosides in peels treated at 600 MPa/CUT had higher bioaccessibility (+17% to +126%) than their controls. The effects of HHP on the bioaccessibility of health-promoting compounds are not exclusively governed by extractability increases of antioxidants in the food matrix (direct effects). In this work we found evidence that indirect effects (effects on the food matrix) could also play a role in the increased bioaccessibility of antioxidants in fruits treated with HHP. 相似文献
47.
Z. Chowdhuri M. Fertl M. Horras K. Kirch J. Krempel B. Lauss A. Mtchedlishvili D. Rebreyend S. Roccia P. Schmidt-Wellenburg G. Zsigmond 《Applied physics. B, Lasers and optics》2014,115(2):257-262
We report on a comparison of spin relaxation rates in a 199Hg magnetometer using different wall coatings. A compact mercury magnetometer was built for this purpose. Glass cells coated with fluorinated materials show longer spin coherence times than if coated with their hydrogenated homologues. The longest spin relaxation time of the mercury vapor was measured with a fluorinated paraffin wall coating. 相似文献
48.
We propose and demonstrate a novel and simple dual-parameter measurement scheme based on a cascaded optical fiber device of long-period grating (LPG) and photonic crystal fiber (PCF) modal interferometer. The temperature and refractive index (RI) can be measured simultaneously by monitoring the spectral characteristics of the device. The implemented sensor shows distinctive spectral sensitivities of -30.82 nm/RIU (refractive index unit) and 47.4 pm/°C by the LPG, and 171.96 nm/RIU and 10.4 pm/°C by the PCF modal interferometer. The simultaneous measurement of the temperature and external RI is experimentally demonstrated by the sensor. The temperature shift and RI shift calculated by the sensor matrix agree well with the actual temperature and RI change in the experiment. 相似文献
49.
Pacheco-Contreras R Dessens-Félix M Borbón-González DJ Paz-Borbón LO Johnston RL Schön JC Posada-Amarillas A 《The journal of physical chemistry. A》2012,116(21):5235-5239
The threshold method is used to explore the potential energy surface of the Pt(1)Pd(12) bimetallic cluster, defined by the Gupta semiempirical potential. A set of helical structures, which follow a Bernal tetrahelix pattern, correspond to local minima for the Pt(1)Pd(12) cluster, characterizing the region of the energy landscape where these structures are present. Both right-handed and left-handed chiral forms were discovered in our searches. Energetic and structural details of each of the tetrahelices are reported as well as the corresponding transition probabilities between these structures and with respect to the icosahedron-shaped global minimum structure via a disconnectivity graph analysis. 相似文献
50.