Summary: PTFE/PES composites were prepared by precipitation of Radel A® into a PTFE latex containing nanoparticles with average diameters of 48 nm and spherical shape. Several samples were prepared by varying the relative ratio between the Radel A® and PTFE content. The combination of SEM and AFM analysis indicates that the precipitation of Radel A in the presence of PTFE leads mainly, if not exclusively, to a bimodal mixture of the two homoparticles. The fractionated crystallization behaviour of these samples is revealing of the PTFE dispersion degree within the Radel A® matrix. When the PTFE amount is lower than 2%, a perfect PTFE nanoparticle dispersion is obtained. When the amount of PTFE is comprised between 5 and 30%, larger PTFE clusters are obtained that, after melting, coalesce and crystallize at higher temperatures depending on the crystallization propensity of their individual heterogeneous nuclei. Finally, in case of samples 40%, only one crystallization exotherm is observed at 310 °C indicating the formation of very large clusters that after melting coalesce into wide domains. 相似文献
We study various methods of aggregating individual judgments and individual priorities in group decision making with the AHP. The focus is on the empirical properties of the various methods, mainly on the extent to which the various aggregation methods represent an accurate approximation of the priority vector of interest. We identify five main classes of aggregation procedures which provide identical or very similar empirical expressions for the vectors of interest. We also propose a method to decompose in the AHP response matrix distortions due to random errors and perturbations caused by cognitive biases predicted by the mathematical psychology literature. We test the decomposition with experimental data and find that perturbations in group decision making caused by cognitive distortions are more important than those caused by random errors. We propose methods to correct the systematic distortions. 相似文献
A comparison is made of the separation and analysis of a test probe, AZD5438 (4-(1-isopropyl-2-methyl-1H-imidazol-5-yl)-N-[4-(methylsulfonyl)phenyl]pyrimidin-2-amine), and its metabolites using conventional LC, UPLC and high temperature liquid chromatography (HTLC). LC and UPLC separations were performed using reversed-phase water:acetonitrile solvent systems whilst HTLC was performed with an entirely aqueous mobile phase, using both isothermal and temperature gradient chromatography. Substantial reductions in run times were observed with both UPLC and HTLC compared to the conventional LC approach without loss in chromatographic resolution for the major metabolites. At temperatures in excess of 100 °C, thermal degradation of some of the metabolites was observed in an isothermal separation, however, the application of a thermal gradient proved successful in maintaining the structural integrity of the analytes and simultaneously separating the parent compound and its major metabolites. 相似文献
From zero to hero? Sulfoxides are generally not considered useful ligand entities in asymmetric metal catalysis. However, a chiral disulfoxide as a chelating ligand in the rhodium‐catalyzed 1,4‐addition of aryl boronic acids to cyclic, α,β‐unsaturated ketones and esters gives impressive catalytic results, thus opening the door to future applications of this new chiral ligand class.
An increasing number of studies use blood obtained noninvasively to monitor organohalogen contaminants; however, blood can
be difficult to analyze because of its aqueous nature and high protein content. We compared five methods for extracting polychlorinated
biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs), organochlorine pesticides, and lipids from serum using National
Institute of Standards and Technology Standard Reference Material 1589a PCBs, Pesticides, PBDEs, and Dioxins/Furans in Human
Serum. Liquid:liquid (LLE), cavity-dispersed microwave-assisted (MAE), focused microwave-assisted (FME), solid-phase (SPE),
and pressurized fluid (PFE) extraction techniques were compared. FME extraction yielded the optimal recovery of internal standards
(IS). All methods resulted in similar contaminant concentrations that also agreed with the certified values for SRM 1589a,
except for only a few compounds measured by methods other than FME. Based on these findings, the FME method was determined
to be the best overall extraction method. One procedural factor was found to affect contaminant concentrations; use of IS
carrier solvents that were immiscible with serum (or when the serum was not directly physically mixed with IS) resulted in
a 30% underestimation of organohalogen concentrations. This study offers valid, novel extraction alternatives beyond traditional
methods (e.g., LLE) for blood contaminant measurements.
Figure 相似文献
The selective enzymatic deacetylation of T-2 toxin to give HT-2 toxin has been investigated in aqueous crude extracts of different
cereals and exploited to develop an analytical method for the determination of the sum of T-2 and HT-2 toxins. The method
has been validated for the analysis of total T-2 and HT-2 toxins in maize, wheat, and oats, showing recoveries from 72 to
97% for maize, from 67 to 84% for wheat, and from 61% to 87% for oats, at spiking levels of 20–400 μg/kg, with relative standard
deviation lower than 10%. Liquid chromatography-tandem mass spectrometry was used for quantitative toxin determination. The
potential biological role of this enzymatic conversion and its perspectives for application in the development of antibody-based
analytical techniques are discussed.
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We describe a system that provides a rapid and simple way of forming suspended lipid bilayers within a microfluidic platform from an aqueous droplet. Bilayer lipid membranes are created in a polymeric device by contacting monolayers formed at a two-phase liquid–liquid interface. Microdroplets, containing membrane proteins, are injected onto an electrode positioned above an aperture machined through a conical cavity that is filled with a lipid–alkane solution. The formation of the BLM depends solely on the device geometry and leads to spontaneous formation of lipid bilayers simply by dispensing droplets of buffer. When an aqueous droplet containing transmembrane proteins or proteoliposomes is injected, straightforward electrophysiology measurements are possible. This method is suitable for incorporation into lab-on-a-chip devices and allows for buffer exchange and electrical measurements.
Figure
Bilayer lipid membranes are formed in a polymeric device by injecting water droplets, containing membrane proteins, directly onto an electrode positioned above an aperture machined into a conical cavity, which is initially filled with a lipid-alkane solution. The water droplet slides down the electrode to the aperture at the bottom of the conical reservoir. The geometry of this system enables the spontaneous formation of a BLM. Ion channel activity is recorded between an electrode in the bottom channel and the electrode in the droplet. The technique is scalable and could be configured as a high throughput multi-site biosensing or drug screening platform. 相似文献