Field confinement with aberration correction for solid immersion lens based fluorescence correlation spectroscopy

The solid immersion lens (SIL) as a tool for increasing the field confinement as well as providing optimal performance by aberration compensation in a confocal fluorescence correlation spectroscopy (FCS) system is illustrated here. Using Zernike polynomials we show that aberration compensation and the resultant pre-shaping of the incident wavefront enables near diffraction-limited performance. This is explained based on vectorial computations for high apertures in the Debye approximation. The obtained axial resolution parameters are compared with the obtained diffusion times in a SIL-FCS experiment for measurements in solutions done at the single molecule level.     

离子色谱法测定大气硫酸盐化速率方法的改进

用离子色谱法测定大气硫酸盐化速率时，采用淋洗液常温浸泡过夜制备样品溶液，回收率为96.7%-102.0%，该样品溶液制备法使离子色谱法测定大气硫酸盐化速率简单、易行。     

Colloidal stability of electrostatically stabilized sol particles. Part I: The role of hydration in coagulation and repeptization of ferric hydroxide sol

FeO(OH)·0.5 H₂O powders were prepared by drying portions of a FeO(OH)·0.5 H₂O sol at different relative vapor pressures, and the adsorption of water on the powders was determined. The magnitude of electrostatic potential barrier for the sol is of about 9 mJ·m^–2. The reduction in the immersion enthalpy and in the surface free-energy in a range of the relative vapor pressures of 0.0–0.9 is as high as 140 mJ·m^–2 and 130 mJ·m^–2, respectively.It follows from the foregoing that two potential barriers may form. The electrostatic barrier presumably regulates the rate of flocculation and the hydration barrier (at closer separations) regulates the rate of particle coalescence or sintering.Peptizability of the FeO(OH)·0.5 H₂O powders dried at relative vapor pressures between 0.4 and 0.9 was found to be fairly high, presumably because the adsorbed water prevented the formation of close contacts between the primer particles. Lowering the vapor pressure, however, resulted in a notable decrease in the peptizable amount, and also a considerable increase in the particle size of the peptized sol.     

Film formation from monodisperse acrylic latices, part 4: the role of coalescing agents in the film formation process

The role of coalescing agents in the film formation process is studied by means of the turbidity technique, i.e., analysis of light transmission and interference. The basic influence of coalescing agents is (a) lowering the minimum film formation temperature of the latex dispersion, (b) increasing the drying time and (c) improvement of coalescence. Application of coalescing agents also causes a change in polymer particle size as coalescing agents made of TEXANOL (2,2,4 trimethyl-1,3 pentanediol monoisobutyrate) and ethylene glycol monobutyl ether (EB) were used. Turbidity is shown to be a better method to optimize the amount of coalescing agent in a film formation process than the usual brass bar.     

Relationship between heat of immersion and surface Gibbs energy of fluorite and cassiterite

Calorimetric measurements were made of the heat of immersion in water of cassiterite that was either untreated or treated with 60% HNO₃. The heats of immersion of cassiterite and fluorite were also calculated theoretically from the surface Gibbs energy components, and compared with the heat of immersion measured for cassiterite and that taken from the literature for fluorite. The results of the measurements and calculation revealed that the heat of immersion depends on the degree of hydration of the surface of cassiterite and fluorite. It was also found that it is possible to predict the heats of immersion in water of cassiterite and fluorite from the Lifshitz-van der Waals and acid-base components of the surface Gibbs energy.     

Comparison of ultrasound-assisted extraction and direct immersion solid-phase microextraction methods for the analysis of monoterpenoids in wine

Ultrasound-assisted extraction (UAE) and direct immersion solid-phase microextraction (DI-SPME) were evaluated for the monoterpenic compounds determination in wine samples. The wine extracts obtained were analyzed by gas chromatography-mass spectrometry (GC-MS). The optimization of the variables affecting UAE and SPME methods was carried out in order to achieve the best extraction efficiency. Both UAE and SPME are quantitative (recoveries in the range 93-97% and 71.8-90.9%, respectively), precise (coefficients of variation below 5.5%), sensitive (limits of detection between 30-39 μg L⁻¹ and 11-25 μg L⁻¹, respectively) and linear over one order of magnitude. The application of both methods to red wine samples showed that UAE provided higher extraction of monoterpenic compounds than SPME. Although SPME remains an attractive alternative technique due to its speed, low sample volume requirements and solvent free character.     

Immersion film‐forming compositions based on high‐molecular polyvinylpyrrolidone

This work presents the results of experimental study of new immersion‐coating compositions based on high‐molecular polyvinylpyrrolidone and different inorganic additions. The formation of transparent polymer coating on the surface of tested optical element is new approach for visual control of optical materials. The film‐forming immersion compositions can be considered as the new and perspective field of the practical application of polymer materials. Copyright © 2016 John Wiley & Sons, Ltd.     

An infinite family of manifolds with bounded total curvature

The negative answer to the following problem of V. I. Arnold is given: Is the number of topologically different -manifolds of bounded total curvature finite?

     

Sn/Pt[111]修饰电极对甲醇氧化的电催化

将Pt[111]电极分别浸在SnSO4 、Sn(SO4 )2 、SnCl4 溶液中,形成的Sn/Pt[111]修饰电极对甲醇氧化的催化效果不一样. 当浸渍溶液为Sn(SO4 )2 或SnCl4 时,在较高电势(0.8 V以上),Sn 能提高Pt[111]电极的电催化活性. 当浸渍溶液为SnSO4 时,Sn 却表现出阻碍作用.研究中还发现,吸附了Sn 的Pt[111]电极灼烧后表现出的催化活性超过浸渍形成的Sn/Pt[111]修饰电极.     

Solid-phase microextraction for the gas chromatography mass spectrometric determination of oxazole fungicides in malt beverages

This paper describes a method for the sensitive, selective, and solvent-free determination of six oxazole fungicide residues (hymexazol, drazoxolon, vinclozolin, chlozolinate, oxadixyl, and famoxadone) in malt beverages. Direct immersion solid-phase microextraction (DI-SPME) coupled to gas chromatography with mass spectrometry in the selected ion monitoring mode, GC-MS(SIM), is used. A comparison of the optimal fiber used, a polar carbowax-divinylbenzene 70-microm fiber, and a nonpolar polydimethylsiloxane 100-microm fiber was carried out. Optimal extraction conditions were 60 degrees C and an extraction time of 30 min under continuous stirring. Desorption was carried out at 250 degrees C for 5 min. Detection limits ranged from 0.006 to 0.3 microg L(-1) at a signal to noise ratio of 3, depending on the compound. The proposed method was successfully applied to malt beverages including malt, beer, and whisky, and none of the samples contained residues higher than detection limits.