Extraction fractionation of segmented polyurethanes according to composition

Extraction of solid polyester-based segmented polyurethanes by chloroform and its mixtures with an increasing amount of N,N-dimethylformamide is described. Unlike the precipitation in a solvent-nonsolvent system, where fractionation according to the molecular weight dominates, the extraction can resolve the copolymer into fractions differing in the content of diisocyanate units. © 1995 John Wiley & Sons, Inc.     

Application of image analysis method to detection and counting of glass fibers from filter samples

Man-made vitreous fibers (MMVFs) are noncrystalline substances made of glass, rock or slag and are widely used as thermal or acoustic insulation materials. There is continued concern about their potential health impacts and thus, their dosimetry and behavior in the environment still require study using filters to collect fiber samples. After deposition or exposure measurements of MMVFs it is often necessary to analyze the filters with deposited fibers. This task is tedious, time-consuming, and requires skill. Therefore, many researchers have tried to simplify or automatize fiber detection and quantification. This article describes features of our in-house software, which automatically detects and counts fibers in images of filter samples. The image analysis is based on the use of a histogram equalization and an adaptive radial convolution filter that enhances fiber contrast and thus, improves the fiber identification. The accuracy of the software analysis was verified by comparison with manual counting using ordinary phase-contrast microscopy method. The correlation between the methods was very high (coefficient of determination was 0.977). However, there were some discrepancies caused by false identifications, which led to implementation of manual corrective functions.

Copyright © 2016 American Association for Aerosol Research     

Sorption of metal ions on lignite and the derived humic substances

The study presents results of sorption of metal ions (Pb2+, Zn2+, Cu2+, and Cd2+) onto lignite mined in South Moravia, Czech Republic, and solid humic substances (humin and humic acid) derived from it. The efficiency of these sorbents has been studied as a function of contact time, solution pH, and metal concentration. The sorption efficiencies were higher for humin and lower for humic acid samples than for the original lignite. With its high sorption capacities of several mmol/g, particularly for Pb2+ and Cd2+, the South Moravian lignite can provide a cheap source material for preparation of sorbents utilizable in removal of toxic metals from wastewaters.     

Dy3+掺杂Ge-Ga-Se硫系玻璃的性质

实验制备了Dy3+掺杂Ge-Ga-Se系统硫系玻璃样品,测试了玻璃的密度、显微硬度、可见-红外透射光谱、荧光光谱以及荧光寿命.根据玻璃的密度计算了玻璃的摩尔体积以及致密度.讨论了玻璃的这些性能随系统平均配位数＜r＞的变化关系.实验结果表明该系统中配位数大于2.67的玻璃在1.3 μm具有较好的发光性能,荧光寿命在440～530μs之间,当玻璃组成位于化学门槛即平均配位数为2.73时玻璃的发光强度最强.     

Oxycellulose modification

Sodium salts of oxycellulose have been prepared by different techniques and under different conditions to obtain a white powder salt of lowest carboxyl group content. Also, Fe(III) and Al(III) salts have been prepared from oxycellulose and from its sodium salt. To prepare amphoteric cation exchange derivatives, anionic oxycellulose was cationized by reaction with Refaktan K, a common commercial cationizing agent which contains diepoxypropyl dimethyl ammonium chloride: different reaction conditions such as percentage cationizing agent, temperature and time have been investigated. Polyelectrolyte titration was used to measure the ion activity of the different products. Infrared spectroscopy of the different samples was carried out and the results analysed and discussed. © 2000 Society of Chemical Industry     

Effects of drawing conditions on the properties of optical fibers made from polystyrene and poly(methyl methacrylate)

Monofilaments possessing various degrees of birefringence were obtained by changing the drawing rate, the molten polymer temperature, and the molecular weight of polystyrene (PS) and poly(methyl methacrylate) (PMMA). The “brittle-toductile” transition point of optically pure PS was found in the range of birefringences of ?0.6 · 10^?3 to ?2.6 · 10^?3. Both the height and position of this point are influenced by M?_w, molecular weight distribution, and polymer melt temperature. The birefringence of PS is higher by two orders of magnitude than that of PMMA in which this transition point has not been observed. The mechanical and optical properties depend not only on the average amount of orientation characterized by the birefringence but on what portion of the relaxation spectrum of the polymer is preferentially oriented. During the drawing of PS and PMMA monofilaments crazes are formed in the centre of the fibers and do not reach the surface.     

FOPS: A new framework for the optimization with variable number of dimensions

A single‐ and multi‐objective optimization package is presented and described in detail. It contains an ensemble of local and global optimization routines. Procedures controlling variable number of dimensions are implemented as well, which is a rare feature among optimization oriented packages. The package is provided as a MATLAB toolbox. It excels in versatility and extensibility, which is demonstrated on a series of examples covering classical electromagnetism and antenna design. It is taken for granted that defining parameters of the optimization method can be set prior to the simulation run. However, its effective performance can be changed during the optimization run thanks to the full control feature. Moreover, it opens new possibilities in merging various algorithms into hybrids, performing complex dynamic programming tasks, or exploiting third party software. These advantages render the package as a perfect tool to deal with nowadays challenging engineering tasks.     

Effects of monomer impurities on the emulsion polymerization of chloroprene and properties of polychloroprene. I. Effect of methyl vinyl ketone

The influences of small amounts (up to 2%) of methyl vinyl ketone in chloroprene on properties of polychloroprene and kinetics of the emulsion polymerization of chloroprene with mercaptans as regulators has been studied. Methyl vinyl ketone causes a substantial increase in molecular weight of polymer, which results in increased viscosity, gel formation, lowered plasticity of polymer, deterioration of processability, decreased tensile strength, and high modulus of vulcanizates. Methyl vinyl ketone interferes with the regulation of molecular weight by both primary and tertiary dodecylmercaptan; some differences are due to lower reactivity of tertiary dodecylmercaptan. In the presence of diisopropyl xanthogene disulfide as a molecular weight regulator the polychloroprene properties are not affected by methyl vinyl ketone. All changes in polymer properties have been proved to be caused by the addition reaction of dodecylmercaptan on methyl vinyl ketone, yielding 1-dodecylthiobutan-3-one. This compound itself has no influence on the polymerization of chloroprene. Methyl vinyl ketone has a marked promoting effect on polymerization rates, which accounts for its high reactivity and solubility in the water phase. A fast polymerization of methyl vinyl ketone takes place in the water phase of emulsion polymerization system simultaneously with the reaction of methyl vinyl ketone with dodecylmercaptan.     

Indirect interference of two modes with different frequencies at the one-photon level

Abstract

The possibility of observing interference with two modes of different frequencies in a one-photon state by means of parametric up-conversion is studied. This phenomenon could be utilized for discernment between pure and mixed states. There is also a close connection to the question of the extent of indefiniteness of the photon's path.