Quantitative x-ray microanalysis of spherical inclusions embedded in a matrix using a SEM and Monte Carlo simulations

The current schemes of quantification of x-ray microanalysis in the SEM [ZAF and σ(ρZ) methods] are valid for specimens of homogeneous composition. The determination of the chemical composition of small inclusions using these techniques is impossible because the volume of x-ray emission is not of homogeneous composition. A scheme of quantification to determine the composition of small inclusions embedded in a matrix has been developed using Monte Carlo simulations. This scheme is similar to that developed by Kyser and Murata (1974) for the quantification of thin foils deposited on a substrate using x-ray microanalysis in the SEM.     

黄原胶用于大体积空腔容器静态泡沫去污初探

黄原胶作为一种用途很广的生物增稠剂和发泡剂,具有抗剪切性和耐酸、耐碱和抗氧化等特点,这些特点恰好满足静态泡沫去污对增稠剂的要求。本文测量并分析了碱性体系中(Na2CO3体系)影响发泡液粘度的几种因素(搅拌速度、黄原胶浓度、碳酸钠浓度及温度);以及酸性体系中(HNO3+H3PO4体系)黄原胶浓度和发泡液放置时间对泡沫稳定性的影响;比较分析了铝片在酸性发泡液及其生成泡沫中的失重情况。试验结果表明黄原胶无论是在碱性溶液还是在酸性溶液中均具有一定的稳定性,能够满足泡沫去污的要求;其稳定性随时间推移而降低的特性有利于泡沫去污产生的二次废液的处理。黄原胶酸性发泡液能够产生稳定的泡沫,对铝片具有良好的腐蚀效果。在本实验中,当铝片处于距底端4cm高度位置时,腐蚀速率达到1.0 mg/(cm2.h)。因此,黄原胶有望作为放射性污染大体积空腔容器静态泡沫去污的增稠剂。     

Asymptotic Properties of Monotonic Nonexpansive Mappings

Let T be a nonexpansive monotonic mapping from C to itself where C is a closed subset of a space of bounded real functions, with the supremum norm. We study asymptotic properties of several average iterates of T, related to the cycle time.     

Prevalence and comparison of genetic profiles of Campylobacter strains isolated from poultry and sporadic cases of campylobacteriosis in humans.

Between July 1998 and June 1999, 93 lots of broiler chickens distributed on 57 farms were sampled in two abattoirs of the province of Quebec (Canada). A total of 2,325 samples of cecal material were analyzed to determine the prevalence of campylobacters. Biotyping and pulsed-field gel electrophoresis (PFGE) were done on 20% of the Campylobacter isolates to study the distribution within poultry production. Macrorestriction profiles were compared with profiles of 24 Campylobacter strains isolated from sporadic cases of human diarrheic patients in order to evaluate genetic relationships. Approximately 40% of the broiler chickens in 60% of the lots and 67% of the farms were colonized. Biotypes I and II of Campylobacter jejuni were the most prevalent biotypes in poultry and human isolates. The PFGE dendograms revealed a high genetic diversity among poultry isolates, with 49 different genotypes from the 56 positive lots. More than 75% of these lots were colonized by a unique genotype. All positive lots raised simultaneously on the same farm had common genotype(s). Different genotypes were isolated from lots raised at different grow-out periods on a farm. In some cases, identical genotypes were found at different grow-out periods on a farm and also from different farms. Macrorestriction profiles showed that approximately 20% of human Campylobacter isolates were genetically related to genotypes found in poultry. This genetic relationship and the high prevalence of C. jejuni biotypes I and II in poultry indicated that Campylobacter in broiler production of the province of Quebec could be a potential source of hazard for public health.     

A method to predict multipath effects on a line-of-sight link

A method that computes the quality of a digital microwave line-of-sight link affected by multipath propagation is presented. The use of a statistical propagation model and of the signature concept allows the propagation effects to be separated from the characteristics of the equipment. Since the variations of the statistical mode coefficients with respect to the characteristics of the link under consideration are not known, experimental results have been achieved using assumptions based on physical considerations. A single channel is considered and the same principles, although more speculative because of the lack of data, are applied to a diversity channel     

Antimicrobial effect of cranberry juice and extracts

The antimicrobial effect of cranberry juice and of three cranberry extracts (water-soluble (E1) and apolar phenolic compounds (E2), and anthocyanins (E3)) was investigated against seven bacterial strains (Enterococcus faecium resistant to vancomycin (ERV), Escherichia coli O157:H7 EDL 933, Escherichia coli ATCC 25922, Listeria monocytogenes HPB 2812, Pseudomonas aeruginosa ATCC 15442, Salmonella Typhimurium SL1344, and Staphylococcus aureus ATCC 29213). Each cranberry sample was analyzed to determine the minimum inhibitory concentration (MIC) and the maximal tolerated concentration (MTC) at neutral pH. The results, reported in μg phenol/mL, indicated that all the bacterial strains, both Gram-positive and Gram-negative, were selectively inhibited by the cranberry phenolic compounds. The extract rich in water-soluble phenolic compounds caused the most important growth inhibitions. The bacteria ERV, and to a lesser degree, P. aeruginosa, S. aureus and E. coli ATCC 25922, were the most sensitive to the antimicrobial activity of extract E1. The growth of P. aeruginosa and E. coli ATCC was also affected by the presence of the anthocyanin-rich cranberry extract E3, although the observed antibacterial effect was not as important as with extract E1. In general, L. monocytogenes, E. coli O157:H7 and S. Typhimurium were the most resistant to the antibacterial activity of the cranberry extracts. Within 30 min of exposure with pure neutralized cranberry juice, L. monocytogenes and ERV were completely inactivated.     

Photo-oxidation in an O2 atmosphere: A powerful tool to elucidate the mechanism of UV-visible light oxidation of polymers - Application to the photodegradation of MDMO-PPV

This article describes a new approach to improve the analysis of the chemical modifications that result from the degradation of polymers under UV-visible light exposure in the presence of oxygen. The tool which is used consists of an irradiation chamber whose atmosphere is composed of ¹⁸O₂. The ¹⁸O₂ pressure inside the chamber and the hygrometry can be adjusted. In this study, particular attention was paid to the photo-oxidation of poly[2-methoxy-5-(3′,7′-dimethyloctyloxy)-1,4-phenylenevinylene] (MDMO-PPV). Using infrared spectroscopy, irradiation under the oxygen 18 atmosphere allowed discrimination between compounds formed via fixation of oxygen from the atmosphere and those formed by reorganisation of the matrix. In addition, irradiation of MDMO-PPV in an ¹⁸O₂ wet atmosphere allowed for detection of the presence of phenyl formate and aromatic ketone functions. This permitted validating the mechanism of photo-oxidation previously proposed. Additionally, with regard to blends made with MDMO-PPV and methano-fullerene[6,6]-phenyl C₆₁-butyric acid methyl ester ([60] PCBM), it was demonstrated that this technique facilitates the identification of the photo-oxidation products formed.     

Spatial encoding in domestic cats (Felis catus).

Four experiments were performed to identify the spatial information that cats used to encode the position of an object they saw move and disappear. In Experiment 1 and 2, several sources of allocentric spatial information were manipulated. Results indicated that the cats used none of these sources and instead relied primarily on their own spatial coordinates (pure egocentric information) to locate the hidden object. In Experiment 3 and 4, pure egocentric information was made unreliable by a detour task. Results showed that the cats encoded a metric source of allocentric spatial information—the relationship between the walls of the room and the hiding place. Together, these results reveal that cats' encoding of spatial information is flexible and adapted to various kinds of situations that can be encountered in the natural environment. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effect of artificial perspiration and cleaning chemicals on the mechanical and chemical properties of ballistic materials

During routine field use of soft body armor, the ballistic panels become saturated with perspiration. This condition motivates the user to clean and/or deodorize the armor, and anecdotal evidence is given for various methods used to accomplish this. Although the cleaning/deodorization is usually performed on the armor liners and coverings, there is concern that the chemicals could seep into the ballistic panels and damage the fibers. The purpose of this study was to assess the effect of artificial perspiration and cleaning chemicals on the mechanical and chemical properties of aramid, poly(p‐phenylene benzobisoxazole), and ultrahigh‐molecular‐weight polyethylene yarns after controlled cycles of exposure to artificial perspiration and dilute solutions of common cleaning chemicals. It was observed that the effect of the artificial perspiration on the properties of all of the materials tested was the same as that of water alone. Of all of the cleaning chemicals used, only chlorine bleach had a detrimental effect on the yarn properties. All other cleaning chemicals had the same effect as water alone. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Characterizing the shape of anatomical structures with Poisson's equation

Poisson's equation, a fundamental partial differential equation in classical physics, has a number of properties that are interesting for shape analysis. In particular, the equipotential sets of the solution graph become smoother as the potential increases. We use the displacement map, the length of the streamlines formed by the gradient field of the solution, to measure the "complexity" (or smoothness) of the equipotential sets, and study its behavior as the potential increases. We believe that this function complexity = f(potential), which we call the shape characteristic, is a very natural way to express shape. Robust algorithms are presented to compute the solution to Poisson's equation, the displacement map, and the shape characteristic. We first illustrate our technique on two-dimensional synthetic examples and natural silhouettes. We then perform two shape analysis studies on three-dimensional neuroanatomical data extracted from magnetic resonance (MR) images of the brain. In the first study, we investigate changes in the caudate nucleus in Schizotypal Personality Disorder (SPD) and confirm previously published results on this structure. In the second study, we present a data set of caudate nuclei of premature infants with asymmetric white matter injury. Our method shows structural shape differences that volumetric measurements were unable to detect.