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121.
Micro-Raman spectroscopy, infrared absorption microspectroscopy, and AFM images of nano- or microsized micelles formed by fulvic acid (FA) solutions, prepared at different pHs, and cast on glass slides or gold island films, are reported. FA films cast on gold islands are characterized by surface-enhanced infrared absorption (SEIRA), surface-enhanced infrared reflection absorption, and surface-enhanced Raman scattering (SERS). Based on spectral evidence, it is expected that the chemisorption of FA on gold island films takes place through thiol groups, which become more active as pH increases. The SEIRA spectra of these films show increased peak intensity, as well as improved band resolution. Microspectroscopy SERS studies show that, at pH 5, FA form small aggregates on gold surfaces. At pH 8, FA tends to expand due to electrostatic repulsion, giving rise to a fractal surface composed of different domains. SERS studies of these domains reveal that the most polar molecules are located on the external faces. At pH 11, fractal conformations are even more pronounced and give rise to radial patterned structures. At this pH, the position of fulvic acid molecules in the fractal micelles is the same as observed at pH 8. In this way, SERS can be viewed as a powerful tool for the analysis of the composition, apparent contribution of the surface functional groups of FA films, and the FA building blocks (i.e., catechol, gallic, salicylic, or ftalic acids) in the structures of these materials. 相似文献
122.
Julian E. Beesley 《Journal of microscopy》1983,129(1):111-112
A method is described for estimating the number of blocked pore channels and pore density and spatial distribution by the staining of the exterior pore openings of unobstructed pores with uranyl acetate, and identification of them using backscattered electron atomic number contrast imaging in the scanning electron microscope. 相似文献
123.
Gel permeation chromatography was used to follow changes in the molecular weight distribution of a polyisobutene, initial M v = 466,000, during degradation induced by sonic irradiation. Seven samples taken at times of 200–163,500 sec. were studied. In general, a steady decrease in molecular weight was observed, although a bimodal distribution was present after 20,000 sec. irradiation. Various measures of inhomogeneity, M w/M n, U, etc., were examined. The function, σn/M w, where σn is the standard deviation of the number distribution, is considered as a measure of the relative distribution. It is shown to be almost constant throughout the degradation. 相似文献
124.
Some Observations on the Semantics of “Information” 总被引:1,自引:0,他引:1
Julian Newman 《Information Systems Frontiers》2001,3(2):155-167
The term Information is widely used in the rhetoric of the Information Society, a rhetoric which some critics have judged to be empty, at least in part because of the overextension and inconsistent use of this word. We review the emergence of the concept of Information, identify a number of dimensions of similarity and difference in the way that the concept of Information is used and defined, and point up some specific areas where further critical attention is needed, of especial concern to the field of Information Systems. In particular we highlight some problems in identifying and understanding Information Work, and some research themes relevant to Virtual Organisations and Computer Supported Collaborative Work. 相似文献
125.
Paweł Smaczyński Małgorzata Sopicka-Lizer Karolina Kozłowska Julian Plewa 《Journal of Electroceramics》2007,18(3-4):255-260
This paper presents synthesis of calcium cobaltites of the nominal composition of Ca3Co4O9 prepared by the solid state reaction. The reaction between CaCO3 and Co3O4 was investigated at 700–900 °C during 20 h and at 800 °C during 2–30 h. Mass changes, phase composition and Co+3, Co+4 content were examined. Stability of the calcined specimens was tested by DTA/TG. It was found that two phases: Ca3Co4O9 and Ca3Co2O6 were present as a result of calcinations above 800 °C. On the other hand, the temperature of 750 °C was too low for calcium
cobaltites to be synthesized. Mono-phase material with Ca3Co4O9 phase was obtained after calcinations at 800 °C but non-stoichiometry of the compound and its relation to the calcinations
time were found. Once synthesized, the compound was stable up to 900 °C. 相似文献
126.
Cuzner R.M. Nowak D.J. Bendre A. Oriti G. Julian A.L. 《Industry Applications, IEEE Transactions on》2007,43(5):1284-1294
A mathematical model that Is developed for a generalized drive system, including common-mode passive and active elements, is used to explore the issues of paralleling soft-switched resonant dc-link drive systems. Differences between the modulation pattern for each drive system cause common voltage disturbances, which lead to significant circulating currents between the drive systems. Control methods for actively compensating for common-mode circulating currents or reducing the common- mode voltage disturbances are investigated. Practical modifications to the drive system controls are implemented to reduce the circulating currents between paralleled systems. 相似文献
127.
128.
Research suggests that online communication may benefit those high in social anxiety. The current study examined Facebook use from the perspective of adult attachment theory, exploring relationships between attachment anxiety and avoidance and Facebook use. Social skills have been found to be related to attachment style and internet use thus we also examined the role of these skills. A diverse sample of adult participants (N = 617; 50.1% female) completed a self report questionnaire measuring attachment dimensions, social skills, and Facebook use and experience. In line with predictions grounded in attachment theory, we found that individuals with high attachment anxiety used Facebook more frequently, were more likely to use it when feeling negative emotions and were more concerned about how others perceived them on Facebook. High attachment avoidance was related to less Facebook use, less openness and less positive attitudes towards Facebook. These relationships remained when social skills were controlled. These results suggest that Facebook may serve attachment functions and provide a basis for understanding how online communication may be related to attachment styles. 相似文献
129.
Julian J. McAuley Arnau Ramisa Tibério S. Caetano 《International Journal of Computer Vision》2013,104(3):343-361
The recently proposed ImageNet dataset consists of several million images, each annotated with a single object category. These annotations may be imperfect, in the sense that many images contain multiple objects belonging to the label vocabulary. In other words, we have a multi-label problem but the annotations include only a single label (which is not necessarily the most prominent). Such a setting motivates the use of a robust evaluation measure, which allows for a limited number of labels to be predicted and, so long as one of the predicted labels is correct, the overall prediction should be considered correct. This is indeed the type of evaluation measure used to assess algorithm performance in a recent competition on ImageNet data. Optimizing such types of performance measures presents several hurdles even with existing structured output learning methods. Indeed, many of the current state-of-the-art methods optimize the prediction of only a single output label, ignoring this ‘structure’ altogether. In this paper, we show how to directly optimize continuous surrogates of such performance measures using structured output learning techniques with latent variables. We use the output of existing binary classifiers as input features in a new learning stage which optimizes the structured loss corresponding to the robust performance measure. We present empirical evidence that this allows us to ‘boost’ the performance of binary classification on a variety of weakly-supervised labeling problems defined on image taxonomies. 相似文献
130.