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Ideally electrical impedance tomography (EIT) should not be oversensitive to electrode positions, but this conflicts with efforts to produce high-resolution images. Two procedures are presented that balance reducing the sensitivity to electrode position errors with generating practicable EIT images. The first provides a criterion based on electrode sensitivity for regularizing the reconstruction through spectral expansion. The main consequences of this are that smoother images are produced and the number of artefacts and their magnitude are generally reduced. The second modification uses the recorded data to compensate for electrode movements that have occurred after the reference data were measured. Image smoothness is used as the criterion for the readjustment. Computer simulation tests have shown that this modification produces improved image fidelity.  相似文献   
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Genetic differentiation among Hereford populations from Britain, Ireland, Sweden, Canada and New Zealand together with six other beef breeds was assessed using blood type polymorphisms. Changes in the genetic structure of the British Hereford population over time were also examined. Loci surveyed were seven red cell antigen systems (A, B, C, F, L, S, Z), and two serum protein loci (transferrin and albumin). Within group variation was measured by the average expected heterozygosity, and between group relationships by genetic distance. There was significant genetic differentiation among Hereford populations from different countries. Differences between Hereford groups, however, were not as large as differences between breeds. There were also significance differences among British herds. The proportion of Canadian genes in the British 'hybrid' population was estimated to have increased from 0.42 (+/- 0.34) in the 1970s to 0.98 (+/- 0.11) in the 1990s. Canadian Hereford groups were found to be less heterozygous than other groups, and replacement of the British population with Canadian animals may lead to loss of variation. Breeding strategies that preserve original native genes in British Hereford populations should be considered by commercial breeders, in order to prevent the long-term loss of genetic variation within the breed.  相似文献   
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Psychotherapists attempt to cultivate sensitivity to difference in their work with diverse client populations. Developing therapists may also benefit from theoretical and practical encounters with difference during graduate training. Although graduate students may thrive in training institutions where orientations resonate with their intuitive understandings, valuable opportunities for growth emerge when students obtain practicum experience at sites using alternative approaches to psychotherapy. This article documents the challenges and opportunities met by one graduate student trained in existential, psychodynamic, humanistic, and sociocultural approaches, when she embarked on a practicum experience in a medical setting, where dialectical behavior therapy (DBT) was the treatment of choice. She discusses professional growth, steps toward psychotherapy integration, and implications for graduate training. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
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A technologically important use of the free-space interference patterns formed by phase gratings is in the creation of the refractive-index variation along optical fiber Bragg gratings. The patterns can be imaged directly by use of a tapered optical fiber tip, which acts as a local probe of the optical field. We present measurements of these patterns under varying conditions and compare them with theoretical predictions. In discussing the results within the context of fiber grating manufacture, we also demonstrate the effects of incident-beam misalignment and wave-front curvature.  相似文献   
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Several proteins, which are recognized components of serum, are not resolved by two-dimensional polyacrylamide gel electrophoresis (2D-PAGE) under standard conditions. One major example is fibronectin, which is detected in fairly high concentration (milligram range) by immunoassays, while undetectable in 2D-PAGE gels. Following several experiments with a combination of zwitterionic and chaotropic substances we obtained a good resolution of the protein in gels containing 0.5 M thiourea plus 8 M urea. By this technique, fibronectin was, for the first time, found to be microheterogeneous between pl values of 5.3 and 5.6. Besides fibronectin we detected three other families of uncharacterized proteins with Mr of 130000, 110000 and 34000 respectively, whose identity and function are currently under investigation.  相似文献   
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