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101.
The physiology of flatfish chromatophores 总被引:3,自引:0,他引:3
Burton D 《Microscopy research and technique》2002,58(6):481-487
Most flatfish, of the order Pleuronectiformes, possess a white lower side, and a brown or grey upper side. This upper side can display integumentary patterning with dark areas and colored or white spots. Chromatophores in flatfish are dermal and epidermal melanophores, as well as dermal xanthophores, erythrophores, iridophores, and leucophores, combinations of which contribute to the color and patterning. Cellular studies demonstrate pattern-related differences in numerical distribution between the types of chromatophores, and in their size, both of which will enhance contrast between areas of the pattern. As well as these morphological characteristics, there are also clear physiological differences, with melanophores from various areas of the patterns demonstrating differential responsiveness to background and to stress/excitement stimuli. Regulation of flatfish melanophore responses is predominantly neural, through the sympathetic nervous system; the pituitary hormones in these fish function in maintaining final equilibria in physiological adaptations to backgrounds. Melanophores from main components of patterns also respond differently in vitro to electrical stimulation, to pituitary hormones, and to sympathomimetic drugs and their antagonists. Sensitivity characteristics with alpha- and beta-adrenergic pharmacological reagents in vitro indicate the existence of a pattern-related balance in alpha- and beta-adrenoceptor mediation in melanophore regulation. The patterning mechanism is complex, with both morphological and physiological differences at the chromatophore level, as well as involvement of central processing and control, which remains to be analysed. 相似文献
102.
In this work, the fluid flow and mass transfer due to the presence of an electric field in a rectangular channel is examined. We consider a mixture of water or another neutral solvent and a salt compound, such as sodium chloride, for which the ionic species are entirely dissociated. Results are produced for the case in which the channel height is much greater than the electric double layer (EDL) (microchannel) and for the case in which the channel height is of the order of the width of the EDL (nanochannel). Both symmetric and nonsymmetric velocity, potential, and mole fraction distributions are considered, unlike previous work on this problem. At small electrolyte concentrations, the Debeye-Huckel picture of the electric double layer is recovered; at larger concentrations, the Gouy-Chapman picture of the electric double emerges naturally. The numerical results presented here agree with analytical solutions of a singular perturbation analysis, which is valid as the channel height increases. In the symmetric case for the electroosmotic flow so induced, the velocity field and the potential are similar. In the asymmetric case corresponding to different wall potentials, the velocity and potential can be vastly different. The fluid is assumed to behave as a continuum, and the volume flow rate is observed to vary linearly with channel height for electrically driven flow, in contrast to pressure-driven flow, which varies as height cubed. This means that very large pressure drops are required to drive flows in small channels. However, useful volume flow rates may be obtained at a very low driving voltage. 相似文献
103.
Spam filtering is a text classification task to which Case-Based Reasoning (CBR) has been successfully applied. We describe
the ECUE system, which classifies emails using a feature-based form of textual CBR. Then, we describe an alternative way to
compute the distances between cases in a feature-free fashion, using a distance measure based on text compression. This distance
measure has the advantages of having no set-up costs and being resilient to concept drift. We report an empirical comparison,
which shows the feature-free approach to be more accurate than the feature-based system. These results are fairly robust over
different compression algorithms in that we find that the accuracy when using a Lempel-Ziv compressor (GZip) is approximately
the same as when using a statistical compressor (PPM). We note, however, that the feature-free systems take much longer to
classify emails than the feature-based system. Improvements in the classification time of both kinds of systems can be obtained
by applying case base editing algorithms, which aim to remove noisy and redundant cases from a case base while maintaining,
or even improving, generalisation accuracy. We report empirical results using the Competence-Based Editing (CBE) technique.
We show that CBE removes more cases when we use the distance measure based on text compression (without significant changes
in generalisation accuracy) than it does when we use the feature-based approach. 相似文献
104.
A widely held view is that phonological processing is always involved in lexical access from print, and is automatic in that it cannot be prevented. This claim was assessed in the context of a priming paradigm. In Experiment 1, repetition priming was observed for both pseudohomophone-word pairs (e.g., brane-brain) and morphologically related word pairs (e.g., marked-mark) in the context of lexical decision. In Experiment 2, subjects searched the prime for the presence of a target letter and then made a lexical decision to a subsequent letter string. Phonological priming from a pseudohomophone was eliminated following letter search of the prime, whereas morphological priming persisted. These results are inconsistent with the claim that a) lexical access from print requires preliminary phonological processing, and b) functional phonological processing cannot be blocked. They are, however, consistent with the conclusion that, for intact skilled readers, lexical access can be accomplished on the basis of orthographic processing alone. These results join a growing body of evidence supporting the claim that there exist numerous points in visual word recognition at which processing can be stopped. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
105.
A word from a dense neighborhood is often read aloud faster than a word from a sparse neighborhood. This advantage is usually attributed to orthography, but orthographic and phonological neighbors are typically confounded. Two experiments investigated the effect of neighborhood density on reading aloud when phonological density was varied while orthographic density was held constant, and vice versa. A phonological neighborhood effect was observed, but not an orthographic one. These results are inconsistent with the predominant role ascribed to orthographic neighbors in accounts of visual word recognition and reading aloud. Consistent with this interpretation, 6 different computational models of reading aloud failed to simulate this pattern of results. The results of the present experiments thus provide a new understanding of some of the processes underlying reading aloud, and new challenges for computational models. (PsycINFO Database Record (c) 2011 APA, all rights reserved) 相似文献
106.
Abstract: It is estimated that 4.6 billion tons of non‐hazardous solid waste materials are produced annually in the USA. The potential reuse for a portion of the materials in the construction of highways and roads suggests that valuable benefits in terms of economic and environmental gains are possible. This paper describes the development of a prototype computer‐assisted tool or expert system to help manufacturers assess and analyze their industrial residuals as potential road construction material. This represents an expansion in the application of intelligent systems to domains where a few, hard‐to‐find technical reports have represented the main source of expertise available to practitioners for years. The system, developed through the use of an object‐oriented software shell, Level5 Object, was designed in a user‐friendly Windows environment which allows users with little or no computer training to effectively evaluate material residuals. 相似文献
107.
China has been attracting overseas construction enterprises with its vast expanding business market. The country is further opening its construction market to overseas businesses as the result of its accession to the World Trade Organization in 2001. In line with this development, there are an increasing number of foreign-invested construction enterprises (FICEs) entering into the market. Using Porter’s competitiveness factor analysis method, this paper identifies the FICEs’ strengths, weaknesses, opportunities, and threats in the Chinese construction market. Data used in the analysis stem from multiple sources including statistical reports, literature review, regulations and policies, and interviews with construction professionals. These findings should provide a valuable reference for overseas construction enterprises who are interested in developing business in the Chinese construction market. 相似文献
108.
109.
Men convicted of drunken driving rated this particular offence as significantly less serious than men from a control group who had no convictions for drunken driving offences. Instead of shame and guilt feelings preventing the person from committing further acts of drunken driving, prosecution and court appearance seems to have a detrimental effect on the offender's attitudes to this type of criminal behaviour. 相似文献
110.