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201.
Human off-vertical axis rotation (OVAR) in the dark typically produces perceived motion about a cone, the amplitude of which
changes as a function of frequency. This perception is commonly attributed to the fact that both the OVAR and the conical
motion have a gravity vector that rotates about the subject. Little-known, however, is that this rotating-gravity explanation
for perceived conical motion is inconsistent with basic observations about self-motion perception: (a) that the perceived
vertical moves toward alignment with the gravito-inertial acceleration (GIA) and (b) that perceived translation arises from
perceived linear acceleration, as derived from the portion of the GIA not associated with gravity. Mathematically proved in
this article is the fact that during OVAR these properties imply mismatched phase of perceived tilt and translation, in contrast
to the common perception of matched phases which correspond to conical motion with pivot at the bottom. This result demonstrates
that an additional perceptual rule is required to explain perception in OVAR. This study investigates, both analytically and
computationally, the phase relationship between tilt and translation at different stimulus rates—slow (45°/s) and fast (180°/s),
and the three-dimensional shape of predicted perceived motion, under different sets of hypotheses about self-motion perception.
We propose that for human motion perception, there is a phase-linking of tilt and translation movements to construct a perception
of one’s overall motion path. Alternative hypotheses to achieve the phase match were tested with three-dimensional computational
models, comparing the output with published experimental reports. The best fit with experimental data was the hypothesis that
the phase of perceived translation was linked to perceived tilt, while the perceived tilt was determined by the GIA. This
hypothesis successfully predicted the bottom-pivot cone commonly reported and a reduced sense of tilt during fast OVAR. Similar
considerations apply to the hilltop illusion often reported during horizontal linear oscillation. Known response properties
of central neurons are consistent with this ability to phase-link translation with tilt. In addition, the competing “standard”
model was mathematically proved to be unable to predict the bottom-pivot cone regardless of the values used for parameters
in the model. 相似文献
202.
Background
Most gene finders score candidate gene models with state-based methods, typically HMMs, by combining local properties (coding potential, splice donor and acceptor patterns, etc). Competing models with similar state-based scores may be distinguishable with additional information. In particular, functional and comparative genomics datasets may help to select among competing models of comparable probability by exploiting features likely to be associated with the correct gene models, such as conserved exon/intron structure or protein sequence features. 相似文献203.
An antimicrobial-surface kinetic test which maximizes probability of cell-to-surface contact has been developed. The measurement of rate of kill by a nonleaching antimicrobial surface is based on the number of surviving bacterial cells at specific times of exposure to various amounts of total treated surface area of test substrate. This method gives information for direct comparison of rate of kill for a variety of antimicrobial surfaces in terms of rate of kill per square centimeter of surface area. Data obtained by this method can also give valuable dose response application information as an indication of the exponential efficiency of concentration in terms of treated surface area. 相似文献
204.
The gaze control system governs distinct gaze behaviors, including visual fixation and gaze reorientations. Transitions between
these gaze behaviors are frequent and smooth in healthy individuals. This study models these gaze-behavior transitions for
different numbers of gaze degrees of freedom. Eye/head gaze behaviors have twice the number of degrees of freedom as eye-only
gaze behaviors. Each gaze behavior is observable in the system dynamics and is correlated with neuronal behaviors in several,
coordinated neural centers, including the vestibular nuclei. The coordination among the neural centers establishes a sensorimotor
state which maintains each gaze behavior. This study develops a mathematical framework for synthesizing the coordination among
neural centers in gaze sensorimotor states and focuses on the role of vestibular nuclei neurons in gaze sensorimotor state
transitions.
Received: 17 December 1999 / Accepted in revised form: 3 May 2001 相似文献
205.
Robert W. McCollum 《The Yale journal of biology and medicine》1979,52(6):598-599
206.
207.
208.
Dannel McCollum 《Current biology : CB》2010,20(11):R484-R486
209.
Factors Affecting Cotyledonal Cracking during the Germination of Beans (Phaseolus Vulgaris) 总被引:3,自引:3,他引:0 下载免费PDF全文
McCollum JP 《Plant physiology》1953,28(2):267-274
210.
The loss of flesh firmness during muskmelon ( Cucumis melo var. reticulatus L. Naud. cv. Galia) fruit ripening was related temporally to modifications of pectic and hemicellulosic polysaccharides, and a net loss of non-cellulosic neutral sugars. An increase in solubility and a decrease in molecular size of polyuronides occurred during ripening; however, the decrease in molecular size was apparently not the result of polygalacturonase (EC 3.2.1.15) activity. Molecular size of hemicelluloses shifted from larger to smaller polymers during ripening, and this decrease was accompanied by changes in neutral sugar composition. Galactose, glucose, and xylose were the predominant neutral sugars in the hemicellulosic polymers. On a mol% basis there were decreases in galactose and glucose in large hemicellulosic polymers with ripening. Relative xylose content approximately doubled in the large polymers during ripening; xylose was the predominant neutral sugar in the small polymers and remained fairly constant. 相似文献