color vision in mammals is based on the expression of at least two cone opsins that are sensitive to different wavelengths of light. Furthermore, retinal pathways conveying color-opponent signals are required for colo...
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color vision in mammals is based on the expression of at least two cone opsins that are sensitive to different wavelengths of light. Furthermore, retinal pathways conveying color-opponent signals are required for color discrimination. Most of the primates are trichromats, and "color-coded channels" of their retinas are unveiled to a large extent. In contrast, knowledge of cone-selective pathways in nonprimate dichromats is only slowly emerging, although retinas of dichromats like mice or rats are extensively studied as model systems for retinal information processing. Here, we review recent progress of research on color-coded pathways in nonprimate dichromats to identify differences or similarities between di- and trichromatic mammals. In addition, we applied immunohistochemical methods and confocal microscopy to retinas of different species and present data on their neuronal properties, which are expected to contribute to color vision. Basic neuronal features such as the "blue cone bipolar cell" exist in every species investigated so far. Moreover, there is increasing evidence for chromatic OFF channels in dichromats and retinal ganglion cells that relay color-opponent signals to the brain. In conclusion, di- and trichromats share similar retinal pathways for color transmission and processing.
When observing an unresolved star, a mask consisting of a linear array non-redundantly spaced apertures placed in front of the telescopic pupil gives rise to an image composed of discrete superimposed fringe patterns ...
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When observing an unresolved star, a mask consisting of a linear array non-redundantly spaced apertures placed in front of the telescopic pupil gives rise to an image composed of discrete superimposed fringe patterns within an Airy disc envelope. Due to atmospheric turbulence the incident luminous wavefronts are subject to phase perturbations given rise to rapid and independent random movements of each fringe system. When analyzed by a scanning slit the image autocorrelation and corresponding spectrum exhibit a deterioration related to the scanning speed and to the characteristic evolution time of the turbulence. Theoretical expressions are developed for this dependence and are shown to be in good agreement with experimental results obtained by laboratory simulation. An optimal scanning speed can be determined for a given set of turbulence, telescope aperture and noise characteristics.
BACKGROUND Mapping and ablation of atrial macroreentrant tachycardia focus on activation mapping with identification of the area of stow conduction. OBJECTIVE The purpose of this study was to evaluate a new concept fo...
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BACKGROUND Mapping and ablation of atrial macroreentrant tachycardia focus on activation mapping with identification of the area of stow conduction. OBJECTIVE The purpose of this study was to evaluate a new concept for analysis and treatment of macroreentrant tachycardia based on color-coded three-dimensional (3D) entrainment mapping and subsequent placement of strategic lesion tines. METHODS Twenty-six patients presented with macroreentrant tachycardia (cycle length 329 +/- 70 ms). Using nonfluoroscopic systems (CARTO 12, NavX 14), sequential mapping of the target atrium was performed. On each mapping point, the 3D Location was paired with color-coded entrainment information so that the reentrant circuit could be directly visualized. RESULTS Procedural duration, fluoroscopy time, and radiofrequency time measured 181 +/- 58, 37 +/- 19, and 31 +/- 17 minutes, respectively. Thirty-nine macroreentrant tachycardias were ablated: perimitral 9, around pulmonary vein ostium 6, through left atrial roof 5, around left atrial appendage 3, right atrial cavotricuspid isthmus dependent 6, around right atrial scar 2, around superior vena cava 1, within the septum 5, and within the coronary sinus 2. Tachycardia termination and noninducibility of any macroreentrant tachycardia was the procedural end-point. In case of Left atrial macroreentrant tachycardia, pulmonary vein isolation was completed. Follow-up with serial 7-day Hotter covered 302 82 days. Two (8%) patients experienced recurrences of a pre-treated macroreentrant tachycardia. CONCLUSION In patients with macroreentrant tachycardia, color-coded 3D entrainment mapping is feasible to accurately determine and visualize the 3D location of the reentrant circuit and to plan a strategic ablation tine concept. That approach, not targeting the area of stow conduction of the circuit, resulted in excellent procedural success (100%), with tong-term freedom from any tachycardia recurrences in 88% of patients.
Midget bipolar cells form the first distinct step in the parvocellular (P-) pathway of the primate visual system, and are the major determinant of the receptive field properties of colour selective midget ganglion cel...
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Midget bipolar cells form the first distinct step in the parvocellular (P-) pathway of the primate visual system, and are the major determinant of the receptive field properties of colour selective midget ganglion cells. This paper describes the sampling properties of the midget bipolar cell population and relates this to the processing of chromatic information in the P-pathway. Immunocytochemical markers were used to label midget bipolar cells so that their spatial density could be compared with that of cones and ganglion cells. Sections through macaque monkey retinae were immunostained with antibodies against cholecystokinin (CCK), and recoverin. In CCK-labelled sections, in addition to blue cone bipolar cells, numerous thin bipolar cell dendrites, which could be associated with individual cone pedicles are stained. CCK-immunoreactive midget bipolar cells are found throughout the retina. A different population of midget bipolar cells is revealed in recoverin-labelled sections. Based on a comparison with midget bipolar cells in Golgi-stained retinae we propose that ON-midget (invaginating) bipolars are immunoreactive for CCK and confirm that OFF-midget (flat) bipolar cells are immunoreactive for recoverin [Milam, Dacey and Dizhoor (1993) Visual Neuroscience, 10 1-12]. The density of recoverin labelled midget bipolars matches the cone density to an eccentricity of about 10 mm;from there outwards it drops to 60% of the cone density. This suggests convergence of several cones to individual midget bipolar cells in Peripheral retina;We conclude that midget bipolar cells are present throughout the entire primate retina, and could, in peripheral as well as in central retina, provide chromatically specific input to the P-pathway.
Describes an optical analog pseudocolor technique in object space which is used to encode the spatial frequency content of an object transparency. The effect is obtained by means of a suitable matching of the source p...
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Describes an optical analog pseudocolor technique in object space which is used to encode the spatial frequency content of an object transparency. The effect is obtained by means of a suitable matching of the source power spectrum with the transmittance characteristics of a non-blocked interference filter as a function both of the wavelength and the angle of incidence. Experimental demonstrations with object gratings are presented.
Two tabular and two graphical techniques for the presentation of laboratory test results were compared in a reaction-time experiment with 22 volunteers. The experimental setup was designed to determine whether one or ...
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Two tabular and two graphical techniques for the presentation of laboratory test results were compared in a reaction-time experiment with 22 volunteers. The experimental setup was designed to determine whether one or more of the presentation techniques facilitated the recognition of four predefined combinations of abnormal test results, Using a conventional, tabular presentation technique as a reference, faster median response times were obtained with each of the other three presentation techniques, irrespective of pattern. The effect on accuracy was less clear, possibly due to the small number of errors made.
This article describes an approach to bridging the gap between the generalist thinking of decision makers and the specialism of modellers by concentrating on the preliminary issue conceptualisation stage of modelling....
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This article describes an approach to bridging the gap between the generalist thinking of decision makers and the specialism of modellers by concentrating on the preliminary issue conceptualisation stage of modelling. A new type of visual facilitation is described using hexagons as a flexible mapping technique to bridge the gap between thoughts and models. A typical team application is described and a link is also made to creative thinking techniques, including the use of cognitive colour-coding. These techniques are supported by new use of magnetic hardware and a specially designed mapping software. In conclusion, the idea of the transitional discipline is introduced as a way in which a variety of specialist decision support methods can be made more user friendly.
We examine the implications of the hypothesis that color information in the cortex is adaptively coded into a factorial (statistically independent) and gain-controlled representation. We show that this hypothesis expl...
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We examine the implications of the hypothesis that color information in the cortex is adaptively coded into a factorial (statistically independent) and gain-controlled representation. We show that this hypothesis explains the results of the recent experiments by Webster and Mollon [(1991) Nature, 349, 235-238] on changes in color appearance following post-receptoral adaptation. We also give a neural network with a deterministically convergent, unsupervised learning algorithm that reproduces the adaptation observed.
A fundamental problem in many applications involving social and biological networks is to identify and count the number of embeddings of a given small subgraph in a large graph. Often, they involve dynamic graphs, in ...
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ISBN:
(纸本)9781479913282
A fundamental problem in many applications involving social and biological networks is to identify and count the number of embeddings of a given small subgraph in a large graph. Often, they involve dynamic graphs, in which the graph changes incrementally (e. g., by edge addition/deletion). We study the Dynamic Subgraph Enumeration (DSE) Problem, where the goal is to maintain a dynamic data structure to solve the subgraph enumeration problem efficiently when the graph changes incrementally. We develop a new data structure that combines two techniques: (i) the color-coding technique of Alon et al., 2008, for enumerating trees, and (ii) a dynamic data structure for maintaining the h-index of the graph (developed by Eppstein and Spiro, 2009). We derive worst case bounds for the update time in terms of the h-index of the graph and the maximum degree. We also study the empirical performance of our algorithm in a large set of real networks, and find significant improvement over the static methods.
We present a new shared-memory parallel algorithm and implementation called FASCIA for the problems of approximate subgraph counting and subgraph enumeration. The problem of subgraph counting refers to determining the...
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ISBN:
(纸本)9780769551173
We present a new shared-memory parallel algorithm and implementation called FASCIA for the problems of approximate subgraph counting and subgraph enumeration. The problem of subgraph counting refers to determining the frequency of occurrence of a given subgraph (or template) within a large network. This is a key graph analytic with applications in various domains. In bioinformatics, subgraph counting is used to detect and characterize local structure (motifs) in protein interaction networks. Exhaustive enumeration and exact counting is extremely compute-intensive, with running time growing exponentially with the number of vertices in the template. In this work, we apply the color coding technique to determine approximate counts of non-induced occurrences of the subgraph in the original network. color coding gives a fixed-parameter algorithm for this problem, using a dynamic programming-based counting approach. Our new contributions are a multilevel shared-memory parallelization of the counting scheme and several optimizations to reduce the memory footprint. We show that approximate counts can be obtained for templates with up to 12 vertices, on networks with up to millions of vertices and edges. Prior work on this problem has only considered out-of-core parallelization on distributed platforms. With our new counting scheme, data layout optimizations, and multicore parallelism, we demonstrate a significant speedup over the current state-of-the-art for subgraph counting.
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