• Review the existing literature on diver visibility. • Carry out experimental determinations of the sighting range of a black disk using DaviesColley’s method together with spectral absorption and attenuation measurements in a wide range of natural optical environments. • Determine the proper wavelength or wavelength combination for the limiting beam attenuation for the horizontal black target...

PURPOSE To evaluate and compare the abilities of enhanced depth imaging (EDI) and high-penetration optical coherence tomography (HP-OCT) to visualize the deep optic nerve head (ONH) and deep parapapillary structures. METHODS Horizontal and vertical optic nerve images were obtained using EDI-OCT and HP-OCT, during the same visit, from 24 eyes of 12 patients with glaucoma. Three graders, using ...

A unit bar-visibility graph is a graph whose vertices can be represented in the plane by disjoint horizontal unit-length bars such that two vertices are adjacent if and only if there is a unobstructed, non-degenerate, vertical band of visibility between the corresponding bars. We generalize unit bar-visibility graphs to [1, k]bar-visibility graphs by allowing the lengths of the bars to be betwe...

An Horizontal Visibility Graph (for short, HVG) is defined in association with an ordered set of non-negative reals. HVGs realize a methodology in the analysis of time series, their degree distribution being a good discriminator between randomness and chaos [B. Luque, et al., Phys. Rev. E 80 (2009), 046103]. We prove that a graph is an HVG if and only if outerplanar and has a Hamilton path. The...

The visibility algorithm has been recently introduced as a mapping between time series and complex networks. This procedure allows us to apply methods of complex network theory for characterizing time series. In this work we present the horizontal visibility algorithm, a geometrically simpler and analytically solvable version of our former algorithm, focusing on the mapping of random series (se...

The type-I intermittency route to (or out of) chaos is investigated within the horizontal visibility (HV) graph theory. For that purpose, we address the trajectories generated by unimodal maps close to an inverse tangent bifurcation and construct their associated HV graphs. We show how the alternation of laminar episodes and chaotic bursts imprints a fingerprint in the resulting graph structure...

PURPOSE To compare the visibility of the lamina cribrosa (LC) in optic disc images acquired from 60 glaucoma and 60 control subjects using three optical coherence tomography (OCT) devices, with and without enhanced depth imaging (EDI) and adaptive compensation (AC). METHODS A horizontal B-scan was acquired through the center of the disc using two spectral-domain (Spectralis and Cirrus; with a...

A compactified horizontal visibility graph for the language network is proposed. It was found that the networks constructed in such way are scale free, and have a property that among the nodes with largest degrees there are words that determine not only a text structure communication, but also its informational structure. Construction of networks with text elements, words, phrases or fragments ...