Search results for "ocular"

A Region-based Gauss-Newton Approach to Real-Time Monocular Multiple Object Tracking

2018

We propose an algorithm for real-time 6DOF pose tracking of rigid 3D objects using a monocular RGB camera. The key idea is to derive a region-based cost function using temporally consistent local color histograms. While such region-based cost functions are commonly optimized using first-order gradient descent techniques, we systematically derive a Gauss-Newton optimization scheme which gives rise to drastically faster convergence and highly accurate and robust tracking performance. We furthermore propose a novel complex dataset dedicated for the task of monocular object pose tracking and make it publicly available to the community. To our knowledge, it is the first to address the common and…

iLocater: a diffraction-limited Doppler spectrometer for the Large Binocular Telescope

2016

We are developing a stable and precise spectrograph for the Large Binocular Telescope (LBT) named "iLocater." The instrument comprises three principal components: a cross-dispersed echelle spectrograph that operates in the YJ-bands (0.97-1.30 microns), a fiber-injection acquisition camera system, and a wavelength calibration unit. iLocater will deliver high spectral resolution (R~150,000-240,000) measurements that permit novel studies of stellar and substellar objects in the solar neighborhood including extrasolar planets. Unlike previous planet-finding instruments, which are seeing-limited, iLocater operates at the diffraction limit and uses single mode fibers to eliminate the effects of m…

Material properties of various intraocular lenses in an experimental study.

2002

<i>Introduction:</i> With the recent introduction of small-incision cataract surgery, requirements for intraocular lens (IOL) flexibility, strength and hydrophilicity have rapidly evolved. The IOL surface, however, remains a critical factor influencing uveal biocompatibility. <i>Purpose:</i> To objectively quantify factors of material properties of various IOLs using contact angle measurements, differential scanning calorimetry, dynamic-mechanical measurements and scanning electron microscopy. <i>Material and Methods:</i> In our study, 17 currently available IOLs were investigated using contact angle measurements to assess hydrophilicity and biocompatibil…

The influence of eye movements on the temporal features of executed and imagined arm movements.

2007

The very close coordination between eye and hand indicates that eye movements are parts of the neural processes underlying the planning and control of arm movements. Eye movements are fundamental during observed actions and play a functional role in visual mental imagery. However, the role of eye movements during imagined actions is still unknown. Here, we report the timing features of eye and arm pointing movements for nine healthy participants in four conditions: Executed movements with orientation saccades (Eyes Free) or with no saccades (Eyes Motionless), and Imagined movements with Eyes Free or with Eyes Motionless. The first result was a facilitation effect of saccades upon both execu…

Tilted discs and central retinal vein occlusion.

1993

Centrins, gatekeepers for the light-dependent translocation of transducin through the photoreceptor cell connecting cilium

2006

Centrins are members of a highly conserved subgroup of the EF-hand superfamily of Ca(2+)-binding proteins commonly associated with centrosome-related structures. In the retina, centrins are also prominent components of the photoreceptor cell ciliary apparatus. Centrin isoforms are differentially localized at the basal body and in the lumen of the connecting cilium. All molecular exchanges between the inner and outer segments occur through this narrow connecting cilium. Ca(2+)-activated centrin isoforms bind to the visual heterotrimeric G-protein transducin via an interaction with the betagamma-subunit. Ca(2+)-dependent assemblies of centrin/G-protein complexes may regulate the transducin mo…

Centrins in retinal photoreceptor cells: regulators in the connecting cilium.

2008

Changes in the intracellular Ca2+ concentration regulate the visual signal transduction cascade directly or more often indirectly through Ca2+-binding proteins. Here we focus on centrins, which are members of a highly conserved subgroup of the EF-hand superfamily of Ca2+-binding proteins in photoreceptor cells of the vertebrate retina. Centrins are commonly associated with centrosome-related structures. In mammalian retinal photoreceptor cells, four centrin isoforms are expressed as prominent components in the connecting cilium linking the light-sensitive outer segment compartment with the metabolically active inner segment compartment. Our data indicate that Ca2+-activated centrin isoforms…

Characteristics of neuronal systems in the visual cortex

1987

The coupling complexity of cortical areas makes it very difficult to analyse them experimentally. Studies of model systems provide the possibility of adapting the analysis to the available data base and elaborating the fundamental properties that depend on the structure of the system. We propose a model system of variable complexity that is spatially two-dimensional and time-dependent, uses feedback for iteration and smoothing, includes the mapping of the cortical networks and can be nonlinear as the case requires. Combining such elementary systems on the basis of neuroanatomical findings enables us to simulate cortical mappings and to interpret neurophysiological data. The decisive factor …

On the analysis of the cat's pattern recognition system

1983

The objective of the paper is to determine in abstract terms the algorithms used by the cat detecting simple patterns and to quantify the contributions of the visual areas 17, 18, 19 for this task. The data incorporated in the algorithm are collected from behavioral experiments where the animals had to distinguish between two patterns. The patterns were superimposed with gaussian noise and the detection probability was measured. The resulting model describes pattern recognition in two steps: first extraction of features and second classification. The test of the validity of the model system was to predict the outcome of similar experiments but with different patterns. With the help of the m…

Donnan phenomena in membranes with charge due to ion adsorption. Effects of the interaction between adsorbed charged groups

1993

A physical model for the modified Donnan phenomenon associated with ion adsorption on localized membrane sites is presented. This model accounts for the dependence of the concentration of adsorbed ions on electrolyte concentration and pH as it is influenced by the electrostatic interaction between adsorbed ions. The equilibrium thermodynamic concepts employed are based on the Donnan formalism for the ion equilibria between membrane and solution, and the Bragg–Williams approximation for an adsorption isotherm that incorported interaction between adsorbed ions. Our results include the concentration of charged groups in the membrane, the pH of the membrane phase solution, and the Donnan potent…