Progress in Multimodal En Face Imaging: feature introduction

This feature issue contains papers that report on the most recent advances in the field of en face optical coherence tomography (OCT) and of combinations of modalities facilitated by the en face view. Hardware configurations for delivery of en face OCT images are described as well as specific signal and image processing techniques tailored to deliver relevant clinical diagnoses. The value of the en face perspective for enabling multimodality is illustrated by several combination modalities

Future developments - Adaptive Optics Applied to Glaucoma Imaging

Scanning laser ophthalmoscopy (SLO) and optical coherence tomography (OCT) have substantially advanced ophthalmic imaging by improving the transversal resolution and axial resolution beyond that which can be achieved by the fundus camera. SLO improved the transversal resolution by using a small aperture in front of the photodetector and OCT improved the axial resolution by employing principles of coherence gating. Combining the two technologies into a single instrument produces an OCT instrument with the transversal resolution of an SLO but the finer axial resolution afforded by OCT principles, typically 5-10 um or less. Transversal resolution of both SLO and OCT instruments is limited by the aberrations of the eye to more than 15 um with a pupil size of less than 3 mm. Transversal resolution in both instruments can, in principle, be improved to less than 3 um resolution by enlarging the beam diameter. In practice, this often fails due to imperfections in the crystalline lens, cornea, intraocular fluid, and tear film that disturb the wavefront, and hence distort the round uniformity of the spot illuminating the retina. Applying adaptive optics (AO) principles, aberrations of the eye can be both measured and compensate

A spatially-VSL gravity model with 1-PN limit of GRT

A scalar gravity model is developed according the 'geometric conventionalist' approach introduced by Poincare (Einstein 1921, Poincare 1905, Reichenbach 1957, Gruenbaum1973). In principle this approach allows an alternative interpretation and formulation of General Relativity Theory (GRT), with distinct i) physical congruence standard, and ii) gravitation dynamics according Hamilton-Lagrange mechanics, while iii) retaining empirical indistinguishability with GRT. In this scalar model the congruence standards have been expressed as gravitationally modified Lorentz Transformations (Broekaert 2002). The first type of these transformations relate quantities observed by gravitationally 'affected' (natural geometry) and 'unaffected' (coordinate geometry) observers and explicitly reveal a spatially variable speed of light (VSL). The second type shunts the unaffected perspective and relates affected observers, recovering i) the invariance of the locally observed velocity of light, and ii) the local Minkowski metric (Broekaert 2003). In the case of a static gravitation field the model retrieves the phenomenology implied by the Schwarzschild metric. The case with proper source kinematics is now described by introduction of a 'sweep velocity' field w: The model then provides a hamiltonian description for particles and photons in full accordance with the first Post-Newtonian approximation of GRT (Weinberg 1972, Will 1993).Comment: v1: 11 pages, GR17 conf. paper, Dublin 2004, v2: WEP issue solved, section on acceleration transformation added, text improved, more references, same results, v3: typos removed, footnotes, added and references updated, v4: appendix added, improved tex

Establishing Nash equilibrium of the manufacturer-supplier game in supply chain management

We study a game model of multi-leader and one-follower in supply chain optimization where n suppliers compete to provide a single product for a manufacturer. We regard the selling price of each supplier as a pre-determined parameter and consider the case that suppliers compete on the basis of delivery frequency to the manufacturer. Each supplier’s profit depends not only on its own delivery frequency, but also on other suppliers’ frequencies through their impact on manufacturer’s purchase allocation to the suppliers. We first solve the follower’s (manufacturer’s) purchase allocation problem by deducing an explicit formula of its solution. We then formulate the n leaders’ (suppliers’) game as a generalized Nash game with shared constraints, which is theoretically difficult, but in our case could be solved numerically by converting to a regular variational inequality problem. For the special case that the selling prices of all suppliers are identical, we provide a sufficient and necessary condition for the existence and uniqueness of the Nash equilibrium. An explicit formula of the Nash equilibrium is obtained and its local uniqueness property is proved

The Pediatric Cell Atlas: defining the growth phase of human development at single-cell resolution

Single-cell gene expression analyses of mammalian tissues have uncovered profound stage-specific molecular regulatory phenomena that have changed the understanding of unique cell types and signaling pathways critical for lineage determination, morphogenesis, and growth. We discuss here the case for a Pediatric Cell Atlas as part of the Human Cell Atlas consortium to provide single-cell profiles and spatial characterization of gene expression across human tissues and organs. Such data will complement adult and developmentally focused HCA projects to provide a rich cytogenomic framework for understanding not only pediatric health and disease but also environmental and genetic impacts across the human lifespan

Combinations of techniques in imaging the retina with high resolution

Developments in optical coherence tomography (OCT) have expanded its clinical applications for high-resolution imaging of the retina, as a standalone diagnostic and in combination with other optical imaging modalities. This review presents currently explored combinations of OCT technology with a variety of complementary imaging modalities along with augmentational technologies such as adaptive optics (AO) and tracking. Some emphasis is on the combination of OCT technology with scanning laser ophthalmoscopy (SLO) as well as on using OCT to produce an SLO-like image. Different OCT modalities such as time domain and spectral domain are discussed in terms of their performance and suitability for imaging the retina. Each modality admits several implementations, such as flying spot or using an area or line illumination. Flying spot has taken two principle forms, en-face and longitudinal OCT. The review presents the advantages and disadvantages of different possible combinations of OCT and SLO with AO, evaluating criteria in choosing the best OCT method to fit a specific combination of techniques. Some of these combinations of techniques evolved from bench systems into the clinic, their merit can be judged on images showing different pathologies of the retina. Other potential combinations of techniques are still in their infancy, in which case the discussion will be limited to their technical principles. The potential of any combined implementation to provide clinical relevant data is described by three parameters, which take into account the number of voxels acquired in unit time, the minimum time required to produce or infer an en-face OCT image (or an SLO-like image) and the number of different types of information provided. The current clinically used technologies as well as those under research are comparatively evaluated based on these three parameters. As the technology has matured over the years, their evolution is discussed as well with their potential for further improvements