Cortical Thickness Related to Compensatory Viewing Strategies in Patients With Macular Degeneration

Retinal diseases like age-related macular degeneration (AMD) or hereditary juvenile macular dystrophies (JMD) lead to a loss of central vision. Many patients compensate for this loss with a pseudo fovea in the intact peripheral retina, the so-called “preferred retinal locus” (PRL). How extensive eccentric viewing associated with central vision loss (CVL) affects brain structures responsible for visual perception and visually guided eye movements remains unknown. CVL results in a reduction of cortical gray matter in the “lesion projection zone” (LPZ) in early visual cortex, but the thickness of primary visual cortex appears to be largely preserved for eccentric-field representations. Here we explore how eccentric viewing strategies are related to cortical thickness (CT) measures in early visual cortex and in brain areas involved in the control of eye movements (frontal eye fields, FEF, supplementary eye fields, SEF, and premotor eye fields, PEF). We determined the projection zones (regions of interest, ROIs) of the PRL and of an equally peripheral area in the opposite hemifield (OppPRL) in early visual cortex (V1 and V2) in 32 patients with MD and 32 age-matched controls (19–84 years) by functional magnetic resonance imaging. Subsequently, we calculated the CT in these ROIs and compared it between PRL and OppPRL as well as between groups. Additionally, we examined the CT of FEF, SEF, and PEF and correlated it with behavioral measures like reading speed and eccentric fixation stability at the PRL. We found a significant difference between PRL and OppPRL projection zones in V1 with increased CT at the PRL, that was more pronounced in the patients, but also visible in the controls. Although the mean CT of the eye fields did not differ significantly between patients and controls, we found a trend to a positive correlation between CT in the right FEF and SEF and fixation stability in the whole patient group and between CT in the right PEF and reading speed in the JMD subgroup. The results indicate a possible association between the compensatory strategies used by patients with CVL and structural brain properties in early visual cortex and cortical eye fields

The chemiluminescent peroxyoxalate system: state of the art almost 50 years from its discovery

Almost fifty years after the discovery of the peroxyoxalate reaction by E. A. Chandross in the early nineteen sixties, this review article intends to give a general overview on mechanistic aspects of this system and to describe the principles of its analytical application. After a short general introduction on the principles of chemiluminescence and the history of peroxyoxalate discovery, mechanistic aspects of high-energy intermediate formation, its structure and its reaction with an activator in the peroxyoxalate system are discussed. Finally, analytical applications of peroxyoxalate chemiluminescence are exemplified using representative recent examples, including oxalic acid detection in biological samples.Fundacao de Amparo a Pesquisa do Estado de Sao Paulo (FAPESP)Fundacao de Amparo a Pesquisa do Estado de Sao Paulo (FAPESP)Deutscher Akademischer Austauschdienst (DAAD)Deutscher Akademischer Austausch Dienst (DAAD)Coordenadoria de Aperfeicoamento de Pessoal de Ensino Superior (CAPES)Coordenadoria de Aperfeicoamento de Pessoal de Ensino Superior (CAPES

The James Webb Space Telescope Mission

Twenty-six years ago a small committee report, building on earlier studies, expounded a compelling and poetic vision for the future of astronomy, calling for an infrared-optimized space telescope with an aperture of at least $4m$. With the support of their governments in the US, Europe, and Canada, 20,000 people realized that vision as the $6.5m$ James Webb Space Telescope. A generation of astronomers will celebrate their accomplishments for the life of the mission, potentially as long as 20 years, and beyond. This report and the scientific discoveries that follow are extended thank-you notes to the 20,000 team members. The telescope is working perfectly, with much better image quality than expected. In this and accompanying papers, we give a brief history, describe the observatory, outline its objectives and current observing program, and discuss the inventions and people who made it possible. We cite detailed reports on the design and the measured performance on orbit.Comment: Accepted by PASP for the special issue on The James Webb Space Telescope Overview, 29 pages, 4 figure

A Persian period bulla from Tel Qedesh, Israel and its implications for relations between Tyre and Nippur

In the 1999 season of excavation at Tel Qedesh, in northern Israel, a small, perfectly intact stamped bulla dating to the Persian period was found. The bulla originally sealed a papyrus document. Thanks to its excellent preservation, it is possible to identify a series of key aspects of the object: the motif and type of seal used to stamp it, the way the bulla was created, and even the way in which the original document was folded and tied. These details allow us to identify the probable origin and date of the seal and contextualize its associated bulla within the site of Qedesh. This evidence, in conjunction with information from the late 5th century b.c.e. Murašû archive in Nippur, allows us to suggest that the seal’s user may have been a person with Tyrian ties—perhaps a member of the Tyrian diaspora—who acquired his seal in Nippur and traveled to Qedesh where he used it to seal a document.Published version2020-10-0

Development of an halbach array for a gisaxs instrument

For nanoparticle research, a Halbach array device has been developed that allows the dynamic reproducible definition of the magnet field strength and orientation at a sample. The maximum achievable field strength is 0.5 Tesla. The main application of the Halbach array will be in the sample environment of the GISAXS instrument GALAXI.The magnet field orientation and strength are defined by rotating permanent magnets with stepper motors. Control of the stepper motors is implemented with a S7-1500 PLC in the ET200SP form factor. All field computations are executed in Nicos which controls the device. One challenge in development is the dynamic positioning of magnets due to changing forces. For vacuum applications, a water-cooling system has been implemented that allows the control of the motor temperatures. Design and implementation of the Halbach array device as well as future plans will be presented

Coupling of mental concepts to a reactive system: incremental approach in system design

Mikhailova I, Heracles M, Bolder B, et al. Coupling of mental concepts to a reactive system: incremental approach in system design. In: Eighth International Conference on Epigenetic Robotics: Modeling Cognitive Development in Robotic Systems. 2008.The design of a system that bootstraps an open-ended development is one of the most intriguing questions in Developmental Robotics. Inspired by evolution we propose an incremental design. We start with a reactive system that provides task-unspecific interaction with the environment. We extend this system by a multi-modal expectation generation system that learns and evaluates the regularities of the system-environment interaction. The two systems are coupled by means of an active resolution of the expectation mismatch. Such an extension allows the transition from reactive behavior to hypothesis testing and goal directed behavior. The proposed architecture is validated on the example of multi-modal learning and evaluation of auditory labels tested on humanoid robot ASIMO

fMRI with Central Vision Loss: Effects of Fixation Locus and Stimulus Type

Purpose In patients with central visual field scotomata, a large part of visual cortex is not adequately stimulated. Patients often use a new eccentric fixation area on intact peripheral retina (preferred retinal locusPRL) that functions as a pseudo-fovea. We used functional magnetic resonance imaging (fMRI) to examine whether stimulating this pseudo-fovea leads to increased activation or altered activation patterns in visual cortex in comparison to stimulating a comparable peripheral area in the opposite hemifield (OppPRL). Methods Nineteen patients with binocular central scotomata caused by hereditary retinal dystrophies and an age-matched control group were tested. The center of the visual field, PRL, and OppPRL were stimulated with flickering checkerboard stimuli and object pictures during fMRI measurement. Results Results show that stimulation with pictures of everyday objects led to overall larger BOLD (blood oxygen level dependent) responses in visual cortex compared to that evoked by stimulation with flickering checkerboards. Patients showed this enhancement as early as in V1. When the PRL was directly stimulated with object pictures, the central representation area in early visual cortex was coactivated in the patients but not in the controls. In higher visual areas beyond retinotopic cortex, BOLD responses to stimulation of the PRL with object pictures were significantly enhanced in comparison to stimulation of the OppPRL area. Highly stable eccentric fixation with the PRL was associated with a higher BOLD signal in visual cortex in patients, and this effect was most pronounced in the conditions with object picture stimulation. Conclusions The observed results suggest that naturalistic images are more likely to trigger top-down processes that regulate activation in early visual cortex in patients with central vision loss

Teaching a Humanoid Robot: Headset-Free Speech Interaction for Audio-Visual Association Learning

Heckmann M, Brandl H, Schmüdderich J, et al. Teaching a Humanoid Robot: Headset-Free Speech Interaction for Audio-Visual Association Learning. In: IEEE International Symposium on Robot and Human Interactive Communication. 2009.Based on inspirations from infant development we present a system which learns associations between acoustic labels and visual representations in interaction with its tutor. The system is implemented on a humanoid robot. Except for a few trigger phrases to start learning all acoustical representations are learned online and in interaction. Similar, for the visual domain the clusters are not predefined and fully learned online. In contrast to other interactive systems the interaction with the acoustic environment is solely based on the two microphones mounted on the robots head. In this paper we give an overview on all key elements of the system and focus on the challenges arising from the headset-free learning of speech labels. In particular we present a mechanism for auditory attention integrating bottom-up and top-down information for the segmentation of the acoustic stream. The performance of the system is evaluated based on offline tests of individual parts of the system and an analysis of the accompanying video showing the system in interaction