Prelude. Cycle 1. Introduction. Cycle 2. Structure defines function. Cycle 3. Diversity of cortical functions is provided by inhibition. Cycle 4. Windows on the brain. Cycle 5. A system of rhythms: from simple to complex dynamics. Cycle 6. Synchronization by oscillation. Cycle 7. The brain's default state: self-organized oscillations in rest and sleep. Cycle 8. Perturbation of the default patterns by experience. Cycle 9. The gamma buzz: gluing by oscillations in the waking brain. Cycle 10. Perceptions and actions are brain state-dependent. Cycle 11. Oscillations in the "other cortex:" navigation in real and memory space. Cycle 12. Coupling of systems by oscillations. Cycle 13. The tough problem. References.

Rhythms of the brain

Animals use the geomagnetic field in many ways: the magnetic vector provides a compass; magnetic intensity and/or inclination play a role as a component of the navigational ‘map’, and magnetic conditions of certain regions act as ‘sign posts’ or triggers, eliciting specific responses. A magnetic compass is widespread among animals, magnetic navigation is indicated e.g. in birds, marine turtles and spiny lobsters and the use of magnetic ‘sign posts’ has been described for birds and marine turtles. For magnetoreception, two hypotheses are currently discussed, one proposing a chemical compass based on a radical pair mechanism, the other postulating processes involving magnetite particles. The available evidence suggests that birds use both mechanisms, with the radical pair mechanism in the right eye providing directional information and a magnetite-based mechanism in the upper beak providing information on position as component of the ‘map’. Behavioral data from other animals indicate a light-dependent compass probably based on a radical pair mechanism in amphibians and a possibly magnetite-based mechanism in mammals. Histological and electrophysiological data suggest a magnetite-based mechanism in the nasal cavities of salmonid fish. Little is known about the parts of the brain where the respective information is processed.

/pdf/magnetic-orientation-and-magnetoreception-in-birds-and-other-3ifs8uqbja.pdf

Magnetic orientation and magnetoreception in birds and other animals

Bacteria, sharks, honey bees, and homing pigeons as well as other organisms seem to detect the direction of the earth's magnetic field. Indirect but reproducible evidence suggests that the bees and birds can also respond to very minute changes in its intensity. The mechanisms behind this sensitivity are not known. Naturally magnetic, biologically precipitated magnetite (Fe3O4) has been found in chitons, magnetotactic bacteria, honey bees, homing pigeons, and dolphins. Its mineralization in localized areas may be associated with the ability of these animals to respond to the direction and intensity of the earth's magnetic field. The presence of large numbers (approximately 10(8)) of superparamagnetic magnetite crystals in honey bees and similar numbers of single-domain magnetite grains in pigeons suggests that there may be at least two basic types of ferrimagnetic magnetoreceptive organelles. Theoretical calculations show that ferrimagnetic organs using either type of grain when integrated by the nervous system are capable of accounting for even the most extreme magnetic field sensitivities reported. Indirect evidence suggests that organic magnetite may be a common biological component, and may account for the results of numerous high field and electromagnetic experiments on animals.

Biogenic magnetite as a basis for magnetic field detection in animals

Honey bees orient to the earth's magnetic field. This ability may be associated with a region of transversely oriented magnetic material in the front of the abdomen. The magnetic moment apparently develops in the pupal state and persists in the adults.

https://science.sciencemag.org/content/sci/201/4360/1026.full.pdf

Bees have magnetic remanence.

Earth observation through remote sensing images allows the accurate characterization and identification of materials on the surface from space and airborne platforms. Multiple and heterogeneous image sources can be available for the same geographical region: multispectral, hyperspectral, radar, multitemporal, and multiangular images can today be acquired over a given scene. These sources can be combined/fused to improve classification of the materials on the surface. Even if this type of systems is generally accurate, the field is about to face new challenges: the upcoming constellations of satellite sensors will acquire large amounts of images of different spatial, spectral, angular, and temporal resolutions. In this scenario, multimodal image fusion stands out as the appropriate framework to address these problems. In this paper, we provide a taxonomical view of the field and review the current methodologies for multimodal classification of remote sensing images. We also highlight the most recent advances, which exploit synergies with machine learning and signal processing: sparse methods, kernel-based fusion, Markov modeling, and manifold alignment. Then, we illustrate the different approaches in seven challenging remote sensing applications: 1) multiresolution fusion for multispectral image classification; 2) image downscaling as a form of multitemporal image fusion and multidimensional interpolation among sensors of different spatial, spectral, and temporal resolutions; 3) multiangular image classification; 4) multisensor image fusion exploiting physically-based feature extractions; 5) multitemporal image classification of land covers in incomplete, inconsistent, and vague image sources; 6) spatiospectral multisensor fusion of optical and radar images for change detection; and 7) cross-sensor adaptation of classifiers. The adoption of these techniques in operational settings will help to monitor our planet from space in the very near future.

Multimodal Classification of Remote Sensing Images: A Review and Future Directions

Homing pigeons were equipped with a pair of small coils around their heads. Birds with an induced field of 0.6 gauss and the south magnetic pole up, oriented toward home normally under both sun and overcast. Birds with the polarity reversed oriented toward home when the sun was visible but often flew away from home under overcast.

https://science.sciencemag.org/content/sci/184/4133/180.full.pdf

Orientation of homing pigeons altered by a change in the direction of an applied magnetic field

Spectroscopy has existed for more than three centuries now. Nonetheless, significant scientific advances have been achieved. We discuss the history of spectroscopy in relation to emerging technologies and applications. Advanced focal plane arrays, optical design, and intelligent on-board logic are prime prospective technologies. Scalable approaches in pre-processing of imaging spectrometer data will receive additional focus. Finally, we focus on new applications monitoring transitional ecological zones, where human impact and disturbance have highest impact as well as in monitoring changes in our natural resources and environment. We conclude that imaging spectroscopy enables mapping of biophysical and biochemical variables of the Earth's surface and atmospheric composition with unprecedented accuracy.

/pdf/the-future-of-imaging-spectroscopy-prospective-technologies-22j9hm4a0z.pdf

The Future of Imaging Spectroscopy Prospective Technologies and Applications

The goal of Delay Tolerant Networking (DTN) is to take a collection of heterogeneous, disparate connections between satellites, space assets, ground stations, and ground infrastructure and bring it together into a cohesive, functioning overlay network. Depending on the systems being considered, one can find links with a one-way light time exceeding minutes (and hours), periodic links which can sometimes be predicted by orbital mechanics, and restrictions based on the variety of capabilities built into these systems. These characteristics preclude traditional network models and routing techniques and have classically led to either rigid routing tables or purely probabilistic models. As the deeper underlying structures remain unknown, development of more DTN-optimized algorithms has lacked the necessary foundation. In a continuation of previous work, the goal of this paper is to identify and study these fundamental structures that exist in delay tolerant networks (DTN), with a focus on space networks. The current routing methodology has been to use contact graph routing (CGR) algorithms. CGR models a series of known contacts as a static graph. For CGR to work, this graph must be globally consistent and must have an accurate picture of the network. Because this is a globally controlled structure, there is little room for flexibility in the event of changes to the network which would naturally occur as the network grows. As a response to the desire for flexibility as the network changes, we introduced the mathematical structure known as sheaves to DTNs last year. The tag-line for sheaves is that they are a mathematically precise way of gluing local data together into unique global data. Thus, sheaves lend extra power to traditional models (and routing algorithms) by taking additional information and merging it, in as consistent a manner as possible, with the representation itself. The clearest example of how Earth-bound networks exhibit behavior that is “sheafy” is link state routers, which build a local-to-global picture of their network by gluing local information together into a global network, exactly as a sheaf would do. For routing within delay tolerant networks to truly exploit this structure, a deeper structure than a graph is required. In this paper, we develop sheaves that can work over directed graphs such as temporal flow networks, we construct a sheaf representation for Dijkstra's algorithm, and we outline a construction for routing sheaves capable of modeling multicast scenarios. Finally, there is a section of future work suggesting follow-on research.

Robert Green

Papers

Orientation of homing pigeons altered by a change in the direction of an applied magnetic field

The Future of Imaging Spectroscopy Prospective Technologies and Applications

Towards Sheaf Theoretic Analyses for Delay Tolerant Networking

The Earth Surface Mineral Dust Source Investigation Planned for the International Space Station

Exploration of the Relationship Between Information Content and Signal-to-Noise Ratio and Spatial Resolution