Guidance algorithms for a free-flying space robot

Robotics is a promising technology for assembly, servicing, and maintenance of platforms in space. Several aspects of planning and guidance for telesupervised and fully autonomous robotic servicers are investigated. Guidance algorithms for proximity operation of a free flyer are described. Numeric trajectory optimization is combined with artificial intelligence based obstacle avoidance. An initial algorithm and the results of its simulating platform servicing scenario are discussed. A second algorithm experiment is then proposed

Developmental gene regulatory network architecture across 500 million years of echinoderm evolution

Evolutionary change in morphological features must depend on architectural reorganization of developmental gene regulatory networks (GRNs), just as true conservation of morphological features must imply retention of ancestral developmental GRN features. Key elements of the provisional GRN for embryonic endomesoderm development in the sea urchin are here compared with those operating in embryos of a distantly related echinoderm, a starfish. These animals diverged from their common ancestor 520-480 million years ago. Their endomesodermal fate maps are similar, except that sea urchins generate a skeletogenic cell lineage that produces a prominent skeleton lacking entirely in starfish larvae. A relevant set of regulatory genes was isolated from the starfish Asterina miniata, their expression patterns determined, and effects on the other genes of perturbing the expression of each were demonstrated. A three-gene feedback loop that is a fundamental feature of the sea urchin GRN for endoderm specification is found in almost identical form in the starfish: a detailed element of GRN architecture has been retained since the Cambrian Period in both echinoderm lineages. The significance of this retention is highlighted by the observation of numerous specific differences in the GRN connections as well. A regulatory gene used to drive skeletogenesis in the sea urchin is used entirely differently in the starfish, where it responds to endomesodermal inputs that do not affect it in the sea urchin embryo. Evolutionary changes in the GRNs since divergence are limited sharply to certain cis-regulatory elements, whereas others have persisted unaltered

Possible thermodynamic structure underlying the laws of Zipf and Benford

We show that the laws of Zipf and Benford, obeyed by scores of numerical data generated by many and diverse kinds of natural phenomena and human activity are related to the focal expression of a generalized thermodynamic structure. This structure is obtained from a deformed type of statistical mechanics that arises when configurational phase space is incompletely visited in a severe way. Specifically, the restriction is that the accessible fraction of this space has fractal properties. The focal expression is an (incomplete) Legendre transform between two entropy (or Massieu) potentials that when particularized to first digits leads to a previously existing generalization of Benford's law. The inverse functional of this expression leads to Zipf's law; but it naturally includes the bends or tails observed in real data for small and large rank. Remarkably, we find that the entire problem is analogous to the transition to chaos via intermittency exhibited by low-dimensional nonlinear maps. Our results also explain the generic form of the degree distribution of scale-free networks.Comment: To be published in European Physical Journal

A Case of Reactive Cervical Lymphadenopathy with Fat Necrosis Impinging on Adjacent Vascular Structures.

A tender neck mass in adults can be a diagnostic challenge due to a wide differential diagnosis, which ranges from reactive lymphadenopathy to malignancy. In this report, we describe a case of a young female with an unusually large and tender reactive lymph node with fat necrosis. The diagnostic imaging findings alone mimicked that of scrofula and malignancy, which prompted a complete workup. Additionally, the enlarged lymph node was compressing the internal jugular vein in the setting of oral contraceptive use by the patient, raising concern for Lemierre's syndrome or internal jugular vein thrombosis. This report shows how, in the appropriate clinical context, and especially with the involvement of adjacent respiratory or neurovascular structures, aggressive diagnostic testing can be indicated

Recent Topics on Very High Energy Gamma-ray Astronomy

With the advent of imaging atmospheric Cherenkov telescopes in late 1980's, ground-based observation of TeV gamma-rays came into reality after struggling trials by pioneers for twenty years, and the number of gamma-ray sources detected at TeV energies has increased to be over seventy now. In this review, recent findings from ground-based very-high-energy gamma-ray observations are summarized (as of 2008 March), and up-to-date problems in this research field are presented.Comment: 6 pages, 4 figures, Proceedings of the International Workshop on Advances in Cosmic Ray Science, March 17-19, 2008, Waseda University, Tokyo, Japan; to be published in Journal of the Physical Society of Japan (supplement

Wiskott-Aldrich Syndrome (WAS) and Dedicator of Cytokinesis 8- (DOCK8) Deficiency

Both Wiskott-Aldrich syndrome (WAS) and dedicator of cytokinesis 8 (DOCK8) deficiency are primary immunodeficiency diseases caused by mutations in genes that result in defective organization of the cytoskeleton in hematopoietic tissues. They share some overlapping features such as a combined immunodeficiency, eczema and a predisposition to autoimmunity and malignancy, but also have some unique features that make them relatively easy to diagnose by clinical means. Both diseases can be cured by HSCT in a large proportion of patients. In WAS it is sometimes difficult to establish an indication for HSCT due to the large variability of disease severity, while HSCT is probably indicated in all patients affected by DOCK8 deficiency. There is considerably more published HSCT experience for WAS than for DOCK8 deficiency, but many open questions remain, which will be discussed in this review

Electric quantum walks with individual atoms

We report on the experimental realization of electric quantum walks, which mimic the effect of an electric field on a charged particle in a lattice. Starting from a textbook implementation of discrete-time quantum walks, we introduce an extra operation in each step to implement the effect of the field. The recorded dynamics of such a quantum particle exhibits features closely related to Bloch oscillations and interband tunneling. In particular, we explore the regime of strong fields, demonstrating contrasting quantum behaviors: quantum resonances vs. dynamical localization depending on whether the accumulated Bloch phase is a rational or irrational fraction of 2\pi.Comment: 5 pages, 4 figure

Years to weeks of seismic unrest and magmatic intrusions precede monogenetic eruptions

Seismic, deformation, and gas activity (unrest) typically precedes volcanic eruptions. Tracking the changes of this activity with monitoring data makes it increasingly possible to successfully forecast eruptions from stratovolcanoes. However, this is not the case for monogenetic volcanoes. Eruptions from these volcanoes tend to be small but are particularly difficult to anticipate since they occur at unexpected locations and there is very limited instrumental monitoring data. Many monogenetic volcanic fields occur in high-density, populated areas and/or tourist destinations, and thus even a small eruption can have a major economic and societal impact. We have gathered the available instrumental data for unrest and combined it with new historical accounts of seismicity. Our occurrences are mainly from high magmatic flux oceanic islands (Canary Islands, Iceland, Papua New Guinea, Mexico, and Japan). We find that seismic activity may start one or two years before eruption, but it intensifies at approximately two or three months, and one or two weeks. The petrological and geochemical characteristics of the deposits show that multiple magma batches interacted in a subvolcanic reservoir, and multiple intrusions occurred on a similar time scales to the seismicity. We propose a general model for these eruptions where early dike intrusions in the crust do not erupt (e.g., stalled intrusions) and make small plumbing systems, but they probably are key in creating a thermal and rheological pathway for later dikes to be able to reach the surface. These observations provide a conceptual framework for better anticipating monogenetic eruptions in similar settings and magmatic fluxes and should lead to improved strategies for mitigation of their associated hazards and risks.This research was partly supported by the National Research Foundation Singapore, the Singapore Ministry of Education (grant MoE2014-T2-2-041), and the Research Centres of Excellence initiativePeer Reviewe