Cooperative Synchronization in Wireless Networks

Synchronization is a key functionality in wireless network, enabling a wide variety of services. We consider a Bayesian inference framework whereby network nodes can achieve phase and skew synchronization in a fully distributed way. In particular, under the assumption of Gaussian measurement noise, we derive two message passing methods (belief propagation and mean field), analyze their convergence behavior, and perform a qualitative and quantitative comparison with a number of competing algorithms. We also show that both methods can be applied in networks with and without master nodes. Our performance results are complemented by, and compared with, the relevant Bayesian Cram\'er-Rao bounds

Cooperative Simultaneous Localization and Synchronization in Mobile Agent Networks

Cooperative localization in agent networks based on interagent time-of-flight measurements is closely related to synchronization. To leverage this relation, we propose a Bayesian factor graph framework for cooperative simultaneous localization and synchronization (CoSLAS). This framework is suited to mobile agents and time-varying local clock parameters. Building on the CoSLAS factor graph, we develop a distributed (decentralized) belief propagation algorithm for CoSLAS in the practically important case of an affine clock model and asymmetric time stamping. Our algorithm allows for real-time operation and is suitable for a time-varying network connectivity. To achieve high accuracy at reduced complexity and communication cost, the algorithm combines particle implementations with parametric message representations and takes advantage of a conditional independence property. Simulation results demonstrate the good performance of the proposed algorithm in a challenging scenario with time-varying network connectivity.Comment: 13 pages, 6 figures, 3 tables; manuscript submitted to IEEE Transaction on Signal Processin

Anterior Primary Total Hip Arthroplasty

Total hip arthroplasty (THA) is the preferred treatment for end-stage osteoarthritis of the hip. The posterior, posterolateral, direct lateral, anterolateral, or the anterior approaches are the currently established surgical approaches for THA. Over the last decade, the anterior approach has gained increasing popularity. Its muscle-sparing nature and fluoroscopy-guided component positioning are the most important benefits. It has been suggested that postoperative recovery is facilitated by an anterior approach. Patients do not need to follow hip precautions, and can return to driving after 1 week. The anterior approach uses a muscle interval between the tensor fasciae latae and the rectus femoris to open the capsule without detachment of muscles. Especially, the external rotators and posterior capsule remain intact and reduce the risk of posterior dislocation. Accuracy of acetabular component positioning has an impact on postoperative dislocation rates, polyethylene wear, and impingement. When the operation is done in a supine position, fluoroscopy is available to check the acetabular component inclination and anteversion during THA as well as leg length and offset. The current chapter reports on the surgical approach, surgical technique, and results of anterior THA

A neutral Pt3 stack unsupported by any bridging ligand

Pt⋯Pt⋯Pt interactions via their d8 orbitals, combined with π–π stacking of deprotonated, chelating 2-(3′-pyrazolyl)pyridine (pyzpy) ligands, are responsible for trans-Pt(pyzpy)2 (2) crystallization in a stack of three molecules unsupported by any bridging ligand

Es fährt ein Zug nach Nirgendwo. Martin Schulz, Angela Merkel und die Bundestagswahl 2017

Als Martin Schulz beim außerordentlichen SPD-Bundesparteitag in Berlin am 19. März 2017 mit 100 % der Delegiertenstimmen zum Parteivorsitzenden und Kanzlerkandidaten gewählt wurde und der „Schulz-Zug“ damit richtig Fahrt aufnahm, hätte sich wohl niemand vorstellen können, dass dieser Zug Martin Schulz binnen Jahresfrist aufs politische Abstellgleis führen würde. In der Tat dürften Tiefe und Geschwindigkeit des politischen Falls selbst für sozialdemokratische Verhältnisse beispiellos sein. Betrachtet man Sigmar Gabriels Ankündigung vom 24. Januar 2017, zugunsten Schulz’ auf Parteivorsitz und Kanzlerkandidatur verzichten zu wollen, als Ausgangspunkt der Entwicklung und Martin Schulz’ Erklärung vom 9. Februar 2018, doch nicht als Außenmister ins Kabinett Merkel IV eintreten zu wollen, als ihren Schlusspunkt, so dauerte es gerade 382 Tage, bis sich Martin Schulz in der öffentlichen Wahrnehmung vom Heilsbringer der Sozialdemokratie zu einem Paria der bundesdeutschen Politik gewandelt hatte

Repeated pulses of vertical methane flux recorded in glacial sediments from the southeast Bering Sea

Author Posting. © American Geophysical Union, 2011. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Paleoceanography 26 (2011): PA2210, doi:10.1029/2010PA001993.There is controversy over the role of marine methane hydrates in atmospheric methane concentrations and climate change during the last glacial period. In this study of two sediment cores from the southeast Bering Sea (700 m and 1467 m water depth), we identify multiple episodes during the last glacial period of intense methane flux reaching the seafloor. Within the uncertainty of the radiocarbon age model, the episodes are contemporaneous in the two cores and have similar timing and duration as Dansgaard-Oeschger events. The episodes are marked by horizons of sediment containing 13C-depleted authigenic carbonate minerals; 13C-depleted archaeal and bacterial lipids, which resemble those found in ANME-1 type anaerobic methane oxidizing microbial consortia; and changes in the abundance and species distribution of benthic foraminifera. The similar timing and isotopic composition of the authigenic carbonates in the two cores is consistent with a region-wide increase in the upward flux of methane bearing fluids. This study is the first observation outside Santa Barbara Basin of pervasive, repeated methane flux in glacial sediments. However, contrary to the “Clathrate Gun Hypothesis” (Kennett et al., 2003), these coring sites are too deep for methane hydrate destabilization to be the cause, implying that a much larger part of the ocean's sedimentary methane may participate in climate or carbon cycle feedback at millennial timescales. We speculate that pulses of methane in these opal-rich sediments could be caused by the sudden release of overpressure in pore fluids that builds up gradually with silica diagenesis. The release could be triggered by seismic shaking on the Aleutian subduction zone caused by hydrostatic pressure increase associated with sea level rise at the start of interstadials.Support for this project was from the National Science Foundation Office of Polar Programs, United States Department of Energy, Oak Foundation, and MARUM at University of Bremen

Cd4+ T Cell Subsets during Virus Infection: Protective Capacity Depends on Effector Cytokine Secretion and on Migratory Capability

To analyze the antiviral protective capacities of CD4+ T helper (Th) cell subsets, we used transgenic T cells expressing an I-Ab–restricted T cell receptor specific for an epitope of vesicular stomatitis virus glycoprotein (VSV-G). After polarization into Th1 or Th2 effectors and adoptive transfer into T cell–deficient recipients, protective capacities were assessed after infection with different types of viruses expressing the VSV-G. Both Th1 and Th2 CD4+ T cells could transfer protection against systemic VSV infection, by stimulating the production of neutralizing immunoglobulin G antibodies. However, only Th1 CD4+ T cells were able to mediate protection against infection with recombinant vaccinia virus expressing the VSV-G (Vacc-IND-G). Similarly, only Th1 CD4+ T cells were able to rapidly eradicate Vacc-IND-G from peripheral organs, to mediate delayed-type hypersensitivity responses against VSV-G and to protect against lethal intranasal infection with VSV. Protective capacity correlated with the ability of Th1 CD4+ T cells to rapidly migrate to peripheral inflammatory sites in vivo and to respond to inflammatory chemokines that were induced after virus infection of peripheral tissues. Therefore, the antiviral protective capacity of a given CD4+ T cell is governed by the effector cytokines it produces and by its migratory capability

Multi-messenger observations of a binary neutron star merger

On 2017 August 17 a binary neutron star coalescence candidate (later designated GW170817) with merger time 12:41:04 UTC was observed through gravitational waves by the Advanced LIGO and Advanced Virgo detectors. The Fermi Gamma-ray Burst Monitor independently detected a gamma-ray burst (GRB 170817A) with a time delay of ~1.7 s with respect to the merger time. From the gravitational-wave signal, the source was initially localized to a sky region of 31 deg2 at a luminosity distance of 40+8-8 Mpc and with component masses consistent with neutron stars. The component masses were later measured to be in the range 0.86 to 2.26 Mo. An extensive observing campaign was launched across the electromagnetic spectrum leading to the discovery of a bright optical transient (SSS17a, now with the IAU identification of AT 2017gfo) in NGC 4993 (at ~40 Mpc) less than 11 hours after the merger by the One- Meter, Two Hemisphere (1M2H) team using the 1 m Swope Telescope. The optical transient was independently detected by multiple teams within an hour. Subsequent observations targeted the object and its environment. Early ultraviolet observations revealed a blue transient that faded within 48 hours. Optical and infrared observations showed a redward evolution over ~10 days. Following early non-detections, X-ray and radio emission were discovered at the transient’s position ~9 and ~16 days, respectively, after the merger. Both the X-ray and radio emission likely arise from a physical process that is distinct from the one that generates the UV/optical/near-infrared emission. No ultra-high-energy gamma-rays and no neutrino candidates consistent with the source were found in follow-up searches. These observations support the hypothesis that GW170817 was produced by the merger of two neutron stars in NGC4993 followed by a short gamma-ray burst (GRB 170817A) and a kilonova/macronova powered by the radioactive decay of r-process nuclei synthesized in the ejecta