Observations of extreme spatial rates of change of ionospheric electron content and the characterization strategy for mitigation applied by the U.S. local area augmentation system are shown. During extreme ionospheric activity, the gradient suffered by a global navigation satellite system user a few kilometers away from a ground reference station may reach as high as 425 mm of delay (at the GPS L1 frequency) per km of user separation. The method of data analysis that produced these results is described, and a threat space that parameterizes these possible threats to user integrity is defined. Certain configurations of user, reference station, global navigation satellite system satellite, and ionospheric storm-enhanced density may inhibit detection of the anomalous ionosphere by the reference station.

By exploiting N-dimensional multiplexing, i.e. 54.139-Gbit/s OFDM-8QAM signals over 368 WDM pol-muxed 26 orbital angular momentum (OAM) modes, we experimentally demonstrate a free-space data link with an aggregate transmission capacity of 1.036 Pbit/s and a high spectral efficiency of 112.6 bit/s/Hz.

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Soft robotic snakes promise significant advantages in achieving traveling curvature waves with a reduced number of active segments as well as allowing for safe and adaptive interaction with the environment and human users. However, current soft robot platforms suffer from a lack of accurate theoretical dynamic models and proprioceptive measurements, which impede advancements toward full autonomy. To address this gap, this paper details our recent results on the design, fabrication, and experimental evaluation of a new-generation pressure-operated soft robotic snake platform we call the WPI SRS, which employs custom magnetic sensors embedded in a flexible backbone to continuously monitor the curvature of each of its four bidirectional bending segments. In addition, we present a complete and accurate dynamic undulatory locomotion model that accounts for the propagation of frictional moments to describe linear and rotational motions of the SRS. Experimental studies indicate that on-board sensory measurements provide accurate real-time curvature feedback, and numerical simulations offer a level of abstraction for lateral undulation under ideal conditions.

Background: Fibrosis in atrial myocardium is a common phenomenon for patients with atrial fibrillation (AF). Remodeling of connexins was found accompanying with AF. The aim of the study is to investigate whether it is by causing the remodeling of connexin 43 (Cx43) that the fibrosis of atrial muscle plays an important role during the initiation and maintenance of AF. Methods: Samples of right atrial appendage were taken from 24 patients with rheumatic valvular disease during surgery. Fibrosis and remodeling of Cx43 was examined by microscopy and ultramicroscopy technique and analyzed by image analyzer. The collagen volume fraction of type I (CVF-I) and the volume fraction of Cx43 (Cx43VF) were studied between AF and sinus rhythm (SR) groups. Results: (1) Microscopic examination demonstrated that CVF-I significantly increased and Cx43VF decreased in patients with AF compared to those with SR. (2) The CVF-I was negatively correlated with the Cx43VF. Conclusion: The results suggest that fibrosis and remodeling of Cx43 are involved in the pathophysiologic mechanism of human AF. Fibrosis of atrial muscle may play an important role in the process of AF by means of interfering with remodeling of connexins.