No abstract

Neuronal cell types are the nodes of neural circuits that determine the flow of information within the brain. Neuronal morphology, especially the shape of the axonal arbor, provides an essential descriptor of cell type and reveals how individual neurons route their output across the brain. Despite the importance of morphology, few projection neurons in the mouse brain have been reconstructed in their entirety. Here we present a robust and efficient platform for imaging and reconstructing complete neuronal morphologies, including axonal arbors that span substantial portions of the brain. We used this platform to reconstruct more than 1,000 projection neurons in the motor cortex, thalamus, subiculum, and hypothalamus. Together, the reconstructed neurons comprise more than 75 meters of axonal length and are available in a searchable online database. Axonal shapes revealed previously unknown subtypes of projection neurons and suggest organizational principles of long-range connectivity.

OpenBU http://open.bu.edu Biomedical Engineering BU Open Access Articles 2019-09-19 Reconstruction of 1,000 projection neurons reveals new cell types and organization of long-ra...

Acoustic detection and tracking of small (swimmer-size) targets while minimizing the incidents of false alerts can be challenging in a shallow, multipath, high-clutter harbor environment. One common problem involves track intermittency where periods or locations of high clutter or multipath interference inhibit detection and cause tracks to fail and restart. This paper describes the results of applying track segment association and related algorithms from airborne and ground radar applications [e.g., Zhang and Bar-Shalom, IEEE Trans. Aerosp. Electron. Syst. 47(3), 1899–1914 (2011)] to an active sonar network for underwater port surveillance [Edelson et al., J.Acoust. Soc. Am. 129(4), 2598 (2011), Stein et al., J. Acoust. Soc. Am. 121(5), 3084 (2007)] using real-world swimmer and synthetic target data.

The significance of seabed shear properties to low-frequency propagation in shallow water is well established, and since the early 1980's the measurement of the properties of the seismic interface, or Scholte waves, has been recognized as the most direct tool fordetermining the shear properties. In Sep. 2011, an experiment was carried out in Singapore harbor aimed at investigating the excitation of Scholte waves by objects dropped from the surface and impacting the seabed. For that purpose, a 100 m aperture array of 10 ocean bottom seismometers (OBS) with logarithmic spacing was deployed in approximately 16 m of water, in an area with close to range-independent seabed stratification. Spherical and cylindrical objects were equipped with 6 degree-of-freedom motion packages which allowed for accurate measurement of the impact forcing. The objects were dropped onto the seabed at various bearings and distances relative to the array, providing a unique, rich data set which provides the opportunity of estimating the statistic of the seabed shear properties. This paper will describe the experimental setup, and the spatial variability of the phase- and group velocity, and attenuation of the Scholte waves and the associated variability of the seabed geoacoustics will be assessed. [Work supported by DSO National Laboratories, Singapore].