The unprecedented volume and rate of transient events that will be discovered by the Large Synoptic Survey Telescope (LSST) demands that the astronomical community update its followup paradigm. Alert-brokers -automated software system to sift through, characterize, annotate and prioritize events for followup -will be critical tools for managing alert streams in the LSST era. The Arizona-NOAO Temporal Analysis and Response to Events System (ANTARES) is one such broker. In this work, we develop a machine learning pipeline to characterize and classify variable and transient sources only using the available multiband optical photometry. We describe three illustrative stages of the pipeline, serving the three goals of early, intermediate and retrospective classification of alerts. The first takes the form of variable vs transient categorization, the second, a multi-class typing of the combined variable and transient dataset, and the third, a purity-driven subtyping of a transient class. While several similar algorithms have proven themselves in simulations, we validate their performance on real observations for the first time. We quantitatively evaluate our pipeline on sparse, unevenly sampled, heteroskedastic data from various existing observational campaigns, and demonstrate very competitive classification performance. We describe our progress towards adapting the pipeline developed in this work into a real-time broker working on live alert streams from time-domain surveys.

Background: Testing MRI gradient-induced heating of implanted medical devices is required by regulatory organizations and others. A gradient heating test of the ISO 10974 Technical Specification (TS) for active implants was adopted for this study of passive hip implants. All but one previous study of hip implants used nonuniform gradient exposure fields in clinical scanners and reported heating of less than 5 C. This present study adapted methods of the TS, addressing the unmet need for identifying worst-case heating via exposures to uniform gradient fields. Purpose: To identify gradient-field parameters affecting maximum heating in vitro for a hip implant and a cylindrical titanium disk. Study Type: Computational simulations and experimental validation of induced heating. Phantom: Tissue-simulating gel. Field Strength: 42 T/s RMS, sinusoidal, continuous B fields with high spatial uniformity Assessment: Hip implant heating at 1-10 kHz, via computational modeling, validated by limited point measurements. Experimental measurements of exposures of an implant at 42 T/s for 4, 6, and 9 kHz, analyzed at 50, 100, and 150 seconds. Statistical Tests: One sample student's t-test to assess difference between computational and experimental results. Experimental vs. computational results were not significantly different (p < 0.05). Results: Maximum simulated temperature rise (10-minute exposure) was 10 C at 1 kHz and 0.66 C at 10 kHz. The ratio of the rise for 21 T/s vs. 42 T/s RMS was 4, after stabilizing at 50 seconds (dB/dt ratio squared). Data Conclusions: Heating of an implant is proportional to the frequency of the B field and the implant's cross-sectional area and is greater for a thickness on the order of its skin depth. Testing with lower values of dB/dt RMS with lower cost amplifiers enables prediction of heating at higher values for dB/dt squared (per ISO TS) with identical frequency components and waveforms, once thermal equilibrium occurs.

We present Arecibo, GBT, VLA, and WIYN/pODI observations of the ALFALFA source AGC 226067. Originally identified as an ultra-compact high velocity cloud and candidate Local Group galaxy, AGC 226067 is spatially and kinematically coincident with the Virgo cluster, and the identification by multiple groups of an optical counterpart with no resolved stars supports the interpretation that this systems lies at the Virgo distance (D = 17 Mpc). The combined observations reveal that the system consists of multiple AGC 226067 and AGC 229490 may be connected by an H i bridge, and AGC 229490 and AGC 229491 are separated by only 0.5 . The current data do not resolve the H i in AGC 229490 and its origin is unclear. We discuss possible scenarios for this system of objects: an interacting system of dwarf galaxies, accretion of material onto AGC 226067, or stripping of material from AGC 226067.

Magnetic resonance imaging is one of the most widely used diagnostic medical imaging modalities used for various diseases. The most common RF body coil design used in the clinical practice consists of a cylindrical tube-like coil known as a birdcage coil. There is increasing use of high field strengths (1.0 T and higher) open-bore vertical MR systems due to an increase in obesity in the patient population. These open-bore MRI systems consist of a planar-pair RF body coil.