Coupling and confinement of current in thermoacoustic phased arrays

When a medium is rapidly heated and cooled, heat transfers to its surroundings as sound. A controllable source of this sound is realized through joule heating of thin, conductive films by an alternating current. Here, we show that arrays of these sources generate sound unique to this mechanism. From the sound alone, we spatially resolve current flow by varying the film geometry and electrical phase. Confinement concentrates heat to such a degree that the film properties become largely irrelevant. Electrical coupling between sources creates its own distinctive sound that depends on the current flow direction, making it unusually sensitive to the interactions of multiple currents sharing the same space. By controlling the flow, a full phased array can be created from just a single film.

Avalanche Statistics Identify Intrinsic Stellar Processes near Criticality in KIC 8462852

The star KIC8462852 (Tabby's star) has shown anomalous drops in light flux. We perform a statistical analysis of the more numerous smaller dimming events by using methods found useful for avalanches in ferromagnetism and plastic flow. Scaling exponents for avalanche statistics and temporal profiles of the flux during the dimming events are close to mean field predictions. Scaling collapses suggest that this star may be near a nonequilibrium critical point. The large events are interpreted as avalanches marked by modified dynamics, limited by the system size, and not within the scaling regime.

Massively parallel WRNN reconstructors for spectrum recovery in astronomical photometrical surveys

The investigation of solar-like oscillations for probing star interiors has enjoyed a tremendous growth in the last decade. Once observations are over, the most notable difficulties in properly identifying the true oscillation frequencies of stars are due to the gaps in the observation time-series and the intrinsic stellar granulation noise. This paper presents an innovative neuro-wavelet reconstructor for the missing data of photometric signals. Firstly, gathered data are transformed using wavelet operators and filters, and this operation removes granulation noise, then we predict missing data by a composite of two neural networks, which together allow a "forward and backward" reconstruction. This resulting error is greatly lower than the absolute a priori measurement error. The devised reconstruction approach gives a signal that is better suited to be Fourier transformed when compared with other existing methods.

Strange nonchaotic stars

The unprecedented light curves of the Kepler space telescope document how the brightness of some stars pulsates at primary and secondary frequencies whose ratios are near the golden mean, the most irrational number. A nonlinear dynamical system driven by an irrational ratio of frequencies generically exhibits a strange but nonchaotic attractor. For Kepler's "golden" stars, we present evidence of the first observation of strange nonchaotic dynamics in nature outside the laboratory. This discovery could aid the classification and detailed modeling of variable stars.

Seismic constraints on rotation of Sun-like star and mass of exoplanet

Rotation is thought to drive cyclic magnetic activity in the Sun and Sun-like stars. Stellar dynamos, however, are poorly understood owing to the scarcity of observations of rotation and magnetic fields in stars. Here, inferences are drawn on the internal rotation of a distant Sun-like star by studying its global modes of oscillation. We report asteroseismic constraints imposed on the rotation rate and the inclination of the spin axis of the Sun-like star HD 52265, a principal target observed by the CoRoT satellite that is known to host a planetary companion. These seismic inferences are remarkably consistent with an independent spectroscopic observation (rotational line broadening) and with the observed rotation period of star spots. Furthermore, asteroseismology constrains the mass of exoplanet HD 52265b. Under the standard assumption that the stellar spin axis and the axis of the planetary orbit coincide, the minimum spectroscopic mass of the planet can be converted into a true mass of 1.85(-0.42)(+0.52)M(Jupiter), which implies that it is a planet, not a brown dwarf.

Post-vision and change: do we know how to change?

The scale and importance of Vision and Change in Undergraduate Biology Education: A Call to Action challenges us to ask fundamental questions about widespread transformation of college biology instruction. I propose that we have clarified the "vision" but lack research-based models and evidence needed to guide the "change." To support this claim, I focus on several key topics, including evidence about effective use of active-teaching pedagogy by typical faculty and whether certain programs improve students' understanding of the Vision and Change core concepts. Program evaluation is especially problematic. While current education research and theory should inform evaluation, several prominent biology faculty-development programs continue to rely on self-reporting by faculty and students. Science, technology, engineering, and mathematics (STEM) faculty-development overviews can guide program design. Such studies highlight viewing faculty members as collaborators, embedding rewards faculty value, and characteristics of effective faculty-development learning communities. A recent National Research Council report on discipline-based STEM education research emphasizes the need for long-term faculty development and deep conceptual change in teaching and learning as the basis for genuine transformation of college instruction. Despite the progress evident in Vision and Change, forward momentum will likely be limited, because we lack evidence-based, reliable models for actually realizing the desired "change."

Shooting for the Stars

Observations with the Kepler space telescope are revealing details of the internal structure of distant stars.