Learning long-range spatial dependencies with horizontal gated-recurrent units

Progress in deep learning has spawned great successes in many engineering applications. As a prime example, convolutional neural networks, a type of feedforward neural networks, are now approaching -- and sometimes even surpassing -- human accuracy on a variety of visual recognition tasks. Here, however, we show that these neural networks and their recent extensions struggle in recognition tasks where co-dependent visual features must be detected over long spatial ranges. We introduce the horizontal gated-recurrent unit (hGRU) to learn intrinsic horizontal connections -- both within and across feature columns. We demonstrate that a single hGRU layer matches or outperforms all tested feedforward hierarchical baselines including state-of-the-art architectures which have orders of magnitude more free parameters. We further discuss the biological plausibility of the hGRU in comparison to anatomical data from the visual cortex as well as human behavioral data on a classic contour detection task.Comment: Published at NeurIPS 2018 https://papers.nips.cc/paper/7300-learning-long-range-spatial-dependencies-with-horizontal-gated-recurrent-unit

Expansion of Thaumarchaeota habitat range is correlated with horizontal transfer of ATPase operons.

Thaumarchaeota are responsible for a significant fraction of ammonia oxidation in the oceans and in soils that range from alkaline to acidic. However, the adaptive mechanisms underpinning their habitat expansion remain poorly understood. Here we show that expansion into acidic soils and the high pressures of the hadopelagic zone of the oceans is tightly linked to the acquisition of a variant of the energy-yielding ATPases via horizontal transfer. Whereas the ATPase genealogy of neutrophilic Thaumarchaeota is congruent with their organismal genealogy inferred from concatenated conserved proteins, a common clade of V-type ATPases unites phylogenetically distinct clades of acidophilic/acid-tolerant and piezophilic/piezotolerant species. A presumptive function of pumping cytoplasmic protons at low pH is consistent with the experimentally observed increased expression of the V-ATPase in an acid-tolerant thaumarchaeote at low pH. Consistently, heterologous expression of the thaumarchaeotal V-ATPase significantly increased the growth rate of E. coli at low pH. Its adaptive significance to growth in ocean trenches may relate to pressure-related changes in membrane structure in which this complex molecular machine must function. Together, our findings reveal that the habitat expansion of Thaumarchaeota is tightly correlated with extensive horizontal transfer of atp operons

RR Lyrae variables in Galactic globular clusters: IV. Synthetic HB and RR Lyrae predictions

We present theoretical predictions concerning horizontal branch stars in globular clusters, including RR Lyrae variables, as derived from synthetic procedures collating evolutionary and pulsational constraints. On this basis, we explore the predicted behavior of the pulsators as a function of the horizontal branch morphology and over the metallicity range Z=0.0001 to 0.006, revealing an encouraging concordance with the observed distribution of fundamentalised periods with metallicity. Theoretical relations connecting periods to K magnitudes and BV or VI Wesenheit functions are presented, both appearing quite independent of the horizontal branch morphology only with Z greater or equal than 0.001. Predictions concerning the parameter R are also discussed and compared under various assumptions about the horizontal branch reference luminosity level.Comment: 11 pages, 10 figures. Accepted for publication in "Astronomy and Astrophysics

Temporal power spectra of the horizontal velocity of the solar photosphere

We have derived the temporal power spectra of the horizontal velocity of the solar photosphere. The data sets for 14 quiet regions observed with the Gband filter of Hinode/SOT are analyzed to measure the temporal fluctuation of the horizontal velocity by using the local correlation tracking (LCT) method. Among the high resolution (~0.2") and seeing-free data sets of Hinode/SOT, we selected the observations whose duration is longer than 70 minutes and cadence is about 30 s. The so-called k-{\omega} diagrams of the photospheric horizontal velocity are derived for the first time to investigate the temporal evolution of convection. The power spectra derived from k-omega diagrams typically have a double power law shape bent over at a frequency of 4.7 mHz. The power law index in the high frequency range is -2.4 while the power law index in the low frequency range is -0.6. The root mean square of the horizontal speed is about 1.1 km/s when we use a tracer size of 0.4" in LCT method. Autocorrelation functions of intensity fluctuation, horizontal velocity, and its spatial derivatives are also derived in order to measure the correlation time of the stochastic photospheric motion. Since one of possible energy sources of the coronal heating is the photospheric convection, the power spectra derived in the present study will be of high value to quantitatively justify various coronal heating models.Comment: 17 pages, 5 figures, accepted for publication in Astrophysical Journa

Nurses’ Perceptions of Horizontal Violence

In this article, I describe a study exploring horizontal violence and nurses’ perceptions of the phenomenon within the context of two 28-bed inpatient hospital units. The purpose of the study was to develop a clearer understanding of horizontal violence, incorporating observation and inquiry to identify the language nurses use to describe their experiences and factors in the nursing work environment that may perpetuate the phenomenon. Observation, review and analysis of policies, and interviews with staff were completed between June and November 2012. Thematic analysis resulted in five themes: (a) behaviors are minimized and not recognized, (b) fear inhibits all reporting, (c) avoidance and isolation are coping strategies, (d) lack of respect and support, and (e) organizational chaos. The findings suggest future interventions must address a range of factors that perpetuate horizontal violence within the nursing work environment with consideration for the embeddedness and complexity of the phenomenon

Rotation of Horizontal Branch Stars in Globular Clusters

The rotation of horizontal branch stars places important constraints on angular momentum evolution in evolved stars and therefore rotational mixing on the giant branch. Prompted by new observations of rotation rates of horizontal branch stars, we calculate simple models for the angular momentum evolution of a globular cluster giant star from the base of the giant branch to the star's appearance on the horizontal branch. We include mass loss, and infer the accompanied loss of angular momentum for each of four assumptions about the internal angular momentum profile. These models are compared to observations of horizontal branch rotation rates in M13. We find that rapid rotation on the horizontal branch can be reconciled with slow solid body main sequence rotation if giant branch stars have differential rotation in their convective envelopes and a rapidly rotating core, which is then followed by a redistribution of angular momentum on the horizontal branch. We discuss the physical reasons why these very different properties relative to the solar case may exist in giants. Rapid rotation in the core of the main sequence precursors of the rapidly rotating horizontal branch star, or an angular momentum source on the giant branch is required for all cases if the rotational velocity of turnoff stars is less than 4 km s$^{-1}$. We suggest that the observed range in rotation rates on the horizontal branch is caused by internal angular momentum redistribution which occurs on a timescale comparable to the evolution of the stars on the horizontal branch. The apparent lack of rapid horizontal branch rotators hotter than 12 000 K in M13 could be a consequence of gravitational settling, which inhibits internal angular momentum transport. Alternative explanations and observational tests are discussed.Comment: 32 pages, 7 figures, submitted to the Astrophysical Journa