My Science Tutor (MyST) -- A Large Corpus of Children's Conversational Speech

This article describes the MyST corpus developed as part of the My Science Tutor project -- one of the largest collections of children's conversational speech comprising approximately 400 hours, spanning some 230K utterances across about 10.5K virtual tutor sessions by around 1.3K third, fourth and fifth grade students. 100K of all utterances have been transcribed thus far. The corpus is freely available (https://myst.cemantix.org) for non-commercial use using a creative commons license. It is also available for commercial use (https://boulderlearning.com/resources/myst-corpus/). To date, ten organizations have licensed the corpus for commercial use, and approximately 40 university and other not-for-profit research groups have downloaded the corpus. It is our hope that the corpus can be used to improve automatic speech recognition algorithms, build and evaluate conversational AI agents for education, and together help accelerate development of multimodal applications to improve children's excitement and learning about science, and help them learn remotely

Weak Lensing by Large-Scale Structure: A Dark Matter Halo Approach

Weak gravitational lensing observations probe the spectrum and evolution of density fluctuations and the cosmological parameters which govern them but are currently limited to small fields and subject to selection biases. We show how the expected signal from large-scale structure arises from the contributions from and correlations between individual halos. We determine the convergence power spectrum as a function of the maximum halo mass and so provide the means to interpret results from surveys that lack high mass halos either through selection criteria or small fields. Since shot noise from rare massive halos is mainly responsible for the sample variance below 10', our method should aid our ability to extract cosmological information from small fields.Comment: 4 ApJ pages, 3 figures; submitted to ApJ Letter

The Luminosity Function of Low-Redshift Abell Galaxy Clusters

We present the results from a survey of 57 low-redshift Abell galaxy clusters to study the radial dependence of the luminosity function (LF). The dynamical radius of each cluster, r200, was estimated from the photometric measurement of cluster richness, Bgc. The shape of the LFs are found to correlate with radius such that the faint-end slope, alpha, is generally steeper on the cluster outskirts. The sum of two Schechter functions provides a more adequate fit to the composite LFs than a single Schechter function. LFs based on the selection of red and blue galaxies are bimodal in appearance. The red LFs are generally flat for -22 < M_Rc < -18, with a radius-dependent steepening of alpha for M_Rc > -18. The blue LFs contain a larger contribution from faint galaxies than the red LFs. The blue LFs have a rising faint-end component (alpha ~ -1.7) for M_Rc > -21, with a weaker dependence on radius than the red LFs. The dispersion of M* was determined to be 0.31 mag, which is comparable to the median measurement uncertainty of 0.38 mag. This suggests that the bright-end of the LF is universal in shape at the 0.3 mag level. We find that M* is not correlated with cluster richness when using a common dynamical radius. Also, we find that M* is weakly correlated with BM-type such that later BM-type clusters have a brighter M*. A correlation between M* and radius was found for the red and blue galaxies such that M* fades towards the cluster center.Comment: Accepted for publication in ApJ, 16 pages, 4 tables, 24 figure

Effect of glyphosate on lipoxygenase of cowpea seed

Foi obtida, com solução de CaCl2 a 0,68 mM e pH 7,5, a atividade máxima de lipoxigenase em sementes de caupi (Vigna unguiculata (L.) Walp). Foram analisadas sementes durante a germinação, e observou-se que a atividade específica de lipoxigenase diminuiu durante o processo. Sementes de plantas tratadas com o herbicida glifosato (N - (fosfonometil) glicina) como dessecante mostraram significante aumento da atividade específica de lipoxigenase. Isto pode ser resultado do efeito do herbicida nas plantas. Tal conclusão é baseada no fato de que a. a lipoxigenase, que teve sua atividade específica aumentada pelo glifosato, pode promover a formação do ácido 12-oxo-fitodienóico; b. este, por sua vez, é um possível precursor do ácido jasmônico, um regulador de crescimento que promove senescência em plantas, explicando-se, desta maneira, a ação do herbicida nelas. Pelo método utilizado, não foi encontrada a enzima em folhas ou outras partes verdes das plantas. The predominant cowpea seed lipoxygenase was optimally activated by calcium at 0.68 mM and at pH 7.5. Seeds were analyzed during germinaton and showed a decrease in lipoxygenase specific activity with time. Seeds from plants treated with the herbicide glyphosate (N - (phosphonomethyl) glycine) showed a significant increase in lipoxygenase content. This could have been a result of senescence, or the effects of the herbicide on those plants. Such a conclusion is basead on findings that a. lipoxygenase, the activity of which was enhanced by glyphosate, has been reported to promote formation of 12-oxo-phytodienoic acid, and b. 12-oxo-phytodienoic acid has been proposed to be a precursor of jasmonic acid, a growth regulator which promotes senescence of plants. With the assay technique utilized, no lipoxygenase was found in mature leaves.

The Galaxy Population of Low-Redshift Abell Clusters

We present a study of the luminosity and color properties of galaxies selected from a sample of 57 low-redshift Abell clusters. We utilize the non-parametric dwarf-to-giant ratio (DGR) and the blue galaxy fraction (fb) to investigate the clustercentric radial-dependent changes in the cluster galaxy population. Composite cluster samples are combined by scaling the counting radius by r200 to minimize radius selection bias. The separation of galaxies into a red and blue population was achieved by selecting galaxies relative to the cluster color-magnitude relation. The DGR of the red and blue galaxies is found to be independent of cluster richness (Bgc), although the DGR is larger for the blue population at all measured radii. A decrease in the DGR for the red and red+blue galaxies is detected in the cluster core region, while the blue galaxy DGR is nearly independent of radius. The fb is found not to correlate with Bgc; however, a steady decline toward the inner-cluster region is observed for the giant galaxies. The dwarf galaxy fb is approximately constant with clustercentric radius except for the inner cluster core region where fb decreases. The clustercentric radial dependence of the DGR and the galaxy blue fraction, indicates that it is unlikely that a simple scenario based on either pure disruption or pure fading/reddening can describe the evolution of infalling dwarf galaxies; both outcomes are produced by the cluster environment.Comment: 28 pages, 6 figures, accepted for publication in Ap

Weak Lensing of the CMB: A Harmonic Approach

Weak lensing of CMB anisotropies and polarization for the power spectra and higher order statistics can be handled directly in harmonic-space without recourse to real-space correlation functions. For the power spectra, this approach not only simplifies the calculations but is also readily generalized from the usual flat-sky approximation to the exact all-sky form by replacing Fourier harmonics with spherical harmonics. Counterintuitively, due to the nonlinear nature of the effect, errors in the flat-sky approximation do not improve on smaller scales. They remain at the 10% level through the acoustic regime and are sufficiently large to merit adoption of the all-sky formalism. For the bispectra, a cosmic variance limited detection of the correlation with secondary anisotropies has an order of magnitude greater signal-to-noise for combinations involving magnetic parity polarization than those involving the temperature alone. Detection of these bispectra will however be severely noise and foreground limited even with the Planck satellite, leaving room for improvement with higher sensitivity experiments. We also provide a general study of the correspondence between flat and all sky potentials, deflection angles, convergence and shear for the power spectra and bispectra.Comment: 17 pages, 5 figures, submitted to PR

Cytological and transcript analyses reveal fat and lazy persister-like bacilli in tuberculous sputum

As nonreplicating tubercle bacilli are tolerant to the cidal action of antibiotics and resistant to multiple stresses, identification of this persister-like population of tubercle bacilli in sputum presents exciting and tractable new opportunities to investigate both responses to chemotherapy and the transmission of tuberculosis

Mycobacterium tuberculosis ClpP Proteases Are Co-transcribed but Exhibit Different Substrate Specificities

PMCID: PMC3613350This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited

Theory of Circle Maps and the Problem of One-Dimensional Optical Resonator with a Periodically Moving Wall

We consider the electromagnetic field in a cavity with a periodically oscillating perfectly reflecting boundary and show that the mathematical theory of circle maps leads to several physical predictions. Notably, well-known results in the theory of circle maps (which we review briefly) imply that there are intervals of parameters where the waves in the cavity get concentrated in wave packets whose energy grows exponentially. Even if these intervals are dense for typical motions of the reflecting boundary, in the complement there is a positive measure set of parameters where the energy remains bounded.Comment: 34 pages LaTeX (revtex) with eps figures, PACS: 02.30.Jr, 42.15.-i, 42.60.Da, 42.65.Y

The global oscillation network group site survey. II. Results

The Global Oscillation Network Group (GONG) Project will place a network of instruments around the world to observe solar oscillations as continuously as possible for three years. The Project has now chosen the six network sites based on analysis of survey data from fifteen sites around the world. The chosen sites are: Big Bear Solar Observatory, California; Mauna Loa Solar Observatory, Hawaii; Learmonth Solar Observatory, Australia; Udaipur Solar Observatory, India; Observatorio del Teide, Tenerife; and Cerro Tololo Interamerican Observatory, Chile. Total solar intensity at each site yields information on local cloud cover, extinction coefficient, and transparency fluctuations. In addition, the performance of 192 reasonable components analysis. An accompanying paper describes the analysis methods in detail; here we present the results of both the network and individual site analyses. The selected network has a duty cycle of 93.3%, in good agreement with numerical simulations. The power spectrum of the network observing window shows a first diurnal sidelobe height of 3 × 10⁻⁴ with respect to the central component, an improvement of a factor of 1300 over a single site. The background level of the network spectrum is lower by a factor of 50 compared to a single-site spectrum