569 research outputs found

    Non-equilibrium dynamics and floral trait interactions shape extant angiosperm diversity.

    Get PDF
    Why are some traits and trait combinations exceptionally common across the tree of life, whereas others are vanishingly rare? The distribution of trait diversity across a clade at any time depends on the ancestral state of the clade, the rate at which new phenotypes evolve, the differences in speciation and extinction rates across lineages, and whether an equilibrium has been reached. Here we examine the role of transition rates, differential diversification (speciation minus extinction) and non-equilibrium dynamics on the evolutionary history of angiosperms, a clade well known for the abundance of some trait combinations and the rarity of others. Our analysis reveals that three character states (corolla present, bilateral symmetry, reduced stamen number) act synergistically as a key innovation, doubling diversification rates for lineages in which this combination occurs. However, this combination is currently less common than predicted at equilibrium because the individual characters evolve infrequently. Simulations suggest that angiosperms will remain far from the equilibrium frequencies of character states well into the future. Such non-equilibrium dynamics may be common when major innovations evolve rarely, allowing lineages with ancestral forms to persist, and even outnumber those with diversification-enhancing states, for tens of millions of years

    Aerogel Scattering Filters for Cosmic Microwave Background Observations

    Get PDF
    We present the design and performance of broadband and tunable infrared-blocking filters for millimeter and sub-millimeter astronomy composed of small scattering particles embedded in an aerogel substrate. The ultra-low-density (< 100 mg/cu cm) aerogel substrate provides an index of refraction as low as 1.05, removing the need for anti-reflection coatings and allowing for broadband operation from DC to above 1 THz. The size distribution of the scattering particles can be tuned to provide a variable cutoff frequency. Aerogel filters with embedded high-resistivity silicon powder are being produced at 40-cm diameter to enable large-aperture cryogenic receivers for cosmic microwave background polarimeters, which require large arrays of sub-Kelvin detectors in their search for the signature of an inflationary gravitational-wave background

    Creative Product Problem-solving Game

    Get PDF
    Creativity is a talent that undergirds invention and innovation, making it an important skill in today’s society. Although students are often told to “be creative,” they many times do not know how and have little practice in this skill. This document presents an analysis of 33 creative products made by adult participants at a state conference for educators working with preK-12 gifted students or their teachers as a model for what teachers can do in their classrooms to allow students to practice creative thinking. During the conference presentation, Torrance’s creative strengths were reviewed with photographic examples, definitions, and suggestions printed on handouts. For the problem-solving game, each participant was given an identical set of recycled/craft materials, and about 30 minutes to create an object or scene fitting with a given theme. This presentation was delivered each of the two days of the conference with a different theme each day: “under water” was the theme the first day and “cool space” was the theme for the products on the second day. Participants each created an object that exhibited creative strengths and followed game-rules using the additional tools of scissors, glue, markers, and thread. Photographs of the final products are shown with their creative strengths identified. Most participants were successful in developing products that showed five creative strengths as required by the game rules. The most common approach to making a creative product that exhibited creative strengths was to tell an original story involving some motion that was detailed, artistically appealing, or humorous, and contained characters with emotional expressions. Because of the success and enthusiasm of participants for the game, the authors recommend it for students, clubs, and recreational activities. [7 Tables, 33 Figures, 6 References

    The Atacama Cosmology Telescope: The LABOCA/ACT Survey of Clusters at All Redshifts

    Full text link
    We present a multi-wavelength analysis of eleven Sunyaev Zel'dovich effect (SZE)-selected galaxy clusters (ten with new data) from the Atacama Cosmology Telescope (ACT) southern survey. We have obtained new imaging from the Large APEX Bolometer Camera (345GHz; LABOCA) on the Atacama Pathfinder EXperiment (APEX) telescope, the Australia Telescope Compact Array (2.1GHz; ATCA), and the Spectral and Photometric Imaging Receiver (250, 350, and 500μm500\,\rm\mu m; SPIRE) on the Herschel Space Observatory. Spatially-resolved 345GHz SZE increments with integrated S/N > 5 are found in six clusters. We compute 2.1GHz number counts as a function of cluster-centric radius and find significant enhancements in the counts of bright sources at projected radii θ<θ2500\theta < \theta_{2500}. By extrapolating in frequency, we predict that the combined signals from 2.1GHz-selected radio sources and 345GHz-selected SMGs contaminate the 148GHz SZE decrement signal by ~5% and the 345GHz SZE increment by ~18%. After removing radio source and SMG emission from the SZE signals, we use ACT, LABOCA, and (in some cases) new Herschel SPIRE imaging to place constraints on the clusters' peculiar velocities. The sample's average peculiar velocity relative to the cosmic microwave background is 153±383kms1153\pm 383\,\rm km\,s^{-1}.Comment: 19 pages, 11 figures, Accepted for Publication in The Astrophysical Journa

    Preliminary seismological and geological studies of the San Fernando, California, earthquake of February 9 1971

    Get PDF
    The San Fernando earthquake was the largest earthquake to occur in the metropolitan Los Angeles area in more than 50 years. It has tentatively been assigned a magnitude, M_L of 6.6, a focal depth of 13.0 km, and an epicentral location about 12 km east of Newhall, California, at 34°24.0'N, 118°23.7'W (Figure 1), but these figures undoubtedly will be modified as further data become available. Although the focal depth is not as well defined as the epicenter, it is consistent with other observations suggesting thrusting on a fault plane dipping north about 45 ° and breaking the surface in the Sylmar-San Fernando area (Figure 1). It should be emphasized that the hypocenter of the main shock represents only the point of initial rupture. Breaking, presumably, then propagated southward and upward from this point, so that the main geological and engineering effects were observed farther south where the fault was shallower and the displacement greater. The location of the main shock is based on readings from permanent stations of the Caltech network, as well as the U. S. Geological Survey station at Point Mugu (SBLG) and the California Department of Water Resources stations at Pyramid (PYR) and Cedar Springs (CSP). Portable Caltech seismographs were installed in the epicentral area as early as 3 hr following the main shock, and, within a few days, there were at least 30 portable units in the region operated by various groups and agencies

    The Atacama Cosmology Telescope: A Measurement of the 600< ell <8000 Cosmic Microwave Background Power Spectrum at 148 GHz

    Full text link
    We present a measurement of the angular power spectrum of the cosmic microwave background (CMB) radiation observed at 148 GHz. The measurement uses maps with 1.4' angular resolution made with data from the Atacama Cosmology Telescope (ACT). The observations cover 228 square degrees of the southern sky, in a 4.2-degree-wide strip centered on declination 53 degrees South. The CMB at arcminute angular scales is particularly sensitive to the Silk damping scale, to the Sunyaev-Zel'dovich (SZ) effect from galaxy clusters, and to emission by radio sources and dusty galaxies. After masking the 108 brightest point sources in our maps, we estimate the power spectrum between 600 < \ell < 8000 using the adaptive multi-taper method to minimize spectral leakage and maximize use of the full data set. Our absolute calibration is based on observations of Uranus. To verify the calibration and test the fidelity of our map at large angular scales, we cross-correlate the ACT map to the WMAP map and recover the WMAP power spectrum from 250 < ell < 1150. The power beyond the Silk damping tail of the CMB is consistent with models of the emission from point sources. We quantify the contribution of SZ clusters to the power spectrum by fitting to a model normalized at sigma8 = 0.8. We constrain the model's amplitude ASZ < 1.63 (95% CL). If interpreted as a measurement of sigma8, this implies sigma8^SZ < 0.86 (95% CL) given our SZ model. A fit of ACT and WMAP five-year data jointly to a 6-parameter LCDM model plus terms for point sources and the SZ effect is consistent with these results.Comment: 15 pages, 8 figures. Accepted for publication in Ap

    The Atacama Cosmology Telescope (ACT): Beam Profiles and First SZ Cluster Maps

    Full text link
    The Atacama Cosmology Telescope (ACT) is currently observing the cosmic microwave background with arcminute resolution at 148 GHz, 218 GHz, and 277 GHz. In this paper, we present ACT's first results. Data have been analyzed using a maximum-likelihood map-making method which uses B-splines to model and remove the atmospheric signal. It has been used to make high-precision beam maps from which we determine the experiment's window functions. This beam information directly impacts all subsequent analyses of the data. We also used the method to map a sample of galaxy clusters via the Sunyaev-Zel'dovich (SZ) effect, and show five clusters previously detected with X-ray or SZ observations. We provide integrated Compton-y measurements for each cluster. Of particular interest is our detection of the z = 0.44 component of A3128 and our current non-detection of the low-redshift part, providing strong evidence that the further cluster is more massive as suggested by X-ray measurements. This is a compelling example of the redshift-independent mass selection of the SZ effect.Comment: 16 pages, 10 figures. Accepted for publication in ApJS. See Marriage et al. (arXiv:1010.1065) and Menanteau et al. (arXiv:1006.5126) for additional cluster result

    The Atacama Cosmology Telescope: Cosmological Parameters from the 2008 Power Spectra

    Full text link
    We present cosmological parameters derived from the angular power spectrum of the cosmic microwave background (CMB) radiation observed at 148 GHz and 218 GHz over 296 deg^2 with the Atacama Cosmology Telescope (ACT) during its 2008 season. ACT measures fluctuations at scales 500<l<10000. We fit a model for the lensed CMB, Sunyaev-Zel'dovich (SZ), and foreground contribution to the 148 GHz and 218 GHz power spectra, including thermal and kinetic SZ, Poisson power from radio and infrared point sources, and clustered power from infrared point sources. The power from thermal and kinetic SZ at 148 GHz is estimated to be B_3000 = 6.8+-2.9 uK^2, where B_l=l(l+1)C_l/2pi. We estimate primary cosmological parameters from the 148 GHz spectrum, marginalizing over SZ and source power. The LCDM cosmological model is a good fit to the data, and LCDM parameters estimated from ACT+WMAP are consistent with the 7-year WMAP limits, with scale invariant n_s = 1 excluded at 99.7% CL (3sigma). A model with no CMB lensing is disfavored at 2.8sigma. By measuring the third to seventh acoustic peaks, and probing the Silk damping regime, the ACT data improve limits on cosmological parameters that affect the small-scale CMB power. The ACT data combined with WMAP give a 6sigma detection of primordial helium, with Y_P = 0.313+-0.044, and a 4sigma detection of relativistic species, assumed to be neutrinos, with Neff = 5.3+-1.3 (4.6+-0.8 with BAO+H0 data). From the CMB alone the running of the spectral index is constrained to be dn/dlnk = -0.034 +- 0.018, the limit on the tensor-to-scalar ratio is r<0.25 (95% CL), and the possible contribution of Nambu cosmic strings to the power spectrum is constrained to string tension Gmu<1.6 \times 10^-7 (95% CL).Comment: 20 pages, 13 figures. Submitted to ApJ. This paper is a companion to Hajian et al. (2010) and Das et al. (2010
    corecore