Microtubules in hyaloclasts from the Hawaii Scientific Drilling Project #2 phase 1 core, Hilo, Hawaii: evidence of microbe-rock interactions

Minute tubules etched into basalt glass in hyaloclastites from the Hawaii Scientific Drilling Project #2 (HSDP) phase 1 borehole are interpreted as trace fossils formed by microbes, i.e. microendolithic borings. Such borings are one to a few micrometers in diameter and up to >100 µm long; they extend into glass shards from free surfaces (broken shards, vesicles, fractures). Morphologic characterization of microendolithic borings quantitatively describes them for comparison with other occurrences and aids in understanding the interactions between microorganisms and basaltic glass that result in the dissolution of the glass. The first step in working with these features as trace fossils was to modify the ichnofabric index of Droser and Bottjer (1986) for use with minute features that extend into homogeneous material. The modification includes six semiquantitative classes of disruption and is scale-independent, applicable to any size feature. The second step was to apply the new microendolithic ichnofabric index (MII) to the HSDP samples. Analysis of the HSDP samples using the MII showed that the abundance of bioerosion varied throughout the core. Assigned MII values ranged from 1 to 3, average MII values ranged from 1 to 2.44, while the mean MII value of 1.2. Areas with the most bioerosion were located between 1,365.9 and 1,478.8 mbsl and a section of the core centered around 2,117.0 mbsl. The MII values of these locations ranged from 2 to 2.5. Areas with low bioerosion (all samples 100 µm long; they extend into glass shards from free surfaces (broken shards, vesicles, fractures). Morphologic characterization of microendolithic borings quantitatively describes them for comparison with other occurrences and aids in understanding the interactions between microorganisms and basaltic glass that result in the dissolution of the glass. The first step in working with these features as trace fossils was to modify the ichnofabric index of Droser and Bottjer (1986) for use with minute features that extend into homogeneous material. The modification includes six semiquantitative classes of disruption and is scale-independent, applicable to any size feature. The second step was to apply the new microendolithic ichnofabric index (MII) to the HSDP samples. Analysis of the HSDP samples using the MII showed that the abundance of bioerosion varied throughout the core. Assigned MII values ranged from 1 to 3, average MII values ranged from 1 to 2.44, while the mean MII value of 1.2. Areas with the most bioerosion were located between 1,365.9 and 1,478.8 mbsl and a section of the core centered around 2,117.0 mbsl. The MII values of these locations ranged from 2 to 2.5. Areas with low bioerosion (all samples <2) were located between 1,079.0 and 1,320.0 mbsl, 1,799.0 and 1,900.0 mbsl, and all depths below 2,500.0 mbsl. Lastly, such features as length, diameter, ornamentation, density, and complexity and tortuosity were measured to better describe the interactions between microorganisms and basaltic hyaloclastite media. The shortest measured 0.907 µm and the longest measured 129.22 µm. Lengths were approximately log-normally distributed with a geometric mean of 18.9 µm. The tortuosity of borings had a median of 1.29 with a range of 1.227 to 1.37. The least tortuous measured 1.22 and the most tortuous measured 16.46. This was one of the first attempts to quantify the range of morphology and density, of euendolithic microborings in basalt glass. This study extends the sampling scale for ichnological study to what is near the minimum size range of trace fossils. It demonstrates that trace fossil abundance does not simply decrease with depth in ocean islands, unlike basalts of oceanic crust, but varies, probably as a result of variation of the rate of accumulation of suitable substrates

Using the Big Ideas in Cosmology to Teach College Students

Recent advances in our understanding of the Universe have revolutionized our view of its structure, composition and evolution. However, these new ideas have not necessarily been used to improve the teaching of introductory astronomy students. In this project, we have conducted research into student understanding of cosmological ideas so as to develop effective web-based tools to teach basic concepts important to modern cosmology. The tools are intended for use at the introductory college level. Our research uses several instruments, including open-ended and multiple choice surveys conducted at multiple institutions, as well as interviews and course artifacts at one institution, to ascertain what students know regarding modern cosmological ideas, what common misunderstandings and misconceptions they entertain, and what sorts of materials can most effectively overcome student difficulties in learning this material. These data are being used to create a suite of interactive, web-based tutorials that address the major ideas in cosmology using real data. Having students engage with real data is a powerful means to help students overcome certain misconceptions. Students master the scientific concepts and reasoning processes that lead to our current understanding of the universe through interactive tasks, prediction and reflection, experimentation, and model building.Comment: 2012 Fermi Symposium proceedings - eConf C12102

CATS: CfAO Treasury Survey of distant galaxies, supernovae, and AGN's

The NSF Science and Technology Center for Adaptive Optics (CfAO) is supporting a major scientific legacy project called the CfAO Treasury Survey (CATS). CATS is obtaining near-infrared AO data in deep HST survey fields, such as GEMS, GOODS-N, & EGS. Besides summarizing the main objectives of CATS, we highlight some recent imaging work on the study of distant field galaxies, AGNs, and a redshift z = 1.32 supernova. CATS plans the first data release to the community in early 2007 (check http://www.astro.ucla.edu/~irlab/cats/index.shtml for more details on CATS and latest updates).Comment: 2 pages. Proceedings of the IAU Symposium 235, "Galaxy Evolution across the Hubble Time", F. Combes & J. Palous (eds.

The Butcher-Oemler Effect at Moderate Redshift

We present the results of Butcher-Oemler-style analysis of three moderate- redshift (0.1<z<0.2) clusters which have bimodal X-ray surface brightness profiles. We find that at least two of these clusters exhibit unusually high fractions of blue galaxies as compared to clusters at comparable redshifts studied by Butcher and Oemler (1984). This implies that star formation is occurring in a high fraction of the galaxies in the two clusters. Our results are consistent with hierarchical clustering models in which subcluster- subcluster mergers create shocks in the intracluster medium. The shocks, in turn, induce simultaneous starbursts in a large fraction of cluster galaxies. Our study therefore lends weight to the hypothesis that the Butcher-Oemler effect is an environmental, as well as evolutionary, phenomenon.Comment: 22 pages, 8 figures; accepted for publication in A

Spectroscopic Observations of Optically Selected Clusters of Galaxies from the Palomar Distant Cluster Survey

We have conducted a redshift survey of sixteen cluster candidates from the Palomar Distant Cluster Survey (PDCS) to determine both the density of PDCS clusters and the accuracy of the estimated redshifts presented in the PDCS catalog (Postman et. al. 1996). We find that the matched-filter redshift estimate presented in the PDCS has an error sigma_z = 0.06 in the redshift range 0.1 < z < 0.35 based on eight cluster candidates with three or more concordant galaxy redshifts. We measure the low redshift (0.1 < z < 0.35) space density of PDCS clusters to be 31.3^{+30.5}_{-17.1} * E-06 h^3 Mpc^-3 (68% confidence limits for a Poisson distribution) for Richness Class 1 systems. We find a tentative space density of 10.4^{+23.4}_{-8.4}* E-06 h^3 Mpc^-3 for Richness Class 2 clusters. These densities compare favorably with those found for the whole of the PDCS and support the finding that the space density of clusters in the PDCS is a factor of ~5 above that of clusters in the Abell catalog (Abell 1958; Abell, Corwin, and Olowin 1989). These new space density measurements were derived as independently as possible from the original PDCS analysis and therefore, demonstrate the robustness of the original work. Based on our survey, we conclude that the PDCS matched-filter algorithm is successful in detecting real clusters and in estimating their true redshifts in the redshift range we surveyed.Comment: 23 pages with 4 figures and 3 seperate tables. To be published in the November Issue of the Astronomical Journa

Matched Pair Calibration for Ranking Fairness

We propose a test of fairness in score-based ranking systems called matched pair calibration. Our approach constructs a set of matched item pairs with minimal confounding differences between subgroups before computing an appropriate measure of ranking error over the set. The matching step ensures that we compare subgroup outcomes between identically scored items so that measured performance differences directly imply unfairness in subgroup-level exposures. We show how our approach generalizes the fairness intuitions of calibration from a binary classification setting to ranking and connect our approach to other proposals for ranking fairness measures. Moreover, our strategy shows how the logic of marginal outcome tests extends to cases where the analyst has access to model scores. Lastly, we provide an example of applying matched pair calibration to a real-word ranking data set to demonstrate its efficacy in detecting ranking bias.Comment: 19 pages, 8 figure