Light pollution at high zenith angles, as measured at Cerro Tololo Inter-American Observatory

On the basis of measurements of the V-band sky brightness obtained at Cerro Tololo Inter-American Observatory in December 2006 and December 2008 we confirm the functional form of the basic model of Garstang (1989, 1991). At high zenith angles we measure an enhancement of a factor of two over Garstang's later model when there is no marine cloud layer over La Serena/Coquimbo. No corresponding enhancement is found in the B-band.Comment: 12 pages, 4 figures, to be published in the March, 2010, issue of Publs. of the Astron. Soc. of the Pacifi

Nonindigenous Herpetofauna of Florida: Patterns of Richness and Case Studies of the Impacts of the Tadpoles of Two Invasive Amphibians, Osteopilus septentrionalis and Bufo marinus

Although invasive species are considered to be a significant threat to native biodiversity, the impacts of very few nonindigenous species are well known. In this dissertation I describe the results of several studies evaluating the impacts of the presence of nonindigenous amphibians and reptiles in Florida. I conducted an analysis to assess the patterns and effects on biodiversity of the establishment of nonindigenous amphibians and reptiles in Florida at the county level. The richness of the 40 established nonindigenous amphibians and reptiles is not distributed evenly across the state, but instead is significantly greater in the southern part of the state and in counties with large human populations. These trends likely reflect the recent breakdown of historical barriers to invasion between Florida and the Caribbean region and the influence of human activities in the establishment of nonindigenous species. I also conducted several experimental case studies of the effects of the presence of the tadpoles of two invasive amphibians, the cane toad (Bufo marinus) and the Cuban treefrog (Osteopilus septentrionalis), in native Floridian tadpole communities. These studies indicated that B. marinus does not significantly affect native tadpoles through competition, while O. septentrionalis tadpoles outcompete and adversely affect native tadpoles, both in laboratory microcosms and naturalistic outdoor mesocosms. Larval O. septentrionalis also prey on native tadpoles, but this effect is probably not significant under natural conditions when alternative food is present. A mechanistic laboratory study indicated that the competitive effects of O. septentrionalis were mediated through exploitation competition with no evidence of interference competition. When keystone predators, eastern newts (Notophthalmus viridescens), were included in the experimental tadpole communities, the negative effects of O. septentrionalis tadpoles on native tadpoles were reduced significantly. Higher mortality of O. septentrionalis larvae suggests that newts preyed selectively on O. septentrionalis tadpoles, supporting their role as keystone predators. If general, this result suggests that keystone predators are important to the maintenance of diversity in invaded communities. Collectively, these results suggests that O. septentrionalis larvae may affect native amphibian populations in Florida through larval interactions, but these impacts may be limited by the presence of keystone predators

Multiscale probability mapping: groups, clusters and an algorithmic search for filaments in SDSS

We have developed a multiscale structure identification algorithm for the detection of overdensities in galaxy data that identifies structures having radii within a user-defined range. Our "multiscale probability mapping" technique combines density estimation with a shape statistic to identify local peaks in the density field. This technique takes advantage of a user-defined range of scale sizes, which are used in constructing a coarse-grained map of the underlying fine-grained galaxy distribution, from which overdense structures are then identified. In this study we have compiled a catalogue of groups and clusters at 0.025 < z < 0.24 based on the Sloan Digital Sky Survey, Data Release 7, quantifying their significance and comparing with other catalogues. Most measured velocity dispersions for these structures lie between 50 and 400 km/s. A clear trend of increasing velocity dispersion with radius from 0.2 to 1 Mpc/h is detected, confirming the lack of a sharp division between groups and clusters. A method for quantifying elongation is also developed to measure the elongation of group and cluster environments. By using our group and cluster catalogue as a coarse-grained representation of the galaxy distribution for structure sizes of <~ 1 Mpc/h, we identify 53 filaments (from an algorithmically-derived set of 100 candidates) as elongated unions of groups and clusters at 0.025 < z < 0.13. These filaments have morphologies that are consistent with previous samples studied.Comment: 22 pages, 14 figures and 6 tables. Accepted for publication in MNRAS. Data products, three-dimensional visualisations and further information about MSPM can be found at http://www.physics.usyd.edu.au/sifa/Main/MSPM/ . v2 contains two additional references. v3 has a slightly altered title and updated reference

Specific targeting of cytosine methylation to DNA sequences in vivo

Development of methods that will allow exogenous imposition of inheritable gene-specific methylation patterns has potential application in both therapeutics and in basic research. An ongoing approach is the use of targeted DNA methyltransferases, which consist of a fusion between gene-targeted zinc-finger proteins and prokaryotic DNA cytosine methyltransferases. These enzymes however have so far demonstrated significant and unacceptable levels of non-targeted methylation. We now report the development of second-generation targeted methyltransferase enzymes comprising enhanced zinc-finger arrays coupled to methyltransferase mutants that are functionally dominated by their zinc-finger component. Both in vitro plasmid methylation studies and a novel bacterial assay reveal a high degree of target-specific methylation by these enzymes. Furthermore, we demonstrate for the first time transient expression of targeted cytosine methyltransferase in mammalian cells resulting in the specific methylation of a chromosomal locus. Importantly, the resultant methylation pattern is inherited through successive cell divisions

Use of altered-specificity binding Oct-4 suggests an absence of pluripotent cell-specific cofactor usage

Oct-4 is a POU domain transcription factor that is critical for maintaining pluripotency and for stem cell renewal. Previous studies suggest that transcription regulation by Oct-4 at particular enhancers requires the input of a postulated E1A-like cofactor that is specific to pluripotent cells. However, such studies have been limited to the use of enhancer elements that bind other POU-protein family members in addition to Oct-4, thus preventing a ‘clean’ assessment of any Oct-4:cofactor relationships. Other attempts to study Oct-4 functionality in a more ‘stand-alone’ situation target Oct-4 transactivation domains to DNA using heterologous binding domains, a methodology which is known to generate artificial data. To circumvent these issues, an altered-specificity binding Oct-4 (Oct-4RR) and accompanying binding site, which binds Oct-4RR only, were generated. This strategy has previously been shown to maintain Oct-1:cofactor interactions that are highly binding-site and protein/binding conformation specific. This system therefore allows a stand-alone study of Oct-4 function in pluripotent versus differentiated cells, without interference from endogenous POU factors and with minimal deviation from bound wild-type protein characteristics. Subsequently, it was demonstrated that Oct-4RR and the highly transactive regions of its N-terminus determined here, and its C-terminus, have the same transactivation profile in pluripotent and differentiated cells, thus providing strong evidence against the existence of such a pluripotent cell-specific Oct-4 cofactor

Multiple Zonal Jets in a Differentially Heated Rotating Annulus

A laboratory experiment of multiple baroclinic zonal jets is described, thought to be dynamically similar to flow observed in the Antarctic Circumpolar Current. Differential heating sets the overall temperature difference and drives unstable baroclinic flow, but the circulation is free to determine its own structure and local stratification; experiments were run to a stationary state and extend the dynamical regime of previous experiments. Atopographic analog to the planetary β effect is imposed by the gradient of fluid depth with radius supplied by a sloping bottom and a parabolic free surface. New regimes of a low thermal Rossby number (RoT ~ 10-3) and high Taylor number (Ta ~ 1011) are explored such that the deformation radius Lp is much smaller than the annulus gap width L and similar to the Rhines length. Multiple jets emerge in rough proportion to the smallness of the Rhines scale, relatively insensitive to the Taylor number; a regime diagram taking the β effect into account better reflects the emergence of the jets. Eddy momentum fluxes are consistent with an active role in maintaining the jets, and jet development appears to follow the Vallis and Maltrud phenomenology of anisotropic wave-turbulence interaction on a ß plane. Intermittency and episodes of coherent meridional jet migration occur, especially during spinup

The magnitude and origin of groundwater discharge to Eastern U.S. and Gulf of Mexico coastal waters

Author Posting. © American Geophysical Union, 2017. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Geophysical Research Letters 44 (2017): 10,396–10,406, doi:10.1002/2017GL075238.Fresh groundwater discharge to coastal environments contributes to the physical and chemical conditions of coastal waters, but the role of coastal groundwater at regional to continental scales remains poorly defined due to diverse hydrologic conditions and the difficulty of tracking coastal groundwater flow paths through heterogeneous subsurface materials. We use three-dimensional groundwater flow models for the first time to calculate the magnitude and source areas of groundwater discharge from unconfined aquifers to coastal waterbodies along the entire eastern U.S. We find that 27.1 km3/yr (22.8–30.5 km3/yr) of groundwater directly enters eastern U.S. and Gulf of Mexico coastal waters. The contributing recharge areas comprised ~175,000 km2 of U.S. land area, extending several kilometers inland. This result provides new information on the land area that can supply natural and anthropogenic constituents to coastal waters via groundwater discharge, thereby defining the subterranean domain potentially affecting coastal chemical budgets and ecosystem processes.National Science Foundation Grant Number: EPS-1208909; NASA Carbon Cycle Science Grant Number: NNX14AM37G2018-04-2

Bridging the university-school divide - Horizontal expertise and the two-worlds pitfall

Research on teacher learning consistently documents the disjuncture between the practices beginning teachers encounter in university teacher preparation courses and those they reencounter in the K-12 classrooms in which they learn to teach. As preservice teachers enter teaching, they gravitate toward conventional K-12 practices, dismissing those endorsed by the university as impractical. In this article, the authors delineate the concept of horizontal expertise and document how its production and use can address this “two-worlds pitfall.” Drawing on the authors\u27 work creating a cross-institutional collaborative, they identify three processes central to the production of horizontal expertise in teacher education: the exchange of tools, the negotiation of social languages, and argumentation. They then trace its use across the university and school settings to show how horizontal expertise can rescript mentoring and expand dialogic practices in the university. The authors conclude by identifying the challenges of developing horizontal expertise in teacher educatio

Kinematic Orbits and the Structure of the Internal Space for Systems of Five or More Bodies

The internal space for a molecule, atom, or other n-body system can be conveniently parameterised by 3n-9 kinematic angles and three kinematic invariants. For a fixed set of kinematic invariants, the kinematic angles parameterise a subspace, called a kinematic orbit, of the n-body internal space. Building on an earlier analysis of the three- and four-body problems, we derive the form of these kinematic orbits (that is, their topology) for the general n-body problem. The case n=5 is studied in detail, along with the previously studied cases n=3,4.Comment: 38 pages, submitted to J. Phys.

Quantifying and Classifying Streamflow Ensembles Using a Broad Range of Metrics for an Evidence‐Based Analysis: Colorado River Case Study

Stochastic hydrology produces ensembles of time series that represent plausible future streamflow to simulate and test the operation of water resource systems. A premise of stochastic hydrology is that ensembles should be statistically representative of what may occur in the future. In the past, the application of this premise has involved producing ensembles that are statistically equivalent to the observed or historical streamflow sequence. This requires a number of metrics or statistics that can be used to test statistical similarity. However, with climate change, the past may no longer be representative of the future. Ensembles to test future systems operations should recognize non‐stationarity and include time series representing expected changes. This poses challenges for their testing and validation. In this paper, we suggest an evidence‐based analysis in which streamflow ensembles, whether statistically similar to and representative of the past or a changing future, should be characterized and assessed using an extensive set of statistical metrics. We have assembled a broad set of metrics and applied them to annual streamflow in the Colorado River at Lees Ferry to illustrate the approach. We have also developed a tree‐based classification approach to categorize both ensembles and metrics. This approach provides a way to visualize and interpret differences between streamflow ensembles. The metrics presented, along with the classification, provide an analytical framework for characterizing and assessing the suitability of future streamflow ensembles, recognizing the presence of non‐stationarity. This contributes to better planning in large river basins, such as the Colorado, facing water supply shortages