Local properties of patterned vegetation: quantifying endogenous and exogenous effects

Dryland ecosystems commonly exhibit periodic bands of vegetation, thought to form due to competition between individual plants for heterogeneously distributed water. In this paper, we develop a Fourier method for locally identifying the pattern wavenumber and orientation, and apply it to aerial images from a region of vegetation patterning near Fort Stockton, Texas. We find that the local pattern wavelength and orientation are typically coherent, but exhibit both rapid and gradual variation driven by changes in hillslope gradient and orientation, the potential for water accumulation, or soil type. Endogenous pattern dynamics, when simulated for spatially homogeneous topographic and vegetation conditions, predict pattern properties that are much less variable than the orientation and wavelength observed in natural systems. Our local pattern analysis, combined with ancillary datasets describing soil and topographic variation, highlights a largely unexplored correlation between soil depth, pattern coherence, vegetation cover and pattern wavelength. It also, surprisingly, suggests that downslope accumulation of water may play a role in changing vegetation pattern properties

How typical is the Coma cluster?

Coma is frequently used as the archetype z~0 galaxy cluster to compare higher redshift work against. It is not clear, however, how representative the Coma cluster is for galaxy clusters of its mass or X-ray luminosity, and significantly: recent works have suggested that the galaxy population of Coma may be in some ways anomolous. In this work, we present a comparison of Coma to an X-ray selected control sample of clusters. We show that although Coma is typical against the control sample in terms of its internal kinematics (substructure and velocity dispersion profile), it has a significantly high (~3sigma) X-ray temperature set against clusters of comparable mass. By de-redshifting our control sample cluster galaxies star-formation rates using a fit to the galaxy main sequence evolution at z < 0.1, we determine that the typical star-formation rate of Coma galaxies as a function of mass is higher than for galaxies in our control sample at a confidence level of > 99 per cent. One way to alleviate this discrepency and bring Coma in-line with the control sample would be to have the distance to Coma to be slightly lower, perhaps through a non-negligible peculiar velocity with respect to the Hubble expansion, but we do not regard this as likely given precision measurements using a variety of approaches. Therefore in summary, we urge caution in using Coma as a z~0 baseline cluster in galaxy evolution studies.Comment: accepted for publication in MNRA

Comparative Genomics of 9 Novel Paenibacillus Larvae Bacteriophages

American Foulbrood Disease, caused by the bacterium Paenibacillus larvae, is one of the most destructive diseases of the honeybee, Apis mellifera. Our group recently published the sequences of 9 new phages with the ability to infect and lyse P. larvae. Here, we characterize the genomes of these P. larvae phages, compare them to each other and to other sequenced P. larvae phages, and putatively identify protein function. The phage genomes are 38–45 kb in size and contain 68–86 genes, most of which appear to be unique to P. larvae phages. We classify P. larvae phages into 2 main clusters and one singleton based on nucleotide sequence identity. Three of the new phages show sequence similarity to other sequenced P. larvae phages, while the remaining 6 do not. We identified functions for roughly half of the P. larvae phage proteins, including structural, assembly, host lysis, DNA replication/metabolism, regulatory, and host-related functions. Structural and assembly proteins are highly conserved among our phages and are located at the start of the genome. DNA replication/metabolism, regulatory, and host-related proteins are located in the middle and end of the genome, and are not conserved, with many of these genes found in some of our phages but not others. All nine phages code for a conserved N-acetylmuramoyl-L-alanine amidase. Comparative analysis showed the phages use the “cohesive ends with 30 overhang” DNA packaging strategy. This work is the first in-depth study of P. larvae phage genomics, and serves as a marker for future work in this area

A search for starlight reflected from HD 75289 b

We have used a doppler tomographic analysis to conduct a deep search for the starlight reflected from the planetary companion to HD 75289. In 4 nights on VLT2/UVES in January 2003, we obtained 684 high resolution echelle spectra with a total integration time of 26 hours. We establish an upper limit on the planet's geometric albedo p < 0.12 (to the 99.9% significance level) at the most probable orbital inclination i ~ 60 degrees, assuming a grey albedo, a Venus-like phase function and a planetary radius R_p = 1.6 R_Jup. We are able to rule out some combinations of the predicted planetary radius and atmospheric albedo models with high, reflective cloud decks.Comment: 5 pages, 5 figures, MNRAS accepted 12 Oct 200

Comparing families of dynamic causal models

Mathematical models of scientific data can be formally compared using Bayesian model evidence. Previous applications in the biological sciences have mainly focussed on model selection in which one first selects the model with the highest evidence and then makes inferences based on the parameters of that model. This “best model” approach is very useful but can become brittle if there are a large number of models to compare, and if different subjects use different models. To overcome this shortcoming we propose the combination of two further approaches: (i) family level inference and (ii) Bayesian model averaging within families. Family level inference removes uncertainty about aspects of model structure other than the characteristic of interest. For example: What are the inputs to the system? Is processing serial or parallel? Is it linear or nonlinear? Is it mediated by a single, crucial connection? We apply Bayesian model averaging within families to provide inferences about parameters that are independent of further assumptions about model structure. We illustrate the methods using Dynamic Causal Models of brain imaging data

Why is the Arkavathy River drying? A multiple-hypothesis approach in a data-scarce region

Water planning decisions are only as good as our ability to explain historical trends and make reasonable predictions of future water availability. But predicting water availability can be a challenge in rapidly growing regions, where human modifications of land and waterscapes are changing the hydrologic system. Yet, many regions of the world lack the long-term hydrologic monitoring records needed to understand past changes and predict future trends. We investigated this “predictions under change” problem in the data-scarce Thippagondanahalli (TG Halli) catchment of the Arkavathy sub-basin in southern India. Inflows into TG Halli reservoir have declined sharply since the 1970s. The causes of the drying are poorly understood, resulting in misdirected or counter-productive management responses. Five plausible hypotheses that could explain the decline were tested using data from field surveys and secondary sources: (1) changes in rainfall amount, seasonality and intensity; (2) increases in temperature; (3) groundwater extraction; (4) expansion of eucalyptus plantations; and (5) fragmentation of the river channel. Our results suggest that groundwater pumping, expansion of eucalyptus plantations and, to a lesser extent, channel fragmentation are much more likely to have caused the decline in surface flows in the TG Halli catchment than changing climate

Nowhere to Run; Nowhere to Hide: The Reality of Being a Law Library Director in Times of Great Opportunity and Significant Challenges

This is an edited version of remarks presented at \u27Nowhere to Run, Nowhere to Hide\u27: The Reality of Being a Law Library Director in Times of Great Opportunity and Significant Challenges, January 5, 2015, at the Association of American Law Schools Annual Meeting, Washington, D.C

Transparency in the reporting of nursing research

Editorial

Does the Milky Way have a Maximal Disk?

The Milky Way is often considered to be the best example of a spiral for which the dark matter not only dominates the outer kinematics, but also plays a major dynamical role in the inner galaxy: the Galactic disk is therefore said to be ``sub-maximal.'' This conclusion is important to the understanding of the evolution of galaxies and the viability of particular dark matter models. The Galactic evidence rests on a number of structural and kinematic measurements, many of which have recently been revised. The new constraints indicate not only that the Galaxy is a more typical member of its class (Sb-Sc spirals) than previously thought, but also require a re-examination of the question of whether or not the Milky Way disk is maximal. By applying to the Milky Way the same definition of ``maximal disk'' that is applied to external galaxies, it is shown that the new observational constraints are consistent with a Galactic maximal disk of reasonable $M/L$. In particular, the local disk column can be substantially less than the oft-quoted required \Sigma_{\odot} \approx 100 \msolar pc^{-2} - as low as 40 \msolar pc^{-2} in the extreme case - and still be maximal, in the sense that the dark halo provides negligible rotation support in the inner Galaxy. This result has possible implications for any conclusion that rests on assumptions about the potentials of the Galactic disk or dark halo, and in particular for the interpretation of microlensing results along both LMC and bulge lines of sight.Comment: Accepted for publication in The Astrophysical Journal. 23 Latex-generated pages, one (new) table, three figures (two new). A few additions to the bibliography, an expanded discussion, and slight quantitative changes, none of which affect the conclusion

The Age Of Globular Clusters In Light Of Hipparcos: Resolving the Age Problem?

We review five independent techniques which are used to set the distance scale to globular clusters, including subdwarf main sequence fitting utilizing the recent Hipparcos parallax catalogue. These data together all indicate that globular clusters are farther away than previously believed, implying a reduction in age estimates. This new distance scale estimate is combined with a detailed numerical Monte Carlo study designed to assess the uncertainty associated with the theoretical age-turnoff luminosity relationship in order to estimate both the absolute age and uncertainty in age of the oldest globular clusters. Our best estimate for the mean age of the oldest globular clusters is now $11.5\pm 1.3$Gyr, with a one-sided, 95% confidence level lower limit of 9.5 Gyr. This represents a systematic shift of over 2 $\sigma$ compared to our earlier estimate, due completely to the new distance scale---which we emphasize is not just due to the Hipparcos data. This now provides a lower limit on the age of the universe which is consistent with either an open universe, or a flat, matter dominated universe (the latter requiring H_0 \le 67 \kmsmpc). Our new study also explicitly quantifies how remaining uncertainties in the distance scale and stellar evolution models translate into uncertainties in the derived globular cluster ages. Simple formulae are provided which can be used to update our age estimate as improved determinations for various quantities become available.Comment: 41 pages, including 10 eps figs, uses aaspp4.sty and flushrt.sty, submitted to Ap.J., revised to incorporate FULL Hipparcos catalogue dat