Hubble-COS Observations of Galactic High-Velocity Clouds: Four AGN Sight Lines through Complex C

We report ultraviolet spectra of Galactic high-velocity clouds (HVCs) in Complex C, taken by the Cosmic Origins Spectrograph (COS) on the Hubble Space Telescope (HST), together with new 21-cm spectra from the Green Bank Telescope. The wide spectral coverage and higher S/N, compared to previous HST spectra, provide better velocity definition of the HVC absorption, additional ionization species, and improved abundances in this halo gas. Complex C has a metallicity of 0.1-0.3 solar and a wide range of ions, suggesting dynamical and thermal interactions with hot gas in the Galactic halo. Spectra in the COS medium-resolution G130M (1133-1468 A) and G160M (1383-1796 A) gratings detect ultraviolet absorption lines from 8 elements in low ionization stages (O I, N I, C II, S II, Si II, Al II, Fe II, P II) and 3 elements in intermediate and high-ionization states (Si III, Si IV, C IV, N V). Our four AGN sight lines toward Mrk 817, Mrk 290, Mrk 876, and PG1259+593 have high-velocity H I and O VI column densities, log N_HI = 19.39-20.05 and log N_OVI = 13.58-14.10, with substantial amounts of kinematically associated photoionized gas. The high-ion abundance ratios are consistent with cooling interfaces between photoionized gas and collisionally ionized gas: N(C IV)/N(O VI) = 0.3-0.5, N(Si IV)/N(O VI) = 0.05-0.11, N(N V)/N(O VI) = 0.07-0.13, and N(Si IV)/N(Si III) = 0.2.Comment: 43 pages, 11 figures (appearing in ApJ, Sept 1, 2011

Large-scale collaboration reveals landscape-level effects of land-use on turtle demography

Freshwater turtles and tortoises are declining worldwide and currently represent one of the most imperiled major vertebrate groups. Identifying the conditions that promote long-term viable populations is a critical conservation need. However, for most species, there is relatively little or no empirical information about the factors influencing population demographics. Large-scale population monitoring efforts necessary to acquire such information remain rare due to the logistic challenges associated with low and variable detectability, which generally preclude large monitoring initiatives by any single entity. The development of collaborative population monitoring programs represents one potential strategy for overcoming these challenges. Our goal was to leverage partnerships to identify the potential factors and relevant scales affecting wood turtle (Glyptemys insculpta) population demographics. Through a large-scale collaborative multi-institutional monitoring effort, we conducted 983 spring stream surveys at 293 sites across the northeastern United States. Wood turtle abundance was negatively associated with agriculture (300 m and 5500 m) and road traffic (5500 m) and positively associated with mature forest (5500 m). Juvenile proportion displayed strong negative relationships with stream gradient and imperviousness (300 m). Sex ratios were more male-skewed with higher mature forest cover (90 m) and road density (5500 m) and less undeveloped land (300 m). These findings suggest that effective conservation of demographically robust turtle populations will require consideration of multiple spatial scales. Landscape-level conservation may be particularly important for ensuring long-term viable populations. This study highlights the valuable role that collaboration across institutions and jurisdictions can play in the conservation of cryptic taxa

Bulk Charge Ordering in the CuO2 Plane of the Cuprate Superconductor YBa2Cu3O6.9 by High-Pressure NMR

Cuprate superconductors still hold many open questions, and recently, the role of symmetry breaking electronic charge ordering resurfaced in underdoped cuprates as a phenomenon that competes with superconductivity. Here, unambiguous nuclear magnetic resonance (NMR) proof is presented for the existence of local charge ordering in nearly optimally doped YBa2Cu3O6.9, even up to room temperature. Increasing pressure and decreasing temperature leads to the highest degree of order in the sense that the two oxygen atoms of the unit cell of the CuO2 plane develop a charge difference of about 0.02 holes, and order throughout the whole crystal. At ambient conditions, a slightly smaller charge difference and a decreased order is found. Evidence from literature data suggests that this charge ordering is ubiquitous to the CuO2 plane of all cuprates. Thus, the role of charge ordering in the cuprates must be reassessed

Challenges and opportunities for improving eco-efficiency of tropical forage-based systems to mitigate greenhouse gas emissions

Forage-based livestock production plays a key role in national and regional economies, for food security and poverty alleviation, but is considered a major contributor to agricultural GHG emissions. While demand for livestock products is predicted to increase, there is political and societal pressure both to reduce environmental impacts and to convert some of the pasture area to alternative uses, such as crop production and environmental conservation. Thus, it is essential to develop approaches for sustainable intensification of livestock systems to mitigate GHG emissions, addressing biophysical, socio-economic and policy challenges. This paper highlights the potential of improved tropical forages, linked with policy incentives, to enhance livestock production, while reducing its environmental footprint. Emphasis is on crop-livestock systems. We give examples for sustainable intensification to mitigate GHG emissions, based on improved forages in Brazil and Colombia, and suggest future perspectives

1‑Methylthio‑d‑xylulose 5‑Phosphate Methylsulfurylase: A Novel Route to 1‑Deoxy‑d‑xylulose 5‑Phosphate in <i>Rhodospirillum rubrum</i>

<i>Rhodospirillum rubrum</i> produces 5-methylthioadenosine (MTA) from <i>S</i>-adenosylmethionine in polyamine biosynthesis; however, <i>R. rubrum</i> lacks the classical methionine salvage pathway. Instead, MTA is converted to 5-methylthio-d-ribose 1-phosphate (MTR 1-P) and adenine; MTR 1-P is isomerized to 1-methylthio-d-xylulose 5-phosphate (MTXu 5-P) and reductively dethiomethylated to 1-deoxy-d-xylulose 5-phosphate (DXP), an intermediate in the nonmevalonate isoprenoid pathway [Erb, T. J., et al. (2012) <i>Nat. Chem. Biol.</i>, in press]. Dethiomethylation, a novel route to DXP, is catalyzed by MTXu 5-P methylsulfurylase. An active site Cys displaces the enolate of DXP from MTXu 5-P, generating a methyl disulfide intermediate