EPOXI at comet Hartley 2

Understanding how comets work--what drives their activity--is crucial to the use of comets in studying the early solar system. EPOXI (Extrasolar Planet Observation and Deep Impact Extended Investigation) flew past comet 103P/Hartley 2, one with an unusually small but very active nucleus, taking both images and spectra. Unlike large, relatively inactive nuclei, this nucleus is outgassing primarily because of CO(2), which drags chunks of ice out of the nucleus. It also shows substantial differences in the relative abundance of volatiles from various parts of the nucleus.     

Trading water for carbon with biological carbon sequestration

Carbon sequestration strategies highlight tree plantations without considering their full environmental consequences. We combined field research, synthesis of more than 600 observations, and climate and economic modeling to document substantial losses in stream flow, and increased soil salinization and acidification, with afforestation. Plantations decreased stream flow by 227 millimeters per year globally (52%), with 13% of streams drying completely for at least 1 year. Regional modeling of U.S. plantation scenarios suggests that climate feedbacks are unlikely to offset such water losses and could exacerbate them. Plantations can help control groundwater recharge and upwelling but reduce stream flow and salinize and acidify some soils.     

Comment on "Protein sequences from mastodon and Tyrannosaurus rex revealed by mass spectrometry"

We used authentication tests developed for ancient DNA to evaluate claims by Asara et al. (Reports, 13 April 2007, p. 280) of collagen peptide sequences recovered from mastodon and Tyrannosaurus rex fossils. Although the mastodon samples pass these tests, absence of amino acid composition data, lack of evidence for peptide deamidation, and association of alpha1(I) collagen sequences with amphibians rather than birds suggest that T. rex does not.     

The importance of thinking big: Large-scale prey conservation drives black-footed ferret reintroduction success

Objective evaluations of wildlife reintroductions are vital for increasing the success of future efforts to re-establish endangered species. Attempts to reintroduce one of the most endangered mammals in North America, the black-footed ferret (Mustela nigripes), have been ongoing for 18 years with no quantitative assessment of factors related to reintroduction success. We examined relationships between ferret reintroduction success and factors associated with disease outbreaks, release strategies, and the distribution and abundance of their primary prey, prairie dogs (Cynomys sp.), at 11 reintroduction sites. The most important factor related to ferret reintroduction success was a cumulative metric incorporating both size of the area occupied by prairie dogs and density of prairie dog burrows within that area. Each of the four successful sites had prairie dog populations that occupied an area of at least 4300 ha. No sites with <4300 ha of prairie dogs were successful in maintaining ?30 adult individual ferrets over multiple years without augmentation even if they had a high prairie dog burrow density. The overarching importance of the availability of high-quality habitat suggests managers should prioritize actions that maintain and enhance the availability of large areas with high prairie dog burrow density, which are becoming increasingly rare due to anthropogenic impacts and disease outbreaks.     

Comparative study of hops-containing products on human cytochrome P450-mediated metabolism

The potential for 15 different ales (6), ciders (2 apple and 1 pear), and porters (6) and 2 non-alcoholic products to affect cytochrome P450 (CYP)-mediated biotransformation and P-glycoprotein-mediated efflux of rhodamine was examined. As in our previous study, a wide range of recovered nonvolatile suspended solids dry weights were noted. Aliquots were also found to have varying effects on biotransformation and efflux. Distinct differences in product ability to affect the safety and efficacy of therapeutic products confirmed our initial findings that some porters (stouts) have a potential to affect the safety and efficacy of health products metabolized by CYP2D6 and CYP3A4 isozymes. Most products, except 2 of the ciders and the 2 non-alcoholic products, also have the potential to affect the safety of CYP2C9 metabolized medications and supplements. Further studies are required to determine the clinical significance of these findings.     

Maize response to broadcast flaming at different growth stages: Effects on growth,yield and yield components

Weed management is a major constraint in organic crop production. Propane flaming could be an additional tool for weed control in organic maize (Zea mays L.) production. However, tolerance of maize to broadcast flaming must be determined first to optimize the use of propane. Field experiments were conducted at the Haskell Agricultural Laboratory of the University of Nebraska, Concord, NE in 2008 and 2009 to determine maize response to five propane doses applied at three growth stages of V2 (2-leaf), V5 (5-leaf) and V7 (7-leaf). The propane doses tested were 0, 13, 24, 44 and 85 kg ha^?1. Flaming treatments were applied utilizing a custom built research flamer mounted on the back of a four-wheeler moving at a constant speed of 6.4 km h^?1. The response of maize to propane flaming was evaluated in terms of visual crop injury (1, 7, 14 and 28 days after treatment—DAT), effects on dry matter (14 DAT), yield components (plants m^?2, ears plant^?1, kernels cob^?1 and 1000-kernel weight) and grain yield. The response of different growth stages of maize to propane doses was described by log–logistic models. Overall, maize response to broadcast flaming varied among growth stages and propane doses. In general, maize at V5 was the most tolerant stage for broadcast flaming, whereas V2 stage was the most susceptible to flaming resulting in the highest visual crop injury ratings, dry matter reductions and the largest loss of yield and its components. At 28 DAT, the maximum visual crop injury rating of 7% was estimated for flaming done at V5 stage compared to significantly higher injuries of 43% and 12% for V2 and V7 growth stages, respectively. An arbitrarily assigned 2.5% yield reduction was evident with 33, 16 and 11 kg ha^?1 of propane for V5, V2 and V7 growth stages, respectively, suggesting that maize flamed at V5 stage can tolerate higher dose of propane for the same yield reduction compared to other growth stages. Moreover, the maximum yield reductions with the highest propane dose of 85 kg ha^?1 were 3% for V5, 11% for V7 and 17% for V2 stage. Based on these results, flaming has a potential to be used effectively in organic maize production when conducted properly at V5 stage. However, there are both benefits and concerns associated with the use of flame weeding. The preservation of the soil from erosion and the protection of the surface and underground water from chemical pollution can be seen as benefits, while the concerns include higher energy use, and the release of greenhouse gasses.     

Evaluation of potentially labile soil organic carbon and nitrogen fractionation procedures

Particulate organic matter (POM) and light fraction (LF) organic matter are potentially labile (active) fractions of soil organic matter (SOM) that have been shown to be indicators of short-term changes in soil management practices (e.g. tillage, manure and fertilizer applications, and crop rotation). These two fractions consist mainly of partially decomposed plant residues, microbial residues, seeds, and spores forming organo-mineral complexes with soil mineral particles; however, they cannot be used as synonyms because of their different chemical composition and structure. Particulate-OM is recovered by size-based procedures while LF is generally recovered in two distinct fractions [free-LF (FLF) and occluded-LF (OLF)] using density-based solutions in conjunction with soil-aggregate disruption. Solutions used in these density-based separations have most commonly varied in density from 1.6 to 2.0 g cm⁻³. Sodium iodide (NaI) and sodium polytungstate (SPT) are the chemicals most often used to prepare the density solutions in LF recovery but comparisons of the effectiveness of two solutions have not been conducted. The objectives of this research were: (1) compare the efficiency of similar density solutions of NaI and SPT in recovering FLF; and (2) compare POM, FLF, and OLF as possible sensitive indices of short-term soil changes due to tillage management. Soil samples were collected at 0-15 cm depth from a cropping system experiment conducted on a silt loam Ultisol. Plots selected for sampling had received either reduced till (RT) or no-till (NT), and cropping was continuous corn silage for a period of 3 years prior to sampling. Solutions of NaI and SPT at densities of 1.6 and 1.8 g cm⁻³ were used to recover FLF, and OLF was recovered with SPT solution at a density of 2.0 g cm⁻³ from the soil pellet remaining after FLF recovery with SPT 1.6 g cm⁻³. The average total soil organic carbon (SOC) content of these samples was of 12.7 g kg⁻¹, and carbon-POM (C-POM), carbon-FLF (C-FLF), and carbon-OLF (C-OLF) represented 22.4, 5.5, and 5.2% of it, respectively. In general, C-FLF and nitrogen-FLF (N-FLF) contents recovered did not differ significantly between chemical solutions (NaI or SPT) adjusted to the same density (1.6 or 1.8 g cm⁻³). Increasing the density within a specific solution (NaI or SPT) resulted in significantly higher C-FLF and N-FLF recovery. For instance, C-FLF recovery averaged 637 and 954 mg kg⁻¹ at 1.6 and 1.8 g cm⁻³, respectively. For both chemicals increasing density from 1.6 to 1.8 g cm⁻³ reduced the variability in recovering C-FLF and N-FLF with coefficient of variation values decreasing from a range of 14.9-19.1% for densities of 1.6 g cm⁻³ to 6.7-10.4% when densities increased to 1.8 g cm⁻³. In the present work, POM and OLF were more sensitive than FLF to changes in tillage management, with significantly greater amounts of the sensitive fractions in RT samples. A better sensitivity of FLF would be expected if treatments dealing with residue input (e.g. crop rotation and cover crop) were evaluated.     

Few apparent short-term effects of elevated soil temperature and increased frequency of summer precipitation on the abundance and taxonomic diversity of desert soil micro- and meso-fauna

Frequent hydration and drying of soils in arid systems can accelerate desert carbon and nitrogen mobilization due to respiration, microbial death, and release of intracellular solutes. Because desert microinvertebrates can mediate nutrient cycling, and the autotrophic components of crusts are known to be sensitive to rapid desiccation due to elevated temperatures after wetting events, we studied whether altered soil temperature and frequency of summer precipitation can also affect the composition of food web consumer functional groups. We conducted a two-year field study with experimentally-elevated temperature and frequency of summer precipitation in the Colorado Plateau desert, measuring the change in abundance of nematodes, protozoans, and microarthropods. We hypothesized that microfauna would be more adversely affected by the combination of elevated temperature and frequency of summer precipitation than either effect alone, as found previously for phototrophic crust biota. Microfauna experienced normal seasonal fluctuations in abundance, but the effect of elevated temperature and frequency of summer precipitation was statistically non-significant for most microfaunal groups, except amoebae. The seasonal increase in abundance of amoebae was reduced with combined elevated temperature and increased frequency of summer precipitation compared to either treatment alone, but comparable with control (untreated) plots. Based on our findings, we suggest that desert soil microfauna are relatively more tolerant to increases in ambient temperature and frequency of summer precipitation than the autotrophic components of biological soil crust at the surface.     

Joint Modeling of Spatial Variability and Within-Row Interplot Competition to Increase the Efficiency of Plant Improvement

Trials in the early stages of selection are often subject to variation arising from spatial variability and interplot competition, which can seriously bias the assessment of varietal performance and reduce genetic progress. An approach to jointly model both sources of bias is presented. It models genotypic and residual competition and also global and extraneous spatial variation. Variety effects were considered random and residual maximum likelihood was used for parameter estimation. Competition at the residual level was examined using two special simultaneous autoregressive models. An equal-roots second-order autoregressive (EAR(2)) model is proposed for trials where competition is dominant. An equal-roots third-order autoregressive (EAR(3)) model allows for competition and spatial variability. These models are applied to two yield data sets from an Australian sugarcane selection program. One data set is in the paper and the other is in supplementary material available online. To determine the effect of simultaneously adjusting for spatial variability and interplot competition on selection, the percentages of superior varieties in common in the top 15% for the joint model and classical approaches were compared. Agreement between the two approaches was 45 and 84%. Hence, for some trials there are large differences in varieties advanced to the next stage of selection.     

Orrorin tugenensis femoral morphology and the evolution of hominin bipedalism

Bipedalism is a key human adaptation and a defining feature of the hominin clade. Fossil femora discovered in Kenya and attributed to Orrorin tugenensis, at 6 million years ago, purportedly provide the earliest postcranial evidence of hominin bipedalism, but their functional and phylogenetic affinities are controversial. We show that the O. tugenensis femur differs from those of apes and Homo and most strongly resembles those of Australopithecus and Paranthropus, indicating that O. tugenensis was bipedal but is not more closely related to Homo than to Australopithecus. Femoral morphology indicates that O. tugenensis shared distinctive hip biomechanics with australopiths, suggesting that this complex evolved early in human evolution and persisted for almost 4 million years until modifications of the hip appeared in the late Pliocene in early Homo.