Classifying Political Similarity of Twitter Users

The emergence of large scale social networks has led to research in approaches to classify similar users on a network. While many such approaches use data mining techniques, recent efforts have focused on measuring the similarity of users using structural properties of the underlying graph representing the network. In this paper, we identify the Twitter followers of the 2016 presidential candidates and classify them as Democrat, Republican or Bipartisan. We did this by designing a new approach to measuring structural similarity, PolRANK. PolRANK computes the similarity of a pair of users by accounting for both the number of candidates they follow from each party and the specific candidates they follow. To test our algorithm, we crawled a data set of all followers of every presidential candidate in June 2015 and then ran experiments on a random subset of 10% of that data. When tested against similar algorithms, PolRANK outperforms SimRank[1], P-Rank[2] and Cosine-Similarity as it is more efficient when used in large data sets. This efficiency is due to PolRANK’s ability to calculate similarity independent of other users. The time complexity of P-Rank is O(n4) while the time complexity of PolRANK is O(n3)

Characterization and expression analysis of Staphylococcus aureus pathogenicity island 3 - Implications for the evolution of staphylococcal pathogenicity islands

We describe the complete sequence of the 15.9-kb staphylococcal pathogenicity island 3 encoding staphylococcal enterotoxin serotypes B, K, and Q. The island, which meets the generally accepted definition of pathogenicity islands, contains 24 open reading frames potentially encoding proteins of more than 50 amino acids, including an apparently functional integrase. The element is bordered by two 17-bp direct repeats identical to those found flanking staphylococcal pathogenicity island 1. The island has extensive regions of homology to previously described pathogenicity islands, particularly staphylococcal pathogenicity islands 1 and bov. The expression of 22 of the 24 open reading frames contained on staphylococcal pathogenicity island 3 was detected either in vitro during growth in a laboratory medium or serum or in vivo in a rabbit model of toxic shock syndrome using DNA microarrays. The effect of oxygen tension on staphylococcal pathogenicity island 3 gene expression was also examined. By comparison with the known staphylococcal pathogenicity islands in the context of gene expression described here, we propose a model of pathogenicity island origin and evolution involving specialized transduction events and addition, deletion, or recombination of pathogenicity island "modules.

The economics of soil c sequestration and agricultural emissions abatement

Peer reviewedPublisher PD

Impact of Nitrogen Fertilization and Cropping System on Carbon Sequestration in Midwestern Mollisols

Growing interest in the potential for agricultural soils to provide a sink for atmospheric C has prompted studies of effects of management on soil organic carbon (SOC) sequestration. We analyzed the impact on SOC of four N fertilization rates (0–270 kg N ha−1) and four cropping systems: continuous corn (CC) (Zea mays L.); corn–soybean [Glycine max (L.) Merr.] (CS); corn–corn–oat–alfalfa (oat, Avena sativa L.; alfalfa, Medicago sativa L.) (CCOA), and corn–oat–alfalfa–alfalfa (COAA). Soils were sampled in 2002, Years 23 and 48 of the experiments located in northeast and north-central Iowa, respectively. The experiments were conducted using a replicated split-plot design under conventional tillage. A native prairie was sampled to provide a reference (for one site only). Cropping systems that contained alfalfa had the highest SOC stocks, whereas the CS system generally had the lowest SOC stocks. Concentrations of SOC increased significantly between 1990 and 2002 in only two of the nine systems for which historical data were available, the fertilized CC and COAA systems at one site. Soil quality indices such as particulate organic carbon (POC) were influenced by cropping system, with CS \u3c CC \u3c CCOA. In the native prairie, SOC, POC, and resistant C concentrations were 2.8, 2.6, and 3.9 times, respectively, the highest values in cropped soil, indicating that cultivated soils had not recovered to precultivation conditions. Although corn yields increased with N additions, N fertilization increased SOC stocks only in the CC system at one site. Considering the C cost for N fertilizer production, N fertilization generally had a net negative effect on C sequestration

Land-based climate solutions for the United States

Funding Information: We thank many colleagues for helpful discussion and feedback during the preparation of this analysis, anonymous reviewers for constructive criticism, and J.L. Schuette for help with data assembly. Financial support was provided by the U.S. Department of Energy Great Lakes Bioenergy Research Center (Award DE‐SC0018409), the U.S. National Science Foundation Long‐term Ecological Research Program (DEB 1832042), the USDA Long‐term Agroecosystem Research program, and Michigan State University AgBioResearch. Additional support (PS) is from the Soils‐R‐GGREAT (NE/P019455/1) and CIRCASA (Agreement 774378) projects of the European Union‘s Horizon 2020 Research and Innovation Programme (Award 774378); and (KP) the U.S. Department of Energy Advanced Research Projects Agency‐Energy program (Award DE‐AR0000826). KP serves as a part‐time advisor to Indigo Ag, Inc., a company that markets soil carbon sequestration credits. The authors declare no other potential conflicts of interest. Publisher Copyright: © 2022 The Authors. Global Change Biology published by John Wiley & Sons Ltd.Peer reviewedPublisher PD

Resolving the ‘Nitrogen Paradox’ of arbuscular mycorrhizas : fertilization with organic matter brings considerable benefits for plant nutrition and growth

Arbuscular mycorrhizal fungi (AMF) can transfer nitrogen (N) to host plants but the ecological relevance is debated, as total plant N and biomass do not generally increase. The extent to which the symbiosis is mutually beneficial is thought to rely on the stoichiometry of N, phosphorus (P) and carbon (C) availability. While inorganic N fertilisation has been shown to elicit strong mutualism, characterised by improved plant and fungal growth and mineral nutrition, similar responses following organic N addition are lacking. Using a compartmented microcosm experiment, we determined the significance to a mycorrhizal plant of placing a 15N‐labelled, nitrogen‐rich patch of organic matter in a compartment to which only AMF hyphae had access. Control microcosms denied AMF hyphal access to the patch compartment. When permitted access to the patch compartment, the fungus proliferated extensively in the patch and transferred substantial quantities of N to the plant. Moreover, our data demonstrate that allowing hyphal access to an organic matter patch enhanced total plant N and P contents, with a simultaneous and substantial increase in plant biomass. Moreover, we demonstrate that organic matter fertilization of arbuscular mycorrhizal plants can foster a mutually beneficial symbiosis based on nitrogen transfer, a phenomenon previously thought irrelevant

Interpretation of soil carbon and nitrogen dynamics in agricultural and afforested soils

Includes bibliographical references (pages 1627-1628).Interpretation of soil organic C (SOC) dynamics depends heavily on analytical methods and management systems studied. Comparison of data from long-term corn (Zea mays)-plot soils in Eastern North America showed mean residence times (MRTs) of SOC determined by 14C dating were 176 times those measured with 13C abundance following a 30-yr replacement of C3 by C4 plants on the same soils. However, MRTs of the two methods were related (r 2 = 0.71). Field 13C MRTs of SOC were also related (R 2 = 0.55 to 0.85) to those measured by 13CO2 evolution and curve fitting during laboratory incubation. The strong relations, but different MRTs, were interpreted to mean that the three methods sampled different parts of a SOC continuum. The SOC of all parts of this continuum must be affected by the same controls on SOC dynamics for this to occur. Methods for site selection, plant biomass, soil sampling and analysis were tested on agricultural, afforested-agriculture, and native forest sites to determine the controls on SOC dynamics. Soil-C changes after afforestation were −0.07 to 0.55 Mg C ha−1 yr−1 on deciduous sites and −0.85 to 0.58 Mg C ha−1 yr−1 under conifers. Soil N changes under afforestation ranged from −0.1 to 0.025 Mg N ha−1 yr−1 Ecosystem N accumulation was −0.09 to 0.08 Mg N ha−1 yr−1 Soil C and N sequestration but not plant biomass were related to soil Ca, Mg, and K contents. Comparative, independent assays of long-term plots provides information for concept testing and the confidence necessary for decision-makers determining C-cycle policies

Modelling Grass Productivity in the Brazilian Amazon

The Amazon Basin covers an area of 7 million km2, and the central part is almost entirely located within Brazilian territory. This region has the highest rates of deforestation in the world, and the total area deforested now exceeds 600,000 km2. Cattle pasture represents the largest single use (about 70%) of this once-forested land in most of the Brazilian Basin, with an estimated area of 20 million hectares. Our main objective was to simulate grass productivity in different forest to pasture chronosequences within the Brazilian Amazon

The economics of soil C sequestration

Abstract. Carbon is a critical component of soil vitality and of our ability to produce food. Carbon sequestered in soils also provides a further regulating ecosystem service, valued as the avoided damage from global climate change. We consider the demand and supply attributes that underpin and constrain the emergence of a market value for this vital global ecosystem service: markets being what economists regard as the most efficient institutions for allocating scarce resources to the supply and consumption of valuable goods. This paper considers how a potentially large global supply of soil carbon sequestration is reduced by economic and behavioural constraints that impinge on the emergence of markets, and alternative public policies that can efficiently transact demand for the service from private and public sector agents. In essence this is a case of significant market failure. In the design of alternative policy options we consider whether soil carbon mitigation is actually cost-effective relative to other measures in agriculture and elsewhere in the economy, and the nature of behavioural incentives that hinder policy options. We suggest that reducing cost and uncertainties of mitigation through soil-based measures is crucial for improving uptake. Monitoring and auditing processes will also be required to eventually facilitate wide-scale adoption of these measures. </jats:p