Dissolved inorganic carbon in soil and shallow groundwater, Konza Prairie LTER Site, NE Kanas, USA

Sources and seasonal trends of dissolved inorganic carbon (DIC) in a shallow limestone aquifer were studied for 1 year at the Konza Prairie LTER (Long-Term Ecological Research) Site in northeastern Kansas, from spring 2010 to spring 2011. Annual cycles of soil air CO2, groundwater DIC, and isotope characteristics showed a strong dependency on weather conditions and soil respiration. Soil air CO2 reached its annual maximum in the middle of the growing season, when moisture was not limiting to soil respiration. Following the maximum, the CO2 decreased because of moisture deficiency in the late summer and temperature decline in the fall and winter. The decrease began first in the shallowest part of the soil and last in the deepest part. Groundwater CO2 reached its annual maximum in October; this lag-time between the soil and groundwater CO2 maxima of 2-3 months may correspond to the travel time of soil-generated CO2 to the water table. The time-variable CO2 caused an annual carbonate-mineral saturation cycle, intensifying limestone dissolution, thus soil CO2 and carbonate minerals are the two main sources of DIC in soil and groundwater. The stable carbon isotope composition of soil air CO2 and DIC exhibited primarily C4 plant signature and were similar to that of soil organic matter, suggesting that both root and bacterial respiration are sources of CO2. DIC was enriched in 7-10 per mil PDB relative to the CO2 source due to isotope fractionation in a system open to soil CO2; the enrichment was smallest under highest pCO2. For this reason, d13CDIC was out of phase with DIC, the lightest in the late growing season. The carbon flux from the unsaturated zone to the unconfined aquifer during the year was variable depending on respiration and precipitation regimes, and had two main pathways. Transport of soil CO2 in the dissolved form with diffuse flow of recharge water was the most effective during the entire growing season. Downward movement of gaseous CO2 and equilibration with groundwater at the water table was possible in July to August. Storm rainfall events rapidly recharged the aquifer through preferential flow and stream-groundwater interaction. Rather than forcing soil gases downward because of water-saturated pores, the main effect of these events was dilution of groundwater. The calculated flux was about 0.3 M/m2/yr of C, which is less than 1% of the CO2 that is released by soil to the atmosphere via efflux. However, the climate prediction of increased respiration rates, temperature, and frequency of extreme rainfall events has the potential to cause higher carbon flux to the saturated zone, intensifying weathering and groundwater acidification

The Phase Diagram of Three-Dimensional SU(3) + Adjoint Higgs Theory

We study the phase diagram of the three-dimensional SU(3)+adjoint Higgs theory with lattice Monte Carlo simulations. A critical line consisting of a first order line, a tricritical point and a second order line, divides the phase diagram into two parts distinguished by =0 and /=0. The location and the type of the critical line are determined by measuring the condensates and , and the masses of scalar and vector excitations. Although in principle there can be different types of broken phases, corresponding perturbatively to unbroken SU(2)xU(1) or U(1)xU(1) symmetries, we find that dynamically only the broken phase with SU(2)xU(1)-like properties is realized. The relation of the phase diagram to 4d finite temperature QCD is discussed.Comment: 21 pages, 8 figure

Genetic tool development in marine protists: Emerging model organisms for experimental cell biology

Diverse microbial ecosystems underpin life in the sea. Among these microbes are many unicellular eukaryotes that span the diversity of the eukaryotic tree of life. However, genetic tractability has been limited to a few species, which do not represent eukaryotic diversity or environmentally relevant taxa. Here, we report on the development of genetic tools in a range of protists primarily from marine environments. We present evidence for foreign DNA delivery and expression in 13 species never before transformed and for advancement of tools for eight other species, as well as potential reasons for why transformation of yet another 17 species tested was not achieved. Our resource in genetic manipulation will provide insights into the ancestral eukaryotic lifeforms, general eukaryote cell biology, protein diversification and the evolution of cellular pathways

Ratios of Fluctuation Observables in the Search for the QCD Critical Point

The QCD critical point can be found in heavy ion collision experiments via the non-monotonic behavior of many fluctuation observables as a function of the collision energy. The event-by-event fluctuations of various particle multiplicities are enhanced in those collisions that freeze out near the critical point. Higher, non-Gaussian, moments of the event-by-event distributions of such observables are particularly sensitive to critical fluctuations, since their magnitude depends on the critical correlation length to a high power. We present quantitative estimates of the contribution of critical fluctuations to the third and fourth moments of the pion and proton, as well as estimates of various measures of pion-proton correlations, all as a function of the same five non-universal parameters. We show how to use nontrivial but parameter independent ratios among these more than a dozen fluctuation observables to discover the critical point. We also construct ratios that, if the critical point is found, can be used to overconstrain the values of the non-universal parameters.Comment: 5 pages, 1 figure - Talk given by C. Athanasiou at Hot Quarks 201

Equation of state near the endpoint of the critical line

We discuss first order transitions for systems in the Ising universality class. The critical long distance physics near the endpoint of the critical line is explicitly connected to microscopic properties of a given system. Information about the short distance physics can therefore be extracted from the precise location of the endpoint and non-universal amplitudes. Our method is based on non-perturbative flow equations and yields directly the universal features of the equation of state, without additional theoretical assumptions of scaling or resummations of perturbative series. The universal results compare well with other methods.Comment: LaTeX, 22 pages with 7 figures, uses epsf.sty and rotate.st

Bidirectional redox cycling of phenazine-1-carboxylic acid by Citrobacter portucalensis MBL drives increased nitrate reduction

Phenazines are secreted metabolites that microbes use in diverse ways, from quorum sensing to antimicrobial warfare to energy conservation. Phenazines are able to contribute to these activities due to their redox activity. The physiological consequences of cellular phenazine reduction have been extensively studied, but the counterpart phenazine oxidation has been largely overlooked. Phenazine-1-carboxylic acid (PCA) is common in the environment and readily reduced by its producers. Here, we describe its anaerobic oxidation by Citrobacter portucalensis strain MBL, which was isolated from topsoil in Falmouth, MA, and which does not produce phenazines itself. This activity depends on the availability of a suitable terminal electron acceptor, specifically nitrate or fumarate. When C. portucalensis MBL is provided reduced PCA and either nitrate or fumarate, it continuously oxidizes the PCA. We compared this terminal electron acceptor-dependent PCA-oxidizing activity of C. portucalensis MBL to that of several other γ-proteobacteria with varying capacities to respire nitrate and/or fumarate. We found that PCA oxidation by these strains in a fumarate-or nitrate-dependent manner is decoupled from growth and correlated with their possession of the fumarate or periplasmic nitrate reductases, respectively. We infer that bacterial PCA oxidation is widespread and genetically determined. Notably, reduced PCA enhances the rate of nitrate reduction to nitrite by C. portucalensis MBL beyond the stoichiometric prediction, which we attribute to C. portucalensis MBL’s ability to also reduce oxidized PCA, thereby catalyzing a complete PCA redox cycle. This bidirectionality highlights the versatility of PCA as a biological redox agent

Three-dimensional Ising model in the fixed-magnetization ensemble: a Monte Carlo study

We study the three-dimensional Ising model at the critical point in the fixed-magnetization ensemble, by means of the recently developed geometric cluster Monte Carlo algorithm. We define a magnetic-field-like quantity in terms of microscopic spin-up and spin-down probabilities in a given configuration of neighbors. In the thermodynamic limit, the relation between this field and the magnetization reduces to the canonical relation M(h). However, for finite systems, the relation is different. We establish a close connection between this relation and the probability distribution of the magnetization of a finite-size system in the canonical ensemble.Comment: 8 pages, 2 Postscript figures, uses RevTe