Diversity-Function Relationships Changed in a Long-Term Restoration Experiment

The central tenet of biodiversity-ecosystem function (BEF) theory, that species richness increases function, could motivate restoration practitioners to incorporate a greater number of species into their projects. But it is not yet clear how well BEF theory predicts outcomes of restoration, because it has been developed through tests involving short-run and tightly controlled (e.g., weeded) experiments. Thus, we resampled our 1997 BEF experiment in a restored salt marsh to test for long-term effects of species richness (plantings with 1, 3, and 6 species per 2 x 2 m plot), with multiple ecosystem functions as response variables. Over 11 years, 1- and 6-species assemblages converged on intermediate richness (mean = 3.9 species/ 0.25-m2 plot), and composition changed nonrandomly throughout the site. While three species became rare, the two most productive species became co-dominant. The two dominants controlled and increased shoot biomass, which appeared to decrease species richness. Diversity-function relationships became less positive over 11 years and differed significantly with (a) the species-richness metric (planted vs. measured), and (b) the indicator of function (shoot biomass, height, and canopy layering). The loss of positive relationships between species richness and function in our restored site began soon after we stopped weeding and continued with increasing dominance by productive species. Where species-rich plantings are unlikely to ensure long-term restoration of functions, as in our salt marsh, we recommend dual efforts to establish (1) dominant species that provide high levels of target functions, and (2) subordinate species, which might provide additional functions under current or future conditions

Tracking Bacteria through the Entire Gastrointestinal Tract of a Beef Steer

Biological processes within beef cattle gastrointestinal tracts (GIT) influence animal health, and the output (feces) is an important vector for zoonotic pathogens and antibiotic resistant bacteria. Historically, outside of the rumen, little attention was paid to the bacteria along the GIT, despite their essential role in catabolizing feed into feces. Here we characterize bacteria from 15 GIT sites within a beef steer and examine the proportion of bacteria contributed by upstream compartments. This animal displayed characteristic differences between tissue and digesta communities in gastric and large-intestine, but not small-intestine, samples. The GIT sites shared between 50 and 80% of the operational taxonomic units (OTUs) with their neighboring upstream compartment, with the exception of the ileum. The ileum shared only 11% with the jejunum but displayed a similar phylum-level taxonomic distribution with the jejunum. It is unclear whether the observed changes between compartments represent a nonrandom decrease in bacterial number or rapid multiplication of certain taxa

Chern-Simons matrix model: coherent states and relation to Laughlin wavefunctions

Using a coherent state representation we derive many-body probability distributions and wavefunctions for the Chern-Simons matrix model proposed by Polychronakos and compare them to the Laughlin ones. We analyze two different coherent state representations, corresponding to different choices for electron coordinate bases. In both cases we find that the resulting probability distributions do not quite agree with the Laughlin ones. There is agreement on the long distance behavior, but the short distance behavior is different.Comment: 15 pages, LaTeX; one reference added, abstract and section 5 expanded, typos correcte

The influence of micronutrients on oral and general health

<p>Abstract</p> <p>Objective</p> <p>The aim of the present clinical pilot study was to examine the influence of a combination of micronutrients on individuals with high stress experience.</p> <p>Methods</p> <p>40 healthy students (28 female, 12 male) with a mean age of 27.1 ± 3.0 years, experiencing high examination stress, were chosen. After approval of the ethics commission, one group of students (n = 19) took a combination of micronutrients (Orthomol vital m/f) for three months, whereas other students (n = 21) served as control group. All participants underwent at the beginning and at the end of the trial a dental examination, a determination of 10 periodontal pathogens, a salivary and a blood analysis. In addition, the participants filled in a questionnaire on nutrition, quality of life and degree of stress experienced during their final examinations.</p> <p>Results</p> <p>The evaluation of the results, obtained at the end of the trial period, showed that for all students a slight worsening of oral hygiene and an increased consumption of unhealthy food could be observed. The intake of the micronutrients led to a slight improvement of the degree of gingival inflammation in comparison to the control group. The blood analysis showed an increase in vitamin (vitamin C, vitamin E) and zinc concentrations, and a lower increase in CRP. In the male subjects, a decrease in the serum concentrations of triglycerides (p = 0.073) and LDL (p = 0.048) was observed.</p> <p>Conclusions</p> <p>This pilot study shows that micronutrients, taken during periods of high stress experience, had a beneficial effect on inflammatory processes and helped reduce the level of some of the plasma lipids in males, and thus can be recommended for supplementing the diet. However, additional studies with a higher number of subjects, also suffering from periodontal disease, are necessary to show the effect of a micronutrient supplementation more clearly.</p

Properties of Random Graphs with Hidden Color

We investigate in some detail a recently suggested general class of ensembles of sparse undirected random graphs based on a hidden stub-coloring, with or without the restriction to nondegenerate graphs. The calculability of local and global structural properties of graphs from the resulting ensembles is demonstrated. Cluster size statistics are derived with generating function techniques, yielding a well-defined percolation threshold. Explicit rules are derived for the enumeration of small subgraphs. Duality and redundancy is discussed, and subclasses corresponding to commonly studied models are identified.Comment: 14 pages, LaTeX, no figure

Lattice Discretization in Quantum Scattering

The utility of lattice discretization technique is demonstrated for solving nonrelativistic quantum scattering problems and specially for the treatment of ultraviolet divergences in these problems with some potentials singular at the origin in two and three space dimensions. This shows that lattice discretization technique could be a useful tool for the numerical solution of scattering problems in general. The approach is illustrated in the case of the Dirac delta function potential.Comment: 9 page

On the Logarithmic Triviality of Scalar Quantum Electrodynamics

Using finite size scaling and histogram methods we obtain numerical results from lattice simulations indicating the logarithmic triviality of scalar quantum electrodynamics, even when the bare gauge coupling is chosen large. Simulations of the non-compact formulation of the lattice abelian Higgs model with fixed length scalar fields on $L^{4}$ lattices with $L$ ranging from $6$ through $20$ indicate a line of second order critical points. Fluctuation-induced first order transitions are ruled out. Runs of over ten million sweeps for each $L$ produce specific heat peaks which grow logarithmically with $L$ and whose critical couplings shift with $L$ picking out a correlation length exponent of $0.50(5)$ consistent with mean field theory. This behavior is qualitatively similar to that found in pure $\lambda\phi^{4}$.Comment: 9 page

Monopole Percolation in the Compact Abelian Higgs Model

We have studied the monopole-percolation phenomenon in the four dimensional Abelian theory that contains compact U(1) gauge fields coupled to unitary norm Higgs fields. We have determined the location of the percolation transition line in the plane $(\beta_g, \beta_H)$. This line overlaps the confined-Coulomb and the confined-Higgs phase transition lines, originated by a monopole-condensation mechanism, but continues away from the end-point where this phase transition line stops. In addition, we have determined the critical exponents of the monopole percolation transition away from the phase transition lines. We have performed the finite size scaling in terms of the monopole density instead of the coupling, because the density seems to be the natural parameter when dealing with percolation phenomena.Comment: 13 pages. REVTeX. 16 figs. included using eps

Universality in percolation of arbitrary Uncorrelated Nested Subgraphs

The study of percolation in so-called {\em nested subgraphs} implies a generalization of the concept of percolation since the results are not linked to specific graph process. Here the behavior of such graphs at criticallity is studied for the case where the nesting operation is performed in an uncorrelated way. Specifically, I provide an analyitic derivation for the percolation inequality showing that the cluster size distribution under a generalized process of uncorrelated nesting at criticality follows a power law with universal exponent $\gamma=3/2$. The relevance of the result comes from the wide variety of processes responsible for the emergence of the giant component that fall within the category of nesting operations, whose outcome is a family of nested subgraphs.Comment: 5 pages, no figures. Mistakes found in early manuscript have been remove

Low thermal conductivity of the layered oxide (Na,Ca)Co_2O_4: Another example of a phonon glass and an electron crystal

The thermal conductivity of polycrystalline samples of (Na,Ca)Co_2O_4 is found to be unusually low, 20 mW/cmK at 280 K. On the assumption of the Wiedemann-Franz law, the lattice thermal conductivity is estimated to be 18 mW/cmK at 280 K, and it does not change appreciably with the substitution of Ca for Na. A quantitative analysis has revealed that the phonon mean free path is comparable with the lattice parameters, where the point-defect scattering plays an important role. Electronically the same samples show a metallic conduction down to 4.2 K, which strongly suggests that NaCo_2O_4 exhibits a glass-like poor thermal conduction together with a metal-like good electrical conduction. The present study further suggests that a strongly correlated system with layered structure can act as a material of a phonon glass and an electron crystal.Comment: 5 pages 3 figures, to be published in Phys. Rev.