Effects of Endophyte Infection in Tall Fescue (Festuca Arundinacea: Poaceae) on Community Diversity

Recent studies have suggested that the presence of endophytes in tall fescue can lead to decreased species richness in the associated plant community. To assess the generality of this hypothesis, a field study tested the effects of endophyte infection on a 3-yr-old successional field dominated by Festuca arundinacea. The potential importance of endophyte infection relative to other environmental factors was tested by including two additional treatments: the effects of soil fertility and mowing. Contrary to previous studies, a positive relationship was found between endophyte infection frequency and diversity (N = 23, F = 5.23, R2 = 0.19, P \u3c 0.03). A strong interaction was found between the mowing treatment and endophyte infection frequency in predicting diversity (N = 22, F = 36.1, R2 = 0.84, P \u3c 0.0001), where the maximum species richness was present in plots that were both mowed and highly endophyte infected. The relationship between endophytes and diversity varied through the successional continuum (the mowing treatments) but was generally positive. The soil in mowed plots was drier than in unmowed plots (t = 2.1, df = 28, P \u3c 0.05). We suggest that heavy mowing decreases soil moisture levels enough to reduce the interspecific competitive ability of infected F. arundinacea, thereby promoting local diversity. Endophyte presence is important, but the previously reported negative relationship between endophyte infection and community diversity is probably overly simplistic in complex ecological settings

Do American Dippers Obtain a Survival Benefit from Altitudinal Migration?

Studies of partial migrants provide an opportunity to assess the cost and benefits of migration. Previous work has demonstrated that sedentary American dippers (residents) have higher annual productivity than altitudinal migrants that move to higher elevations to breed. Here we use a ten-year (30 period) mark-recapture dataset to evaluate whether migrants offset their lower productivity with higher survival during the migration-breeding period when they occupy different habitat, or early and late-winter periods when they coexist with residents. Mark-recapture models provide no evidence that apparent monthly survival of migrants is higher than that of residents at any time of the year. The best-supported model suggests that monthly survival is higher in the migration-breeding period than winter periods. Another well-supported model suggested that residency conferred a survival benefit, and annual apparent survival (calculated from model weighted monthly apparent survival estimates using the Delta method) of residents (0.511 ± 0.038SE) was slightly higher than that of migrants (0.487 ± 0.032). Winter survival of American dippers was influenced by environmental conditions; monthly apparent survival increased as maximum daily flow rates increased and declined as winter temperatures became colder. However, we found no evidence that environmental conditions altered differences in winter survival of residents and migrants. Since migratory American dippers have lower productivity and slightly lower survival than residents our data suggests that partial migration is likely an outcome of competition for limited nest sites at low elevations, with less competitive individuals being forced to migrate to higher elevations in order to breed

Simulation of the Zero Temperature Behavior of a 3-Dimensional Elastic Medium

We have performed numerical simulation of a 3-dimensional elastic medium, with scalar displacements, subject to quenched disorder. We applied an efficient combinatorial optimization algorithm to generate exact ground states for an interface representation. Our results indicate that this Bragg glass is characterized by power law divergences in the structure factor $S(k)\sim A k^{-3}$. We have found numerically consistent values of the coefficient $A$ for two lattice discretizations of the medium, supporting universality for $A$ in the isotropic systems considered here. We also examine the response of the ground state to the change in boundary conditions that corresponds to introducing a single dislocation loop encircling the system. Our results indicate that the domain walls formed by this change are highly convoluted, with a fractal dimension $d_f=2.60(5)$. We also discuss the implications of the domain wall energetics for the stability of the Bragg glass phase. As in other disordered systems, perturbations of relative strength $\delta$ introduce a new length scale $L^* \sim \delta^{-1/\zeta}$ beyond which the perturbed ground state becomes uncorrelated with the reference (unperturbed) ground state. We have performed scaling analysis of the response of the ground state to the perturbations and obtain $\zeta = 0.385(40)$. This value is consistent with the scaling relation $\zeta=d_f/2- \theta$, where $\theta$ characterizes the scaling of the energy fluctuations of low energy excitations.Comment: 20 pages, 13 figure

Representation to the accident and emergency department within 1-year of a fractured neck of femur

Background: The fractured neck of femur (NOF) is a leading cause of morbidity and mortality. The mortality attendant upon such fractures is 10% at 1 month and 30% at one year with a cost to the NHS of £1.4 billion annually. This retrospective study sought to examine rates and prevailing trends in representation to A&E in the year following a NOF fracture in an attempt to identify the leading causes behind the morbidity and mortality associated with this fracture. Methods: 1108 patients who suffered a fractured NOF between 1 January 2002 and 31 December 2007 were identified from a University Hospital A&E database. This database was then used to identify those patients who represented within 1-year following the initial fracture. The presenting complaint, provisional diagnosis and the outcome of this presentation were identified at this time. Results: 234 patients (21%) returned to A&E on 368 occasions in the year following a hip fracture. 77% (284/368) of these presentations necessitated admission. Falls, infection and fracture were the leading causes of representation. Falls accounted for 20% (57/284) of admissions; 20.7% of patients were admitted because of a fracture, while 56.6% of admissions were for medical ailments of which infection was the chief precipitant (28% (45/161)). Discussion: The causes for representation are varied and multifactorial. The results of this study suggest that some of those events or ailments necessitating readmission may be obviated and potentially reduced by interventions that can be instituted during the primary admission and continued following discharge

Antenatal corticosteroids for fetal lung maturation: an overview of Cochrane reviews

This is the protocol for a review and there is no abstract. The objectives are as follows: The objective is to summarise the available evidence from Cochrane systematic reviews for the effectiveness and safety of antenatal corticosteroid therapy to improve infant outcomes

Supercooled Lennard-Jones Liquids and Glasses: a Kinetic Monte Carlo Approach

A kinetic Monte Carlo (KMC) method is used to study the structural properties and dynamics of a supercooled binary Lennard-Jones liquid around the glass transition temperature. This technique permits us to explore the potential energy surface and barrier distributions without suffering the exponential slowing down at low temperature that affects molecular dynamics simulations. In agreement with previous studies we observe a distinct change in behaviour around $T=0.45$, close to the dynamical transition temperature $T_c$ of mode coupling theory (MCT). Below this temperature the number of different local minima visited by the system for the same number of KMC steps decreases by more than an order of magnitude. The mean number of atoms involved in each jump between local minima and the average distance they move also decreases significantly, and new features appear in the partial structure factor. Above $T~0.45$ the probability distribution for the magnitude of the atomic displacement per KMC step exhibits an exponential decay, which is only weakly temperature dependent.Comment: Accepted for J. Non-Cryst. Solid

Assessing urinary flow rate, creatinine, osmolality and other hydration adjustment methods for urinary biomonitoring using NHANES arsenic, iodine, lead and cadmium data

Background There are numerous methods for adjusting measured concentrations of urinary biomarkers for hydration variation. Few studies use objective criteria to quantify the relative performance of these methods. Our aim was to compare the performance of existing methods for adjusting urinary biomarkers for hydration variation. Methods Creatinine, osmolality, excretion rate (ER), bodyweight adjusted ER (ERBW) and empirical analyte-specific urinary flow rate (UFR) adjustment methods on spot urinary concentrations of lead (Pb), cadmium (Cd), non-arsenobetaine arsenic (AsIMM) and iodine (I) from the US National Health and Nutrition Examination Survey (NHANES) (2009–2010 and 2011–2012) were evaluated. The data were divided into a training dataset (n = 1,723) from which empirical adjustment coefficients were derived and a testing dataset (n = 428) on which quantification of the performance of the adjustment methods was done by calculating, primarily, the correlation of the adjusted parameter with UFR, with lower correlations indicating better performance and, secondarily, the correlation of the adjusted parameters with blood analyte concentrations (Pb and Cd), with higher correlations indicating better performance. Results Overall performance across analytes was better for Osmolality and UFR based methods. Excretion rate and ERBW consistently performed worse, often no better than unadjusted concentrations. Conclusions Osmolality adjustment of urinary biomonitoring data provides for more robust adjustment than either creatinine based or ER or ERBW methods, the latter two of which tend to overcompensate for UFR. Modified UFR methods perform significantly better than all but osmolality in removing hydration variation, but depend on the accuracy of UFR calculations. Hydration adjustment performance is analyte-specific and further research is needed to establish a robust and consistent framework

The favoured cluster structures of model glass formers

We examine the favoured cluster structures for two new potentials, which both behave as monatomic model glass-formers in bulk. We find that the oscillations in the interatomic potential lead to global minima that are non-compact arrangements of linked 13-atom icosahedra. We find that the structural properties of the clusters correlate with the glass-forming propensities of the potentials, and with the fragilities of the corresponding supercooled liquids.Comment: 9 pages, 7 figures; new section added and error in potential parameters correcte

Raman Spectroscopy with 2D Perturbation Correlation Moving Windows for the Characterization of Heparin–Amyloid Interactions

It has been shown extensively that glycosaminoglycan (GAG)–protein interactions can induce, accelerate, and impede the clearance of amyloid fibrils associated with systemic and localized amyloidosis. Obtaining molecular details of these interactions is fundamental to our understanding of amyloid disease. Consequently, there is a need for analytical approaches that can identify protein conformational transitions and simultaneously characterize heparin interactions. By combining Raman spectroscopy with two-dimensional (2D) perturbation correlation moving window (2DPCMW) analysis, we have successfully identified changes in protein secondary structure during pH- and heparin-induced fibril formation of apolipoprotein A-I (apoA-I) associated with atherosclerosis. Furthermore, from the 2DPCMW, we have identified peak shifts and intensity variations in Raman peaks arising from different heparan sulfate moieties, indicating that protein–heparin interactions vary at different heparin concentrations. Raman spectroscopy thus reveals new mechanistic insights into the role of GAGs during amyloid fibril formation