TAILORING POINT COUNTS FOR INFERENCE ABOUT AVIAN DENSITY: DEALING WITH NONDETECTION AND AVAILABILITY

Point counts are commonly used for bird surveys, but interpretation is ambiguous unless there is an accounting for the imperfect detection of individuals. We show how repeated point counts, supplemented by observation distances, can account for two aspects of the counting process: (1) detection of birds conditional on being available for observation and (2) the availability of birds for detection given presence. We propose a hierarchical model that permits the radius in which birds are available for detection to vary with forest stand age (or other relevant habitat features), so that the number of birds available at each location is described by a Poisson‐gamma mixture. Conditional on availability, the number of birds detected at each location is modeled by a beta‐binomial distribution. We fit this model to repeated point count data of Florida scrub‐jays and found evidence that the area in which birds were available for detection decreased with increasing stand age. Estimated density was 0.083 (95%CI: 0.060–0.113) scrub‐jays/ha. Point counts of birds have a number of appealing features. Based on our findings, however, an accounting for both components of the counting process may be necessary to ensure that abundance estimates are comparable across time and space. Our approach could easily be adapted to other species and habitats.     

MULTISPECIES MODELING FOR ADAPTIVE MANAGEMENT OF HORSESHOE CRABS AND RED KNOTS IN THE DELAWARE BAY

Abstract Adaptive management requires that predictive models be explicit and transparent to improve decisions by comparing management actions, directing further research and monitoring, and facilitating learning. The rufa subspecies of red knots (Calidris canutus rufa), which has recently exhibited steep population declines, relies on horseshoe crab (Limulus polyphemus) eggs as their primary food source during stopover in Delaware Bay during spring migration. We present a model with two different parameterizations for use in the adaptive management of horseshoe crab harvests in the Delaware Bay that links red knot mass gain, annual survival, and fecundity to horseshoe crab dynamics. The models reflect prevailing hypotheses regarding ecological links between these two species. When reported crab harvest from 1998 to 2008 was applied, projections corresponded to the observed red knot population abundances depending on strengths of the demographic relationship between these species. We compared different simulated horseshoe crab harvest strategies to evaluate whether, given this model, horseshoe crab harvest management can affect red knot conservation and found that restricting harvest can benefit red knot populations. Our model is the first to explicitly and quantitatively link these two species and will be used within an adaptive management framework to manage the Delaware Bay system and learn more about the specific nature of the linkage between the two species.     

The Lennard-Jones-Devonshire cell model revisited

The cell theory of Lennard-Jones and Devonshire is re-analysed and it is found that, in addition to the critical point originally reported for the 12-6 potential (and widely quoted in standard textbooks), the model exhibits a further critical point. The latter is shown to be actually a more appropriate candidate for liquid-gas criticality than the original critical point.     

A self-consistent method for the generation of configuration interaction coefficients using variational Monte Carlo

We have developed a new method for calculating configuration interaction coefficients for trial wavefunctions used in quantum Monte Carlo calculations of molecular structure. These numerical calculations can be carried out with optimized Jastrow functions included in the wavefunction. These calculations produce coefficients different from those obtained through methods using analytical integration without the Jastrow functions and lead to more accurate trial wavefunctions. We tested the method on the beryllium atom and found that the VMC energy obtained with improved coefficients (—14.6615 hartrees) was 0.9 millihartrees lower than the energy obtained using coefficients from analytical calculations (—14.6606 hartrees). This energy difference corresponds to about 1% of the correlation energy.     

PREDICTING GULL/HUMAN CONFLICTS WITH MATHEMATICAL MODELS: A TOOL FOR MANAGEMENT

Abstract Gulls are highly adaptable animals that thrive in proximity to humans. Although gulls enjoy legal protection in North America, England, and Europe, they often conflict with human interests by spreading disease, transporting contaminants, fouling public areas with droppings, and colliding with aircraft. Of particular concern are aggregates of “loafing” gulls that gather on parking lots, rooftops, and airport runways. Loafing in birds is a general state of immobility that involves behaviors such as sleeping, sitting, standing, resting, preening, and defecating. The ability to predict the incidence of aggregated loafing provides a first step toward the amelioration of bird/human conflicts. We used mathematical models to predict the aggregate loafing behavior of gulls as a function of environmental conditions and tested model portability across years, phase of breeding cycle, loafing location, and species. Because groups of loafing birds quickly reassemble after disturbance, algebraic models for the steady‐state dynamics can be obtained from the differential equations using time‐scale analysis. The accessible management tool requires data collection on an appropriate time scale and information‐theoretic model selection from a suite of alternative algebraic models.     

A quadratic configuration interaction study of N2O and N2O·−

The geometries and vibrational frequencies of both N₂O and N₂O^·– were calculated at the QCISD and QCISD(T) levels of theory using aug-cc-pVDZ and aug-cc-pVTZ basis sets. The electron affinity of N₂O was determined to be ?0.15 eV. This work corroborates an earlier G2 study and suggests that the currently accepted value for the electron affinity, 0.22eV, is in error. This study represents the best calculation to date for the geometry and vibrational frequencies of N₂O^·?     

Constrained Optimal Design of Columns Against Buckling∗

The buckling loads of straight, simply supported columns, loaded by axial thrust are maximized, subject to the restriction that the available volume of structural material is specified. In addition, a constraint is placed upon the maximum allowable prebuckling stress. Analytic solutions are presented for a variety of different cross-sectional geometries.     

An error bound for the finite element approximation of a model for phase separation of a multi-component alloy

An error bound is proved for a fully practical piecewise linearfinite element approximation, using a backward-Euler time discretization,of a model for phase separation of a multi-component alloy.Numerical experiments with three components in one and two spacedimensions are also presented.     

FLUORESCENCE OF 5-METHYLCYTOSINE

Abstract— 5-Methylcytosine and 5-methyldeoxycytidylic acid are fluorescent in aqueous solution at room temperature and neutral pH. 5-Methylcytosine, 10^-3M, pH 8.5, 25°C, has a quantum yield of 5 ×10^-4, 5-Methyldeoxycitydylic acid, 10^-4M, pH 7.5, 20°C, has a quantum yield of 8 × 10^-4. Emission maxima are 2.91 and 2.80μ^-1. At pH 14, the quantum yield of 5-methylcytosine is 1.6 × 10^-2; the emission maximum is 2.82μ^-1. At pH I, the quantum yield of both compounds is less than or equal to 10^-4. Both compounds were chromatographically homogeneous, had absorption spectra which agreed with published data, and excitation spectra which agreed closely with absorption spectra.