Extracting Long-Term Patterns of Population Changes from Sporadic Counts of Migrant Birds

Declines of many North American birds are of conservation concern. Monitoring their population changes has largely depended on formally structured Breeding Bird Surveys, and Migration Monitoring Stations, although some use has been made of lists by birders. For almost 40 years, birders have kept daily counts of migrant landbirds during visits to Seal Island, of Nova Scotia's south tip. Here we present results for several common migrants using day-counts made between August 15 and November 15. Most existing analyses have used linear models to extract trends and other variables from such long-term data sets. Instead we applied Generalized Additive Models (GAMs) to extract the continuous trend functions and patterns of influence of observer number, wind speed, wind direction on count nights and prior nights, and moon phase. The results suggest that GAMs are a powerful way of dealing with such "noisy" data of the sort collected by birders in their recreational pursuits. In addition, it is possible to analyse groups of species (related taxonomically or ecologically) simultaneously with the potential of determining overall more general trends.Seal Island, Generalized additive models, Count data, Overdisperson

Mathematical and experimental approaches to the dimer catastrophe theory

Multicopy plasmids rely on random distribution for stable inheritance by daughter cells at division. Threats to plasmid copy number increase the probability of plasmid loss, which can be detrimental to both plasmid and host. Plasmid dimers emerge through homologous recombination. Dimers have two independent origins of replication and thus have a replicative advantage and reduced copy number. Models of plasmid behaviour suggest that dimers would overtake a cell population, but that this can be prevented if they impose a small metabolic load, which has been observed in vivo. Plasmid ColE1 also contains a cer site, which allows for dimer resolution by XerCD site-specific recombination. A small RNA, Rcd, is expressed from the cer site in dimers and interacts with tryptophanase to increase the concentration of indole in the cell. It is proposed that, as indole inhibits cell division, Rcd imposes a checkpoint on the cell until plasmid dimers are resolved. In this work, plasmid behaviour in a growing cell population was modelled stochastically in more detail than previous work. A plasmid replication model suggested that dimers replicate to more than half the average copy number of monomers, perhaps accounting for their increased metabolic load. A cell population model suggested that the presence of dimer-only cells decreased the average plasmid stability by less than in previous models, which used a fixed plasmid copy number. The rate of dimer resolution required to affect plasmid stability was unreasonably high, indicating the necessity of the Rcd checkpoint. The model thus suggested that the checkpoint may be an escape route for dimer-only cells rather than an immediate response to the emergence of an initial dimer. The Rcd checkpoint itself was also subject to critical analysis. It was realised that neither inhibition of cell division nor cell growth were sufficient to assist dimer resolution; inhibition of plasmid replication was required. Experiments in vivo found that indole inhibited plasmid replication at a concentration that may be achievable endogenously. DNA gyrase was investigated as a component of the mechanism of this inhibition, and indole was found to inhibit its supercoiling activity in vitro.The author of this work was the recipient of a PhD studentship from the Medical Research Council (UK

Global scale climate–crop yield relationships and the impacts of recent warming

Changes in the global production of major crops are important drivers of food prices, food security and land use decisions. Average global yields for these commodities are determined by the performance of crops in millions of fields distributed across a range of management, soil and climate regimes. Despite the complexity of global food supply, here we show that simple measures of growing season temperatures and precipitation—spatial averages based on the locations of each crop—explain ∼30% or more of year-to-year variations in global average yields for the world’s six most widely grown crops. For wheat, maize and barley, there is a clearly negative response of global yields to increased temperatures. Based on these sensitivities and observed climate trends, we estimate that warming since 1981 has resulted in annual combined losses of these three crops representing roughly 40 Mt or $5 billion per year, as of 2002. While these impacts are small relative to the technological yield gains over the same period, the results demonstrate already occurring negative impacts of climate trends on crop yields at the global scale

Small-sample asymptotic distributions of M-estimators of location

Asymptotic formulae for the distribution of M-estimators, i.e. maximum likelihood type estimators, of location, including the arithmetic mean, are derived which numerical studies show to give relative errors for densities and tail areas of the order of magnitude of 1% down to sample sizes 3 and 4 even in the extreme tails. The paper is the continuation of earlier work by the second author and is also closely related to Daniels's work on the saddlepoint approximation. The method consists in expanding the derivative of the logarithm of the unstandardized density of the estimator in powers of 1/n at each point, using recentring by means of conjugate distributions. This method yields a unified point of view for the comparison of other asymptotic methods, namely saddlepoint method, Edgeworth expansion and large deviations approach, which are also compared numericall

End-periodic homeomorphisms and volumes of mapping tori

Given an irreducible, end-periodic homeomorphism f of a surface S with finitely many ends, all accumulated by genus, the mapping torus is the interior of a compact, irreducible, atoroidal 3-manifold with incompressible boundary. Our main result is an upper bound on the infimal hyperbolic volume of the compactified mapping torus in terms of the translation length of f on the pants graph of S. This builds on work of Brock and Agol in the finite-type setting. We also construct a broad class of examples of irreducible, end-periodic homeomorphisms and use them to show that our bound is asymptotically sharp.Comment: 42 pages, 9 figure

Regional and racial inequality in infectious disease mortality in U.S. cities, 1900-1948

In the first half of the twentieth century, the rate of death from infectious disease in the United States fell precipitously. Although this decline is well-known and well-documented, there is surprisingly little evidence about whether it took place uniformly across the regions of the U.S. We use data on infectious disease deaths from all reporting U.S. cities to describe regional patterns in the decline of urban infectious mortality from 1900 to 1948. We report three main results: First, urban infectious mortality was higher in the South in every year from 1900 to 1948. Second, infectious mortality declined later in southern cities than in cities in the other regions. Third, comparatively high infectious mortality in southern cities was driven primarily by extremely high infectious mortality among African Americans. From 1906 to 1920, African Americans in cities experienced a rate of death from infectious disease greater than what urban whites experienced during the 1918 flu pandemic.First author draf

Integration of median filter and oriented field estimation for fingerprint identification system

The Fingerprint Identification System (FIS) has been used and applied into various aspects. The system used identification based on fingerprint to give an authorization and identification to every person that wants to access the system. However, there are some research issues that affect the system accuracy such as noise element and low-quality fingerprint image. To solve this problem, this project will proposed two selection methods; which are Median filter to reduce noise element and Orientation Field Extimation method to enhance the low quality image. This proposed methods is implement in order to get an accurate result and high performance system. In order to verify the system identification, two experiments has been done which are functional test and accuracy test. This test will used 16 images from FVC2004DB1 set. From this test, there will be three results that being focus on which are the computational time, high peak value, False Rejection Rate (FRR), False Acceptance Rate (FAR) and Matching Rate. These values are used in order to verify high performance in the system, by comparing the proposed system with other existing system. By doing this experiment, it shown that by using the proposed methods it has lower value in average time and FRR value; which is good in order to get a high performance working system. However, for FAR value the other existing work has more accurate result in identifying fingerprint image compared to proposed work. Based from the experimental test, it shown that by using the proposed methods it is effective in order to identify low-quality and noises image with an accurate matching result and high performance system