UK Seabirds in 2005 : results from the UK Seabird Monitoring Programme

Seabirds in the UK were generally more productive in 2005 than in 2004, when productivity for many species reached an all-time low. A presumed scarcity of sandeels in 2004, especially in the North Sea, led to widespread starvation of chicks in the Northern Isles and in many places along the east coast of Britain (there is also recent evidence that prey fish were of unusually low energy content in 2004 around SE Scotland). The likely knock-on effect for 2005 was that there were few larger sandeels present (those that hatched in 2004) and it is thought that feeding on these fish allow adults to attain breeding condition in spring. This food scarcity and a cold spring led to what was among the latest breeding seasons on record. However, a late appearance of young sandeels allowed some chicks to fledge, and alternative prey species (such as sprat and small haddock) were taken also. However, it is thought that some chicks starved in this late season, as sandeels become unavailable in late summer, when they settle on the seabed. Unusually, 2005 was a very poor breeding season for many species in NW Scotland, which was spared the food shortages of 2004 and previous years; preferred prey during chick rearing were scarce in this region in 2005

ATP-Sensitive Potassium Channel-Mediated Lactate Effect on Orexin Neurons: Implications for Brain Energetics during Arousal

Active neurons have a high demand for energy substrate, which is thought to be mainly supplied as lactate by astrocytes. Heavy lactate dependence of neuronal activity suggests that there may be a mechanism that detects and controls lactate levels and/or gates brain activation accordingly. Here, we demonstrate that orexin neurons can behave as such lactate sensors. Using acute brain slice preparations and patch-clamp techniques, we show that the monocarboxylate transporter blocker α-cyano-4-hydroxycinnamate (4-CIN) inhibits the spontaneous activity of orexin neurons despite the presence of extracellular glucose. Furthermore, fluoroacetate, a glial toxin, inhibits orexin neurons in the presence of glucose but not lactate. Thus, orexin neurons specifically use astrocyte-derived lactate. The effect of lactate on firing activity is concentration dependent, an essential characteristic of lactate sensors. Furthermore, lactate disinhibits and sensitizes these neurons for subsequent excitation. 4-CIN has no effect on the activity of some arcuate neurons, indicating that lactate dependency is not universal. Orexin neurons show an indirect concentration-dependent sensitivity to glucose below 1mM, responding by hyperpolarization, which is mediated by ATP-sensitive potassium channels composed of Kir6.1 and SUR1 subunits. In conclusion, our study suggests that lactate is a critical energy substrate and a regulator of the orexin system. Together with the known effects of orexins in inducing arousal, food intake, and hepatic glucose production, as well as lactate release from astrocytes in response to neuronal activity, our study suggests that orexin neurons play an integral part in balancing brain activity and energy supply

Analysis of laser-irradiated silicon crystal using x-ray topography [abstract]

Abstract only availableA silicon crystal was irradiated with an ultrafast laser with different peak fluences. The damage caused by the laser is being characterized by x-ray topography measurement made with synchrotron radiation and a digital area detector. This project examines various means of characterizing the damage produced, in order to help understand the interactions between an ultrafast laser and a semiconductor.College of Engineering Honors Undergraduate Research Optio

"State Dependence and Long Term Site Capital in a Random Utility Model of Recreation Demand"

Conventional discrete choice Random Utility Maximization (RUM) models of recreation demand ignore the influence of knowledge, or site capital, gained over past trips on current site choice, despite its obvious impact. We develop a partially dynamic RUM model that incorporates a measure of site capital as an explanatory variable in an effort to address this shortcoming. To avoid the endogeneity of past and current trip choices, we estimate an auxiliary instrumental variable regression to purge site capital of its correlation with the error terms in current site utility. Our instrumental variable regression gives a fitted value ranging between 0 and 1 for each alternative for each person – a prediction of whether or not a person visited a site. Results suggest that the presence of accumulated site capital is an important predictor of current trips, and that failure to account for site capital will likely lead to underestimates of potential welfare effects.Random Utility Model; State Dependence; Non-Market Valuation

Resource partitioning and competition in shorebirds at Teesmouth, with particular reference to grey plover pluvialis squatarola. curlew numenius arquata and bar-tailed godwit limosa lapponica

Two shorebird assemblages were identified as providing high potential for interspecific competition - sanderling, knot, oystercatcher and turnstone on a rocky shore, and curlew, bar-tailed godwit and grey plover on soft substrates. Observations were concentrated on the latter group which all fed chiefly on ragworm Nereis diversicolor. Sizes of prey taken by the three species were estimated by two independent methods. Sexual and age differences in diet within species were examined. Dietary overlap between species was high only between certain age/sex classes. Depletion of prey by each species was estimated. Between 44 and 77 percent of the larger size class of Nereis was consumed in a favoured feeding area over one winter. Implications for competition are discussed. Interspecific aggression rates were very low compared to rates within species. All three species were present on Seal Sands, Teesmouth, in high densities in mid-winter, but temporal segregation between grey plover and curlew occurred on a favoured feeding site within a low water period. Segregation resulted from different micro-habitat choice by the two species, rather than avoidance, since grey plovers exhibited identical behaviour at times of year when densities of curlews were low. Within a period of exposure, grey plovers moved feeding site when their energy intake rate decreased due to drying of the sediments. Energy intake rate of grey plovers was not reduced in proportion to the density of curlew surrounding them, except at very high curlew densities. Competition between the three large species during the study was not important. Partitioning of prey size, temporal partitioning of feeding areas, and use of different sediment types enabled their coexistence. Competition may occur during years of high shorebird populations and low densities of available prey. Evidence from the rocky shore assemblage showed significant avoidance of knot by sanderling when feeding area was limited

A Sensitivity and Array-Configuration Study for Measuring the Power Spectrum of 21cm Emission from Reionization

Telescopes aiming to measure 21cm emission from the Epoch of Reionization must toe a careful line, balancing the need for raw sensitivity against the stringent calibration requirements for removing bright foregrounds. It is unclear what the optimal design is for achieving both of these goals. Via a pedagogical derivation of an interferometer's response to the power spectrum of 21cm reionization fluctuations, we show that even under optimistic scenarios, first-generation arrays will yield low-SNR detections, and that different compact array configurations can substantially alter sensitivity. We explore the sensitivity gains of array configurations that yield high redundancy in the uv-plane -- configurations that have been largely ignored since the advent of self-calibration for high-dynamic-range imaging. We first introduce a mathematical framework to generate optimal minimum-redundancy configurations for imaging. We contrast the sensitivity of such configurations with high-redundancy configurations, finding that high-redundancy configurations can improve power-spectrum sensitivity by more than an order of magnitude. We explore how high-redundancy array configurations can be tuned to various angular scales, enabling array sensitivity to be directed away from regions of the uv-plane (such as the origin) where foregrounds are brighter and where instrumental systematics are more problematic. We demonstrate that a 132-antenna deployment of the Precision Array for Probing the Epoch of Reionization (PAPER) observing for 120 days in a high-redundancy configuration will, under ideal conditions, have the requisite sensitivity to detect the power spectrum of the 21cm signal from reionization at a 3\sigma level at k<0.25h Mpc^{-1} in a bin of \Delta ln k=1. We discuss the tradeoffs of low- versus high-redundancy configurations.Comment: 34 pages, 5 figures, 2 appendices. Version accepted to Ap

Active Vibration Control Using Optimized Piezoelectric Topologies

This work investigates the optimal topology of an actively controlled piezoelectric actuator bonded to an elastic cantilever beam under steady-state harmonic loading near the first natural frequency of the beam. The actuator is discretized using finite elements, and control is applied to the actuator based on the sensor’s degrees of freedom using proportional control. This study investigates the optimal distribution of actuator material for one and five layers of finite elements. The optimized actuator topology shows substantial improvement over initial piezoelectric topologies and over traditional actuator placement. This study has two main topics, material homogenization and topology optimization. The piezoelectric actuator is homogenized to determines it’s relation to volume fraction of material. This continuous relationship to volume fraction is a more “realistic” material variation compared with the typical artificial material model used in topology optimization. The actuator topology of the actuator is optimized to minimize the vibration amplitude. To the author’s knowledge, little work has focused on the optimal topologies of a piezoelectric actuator to minimize the amplitude displacement at the first mode of a cantilever beam

FAMILIAR AND FAVORITE SITES IN A RANDOM UTILITY MODEL OF BEACH RECREATION

We estimate a random utility model of recreation demand accounting for choice set familiarity and favorite sites. Our approach differs from existing approaches by retaining all sites in estimating the parameters of site utility. Familiar and unfamiliar sites are specified with different utility functions. Favored sites are assumed to have higher utility than nonfavored sites in estimation.Resource /Energy Economics and Policy,

Outcome assessment after hip fracture : is EQ-5D the answer?

Objectives: To study the measurement properties of a joint specific patient reported outcome measure, a measure of capability and a general health-related quality of life (HRQOL) tool in a large cohort of patients with a hip fracture. Methods: Responsiveness and associations between the Oxford Hip Score (a hip specific measure: OHS), ICEpop CAPability (a measure of capability in older people: ICECAP-O) and EuroQol EQ-5D (general health-related quality of life measure: EQ-5D) were assessed using data available from two large prospective studies. The three outcome measures were assessed concurrently at a number of fixed follow-up time-points in a consecutive sequence of patients, allowing direct assessment of change from baseline, inter-measure associations and validity using a range of statistical methods. Results: ICECAP-O was not responsive to change. EQ-5D was responsive to change from baseline, with an estimated standardised effect size for the two datasets of 0.676 and 0.644 at six weeks and four weeks respectively; this was almost as responsive to change as OHS (1.14 at four weeks). EQ-5D correlated strongly with OHS; Pearson correlation coefficients were 0.74, 0.77 and 0.70 at baseline, four weeks and four months. EQ-5D is a moderately good predictor of death at 12 months following hip fracture. Furthermore, EQ-5D reported by proxies (relatives and carers) behaves similarly to self-reported scores. Conclusions: Our findings suggest that a general HRQOL tool such as EQ-5D could be used to measure outcome for patients recovering from hip fracture, including those with cognitive impairment