Toxicity of Prudhoe Bay Crude Oil to Alaskan Arctic Zooplankton

Bioassay experiments were conducted to determine the relative susceptibilities of three arctic zooplankton species to oil pollution, and the results were compared with the effects of an actual oil spill on a pond near Barrow. In both the bioassays and the pond, the addition of Prudhoe Bay crude oil was toxic to fairy shrimp (Branchionecta paladosa O. F. Müller), which seemed most sensitive, Daphnia middendorffiana Fischer, which was next most susceptible and Heterocope septentrionalis Juday and Muttkowski, which appeared somewhat resistant to the effects of oil. Cyclopoid copepods were the only common zooplankters able to survive the pond oil spill, and these were still present two and one half weeks after the spill. The rapid deaths of the other species, especially the branchiopods, suggest that zooplankton may be the most susceptible of all arctic freshwater organisms to oil pollution

Arctic Zooplankton Community Structure: Exceptions to Some General Rules

Commonly accepted theories of zooplankton species distribution hold that: 1) large-bodied zooplankton species are excluded by fish predation and so are found only in lakes and ponds without fish; and 2) because small-bodied species are unable to compete successfully against large ones and also are preyed upon heavily by invertebrate predators, they exist primarily in lakes with fish. This pattern is not followed in a group of lakes and ponds in arctic Alaska. Some of these lakes were found to support both large and small zooplankton species along with populations of facultative planktivorous fish. Other lakes that had no fish had a small-bodied zooplankton species co-existing with a more typical large-bodied community. Close analysis of these unusual distributions reveals that the mechanisms affecting zooplankton community dynamics are more subtle and complex than generally recognized, particularly in such harsh environments as the Arctic

Apparent Size as the Determinant of Prey Selection by Bluegill Sunfish (Lepomis Macrochirus)

Copyright by the Ecological Society of America. This is the publisher's version, also available electronically from http://www.jstor.org/stable/1935055.Although it is known that visual predation by planktivorous fish tends to be size selective, the mechanism by which fish select their prey has not previously been described. Experiments in which bluegill sunfish (Lepomis macrochirus) were given a binary choice between prey of different sizes presented at different distances showed the fish selected the prey that appeared largest, either because of its actual size or its proximity to the fish. This paper incorporates this mechanism of prey selection by apparent size into a model of bluegill predation. According to the model, bluegill, in choosing the apparently largest prey under all conditions, alter their diet composition depending upon the abundance of prey. When prey are abundant, bluegill predominantly select prey of the largest size class available because these have the greatest probability of appearing largest; as large prey become scarce and smaller prey have a greater chance of appearing large, the fish tend to eat more prey from smaller size classes. When the model is tested against data from published fish-feeding experiments, the predicted size ratios of prey eaten correlate accurately with the observed ratios and numbers of prey eaten

The serotype distribution among healthy carriers before vaccination is essential for predicting the impact of pneumococcal conjugate vaccine on invasive disease.

Pneumococcal conjugate vaccines (PCVs) have substantially reduced morbidity and mortality of pneumococcal disease. The impact of the 7-valent PCV on all-serotype invasive pneumococcal disease (IPD) among children was reported to vary between high-income countries. We investigate the ability to predict this heterogeneity from pre-vaccination data. We propose a parsimonious model that predicts the impact of PCVs from the odds of vaccine serotype (VT) among carriers and IPD cases in the pre-PCV period, assuming that VT are eliminated in a mature PCV programme, that full serotype replacement occurs in carriage and that invasiveness of the NVT group is unchanged. We test model performance against the reported impact of PCV7 on childhood IPD in high-income countries from a recent meta-analysis. The odds of pre-PCV7 VT IPD, PCV schedule, PCV coverage and whether a catch up campaign was used for introduction was gathered from the same analysis. We conducted a literature review and meta-analysis to obtain the odds of pre-PCV7 VT carriage in the respective settings. The model predicted the reported impact on childhood IPD of mature PCV programmes; the ratio of predicted and observed incidence risk ratios was close to 1 in all settings. In the high income settings studied differences in schedule, coverage, and catch up campaigns were not associated with the observed heterogeneity in impact of PCV7 on childhood all-serotype IPD. The pre-PCV7 proportion of VT IPD alone also had limited predictive value. The pre-PCV7 proportion of VT carriage and IPD are the main determinants for the impact of PCV7 on childhood IPD and can be combined in a simple model to provide predictions of the vaccine preventable burden of IPD

Exploring Mars at the nanoscale: applications of transmission electron microscopy and atom probe tomography in planetary exploration

The upcoming Mars Sample Return (MSR) mission aims to deliver small quantities of Martian rocks to the Earth. Investigating these precious samples requires the development and application of techniques that can extract the greatest amount of high quality data from the minimum sample volume, thereby maximising science return from MSR. Atom probe tomography (APT) and transmission electron microscopy (TEM) are two complementary techniques that can obtain nanoscale structural, geochemical and, in the case of atom probe, isotopic information from small sample volumes. Here we describe how both techniques operate, as well as review recent developments in sample preparation protocols. We also outline how APT has been successfully applied to extraterrestrial materials in the recent past. Finally, we describe how we have studied Martian meteorites using TEM and APT in close coordination in order to characterise the products of water/rock interactions in t h e cru st of Ma r s – a k ey sc ie n ce goal of MSR. Our results provide new insights into the Martian hydrosphere and the mechanisms of anhydrous-hydrous mineral replacement. In light of the unique results provided by these tools, APT and TEM should form a crucial part at the culmination of a correlative analytical pipeline for MSR mission materials

Trauma and depressive symptomatology in middle-aged persons at high risk of dementia: the PREVENT Dementia Study

Objective: Depression and trauma are associated with changes in brain regions implicated in Alzheimer’s disease. The present study examined associations between childhood trauma, depression, adult cognitive functioning and risk of dementia. Methods: Data from 378 participants in the PREVENT Dementia Study aged 40–59 years. Linear and logistic models were used to assess associations between childhood trauma, depression, dementia risk, cognitive test scores and hippocampal volume. Results: Childhood trauma was associated with depression and reduced hippocampal volume but not current cognitive function or dementia risk. Poorer performance on a delayed face/name recall task was associated with depression. Childhood trauma was associated with lower hippocampal volume however poorer cognitive performance was mediated by depression rather than structural brain differences. Conclusion: Depressive symptomatology may be associated with dementia risk via multiple pathways, and future studies should consider subtypes of depressive symptomatology when examining its relationship to dementia

A Composite HST Spectrum of Quasars

We construct a composite quasar spectrum from 284 HST FOS spectra of 101 quasars with redshifts z > 0.33. The spectrum covers the wavelengths between 350 and 3000 A in the rest frame. There is a significant steepening of the continuum slope around 1050 A. The continuum between 1050 and 2200 A can be modeled as a power law with alpha = -0.99. For the full sample the power-law index in the extreme ultraviolet (EUV) between 350 and 1050 A is alpha = -1.96. The continuum flux in the wavelengths near the Lyman limit shows a depression of about 10 percent. The break in the power-law index and the slight depression of the continuum near the Lyman limit are features expected in Comptonized accretion-disk spectra.Comment: 10 figures To appear in the February 1, 1997, issue of the Ap.

Assessing the efficiency of catch-up campaigns for the introduction of pneumococcal conjugate vaccine: a modelling study based on data from PCV10 introduction in Kilifi, Kenya.

BACKGROUND: The World Health Organisation recommends the use of catch-up campaigns as part of the introduction of pneumococcal conjugate vaccines (PCVs) to accelerate herd protection and hence PCV impact. The value of a catch-up campaign is a trade-off between the costs of vaccinating additional age groups and the benefit of additional direct and indirect protection. There is a paucity of observational data, particularly from low- and middle-income countries, to quantify the optimal breadth of such catch-up campaigns. METHODS: In Kilifi, Kenya, PCV10 was introduced in 2011 using the three-dose Expanded Programme on Immunisation infant schedule and a catch-up campaign in children <5 years old. We fitted a transmission dynamic model to detailed local data, including nasopharyngeal carriage and invasive pneumococcal disease (IPD), to infer the marginal impact of the PCV catch-up campaign over hypothetical routine cohort vaccination in that setting and to estimate the likely impact of alternative campaigns and their dose efficiency. RESULTS: We estimated that, within 10 years of introduction, the catch-up campaign among children <5 years old prevents an additional 65 (48-84) IPD cases across age groups, compared to PCV cohort introduction alone. Vaccination without any catch-up campaign prevented 155 (121-193) IPD cases and used 1321 (1058-1698) PCV doses per IPD case prevented. In the years after implementation, the PCV programme gradually accrues herd protection, and hence its dose efficiency increases: 10 years after the start of cohort vaccination alone the programme used 910 (732-1184) doses per IPD case averted. We estimated that a two-dose catch-up among children <1 year old uses an additional 910 (732-1184) doses per additional IPD case averted. Furthermore, by extending a single-dose catch-up campaign to children aged 1 to <2 years and subsequently to those aged 2 to <5 years, the campaign uses an additional 412 (296-606) and 543 (403-763) doses per additional IPD case averted. These results were not sensitive to vaccine coverage, serotype competition, the duration of vaccine protection or the relative protection of infants. CONCLUSIONS: We find that catch-up campaigns are a highly dose-efficient way to accelerate population protection against pneumococcal disease

The reintroduction of large carnivores to the Eastern Cape, South Africa: an assessment

Recently, conservation estate in South Africa's Eastern Cape Province has increased 10-fold resulting in large predators being increasingly reintroduced to restore ecological integrity and maximize tourism. We describe the reintroductions of large carnivores (>10 kg) that have occurred in the Eastern Cape and use various criteria to assess their success. Lion Panthera leo reintroduction has been highly successful with a population of 56 currently extant in the region and problems of overpopulation arising. The African wild dog Lycaon pictus population has increased to 24 from a founder population of 11. Preliminary results for spotted hyaenas Crocuta crocuta also indicate success. Wild populations of leopards Panthera pardus exist on several reserves and have been supplemented by translocated individuals, although deaths of known individuals have occurred and no estimate of reproduction is available. Cheetah Acinonyx jubatus reintroduction has also been less successful with 36 individuals reintroduced and 23 cubs being born but only 41 individuals surviving in 2005. Criteria for assessing the success of reintroductions of species that naturally occur in low densities, such as top predators, generally have limited value. Carrying capacity for large predators is unknown and continued monitoring and intensive management will be necessary in enclosed, and possibly all, conservation areas in the Eastern Cape to ensure conservation success

The Potential for Reducing the Number of Pneumococcal Conjugate Vaccine Doses While Sustaining Herd Immunity in High-Income Countries.

Stefan Flasche and colleagues consider whether the number of PCV doses in the infant schedule could be reduced without compromising its public health benefit in high-income settings