Persistence in diving American mink

Background American mink forage on land and in water, with aquatic prey often constituting a large proportion of their diet. Their long, thin body shape and relatively poor insulation make them vulnerable to heat loss, particularly in water, yet some individuals dive over 100 times a day. At the level of individual dives, previous research found no difference in dive depth or duration, or the total number of dives per day between seasons, but mink did appear to make more dives per active hour in winter than in summer. There was also no difference in the depth or duration of individual dives between the sexes, but there was some evidence that females made more dives per day than males. However, because individual mink dives tend to be extremely short in duration, persistence (quantified as the number of consecutive dives performed) may be a more appropriate metric with which to compare diving behaviour under different scenarios. Results Mink performed up to 28 consecutive dives, and dived continually for up to 36 min. Periods of more loosely aggregated diving (termed ‘aquatic activity sessions’) comprised up to 80 dives, carried out over up to 162.8 min. Contrary to our predictions, persistence was inversely proportional to body weight, with small animals more persistent than large ones, and (for females, but not for males) increased with decreasing temperature. For both sexes, persistence was greater during the day than during the night. Conclusions The observed body weight effect may point to inter-sexual niche partitioning, since in mink the smallest animals are females and the largest are males. The results may equally point to individual specialism’s, since persistence was also highly variable among individuals. Given the energetic costs involved, the extreme persistence of some animals observed in winter suggests that the costs of occasional prolonged activity in cold water are outweighed by the energetic gains. Analysing dive persistence can provide information on an animal’s physical capabilities for performing multiple dives and may reveal how such behaviour is affected by different conditions. Further development of monitoring and biologging methodology to allow quantification of hunting success, and thus the rewards obtained under alternative scenarios, would be insightful.

Re-creation of heathland on improved pasture using topsoil removal and sulphur amendments: edaphic drivers and impacts on ericoid mycorrhizas

Understanding the factors that drive successful re-creation and restoration of lowland heaths is crucially important for achieving the long-term conservation of this threatened habitat type. In this study we investigated the changes in soil chemistry, plant community and interactions between Calluna vulgaris and symbiotic ericoid mycorrhizas (ERM) that occurred when improved pasture was subjected to one of three treatments (i) acidification with elemental sulphur (ii) acidification with ferrous sulphur (iii) removal of the topsoil. We found that the soil stripping treatment produced the greatest reduction in available phosphate but did not decrease soil pH. Conversely, acidification with elemental sulphur decreased pH but increased availability of phosphate and potentially toxic cations. The elemental sulphur treatment produced plant communities that most closely resembled those on surrounding heaths and acid grasslands. The most important driver was low pH and concomitant increased availability of potentially toxic cations. Plant community development was found to be little related to levels of available soil phosphate, particularly at low pH. The elemental sulphur treatment also produced the best germination and growth of C. vulgaris over 4–5 years. However, this treatment was found to inhibit the development of symbiotic relationships between C. vulgaris and ERM. This may affect the long-term persistence of re-created vegetation and its interactions with other components of heathland communities.

The cooler side of mycorrhizas: their occurrence and functioning at low temperatures

Mycorrhizal associations occur in a range of habitats in which soils are subject to low temperature (≤15 °C) for a significant part of the year. Despite this, most of our understanding of mycorrhizal fungi and their interactions with their plant hosts is based on physiological investigations conducted in the range 20–37 °C using fungi of temperate origin. Comparatively little consideration has been given to the cold edaphic conditions in which many mycorrhizas survive and prosper, and the physiological and ecological consequences of their low temperature environments. In this review, we consider the distribution and persistence of arbuscular and ectomycorrhizal mycorrhizal associations in cold environments and highlight progress in understanding adaptations to freezing resistance and nutrient acquisition at low temperature in mycorrhizal fungi.

Considerations on the use of the p-nitrophenyl phosphomonoesterase assay in the study of the phosphorus nutrition of soil borne fungi

The p-nitrophenyl phosphomonoesterase assay (p NPPase) is commonly used to measure cell-wall-associated and extracellular phosphatase activity of soil fungi. p NPPases are usually assayed in the context of fungal nutrition, where inorganic P supply might be enhanced by the mineralisation of monoester organic P sources in the soil. The importance of the assay to the P nutrition of soil fungi is considered based on the evidence currently available including the consistency of methodological approach. The nature of organic P in the soil and the relevance of the assay to some specific soil substrates is discussed, particularly the chemistry and bioavailability of myo-inositol hexakisphosphate and the lower inositol phosphates. The evidence for the long-term stability of p NPPases in the soil is examined in the light of the persistence of p NPPase in soils. The role of persistent extracellular fungal p NPPases in the soil P cycle is discussed. Conclusions from p NPPase based studies must be based upon an appreciation of the constraints of the assay and the complex chemistry of organic P and p NPPase in the soil.

The influence of sea ice dynamics on the climate sensitivity and memory to increased Antarctic sea ice

The study analyzes the sensitivity and memory of the Southern Hemisphere coupled climate system to increased Antarctic sea ice (ASI), taking into account the persistence of the sea ice maxima in the current climate. The mechanisms involved in restoring the climate balance under two sets of experiments, which differ in regard to their sea ice models, are discussed. The experiments are perturbed with extremes of ASI and integrated for 10 yr in a large 30-member ensemble. The results show that an ASI maximum is able to persist for ; 4 yr in the current climate, followed by a negative sea ice phase. The sea ice insulating effect during the positive phase reduces heat fluxes south of 60 8 S, while at the same time these are intensified at the sea ice edge. The increased air stability over the sea ice field strengthens the polar cell while the baroclinicity increases at midlatitudes. The mean sea level pressure is reduced (increased) over high latitudes (midlatitudes), typical of the southern annular mode (SAM) positive phase. The Southern Ocean (SO) becomes colder and fresher as the sea ice melts mainly through sea ice lateral melting, the consequence of which is an increase in the ocean stability by buoyancy and mixing changes. The climate sensitivity is triggered by the sea ice insulating process and the resulting freshwater pulse (fast response), while the climate equilibrium is restored by the heat stored in the SO subsurface layers (long response). It is concluded that the time needed for the ASI anomaly to be dissipated and/or melted is shortened by the sea ice dynamical processes.

Abrupt transitions in the NAO control of explosive North Atlantic cyclone development

Explosive cyclones are intense extra-tropical low pressure systems featuring large deepening rates. In the Euro-Atlantic sector, they are a major source of life-threatening weather impacts due to their associated strong wind gusts, heavy precipitation and storm surges. The wintertime variability of the North Atlantic cyclonic activity is primarily modulated by the North Atlantic Oscillation (NAO). In this study, we investigate the interannual and multi-decadal variability of explosive North Atlantic cyclones using track density data from two reanalysis datasets (NCEP and ERA-40) and a control simulation of an atmosphere/ocean coupled General Circulation Model (GCM—ECHAM5/MPIOM1). The leading interannual and multi-decadal modes of variability of explosive cyclone track density are characterized by a strengthening/weakening pattern between Newfoundland and Iceland, which is mainly modulated by the NAO at both timescales. However, the NAO control of interannual cyclone variability is not stationary in time and abruptly fluctuates during periods of 20–25 years long both in NCEP and ECHAM5/MPIOM1. These transitions are accompanied by structural changes in the leading mode of explosive cyclone variability, and by decreased/enhanced baroclinicity over the sub-polar/sub-tropical North Atlantic. The influence of the ocean is apparently important for both the occurrence and persistence of such anomalous periods. In the GCM, the Atlantic Meridional Overturning Circulation appears to influence the large-scale baroclinicity and explosive cyclone development over the North Atlantic. These results permit a better understanding of explosive cyclogenesis variability at different climatic timescales and might help to improve predictions of these hazardous events.

North Atlantic subtropical mode waters and ocean memory in HadCM3

A study of the formation and propagation of volume anomalies in North Atlantic Mode Waters is presented, based on 100 yr of monthly mean fields taken from the control run of the Third Hadley Centre Coupled Ocean-Atmosphere GCM (HadCM3). Analysis of the temporal and. spatial variability in the thickness between pairs of isothermal surfaces bounding the central temperature of the three main North Atlantic subtropical mode waters shows that large-scale variability in formation occurs over time scales ranging from 5 to 20 yr. The largest formation anomalies are associated with a southward shift in the mixed layer isothermal distribution, possibly due to changes in the gyre dynamics and/or changes in the overlying wind field and air-sea heat fluxes. The persistence of these anomalies is shown to result from their subduction beneath the winter mixed layer base where they recirculate around the subtropical gyre in the background geostrophic flow. Anomalies in the warmest mode (18 degrees C) formed on the western side of the basin persist for up to 5 yr. They are removed by mixing transformation to warmer classes and are returned to the seasonal mixed layer near the Gulf Stream where the stored heat may be released to the atmosphere. Anomalies in the cooler modes (16 degrees and 14 degrees C) formed on the eastern side of the basin persist for up to 10 yr. There is no clear evidence of significant transformation of these cooler mode anomalies to adjacent classes. It has been proposed that the eastern anomalies are removed through a tropical-subtropical water mass exchange mechanism beneath the trade wind belt (south of 20 degrees N). The analysis shows that anomalous mode water formation plays a key role in the long-term storage of heat in the model, and that the release of heat associated with these anomalies suggests a predictable climate feedback mechanism.

Case studies in interannual to decadal climate predictability

The predictability of ocean and climate variables is investigated, using a perfect model-based case study approach that recognises that predictability is dependent on the initial climate state. In line with previous studies, large scale ocean variables, show predictability for several years or more; by contrast, the predictability of climate variables is generally limited to, 2 years at most. That predictability shows high sensitivity to the initial state is demonstrated by predictable climate signals, arising in different regions, variables and seasons for different initial conditions. The predictability of climate variables, in the second year is of particular interest, because this is beyond the timescale that is usually considered to be the limit, of seasonal predictability. For different initial conditions, second year predictability is found in: temperatures in southeastern, North America (winter) and western Europe (winter and summer), and precipitation in India (summer monsoon) and in the tropical, South Atlantic. Second year predictability arises either from persistence of large-scale sea surface temperature (SST) and, related ocean heat content anomalies, particularly in regions such as the North Atlantic and Southern Ocean, or from mechanisms, that involve El Nino Southern Oscillation (ENSO) dynamics.

Explaining deviations from NAV in UK property companies: rationality and sentimentality

One of the most vexing issues for analysts and managers of property companies across Europe has been the existence and persistence of deviations of Net Asset Values of property companies from their market capitalisation. The issue has clear links to similar discounts and premiums in closed-end funds. The closed end fund puzzle is regarded as an important unsolved problem in financial economics undermining theories of market efficiency and the Law of One Price. Consequently, it has generated a huge body of research. Although it can be tempting to focus on the particular inefficiencies of real estate markets in attempting to explain deviations from NAV, the closed end fund discount puzzle indicates that divergences between underlying asset values and market capitalisation are not a ‘pure’ real estate phenomenon. When examining potential explanations, two recurring factors stand out in the closed end fund literature as often undermining the economic rationale for a discount – the existence of premiums and cross-sectional and periodic fluctuations in the level of discount/premium. These need to be borne in mind when considering potential explanations for real estate markets. There are two approaches to investigating the discount to net asset value in closed-end funds: the ‘rational’ approach and the ‘noise trader’ or ‘sentiment’ approach. The ‘rational’ approach hypothesizes the discount to net asset value as being the result of company specific factors relating to such factors as management quality, tax liability and the type of stocks held by the fund. Despite the intuitive appeal of the ‘rational’ approach to closed-end fund discounts the studies have not successfully explained the variance in closed-end fund discounts or why the discount to net asset value in closed-end funds varies so much over time. The variation over time in the average sector discount is not only a feature of closed-end funds but also property companies. This paper analyses changes in the deviations from NAV for UK property companies between 2000 and 2003. The paper present a new way to study the phenomenon ‘cleaning’ the gearing effect by introducing a new way of calculating the discount itself. We call it “ungeared discount”. It is calculated by assuming that a firm issues new equity to repurchase outstanding debt without any variation on asset side. In this way discount does not depend on an accounting effect and the analysis should better explain the effect of other independent variables.

Winter floods in Britain are connected to atmospheric rivers

Damage from flooding in the winter and fall seasons has been widespread in the United Kingdom (UK) and Western Europe over recent decades. Here we show that winter flood events in the UK are connected to Atmospheric Rivers (ARs), narrow ribbons along which a large flux of moisture is transported from the subtropics to the mid-latitudes. Combining river flow records with rainfall measurements, satellite data and model simulations, we demonstrate that ARs occur simultaneously with the 10 largest winter flood events since 1970 in a range of British river basins, suggesting that ARs are persistently critical in explaining extreme winter flooding in the UK. Understanding the physical processes that determine the persistence of AR events will be of importance in assessing the risk of future flooding over north-western Europe and other mid-latitude regions.

Structure variation and evolution in microphase-separated grafted diblock copolymer films

The phase behavior of grafted d-polystyrene-block-poly(methyl methacrylate) diblock copolymer films is examined, with particular focus on the effect of solvent and annealing time. It was observed that the films undergo a two-step transformation from an initially disordered state, through an ordered metastable state, to the final equilibrium configuration. It was also found that altering the solvent used to wash the films, or complete removal of the solvent prior to thermal annealing using supercritical CO2, could influence the structure of the films in the metastable state, though the final equilibrium state was unaffected. To aid in the understanding to these experimental results, a series of self-consistent field theory calculations were done on a model diblock copolymer brush containing solvent. Of the different models examined, those which contained a solvent selective for the grafted polymer block most accurately matched the observed experimental behavior. We hypothesize that the structure of the films in the metastable state results from solvent enrichment of the film near the film/substrate interface in the case of films washed with solvent or faster relaxation of the nongrafted block for supercritical CO2 treated (solvent free) films. The persistence of the metastable structures was attributed to the slow reorganization of the polymer chains in the absence of solvent.

Escherichia coli O157:H7 colonization in small domestic ruminants

Enterohaemorrhagic Escherichia coli O157:H7 was first implicated in human disease in the early 1980s, with ruminants cited as the primary reservoirs. Preliminary studies indicated cattle to be the sole source of E. coli O157:H7 outbreaks in humans; however, further epidemiological studies soon demonstrated that E. coli O157:H7 was widespread in other food sources and that a number of transmission routes existed. More recently, small domestic ruminants (sheep and goats) have emerged as important sources of E. coli O157:H7 human infection, particularly with the widespread popularity of petting farms and the increased use of sheep and goat food products, including unpasteurized cheeses. Although the colonization and persistence characteristics of E. coli O157:H7 in the bovine host have been studied intensively, this is not the case for small ruminants. Despite many similarities to the bovine host, the pathobiology of E. coli O157:H7 in small domestic ruminants does appear to differ significantly from that described in cattle. This review aims to critically review the current knowledge regarding colonization and persistence of E. coli O157:H7 in small domestic ruminants, including comparisons with the bovine host where appropriate.

The ENSO-Asian monsoon interaction in a coupled ocean-atmosphere GCM

In this study, the authors evaluate the (El Niño–Southern Oscillation) ENSO–Asian monsoon interaction in a version of the Hadley Centre coupled ocean–atmosphere general circulation model (CGCM) known as HadCM3. The main focus is on two evolving anomalous anticyclones: one located over the south Indian Ocean (SIO) and the other over the western North Pacific (WNP). These two anomalous anticyclones are closely related to the developing and decaying phases of the ENSO and play a crucial role in linking the Asian monsoon to ENSO. It is found that the HadCM3 can well simulate the main features of the evolution of both anomalous anticyclones and the related SST dipoles, in association with the different phases of the ENSO cycle. By using the simulated results, the authors examine the relationship between the WNP/SIO anomalous anticyclones and the ENSO cycle, in particular the biennial component of the relationship. It is found that a strong El Niño event tends to be followed by a more rapid decay and is much more likely to become a La Niña event in the subsequent winter. The twin anomalous anticyclones in the western Pacific in the summer of a decaying El Niño are crucial for the transition from an El Niño into a La Niña. The El Niño (La Niña) events, especially the strong ones, strengthen significantly the correspondence between the SIO anticyclonic (cyclonic) anomaly in the preceding autumn and WNP anticyclonic (cyclonic) anomaly in the subsequent spring, and favor the persistence of the WNP anomaly from spring to summer. The present results suggest that both El Niño (La Niña) and the SIO/WNP anticyclonic (cyclonic) anomalies are closely tied with the tropospheric biennial oscillation (TBO). In addition, variability in the East Asian summer monsoon, which is dominated by the internal atmospheric variability, seems to be responsible for the appearance of the WNP anticyclonic anomaly through an upper-tropospheric meridional teleconnection pattern over the western and central Pacific.

Interaction between attaching and effacing Escherichia coli serotypes O157:H7 and O26:K60 in cell culture

Ruminants harbour both O157:H7 and non-O157 Attaching Effacing Escherichia coli (AEEC) strains but to date only nonO157 AEEC have been shown to induce attaching effacing lesions in naturally infected animals. However, O157 may induce lesions in deliberate oral inoculation studies and persistence is considered dependent upon the bacterially encoded locus for enterocyte effacement. In concurrent infections in ruminants it is unclear whether non-O157 AEEC contribute either positively or negatively to the persistence of E. coli O157:H7. To investigate this, and prior to animal studies, E. coli O157:H7 NCTC 12900, a non-toxigenic strain that persists in conventionally reared sheep, and non-toxigenic AEEC O26:K60 isolates of sheep origin were tested for adherence to Hep-2 tissue culture alone and in competition one with another. Applied together, both strains adhered in similar numbers but lower than when either was applied separately. Pre-incubation of tissue culture with either one strain reduced significantly (P < 0.05) the extent of adherence of the strain that was applied second. It was particularly noticeable that AEEC O26 when applied first reduced adherence and inhibited microcolony formation, as demonstrated by confocal microscopy, of E. coli 01 57:H7. The possibility that prior colonisation of a ruminant by non-O157 AEEC such as O26 may antagonise O157 colonisation and persistence in ruminants is discussed. (C) 2004 Elsevier B.V. All rights reserved.

Naturally acquired attaching and effacing Escherichia coli in sheep

In a series of experiments involving the inoculation of sheep with Escherichia coli O157:H7, and subsequent detailed histopathological examination of the intestinal mucosa, attaching-effacing (AE) lesions formed by elements of the natural flora were observed in 18% of animals. These incidental AE lesions typically were small and sparse, and were not associated with clinical disease. It was possible to identify further some of the lesional bacteria, revealing that E. coli O115 had formed lesions in one of the seven affected animals, and similarly E. coli O26 had formed some of the lesions in another. As AE strains, source flocks, housing and feed sources were diverse, a common source of lesion-forming bacteria appears to be unlikely. It is postulated that subclinical AE lesions are a mechanism of persistence of AE bacteria in sheep.