Uncertainties in forces extracted from non-contact atomic force microscopy measurements by fitting of long-range background forces

In principle, non-contact atomic force microscopy (NC-AFM) now readily allows for the measurement of forces with sub-nanonewton precision on the atomic scale. In practice, however, the extraction of the often desired ‘short-range’ force from the experimental observable (frequency shift) is often far from trivial. In most cases there is a significant contribution to the total tip–sample force due to non-site-specific van der Waals and electrostatic forces. Typically, the contribution from these forces must be removed before the results of the experiment can be successfully interpreted, often by comparison to density functional theory calculations. In this paper we compare the ‘on-minus-off’ method for extracting site-specific forces to a commonly used extrapolation method modelling the long-range forces using a simple power law. By examining the behaviour of the fitting method in the case of two radically different interaction potentials we show that significant uncertainties in the final extracted forces may result from use of the extrapolation method

Macrofaunal and foraminiferal community structure and their response to simulated phytodetrital food pulses

To learn more about deep-sea ecosystem functioning, this thesis has focused on elucidating the role of macrofauna and Foraminifera in deep-sea C-cycling. The first manuscript describes the composition of, and for the first time, the response by macrofauna to a simulated organic matter (OM) pulse at an abyssal Station in the NE Pacific. In each experiment, 1.2 g C m-2 of 13C-labelled Skeletonema costatum was deposited onto the seafloor using a benthic chamber lander. Macrofaunal abundance and biomass were found to be significantly higher at 0-5 cm depth compared to 5-10 cm, and were dominated by the Nematoda and Crustacea, respectively. Twenty-five percent of the macrofauna specimens showed 13C-signatures indicative of label ingestion, but specific uptake and C-turnover rates varied strongly between and within taxa. Two organisms, a single cumacean from chamber two and a paraonid polychaete from chamber three, were responsible for the majority of C-turnover, and had ingested up to 2.3 % of their body weight in C. Macrofaunal C-turnover was much lower than recorded in the abyssal NE Atlantic, which is most likely due to differences in the timing of the experiments relative to the spring/ summer bloom, different experimental durations and disparities in macrofaunal community structure. These results emphasize the degree of plasticity inherent in the macrofaunal response to a food pulse and stress the need for comprehensive in-situ investigations to further our understanding of deep-sea benthic ecosystem functioning. The second manuscript of this thesis describes the response by bathyal macrofauna from a deep western Norwegian fjord to a simulated OM pulse. In each experiment, 1 g Corg m-2 of 13C-labelled Skeletonema costatum was deposited onto intact sediment cores collected from 688 m water depth and incubated ex-situ for 2, 7 and 14 d. Macrofaunal abundance and biomass estimates were comparable to other deep-sea continental margin sediments of similar depths but in contrast to previous fjord studies, the macrofaunal community was numerically dominated by ostracods. Tracer experiments revealed highest uptake of tracer after 7 and 14 d compared to 2 d. Of the 7 deposit feeding polychaete families, only the Paraonidae & Cirratulidae - together with the largely carnivorous Lumbrineridae - showed a significant response to our labelled C-source. The lack of response by the majority of deposit feeders, and the unexpected feeding mode of the Lumbrineridae may be attributable to species- rather than family-specific feeding-ecologies and/ or ontogenetic changes in diet/ feeding mode. Total macrofaunal C-turnover was much lower than recorded in the deep Sognefjord in a 3 d feeding experiment, and is most likely a result of 1) distinct differences in macrofaunal community composition between the two sites, with a predominantly sub-surface feeding macrofaunal assemblage in the Korsfjorden as opposed to a surface-feeding community in the Sognefjord and/ or 2) variations in OM supply and demand. In conclusion, this investigation highlights the importance of ecological information on species level for a detailed understanding of C-cycling and early diagenesis in marine sediments. Finally, the third manuscript describes the response by Foraminifera to labile OM from the same study as that described in chapter 2. The Foraminiferal community ( 250 micron) from the Korsfjordenen was largely dominated (91 %) by the deep-dwelling species Globobulimina turgida and Melonis barleeanum, aswell as the shallow infaunal species Hyalinea balthica. With the exception of H. balthica, Foraminiferal average living depths (ALD) were continuously deep, indicating that the majority of Foraminifera were not vertically migrating to the surface to feed on the fresh organic matter pulse. Hyalinea balthica did migrate towards the sediment surface, but did not feed on our 13C-tracer, suggesting that migration was due to another factor, possibly microhabitat restabilization following initial sub-optimal living conditions. No Foraminifera were involved in C-turnover during the first 7 d. After 14 d, 3 % of the Foraminifera samples possessed delta 13C-signatures indicative of C-uptake, but uptake was confined to G. turgida. Foraminifera contributed 2.4 % to faunal C-turnover (Foraminifera plus macrofauna), despite them making up 24 % of the combined biomass. The dominance of deep-infaunal species such as G. turgida and M. barleeanum (68 %) that prefer degraded organic matter over more labile material, as well as the coarse size fraction of Foraminifera analysed, which are known to respond slower to phytodetritus deposition than smaller, more opportunistic taxa, are likely reasons for the retarded response to food input observed in this study

Development and application of diffusive gradients in thin films (DGT) for in situ monitoring of emerging contaminants in aquatic environments

There has been increasing concern about the environmental release and dispersal of emerging contaminants (ECs) and their potential risks to human and ecosystem health. The in situ passive sampling tool, diffusive gradients in thin films (DGT), has been developed as a promising alternative to traditional grab sampling in environmental research of ECs, such as pharmaceuticals, endocrine disrupting chemicals (EDCs), and some types of flame retardants. This thesis explored the role of DGT in determining ECs and understanding their sources, fate and impact in aquatic environments. The property range of organic compounds which can be routinely sampled with the present design of DGT device (PTFE membrane filter, agarose gel diffusion layer, and HLB binding layer) was investigated. Sorption experiments and DGT deployment with 9 model chemicals [organophosphate esters (OPEs) with a wide range of log KOW (0.8−9.5), molecular weight (182−435 Da)] and different functional groups showed compounds with high hydrophobicity and aromatic rings are prone to retention on membrane filters, which slows the transport of chemical to the binding resin of the sampler. The limitation of the current DGT device for some trace organics is adsorption in the diffusion layer, mainly in the membrane filter. However, it is possible to extend the DGT technique for a wider range of chemicals, for example, by replacing the current DGT membrane filter with a new type of membrane filter which does not interact with target analytes. The potential effects of biofouling and post-deployment sample storage on DGT measurements were systematically investigated. Biofilms generated at the surface of DGT devices (8-day and 15-day) in summer and winter from a typical urban wastewater treatment plant were tested with 13 ECs; this study showed no effect on DGT measurements for most compounds. Four storage methods up to 2-month were evaluated; this study showed that intact samplers can be kept for up to 2-months at refrigerated temperature (4 °C) without significant effect on the measured concentration of the compounds, but if no refrigerators were available, keeping binding gels in elution solvent at room temperature would achieve comparable results. DGT and grab sampling were used together to study sources and environmental fate of ECs in a dynamic river catchment, the River Thames in the United Kingdom. For chemicals that were relatively stable in the rivers, DGT and grab sampling provided equally good representativeness. For chemicals that showed high dynamic variation in water bodies, the DGT provided a better integral of loadings and exposure than grab sampling. It took a similar time to set up and collect the DGT passive sampling system and to collect grab samples. However, for later storage and sample treatment, DGT is much more space-, cost- and time-effective. DGT, for the first time, was combined with a water quality model (LF2000-WQX) to study sources and environmental fate of ECs, taking trimethoprim as a case study. The model needs the following key input information for the EC: per capita emission, WWTPs and in-river removal rates. DGT measurements in the River Thames network were used to assess the ability of the model to predict reasonable concentrations. This study showed that LF2000-WQX is suitable for predicting point-source ECs; predicted concentrations agreed very well with DGT measurements in winter and the model performance can be improved by improving in-river removal rate, i.e., using different in-river removal rates considering local environmental conditions such as DOC in different river reaches. The work in this thesis is a step forward to understand the current performance of the DGT sampler and to explore its role in studying organic contaminants. It has shown that DGT is an effective tool for studying environmental issues of trace organic contaminants

Spatially Explicit Large-Scale Environmental Risk Assessment of Pharmaceuticals in Surface Water in China

With improving healthcare and an aging population, the consumption of human pharmaceuticals in China has been increasing dramatically. Environmental risks posed by many active pharmaceutical ingredients (APIs) are still unknown. This study used a spatially explicit dilution-factor methodology to model predicted environmental concentrations (PECs) of 11 human-use APIs in surface water for a preliminary environmental risk assessment (ERA). Median PECs in surface water across China range between 0.01 and 8.0 × 103 ng/L for the different APIs, under a moderate patient use scenario. Higher environmental risks of APIs in surface water are in regions with high water stress, e.g., northern China. Levonorgestrel, estradiol, ethinyl estradiol and abiraterone acetate were predicted to potentially pose a high or moderate environmental risk in China if consumption levels reach those in Europe. Relative risks of these four APIs have the potential to be among those chemicals with the highest impact on surface water in China when compared to the risks associated with other regulated chemicals, including triclosan and some standard water quality parameters including BOD5 (5-day biological oxygen demand), COD (chemical oxygen demand), Cu, Zn, and Hg and linear alkylbenzene sulfonate. This method could support the regulation of this category of chemicals and risk mitigation strategies in China

Direct evidence of an efficient energy transfer pathway from jellyfish carcasses to a commercially important deep-water species

Here we provide empirical evidence of the presence of an energetic pathway between jellyfish and a commercially important invertebrate species. Evidence of scavenging on jellyfish carcasses by the Norway lobster (Nephrops norvegicus) was captured during two deployments of an underwater camera system to 250–287 m depth in Sognefjorden, western Norway. The camera system was baited with two Periphylla periphylla (Scyphozoa) carcasses to simulate the transport of jellyfish detritus to the seafloor, hereby known as jelly-falls. N. norveigus rapidly located and consumed a large proportion (>50%) of the bait. We estimate that the energy input from jelly-falls may represent a significant contribution to N. norvegicus energy demand (0.21 to 10.7 times the energy required for the population of N. norvegicus in Sognefjorden). This potentially high energetic contribution from jelly-falls highlights a possible role of gelatinous material in the support of commercial fisheries. Such an energetic pathway between jelly-falls and N. norvegicus could become more important with increases in jellyfish blooms in some regions

The Review of Economic Performance and Social Progress 2002: Towards a Social Understanding of Productivity

Skills, innovation and human capital as they feature prominently on the policy agenda of industrialized countries concerned with productivity and competitiveness issues. Not surprisingly, formal education is the preferred and most conventional policy instrument of governments in pursuing these objectives. Indeed, "more is better" is often the guiding principle here. The actual linkages, however, are not as straightforward as they may appear. Certainly, there are gains to be achieved through a better understanding of the relationship between the skills developed through formal education and their causal impact on productivity, as well as a more nuanced approach to policy in this area. In this chapter, Arthur Sweetman points out, "the issue is not whether education has benefits but, rather, the magnitude of its 'true' benefits, the benefits relative to costs, and the distribution of costs and benefits. Sweetman examines three different sets of evidence, focusing on the impact of education on earnings at the individual level and on productivity at the macroeconomic level, and on issues related to the operation of the Canadian educational system.Education, Skills, Growth, Productivity, Labour Productivity, Labor Productivity, Educational Attainment, Human Capital, Knowledge, Quality, Education Quality, Private Benefit, Social Benefit, Value, Investment

The distribution of Polychlorinated Biphenyls (PCBs) in the River Thames Catchment under the scenarios of climate change

Measurements have shown low levels of PCBs in water but relatively high concentrations in the resident fish of the River Thames (UK). To better understand the distribution and behaviour of PCBs in the Thames river basin and their potential risks, a level III fugacity model was applied to selected PCB congeners (PCB 52, PCB 118 and PCB 153). The modelling results indicated that fish and sediments represent environmental compartments with the highest PCB concentrations; but the greatest mass of PCBs (over 70%) is likely to remain in the soil. As emissions decline, soil could then act as a significant secondary source of PCBs with the river bed-sediment functioning as a long-term reservoir of PCBs. The predicted changes in temperature and rainfall forecast in the UK Climate Projections 2009 (UKCP09) over the next 80 years had only a modest influence on PCB fate in the model. The most significant result was a tendency for climate change to enhance the evaporation of PCBs from soil to air in the Thames catchment. (C) 2015 Elsevier B.V. All rights reserved

Regional multi-compartment ecological risk assessment:establishing cadmium pollution risk in the northern Bohai Rim, China

Ecological risk assessment (ERA) has been widely applied in characterizing the risk of chemicals to organisms and ecosystems. The paucity of toxicity data on local biota living in the different compartments of an ecosystem and the absence of a suitable methodology for multi-compartment spatial risk assessment at the regional scale has held back this field. The major objective of this study was to develop a methodology to quantify and distinguish the spatial distribution of risk to ecosystems at a regional scale. A framework for regional multi-compartment probabilistic ecological risk assessment (RMPERA) was constructed and corroborated using a bioassay of a local species. The risks from cadmium (Cd) pollution in river water, river sediment, coastal water, coastal surface sediment and soil in northern Bohai Rim were examined. The results indicated that the local organisms in soil, river, coastal water, and coastal sediment were affected by Cd. The greatest impacts from Cd were identified in the Tianjin and Huludao areas. The overall multi-compartment risk was 31.4% in the region. The methodology provides a new approach for regional multi-compartment ecological risk assessment

Admiration regulates social hierarchy:Antecedents, dispositions, and effects on intergroup behavior

In four studies, we report evidence that admiration affects intergroup behaviors that regulate social hierarchy. We demonstrate that manipulating the legitimacy of status relations affects admiration for the dominant and that this emotion negatively predicts political action tendencies aimed at social change. In addition, we show that greater warmth and competence lead to greater admiration for an outgroup, which in turn positively predicts deferential behavior and intergroup learning. We also demonstrate that, for those with a disposition to feel admiration, increasing admiration for an outgroup decreases willingness to take political action against that outgroup. Finally, we show that when the object of admiration is a subversive “martyr,” admiration positively predicts political action tendencies and behavior aimed at challenging the status quo. These findings provide the first evidence for the important role of admiration in regulating social hierarchy