Formation of iron sulfide at faecal pellets and other microniches within suboxic surface sediment.

Faecal pellet deposition and bioturbation may lead to heterogeneously distributed particles of localized highly reactive organic matter (microniches) being present below the oxygen penetration depth. Where O2, NO3-, and Fe/Mn oxyhydroxides become depleted within these microniches or where they exist in zones of sulfate reduction, significant localized peaks in sulfide concentration can occur. These discrete zones of sulfide evolution can cause formation of iron sulfides that would not be predicted by analysis of the ‘bulk’ sediment. Using a reaction-transport model developed specifically for investigating spherical microniches, and incorporating 3D diffusion, we investigated how the rate constants of organic matter (OM) degradation, particle porosity and niche lifetime, affect dissolved sulfide and iron concentrations, and formation of iron sulfide at such niches. For all of the modelled scenarios the saturation index for iron sulfide is positive, indicating favourable conditions for FeS precipitation in all niches. Those simulations within the microniche lifetime range of 2.5 to 5 days gave comparable concentration ratios of sulfide to iron in solution within the niche to experimentally observed values. Our model results provide insight into the mechanisms of preservation of OM, including soft tissue, in the paleo record, by predicting the conditions that result in preferential deposition of precipitates at the edge of microniches. Decreases in porosity, shorter niche lifetimes and increases in OM degradation rate constants, all tend to increase the likelihood that FeS precipitation will preferentially occur at the edges of a niche, rather than uniformly throughout the niche volume

2D simultaneous measurement of the oxyanions of P, V, As, Mo, Sb, W and U.

Previous work used the sampling technique diffusive gradients in thin-films analysed by laser ablation mass spectrometry to measure sulphide, P, V and As at a microniche of reactive organic carbon in a freshwater sediment. Here we present new developments of this technique. The number of analytes has been extended and we demonstrate the technique for depth profiling of analytes in both one and two dimensions. The physical dimensions of the cell in the laser ablation unit restrict the maximum length of gel that can be analysed. We address this problem by proposing a method for obtaining better data continuity when analysing multiple segments of gel from the same probe. 13C is used as the internal standard for each gel segment. For the cross standardisation of different gel segments 58Fe signals are obtained from ablation of a small piece of standard ferrihydrite gel analysed during the same run as the sample gel. As the ferrihydrite gel is a subsection of a much larger gel (i.e. the Fe concentration is consistent for all subsection), then any difference in signal can be attributed to changes in detector sensitivity and gels across different runs and performed on different days can be standardised

Spiranthes cernua (L.) Rich.

https://thekeep.eiu.edu/herbarium_specimens_byname/4167/thumbnail.jp

The association of cobalt with iron and manganese (oxyhydr)oxides in marine sediment.

Formation and dissolution of authigenic Fe and Mn (oxyhydr)oxides influence cycling of trace metals in oxic/suboxic surface sediments.We used the diffusive gradients in thin films technique (DGT) to estimate the association of cobalt with iron and manganese oxides. We compared Co, Fe and Mn maxima measured by DGT in the pore waters of fresh and aged marine sediment cores and estimated the Co/Fe and Co/Mn ratios in the metal oxides. A Mn maximum was not visible in DGT concentration profiles of freshly collected sediment cores, but after ageing the sediment we observed a distinct Mn peak, presumably due to broadening of the depth range over which the various electron acceptors occur. Estimated Co/Mn ratios from both experiments are within the range of literature values for marine sediments, but the value from the aged experiment is at the lower end of the range. This is attributed to stimulation of sulphate reduction and precipitation of cobalt sulfides. The good correlation between Co and Fe maxima in the fresh sediments is attributed to the similarity of their reactions with sulphide rather than Co being released during authigenic Fe oxide reduction

The measurement of the natural potential of sites in the Eastern Highlands of Scotland for downhill skiing

SIGLEAvailable from British Library Document Supply Centre- DSC:D66382/86 / BLDSC - British Library Document Supply CentreGBUnited Kingdo

The Narrative of Flippy Johnson: The Three Act Structure - Criticisms and Alternatives Script and Script Analysis

In this feature screenplay, I have incorporated the complexities of an intertwining multi-strand narrative, while manipulating the materials of time and space. This has enabled me to begin my exploration into finding a suitable structure in which to tell a story that features a number of characters, all of whom are intended to represent some of human nature's darkest emotions. I have attempted to distinguish my script from the standard three-act structure. However, I do believe it is a fundamental requirement to know all the rules of a classical three-act structure in order to subvert its conventions. The three-act structure has long been a successful model for transmitting a story to the screen. It has provided the basis for many a film where a character triumphs over adversity; where good defeats bad and heroes fall in love. But what about characters that are not heroes? Protagonists who cannot be defined under the even broadest definition of heroism? Can these people thrive within the strict guidelines of a three-act structure, with its strong reliance on a hero's journey? Is there an alternative structure that can deal with these characters, a structure that can incorporate them in a narrative? This MA will attempt to answer these questions, while also investigating if the materials of time and space can be manipulated and understood when working outside the guidelines of a formulaic structure. The materials of time and space are unique to all films and they are both dealt with in different ways by screenwriters and filmmakers alike. Temporal and spatial characteristics have been studied in depth by many critics including, of particular importance to this MA, David Bordwell. Bordwell has used time and space as a way of making sense of narrative and of engaging with a film. This is something that I am attempting to achieve in the following script and commentary. Furthermore, I will try to articulate the manipulation of time and space, with the challenges of multiple strands of narrative and multiple protagonists

A Comparison of Predation Rates on Real and Artificial Nests of Grassland Birds

I compared rates of predation between real and artificial nests of grassland birds in order to test the impact of nest type, nest position, and egg size on predation rates. I distributed wicker avicultural baskets and realistic grass nests baited with a clay egg and either northern bobwhite (Colinus virginianus) or house sparrow (Passer domesticus) eggs in four Conservation Reserve Program (CRP) grasslands in east-central Illinois. Nest success averaged 86.5% for 12 days of exposure for artificial nests. For real nests, nest success was markedly lower; averaging 39% over the entire nesting cycle and 59% during approximately 12 days of incubation. Wicker nests were depredated more often than realistic grass artificial nests (18% versus 8%), and nests baited with house sparrow eggs were depredated more often than nests baited with quail eggs (22% versus 9%). Elevated and ground nests were depredated at the same rate. No edge effects were detected for real or artificial nests at road, rowcrop, or wooded edges. Patterns of nest predation on wicker nests were markedly different from depredation patterns on real nests over time and among fields. In contrast, patterns of nest predation on realistic grass artificial nests corresponded much more closely with predation rates of real nests over time and among fields. I suggest that future artificial nest studies use nests and eggs that mimic as closely as possible the real nests and eggs of target species. Use of unrealistic artificial nests and eggs, at least in grasslands, may result in patterns of predation that do not accurately reflect the variation in predation rates over time and locations for real nests

Predation Rates on Real and Artificial Nests of Grassland Birds

We estimated nesting success at real and artificial nests of grassland birds to test the influence of nest type, nest position, and egg size on predation rates. We distributed wicker nests and realistic woven-grass nests baited with a clay egg and either a Northern Bobwhite (Colinus virginianus) egg or a House Sparrow (Passer domesticus) egg in four grasslands that were part of the Conservation Reserve Program in east-central Illinois. Nesting success averaged 86.5% for 12 days of exposure for artificial nests. For real nests, nesting success was markedly lower, averaging 39% over the entire nesting cycle and 59% during approximately 12 days of incubation. Wicker nests were depredated more often than wovengrass artificial nests (18% vs. 8%), and nests baited with House Sparrow eggs were depredated more often than nests baited with Northern Bobwhite eggs (22% vs. 9% ). Elevated and ground nests were depredated at the same rate. Patterns of nest predation on wicker nests were markedly different from depredation patterns on real nests over time and among fields. In contrast, patterns of nest predation on realistic woven-grass nests corresponded much more closely with predation rates of real nests over time and among fields. We suggest that future artificial nest studies use nests and eggs that mimic as closely as possible the real nests and eggs of target species. Use of unrealistic artificial nests and eggs, at least in grasslands, may result in patterns of predation that do not accurately reflect those of real nests. Artificial nests of any type appear to underestimate predation rates on nests of grassland birds, possibly because of a lack of snake predation on artificial nests

Blood pressure variability following ischaemic stroke

Variability in blood pressure (BP) may influence ischaemic stroke outcomes in addition to mean BP. However, how best to measure BP variability (BPV) and whether different measurements are equivalent is unknown, as is whether treatment can reduce BPV. This thesis aimed to investigate relationships between BP and BPV measurements from different devices in patients with ischaemic cerebrovascular disease, relationships between BPV and stroke severity, and whether antihypertensive medications can reduce BPV. Three trials that recruited patients following an ischaemic cerebrovascular event provided data. Correlations and limits of agreement between mean BP and BPV from different measurement devices were assessed. Relationships between baseline BPV and stroke severity were investigated, along with differences in baseline BPV in those treated with calcium channel blockers (CCB) or renin-angiotensin system inhibitors. A feasibility trial was developed to compare the effects of these medication classes on reduction of BPV post stroke. BP from daytime ambulatory monitoring was significantly lower than home BP monitoring and BPV values from different devices were unrelated. There was an inverse relationship between baseline BPV and stroke severity, with BPV increased in lacunar infarction. There was no difference in baseline BPV with the medication regimens specified above. Recruitment to the feasibility trial was insufficient due to patient ineligibility, but a reduction in BPV over three month follow-up was demonstrated. In patients with ischaemic cerebrovascular disease, BP and BPV recorded using different devices are not equivalent. Work to standardise BPV measurement and establish if any method is clinically superior is required. Treatment to reduce BPV may particularly benefit certain stroke patients, yet establishing that it is possible to target BPV, and doing so improves outcomes, is prerequisite. The feasibility trial in this thesis requires modification to be scaled up, but a definitive trial could be successful if recruitment were improved