Mortality, protoplasm decay rate, and reliability of staining techniques to recognise 'living' foraminifera: a review.

Non-vital staining, especially with rose Bengal, has been widely used in ecological studies to differentiate between the tests of dead(unstained) foraminifera from those presumed to be living at the time of collection (stained). Doubts have been expressed about staining methods because of the possibility that dead individuals may retain undecayed protoplasm for weeks or months after death; when stained, such individuals would be recorded as living. To assess the importance of such false positives, it is necessary to examine rates of mortality, and the modes of generation of empty tests, i.e., whether due to reproduction, growth stages (leaving empty tests during growth) or death. It can be argued that reproduction, ontogeny, and death through predation lead to tests devoid of protoplasm. Whereas reproduction may affect only a small proportion of the population of each species (due to high pre-reproductive mortality), predation in oxygenated environments may be responsible for the major part of that pre-reproductive mortality. In oxygenated environments, disease or adverse environmental conditions are most likely to lead to dead individuals having tests containing protoplasm. In dysaerobic/anoxic environments, predation by macrofauna may be excluded, so foraminifera die through other causes and thus more tests with dead protoplasm may be potentially available for staining. Therefore, for most other environments, the problem of staining dead individuals is almost certainly overstated. Furthermore, from comparative studies, it seems that the most commonly used technique (staining with rose Bengal) is as reliable as others. Now that new vital staining techniques, especially the use of fluorescent probes, are being introduced, it is timely for further objective comparative studies of all techniques to be made in order to evaluate data already gathered and to develop the best strategies for future ecological studies according to whether they are field-based or experimental

Controls on the standing crop of benthic foraminifera at an oceanic scale

Currently there is very little basin-scale information on patterns of standing crop in marine organisms or their structuring forces. Understanding modern patterns and controls on foraminifera is particularly critical because of their abundance and importance in benthic systems as well as their role as palaeoceanographic proxies. Here, we examine for the first time basin-scale patterns and predictors of benthic foraminiferal standing crop from shelf to abyssal deep sea in the Atlantic Ocean and adjacent seas using a large database of 967 quantitative samples. Spatial regression analyses reveal that the flux of particulate organic matter (POC) is a major control on standing crop size across all depths investigated, with increasing food supply increasing foraminiferal standing crops. Other factors also play a role. Dissolved oxygen is significant at slope depths and negatively related to standing crop. Temperature and possibly salinity are significant factors in the abyss. Dissolved silicate was important and positively related to standing crop in shelf seas, potentially indicating the importance of the nature of the organic material available. This study demonstrates that productivity is important in describing foraminiferal standing crop at a basin scale, supporting the use of paleoceanographic proxies, but also demonstrates that other environmental variables are also likely important in controlling the standing crop and should be considered in reconstruction of Earth’s past marine environment

The niche of benthic foraminifera, critical thresholds and proxies

Ecological studies of benthic foraminifera are carried out to explain patterns of distribution and the dynamics of communities. They are also used to provide data to establish proxy relationships with selected factors. According to niche theory, the patterns of distribution of benthic foraminifera are controlled by those environmental factors that have reached their critical thresholds. For each species, in variable environments, different factors may be limiting distributions both temporally and spatially. For a species or an assemblage to be useful as a proxy its abundance must show a strong correlation with the chosen factor. Since numerous factors influence each species, it is only in those environments where the majority of factors show little variation but one particular factor shows significant variation that the proxy relationship for that factor can be determined. On theoretical grounds, the reliability of using foraminiferal abundance as a proxy of a selected environmental factor should be restricted to the range close to the upper and lower thresholds. For oxygen, foraminifera are potential proxies for the lower limits but once oxygen levels rise to values of perhaps >1 or 2 ml l-1, there is no longer a relationship between oxygen levels and abundance. By contrast, the flux of organic matter over a large range shows a sufficiently close relationship with foraminiferal assemblages so that transfer functions can be derived for the deep sea. However, the relationship at species level is far less clear cut. Much more accurate estimates of primary productivity and modern organic flux rates are required to improve the determination of past flux rates

Effect of post processing on the creep performance of laser powder bed fused Inconel 718

In this study, the creep performance of laser powder bed fusion manufactured Inconel 718 specimens is studied in detail and compared with conventional hot-rolled specimens alongside as-built then heat-treated and as-built then hot-isostatic pressed specimens. Hot-rolled specimens showed the best creep resistance, while the hot-isostatic pressed specimens yielded the worst performance, inferior to the as-built condition. Creep testing of all samples showed increased secondary creep rate was consistently correlated with a reduced life. Fractography revealed intergranular fracture was the primary failure mode for all as-built samples. Preferential intergranular precipitation in the case of the hot-isostatic pressed specimens during hot-isostatic pressing extensive intergranular cracking as the primary failure mechanism. Heat-treated specimens possessed only sparse intergranular precipitates, thereby explaining an improved creep lifetime. The hot-rolled specimens, having smallest grain size, showed the least extensive cracking, particularly in locations of finest grains, explaining avoidance of intergranular fracture as a key creep mechanism, thereby explaining the ductile creep fracture surfaces in the case of the hot-rolled samples

Electrolyte jet machining for surface texturing of Inconel 718

Electrolyte jet machining is an emerging non-conventional machining process which is capable of selectively applying multi-scale surface textures. Surfaces processed in this way do not suffer from thermal damage and hence this technique is highly suited to finishing procedures in high value manufacturing across the aerospace and biomedical sectors. Furthermore, input variables can be modified dynamically to create functional graduation across component surfaces. In this study, the development and design of a custom-built EJM system is described, and the capability of the EJM platform to machine and create surface textures in Inconel 718, a widely used nickel based super alloy, is investigated. Through control of machine path programming and parameter variation, multi-scale surface textures are created which have the potential to enhance bonding with subsequent coating layers and also provide fluid dynamic advantage

Spheroidisation of metal powder by pulsed electron beam irradiation

A new powder spheroidisation process has been demonstrated using a large-area, pulsed electron beam technique. This was used to dramatically improve the surface morphology of Stellite 6 metal powder. Powder surface asperities up to 20 μm size can be eliminated by melting and incorporation into the near-surface of the particle. Surface finish is significantly improved. Agitation and rotation of particles due to a beam-induced stress wave enables the irradiation of multiples sides of particles, resulting in uniformly smoothed particles after sufficient pulses. Elemental analysis revealed no measurable contamination as a result of the process. Transmission electron microscopy showed a dense layer is produced within a zone up to 3 μm beneath the surface, with a substantially reduced grain size from ca. 2 μm diameter in the bulk to ca. 40 nm. Elemental homogenisation also was accompanied by grain refinement. The irradiated Stellite 6 showed a reduced basic flowability energy (583 mJ compared to 627 mJ for the untreated), explained by reduced particle-particle cohesion and interlocking, and an increased conditioned bulk density of 4.57 g/ml compared to 4.33 g/ml due to satellite/asperity reduction

Circulating interleukin-10 and risk of cardiovascular events: a prospective study in the elderly at risk

<p><b>Objective:</b> The goal of this study was to examine the association of the antiinflammatory interleukin-10 (IL-10) with risk of cardiovascular disease (CVD).</p> <p><b>Methods and Results:</b> In the PROSPER (PROspective Study of Pravastatin in the Elderly at Risk) cohort, we related baseline concentrations of circulating IL-10 to risk of CVD events in a nested case (n=819)-control (n=1618) study of 3.2 years of follow-up. Circulating IL-10 showed few strong associations with classical risk factors but was positively correlated with IL-6 and C-reactive protein. IL-10 was positively associated with risk of CVD events (odds ratio [OR] 1.17, 95% CI 1.05 to 1.31 per unit increase in log IL-10) after adjusting for classical risk factors and C-reactive protein. Furthermore, IL-10 was associated more strongly with CVD risk among those with no previous history of CVD (OR 1.42, 95% CI 1.18 to 1.70), compared with those with previous CVD (OR 1.04, 95% CI 0.90 to 1.19; P=0.018). Overall, IL-10 showed a modest ability to add discrimination to classical risk factors (C-statistic +0.005, P=0.002).</p> <p><b>Conclusion:</b> Baseline circulating levels of the antiinflammatory IL-10 are positively associated with risk of CVD among the elderly without prior CVD events, although the association is less evident in those with a history of CVD. Additional epidemiological and mechanistic studies investigating the role of IL-10 in CVD are warranted.</p&gt

Erosion resistance of laser clad Ti-6Al-4V/WC composite for waterjet tooling

AbstractIn waterjet operations, milled surfaces are left with some undesirable dimensional artefacts, thus the use of abrasion resistant mask has been proposed to improve the surface quality of machined components. In this study, the erosion performance of laser clad Ti-6Al-4V/WC composite coating subjected to plain water jet (PWJ) and abrasive water jet (AWJ) impacts to evaluate its potentials for use as waterjet impact resistant mask material and coating on components was investigated. Results showed that composite with 76wt.% WC composition subjected to PWJ and AWJ impacts offered resistance to erosion up to 13 and 8 times that of wrought Ti-6Al-4V respectively. Scanning electron microscopy (SEM) examination of the eroded composite surfaces showed that the erosion mechanism under PWJ impacts is based on the formation of erosion pits, tunnels and deep cavities especially in the interface between the WC particles and the composite matrix owing to lateral outflow jetting and hydraulic penetration. Composite suffered ploughing of the composite matrix, lateral cracking and chipping of embedded WC particles and WC pull-out under AWJ impacts. The composite performance is attributed to the embedded WC particles and the uniformly distributed nano-sized reaction products (TiC and W) reinforcing the ductile β-Ti composite matrix, with its mean hardness enhanced to 6.1GPa. The capability of the Ti-6Al-4V/WC composite coating was demonstrated by effective replication of a pattern on a composite mask to an aluminium plate subjected to selective milling by PWJ with an overall depth of 344μm. Thus, composite cladding for tooling purpose would make it possible to enhance the lifetime of jigs and fixtures and promote rapid machining using the water jet technique

Productivity of Boran cattle maintained by chemoprophylaxis under trypanosomiasis risk

Evaluates the productivity of grade Boran cattle maintained by chemoprophylaxis under severe trypanosomiasis risk at Mkwaja ranch, Tanzania; uses data based on more than 20,000 calving records over the 10-year period from 1973 to 1982; discusses environmental influences on performance traits and links between tsetse population dynamics & cattle; includes comparison of Boran genotypes and its effect on pre-weaning growth characters

Formation mechanism of electrical discharge TiC-Fe composite coatings

Comparison of electric discharge (ED) processed single deposit and continuum TiC-Fe cermet coatings, formed from a sacrificial powder metallurgy TiC tool electrode at negative polarity, on 304 stainless steel, provided insight into the ED coating (EDC) formation mechanism. A deposit from a single spark event was dominated by TiC, phase separated from a ∼2 wt% Fe matrix, with strongly aligned grains and banded microstructure, indicative of solidification from the coating/substrate interface. Conversely, a continuum coating, subjected to ∼200 spark events per location, exhibited a more complex, banded microstructure, with a mixture of equiaxed and columnar TiC grains within a ∼30 wt% Fe-based matrix, along with some concentrations of carbon from the oil dielectric. It is considered that each sparking event remelts previously solidified coating material, with or without further TiC particle incorporation, leading to gradual TiC dilution and the development of a TiC-Fe composite coating with increasing levels of substrate material forming the matrix