Disturbance, sediment stability, and trophic structure of soft-bottom communities

Previous studies of marine soft-bottom communities have shown (1) that natural disturbances (especially biologically-mediated disturbances, which are usually localized and recur reasonably frequently) help maintain spatio-temporal heterogeneity of communities, and (2) that biogenic modification of sediment can affect sediment stability with respect to fluid forces and geotechnical properties and that this is an important factor in community organization, particularly in the trophic structure of the macrofauna. It is argued in this paper that natural disturbances, and the ensuing biogenic alterations to sediment stability, may be important in maintaining trophically-mixed communities where deposit feeders do not have an overriding influence on sedimentary properties. The hypothesis is presented that an initial post-disturbance response by micro- and meiobenthos leads to an increase in sediment stability as a result of mucous-binding of sediment, and that this stage may be of critical significance to potential suspension-feeding colonists if they are competing with deposit feeders for space. It is suggested, partly as a corollary to this hypothesis, that there may be marked differences in the structure and function of meiofaunal communities co-occurring with deposit-feeding and suspension-feeding macrofaunas. Implications for macrofaunal trophic structure of seasonal changes in sediment stability are also examined. Several areas for future research are recommended

Abundance of small individuals influences the effectiveness of processing techniques for deep-sea nematodes

Nematodes are the most abundant metazoans of deep-sea benthic communities, but knowledge of their distribution is limited relative to larger organisms. Whilst some aspects of nematode processing techniques, such as extraction, have been extensively studied, other key elements have attracted little attention. We compared the effect of (1) mesh size (63, 45, and 32 μm) on estimates of nematode abundance, biomass, and body size, and (2) microscope magnification (50 and 100×) on estimates of nematode abundance at bathyal sites (250-3100 m water depth) on the Challenger Plateau and Chatham Rise, south-west Pacific Ocean. Variation in the effectiveness of these techniques was assessed in relation to nematode body size and environmental parameters (water depth, sediment organic matter content, %silt/clay, and chloroplastic pigments). The 63-μm mesh retained a relatively low proportion of total nematode abundance (mean ±SD = 55 ±9%), but most of nematode biomass (90 ± 4%). The proportion of nematode abundance retained on the 45-μm mesh in surface (0-1 cm) and subsurface (1-5 cm) sediment was significantly correlated (P < 0.01) with %silt/clay (R² = 0.39) and chloroplastic pigments (R² = 0.29), respectively. Variation in median nematode body weight showed similar trends, but relationships between mean nematode body weight and environmental parameters were either relatively weak (subsurface sediment) or not significant (surface sediment). Using a low magnification led to significantly lower (on average by 43%) nematode abundance estimates relative to high magnification (P < 0.001), and the magnitude of this difference was significantly correlated (P < 0.05) with total nematode abundance (R²p = 0.53) and the number of small (≤ 250 μm length) individuals (R²p = 0.05). Our results suggest that organic matter input and sediment characteristics influence the abundance of small nematodes in bathyal communities. The abundance of small individuals can, in turn, influence abundance estimates obtained using different mesh sizes and microscope magnifications

Evaluation of a Liquid Amine System for Spacecraft Carbon Dioxide Control

The analytical and experimental studies are described which were directed toward the acquisition of basic information on utilizing a liquid amine sorbent for in use in a CO2 removal system for manned spacecraft. Liquid amine systems are successfully used on submarines for control of CO2 generated by the crew, but liquid amines were not previously considered for spacecraft applications due to lack of development of satisfactory rotary phase separators. Developments in this area now make consideration of liquid amines practical for spacecraft system CO2 removal. The following major tasks were performed to evaluate liquid amine systems for spacecraft: (1) characterization, through testing, of the basic physical and thermodynamic properties of the amine solution; (2) determination of the dynamic characteristics of a cocurrent flow absorber; and (3) evaluation, synthesis, and selection of a liquid amine system concept oriented toward low power requirements. A low weight, low power system concept was developed. Numerical and graphical data are accompanied by pertinent observations

Authentic Intervention in Information Systems Practice

In this paper the philosophical concept of authenticity is used as a framing device for providing an interpretation of aspects of both ethical and practical action on the part of information systems (IS) professionals. It is argued that ethical codes and IS methods may be of limited value in IS work. Both ethical codes and IS methods are complicated by the need to adopt positions on, and give recommendations about, IS practice. One key problem here is that IS analysts and designers have to intervene in organisations (and thereby intervene in the lives of the members of those organisations). It is argued that an important issue for IS research is whether they to do so in (what will be characterised as) an authentic manner, or in sincere adherence with either a code of professional ethics or with a series of methodological precepts

Comparison of Simulation Codes for the Beam Dynamics of Low-Energy Ions

Results are presented of the simulation of low&#8211;energy ion dynamics with three different codes: KOBRA, IGUN and CPO. To share work between different codes one needs to be confident that they agree. For test cases, good agreement was found between the codes and analytical solutions. Where possible, results have been compared to experimental data from the CERN Laser Ion Source. These simulations are in general agreement with the data of the real beam line. c The following article has been submitted to Review of Scientific Instruments. After it is published, it will be found at http://ojps.aip.org/rsio/

Hepatic effects of tartrazine (E 102) after systemic exposure are independent of oestrogen receptor interactions in the mouse

Tartrazine is a food colour that activates the transcriptional function of the human oestrogen receptor alpha in an in vitro cell model. Since oestrogens are cholestatic, we hypothesised tartrazine will cause periportal injury to the liver in vivo. To test this hypothesis, tartrazine was initially administered systemically to mice resulting in a periportal recruitment of inflammatory cells, increased serum alkaline phosphatase activity and mild periportal fibrosis. To determine whether an oestrogenic effect may be a key event in this response, tartrazine, sulphonated metabolites and a food additive contaminant were screened for their ability to interact with murine oestrogen receptors. In all cases, there were no interactions as agonists or antagonists and further, no oestrogenicity was observed with tartrazine in an in vivo uterine growth assay. To examine the relevance of the hepatic effects of tartrazine to its use as a food additive, tartrazine was orally administered to transgenic NF-κB-Luc mice. Pre- and concurrent oral treatment with alcohol was incorporated given its potential to promote gut permeability and hepatic inflammation. Tartrazine alone induced NF- κB activities in the colon and liver but there was no periportal recruitment of inflammatory cells or fibrosis. Tartrazine, its sulphonated metabolites and the contaminant inhibited sulphotransferase activities in murine hepatic S9 extracts. Given the role of sulfotransferases in bile acid excretion, the initiating event giving rise to periportal inflammation and subsequent hepatic pathology through systemic tartrazine exposure is therefore potentially associated an inhibition of bile acid sulphation and excretion and not on oestrogen receptor-mediated transcriptional function. However, these effects were restricted to systemic exposures to tartrazine and did not occur to any significant effect after oral exposure