Clays for polymeric nanocomposites

We discuss test methods and results for determining individual clay platelets shape, size, size distribution, elemental composition, and impurities. Commercial sodium salt varieties of natural, semisynthetic and synthetic clay (Cloisite®‐Na⁺, Somasif ME‐100, and Topy‐Na⁺, respectively) were analyzed. In this international collaboration, eight laboratories on three continents carried out the work within the VAMAS TWA‐33 activities. There are large differences between the three nanofillers as far as: (1) the platelet orthogonal dimensions, (2) chemical composition, and (3) contaminants (their diversity and quantity) are concerned. Elaborate purification of natural clays leaves behind 2–5 wt% of organic and mineral impurities, whose nature, shape, size, and chemistry depend on the clay origin. These contaminants affect nanocomposite performance, thus controlling their composition and quantity is essential. The article describes the developed methods, summarizes the preliminary results, discusses the encountered difficulties, and proposes methods for solving them. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers     

Rehabilitation of timber structures: novel test method to assess the durability of bonded-in rod connections

Rehabilitation/restoration systems involving bonded-in rods represent an efficient alternative method for the repair and/or reinforcement of structural timber members. However, in spite of their advantages, their use is still restrained by the lack of knowledge about their long-term performance. In order to correct this situation it is necessary to gain a greater understanding of their durability, creep and fatigue behaviour. However, reliable and realistic accelerated ageing tests do not yet exist, and the application of the existing European or American standards to epoxy bonded products are much too penalising, since they merely impose severe conditions that are not verified in service although these may be suitable for other adhesives. To address these concerns a test procedure to assess long-term behaviour of bonded-in rod connections was developed with the aim of providing a simple method for the selection of candidate repair system materials for specific applications. The data collected so far using the realistic performance assessment test (RPAT) appears to predict correctly the end-use performance for different adhesives as well as for different timbers.     

In vitro development of pig preantral follicles cultured in a serum-free medium and the effect of angiotensin II

A novel culture system is reported in which pig preantral follicles (< 300 microm in diameter) with an intact thecal cell layer were isolated and cultured in a serum-free medium for up to 30 days. The medium supported follicle culture after isolation, while maintaining both somatic cell and oocyte viability. Follicles were cultured in groups (n = 3 per group) on collagen-coated wells for 16 days, during which they retained a three-dimensional structure, maintained oocyte viability and increased in diameter and number of somatic cells. Follicle culture for 30 days resulted in a further increase in number of cells, oocyte viability was maintained, and a significant increase in follicle diameter was observed (P < 0.001), with 29% of follicles forming an antrum. Follicles synthesized measurable quantities of progesterone (168 pg per 100 microl per 48 h; no significant increase with time) and increasing quantities of oestradiol (136 pg per 100 microl per 48 h; P < 0.001 with time). Further supplementation of the medium with 100 micromol testosterone l(-1) at day 28 resulted in a significant increase in oestradiol secretion by both antral (P < 0.01) and preantral follicles (P < 0.05). Culture over 30 days in medium with 10(-10) mol angiotensin II l(-1) and further supplementation at day 28 with 100 micromol testosterone l-1 also increased oestradiol synthesis (P < 0.001). These results show that viable preantral follicles may be cultured for extended periods, and indicate that the possible role of angiotensin II in folliculogenesis and steroidogenesis in early development of pig follicles requires further investigation.     

From Soviet to Post-Soviet with Transformation of the Fragmented Urban Landscape: The Case of Garage Areas in Estonia

Demands on land use in heavily populated landscapes create mosaic structures where semi-natural habitat patches are generally small and dominated by edges. Small patches are also more exposed and thus more vulnerable to adverse weather and potential effects of climate change. These conditions may be less problematic for generalist species than for specialists. Using insectivorous woodland birds (great tits and blue tits) as an example, we demonstrate that even generalists suffer reduced breeding success (in particular, rearing fewer and poorer-quality young) and increased parental costs (daily energy expenditure) when living in such highly modified secondary habitats (small woods, parks, farmland). Within-habitat heterogeneity (using the example of Monks Wood NNR) is generally associated with greater species diversity, but to benefit from heterogeneity at a landscape scale may require both high mobility and the ability to thrive in small habitat patches. Modern landscapes, dominated by small, modified and scattered habitat patches, may fail to provide specialists, especially sedentary ones, with access to sufficient quantity and quality of resources, while simultaneously increasing the potential for competition from generalists.     

Microstructural characterization of porous manganese thin films for electrochemical supercapacitor applications

An in-depth microstructural characterization was performed on manganese oxide materials that have been produced for electrochemical supercapacitor applications using a novel physical vapor deposition process. Manganese was e-beam evaporated and deposits as a combination of the cubic forms of Mn and MnO with a porous zigzag structure. The electrochemically oxidized sample that is used as the supercapacitor base material is tetragonal Mn₃O₄. An apparent active layer with increased sodium levels was imaged by STEM, lending some credence to the argument that the pseudocapacitance effect is based entirely on a surface layer of adsorbed sodium. Upon furnace annealing the zigzag structure near the free surface is destroyed and replaced with a columnar oxide layer of cubic MnO and tetragonal Mn₃O₄. This capping effect ultimately reduces the usable surface area and is thought to account for the reduction in capacitance seen on annealing.     

Management of the brown recluse spider bite to the glans penis

A significant number of people are bitten by the brown recluse spider (BRS) each year. Medical treatment regimens are sometimes unsatisfactory and surgical intervention is often necessary to debride the necrotic wound. This case study reports the treatment given to a 19-year-old active duty United States Army soldier who suffered a BRS bite to the glans penis. This patient received immediate medical attention and was started on intravenously administered diphenhydramine, methylprednisolone, calcium gluconate, and famotidine. Oral dapsone treatment was begun in the emergency room. Within 24 hours after his injury, the patient received his first hyperbaric oxygen treatment, which was continued twice daily for 5 days. Skin necrosis was avoided, the patient did not require any surgical intervention, and he was discharged after 8 days without sequelae.     

Radar measurement of bridge scour

Scour around bridge piers and abutments has resulted in many structural failures over the past decade and considerable research has been carried out to develop methods which can be used to evaluate the risk of scour affecting the integrity of these major structures. Traditional site investigation methods based on borehole core and samples of the riverbed sediments are expensive and time-consuming and may not always give a complete assessment of the lithological variation in the riverbed sediments. Geophysical methods can be used to determine the riverbed profile beneath the water in a river and may also be of value for obtaining the previous scour history below the riverbed level.Trials of ground penetrating radar (GPR) have indicated that this geophysical method is particularly effective in determining the sub-bottom geological structure in a shallow freshwater environment. In this presentation the results from a number of scour surveys using GPR are presented and discussed. It is concluded that GPR surveys can be effective in determining both the water depth and sub-bottom geological structure near bridge piers and abutments provided that the correct instrumentation and operational procedures are adopted.