Tissue distribution of perfluoroalkyl acids and health status in wild Mozambique tilapia (Oreochromis mossambicus) from Loskop Dam, Mpumalanga, South Africa

This study examined concentrations of 15 perfluoroalkyl acids (PFAAs) in tissues from male Mozambique tilapia (Oreochromis mossambicus) collected at Loskop Dam, Mpumalanga, South Africa in 2014 and 2016. Nine of the 15 PFAAs were detected frequently and were included in statistical analysis and included two of the most commonly known PFAAs, perfluorooctanesulfonic acid (PFOS) (median, 41.6 ng/g) and perfluorooctanoic acid (PFOA) (median, 0.0825 ng/g). Of the tissues measured, plasma (2016 and 2014 median, 22.2 ng/g) contained the highest PFAA burden followed by (in descending order): liver (median, 11.6 ng/g), kidney (median, 9.04 ng/g), spleen (median, 5.92 ng/g), adipose (median, 2.54 ng/g), and muscle (median, 1.11 ng/g). Loskop Dam tilapia have been affected by an inflammatory disease of the adipose tissue known as pansteatitis, so this study also aimed to investigate relationships between PFAA tissue concentrations and incidence of pansteatitis or fish health status. Results revealed that healthy tilapia exhibited an overall higher (p-value < 0.05) PFAA burden than pansteatitis-affected tilapia across all tissues. Further analysis showed that organs previously noted in the literature to contain the highest PFAA concentrations, such as kidney, liver, and plasma, were the organs driving the difference in PFAA burden between the two tilapia groups. Care must be taken in the interpretations we draw from not only the results of our study, but also other PFAA measurements made on populations (human and wildlife alike) under differing health status.     

Vulnerability of agro-ecological zones in India under the earth system climate model scenarios

India being a developing economy dependent on climate-sensitive sector like agriculture is highly vulnerable to impacts of global climate change. Vulnerability to climate change, however, differs spatially within the country owing to regional differences in exposure, sensitivity, and adaptive capacity. The study uses the Hadley Centre Global Environment Model version 2-Earth System (HadGEM-ES) climate projections to assess the dynamics in vulnerability across four climate change exposure scenarios developed using Representative Concentration Pathways (RCPs). The analysis was carried out at subnational (district) level; the results were interpreted and reported for their corresponding agro-ecological zones. Vulnerability of each district was quantified using indicators capturing climatic variability, ecological and demographic sensitivity, and socio-economic capacity. Our analysis further assigns probabilities to vulnerability classes of all the 579 districts falling under different agro-ecological zones. The results of the vulnerability profile show that Western plains, Northern plains, and central highlands of the arid and semi-arid agro-ecological zones are the most vulnerable regions in the current scenario (1950–2000). In the future scenario (2050), it extends along districts falling within Deccan plateau and Central (Malwa) highlands, lying in the arid and semi-arid zones, along with regions vulnerable in the current scenario, recording the highest vulnerability score across all exposure scenarios. These regions exhibit highest degree of variation in climatic parameters, ecological fragility, socio-economic marginality, and limited accessibility to resources, generating conditions of high vulnerability. The study emphasizes on the priority to take up adaptive management actions in the identified vulnerable districts to not only reduce risks of climate change, but also enhance their inherent capacity to withstand any future changes in climate. It provides a systematic approach to explicitly identify vulnerable regions, where regional planners and policy makers can build on existing adaptation decision-making by utilizing an interdisciplinary approach in the context of global change scenario.     

Context dependency and generality of fever in insects

Fever can reduce mortality in infected animals. Yet, despite its fitness-enhancing qualities, fever often varies among animals. We used several approaches to examine this variation in insects. Texas field crickets (Gryllus texensis) exhibited a modest fever (1 °C increase in preferred body temperature, T _pref) after injection of prostaglandin, which putatively mediates fever in both vertebrates and invertebrates, but they did not exhibit fever during chronic exposure to heat-killed bacteria. Further, chronic food limitation and mating status did not affect T _pref or the expression of behavioural fever, suggesting limited context dependency of fever in G. texensis. Our meta-analysis of behavioural fever studies indicated that behavioural fever occurs in many insects, but it is not ubiquitous. Thus, both empirical and meta-analytical results suggest that the fever response in insects ‘is widespread, although certainly not inevitable’ (Moore 2002). We highlight the need for future work focusing on standardizing an experimental protocol to measure behavioural fever, understanding the specific mechanism(s) underlying fever in insects, and examining whether ecological or physiological costs often outweigh the benefits of fever and can explain the sporadic nature of fever in insects.     

Pollination syndromes ignored: importance of non-ornithophilous flowers to Neotropical savanna hummingbirds

Generalization prevails in flower–animal interactions, and although animal visitors are not equally effective pollinators, most interactions likely represent an important energy intake for the animal visitor. Hummingbirds are nectar-feeding specialists, and many tropical plants are specialized toward hummingbird-pollination. In spite of this, especially in dry and seasonal tropical habitats, hummingbirds may often rely on non-ornithophilous plants to meet their energy requirements. However, quantitative studies evaluating the relative importance of ornithophilous vs. non-ornithophilous plants for hummingbirds in these areas are scarce. We here studied the availability and use of floral resources by hummingbirds in two different areas of the Cerrado, the seasonal savannas in Central Brazil. Roughly half the hummingbird visited plant species were non-ornithophilous, and these contributed greatly to increase the overall nectar availability. We showed that mean nectar offer, at the transect scale, was the only parameter related to hummingbird visitation frequency, more so than nectar offer at single flowers and at the plant scale, or pollination syndrome. Centrality indices, calculated using hummingbird–plant networks, showed that ornithophilous and non-ornithophilous plants have similar importance for network cohesion. How this foraging behaviour affects reproduction of non-ornithophilous plants remains largely unexplored and is probably case specific, however, we suggest that the additional energy provided by non-ornithophilous plants may facilitate reproduction of truly ornithophilous flowers by attracting and maintaining hummingbirds in the area. This may promote asymmetric hummingbird–plant associations, i.e., pollination depends on floral traits adapted to hummingbird morphology, but hummingbird visitation is determined more by the energetic "reward" than by pollination syndromes.     

Simulations and experiments in punching spring-steel devices with sub-millimeter features

This work demonstrates the feasibility of meso-scale (100 μm to mm) punching of multiple holes of intricate shapes in metals. Analytical modeling, finite element (FE) simulation, and experimentation are used in this work. Two-dimensional FE simulations in ABAQUS were done with an assumed material modeling and plane-strain condition. A known analytical model was used and compared with the ABAQUS simulation results to understand the effects of clearance between the punch and the die. FE simulation in ABAQUS was done for different clearances and corner radii of the punch, die, and holder. To complement modeling with real experiments and for the purpose of comparison, a set of punches and dies were made to punch out a miniature spring-steel gripper. Comparison of compliant grippers made by wire-cut electro discharge machining (EDM) and punching shows that realizing sharp interior and re-entrant corners by punching is not easy to achieve. However, the promise of realizing meso-scale parts with complicated shapes through punching is demonstrated in this work; and further work is identified and some strategies are suggested for improvement. The main contribution of this paper is in adapting the well-established punching and blanking operations to the meso-scale as a viable alternative to making miniature devices currently dominated by lithography-based techniques.     

Warm forming die design,part I: Experimental validation of a novel thermal finite element modeling code

Finite element analysis (FEA) has become an invaluable tool in the design of sheet metal stamping dies and processes. FEA has gained widespread acceptance as the best method of optimizing dies for conventional stamping processes. More recently, FEA has been shown to be an effective method of designing tooling for sheet forming processes. In this work, an FEA based approach is applied to the warm stamping (warm forming) process. This work introduces a new thermal finite element analysis software called PASSAGE®/Forming (PASSAGE) that enables the up-front design of the thermal management of warm forming dies. This thermal finite element analysis software is designed to specifically handle the forming and optimization scenarios related to the heating of a stamping die while minimizing user interface time. In this work, PASSAGE has been applied to a simple block of steel embedded with cartridge heaters to validate the prediction capability of this software under two different heating conditions. The results show that PASSAGE is capable of predicting the actual steady-state temperature distribution within the block with an acceptable level of accuracy while yielding notable information to the user with respect to specifying power requirements. A finite element software package like PASSAGE is a valuable tool that will aid greatly in the implementation of warm forming as a manufacturing process beyond the scope of the laboratory and into production.     

Investigation on the changes effected by tool profile on mechanical and tribological properties of friction stir processed AZ31B magnesium alloy

The present study investigates the effect of tool shoulder profile on the mechanical and tribological properties of friction stir processed AZ31B magnesium alloy. The tool rotational speed and feed rate are the chosen process parameters. The experiments were conducted with 3 level 2 factors full factorial design. The recorded responses were tensile strength, wear losses and corrosion rate. The results were analyzed with the help microstructures of the processed samples. The study reveals that, for concave shoulder tool, the strain hardening effect was playing a major role in determining the properties of the processed materials and for the step shoulder tool, the grain size plays a major role in determining the properties of the processed materials.