Colonization and Persistence of the Freshwater Amphipod, Crangonyx pseudogracilis, in Temporary Ponds: Aspects of its Ecology, Resistance to Desiccation, and Dispersal Abilities

Crangonyctid amphipods occupy temporary habitats throughout northeastern North America but they are mostly known as permanent water species. Crangonyx pseudogracilis is found at high densities in temporary ponds in western New York but the means by which it colonizes and persists in temporary ponds were not well understood before my study. My objectives were to 1) learn more about and quantify the colonization abilities of C. pseudogracilis by performing experiments where holes were dug around temporary ponds; 2) explore the ability of the amphipods and other invertebrates to descend through inundated porous substrates in the laboratory; 3) compare the lifecycles of permanent and temporary populations and how the timing of mating and releasing of broods may be related to survival through the dry season; and 4) understand how and where the amphipods find refuge when a pond dries. During periods of inundation, C. pseudo gracilis was found in the top 15 cm of soil below and at the edges of the pond basin. After the pond basin became dry, they probably descended in the soil to depths greater than 45 cm. C. pseudogracilis and planarian flatworms readily colonized holes dug on the perimeter of the pond. In the lab, amphipods, flatworms, and ostracods readily descended through porous substrates. C. pseudogracilis has an annual lifecycle; the previous year\u27s generation began dying in May and was gone by the end June. Ovigerous females were found from 23 March until 28 May. In the laboratory, amphipods survived in soil with an average moisture content of 51 % for 15 weeks. My results suggest further studies. 1) Populations of C. pseudo gracilis in permanent waters migrate to deep water during the same time of year as the temporary ponds I studied dried up. Whether amphipods in permanent waters burrow into bottom sediments during the dry season should be studied. 2) Determine how deep amphipods descend into pond sediments of temporary waters during the dry season. 3) Examine in detail the importance of the soil/water ecotone for organisms living in temporary waters

Colonization and persistence of Crangonyx pseudogracilis (Bousfield 1958) in temporary pools

Crangonyctid amphipods occupy temporary habitats across northeastern North America, but they are mostly known as permanent-water species. Crangonyx pseudogracilis (Bousfield 1958) is found at high densities in temporary pools in western New York, but the means by which it persists are not well understood. Our objectives were to: 1) assess the dispersal abilities of C. pseudogracilis, 2) explore its ability to descend through inundated porous substrates, 3) assess whether its life cycle and brood releases are related to survival through the dry season, and 4) find their dry-season refugia and measure the period for which they can survive desiccation. During periods of inundation, C. pseudogracilis was found in the top 15 cm of soil in holes \u3c10 m from pools. After pools dried in mid-June or early July, C. pseudogracilis was not found in the soil to a depth of 45 cm, even when rains temporarily refilled the pools. In the laboratory, small C. pseudogracilis descended easily through substrates with ≥ 0.7-mm pore radii but large (≥ 7 mm) and ovigerous C. pseudogracilis were unable to descend. In the field, ovigerous females were found from mid-March until late May. The previous year’s generation of large and ovigerous individuals began dying in May and was gone by the end June. In the laboratory, C. pseudogracilis survived in damp soil (51% average free moisture content) for 15 wk. Crangonyx pseudogracilis lacks specialized strategies for survival in temporary waters (e.g., resting eggs, dormant juvenile stages, active burrowing), but has ecological traits well suited for temporary pools and similar environment

More-than-human participation: Design for sustainable smart city futures

In this forum we highlight innovative thought, design, and research in the area of interaction design and sustainability, illustrating the diversity of approaches across HCI communities. — Roy Bendor, Edito

Transport and Magnetic Properties of FexVse2 (x = 0 - 0.33)

We present our results of the effect of Fe intercalation on the structural, transport and magnetic properties of 1T-VSe2. Intercalation of iron, suppresses the 110K charge density wave (CDW) transition of the 1T-VSe2. For the higher concentration of iron, formation of a new kind of first order transition at 160K takes place, which go on stronger for the 33% Fe intercalation. Thermopower of the FexVSe2 compounds (x = 0 - 0.33), however do not show any anomaly around the transition. The intercalation of Fe does not trigger any magnetism in the weak paramagnetic 1T-VSe2, and Fe is the low spin state of Fe3+.Comment: 7 pages, 8 figures, 2 table

In the social amoeba, Dictyostelium discoideum , density, not farming status, determines predatory success on unpalatable Escherichia coli

Background The social amoeba Dictyostelium discoideum interacts with bacteria in a variety of ways. It is a predator of bacteria, can be infected or harmed by bacteria, and can form symbiotic associations with bacteria. Some clones of D. discoideum function as primitive farmers because they carry bacteria through the normally sterile D. discoideum social stage, then release them after dispersal so the bacteria can proliferate and be harvested. Some farmer-associated bacteria produce small molecules that promote host farmer growth but inhibit the growth of non-farmer competitors. To test whether the farmers’ tolerance is specific or extends to other growth inhibitory bacteria, we tested whether farmer and non-farmer amoebae are differentially affected by E. coli strains of varying pathogenicity. Because the numbers of each organism may influence the outcome of amoeba-bacteria interactions, we also examined the influence of amoeba and bacteria density on the ability of D. discoideum to grow and develop on distinct bacterial strains. Results A subset of E. coli strains did not support amoeba proliferation on rich medium, independent of whether the amoebae were farmers or non-farmers. However, amoebae could proliferate on these strains if amoebae numbers are high relative to bacteria numbers, but again there was no difference in this ability between farmer and non-farmer clones of D. discoideum. Conclusions Our results show that farmer and non-farmers did not differ in their abilities to consume novel strains of E. coli, suggesting that farmer resistance to their own carried bacteria does not extend to foreign bacteria. We see that increasing the numbers of bacteria or amoebae increases their respective likelihood of competitive victory over the other, thus showing Allee effects. We hypothesize that higher bacteria numbers may result in higher concentrations of a toxic product or in a reduction of resources critical for amoeba survival, producing an environment inhospitable to amoeba predators. Greater amoeba numbers may counter this growth inhibition, possibly through reducing bacterial numbers via increased predation rates, or by producing something that neutralizes a potentially toxic bacterial product

Practices of readiness: punctuation, poise and the contingencies of participatory design

How do we ready ourselves to intervene responsively in the contingent situations that arise in co-designing to make change? How do we attune to group dynamics and respond ethically to unpredictable developments when working with ‘community’? Participatory Design (PD) can contribute to social transitions, yet its focus is often tightly tuned to technique for designing ICT at the cost of participatory practice. We challenge PD conventions by addressing what happens as we step into a situation to alter it with others, an aspect of practice that cannot be replicated or interchanged. We do so to argue that practices of readiness are constituted by personal histories, experiences, philosophies and culture. We demonstrate this political argument by giving reflexive accounts of our dimensions of preparation. The narratives here are distinct, yet reveal complementary theories and worldviews that shape PD ontologies. We have organized these around the qualities of punctuation and poise as a way to draw out some less easily articulated aspects of PD practice

Effects of a Three-week Core Training Program on Different Unstable Platforms

Please see the pdf version of the abstract

Giant Thermoelectric Effect from Transmission Supernodes

We predict an enormous order-dependent quantum enhancement of thermoelectric effects in the vicinity of a higher-order `supernode' in the transmission spectrum of a nanoscale junction. Single-molecule junctions based on 3,3'-biphenyl and polyphenyl ether (PPE) are investigated in detail. The nonequilibrium thermodynamic efficiency and power output of a thermoelectric heat engine based on a 1,3-benzene junction are calculated using many-body theory, and compared to the predictions of the figure-of-merit ZT.Comment: 5 pages, 6 figure

Design, Participation, and Social Change: What Design in Grassroots Spaces Can Teach Learning Scientists

hile a science of design (and theory of learning) is certainly useful in design-based research, a participatory design research framework presents an opening for learning scientists to rethink design and learning as processes. Grounded in the autoethnographic investigation of a grassroots organization\u27s design of a local campaign, the author traces the successive transformations of design artifacts, delineating a narrative character to design within grassroots spaces. One major lesson is that centering the question of participation is not just about including historically marginalized peoples at the core of design; it has the potential to “desettle” projects at a fundamental level, challenging dominant epistemologies that inform the practices of learning scientists, and thus transforming the field in ways that have yet to be systematically explored. More broadly, this study highlights the need for future research on design practices as they take form within understudied spaces, such as grassroots organizations