Designing Community-Based Placements in Engineering Education: Enabling the Student Voice

This practice paper captures the reflections of a workshop carried out at the Engineering Education Research Network Annual Symposium, in June 2023. Based on our on-going exploration of the experience of community-based placements for engineering in higher education, this opportunity supported us to gather insight from academic members of staff on the perceived role and value of this learning experience. The reflections indicated that the contributors felt that more clarity surrounding the role of community-based placements is required; that involvement of all stakeholders in placement design is needed; and that consideration for the approaches implemented to include students in learning design is also necessary

Statistical Topology of Cellular Networks in Two and Three Dimensions

Cellular networks may be found in a variety of natural contexts, from soap foams to biological tissues to grain boundaries in a polycrystal, and the characterization of these structures is therefore a subject of interest to a range of disciplines. An approach to describe the topology of a cellular network in two and three dimensions is presented. This allows for the quantification of a variety of features of the cellular network, including a quantification of topological disorder and a robust measure of the statistical similarity or difference of a set of structures. The results of this analysis are presented for numerous simulated systems including the Poisson-Voronoi and the steady-state grain growth structures in two and three dimensions

Autotransporters and Their Role in the Virulence of Burkholderia pseudomallei and Burkholderia mallei

Burkholderia pseudomallei and Burkholderia mallei are closely related Gram-negative bacteria responsible for the infectious diseases melioidosis and glanders, respectively. Autotransporters (ATs) comprise a large and diverse family of secreted and outer membrane proteins that includes virulence-associated invasins, adhesins, proteases, and actin-nucleating factors. The B. pseudomallei K96243 genome contains 11 predicted ATs, eight of which share homologs in the B. mallei ATCC 23344 genome. This review distils key findings from in silico, in vitro, and in vivo studies on the ATs of B. pseudomallei and B. mallei. To date, the best characterized of the predicted ATs of B. pseudomallei and B. mallei is BimA, a predicted trimeric AT mediating actin-based motility which varies in sequence and mode of action between Burkholderia species. Of the remaining eight predicted B. pseudomallei trimeric autotransporters, five of which are also present in B. mallei, two (BoaA and BoaB), have been implicated in bacterial adhesion to epithelial cells. Several predicted Burkholderia ATs are recognized by human humoral and cell-mediated immunity, indicating that they are expressed during infection and may be useful for diagnosis and vaccine-mediated protection. Further studies on the mode of secretion and functions of Burkholderia ATs will facilitate the rational design of control strategies

Robustness of the filamentation instability as shock mediator in arbitrarily oriented magnetic field

The filamentation instability (sometimes also referred to as "Weibel") is a key process in many astrophysical scenario. In the Fireball model for Gamma Ray Bursts, this instability is believed to mediate collisionless shock formation from the collision of two plasma shells. It has been known for long that a flow aligned magnetic field can completely cancel this instability. We show here that in the general case where there is an angle between the field and the flow, the filamentation instability can never be stabilized, regardless of the field strength. The presented model analyzes the stability of two symmetric counter-streaming cold electron/proton plasma shells. Relativistic effects are accounted for, and various exact analytical results are derived. This result guarantees the occurrence of the instability in realistic settings fulfilling the cold approximation.Comment: To appear in Physics of Plasmas Letter

Community Composition and Abundance of Bacterial, Archaeal and Nitrifying Populations in Savanna Soils on Contrasting Bedrock Material in Kruger National Park, South Africa

Savannas cover at least 13% of the global terrestrial surface and are often nutrient limited, especially by nitrogen. To gain a better understanding of their microbial diversity and the microbial nitrogen cycling in savanna soils, soil samples were collected along a granitic and a basaltic catena in Kruger National Park (South Africa) to characterize their bacterial and archaeal composition and the genetic potential for nitrification. Although the basaltic soils were on average 5 times more nutrient rich than the granitic soils, all investigated savanna soil samples showed typically low nutrient availabilities, i.e., up to 38 times lower soil N or C contents than temperate grasslands. Illumina MiSeq amplicon sequencing revealed a unique soil bacterial community dominated by Actinobacteria (20–66%), Chloroflexi (9–29%), and Firmicutes (7–42%) and an increase in the relative abundance of Actinobacteria with increasing soil nutrient content. The archaeal community reached up to 14% of the total soil microbial community and was dominated by the thaumarchaeal Soil Crenarchaeotic Group (43–99.8%), with a high fraction of sequences related to the ammonia-oxidizing genus Nitrosopshaera sp. Quantitative PCR targeting amoA genes encoding the alpha subunit of ammonia monooxygenase also revealed a high genetic potential for ammonia oxidation dominated by archaea (~5 × 107 archaeal amoA gene copies g−1 soil vs. mostly < 7 × 104 bacterial amoA gene copies g−1 soil). Abundances of archaeal 16S rRNA and amoA genes were positively correlated with soil nitrate, N and C contents. Nitrospira sp. was detected as the most abundant group of nitrite oxidizing bacteria. The specific geochemical conditions and particle transport dynamics at the granitic catena were found to affect soil microbial communities through clay and nutrient relocation along the hill slope, causing a shift to different, less diverse bacterial and archaeal communities at the footslope. Overall, our results suggest a strong effect of the savanna soils' nutrient scarcity on all microbial communities, resulting in a distinct community structure that differs markedly from nutrient-rich, temperate grasslands, along with a high relevance of archaeal ammonia oxidation in savanna soils

Identification of linear and nonlinear sensory processing circuits from spiking neuron data

Inferring mathematical models of sensory processing systems directly from input-output observations, while making the fewest assumptions about the model equations and the types of measurements available, is still a major issue in computational neuroscience. This letter introduces two new approaches for identifying sensory circuit models consisting of linear and nonlinear filters in series with spiking neuron models, based only on the sampled analog input to the filter and the recorded spike train output of the spiking neuron. For an ideal integrate-and-fire neuron model, the first algorithm can identify the spiking neuron parameters as well as the structure and parameters of an arbitrary nonlinear filter connected to it. The second algorithm can identify the parameters of the more general leaky integrate-and-fire spiking neuron model, as well as the parameters of an arbitrary linear filter connected to it. Numerical studies involving simulated and real experimental recordings are used to demonstrate the applicability and evaluate the performance of the proposed algorithms

Particle-in-cell Simulations of the Parallel Proton Firehose Instability Influenced by the Electron Temperature Anisotropy in Solar Wind Conditions

In situ observations of the solar wind show a limited level of particle temperature anisotropy with respect to the interplanetary magnetic field direction. Kinetic electromagnetic instabilities are efficient to prevent the excessive growth of the anisotropy of particle velocity distribution functions. Among them, the firehose instabilities are often considered to prevent the increase of the parallel temperature and hence to shape the velocity distribution functions of electrons and protons in the solar wind. We present a nonlinear modeling of the parallel firehose instability, retaining a kinetic description for both the electrons and protons. One-dimensional (1D) fully kinetic particle-in-cell simulations using the energy conserving semi-implicit method (ECsim) are performed to clarify the role of the electron temperature anisotropy in the development of the parallel proton firehose instability. We found that in the presence of an electron temperature anisotropy, such that the temperature parallel to the background magnetic field is higher than the temperature in the perpendicular direction, the onset of the parallel proton firehose instability occurs earlier and its growth rate is faster. The enhanced wave fluctuations contribute to the particle scattering reducing the temperature anisotropy to a stable, nearly isotropic state. The simulation results compare well with linear theory. A test case of 1D simulations at oblique angles with respect to the magnetic field is also considered, as a first step to study the cumulative effect of protons and electrons on the full spectrum of instabilities

Choices:Future trade-offs and plausible pathways

Policy development and management of deltas in the Anthropocene involves the consideration of trade-offs and the balancing of positive and negative consequences for delta functions and the societies that rely on them. This assessment outlines policy-driven and spatial trade-offs that dominate the landscape of choice. It highlights examples of such trade-offs using plausible delta futures and the governance choices associated with them. The analysis is based on modelling broad-scale processes and individual adaptive actions. It highlights how policy choices to maximise economic growth can, for example, have unforeseen consequences such as diminished well-being for some populations. Hence the chapter concludes that trade-offs are a crucial governance challenge for future sustainability of deltas