Emergent Run-and-Tumble Behavior in a Simple Model of Chlamydomonas with Intrinsic Noise

Recent experiments on the green alga Chlamydomonas that swims using synchronized beating of a pair of flagella have revealed that it exhibits a run-and-tumble behavior similar to that of bacteria such as E. Coli. Using a simple purely hydrodynamic model that incorporates a stroke cycle and an intrinsic Gaussian white noise, we show that a stochastic run-and-tumble behavior could emerge, due to the nonlinearity of the combined synchronization-rotation-translation dynamics. This suggests the intriguing possibility that the alga might exploit nonlinear mechanics---as opposed to sophisticated biochemical circuitry as used by bacteria---to control its behavior.Comment: 5 pages, 2 composite figures (made of 12 separate EPS files

Phase Dependent Forcing and Synchronization in the three-sphere model of Chlamydomonas

The green alga {\it Chlamydomonas} swims with synchronized beating of its two flagella, and is experimentally observed to exhibit run-and-tumble behaviour similar to bacteria. Recently we studied a simple hydrodynamic three-sphere model of {\it Chlamydomonas} with a phase dependent driving force which can produce run-and-tumble behaviour when intrinsic noise is added, due to the non-linear mechanics of the system. Here, we consider the noiseless case and explore numerically the parameter space in the driving force profiles, which determine whether or not the synchronized state evolves from a given initial condition, as well as the stability of the synchronized state. We find that phase dependent forcing, or a beat pattern, is necessary for stable synchronization in the geometry we work with.Comment: 17 pages, 10 composite figures (made of 32 separate files

Self-authorship to Create and Shape the Identity of Women in STEM

Problem: The very low and declining percentage of females undertaking advanced science and mathematics subjects in Year 12 has been noted by the Office of the Chief Scientist (2014) and the Australian Mathematical Sciences Institute (Roberts, 2014). In 2011, only 28% of STEM-employed Australians were female, and this figure dropped to 14% for engineering students (Professionals Australia, 2014). Similar figures are evident in the US where Nobel Laureate Carol Grinder notes not only a deficit of women entering STEM-related fields, but also that many women experience many practical, psychological, and social barriers to continuing and advancing in their STEM careers 1. Given the low level of females employed in STEM-related careers and the high proportion of female primary preservice teachers, the focus on supporting and developing female STEM teachers is crucial. This study asserts that the communication and collaboration between female STEM teachers and females employed in STEM-related industries is key to raising the profile of females in this space, creating communities, and sharing expertise. Plan: To support the development of empowered and resilient women in STEM, the project employed a process of self-authorship (Kegan, 1994) to support and capture the emergent STEM identity of preservice teachers and engineering students. Self-authorship is “the ability to collect, interpret, and analyse information and reflect on one’s own beliefs in order to form judgements” (Baxter Magolda, 1998, p. 143). Self-authorship is “about the cognitive process people use to make meaning” (Creamer & Laughlin, 2005, p. 14). Action: Whilst working as members of a STEM Community of Practice comprising pre-service teachers and engineering students at Curtin University, members (students and academics) participated in guided reflective writing. Guiding questions asked about participants’ interest in STEM, influential others, their self-view as Steminists, how their self-view developed over the period of the project, and how they envisaged their future STEM selves. The Community of Practice was formed during an internally funded Makerspace in STEM project in 2016 that engaged higher education students on campus in a designated physical Makerspace in the Engineering Pavilion, virtually (via a closed Facebook site), and at an Independent Catholic girls’ school in Perth. Reflection: This presentation reports on the initial questions of influence and impact of the project, in particular the Community of Practice as an incubator to nurture professional identity. The narratives authored by the students and the research team (female academics) indicate diverse reasons for participating in the community and the reflections on personal and professional growth were insightful and support the physical and virtual modes of the community

Toward Automation of the Supine Pressor Test for Preeclampsia

Preeclampsia leads to increased risk of morbidity and mortality for both mother and fetus. Most previous studies have largely neglected mechanical compression of the left renal vein by the gravid uterus as a potential mechanism. In this study, we first used a murine model to investigate the pathophysiology of left renal vein constriction. The results indicate that prolonged renal vein stenosis after 14 days can cause renal necrosis and an increase in blood pressure (BP) of roughly 30 mmHg. The second part of this study aimed to automate a diagnostic tool, known as the supine pressor test (SPT), to enable pregnant women to assess their preeclampsia development risk. A positive SPT has been previously defined as an increase of at least 20 mmHg in diastolic BP when switching between left lateral recumbent and supine positions. The results from this study established a baseline BP increase between the two body positions in nonpregnant women and demonstrated the feasibility of an autonomous SPT in pregnant women. Our results demonstrate that there is a baseline increase in BP of roughly 10-14 mmHg and that pregnant women can autonomously perform the SPT. Overall, this work in both rodents and humans suggests that (1) stenosis of the left renal vein in mice leads to elevation in BP and acute renal failure, (2) nonpregnant women experience a baseline increase in BP when they shift from left lateral recumbent to supine position, and (3) the SPT can be automated and used autonomously

Peripheral α2-adrenoceptor antagonism affects the absorption of intramuscularly coadministered drugs

Objective: We determined the possible effects of a peripherally acting alpha2-adrenoceptor antagonist, MK-467, on the absorption of intramuscularly (IM) co-administered medetomidine, butorphanol and midazolam. Study design: Randomized, experimental, blinded cross-over study. Animals: Six healthy Beagle dogs. Methods: Two IM treatments were administered: 1) medetomidine hydrochloride (20 μg kg-1) + butorphanol (100 μg kg-1) + midazolam (200 μg kg-1) (MBM), and; 2) MBM + MK-467 hydrochloride (500 μg kg-1) (MBM-MK), mixed in a syringe. Heart rate was recorded at regular intervals. Sedation was assessed with visual analog scales (0 – 100 mm). Drug concentrations in plasma were analyzed with liquid chromatography - tandem mass spectrometry, with chiral separation of dex- and levomedetomidine. Maximum drug concentrations in plasma (Cmax) and time to Cmax (Tmax) were determined. Paired t-tests, with Bonferroni correction when appropriate, were used for comparisons between the treatments. Results: Data from five dogs were analyzed. Heart rate was significantly higher from 20 until 90 minutes after MBM-MK. The Tmax for midazolam and levomedetomidine (mean ± standard deviation) were approximately halved with co-administration of MK-467, from 23 ± 9 to 11 ± 6 minutes (p = 0.049) for midazolam and from 32 ± 15 to 18 ± 6 minutes for levomedetomidine (p = 0.036), respectively. Conclusions and clinical relevance: MK-467 accelerated the absorption of IM co-administered drugs. This is clinically relevant as it may hasten the onset of peak sedative effects.Peer reviewe

Spatially explicit land-use and land-cover scenarios for the Great Plains of the United States

The Great Plains of the United States has undergone extensive land-use and land-cover change in the past 150 years, with much of the once vast native grasslands and wetlands converted to agricultural crops, and much of the unbroken prairie now heavily grazed. Future land-use change in the region could have dramatic impacts on ecological resources and processes. A scenario-based modeling framework is needed to support the analysis of potential land-use change in an uncertain future, and to mitigate potentially negative future impacts on ecosystem processes. We developed a scenario-based modeling framework to analyze potential future land-use change in the Great Plains. A unique scenario construction process, using an integrated modeling framework, historical data, workshops, and expert knowledge, was used to develop quantitative demand for future land-use change for four IPCC scenarios at the ecoregion level. The FORE-SCE model ingested the scenario information and produced spatially explicit land-use maps for the region at relatively fine spatial and thematic resolutions. Spatial modeling of the four scenarios provided spatial patterns of land-use change consistent with underlying assumptions and processes associated with each scenario. Economically oriented scenarios were characterized by significant loss of natural land covers and expansion of agricultural and urban land uses. Environmentally oriented scenarios experienced modest declines in natural land covers to slight increases. Model results were assessed for quantity and allocation disagreement between each scenario pair. In conjunction with the U.S. Geological Survey\u27s Biological Carbon Sequestration project, the scenario-based modeling framework used for the Great Plains is now being applied to the entire United States