A Streamwise Constant Model of Turbulence in Plane Couette Flow

Streamwise and quasi-streamwise elongated structures have been shown to play a significant role in turbulent shear flows. We model the mean behavior of fully turbulent plane Couette flow using a streamwise constant projection of the Navier Stokes equations. This results in a two-dimensional, three velocity component ($2D/3C$) model. We first use a steady state version of the model to demonstrate that its nonlinear coupling provides the mathematical mechanism that shapes the turbulent velocity profile. Simulations of the $2D/3C$ model under small amplitude Gaussian forcing of the cross-stream components are compared to DNS data. The results indicate that a streamwise constant projection of the Navier Stokes equations captures salient features of fully turbulent plane Couette flow at low Reynolds numbers. A system theoretic approach is used to demonstrate the presence of large input-output amplification through the forced $2D/3C$ model. It is this amplification coupled with the appropriate nonlinearity that enables the $2D/3C$ model to generate turbulent behaviour under the small amplitude forcing employed in this study.Comment: Journal of Fluid Mechanics 2010, in pres

Feedback regulation of the heat shock response in E. coli

Survival of organisms in extreme conditions has necessitated the evolution of stress response networks that detect and respond to environmental changes. Among the extreme conditions that cells must face is the exposure to higher than normal temperatures. In this paper, we propose a detailed biochemical model that captures the dynamical nature of the heat-shock response in Escherichia coli. Using this model, we show that both feedback and feedforward control are utilized to achieve robustness, performance, and efficiency of the response to the heat stress. We discuss the evolutionary advantages that feedback confers to the system, as compared to other strategies that could have been implemented to get the same performance

Total synthesis of the post-translationally modified polyazole peptide antibiotic goadsporin

The structurally unique polyazole antibiotic goadsporin contains six heteroaromatic oxazole and thiazole rings integrated into a linear array of amino acids that also contains two dehydroalanine residues. An efficient total synthesis of goadsporin is reported in which the key steps are the use of rhodium(II)-catalyzed reactions of diazocarbonyl compounds to generate the four oxazole rings, which demonstrates the power of rhodium carbene chemistry in organic chemical synthesis

Motifs, Control, and Stability

The interactions of networks of transcription factors and signaling molecules can be understood, in part, through concepts from control theory and engineering

Natural recovery of genetic diversity by gene flow in reforested areas of the endemic Canary Island pine, Pinus canariensis

The endemic pine, Pinus canariensis, forms one of the main forest ecosystems in the Canary Islands. In this archipelago, pine forest is a mosaic of natural stands (remnants of past forest overexploitation) and artificial stands planted from the 1940's. The genetic makeup of the artificially regenerated forest is of some concern. The use of reproductive material with uncontrolled origin or from a reduced number of parental trees may produce stands ill adapted to local conditions or unable to adapt in response to environmental change. The genetic diversity within a transect of reforested stands connecting two natural forest fragments has been studied with nuclear and chloroplast microsatellites. Little genetic differentiation and similar levels of genetic diversity to the surrounding natural stands were found for nuclear markers. However, chloroplast microsatellites presented lower haplotype diversity in reforested stands, and this may be a consequence of the lower effective population size of the chloroplast genome, meaning chloroplast markers have a higher sensitivity to bottlenecks. Understory natural regeneration within the reforestation was also analysed to study gene flow from natural forest into artificial stands. Estimates of immigration rate into artificially regenerated forest were high (0.68-0.75), producing a significant increase of genetic diversity (both in chloroplast and nuclear microsatellites), which indicates the capacity for genetic recovery for P. canariensis reforestations surrounded by larger natural stands

Undergraduate Course in Environmental Design and Manufacturing

This paper is a progress report on the development of an undergraduate course in environmental design and manufacturing. The importance of the topic is clear from National Academy of Engineering statements regarding the need to incorporate content on sustainable technology. The multidisciplinary team includes academic faculty from engineering, science, liberal studies, and business in collaboration with industry partners. The team\u27s approach is to create a case-based course by adapting existing educational modules from Ford Motor Company. The group has received National Science Foundation funding for this project (DUE-0511322), and the project is currently in its beginning phases

Agitation near the end of life with dementia: An ethnographic study of care

Background and objectives Agitation is common in people living with dementia especially at the end of life. We examined how staff interpreted agitation behavior in people with dementia nearing end of life, how this may influence their responses and its impact on the quality of care. Research design Ethnographic study. Structured and semi-structured non-participant observations (referred to subsequently in this paper as “structured observations”) of people living with dementia nearing the end of life in hospital and care homes (south-east England) and in-depth interviews with staff, conducted August 2015-March 2017. Methods Three data sources: 1) detailed field notes, 2) observations using a structured tool and checklist for behaviors classed as agitation and staff and institutional responses, 3) staff semi-structured qualitative interviews. We calculated the time participants were agitated and described staff responses. Data sources were analyzed separately, developed continuously and relationally during the study and synthesized where appropriate. Results We identified two main ‘ideal types’ of staff explanatory models for agitation: In the first, staff attribute agitated behaviors to the person’s “moral judgement”, making them prone to rejecting or punitive responses. In the second staff adopt a more “needs-based” approach in which agitation behaviors are regarded as meaningful and managed with proactive and investigative approaches. These different approaches appear to have significant consequences for the timing, frequency and quality of staff response. While these models may overlap they tend to reflect distinct organizational resources and values. Conclusions Care worker knowledge about agitation is not enough, and staff need organizational support to care better for people living with dementia towards end of life. Positional theory may help to explain much of the cultural-structural context that produces staff disengagement from people with dementia, offering insights on how agitation behavior is reframed by some staff as dangerous. Such behavior may be associated with low-resource institutions with minimal staff training where the personhood of staff may be neglected