Osmotically induced deformation of capsid-like icosahedral vesicles

International audienceWe report the osmotic deformation of micron-size catanionic vesicles with icosahedral symmetry (20 faces, 12 vertices) upon incubation in small solutes (NaCl, glucose). The vesicles remain icosahedral at low osmotic pressure gradients across the bilayer, or spherical for outwards gradients. Above a threshold value of inwards pressure, the icosahedra develop a buckling instability: a depression is initiated at one or two ridges, grows until one vertex snaps into the icosahedra, leading to full collapse of one half of the vesicle into the other. Despite large local inversions in curvature, no release of encapsulated solutes is observed before the residual volume reaches negligible small values. Thin shell models correctly capture the buckling patterns of icosahedra in the low deformation limit. Comparison of experimental results with Monte Carlo simulations provides a first estimate for the conditions of shell disruption, and suggests it is predominantly driven by curvature rather than two-dimensional stretching or compression. The relevance of these results for the mechanics of viral capsids and controlled release applications is discussed

Interfacial behaviour of Catanionic surfactants

International audienceWe report a dramatic increase of foam stability for catanionic mixtures (myristic acid and cetyl trimethylammonium bromide, CTABr) with respect to pristine CTABr solutions. This increase was related to the low surface tension, high surface concentration and high viscoelastic compression moduli, as measured with rising bubble experiments and ellipsometry. Dialysis of the catanionic mixtures has been used to decrease the concentration of free surfactant ions (CTA+). The equilibrium surface tension is reached faster for non dialysed samples, due to the presence of these free ions. As a consequence, the foamability of the dialysed solutions is lower. Foam coarsening has been studied using multiple light scattering: it is similar for dialysed and non dialysed samples and much slower than for pure CTABr foams

Engagement as Theory: Architecture, Planning, and Placemaking in the Twenty-First Century City

This paper was presented at the 2020 Schools of Thought Conference hosted by the Christopher C. Gibbs College of Architecture at the University of Oklahoma.Our recent book, "The City Creative: The Rise of Urban Placemaking in Contemporary America" (University of Chicago Press, 2021), details how participatory design and community engagement can lead to democratically planned, inclusive urban communities. After visiting more than two hundred projects in more than forty cities, we have come to understand that planning, policy, and architectural design should be oriented by local communities and deep engagement with intervention sites. Of course, we are not the first to reach such a conclusion. In many ways, our work builds off contributions made by individuals, including Jane Jacobs, Kevin Lynch, and Christopher Alexander, and such movements as Team 10 and the advocacy architecture movement of the 1960s. Nevertheless, we need to broaden this significant conversation. Importantly, our classroom work has allowed us to better understand how histories often left out of such discussions can inform this new approach. To that end, we have developed community-student partnerships in underserved neighborhoods in cities like Milwaukee and Detroit. Through these connections and their related design-build projects, we have seen how the civil rights movement, immigration narratives, hip-hop culture, and alternative redevelopment histories, such as in urban agriculture, can inform the theory and practice of design. We want to bring these perspectives into dialogue with the mainstream approach to development and design. How does this look and work? Using a case study from the Milwaukee School of Engineering (MSOE) University Scholars Honors Program curriculum, we highlight the redevelopment of Milwaukee’s Fondy Park, an effort to create community-centered spaces and programming in an underserved African American community. Lessons include those essential for pedagogy and education, as well as for how these issues are theorized and professionally practiced, with implications for institutions, programs, and individuals.Ye

Development of a Standard Test Scenario to Evaluate the Effectiveness of Portable Fire Extinguishers on Lithium-ion Battery Fires

Many sources of fuel are present aboard current spacecraft, with one especially hazardous source of stored energy: lithium ion batteries. Lithium ion batteries are a very hazardous form of fuel due to their self-sustaining combustion once ignited, for example, by an external heat source. Batteries can become extremely energetic fire sources due to their high density electrochemical energy content that may, under duress, be violently converted to thermal energy and fire in the form of a thermal runaway. Currently, lithium ion batteries are the preferred types of batteries aboard international spacecraft and therefore are routinely installed, collectively forming a potentially devastating fire threat to a spacecraft and its crew. Currently NASA is developing a fine water mist portable fire extinguisher for future use on international spacecraft. As its development ensues, a need for the standard evaluation of various types of fire extinguishers against this potential threat is required to provide an unbiased means of comparing between fire extinguisher technologies and ranking them based on performance

Efficient Approximation of Multiparameter Persistence Modules

Topological Data Analysis is a growing area of data science, which aims at computing and characterizing the geometry and topology of data sets, in order to produce useful descriptors for subsequent statistical and machine learning tasks. Its main computational tool is persistent homology, which amounts to track the topological changes in growing families of subsets of the data set itself, called ltrations, and encode them in an algebraic object, called persistence module. Even though algorithms and theoretical properties of modules are now well-known in the single-parameter case, that is, when there is only one ltration to study, much less is known in the multi-parameter case, where several ltrations are given at once. ough more complicated, the resulting persistence modules are usually richer and encode more information, making them be er descriptors for data science. In this article, we present the rst approximation scheme, which is based on bered barcodes and exact matchings, two constructions that stem from the theory of single-parameter persistence, for computing and decomposing general multi-parameter persistence modules. Our algorithm has controlled complexity and running time, and works in arbitrary dimension, i.e., with an arbitrary number of ltrations. Moreover, when restricting to speci c classes of multi-parameter persistence modules, namely the ones that can be decomposed into intervals, we establish theoretical results about the approximation error between our estimate and the true module in terms of interleaving distance. Finally, we present empirical evidence validating output quality and speed-up on several data sets

Surface decoration of catanionic vesicles with superparamagnetic iron oxide nanoparticles: a model system for triggered release under moderate temperature conditions

International audienceWe report the design of new catanionic vesicles decorated with iron oxide nanoparticles, which could be used as a model system to illustrate controlled delivery of small solutes under mild hyperthermia. Efficient release of fluorescent dye rhodamine 6G was observed when samples were exposed to an oscillating magnetic field. Our system provides direct evidence for reversible permeability upon magnetic stimulation

Molten fatty acid based microemulsions †

International audiencea We show that ternary mixtures of water (polar phase), myristic acid (MA, apolar phase) and cetyltrimethyl-ammonium bromide (CTAB, cationic surfactant) studied above the melting point of myristic acid allow the preparation of microemulsions without adding a salt or a co-surfactant. The combination of SANS, SAXS/ WAXS, DSC, and phase diagram determination allows a complete characterization of the structures and interactions between components in the molten fatty acid based microemulsions. For the different structures characterized (microemulsion, lamellar or hexagonal phases), a similar thermal behaviour is observed for all ternary MA/CTAB/water monophasic samples and for binary MA/CTAB mixtures without water: crystalline myristic acid melts at 52 1C, and a thermal transition at 70 1C is assigned to the breaking of hydrogen bounds inside the mixed myristic acid/CTAB complex (being the surfactant film in the ternary system). Water determines the film curvature, hence the structures observed at high temperature, but does not influence the thermal behaviour of the ternary system. Myristic acid is partitioned in two ''species'' that behave independently: pure myristic acid and myristic acid associated with CTAB to form an equimolar complex that plays the role of the surfactant film. We therefore show that myristic acid plays the role of a solvent (oil) and a co-surfactant allowing the fine tuning of the structure of oil and water mixtures. This solvosurfactant behaviour of long chain fatty acid opens the way for new formulations with a complex structure without the addition of any extra compound

Air–Liquid Interface Exposure of Lung Epithelial Cells to Low Doses of Nanoparticles to Assess Pulmonary Adverse Effects

Reliable and predictive in vitro assays for hazard assessments of manufactured nanomaterials (MNMs) are still limited. Specifically, exposure systems which more realistically recapitulate the physiological conditions in the lung are needed to predict pulmonary toxicity. To this end, air-liquid interface (ALI) systems have been developed in recent years which might be better suited than conventional submerged exposure assays. However, there is still a need for rigorous side-by-side comparisons of the results obtained with the two different exposure methods considering numerous parameters, such as different MNMs, cell culture models and read outs. In this study, human A549 lung epithelial cells and differentiated THP-1 macrophages were exposed under submerged conditions to two abundant types of MNMs i.e., ceria and titania nanoparticles (NPs). Membrane integrity, metabolic activity as well as pro-inflammatory responses were recorded. For comparison, A549 monocultures were also exposed at the ALI to the same MNMs. In the case of titania NPs, genotoxicity was also investigated. In general, cells were more sensitive at the ALI compared to under classical submerged conditions. Whereas ceria NPs triggered only moderate effects, titania NPs clearly initiated cytotoxicity, pro-inflammatory gene expression and genotoxicity. Interestingly, low doses of NPs deposited at the ALI were sufficient to drive adverse outcomes, as also documented in rodent experiments. Therefore, further development of ALI systems seems promising to refine, reduce or even replace acute pulmonary toxicity studies in animals

Modelling the joint distribution of competing risks survival times using copula functions

The problem of modelling the joint distribution of survival times in a competing risks model, using copula functions is considered. In order to evaluate this joint distribution and the related overall survival function, a system of non-linear differential equations is solved, which relates the crude and net survival functions of the modelled competing risks, through the copula. A similar approach to modelling dependent multiple decrements was applied by Carriere (1994) who used a Gaussian copula applied to an incomplete double decrement model which makes it difficult to calculate any actuarial functions and draw relevant conclusions. Here, we extend this methodology by studying the effect of complete and partial elimination of up to four competing risks on the overall survival function, the life expectancy and life annuity values. We further investigate how different choices of the copula function affect the resulting joint distribution of survival times and in particular the actuarial functions which are of importance in pricing life insurance and annuity products. For illustrative purposes, we have used a real data set and used extrapolation to prepare a complete multiple decrement model up to age 120. Extensive numerical results illustrate the sensitivity of the model with respect to the choice of copula and its parameter(s)

The PREVENT dementia programme: baseline demographic, lifestyle, imaging and cognitive data from a midlife cohort study investigating risk factors for dementia

PREVENT is a multi-centre prospective cohort study in the UK and Ireland that aims to examine midlife risk factors for dementia and identify and describe the earliest indices of disease development. The PREVENT dementia programme is one of the original epidemiological initiatives targeting midlife as a critical window for intervention in neurodegenerative conditions. This paper provides an overview of the study protocol and presents the first summary results from the initial baseline data to describe the cohort. Participants in the PREVENT cohort provide demographic data, biological samples (blood, saliva, urine and optional cerebrospinal fluid), lifestyle and psychological questionnaires, undergo a comprehensive cognitive test battery and are imaged using multi-modal 3-T MRI scanning, with both structural and functional sequences. The PREVENT cohort governance structure is described, which includes a steering committee, a scientific advisory board and core patient and public involvement groups. A number of sub-studies that supplement the main PREVENT cohort are also described. The PREVENT cohort baseline data include 700 participants recruited between 2014 and 2020 across five sites in the UK and Ireland (Cambridge, Dublin, Edinburgh, London and Oxford). At baseline, participants had a mean age of 51.2 years (range 40–59, SD ± 5.47), with the majority female (n = 433, 61.9%). There was a near equal distribution of participants with and without a parental history of dementia (51.4% versus 48.6%) and a relatively high prevalence of APOEɛ4 carriers (n = 264, 38.0%). Participants were highly educated (16.7 ± 3.44 years of education), were mainly of European Ancestry (n = 672, 95.9%) and were cognitively healthy as measured by the Addenbrookes Cognitive Examination-III (total score 95.6 ± 4.06). Mean white matter hyperintensity volume at recruitment was 2.26 ± 2.77 ml (median = 1.39 ml), with hippocampal volume being 8.15 ± 0.79 ml. There was good representation of known dementia risk factors in the cohort. The PREVENT cohort offers a novel data set to explore midlife risk factors and early signs of neurodegenerative disease. Data are available open access at no cost via the Alzheimer’s Disease Data Initiative platform and Dementia Platforms UK platform pending approval of the data access request from the PREVENT steering group committee