123 research outputs found
On the Role of External Representations in Designing for Participatory Sensemaking
Public issues demand highly complex collaborations in which different (public, private) stakeholders, each with their own complementary or conflicting interests, expertise and experiences, work toward public good. Typically, collaborative technological applications function to represent peopleâs ideas and to enable the exchange of representational messages between people. By contrast, we designed [X]Changing Perspectives ([X]CP): an interactive table-system for multi-stakeholder collaboration around public issues. The system aims, not to represent views but rather, to scaffold the emergence of situated meaningful couplings in face-to-face interactions. It helps people to align their visual attention, materialises their input and provokes associations. However, [X]CP does contain representations, such as symbols, tangibles and an interactive visualisation. In reflecting on its design and use, we analyse what these representations do, as seen from the perspective of embodied, participatory sensemaking. We explain how representations are not the foundational building blocks of the system, and how they do not have fixed meanings. Rather, as scaffolds, our representations add a layer of artificial structure that guides the ongoing interactive couplings between people, contributing to participatory sensemaking. Applying this approach to the design of mediating technologies for multi-stakeholder collaborations can open up new ways of interacting and understanding between stakeholders without disrupting their collaboration
Constraining a Historical Black Carbon Emission Inventory of the United States for 1960â2000
We present an observationally constrained United States black carbon emission inventory with explicit representation of activity and technology between 1960 and 2000. We compare measured coefficient of haze data in California and New Jersey between 1965 and 2000 with predicted concentration trends and attribute discrepancies between observations and predicted concentrations among several sources based on seasonal and weekly patterns in observations. Emission factors for sources with distinct fuel trends are then estimated by comparing fuel and concentration trends and further substantiated by inâdepth examination of emission measurements. We recommend (1) increasing emission factors for preregulation vehicles by 80â250%; (2) increasing emission factors for residential heating stoves and boilers by 70% to 200% for 1980s and before; (3) explicitly representing naturally aspired offâroad engines for 1980s and before; and (4) explicitly representing certified wood stoves after 1985. We also evaluate other possible sources for discrepancy between model and measurement, including bias in modeled meteorology, subgrid spatial heterogeneity of concentrations, and inconsistencies in reported fuel consumption. The updated U.S. emissions are higher than the a priori estimate by 80% between 1960 and 1980, totaling 690 Gg/year in 1960 and 620 Gg/year in 1970 (excluding open burning). The revised inventory shows a strongly decreasing trend that was present in the observations but missing in the a priori inventory.Key PointsSystematic evaluation of longâterm U.S. black carbon observations identifies a small number of poorly estimated emission sourcesUpdated black carbon emission is higher than the previous estimate by 80% for 1960â1980, showing a decreasing trend as found in observationEmission factors for preregulation vehicles, offâroad engines, and residential heating stoves in 1980 and before should be increasedPeer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/149266/1/jgrd55339_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/149266/2/jgrd55339.pd
Chemotactic response and adaptation dynamics in Escherichia coli
Adaptation of the chemotaxis sensory pathway of the bacterium Escherichia
coli is integral for detecting chemicals over a wide range of background
concentrations, ultimately allowing cells to swim towards sources of attractant
and away from repellents. Its biochemical mechanism based on methylation and
demethylation of chemoreceptors has long been known. Despite the importance of
adaptation for cell memory and behavior, the dynamics of adaptation are
difficult to reconcile with current models of precise adaptation. Here, we
follow time courses of signaling in response to concentration step changes of
attractant using in vivo fluorescence resonance energy transfer measurements.
Specifically, we use a condensed representation of adaptation time courses for
efficient evaluation of different adaptation models. To quantitatively explain
the data, we finally develop a dynamic model for signaling and adaptation based
on the attractant flow in the experiment, signaling by cooperative receptor
complexes, and multiple layers of feedback regulation for adaptation. We
experimentally confirm the predicted effects of changing the enzyme-expression
level and bypassing the negative feedback for demethylation. Our data analysis
suggests significant imprecision in adaptation for large additions.
Furthermore, our model predicts highly regulated, ultrafast adaptation in
response to removal of attractant, which may be useful for fast reorientation
of the cell and noise reduction in adaptation.Comment: accepted for publication in PLoS Computational Biology; manuscript
(19 pages, 5 figures) and supplementary information; added additional
clarification on alternative adaptation models in supplementary informatio
Additively manufactured device for dynamic culture of large arrays of 3D tissue engineered constructs
The ability to test large arrays of cell and biomaterial combinations in 3D environments is still rather limited in the context of tissue engineering and regenerative medicine. This limitation can be generally addressed by employing highly automated and reproducible methodologies. This study reports on the development of a highly versatile and upscalable method based on additive manufacturing for the fabrication of arrays of scaffolds, which are enclosed into individualized perfusion chambers. Devices containing eight scaffolds and their corresponding bioreactor chambers are simultaneously fabricated utilizing a dual extrusion additive manufacturing system. To demonstrate the versatility of the concept, the scaffolds, while enclosed into the device, are subsequently surface-coated with a biomimetic calcium phosphate layer by perfusion with simulated body fluid solution. 96 scaffolds are simultaneously seeded and cultured with human osteoblasts under highly controlled bidirectional perfusion dynamic conditions over 4 weeks. Both coated and noncoated resulting scaffolds show homogeneous cell distribution and high cell viability throughout the 4 weeks culture period and CaP-coated scaffolds result in a significantly increased cell number. The methodology developed in this work exemplifies the applicability of additive manufacturing as a tool for further automation of studies in the field of tissue engineering and regenerative medicine.P.F.C. and D.W.H. contributed equally to this work. This work was supported by the Australian Research Council. P.F.C. acknowledges the Portuguese Foundation for Science and Technology for his PhD grant (SFRH/BD/62452/2009)
Influence of flow rate and scaffold pore size on cell behavior during mechanical stimulation in a flow perfusion bioreactor
Closing the gate: Part-Time faculty instruction in gatekeeper courses and first-year persistence
The Influence of Mineralization on Intratrabecular Stress and Strain Distribution in Developing Trabecular Bone
The load-transfer pathway in trabecular bone is largely determined by its architecture. However, the influence of variations
in mineralization is not known. The goal of this study was to examine the influence of inhomogeneously distributed degrees
of mineralization (DMB) on intratrabecular stresses and strains. Cubic mandibular condylar bone specimens from fetal and newborn
pigs were used. Finite element models were constructed, in which the element tissue moduli were scaled to the local DMB. Disregarding
the observed distribution of mineralization was associated with an overestimation of average equivalent strain and underestimation
of von Mises equivalent stress. From the surface of trabecular elements towards their core the strain decreased irrespective
of tissue stiffness distribution. This indicates that the trabecular elements were bent during the compression experiment.
Inhomogeneously distributed tissue stiffness resulted in a low stress at the surface that increased towards the core. In contrast,
disregarding this tissue stiffness distribution resulted in high stress at the surface which decreased towards the core. It
was concluded that the increased DMB, together with concurring alterations in architecture, during development leads to a
structure which is able to resist increasing loads without an increase in average deformation, which may lead to damage
Design and development of low cost polyurethane biopolymer based on castor oil and glycerol for biomedical applications
In the current study, we present the synthesis of novel low cost bioâpolyurethane compositions with variable mechanical properties based on castor oil and glycerol for biomedical applications. A detailed investigation of the physicochemical properties of the polymer was carried out by using mechanical testing, ATRâFTIR, and Xâray photoelectron spectroscopy (XPS). Polymers were also tested in short term inâvitro cell culture with human mesenchymal stem cells to evaluate their biocompatibility for potential applications as biomaterial. FTIR analysis confirmed the synthesis of castor oil and glycerol based PU polymers. FTIR also showed that the addition of glycerol as coâpolyol increases crosslinking within the polymer backbone hence enhancing the bulk mechanical properties of the polymer. XPS data showed that glycerol incorporation leads to an enrichment of oxidized organic species on the surface of the polymers. Preliminary investigation into in vitro biocompatibility showed that serum protein adsorption can be controlled by varying the glycerol content with polymer backbone. An alamar blue assay looking at the metabolic activity of the cells indicated that castor oil based PU and its variants containing glycerol are nonâtoxic to the cells. This study opens an avenue for using low cost bioâpolyurethane based on castor oil and glycerol for biomedical applications
Mechanical signals modulated vascular endothelial growth factor-A (VEGF-A) alternative splicing in osteoblastic cells through actin polymerisation
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