Surface-attached bacterial biofilms are self-replicating active liquid crystals and the dominant form of bacterial life on earth ( 1 – 4 ). In conventional liquid crystals and solid-state materials, the interaction potentials between the molecules that comprise the system determine the material properties. However, for growth-active biofilms it is unclear whether potential-based descriptions can account for the experimentally observed morphologies, and which potentials would be relevant. Here, we overcame previous limitations of single-cell imaging techniques ( 5 , 6 ) to reconstruct and track all individual cells inside growing three-dimensional (3D) biofilms with up to 10,000 individuals. Based on these data, we identify, constrain, and provide a microscopic basis for an effective cell-cell interaction potential, which captures and predicts the growth dynamics, emergent architecture, and local liquid crystalline order of Vibrio cholerae biofilms. Furthermore, we show how external fluid flows control the microscopic structure and 3D morphology of biofilms. Our analysis implies that local cellular order and global biofilm architecture in these active bacterial communities can arise from mechanical cell-cell interactions, which cells can modulate by regulating the production of particular matrix components. These results establish an experimentally validated foundation for improved continuum theories of active matter and thereby contribute to solving the important problem of controlling biofilm growth.

In the last decade, the way tourists use communication technology has become a strong focus of tourism research. Nevertheless there are some locations where there is limited or no internet technology access. These locations can be labeled dead zones. The aims of the present research focus on how tourists think about and react to situations where their normal connectivity with their larger social and information world is disrupted. This study uses the results from five focus groups as well as considerable supporting literature to map the kinds of experiential outcomes tourists report when they are in dead zones. The work reviews tourists' positive and negative experiential outcomes arising from operating outside of their usual technology support systems. In particular the study found that there are major tensions arising from dead zone tourism; specifically stress related to social communication, work communication, safety versus escape, and refreshing or learning the skills of being fully engaged with the present company and setting. In the last decade, the way tourists use communication technology has become a strong focus of tourism research. Nevertheless there are some locations where there is limited or no internet technology access. These locations can be labelled dead zones. The aims of the present research focus on how tourists think about and react to situations where their normal connectivity with their larger social and information world is disrupted. This study uses the results from five focus groups as well as considerable supporting literature to map the kinds of experiential outcomes tourists report when they are in dead zones. The work reviews tourists' positive and negative experiential outcomes arising from operating outside of their usual technology support systems. In particular the study found that there are major tensions arising from dead zone tourism; specifically stress related to social communication, work communication, safety versus escape, and refreshing or learning the skills of being fully engaged with the present company and setting.

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During pregnancy, oxygen diffuses from maternal to fetal blood through villous trees in the placenta. In this paper, we simulate blood flow and oxygen transfer in feto-placental capillaries by converting three-dimensional representations of villous and capillary surfaces, reconstructed from confocal laser scanning microscopy, to finite-element meshes, and calculating values of vascular flow resistance and total oxygen transfer. The relationship between the total oxygen transfer rate and the pressure drop through the capillary is shown to be captured across a wide range of pressure drops by physical scaling laws and an upper bound on the oxygen transfer rate. A regression equation is introduced that can be used to estimate the oxygen transfer in a capillary using the vascular resistance. Two techniques for quantifying the effects of statistical variability, experimental uncertainty and pathological placental structure on the calculated properties are then introduced. First, scaling arguments are used to quantify the sensitivity of the model to uncertainties in the geometry and the parameters. Second, the effects of localized dilations in fetal capillaries are investigated using an idealized axisymmetric model, to quantify the possible effect of pathological placental structure on oxygen transfer. The model predicts how, for a fixed pressure drop through a capillary, oxygen transfer is maximized by an optimal width of the dilation. The results could explain the prevalence of fetal hypoxia in cases of delayed villous maturation, a pathology characterized by a lack of the vasculo-syncytial membranes often seen in conjunction with localized capillary dilations.