Anisotropy links cell shapes to tissue flow during convergent extension

Within developing embryos, tissues flow and reorganize dramatically on timescales as short as minutes. This includes epithelial tissues, which often narrow and elongate in convergent extension movements due to anisotropies in external forces or in internal cell-generated forces. However, the mechanisms that allow or prevent tissue reorganization, especially in the presence of strongly anisotropic forces, remain unclear. We study this question in the converging and extending Drosophila germband epithelium, which displays planar polarized myosin II and experiences anisotropic forces from neighboring tissues, and we show that in contrast to isotropic tissues, cell shape alone is not sufficient to predict the onset of rapid cell rearrangement. From theoretical considerations and vertex model simulations, we predict that in anisotropic tissues two experimentally accessible metrics of cell patterns, the cell shape index and a cell alignment index, are required to determine whether an anisotropic tissue is in a solid-like or fluid-like state. We show that changes in cell shape and alignment over time in the Drosophila germband predict the onset of rapid cell rearrangement in both wild-type and snail twist mutant embryos, where our theoretical prediction is further improved when we also account for cell packing disorder. These findings suggest that convergent extension is associated with a transition to more fluid-like tissue behavior, which may help accommodate tissue shape changes during rapid developmental events

Active Tension Network model suggests an exotic mechanical state realized in epithelial tissues.

Mechanical interactions play a crucial role in epithelial morphogenesis, yet understanding the complex mechanisms through which stress and deformation affect cell behavior remains an open problem. Here we formulate and analyze the Active Tension Network (ATN) model, which assumes that the mechanical balance of cells within a tissue is dominated by cortical tension and introduces tension-dependent active remodeling of the cortex. We find that ATNs exhibit unusual mechanical properties. Specifically, an ATN behaves as a fluid at short times, but at long times supports external tension like a solid. Furthermore, an ATN has an extensively degenerate equilibrium mechanical state associated with a discrete conformal - "isogonal" - deformation of cells. The ATN model predicts a constraint on equilibrium cell geometries, which we demonstrate to approximately hold in certain epithelial tissues. We further show that isogonal modes are observed in the fruit y embryo, accounting for the striking variability of apical areas of ventral cells and helping understand the early phase of gastrulation. Living matter realizes new and exotic mechanical states, the study of which helps to understand biological phenomena

Chemical Effects Head-Loss Research in Support of Generic Safety Issue 191.

This summary report describes studies conducted at Argonne National Laboratory on the potential for chemical effects on head loss across sump screens. Three different buffering solutions were used for these tests: trisodium phosphate (TSP), sodium hydroxide, and sodium tetraborate. These pH control agents used following a LOCA at a nuclear power plant show various degrees of interaction with the insulating materials Cal-Sil and NUKON. Results for Cal-Sil dissolution tests in TSP solutions, settling rate tests of calcium phosphate precipitates, and benchmark tests in chemically inactive environments are also presented. The dissolution tests were intended to identify important environmental variables governing both calcium dissolution and subsequent calcium phosphate formation over a range of simulated sump pool conditions. The results from the dissolution testing were used to inform both the head loss and settling test series. The objective of the head loss tests was to assess the head loss produced by debris beds created by Cal-Sil, fibrous debris, and calcium phosphate precipitates. The effects of both the relative arrival time of the precipitates and insulation debris and the calcium phosphate formation process were specifically evaluated. The debris loadings, test loop flow rates, and test temperature were chosen to be reasonably representative of those expected in plants with updated sump screen configurations, although the approach velocity of 0.1 ft/s used for most of the tests is 3-10 times that expected in plants with large screens . Other variables were selected with the intent to reasonably bound the head loss variability due to arrival time and calcium phosphate formation uncertainty. Settling tests were conducted to measure the settling rates of calcium phosphate precipitates (formed by adding dissolved Ca to boric acid and TSP solutions) in water columns having no bulk directional flow. For PWRs where NaOH and sodium tetraborate are used to control sump pH and fiberglass insulation is prevalent, relatively high concentrations of soluble aluminum can be expected. Tests in which the dissolved aluminum (Al) resulted from aluminum nitrate additions were used to investigate potential chemical effects that may lead to high head loss. Dissolved Al concentrations of 100 ppm were shown to lead to large pressure drops for the screen area to sump volume ratio and fiber debris bed studied. No chemical effects on head loss were observed in sodium tetraborate buffered solutions even for environments with high ratios of submerged Al area to sump volume. However, in tests with much higher concentrations of dissolved Al than expected in plants, large pressure drops did occur. Interaction with NUKON/Cal-Sil debris mixtures produced much lower head losses than observed in corresponding tests with TSP, although tests were not performed over the full range of Cal-Sil that might be of interest

Correction to: Effectiveness of a new model of primary care management on knee pain and function in patients with knee osteoarthritis: Protocol for THE PARTNER STUDY

After the publication of this protocol [1], our collaborator Prima Health solutions advised us of their intent to withdraw from the study. Their primary role was to provide remotely delivered weight-loss services (via the Healthy Weight for Life program) to eligible participants in the intervention group. These services were partly provided as in-kind and partly funded through the study. We have received ethical approval from the University of Sydney to replace the Healthy Weight for Life program with the Commonwealth Scientific and Industrial Research Organisation's (CSIRO) Total Wellbeing Diet. The amended weight loss advice and support paragraph of the manuscript is outlined below. All changes to the protocol were made and approved before starting the trial and were prospectively changed on our trial registration (ACT RN12617001595303). Amended weight loss advice and support paragraph: If the patient has a BMI =27 kg/m2, the patient will be offered the option of participating in the remotelydelivered weight loss program. The Australian Commonwealth Scientific and Industrial Research Organisation's (CSIRO) "Total Wellbeing Diet" is based on an evidence-based weight management strategy that utilises a structured, nutritionally balanced eating plan designed to be incorporated into a balanced lifestyle program [2, 3]. The program is a 12- week, low glycaemic index, high protein, healthy eating program with online support and tracking tools, meal plans and educational resources on a healthy diet. It is delivered by SP Health (http://www.sphealth.com/) on behalf of the CSIRO. After completion of the 12-week program, patients may elect to continue the basic program for an additional 12-weeks. Patients who elect to undertake the online weight-loss program will continue to be supported by the PARTNER Care Support Team throughout their time on the weight-loss program. This program will be undertaken in conjunction with the PARTNER exercise program and educational resources on healthy lifestyle change.

Single-crosslink microscopy in a biopolymer network dissects local elasticity from molecular fluctuations

Polymer networks are fundamental from cellular biology to plastics technology but their intrinsic inhomogeneity is masked by the usual ensemble-averaged measurements. Here, we construct direct maps of crosslinks-symbolic depiction of spatially-distributed elements highlighting their physical features and the relationships between them-in an actin network. We selectively label crosslinks with fluorescent markers, track their thermal fluctuations, and characterize the local elasticity and cross-correlations between crosslinks. Such maps display massive heterogeneity, reveal abundant anticorrelations, and may contribute to address how local responses scale up to produce macroscopic elasticity. Single-crosslink microscopy offers a general, microscopic framework to better understand crosslinked molecular networks in undeformed or strained states

Fermilab Main Injector Beam Position Monitor Upgrade

An upgrade of the Beam Position Monitor (BPM) signal processing and data acquisition system for the Fermilab Main Injector is described. The Main Injector is a fast cycling synchrotron that accelerates protons or antiprotons from 8 to 150 GeV. Each Main Injector cycle can have a totally different magnet ramp, RF frequency configuration, beam bunch structure, and injection/extraction pattern from the previous cycle. The new BPM system provides the capabilities and flexibility required by the dynamic and complex machine operations. The system offers measurement capability in the 2.5 MHz and 53 MHz channels to detect the range of bunch structures for protons and antiprotons in both wideband (turn-by-turn) and narrowband (closed-orbit) modes. The new BPM read-out system is based on the digital receiver concept and is highly configurable, allowing the signal processing of nearly all Main Injector beam conditions, including the detection of individual batches. An overview of the BPM system in the Main Injector operating environment, some technology details and first beam measurements are presented