Microscopic biophysical model of self-organization in tissue due to feedback between cell- and macroscopic-scale forces

We develop a microscopic biophysical model for self-organization and reshaping of artificial tissue, that is codriven by microscopic active forces between cells and an extracellular matrix (ECM), and macroscopic forces that develop within the tissue, finding close agreement with experiment. Microscopic active forces are stimulated by μm-scale interactions between cells and the ECM within which they exist, and when large numbers of cells act together these forces drive, and are affected by, macroscopic-scale self-organization and reshaping of tissues in a feedback loop. To understand this loop, there is a need to (1) construct microscopic biophysical models that can simulate these processes for the very large number of cells found in tissues, (2) validate and calibrate those models against experimental data, and (3) understand the active feedback between cells and the extracellular matrix, and its relationship to macroscopic self-organization and reshaping of tissue. Our microscopic biophysical model consists of a contractile network representing the ECM, that interacts with a large number of cells via dipole forces, to describe macroscopic self-organization and reshaping of tissue. We solve the model using simulated annealing, finding close agreement with experiments on artificial neural tissue. We discuss the calibration of model parameters. We conclude that feedback between microscopic cell-ECM dipole interactions and tissue-scale forces is a key factor in driving macroscopic self-organization and reshaping of tissue. We discuss the application of the biophysical model to the simulation and rational design of artificial tissues

Measurements of DT and DD neutron yields by neutron activation on TFTR

A variety of elemental foils have been activated by neutron fluence from TFTR under conditions with the DT neutron yield per shot ranging from 10{sup 12} to over 10{sup 18}, and with the DT/(DD+DT) neutron ratio varying from 0.5% (from triton burnup) to unity. Linear response over this large dynamic range is obtained by reducing the mass of the foils and increasing the cooling time, all while accepting greatly improved counting statistics. Effects on background gamma-ray lines from foil-capsule-material contaminants, and the resulting lower limits on activation foil mass, have been determined. DT neutron yields from dosimetry standard reactions on aluminum, chromium, iron, nickel, zirconium, and indium are in agreement within the {+-}9% (one-sigma) accuracy of the measurements; also agreeing are yields from silicon foils using the ACTL library cross-section, while the ENDF/B-V library has too low a cross-section. Preliminary results from a variety of other threshold reactions are presented. Use of the {sup 115}In(n.n{prime}) {sup 115m}In reaction (0.42 times as sensitive to DT neutrons as DD neutrons) in conjunction with pure-DT reactions allows a determination of the DT/(DD+DT) ratio in trace tritium or low-power tritium beam experiments

Measurements of DT and DD neutron yields by neutron activation on TFTR

A variety of elemental foils have been activated by neutron fluence from TFTR under conditions with the DT neutron yield per shot ranging from 10{sup 12} to over 10{sup 18}, and with the DT/(DD+DT) neutron ratio varying from 0.5% (from triton burnup) to unity. Linear response over this large dynamic range is obtained by reducing the mass of the foils and increasing the cooling time, all while accepting greatly improved counting statistics. Effects on background gamma-ray lines from foil-capsule-material contaminants, and the resulting lower limits on activation foil mass, have been determined. DT neutron yields from dosimetry standard reactions on aluminum, chromium, iron, nickel, zirconium, and indium are in agreement within the {+-}9% (one-sigma) accuracy of the measurements; also agreeing are yields from silicon foils using the ACTL library cross-section, while the ENDF/B-V library has too low a cross-section. Preliminary results from a variety of other threshold reactions are presented. Use of the {sup 115}In(n.n{prime}) {sup 115m}In reaction (0.42 times as sensitive to DT neutrons as DD neutrons) in conjunction with pure-DT reactions allows a determination of the DT/(DD+DT) ratio in trace tritium or low-power tritium beam experiments

Does co-creation impact public service delivery?:The importance of state and governance traditions

Co-creation in public service delivery requires partnerships between citizens and civil servants. The authors argue that whether or not these partnerships will be successful depends on state and governance traditions (for example a tradition of authority sharing or consultation). These traditions determine the extent to which co-creation can become institutionalized in a country’s governance framework

Local representative democracy and protest politics:the case of the Five-star Movement

In recent years, protest politics has become a relevant phenomenon in various European countries. Italy has witnessed the rise of the Five-star Movement (M5S), an anti-establishment party, which, at the 2013 general election, obtained one-fourth of the total votes. However, the story of this ‘party-movement’ started at the local level, as a civic network aimed at changing administrative practices in municipal government. By using an original dataset on representation in 671 Italian municipalities from 2010 to 2014, this article aims to explain not only the subnational political success of the M5S but also the challenges and contradictions that a newly formed movement faces in multi-level electoral arenas

Cross-calibration of neutron detectors for deuterium-tritium operation in TFTR

During the initial deuterium-tritium experiments on TFTR, neutron emission was measured with {sup 235}U and {sup 238}U fission chambers, silicon surface barrier diodes, spatially collimated {sup 4}He proportional counters and ZnS scintillators, and a variety of elemental activation foils. The activation foils, {sup 4}He counters and silicon diodes can discriminate between 14 MeV and 2.5 MeV neutrons. The other detectors respond to both DD and DT neutrons but are more sensitive to the latter. The proportional counters, scintillators, and some of the fission chambers were calibrated absolutely, using a 14-MeV neutron generator positioned at numerous locations inside the TFTR vacuum vessel. Although the directly calibrated systems were saturated during the highest power deuterium-tritium operation, they allowed cross-calibration of less sensitive fission chambers and silicon diodes. The estimated absolute accuracy of the uncertainty-weighted mean of these cross-calibrations, combined with an independent calibration derived from activation foil determinations of total neutron yield, is {plus_minus}7%

Cross calibration of neutron detectors for deuterium‐tritium operation in TFTR

During the initial deuterium-tritium experiments on TFTR, neutron emission was measured with {sup 235}U and {sup 238}U fission chambers, silicon surface barrier diodes, spatially collimated {sup 4}He proportional counters and ZnS scintillators, and a variety of elemental activation foils. The activation foils, {sup 4}He counters and silicon diodes can discriminate between 14 MeV and 2.5 MeV neutrons. The other detectors respond to both DD and DT neutrons but are more sensitive to the latter. The proportional counters, scintillators, and some of the fission chambers were calibrated absolutely, using a 14-MeV neutron generator positioned at numerous locations inside the TFTR vacuum vessel. Although the directly calibrated systems were saturated during the highest power deuterium-tritium operation, they allowed cross-calibration of less sensitive fission chambers and silicon diodes. The estimated absolute accuracy of the uncertainty-weighted mean of these cross-calibrations, combined with an independent calibration derived from activation foil determinations of total neutron yield, is {plus_minus}7%

Modification of Collagen by 3-Deoxyglucosone Alters Wound Healing through Differential Regulation of p38 MAP Kinase

Background: Wound healing is a highly dynamic process that requires signaling from the extracellular matrix to the fibroblasts for migration and proliferation, and closure of the wound. This rate of wound closure is impaired in diabetes, which may be due to the increased levels of the precursor for advanced glycation end products, 3-deoxyglucosone (3DG). Previous studies suggest a differential role for p38 mitogen-activated kinase (MAPK) during wound healing; whereby, p38 MAPK acts as a growth kinase during normal wound healing, but acts as a stress kinase during diabetic wound repair. Therefore, we investigated the signaling cross-talk by which p38 MAPK mediates wound healing in fibroblasts cultured on native collagen and 3DG-collagen. Methodology/Principal Findings: Using human dermal fibroblasts cultured on 3DG-collagen as a model of diabetic wounds, we demonstrated that p38 MAPK can promote either cell growth or cell death, and this was dependent on the activation of AKT and ERK1/2. Wound closure on native collagen was dependent on p38 MAPK phosphorylation of AKT and ERK1/2. Furthermore, proliferation and collagen production in fibroblasts cultured on native collagen was dependent on p38 MAPK regulation of AKT and ERK1/2. In contrast, 3DG-collagen decreased fibroblast migration, proliferation, and collagen expression through ERK1/2 and AKT downregulation via p38 MAPK. Conclusions/Significance: Taken together, the present study shows that p38 MAPK is a key signaling molecule that plays

Complex circular subsidence structures in tephra deposited on large blocks of ice: Varða tuff cone, Öræfajökull, Iceland

Several broadly circular structures up to 16 m in diameter, into which higher strata have sagged and locally collapsed, are present in a tephra outcrop on southwest Öræfajökull, southern Iceland. The tephra was sourced in a nearby basaltic tuff cone at Varða. The structures have not previously been described in tuff cones, and they probably formed by the melting out of large buried blocks of ice emplaced during a preceding jökulhlaup that may have been triggered by a subglacial eruption within the Öræfajökull ice cap. They are named ice-melt subsidence structures, and they are analogous to kettle holes that are commonly found in proglacial sandurs and some lahars sourced in ice-clad volcanoes. The internal structure is better exposed in the Varða examples because of an absence of fluvial infilling and reworking, and erosion of the outcrop to reveal the deeper geometry. The ice-melt subsidence structures at Varða are a proxy for buried ice. They are the only known evidence for a subglacial eruption and associated jökulhlaup that created the ice blocks. The recognition of such structures elsewhere will be useful in reconstructing more complete regional volcanic histories as well as for identifying ice-proximal settings during palaeoenvironmental investigations