Flow dynamics control the effect of sphingosine-1-phosphate on endothelial permeability in a microfluidic vessel bifurcation model

Blood vessels are lined by endothelial cells that form a semipermeable barrier to restrict fluid flow across the vessel wall. The endothelial barrier is known to respond to various molecular mechanisms, but the effects of mechanical signals that arise due to blood flow remain poorly understood. Here, we report a microfluidic model that mimics the flow conditions and endothelial/extracellular matrix (ECM) architecture of a vessel bifurcation to enable systematic investigation of how flow dynamics that arise within bifurcating vessels guides the endothelial response to biochemical signals. Applying the strengths of our system, we further investigate the endothelial response to sphingosine-1-phosphate, a bioactive lipid that has demonstrated flow-dependent regulation of vascular permeability. We demonstrate that bifurcated fluid flow (BFF) that arises at the base of vessel bifurcations and laminar shear stress (LSS) that arises along downstream vessel walls induce a decrease in endothelial permeability. Furthermore, we identify that flow-dynamics and chaperone proteins regulate the endothelial response to S1P. Through pharmacological inhibition of S1P receptors 1 and 2, we report ligand-independent mechanical activation of S1P receptors 1 and 2, providing support for the role of G protein-coupled receptors as mechanosensors. These findings introduce BFF as an important regulator of vascular permeability, and establish flow dynamics as a determinant of the endothelial response to S1P.Pelotonia Fellowship ProgramBarry M. Goldwater Excellence in Education FoundationThe Ohio State University College of EngineeringA one-year embargo was granted for this item.Academic Major: Biomedical Engineerin

Competing feedback in an idealized tide-influenced delta network

The morphodynamic evolution of river deltas is intimately tied to flow and sediment partitioning at bifurcations. In this work, the long-term equilibrium configuration of a simple delta network is investigated by means of an analytical model, which accounts for the effect of small tidal oscillations. Differently from individual bifurcations where tidal action is always a stabilizing factor, in the case of a tree-like delta with multiple bifurcations a dual response emerges. Specifically, depending on the values of four reference parameters functions of tidal amplitude, upstream flow conditions, and channels geometry, tides can either promote or discourage an unbalanced discharge distribution. This behavior primarily concerns the apex bifurcation, which is affected by the variations of the relative tidal amplitude at the internal nodes. In turn these variations depend on how flow and sediment are diverted upstream. The stability of steady-state solutions is found to be governed by the sign and magnitude of the slope asymmetry between channels. This work provides a basic modeling framework for the interpretation of the autogenic response of multiple coupled micro-tidal bifurcations, which can potentially be extended to include in a unified scheme erosional and depositional processes typical of fluvio-deltaic systems

Performance Optimization and Dynamics Control for Large-scale Data Transfer in Wide-area Networks

Transport control plays an important role in the performance of large-scale scientific and media streaming applications involving transfer of large data sets, media streaming, online computational steering, interactive visualization, and remote instrument control. In general, these applications have two distinctive classes of transport requirements: large-scale scientific applications require high bandwidths to move bulk data across wide-area networks, while media streaming applications require stable bandwidths to ensure smooth media playback. Unfortunately, the widely deployed Transmission Control Protocol is inadequate for such tasks due to its performance limitations. The purpose of this dissertation is to conduct rigorous analytical study of the design and performance of transport solutions, and develop an integrated transport solution in a systematical way to overcome the limitations of current transport methods. One of the primary challenges is to explore and compose a set of feasible route options with multiple constraints. Another challenge essentially arises from the randomness inherent in wide-area networks, particularly the Internet. This randomness must be explicitly accounted for to achieve both goodput maximization and stabilization over the constructed routes by suitably adjusting the source rate in response to both network and host dynamics.The superior and robust performance of the proposed transport solution is extensively evaluated in a simulated environment and further verified through real-life implementations and deployments over both Internet and dedicated connections under disparate network conditions in comparison with existing transport methods

Optimal Wide Area Controller and State Predictor for a Power System

An optimal wide area controller is designed in this paper for a 12-bus power system together with a Static Compensator (STATCOM). The controller provides auxiliary reference signals for the automatic voltage regulators (AVR) of the generators as well as the line voltage controller of the STATCOM in such a way that it improves the damping of the rotor speed deviations of the synchronous machines. Adaptive critic designs theory is used to implement the controller and enable it to provide nonlinear optimal control over the infinite horizon time of the problem and at different operating conditions of the power system. Simulation results are provided to indicate that the proposed wide area controller improves the damping of the rotor speed deviations of the generators during large scale disturbances. Moreover, a robust radial basis function network based identifier is presented in this paper to predict the states of a multimachine power system in real-time. This wide area state predictor (WASP) compensates for transport lags associated with the present communication technology for wide area monitoring of the electric power grid. The WASP is also robust to partial loss of information caused by larger than expected transport lags or even failed sensors throughout the network

Field migration rates of tidal meanders recapitulate fluvial morphodynamics

The majority of tidal channels display marked meandering features. Despite their importance in oil-reservoir formation and tidal landscape morphology, questions remain on whether tidalmeander dynamics could be understood in terms of fluvial processes and theory. Key differences suggest otherwise, like the periodic reversal of landscape-forming tidal flows and the widely accepted empirical notion that tidal meanders are stable landscape features, in stark contrast with their migrating fluvial counterparts. On the contrary, here we show that, once properly normalized, observed migration rates of tidal and fluvial meanders are remarkably similar. Key to normalization is the role of tidal channel width that responds to the strong spatial gradients of landscape-forming flow rates and tidal prisms. We find that migration dynamics of tidal meanders agree with nonlinear theories for river meander evolution. Our results challenge the conventional view of tidal channels as stable landscape features and suggest that meandering tidal channels recapitulate many fluvial counterparts owing to large gradients of tidal prisms across meander wavelengths

Feedback Control Goes Wireless: Guaranteed Stability over Low-power Multi-hop Networks

Closing feedback loops fast and over long distances is key to emerging applications; for example, robot motion control and swarm coordination require update intervals of tens of milliseconds. Low-power wireless technology is preferred for its low cost, small form factor, and flexibility, especially if the devices support multi-hop communication. So far, however, feedback control over wireless multi-hop networks has only been shown for update intervals on the order of seconds. This paper presents a wireless embedded system that tames imperfections impairing control performance (e.g., jitter and message loss), and a control design that exploits the essential properties of this system to provably guarantee closed-loop stability for physical processes with linear time-invariant dynamics. Using experiments on a cyber-physical testbed with 20 wireless nodes and multiple cart-pole systems, we are the first to demonstrate and evaluate feedback control and coordination over wireless multi-hop networks for update intervals of 20 to 50 milliseconds.Comment: Accepted final version to appear in: 10th ACM/IEEE International Conference on Cyber-Physical Systems (with CPS-IoT Week 2019) (ICCPS '19), April 16--18, 2019, Montreal, QC, Canad