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Cell Protrusion and Retraction Driven by Fluctuations in Actin Polymerization: A two-dimensional Model
No full textAnimal cells that spread onto a surface often rely on actin‐rich lamellipodial extensions to execute protrusion. Many cell types recently adhered on a two‐dimensional substrate exhibit protrusion and retraction of their lamellipodia, even though the cell is not translating. Travelling waves of protrusion have also been observed, similar to those observed in crawling cells. These regular patterns of protrusion and retraction allow quantitative analysis for comparison to mathematical models. The periodic fluctuations in leading edge position of XTC cells have been linked to excitable actin dynamics using a one‐dimensional model of actin dynamics, as a function of arc‐length along the cell. In this work we extend this earlier model of actin dynamics into two dimensions (along the arc‐length and radial directions of the cell) and include a model membrane that protrudes and retracts in response to the changing number of free barbed ends of actin filaments near the membrane. We show that if the polymerization rate at the barbed ends changes in response to changes in their local concentration at the leading edge and/or the opposing force from the cell membrane, the model can reproduce the patterns of membrane protrusion and retraction seen in experiment. We investigate both Brownian ratchet and switch‐like force‐velocity relationships between the membrane load forces and actin polymerization rate. The switch‐like polymerization dynamics recover the observed patterns of protrusion and retraction as well as the fluctuations in F‐actin concentration profiles. The model generates predictions for the behavior of cells after local membrane tension perturbations
A Queueing Model for Crowdsourcing
No full textCrowdsourcing is getting popular after a number of industries such as food, consumer products, hotels, electronics, and other large retailers bought into this idea of serving customers. In this paper, we introduce a multi-server queueing model in the context of crowdsourcing. We assume that two types, say, Type 1 and Type 2, of customers arrive to a c-server queueing system. A Type 1 customer has to receive service by one of c servers while a Type 2 customer may be served by a Type 1 customer who is available to act as a server soon after getting a service or by one of c servers. We assume that a Type 1 customer will be available for serving a Type 2 customer (provided there is at least one Type 2 customer waiting in the queue at the time of the service completion of that Type 1 customer) with probability p; 0≤p≤1. With probability q = 1 p, a Type 1 customer will opt out of serving a Type 2 customer provided there is at least one Type 2 customer waiting in the system. Upon completion of a service a free server will offer service to a Type 1 customer on an FCFS basis; however, if there are no Type 1 customers waiting in the system, the server will serve a Type 2 customer if there is one present in the queue. If a Type 1 customer decides to serve a Type 2 customer, for our analysis purposes that Type 2 customer will be removed from the system as Type 1 customer will leave the system with that Type 2 customer. Under the assumption of exponential services for both types of customers we study the model in steady state using matrix analytic methods and establish some results including explicit ones for the waiting time distributions. Some illustrative numerical examples are presented
SMaRT: Small Machine for Research and Teaching
Get PDFWe introduce SMaRT, a 16-bit single-cycle RISC-type processor with 16-bit-wide instructions. SMaRT features the novel concept of 2.5-address instructions to avoid the data loss that inherently exists in 2-address processors. Additionally, SMaRT’s short-branch instructions take advantage of the temporal locality of reference in accessing the upper or lower halves of the CPU’s 16x16 orthogonal register file. This allows SMaRT to significantly extend the range of the short-branch instructions. We show that these novelties are achieved at almost no performance cost and negligible hardware cost. SMaRT has four operation modes, namely Single-Step, to execute one instruction at a time, Manual, to display and inspect individual locations of data memory, Run, to run the whole code nonstop, and Init, to copy a read-only memory to the data memory for initialization purposes. We also implement and present an input/output port and a sorting coprocessor, and then hook it up to SMaRT through the port as an example. We have successfully synthesized the combined SMaRT and the sorting coprocessor into the Altera Cyclone II FPGA chip, and tested them
Effect of Control-Display Gain and Mapping and Use of Armrests on Accuracy in Temporally Limited Touchless Gestural Steering Tasks
No full textTouchless gestural controls are becoming an important natural input technique for interaction with emerging virtual environments but design parameters that improve task performance while at the same time reduce user fatigue require investigation. This experiment aims to understand how control-display (CD) parameters such as gain and mapping as well as the use of armrests affect gesture accuracy in specific movement directions. Twelve participants completed temporally constrained two-dimensional steering tasks using free-hand fingertip gestures in several conditions. Use of an armrest, increased CD gain, and horizontal mapping significantly reduced success rate. The results show that optimal transfer functions for gestures will depend on the movement direction as well as arm support features
President Robert McMahan, Dr. Diane Peters, and Provost James Zhang
No full textPresident Robert McMahan, Dr. Diane Peters, and Provost James Zhang at the Autodrive Challenge announcement event at SAE World Congress 2017.https://digitalcommons.kettering.edu/autodrive_gallery/1000/thumbnail.jp
AutoDrive Section A Full Team Picture September 20th, 2017
No full textThis is an Autodrive team picture taken on Wednesday September 20th, 2017 for A section, containing teams, sub-teams, faculty, and staff.https://digitalcommons.kettering.edu/autodrive_gallery/1005/thumbnail.jp
