Random motion and Brownian rotation

Most free-swimming bacteria move in approximately straight lines, interspersed with random reorientation phases. A key open question concerns varying mechanisms by which reorientation occurs. We combine mathematical modelling with analysis of a large tracking dataset to study the poorly understood reorientation mechanism in the monoflagellate species Rhodobacter sphaeroides . The flagellum on this species rotates counterclockwise to propel the bacterium, periodically ceasing rotation to enable reorientation. When rotation restarts the cell body usually points in a new direction. It has been assumed that the new direction is simply the result of Brownian rotation. We consider three variants of a self-propelled particle model of bacterial motility. The first considers rotational diffusion only, corresponding to a non-chemotactic mutant strain. Two further models incorporate stochastic reorientations, describing ‘run-and-tumble’ motility. We derive expressions for key summary statistics and simulate each model using a stochastic computational algorithm. We also discuss the effect of cell geometry on rotational diffusion. Working with a previously published tracking dataset, we compare predictions of the models with data on individual stopping events in R. sphaeroides . This provides strong evidence that this species undergoes some form of active reorientation rather than simple reorientation by Brownian rotation.

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Cyclic Variation in an SI Engine Due to the Random Motion of the Flame Kernel

10.4271/961152 ◽

1996 ◽

Cited By ~ 14

Author(s):

Karin Holmström ◽

Ingemar Denbratt

Keyword(s):

Random Motion ◽

Cyclic Variation ◽

Si Engine ◽

Flame Kernel

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Control of Multiple Mobile Agents Via Artificial Potential Functions and Random Motion

Volume 9: Mechanical Systems and Control, Parts A, B, and C ◽

10.1115/imece2007-41521 ◽

2007 ◽

Cited By ~ 1

Author(s):

Manish Kumar ◽

Devendra P. Garg ◽

Randy Zachery

Keyword(s):

Potential Function ◽

Mobile Agents ◽

Formation Control ◽

Cluster Formation ◽

Limited Range ◽

Random Motion ◽

Potential Functions ◽

Random Behavior ◽

Artificial Potential Function ◽

Multiple Mobile Agents

This paper investigates the effectiveness of designed random behavior in cooperative formation control of multiple mobile agents. A method based on artificial potential functions provides a framework for decentralized control of their formation. However, it implies heavy communication costs. The communication requirement can be replaced by onboard sensors. The onboard sensors have limited range and provide only local information, and may result in the formation of isolated clusters. This paper proposes to introduce a component representing random motion in the artificial potential function formulation of the formation control problem. The introduction of the random behavior component results in a better chance of global cluster formation. The paper uses an agent model that includes both position and orientation, and formulates the dynamic equations to incorporate that model in artificial potential function approach. The effectiveness of the proposed method is verified via extensive simulations performed on a group of mobile agents and leaders.

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A Wall of Funnels Concentrates Swimming Bacteria

Journal of Bacteriology ◽

10.1128/jb.01033-07 ◽

2007 ◽

Vol 189 (23) ◽

pp. 8704-8707 ◽

Cited By ~ 240

Author(s):

Peter Galajda ◽

Juan Keymer ◽

Paul Chaikin ◽

Robert Austin

Keyword(s):

Escherichia Coli ◽

Porous Media ◽

Biological Tissue ◽

Selection Pressure ◽

Random Motion ◽

Swimming Bacteria ◽

Multistage Pump ◽

Narrow Opening ◽

Arbitrary Shapes ◽

Motile Bacteria

ABSTRACT Randomly moving but self-propelled agents, such as Escherichia coli bacteria, are expected to fill a volume homogeneously. However, we show that when a population of bacteria is exposed to a microfabricated wall of funnel-shaped openings, the random motion of bacteria through the openings is rectified by tracking (trapping) of the swimming bacteria along the funnel wall. This leads to a buildup of the concentration of swimming cells on the narrow opening side of the funnel wall but no concentration of nonswimming cells. Similarly, we show that a series of such funnel walls functions as a multistage pump and can increase the concentration of motile bacteria exponentially with the number of walls. The funnel wall can be arranged along arbitrary shapes and cause the bacteria to form well-defined patterns. The funnel effect may also have implications on the transport and distribution of motile microorganisms in irregular confined environments, such as porous media, wet soil, or biological tissue, or act as a selection pressure in evolution experiments.

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A Sensitive Chemotaxis Assay Using a Novel Microfluidic Device

BioMed Research International ◽

10.1155/2013/373569 ◽

2013 ◽

Vol 2013 ◽

pp. 1-8 ◽

Cited By ~ 6

Author(s):

Chen Zhang ◽

Sunyoung Jang ◽

Ovid C. Amadi ◽

Koichi Shimizu ◽

Richard T. Lee ◽

...

Keyword(s):

Smooth Muscle ◽

Smooth Muscle Cells ◽

Microfluidic Device ◽

Muscle Cells ◽

Random Motion ◽

Cellular Migration ◽

Sensitive Assay ◽

Chemotaxis Assay ◽

Chemokine Gradient ◽

Over Time

Existing chemotaxis assays do not generate stable chemotactic gradients and thus—over time—functionally measure only nonspecific random motion (chemokinesis). In comparison, microfluidic technology has the capacity to generate a tightly controlled microenvironment that can be stably maintained for extended periods of time and is, therefore, amenable to adaptation for assaying chemotaxis. We describe here a novel microfluidic device for sensitive assay of cellular migration and show its application for evaluating the chemotaxis of smooth muscle cells in a chemokine gradient.

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Video-Based Human Motion Analysis

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.403-408.2593 ◽

2011 ◽

Vol 403-408 ◽

pp. 2593-2597

Author(s):

Hong Bao ◽

Zhi Min Liu

Keyword(s):

Motion Analysis ◽

Human Body ◽

Body Shape ◽

Human Motion ◽

Random Motion ◽

Human Motion Analysis ◽

Mass Center ◽

Shape Features ◽

Skeleton Model ◽

Regular Motion

In the analysis of human motion, movement was divided into regular motion (such as walking and running) and random motion (such as falling down).Human skeleton model is used in this paper to do the video-based analysis. Key joints on human body were chosen to be traced instead of tracking the entire human body. Shape features like mass center trajectory were used to describe the movement, and to classify human motion. desired results achieved.

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Measurements of cell adhesion

Development ◽

10.1242/dev.30.2.499 ◽

1973 ◽

Vol 30 (2) ◽

pp. 499-509

Author(s):

Janet E. Hornby

Keyword(s):

Cell Types ◽

Random Motion ◽

Chick Embryos ◽

Collision Efficiency ◽

20 Nm ◽

Kidney Liver ◽

Different Cell Types ◽

Laminar Shear ◽

Lyophobic Sols

Cell suspensions were prepared from the kidney, liver and heart of chick embryos of 5 or 8 days of incubation, and from the limb-buds of chick embryos of 5, 6, 7, 8 or 9 days of incubation. When these suspensions were aggregated under laminar shear in a Couette viscometer or random motion in a reciprocating shaker they obeyed the theoretical relationships derived for flocculating lyophobic sols. The values of the collision efficiency found for the different cell types under given conditions were used to calculate the force of interaction between cells of each type. The force of interaction ranged between 9 × 10−11 N (8-day heart) and 3 × 10−9 N (8-day liver). The forces of interaction between cells appear to be responsible for aligning the membranes of adjacent cells with a 10–20 nm gap. It is possible to arrange the cell types in a hierarchy based on the forces of interaction between them. The possible role of these forces in cell specificity is considered.

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