Simon Rainville

• PhD
• Professor (Full) at Université Laval

This article demonstrates a new approach enabling the active control of swimming trajectories of flagellated bacteria in space and time. Bacteria were mixed with water solutions of disodium cromoglycate (DSCG), a lyotropic chromonic liquid crystal (LCLC) that mimics the anisotropic properties of many biological environments. It has been well establ...

Many bacteria swim through liquids or crawl on surfaces by rotating long appendages called flagella. Flagellar filaments are assembled from thousands of subunits that are exported through a narrow secretion channel and polymerize beneath a capping scaffold at the tip of the growing filament. The assembly of a flagellum uses a significant proportion...

Flagellated bacteria often proliferate in inhomogeneous environments, such as biofilms, swarms and soil. In such media, bacteria are observed to move efficiently only if they can get out of “dead ends” by changing drastically their swimming direction, and even to completely reverse it. Even though these reorientations are ubiquitous, we have only r...

Unraveling the structure and function of two-component and chemotactic signaling along with different aspects related to motility of bacteria and archaea are key research areas in modern microbiology. Escherichia coli is the traditional model organism to study chemotaxis signaling and motility. However, the recent study of a wide range of bacteria...

Parameters kon and D of the injection-diffusion model fits of Figure 5—figure supplement 3.DOI: http://dx.doi.org/10.7554/eLife.23136.016

The bacterial flagellum is a self-assembling nanomachine. The external flagellar filament, several times longer than a bacterial cell body, is made of a few tens of thousands subunits of a single protein: flagellin. A fundamental problem concerns the molecular mechanism of how the flagellum grows outside the cell, where no discernible energy source...

Although the science of rheology is well established, some important challenges still persist to measure the viscoelastic properties of complex fluids, such as biological solutions and liquid crystals (LC). In this work, we present a method, based on the calculation of the step length of Brownian particles, to measure the effective local viscosity...

The water solubility of lyotropic liquid crystals (LCs) makes them very attractive to study the behavior of biological microorganisms in an environment where local symmetry is broken (as often encountered in nature). Several recent studies have shown a dramatic change in the behavior of flagellated bacteria when swimming in solutions of the lyotrop...

Several experimental approaches are explored to introduce the E. coli bacteria in a liquid anisotropic host. Fonctionalization of the bacterial surface is experimented with 2 different molecules. The 5CB is first used as host and it is shown that, while the bacteria survive at short term in such an environment, they aggregate into colonies. Water s...

Although the influence on bacterial motility of many genetic and biochemical factors has been extensively studied, there have been limited studies of the impact of physical parameters. Indeed, despite the fact that natural environments are often asymmetric (such as stretched supramolecular structures), the majority of behavioral experiments with ba...

Contains reports on five research projects.

Numerous types of bacteria swim in their environment by rotating long helical filaments. At the base of each filament is a tiny rotary motor called the bacterial flagellar motor. A lot is already known about the structure, assembly and function of this splendid molecular machine of nanoscopic dimensions. Nevertheless many fundamental questions rema...

Numerous types of bacteria swim in their environment by rotating long helical filaments. At the base of each filament is a tiny rotary motor called the bacterial flagellar motor. A lot is already known about the structure, assembly and function of this splendid molecular machine of nanoscopic dimensions. Nevertheless many funda- mental questions re...

One of the most striking predictions of Einstein's special theory of relativity is also perhaps the best known formula in all of science: E=mc(2). If this equation were found to be even slightly incorrect, the impact would be enormous--given the degree to which special relativity is woven into the theoretical fabric of modern physics and into every...

This thesis describes the demonstration of a new technique that allows masses to be compared with fractional uncertainty at or below 1 x 10-11, an order of magnitude improvement over our previous results. By confining two different ions in a Penning trap we can now simultaneously measure the ratio of their two cyclotron frequencies, making our mass...

We have developed a technique to simultaneously compare the cyclotron frequencies of two single ions to obtain atomic mass ratios with fractional accuracies at or below 10−11. Much like a balance scale, this two‐ion technique cancels many sources of noise and error — chief among them magnetic field noise. The new mass comparisons are used in combin...

The cyclotron frequency of a charged particle in a uniform magnetic field B is related to its mass m and charge q by the relationship omega(c) = qB/m. This simple relationship forms the basis for sensitive mass comparisons using ion cyclotron resonance mass spectroscopy, with applications ranging from the identification of biomolecules and the stud...

We have developed the analog of a double-pan balance for determining the masses of single molecular ions from the ratio of their two cyclotron frequencies. By confining two different ions on the same magnetron orbit in a Penning trap, we balance out many sources of noise and error (such as fluctuations of the magnetic field). To minimize the system...

Using a Penning trap single ion mass spectrometer, our group has measured the atomic masses of 14 isotopes with a fractional accuracy of about 10−10. The masses were extracted from 28 cyclotron frequency ratios of two ions altenately confined in our trap. The precision on these measurements was limited by the temporal fluctuations of our magnetic f...

We have improved upon some of the world's most accurate mass comparisons by an order of magnitude to a fractional accuracy of 10-11. Key to this accomplishment was achieving common-mode rejection of magnetic field noise by performing simultaneous cyclotron frequency comparisons of two ions in a Penning trap. To minimize systematic errors due to ion...

By simultaneously trapping two different ions in a Penning trap and precisely controlling their relative motions, we have recently achieved mass comparisons with a relative accuracy of about 10-11 (as described by my colleague James K. Thompson in another talk at this conference). We have used this novel technique to measure the mass ratios ^32SH^+...

By trapping two different ions in the same Penning trap at the same time, we simultaneously measured the ratio of their cyclotron frequencies (from which we obtain their atomic mass ratio) with a precision of about 10^-11 in only a few hours. In order to perform these comparisons, we must be able to measure and control all three normal mo...

By simultaneously trapping two different ions in a Penning trap, we compared their cyclotron frequencies (whose ratio gives their atomic mass ratio) with a precision of about 10-11 in only a few hours. Unfortunately we observed large abrupt changes in the ratio for which we do not have an explanation.

The MIT Ion Cyclotron Resonance Lab has determined the atomic mass of 13 neutral atoms with accuracies of ~ 10-10 by comparing the cyclotron frequencies of single ions stored in a Penning trap. During the past year, we have developed an electronic refrigeration technique which uses feedback to reduce the effective temperature of the superconducting...

Using a Penning trap single ion mass spectrometer, we have measured the atomic masses of 13 isotopes, many important for fundamental metrology and fundamental constants. The accuracy of the measurements, ~10-10, is typically two orders of magnitude better than previously accepted values. A wide variety of self consistency checks greatly reduces the...

We report new values for the atomic masses of the alkali 133Cs, 87Rb, 85Rb, and 23Na with uncertainties ≤ 0.2 ppb. These results, obtained using Penning trap single ion mass spectrometry, are typically two orders of magnitude more accurate than previously measured values. Combined with values of h/m atom from atom interferometry measurements and ac...

The use of single ions in Penning traps has made possible the measurement of some atomic and molecular masses with a precision of about a part in 10^10. This is achieved by measuring the cyclotron frequency of an ion trapped in a strong magnetic field, and comparing it to the cyclotron frequency of a reference ion trapped in the same field several...

We report new values for the atomic masses of the alkali ^133Cs, ^87Rb, ^85Rb, and ^23Na with uncertainties

We report new values from Penning trap single ion mass spectrometry for the atomic masses of 133Cs, 87Rb, 85Rb, and 23Na with uncertainties ≤0.2 ppb, a factor of 100 improvement over the accuracy of previously measured values. We have found M(133Cs) = 132.905 451 931(27)u, M(87Rb) = 86.909 180 520(15)u, M(85Rb) = 84.911 789 732(14)u, and M(23Na) =...

We previously determined the atomic masses of 14 neutrals ranging from H and n to ^133Cs all with a precision of a few parts in 10^10. This was accomplished by comparing the cyclotron frequencies of single atomic or molecular ions alternately stored in a Penning trap. The precision of these measurements was limited by magnetic field changes during...