A wave-based reduction technique for the dynamic behavior of periodic structures

International audienceThe wave finite element (WFE) method is investigated to describe the dynamic behavior of periodic structures like those composed of arbitrary-shaped substructures along a certain straight direction. A generalized eigenproblem based on the so-called S + S −1 transformation is proposed for accurately computing the wave modes which travel in right and left directions along those periodic structures. Besides, a model reduction technique is proposed which involves partitioning a whole periodic structure into one central structure surrounded by two extra substructures. In doing so, a few wave modes are only required for modeling the central periodic structure. A comprehensive validation of the technique is performed on a 2D periodic structure. Also, its efficiency in terms of CPU time savings is highlighted regarding a 3D periodic structure that exhibits substructures with large-sized FE models

Employee work–life balance and work satisfaction: an empirical study of entrepreneurial career transition and intention across 70 different economies

Purpose: The purpose of this research is to determine whether dissatisfaction with salaried work and low potential for work–life balance can explain a person's intention to go into business using the entrepreneurial event model from Shapero and Sokol (1982) and whether these factors are more prevalent for women than men. Design/methodology/approach: A sample of 36,129 salaried workers from 70 countries from the 2013 Global Entrepreneurship Monitor (GEM) Adult Population Survey is assembled to test the entrepreneurial event model's prediction. Findings: In innovation-driven economies, job satisfaction and work–life balance in the current occupation decrease the likelihood of having the intention to start a business for a salaried person. The impact of work–life balance on the intention to start a business in the same for men and women. Research limitations/implications: In innovation-driven economies, organizations relying on employees with strong entrepreneurial potential to innovate and develop markets should also take into consideration job satisfaction and work–life balance factors to keep them engaged in entrepreneurial activities. A longitudinal analysis of the impact of institutional, economic and cultural factors associated with job satisfaction and work–life balance would be needed to identify the causal impacts. Originality/value: Findings suggest that displacement factors related to the entrepreneurial event model (Shapero and Sokol, 1982) are relevant to study career transition from salaried work to entrepreneurship, and vice-versa. © 2020, Emerald Publishing Limited

Membrane binding and oligomer formation by the calcium-dependent lipopeptide antibiotic A54145: a quantitative study with pyrene excimer fluorescence

The final publication is available at Elsevier via http://doi.org/10.1016/j.bpj.2016.07.018 © 2016. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/A54145 is a lipopeptide antibiotic related to daptomycin that permeabilizes bacterial cell membranes. Its action requires both calcium and phosphatidylglycerol in the target membrane, and it is accompanied by the formation of membrane-associated oligomers. We here probed the interaction of A54145 with model membranes composed of dimyristoylphosphatidylcholine and dimyristoylphosphatidylglycerol, using the steady-state and time-resolved fluorescence of a pyrene-labeled derivative (Py-A54145). In solution, the labeled peptide was found to exist as a monomer. Its membrane interaction occurred in two stages that could be clearly distinguished by varying the calcium concentration. In the first stage, which was observed between 0.15 and 1 mM calcium, Py-A54145 bound to the membrane, as indicated by a strong increase in pyrene monomer emission. At the same calcium concentration, excimer emission increased also, suggesting that Py-A54145 had oligomerized. A global analysis of the time-resolved pyrene monomer and excimer fluorescence confirmed that Py-A54145 forms oligomers quantitatively and concomitantly with membrane binding. When calcium was raised beyond 1 mM, a distinct second transition was observed that may correspond to a doubling of the number of oligomer subunits. The collective findings confirm and extend our understanding of the action mode of A54145 and daptomycin.This work was supported by the Natural Sciences and Engineering Research Council of Canada operating grants to J.D. (201603-2013), M.P. (250265-2013), and S.T. (155283-2012)

Influence of sliding interfaces on the response of a layered viscoelastic medium under a moving load

This article presents a method to compute the response of a viscoelastic layered half-space to a moving load when interlayer slip is considered. The Navier equations of equilibrium are solved for each layer in the frequency domain. The solution in the spatial coordinate system is subsequently obtained by means of Fast Fourier Transform and quadrature rules applied to integrable singularities. Following the global solution technique, the developed method compiles all the interface and the boundary conditions within a global matrix and it solves a unique linear system per couple of wave numbers. This method proves to be effective and is validated in an elastic case by comparison with the ALIZE-LCPC software that implements the Burmister axisymmetric solution. The influence of the interface sliding condition on the response of a layered viscoelastic medium is studied through an application to pavement structures. In this application, the effect of the load speed on vertical and horizontal profiles of the longitudinal strain and the normal stress is analyzed. It is shown, inter alia, that the maximum extension in the medium is not systematically observed at the location of an interface and that, as expected, low speeds and interlayer slip are more damaging to the structure when either a strain or a stress criterion is considered

Scattering by a cylinder covered with an arbitrary distribution of impedance and application to the optimization of a tramway noise abatement system

International audienceA semi-analytical solution for the two-dimensional scattering of a line source by a cylinder with an arbitrary distribution of surface impedance and its image with respect to a vertical baffle is derived. This description is used to model the shadowing due to a low-height semi-cylindrical noise barrier close to a tramway. After validation against the boundary element method, this solution is used in a gradient-based optimization approach of the admittance distribution to maximize the broadband insertion loss in a given receiver zone. First, a hypothetical but passive distribution is found, showing an improvement of more than 20 dB(A) with respect to a purely rigid barrier. Second, a feasible optimized surface treatment made of a porous layer and a micro-perforated resonant panel is proposed, with an improvement of 14 dB(A) with respect to an entirely rigid barrier and 8 dB(A) with respect to a uniform absorbent barrier. The optimization provides an automatic way of tuning the resonant panel so that the attenuation is enhanced in the frequency band where the source has the most spectral content. The benefit of using a non-uniform admittance distribution is evaluated in this idealized context to be about 8 dB(A)

Probing Side Chain Dynamics of Branched Macromolecules by Pyrene Excimer Fluorescence

This document is the Accepted Manuscript version of a Published Work that appeared in final form in Macromolecules, copyright © American Chemical Society after peer review and technical editing by publisher. To access the final edited and published work see http://dx.doi.org/10.1021/acs.macromol.5b02476Four different pyrene-labeled polymers were prepared by radical copolymerization of n-butyl methacrylate (BMA) and 1-pyrenemethyl methacrylate (PyEG(0)-MA), 1-pyrenemethoxyethyl methacrylate (PyEG(1)-MA), 1-pyrene-methoxyethoxyethyl methacrylate (PyEG(2)-MA), and 1-pyrene-methoxydiethoxyethyl methacrylate (PyEG(3)-MA) to yield PyEG(0)-PBMA, PyEG(1)-PBMA, PyEG(2)-PBMA, and PyEG(3)-PBMA, respectively. The only structural difference between the polymers was the length of the oligo(ethylene glycol) spacer separating the pyrene label from the main chain. Steady-state and time-resolved fluorescence were applied to investigate how the length of the spacer affected the photophysical properties of the pyrene-labeled polymers. Excimer formation between an excited-state and a ground-state pyrene was enhanced by a longer spacer which increased the probability of encounter between two pyrene labels. This conclusion was supported through the analysis of the fluorescence decays of the polymers according to the fluorescence blob model (FBM) which yielded the number (N-blob) of monomers constituting the volume in the polymer coil probed by an excited pyrene and the rate constant of excimer formation, k(blob), inside a blob. N-blob increased more or less linearly with increasing spacer length reflecting a larger blob volume. k(blob) for PyEG(0)-PBMA was small due to steric hindrance while k(blob) took a larger but similar value within experimental error for all polymers labeled with pyrene derivatives having oligo(ethylene glycol) spacers. These experiments demonstrate that for a branched macromolecule the volume probed by the tip of a side chain and its dynamics can be characterized quantitatively by monitoring pyrene excimer fluorescence. They are expected to provide important dynamic and structural information about the numerous highly branched macromolecules that are currently under intense scientific scrutiny.NSER

Long Range Polymer Chain Dynamics Studied by Fluorescence Quenching

This document is the Accepted Manuscript version of a Published Work that appeared in final form in Macromolecules, copyright © American Chemical Society after peer review and technical editing by publisher. To access the final edited and published work see http://dx.doi.org/10.1021/acs.macromol.6b01295Over the years, fluorescence quenching experiments have provided a robust analytical means to retrieve information about the internal dynamics of macromolecules in general and the long range polymer chain dynamics (LRPCD) of linear chains in particular. This report reviews the results obtained to. date with the two main fluorescence experiments based on collisional quenching that have been used over the years to describe LRPCD. These experiments involve the labeling of a chain with dyes and quenchers either at the ends of a monodisperse chain for fluorescence quenching end-to-end cyclization (fqEEC) experiments or randomly along a polydisperse chain for fluorescence decay analysis with the fluorescence blob model (FBM). The advantages and disadvantages of these two types Of experiments are discussed as well as their range of applications and applicability to the field of protein folding. In particular, this Perspective illustrates how fqEEc experiments are being applied to probe loop formation in polypeptides and how FBM analysis of randomly labeled polypeptides could help determine the size of foldons which are expected to solve Levinthal's long-standing paradox

Extraction of Oil from Oil Sands Using Thermoresponsive Polymeric Surfactants

This document is the Accepted Manuscript version of a Published Work that appeared in final form in ACS Applied Materials & Interfaces, copyright © American Chemical Society after peer review and technical editing by publisher. To access the final edited and published work see http://dx.doi.org/10.1021/am509231kSeveral thermoresponsive block copolymers constituted of a poly(ethylene glycol) (PEG) and a poly(2-(2-methoxyethoxy) ethyl methacrylate) (PMEO(2)MA) block were prepared by atom transfer radical polymerization (ATRP) and their ability to extract oil from oil sands was evaluated. The chemical composition of the PEG(113)-b-PMEO(2)MAX block copolymers was determined by H-1 NMR and gel permeation chromatography (GPC) with X-values ranging between 48 and 80. Aqueous solutions of block copolymers showed a cloud point of 34 +/- 1 degrees C as determined by turbidimetry and dynamic light scattering (DLS) measurements. DLS experiments indicated that these polymers formed stable block copolymer micelles due to association of the PMEO(2)MA blocks at temperatures greater than 45 degrees C with a unimodal distribution of hydrodynamic diameters. Since characterization of the block copolymer solutions as a function of temperature indicated the formation of hydrophobic domains in water for T > 45 degrees C, extractions of oil from oil sands with the block copolymers were conducted at T = 45 and 50 degrees C. At these temperatures, 15 mL of a 1 mg/mL PEG(113)-b-PMEO(2)MA(77) aqueous solution extracted 100% of the oil trapped in 1 g of oil sand if 60 mg of toluene was added to the mixture. When the extraction was conducted under the same experimental conditions without block copolymer, a poor oil recovery of less than 30% was achieved. Starting with a 1 mg/mL block copolymer concentration, the block copolymer aqueous solution could be recycled up to five successive extractions while maintaining satisfying oil recovery. Each extraction cycle led to a 22% mass loss of block copolymer, certainly due to association with the toluene, oil, and sand particles. Together these experiments demonstrate that thermoresponsive block copolymers can be powerful aids to enhance the oil recovery of oil sands.Imperial OilNSER

Pyrenyl Derivative with a Four-Atom Linker That Can Probe the Local Polarity of Pyrene-Labeled Macromolecules

This document is the Accepted Manuscript version of a Published Work that appeared in final form in the Journal of Physical Chemistry B, copyright © American Chemical Society after peer review and technical editing by publisher. To access the final edited and published work see: http://dx.doi.org/10.1021/acs.jpcb.5b11154The fluorescent probe 1-pyrenemethoxyethanol (PyMeEGOH) was designed to replace commercially available 1-pyrenebutanol (PyButOH) as an alternative fluorescent label to probe the internal dynamics and interior polarity of macromolecules by steady-state and time-resolved fluorescence. While excimer formation and sensitivity to solvent polarity are two well-recognized properties of pyrene, much less known is that these properties are often mutually exclusive when a 1-pyrenebutyl derivative is used to prepare pyrene-labeled macromolecules (PyLMs). As the sensitivity of pyrene to solvent polarity is a result of its symmetry, attaching a butyl group to pyrene breaks the symmetry of pyrene, so that the 1-pyrenebutyl derivatives are much less sensitive to the polarity of their environment compared to unmodified pyrene. This report demonstrates that replacement of a methylene group in the β-position of PyButOH by an oxygen atom, such as in PyMeEGOH, restores the sensitivity of this pyrene derivative to the polarity of its local environment to the same level as that of molecular pyrene without impeding pyrene excimer formation upon incorporation into PyLMs.Natural Sciences and Engineering Research Council || RGPIN/20160

A discrete element study of settlement in vibrated granular layers: role of contact loss and acceleration

This paper deals with the vibration of granular materials due to cyclic external excitation. It highlights the effect of the acceleration on the settlement speed and proves the existence of a relationship between settlement and loss of contacts in partially confined granular materials under vibration. The numerical simulations are carried out using the Molecular Dynamics method, where the discrete elements consist of polygonal grains. The data analyses are conducted based on multivariate autoregressive models to describe the settlement and permanent contacts number with respect to the number of loading cycles