Search results for " Applied"
showing 10 items of 2189 documents
Evidence of atrazine mineralization in a soil from the Nile Delta: Isolation of Arthrobacter sp. TES6, an atrazine-degrading strain
2011
International audience; The s-triazine herbicide atrazine was rapidly mineralized (i.e., about 60% of C-14-ring-labelled atrazine released as (CO2)-C-14 within 21 days) by an agricultural soil from the Nile Delta (Egypt) that had been cropped with corn and periodically treated with this herbicide. Seven strains able to degrade atrazine were isolated by enrichment cultures of this soil. DNA fingerprint and phylogenetic studies based on 165 rRNA analysis showed that the seven strains were identical and belonged to the phylogeny of the genus Arthrobacter (99% similarity with Arthrobacter sp. AD38, EU710554). One strain, designated Arthrobacter sp. strain TES6, degraded atrazine and mineralized…
Guidance of surface elastic waves along a linear chain of pillars
2016
International audience; The propagation of surface elastic waves, or surface phonons, is considered along a linear and periodic chain of cylindrical pillars sitting on a semi-infinite solid substrate. A variety of guided modes, some of them exhibiting a very low group velocity, are shown to exist at frequencies close to the resonance frequencies of the pillars. Although the pillar diameter is typically smaller than half the relevant wavelength, lateral radiation on the surface is found to be canceled. Surface guidance is explained by the hybridization of the resonating pillars with the continuum of elastic waves of the substrate.
Guiding and confinement of interface acoustic waves in solid-fluid pillar-based phononic crystals
2016
International audience; Pillar-based phononic crystals exhibit some unique wave phenomena due to the interaction between surface acoustic modes of the substrate and local resonances supported by pillars. In this paper, we extend the investigations by taking into account the presence of a liquid medium. We particularly demonstrate that local resonances dramatically decrease the phase velocity of Scholte-Stoneley wave, which leads to a slow wave at the solid/fluid interface. Moreover, we show that increasing the height of pillars introduces a new set of branches of interface modes and drastically affects the acoustic energy localization. Indeed, while some modes display a highly confined pres…
Extensive tailorability of sound absorption using acoustic metamaterials
2017
We present an experimental demonstration of sound absorption tailorability, using acoustic metamaterials made of resonant cavities that does not rely on any dissipative material. As confirmed by numerical calculation, we particularly show that using quarter-wave-like resonators made of deep subwavelength slits allows a high confinement of the acoustic energy of an incident wave. This leads to enhance the dissipation in the cavities and, consequently, generates strong sound absorption, even over a wide frequency band. We finally demonstrate experimentally the key role of the filling ratio in tailoring such an absorption, using a metamaterial constituted of space-coiled cavities embedded in a…
Acoustic Topological Circuitry in Square and Rectangular Phononic Crystals
2021
International audience; We systematically engineer a series of square and rectangular phononic crystals to create experimental realizations of complex topological phononic circuits. The exotic topological transport observed is wholly reliant upon the underlying structure which must belong to either a square or rectangular lattice system and not to any hexagonal-based structure. The phononic system chosen consists of a periodic array of square steel bars which partitions acoustic waves in water over a broadband range of frequencies (∼0.5MHz). An ultrasonic transducer launches an acoustic pulse which propagates along a domain wall, before encountering a nodal point, from which the acoustic si…
Combustion wave structure during the MoSi2 synthesis by Mechanically-Activated Self-propagating High-temperature Synthesis (MASHS): In situ time-reso…
2006
Abstract In situ synchrotron time-resolved X-ray diffraction experiments coupled with an infrared imaging camera have been used to reveal the combustion wave structure during the production of MoSi2 by Mechanically Activated Self-propagating High-temperature Synthesis (MASHS). The fast combustion front exhibits a form described as an ‘equilibrium structure’ where the chemical reaction is the sole major driving force. In the MASHS process, oxide-free interfaces between Mo and Si nanocrystallites enhance the reaction Mo+2Si→MoSi2. Exhaustive time-resolved investigations show a possible solid-state process in the first second of the reaction within the combustion front. If preheating is added,…
Reliable numerical solution of a class of nonlinear elliptic problems generated by the Poisson-Boltzmann equation
2020
We consider a class of nonlinear elliptic problems associated with models in biophysics, which are described by the Poisson-Boltzmann equation (PBE). We prove mathematical correctness of the problem, study a suitable class of approximations, and deduce guaranteed and fully computable bounds of approximation errors. The latter goal is achieved by means of the approach suggested in [S. Repin, A posteriori error estimation for variational problems with uniformly convex functionals. Math. Comp., 69:481-500, 2000] for convex variational problems. Moreover, we establish the error identity, which defines the error measure natural for the considered class of problems and show that it yields computa…
Ab-Initio Calculations of Oxygen Vacancy in Ga2O3 Crystals
2021
The research has been funded by the Science Committee of the Ministry of Education and Science of the Republic of Kazakhstan (Grant No. AP08856540). J. Purans and A.I.Popov acknowledge the ERAF project 1.1.1.1/20/A/057 “Functional Ultrawide Bandgap Gallium Oxide and Zinc Gallate Thin Films and Novel Deposition Technologies”. The Institute of Solid State Physics, University of Latvia (Latvia) as the Centre of Excellence has received funding from the European Union’s Horizon 2020 Framework Programme H2020-WIDESPREAD01-2016-2017-Teaming Phase2 under grant agreement No. 739508, project CAMART2.
Identifiability problem for recovering the mortality rate in an age-structured population dynamics model
2014
In this article is studied the identifiability of the age-dependent mortality rate of the Von Foerster–Mc Kendrick model, from the observation of a given age group of the population. In the case where there is no renewal for the population, translated by an additional homogeneous boundary condition to the Von Foerster equation, we give a necessary and sufficient condition on the initial density that ensures the mortality rate identifiability. In the inhomogeneous case, modelled by a non-local boundary condition, we make explicit a sufficient condition for the identifiability property, and give a condition for which the identifiability problem is ill-posed. We illustrate this latter case wit…