Simultaneous determination of apparent tortuosity and microstructure length scale and shape: Application to rigid open cell foams

Álvarez-Arenas, Tomás Gómez; Fuente, Sonia de la; González, Itzı́ar

doi:10.1063/1.2208921

Cited by 14 publications

(4 citation statements)

References 31 publications

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“…Classical theories of diffusion suggest that the effect of elastic collisions with static obstacles is to reduce the D free of AMPAR to a lower constant value known as the apparent diffusion coefficient (D app ) [17] , [22] . This effect is referred to as tortuosity [38] . Instead, we found that this relationship grew increasingly non-linear as a function of C ( Fig.…”

Section: Resultsmentioning

confidence: 99%

Quantifying the Effects of Elastic Collisions and Non-Covalent Binding on Glutamate Receptor Trafficking in the Post-Synaptic Density

et al. 2010

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One mechanism of information storage in neurons is believed to be determined by the strength of synaptic contacts. The strength of an excitatory synapse is partially due to the concentration of a particular type of ionotropic glutamate receptor (AMPAR) in the post-synaptic density (PSD). AMPAR concentration in the PSD has to be plastic, to allow the storage of new memories; but it also has to be stable to preserve important information. Although much is known about the molecular identity of synapses, the biophysical mechanisms by which AMPAR can enter, leave and remain in the synapse are unclear. We used Monte Carlo simulations to determine the influence of PSD structure and activity in maintaining homeostatic concentrations of AMPARs in the synapse. We found that, the high concentration and excluded volume caused by PSD molecules result in molecular crowding. Diffusion of AMPAR in the PSD under such conditions is anomalous. Anomalous diffusion of AMPAR results in retention of these receptors inside the PSD for periods ranging from minutes to several hours in the absence of strong binding of receptors to PSD molecules. Trapping of receptors in the PSD by crowding effects was very sensitive to the concentration of PSD molecules, showing a switch-like behavior for retention of receptors. Non-covalent binding of AMPAR to anchored PSD molecules allowed the synapse to become well-mixed, resulting in normal diffusion of AMPAR. Binding also allowed the exchange of receptors in and out of the PSD. We propose that molecular crowding is an important biophysical mechanism to maintain homeostatic synaptic concentrations of AMPARs in the PSD without the need of energetically expensive biochemical reactions. In this context, binding of AMPAR with PSD molecules could collaborate with crowding to maintain synaptic homeostasis but could also allow synaptic plasticity by increasing the exchange of these receptors with the surrounding extra-synaptic membrane.

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Section: Resultsmentioning

confidence: 99%

Quantifying the Effects of Elastic Collisions and Non-Covalent Binding on Glutamate Receptor Trafficking in the Post-Synaptic Density

et al. 2010

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“…Regicell 10 160 × 10 −9 Regicell 30 39 × 10 −9 Regicell 60 6 × 10 −9 FXI Z10FRB 206 × 10 −9 FXI Z20FRB 137 × 10 −9 FXI Z30FRB 47 × 10 −9 FXI Z50M 15 × 10 −9 FXI Z80CLE 3 × 10 −9 Clifton et al ( 2008) (Table 1), suggesting that intrinsic permeability of reticulated foam with the same specified pores per linear inch (PPI) but different manufacturers (here Regicell and FXI Corporation) must be determined experimentally. Permeability measured for the FXI samples in Table 1 span expected snow permeability values ranging from lightly compacted snow (low permeability) to depth hoar (high permeability) (Arakawa et al, 2009).…”

Section: Foam Typementioning

confidence: 78%

A low-cost acoustic permeameter

Drake¹,

Selker²,

Higgins³

2016

Preprint

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Abstract. Intrinsic permeability is an important parameter that regulates air exchange through porous media such as snow. Standard methods of measuring snow permeability are inconvenient to perform outdoors, fraught with sampling errors and require specialized equipment, while bringing intact samples back to the laboratory is also challenging. To address these issues, we designed, built, and tested a low-cost acoustic permeameter that allows computation of volume-averaged intrinsic permeability for a homogenous medium. Permeameter elements were designed for use in snow but the measurement methods are not snow-specific. The electronic components, consisting of a signal generator, amplifier, speaker, microphone and oscilloscope, are inexpensive and easily obtainable. The system is suitable for outdoor use when it is not precipitating but the electrical components require protection from the elements in inclement weather. The permeameter can be operated with a microphone either internally mounted or buried a known depth in the medium. The calibration method depends on choice of microphone positioning. For an externally located microphone, calibration was based on a low-frequency approximation applied at 500 Hz that provided an estimate of both intrinsic permeability and tortuosity. The low-frequency approximation that we used is valid up to 2 kHz but we chose 500 Hz because data reproducibility was maximized at this frequency. For an internally mounted microphone, calibration was based on attenuation at 50 Hz and returned only intrinsic permeability. We found that 50 Hz corresponded to a wavelength that minimized resonance frequencies in the acoustic tube and was also within the response limitations of the microphone. We used reticulated foam of known permeability (ranging from 2 × 10−7 m2 to 3 × 10−9 m2) and estimated tortuosity of 1.05 to validate both methods. For the externally mounted microphone the mean normalized standard deviation was 6 % for permeability and 2 % for tortuosity. The mean relative error from known measurements was 17 % for permeability and 2 % for tortuosity. For the internally mounted microphone the mean normalized standard deviation for permeability was 10 % and the relative error was also 10 %. Permeability determination for an externally mounted microphone is less sensitive to environmental noise than is the internally mounted microphone and is therefore the recommended method. The approximation using the internally mounted microphone was developed as an alternative for circumstances in which placing the microphone in the medium was not feasible. Environmental noise degrades precision of both methods and is recognizable as increased scatter for replicate data points.

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“…The prediction of acoustic attenuation in air-saturated porous media allows one to anticipate the control of noise pollution in the fields of housing [10], aeronautics [11], cars, urban transport [12][13][14][15][16] and public space [17]. Several methods have been developed for the characterization of air saturated porous materials [1,[18][19][20][21][22][23][24][25][26][27][28][29][30][31][32] and more particularly the so-called acoustic methods, based on the experimental detection of waves transmitted and/or reflected by the porous material [33][34][35][36][37].…”

Section: Introductionmentioning

confidence: 99%

Influence of Higher Order Viscous and Thermal Effects on an Ultrasonic Wave Reflected from the First Interface of a Porous Material

et al. 2022

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Ultrasound propagation in porous materials involves some higher order physical parameters whose importance depends on the acoustic characteristics of the materials. This article concerns the study of the influence of two parameters recently introduced, namely, the viscous and thermal surfaces, on the acoustic wave reflected by the first interface of a porous material with a rigid structure. These two parameters describe the fluid/structure interactions in a porous medium during the propagation of the acoustic wave in the high-frequency regime. Both viscous and thermal surfaces are involved in Laurent expansion, which is limited to the dynamic tortuosity and compressibility to a higher order and corrects the visco-thermal losses. A sensitivity study is performed on the modulus of the reflection coefficient at the first interface as a function of frequency and on the waveforms reflected by the porous material in the time domain. The results of this study show that absorbent porous materials are the most sensitive to viscous and thermal surfaces, which makes the consideration of these two parameters paramount for the characterization of highly absorbent porous materials using the waves reflected from the first interface.

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Simultaneous determination of apparent tortuosity and microstructure length scale and shape: Application to rigid open cell foams

Abstract: Articles you may be interested inA general methodology for inverse estimation of the elastic and anelastic properties of anisotropic open-cell porous materials-with application to a melamine foam

Cited by 14 publications

References 31 publications

Quantifying the Effects of Elastic Collisions and Non-Covalent Binding on Glutamate Receptor Trafficking in the Post-Synaptic Density

Quantifying the Effects of Elastic Collisions and Non-Covalent Binding on Glutamate Receptor Trafficking in the Post-Synaptic Density

A low-cost acoustic permeameter

Influence of Higher Order Viscous and Thermal Effects on an Ultrasonic Wave Reflected from the First Interface of a Porous Material

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