What is the primary mover of water dynamics?

Ishai, Paul Ben; Tripathi, Saroj R.; Kawase, Kodo; Puzenko, Alexander; Feldman, Yuri

doi:10.1039/c5cp01871d

Cited by 37 publications

(24 citation statements)

References 43 publications

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“…Moreover, as suspected since long [19] and recently clearly revealed by broadband spectra extending into the THz range [8,15,18,20,21,22,23,24], at the high-frequency flank of the dominating 20 GHz loss peak (between about 300 GHz and 2 THz), excess intensity is detected, indicating contributions from a faster dynamic process. It shows up as a second, more shallow power law, superimposed to the  --1 decrease found for a Debye relaxation [ Fig.…”

Section: Introductionmentioning

confidence: 65%

“…It was recently pointed out [23] that the HFPL in dielectric spectra of water closely resembles the so-called excess wing (EW) found in dielectric loss spectra of many supercooled liquids [29,30,31]. This phenomenon is often assumed [32,33,34,35,36,37] to arise from a so-called  relaxation [38], partly submerged under the dominating  peak.…”

Section: Introductionmentioning

confidence: 86%

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Electromagnetic-radiation absorption by water

et al. 2017

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Why does a microwave oven work? How does biological tissue absorb electromagnetic radiation? Astonishingly, we do not have a definite answer to these simple questions because the microscopic processes governing the absorption of electromagnetic waves by water are largely unclarified. This absorption can be quantified by dielectric loss spectra, which reveal a huge peak at a frequency of the exciting electric field of about 20 GHz and a gradual tailing off towards higher frequencies. The microscopic interpretation of such spectra is highly controversial and various superpositions of relaxation and resonance processes ascribed to single-molecule or molecule-cluster motions have been proposed for their analysis. By combining dielectric, microwave, THz, and farinfrared spectroscopy, here we provide nearly continuous temperature-dependent broadband spectra of water. Moreover, we find that corresponding spectra for aqueous solutions reveal the same features as pure water. However, in contrast to the latter, crystallization in these solutions can be avoided by supercooling. As different spectral contributions tend to disentangle at low temperatures, this enables to deconvolute them when approaching the glass transition under cooling. We find that the overall spectral development, including the 20 GHz feature (employed for microwave heating), closely resembles the behavior known for common supercooled liquids. Thus, water's absorption of electromagnetic waves at room temperature is not unusual but very similar to that of glassforming liquids at elevated temperatures, deep in the low-viscosity liquid regime, and should be interpreted along similar lines.

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Section: Introductionmentioning

confidence: 65%

Section: Introductionmentioning

confidence: 86%

Electromagnetic-radiation absorption by water

et al. 2017

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“…This function was recently used by Ishasi et al to fit the high frequency excess in water. 8 A cutoff frequency ω c is required, since otherwise this expression violates the Kramers-Kronig relations. In our experiments with this fit function, we found this cutoff could be ignored.…”

Section: Fitting the High Frequency Excessmentioning

confidence: 99%

“…6? In this paper we focus on the dielectric relaxation of water, about which an enormous literature already exists, including several recent detailed theoretical studies. [7][8][9][10][11] In our review of this literature, we found a lack of agreement on the molecular origins of the Debye relaxation and further disagreement on how to fit excess response on the high frequency side of the Debye relaxation, which historically had been fit with a secondary Debye relaxation. Some authors relate Debye relaxation to particular translational and/or rotational motions of a single molecules after breaking one or more hydrogen bonds.…”

Section: Introductionmentioning

confidence: 99%

The origin of the Debye relaxation in liquid water and fitting the high frequency excess response

Elton

2017

Phys. Chem. Chem. Phys.

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We critically review the literature on the Debye absorption peak of liquid water and the excess response found on the high frequency side of the Debye peak. We find a lack of agreement on the microscopic phenomena underlying both of these features. To better understand the molecular origin of Debye peak we ran large scale molecular dynamics simulations and performed several different distance-dependent decompositions of the low frequency dielectric spectra, finding that it involves processes that take place on scales of 1.5-2.0 nm. We also calculated the k-dependence of the Debye relaxation, finding it to be highly dispersive. These findings are inconsistent with models that relate Debye relaxation to local processes such as the rotation/translation of molecules after H-bond breaking. We introduce the spectrumfitter Python package for fitting dielectric spectra and analyze different ways of fitting the high frequency excess, such as including one or two additional Debye peaks. We propose using the generalized Lydanne-Sachs-Teller (gLST) equation as a way of testing the physicality of model dielectric functions. Our attempts at fitting the experimental spectrum using the gLST relation as a constraint indicate that the traditional way of fitting the excess response with secondary and tertiary Debye relaxations is problematic. All of our work is consistent with the recent theory of Popov et al. (2016) that Debye relaxation is due to the migration of Bjerrum-like defects in the hydrogen bond network. Under this theory, the mechanism of Debye relaxation in liquid water is similar to the mechanism in ice, but the heterogeneity and power-law dynamics of the H-bond network in water results in excess response on the high frequency side of the peak.

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“…It is well known that the main component of blood is water, the dielectric properties of which have been recently studied extensively in Ref. . Here, the performance of previously introduced RF sensor is evaluated using aqueous glucose solutions, ranging from 40 to 400 mg/dL, as shown in Figure A.…”

Section: Measurement Setupmentioning

confidence: 99%

In vitro analysis of a microwave sensor for noninvasive glucose monitoring

Sethi

Issa

Ashraf

et al. 2018

Micro & Optical Tech Letters

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In this article, we present in vitro analysis for a microwave sensor proposed for noninvasive glucose monitoring. The sensor is a microstrip‐fed rectangular slot with a dielectric resonator having an elliptical shape resembling a human thumb. It has been demonstrated experimentally and by simulations that the microwave sensor is capable of detecting variations in glucose concentrations (40‐400 mg/dL) by observing shifts in the sensor's resonant frequencies. A Debye model is first developed to predict permittivity and loss tangent values of given glucose concentrations. Knowledge of such values is essential to facilitate simulation of glucose sensor. The simulations and measuremental results show similar behaviors with respect to resonances in the frequency band of interest, which makes the proposed microwave sensor a potential and convenient choice for noninvasive glucose monitoring.

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What is the primary mover of water dynamics?

Cited by 37 publications

References 43 publications

Electromagnetic-radiation absorption by water

Electromagnetic-radiation absorption by water

The origin of the Debye relaxation in liquid water and fitting the high frequency excess response

In vitro analysis of a microwave sensor for noninvasive glucose monitoring

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