Bovine milk is a complex colloidal liquid exhibiting a multi-scaled structure. It is of particular importance, both commercially and scientifically, to investigate both its dynamic and structural properties. In the current study we have employed the broadband dielectric spectroscopy (BDS) technique in the frequency range of 10(-1)-10(6) Hz and the temperature range of 176-230 K in order to examine the molecular structure and dynamics of quenched bovine milk. Four dielectric relaxation processes were identified. Three of them are associated with water in its different forms: water-lactose complexes, bulk hexagonal and cubic ices. The fourth process is attributed to domain wall relaxations linked to the presence of micro-cracks in the ice structures. In addition, the first process, attributed to water-lactose complexes, obeys the Meyer-Neldel compensation law and can be taken as evidence of differing interfaces of these complexes with the bulk water of the milk, mediated by the lactose concentration. Furthermore, an intriguing structural-dynamic transition around 200 K was observed. Considering the mentioned above, we conclude that our results emphasize the structural and dynamical significance of water in bovine milk. (C) 2016 Elsevier B.V. All rights reserved.

Although relating to the same system, the interpretations of the water spectra from Raman and Dielectric spectroscopy present independent pictures of the nature of water. We show that in the overlap region of the two methods it is possible to combine these views into a coherent concept of what drives the dynamic features of water. In this work, we develop the idea that the dielectric relaxation in water is driven by the migration of defects through the H-bond network, leading to a Debye-like peak in the lower frequencies. The deviation from the Debye law in the higher sub-THz frequencies is traced to a global fluctuation of the same H-bond network, clearly evident in the Raman Spectra. By incorporating these two views, a mathematical formalism is presented that can aptly explicate the dielectric spectra of liquid water.

The main mechanism of the dielectric relaxation process of ordinary hexagonal ice (ice I-h) and its temperature dependence remains unclear. The most interesting and as yet unexplained feature of ice is the presence of the dynamical crossover in relaxation time behavior around T-c = 230 +/- 3 K. Since there are no phase transitions in the ice at this temperature (first or second order), we cannot correlate the origin of this crossover with any structural change. Here we present a model according to which the temperature of the crossover is defined by the polarization mechanism. The dielectric relaxation driven by the diffusion of L-D orientational Bjerrum defects (at high temperature, T > T-c) is transformed into a dielectric relaxation dominated by the diffusion of intrinsic ionic H3O+/OH- defects (at low temperature, T < T-c). In the framework of the model, we propose an analytical equation for the complex dielectric permittivity that takes into account the contribution of both types of defects.

It is demonstrated that the thermal origin of the excess wing in the THz portion of the dielectric spectrum of water is the same as that of the main dielectric peak. The implication is that models positing the free rotation of water molecules to account for the Excess wing are not correct. A self-terminating Proton cascade is one possible explanation.

Over the last decade, discussions on a possible liquid-liquid transition (LLT) have strongly intensified. The LLT proposed by several authors focused mostly on explaining the anomalous properties of water in a deeply supercooled state. However, there have been no direct experimental observations yet of LLT in bulk water in the so-called `no man's land', where water exists only in the crystalline states. Recently, a novel experimental strategy to detect LLT in water has been employed using water-glycerol (W-G) mixtures, because glycerol can generate a strong hindrance for water crystallization. As a result, the observed first-order phase transition at a concentration of glycerol around c(g) approximate to 20 mol% was ascribed to the LLT. Here we show unambiguously that the first order phase transition in W-G mixtures is caused by the ice formation. We provide additional dielectric measurements, applying specific annealing temperature protocols in order to reinforce this conclusion. We also provide an explanation, why such a phase transition occurs only in the narrow glycerol concentration range. These results clearly demonstrate the danger of analysis of phase-separating liquids to gain better insights into water dynamics. These liquids have complex phase behavior that is affected by temperature, phase stability and segregation, viscosity and nucleation, and finally by crystallization, that might lead to significant misinterpretations.

Recent publications show strong correlation between the sub-THz reflection coefficient of a human skin and various stress related ECG parameters. The main hypothesis explaining the phenomenon is based on the coiled nature of human sweat ducts. The way to the development of disruptive commercial applications exploiting this phenomena, traverses through multi-pixel imaging of the human skin tissue (in the sub-THz range). Towards that goal, a fully integrated and packaged SiGe based total-power single pixel receiver (operating in the W-band) has been employed for human stress gauging in both reflectometric and radiometric modes. Initial (and quite encouraging) results are brought forth in this article.

The study of dielectric properties of biological systems and their components is important not only for the fundamental scientific knowledge but also for its applications in medicine, biology, and biotechnology. The technique - known as dielectric spectroscopy (DS) - received impetus from the advent of impedance and network vector analyzers in late nineteen eighties. This new technology made it possible for researchers quickly and accurately to acquire time- or frequency-spectra of permittivity and conductivity in an extremely wide frequency band (10(-6)-10(12)Hz). The link between well-developed traditional DS and the recently appeared THz spectroscopy will be briefly reviewed in the paper.

The upper part of the human eccrine sweat ducts, embedded within the epidermis layer, have a well-defined helical structure. It was recently suggested that, as electromagnetic entities, the sweat ducts interact with sub-mm waves [Y. Feldman et al., Phys. Rev. Lett. 100, 128102 ( 2008)]. Although correlation between changes in the reflectance spectrum in this frequency range and physiological activities has been shown, a direct link between the electromagnetic reflection and the helical structure itself has remained to be established. The fact that the sweat ducts manifest natural homochirality is henceforth used to produce this link. We report the detection of circular polarization asymmetry in the electromagnetic reflection from the human skin at sub-THz frequencies in vivo. We compare the results to numerical simulations and to measurements of a fabricated metamaterial. We argue that the observed circular dichroism can be interpreted uniquely as the signature of the helical structure itself. By twisting reflected electromagnetic waves, the human skin exhibits properties which are usually discussed only in the framework of metamaterial science.

It has recently been established that the coiled nature of the human sweat duct can lead to electromagnetic behavior reminiscent of a helical antenna. Previously, it was reported that both physical and mental stress could be traced through the reflection coefficient of the hand, influenced by the activity of the sweat ducts, in the (75 GHz-110 GHz) and (110 GHz-170 GHz) frequency bands. The reflected signal was monitored from a distance of 72 cm using a Vector Network Analyzer, while the subjects Electrocardiograms (ECGs) were concurrently registered. In the current work we report on a correlation between the reflection coefficient in the same frequency bands and some of the parameters of the ECG, principally to the ST elevation. This connection bears clinical importance because of the importance of the ST segment for the diagnosis of myocardial infarction. This correlation is explored in the article.

The study of confined water dynamics in clay minerals is a very important topic in aluminosilicate-surface chemistry. Aluminosilicates are among the most technologically versatile materials in industry today. Dielectric spectroscopy is a very useful method for investigating the structure and dynamics of water adsorbed on solid matrix surfaces and water in the vicinity of ions in solutions. Use of this method for the study of clay minerals has been underutilized to date, however. The main goal of the present research was to understand the relaxation mechanisms of water molecules interacting with different hydration centers in clay minerals, with a view to eventually control this interaction. Two types of natural layered aluminosilicates (clay minerals) - montmorillonite with exchangeable K+, Co2+, and Ni2+ cations and kaolinite with exchangeable K+ and Ba2+ cations - were examined by means of dielectric spectroscopy over wide ranges of temperature (from -121 degrees C to +300 degrees C) and frequency (1 Hz-1 MHz). An analysis of the experimental data is provided in terms of four distributed relaxation processes. The low-temperature relaxation was observed only in montmorillonites and could be subdivided into two processes, each related to a specific hydration center. The cooperative behavior of water at the interface was observed in the intermediate temperature region, together with a proton percolation. The dielectric properties of ice-like and confined water structures in the layered clay minerals were compared with the dielectric response observed in porous glasses. The spatial fractal dimensions of the porous aluminosilicates were calculated by two separate methods - from an analysis of the fractality found in photomicrographs and from the dielectric response.

Water is the universal solvent in nature. Does this imply, however, that its interaction with its environment is also a universal feature? While this question maybe too fundamental to be answered by one method only, we present evidence that the broadening of the dielectric spectra of water presents universal features of dipolar interactions with different types of matrixes. If in aqueous solutions the starting point of water's state can be considered as bulk, with only partial interactions with the solute, then the state of water adsorbed in heterogeneous materials is determined by various hydration centers of the inhomogeneous material (the matrix) and it is significantly different from the bulk. In both cases, the dielectric spectrum of water is symmetrical and can be described by the Cole-Cole (CC) function. The phenomenological model that describes a physical mechanism of the dipole-matrix interaction in complex systems underlying the CC behavior has been applied to water adsorbed in porous glasses. It was then extended to analyses of the dynamic and structural behavior of water in nonionic and ionic aqueous solutions. The same model is then used to analyze the CC relaxation processes observed in clays, aqueous solutions of nucleotides, and amino acids.

In this paper, the fourth one of our series on the dielectric spectrum symmetrical broadening of water, we consider amino acid (AA) aqueous solutions. The developed 3D-trajectory is applied here to the variety of zwitterion amino acids representing both the hydrophobic and hydrophilic nature of their residues. The dipole moment of amino acids due to their zwitterion determines their interaction with the solvent and reflects mostly the dipole-matrix interactions described in our Paper I [E. Levy et al., J. Chem. Phys. 136, 114502 (2012)]. It is also shown that in the case of charged AAs at high concentrations, the shape of the 3D trajectory transforms to the pattern typical of the dipole-charge interactions that were described in our Paper III [A. Puzenko et al., J. Chem. Phys. 137, 194502 (2012)]. (C) 2014 AIP Publishing LLC.

The effect induced by the presence of a polaron related relaxation process on the dielectric properties of a ferroelectric KTa1-xNbxO3 (KTN) crystal was investigated (10(-2)-10(6) Hz, at 300-375 K) using broadband dielectric spectroscopy. Characterization of the process using just the standard frequency domain dielectric parameters can nonetheless provide penetrating insight into its nature and origins. The three parameters, namely: relaxation time (tau), Cole-Cole loss broadening (alpha), and dielectric strength (Delta epsilon) provide each one in its own way, much useful and often overlooked information. The Activation Energy along with the Meyer-Neldel dependance, both extracted from tau serve to illuminate the dynamic properties. At the same time, alpha and especially the combined alpha(ln tau) relationship, expose the fractal structure of the underlying landscape. Finally, the static parameter. Delta epsilon, enables quantification of the dipolar correlations. Hydrostatic pressure (up to 7.5 kbar) was applied to gently perturb the system and observe the outcome on all of the various parameters. This additional degree of freedom allows for a much more comprehensive exploration of the phase space behavior of the system.