Chemometrics: An Excavator in Temperature-Dependent Near-Infrared Spectroscopy

Temperature-dependent near-infrared (NIR) spectroscopy has been developed and taken as a powerful technique for analyzing the structure of water and the interactions in aqueous systems. Due to the overlapping of the peaks in NIR spectra, it is difficult to obtain the spectral features showing the structures and interactions. Chemometrics, therefore, is adopted to improve the spectral resolution and extract spectral information from the temperature-dependent NIR spectra for structural and quantitative analysis. In this review, works on chemometric studies for analyzing temperature-dependent NIR spectra were summarized. The temperature-induced spectral features of water structures can be extracted from the spectra with the help of chemometrics. Using the spectral variation of water with the temperature, the structural changes of small molecules, proteins, thermo-responsive polymers, and their interactions with water in aqueous solutions can be demonstrated. Furthermore, quantitative models between the spectra and the temperature or concentration can be established using the spectral variations of water and applied to determine the compositions in aqueous mixtures.

CONTROL OF POTENTIAL MUSSEL RECRUITMENT TAKING INTO ACCOUNT SOME ENVIRONMENTAL PARAMETERS IN SEVASTOPOL ESTUARINE ZONE

In 2020-2021, potential recruitment of the mussel Mytilus galloprovincialis was measured in Sevastopol estuarine waters with regard to temperature, salinity, and pH in three depth horizons 1–3, 7, and 11 m. Compared to the previous annual period in 2021, spring mussel recruitment at all depth horizons in-creased by an order of magnitude. This increase was preceded by a mild winter. Also in 2021, a decrease in salinity and an increase in the vertical variability of the thermohaline structure of water were observed. The obtained data may indirectly indicate the improvement of environmental conditions for mussel productivity increase in 2021. The necessity of improving the method of the control for mussel recruit-ment related to possible vertical migrations of its post-larvae is shown.

Temperature-Induced Change of Water Structure in Aqueous Solutions of Some Kosmotropic and Chaotropic Salts

The hydrogen bond structure of water was examined by comparing the temperature dependent OH-stretching bands of water and aqueous NaClO4, KClO4, Na2SO4, and K2SO4 solutions. Results called attention to the role of cations on top of the importance of anions determining the emerging structure of a multi-layered system consisting single water rings or multi-ring water-clusters.

Impact of Magnesium Salt on the Mechanical and Thermal Properties of Poly(vinyl alcohol)

The effects of magnesium salts with various anion species on the structure and properties of a poly(vinyl alcohol) (PVA) film were studied. The glass transition temperature of the PVA film increased following the addition of a magnesium salt. Furthermore, the salt greatly enhanced the modulus and yield stress and reduced the crystallinity of the film. These effects were attributed to the strong ion–dipole interactions between the magnesium salts and the PVA chains. The strength of interaction, i.e., the reduction of segmental motions, depended on the anion species in the following order: Mg(ClO4)2, MgBr2, MgCl2, Mg(CH3COO)2, and MgSO4. The order corresponded to the Hofmeister series, which predicts the ability to break the structure of water.

Hydrogen-Bonded Structure of Water in the Loop of Anchored Polyrotaxane Chain Controlled by Anchoring Density

Hydrogen-bonded network of water surrounding polymers is expected to be one of the most relevant factors affecting biocompatibility, while the specific hydrogen-bonded structure of water responsible for biocompatibility is still under debate. Here we study the hydrogen-bonded structure of water in a loop-shaped poly(ethylene glycol) chain in a polyrotaxane using synchrotron soft X-ray emission spectroscopy. By changing the density of anchoring molecules, hydrogen-bonded structure of water confined in the poly(ethylene glycol) loop was identified. The XES profile of the confined water indicates the absence of the low energy lone-pair peak, probably because the limited space of the polymer loop entropically inhibits the formation of tetrahedrally coordinated water. The volume of the confined water can be changed by the anchoring density, which implies the ability to control the biocompatibility of loop-shaped polymers.

EVALUATION OF THE FEATURES OF THE STRUCTURE OF WATER AND AQUEOUS SOLUTIONS NEAR A SOLID SURFACE

The paper evaluates changes in the structure of water and aqueous solutions of sodium chloride in the wall layer on the basis of dielectrometry and correlation analysis. It is shown that when the distance to the solid surface decreases, there is a multi-fold nonlinear decrease in the electrical capacitance and a nonlinear change in the Sr parameter, which characterizes the magnitude of the change in the electrical capacitance of the conduction fluid when the distance to the solid surface changes. The parameters used in the work (electric capacity of liquids and Sr ) can be used to evaluate the changes in the structural organization of aqueous solutions in the wall (boundary) layer and to interpret the processes occurring in the liquid layer at the interface of the solid – aqueous solution phases.