Integrated methodology for gas content assessment and prediction in shallow muddy lake sediments: acoustic mapping and correlation analysis.

This paper provides a step-by-step description of integrated methodology for quantification and prediction of gas (methane, CH) content dynamics in shallow aquatic sediments under changing spatial and temporal conditions. Presence of gas bubbles even in small concentrations significantly affects sediment compressibility, which in turn decreases sound speed in sediment. Our integrated methodology consists of two basic steps.

Effect of an internal Kelvin wave on sound propagation in a coastal wedgea).

Spatiotemporal variability of the low-frequency sound field in a coastal wedge in the presence of an internal Kelvin wave (IKW) is studied both experimentally and theoretically. The experiments were carried out in Lake Kinneret, Israel (also known as the Sea of Galilee) in August 2021, with a wideband sound source deployed near the shore and receiving vertical line arrays located at the lake's center. Parameters of the IKW were obtained earlier from long-term thermistor string measurements combined with conductivity, temperature, and depth data.

Evaluation of Chemical and Biological Properties of Biodegradable Composites Based on Poly(3-hydroxybutyrate) and Chitosan.

In this study, composite films and scaffolds of polyester poly(3-hydroxybutyrate) and polysaccharide chitosan obtained via a simple and reproducible blending method using acetic acid as a solvent were considered. The degradation process of the films was studied gravimetrically in a model biological medium in the presence of enzymes in vitro for 180 days. The kinetics of weight reduction depended on the amount of chitosan in the composition.

Methane gas dynamics in sediments of Lake Kinneret, Israel, and their controls: Insights from a multiannual acoustic investigation and correlation analysis.

Methane (CH) is the simplest and most common hydrocarbon in nature. CH gas content is accommodated in discrete bubbles in shallow aquatic sediments. The bubble dynamics there are controlled by a diversity of physical, mechanical and biogeochemical processes that vary spatially and temporally over the aquatic ecosystem.

Chemical modification of chitosan for developing of new hemostatic materials: A review.

Uncontrolled bleeding that occurs during surgery, trauma, and in combat conditions is critical and require immediate action. Chitosan is a polysaccharide, obtained from natural sources with unique biological properties. It is often used as basis for local hemostatic agents (LHA).

New N-Methylimidazole-Functionalized Chitosan Derivatives: Hemocompatibility and Antibacterial Properties.

Novel imidazole derivatives of the low molecular weight chitosan N-(2-hydroxypropyl)-1H-1,2,3-triazol-4-yl)methyl)-1-methyl-1H-imidazol-3-ium chitosan chloride (NMIC) were synthesized using copper-catalyzed azide-alkyne cycloaddition (CuAAC). The degrees of substitution (DSs) for the new derivatives were 18-76%. All chitosan derivatives (2000 µg/mL) were completely soluble in water.

Synthesis of Selenium Nanoparticles Modified by Quaternary Chitosan Covalently Bonded with Gallic Acid.

Quaternary chitosan derivative with covalently bonded antioxidant (QCG) was used as media for synthesis of selenium nanoparticles (SeNPs). SeNPs were characterized using AFM, TEM, and DLS methods. The data confirmed the formation of stable nanoparticles with a positive charge (34.

Effect of Seed Priming with Chitosan Hydrolysate on Lettuce () Growth Parameters.

Seed priming increases germination, yield, and resistance to abiotic factors and phytopathogens. Chitosan is considered an ecofriendly growth stimulant and crop protection agent. Chitosan hydrolysate (CH) is an unfractionated product of hydrolysis of high-molecular-weight crab shell chitosan with a molecular weight of 1040 kDa and a degree of deacetylation of 85% with nitric acid.

Investigation of the Antioxidant Properties of the Quaternized Chitosan Modified with a Gallic Acid Residue Using Peroxidase that Produces Reactive Oxygen Species.

Chitosan modified with a (2-hydroxy-3-trimethylammonium) propyl group and gallic acid residue, or quaternized chitosan with gallic acid (QCG), was synthesized. Antioxidant properties of the produced QCG have been investigated. Peroxidase in combination with NADH and salicyl hydroxamate (SHAM) caused consumption of oxygen and production of H2O2 in aqueous solution as a result of O2 reduction in the peroxidase-oxidase reactions.

Modeling underwater sound propagation in an arctic shelf region with an inhomogeneous bottom.

The seabed data from the Kara Sea (a part of the Arctic Shelf) are used to build a low-frequency (up to 250 Hz) acoustic waveguide model and study sound propagation in this region. A 30-m deep, well-mixed, and homogenous water layer over a flat seafloor is considered. The seabed's acoustic model is based on the spatial distribution of a sound speed recorded during a three-dimensional seismic survey in the Kara Sea, as well as density data from core sample analysis.

Simple method for ultrasound assisted «click» modification of azido-chitosan derivatives by CuAAC.

New quaternized chitosan derivatives HT-TMC were synthesized as a result of copper catalyzed azide-alkyne [3 + 2] cycloaddition (CuAAC). The structure of the HT-TMC was verified by 2D NMR. The synthesis was carried out as a result of the formation of Cu(I) in situ, under the action of ultrasound in aerobic conditions in the presence of acetic acid and metallic copper (copper turnings).

Collagen/Chitosan Gels Cross-Linked with Genipin for Wound Healing in Mice with Induced Diabetes.

Diabetes mellitus continues to be one of the most common diseases often associated with diabetic ulcers. Chitosan is an attractive biopolymer for wound healing due to its biodegradability, biocompatibility, mucoadhesiveness, low toxicity, and hemostatic effect. A panel of hydrogels based on chitosan, collagen, and silver nanoparticels were produced to treat diabetic wounds.

Antifungal action of chitosan in combination with fungicides in vitro and chitosan conjugate with gallic acid on tomatoes against Botrytis cinerea.

In the present work, a positive effect was obtained by using low molecular weight chitosan compounds in combination with synthetic fungicides. Antifungal activity against Botrytis cinerea, determined by the radial growth method, was more than 75%, with a 25 × 10 g/L concentration of fludioxonil or difenoconazole in compounds. Metabolic activity of B.

Using discrete low-frequency components of shipping noise for gassy sediment characterization in shallow water.

This work shows that normal-mode attenuation coefficients can be extracted from ship noise and used to estimate the sound speed in gas-saturated sediments. In an experiment in the Sea of Galilee, a research vessel served as a noise source approaching a vertical hydrophone array at a constant speed. Twelve narrow-band components of the vessel noise in the frequency band 20-100 Hz were identified and mode filtered to estimate the normal-mode attenuation coefficients.

Hemocompatibility of Silver Nanoparticles Based on Conjugate of Quaternized Chitosan with Gallic Acid in In Vitro Experiments.

We studied hemocompatibility of silver nanoparticles synthesized on the basis of a conjugate of quaternized chitosan with gallic acid (QChit-Gal). For the three variants of silver particles (Nos. 1, 2, and 3), the QChit-Gal:AgNO ratio was 5:1, 5:3, and 1:1, respectively.

Chitin/Chitosan and Its Derivatives: Fundamental Problems and Practical Approaches.

In this review, we present the data on the natural occurrence of chitin and its partially or fully deacetylated derivative chitosan, as well as their properties, methods of modification, and potential applications of derivatives with bactericidal, fungicidal, and antioxidant activities. The structure and physicochemical characteristics of the polymers, their functions, and features of chitin microbial synthesis and degradation, including the processes occurring in nature, are described. New data on the hydrolytic microorganisms capable of chitin degradation under extreme conditions are presented.

Synthesis of silver nanoparticles using gallic acid-conjugated chitosan derivatives.

In presented study, various chitosan derivatives containing covalently bounded gallic acid were obtained: chitosan with gallic acid (CG), quaternized chitosan with gallic acid (QCG), and succinylated chitosan with gallic acid (SCG). Chitosan derivatives were used as stabilizing and reducing agents in the synthesis of silver nanoparticles (AgNPs). The dimensional characteristics of nanomaterials were determined by transmission electron (TEM), dynamic light scattering (DLS) and atomic force (AFM) microscopy, antibacterial activity (against E.

Investigation of the properties of N-[(2-hydroxy-3-trimethylammonium) propyl] chloride chitosan derivatives.

N-[(2-Hydroxy-3-Trimethylammonium) Propyl] Chitosan Chloride Derivatives (HTCC), based on low molecular weight crab chitosan, were synthesized by the alkylation reaction with a degree of substitution of 10-98%. The chemical structure was confirmed by H NMR and IR-spectra. Physical and chemical characteristics and a number of properties were defined.

Interference pattern of the sound field in the presence of an internal Kelvin wave in a stratified lake.

Internal Kelvin waves (IKWs) initiated by rotation of the Earth are one of the main hydrodynamic phenomena in large stratified lakes where baroclinic Rossby radius of deformation is smaller than the horizontal scale of the lake. IKWs can be identified using the spectra of internal waves, where in the presence of IKWs, the inertial frequency is at maximum. IKWs play a rather important role in the lake's dynamics for different processes, both in the water layer and sediment, especially at the periphery of lake.

Modeling the effects of linear shallow-water internal waves on horizontal array coherence.

The coherence length of a horizontal array is the maximum separation between two points where coherent processing gives useful gain when a distant source is at broadside. In shallow water, the coherence length is limited by the environmental variability caused by several relevant oceanographic processes. In the present study, a statistical model is developed that quantifies how one oceanographic process, linear internal waves, affects the coherence length.

[Individual porosity characteristics of human tubular bones].

The diaphyses of the tubular bones of seven men aged 40-60 years without the bone pathology were studied. Porosity characteristics of the compact substance were measured in the tibia and the humerus bones by the method of centrifugal porometry. This method is based on the filling of the objects studied with the wetting fluid and sequential removal of it by the centrifugation at increasing values of the centrifugal acceleration; as a result, the values of the radii of the pores and the respective distribution function of the pore volume could be obtained.

[The diameters of the central canals of the osteons in tubular bones (based on data from scanning electron microscopy and centrifugal porosimetry)].

The centrifugal poremetry is based on preliminary filling the pores of prepared samples with the working fluid and the following removal of it from the pores at different fixed velocities of rotation. Measurement of the quantity of the remaining fluid after each rotation allows obtaining the distribution of the pore volume depending on their radius. Since the samples are not destroyed they can be used for measuring the pores diameter in electron micrograph.