Investigation of Gelation Techniques for the Fabrication of Cellulose Aerogels.

Because of the pronounced degradation of the environment, there has been an escalated demand for the fabrication of eco-friendly and highly efficient products derived from renewable sources. Cellulose aerogels have attracted significant interest attributable to their structural characteristics coupled with biodegradability and biocompatibility. The features of the molecular structure of cellulose allow for the use of various methods in the production of gels. For instance, the presence of hydroxyl groups on the cellulose surface allows for chemical crosslinking via etherification reactions. On the other hand, cellulose gel can be procured by modulating the solvent power of the solvent. In this study, we investigate the impact of the gelation methodology on the structural attributes of aerogels. We present methodologies for aerogel synthesis employing three distinct gelation techniques: chemical crosslinking, cryotropic gelation, and CO2-induced gelation. The outcomes encompass data derived from helium pycnometry, Fourier-transform infrared spectroscopy, nitrogen porosimetry, and scanning electron microscopy. The resultant specimens exhibited a mesoporous fibrous structure. It was discerned that specimens generated through cryotropic gelation and CO2-induced gelation manifested higher porosity (93-95%) and specific surface areas (199-413 m2/g) in contrast to those produced via chemical crosslinking (porosity 72-95% and specific surface area 25-133 m2/g). Hence, this research underscores the feasibility of producing cellulose-based aerogels with enhanced characteristics, circumventing the necessity of employing toxic cross-linking agents. The process of gel formation through chemical crosslinking enables the creation of gels with enhanced mechanical properties and a more resilient structure. Two alternative methodologies prove particularly advantageous in applications necessitating biocompatibility and high porosity. Notably, CO2-induced gelation has not been hitherto addressed in the literature as a means to produce cellulose gels. The distinctive feature of this approach resides in the ability to combine the stages of obtaining an aerogel in one apparatus.

Tunable in situ near-UV pulses by transient plasmonic resonance in nanocomposites.

We propose a concept for generation of ultrashort pulses based on transient field-induced plasmonic resonance in nanoparticle composites. Photoionization and free-carrier plasma generation change the susceptibility of nanoparticles on a few-femtosecond scale under the action of the pump pulse. This opens a narrow time window when the system is in plasmonic resonance, which is accompanied by a short burst of the local field. During this process, frequency-tunable few-fs pulses can be emitted. This paves a way to ultra-compact yet efficient generation of ultrashort pulses at short wavelengths.

Physical, Mechanical, and Structural Properties of the Polylactide and Polybutylene Adipate Terephthalate (PBAT)-Based Biodegradable Polymer during Compost Storage.

Today, packaging is an integral part of any food product, preserving its quality and safety. The use of biodegradable packaging as an alternative to conventional polymers reduces the consumption of synthetic polymers and their negative impacts on the environment. The purpose of this study was to analyze the properties of a biodegradable compound based on polylactide (PLA) and polybutylene adipate terephthalate (PBAT). Test samples were made by blown extrusion. The structural, physical, and mechanical properties of the PLA/PBAT material were studied. The property variations during compost storage in the lab were monitored for 365 days. The physical and mechanical properties were measured in accordance with the GOST 14236-2017 (ISO 527-2:2012) standard. We measured the tensile strength and elongation at rupture. We used attenuated total reflectance Fourier transform infrared microscopy (ATR-FTIR) to analyze the changes in the material structure. This paper presents a comparative analysis of the strengths of a biodegradable material and grade H polyethylene film (manufactured to GOST 10354-82). PLA/PBAT's longitudinal and transverse tensile strengths are 14.08% and 32.59% lower than those of LDPE, respectively. Nevertheless, the results indicate that, given its physical and mechanical properties, the PLA/PBAT material can be an alternative to conventional PE film food packaging. The structural study results are in good agreement with the physical and mechanical tests. Micrographs clearly show the surface deformations of the biodegradable material. They increase with the compost storage duration. The scanning microscopy (SEM) surface analysis of the original PLA/PBAT films indicated that the PLA structure is similar to that of a multilayer shell or sponge, which is visible at medium and especially high magnification. We conclude that PLA/PBAT-based biodegradable materials are potential substitutes for conventional PE polymer films.

Ca2+-dependent oxidation of exogenous NADH and NADPH by the mitochondria of spring wheat and its relation with AOX capacity and ROS content at high temperatures.

Mitochondria are sources of reactive oxygen species (ROS) in a plant cell under high temperature. Mitochondrial alternative NAD(P)H dehydrogenases (type II NAD(P)H DHs) and cyanide-resistant oxidase (AOX) can regulate ROS production, but their role at high temperatures is unknown. This study investigates the influence heat acclimation (37 °C) and heat shock (50 °C) temperatures on ROS content, activity and protein abundance of external Ca2+-dependent NAD(P)H DHs (NDB) and AOX in mitochondria of 4- and 8-day-old seedlings of spring wheat (Triticum aestivum L., var. Novosibirskya 29). The shoots of 4-day-old seedlings contained more carbohydrates, had a higher rate of total respiration and a high rate of oxidation of exogenous NADH, a greater AOX capacity and a lower of ROS content, as compared to leaves of 8-day-old seedlings, and were more resistant to heat shock. The activity of external NADH DH was higher than the one of NADPH DH in mitochondria of both shoots and leaves. At 37 °C, high NADH oxidation was associated with increased AOX capacity in mitochondria of both shoots and leaves, whereas NADPH oxidation with COX capacity. At 50 °C, the NADPH oxidation by shoots' mitochondria increased and the NADH oxidation stayed high. The content of NDB and AOX proteins depends on heat treatments and differs between mitochondria of shoots and leaves. Our data indicate that Ca2+-dependent type II NAD(P)H DHs can regulate the ROS content and together with AOX are involved in heat tolerance, depending on the development phase of spring wheat and is, probably, tissue-specific.

Microscopic and Structural Studies of an Antimicrobial Polymer Film Modified with a Natural Filler Based on Triterpenoids.

The aspects of component visualization of the antimicrobial triterpenoids (betulin) additive, both on the surface and in the bulk of the polymer, constituting food film packaging, are considered. This paper presents new knowledge about the morphology and surface structure of modified films using three independent methodological approaches: optical microscopy; a histological method adapted to packaging materials; and a method of attenuated total internal reflection (ATR) spectroscopy in the infrared region with Fourier transform. The use of these methods shows the betulin granules, individual or forming chains. To visualize the antimicrobial additive in the polymer bulk, a modified histological method adapted for film materials and attenuated total internal reflection (ATR) spectroscopy in the infrared region were used with Fourier transform using a Lumos Bruker microscope (Germany) (ATR crystal based on germanium). Sample sections were analyzed using Leica 818 blades at an angle of 45 degrees. The histological method consists of the study of a biological object thin section, in the transmitted light of a microscope, stained with contrast dyes to reveal its structures, and placed on a glass slide. In the method modified for the present study, instead of a biological one, a synthetic object was used, namely the developed film materials with the addition of natural organic origin. Individual granules are about 2 µm long; chains can be up to 10 µm long. The thickness of the granules ranged from 1 to 1.5 microns. It can be seen that the depth distribution of granules in the film from the inner surface to the outer one is rather uniform. Spectroscopic studies using the method of automatic ATR mapping in the region of 880 cm-1 made it possible to evaluate the distribution of an antimicrobial additive based on triterpenoids on the surface and in the polymer bulk.

High-intensive femtosecond singular pulses in Kerr dielectrics.

The nonlinear dynamics of a high-power femtosecond singular pulse in Kerr media are analyzed numerically upon optically induced ionization. We examine the plasma inertia impact to stable propagation of optical vortices. Multifoci behavior of vortices in medium are revealed. Next we numerically demonstrate that inertial character of plasma formation provides a quasi-soliton regime of vortex propagation resistant to symmetry-breaking perturbation.

Mesenchymal stem cells transplantation could be beneficial for treatment of experimental ischemic stroke in rats.

Cell therapy is prospective, modern attempt to ischemic stroke treatment. It has been being widely worked out recently. We suggest mesenchymal stem cells (MSC) as a cell therapy agent in the therapy of this disease. Experiments were carried out in inbred male Wistar-Kyoto rats. Animals were subjected to middle cerebral artery occlusion (MCAO). MSCs were isolated from rat bone marrow, expanded in culture and labelled with vital fluorescent dye PKH-26. Then 5 x 10(6) cells were injected into the tail vein on the day of MCAO and three days later. Control group animals received PBS injection (negative control). Cognitive function restoration was estimated by Morris Water Maze testing during 6 weeks after MCAO. Animals were sacrificed 1, 2, 3, 5 days and 1, 2, 4 and 6 weeks after operation. Intravenous MSC transplantation decreased post-operation mortality and benefited behavioural and neurological recovery. Experimental groups animals revealed changes in aseptic inflammation processes which were completed faster comparing to control group. That effect correlated with accelerated glial scar formation. Reduction of the infarct volumes and such post-stroke after-effects as border zone gliosis and liquor cysts formation accompanied by increased angiogenesis and subventricular zone cells proliferation were shown after cell therapy. The obtained results referred to both cell therapy groups. Thus, MSC injection benefited post-stroke rehabilitation irrespective of transplantation time. However, further investigation should be carried out in order to find out the mechanism of their action.