The age, growth, and fertility of two populations of
Ablepharus bivittatus
in the Talysh Mountains are presented. Altogether, 59 individuals were studied from two localities in the Ardabil Province, ...Iran, one being the village of Khanegah-e-Oliya in Namin region and the other the village of Majara in Khalkhal region. The age of the lizards was determined using skeletochronology. The average age in females was 3.6 ± 1.15 years (maximum of six years), in males 2.6 ± 1.24 (maximum of five years). The sections of tubular bones of many individuals were noted to have lines of arrested growth corresponding to hibernation and aestivation. Lizards grow intensely during the first three years of life, but then their growth slows down. Animals in the age groups of three years and older do not differ in body length. The age of pregnant lizards is 2–5 years, on average, 3.7 ± 0.91 years. The fertility of females does not depend on age.
This article focuses on new method to estimate biological activity of peat humic acids (HAs) using artificial neural network (ANN) to process spectroscopic measurements in infrared and visible ...ranges. Conventional approaches generally rely on biological models and direct detection of chemical substances related to bioactivity. These methods proved to be accurate and reliable, but at the expense of speed and simplicity.
Recently, a conception of quantitative structure-activity relationship (QSAR) has been introduced and successfully implemented to predict effects of HAs on toxicity of polycyclic aromatic hydrocarbons. Our research stems from this conception, but employs multilayer perceptron (MLP) model to improve overall performance. The developed MLP model allowed us to estimate biological activity of the complete vertical peat cores collected from oligotrophic peat bog, located in southern taiga zone of West Siberia (north-eastern spurs of the Great Vasyugan Mire, 56°58′ N 82о36’ E). In total, 42 samples taken from the cores were collected. The protocol included spectroscopy (in infrared and visible ranges) and biological model with peritoneal activated macrophages as a reference method to directly measure biological activity of HAs.
and discussion. Numerical experiments confirmed consistency of the measured and estimated bioactivity, coefficient of determination R2 = 0.97. These experiments also showed that the MLP model significantly outperforms conventional linear multiple regression models, mainly due to essential nonlinearity of structure-activity relationships.
Our research demonstrates that biological activity of HAs extracted from peat samples can be estimated using an artificial neural network model trained on infrared and visible spectra.
•Humic acids demonstrate highly variable bioactivity depending on chemical composition.•Biological activity of humic acids can be estimated using infrared spectrometry data.•The proposed screening method allows fast and inexpensive preselection of peat samples.
The reactivity and activation parameters for the ring-opening metathesis polymerization of eight norbornene esters in the presence of a N-chelating Hoveyda-Grubbs II type catalyst were determined ...using
in situ
1
H-NMR. The ester molecules differ in the structure of substituent and the location of ester groups. Kinetic studies have shown that effective polymerization constants and activation parameters highly depend on the monomer structures. It was demonstrated that the elongation of the aliphatic chain does not significantly affect the reactivity of the ester, but has a high impact on the activation parameters of the reaction. Branching of the aliphatic substituent has a significant influence on the reactivity and activation parameters. Furthermore, the orientation of the ester substituents in the norbornene ring substantially affects the activation parameters.
The reactivity and activation parameters for the ROMP of eight norbornene esters in the presence of a N-chelating Hoveyda-Grubbs II type catalyst were determined. Kinetic studies prove that these parameters highly depend on the monomer structures.
—The stress–strain properties of radiation-modified polydicyclopentadiene synthesized by the PolyHIPE technology are studied. The dependence of the tensile strength on the absorbed dose follows a ...complex pattern. A rise in the dependence in the low-dose region, that is, in the range from 10 to 40 kGy, may be associated with the predominance of radiation crosslinking over degradation. With the increase in the absorbed dose above 40 kGy, the test material generally behaves as predominantly destructuring. Experimentally detected are the signs of tensile strength recovery in the dose range from 20 to 40 kGy to the corresponding values for the unirradiated sample, which indicates the enhanced strength properties of the material. When comparing the values obtained for the material irradiated with a dose of 40 kGy and the unirradiated material, it is clear that the tensile strength decreases by just 5%. It is found that, in the dose range from 0 to 10 kGy, degradation reactions dominate, leading to a low content of the gel fraction. With a further increase in the radiation dose, the intensity of crosslinking of macromolecules becomes higher than the intensity of degradation, which leads to an increase in the proportion of the gel fraction. In the range of 30–50 kGy, the character of this dependence indicates that radiation crosslinking predominates over degradation and it is maximal at a dose of 40 kGy, as follows from a small amount of the dissolved part of the polymer.
The polymerization process of dicyclopentadiene using a multicomponent catalytic system based on bis(cyclopentadienyl)titanium dichloride and diethylaluminum chloride was studied. It was demonstrated ...that the application of an excess of the aluminum component leads to the formation of stable charged complexes of blue discoloration, which initiate cationic polymerization of dicyclopentadiene. Unstabilized thin layers of obtained polydicyclopentadiene undergo oxidation and structuring under atmospheric oxygen. Oxidation of polydicyclopentadiene films in air occurs slowly during several weeks and can be determined by the increase of carbonyl and hydroxyl adsorption bands in infrared spectra. Along with oxidation, cross-linking processes occur in polymers, which lead to a change in physical parameters of the layers, and more precisely to a decrease in the permeability of atmospheric oxygen through the layers. Consequently, this leads to the transition of the oxidation from a kinetic mode into a diffusive mode. Such structural changes do not occur in a polymer that was stabilized by adding an antioxidant.
The ring opening metathesis polymerization of dicyclopentadiene in the presence of ruthenium-based complexes is a facile way to introduce the fillers into resin bulk. The unexpanded microspheres used ...as fillers allow decreasing in polymer density. Optimum conditions were found that provide a balance between the expansion rate of microspheres and the curing rate of dicyclopentadiene. In addition, the impact of the type and concentration of microspheres on the density of the obtained polymers and their physical and mechanical properties was studied. The optimal content of microspheres, creating a good balance between lower density and properties, should be considered as 1%, while the optimal concentration to obtain the lowest density is 5%.
This article considers the thermodynamic aspects, thermo- and rheokinetics of
endo
-dicyclopentadiene polymerization in the presence of the original metathesis second Hoveyda-Grubbs catalyst with an
...N
-chelating ligand. The activation energy of
endo
-dicyclopentadiene polymerization was determined as 88.9–89.2 kJ/mol. The thermal effect of the ring-opening metathesis
endo
-dicyclopentadiene polymerization reaction reaches 52.7 kJ/mol. This is lower than the values for molybdenum- and tungsten-containing catalysts reported in the literature, which can be explained by a different microstructure of the polymer produced in the presence of ruthenium-based metathesis catalysts.
The stress–strain properties of polydicyclopentadiene synthesized by ring opening metathesis polymerization are studied depending on the absorbed dose and radiation type. The dependence of the ...ultimate strength on the absorbed dose has a complex nature. Signs of restoration of the ultimate strength of polydicyclopentadiene in the dose range from 0.4 and 0.7 MGy to the corresponding value of the unirradiated sample are revealed. The ultimate strength of the sample irradiated at a dose of 0.5 MGy is reduced by no more than 12% compared to the unirradiated sample. Other changes in the strength remain within 6.0–0.5%. Polydicyclopentadiene generally behaves as predominantly radiation-resistant. Regardless of the radiation type (electron beam or γ) and manufacturing method, polydicyclopentadiene has the ability to be crosslinked under irradiation. A hypothesis is proposed to explain processes occurring in the structure of the material.
The results of experimentally obtained data on the change in the physicomechanical properties of a thermosetting polymer with a unique complex of technically valuable properties are considered and ...analyzed. In the study of mechanical properties, the dependence of the tensile strength of radio-modified polydicyclopentadiene synthesized by the PolyHIPE technology on the dose was revealed. A study of the modification of the physicomechanical properties of the polymer showed an inhomogeneity in the dependence of the voltage change on deformation, observed when the samples were irradiated by electrons in the entire range of doses, at 50 kGy, this effect is most clearly represented. A reduction in the strength limit by 42% was established for irradiation. The growth of tensile stress in the dose range from 20 to 40 kGy was determined experimentally to the value for the unirradiated sample. A graph of the strain-force dependency family is presented for irradiation with different doses, irradiation with a dose of 40 kGy, the curve characterizes the change in the deformation properties of the material, despite a general decrease in the strength characteristics of the material.
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