Calculation of the surface energy of homo- and copolymers from the cohesion parameters and refractometric characterisics of the respective monomers

The results of investigations begun more than ten years ago, on a new type of inhibitors of thermal-oxidative degradation of polymers, namely polyarylenealkylenes and their hydroperoxides, are discussed. A comparative assessment of the reactivity of polyarylenealkylenes in liquid and viscous media is given. The nature of the inhibiting effect of polyarylenealkylenes in thermal degradation of polymers, and the reason for the high thermal stability of poly(alkyl methacrylates) obtained by polymerization of the monomers in the presence of polyarylenealkylene hydroperoxides as initiators, are discussed. The evidence obtained enables a fresh look to be taken at the reactivity of arylenemethylene groups in free radical reactions, where there is hindrance to access of the hydrogen donor.

Free radical reactions of polyarylenealkylenes and their hydroperoxides. Review

The data set presented represents 15 years of collection. It contains tree-ring width measurements from 64 sites of living trees and ten historical chronologies based on archaeological and construction wood up to year 572 CE, altogether 2909 tree-ring series and more than 450000 measured and cross-dated tree rings. It covers the vast territory of European Russia, including its forested northern and central parts, and the Northern Caucasus mountains. The potential use of these data include climatic reconstructions of regional and hemispheric scale, dendrochronological dating of historical and cultural wood, ecological and remote sensing studies. 

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Tree-ring data set for dendroclimatic reconstructions and dendrochronological dating in European Russia

After high temperature oxidation in air, polyarylene methylenes are able to inhibit liquid phase processes of radical polymerization and oxidation of cumene. Polyarylene ethylenes oxidized in air do not have a similar effect. This behaviour is based on various products of thermal of oxidizing breakdown of polyarylene alkylenes. Heat treatment of polyphenoxy phenylene alkylenes in vacuum, in contrast to other polyarylene alkylenes, also results in an ability to inhibit liquid phase processes, which is evidently due to processes of regrouping.

Effect of heat treatment on the reactivity of polyarylene alkylenes

Radial tree growth is sensitive to environmental conditions, making observed growth increments an important indicator of climate change effects on forest growth. However, unprecedented climate variability could lead to non‐stationarity, that is, a decoupling of tree growth responses from climate over time, potentially inducing biases in climate reconstructions and forest growth projections. Little is known about whether and to what extent environmental conditions, species, and model type and resolution affect the occurrence and magnitude of non‐stationarity. To systematically assess potential drivers of non‐stationarity, we compiled tree‐ring width chronologies of two conifer species, Picea abies and Pinus sylvestris, distributed across cold, dry, and mixed climates. We analyzed 147 sites across the Europe including the distribution margins of these species as well as moderate sites. We calibrated four numerical models (linear vs. non‐linear, daily vs. monthly resolution) to simulate growth chronologies based on temperature and soil moisture data. Climate–growth models were tested in independent verification periods to quantify their non‐stationarity, which was assessed based on bootstrapped transfer function stability tests. The degree of non‐stationarity varied between species, site climatic conditions, and models. Chronologies of P. sylvestris showed stronger non‐stationarity compared with Picea abies stands with a high degree of stationarity. Sites with mixed climatic signals were most affected by non‐stationarity compared with sites sampled at cold and dry species distribution margins. Moreover, linear models with daily resolution exhibited greater non‐stationarity compared with monthly‐resolved non‐linear models. We conclude that non‐stationarity in climate–growth responses is a multifactorial phenomenon driven by the interaction of site climatic conditions, tree species, and methodological features of the modeling approach. Given the existence of multiple drivers and the frequent occurrence of non‐stationarity, we recommend that temporal non‐stationarity rather than stationarity should be considered as the baseline model of climate–growth response for temperate forests.

Ecological and methodological drivers of non‐stationarity in tree growth response to climate

A study was made of the structure and molecular weight of polyarylene alkylenes (PAA) and the presence of functional groups on inhibiting activity under conditions of thermal oxidative breakdown of PMMA. The inhibiting activity of PAA was evaluated in comparison with other inhibitors, according to weight loss under isothermal conditions using DTA and TGA.

Inhibition of thermal oxidative breakdown of polymethylmethacrylate with polyarylene alkylenes

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T.S. Bebchuk

Papers

Inhibition of thermal oxidative breakdown of polymethylmethacrylate with polyarylene alkylenes

Tree-ring data set for dendroclimatic reconstructions and dendrochronological dating in European Russia

Tree-ring data set for dendroclimatic reconstructions and dendrochronological dating in European Russia