Thermal decomposition of poly(vinyl chloride) and chlorinated poly(vinyl chloride). I. ESR and TGA studies

Significant effort has been made in the past by many workers to investigate the mechanism of thermal decomposition of poly(vinyl chloride) (PVC). The presence and role of free radicals has been controversial in this regard. Our data on PVC and chlorinated PVC systems demonstrate the existence of macroradicals in the early stage of thermal decomposition under inert and oxidative atmospheres. Data from conventional thermogravimetric experiments are used in conjunction with the electron spin resonance findings.     

Photoelectron spectroscopy of azulenes

The photoelectron spectra of azulene and ten of its derivatives (halo-, methyl-, phenyl-, acetyl- and benzoylazulenes) are presented and assigned. Assignments based on a composite-molecule view are validated by computations (CNDO/S). Conjugative interactions in the phenylazulenes lead to an inversion of the usual order of the two phenyl group e_1g component orbitals. Many of the azulenes have very low ionization energies, and it is suggested that they constitute a class of excellent π-electron donor molecules.     

Enhanced photodegradation of methylene blue with alkaline and transition‐metal ferrite nanophotocatalysts under direct sun light irradiation

It is highly desired to synthesize low‐cost photocatalysts for the degradation of colored dyes to safeguard our environment for the future generations. Here, we report an extremely efficient and low‐cost synthesis of alkaline earth and transition‐metal ferrite photocatalysts (MgFe₂O₄, CaFe₂O₄, BaFe₁₂O₁₉, CuFe₂O₄, and ZnFe₂O₄) from their chloride salts and their applications for the degradation of methylene blue (MB) dye under UV–visible and direct sunlight irradiation. The as‐prepared photocatalysts displayed enhanced photoactivities under both conditions of irradiation. After calcination at 600°C, the photocatalytic degradation increased significantly, and 96 and 85% MB was removed with ZnFe₂O₄ under UV–visible and direct sunlight irradiation, respectively. Moreover, large amounts of hydroxyl free radicals were produced under both irradiation conditions, which participated in the degradation of MB. The enhanced photodegradation activities of these photocatalysts are attributed to their extended visible light absorption and low bandgaps. This work will provide a feasible route to the synthesis of efficient and low‐cost photocatalysts to utilize sunlight for environmental remediation.     

Selection of overwintering microhabitats used by the arctic woollybear caterpillar,Gynaephora groenlandica

In extreme environments such as the High Arctic, climatic conditions challenge physiological tolerance of insects resulting in prolonged dormancy and extended life cycles. Therefore, the selection of suitable microhabitats for overwintering is crucial. At two field sites on Ellesmere Island, we located hibernacula (silk overwintering structures) used by the Arctic woollybear caterpillar, Gynaephora groenlandica (W?cke) (Lepidoptera: Lymantriidae) during their 11 month dormancy. All hibernacula found were anchored to the base of rocks and were not associated with vegetation. Rocks may function to absorb solar radiation and re-radiate heat, accelerating localized snowmelt, thus allowing caterpillars to emerge as early as possible in spring to begin foraging. Temperatures experienced by G. groenlandica in hibernacula throughout the winter were well within their physiological tolerance range. During late summer aestivation, hibernaculum temperatures were similar to, but more stable than, nearby soil surface temperatures. Lower maximum daily hibernaculum temperatures during the warmest month (July) may reduce metabolic rates and provide some energy savings. Since hibernacula were not randomly distributed around rocks, this suggests that G. groenlandica key in on some feature of the hibernaculum site. The northeast orientation of hibernacula at Eastwind Lake corresponds to the leeward side of rocks. Therefore wind patterns may be important in hibernaculum site selection. Other potential cues that may guide selection of hibernacula sites remain unclear: no seasonal changes in preference for light or soil moisture were observed between active and dormant caterpillars, and thermotaxis could not be distinguished from thigmotaxis.