The deadwood contributes to an increase in soil heterogeneity due to the changing the microrelief (by the formation of windthrow-soil complexes), as well as changes in physical and chemical ...characteristics of decaying wood directly during xylolysis. We hypothesized that fallen logs as an element of microrelief influence the species composition and cover structure of vascular plants. We studied the influence of Picea abies (L.) Karst fallen logs of moderate and advanced decay stages on the horizontal distribution and heterogeneity of vascular plant cover in different microsite types (small boreal grass type, blueberry type, small boreal grass-blueberry type, herbs, and blueberry type) in old-growth middle taiga spruce forest in the Kivach State Nature Reserve (Republic of Karelia, Russia). The fallen deadwood acts as a factor of heterogeneity, causing reversible changes in the homogeneity of the original plant cover. The decaying logs influence the horizontal distribution of small herbs by changing the occurrence and density of shoots of Oxalis acetosella L., Maianthemum bifolium (L.) F.W. Schmidt, Vaccinium myrtillus L., and Vaccinium vitis-idaea L., as well as the occurrence of Luzula pilosa (L.) Willd. and Calamagrostis arundinacea (L.) Roth. Its impact on the heterogeneity parameters can be traced up to 20 cm from the log. The differences in vascular plant cover between fallen logs and the surrounding forest floor depend on the soil conditions of the microsite. The heterogeneity of conditions created by the logs smoothed out with increasing decay class, resulting in decreasing differences in the heterogeneity parameters of vascular plant cover between deadwood and forest floor. The changes in the homogeneity of the initial vascular plant cover by deadwood and the gradual smoothing of heterogeneity between the logs and the forest floor in rich and poor conditions have different, mainly opposite, trends. Finally, the structure of the vegetation cover reaches a state that is typical of particular growth conditions beyond deadwood.
•Ring-shaped crystallization is possible under the action of cylindrical light beams.•Cylindrical beams provide more uniform crystallization of GST225 than HG00 mode.•Images brightness analysis shows ...a gradual crystallization consistent with intensity.•Raman spectra study correlate with image brightness analysis.
Chalcogenide phase-change materials are promising for optical technologies, since they allow rapid (tens of nanoseconds) reversible switching between the amorphous and crystalline phase states characterized by significantly different electrical and optical parameters. In this work we experimentally studied the local optical transition of as-deposited amorphous Ge2Sb2Te5 thin films into the crystalline state under the action of structured continuous-wave laser beams. For cylindrical laser beams with an annular intensity profile obtained through the phase singularity or through the axially symmetric polarization distribution, significantly more efficient crystallization was observed in comparison with the commonly used fundamental Hermite–Gaussian HG00 mode. The numerical simulation showed that the annular intensity distribution results in a more uniform temperature profile inside the irradiated region, which is necessary for more uniform crystallization. To analyze the degree of crystallinity we used Raman spectroscopy and optical microscopy, enhanced with digital brightness filtering for characterization of the reflectance within the modified region.
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