Two reasons for the appearance of pushed wavefronts in the Belousov-Zhabotinsky system with spatiotemporal interaction

We prove the existence of the minimal speed of propagation $c_*(r,b,K) \in [2\sqrt{1-r},2]$ for wavefronts in the Belousov-Zhabotinsky system with a spatiotemporal interaction defined by the convolution with (possibly, "fat-tailed") kernel $K$. The model is assumed to be monostable non-degenerate, i.e. $r\in (0,1)$. The slowest wavefront is termed pushed or non-linearly determined if its velocity $c_*(r,b,K) > 2\sqrt{1-r}$. We show that $c_*(r,b,K)$ is close to 2 if i) positive system's parameter $b$ is sufficiently large or ii) if $K$ is spatially asymmetric to one side (e.g. to the left: in such a case, the influence of the right side concentration of the bromide ion on the dynamics is more significant than the influence of the left side). Consequently, this reveals two reasons for the appearance of pushed wavefronts in the Belousov-Zhabotinsky reaction.Comment: 22 pages, submitte

Effect of Wood Hemicellulose Composition on Binding Interactions with Caffeine

Wood is one of the important construction materials and it is necessary to protect it from biological pests. Hemicellulose in wood consist of various sugar hexoses or pentoses depending on the tree species. This composition can have significant effects on interactions with chemical substance as biocides or coatings. Interactions of glucose, arabinose, mannan, galactomannan, glucogalactomannan, xylan, and hemicellulose corresponding its structure in spruce, pine and beech with biocidal substance caffeine was studied in the present study. Chemical analyses were performed spectrometrically at the caffeine optimal wavelength of 287 nm. The results indicate variable rate of interactions between caffeine and the tested sugar monomers or polymers. The largest interactions between caffeine were observed for simple sugars glucose (71%) and arabinose (67%). Mannan and hemicellulose composted of mannan units had very low interactive potential with caffeine (1–9%), the models of woody plants showed no statistically significant difference (25–30%). Nevertheless, hemicellulose in some previous research showed less potential to bind caffeine than lignin, but greater than completely inactive cellulose. It is evident that the structure of individual sugars and their mixture in polymer hemicellulose has effects on binding interactions with caffeine; however, other research in this area will be necessary in the future

Těžké kovy v drobných městských tocích a jejich význam

21722

Academic procrastination and factors contributing to its overcoming

Procrastination is generally understood as the practice of irrationally putting activities or tasks off to a later time. In the case of academic procrastination, it is a tendency to put off academic tasks. The main objective of the presented research study was to map strategies of Slovak university students used for overcoming academic procrastination, as well as to test the relationship of procrastination with potential protective factors-volitional regulation and achievement motivation. Based on the results of our research, strategies of social motivation and positive attitude are, on average, the most frequently used to overcome academic procrastination. Results of the research also confirmed a negative correlation of procrastination with volitional regulation and its dimensions, as well as with some dimensions of achievement motivation

Vazebné chování vybraných kovů v sedimentu stoky a ovlivněného recipientu

11211

Identification of biofilm composition covering lime-based materials

This paper aims at identification of biofilms composition taken from lime and lime-cement plasters. The samples of plasters were exposed to natural weathering for more than three years to weather conditions of Prague as a representative of Central European continental climate. After biofilms sampling, they were cultivated using specific nutrient solutions and analysed using various types of microscopes. It was found, that the plasters were covered mostly by green algae (Hematococcus pluvialis, Klebsormidium sp., Trebouxiophyceae, Chlorophyceae and Chlorellaceae), cyanobacteria (Nostoc, Anabaena, Leptolyngbya, Phormidium, Plectonema, Synechococcales and Oscillatoriale), moulds (Aspergillus niger, Alternaria) and moss (Ceratodon purpureus). Possible influence of these organisms on hygrothermal behaviour of the base materials is subsequently discussed