The market value of essential oils is steadily increasing every year. They are mainly used as aromas and preservatives in food and cosmetics industries. The content and yield of the obtained extracts change across the seasons of the year. The knowledge of these differences is important for essential oils industry to gain the best quality and quantity of products. In this study Thuja occidentalis L. (Eng. northern white cedar) extract was obtained from leaves by maceration in dichloromethane. Plant material was collected during each season of the year and the finished products were thoroughly examined through GC-MS analysis. The seasonal variations of volatile compound composition showed that the most adequate period to obtain T. occidentalis extract on an industrial scale is spring. This is due to the best efficiency (almost 10%) and the highest content of monoterpenes (67%).

In the paper the idea of rational polynomial windows optimised towards low level of Fourier spectrum's sidelobes is presented. A relevant advantage of the polynomial windows family and their modifications is their ability to easily change their properties changing only the values of the polynomial coefficients. The obtained frequency characteristics demonstrate better properties of proposed rational Windows than their standard polynomial equivalents requiring only the additional division operation. Such approach does not increase the computational complexity in significant way and the great advantage of polynomial windows which is their low computational complexity is preserved.

The article depicts the personage of Karol Modzelewski (1937–2019) the outstanding activist for freedom of Poland, long-term political prisoner, prominent medievalist historian and full member of the Polish Academy of Sciences.