In this article, gold is analyzed from an investment perspective as an asset that allows you to increase your wealth. The analysis is twofold. First, it is about examining to what extent changes in gold prices in the world markets translate into changes in the prices of shares of companies that extract gold. Second, it was checked whether there is a financial leverage effect, which in this case means that changes in the price of shares of gold mining companies are greater than changes in the price of gold itself. Methodically, the Sharpe model was used and two basic parameters of the model were estimated, i.e. the intercept (alpha), and the beta coefficient as a measure of systematic risk, for the gold market and the equity market of gold mining companies and ET Fs based on these companies.
The research carried out in accordance with the logic of the Sharpe model shows that the obtained value of the alpha parameter for the stock market was positive, while for the gold market it was negative. At the same time, higher levels of this parameter are beneficial to the investor, which means that an advantage of the stock market over the gold market exists. In turn, the estimated beta for the stock market is much lower than for the gold market. The systematic risk level for stocks is 0.45, and for the gold market it is 1.98, which is a significant difference. The stocks of gold mining companies can be classified as defensive against the stock market (the rate of return of the gold mine stock is insensitive to market movements) and aggressive against the gold market (the rate of return of the gold mine shares reacts more strongly than the movement in the price of gold).

Artificial roughness has been found to enhance the thermal performance from the collector to air in the solar air heater duct. This paper presents the results of experimental investigation on thermal performance of three sides solar air heater roughened with combination of multiple-v and transverse wire. The range of variation of system and operating parameters is investigated within the limits of relative roughness pitch of 10−25, relative roughness height of 0.018−0.042, angle of attack of 30°−75° at varying flow Reynolds number in the of range of 3000−12000 for fixed value of relative roughness width of 6. The augmentation in fluid temperature flowing under three side’s roughened duct is found to be 36.57% more than that of one side roughened duct. The maximum thermal efficiency is obtained at relative roughness pitch of 10 and relative roughness height of 0.042, and angle of attack of 60°. The augmentation in thermal efficiency of three sides over those of one side roughened duct is found to be 46−57% for varying values of relative roughness pitch, 38−50% for varying values of relative roughness height, and 40−46% for varying values of angle of attack.

Duringthe evolution organisms are subjected to the continuous impact of environmental factors. In recent years an increasing number of studies have focused on the physicochemical limits of lifeon Earthsuch as temperature, pressure, drought, salt content, pH, heavy metals, etc. Extreme environmental conditions disrupt the most important interactions that support the function and structure of biomolecules.Forthis reason,organisms inhabiting extreme habitats have recently become of particularlygreat interest. Although filamentous fungi are an important partof the polar ecosystem, information about their distribution and diversity, as well as their adaptation mechanisms, is insufficient. In the present study,the fungal strain Penicillium griseofulvum isolated from an Antarctic soil sample was used as a study model. The fungal cellular response against short term exposure to low temperature was observed. Our results clearly showed that short-term low temperature exposure caused oxidative stress in fungal cells and resulted in enhanced level of oxidative damaged proteins, accumulation of reserve carbohydrates and increased activity of the antioxidant enzyme defence. Ultrastructural changes in cell morphology wereanalysed. Different pattern of cell pathology provoked by the application of two stress temperatures was detected. Overall, this study aimed to observe the survival strategy of filamentous fungi in extremely cold habitats, and to acquire new knowledge about the relationship between low temperature and oxidative stress.