Comparative screening of the anti-oxidant and antimicrobial activities of Sempervivum marmoreum L. extracts obtained by various extraction techniques

This paper presents a comparative study of the anti-oxidant and anti-microbial activities, total phenolic compounds and total flavonoids in extracts obtained from houseleek (Sempervivum marmoreum L.) leaves by the classical (maceration), ultrasonic and Soxhlet extraction (CE, UE and SE, respectively). The extract obtained by the CE contained higher amounts of phenolic and flavonoid compounds and showed a better antioxidant activity than those obtained using other two techniques. All the extracts, independent of the extraction technique applied, showed antimicrobial activities against Aspergillus niger and Candida albicans only but not against the tested bacteria

PHENOLIC COMPOUNDS CONTENT AND RADICAL SCAVENGING CAPACITY OF WHEAT-LENTIL DOUGH

The lentil (Lens culinarisL.) is a legume plant, one of the oldest known food crops and medicinal plants. The health benefits of lentil are well known: its consumption reduces the risks of cardiovascular diseases and some cancers. It has a low glycemic food index and is important in the dietary treatment of diabetes mellitus.Unfortunately, its consumption in many countries is low. Since bread is a daily consumed food this can be improved by adding the lentil in wheat flour. In this paper the content and DPPH (2,2-diphenyl-1-picrylhydrazyl) scavenging capacity of phenolic compounds from wheat dough and dough obtained by wheat flour supplemented with 40% of lentil flour were examined and compared. The dough with lentil flour had higher content of phenolic compounds than the dough with wheat flour only (2144.7 and 1592.5 g of chlorogenic acid/g, respectively) and achieved higher DPPH scavenging capacity (SC50 value was 21.2 and 56.3 mg/mL, respectively). Results showed that, after baking, the dough retained the same value of DPPH scavenging capacity, while baked wheat-lentil dough had near three times higher antioxidant activity than baked wheat dough. These investigations indicate that the lentil flour is useful food ingredient for improving the antioxidative potential of wheat flour.Key words: Lentil, dough, phenolic compound, scavenging capacit

Procedure for selecting the low alloy-tempered steel for manufacturing the responsible highly loaded parts

The procedure for selecting the optimal material for manufacturing the highly loaded responsible parts is presented in this paper. The proper selection of material can be done exclusively based on the theoretical and experimental analysis of properties of steel in question. The theoretical and experimental selecting of adequate steel for manufacturing the machine parts is done based on requirements arising from their working conditions. Based on the available data for various steels, chemical composition, mechanical and technological properties, available CCT diagram, the optimal steel was selected for the given working conditions. After the selection of the material, experimental investigations were conducted on specially prepared material samples. The real chemical composition of material was established, its most important mechanical properties were determined, the hardness was measured and the microstructure was determined, as well. After the conducted theoretical and experimental investigations, the responsible machine part was manufactured by forging. Then, the mechanical and heat processing was executed, after which the part was tested in the real working conditions. Based on investigations of part's behavior in the real working conditions it was concluded that the selection of the material was adequate.Publishe

Selecting the low alloy-tempered steel for manufacturing the highly loaded responsible parts

The selecting procedure of the optimal material for manufacturing the highly loaded responsible parts for military applications is presented in this paper. The considered part is in exploitation subjected to complex compressive-impact loading and cyclically to high temperatures, as well. The proper selection of material can be done exclusively based on the theoretical and experimental analysis of properties of the steel in question. The theoretical and experimental selecting of adequate steel for manufacturing such parts is done based on requirements arising from their working conditions. Based on the available data for various steels, chemical composition, mechanical and technological properties, available CCT diagram, the optimal steel was selected for the given working conditions. After the selection of the material, experimental investigations on specially prepared material samples were conducted. The real chemical composition of material was established, its most important mechanical properties were determined, the hardness was measured and the microstructure was determined, as well. After the conducted theoretical and experimental investigations, the responsible machine part was manufactured from the selected material by forging. Then, the mechanical and heat processing was executed, after which the part was tested in the real working conditions. Based on investigations of part's behavior in the real working conditions, it was concluded that the selection of the material was adequate.This research was partially financially supported by the European regional development fund and Slovak state budget by the project “Research Centre of the University of Zilina” – ITMS 26220220183 and by the Ministry of Education, Science and Technological Development of Republic of Serbia through grants: ON174004 and TR35024.Publishe

THEORETICAL-EXPERIMENTAL ESTIMATION OF WELDABILITY OF DIFFERENT TYPES OF STEELS BY HARD FACING

U ovom radu razmatra se zavarljivost ugljeničnih i legiranih čelika primenom navarivanja. U teorijskom delu rada istaknuti su načelni principi vezani za zavarljivost, spomenute su najvažnije metode ispitivanja zavarljivosti i prikazan je način procene zavarljivosti. U eksperimentalnom delu analizirana su dva ugljenična i dva legirana čelika navarena različitim dodatnim materijalima. Posle navarivanja pripremljeni su uzorci za merenje tvrdoće i analizu mikrostrukture specifičnih zona navara. Zavarljivost analiziranih čelika je određena na osnovu sprovedenih ispitivanja tvrdoće i mikrostrukture i upoređena je sa teorijskom procenom.Zahvaljujemo se kompaniji Alfa Technics d.o.o iz Svilajnca koja je obezbedila sav potreban osnovni i dodatni materijal za navarivanje, kao i materijalne i ljudske resurse neophodne za pripremu i ispitivanje uzoraka.Publishe

Tehnologija obrade metala rezanjem, Izbor režima obrade

Publishe

Ozone absorption in a mechanically stirred reactor

Ozone absorption in water was investigated in a mechanically stirred reactor, using both the semi-batch and continuous mode of operation. A model for the precise determination of the volumetric mass transfer coefficient in open tanks without the necessity of the measurement the ozone concentration in the outlet gas was developed. It was found that slow ozone reactions in the liquid phase, including the decomposition of ozone, can be regarded as one pseudo-first order reaction. Under the examined operating conditions, the liquid phase was completely mixed, while mixing in a gas phase can be described as plug flow. The volumetric mass transfer coefficient was found to vary with the square of the impeller speed