The possibility of obtaining beta-anhydrite from waste nitrogypsum

The possibility of obtaining β - anhydrite from nitrogypsum, which is waste from a nitrocellulose plant, was investigated. It was shown by means of qualitative IR analysis that the product obtained by heating nitrogypsum for 5 hours at 700 o C was â - anhydrite. When the β- anhydrite was mixed with water at a W/S (water/solid) ratio of 0.54 in presence of different accelerators (CaO, mixture CaO - ash, ash, Na2SO4 and K2SO4), pastes were formed which hardened on standing. The compressive strength of the hardened samples was measured after 7 and 28 days and their composition determined by qualitative IR analysis. On the basis of these results, it was observed that a relationship exists between the composition (depending on the used accelerator) and the compression strength of the samples. Namely, the formation of large cores of double salts: syngenite (K2SO4 ⋅CaSO4 ⋅H2O) and glauberite (Na2SO4 ⋅CaSO4), in the presence of the accelerators K2SO4 and Na2SO4, respectively, was due to the rapid and complete crystallization of the dihydrate (CaSO4 ⋅2H2O). This fast crystal growth of the dihydrate resulted in high compressive strengths of these samples. In the other samples (prepared in presence of the accelerators: CaO, mixture CaO - ash and ash), dihydrate did not form and, consequently, their compressive strength was low

Evaluation of excavator energy consumption and overburden cutting resistance using multiple linear regression

In present paper the energy consumption of the excavator and overburden linear cutting resistance by invoking the multiple linear regression was examined. As a result, the corresponding models as nonlinear functions of physical and mechanical overburden properties: grain size, unit weight, cohesion, and friction angle, were proposed. The analysis was based on records made at ''Tamnava Eastern Field'' mine for the bucket-wheel excavator with new excavation teeth. The obtained results indicated that excavator energy consumption significantly depended on the grain size and cohesion, as individual factors, while the effect of two-factor interactions was particularly significant: clay percentage with cohesion and small grained sand fraction, and friction angle with medium grained sand and cohesion. On the other hand, linear cutting resistance of the overburden was largely controlled by all the examined physical and mechanical properties (grain size, unit weight, and shear strength), with the following significant two-factors interactions: shear strength parameters with all grain size fractions, different grain size fractions among each other, and friction angle with unit weight

Detailed investigation of the superconducting transition of niobium disks exhibiting the paramagnetic Meissner effect

The superconducting transition region in a Nb disk showing the paramagnetic Meissner effect (PME) has been investigated in detail. From the field-cooled magnetization behavior, two well-defined temperatures can be associated with the appearance of the PME: T_1 (< T_c) indicates the characteristic temperature where the paramagnetic moment first appears and a lower temperature T_p (< T_1) defines the temperature where the positive moment no longer increases. During the subsequent warming, the paramagnetic moment begins to decrease at T_p and then vanishes at T_1 with the magnitude of the magnetization change between these two temperatures being nearly the same as that during cooling. This indicates that the nature of the PME is reversible and not associated with flux motion. Furthermore, the appearance of this paramagnetic moment is even observable in fields as large as 0.2 T even though the magnetization does not remain positive to the lowest temperatures. Magnetic hysteresis loops in the temperature range between T_1 and T_p also exhibit a distinct shape that is different from the archetypal shape of a bulk type-II superconductor. These behaviors are discussed in terms of the so-called 'giant vortex state'.Comment: Total 4 printed pages, 4 Figure

The influence of the UV irradiation intensity on photocatalytic activity of ZnAl layered double hydroxides and derived mixed oxides

Layered double hydroxides (LDHs) have been studied to a great extent as environmental-friendly complex materials that can be used as photocatalysts or photocatalyst supports. ZnAl layered double hydroxides and their derived mixed oxides were chosen for the investigation of photocatalytic performances in correlation with the UV intensities measured in the South Pannonia region. Low supersaturation coprecipitation method was used for the ZnAl LDH synthesis. For the characterization of LDH and thermal treated samples powder X-ray diffraction (XRD), scanning electron microscopy (SEM), electron dispersive spectroscopy (EDS), nitrogen adsorption-desorption were used. The decomposition of azodye, methylene blue was chosen as photocatalytic test reaction. The study showed that the ZnAl mixed oxide obtained by thermal decomposition of ZnAl LDH has stable activity in the broader UV light irradiation range characterizing the selected region. Photocatalytic activity could be mainly attributed to the ZnO phase, detected both in LDH and thermally treated samples. The study showed that the ZnAl mixed oxide obtained by the calcination of ZnAl LDH has a stable activity within the measured UV light irradiation range; whereas the parent ZnAl LDH catalyst did not perform satisfactory when low UV irradiation intensity is implied

Phenolics content and antioxidant capacity of commercial red fruit juices

The content of phenolics: total phenols (TP), flavonoids (TF), anthocyanins (TA) and hydroxicinnamic acid as well as the total antioxidant capacity (TAC) in nine commercial red fruit juices (sour cherry, black currant, red grape) produced in Serbia were evaluated. The total compounds content was measured by spectrophotometric methods, TAC was determined using DPPH assays, and individual anthocyanins and hydroxycinnamic acids was determined using HPLC-DAD methods. Among the examined fruit juices, the black currant juices contained the highest amounts of all groups of the phenolics and exhibited strong antioxidant capacity. The amount of anthocyanins determined by HPLC method ranged from 92.36 to 512.73 mg/L in red grape and black currant juices, respectively. The anthocyanins present in the investigated red fruit juices were derivatives of cyanidin, delphinidin, petunidin, peonidin and malvidin. The predominant phenolic acid was neoclorogenic acid in sour cherry, caffeic acid in black currant, and p-coumaric acid in black grape juices. Generally, the red fruit juices produced in the Serbia are a rich source of the phenolic, which show evident antioxidant capacity

Polyphenol content and antioxidant activity of sour cherries from Serbia

The aim of this study is to evaluate the content of phenolics: the total phenols (TP), flavonoids (TF), anthocyanins (TA), as well as the total antioxidant capacity (TAC) in three sour cherry cultivars (Prunus cerasus L.) introduced to the southeast Serbia climate conditions. Among the researched sour cherries, ‘Oblacinska’ cultivar contained the highest amounts of all groups of phenolics, followed by ‘Cigancica’ &gt; ‘Marela’. A significant difference were observed in the phenolic content among different cultivars and growing seasons (p&lt;0.05), and the phenolic compounds were significantly higher in the growing season 2009. The examined cultivars possess a high antioxidant capacity, and all phenolics of highy correlation with TAC. The following compounds were identified and quantified using HPLC-DAD: 4 anthocyanins, the most abundant of which was cyaniding-3-glucoside in ‘Marela’ and ‘Oblacinska’, and cyanidin-3-glucosylrutinoside in ‘Cigancica’, and 4 hydroxycinnamic acids, the most abundant of which was neochlorogenic acid in all sour cherry cultivars. The growing and ripening process on the tree of sour cherry cv. Oblacinska was evaluated, also. The results showed significant increases in total phenols during the ripening, the total anthocyanins and total antioxidant capacity and 4 quantified anthocyanins, however the neochlorogenic acid decreased during the ripening. The study indicated that the growing and climate conditions in southeast Serbia are convenient for introducing sour cherry cultivars

Supplementary data for article : Kolarević, S.; Milovanović, D.; Kračun-Kolarević, M.; Kostić, J.; Sunjog, K.; Martinović, R.; Đorđević, J.; Novaković, I.; Sladić, D.; Vuković-Gačić, B. Evaluation of Genotoxic Potential of Avarol, Avarone, and Its Methoxy and Methylamino Derivatives in Prokaryotic and Eukaryotic Test Models. Drug and Chemical Toxicology 2019, 42 (2), 130–139. https://doi.org/10.1080/01480545.2017.1413108

Supplementary material for: [https://doi.org/10.1080/01480545.2017.1413108]Related to published version: [http://cherry.chem.bg.ac.rs/handle/123456789/322

Chemical composition and bioactive properties of byproducts from two different kiwi varieties

Kiwis are an example of fruits with excellent bioactive properties worldwide appreciated and consumed generating tons of waste. Thus, the objective of this work was to compare two varieties of kiwi: Actinidia deliciosa cv. “Hayward” (green) and Actinidia spp. (red) regarding the nutritional value of their pulps, chemical composition and bioactivities of each pulp and peel. The results revealed that pulps have a high water content and low amount of other macronutrients. Both parts of red kiwi presented the highest tocopherols content and red kiwi pulp presented the highest content in ascorbic acid. In general, the peels exhibited the highest antioxidant activity and green kiwi peels showed cytotoxicity and anti-inflammatory activity, which could be related to its higher content in phenolic compounds, especially B-type (epi)catechin dimer. Therefore, kiwi components currently underutilized may be indicated as a source of natural functionalizing ingredients with several benefits for human health.The authors are grateful to the Foundation for Science andTechnology (FCT, Portugal) and FEDER under Programme PT2020 forfinancial support to CIMO (UID/AGR/00690/2019); national funding by FCT, P.I., through the institutional scientific employment program-contract for L. Barros and R. Calhelha’s contract, and Carla Pereira’s contract though the celebration of program-contract foreseen in No. 4,5 and 6 of article 23° of Decree-Law No. 57/2016, of 29th August,amended by Law No. 57/2017, of 19th July; to FEDER-Interreg España-Portugal programme forfinancial support through the project 0377_Iberphenol_6_E. The authors are grateful for financial support to the Ministry of Education. Science and Technological Development of Republic of Serbia, grant number 173032. The authors also thank the company Kiwi Coop (Oliveira do Bairro, Portugal) for providing the kiwi samplesinfo:eu-repo/semantics/publishedVersio