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1.
Antioxidant and antimicrobial activity of guarana seed extracts
Lucija Majhenič, Mojca Škerget, Željko Knez, 2007, izvirni znanstveni članek

Opis: The antioxidant and antibacterial activities of guarana (Paullinia cupana) seed extracts were determined. The seeds were extracted with water, methanol, 35% acetone and 60% ethanol at room (TR) and at boiling (TB) temperature of solvent.Extracts were analyzed for the contents of caffeine and catechins, epicatechin (EC), catechin (C) and epicatechin gallate (ECG), by high performance liquid chromatography (HPLC). The contents of total phenols (according to the Folin-Ciocalteu procedure) and proanthocyanidins were analysed by UV spectrophotometry. The guarana seed water extract obtained at room temperature contained higher amounts of caffeine and catechins than did alcoholic guarana seed extracts. The antioxidant and radical-scavenging activities of guarana seed extracts were evaluated using the ß-carotene-linoleic acid emulsion system and the stable free radical 2,2-diphenyl-1-picrylhydrazyl (DPPH ). All tested guarana seed extracts displayed strong antioxidant and radical-scavenging properties. The guarana seed extracts were tested against three food-borne fungi: Aspergillus niger, Trichoderma viride and Penicillium cyclopium, and three health-damaging bacteria: Escherichia coli, Pseudomonas fluorescens and Bacillus cereus by theagar well diffusion and broth dilution assay. The alcoholic guarana seed extracts displayed stronger antimicrobial activity against all tested microorganisms than did water extracts. Results presented here may suggest that seed extracts of guarana possess strong antimicrobial and antioxidant properties, and they can therefore be used as a natural additive in food, cosmetic and pharmaceutical industries.
Ključne besede: chemical processing, guarana extract, Paullinia cupana, seed extracts, antimicrobial properties, antioxidative properties
Objavljeno: 31.05.2012; Ogledov: 1162; Prenosov: 69
URL Povezava na celotno besedilo

2.
Detecting and analysing condition of hydraulic oils with on-line sensors
Vito Tič, Darko Lovrec, 2011, izvirni znanstveni članek

Opis: On-line condition monitoring of the entire system or individual components can be used for detection of impending system break-down. The on-line monitoring of the state of hydraulic system and fluid plays a decisive role in general on-line condition monitoring. Friction, wear, leakage and excessive temperatures all have impact on lubricating properties of the oil. Apart from this, the oil its self is prone to aging and deterioration processes, which can also result in corrosion and equipment failures. The oil condition can be understood as a fingerprint of the condition of the complete system. Due to a widespread availability of robust and cost-effective on-line sensors for measuring various fluid properties, latest developments deal with on-line oil condition monitoring to determine the condition of hydraulic system and fluid. This allows for maintenance work to be carried out based on the detected system condition.
Ključne besede: oil ageing, condition monitoring, physical properties, chemical properties
Objavljeno: 01.06.2012; Ogledov: 839; Prenosov: 15
URL Povezava na celotno besedilo

3.
Gold in the past, today and future
Rebeka Rudolf, Maša Anžel, Evgenija Marković, Miodrag Čolić, Dragoslav Stamenković, 2012, pregledni znanstveni članek

Opis: This paper deals with gold, which is described as a chemical element. Special attention is paid to its physical-chemical properties and, furthermore, where or in what form it can be found in nature. We discuss the role it has played through history and we inform how gold has been developed to the level it has reached today's value. Still more, when gold is broken into nanoparticles, this form could be highly useful for a wide range of processes, including general nanotechnology, electronics manufacturing and the synthesizing of different functional materials. It is important that we know that gold is also used in industry in many engineering applications (contacts in micro-electronics) and medicine (dental alloys, implants).
Ključne besede: gold, physical-chemical properties, nano-particles, applications
Objavljeno: 01.06.2012; Ogledov: 1598; Prenosov: 56
.pdf Celotno besedilo (144,60 KB)
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Neutralization of waste filter dust with CO[sub]2
Ana Kračun, Ivan Anžel, Lidija Fras Zemljič, Andrej Stergaršek, 2015, strokovni članek

Opis: In this paper we report on the possibility of neutralizing filter dust from Talum Livarna d.o.o. The filter dust that remains after cleaning flue gas with the classification number of waste 10 10 09* is alkaline and contains heavy metals, non-metals, organic pollutants, and, therefore, has the properties of hazardous waste. The possibility of neutralizing this dust with CO2 was studied. The results showed that the treatment successfully lowered the pH value between the limits 6 and 9, which is within the legal constraints of pollution for strong acidic or alkaline waste. The contents of the hazardous substances were lowered, i.e., As, Cu, Ba, Zn, Cd, Cr, Ni, Pb, Sn, Mn and V, with percolation values that are below the level of the prescribed threshold-limit values for substances that allows their disposal in non-hazardous waste landfills. Only the percolation values of Sb, Cd, Mo and Se exceed the prescribed threshold limit values of substances that allow their disposal in inert waste landfills. The XRD analysis after the neutralization of the filter dust using CO2 showed no presence of CaO. The neutralized filter dust can be land filled as a stabilized and unreactive waste in landfills for nonhazardous wastes. Their properties also offer the possibility for incorporating them into some other material or product, such as the production of new composite materials, their use in construction products and perhaps cements or usage in backfills.
Ključne besede: hazardous waste, filter dust, neutralization, stabilization, chemical properties
Objavljeno: 17.03.2017; Ogledov: 308; Prenosov: 40
.pdf Celotno besedilo (438,33 KB)
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6.
An evaluation of marine sediments in terms of their usability in the brick industry
Patrik Baksa, Franka Cepak, Rebeka Kovačič Lukman, Vilma Ducman, 2018, izvirni znanstveni članek

Opis: A dredging process is essential for the development of harbours and ports, allowing the functional daily operation of the port. The management of dredged material represents a worldwide challenge, especially considering unwanted deposition of material. Because of their chemical, petrographic, mineralogical and homogeneity composition, marine sediments could represent an appropriate raw material for the brick industry, particularly for the production of clay blocks, roofing and ceramic tiles. In this study dredged material from Port of Koper was tested for such use, thus various analyses were carried out in order to determine if the dredged material is environmentally friendly and suitable for use in the brick industry. These included: chemical analysis, mineralogical analysis, particle size analysis, chloride content analysis and tests of firing in a gradient furnace. Furthermore, tests of mechanical properties, as well as tests of the frost-resistance of the samples were carried out. On the basis of the primary analyses and samples prepared in a laboratory, it was confirmed that marine sediments from the Port of Koper, without any additives are only conditionally suitable as a source material for producing brick products, because without additives they exhibit too much shrinkage on drying and firing, as well as high water absorption, this can be improved by the incorporation of suitable additives, for example, virgin clay or other suitable waste material. The approach described herewith can also be followed to assess sediments from other ports and rivers regarding its potential use in clay brick sector.
Ključne besede: dredge marine sediment, recycling, clay bricks, mechanical properties, chemical analysis
Objavljeno: 21.12.2017; Ogledov: 743; Prenosov: 48
.pdf Celotno besedilo (447,79 KB)
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