Croatian Waters

Rijeka, Croatia

Croatian Waters

Rijeka, Croatia
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Schymanski E.L.,Eawag - Swiss Federal Institute of Aquatic Science and Technology | Singer H.P.,Eawag - Swiss Federal Institute of Aquatic Science and Technology | Slobodnik J.,R.Ø.S.A. | Ipolyi I.M.,R.Ø.S.A. | And 25 more authors.
Analytical and Bioanalytical Chemistry | Year: 2015

In this article, a dataset from a collaborative non-target screening trial organised by the NORMAN Association is used to review the state-of-the-art and discuss future perspectives of non-target screening using high-resolution mass spectrometry in water analysis. A total of 18 institutes from 12 European countries analysed an extract of the same water sample collected from the River Danube with either one or both of liquid and gas chromatography coupled with mass spectrometry detection. This article focuses mainly on the use of high resolution screening techniques with target, suspect, and non-target workflows to identify substances in environmental samples. Specific examples are given to emphasise major challenges including isobaric and co-eluting substances, dependence on target and suspect lists, formula assignment, the use of retention information, and the confidence of identification. Approaches and methods applicable to unit resolution data are also discussed. Although most substances were identified using high resolution data with target and suspect-screening approaches, some participants proposed tentative non-target identifications. This comprehensive dataset revealed that non-target analytical techniques are already substantially harmonised between the participants, but the data processing remains time-consuming. Although the objective of a “fully-automated identification workflow” remains elusive in the short term, important steps in this direction have been taken, exemplified by the growing popularity of suspect screening approaches. Major recommendations to improve non-target screening include better integration and connection of desired features into software packages, the exchange of target and suspect lists, and the contribution of more spectra from standard substances into (openly accessible) databases. [Figure not available: see fulltext.] © 2015 Springer-Verlag Berlin Heidelberg

Finite difference procedures for flux determination are not well suited for application to field results obtained from finite element calculations. A novel method for flux calculation has been derived. This method is based on the weak formulation and is suitable for use with finite elements. A matrix formulation for local and global application to finite element formulations is presented. An additional benefit of the method is that Neumann boundary conditions can be easily incorporated in the finite element formulation of the nonlinear field problem. A comparison between the finite difference, Pade derivative and novel finite element procedures is demonstrated through one- and two-dimensional examples. © 2017, Strojarski Facultet. All Rights Reserved.

Lozzi-Kozar D.,Croatian Waters | Kozar I.,University of Rijeka
Engineering Review | Year: 2017

This paper presents a part of a computer model that is suitable for limited temperature prediction and its application for Lake Botonega, which is located in Istria, Croatia. The main assumption of this study is that the heat transfer can be described by the eddy diffusivity model to formulate the model of the heating and cooling of a lake using a series of water and air temperature measurements. The coefficient of thermal diffusion, which is a function of the lake depth, is determined using the inverse model of eddy thermal diffusivity. The inverse model is linearized using the finite element approach. The model of lake thermal diffusivity consists of a conductive part and a radiative part, with the latter part being replaced with the heat flux on the boundary. The model parameters are calculated in two steps - a predictor step and a corrector step - and the coefficient of conduction is calculated instead of the diffusion. The estimated parameters are intended for inclusion in a simple three-dimensional thermal model, which provides the lake temperature prediction that is based on previous temperature measurements, as demonstrated in the examples.

Benac C.,University of Rijeka | Dugonjic S.,University of Rijeka | Arbanas Z.,University of Rijeka | Arbanas Z.,Institut IGH d.d. | And 2 more authors.
Rock Engineering in Difficult Ground Conditions - Soft Rocks and Karst - Proceedings of the Regional Symposium of the International Society for Rock Mechanics, EUROCK 2009 | Year: 2010

This paper presents the origin and the type of instability phenomena in the Rječina and Sušačka draga valleys near the town Rijeka, Croatia. Both locations are part of unique morphostructural unit. Karstified carbonate rocks prevail in this area. Paleogene siliciclastic sedimentary rock complex, i.e. flysch, has a form of a squeezed syncline between carbonate rocks. Geological boundaries between carbonate and flysch rock mass are tectonic, but with different mechanism of origin. Erosion processes and gravitational forces have caused disintegration of the carbonate rock mass, separation of blocks and their sliding over the flysch bedrock, as well as the accumulation of talus on the toe of rocky scarps. During the time, coarse grained fragments originating from the rockfalls were mixed with soil-like material from flysch weathered zone. Disintegration of carbonate scarps, rockfall and talus displacements are a permanent phenomena. The comparisons of a recent instability show a distinction between Rječina and Sušačka draga valleys. © 2010 Taylor & Francis Group, London.

Penezic A.,Ruder Boskovic Institute | Gasparovic B.,Ruder Boskovic Institute | Stipanicev D.,Croatian Waters | Nelson A.,University of Leeds
Environmental Chemistry | Year: 2014

Environmental context Polycyclic aromatic hydrocarbons (PAHs) are potentially carcinogenic and mutagenic compounds found in the atmosphere, soil, sediments and water. They can bioaccumulate in marine organisms where they pose a threat to the health of the organisms. We are developing a low-cost and simple electrochemical method to monitor the concentrations of these compounds in the aquatic environment. Abstract A new sensing system for polycyclic aromatic hydrocarbons (PAHs) in waters is being developed. The system consists of a wafer-based device with a chip-based mercury on platinum microelectrode as a working electrode and a platinum auxiliary electrode, incorporated into a flow cell system with an external reference electrode. The Hg microelectrode was coated with a phospholipid-triglyceride mixed layer and interactions between anthracene, phenanthrene, pyrene and fluoranthene and the layer were monitored using rapid cyclic voltammetry. The layer proved sensitive to interactions with PAHs in 'organic matter free' seawater, with respective detection limits of 0.33, 0.35, 0.15 and 0.32μgL-1 for phenanthrene, pyrene, anthracene and fluoranthene. Tested interferences, such as sodium humate, dextran T-500 and bovine serum albumin, representing humic substances, polysaccharides and proteins, did not have an influence on the layer response. The system was also tested with a river water sample where concentrations of PAHs were determined using the standard addition method and compared with the results obtained by using gas chromatography-mass spectrometry (GC-MS). The concentration of total PAHs obtained by the standard addition method is ∼80% lower compared with the results obtained by GC-MS analysis. The difference is explained by the fact that the electrochemical method measures water-soluble and free PAHs whereas the chromatographic method measures both dissolved and particulate-organic PAHs. © 2014 CSIRO.

In the present study were conducted the effect of pH (5.5, 6.0 and 6.5) and concentration of new synthesized 3-/2-aminophenylimino-(p-toluoyl)/-4-hydroxy-6-(p-tolyl)-2H-pyrane-2-one (Schiff base) on decrease the concentration of aflatoxin M 1 (AFM 1) in raw milk contaminated with known concentration of this toxin. Experiments were carried out at temperature of 4 °C during 35 days. At pH 5.5 Schiff base concentration of 0.1 μmol/L was lessening the concentration of AFM 1 after 35 days by 55%. However, at pH 6.5 the most effective concentration for lessening of AFM 1 was 0.5 μmol/L. a at pH value of 7 or higher. The ability of Schiff base to act as antimycotoxigenic agent provides new perspective for possibly using this compound to control AFM 1 contamination in milk and to extent shelf lives of this food. Detection of toxicity of investigated Schiff base was performed by using the brine shrimp (Artemia salina) larvae as an biological indicator to determine their sensitivity to this chemical agent.

Durakovic L.,University of Zagreb | Delas F.,University of Zagreb | Tudic A.,Croatian Waters | Huic-Babic K.,University of Zagreb | Redzepovic S.,University of Zagreb
Mljekarstvo | Year: 2012

Dehydroacetic acid (DHA) and its new synthesized analogues, 4-hydroxy-3-(p-toluoyl)-6-(ptolyl)- 2H-pyrane-2-one (DHT) and 5-Bromo-4-hydroxy-3-(p-toluoyl)-6-(p-tolyl)-2H-pyrane-2-one (BrDHT) were tested for removal of aflatoxin M1 (AFM1) from artificially contaminated yoghurt with known concentrations of this toxin to determine the possible use of these chemicals as a means of controlling AFM1 accumulation. Yoghurt from cow's milk was artificially contaminated with AFM1 at levels of 0.01 to 0.5 μg/L. Yoghurts were stored at 4 °C and 7 °C, respectively, for up to 28 days. Analysis of AFM1 in yoghurt was carried out using two-dimensional thin-layer chromatography (TLC) - visual estimation. The limit of detection was 0.15 ng/L. The recoveries of AFM1 from the samples spiked at levels of 10, 50, 100, and 500 ng/L were between 80.6 and 107.8 %, respectively. Concentrations of DHA and DHT of 0.01 and 0.03 μmol/L had non or little effect on AFM1 content in experimentally contaminated yoghurt, whereas concentrations higher than 0.05 μmol/L, partially inhibited AFM1 content. The percentage loss of the initial AFM1 amount in yoghurt was estimated by about 15 and 25 %, and 22 to 45 % by the end of storage, respectively. In experiments with 0.01 and 0.05 μmol/L of BrDHT or higher, the concentration of AFM1 was reduced after 28 days by 20 to 95 % or completely, respectively, depending on the time and temperature of deposit. Detection of toxicity of investigated analogues was evaluated by using the brine shrimp (Artemia salina) larvae as a screening system for the determination of their sensitivity to some chemicals.

Durakovic L.,University of Zagreb | Blazinkov M.,University of Zagreb | Seol B.,University of Zagreb | Tudic A.,Croatian Waters | And 6 more authors.
Agriculturae Conspectus Scientificus | Year: 2010

The eff ect of newly synthesized derivative of 11-hydroxy-7-imino-7H-7a, 12-diazabenzo/a/anthracen- 6-one, on growth and afl atoxin B1 and G1 (AFB1 and AFG1) accumulation by toxigenic mould Aspergillus fl avus ATCC 26949 was studied on a solid substrate (maize grains) to determine the possible use of this compound as a mean of controlling afl atoxin accumulation. Experiments were carried out in a stationary culture at temperature of 28°C during 21 days. The growth of mould was monitored by measuring the analysis of chitin as glucosamine, as a criterion, and concentration of AFB1 and AFG1 was measured by HPLC method using Hewlett-Packard instrument with fl ourescence detector. Concentration of investigated coumarine of 0.05 mmol x g-1 stimulated mould growth and afl atoxin accumulation, but concentration of 0.2 mmol x g-1 or higher produced an inhibitory eff ect. In the presence of 0.2 and 0.5 mmol x g-1 of this compound, mould growth was decreased by 22% and 65%, respectively. Concentration of AFB1 in these investigations was reduced by 30% and 90%, and concentration of AFG1 was reduced almost completely in respect to values obtained in control experiments. In experiments with 2.0 mmol x g-1 of this inhibitor no synthesis of both investigated afl atoxins was found in the sample although small increment of biomass was detected.

Glavas Z.,University of Zagreb | Strkalj A.,University of Zagreb | Maldini K.,Croatian Waters
Metallurgical and Materials Transactions B: Process Metallurgy and Materials Processing Science | Year: 2016

Effects of Sb additions on the graphite morphology of ductile iron castings in different wall thicknesses (3, 12, 25, 38, 50, 75, and 100 mm) were analyzed in this paper. In the wall thicknesses of 3, 12, and 25 mm, low contents of rare earth (RE) elements showed a beneficial effect on nodule count and nodularity. Nodularity >80 pct and a high nodule count were achieved without the addition of Sb. In the wall thicknesses of 38, 50, 75, and 100 mm, nodularity >80 pct was not achieved without the use of the chill or proper content of Sb. Excess of RE elements was neutralized with the addition of proper amount of Sb to the wall thickness. Addition of 0.01 wt pct Sb (ratio of RE/Sb = 0.34, ratio of RE/SE = 0.105) was sufficient to achieve nodularity >80 pct in the wall thicknesses of 38, 50, 75, and 100 mm. © 2016 The Minerals, Metals & Materials Society and ASM International

Benac C.,University of Rijeka | Ostric M.,Croatian Waters | Dugonjic Jovancevic S.,University of Rijeka
Geologia Croatica | Year: 2014

The Grohovo landslide is the largest active slope movement along the Croatian coast, situated on the north-eastern slope in the central part of the Rječina River Valley (north-eastern coastal part of Adriatic Sea, Croatia). Slopes in this valley are formed of siliciclastic rocks (i.e., flysch), while the limestone rock mass is visible on the cliffs around the top of the river valley. The slopes are at the limit of a stable equilibrium state, and slope movement phenomena have been recorded since the 19th century. Samples for laboratory testing were taken from the flysch bedrock, weathered zone and slope deposits to provide specimens for determination of their mineralogical, physical and geotechnical properties. Correlation between mine-ralogical and geotechnical properties and their influence on sliding processes are presented here. The clay fraction in samples ranges from 17% to 38%. Clay activity of the tested samples is from 0.45 to 0.89, and the residual friction angle varies from 13.0° to 17.7°. These results correspond to the presence of kaolinite and illite groups of clay mineral. Both the mineral composition and decrease in strength of fine-grained soil materials, due to the increase of pore water pressures, contributes to slope movements.

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