Sharply-Topped Alluvial Gravel Sheets in the Palaeogene Promina Basin (Dinarides, Croatia)

The upper part of the Promina Beds at their western extent is represented by two alluvial units: the Kunovac Beds and the Upper Alluvial Unit. The Kunovac Beds contain a high proportion of fine-grained sediments, and generally lacks debris flow deposits. The principal architectural components of the Kunovac Beds are (1) complex (multilateral, multi-storey) gravel-dominated sheets, which originated by the advance of mobile-channel belts, and were terminated by sudden abandonment, (2) smaller heterogeneous gravelly-sandy sheets, which originated in fluvial belts from a combination of sheet flows and channelized flows, (3) small isolated ribbons reflecting the filling of small channels, and (4) floodplain mudstones and sandstones. The basic style by which the Kunovac Beds, as well as the most part of the Promina alluvium were built up are the repeated advances and abandonments of the alluvial belts, and related stacking of coarse-grained sheets and floodplain deposits. The most important factors responsible for the dominance of this sheet-like geometry are high sediment supply and high aggradation and subsidence rates. Deposition of the Kunovac Beds occurred on alluvial plains, situated between the basin-margin proximal alluvium (including fans) and marginal-marine zone of the Promina Basin. The alluvial Promina Beds represent a transverse type of basin-fill pattern, whereas the deepest portion of the basin experienced longitudinal palaeotransport

Nearshore Deposits in the Middle Eocene Clastic Succession in Northern Dalmatia (Dinarides, Croatia)

The Middle Eocene clastic succession in the Radovin Syncline is approximately 900 m thick and consists of hemipelagic and flysch-type deposits in its lower part, and shallow-marine sediments in its upper portion. The upper portion embraces a unit of sandstones and conglomerates, which is represented by several facies. Flat- and low-angle laminated, and hummocky cross-stratified sandstones (S1) originated by storm-related processes in the shoreface. Cross-bedded sandstones (S2) reflect longshore, offshore, and onshore flows also in shoreface settings. Flat-laminated sandstones with planar truncations (S3) reflect swash processes. Some sandstones possibly originated in the offshore transition zone. Conglomerate-sandstone couplets (CS) originated by storm-induced flows in the shoreface. Main conglomerates (CM) mostly reflect various processes and modifications performed in upper shoreface and beachface settings of a reflective coast. Most Cross-bedded conglomerates (CX) reflect longshore flows and dissipative conditions. There are also conglomerates which have possibly been deposited by gravity flows related to river floods. The shoreline was oriented NW-SE. The architecture of the sandstone-conglomerate unit is thought to result from the interfingering of deltas and nearshore sandy systems. Deltas were of the shelf-type, and were predominantly “wave-dominated”. The sediments studied reflect molasse-type deposition, which was induced by early post-flysch changes in basin evolution and the palaeogeography of the Palaeogene clastic basin in the coastal Dinarides

Hydrologic Evolution of a Carbonate Aquifer (Dinaric Karst, Croatia)

Dinaric Karst terrains contain specific, laminated speleothems, which line all surfaces of subterranean voids including Cretaceous bedrock limestone, and older vadose speleothems and clastic sediments. These speleothems may attain a thickness of one metre. Deposition of these speleothems took place during a long-term phreatic period in the Late Quaternary. This is in contrast to well-known, widespread speleothems, which were, and are deposited in vadose and uppermost phreatic settings. Furthermore, the origin of these phreatic speleothems departs from common experience by the dominant dissolutional widening of underground conduits when saturated. Phreatic speleothems can be important stratigraphic marker for the stratigraphy of cave sediments. This approach revealed a sequence of three hydrologic stages: (1) pre-phreatic stage with dominant vadose conditions and dissolution processes, (2) phreatic stage when the ground-water level was very high in the large karst area, and when the volume of the voids decreased, and (3) the last, dominantly vadose stage during which voids were enlarged for the second time, and phreatic speleothems may be covered by younger clastics and vadose speleothems

An Association of Marine Tractive and Gravity Flow Sandy Deposits in the Eocene of the NW Part of the Island of Pag (Outer Dinarides, Croatia)

The Eocene clastics of the NW part of the island of Pag overlie carbonate platform deposits and are dominantly sandy. Besides minor components, they include cross-laminated and cross-bedded sandstones produced by marine tractive flows, mostly directed toward E, and ESE, and dominantly massive sandstones probably deposited by gravity flows. The area was situated close to sand-rich sources and river mouth(s). Possible settings include a delta-related shallow-marine area, and a sea strait. Structural deformation intervened very early in the history of a complex outer dinaric foreland realm and governed its subsequent evolution, in contrast to a simple foreland trough envisaged before

Correlation of the liquid mixture viscosities

In this paper forty two selected correlation models for liquid mixture viscosities of organic compounds were tested on 219 binary and 41 ternary sets of experimental data taken from literature. The binary sets contained 3675 experimental data points for 70 different compounds. The ternary sets contained 2879 experimental data points for 29 different compounds. The Heric I, Heric-Brewer II, and Krishnan-Laddha models demonstrated the best correlative characteristics for binary mixtures (overall absolute average deviation < 2%). The Heric I, Heric-Brewer II, Krishnan-Laddha and Heric II models demonstrated the best correlative characteristics for ternary mixtures (overall absolute average deviation < 3%)

Srednjoeocenska starost navodnih oligocenskih sedimenata u flišu Pazinskoga bazena (Istra, Vanjski Dinaridi)

The dating of the flysch sediments of the coastal Dinarides is critical for considering the evolution of the Dinaric chain. The flysch of the Pazin Basin, Istria has been considered to be Late Lutetian to Late Eocene in age by many workers. The recently reported Late Oligocene age of a part of this flysch (ŠPARICA et al., 2005) is highly relevant when considering the sedimentary and tectonic evolution of the area, as well as the western Dinarides in general. The importance of the Late Oligocene dating, and the character of the succession of the area in question, which shows similarities with Middle Eocene sediments in other parts of the basin, provoked the need for a reevaluation of the dating of these specific sediments. The results presented here support the Middle Eocene age of these sediments, which is consistent with the dating proposed by previous workers, and agrees with the character of the relevant sedimentary succession.Dosadašnja istraživanja i shvaćanja, kako o starosti, tako i karakteru slijeda sedimenata fliša Pazinskoga bazena u Istri, upućivala su na ukupnu starost fliša od kasnoga lutecija do starijega priabonija. Međutim, nedavno su prikazani podaci, prema kojima jedan dio tih sedimenata odgovara kasnom oligocenu, što je bitna novost za razmatranje razvitka toga bazena, kao i orogena Dinarida. Ovaj rad odgovara na potrebu dodatne provjere starosti tih sedimenata zbog važnosti odnosnoga datiranja. Prikazani rezultati temelje se na usporedbi karaktera i slijeda sedimenata iz predjela odakle potječu nedavni podaci o oligocenu sa sedimentima drugih dijelova Pazinskoga bazena, te na biostratigrafskom datiranju pomoću planktonskih foraminifera i nanoplanktona. Ustanovljene biozone odgovaraju gornjem luteciju i donjem bartoniju, dakle, donjemu dijelu ukupnoga raspona starosti Pazinskoga fliša

Priprava taložnog kalcijeva karbonata šaržnim i semikontinuiranim postupkom

A comparison of the physical-chemical properties of precipitated calcium carbonate (PCC), prepared by batch and semicontinuous processes, is presented. In both processes, PCC, was synthesized by carbonation of slaked lime. In the batch process the experiments were performed by varying the initial mass concentration and temperature, and the semicontinuous process was conducted by varying the initial supersaturation and temperature. Calcite was the only calcium carbonate polymorph that appeared under the experimental conditions investigated. It was found, that in the batch experiments the specific surface area and the average size of calcite particles decreased with the increase of temperature. At the same time, the increase of the initial mass concentration of slaked lime enhanced the degree of precipitate aggregation. PCC prepared by the semicontinuous process, conducted at low temperatures and high supersaturations, was of high specific surface area. By careful tuning of the semicontinuous process parameters, calcite in the form of rhombohedral, scalenohedral or nanosized spherical particles can be producedU ovom su radu uspoređena fizičko-kemijska svojstva taložnog kalcijeva karbonata (TKK) pripravljenog karbonatizacijom vapnenog mlijeka u šaržnom i semikontinuiranom reaktoru. U šaržnom su postupku varirane temperatura i početna masena koncentracija vapnenog mlijeka, dok su u semikontinuiranom mijenjani temperatura i prezasićenost sustava. Pri svim je istraživanim uvjetima nastao kalcit. Utvrđeno je da se specifična površina i prosječni promjer čestica kalcita, pripravljenog šaržnim postupkom, smanjuju s povećanjem temperature, dok se s povišenjem početne masene koncentracije poboljšava stupanj agregiranosti taloga. TKK pripravljen semikontinuiranim postupkom, vođenim pri niskim temperaturama ili visokim prezasićenostima, velike je specifične površine. Odabirom procesnih parametara semikontinuiranog postupka moguće je pripraviti kalcit u obliku romboedarskih, skalenoedarskih ili kuglastih čestica nanometarskih dimenzija

Electrochemical oxidation of methanol on Pt/(RuxSn1-x)O2 nanocatalyst

The Ru-doped SnO2 powder, (RuxSn1-x)O2, with the Sn:Ru atomic ratio of 9:1 was synthesized and used as a support for Pt nanoparticles (30 mass% loading). The (RuxSn1-x)O2 support and Pt/(RuxSn1-x)O2 catalyst were characterized by X-ray diffraction, energy dispersive X-ray spectroscopy and transmission electron microscopy (TEM). (RuxSn1-x)O2 was found to be two-phase material consisting of probably solid solution of RuO2 in SnO2 and pure RuO2. The average Pt particle size determined by TEM was 5.3 nm. Cyclic voltammetry of Pt/(RuxSn1-x)O2 indicated good conductivity of the sup-port and displayed usual features of Pt. The results of the electrochemical oxidation of COads and methanol on Pt/(RuxSn1-x)O2 were compared with those on commercial Pt/C and PtRu/C catalysts. Oxidation of COads on Pt/(RuxSn1-x)O2 starts at less positive potentials than on PtRu/C and Pt/C. Potentiodynamic polarization curves and chronoamperometric curves of methanol oxidation indicated higher initial activity of Pt/(RuxSn1-x)O2 catalyst compared to PtRu/C, but also a greater loss in the current density over time. Potentiodynamic stability test of the catalysts revealed that deactivation of the Pt/(RuxSn1-x)O2 and Pt/C was primarily caused by the poisoning of Pt surface by the methanol oxidation residues, which mostly occurred during the first potential cycle. In the case of PtRu/C the poisoning of the surface was minor and deactivation was caused by the PtRu surface area loss. [Projekat Ministarstva nauke Republike Srbije, br. ON-172054

Uticaj prisustva volfram-karbida u ugljeničnom nosaču Pt nanočestica na elektrohemijsku redukciju kiseonika u kiselom rastvoru

Tungsten carbide was synthesized by calcination of carbon cryogel with embedded tungsten in a form of metatungstate. This material was used as a support for Pt nanoparticles. XRD pattern of W-C support indicated the presence of WC, W2C, and unreacted W, as well as graphitized carbon. According to previous TEM analysis of W-C support, it contains particles with core-shell structure, where the W particle was covered with the shell of a mixture of WC and W2C. The average Pt grain size calculated from XRD pattern was about 6 nm. A cyclic voltammogram of W-C support was recorded within the potential range relevant for its application as a catalyst support in fuel cells. The pair of anodic/cathodic peaks close to the negative potential limit could be ascribed to the intercalation of hydrogen within hydrous tungsten oxide, which is always present on the surface of WC in aqueous solutions. The cyclic voltammogram of Pt/W-C indicated that tungsten oxide species are present on tungsten carbide shell as well as on the surface of Pt nanoparticles. The Pt surface is only partially covered by hydrous tungsten oxide. Hydrogen intercalation in hydrous tungsten oxide is enhanced in the presence of Pt nanoparticles. Also, the presence of hydrated tungsten oxide leads to the decrease of OH chemisorbed on Pt surface. Stripping of underpotentially deposited copper was used for the assessment of Pt surface area and the specific surface area of Pt was estimated to be 41 m2 g-1. The electrochemical oxygen reduction reaction was examined on the synthesized Pt/W-C catalyst and compared with the results on the commercial Pt/C catalyst. It was found that the current densities at Pt/W-C were almost twice as high as those on Pt/C. The Tafel plots for both catalysts are characterized with two Tafel slopes: -0.060 V dec-1 at low current densities, and -0.120 V dec-1 at high current densities. From the rotational dependence of the reaction rate, it was found that oxygen reduction on both Pt/W-C and Pt/C follows the first order kinetics with respect to O2 and that four electrons are transferred per O2 molecule. The results show that the presence of tungsten carbide in support material, i.e. hydrous tungsten oxide on Pt surface, leads to promotion of oxygen reduction on the Pt/W-C catalyst. It was assumed that oxophilic hydrated tungsten oxide hinders OH adsorption on Pt surface, thus increasing Pt surface area available for O2 adsorption and its electrochemical reduction.Sintetizovan je nosač katalizatora u kojem se na ugljeničnoj osnovi nalaze nanočestice metalnog volframa obavijene volfram-karbidom i na njega su nanete nanočestice Pt. Karakterizacija sintetizovanog uzorka cikličnom voltametrijom u kiseloj sredini ukazala je na oksidaciju volframovih vrsta iz nosača i formiranje hidratisanih oksidnih vrsta volframa na površini Pt. Elektrohemijska redukcija O2 u kiseloj sredini je ispitivana na sintetizovanom uzorku i rezultati su upoređeni sa komercijalnim katalizatorom u kojem su nanočestice Pt na nosaču od ugljenika razvijene površine. Pokazano je da redukcija O2, bez obzira na nosač katalizatora, sledi kinetiku prvog reda po O2 uz razmenu četiri elektrona, ali da su gustine struje veće u slučaju nosača sa volfram-karbidom. Povećana aktivnost sintetizovanog katalizatora je posledica prisustva oksofiličnih hidratisanih oksida volframa koji sprečavaju adsorpciju hidratisanog oksida na površini Pt i tako povećavaju površinu Pt dostupnu za adsorpciju i redukciju molekula kiseonika

Quality Parameters and Antioxidant Activity of Three Clover Species in Relation to the Livestock Diet

Products of metabolism that are directly involved in growth, development and reproduction and also secondary products of metabolism were studied in 16 natural populations of three species of the genus Trifolium (T. repens – four populations, T. alpestre – three populations, T. pannonicum – nine populations), collected from the central Balkans region, i.e. territory of Serbia. Statistical analysis showed the presence of variability in all species of the test material. The best quality of dry matter, estimated by the ratio of crude protein and crude fiber, was achieved in the populations of white clover. In this species, average protein content was 216.4 g kg-1 while the average content of crude fiber was 222.4 g kg-1. The highest average content of total phenols (77.9 mg GA g-1), flavonoids (159.7 mg Ru g-1) and antioxidant activity (70.2 μg ml-1) was measured in populations of T. pannonicum by phytochemical analysis of aerial parts of plants. The content of secondary metabolites and antioxidant activity in other species were extremely low. Populations of T. pannonicum were notable for fodder quality and antioxidant activity: CS091 with 186.2 g kg-1 of crude protein and antioxidant activity of 55 μg ml-1; RA123 with 175.6 g kg-1 of crude protein and a high level of antioxidant activity of 44.8 μg ml-1. It can be concluded that the selection of these populations may lead to creation of different varieties of fodder crops that could give safe animal feed and would be suitable for growing under adverse conditions of mountainous climate