Time filter

Source Type

Jaric I.,Serbian Institute for Multidisciplinary Research | Ebenhard T.,Swedish University of Agricultural Sciences
Wildlife Biology

It is a very important, but also a very difficult task, to establish how long a certain species has to remain unregistered before we can declare it extinct. The wrong assumption regarding species extinction could result in a type I or type II statistical error, leading to inappropriate management actions or even species extinction. Recent development of the methods for inferring the threat of extinction, when the only available information is a record of sightings, has enabled a quantitative approach to the problem. In our study we present an index that infers extinction probability based on trends in sighting intervals. Our study comprises a description of the sighting trend index, a sensitivity analysis and an application of the index to the sighting record of the black-footed ferret Mustela nigripes. The main advantage of this method could be its sensitivity to changes in sighting frequency within the sighting record. However, further testing of the method on different data sets could be important for gaining additional knowledge regarding its adequate application in the field of conservation biology. © 2010 Wildlife Biology, NKV. Source

Jovalekic C.,Serbian Institute for Multidisciplinary Research | Zdujic M.,Serbian Academy of Science and Arts
Ceramics International

The effect of thermal treatment atmosphere (argon, air or oxygen) on the electret behavior of bismuth titanate (Bi4Ti3O12) ceramics was investigated. Polycrystalline ferroelectric ceramics were prepared by reactive liquid phase sintering. Sintered samples were polarized applying an electric field, Ep = 1 MV m-1 at 100 °C for 60 min. Effective surface density, σeff of free charges was determined by compensation voltage measurements. Thermally treated samples in oxygen atmosphere exhibit a significant decrease of σeff while those treated in argon exhibit an increase of σeff accompanied by the improvement in stability of electret charge. In all cases homocharge with a time independent sign was obtained. © 2009 Elsevier Ltd and Techna Group S.r.l. Source

Nikolic N.D.,University of Belgrade | Brankovic G.,Serbian Institute for Multidisciplinary Research
Materials Letters

Formation of open porous copper structures by the electrodeposition processes in the hydrogen co-deposition range was considered. Morphologies of copper deposits obtained by the reversing current (RC) regimes at the same average current density but with the different the anodic current density/anodic pulse ratios were compared with those obtained by the pulsating current (PC) regime at the same average current density and in the constant galvanostatic mode at the current density which was equal to this average current density. The considerable increase of the specific surface area of the honeycomb-like structures, determined by the increase of number of holes, as well as by the decrease of both holes size and wall width among them, can be attained if the appropriate parameters of the RC regimes are applied. In this way, it is shown that the regime of reversing current (RC) is superior in the production of open porous structures suitable to be used as electrodes in many electrochemical devices in relation to other current regimes of electrolysis, such as the PC and the galvanostatic regimes. © 2011 Elsevier B.V. All rights reserved. Source

Nikolic N.D.,University of Belgrade | Brankovic G.,Serbian Institute for Multidisciplinary Research | Popov K.I.,University of Belgrade
Materials Chemistry and Physics

Optimization of process of formation of open and porous copper electrodes, denoted as the honeycomb-like ones, by the regime of pulsating current (PC) is considered. The square-waves PC were consisted of the same amplitude current density and pause duration of 10 ms, while the analyzed deposition pulses were: 1, 4, 7, 10 and 20 ms. Morphologies of electrodeposited copper and the quantities of evolved hydrogen during electrodeposition processes were compared with the surface morphology and the quantity of evolved hydrogen obtained by copper electrodeposition in the galvanostatic mode. In galvanostatic mode, electrodeposition of copper was performed at a current density which corresponded to the amplitude current density in the PC regimes. Honeycomb-like deposits were formed at the constant current density and by the PC regimes with deposition pulses of 7, 10 and 20 ms. The mixture of holes constructing the honeycomb-like structure and dish-like holes was obtained with a deposition pulse of 4 ms. Finally, dish-like holes were only formed with a deposition pulse of 1 ms. The change of the shape of holes was discussed by the change of hydrodynamic conditions in the near-electrode layer caused by evolved hydrogen. The specific energy consumption in the PC regimes of electrolysis was also discussed. Analysis of the specific energy consumption showed that energy saving of about 15% can be attained in the production of honeycomb-like electrodes by the choice of the appropriate PC regime. © 2010 Elsevier B.V. All rights reserved. Source

Jaric I.,Serbian Institute for Multidisciplinary Research | Ebenhard T.,Swedish University of Agricultural Sciences | Lenhardt M.,Sinisa Stankovic Institute for Biological Research
Reviews in Fish Biology and Fisheries

Populations of six sturgeon species in the Danube River (beluga, Russian sturgeon, stellate sturgeon, sterlet, ship sturgeon and Atlantic sturgeon) have experienced severe decline during the last several decades, mostly due to the unsustainable fishery, river fragmentation and water pollution. Present lack of knowledge on basic sturgeon demography, life history and relative effects of different negative factors is further hindering implementation of efficient policy and management measures. In the present study, population viability analysis in a Vortex simulation model has been conducted in order to assess the state of the six Danube sturgeon species, their future risk of extinction and to determine the most suitable conservation and management measures. Population viability analysis has revealed a large sensitivity of the Danube sturgeon populations to changes in the natural mortality, fecundity, age at maturity and spawning frequency. It was also confirmed that the sturgeons are highly susceptible to even moderate levels of commercial fishery, and that their recovery is a multi-decadal affair. Stocking with adult individuals was shown to produce considerably greater effect on population persistence than stocking with juveniles, but the latter approach is probably still preferable since it avoids many inherent problems of aquaculture cultivation. This study represents the first population viability analysis of the Danube sturgeons. © 2009 Springer Science+Business Media B.V. Source

Discover hidden collaborations