32 research outputs found

    Pregled trenutnih izazova i principa organskog uzgoja šarana (cyprinus carpio) u jezerima u Evropi

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    Šaran (Cyprinus carpio) je jedna od najznačajnijih vrsta ribe u akvakulturi u slatkovodnim jezerima. Akvakultura u slatkovodnim jezerima se često karakteriše kao sistem sa malim novčanim i ulaganjima radne snage, i najčešće služi lokalnom tržištu. Šaran je nedavno klasifikovan: kada je reč o svetkoj proizvodnji zauzima treće mesto, a kada je reč o vrednosti, sedmo (Tabela 1). U 2013. godini, ukupna EU27 proizvodnja šarana iznosila je 57,254 tone (FEAP 2014). Zemlja sa najvećom proizvodnjom šarana bila je Poljska (31% ukupne EU27 proizvodnje šarana), Češka (29%), Mađarska (17%), Nemačka (10%) i Francuska (6%). Ipak, izveštaji o organskom gajenju šarana dolaze samo iz Mađarske ( 700 t), Nemačke ( 200 t) i Austrije ( 150 t). Jezerske oblasti gde se gaji šaran na organski način zauzimaju 4700 ha u Mađarskoj i 550 ha u Austriji, što predstavlja približno 20% ukupne oblasti u kojima se gaji riba u obe zemlje (Varadi, Phuong 2007). Šaran je idealan kandidat za organsko gajenje jer zauzima nisko mesto u lancu ishrane, hrani se prirodnom hranom, u jezerima, i ima minimalan uticaj na životnu sredinu. Iako je način na koji se šaran gaji u jezerima kvazi organski i prelaz na sertifikovano organsko gajenje nije zahtevan kao kod drugih vrsta, prisustvo šarana na organskom tržištu ribe je još uvek jako nisko. Takođe, neke druge, dodatne vrste riba koje se mogu gajiti zajedno sa šaranom pokazuju visok potencijal za organsko gajenje, zbog minimalnih potreba u smislu upravljanja jezerom i sertifikacije. Trenutni standardi za organsko gajenje šarana ipak nisu sasvim usklađeni kada je reč o prihvatljivim načinima za reprodukciju. Takođe, postoje glavna ograničenja i problemi kao što je nedostatak organske hrane, predatori, razlikovanje od neorganskih proizvoda, nedostatak saradnje kada nastanu tehnički problem i marketing, pojava kostiju i stav potrošača da je šaran jevtina hrana. Marža za organskog šarana može da bude dobra ukoliko je prodajna cena znatno viša od troškova proizvodnje. Potrebno je harmonizovati standarde, poboljšati preradu i marketing (kada je reč o filetima bez kostiju) i podržati bolju sardanju među organskim uzgajivačima. Budućnost je svetla, što se tiče svih gore navedenih stavki, međutim trenutna potrošnja organskog šarana opada. Potrebno je repozicionirati organskog šarana na tržištu i proizvoditi više filetirane nego cele ribe.Common carp (Cyprinus carpio) is one of the most important fish species in freshwater pond aquaculture which is often characterized as a low input system with low labour productivity and low capital intensity, serving mainly local markets. Recently, common carp is classified on 3rd and 7th rank regarding world production and its value, respectively (Table 1). In 2013, the total EU27 aquaculture carp production was 57,254 tonnes (FEAP 2014) being mostly produced in Poland (31 % of total EU27 carp production), Czech Republic (29 %), Hungary (17 %), Germany (10 %) and France (6 %). Nevertheless, organic carp production is currently reported just from Hungary ( 700 t), Germany ( 200 t) and Austria ( 150 t). Pond areas with organic carp production occupy 4700 ha and 550 ha in Hungary and Austria respectively, which represents approximately 20% of the total fishpond area in both countries (Varadi, Phuong 2007). Carp represents an ideal candidate for organic status since it is low in the food chain, feeds naturally and in pond farming, it has a minimum impact on the environment. Despite the way carp are farmed in ponds is already quasi-organic and the shift to their certified organic farming is not as demanding as it is for some other species, the proportion of carp on the organic fish market is still very low. Obviously, also the other supplementary carp pond fish species prove a high potential to be considered as organic products with minimum requirements in sense of pond management and certification. Current organic standards for common carp are, however, facing some inconsistencies such as acceptable ways of reproduction, as well as the main constraints and problems such as shortage of organic feed, predation of wild animals, differentiation from non-organic product, lack of cooperation on technical issues and marketing, bones appearance and consumer perception of carp as a cheap food. The margins for organic carp can be good with sales price being significantly higher than production costs. Organic carp culture needs help to harmonise standards, to improve processing and marketing (boneless fillets) and to support greater cooperation among organic farmers. There are good long term prospects with this respect, though current consumption is on the wane. There is a need to reposition organic carp in the market and produce more fillets rather than just live and/or whole fish

    LOW-TEMPERATURE SYNTHESES OF VANADIUM(III) AND MOLYBDENUM(IV) BROMIDES BY HALIDE EXCHANGE

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    Halide-exchange reactions of VCl4 or MoCl5 with dry HBr at temperatures between ca. -50 and +20-degrees-C afforded the corresponding bromides, VBr3 or MoBr4, in good yields, presumably via the formation of unstable higher-valent bromide intermediates which undergo spontaneous loss of bromine. In corresponding reactions with HI the exchange was incomplete and mixed halides were obtained. At room temperature the VCl4-HI system gave VCl3 in an almost quantitative yield. By reaction of MoBr4 with tetrahydrofuran (thf) [MoBr3(thf)3] was isolated and its crystal structure determined: orthorhombic, space group Pbcn (no. 60), a = 8.812(2), b = 13.882(5), c = 14.279(3) angstrom, z = 4, R = 0.063. The molecule has the usual meridional geometry, typical of other [MoX3(thf)3] derivatives (X = Cl or I)

    Solution behavior of poly(styrene)-block-poly(2-vinylpyridine micelles containing gold nanoparticles

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    Formation and structural transformation of inverse poly(styrene)-block-poly(2-vinylpyridine) micelles whose polyvinylpyridine core was loaded with HAuCl4 or with elementary gold nanoclusters was studied by combined static and dynamic light scattering. A transformation in the morphology from spherical particles (small Rg/Rh ratio) to large anisomeric objects (large Rg/Rh ratio) was observed by decreasing the concentration of the block copolymer below the critical micelle concentration. At this point, the polymer chains are molecularly dispersed and no longer able to prevent uncontrolled growth of the gold nanoclusters

    Preparation, Characterization And Electrochemical Studies Of 1,1′-bis(diphenylphosphino)ferrocene (dppf) Derivatives. Crystal Structure Of [dppfco(no)2] [sbf6]

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    The neutral dppfFe(NO)2 (1), the novel cationic [dppfCo(NO)2] [SbF6] (2), as well as the dppfFe(CO)3 (3) (dppf=1,1′-bis-(diphenylphosphino)ferrocene) complexes were prepared and characterized. The interaction between the two metallic centers through the dppf ligand was studied in the solid state by 57Fe Mössbauer spectroscopy and in solution by cyclic voltammetry. The Mössbauer parameters are compared with those of other dppfMLn complexes. Electrochemical studies performed on these complexes show the great influence of the MLn moiety on the redox processes of the dppf iron center. The crystal structure of complex 2 was determined (C34H28CoF6FeN2O2P 2Sb). The compound crystallizes in the triclinic, space group P1̄, a = 10.441(2), b= 10.755(2), c= 17.320(5) Å, α = 104.10(2), β = 0.504(10), γ = 111.504(10)°, U= 1744.7(7) Å3, Z = 2, R = 0.0765, wR2 = 0.1878. 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    A combined top-down/bottom-up approach to the microscopic localization of metallic nanodots

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    Periodic and aperiodic two-dimensional nanostructures with hierarchical order have been prepared by a combined top–down/bottom–up approach. This method allows 7 nm nanoparticles to be positioned with a accuracy of 10 nm or less, with a separation distance of several micrometers. The Figure is an optical dark field microscopy image of a square arrangement of Au dots on a Si wafer

    Ordered deposition of inorganic clusters from micellar block copolymer films

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    A method is presented for generating quasiregular arrays of nanometer-sized noble metal and metal oxide clusters on flat substrates by the use of a polymer template. The approach is of general applicability to other metals and various oxides. In the first step, polymeric micelles with a polar core were generated by dissolution of poly(styrene)-block-poly(2-vinylpyridine) in toluene. These micelles were used as nanocompartments that were loaded with a defined amount of a metal precursor. The metal ions can be reduced in such a way that exactly one elemental or oxidic particle is formed in each micelle, where each particle is of equal size. By dipping a flat substrate into a dilute solution, a monolayer of the micelles was obtained whereby the embedded equally large particles became arranged in a mesoscopic quasihexagonal two-dimensional (2-D) lattice. Exposure to an oxygen plasma allowed removal of the polymer completely, leaving the naked metal particles firmly attached to the substrate in the same quasihexagonal order as in the monomicellar film. A modified procedure in which the precursor salt was not reduced before the plasma treatment yielded clusters of identical size and in the same 2-D order. The size (height) of the clusters could be varied between 1 and 15 nm depending on the concentration of the metal salt. The interparticle distance could be varied between 30 and 140 nm by using block copolymers with different lengths of the blocks. Such lattices of Au particles have been used to bind streptavidin proteins in an ordered array

    Order-disorder transition in surface-induced nanopattern of diblock copolymer films

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    Formation of surface-induced nanopattern (SINPAT) in ultrathin diblock copolymer films is studied by scanning force microscopy and Monte Carlo simulation. The pattern is caused by strong adsorption of one of the two blocks forming a quasi-two-dimensional coil while the other block dewets this adsorption layer. Scanning force microscopy allowed to observe an order−disorder transition for a SINPAT film of polystyrene-block-poly(2-vinylpyridine) on mica when the length of the dewetting polystyrene block was varied. The experimental data are compared with the Monte Carlo simulations which demonstrate how the pattern formation depends on the degree of polymerization of the dewetting block and the unfavorable interaction potential between the different components
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