Axial light emission and Ar metastable densities in a parallel plate dc micro discharge in steady state and transient regimes

Axial emission profiles in a parallel plate dc micro discharge (feedgas: argon; discharge gap d=1mm; pressure p=10Torr) were studied by means of time resolved imaging with a fast ICCD camera. Additionally, volt-ampere (V-A) characteristics were recorded and Ar* metastable densities were measured by tunable diode laser absorption spectroscopy (TDLAS). Axial emission profiles in the steady state regime are similar to corresponding profiles in standard size discharges (d=1cm, p=1Torr). For some discharge conditions relaxation oscillations are present when the micro discharge switches periodically between low current Townsend-like mode and normal glow. At the same time the axial emission profile shows transient behavior, starting with peak distribution at the anode, which gradually moves towards the cathode during the normal glow. The development of argon metastable densities highly correlates with the oscillating discharge current. Gas temperatures in the low current Townsend-like mode (T= 320-400K) and the high current glow mode (T=469-526K) were determined by the broadening of the recorded spectral profiles as a function of the discharge current.Comment: submitted to Plasma Sources Sci. Techno

Analysis of weld joints made of titanium alloy GRADE 2 produced by electron beam welding

Selected properties of welded joints of 2 mm thick titanium alloy Grade 2 produced by different welding parameters of electron beam welding were investigated. The visual inspection, macro and micro analysis, tensile strength test and microhardness measurements were performed. Samples manufactured by appropriate welding parameters had no internal defects, heat-affected zone (HAZ) was narrow and transformation from α phase to β phase was observed in this area. The failure occurred in the base metal during tensile test, while maximum ultimate tensile strength reached 454,3 MPa

Fatty acid composition of maize germ oil from high-oil hybrids wet-milling processing

Maize germ was obtained by wet-milling laboratory processing of domestic high-oil maize hybrids. After separation, the germ was subjected to extraction of maize oil. Fatty acid composition of maize germ oil was determined by gas chromatography. The results showed very high levels of unsaturated fatty acids and a constant sum of oleic and linoleic acids in oils of different maize hybrids

Possibilities of using some wild and cultivated plants for soil remediation

Proizvodnja bakra u Boru tokom poslednjih 100 godina predstavlja najveći izvor zagađenja životne sredine. Zagađivači u vidu prašine, otpadnih voda, jalovine i zagađenog vazduha, utiču na kvalitet zemljišta, voda i vazduha. Preko 2.000 hektara plodnog zemljišta oštećeno je izlivom flotacijske jalovine iz borskog rudnika bakra. Cilj ovog rada je da se odredi sadržaj teških metala kod divljih biljaka (17 vrsta) koje prirodno rastu na oštećenom zemljištu i kod gajenih biljaka (devet vrsta), koje su zasejane na istom mestu. Sadržaj teških metala (Pb, Cu i Fe) je analiziran u oštećenom zemljištu. Ovom studijom su ispitivane divlje i kultivisane biljke koje su u stanju da rastu na kontaminiranom zemljištu u oblasti intenzivne industrijske proizvodnje bakra u Boru, što znači da mogu da tolerišu i akumuliraju teške metale u svojim nadzemnim tkivima. Ustanovljeno je da se sadržaj svih metala u kontaminiranom zemljištu smanjuje značajno na kraju eksperimenta. Kao što je očekivano, sve biljne vrste mogu da akumuliraju istraživane metale. Sve testirane biljke, kako divlje tako i kultivisane, izgledale su sasvim zdrave na podlogi koja je sadržala ekstremno visoke koncentracije bakra.The copper production in Bor (East Serbia) during the last 100 years presents an important source of the pollution of environment. Dust, waste waters, tailing, and air pollutants influence the quality of soil, water, and air. Over 2,000 ha of fertile soil have been damaged by the flotation tailing from Bor’s facilities. The goal of the present work has been to determine the content of Pb, Cu, and Fe in wild plants (17 species) naturally growing in the damaged soil and in fodder crops (nine species) planted at the same place. The content of Pb, Cu, and Fe has been analyzed in damaged soil as well. This study has also searched for native (wild) and cultivated plants which are able to grow in contaminated soil in the area of the intense industrial activity of copper production in Bor, which means that they can accumulate and tolerate heavy metals in their above-ground tissues. It has been found out that the content of all metals in contaminated soil decreases considerably at the end of the experiment. As it has been expected, all plant species could accumulate investigated metals. All tested plants, both wild-growing and cultivated plants, seem to be quite healthy on the substrate which contained extremely high concentrations of copper

Procena ekološkog rizika u funkciji zaštite životne sredine

This paper proposes an appropriate methodology for ecological risk assessment. The methodology has been applied in the region of Boka Kotorska Bay (Bay), Montenegro. The emphasis of the research is on the analysis of the impact of various stressors on the ecological components of Bay. The consequences of that impact can be seen in an increased level of eutrophication of water environment, mostly through the influence of nitrogen and its compounds. The actual research at/about the region of Boka Kotorska Bay was performed in the period of 2008. The study emphasized the importance of the acquisition, processing and analysis of various ecologically related data for more efficient monitoring and management of the environment. The suggested methodology of the ecological risk assessment is, therefore, a remarkable scientific and expert contribution in the area of environmental protection in our country and in general.U radu je predstavljena primena metodologije procene ekološkog rizika. Metodologija je primenjena na primeru Bokokotorskog zaliva (Zaliv). Istraživanjem je razmatrana procena uticaja većeg broja stresora na ekološke komponente Zaliva. Posledice ovih uticaja ispoljene su kroz povećan stepen eutrofikacije vodene sredine i dovode se u vezu sa koncentracijom azotnih jedinjenja (nitrata i nitrita) Konkretna merenja vršena su u 2008. godini. Istraživanjem je posebno ukazano na značaj razvoja sistema prikupljanja i obrade ekoloških i drugih informacija radi efikasnijeg upravljanja životnom sredinom datog prostora. Primenjena metodologija procene ekološkog rizika trebalo bi da u naučnom i stručnom pogledu predstavlja doprinos u oblasti zaštite životne sredine,kako kod nas, tako i u svetu

Domoic acid in phytoplankton net samples and shellfish from the Krka River estuary in the Central Adriatic Sea

This paper deals with the precise identification of species of Pseudo-nitzschia, focusing on those which are a potential source of domoic acid, from the Krka River estuary of the Central Adriatic Sea. Domoic acid was measured in phytoplankton net samples and shellfish collected in the winter and early spring of 2011 and 2012. Domoic acid was only detected in early March 2011, both in plankton net samples and shellfish extracts, during a Pseudo-nitzschia species bloom. The measured concentrations of particulate domoic acid (DA) in filtered concentrated seawater varied from 3.1˗6.2 ng DA ml-1. In shellfish sample DA concentration was 0.2 μg g-1. Species belonging to the Pseudo-nitzschia delicatissima complex were more common than those from the Pseudo-nitzschia seriata complex. Morphological analyses by electron microscopy revealed the presence of three potentially toxic species: P. calliantha, P. pseudodelicatissima and P. pungens, and one non-toxic species: P. subfraudulenta. However, P. calliantha and P. pseudodelicatissima dominated during the March 2011 bloom. This study presents the first evaluation of particulate domoic acid along the Eastern Adriatic Sea and the first record of the presence of P. calliantha, P. pseudodelicatissima, P. pungens and P. subfraudulenta in the Krka River estuary

Spatiotemporal profile of emission from oscillating dc micro discharges

The axial light distributions in parallel-plate dc microdischarges in argon show similar behavior to large scale discharges. Between the low-current Townsend mode and the high current glow mode exists a large region of currents where different oscillations appear and the dynamic Volt-Ampere characteristic shows hysteresis behavior. During the oscillations the maximum peak intensity moves closer to the cathode, which is characteristic for the abnormal glow regime even though the average current is considerably smaller.Comment: submitted to: IEEE Trans. Plasma Sci., Spec. Issue on Images in Plasma Sc