Reactive Oxygen Emission From Microwave Discharge Plasmas

Metastable oxygen atoms and molecules have received increased interest because of their function in surface modification, bio-decontamination and many other industrial applications, in addition to the role in the upper atmospheric layer chemistry. We review work on production and detection of metastable oxygen and we describe our experiments, including the development of techniques for measurement of metastable molecular oxygen. We show that either metastable oxygen molecules or metastable oxygen atoms can be produced in large quantities in electrical discharges, carefully tailored to promote the required kinetics. Although the two species may coexist, colder discharge regimes favor production of molecules, while at higher temperature conditions atomic oxygen prevails. We found that microwave cavity discharges in He/O2 mixtures favor molecular production, but that an arc-seeded microwave torch in air shows preference of atomic production. Result on the specific yield of molecular oxygen in the microwave cavity discharge shows qualitative agreement with the models

Plasma Treatment of Bulk Nb Surface in the Ar/Cl2 Discharge

The preparation of the cavity walls has been one of the major challenges in the superconducting radio-frequency (SRF) accelerator technology. Therefore, constant research and development effort is devoted to develop surface preparation processes that will improve roughness and lower the level of impurities, like hydrogen or oxygen, embedded in bulk Nb, having in the same time reasonable etching rates. Plasma based surface modification provides an excellent opportunity to achieve these goals. We present Ar/Cl2 discharge treatment of bulk Nb where we achieved etching rates comparable to the rates obtained with the electropolishing method without introducing impurities in Nb. The current experiments were performed on disk shaped Nb samples, exposed to plasma produced in a microwave discharge system. Surface composition and topology measurements were carried out before and after plasma treatment. Upon determining optimal experimental condition on disk shaped samples, we will apply the same procedure on the single cell cavities, pursuing improvement of their RF performance

Plasma Treatment of Bulk Niobium Surface for Superconducting RF Cavities: Optimization of the Experimental Conditions on Flat Samples

Accelerator performance, in particular the average accelerating field and the cavity quality factor, depends on the physical and chemical characteristics of the superconducting radio-frequency (SRF) cavity surface. Plasma based surface modification provides an excellent opportunity to eliminate nonsuperconductive pollutants in the penetration depth region and to remove the mechanically damaged surface layer, which improves the surface roughness. Here we show that the plasma treatment of bulk niobium (Nb) presents an alternative surface preparation method to the commonly used buffered chemical polishing and electropolishing methods. We have optimized the experimental conditions in the microwave glow discharge system and their influence on the Nb removal rate on flat samples. We have achieved an etching rate of 1.7 μm/min using only 3% chlorine in the reactive mixture. Combining a fast etching step with a moderate one, we have improved the surface roughness without exposing the sample surface to the environment. We intend to apply the optimized experimental conditions to the preparation of single cell cavities, pursuing the improvement of their rf performance

Fatty acid profile in muscles of carp (cyprinus carpio l.) Raised in a semi-intensive production system fed with grains, pelleted and extruded feed

The effects of grains, pelleted and extruded feed on the fatty acid content in carp meat has not been examined yet. In this work, we present evidence that the high carbohydrate content in all three types of feed causes oleic acid to predominate in all meat samples. A higher PUPA content in the meat of fish fed with granulated feed was detected. The extruded feed diet led to 69% greater n-3, and 53% lower n-6 fatty acid contents. Their ratio is thus 2.64-fold higher than in meat of carp fed with pelleted feed. A higher content of n-3 fatty acids in fish fed with extruded feed was the consequence of higher DNA (1.6 times) and EPA (3.3 times) contents. The detected differences could be the consequence of the thermal treatment of extruded feed that makes the proteins, carbohydrates and lipids more accessible to fish than in a pelleted feed

Uspostavljanje programa selektivnog uzgoja kalifornijske pastrmke (oncorhynchus mykiss, walbaum) u Srbiji

Zahtev za sve većim količinama hrane za ljudsku upotrebu, efikasnost iskorišćavanja hraniva i prostora za gajenje domaćih životinja, kao i pojava mnogih bolesti doveli su do intenzivnog razvijanja selekcionih programa u svim granama poljoprivrede. Za razliku od ostalih gajenih životinja, programi selekcije u akvakulturi su se razvili nešto kasnije usled nedostatka potrebnih procena heritabilnosti, koeficijenata varijacija i korelacija za ekonomski bitne osobine. Trenutno se u akvakulturi samo 1-2% od ukupne proizvodnje zasniva na genetički unapređenim vrstama riba (Gjedrem, 1997). Korišćenjem selektovanih linija riba postiže se više korisnih stvari. Na prvom mestu, programi selekcije riba predstavljaju jedini način stalnog unapređenja ekonomski bitnih osobina kao sto su prirast, konverzija hrane, otpornost na bolesti, smanjenje masnoće u mesu riba. Ribe iz selektovanih linija efikasnije iskorišćavaju hraniva i na taj način smanjuju pritisak na divlje populacije riba koje se koriste za proizvodnju ribljeg brašna, kao glavnog izvora proteina u smešama za ishranu pastrmki. Ribe koje potiču iz divljine ne napreduju zadovoljavajućim brzinom, što znači da su konstantno pod stresom, za razliku od riba poreklom iz selekcionih programa koje pokazuju manji uticaj stresa usled gajenja u zarobljeništvu. Tako se na ovaj način korišćenjem selektovanih linija riba postiže efikasna i održiva proizvodnja uz vođenje računa o dobrobiti životinja. Drugi dobar razlog za uspostavljanje programa selekcije pastrmke u Srbiji je dobro dokumentovano postojanje interakcije genotip x okolina kod kalifornijske pastrmke, kao što su pokazala istraživanja (McKay et al., 1984; Hanke et al., 1989; Sylven et al., 1991; Winkelman and Peterson, 1994; Kettunen et al., 1999; Kause et al., 2003). Na kraju, ali ne i najmanje važna je i kontrola bolesti kod kalifornijske pastrmke i mogućnost stvaranja otpornih linija pastrmki na neke bolesti putem selektivnog uzgoja (Henrion, 2005). Jedno od rešenja za ovaj ozbiljan problem, pored boljeg sistema kontrole pastrmske ikre poreklom iz uvoza, je i stvaranje lokalnih selektovanih matičnih jata sa proverenim poreklom i povećenom otpornošću na bolesti. Obzirom da za kalifornijsku pastrmku postoje pouzdani podaci o varijabilnosti i heritabilnosti proizvodnih osobina ovo pruža mogućnost efikasne selekcije, a samom tim i značajnog unapređenja proizvodnje uz smanjen ukupni mortalitet, putem odgovarajućeg programa selekcije u Srbiji

Plasma Treatment of Bulk Niobium Surfaces for SRF Cavities

Two types of electric discharges were used to demonstrate the validity of plasma surface treatment for superconducting radio-frequency (SRF) cavities. The experiments were performed on disc-shaped Nb samples and compared with identical samples treated with buffer chemical polishing (BCP) techniques. Surface analysis indicates comparable or superior properties of plasma-treated samples. These promising results are still preliminary and additional work is in progress

Program selektivnog uzgoja šarana (Cyprinus carpio L.) u Srbiji - preliminarni rezultati

The aim of this study was to estimate heritability and genetic correlations between weight, length and height of common carp in Serbia (Cyprinus carpio L.) during 3-year growth period. The 50 families of common carp were produced in 2007 and used for the estimation of genetic parameters. The fish were measured at tagging for weight, length and height (W0, L0, H0), then during the first autumn (W1, L1, H1) and during the second autumn (W2, L2, H2). Based on univariate models heritability estimates were high for all traits (0.39, 0.34 and 0.45 for W1, L1 and H1, respectively) and also for the second production year (0.49, 0.47 and 0.44 for W2, L2 and H2, respectively). The genetic correlations were estimated using multivariate models and they were high between W1 and L1 and H1 (0.81 ± 0.06 and 0.91 ± 0.03 for L1 and H1, respectively), while between H1 and L1 were moderately correlated (0.54 ± 0.12). In the second production year genetic correlations were also high, between W2 and L2 and H2 (0.64 ± 0.09 and 0.74 ± 0.06, respectively), while between length and height they were lower (0.24 ± 0.15). Based on the current results improving growth rate of common carp through genetic selection is expected to be effective.Cilj ove studije je bio da se procene heritabilnost i genetičke korelacije telesne mase, dužine i visine šarana u Srbiji u toku trogodišnjeg ciklusa. U toku 2007. godine proizvedeno je 50 familija šarana i ove jedinke iskorišćene su za procenu heritabilnosti i genetičke korelacije. Merenja riba su obavljena za osobine telesna masa, dužina i visina u momentu označavanja (W0, L0, H0), zatim pri starosti riba prva jesen (W1, L1, H1) i pri starosti druga jesen (W2, L2, H2). Na osnovu jednovarijantnih statističkih modela za svaku osobinu procene heritabilnosti su bile visoke (0.39, 0.34 i 0.45 za W2, L2 i H2). Genetičke korelacije su procenjene na osnovu multivarijacionih statističkih modela i bile su visoke između W1 i, L1 i H1 (0.81 ± 0.06 i 0.91 ± 0.03 za L1 i H1), dok su između H1 i L1 bile umereno korelisane (0.54 ± 0.12). U drugoj produkcionoj godini korelacije su takođe bile visoke, između W2 i, L2 i H2 (0.64 ± 0.09 i 0.74 ± 0.06), dok su između osobina dužina i visina, L2 i H2, bile niže (0.24 ± 0.15). Na osnovu navedenih rezultata očekuje se da bi poboljšanje prirasta u navedenoj populaciji šarana u Srbiji, putem selekcije familija, bilo uspešno

PLASMA TREATMENT OF NIOBIUM SRF CAVITY SURFACES*

Abstract Plasma based surface modification provides an excellent opportunity to eliminate non-superconductive pollutants in the penetration depth region of the SRF cavity surface and to remove mechanically damaged surface layer improving surface roughness. We have demonstrated on flat samples that plasma etching in Ar / Cl 2 of bulk Nb is a viable alternative surface preparation technique to BCP and EP methods, with comparable etching rates. The geometry of SRF cavities made of bulk Nb defines the use of asymmetric RF discharge configuration for plasma etching. In a specially designed single cell cavity with sample holders, discharge parameters are combined with etched surface diagnostics to obtain optimum combination of etching rates, roughness and homogeneity in a variety of discharge types, conditions, and sequences. The optimized experimental conditions will ultimately be applied to single cell SRF cavities

Mogućnost poboljšanja proizvodnih osobina šarana (Cyprinus carpio l) putem selekcije

Selective breeding for growth rate in common carp (Cyprinus carpio L.) has not been actively pursued after some early unsuccessful selection experiments. Prerequisite for successful selective breeding is accurate and objective evaluation of genetic parameters used in the planning and implementation of selection methods. The aim of this work was to assess the possibilities of improving production traits (weight, length and height) that are related to the growth of carp, through selection. Estimated variation and heritabilities were significantly high for all examined characteristics. Based on the obtained results can be expected to improve growth rate of common carp through selective breeding