Activity coefficients of ternary aqueous solutions of electrolytes with common potassium ion at T = 298.15 K.

Predmet ovog rada je proučavanje termodinamičkih osobina trokomponentnih vodenih rastvora elektrolita sa zajedničkim kalijumovim jonom: {yKCl+(1-y)K2HPO4}(aq), {yKNO3+(1-y)K2HPO4}(aq), {yKBr+(1-y)K2HPO4}(aq) na temperaturi 298.15 K. Primenom izopiestičke metode određeni su osmotski koeficijenti u navedenim sistemima kao i rastvorljivost K2HPO4 u sistemu K2HPO4(aq) na temperaturi 298.15 K. Obrada eksperimentalnih rezultata za čiste rastvore elektrolita K2HPO4(aq), KNO3(aq) i KBr(aq) izvedena je proširenim modelom Pitzer-a i modelom Clegg-a. Oba modela daju zadovljavajuće rezultate fitovanja eksperimentalnih podataka i standardnu devijaciju reda veličine 10–3. Na osnovu izopiestičkih rezultata utvrđeno je da molalnost zasićenog rastvora K2HPO4(aq) na temperaturi 298,15 K u ravnoteži sa K2HPO4∙xH2O(cr) iznosi msat=10.6 mol∙kg–1 a u ravnoteži sa K2HPO4∙3H2O(cr) iznosi msat= 9.7429±0.0023 mol⋅kg-1. Obrada eksperimentalnih rezultata mešanih rastvora elektrolita izvedena je modelima: Scatchard–a, Pitzer-a i Clegg-a, pri čemu je u modelima Pitzer–a i Clegg-a razmatran i uticaj elektrostatičkih članova višeg reda. Primena članova ne daje znatno bolje rezultate fitovanja. Sva tri modela daju zadovoljavajuće rezultate fitovanja osmotskih koeficijenata u ispitivanim sistemima a standardna devijacija je reda veličine 10-3.. Model Scathard–a sa šest parametara mešanja daje najbolje slaganje eksperimentalnih i proračunatih vrednosti osmotskih koeficijenata. Vrednosti koeficijenta aktivnosti K2HPO4 u sva tri sistema opadaju sa porastom jonske jačine sistema i rastu sa porastom udela jonske jačine drugog elektrolita u sistemima {yKCl+(1-y)K2HPO4}(aq), {yKBr+(1-y)K2HPO4}(aq) a opadaju u sistemu {yKNO3+(1-y)K2HPO4}(aq). Vrednosti koeficijenta aktivnosti KCl i KBr opadaju sa porastom jonske jačine do I ≈4 mol∙kg–1 a rastu sa porastom udela jonske jačine KCl i KBr. U sistemu {yKNO3+(1-y)K2HPO4}(aq) koeficijent aktivnosti KNO3 opada sa porastom jonske jačine i udela jonske jačine KNO3...The object of this work is the study of thermodynamic properties of ternary aqueous solutions of electrolytes with common, potassium cation: {yKCl+(1-y)K2HPO4}(aq), {yKNO3+(1-y)K2HPO4}(aq), {yKBr+(1-y)K2HPO4}(aq) at temperature 298.15 K. Isopiestic method was used for determination of osmotic coefficients of former ternary systems as well as for solubility of K2HPO4 in the system K2HPO4(aq) at temperature 298.15 K. Treatment of experimental data of binary aqueous solutions of electrolytes K2HPO4(aq), KNO3(aq) and KBr(aq) is performed by the Extended Pitzer model and Clegg’s model. Both models are giving satisfying results of fitting the experimental data with standard deviation of fit being of the order 10–3. On the bases of isopiestic results it is determined that the molality of saturated solution K2HPO4(aq) at temperature 298,15 K in equilibrium with solid phase K2HPO4∙xH2O(cr) is msat=10.6 mol∙kg–1. and in equilibrium with K2HPO4∙3H2O(cr) is msat= 9.7429±0.0023 mol⋅kg-1. Treatment of experimental results of ternary aqueous solutions of electrolyte was perfomed using the Scatchard, Pitzer and Clegg models where in last two models the influence of higher order electrostatic terms was taken into account. These higher order electrostatic terms didn’t give much of improvement in fitting the results. All three models gave standard deviation of fitting osmotic coefficients of the order 10-3. The Scatchard model with six mixing parameters gave the best agreement between experimental and calculated osmotic coefficients values for all the investigated systems. Values of activity coefficient of K2HPO4 in all three systems decrease with increasing total ionic strength of the system and with higher ionic strength fraction of other electrolyte show increasment in the systems {yKCl+(1-y)K2HPO4}(aq), {yKBr+(1-y)K2HPO4}(aq) and decreasment in the system {yKNO3+(1-y)K2HPO4}(aq). Values of activity coefficient of KCl and KBr decrease with increasing total ionic strength of the system up to I ≈4 mol∙kg–1 but increase with higher ionic strength fraction of KCl and KBr. In the solution {yKNO3+(1-y)K2HPO4}(aq) mean ionic activity coefficient of KNO3 is lowering with the increase of both total ionic strength and ionic strength fraction of KNO3..

KARAKTERIZACIJA SADRŽAJA IZOFLAVONA U HRVATSKOJ KOLEKCIJI CRVENE DJETELINE

Red clover is a perennial forage crop rich in isoflavones, the bioactive compounds with a positive effect on human and animal health. The aim of the research was to determine a variation in the isoflavone contents in the Croatian red clover collection and to identify the most promising materials to be used in the breeding program for the development of new cultivars for specific purposes. Leaf samples of 29 red clover cultivars/populations (two cultivars, twenty breeding populations, and seven local populations) were collected in a full flowering stage, and the identification and quantification of isoflavones was performed using the HPLC analysis. The most common isoflavones in the red clover cultivars/populations were formononetin and biochanin A. A significant variation among the cultivars/populations in the total and individual isoflavone content was determined. The populations with very high and low contents of both the total and of the individual isoflavones were identified to be used for the breeding purposes in order to develop new forage cultivars, or for specific goals in the pharmaceutical industry.Crvena djetelina višegodišnja je krmna kultura bogata izoflavonima, bioaktivnim spojevima s pozitivnim utjecajem na zdravlje ljudi i životinja. Cilj istraživanja bio je utvrditi varijabilnost sadržaja izoflavona hrvatske kolekcije crvene djeteline te identificirati najzanimljivije materijale koji će se koristiti u oplemenjivačkome programu za razvoj novih sorata za specifične namjene. Uzorci lista prikupljeni su u stadiju pune cvatnje iz 29 sorata/populacija crvene djeteline (dvije sorte, dvadeset oplemenjivačkih populacija, sedam lokalnih populacija), a identifikacija i kvantifikacija izoflavona obavljena je pomoću HPLC analize. Najzastupljeniji izoflavoni u sortama/populacijama crvene djeteline bili su formononetin i biohanin A. Utvrđena je značajna varijabilnost među sortama/populacijama u sadržaju ukupnih i individualnih izoflavona. Identificirane su populacije s vrlo visokim i niskim sadržajem kako ukupnih, tako i pojedinačnih izoflavona koje će se koristiti u oplemenjivačke svrhe za razvoj novih krmnih kultivara ili za specifične namjene u farmaceutskoj industrij

OPTIMIZATION OF HORSERADISH PEROXIDASE ENCAPSULATION WITHIN TYRAMINE-ALGINATE FOR PHENOL REMOVAL

Phenolic compounds are one of the most common pollutants in aqueous systems, so their removal from water is of major interest. Among biocatalysts used for phenol removal, horseradish peroxidase is the most investigated for this purpose. Enzyme inactivation is a major problem which could be successfully overcome by immobilization of the enzyme onto different polymers. Tyramine-alginate micro-beads were tested for the immobilization of horseradish peroxidase. Different concentrations of tyramine-alginate were used and their influence on specific activity of the enzyme was tested. Increasing concentration of oxidized alginate results in increase of specific activity. Immobilized HRP was tested for phenol removal in a batch reactor. Presented results were obtained with HRP immobilized within 10 mol% tyramine-alginate micro-beads. These biocatalysts can be used up to three cycles

Matrix-assisted laser desorption/ionization time of flight mass spectrometry identification of Vibrio (Listonella) anguillarum isolated from sea bass and sea bream

Vibrio (Listonella) anguillarum is a pathogenic bacterium causing septicaemia in a wide range of marine organisms and inducing severe mortalities, thus it is crucial to conduct its accurate and rapid identification. The aim of this study was to assess MALDI-TOF MS as a method of choice for identification of clinical V. anguillarum isolates from affected marine fish. Since the method accuracy might be influenced by the type of the medium used, as well as by the incubation conditions, we tested V. anguillarum isolates grown on standard media with and without the addition of NaCl, cultured at three incubation temperatures, and at three incubation periods. The best scores were retrieved for V. anguillarum strains grown on NaCl-supplemented tryptone soy agar (TSA) at 22°C and incubated for 48h (100 % identification to species level ; overall score 2.232), followed by incubation at 37°C and 48h (100 % to species level ; score 2.192). The strains grown on non-supplemented TSA gave the best readings when incubated at 22°C for 72h (100 % identification to species level ; overall score 2.182), followed by incubation at 15°C for 72h (100 % to species level ; score 2.160). Unreliable identifications and no- identifications were growing with the incubation duration at 37°C, on both media, amounting to 88.89 % for 7d incubation on supplemented TSA, and 92.60 % for 7d incubation on non-supplemented TSA. The age of the cultured strains and use of media significantly impacted the mass spectra, demonstrating that for reliable identification, MALDI-TOF MS protein fingerprinting with the on-target extraction should be performed on strains grown on a NaCl-supplemented medium at temperatures between 15 and 22°C, incubated for 48-72 hours

Can School Children Support Ecological Research? Lessons from the Oak Bodyguard Citizen Science Project

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A crosslinguistic study of symmetrical judgments

A longstanding puzzle in developmental linguistics is why children are more permissive than adults in assigning distributive interpretations to sentences with the universal quantifiers each, every, and all under certain experimental conditions. One well-known controversial issue in this area is children’s symmetrical judgments of universally quantified sentences. Symmetrical judgments are elicited when a child is asked to judge if a sentence including a universal quantifier describes a visual context depicting an incomplete distributive relation. The following three judgment types have been included in the set of symmetrical judgment types in the literature (examples from Kang, 2001).peer-reviewe