Mechanism and kinetics of thermally activated degradation of transition metal complexes with anions of polycarboxylic acids.

U disertaciji je ispitana termička stabilnost pet kompleksa prelaznih metala (Cu, Ni i Zn) sa anjonima aromatičnih polikarboksilnih kiselina: ftalne (pht), izoftalne (ipht) i piromelitne (pyr) kiseline i različitim aminskim ligandima, kao što su etilendiamin (en), bipiridin (bipy) i 2,2'-dipiridilamin (dipya). Razmatrani kompleksi [Cu2(bipy)2(pht)2]·4H2O, Na2[Cu(pht)2]·2H2O, K2[Cu(pht)2]·2H2O, [Zn(dipya)(ipht)]n i [Ni2(en)2(H2O)6(pyr)]·4H2O sintetisani su reakcijom izmene liganada. Strukture kompleksa detaljno su opisane zajedno sa uporednom analizom strukturnih karakteristika. Posebna pažnja posvećena je načinu koordinacije odgovarajućeg polikarboksilato-jona i konformaciji karboksilat-grupa koji uslovljavaju različitu dimenzionalnost (0 – 2D) ispitivanih materijala...Thermal stability of five transition metal (Cu, Ni and Zn) complexes containing the anions of aromatic polycarboxylic acids: phthalic (pht), isophthalic (ipht) and pyromellitic acid (pyr), and different amine ligands such as ethylenediamine (en), bipyridine (bipy) and 2,2'-dipyridylamine (dipya) was investigated. The examined complexes [Cu2(bipy)2(pht)2]·4H2O, Na2[Cu(pht)2]·2H2O, K2[Cu(pht)2]·2H2O, [Zn(dipya)(ipht)]n and [Ni2(en)2(H2O)6(pyr)]·4H2O were synthesized by ligand exchange reaction. Structures of the complexes are described in detail together with a comparative analysis of structural characteristics. Special attention has been devoted to the coordination mode of the corresponding polycarboxylato ion and the conformation of the carboxylate groups which cause the different dimensionality (0 – 2D) of the investigated materials..

Uticaj termičke obrade plodova paradajza na antioksidativnu aktivnost, sadržaj vitamina E, suve materije i ukupnih šećera

The objective of this study was the determination of total antioxidant activity, contents of vitamin E, sugar and total dry matter in fresh and thermally processed (dried and juiced) tomato fruits of different selected tomato lines with the aim to establish the nutritive profile and distinguish superior genotypes in order to obtain high-quality final product with more benefit to human health. Content of vitamin E, total antioxidant activity, dry matter and total sugars, in fresh and dried fruits (dried in parallel hot air dryer at 60 °C, until the final product reached the moisture lower than 10% and in tomato juice pasteurized at 100 °C, for 7 minutes) was studied. Comparative trial with 7 genotypes: one commercial variety (SP-109) and 6 selected high inbreeding generation lines (SPP, SPSM, SPRZ, SPRM-20, S-60 and SPO), was set up. Genotype SPRZ had the highest vitamin E content and total antioxidant capacity, both in fresh fruit and after the treatments. Thermal processing by drying at 60°C and pasteurization of tomato changed the level of total sugar and dry matter content. Total antioxidant activity decreased by drying, comparing to fresh fruit while the level of vitamin E decreased in juice pasteurized at high temperature (100 °C). .Cilj istraživanja je određivanje ukupne antioksidativne aktivnosti, sadržaja vitamina E, sadržaja šećera i ukupne suve materije u svežim i termički obrađenim (sušeni plodovi i sok) plodovima različitih selekcionih linija paradajza, sa ciljem utvrđivanja nutritivnog kvaliteta i izdvajanja superiornih genotipova, čijom preradom bi se dobio kvalitetniji krajnji proizvod sa pozitivnim dejstvom na ljudsko zdravlje. Ispitivani su sadržaj vitamina E, ukupna antioksidativna aktivnost, suva materija, i ukupni sadržaj šećera, kod svežih plodova, sušenih plodova (sušenje toplim vazduhom na 60 °C, do konačne vlage uzorka manje od 10%) i soka paradajza (pasterizacijom na 100 °C, u trajanju od 7 minuta). Izveden je komparativni ogled sa 7 genotipova, jedna komercijalna sorta (SP-109) i 6 selekcionisanih linija (SPP, SPSM, SPRZ, SPRM-20, S-60 I SPO) visokih generacija inbridinga. Termička obrada plodova paradajza (sušenjem na 60 °C) i pravljenjem soka dovodi do promene ukupnog sadržaja šećera i sadržaja ukupne suve materije. Ispitivanjem ukupne antioksidativne aktivnosti utvrđeno je da se ona gubi sušenjem u odnosu na svež plod, a sadržaj vitamina E se smanjio u soku koji je dobijen obradom na višim temperaturama (100 °C). Genotip SPRZ imao je najviše vrednosti za sadržaj vitamina E i ukupan antioksidativni kapacitet kako u svežem stanju tako i nakon primenjene obrade. Izborom superiornih genotipova i akumulacijom nutrijenata kroz oplemenjivačke programe, može se poboljšati kvalitet krajnjeg proizvoda i postići dobijanje prerađevina sa većim pozitivnim uticajem na zdravlje ljudi

The change of phytochemical profile in beet juice and the influence of different storage conditions during one year

Many scientific researches proved the antioxidative impact of beet and its products. The use of vegetable juices is getting more popular in human diet. The way of storage plays an important role in preservation, long life and minimal variability of phytonutrients. The storage of products, usually in inappropriate conditions, leads to additional loss of phytonutrients, which have already been decreased by processing. In this research, we studied the impact of three ways of storage of pasteurised beet juice during one year, on content of some nutrients (total sugars, vitamin C, phenols and total antioxidative capacity). Pasteurised juice was stored in three ways: in light, at room temperature, in dark, at room temperature and in dark, at temperature of 4 °C. The change of content and differences have been followed during one month and confirmed with ANOVA and Tukey's test. The lowest changes of total sugars have been recorded in storage in dark at 4 °C, while in storage in light, the sugar content increased. The losses of vitamin C during one year of storage had linear trend of decrease. Antioxidative capacity of beet juice depends on concentration of phenol compounds and loss of these parameters was similar during period of one year. The best way of storage was dark place at low temperature

Rooting and preventing shoot-tip necrosis of in vitro cultured horse chestnut shoots

Efficient bud regeneration was achieved from germinating horse chestnut (Aesculus hippocastanum L.) somatic embryos cultivated on 1-10 μM benzyladenine (BA). Adventitious buds were detached from the mother tissue and used to establish permanent shoot cultures on 0-20 μM BA. Secondary buds were regenerated from the shoot base of the explants. Bud multiplication was very poor (1.9) and shoot-tip necrosis was very high (100%) on plant growth regulator (PGR)-free medium. The highest multiplication was achieved on 5 and 10 μM BA (16.8 and 18.7, respectively), with no shoot-tip necrosis, while hyperhydration was rather frequent on shoots cultivated on BA above 5 μM. Individual shoots were elongated on medium with 1 μM BA and 500 mg/l polyvinylpyrrolidone (PVP MW40 000) for 4 weeks. However, it was necessary to reduce BA level below 1 μM for shoot rooting and that caused mass shoot-tip necrosis. As classical rooting methods failed, the basal part of each elongated shoot was first wounded by cutting with a sterile blade and then dipped into a 0, 5 or 10 mM indole-3-butyric acid solution for 1 min and cultivated on solid half-strength MS PGR-free medium with 0.02% activated charcoal for 2-3 weeks. To prevent shoot tip necrosis during this phase, a BA solution was applied directly on apical meristem. Shoot-tip necrosis was completely eliminated by weekly application of 10 μl of 1 μM BA. As soon as the root initials were observed, the shoots were transferred to MS medium supplemented with 500 mg/l PVP and 5 μM BA. The frequency of rooting was 23%, and further optimisation of root-inducing phase is needed

The impact of different thermal processing of tomato to its antioxidant activity, vitamin E, dry matter and sugar content

The objective of this study was the determination of total antioxidant activity, contents of vitamin E, sugar and total dry matter in fresh and thermally processed (dried and juiced) tomato fruits of different selected tomato lines with the aim to establish the nutritive profile and distinguish superior genotypes in order to obtain high-quality final product with more benefit to human health. Content of vitamin E, total antioxidant activity, dry matter and total sugars, in fresh and dried fruits (dried in parallel hot air dryer at 60 °C, until the final product reached the moisture lower than 10% and in tomato juice pasteurized at 100 °C, for 7 minutes) was studied. Comparative trial with 7 genotypes: one commercial variety (SP-109) and 6 selected high inbreeding generation lines (SPP, SPSM, SPRZ, SPRM-20, S-60 and SPO), was set up. Genotype SPRZ had the highest vitamin E content and total antioxidant capacity, both in fresh fruit and after the treatments. Thermal processing by drying at 60°C and pasteurization of tomato changed the level of total sugar and dry matter content. Total antioxidant activity decreased by drying, comparing to fresh fruit while the level of vitamin E decreased in juice pasteurized at high temperature (100 °C).

Bis(2,2 '-bipyridine)-bis(mu(3)-phthalato)-dicopper(II) tetrahydrate as molecular sieve with zero-dimensional structure

Crystal structure of the title compound: [Cu-2(bipy)(2)(pht)(2)]center dot 4H(2)O (bipy = 2,2'-bipyridine, pht = dianion of phthalic acid), CuBP center dot 4H(2)O, consists of dinuclear entities, which are further connected by pi-pi stacking interactions between bipy ligands. In this way small channels (micropores) oriented parallel to the [001] direction and containing loosely hydrogen bonded water molecules are formed. The structural changes during dehydration-rehydration have been thoroughly investigated using TG/DSC analysis, FT-IR spectroscopy, X-ray powder diffraction, optical and scanning electron microscopy, and sorption experiments. In addition, dehydration process was analyzed from the aspect of kinetics. A complete reversibility of the dehydration-rehydration CuBP center dot 4H(2)O(s) reversible arrow CuBP(s) + 4H(2)O(g) process was confirmed by all means. Therefore, CuBP center dot 4H(2)O can be classified as molecular sieve with quite unexpected zero-dimensional structure

Thermal stability and degradation of binuclear hexaaqua-bis(ethylenediamine)-(μ 2-pyromellitato)dinickel(II) tetrahydrate

Thermal degradation of ternary transition metal complex containing tetraanion of pyromellitic acid, pyr, and ethylenediamine, en, [Ni2(en)2(H2O)6(pyr)]·4H2O, 1, was investigated under non-isothermal conditions. The mechanism of thermal degradation, which occurs in three steps, was clarified by TG/DSC measurements in conjunction with FT-IR spectroscopy and XRPD analysis. The complexity of all degradation steps has been revealed using isoconversional methods. Dehydration comprises the loss of ten water molecules in a relatively narrow temperature interval, resulting in a very complicated reaction mechanism. In addition, density functional theory calculations have been applied for better understanding of dehydration. The second degradation step, related to loss of en, was separated into two single-step processes with Fraser–Suzuki function. The obtained individual steps were described by Johnson–Mehl–Avrami A2 model and Šesták–Berggren model, respectively. Validation of the proposed kinetic triplets for individual steps was performed using master plot and Pérez-Maqueda criteria. The third degradation step is related to the fragmentation of pyr ion most likely followed with the release of a number of gaseous products

Detection of PBP2a (penicillin-binding protein 2a) and mecA gene in methicillin resistant staphylococci originated from animals

For the purpose of detecting methicillin (oxacillin) resistance in staphylococcal strains, in a number of microbiological laboratories only disc diffusion method with cefoxitin and/or oxacillin discs is used. Besides this method, it is desirable to determine MIC values for cefoxitin and/or oxacillin. After examination by disc diffusion and dilution methods, latex agglutination is used for the detection of PBP2a and PCR is used for the detection of mecA gene. Use of PCR is not possible in a large number of diagnostic laboratories and as method of choice, latex agglutination test for rapid detection of PBP2a is recommended. In this investigation, as confirmatory methods, latex agglutination and PCR were used for strains that were resistant to oxacillin and/or cefoxitin by disc diffusion and broth microdilution methods. In total, 14 strains of coagulase-negative staphylococci originating from clinical specimens of cats, dogs and chicken were examined. Among isolated strains, it was established that the dominating species was Staphylococcus haemolyticus with 11 isolated strains. Other isolated species were Staphylococcus epidermidis, Staphylococcus capitis and Staphylococcus vitulinus, each with one isolated strain. For all 14 strains, oxacillin MIC values ranged from 0.5 μg/mL to >64 μg/mL and cefoxitin MIC values ranged from 1 μg/mL to >256 μg/mL. Positive agglutination reaction by latex agglutination test was recorded in 13 out of 14 strains. The PCR assay for mecA gene was positive in 12 investigated strains. [Projekat Ministarstva nauke Republike Srbije, br. 31079

Origin of the Intrinsic Coercivity Field Variations and Magnetic Study of ε-Fe2O3

Abstract: Origin of the intrinsic coercivity field variations observed by hysteretic measurements established by Nikolic et al. was investigated in detail by ZFC/FC measurements. In this study, magnetic behavior of the samples is further examined by calculation of the ZFC Mn(T) and Mn(H) first derivatives. Performed study showed that the main contribution to the measured coercivity comes from the ε-Fe2O3 particles, characterized by Hci = 24 kOe, although both samples posses SPM ε-Fe2O3 fraction. As a result, Hci values of the samples are differed dependent on the quantity of the SPM ε-Fe2O3 particles in the sample. Mechanism of the intrisic coercivity field variations is discussed. © 2019, Pleiades Publishing, Ltd

Origin of the Intrinsic Coercivity Field Variations of ε-Fe2O3

ε-Fe2O3 phase is recognized as an attractive material, in both technological and scientific point of view, since it can achieve very high room-temperature coercivity (10–20 kOe). In this paper, multi-phase samples Fe2O3/SiO2 with slightly different Fe/Si molar ratio were produced by sol–gel synthesis route. The obtained samples were characterized by various experimental techniques including XRD, TA, FTIR, and SQUID (DC and AC magnetic measurements). It was found that both samples consisted of α-Fe2O3 and ε‑Fe2O3 phases embedded in the silica matrix, and showed very similar structural and magnetic properties, except that displayed significantly different room-temperature intrinsic coercivity field values: HciS1 = 14.3 kOe and HciS2 = 7.5 kOe. We have discussed possible origin of thus high intrinsic coercivity field variation. © 2019, Pleiades Publishing, Ltd