Various copper(II) complexes as guests were immobilised among the layers of montmorillonite or on silica gel as hosts. Anchoring took place through hydrogen bonds and ion exchange for montmorillonite, while the forces of interaction were either hydrogen bonding or covalent bonds for the copper complex-silica gel nanohybrids. The thermal stabilities of these substances were studied under oxidizing atmosphere and it was found that anchoring increased the durability of the host-guest complexes relative to the host-free ones.
Poly-(butanediol-1,4-adipate) and poly-(diethyleneglycol-succinate) polyesters and their “ionized” derivatives, containing Mg2+ and Zn2+ ions with different stoichiometric ratios to the chain-end COOH groups of the polyesters have been investigated by derivatograph.
Authors:E. Princz, I. Szilágyi, K. Mogyorósi, and I. Labádi
Ethylenediaminotetramethylenephosphonic acid (EDTMP, H8L) was prepared and its complexes with some lanthanide ions (La, Eu, Gd and Sm) were isolated under various conditions. IR spectra and thermal stabilities of EDTMP and its complexes were studied. The experimental conditions of the preparation influence to the composition of the complexes were shown. In alkaline solution (pH=8) deprotonated (P(O)(O–)2), and in acidic solution (pH=3–4) deprotonated and partly protonated (P(O)(O–)(OH)) and non-protonated (P(O)(OH)2) phosphonic groups are present in the complexes. All the complexes contain coordinated water molecules. The complexes containing a protonated phosphonic group contain coordinated and hydrogen-bonded water molecules.
Authors:I. Oláh, Zs. Bendő, Gy. Szakmány, V. Szilágyi, and B. Péterdi
The authors carried out the archaeometric analyses of 9 basalt preforms found at the Kádárta site in Veszprém county. Most of the analyses used non-destructive methods (macroscopic petrography, PGAA, MS and electron-microprobe (EDXEPMA) method developed within the frames of these investigations) and the traditional destructive petrographic and mineral chemical analyses were carried out on a small flake. All the analyses demonstrated that the nine basalt artefacts were prepared from the same raw material. According to the material collected so far from the basalt volcanoes of the Pannonian Basin, this raw material came from the volcanic territory of the Little Hungarian Plain and the Balaton Highlands. Within these territories the most probable provenance of the raw material is the lava rocks in the region of Boncsos-tető, although Hegyestű, Somló and Haláp cannot definitely be excluded.
Authors:J. Zsakó, I. Szilágyi, Á. Simay, Cs. Várhelyi, and K. Kerekes
A number of 7 complexes of the [Co(DH)2(amine)2)]I type (DH2 stands for dimethyloxime) have been studied by means of thermogravimetry and differential scanning calorimetry in nitrogen atmosphere, by using heating rates of 2.5, 5 and 10 K min–1. In all cases an endothermal deamination reaction occurs leading to the relatively stable [Co(DH)2I(amine)] intermediate. For this reaction apparent kinetic parameters have been derived. The influence of heating rate is discussed. The validity of a linear and a non-linear kinetic compensation law was verified.
Authors:Luciana Fernandes, W. Oliveira, J. Sztatisz, I. Szilágyi, and Cs. Novák
Inclusion complexes of Lippia sidoides essential oil and β-cyclodextrin were obtained by slurry method and its solid powdered form was prepared using spray drying.
The influence of the spray drying, as well as the different essential oil:β-cyclodextrin ratio on the characteristics of the
final product was investigated. With regard to the total oil retention 1:10 mass/mass ratio as optimal was found between the
essential oil and β-cyclodextrin.
Thermoanalytical techniques (TG, EGD, TG-MS) were used to support the formation of inclusion complex and to examine their
physicochemical properties after accelerated storage conditions. It may be assumed that the thermal properties of the complexes
were influenced not only by the different essential oil/ β-cyclodextrin ratio but also by the storage conditions. In the aspect
of their thermal stabilities, complex prepared with 1:10 m/m ratio (essential oil:β-cyclodextrin) was the most stable one.
Authors:I. Szilágyi, J. Madarász, F. Hange, and G. Pokol
Thermal decomposition of ammonium paratungstate
tetrahydrate, (NH4)10[H2W12O42]4H2O has been followed by simultaneous TG/DTA and online evolved
gas analysis (TG/DTA-MS) in flowing 10% H2/Ar directly
up to 900C. Solid intermediate products have been structurally evaluated
by FTIR spectroscopy and powder X-ray diffraction (XRD). A previously unexplained
exothermic heat effect has been detected at 700–750C. On the basis
of TG/DTA as well as H2O and NH3
evolution curves and XRD patterns, it has been assigned to the formation and
crystallization heat of γ-tungsten-oxide (WO2.72/W18O49)
from β-tungsten-oxide (WO2.9/W20O58)
and residual ammonium tungsten bronze.
Authors:Á. Móréh, F. Jordán, A. Szilágyi, and I. Scheuring
There is increasing evidence that regime shifts occur at several scales in ecosystems (from the spatiotemporal alternation of two species to large-scale, ecosystem-level rearrangements). Yet, the theoretical background for understanding these changes is far from clear. Since fishing down in marine ecosystems is well-documented trend, and its top-down cascading effects in food webs have been richly documented, it is a current question whether overfishing, in general, can also influence regime shifts at lower levels. We model simple marine ecosystems by dynamical food webs and investigate the probability of regime shifts emerging among primary consumers. We considered cases where only one of the primary consumers is persistent in the stationary state. By perturbing the death rates in the food web, we studied the circumstances when the previously persistent primary producer is indirectly changed by the previously non-persistent one. Whether and how regime shifts (e.g., change in primary consumers) can occur depends on (1) food web topology (presence of top-predator and alternative producer), (2) the relative strength of perturbation of primary consumers’ death rates, and (3) the dynamical parameters of the recovering consumer. We found that overfishing, food web topology and dynamical parameters together determine the probability of regime shifts. Thus, integrative and complex models are needed in multispecies fisheries.
Authors:Viktória Tóth, Melinda Szilágyi, Fruzsina Anton, Éva Leiter, I. Pócsi, and T. Emri
Pairwise interactions between four antifungal compounds were studied. The β-1,3-glucan synthase inhibitor echinocandin B (ECB) showed synergistic effect with the cell wall hydrolase ChiB chitinase and EngA β-1,3-glucanase on Saccharomyces cerevisiae, Candida albicans, Aspergillus rugulosus and A. fumigatus. The antifungal protein of Penicillium chrysogenum (PAF) did not influence the antifungal activity of ChiB or EngA, but showed antagonistic effect with ECB on A. nidulans, A. rugulosus and A. fumigatus. PAF had no significant effect on the growth of the tested yeasts as it was expected and did not influence significantly the antifungal activity of ECB, ChiB or EngA against yeasts.
Authors:M. Szilágyi, Zs. I. Németh, L. Albert, P. Sarlós, and E. Tyihák
On the basis of recent observations it is supposed that seminal fluids may contain - mainly in hydroxymethyl groups - formaldehyde (HCHO) and quaternary ammonium compounds as potential HCHO generators, therefore, preliminary investigations were carried out for the identification of these compounds in pig seminal fluids using OPLC, HPLC and MALDI MS techniques. The fresh pig seminal fluid was frozen in liquid nitrogen, powdered and aliquots (0.25 g) were treated with 0.7 ml ethanolic dimedone solution. The suspension was centrifuged and the clear supernatant was used for analysis by OPLC or after dilution with HPLC or MALDI MS technique. After OPLC separation of formaldemethone the fully N-methylated compounds which are stayed on the start point were separated by OPLC using an other eluent system. It has been established that the HCHO is really a normal component of the pig seminal fluid, as well. It can be isolated and identified in dimedone adduct form. The measurable amount of HCHO depended on the concentration applied of dimedone. According to OPLC and MALDI MS investigations L-carnitine is the main quaternary ammonium compound in pig seminal fluid which can generate a protection of the sperm cells against environmental and other influences. Considerable differences have been found among individuals concerning concentrations of quaternary ammonium compounds in the seminal fluid of pigs.