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101.
Josip Poar Marija Cvetni Andrea Usenik Nikola Cindro Gordan Horvat Katarina Leko Matija Modruan Vladislav Tomii 《Molecules (Basel, Switzerland)》2022,27(2)
The binding of alkali metal cations with two tertiary-amide lower-rim calix[4]arenes was studied in methanol, N,N-dimethylformamide, and acetonitrile in order to explore the role of triazole and glucose functionalities in the coordination reactions. The standard thermodynamic complexation parameters were determined microcalorimetrically and spectrophotometrically. On the basis of receptor dissolution enthalpies and the literature data, the enthalpies for transfer of reactants and products between the solvents were calculated. The solvent inclusion within a calixarene hydrophobic basket was explored by means of 1H NMR spectroscopy. Classical molecular dynamics of the calixarene ligands and their complexes were carried out as well. The affinity of receptors for cations in methanol and N,N-dimethylformamide was quite similar, irrespective of whether they contained glucose subunits or not. This indicated that sugar moieties did not participate or influence the cation binding. All studied reactions were enthalpically controlled. The peak affinity of receptors for sodium cation was noticed in all complexation media. The complex stabilities were the highest in acetonitrile, followed by methanol and N,N-dimethylformamide. The solubilities of receptors were greatly affected by the presence of sugar subunits. The medium effect on the affinities of calixarene derivatives towards cations was thoroughly discussed regarding the structural properties and solvation abilities of the investigated solvents. 相似文献
102.
Prof. Dr. Guoxiu Wang Hao Liu Prof. Josip Horvat Bei Wang Prof. Dr. Shizhang Qiao Jinsoo Park Prof. Dr. Hyojun Ahn 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(36):11020-11027
Highly ordered mesoporous Co3O4 nanostructures were prepared using KIT‐6 and SBA‐15 silica as hard templates. The structures were confirmed by small angle X‐ray diffraction, high resolution transmission electron microscopy, and N2 adsorption–desorption isotherm analysis. Both KIT‐6 cubic and SBA‐15 hexagonal mesoporous Co3O4 samples exhibited a low Néel temperature and bulk antiferromagnetic coupling due to geometric confinement of antiferromagnetic order within the nanoparticles. Mesoporous Co3O4 electrode materials have demonstrated the high lithium storage capacity of more than 1200 mAh g?1 with an excellent cycle life. They also exhibited a high specific capacitance of 370 F g?1 as electrodes in supercapacitors. 相似文献
103.
Structured mathematical models of oxygen electrode and biological waste water treatment were combined to optimise the position of electrode in the bioreactor. Parameters sensibility testing of mathematical model has shown that the model was most sensitive to the change of these parameters (in decreasing order of significance): oxygen consumption per unit of BOD5, specific consumption rate of adsorbed BOD5, volumetric coefficient of oxygen transfer rate (kLa), and waste water inflow. Two positions of electrode were tested: in the bioreactor and in the bioreactors syphon outlet shaft. Results obtained for the exchange of the oxic/anoxic phase and sludge recycling plant indicated that a reduction of electrical power for the aeration could be achieved if O2 electrode is placed in the bioreactor tank, compared to position in outlet shaft. Better positioning of electrode has resulted in shortening of the oxic/anoxic cycle by 13% and the daily working time of aerators for 0.5 h per day, respectively. In the same time, the number of oxic/anoxic cycles per day was increased by 29%. In addition, results obtained by mathematical modelling indicated no debasement of chemical composition in out coming purified water if new position will be used. 相似文献
104.
Ivo Crnolatac Iva Rogan Boris Majić Sanja Tomić Todor Deligeorgiev Gordan Horvat Damjan Makuc Janez Plavec Gennaro Pescitelli Ivo Piantanida 《Analytica chimica acta》2016
Two small molecules showed intriguing properties of analytical multipurpose probes, whereby one chromophore gives different signal for many different DNA/RNA by application of several highly sensitive spectroscopic methods. Dyes revealed pronounced fluorescence ratiomeric differentiation between ds-AU-RNA, AT-DNA and GC-DNA in approximate order 10:8:1. Particularly interesting, dyes showed specific fluorimetric response for poly rA even at 10-fold excess of any other ss-RNA, and moreover such emission selectivity is preserved in multicomponent ss-RNA mixtures. The dyes also showed specific chiral recognition of poly rU in respect to the other ss-RNA by induced CD (ICD) pattern in visible range (400–500 nm), which was attributed to the dye-side-chain contribution to binding (confirmed by absence of any ICD band for reference compound lacking side-chain). Most intriguingly, minor difference in the side-chain attached to dye chromophore resulted in opposite sign of dye-ICD pattern, whereby differences in NMR NOESY contacts and proton chemical shifts between two dye/oligo rU complexes combined with MD simulations and CD calculations attributed observed bisignate ICD to the dimeric dye aggregate within oligo rU. 相似文献
105.
Danijela Ašperger Vesna Tišler Mirta Zrnčić Dragana Mutavdžić Pavlović Sandra Babić Alka J. M. Horvat Marija Kaštelan-Macan 《Chromatographia》2014,77(15-16):1059-1066
A simple and robust method suitable for routine analysis of pharmaceuticals from different classes in pharmaceutical industry wastewater samples is presented. Seven veterinary pharmaceuticals (antibiotics and anesthetic) were simultaneously isolated from a highly complex wastewater matrix. Target compounds were three sulfonamide antibiotics (sulfaguanidine, sulfadiazine, and sulfamethazine), three fluoroquinolone antibiotics (ciprofloxacin, enrofloxacin, norfloxacin), and one anesthetic, procaine. The investigated compounds were simultaneously pre-concentrated and cleaned up by solid-phase extraction using Strata-X extraction cartridges. The analysis was performed using liquid chromatography (LC) with diode array and fluorescence detectors connected in series to the chromatographic system. LC separation was performed on a C18 modified column (Phenomenex) with a gradient elution of mobile phase (0.1 % acetic acid in water and 0.1 % acetic acid in acetonitrile) in 25 min at 30 °C. Recoveries ranged from 86.9 to 110 % with relative standard deviations below 10.1 %. Method limits of quantification were in the range of 0.005–0.1 μg L?1 depending on the fluorescence intensity after precolumn derivatization by fluorescamine. 相似文献
106.
The gas-phase adsorption of 1,2,3-triazole, benzotriazole, and naphthotriazole-considered as corrosion inhibitors-on copper surfaces was studied and characterized using density functional theory (DFT) calculations. We find that the molecule-surface bond strength increases with increasing molecular size, thus following the sequence: triazole相似文献
107.
Lana Horvat 《Journal of Mathematical Analysis and Applications》2005,304(2):531-541
It is known that for any Sobolev function in the space Wm,p(RN), p?1, mp?N, where m is a nonnegative integer, the set of its singular points has Hausdorff dimension at most N−mp. We show that for p>1 this bound can be achieved. This is done by constructing a maximally singular Sobolev function in Wm,p(RN), that is, such that Hausdorff's dimension of its singular set is equal to N−mp. An analogous result holds also for Bessel potential spaces Lα,p(RN), provided αp<N, α>0, and p>1. The existence of maximally singular Sobolev functions has been announced in [Chaos Solitons Fractals 21 (2004), p. 1287]. 相似文献
108.
109.
Gibicar D Logar M Horvat N Marn-Pernat A Ponikvar R Horvat M 《Analytical and bioanalytical chemistry》2007,388(2):329-340
Because of increasing awareness of the potential neurotoxicity of even low levels of organomercury compounds, analytical techniques
are required for determination of low concentrations of ethylmercury (EtHg) and methylmercury (MeHg) in biological samples.
An accurate and sensitive method has been developed for simultaneous determination of methylmercury and ethylmercury in vaccines
and biological samples. MeHg and EtHg were isolated by acid leaching (H2SO4–KBr–CuSO4), extraction of MeHg and EtHg bromides into an organic solvent (CH2Cl2), then back-extraction into Milli-Q water. MeHg and EtHg bromides were derivatized with sodium tetrapropylborate (NaBPr4), collected at room temperature on Tenax, separated by isothermal gas chromatography (GC), pyrolysed, and detected by cold-vapour
atomic fluorescence spectrometry (CV AFS). The repeatability of results from the method was approximately 5–10% for EtHg and
5–15% for MeHg. Detection limits achieved were 0.01 ng g−1 for EtHg and MeHg in blood, saliva, and vaccines and 5 ng g−1 for EtHg and MeHg in hair. The method presented has been shown to be suitable for determination of background levels of these
contaminants in biological samples and can be used in studies related to the health effects of mercury and its species in
man. This work illustrates the possibility of using hair and blood as potential biomarkers of exposure to thiomersal. 相似文献
110.
Ribeiro Guevara S Zizek S Repinc U Pérez Catán S Jaćimović R Horvat M 《Analytical and bioanalytical chemistry》2007,387(6):2185-2197
Mercury tracers are powerful tools that can be used to study mercury transformations in environmental systems, particularly
mercury methylation, demethylation and reduction in sediments and water. However, mercury transformation studies using tracers
can be subject to error, especially when used to assess methylation potential. The organic mercury extracted can be as low
as 0.01% of the endogenous labeled mercury, and artefacts and contamination present during methylmercury (MeHg) extraction
processes can cause interference. Solvent extraction methods based on the use of either KBr/H2SO4 or HCl were evaluated in freshwater sediments using 197Hg radiotracer. Values obtained for the 197Hg tracer in the organic phase were up to 25-fold higher when HCl was used, which is due to the coextraction of 197Hg2+ into the organic phase during MeHg extraction. Evaluations of the production of MeHg gave similar results with both MeHg
extraction procedures, but due to the higher Hg2+ contamination of the controls, the uncertainty in the determination was higher when HCl was used. The Hg2+ contamination of controls in the HCl extraction method showed a nonlinear correlation with the humic acid content of sediment
pore water. Therefore, use of the KBr/H2SO4 method is recommended, since it is free from these interferences. 197Hg radiotracer (T
1/2 = 2.673 d) has a production rate that is about 50 times higher than that of 203Hg (T
1/2 = 46.595 d), the most frequently used mercury radiotracer. Hence it is possible to obtain a similar level of performance
to 203Hg when it is used it in short-term experiments and produced by the irradiation of 196Hg with thermal neutrons, using mercury targets with the natural isotopic composition. However, if the 0.15% natural abundance
of the 196Hg isotope is increased, the specific activity of the 197Hg tracer can be significantly improved. In the present work, 197Hg tracer was produced from mercury 51.58% enriched in the 196Hg isotope, and a 340-fold increase in specific activity with respect to natural mercury targets was obtained. When this high
specific activity tracer is employed, mercury methylation and reduction experiments with minimum mercury additions are feasible.
Tracer recovery in methylation experiments (associated with Me197Hg production from 197Hg2+ spike, but also with Hg2+ contamination and Me197Hg artefacts) with marine sediments was about 0.005% g−1 WS (WS: wet sediment) after 20 h incubation with mercury additions of 0.05 ng g−1 WS, which is far below natural mercury levels. In this case, the amount of Hg2+ reduced to Hg0 (expressed as the percent 197Hg0 recovered with respect to the 197Hg2+ added) varied from 0.13 to 1.6% g−1 WS. Me197Hg production from 197Hg2+ spike after 20 h of incubation of freshwater sediment ranged from 0.02 to 0.13% g−1 WS with mercury additions of 2.5 ng g−1 WS, which is also far below natural levels. 197Hg0 recoveries were low, 0.0058 ± 0.0013% g−1 WS, but showed good reproducibility in five replicates. Me197Hg production from 197Hg2+ spiked in freshwater samples ranged from 0.1 to 0.3% over a period of three days with mercury additions of 10 ng L−1. A detection limit of 0.05% for Me197Hg production from 197Hg2+ spike was obtained in seawater in a 25 h incubation experiment with mercury additions of 12 ng L−1. 相似文献