Effect of humic and fulvic acid concentrations and ionic strength on copper and lead binding

We investigated the influence of humic and fulvic acid concentration (in the range of 1-1000 mg/L) on the binding of the two trace metals Cu(II) and Pb(II). The ability of the non-ideal competitive adsorption (NICA)-Donnan model to correctly predict Cu and Pb binding at low humic or fulvic acid concentration and lower ionic strength (0.01 M NaNO3), based on model parameters obtained from experiments conducted at high humic or fulvic acid concentrations (approximately 1000 mg/L) and higher ionic strength (0.1 M NaNO3), was tested. The binding of Cu and Pb to humic and fulvic acid in 0.01 M NaNO3 was determined over wide ranges in proton and metal ion activities using three different methods: ligand exchange-adsorptive differential pulse cathodic stripping voltammetry at low humic or fulvic acid concentrations (1-3 mg/L), differential pulse anodic stripping voltammetry at intermediate humic or fulvic acid concentrations (10-20 mg/L), and ion-selective electrodes at high humic or fulvic acid concentrations (approximately 1000 mg/L). The results demonstrate that binding isotherms for Cu and Pb can be measured at low humic or fulvic acid concentration using suitable voltammetric techniques. The binding isotherms for Cu and Pb to humic and fulvic acid obtained at constant pH values in the range of pH 4-8 are shown to be independent of humic and fulvic acid concentration. The NICA-Donnan model, calibrated for Cu and Pb binding using data measured at high humic and fulvic acid concentrations and an ionic strength of 0.1 M, accurately predicts Cu and Pb binding at low humic and fulvic acid concentrations and lower ionic strength (0.01 M). We conclude that NICA-Donnan parameters obtained by fitting experimental data measured with ion-selective electrodes at high humic or fulvic acid concentrations can be used for geochemical modeling of soils and aquatic environments with much lower concentrations of humic or fulvic acids.     

Dark chocolates supplemented with <Emphasis Type="Italic">Lactobacillus</Emphasis> strains

Dark chocolate masses and chocolates were supplemented with viable cells of two bacterial strains Lactobacillus caseii and Lactobacillus paracasei with potential probiotic properties, which were lyophilized in milk. Total number of live bacteria in the lyophilizate was 7.9×10⁹ cfu/g. Sucrose or isomalt and aspartame were used as bulking substances and sweeteners. Sensory attributes of these chocolates were not different from that of traditional chocolates. Calorie value of sucrose-free chocolate was lower by approximately 11.1–14.6% (dependent on their formulation) relative to chocolate sweetened with sucrose. Chocolate, which contains isomalt and aspartame can be consumed by diabetics. Numbers of live L. casei and L. paracasei cells in the examined batches of chocolate were very high and approached 10⁶–10⁷ cfu/g after 12 months of keeping at 4 and 18 °C. Neither the texture nor the total and volatile acidity of chocolate masses were changed by addition of the lyophilized preparation of Lactobacillus cells. Casson yield values of dark sucrose-free chocolate masses supplemented with this lyophilizate were decreased by approximately 3–55% (dependently on fat contents in these masses) as compared to that of analogous chocolate masses sweetened with sucrose.     

Formation of thin boron nitride coating on multiwall carbon nanotube surfaces

Thin boron nitride films were deposited onto outer surfaces of multiwall carbon nanotubes (MWCNTs) by dip coating, which involves infiltration by boric acid solutions and subsequent nitridation of the boron oxide in ammonia flow at 1050 °C. The overall composition of the samples was determined by electron energy loss (EELS) and X-ray photoelectron spectroscopy (XPS), the surface composition and chemical structure of the BN coatings by XPS, the morphology of the BN/MWCNT composites by scanning and transmission electron microscopy (SEM, TEM), and the resistance against oxidation at elevated temperatures by thermal analysis (TGA). It was proved that single and multilayer BN coverage were achieved at the applied experimental conditions, and the coated samples showed significantly increased oxidation resistance compared to the uncoated MWCNTs.     

HPLC–ESI-MS investigation of tyrosol and hydroxytyrosol oxidation products in virgin olive oil

The aim of this research is the characterisation of the oxidation products of several hydrophilic phenols of virgin olive oil (VOO), such as hydroxytyrosol (3,4-DHPEA) and tyrosol (p-HPEA) and, their identification in the product during storage. This work is aimed at finding analytical indicators that can be used both as molecular markers of VOO “freshness” and for the evaluation of the shelf life of the product itself. Two oxidation systems were examined for the oxidation of p-HPEA and 3,4-DHPEA: enzymatic oxidation and Fenton oxidation. Reaction products were different for the two systems and were identified as quinones, dimers, and acids. During the autoxidation process, Fenton reaction oxidation products, but not enzymatic oxidation products, were found in VOO.     

The use of intensity-dependent weight functions to “Weberize” $$L^2$$ L 2 -based methods of signal and image approximation

Optimization and Engineering - We consider the problem of modifying $$L^2$$ -based approximations so that they “conform” in a better way to Weber’s model of perception: Given a...     

Comparitative Research of Pollen Morphology of Common Flax Cultivars (Linum usitatissimum L., Linaceae)

Pollen morphology of 11 cultivars of different purpose use of Linum usitatissimum was studied with LM and SEM microscopy. On average, pollen grains were radially symmetrical, isopolar, and prolate spheroidal in shape, tricolpate and of large size. All grains were semitectate with discontinuous tectum due to partial fusion of heads of the clavae. The clavae were dimorphic, clearly differ in size, but morphologically similar. The smaller ones were dominant. All observed cultivars were very similar in pollen structure and the differences among their pollen grains were primarily quantitative.     

Effects of dykes on plant species composition in a large lowland river floodplain

The effects of floodplain fragmentation by dykes on grassland vegetation were evaluated through field studies along the Middle Elbe River (federal states Saxony‐Anhalt and Brandenburg, Germany). Plant species composition was examined in 206 sites between 1996 and 1998 in the entire floodplain, which can be divided into the floodplain types ‘recent floodplain’, ‘older floodplain’ (which is separated from the recent one by dykes) and the ‘margin of the floodplain’ (which is the part of the older floodplain that forms the boundary and is furthest from the river). Dynamics in hydrology were examined weekly between November 1996 and February 1999 with the help of 40 water level wells which were installed near the studied sites. The hydrological parameters ‘average water level’, ‘average groundwater level’, ‘flooding duration’, ‘flooding depth higher 50 cm above soil surface’ and ‘standard deviation of the water level line’ were calculated to characterize the considered floodplain types and to relate species composition to hydrology. Furthermore several parameters of current management of the vegetation were recorded to evaluate the importance of land use versus hydrology for floodplain grasslands. Detrended and canonical correspondence analysis (DCA, CCA) were used to identify major environmental gradients governing the vegetation and to determine if there is a relationship between the different locations within the floodplain, variation in species composition, and gradients of measured environmental variables. The results indicate that the vegetation is closely related to a combination of water level fluctuations, which are different among the floodplain types, and soil moisture, while type and intensity of current management are not important in this context. The results of contingency tables underline the significance of dykes for the occurrence and absence of individual species among the floodplain types. The observed patterns can also be explained by the different hydrological properties of the recent and older floodplain as the results of logistic regression reveal. Furthermore, disturbance and dispersal processes and their alteration by dykes have to be taken into account to explain the pattern of species occurrence. Partial ordination detected residual differences in vegetation among the different floodplain types after accounting for the effects of the measured environmental variables. Grain size distribution is discussed as a further factor that might influence species composition. Copyright © 2004 John Wiley & Sons, Ltd.     

Isolation and structure/activity features of halomon-related antitumor monoterpenes from the red alga Portieria hornemannii

Ten halogenated monoterpenes (2-6 and 8-12) related to the novel antitumor compound halomon (1) or to the carbocyclic analog 7 have been isolated from different geographic collections of the red alga, Portieria hornemannii. Structures were assigned to the basis of spectral analyses (primarily NMR and MS). The absolute configuration of isohalomon (2) was further established by X-ray crystallography. The compounds were comparatively evaluated alongside 1 and 7 in the U.S. National Cancer Institute's in vitro human tumor cell line screening panel. The results provide some interesting initial insights into the structure/activity relationships in this series.