Study on the protective role of selenium against cadmium toxicity in lactic acid bacteria: an advanced application of ICP-MS

In this work, Lactobacillus casei rhamnosus were obtained from the commercial product of fermented milk and possible antagonistic effect of selenium (as sodium selenite) against cadmium toxicity was studied. The bacteria capability to incorporate Se was demonstrated: after 1 week exposure to Se(IV), its total concentration in the freeze-dried biomass was 405+/-28 microg/g (7.4+/-0.8 microg/g in control). In the presence of Se(IV) and Cd(II), the bacterial growth and cell viability were improved and lipid peroxidation less marked with respect to bacteria exposed to Cd(II) alone. The distribution of Se and Cd in molecular mass fractions of bacteria extracts was investigated by size exclusion chromatography with diode array and ICP-MS detection. The results obtained suggest that the antagonistic effect of Se is due to lower incorporation of cadmium at a high molecular mass (MM<600 kDa). Slightly different distribution of elements in the fractions of MM<40 kDa suggests the formation of new chemical species involving Cd and Se in bacteria exposed to Cd(II)+Se(IV) as compared to those exposed to Cd(II) alone. The study illustrates the high utility of atomic spectrometry to critically inform molecular questions that could be important in the industrial processes based on bacterial activity.     

Pentachlorophenol sorption in nylon fiber and removal by immobilized Rhizopus oryzae ENHE

This study describes pentachlophenol (PCP) sorption in nylon fiber in which Rhizopus oryzae ENHE was immobilized to remove the chemical compound. The experimental sorption data were analyzed using the Langmuir, Freundlich, and Redlich-Peterson isotherm models using non-linear error functions to fit the experimental data to the three models. Results showed that the isotherm obtained from the data fitted the three models used. However, the g parameter from Redlich-Peterson model showed that the isotherm obtained approaches the Freundlich model. This support reached the sorption equilibrium concentration at 3mg PCPg(-1)nylon. To study PCP removal capability by R. oryzae ENHE and to eliminate the error caused by PCP sorbed by the nylon fiber during its quantification, nylon fiber at PCP equilibrium sorption concentration was used to immobilize R. oryzae ENHE. It was found that this fungus grew within nylon fiber cubes in presence or not of PCP, even when PCP caused growth inhibition. Maximum biomass accumulated into nylon cubes without PCP was of 32 mg biomass g(-1)nylon and into nylon cubes at PCP equilibrium concentration was of 18 mg g(-1)nylon. The results showed that R. oryzae ENHE immobilized into nylon fiber removed 88.6% and 92% of PCP in cultures with 12.5 and 25 mg PCPL(-1), as initial concentration, respectively. This is the first work to report that a zygomycete, such as R. oryzae ENHE, immobilized into nylon fiber kept its potential to remove PCP.     

Waveguide-modulated surface plasmon-coupled emission of Nile blue in poly(vinyl alcohol) thin films

Surface plasmon-coupled emission (SPCE) phenomenon is the coupling of excited fluorophores near a silver film with surface plasmons, resulting in directional emission into the underlying glass substrates. We report a complex coupling of Nile Blue fluorophore with 50 nm silver mirror, resulting in emission at several angles in the glass substrate, with either s or p polarization. This complex pattern of directional and polarized emission appears to be due to optical waveguide effects occurring when the sample thickness becomes comparable to the emission wavelength. We expect waveguide-modulated SPCE to have applications to biophysics and sensing.     

Multiresolution MUAPs decomposition and SVM-based analysis in the classification of neuromuscular disorders

This paper describes a new method for the classification of neuromuscular disorders based on the analysis of scalograms determined by the Symlet 4 wavelet technique. The approach involves isolating single motor unit action potentials (MUAPs), computing their scalograms, taking the maximum values of the scalograms in five selected scales, and averaging across MUAPs to give a single 5-dimensional feature vector per subject. After SVM analysis, the vector is reduced to a single decision parameter, called the Wavelet Index, allowing the subject to be assigned to one of three groups: myogenic, neurogenic or normal. The software implementation of the method described above created a tool supporting electromyographic (EMG) examinations. The method is characterized by a high probability for the accurate diagnosis of muscle state. The method produced 5 misclassifications out of 800 examined cases (total error of 0.6%).     

Determination of aldehydes in tequila by high-performance liquid chromatography with 2,4-dinitrophenylhydrazine derivatization

In this work, the determination of aldehydes in different tequila brands was carried out by high-performance liquid chromatography after derivatization with 2,4-dinitrophenylhydrazine. For the comparative purposes, two commercial brandies were also analyzed. The derivatization agent (50 μl of 3.5 mmol l⁻¹ DNPH in HCl, 2 mol l⁻¹) was added directly to the sample (500 μl) and dinitrophenylhydrazones formed were extracted with hexane. After evaporation of the solvent in nitrogen stream, the residues were dissolved in 100 μl of acetonitrile. The calibration standards were prepared from respective dinitrophenylhydrazones, following the same procedure as for beverage samples. Reversed phase chromatographic separation was achieved on Luna C18 column (250 mm×4.6 mm, 5 μm), using gradient elution (acetonitrile:water, from 68 to 80% of acetonitrile in 20 min) and a total flow rate 1 ml min⁻¹. Spectrophotometric detection for furanic aldehydes was at 390 nm (for other aldehydes at 365 nm). The assignation of chromatographic peaks was accomplished by comparison of their relative retention times and UV/Vis spectra with those of external standards. The method of standard addition was also used. The aldehydes identified were 5-hydroxymethylfurfuraldehyde (t _ret=4.1 min), formaldehyde (t _ret=5.1 min), syringaldehyde (t _ret=5.6 min), acetaldehyde (t _ret=6.2 min), 2-furaldehyde (t _ret=7.2 min) and 5-methylfurfuraldehyde (t _ret=8.9 min). At least four chromatographic peaks with retention times higher than 12 min remained unidentified. The quantification results showed drastically higher concentrations of 2-furaldehyde and 5-methylfuraldehyde in tequilas as referred to brandies. Furthermore, 100% tequilas contained higher levels of these two compounds (for four brands analyzed, mean values 18.6 and 5.97 μg ml⁻¹, respectively) as compared to the mixed brands (five brands analyzed, mean values 6.46 and 3.30 μg ml⁻¹). The results obtained confirm that the profile of furanic aldehydes depends on the type of fructans contained in the raw material and also on heating treatment applied or not prior to fermentation. In contrast to other polysaccharides, inulin hydrolyzes at elevated temperature and the contribution of Maillard browning reactions increases the production of furanic compounds. Our results indicate that the levels of 2-furaldehyde and 5-methylfuraldehyde could be used for discrimination between 100% and mixed tequila brands.     

Electrochemical properties of composite anodes for cathodic protection

Comparative results of electrochemical investigations of polymeric composites with different contents of carbon black and graphite activated with ruthenium oxides are presented. Electrochemical impedance measurements (EIS), enabling determination of electrical and electrochemical properties of polymeric composites, were accompanied by potential measurements performed during a 21-day galvanostatic polarization at 5 A m^–2 current density. Gravimetric measurements were also made to determine the extent of anode consumption. It was demonstrated that the presence of ruthenium oxides characterised by high electrocatalytic activity in the polymeric composites causes an improvement in the polarisation characteristics, a decrease in the value and improvement in stability of the potential during long-term operation, and also a decrease in the anode consumption, as compared to composites exclusively containing activated carbon black.     

The effect of stainless steel structure on the performance of rubber-graphite under conditions of water lubrication

A new sliding bearing material based on rubber filled with different graphites was assessed against stainless steels of various structures under conditions of water lubrication in an Amsler machine. The tribological characteristics of the rubber-graphite depend upon the fillers used. The wear of stainless steel journals depends upon the material structure and the chromium carbide present.     

Determination of occurrence of anodic excursion peaks by dynamic electrochemical impedance spectroscopy,atomic force microscopy and cyclic voltammetry

The compositions of lead anodic layers and structure strongly depends on, additives, concentration of sulfuric acid, and on potential region. A phenomenon of anodic excursion peaks was always in focus of many researches. In this work the behaviour of anodic excursion peak (AEP) in 0.5 M H₂SO₄ solution is widely investigated by dynamic electrochemical impedance spectroscopy (DEIS), atomic force microscopy (AFM) and cyclic voltammetry (CV) methods. The changes of the impedance spectra and AFM images as a function of potential are presented in this paper. It is suggested that the occurrence of anodic excursion peaks cannot be caused by oxidation of bare metal induced by cracking, it can be related to the oxidation of anodic layer to the oxides with higher non-stoichiometric coefficient.