The Role of Cu(I) in the Process of Forming Cu2–xS Coatings by a Chemical Route

The interaction of the Cu₂O adsorbed with Na₂S_n (n = 1–4), during formation of the Cu_2–xS coatings has been investigated by cyclic voltammetry.

The summarized reaction of this process has been shown to correspond to the equation:

Na₂S_n + Cu₂O_ad + H₂0 → Cu₂S_ad + (n–1)S^o + 2NaOH,

where S^o/Cu=(n–1)/2. Such a stoichiometry of reaction can be explained by the formation of an intermediate—the adsorbed polysulphide of Cu(I)—and by its subsequent decomposition into Cu₂S and S^o.

When a thicker coating is being formed, i.e., when the surface being coated is repeatedly immersed into an ammoniate solution of Cu(I) and S^o fully bounded:

S^o_ad + 2 Cu⁺ → CuS + Cu²⁺.

At the same time due to different solubility products (L=2.5·10^?48 and 6.3·10^?36 for Cu₂S and CuS respectively), an exchange

CuS_ad + 2(1–x)Cu⁺ → Cu_2–xS_ad+ (1–x)Cu²+ occurs.

After formation of Cu²⁺, parallel processes characteristic for the interaction of Cu(II) with Na₂S_n start to take place, during which S^o is also formed.     

Kinetic investigations of CO disproportionation on Fe catalyst

On the surface of a Fe catalyst carbon monoxide disproportionates into C (carbon black) and CO₂. Kinetic parameters of this reaction (reaction rate constant, order, and occupancy of catalyst surface) were established in the range of temperatures 430–490°C. At the beginning of the process in all cases an induction period was observed. Under definite conditions the process develops with oscillating dynamics. Induction period and oscillations indicate an autocatalytical nature of the process. The distribution of the Fe catalyst in the profile of the reaction zone (in the bulk of carbon black and on the surface of small crystals) was investigated.     

Electroplating tin from acidic sulfate baths containing benzaldehyde

Voltammetry and electrochemical impedance spectroscopy (EIS) are used in studying the kinetics of electroplating tin from 0.01 M Sn(II) baths containing 1 M H₂SO₄ and millimolar benzaldehyde (BA) additives. BA substantially decreases the reduction rate of Sn(II) in a broad range of cathodic polarization. Experimental EIS data are analyzed in terms of an equivalent R_ω(Q_dl[R_aC_aW_a][R_ctQ_d]) circuit, including a Faraday process impedance ([R_ctQ_d] subcircuit), as well as diffusion and kinetic stages of BA adsorption ([R_aC_aW_a] subcircuit). Values of the subcircuit elements are found to depend on the duration of a contact between the electrode and solution and on the BA concentration. An increase in the charge transfer resistance (R_ct) and a simultaneous decrease in the double layer capacitance (Q_dl) indicate that the electrochemical reduction of Sn(II) is inhibited by the BA adsorption. With an increase in the cathodic polarization, the effect becomes more pronounced, which is manifested in the low current densities and negative impedance values.     

Electron mobility and electron scattering by polar optical phonons in heterostructure quantum wells

Basic features of confined electron scattering in quantum wells (QWs) by confined polar optical (PO) phonons are analyzed. The dependence of electron mobility in Al_0.25Ga_0.75As/GaAs/Al_0.25Ga_0.75As QWs on the well width is calculated. It is demonstrated that increases and decreases in electron mobility (relative to the bulk value) as a function of the QW width occur due to resonance intersubband scattering. The dependence of electron mobility limited by PO phonon scattering on the electron density n _s in the QW is calculated. It is shown that anomalous behavior of electrical conductivity, which in certain cases decreases with increasing electron density, can take place in Al_0.25Ga_0.75As/GaAs/Al_0.25Ga_0.75As QWs for n _s >10¹⁶ m^?2.     

Characterisation of hydrogels and aerogels as carriers for sea buckthorn pomace extract

In this study, aerogels were prepared from kognac glucomannan (KG) or whey proteins loaded with bioactive sea buckthorn pomace extract. KG was diacetylated with Na₂CO₃ (0.1; 0.2; 0.3; 0.4 m ) resulting hydrogel formation that were further freeze-dried to obtain an aerogel structure. Whey protein aerogels were prepared by removing pore fluid from alcogels using supercritical CO₂ drying. Produced aerogels evaluated for microstructure, porosity, specific surface area, absorption capacity, encapsulation efficiency and antioxidant capacity of the extract. It was found that higher concentration of alkali induced higher hardness, resilience and elastic modulus values. It was also obtained that pores in the konjac glucomannan aerogels were irregular in shape and a decrease in total pore volume (0.026 to 0.019 cc/g) and surface area (12.39 to 11.40 m²/g) after increasing the carbonate concentration was observed. These aerogels were found to have better encapsulation efficiency properties for sea buckthorn pomace extract (17 to 20%) in comparison to whey protein aerogels (0.05 to 0.36%). Overall, the KG aerogels show potential for applications in the food industry as a carrier of bioactive sea buckthorn pomace extract, while whey proteins must be used in combination with other biopolymers to enhance their bioactive compound loading capacity.     

Anthocyanins,Antioxidative, and Antimicrobial Properties of American Cranberry (Vaccinium macrocarpon Ait.) and their Press Cakes

ABSTRACT: Amounts of total phenolics, anthocyanins, and ascorbic acid in 4 American cranberry varieties harvested at 4 stages of maturity were measured. The larger amount of phenolic compounds was found in berries of “Black Veil” cultivar (504 mg/100 g) at II stage of maturity. Significantly larger amounts of anthocyanins were determined in the overripe berries of the cultivars “Ben Lear” and “Black Veil.” The amount of ascorbic acid in berries increased during ripening from I to III stage, and slightly decreased in the overripe berries. The biggest quantities of ascorbic acid were found in the ripe berries of “Ben Lear” cultivar (15.8 mg/100 g). The distribution of anthocyanins pigments was determined by HPLC‐UV/MS in mature berries. The composition of individual anthocyanins in berries was quite similar in all the studied cranberry cultivars. While skins of cranberries are rich in anthocyanins and other phenolic compounds, the extracts of the by‐products of cranberries juice—berry cakes, were analyzed and obtained results were compared with the properties of extracts made from whole berries. The anthocyanins and total phenolics content, radical scavenging activity, antimicrobial activity of the whole berries, and their press cakes extracts were measured. All investigated extracts from berries and their press cakes showed good radical scavenging activity and revealed antimicrobial properties. It was found that Bacillus cereus (ATCC 10876) and Micrococcus luteus (ATCC 9341) were the most sensitive among 10 tested Gram‐negative and Gram‐positive bacteria.     

Detection of Salmonella spp., Yersinia enterocolitica,Listeria monocytogenes and Campylobacter spp. by real‐time multiplex PCR using amplicon DNA melting analysis and probe‐based assay

Syto9 and probe‐based multiplex real‐time PCR assays for simultaneous detection of a group of foodborne pathogens (named SYLC group), targeting Salmonella spp. (invA gene), Yersinia enterocolitica (ystA gene), Listeria monocytogenes (hly gene) and Campylobacter spp. (rrna gene), have been developed. The Syto9 assay generates amplicon DNA melting curve with four peaks of 86.5 ± 0.5, 84 ± 0.5, 81.5 ± 0.5 and 90.5 ± 0.5 °C corresponding Salmonella spp., Y. enterocolitica, L. monocytogenes and Campylobacter spp. targets, respectively. The sensitivities of the Syto9 and TaqMan assays in artificially inoculated chicken wing rinses were in a range of 3.2 × 10² to 3.1 × 10⁴ and 9.8 × 10² to 1.9 × 10⁴ colony‐forming units per millilitre, respectively, depending on the pathogen. All tested target strains (n = 100) were correctly detected by the both assays, whereas nontarget strains (n = 100) demonstrated no cross‐reactivity representing 100% specificity. The assays are suitable for application in qualitative and quantitative detection of SYLC group pathogens in food matrices.     

The use of constrained and unconstrained optimization models in gradation design of hot mix asphalt mixture

The paper describes the essential differences in determining optimal gradation of hot mix asphalt (HMA) mixture used in road building at the stages of its selection, initial design and production, and presents the respective algorithms. The models of constrained and unconstrained non-linear optimization are developed, allowing us to choose the best HMA mixture gradation based on mineral materials, whose gradation is known, when the total percent passing of HMA mixture aggregates is considered to be equally important for all sieves, or when preference is given to some of the sieves. A new linear optimization problem best suited for practical use due to its simplicity is offered. By introducing weight coefficients for the dimensions of the objective function of the model, zero deviations of the percent passing of HMA mixture aggregates from their standard values may be easily obtained, based on the preferences set. All mineral materials (aggregates) obtained at batch-type asphalt mixing plants should be used for HMA production. Their total mass is equal to unity, while the mass of each material is a positive quantity, and a predetermined relationship between the masses of imported filler and the reclaimed dust is used. In the experimental part of the work, the problems were solved using the SAS system.