Abstract
In the present study, a method for the synthesis of gelatin-stabilized copper oxide nanoparticles was developed. Synthesis was carried out by direct chemical precipitation. Copper sulfate, ...chloride, and acetate were used as precursors for the copper oxide synthesis. Gelatin was used as a stabilizer. It was found that the formation of monophase copper oxide II only occurred when copper acetate was used as a precursor. Our results showed that particles of the smallest diameter are formed in an aqueous medium (18 ± 6 nm), and those of th largest diameter—in an isobutanol medium (370 ± 131 nm). According to the photon correlation spectroscopy data, copper oxide nanoparticles synthesized in an aqueous medium were highly stable and had a monomodal size distribution with an average hydrodynamic radius of 61 nm. The study of the pH effect on the colloidal stability of copper oxide nanoparticles showed that the sample was stable in the pH range of 6.8 to 11.98. A possible mechanism for the pH influence on the stability of copper oxide nanoparticles is described. The effect of the ionic strength of the solution on the stability of the CuO nanoparticles sol was also studied, and the results showed that Ca
2+
ions had the greatest effect on the sample stability. IR spectroscopy showed that the interaction of CuO nanoparticles with gelatin occurred through the hydroxyl group. It was found that CuO nanoparticles stabilized with gelatin have a fungicidal activity at concentration equivalent 2.5 · 10
−3
mol/L and as a material for food nanopackaging can provide an increase in the shelf life of products on the example of strawberries and tomatoes. We investigated the possibility of using methylcellulose films modified with CuO nanoparticles for packaging and storage of hard cheese “Holland”. The distribution of CuO nanoparticles in the methylcellulose film was uniform. We found that methylcellulose films modified with CuO nanoparticles inhibited the growth and development of QMAFAM, coliforms, yeast and mold in experimental cheese sa mples. Our research has shown that during the cheese storage in thermostat at 35 ± 1 °C for 7 days, CuO nanoparticles migrated to the product from the film. Nevertheless, it is worth noting that the maximum change in the concentration of copper in the experimental samples was only 0.12 µg/mg, which is not a toxic concentration. In general, the small value of migration of CuO nanoparticles confirms the high stability of the developed preparation. Our results indicated that the CuO nanoparticles stabilized with gelatin have a high potential for use in food packaging – both as an independent nanofilm and as part of other packaging materials.
Abstract
The charge carrier density distribution in uniformly doped AlGaAs/GaAs superlattices with layer thicknesses of 1.5/10 nm and different numbers of quantum wells was studied. Both energy band ...theory and capacitance–voltage profiling were used to determine the carrier concentration profiles of the structures. During the analysis of the experimental and simulated capacitance–voltage characteristics, it was found that the maximum electron concentrations increase with an increase in the number of quantum wells from ∼
7.1
⋅
10
16
cm
−
3
for three wells to ∼
9.3
⋅
10
16
cm
−
3
for 25 wells with an overall superlattice doping level of ∼
10
17
cm
−
3
.
We provide conditions for the existence of measurable solutions to the equation \xi (T\omega )=f(\omega ,\xi (\omega )), where T:\Omega \rightarrow \Omega is an automorphism of the probability space ...\Omega and f(\omega ,\cdot ) is a strictly nonexpansive mapping. We use results of this kind to establish a stochastic nonlinear analogue of the Perron-Frobenius theorem on eigenvalues and eigenvectors of a positive matrix. We consider a random mapping D(\omega ) of a random closed cone K(\omega ) in a finite-dimensional linear space into the cone K(T\omega ). Under the assumptions of monotonicity and homogeneity of D(\omega ), we prove the existence of scalar and vector measurable functions \alpha (\omega )>0 and x(\omega )\in K(\omega ) satisfying the equation \alpha (\omega )x(T\omega )=D(\omega )x(\omega ) almost surely.
There is a need to improve the methods of control of supersonic aircraft in order to increase the efficiency and reliability of their control elements. In this work, theoretical calculations of the ...flow around a body with a system of supersonic jets are carried out. Using numerical methods, the possibility of control the flow around a body using a system of jets has been investigated. The numerical study was based on a model of an inviscid perfect gas described by the Navier-Stokes equations.
Half-Life and the Uncertainty Principle Petrova, E. N.; Pirogov, S. A.
Problems of information transmission,
12/2023, Letnik:
59, Številka:
4
Journal Article
Recenzirano
An attempt is made to give an accurate mathematical interpretation of the energy–time uncertainty relation.
We consider contact processes on locally compact separable metric spaces with birth and death rates that are heterogeneous in space. We formulate conditions on the rates that ensure the existence of ...invariant measures of contact processes. One of the crucial conditions is the so-called critical regime condition. To prove the existence of invariant measures, we use the approach proposed in our preceding paper. We discuss in detail the multi-species contact model with a compact space of marks (species) in which both birth and death rates depend on the marks.
Heterostructures with strongly-coupled multiple quantum wells, such as super-multiperiod superlattices with high perfection, may contain hundreds of layers, whose thicknesses can vary by orders of ...magnitude. The proposed method of characterization, consisting of the matched application of high-resolution X-ray diffractometry and reflectometry, makes it possible to study super-multiperiod structures of various types, including those with long periods and thin layers, and with high accuracy to determine the thicknesses of layers and roughness/diffuseness of boundaries. The difference between the expected and resulting thicknesses of the layers was 2–7% and 1–3% for the type I (InAs/GaAs) and type II (GaAs/Al
0.3
Ga
0.7
As) samples, respectively. Both types of structures are characterized by sharp interfaces with the RMS width of the transition layers of the order of several Å. Based on the best solution of inverse scattering problems, it is possible to determine with high accuracy both the morphology of the layers and their composition. That can be considered as the first step in the analysis of structures with a very large number of periods.
Instrumental and technological methods of intensifying the processes of heat and mass transfer in the column reactors with a packing are considered. It has been shown that one of the most promising ...areas for increasing the intensity of heat- and mass-transfer processes is the operation of a multilayer packing apparatus at gas flow rates close to the rate of suspension of the liquid phase.
We consider contact processes on locally compact separable metric spaces with birth and death rates that are heterogeneous in space. We formulate conditions on the rates that ensure the existence of ...invariant measures of contact processes. One of the crucial conditions is the so-called critical regime condition. To prove the existence of invariant measures, we use the approach proposed in our preceding paper. We discuss in detail the multi-species contact model with a compact space of marks (species) in which both birth and death rates depend on the marks.
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