Electrocaloric Response of the Dense Ferroelectric Nanocomposites

Using the Landau-Ginzburg-Devonshire approach and effective media models, we calculated the spontaneous polarization, dielectric, pyroelectric, and electrocaloric properties of BaTiO$_3$ core-shell nanoparticles. We predict that the synergy of size effects and Vegard stresses can significantly improve the electrocaloric cooling (2- 7 times) of the BaTiO$_3$ nanoparticles with diameters (10-100) nm stretched by (1-3)% in comparison with a bulk BaTiO$_3$. To compare with the proposed and other known models, we measured the capacitance-voltage and current-voltage characteristics of the dense nanocomposites consisting of (28 -35) vol.% of the BaTiO$_3$ nanoparticles incorporated in the poly-vinyl-butyral and ethyl-cellulose polymers covered by Ag electrodes. We determined experimentally the effective dielectric permittivity and losses of the dense composites at room temperature. According to our analysis, to reach the maximal electrocaloric response of the core-shell ferroelectric nanoparticles incorporated in different polymers, the dense composites should be prepared with the nanoparticles volume ratio of more than 25 % and fillers with low heat mass and conductance, such as Ag nanoparticles, which facilitate the heat transfer from the ferroelectric nanoparticles to the polymer matrix. In general, the core-shell ferroelectric nanoparticles spontaneously stressed by elastic defects, such as oxygen vacancies or any other elastic dipoles, which create a strong chemical pressure, are relevant fillers for electrocaloric nanocomposites suitable for advanced applications as nano-coolers.Comment: 38 pages, including 10 figures and 2 appendixe

Pathogenetic Effects of Bacteria of the Genus <i>Desulfovibrio</i>. Experimental Study. Part One: Iron Metabolism

The aim of the work was to study specific systemic effect of sulfate-reducing bacteria of the genus Desulfovibrio on organism systems through creating an experimental model of intragastric bacterial invasion against the background of dysbiotic conditions of rodent gastrointestinal tract. Materials and methods. The experimental study was conducted on Wistar rats. Intestinal dysbiosis was modeled with the help of antibiotics, amoxicillin and metronidazole. Typical strain Desulfovibrio desulfuricans subsp. desulfuricans VKM B-1799T was used as an infectious agent. Results and discussion. As a result of the experiment performed, during the period of acute infection (on day 15 of the experiment), a direct correlation between the concentration of the injected D. desulfuricans VKM B-1799T bacteria suspension and the serum iron level was observed: the higher the infectious agent dose, the lower the serum iron concentration. During the phase of remote effects (day 38 of the experiment), the inverse correlation between the concentrations of D. desulfuricans VKM B-1799T in the intestines of rodents was revealed: when the concentration of the infecting agent increased from 103 CFU/g and higher, the iron level decreased from 43.5 μmol/l to 38.5 μmol/l. When comparing the level of transferrin and unsaturated iron binding capacity (UIBC), an increase in those parameters was observed in all groups of rats both during the period of acute infection and the period of long-term effects, and the percentage of transferrin iron saturation decreased, indicating the occurrence of iron deficiency against the background of exposure to the infectious agent. Intestinal dysbiosis promotes colonization by opportunistic flora, including Desulfovibrio sp. Changes in the iron metabolism markers in experimental animals against the background of D. desulfuricans VKM B-1799T infestation above 103 CFU/g and the ability of this microorganism to bind iron into an unavailable form suggest that the bacteria Desulfovibrio sp. are one of the key etiological factors of iron deficiency anemia

Podejście systemowe do projektowania instalacji sygnalizacji pożarowej

The article is devoted to the issue of designing fire alarm techniques with the use of a system approach. The analysis of the results of the previous research in this area is presented. The purposes of fire detection are formulated on the basis of the provisions of the existing legal and normative base on fire safety. The mathematical models describing the conditions for achieving these objectives are submitted. The model of hydrocarbon liquids combustion under conditions of the presence of air flows and the pollution of the atmosphere with dusts and air dredges is examined from the position of justification of spatial parameters of fire detectors placement (thermal detectors, thermal detectors of differential action, flame detectors). The examples of calculations according to the developed models are considered.Artykuł poświęcony jest kwestiom projektowania instalacji sygnalizacji pożarowej w oparciu o podejście systemowe. Przedstawiona została analiza wyników wcześniej przeprowadzonych badań w tej dziedzinie. Na podstawie obowiązującej bazy aktów prawnych dotyczących bezpieczeństwa przeciwpożarowego sformułowane zostały cele wykrycia pożaru oraz modele matematyczne opisujące warunki ich osiągnięcia. Uzasadnienie parametrów przestrzennych rozmieszczenia detektorów pożaru (termicznych, termicznych o zróżnicowanym działaniu, detektorów płomienia) umożliwiło opracowanie modelu spalania cieczy węglowodorowych w warunkach obecności przepływów powietrza oraz w warunkach zanieczyszczenia powietrza pyłami i kurzami. Zaprezentowane zostały przykłady obliczeń do opracowanych modeli

Development and validation of a method for determination of Eculizumab concentration in human plasma by biolayer interferometry

The article describes a new method for measurement of monoclonal antibody Eculizumab concentration in human plasma in a range of 3-250 μg/ml. In this method we used an antibody Fab fragment, capable of binding to eculizumab specifically in human plasma. The method uses the biolayer interferometry for determination of Eculizumab concentration without additional tag in the analyzing substances. This method was comparatively validated along with the traditional ELISA. Comparative validation demonstrated that the biolayer interferometry based method has an advantage to the ELISA in such important statistical criteria as an analytical range, accuracy, precision, specificity and selectivity (matrix effect)