Non-ohmic conduction in tin dioxide based ceramics with copper addition

The current-voltage characteristics and temperature dependences of electrical conductivity in SnO₂-Co₃O₄-Nb₂O₅-Cr₂O₃-CuO semiconductor ceramics are studied, and possible mechanism of non-ohmic conduction in these materials is discussed. Due to addition of CuO up to 0.5 mol.%, the nonlinearity coefficient is increased up to 75, and the electric field is decreased down to 3900 V∙cm¹ (at 1 mA∙cm⁻²). It makes CuO addition useful for the preparation of SnO₂-based varistors. It is concluded that the electrical conduction is controlled by grain-boundary barriers. The activation energy of electrical conduction (the barrier height φ) is decreased with an increase in the electric field E. The higher slope of the dependence at high fields can be related to a participation of minority carriers (holes). The addition of more than 0.5 mol.% CuO leads to degradation of the varistor effect due to percolation via quite conductive CuO-based intergranular phase

Estimating the Fractal Dimension, K_2-entropy, and the Predictability of the Atmosphere

The series of mean daily temperature of air recorded over a period of 215 years is used for analysing the dimensionality and the predictability of the atmospheric system. The total number of data points of the series is 78527. Other 37 versions of the original series are generated, including ``seasonally adjusted'' data, a smoothed series, series without annual course, etc. Modified methods of Grassberger and Procaccia are applied. A procedure for selection of the ``meaningful'' scaling region is proposed. Several scaling regions are revealed in the ln C(r) versus ln r diagram. The first one in the range of larger ln r has a gradual slope and the second one in the range of intermediate ln r has a fast slope. Other two regions are settled in the range of small ln r. The results lead us to claim that the series arises from the activity of at least two subsystems. The first subsystem is low-dimensional (d_f=1.6) and it possesses the potential predictability of several weeks. We suggest that this subsystem is connected with seasonal variability of weather. The second subsystem is high-dimensional (d_f>17) and its error-doubling time is about 4-7 days. It is found that the predictability differs in dependence on season. The predictability time for summer, winter and the entire year (T_2 approx. 4.7 days) is longer than for transition-seasons (T_2 approx. 4.0 days for spring, T_2 approx. 3.6 days for autumn). The role of random noise and the number of data points are discussed. It is shown that a 15-year-long daily temperature series is not sufficient for reliable estimations based on Grassberger and Procaccia algorithms.Comment: 27 pages (LaTex version 2.09) and 15 figures as .ps files, e-mail: [email protected]

Електричні параметри варисторної кераміки на основі SnO2 з домішками оксидів CaO і BaO

In the tested SnO2-Co3O4-Nb2O5-Cr2O3-CuO varistor ceramics the adding of CaO or BaO oxides leads to the decrease of the electric conductivity in the low electric field and correlated increase of the potential barrier height at the SnO2 grain boundaries (from 0.7 to 1.0 eV). The coordinated changes of electrical parameters with the increase of the burning temperature from 1520 to 1620 К (the increase of the linear shrinkage, a grain size, an electric conductivity, a nonlinear coefficient , a normalized nonlinear coefficient , a dielectric permittivity and the decrease of the qualifying electric field E1, an activation energy of electric conduction and a grain specific resistance) prove the barrier mechanism of electric conductivity in the SnO2 based ceramics. The highest data  and = 0.02 cm·V-1 has ceramics with CaO addition baked at 1620 K. According to the impulse experimental data in the high electric field the increase of burning temperature causes the increase of SnO2 grain average size and the decrease of their grain specific resistance . The obtained value  = 1.1 Ohm·cm for SnO2-Co3O4-Nb2O5-Cr2O3-CuO ceramics is the lowest among those found in SnO2 based ceramics.  В дослідженій варисторній кераміці SnO2-Co3O4-Nb2O5-Cr2O3-CuO додавання оксидів CaO або BaO призводить до зменшення електропровідності в слабкому електричному полі й корельованого збільшення висоти потенціальних бар’єрів на межах зерен SnO2 (з 0,7 до 1,0 еВ). Координовані зміни електричних параметрів при підвищенні температури випалу з 1520 до 1620 К (збільшення значень лінійної усадки, розміру зерен, електричної провідності, коефіцієнта нелінійності , нормалізованого коефіцієнта нелінійності  і діелектричної проникності та зменшення значень класифікаційної напруженості електричного поля, енергії активації електропровідності й питомого опору зерен) підтверджують бар’єрний механізм електропровідності в кераміці на основі SnO2. Найбільші значення  і = 0,02 см·В-1 має кераміка з домішкою CaO, спечена при 1620 К. За даними імпульсних досліджень в області сильних електричних струмів підвищення температури випалу обумовлює збільшення середнього розміру зерен SnO2 і зменшення їх питомого опору . Отримане значення  = 1,1 Ом·cм для кераміки SnO2-Co3O4-Nb2O5-Cr2O3-CuO є найменшим серед визначених в оксидно-олов’яній кераміці. Додавання оксидів CaO або BaO збільшує питомий опір зерен і зменшує їх середній розмір

Probiotics and animal feed in primates feeding

This paper presents the results of experiments on primates feeding. In diet structures that were used animal feed, of which fish flour is the most valuable, as found, for monkeys, due to its unique chemical composition. And the effect of the probiotic complex “Bactistatin” on the digestibility of feed in the diet of rhesus monkeys was studied. This preparation belongs to the new generation of probiotics. It is a biological product with immobilized probiotic strains and their metabolites. The study was conducted on a large population of male rhesus macaques in enclosure conditions. Feeding diets, their nutritional value as a result of the inclusion of fish flour in the amount of 18% were studied. And also, the effect of “Bactistatin” in the amount of 3 g/head, on the formation of symbiotic microflora of the gastrointestinal tract, was studied in order to improve the absorption of nutrients in complete feed. Changes in homeostasis during the experiment were controlled by hematological and biochemical parameters of the blood of both experimental and control primates. At the end of the experiment, the cost of feed, nutrients, and exchange energy per head was calculated. The experimental data obtained were analyzed and mathematically processed