Hypoxia stimulates ventilation, but when it is sustained, a decline in the ventilatory response is seen. The mechanism responsible for this decline lies within the CNS, but still remains unknown. In this study, we attempted to elucidate the possible role of hypoxia-induced depression of respiratory neurons by comparing the ventilatory response to hypoxia in intact rats and those with denervated carotid bodies. A whole-body plethysmograph was used to measure tidal volume, frequency of breathing and minute ventilation (VE) in awake and anesthetized intact rats and rats after carotid body denervation during exposure to hypoxia (FIO2 0.1). Fifteen-minute hypoxia induced an initial increase of VE in intact rats (to 248 % of control ventilation in awake and to 227 % in anesthetized rats) followed by a consistent decline (to 207 % and 196 % of control VE, respectively). Rats with denervated carotid bodies responded with a smaller increase in VE (to 134 % in awake and 114 % in anesthetized animals), but without a secondary decline (145 % and 129 % of control VE in the 15th min of hypoxia). These results suggest that afferentation from the carotid bodies and/or the substantial increase in ventilation are crucial for the biphasicity of the ventilatory response to sustained hypoxia and that a central hypoxic depression cannot fully explain the secondary decline in VE., H. Maxová, M. Vízek., and Obsahuje bibliografii
Aims of the study were to compare the development of electrocardiographic responses of the ischemia-induced heterogeneities of activation and repolarization in the ventricular myocardium of normal and diabetic animals. Body surface ECGs and unipolar electrograms in 64 epicardial leads were recorded before and during 20 min after the ligation of the left anterior descending artery in diabetic (alloxan model, 4 weeks, n=8) and control (n=8) rabbits. Activation times (ATs), end of repolarization times (RTs) and repolarization durations (activation-recovery intervals, ARIs) were determined in ischemic and periischemic zones. In contrast to the controls, the diabetic rabbits demonstrated the significant prolongation of ATs and shortening of ARIs (P<0.05) during ischemia in the affected region resulting in the development and progressive increase of the ARI and RT gradients across the ischemic zone boundary. The alterations of global and local dispersions of the RTs in diabetics correlated with the Tpeak-Tend interval changes in the limb leads ECGs. In the ischemic conditions, the diabetic animals differed from the controls by the activation delay, significant repolarization duration shortening, and the increase of local repolarization dispersion; the latter could be assessed by the Tpeak-Tend interval measurements in the body surface ECGs., K. A. Sedova, M. A. Vaykshnorayte, A. O. Ovechkin, P. Kneppo, O. G. Bernikova, V. A. Vityazev, J. E. Azarov., and Obsahuje bibliografii
This work deals with the changes of rhetorical education and emotional orders in the second half of the 18th century. The aim of the research is to assess the relations among language education, funtions of medias, anthropological models and expression of emotions on the Threshold of enlightenment. The background of the research shapes the transformation of rhetorical tradition. The research of the broad field of pedagogical, rhetorical and moral discurs is focused on the collegium of Karl Heinrich Seibt., Václav Smyčka., and Obsahuje bibliografické odkazy
We verify functional a posteriori error estimate for obstacle problem proposed by Repin. Simplification into 1D allows for the construction of a nonlinear benchmark for which an exact solution of the obstacle problem can be derived. Quality of a numerical approximation obtained by the finite element method is compared with the exact solution and the error of approximation is bounded from above by a majorant error estimate. The sharpness of the majorant error estimate is discussed.
We verify functional a posteriori error estimates proposed by S. Repin for a class of obstacle problems in two space dimensions. New benchmarks with known analytical solution are constructed based on one dimensional benchmark introduced by P. Harasim and J. Valdman. Numerical approximation of the solution of the obstacle problem is obtained by the finite element method using bilinear elements on a rectangular mesh. Error of the approximation is measured by a functional majorant. The majorant value contains three unknown fields: a gradient field discretized by Raviart-Thomas elements, Lagrange multipliers field discretized by piecewise constant functions and a scalar parameter β. The minimization of the majorant value is realized by an alternate minimization algorithm, whose convergence is discussed. Numerical results validate two estimates, the energy estimate bounding the error of approximation in the energy norm by the difference of energies of discrete and exact solutions and the majorant estimate bounding the difference of energies of discrete and exact solutions by the value of the functional majorant.
The article presents results of the verification calculation of the method for the calculation of natural frequencies and mode shapes of a linear undamped rotationally periodic systems considering the possibility of the elimination of degrees of freedom. As the test example a thin circular plate was chosen. The method can be applied e.g. for the calculation of the natural vibration characteristics of the steam turbine bladed disks. and Obsahuje seznam literatury
At the modernization of the ŠKODA 22 Tr low-floor articulated trolleybus a different type of an articulated joint and a different type of driving axles were used in its construction besides other changes. During test drives with the modernized trolleybus, which were focused on the driving stability of the vehicle, a large roll of the rear section appeared. A suitable structural solution for reducing the rear section roll angle of the modernized trolleybus was the using of a rear section stabilizer bar. The stabilizer effect on dynamic properties of the vehicle and a suitable bar diameter were determined on the basis of the results of the computer simulations with the trolleybus multibody models. The text drives focused on the vehicle driving stability were performed again with the loaded real trolleybus, in the structure of which the designed rear section stabilizer bar was applied. On the basis of computer simulations of the test drives with the trolleybus multibody models the correctness of the experimantal-simulation approach used for the stabilizer bar structural design was verified. and Obsahuje seznam literatury
Vermiculite in its macroscopic form occurs in the Archaean supracrustal rocks exposed towards east of Sargur supracrustal complex in Karnataka state. The present study forms the first detailed work on the occurrence of vermiculite associated with the ultramafic rocks in the Agasthyapura, which lies in the long. 76° 50’ 658” and lat. 12° 15’ 976”. Petrography, X-ray diffraction, FTIR, DTA&TGA, SEM, fluid inclusion and electron probe analyses are presented in this contribution study. The probable origin of vermiculite from biotite through hydrobiotite is discussed., Kikkeri N. Prakash Narasimha, Honnaiah Ramalingaiah, Karel Melka, K. Krishnaveni, Pinnelli S. R. Prasad, Chikkamadaiah Krishnaiah, Katihalli S. Jayappa and Atni V. Ganesha., and Obsahuje bibliografické odkazy
In presented work natural expanded vermiculite was used as a starting material for synthesis of Fe-doped catalysts. Material was modified with increasing amount of Fe by ion-exchange and precipitation of iron oxide. Composite materials were characterized with respect to their structure (X-ray diffraction, Infrared spectra using Diffuse Reflectance), agglomeration state of Fe (Ultraviolet-Visible spectra using Diffuse Reflectance) and chemical composition. Activity in H2O2 decomposition as well as in phenol oxidation was studied in liquid phase at atmospheric pressure and temperature up to 70 °C. It was shown that doping with Fe increases catalytic activity. However, excess of iron resulted in formation of undesired side-products., Agnieszka Węgrzyn, Lucjan Chmielarz, Paweł Zjeżdżalka, Magdalena Jabłońska, Andrzej Kowalczyk, Agata Żelazny, Manuel Vázquez Sulleiro and Marek Michalik., and Obsahuje bibliografii