The main maturation stages of Norway rat megakaryocytic series, megakaryoblasts and mature megakaryocytes, stained by silver for demonstration of argyrophil nucleolus organizer regions (AgNORs) were investigated to provide basic information on the number of nucleoli and interphasic AgNORs in these cells. The results showed that megakaryoblasts as well as mature megakaryocytes possess numerous nucleoli; their number and also the number of AgNORs is significantly higher in less mature than in more mature cells. The number of AgNORs in megakaryocytes of the Norway rat and man are virtually the same, although the numbers of nucleolar organizers per haploid chromosome set differ markedly. This fact leads to the conclusion that the number of interphasic AgNORs depends on the function and metabolic state of the cell rather than on the number of nucleolar organizers.
Nudaciraxine imperium sp. n. (Monogenea: Axinidae) is described from the gills of the needlefish Tylosurus acus imperialis (Rafinesque) caught in the Gulf of Gabès, Tunisia. This new species mainly differs from both previously described species, Nudaciraxine gracilis (Linton, 1940) Price, 1962 from Strongylura marina (Walbaum) and Nudaciraxine cabosanlucensis Payne, 1990 from Ablennes sp., by having more testes (42 vs. 20-22 and 32, respectively). Nudaciraxine imperium also differs from N. gracilis by having a median vaginal pore (submedian in N. gracilis), narrower clamps (52-70 µm vs. 75-100 µm) and differently shaped haptoral lateral hamuli. From N. cabosanlucensis it can be distinguished by a J-shaped rather than U-shaped ovary, a longer cirrus pouch (125-190 µm vs. 64-70 µm), an oesophageal bifurcation slightly anterior to genital complex (immediately after pharynx in N. cabosanlucensis) and a wider guard on the lateral hamuli. In agreement with Payne (1990), the diagnosis of the genus Nudaciraxine Price, 1962 is amended as follows: vaginal pore dorsal, median to submedian, armed or not with horn-like spines. This is the first report of the genus Nudaciraxine in the Mediterranean Sea. The potential use of axinid monogeneans as biological tags for subspecies of belonid fishes is discussed.
The paper introduces the group of nuclear magnetic resonance, its historic roots and prospects. The topics studied are represented by two examples. One is methodological - a successful method for single-voxel proton MR spectroscopy at high field with extremely short echo-time is described, as a milestone on the way to highquality spectroscopic imaging. The other example demonstrates an application - the analysis of MR compatibility of dental alloys., Článek představuje skupinu nukleární magnetické rezonance ÚPT, její historické kořeny a vyhlídky. Studovaná problematika je ilustrována dvěma příklady. První je metodologický - je popsána úspěšná metoda pro jednovoxelovou protonovou MR in-vivo spektroskopii ve vysokých polích s extrémně krátkým echo-časem jakožto milník na cestě ke kvalitnímu spektroskopickému zobrazování. Druhý popisovaný výsledek je aplikační - analýza kompatibility dentálních slitin s magnetorezonančním vyšetřením., and Autor: Zenon Starčuk jr.
Modelling of turbulent flow in curved channels and diffusers of rectangular cross-section was aimed at the evolution of secondary flow and origin of flow separation and their connection with energy losses and pressure recovery. Results of numerical simulations carried out using software CFX TASCflow 2.12 were compared with experiments made in a water channel. Turbulent flow in diffusers of rectangular cross-section with the constant channel height, flow turn angle 90 deg and area ratio AR = 1.5 was investigated. Numerical simulation was carried out for flow in diffusers with the cylindrical inner wall and with the cylindrical centreline. Turbulent flow in a curved channel of constant cross-section was investigated for comparison. Further, the effect of the inner wall radius on the character of flow in the diffuser was studied. Flow separation occurs on the inner wall of the channel before the bend exit and its extent is restricted to the central part of the channel due to secondary flow going from the sidewalls to the channel axis. The extent of separation region and consequently the energy losses decrease with the increasing radius of the inner wall curvature. and Obsahuje seznam literatury
This work with numerical and experimental studies of specific issues of natural convection flow around a horizontal cylinder in a space limited by rectangular cavity. Physical models of laminar unsteady flows have been used for numerical calculations of heat transfer coefficients of four different diameters of horizontal cylinders and for several temperature gradients. Procedures and results of the experimental studies are contained in the next section. All results were compared with different authors and different approaches, However the Nusselt numbers can be estimated due to the temperature interval, the results indicate need for further investigation. and Obsahuje seznam literatury
This paper presents the results of an experimental and numerical study of a vertical slot fishway (VSF). A 2-D depth-averaged shallow water numerical model PCFLOW2D coupled with three different turbulent models (constant eddy viscosity, Smagorinsky and k - ε) was used. A detailed analysis of numerical parameters needed for a correct simulation of the phenomenon was carried out. Besides the velocity field, attention was paid to important hydraulic parameters such as maximum velocity in the slot region and energy dissipation rate ε in order to evaluate the performance of VSF. A scaled physical hydraulic model was built to ensure reliable experimental data for the validation of the numerical model. Simulations of variant configurations of VSF showed that even small changes in geometry can produce more fishfriendly flow characteristics in pools. The present study indicates that the PCFLOW2D program is an appropriate tool to meet the main demands of the VSF design.
In this paper, two- and three-dimensional numerical modeling is applied in order to simulate water flow behavior over the new Niedów barrage in South Poland. The draining capacity of one of the flood alleviation structures (ogee weir) for exploitation and catastrophic conditions was estimated. In addition, the output of the numerical models is compared with experimental data. The experiments demonstrated that the draining capacity of the barrage alleviation scheme is sufficiently designed for catastrophic scenarios if water is flowing under steady flow conditions. Nevertheless, the new cofferdam, which is part of the temporal reconstruction works, is affecting the draining capacity of the whole low-head barrage project.
The flow of a solid-water mixture through an upward-facing step in a channel is numerically investigated. The effect of expansion ratio, mean solids volume fraction and particle diameter on the velocity field, pressure distribution and solid volume fraction field is studied. Expansion ratios of 0.50 and 0.67, particle diameter of 125 µm and 440 µm and mean solid volume fraction between 0.05 and 0.20 are considered. Particle density is 2465 kg m-3 . An Eulerian twofluid model is used to simulate the flow. Due to the lack of experimental data, the model was validated by comparison to other numerical investigations and to experimental data about the horizontal pipe case. Afterwards, it is studied the effect of the above mentioned parameters upon the degree of coupling between the phases and the extension of the disturbance region in the pressure and solid volume fraction fields downstream the step. Parameters of engineering interest, such as the reattachment length and the pressure recovery downstream the enlargement, are investigated.
We propose unified approach for analysis of finite discrete time Markov chains. We show some possibilities for computing stationary probabilty vectors even in the case of reducible transition matrix. Finally we show one method for computing of Mean First Passage Times Matrices. and Obsahuje seznam literatury