Semithin and in particular ultrathin sections of the glandular subdivisions in the oviduct of the terrestrial egg laying, direct developing plethodontid salamanders Bolitoglossa pesruba and Oedipina uniformis revealed remarkable structural differences of secretory products between the two species and in B. pesrubra between the different subdivisions of the duct. In the latter species structure of the secretory granules confirmed the previously described histological differentiation of the glandular portion of the oviduct in four subdivisions. In the first subdivision most secretory granules were moderately electron-dense having a distinct osmiophilic core, in the second these cores are absent, in the third granules revealed a complex inner structure and in the fourth they are more or less homogeneous and electron dense. In O. uniformis, however, secretory granules were differently stained in semithin sections with toluidine blue, but showed a homogeneous moderately electron-dense appearance along the entire oviduct. As oviductal secretions form the generally multi-layered glycoproteinaceous egg jelly enveloping the ovum when passing down the oviduct, our results suggest that in terrestrial breeders considerable differences exist in these secretions even at the structural level and, therefore, very likely in number and nature of egg jelly layers.
In this paper a novel method is proposed for the structural identifiability analysis of nonlinear time delayed systems. It is assumed that all the nonlinearities are analytic functions and the time delays are constant. We consider the joint structural identifiability of models with respect to the ordinary system parameters and time delays by including delays into a unified parameter set. We employ the Volterra series representation of nonlinear dynamical systems and make use of the frequency domain representations of the Volterra kernels, i. e. the Generalized Frequency Response Functions (GFRFs), in order to test the unique computability of the parameters. The advantage of representing nonlinear systems with their GFRFs is that in the frequency domain representation the time delay parameters appear explicitly in the exponents of complex exponential functions from which they can be easily extracted. Since the GFRFs can be symmetrized to be unique, they provide us with an exhaustive summary of the underlying model structure. We use the GFRFs to derive equations for testing structural identifiability. Unique solution of the composed equations with respect to the parameters provides sufficient conditions for structural identifiability. Our method is illustrated on non-linear dynamical system models of different degrees of non-linearities and multiple time delayed terms. Since Volterra series representation can be applied for input-output models, it is also shown that after differential algebraic elimination of unobserved state variables, the proposed method can be suitable for identifiability analysis of a more general class of non-linear time delayed state space models.
The structural reorganization of pea thylakoid systems in response to osmotic shock in a wide range of temperatures (36-70°C) was studied. At temperatures 40-46°C, the configuration of thylakoid systems changed from a flattened to a nearly round, whereas thylakoids themselves remained compressed. The percentage of thylakoids stacked into grana at 44°C decreased from 71 % in the control to 40 % in experimental samples, reaching 59 % at 48°C. At 44°C and above, thylakoid systems ceased to respond to the osmotic shock by disordering, in contrast to what happened at lower temperatures (36-43°C) and in the control, and retained the configuration inherent in thylakoid systems at these temperatures. At 50°C and above, the packing of thylakoids in grana systems changed, and thylakoids formed extended strands of pseudograna. Simultaneously, single thylakoids formed a network of anastomoses through local fusions. At temperatures of 60-70°C, thylakoid systems appeared as spherical clusters of membrane vesicles with different degree of separation.
In this paper, we have attempted to give a general framework (from bifurcation theory point of view) for understanding the structural stability and bifurcation behavior in following phase synchronized systems: (a) coupled Poincare systems; (b) controlled linear oscillator and (c) ‘predator-prey’ system, on the base of a specifíc version of bifurcational theory (based on the computing first Lyapunov value (not exponent)). Our results suggest that for these three systems soft stability loss take place. and Obsahuje seznam literatury
Th e approach of structuralism came to philosophy from social science. It was also in social science where, in 1950–1970s, in the form of the French structuralism, the approach gained its widest recognition. Since then, however, the approach fell out of favour in social science. Recently, structuralism is gaining currency in the philosophy of mathematics. Aft er ascertai ning that the two structuralisms indeed share a common core, the question stands whether general structuralism could not fi nd its way back into social science. Th e nature of the major objections raised against French structuralism – concerning its alleged ahistoricism, methodological holism and universalism – are reconsidered. While admittedly grounded as far as French structuralism is concerned, these objections do not aff ect general structuralism as such. Th e fate of French structuralism thus does not seem to preclude the return of general structuralism into social science, rather, it provides some hints where the diffi culties may lie. and Strukturalismus přišel do fi losofi e ze společenských věd. Byly to také společenské vědy kde, v letech 1950–1970 v podobě Francouzského strukturalismu, získal strukturalismus nejširší uznání. Od té doby však jeho popularita ve společenských vědách opadla. V nedávné době však začal strukturalismus nabývat na popularitě ve fi losofi i matematiky. Ukazuje se, že tyto dvě formy strukturalismu mají na obecné úrovni mnoho společného. Otázkou pak je, zda neexistuje možnost, aby se obecně chápaný strukturalismus navrátil do společenských věd. Hlavní námitky proti Francouzskému strukturalismu – jeho ahistorismus, metodologický holismus a universalismus – jsou opětovně uváženy. Ačkoliv jsou námitky relevantní, pokud jde o Francouzský strukturalismus, nejedná se o námitky proti obecnému strukturalismu jako takovému. Osud Francouzského strukturalismu se tak nezdá být překážkou pro případný návrat obecného strukturalismu do společenských věd, spíše poskytuje postřehy, kde by se mohly vyskytnout největší obtíže.
Preferential flow paths in the crust, as caused by the presence of the Luchlompolo fault in the drilled section of the Kola Superdeep Borehole (SG-3) and the dip angle of the rock structural elements (layering, schistosity, banding), are favourable for migration of deep fluids to the Earth’s surface. An investigation of the structure, anisotropy and permeability of rocks under PT-conditions in the SG-3 section, in addition to the occurrence of He-isotopes, reveals that the high-permeability zones of the exposed crustal segment are related to two important structural elements of the section: in the upper zone - to the Luchlompolo fault, in the lower one to the contact between the Proterozoic and Archaean complexes. The obtained results on the rock samples from SG-3 indicate a rough correlation between permeability and elastic anisotropy of various rock samples. Simulating increased PT-conditions, corresponding to the relevant depths of 6-8 km document the overlapping temperature and pressure effect, i.e. resulting in a sharp decrease of rock permeability., Felix F. Gorbatsevich, Serafim V. Ikorsky and Andrey V. Zharikov., and Obsahuje bibliografii
This paper discusses the comparison of the flow field downstream of two different swirl generators. Both swirl generators are used to imitate the flow at the exit of the hydraulic turbine runner and study spatio-temporal behaviour of the swirling flow in the draft tube (i.e. outlet diffuser part of the hydraulic turbine), which undergoes breakdown into vortex rope. Unsteady CFD computations are carried out for identical Reynolds number. Resulting velocity and vorticity profiles are correlated with the structure of the vortex rope. Difference in excited pressure pulsations is illustrated on amplitude-frequency spectra of static wall pressure. and Obsahuje seznam literatury
In this note we describe for the first time the inner structure of bezoars found in the stomach of a free-living crested porcupine. These foreign bodies were composed by three concentric layers made up of vegetal matter. The presence of nettle trichomes in the central core, probably due to an accidental ingestion, may have determined the development of these foreign bodies.