This contribution presents a review of resonance phenomena associated with the orbital motion of artificial satellites. Following an outline of the principal features of satellite motion and tracking
methods the topic of passage through high-order resonances is discussed. Next, a brief description of geostationary and other
low-order resonant orbits is presented. The paper is concluded with an historie account of the well-known critical inclination problem.
The claim by many authors that Spinitectus inermis (Zeder, 1800), a narrowly specific parasite of European eels Anguilla anguilla (L.), is a rare species is considered at three levels: its geographical range, its frequency of occurrence compared to other eel parasites and its relative abundance in component communities. The parasite is widely distributed in freshwater throughout the European range of the eel but its occurrence is erratic and unpredictable, being known from only 8 countries. Surveys of eel parasites in the United Kingdom and in Continental Europe show that it is present in only 13% of British and 29% of continental localities. This satisfies one of the criteria for rarity. When present, its prevalence ranges from 1.8% to 43.3%, so it can be considered rare in some localities but in a few it may be common and on occasion it may be the dominant species in the gastro-intestinal community. Populations of S. inermis are almost always characterised by high levels of overdispersion, even at low prevalence. The species also displays an ability to colonise a locality following introduction there. Overall it meets many of the criteria of a rare species including a restricted distribution and a low frequency of occurrence and so it can be considered to exhibit diffusive rarity.
Eight species of fishes from rivers of Northern Portugal were examined for cestodes but only one, Barbus barbus bocagei (Steindachner), was infected: river Este (4 of 12 infected, 1,1,4 adult and 37 juvenile cestodes found respectively), Lima (1 of 8 infected, 1 juvenile cestode), Paiva (1 of 5 infected, 57 juvenile cestodes) and Sousa (1 of 13 infected, 1 adult cestode). The cestodes were Caryophyllidea. The fan-shaped scolex had very shallow incisions, with the scolex separated from the hindbody by a neck. The first vitelline follicles started a considerable distance anterior to the testes, with some vitelline follicles along the lateral margins of the cirrus sac, uterine coils and H-shaped ovary. The uterine coils extended forward to the posterior half of the cirrus sac. Transverse transmission electron microscope sections showed cortical vitelline follicles and medullary testes validating Lytocestidae. These features identify Khawia baltica Szidat, 1941, described from tench Tinca tinca (L.) in East Prussia and subsequently reported from barbel B. barbus and T. tinea in Russia, This is a new host and first record from Portugal and western Europe, thus extending the known range of distribution of K. baltica.
We study a parameter depending semilinear elliptic PDE on a rectangle with Signorini boundary conditions on a part of one edge and mixed (zero Dirichlet and Neumann) boundary conditions on the rest of the boundary. We describe smooth branches of smooth nontrivial solutions bifurcating from the trivial solution branch in eigenvalues of the linearized problem. In particular, the contact sets of these nontrivial solutions are intervals which change smoothly along the branch. The main tools of the proof are first a certain local equivalence of the unilateral BVP to a system consisting of a corresponding classical BVP and of two scalar equations (which determine the ends of the contact intervals), and secondly an application of the classical Crandall-Rabinowitz type local bifurcation techniques (scaling and application of the Implicit Function Theorem) to that system.
A class of q-nonlinear parabolic systems with a nondiagonal principal matrix and strong nonlinearities in the gradient is considered.We discuss the global in time solvability results of the classical initial boundary value problems in the case of two spatial variables. The systems with nonlinearities q ∈ (1, 2), q = 2, q > 2, are analyzed.