Pathological and histopatnotogical studies of the swimbladder of eels Anguilla anguitla infected by Angutlticpta crassus (Nemafoda: Dracuncuioidea)

The swimbladder lesions produced by Anguillicola crassus (Nematoda) infection, causing mass mortality among eels in Lake Balaton (Hungary) were studied by histological methods. In the initial phase of infection, no severe changes developed in the swimbladder wall despite the presence and intensive blood-sucking activity of worms that filled the lumen of the swimbladder. After disruption of the worms and primarily because of repeated reinfection by larvae, however, the wall of the swimblaader markedly thickened and showed degenerative, inflammatory and proliferative changes. Acute processes were characterized by epithelial hyperplasia and hyperaemia of the swimbladder wall. In cases of chronic swimbladder inflammation, oedema and hyperplasia of tissues of the tunica propria, submucosa and serosa could be observed, as well as granulomatoid infiltration by mononuclear cells and fibrinoid degeneration around the larvae

MOULDED, PLASTIC PGA PACKAGES

The increase of the size of le chips and the numbers of the pins made it necessary to develop a new kind of package a couple of years ago. PGA packages have appeared and have been used. The authors of this article present a new type of plastic PGA construction. The technology of the package combines the advantages of the production of moulding technologies of packages with PWB. The new plastic PGA package has good electrical and thermal properties and it is cheap. The construction and technology used allow to meet the demands of individual consumers as well - by shortening the time from design to manufacturing. The article describes in detail the testing of the thermal properties of the plastic PGA package

On the Possibility and Consequences of Negative Mass

We investigate the possibility and consequences of the existence of particles having negative relativistic masses, and show that their existence implies the existence of faster- than-light particles (tachyons). Our proof requires only two postulates concerning such particles: that it is possible for particles of any (positive, negative or zero) relativistic mass to collide inelastically with 'normal' (i.e. positive relativistic mass) particles, and that four-momentum is conserved in such collisions

Groups of worldview transformations implied by isotropy of space

Given any Euclidean ordered field, Q, and any 'reasonable' group, G, of (1+3)-dimensional spacetime symmetries, we show how to construct a model MG of kinematics for which the set W of worldview transformations between inertial observers satisfies W=G. This holds in particular for all relevant subgroups of Gal, cPoi, and cEucl (the groups of Galilean, Poincaré and Euclidean transformations, respectively, where c∈Q is a model-specific parameter orresponding to the speed of light in the case of Poincaré transformations). In doing so, by an elementary geometrical proof, we demonstrate our main contribution: spatial isotropy is enough to entail that the set W of worldview transformations satisfies either W⊆Gal, W⊆cPoi, or W⊆cEucl for some c>0. So assuming spatial isotropy is enough to prove that there are only 3 possible cases: either the world is classical (the worldview transformations between inertial observers are Galilean transformations); the world is relativistic (the worldview transformations are Poincaré transformations); or the world is Euclidean (which gives a nonstandard kinematical interpretation to Euclidean geometry). This result considerably extends previous results in this field, which assume a priori the (strictly stronger) special principle of relativity, while also restricting the choice of Q to the field of reals. As part of this work, we also prove the rather surprising result that, for any G containing translations and rotations fixing the time-axis t, the requirement that G be a subgroup of one of the groups Gal, cPoi or cEucl is logically equivalent to the somewhat simpler requirement that, for all g∈G: g[t] is a line, and if g[t]=t then g is a trivial transformation (i.e. g is a linear transformation that preserves Euclidean length and fixes the time-axis setwise)