Ultrastructural Observations on the Septal Pore in Cronartium Flaccidum (Alb. Et Schw.) Wint. Also in Relation to the Taxonomy of the Uredinales

SUMMARYThe fine structure of the septum and pore in the monokaryotic and dikaryotic vegetative mycelium of Cronartium flaccidum was studied. Some ultrastructural observations on the hyphal cell of this fungus were also carried out. The hyphal septa become progressively thinner towards the pore; the septal pore shows none of the swellings and of the structures resembling the parenthesome which characterize the dolipore septum of higher Basidiomycetes. The septal pore of C. flaccidum as it as been seen in other Uredinales investigated up now, is a very simple structure morphologically similar to the septal pore of Ascomycetes. Some formations which make up the septal pore apparatus that is amorphous and electron-dense material, differentiated organelle-free cytoplasm and microbodies were observed near the septum and pore in both nuclear phases of the mycelium. It is accepted a relationship between the occurrence of microbodies and the occurrence and function of the dense material at the pore region likely t..

Neural Nets and Star/Galaxy Separation in Wide Field Astronomical Images

One of the most relevant problems in the extraction of scientifically useful information from wide field astronomical images (both photographic plates and CCD frames) is the recognition of the objects against a noisy background and their classification in unresolved (star-like) and resolved (galaxies) sources. In this paper we present a neural network based method capable to perform both tasks and discuss in detail the performance of object detection in a representative celestial field. The performance of our method is compared to that of other methodologies often used within the astronomical community.Comment: 6 pages, to appear in the proceedings of IJCNN 99, IEEE Press, 199

Penetration and early colonization in basidiosporederived infection on needles of Pinus pinea L. by Cronartium flaccidum (Alb. et Schw.) Wint.

Abstract The behaviour and the morphology of the infection structures of the monokaryotic phase of Cronartium flaccidume studied on needles of Pinus pinea seedlings inoculated with the rust basidiospore. It was found that the penetration and early colonization structures of C. flaccidum in the monokaryotic phase maintained the morphological and functional significance of the typical monokaryotic ones, even if some aspects of their behaviour seemed to recall those of the dikaryon. A possible hypothesis as to the reason for the dynamics of penetration carried out on the markedly cutinized needles of pine by C. flaccidum in the monokaryotic phase is discussed. It can be concluded that in C. flaccidum in the monokaryotic phase it is the nuclear set which determines the morphology and function of the structures involved in the infection process; this is true even if the histological characteristics of the host organ which this rust species has evolved to infect in nature, condition its way of penetration

Astrophysics in S.Co.P.E

S.Co.P.E. is one of the four projects funded by the Italian Government in order to provide Southern Italy with a distributed computing infrastructure for fundamental science. Beside being aimed at building the infrastructure, S.Co.P.E. is also actively pursuing research in several areas among which astrophysics and observational cosmology. We shortly summarize the most significant results obtained in the first two years of the project and related to the development of middleware and Data Mining tools for the Virtual Observatory

Why do Large Animals Never Actuate Their Jumps with Latch-Mediated Springs? Because They can Jump Higher Without Them.

As animals get smaller, their ability to generate usable work from muscle contraction is decreased by the muscle's force-velocity properties, thereby reducing their effective jump height. Very small animals use a spring-actuated system, which prevents velocity effects from reducing available energy. Since force-velocity properties reduce the usable work in even larger animals, why don't larger animals use spring-actuated jumping systems as well? We will show that muscle length-tension properties limit spring-actuated systems to generating a maximum one-third of the possible work that a muscle could produce-greatly restricting the jumping height of spring-actuated jumpers. Thus a spring-actuated jumping animal has a jumping height that is one-third of the maximum possible jump height achievable were 100% of the possible muscle work available. Larger animals, which could theoretically use all of the available muscle energy, have a maximum jumping height that asymptotically approaches a value that is about three times higher than that of spring-actuated jumpers. Furthermore, a size related "crossover point" is evident for these two jumping mechanisms: animals smaller than this point can jump higher with a spring-actuated mechanism, while animals larger than this point can jump higher with a muscle-actuated mechanism. We demonstrate how this limit on energy storage is a consequence of the interaction between length-tension properties of muscles and spring stiffness. We indicate where this crossover point occurs based on modeling and then use jumping data from the literature to validate that larger jumping animals generate greater jump heights with muscle-actuated systems than spring-actuated systems