Showing papers by "University of Los Andes published in 1978"

Model of Einstein and Hopf for protons in zero-point field and cosmic-ray spectrum

Abstract: It is proposed that an agent responsible for the acceleration of cosmic-ray particles, and in particular for the acceleration of cosmic-ray protons, is the zero-point universal background radiation. This proposition is based first on a classical model for polarizable particles interacting with a random electromagnetic field, due to Einstein and Hopf, and second on the conjecture that some cosmic-ray particles and in particular protons, due to their inner structure, can be polarized and respond like linear oscillators. An energy spectrum for cosmic-ray protons is derived and the braking effect of the microwave background as well as collisions with interstellar or intergalactic gas particles are discussed. Numerical fittings and simple predictions are presented. The analysis is carried classically in the manner of random or stochastic electrodynamics.

Azimuthal brightness variation of Saturn's ring-A and size of particles

Abstract: OBSERVATIONS of the brightness of ring A of Saturn, indicate that it is not constant in azimuth. This was discovered by Camichel1, and later studied by me2. Reitsema et al.3 and Lumme and Irvine4, have confirmed these observations. The A ring is fainter in quadrants following conjunction of the particles with the Earth–Saturn line, and brighter in quadrants preceding conjunction. No azimuthal brightness variation of this type is found for the B-ring5. Because these observations do not show any time dependence, the effect is stationary. We will call this, fact A. A possible explanation for it has been given by Colombo et al.8. Here we give an alternative explanation for fact A, which would be valid if the particles in ring A are large, which we will show is indeed the case, using a recent measurement11 of the total mass of the rings.

Analysis of characters and classification based on information theory in the species of the Greater Antilles of the fern familiy Gleicheniaceae

Abstract: We define a set of characters for the study of the fern family Gleicheniaceae. These characters have no ordered states. We establish a classification, through a divisive strategy, on the basis of these characters applied to the species occurring in the Greater Antilles. We used a technique based on information theory. A computational program was implemented to obtain this classification. With the same technique a procedure is used in order to compare a set of classifications reached under a different set of characters. The results obtained under three classifications on the family of this study are shown. Zur Untersuchung der Farn-Familie Gleicheniaceae wird eine Gruppe von willkurlich ausgewahlten Merkmalen herangezogen. Diese Merkmale dienen als Basis fur mathematische Operationen, mit denen eine Klassifizierung begrundet wird. Die Methode wird an Gleicheniaceen-Sippen von den Grosen Antillen demonstriert. Die angewandte Technik basiert auf der Informations-Theorie. Um diese Klassifikation aufzustellen, wird ein Computer-Programm durchgefuhrt. Mit der gleichen Technik werden Klassifizierungen verglichen, die mit unterschiedlichen Merkmalsgruppen aufgestellt wurden. Die Ergebnisse von drei Klassifizierungen der untersuchten Familie werden dargestellt.

A taxonomical revision of Lygodium (Filicinae) in America

Abstract: This work summarizes the taxonomical status of the American species of the fern genus Lygodium. Each species is described under a given set of characters. The information content of the character-states was performed and some implications of these measurements are discussed. Besides a dichotomic identification key for species, synonymy, and its distribution on each country are given. It is recognized 8 taxa at the specific level and 47 taxa (16 infraspecific) are be regarded as synonyms. In dieser Arbeit wird der taxonomische Status der amerikanischen Arten der Farn-Gattung Lygodium zusammengefast. Jede Art wird an Hand einer gegebenen Anzahl von Merkmalen beschrieben. Der Inhalt der Information dieser Merkmalswerte wird ausgewertet und einige Ergebnisse dieser Messungen werden beschrieben. Auserdem wird ein zweiteiliger Schlussel fur die Identifizierung der Arten, Synonyme und ihrer geographischen Verbreitung festgelegt. Es werden 8 Taxa mit spezifischem Niveau anerkannt und 47 (16 mit infraspezifischem Niveau) werden als Synonyme angesehen.

Quantum mechanics with density operators

Abstract: Publisher Summary The general definition of a quantum mechanical state as a density operator on Hilbert space is known for a long time especially in quantum statistical mechanics This chapter presents a system of axioms for nonrelativistic quantum mechanics that emphasizes the role of density operators as states It discusses specific connections of that theory with other formulations of quantum theory It explains that standard set of axioms for quantum mechanics in Hilbert space differs to some extent from other axiom systems present in literature After stating the axioms, the chapter discusses the reasons that will in part justify those differences It also highlights that the use of density operators should be preferred even in the quantum mechanics of a single particle