We consider the simple case of a nonrelativistic charged harmonic oscillator in one dimension, to investigate how to take into account the radiation reaction and vacuum fluctuation forces within the Schrödinger equation. The effects of both zero-point and thermal classical electromagnetic vacuum fields, characteristic of stochastic electrodynamics, are separately considered. Our study confirms that the zero-point electromagnetic fluctuations are dynamically related to the momentum operator p=−i ℏ ∂/∂ x used in the Schrödinger equation.

We make a brief review of the Kramers escape rate theory for the probabilistic motion of a particle in a potential well U(x), and under the influence of classical fluctuation forces. The Kramers theory is extended in order to take into account the action of the thermal and zero-point random electromagnetic fields on a charged particle. The result is physically relevant because we get a non-null escape rate over the potential barrier at low temperatures (T → 0). It is found (...) that, even if the mean energy is much smaller than the barrier height, the classical particle can escape from the potential well due to the action of the zero-point fluctuating fields. These stochastic effects can be used to give a classical interpretation to some quantum tunneling phenomena. Relevant experimental data are used to illustrate the theoretical results. (shrink)

A coordinate-free formulation is established for (semi) classical particle-field interactions. The exterior language of spacetime chains and De-Rham currents enables the description to include extended strings and membranes besides point particles. Treating physical fields in terms of sections of particular bundles, a unified account of interactions is presented in terms of an intrinsic action principle on a bundle of jets over spacetime. The theory is illustrated by considering the specific model of point particles with intrinsic spin covariantly coupled to theU(1) (...) andSL(2, C) connections describing the electromagnetic and gravitational fields, respectively. The notion of dual spin is examined in this context and coupled equations for this particle-field system are explicitly derived in a local chart. Attention is drawn to the global implications of the theory. (shrink)

Professor Austin explores four main areas in this paper. First of all he outlines the physical development of sex differentiation in the embryo. He develops this by describing the clinical manifestations of abnormality which can appear at that stage. Professor Austin points out that there are relatively few people with abnormalities and that those who do show homosexual tendencies are not noticeably different from the norm in terms of their sexual equipment and hormone levels. It is much more likely that (...) their psychological and social development has a greater influence in differentiating them sexually. The last section of the paper is a synopsis of society's reactions to homosexuality or bisexuality which term in Professor Austin's opinion is more accurate and descriptive of the condition. (shrink)

This paper, which gives continuity to another article, analyzes the content of I Dialogus V, 14-22 and, in an appendix, presents our Portuguese translation of this excerpt. In these chapters, the Inceptor Venerabilis discusses whether St. Peter and the Roman Church possess primacy over all other apostles and churches; andwhether this primacy is granted by God himself. Ockham first presents, not ad litteram, the opinion of those who refute the thesis that Christ did not give primacy to Peter and the (...) Roman Church. Then, because this thesis fully deflates papal power, he proposes a contrary thesis based on five proofs. We conclude that Ockham’s unnamed opponent is Marsilius of Padua, whose opinions are in his Defensor Pacis. (shrink)

The preparation of layers of amorphous Se by plasma-enhanced CVD using the hydride H2Se as precursor gas is described. Information concerning the structure of the films was obtained from Raman spectroscopy. The spectra of amorphous Se indicated that the dominant molecular structure is the eight-membered ring and/or a chain with Se8 molecular fragments. This material exhibited reversible photodarkening when illuminated at 77 K. In order to explain this phenomenon, we propose a mechanism which takes into account the role of the (...) lone-pair electron orbitals of Se in their contribution to structural ordering. Illumination can cause a distortion in the normal bonding direction between nearest-neighbour Se atoms and induce in this way intrinsic defect states located at the band edges. In the photo-darkened state, optical transition will occur between these defect states. (shrink)

Govind Chandra Pande, b. 1923, Indian philosopher and historian; contributed articles.

Vijf Nederlandse filosofen geven elk vanuit een andere filosofische achtergrond weer wat hun mensbeeld is.

Adaptive management is commonly identified as a way to address situations where ecological and social uncertainty exists. Two discourses are common: a focus on experimentation, and a focus on collaboration. The roles of experimental and collaborative adaptive management in contemporary practice are reviewed to identify tools for bridging the discourses. Examples include broadening the scope of contributions during the buy-in and goal-setting stages, using conceptual models and decision support tools to include stakeholders in model development, experimentation using indicators of concern (...) to stakeholders, an experimental focus that reflects the level of statistical confidence required by management, and the engagement of stakeholders in data interpretation so that those affected by management outcomes can learn and adapt accordingly. In this context, a framework of questions that managers can use to reflect on both ecological and social uncertainties as they relate to individual management contexts is proposed. (shrink)