Bar-Ilan University

About: Bar-Ilan University is a education organization based out in Ramat Gan, Israel. It is known for research contribution in the topics: Population & Poison control. The organization has 12835 authors who have published 34964 publications receiving 995648 citations. The organization is also known as: Bar Ilan University & BIU.

Wave-field phase singularities: The sign principle

Abstract: Phase singularities (topological charges, dislocations, defects, vortices, etc.), which may be either positive or negative in sign, are found in many different types of wave fields. We show that on every zero crossing of the real or imaginary part of the wave field, adjacent singularities must be of opposite sign. We also show that this ``sign principle,'' which is unaffected by boundaries, leads to the surprising result that for a given set of zero crossings, fixing the sign of any given singularity automatically fixes the signs of all other singularities in the wave field. We show further how the sign of the first singularity created during the evolution of a wave field determines the sign of all subsequent singularities and that this first singularity places additional constraints on the future development of the wave function. We show also that the sign principle constrains how contours of equal phase may thread through the wave field from one singularity to another. We illustrate these various principles using a computer simulation that generates a random Gaussian wave field.

Plastic Vortex Creep in YBa2Cu3O7-x Crystals.

Abstract: Local magnetic relaxation measurements in YBa{sub 2}Cu{sub 3}O{sub 7{minus}{ital x}} crystals show evidence for plastic vortex creep associated with the motion of dislocations in the vortex lattice. This creep mechanism governs the vortex dynamics in a wide range of temperatures and fields below the melting line and above the field corresponding to the peak in the {open_quote}{open_quote}fishtail{close_quote}{close_quote} magnetization. In this range the activation energy {ital U}{sub pl}, which decreases with field, drops below the elastic (collective) creep activation energy, {ital U}{sub el}, which increases with field. A crossover in flux dynamics from elastic to plastic creep is shown to be the origin of the fishtail in YBa{sub 2}Cu{sub 3}O{sub 7{minus}{ital x}}. {copyright} {ital 1996 The American Physical Society.}

Attachment Security, Compassion, and Altruism:

Abstract: Theoretically, people who have the benefits of secure social attachments should find it easier to perceive and respond to other people's suffering, compared with those who have insecure attachments. This is because compassionate reactions are products of what has been called the caregiving behavioral system, the optimal functioning of which depends on its not being inhibited by attachment insecurity (the failure of the attachment behavioral system to attain its own goal, safety and security provided by a caring attachment figure). In a series of recent studies, we have found that compassionate feelings and values, as well as responsive, altruistic behaviors, are promoted by both dispositional and experimentally induced attachment security. These studies and the theoretical ideas that generated them provide guidelines for enhancing compassion and altruism in the real world.