SuperlensA superlens, or super lens, is a lens which uses metamaterials to go beyond the diffraction limit. The diffraction limit is a feature of conventional lenses and microscopes that limits the fineness of their resolution depending on the illumination wavelength and the numerical aperture NA of the objective lens. Many lens designs have been proposed that go beyond the diffraction limit in some way, but constraints and obstacles face each of them. In 1873 Ernst Abbe reported that conventional lenses are incapable of capturing some fine details of any given image.
Stress–energy tensorThe stress–energy tensor, sometimes called the stress–energy–momentum tensor or the energy–momentum tensor, is a tensor physical quantity that describes the density and flux of energy and momentum in spacetime, generalizing the stress tensor of Newtonian physics. It is an attribute of matter, radiation, and non-gravitational force fields. This density and flux of energy and momentum are the sources of the gravitational field in the Einstein field equations of general relativity, just as mass density is the source of such a field in Newtonian gravity.
Use of forceThe use of force, in the context of law enforcement, may be defined as the "amount of effort required by police to compel compliance by an unwilling subject". Use of force doctrines can be employed by law enforcement officers and military personnel on guard duty. The aim of such doctrines is to balance the needs of security with ethical concerns for the rights and well-being of intruders or suspects. Injuries to civilians tend to focus attention on self-defense as a justification and, in the event of death, the notion of justifiable homicide.
Use of force continuumA use of force continuum is a standard that provides law enforcement officers and civilians with guidelines as to how much force may be used against a resisting subject in a given situation. In some ways, it is similar to the U.S. military's escalation of force (EOF). The purpose of these models is to clarify, both for law enforcement officers and civilians, the complex subject of use of force. They are often central parts of law enforcement agencies' use of force policies.
Motion (geometry)In geometry, a motion is an isometry of a metric space. For instance, a plane equipped with the Euclidean distance metric is a metric space in which a mapping associating congruent figures is a motion. More generally, the term motion is a synonym for surjective isometry in metric geometry, including elliptic geometry and hyperbolic geometry. In the latter case, hyperbolic motions provide an approach to the subject for beginners. Motions can be divided into direct and indirect motions.
