In accelerator physics, rigidity is a concept used to determine the effect of particular magnetic fields on the motion of the charged particles.
It is a measure of the momentum of the particle, and it refers to the fact that a higher momentum particle will have a higher resistance to deflection by a magnetic field. It is defined as R= Bρ= p/q, where B is the magnetic field, ρ is the gyroradius of the particle due to this field, p is the particle momentum, and q is its charge. It is frequently referred to as simply "Bρ".
It is important to note that the rigidity is defined by the action of a static magnetic field, whose direction is perpendicular to the velocity vector of the particle. This will cause a force perpendicular both to the velocity vector, and to the field, defining a plane through which the particle moves. The definition of the Lorentz force implies that the particle's motion will be circular in a uniform field, thus giving a constant radius of curvature.
Hypokinesia refers to decreased bodily movement. One of the two categories of movement disorders, hypokinesia is characterized by a partial or complete loss of muscle movement due to a disruption in the basal ganglia. Patients with hypokinetic disorders like Parkinson's disease experience muscle rigidity and an inability to produce movement. It is also associated with mental health disorders and prolonged inactivity due to illness, amongst other diseases.
The other category of movement disorder resulting from damage to the basal ganglia, hyperkinesia, features an exaggeration of unwanted motion, like twitching or writhing in Huntington's disease or Tourette syndrome.
Spectrum of disorders
Hypokinesia describes a variety of more specific disorders:
Pathophysiology
Associated neurotransmitters
Dopamine
The main neurotransmitter thought to be involved in hypokinesia is dopamine. Essential to the basal ganglionic-thalamocortical loop, which processes motor function, dopamine depletion is common in these areas of hypokinesic patients.Bradykinesia is correlated with lateralized dopaminergic depletion in the substantia nigra. The dopamine pathway in the substantia nigra is essential to motor function, and commonly a lesion in this area correlates with displayed hypokinesia. Tremor and rigidity, however, seem to be only partially due to dopamine deficits in the substantia nigra, suggesting other processes are involved in motor control. Treatments for hypokinesia often either attempt to prevent dopamine degradation by MAO-B or increase the amount of neurotransmitter present in the system.
Rigidity is the property of a structure that it does not bend or flex under an applied force. The opposite of rigidity is flexibility. In structural rigidity theory, structures are formed by collections of objects that are themselves rigid bodies, often assumed to take simple geometric forms such as straight rods (line segments), with pairs of objects connected by flexible hinges. A structure is rigid if it cannot flex; that is, if there is no continuous motion of the structure that preserves the shape of its rigid components and the pattern of their connections at the hinges.
There are two essentially different kinds of rigidity. Finite or macroscopic rigidity means that the structure will not flex, fold, or bend by a positive amount. Infinitesimal rigidity means that the structure will not flex by even an amount that is too small to be detected even in theory. (Technically, that means certain differential equations have no nonzero solutions.) The importance of finite rigidity is obvious, but infinitesimal rigidity is also crucial because infinitesimal flexibility in theory corresponds to real-world minuscule flexing, and consequent deterioration of the structure.
Plasmonics is a field that leverages the interaction between light and free electrons in metals to create extremely confined electromagnetic fields. Traditionally, plasmonic materials have been rigid and possess limited design possibilities ... Also Read.
