לוח שנה משולב

Neurons and networks must constantly rebuild themselves in response to the continual and ongoing turnover of all of the ion channels and receptors that are necessary for neuronal signaling. A good deal of work argues that stable neuronal and network function arises from homeostatic negative feedback mechanisms. Nonetheless, while these mechanisms can produce a target activity or performance, they are also consistent with a good deal of recent theoretical and experimental work that shows that similar circuit outputs can be produced with highly variable circuit parameters. This work argues that the nervous system of each healthy individual has found a set of different solutions that give “good enough circuit performance. I will describe new computational models (O’Leary et al., PNAS 2013; Neuron in press, 2014) for cellular homeostasis that give insight into a variety of experimental observations, including correlations in the expression of ion channel genes. In response to perturbation these homeostatic models usually compensate for perturbations, but some perturbations elude compensation. Moreover, situations can arise in which the homeostatic mechanisms result in aberrant behavior, such as may occur in disease.

At intensities above 1018 W/cm-2 relativistic effects start to dominate the interaction of light and matter. Of particular interest is the acceleration of particles by intense laser light. Electrons may be accelerated to GeV energies and protons up to 100 MeV have been generated. Applications of such novel techniques include the development of proton beams for the radiation therapy of cancer, innovative x-ray sources based on Compton-scatting of laser light at a 40 MeV electron beam or even new experiments to explore the dielectric properties of the vacuum.