In STM, an elevation of the tip above the surface being scanned can be determined with a great precision, because the tunneling-electron current between surface atoms and the atoms of the tip is extremely sensitive to the variation of the separation gap between them from point to point along the surface. Assuming that the tunneling-electron current is in direct proportion to the tunneling probability and that the tunneling probability is to a good approximation expressed by the exponential function \(e^{-2 \beta L} \text { with } \beta=10.0 / \mathrm{nm}\), determine the ratio of the tunneling current when the tip is 0.500 nm above the surface to the current when the tip is 0.515 nm above the surface.
Text Transcription:
e^-2 beta L with beta=10.0/nm
EXAM 2 NOTES 9/21/16 OUTLINE The nervous system as a machine The 3box model o DATA – in – sensory From the periphery o Analysis – integration CNS (brain and spinal cord) o DATA out – motor Biological definitions: o Peripheral nervous system: Sensory in Afferents o “Toward” the CNS Motor out Efferents o “Away” from the CNS o Central nervous system Brain and spinal cord Sensory transduction: o Change in form of energy Conversion to ion movements across membranes o Types of energy: Electromagnetic Mechanical Chemical The neuron doctrine o The neuron as the fundamental structural and functional unit of the nervous system 3Box Model Data in Analysis Data out Take this simple 3 step paradigm and apply it to the nervous system o In this case, the data coming in is sensory information Take the sensory info and integrate it o Motor out As we sit here and currently don’t worry about things like lions, we still have sensory info coming in o We make decisions to sit still, stay put, or leave o The idea of integration
