Excited gradient

A common example is the Belousov - Zhabotinsky reaction [24], Beautiful patterns of chemical wave propagation can be created in a chemical reaction - diffusion system with a spatiotemporal feedback. The wave behavior can be controlled by feedback-regulated excitability gradients that guide propagation in the specified directions [25, 26]. 

The heating of an emulsion produces temperature gradients, which in their own turn cause thermocapillary migration of the droplets driven by thermally excited gradients of surface tension (170—172) ... 

In this section we discuss the frequency spectrum of excitations on a liquid surface. Wliile we used linearized equations of hydrodynamics in tire last section to obtain the density fluctuation spectrum in the bulk of a homogeneous fluid, here we use linear fluctuating hydrodynamics to derive an equation of motion for the instantaneous position of the interface. We tlien use this equation to analyse the fluctuations in such an inliomogeneous system, around equilibrium and around a NESS characterized by a small temperature gradient. More details can be found in [9, 10]. 

Most NC-AFMs use a frequency modulation (FM) teclmique where the cantilever is mounted on a piezo and serves as the resonant element in an oscillator circuit [101. 102]. The frequency of the oscillator output is instantaneously modulated by variations in the force gradient acting between the cantilever tip and the sample. This teclmique typically employs oscillation amplitudes in excess of 20 mn peak to peak. Associated with this teclmique, two different imaging methods are currently in use namely, fixed excitation and fixed amplitude. 

If the electrodes are moved closer together, the positive column begins to shorten as it moves through the Faraday dark space because the ions and electrons within it have a shorter distance through which to diffuse. Near the cathode, however, the electric-field gradient becomes steeper and electrons from the cathode are accelerated more quickly. Thus atom excitation through collision with electrons occurs nearer and nearer to the cathode, and the cathode glow moves down toward the electrode. 

Ion Channels. The excitable cell maintains an asymmetric distribution across both the plasma membrane, defining the extracellular and intracellular environments, as well as the intracellular membranes which define the cellular organelles. This maintained a symmetric distribution of ions serves two principal objectives. It contributes to the generation and maintenance of a potential gradient and the subsequent generation of electrical currents following appropriate stimulation. Moreover, it permits the ions themselves to serve as cellular messengers to link membrane excitation and cellular... 

The resting membrane potential of most excitable cells is around —60 to —80 mV. This gradient is maintained by the activity of various ion channels. When the potassium channels of the cell open, potassium efflux occurs and hyperpolari2ation results. This decreases calcium channel openings, which ia turn preveats the influx of calcium iato the cell lea ding to a decrease ia iatraceUular calcium ia the smooth muscles of the vasculature. The vascular smooth muscles thea relax and the systemic blood pressure faUs. 

The A matrix involves elements between singly excited states while B is given by matrix elements between doubly excited states and the reference. The P/Q elements are matrix elements of the operator between the reference and a singly excited state. If P = r this is a transition moment, and in the general case it is often denoted a property gradient , in analogy with the case where the operator is the Hamiltonian (eq. (3.67). 

Voltage-gated Ca2+ channels are Ca2+-selective pores in the plasma membrane of electrically excitable cells, such as neurons, muscle cells, (neuro) endocrine cells, and sensory cells. They open in response to membrane depolarization (e.g., an action potential) and permit the influx of Ca2+ along its electrochemical gradient into the cytoplasm. 

Potassium channels are a diverse and ubiquitous family of membrane proteins present in both excitable and nonexcitable cells that selectively conduct K+ ions across the cell membrane along its electrochemical gradient at a rate of 106-108 ions/s. 

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