Chemical stimulation concentration

The chemical effect of high pressure is to stimulate the selectivity and the rate of reaction together with better product properties and quality as well as improved economy. This is based on better physico-chemical and thermodynamic reaction conditions such as density, activation volume, chemical equilibria, concentration and phase situation. Many successful reactions are basically enhanced by catalysis. 

The physico-chemical parameters of the chemical stimuli which have been shown to have relevance and to be interrelated to the sensory response it elicits as specific odor or taste, are the factors controlling concentration at the receptor areas (solubility, hydrophilicity, lipophilicity, volatility, and partition coefficients), molecular features (size, shape, stereochemical and chirality factors and functional groups), and electronic features (polarity and dipoles) controlling positioning and contact at receptor surfaces (53). Many of these physico-chemical data are not available for many of the chemical stimulants, and till they are gathered, structure-response studies will be much restricted. The effects of interactions of the above parameters appear to a larger degree in the perception of odor, the dimensions of which are many and complex viz. nuances, composite... 

Fig. 11.10. Synthetic multifunctional ion channels and pores either (A) open or (B) close in response to chemical stimulation. Dose response curves for (A) ligand gating or (B) blockage are characterized by effective (EC50) or inhibitory concentrations (/C50) and Hill coefficients (n). (C) Woodhull analysis of the voltage dependence of blockage reveals the depth of molecular recognition. (D) The special case of blockage by permeant electrolytes is described by /C50 and gwAX (the maximal conductance).

Palmer AM, Hutson PH, Lowe SL, Bowen DM (1989) Extracellular concentrations of aspartate and glutamate in rat neostriatum following chemical stimulation of frontal cortex. Exp Brain Res 75 659-663. 

This method only works for chemical stimulation where the ion concentration for each species a is independent of the local position in the gel. 

The TPM is generally designated for the chemical stimulation and can provide local chemical as well as mechanical unknowns. In most cases, the gel phase only is investigated by prescribing the concentrations at the boundary of the gel (at the gel-solution interface) by using the Donnan Equation (7) together with the electroneutrality condition of (6). 

In the first test case, the chemo-electrical behaviour of the polymer gel film under chemical stimulation, i.e. change of salt concentration in the solution, is investigated. The material parameters and initial conditions applied in all the test cases are given in Table 1. The concentration of the bound charges in the gel is prescribed to... 

Fig. 13 Steady-state results (a) of the mobile concentrations and c and (b) of the electric potential after chemical stimulation...

Summarizing, a change of the concentration in the solution by a chemical stimulation provokes a change of the concentration, of the electric potential, and of the gel domain. This fully chemo-electro-mechanical coupling is quite robust and works as a kind of limiter for the change of the chemical, electrical and mechanical unknowns compared to the unidirectional chemo-electrical to mechanical coupling. 

The mechanical deformation under electrical stimulation is much smaller than under chemical stimulation. Under electrical stimulation, an unsymmetrical distribution of the concentrations and thus of the osmotic pressure difference leads to an unsymmetrical deformation. It can be seen that the chemical stimulation triggers a homogeneous swelling of the gel film, while the electrical stimulation leads to an... 

Criteria for transmitter status To be accepted as a neurotransmitter. a candidate chemical must be present in higher concentration in the synaptic area than in other areas (ie, must be localized in appropriate areas), must be released by electrical or chemical stimulation via a calcium-dependent mechanism, and must produce the same sort of postsynaptic response that is seen with physiologic activation of the synapse (ie, must exhibit synaptic mimicry). Table 21-2 lists the most important chemicals currently accepted as neurotransmitters in the CNS. 

Current knowledge of taste perception indicates that within the neuron, in each taste cell, the potassium ion concentration is higher within the cell than without, the converse being true with sodium ions so that a resting potential exists across the cell wall. It is thought that when a chemical stimulant arrives on the surface of a receptor it momentarily modifies the cell wall and allows K+ ions to move out and Na+ ions to move in, and the resultant depolarization is transmitted along the nerve. Once the neuron has fired, the membrane potential is re-established within about a millisecond and the process is repeated as long as there is sufficient stimulant. The frequency with which these impulses are sent to the brain, up to a maximum of 100-200/s, determines the intensity... 

Ninety-two percent of the oil is produced before breakthrough of the hydroxyl ion at T = 1.45 PV. The first evidence of an acid-base reaction occurs at the trailing edge of the primary oil bank at T = 0.78 PV. The oleic acid concentration in the oil phase is a minimum at T = 0.78 PV. The surface active oleates of calcium which are formed by the interfacial chemical reaction stimulate the production of a secondary oil bank. The oleic acid concentration in the oil phase peaks at the oil cut peak of the chemically stimulated oil bank at T = 1.72 PV during a period of minimum contact. The concentration of the oleic acid displays a diffuse minimum at the trailing edge of the secondary oil bank. Incremental recovery of acidic oil by an Emulsification and Coalescence mechanism in the secondary calcium hydroxide flood can be inferred from the following experimental observations ... 

The sense of taste originates when chemical stimulation of the taste buds occurs. These are collections of cells concentrated in certain areas of the tongue. The sides, tip and rear third of the organ have the most taste buds. The back of the tongue most readily detects bitterness and the tip sweetness. 

The earliest experiments of this type employed voltammetry as a detection scheme. Fast-scan cyclic voltammetry can be used to discriminate between released substances with different oxidation/reduction properties. Voltammetric measurements of absolute concentrations released from single vesicles undergoing exocytosis have proven to be difficult however, because the amount of transmitter released is only at zeptomole levels and because the events occur on the millisecond time scale [13]. Furthermore, although elicited by chemical stimulation, these events do not occur at precise times. Although several neurotransmitters have been identified on the basis of characteristic voltammograms, it is difficult to distinguish catecholamines with this technique. However, fast-scan cyclic voltammetry has been used to identify the seaeted catecholamines norepinephrine and epinephrine [14]. 

In general, during chemical stimulations, the process of acidification implies solutions of HCl, HF, KCl, or NH4C1, with concentrations around... 

The chemical senses are composed of stimuli from the external environment which act on specialized cells. They are conmonly divided into three classes 1) olfaction, 2) gustation, and 3) the common chemical sense. Olfaction permits reception of distant airborne volatile substances often at very diluted concentrations while gustation generally requires contact with the chemical stimulant source. Irritants are the main stimulants for the common chemical sense and involve little specificity. 

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