Relaxation effect response

Debye and Falkenhagen predicted that the ionic atmosphere would not be able to adopt an asymmetric configuration corresponding to a moving central ion if the ion were oscillating in response to an applied electrical field and if the frequency of the applied field were comparable to the reciprocal of the relaxation time of the ionic atmosphere. This was found to be the case at frequencies over 5 MHz where the molar conductivity approaches a value somewhat higher than A0. This increase of conductivity is caused by the disappearance of the time-of-relaxation effect, while the electrophoretic effect remains in full force. 

The difference between the static or equilibrium and dynamic surface tension is often observed in the compression/expansion hysteresis present in most monolayer Yl/A isotherms (Fig. 8). In such cases, the compression isotherm is not coincident with the expansion one. For an insoluble monolayer, hysteresis may result from very rapid compression, collapse of the film to a surfactant bulk phase during compression, or compression of the film through a first or second order monolayer phase transition. In addition, any combination of these effects may be responsible for the observed hysteresis. Perhaps understandably, there has been no firm quantitative model for time-dependent relaxation effects in monolayers. However, if the basic monolayer properties such as ESP, stability limit, and composition are known, a qualitative description of the dynamic surface tension, or hysteresis, may be obtained. 

Neuromuscular Nicotinic receptors are responsible for transmission at the neuromuscular junction. While briefly causing stimulation, this phase is rapidly obscured by desensitization and neuromuscular blockade. Thus, nicotine has muscle-relaxant effects. 

Nonselective antimuscarinic drugs have been employed in the therapy of peptic ulcers (see Chapter 40) because they can reduce gastric acid secretion they also have been used as adjunctive therapy in the treatment of irritable bowel syndrome. Antimuscarinic drugs can decrease the pain associated with postprandial spasm of intestinal smooth muscle by blocking contractile responses to ACh. Some of the agents used for this disorder have only antimuscarinic activity (e.g., propantheline), while other drugs have additional properties that contribute to their antispasmodic action. Dicyclomine (Bentyl) and oxybutynin (Ditropan) at therapeutic concentrations primarily have a direct smooth muscle relaxant effect with little antimuscarinic action. 

The benzodiazepines are probably the most clinically important class of GABA-active compounds. Benzodiazepines modify affective responses to sensory perceptions specifically, they render individuals less responsive to anxiety-producing stimuli and therefore exert a strong anxiolytic action. In addition, benzodiazepines exert sedating, anticonvulsant, and muscle relaxant effects. 

Sildenafil It is orally active selective inhibitor of phosphodiesterase type 5 useful in treatment of erectile dysfunction. It results in reduced breakdown of cyclic guanosine monophosphate (cGMP) which is responsible for nitric acid (NO) mediated vasodilatation in corpora cavernosa. Thus inducing an erectile response to sexual stimulation. It has no direct relaxant effect on smooth muscle of corpus cavernosa and has no effect in absence of sexual stimulation. 

Additional studies conducted in this laboratory revealed that NO was responsible for the vascular smooth muscle relaxant effects of several different nitro-vasodilators, and that S-nitrosothiols were intermediates in the intracellular formation of NO (Ignarro et al., 1981). We showed also that NO was a potent inhibitor of human platelet aggregation, and that NO elicited such effects by... 

The fundamental neurobiological importance of the GABA A receptor is underscored by observations that even more receptor sites exist at or near this complex (Fig. 8—20). This includes receptor sites for nonbenzodiazepine sedative-hypnotics such as zolpidem and zaleplon, for the convulsant drug picrotoxin, for the anticonvulsant barbiturates, and perhaps even for alcohol. This receptor complex is hypothetically responsible in part for mediating such wide-ranging CNS activities as seizures, anticonvulsant drug effects, and the behavioral effects of alcohol, as well as the known anxiolytic, sedative-hypnotic, and muscle relaxant effects of the benzodiazepines. 

Dominant contributions are responsible for the a, fi, and y dispersions. They include for the a-effect, apparent membrane property changes as described in the text for the fi-effect, tissue structure (Maxwell-Wagner effect) and for the y-effect, polarity of the water molecule (Debye effect). Fine structural effects are responsible for deviations as indicated by the dashed lines. These include contributions from subcellular organelles, proteins, and counterion relaxation effects (see text). 

Impedance spectroscopy is discussed in depth in the monograph edited by J.Ross Macdonald [17]. It has its origins in the classical work of K.S. Cole and R.H. Cole, published more than 60 years ago, concerned with methods of plotting the response of a dielectric material to applied voltages as a function of frequency. The method assists in identifying observed relaxation effects with processes at the atomic and microstructural levels. For a system having a single well-defined... 

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