Dissociation effects

Fragmentor voltage Over 220 V Under 90 V 110-150V Collision-induced dissociation effect Poor ionization efficiency Good ionization efficiency... 

The conductivity also increases in solutions of weak electrolytes. This second Wien effect (or field dissociation effect) is a result of the effect of the electric field on the dissociation equilibria in weak electrolytes. For example, from a kinetic point of view, the equilibrium between a weak acid HA, its anion A" and the oxonium ion H30+ has a dynamic character ... 

Curran HV and Hildebrandt M (1999). Dissociative effects of alcohol on recollective experience. Consciousness and Cognition, 8, 497-509. 

The following treatment has been suggested by Shiu et al. (1994) and is reproduced briefly below. The simplest, first-order approach is to take into account the effect of dissociation by deducing the ratio of ionic to non-ionic species I, the fraction ionic x and the fraction non-ionic xN for the chemical at both the pH and temperature of experimental data determination (/D, xID, xND) and at the pH and temperature of the desired environmental simulation (/E, xIE, xNE). It is assumed that dissociation takes place only in aqueous solution, not in air, organic carbon, octanol or lipid phases. Some ions and ion pairs are known to exist in the latter two phases, but there are insufficient data to justify a general procedure for estimating the quantities. No correction is made for the effect of cations other than H+. This approach must be regarded as merely a first correction for the dissociation effect. An accurate evaluation should preferably be based on experimental... 

Rusted JM. (1988). Dissociative effects of scopolamine on working memory in healthy young volunteers. Psychopharmacology (Berlin). 96(4) 487-92. 

At high field strengths a conductance Increase Is observed both In solution of strong and weak electrolytes. The phenomena were discovered by M. Wien (6- ) and are known as the first and the second Wien effect, respectively. The first Wien effect Is completely explained as an Increase In Ionic mobility which Is a consequency of the Inability of the fast moving Ions to build up an Ionic atmosphere (8). This mobility Increase may also be observed In solution of weak electrolytes but since the second Wien effect Is a much more pronounced effect we must Invoke another explanation, l.e. an Increase In free charge-carriers. The second Wien effect Is therefore a shift in Ionic equilibrium towards free ions upon the application of an electric field and is therefore also known as the Field Dissociation Effect (FDE). Only the smallness of the field dissociation effect safeguards the use of conductance techniques for the study of Ionization equilibria. 

Before proceeding to a complete calculation relating the conductance Increase to the amplitude of the field dissociation effect and Its temporal behavior we will give a short description of the actual circuit used for the field modulation technique (Figure 1) with reference to the previous discussion. 

The addition of electrolyte has a dissociating effect on coacervate complexes. 

Bishop, K.I., Curran, H.V., and Lader, M., Do scopolamine and lorazepam have dissociable effects on human memory systems A dose-response study with normal volunteers, Exp. Clin. Psychopharmacol., 4, 292, 1996. 

The enzyme contains six Zn2+ per molecule, two per R subunit. The zinc is not required for catalytic activity, but is essential for the maintenance of the quaternary structure. The structure has been determined to a resolution of 2.8 A in the presence and absence of CTP.528 The zinc-binding site is located in the C-terminal region of the R chains, and involves four cysteinyl residues, with tetrahedral geometry. The zinc domain represents the major site of interaction between the R and C chains, explaining the importance of zinc for the association of the subunits and the dissociative effect of mercurial reagents. When E. coli is grown in a zinc-deficient medium, some 70% of the enzyme is found to be dissociated into subunits.529... 

If the initiator is consumed rapidly and irreversibly in the first stages of copolymerization, the anions formed, irrespective of whether alkoxide or carboxylate, are the same for the given copolymerization system. Taking into account the dissociation effect of the initiator and the growing chain, the copolymerizing... 

Heats of dissociation for all three structures are largely determined by hydrogen bonding and the cavity occupation, as shown in Example 2.2. When similar cavities are occupied, the heats of dissociation are similar (regardless of the guest) within the restrictions listed. Detailed evidence for heats of dissociation effects is presented in Chapter 4.6.1.1. 

Bass, L. Moore, W. J. A model of nervous excitation based on the Wien dissociation effect. In "Structural Chemistry and Molecular Biology" A. Rich C. M. Davidson, Eds. Freeman ... 

Such objections deserve mention, because results for individual users are variable. Some users may get the exaltation described in a few of the above accounts, like those from Joseph Kopdc, Rokuya Imazeki and Johann Georgi. Others have experienced little more than sedative or dissociative effects. 

Joyce EM, Iversen SD (1984) Dissociable effects of 6-OHDA-induced lesions of neostriatum on anorexia, locomotor activity and stereotypy the role of behavioural competition. Psychopharmacology... 

Mehta MA, Manes FF, Magnolfi G, Sahakian BJ, Robbins TW (2004) Impaired set-shifting and dissociable effects on tests of spatial working memory following the dopamine D2 receptor antagonist sulpiride in human volunteers. Psychopharmacology (in press)... 

Evans RW, Gualtieri T, Amara I (1986) Methylphenidate and memory dissociated effects in hyperactive children. Psychopharmacology 90 211-216. 

One obstacle when studying dopamine receptors in schizophrenic subjects, is that most schizophrenics have been treated with antipsychotic agents, all of which block D2 and D3 receptors, and many also block D4 dopamine receptors. Thus, it can be difficult to dissociate effects specific to the disease from the effects of disease treatment. This is an... 

The pte value of 4.4 (see Table 3-2) for DNOC suggests that in natural waters with a pH 5-9, >50% of the compound exists in the ionic state at pH 5 and the percent of ionic forms increases as the pH increases. In addition to this dissociation effect, DNOC may form H-bonds in water (EPA 1979), reducing its vapor pressure and chances of volatility from water. Using a Henry s law constant value of 1.4x10" atm-m /mole (Shen et al. 1982a, 1982b) and an estimation method (Thomas 1990), the estimated volatilization half-life of DNOC from a typical river 1 meter deep, with a current speed of 1 m/second, and an overhead wind speed of 3 m/second, is 36 days. Therefore, direct volatilization from water will not be significant for DNOC. 

Using a very simple model (neglecting dissociation effects), the flame temperature of an exploding gas-air mixture in a constant volume V can be calculated. For an ideal gas it is ... 

For the logarithmic value of kAc, Equation 13 and its modification, Equation 14, were formulated, where KA° is the dissociation constant of sulfanilamide, a, p c p, and c are constants, and [H+] is the hydrogen ion concentration in the blood. We used Equation 14 to analyze the acetylation data. The second term on the left of Equation 14 expresses the dissociation effect of the free drug, but it does not mean that the neutral form is only responsible for metabolism. 

---