Dissociation phenomena

The highest surface activity of fraction A3 extracted from shale oil needs to be explored in detail in order to understand this very unique phenomena. The benchmark experiments performed by Lee et al. (22) in studies of dissociation phenomena of Stuart oil shale in an alkaline environment proved the formation of carboxylic acids as it was verified from GC results. In another study by Lee et al. (23), it was shown that the hydroxyl ions from an alkaline solution could decompose the silicate and aluminasilicate structures in oil shale samples, provided that ultrasonic radiation and electrolytic current were simultaneously applied. 

Dissociative Disorders. Many of the reexperiencing symptoms of PTSD are, in fact, dissociative phenomena. The numbing symptoms of PTSD also resemble the depersonalization and derealization experienced by those with dissociative disorders. Furthermore, dissociative symptoms are the principal manifestation of acute stress disorder, the predecessor to PTSD that arises in the first month after a trauma. The diagnosis of a dissociative disorder is warranted when dissociative symptoms exceeding the PTSD criteria, (e.g., amnesia or profound identity disturbance) are present. 

Current studies of unimolecular reactions can be broadly divided into three categories, based on different methods of activation of the decomposing species. The first, most classical, method is that of thermal activation of the type first envisioned by Lindemann to explain unimolecular dissociation phenomena brought about by heat energy. The second method involves chemical activation, ... 

Since the design of the measuring cell for field modulation studies is not very critical it was relatively easy to study also the pressure-dependence of ion-pair dissociation and ionic recombination (1 4). Here also the values (Table II) for the activation volumes show the essentially diffusion controlled aspects of the association-dissociation phenomena, since the calculated values, essentially the pressure dependence of the viscosity, and the experimentally determined values agree rather well. 

Dissociation is a robust phenomenon with dramatic and specific clinical meaning, but it has until now been without any secure tie to underlying brain activity. As an initial attempt to formulate a brain model of dissociation, it may therefore be strategically useful to examine some far less dramatic and even commonplace dissociations that occur at the boundaries of major states of consciousness. Many of these dissociative phenomena already have known physiological substrates, and others may constitute more reasonable targets for neurobiological analysis than clinical dissociations. 

A nonlinear relationship between enzyme concentration and measured activity is indicative of a more complex reaction system. Complications of this nature may arise from such things as changes in the composition of the reaction mixture (e.g., pH due to the addition of increasing amounts of enzyme solution), assay limitations (e.g., insufficient substrate), limited coupling-enzyme (where assays are based on coupled enzyme systems), the presence of inhibitors, and enzyme-cofactor or enzyme-enzyme dissociation phenomena. Nonlinear relationships may also be an inherent... 

In the last decade, further research and anecdotal evidence have accumulated to suggest that the mental effects of ketamine can be grouped into six broad categories (1) dissociation, resulting in an almost totally dispassionate perspective, and classic dissociative phenomena such as "out-of-body," "astral travel," and "near-death"-type experiences (2) entry into "information networks" in a kind of "cyberspace" specific to this compound (3) contact with and participation in "alternative realities" (4) communication with "extraterrestrials" or "disembodied entities" (5) Tantra-like enhancement of sexual activity and (6) assistance in personal and creative problem solving. 

Exact calculations on burning processes in rocket motors must include dissociation phenomena this is done on computer facilities (at leading national institutes ), and the relevant industrial laboratories in this field are nowadays equipped with computers and programs. The following explanations are based on simplifying assumptions. 

Regarding hydrochloric acid, in a concentration range of 30.10 4 to 300.10 4 mol/L, equivalent conductance assumes an extremely low and constant value of 0.03 S cm2/mol, as seen in Figure 3. This behavior certainly cannot be explained on the basis of simple dissociation phenomena. Thus we have interpreted these results on the basis of theoretical work by Caruso and co-workers (31) who consider the conductometric, potentiometric, and spectrophotometric behavior of weak acids and bases in nonaqueous solvents. In these solvents a weak acid, HA, besides undergoing simple ionic dissociation, also may undergo conjugation phenomena by the H+ and A" ions which lead to the formation of ionic complex species A(HA)/ or H(HA)/. Caruso shows that the... 

Various criteria have been followed in an attempt to establi quantitative scales of acidity and basicity. In order to account for solvation and ionic dissociation phenomena Gutmarm introduced a parameter called donor number, DN, which correlates the behaviour of a donor sdvent towards a given solute with respect to the coordinating ability of a reference solvent towards the same sdute. The basicity of a solvent can be related to the enthalpy of its reaction with a reference acid. Gutmann s DN scale is built on the equation... 

Much more satisfactory applications of Gapeyron s formula to dissociation phenomena have been made by Bonnefoi. They treat of the combinations of lithium chloride and lithium bromide with ammonia and the amines the following reactions liberate a quantity of heat Q which has been both measured by thermochemical methods (Qobs.) And calculated by Clape nx)n s equation from the dissociation tensions (Qcaio.) ... 

Dissociation tensions.— Dupr4 s formula must apply likewise, as is evident, to dissociation phenomena, when a sin e gas is concerned in the reaction. Bertrand showed, in fact, that formulae of this type could represent in a satisfactory manner the... 

By analogy with the mechanism proposed for the solvated anions, these fractional kinetic orders can be ascribed to association-dissociation phenomena involving the growing chains. Because ionic dissociation is not a viable assumption for such low dielectric media, ion-pair association is assumed. Thus,... 

The application of the second law of thermodynamics to chemistry, first occurring notably in the study of dissociation phenomena in solids, influenced Horstman in 1873 to point out that such changes are exactly similar to physical changes of state, and that the thermodynamic equation derived by Clapeyron and Clausius for changes of state are also applicable here, i.e., dp/dT QjT d - v), where p is the dissociation pressure, Q is the heat of dissociation, T is the absolute temperature, and C and v are the volumes of the system after and before dissociation. In the case in which a gas or vapor formed is supposed to behave as an ideal gas, and the volume of the solids is neglected in comparison with that of the gas, the equation becomes d log p/dT Q/RT, where R is the universal gas constant. ... 

One of the important features of SEP, in common with other optical-optical double-resonance techniques, is the simplification of the spectra because laser I excites a single upper state. Thus, selection rules between the intermediate and final states greatly reduce the final allowed states. Of particular interest for the study of dissociation phenomena is that SEP allows for considerable control of the final states that are... 

The classifications and general relations developed here together with evidence presented in a paper published some years ago (K. G. Falk and J. M. Nelson, Jour. Amer. Chem. Soc. 87, 1732 (1915)) apparently justify the conclusion that the changes occurring in chemical reactions do not depend upon the electrolytic dissociations of the reacting substances. The chemical changes are accompanied very often by electrolytic dissociation phenomena, but the latter... 

The Debye equation is based on the following physical description of the sample. This is a monodisperse solution of identical particles, which are in random orientations relative to the incident primary beam, and act as independent entities (i.e. there are no interparticle spatial correlations). The above derivation has presumed also that the particles are in vacuo. If they are in solution, they are required to form a two-phase system of solute and solvent. In biology, this corresponds to dilute solutions of pure proteins or glycoproteins in a low-salt buffer. Complications arise in the case of polyionic macromolecules in low-salt buffers, such as nucleic acids. Here, interparticle correlation effects can readily occur and the macromolecule is surrounded by an ion-cloud of opposite charge (i.e. a three-phase system). Other complications can arise in the cases of polydisperse distributions of macromolecules, oligomerization or dissociation phenomena, and conformational changes. Different formuhsms have to be derived for the analyses of these systems. 

Since solubility of electrolytes involves dissociation phenomena, factors affecting dissociation either directly (ionic strength) or indirectly (reactions involving ions formed) will inevitably affect solubility. These factors will now be considered in detail. 

Solvation, solvolysis and ionic dissociation phenomena in both aqueous and non-aqueous solutions... 

Solvatation, solvolysis and ionic dissociation phenomena, in both aqueous and nonaqueous solutions are subsumed by the Lewis definitions. In addition to the previous discussion of the dual polarity character of Lewis acids and bases, it should be noted that many of them are amphoteric, by definition. Donor number, DN, was developed in order to correlate the behavior of a solute in a variety of donor solvents with a given basicity or donicity. A relative measurement of the basicity of a solvent D is given by the enthalpy of its reaction with an arbitrarily chosen reference acid (SbCls in the Gutmann s scale). Latter Mayer introduced an acceptor number, AN, as the relative P NMR shift induced by triethylphosphine, and relative to acidic strength (AN=0 for hexane and 100 for SbCls). In 1989, Riddle and Fowkes modify these AN numbers, to express them, AN ", in correct enthalpic unit (kcaLmol). Table 10.2.3 gathers electron acceptor number AN and AN " and electron donor number DN for amphoteric solvents. 

The renewal of interest in Brillouin-Wigner perturbation theory for many-body systems seen in recent years, is driven by the need to develop a robust multi-reference theory. Multi-reference formalisms are an important prerequisite for theoretical descriptions of dissociative phenomena and of many electronically excited states. Brillouin-Wigner perturbation theory is seen as a remedy to a problem which plagues multi-reference Rayleigh-Schrodinger perturbation theory the so-called intruder state problem. 

The acid dissociation phenomena observed for these three ligands require the following explanatory scheme. 

Jolley, R. L., Robb, D. A., and Mason, H. S., 1969, The multiple forms of mushroom tyrosinase. Association-dissociation phenomena, Biol. Chem. 244 1593. 

The behavior of concentrated solutions can be explained in terms of the re-dissociation phenomena (Corti and Femandez-Prini, 1986) which take place at low reduced temperature, T, and high packing fraction (pcr ). In this regime an ion is surroxmded by ions of die same and opposite charge and the net result of the ion interactions is that the ions move essentially as free ions, as it occur in molten salts. 

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