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The nuclear magnetic I elaxation times of protons in aqueous solutions of paramagnetic ions have been measured as a function of temperature. For Mn++ ions, the proton TI and T2 were measured at 10 20 and 28 Mc/sec, and for Co++, Cu++, and Gd+++ ions, 20 Mc/sec. The temperature effects observed ca~ b~ explained by incorporating the proper temperature dependences of the several correlation times into the general Bloembergen· Solomon relaxation expressions.In the ~ase of Mn++ solutions, which have a TJ/T2 ratio of about 5.5 at room temperature and 20 Mc/ sec, chemtcal as well as electron exchange and dipolar interactions are found to be important. Analysis of the data by mean? of the e~uations developed pro~ides information concerning the chemical exchange of solvent protons with those m the hydrated Mn++ IOn. An activation energy of 8.4 kcal/mole and other parameters for this process are evaluated.The temperature dependence of TI and Tz in the Co++, Cu++, and Gd+++ solutions can be explained by the temperature dependence of the dipolar interaction alone. Varying the anion in Cu++ solutions had little effect on 1' .1 or its temperature dependence; also, TI for Cu++ solutions was found to vary inversely with concentratIOn over the whole temperature range studied.

The problem of deriving an optimal set of thermodynamic properties of minerals from a diverse experimental data base is reviewed and a preferred methodology proposed. Mathematical programming(MAP) methods extend the linear programming (LIP) approach first presented by Gordon (1973), and make it possible to account for the type of information conveyed, and the uncertainties attending both phase equilibrium data and direct measurements of phase properties. For phase equilibrium data which are (in most cases) characterized by non-normal error distributions across experimental brackets, the midpoint of a bracket is no more probable than other points, and the data are best treated by considering the inequality in the change in Gibbs free energy of reaction at each half-bracket. Direct measurements of phase properties can be assumed to have approximately normal error distributions, and the MAP technique optimizes agreement with these values by using the principles of least squares in the definition of an objective function. The structure of this problem, treatment of uncertainties in various types of experimental data, and method of optimizing final solutions are discussed in some detail.The method is applied to experimental data in the MgO-SiO 2 -H 2 O system, where inconsistencies among the data are resolved and an optimal set of thermodynamic properties is presented. The derived standard state entropies and volumes agree with all direct measurements (within their uncertainties), as do enthalpies of formation from the elements except for those of talc (+16 kJ mol" •), anthophyllite (+ 14 kJ mol~'), and brucite (-1 kJ mol~'). Stable phase relations in the system have the topology predicted by Greenwood (1963Greenwood ( , 1971, with quartz-and forsterite-absent invariant points at 683 "C-6-4 kb and 797 °C-12 kb respectively, repeating at 552 °C-120 b and 550 °C-55 b. The thermodynamic analysis indicates little remaining flexibility in the phase relations, which, when combined with suitable activity models for solid solution, should allow for accurate determination of the conditions of metamorphism of ultramafic rocks.

Neuronal structure-function relationships were studied in rat brain slices containing the perirhinal cortex (PR) and immediately adjacent lateral nucleus of the amygdala (ALa). Using video microscopy, whole-cell recordings were made from visually preselected neurons that were labeled with biocytin for subsequent anatomical reconstructions. Most cells were 1 of 4 primary neurophysiological types: fast-spiking (FS), regular-spiking (RS), late-spiking (LS), and burst-spiking (BS). Fast-spiking neurons (small somata) were found throughout PR; RS neurons (stellates and pyramids) were present from layer II/III through VI of PR; BS neurons (large pyramids with thick nonbifurcating apical dendrites) were found in layer Va of PR; and LS neurons (stellates, small pyramids, and cone cells) were encountered in layers II/III and VI of PR. One subpopulation of LS neurons (small pyramids) was found in layer II/III; another (cone cells) was found in clusters spanning layer VI through the lateral portion of ALa. Layer Va also contained large RS pyramidal neurons whose axons were seen traveling in the external capsule, but not entering the ALa. Conversely, the axons of large RS pyramidal neurons in layer Vb typically projected deep into the ALa. The four primary firing patterns were present in ALa, which also contained irregular-spiking, slow-charging, and single-spiking cells. Spontaneous synaptic currents differed markedly among cell types and layers. There was excellent agreement between somatic areas measured from video images of living neurons and somatic areas from the same neurons following fixation. Representative montages, which combined the cellular neuroanatomy and neurophysiology, suggested a circuit-level organization that helps elucidate information processing through the PR-ALa region.

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