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Abstract— The effects of l‐glutamate and a number of structural analogues on the spontaneous release of [3H]dopamine from slices of rat striatum were examined. Glutamate, and other excitatory amino acids produced a marked stimulation of [3H]DA release which was Ca2+‐dependent and unaffected by either procaine or tetrodotoxin. The glutamate‐stimulated release was abolished in kainate‐lesioned striatum. The action of glutamate was effectively antagonised by glutamamate diethylester and 2‐amino‐4‐phosphonobutyric acid, but only weakly by l‐methionine‐dl‐sulfoximine. Other proposed amino acid antagonists were inactive. The likely site of the releasing action of l‐glutamate on presynaptic sites on nigro‐striatal DA terminals is discussed.

In this paper we review and exemplify a new and rigorous approach to the problem of molecular structure and its morphogenesis: the theory of quantum topology. The basis for this approach is provided by the topology of the total charge density in a given molecular system. The essential observation is that the only local maxima of a ground state distribution occur at the positions of the nuclei. The nuclei are therefore identified as point attractors of the gradient vector field of the charge density. The associated basins partition the molecular system into atomic fragments. Each atom is a stable structural unit defined as the union of an attractor and its basin. The common boundary of two neighbouring atomic fragments, the interatomic surface, contains a particular critical point, which generates a pair of gradient paths linking the two neighbouring attractors. The union of this pair of gradient paths and their endpoints is called a bond path. The network of bond paths defines a molecular graph of the system. Having defined a unique molecular graph for any molecular geometry, the total configuration space is partitioned into a finite number of regions. Each region is associated with a particular structure defined as an equivalence class of molecular graphs. A chemical reaction in which chemical bonds are broken and/or formed is therefore a trajectory in configuration space which must cross one of the boundaries between two neighbouring structural regions. These boundaries form the catastrophe set of the system which, like a phase diagram in thermodynamics, denotes the points of “balance” between neighbouring structures. A general analysis of the structural changes in an ABC type system is given in detail together with specific examples of all possible structural elements in a molecular system. The properties of the topologically defined atoms and their temporal changes are identified within a general formulation of subspace quantum mechanics. It is shown that the quantum mechanical partitioning of a system into subsystems coincides with the topological partitioning: both are defined by the same set of “zero flux” surfaces. Consequently the total energy, or any other property, is partitioned into additive atomic contributions. We show that, in general, a definite structure can be assigned to a given molecular system. Quantum mechanically this structure is associated with an open neighbourhood of the most probable nuclear geometry. Finally we generalize the notion of molecular structure to non‐isolated molecules and, in contrast to recent work by Woolley, we conclude that molecular structure exists in spite of intermolecular interactions and not as a result of them.

High-resolution x-ray photoelectron spectroscopy has been used to study the formation of the aluminum/polyimide (Al/PI) interface at room temperature. Aluminum films up to 80 Å thick were vapor deposited onto cured polyimide in situ. Our results show that Al is chemically active for coverages below ∼20 Å. Preferential aluminum bonding with PI occurs at carbonyl sites, as evidenced by the rapid attenuation of the carbonyl C 1s core level photoemission intensity. In the initial reaction stage (1–2 Å), Al preferentially occupies planar imide rings. These adatoms transfer charge to carbonyl carbon atoms via oxygen and this resonance hybrid state of C–O–Al weakens, but does not break, carbonyl bonds. With increasing Al coverage, the formation of strong Al–O bonds is observed and is attributed to a C–O–Al complex compound. Metallic Al is observed at a nominal coverage of 2 to 5 Å. The Al/PI interface exhibits the attenuation behavior characteristic of cluster growth through both reacted and unreacted regions. Annealing the 80-Å Al/PI interface at 300 °C results in extended reaction with less selective chemical interaction of Al with PI.

The relation between the structural stability of a molecular system as determined by the topological properties of its charge distribution and the energetic stability of the same system as determined by the properties of its potential energy hypersurface is studied. In general, it is found that one may associate a given molecular structure with an open neighborhood of an energetically stable geometry of the system. A change in molecular structure is an abrupt process, and examples are given in which the change in structure is found to occur in the immediate neighborhood of the transition state geometry. These observations suggest that topologically unstable structures correspond to energetically unstable geometries of a system. Such a correspondence can be rationalized in terms of the Hellmann–Feynman theorem which is shown to relate the gradients of the energy hypersurface to the gradient vector field of the charge density—the field whose instabilities determine the instabilities in molecular structure.