University of St Andrews

About: University of St Andrews is a education organization based out in St Andrews, Fife, United Kingdom. It is known for research contribution in the topics: Population & Laser. The organization has 16260 authors who have published 43364 publications receiving 1636072 citations. The organization is also known as: St Andrews University & University of St. Andrews.

Ionothermal synthesis of zeolites, metal-organic frameworks, and inorganic-organic hybrids.

Abstract: Ionothermal synthesis, the use of ionic liquids as both solvent and template (structure-directing agent), has been used to prepare zeolites and inorganic-organic hybrids such as metal-organic frameworks. The underlying properties of the ionothermal method are discussed, and it is compared with traditional hydrothermal preparative methods. The materials resulting from ionothermal synthesis are described, and any structural features that can be related to the ionic liquid used as the solvent are discussed. Future areas of potential interest are also considered.

Electrostatic solitary structures in non‐thermal plasmas

Abstract: Solitary electrostatic structures involving density depletions have been observed in the upper ionosphere by the Freja satellite [Dovner et al., 1994]. If these are interpreted as ion sound solitons, the difficulty arises that the standard Korteweg-de Vries description predicts structures with enhanced rather than depleted density. Here we show that the presence of non-thermal electrons may change the nature of ion sound solitary structures and allow the existence of structures very like those observed.

Learning by imitation: A hierarchical approach

Abstract: To explain social learning without invoking the cognitively complex concept of imitation, many learning mechanisms have been proposed. Borrowing an idea used routinely in cognitive psychology, we argue that most of these alternatives can be subsumed under a single process, priming, in which input increases the activation of stored internal representations. Imitation itself has generally been seen as a "special faculty." This has diverted much research towards the all-or-none question of whether an animal can imitate, with disap- pointingly inconclusive results. In the great apes, however, voluntary, learned behaviour is organized hierarchically. This means that im- itation can occur at various levels, of which we single out two clearly distinct ones: the "action level," a rather detailed and linear speci- fication of sequential acts, and the "program level," a broader description of subroutine structure and the hierarchical layout of a behavioural "program." Program level imitation is a high-level, constructive mechanism, adapted for the efficient learning of complex skills and thus not evident in the simple manipulations used to test for imitation in the laboratory. As examples, we describe the food- preparation techniques of wild mountain gorillas and the imitative behaviour of orangutans undergoing "rehabilitation" to the wild. Rep- resenting and manipulating relations between objects seems to be one basic building block in their hierarchical programs. There is evi- dence that great apes suffer from a stricter capacity limit than humans in the hierarchical depth of planning. We re-interpret some chimpanzee behaviour previously described as "emulation" and suggest that all great apes may be able to imitate at the program level. Action level imitation is seldom observed in great ape skill learning, and may have a largely social role, even in humans.

Model uncertainty in cross‐country growth regressions

Abstract: Summary We investigate the issue of model uncertainty in cross-country growth regressions using Bayesian Model Averaging (BMA) We flnd that the posterior probability is very spread among many models suggesting the superiority of BMA over choosing any single model Out-of-sample predictive results support this claim In contrast with Levine and Renelt (1992), our results broadly support the more \optimistic" conclusion of Sala-i-Martin (1997b), namely that some variables are important regressors for explaining cross-country growth patterns However, care should be taken in the methodology employed The approach proposed here is flrmly grounded in statistical theory and immediately leads to posterior and predictive inference