Developing categorization schemes involves discovering structures in the world that support a learner's goals. Existing models of category learning, such as ex emplar and prototype models, neglect the role of goals in shaping conceptual organization. Here, a clustering ap proach is discussed that reflects the joint influences of the environment and goals in directing category acquisition. Clust...

A combined experimental and theoretical study shows that the photooxidative activity of two isostructural metal oxide clusters depends on their internal templates. To this end, two halide-templated bismuth vanadium oxide clusters [X(Bi(dmso)3 )2 V12 O33 ](-) (X=Cl(-) , Br(-) ) are reported and fully characterized. The two clusters show similar absorption features and illustrate that bismuth inc...

DNA microarrays and, more recently, protein microarrays, have become important tools for high-throughput genomic and proteomic studies. Transfected cell microarrays are a complementary technique in which array features comprise clusters of cells overexpressing defined cDNAs. Complementary DNAs cloned in expression vectors are printed on microscope slides, which become living arrays after the ad...

This paper questions the prevailing notions that firms within industrial clusters have privileged access to ‘tacit knowledge’ that is unavailable – or available only at high cost – to firms located elsewhere, and that such access provides competitive advantages that help to explain the growth and development of both firms and regions. It outlines a model of cluster dynamics emphasizing two comp...

In feed forward neural networks, hidden layer neurons’ saturation conditions, which are the cause of flat spots on the error surface, is one of the main disadvantages of any conventional gradient descent learning algorithm. In this paper, we propose a novel complementary scheme for the learning based on a suitable combination of anti saturated hidden neurons learning process and accelerating me...

We present a method for analysis of clustering results. This method represents every cluster as a stratified hierarchy of its subsets of objects (strata) ordered along a scale of their internal similarities. The “layered structures” can be described as a tool for interpretation of individual clusters rather than for describing the model of the entire data. It can be used not only for comparison...

In the case of concept learning from positive and negative examples, it is rarely possible to find a unique discriminating conjunctive rule; in most cases, a disjunctive description is needed. This problem, known as disjunctive learning, is mainly solved by greedy methods, iteratively adding rules until all positive examples are covered. Each rule is determined by discriminating properties, whe...

The formation of neutral bimolecular clusters of unsubstituted nucleobases and mononucleosides in the gas phase has been studied by IR laser desorption of the neutral molecules into a supersonic beam expansion. The complementary nucleobase pairs adenine-thymine and cytosine-guanine of DNA have been found to be formed in preference to non complementary base pairs. Association constants for the f...