CDUL: Class directed unsupervised learning

A novel neural network called Class Directed Unsupervised Learning (CDUL) is introduced. The architecture, based on a Kohonen self-organising network, uses additional input nodes to feed class knowledge to the network during training, in order to optimise the final positioning of Kohonen nodes in feature space. The structure and training of CDUL networks is detailed, showing that (a) networks cannot suffer from the problem of single Kohonen nodes being trained by vectors of more than one class, (b) the number of Kohonen nodes necessary to represent the classes is found during training, and (c) the number of training set passes CDUL requires is low in comparison to similar networks. CDUL is subsequently applied to the classification of chemical excipients from Near Infrared (NIR) reflectance spectra, and its performance compared with three other unsupervised paradigms. The results thereby obtained demonstrate a superior performance which remains relatively constant through a wide range of network parameters.     

Size and ageing of the scientific community in Chile

The size and ageing of the Chilean scientific community was studied using as data the individuals actively engaged in research projects funded by the National Fund for Scientific and Technological Development (FONDECYT). Between 1982 and 1991, 4966 individuals participated at least once, either as responsible for the research or as qualified associate in one term of the funding period. From this population, 2765 persons can be considered further committed with scientific research. As for sex, about 30% of the researchers are women. Taking into account all the disciplines, and in addition to the fact that the size of the Chilean scientific community seems to be subcritical, the study reveals that the workforce has been ageing dangerously through the years. The number of young scientists becoming part of the scientific workforce is decreasing. Research in mathematics, physics and chemistry, although qualitatively competitive, relies only on an extremely small group of excellent scientists, situation which is seriously affecting the scientific capacity that the country needs. Biology, although with a higher number of individuals, exhibits a pattern of ageing which will also affects the possibilities to strengthen the scientific demands. The global context in which science develops, leads to a brain drain that Third World countries will have to overcome, implementing public policies to offer the support that young people require to nurture the scientific strength. Indigenous Ph. D. programs demand urgent attention of policy decision makers as well as from research universities which need to offer opportunities to substitute, when existing, their incompetent faculty.     

Process design for the production of a ceramic-like body from recycled waste glass

The influence of fabrication variables on the sintering behaviour of a ceramic-like body containing 90% recycled waste glass was inferred from measurements of some of the fired properties (moduli of rupture and elasticity, firing shrinkage, bulk density and porosity). Interpretation of these results in terms of viscous sintering theory indicates the relative influence on the sintering behaviour of factors such as particle size and distribution, clay binder content and plasticity, pressing pressure, heating/cooling rate, firing temperature and time, thus enabling the fabrication variables to be optimized. Comparison of the physical properties of the resulting glass-based bodies with those of commercial ceramic tile bodies indicates that the glass-based bodies are very comparable with the best ceramic tiles tested, and considerably better than several commercially-produced clay-based bodies.     

Molecular characterization of a broad selectivity neutral solute channel

In all living cells, coordination of solute and water movement across cell membranes is of critical importance for osmotic balance. The current concept is that these processes are of distinct biophysical nature. Here we report the expression cloning of a liver cDNA encoding a unique promiscuous solute channel (AQP9) that confers high permeability for both solutes and water. AQP9 mediates passage of a wide variety of non-charged solutes including carbamides, polyols, purines, and pyrimidines in a phloretin- and mercury-sensitive manner, whereas amino acids, cyclic sugars, Na+, K+, Cl-, and deprotonated monocarboxylates are excluded. The properties of AQP9 define a new evolutionary branch of the major intrinsic protein family of aquaporin proteins and describe a previously unknown mechanism by which a large variety of solutes and water can pass through a single pore, enabling rapid cellular uptake or exit of metabolites with minimal osmotic perturbation.     

Comparison of polymerase chain reaction and culture methods for detection of Actinobacillus actinomycetemcomitans and Porphyromonas gingivalis in subgingival plaque samples

In a formerly drug-dependent patient of 35 years of age suffering from an advanced HIV infection there was a development within a period of a few months of rapid weight loss amounting to 12 kg, persistent subfebrile temperatures and progressive dyspnoea on exercise. The histological pattern obtained via bronchoscopy revealed not only pneumocystis carinii pneumonia, which had already been suspected clinically, but also a not very differentiated adenocarcinoma of the lung with lymphangiosis carcinomatosa. The patient died three months after tis diagnosis was established, which had been followed by the usual pneumocystosis therapy and palliative treatment with glucocorticoids.     

Formiminotransferase cyclodeaminase from porcine liver. An octomeric enzyme containing bifunctional polypeptides

Estimation of the proportion of degenrate retina in rd/rd and +/+ (or +/rd) chimaeras, using a linear analysis of histological sections, suggests a considerable preponderance of the normal phenotype, while analyses based on the area of the surviving tissue suggest that the proportion of each component is similar to that in other tissues. This argues against the validity of the linear analyses used by other authors. It is suggested that cell movement occurs in the outer nuclear layer, following the degeneration of the rd/rd population, and results in a distortion of the original patches of normal cells.