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At least 685 records · Page 38Linked to original sources
PubMed1983

Diagenesis of metals chemically complexed to bacteria: laboratory formation of metal phosphates, sulfides, and organic condensates in artificial sediments.

Cells of Bacillus subtilis, when suspended in a 5mM metal solution, bind metals tenaciously to their cell walls. These metal-loaded cells, when mixed with a synthetic sediment and put under laboratory conditions to simulate low-temperature sediment diagenesis, nucleate the formation of a mixed assemblage of crystalline metal phosphates, metal sulfides, and polymeric, metal-complexed, organic residues. The sequential series of diagenetic events leading to the formation of authigenic mineral phases was followed by transmission electron microscopy and energy-dispersive X-ray analysis. The minerals quartz (SiO(2)) and calcite (CaCO(3)) were employed in the synthetic sediment. Crystalline magnetite (Fe(2)O(3)) and elemental sulfur were added as redox buffering agents to ensure anoxic conditions. Quartz and magnetite appeared unreactive throughout the experimental conditions. Elemental sulfur interacted with the metal-loaded cells, affected both the eventual chemistry and crystal habit of the metal phosphates, and formed a variety of crystalline metal sulfides. Calcite raised the pH of the fluid phase of the sediment, which influenced phosphate mineralization and inhibited metal sulfide genesis.

Journal Article↗
PubMedDate not supplied

Automatic monitoring system for artificial hearts using self organizing map.

This study presents an automatic monitoring system for artificial hearts. The self organizing map (SOM) was applied to monitoring and analysis of an aortic pressure (AoP) signal measured from an adult goat equipped with a total artificial heart. In the proposed system, two different SOMs were used to detect and classify abnormalities in the measured AoP signal. In the first stage, an ordinary SOM, taught with only normal AoP data, was used for detection of abnormalities on the basis of the quantization error in the real-time monitoring task. In the second stage, a supervised SOM was used for classification of abnormalities. The supervised SOM can be regarded as an ordinary SOM with an extra class vector for solving the classification problem. The class vector is assigned to every node in the second SOM as an output weight learned according to Kohonen's learning rule. The effectiveness of detection and classification of abnormalities using these two SOMs was confirmed.

Animals↗
PubMed2005

Engineering of a vascularized scaffold for artificial tissue and organ generation.

Tissue engineering is an emerging field in regenerative medicine to overcome the problem of end-stage organ failure. However, complex tissues and organs need a vascular supply to guaranty graft survival and render bioartificial organ function. Here we developed methods to decellularize porcine small bowl segments and repopulate the remaining venous and arterial tubular structures within these matrices with allogeneic porcine endothelial progenitor cells. Cellular adherence and vitality was characterized by quantitative 2-[18F]-fluoro-2'-desoxy-glucose (FDG) positron emission tomography (PET) and subsequent immunohistological work up. The generated matrices showed insulin-dependent FDG uptake predominantly in the region of the former vascular structures. Stain for vitality and the specific endothelial markers CD31, VE-Cadherin and Flk-1 matched this functional finding. Providing evidence for vitality up to 3 weeks post reconstitution and typical endothelial differentiation, these results indicate that our generated matrix allows the generation of complex bioartificial tissues and organs for experimental and future clinical application.

Animals↗
PubMed1984

Artificial intelligence in organic synthesis. SST: starting material selection strategies. An application of superstructure search.

A program for the interactive selection of potential starting materials given a desired target molecule is described. The program uses hierarchical search to rapidly select candidates from a large starting material library and contains a function to evaluate the appropriateness of the functionality of the starting material. The user can specify restrictions on features such as the number of atoms in the starting material, price limitations, chirality, and whether to use superstructure or substructure searching. Several examples of the results of the program are presented.

Chemistry, Organic↗
PubMed2000

Classification of ancient Roman glazed ceramics using the neural network of Self-Organizing Maps.

Artificial neural networks with unsupervised learning strategy known as Self-Organizing Maps were applied to classify ancient Roman glazed ceramics. Their clay ceramic bodies were analyzed by Inductively Coupled Plasma-Atomic Emission Spectroscopy and the chemical composition obtained was processed by this neural algorithm. The results obtained provide two types of information: firstly, classification of ceramic samples with identification of several groups and secondly, differentiation between the elemental chemical information. It was found that there are certain chemical elements which can be considered as principal and which can serve to differentiate between ceramics, whereas other elements give redundant information and do not contribute to sample differentiation. Seven chemical elements were considered principal and provide the necessary information. Two types of element were identified: 1- a group formed by common elements, such as: Ca, Fe, Mg, Mn and 2- another formed by optional elements: K or Na and Ba or Sr and Al or Ti.

Journal Article↗
PubMed1989

The artificial worlds approach to emergent evolution.

Artificial worlds models of evolutionary systems are computer models that map the essential logical structure of ecological systems, defined as self-sustaining biological organizations. The artificial world comprises an artificial environment, with mass components, energy input, and physical states. It also comprises artificial organisms, including a genome, a phenome, and a (developmental) map that connects the genome to the phenome. Mass components are cycled and space is limited. The evolution process results, as in nature, from genetic variation combined with natural selection imposed by the finiteness of the environment. The selection criteria (fitness values) are not imposed, but rather emerge from the interactions of the organisms with each other and with the environment. The dynamics at the population level also emerges from these basic interactions. In this paper we describe the comparative properties of the EVOLVE family of artificial worlds models.

Artificial Intelligence↗
PubMed1997

Artificial cells and bioencapsulation in bioartificial organs.

The most common use of artificial cells is for bioencapsulation of biologically active materials. Many combination of materials can be bioencapsulated. The permeability, composition and configurations of artificial cell membrane can be varied using different types of synthetic or biological materials. These possible variations in contents and membranes allow for large variations in the properties and functions of artificial cells.

Animals↗