National Autonomous University of Mexico

About: National Autonomous University of Mexico is a education organization based out in Mexico City, Distrito Federal, Mexico. It is known for research contribution in the topics: Population & Galaxy. The organization has 72868 authors who have published 127797 publications receiving 2285543 citations. The organization is also known as: UNAM & Universidad Nacional Autónoma de México.

Properties and performance of the prototype instrument for the Pierre Auger Observatory

Abstract: Construction of the first stage of the Pierre Auger Observatory has begun. The aim of the Observatory is to collect unprecedented information about cosmic rays above 1018 eV. The first phase of the project, the construction and operation of a prototype system, known as the engineering array, has now been completed. It has allowed all of the sub-systems that will be used in the full instrument to be tested under field conditions. In this paper, the properties and performance of these sub-systems are described and their success illustrated with descriptions of some of the events recorded thus far. © 2003 Elsevier B.V. All rights reserved.

EcoCyc: a comprehensive database resource for Escherichia coli

Abstract: The EcoCyc database (http://EcoCyc.org/) is a comprehensive source of information on the biology of the prototypical model organism Escherichia coli K12. The mission for EcoCyc is to contain both computable descriptions of, and detailed comments describing, all genes, proteins, pathways and molecular interactions in E.coli. Through ongoing manual curation, extensive information such as summary comments, regulatory information, literature citations and evidence types has been extracted from 8862 publications and added to Version 8.5 of the EcoCyc database. The EcoCyc database can be accessed through a World Wide Web interface, while the downloadable Pathway Tools software and data files enable computational exploration of the data and provide enhanced querying capabilities that web interfaces cannot support. For example, EcoCyc contains carefully curated information that can be used as training sets for bioinformatics prediction of entities such as promoters, operons, genetic networks, transcription factor binding sites, metabolic pathways, functionally related genes, protein complexes and protein-ligand interactions.

Controlled production of aligned-nanotube bundles

Abstract: Carbon nanotubes1, 2 might be usefully employed in nanometre-scale engineering and electronics. Electrical conductivity measurements on the bulk material3, 4, on individual multi-walled5, 6 and single-walled7 nanotubes and on bundles of single-walled nanotubes8, 9 have revealed that they may behave as metallic, insulating or semiconducting nanowires, depending on the method of production—which controls the degree of graphitization, the helicity and the diameter. Measurements of Young's modulus show10 that single nanotubes are stiffer than commercial carbon fibres. Methods commonly used to generate nanotubes—carbon-arc discharge techniques1, 2, 4, catalytic pyrolysis of hydrocarbons11, 12 and condensed-phase electrolysis13, 14—generally suffer from the drawbacks that polyhedral particles are also formed and that the dimensions of the nanotubes are highly variable. Here we describe a method for generating aligned carbon nanotubes by pyrolysis of 2-amino-4,6-dichloro-s-triazine over thin films of a cobalt catalyst patterned on a silica substrate by laser etching. The use of a patterned catalyst apparently encourages the formation of aligned nanotubes. The method offers control over length (up to about 50 mum) and fairly uniform diameters (30–50 nm), as well as producing nanotubes in high yield, uncontaminated by polyhedral particles.