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.

Forces in molecules.

Abstract: Chemistry is determined by the electrostatic forces acting within a collection of nuclei and electrons. The attraction of the nuclei for the electrons is the only attractive force in a molecule and is the force responsible for the bonding between atoms. This is the attractive force acting on the electrons in the Ehrenfest force and on the nuclei in the Feynman force, one that is countered by the repulsion between the electrons in the former and by the repulsion between the nuclei in the latter. The virial theorem relates these forces to the energy changes resulting from interactions between atoms. All bonding, as signified by the presence of a bond path, has a common origin in terms of the mechanics determined by the Ehrenfest, Feynman and virial theorems. This paper is concerned in particular with the mechanics of interaction encountered in what are classically described as ‘nonbonded interactions’—are atoms that ‘touch’ bonded or repelling one another?

Hacia una sintesis biogeografica de Mexico

Abstract: EL RECONOCIMIENTO DE COMPONENTES BIOTICOS CONSTITUYE UNA PRIMERA ETAPA HACIA UNA TEORIA BIOGEOGRAFICA SINTETICA. EN MEXICO PODEMOS CARACTERIZAR 3 COMPONENTES BIOTICOS PRINCIPALES, CADA UNO CON UNA COMBINACION DIFERENTE DE ELEMENTOS BIOTICOS. EL COMPONENTE NEARTICO (REGION NEARTICA) INCLUYE LAS AREAS ARIDAS SUBTROPICALES DEL NORTE DEL PAIS, EN LAS PROVINCIAS BIOGEOGRAFICAS DE CALIFORNIA, BAJA CALIFORNIA, SONORA, ALTIPLANO MEXICANO Y TAMAULIPAS. EN ESTE COMPONENTE PREDOMINA EL ELEMENTO ORIGINAL (SEPTENTRIONAL ANTIGUO O PALEOAMERICANO), JUNTO CON OTRO DE DISPERSION MAS RECIENTE (NEARTICO) Y UN TERCERO NEOTROPICAL ANTIGUO. LOS EVENTOS VICARIANTES ASOCIADOS CON LA EVOLUCION BIOTICA DEL COMPONENTE NEARTICO SE RELACIONAN CON LA FORMACION DE LA SIERRA MADRE OCCIDENTAL, QUE AISLO EL DESIERTO DE CHIHUAHUA DE LOS DESIERTOS DE SONORA Y MOHAVE; Y LA EXPANSION DEL MAR DE CORTES, QUE AISLO LA PENINSULA DE BAJA CALIFORNIA DEL CONTINENTE. EL COMPONENTE TRANSICIONAL (ZONA DE TRANSICION MEXICANA) INCLUYE LAS AREAS BASICAMENTE MONTANOSAS DEL CENTRO DEL PAIS, QUE SE ASIGNAN A LAS PROVINCIAS BIOGEOGRAFICAS DE LA SIERRA MADRE ORIENTAL, SIERRA MADRE OCCIDENTAL, EJE VOLCANICO TRANSMEXICANO, CUENCA DEL BALSAS Y SIERRA MADRE DEL SUR. EN ESTE COMPONENTE COEXISTEN LOS ELEMENTOS PALEOAMERICANO, NEARTICO, MESOAMERICANO TROPICAL Y MESOAMERICANO DE MONTANA. LOS EVENTOS VICARIANTES ASOCIADOS CON LA EVOLUCION BIOTICA DEL COMPONENTE TRANSICIONAL SE RELACIONAN CON EL DESARROLLO DE LAS SIERRAS MADRE Y EL VULCANISMO DEL EJE VOLCANICO TRANSMEXICANO. EL COMPONENTE NEOTROPICAL (REGION NEOTROPICAL) INCLUYE AREAS TROPICALES HUMEDAS Y SUBHUMEDAS DEL SUR DE MEXICO, ASIGNADAS A LAS PROVINCIAS BIOGEOGRAFICAS DE LA COSTA PACIFICA MEXICANA, GOLFO DE MEXICO, CHIAPAS Y PENINSULA DE YUCATAN. EN ESTE PREDOMINA EL ELEMENTO MESOAMERICANO TROPICAL, AUNQUE TAMBIEN PRESENTA LOS ELEMENTOS NEARTICO Y ANTILLANO. LOS EVENTOS VICARIANTES ASOCIADOS CON LA EVOLUCION BIOTICA DEL COMPONENTE NEOTROPICAL SE RELACIONAN CON EL DESARROLLO DE LOS ISTMOS DE TEHUANTEPEC Y PANAMA Y LA INUNDACION DE LAS TIERRAS BAJAS DE NICARAGUA Y DE LA PENINSULA DE YUCATAN.

Phosphorus Stress in Common Bean: Root Transcript and Metabolic Responses

Abstract: Phosphorus (P) is an essential element for plant growth. Crop production of common bean (Phaseolus vulgaris), the most important legume for human consumption, is often limited by low P in the soil. Functional genomics were used to investigate global gene expression and metabolic responses of bean plants grown under P-deficient and P-sufficient conditions. P-deficient plants showed enhanced root to shoot ratio accompanied by reduced leaf area and net photosynthesis rates. Transcript profiling was performed through hybridization of nylon filter arrays spotted with cDNAs of 2,212 unigenes from a P deficiency root cDNA library. A total of 126 genes, representing different functional categories, showed significant differential expression in response to P: 62% of these were induced in P-deficient roots. A set of 372 bean transcription factor (TF) genes, coding for proteins with Inter-Pro domains characteristic or diagnostic for TF, were identified from The Institute of Genomic Research/Dana Farber Cancer Institute Common Bean Gene Index. Using real-time reverse transcription-polymerase chain reaction analysis, 17 TF genes were differentially expressed in P-deficient roots; four TF genes, including MYB TFs, were induced. Nonbiased metabolite profiling was used to assess the degree to which changes in gene expression in P-deficient roots affect overall metabolism. Stress-related metabolites such as polyols accumulated in P-deficient roots as well as sugars, which are known to be essential for P stress gene induction. Candidate genes have been identified that may contribute to root adaptation to P deficiency and be useful for improvement of common bean.