La obturación de valles por procesos de ladera: el origen de La Vega de Metztitlan (México)

[Resumen] En las estribaciones de la Sierra Madre Oriental (México) se localiza el lago de Metztitlán y la vega del mismo nombre. Su origen se debe a la obturación del valle por un importante deslizamiento y posteriormente un desprendimiento. En este trabajo se exponen los primeros resultados del estudio geomorfológico, se aporta una cartografía de detalle y se propone una primera explicación de la evolución del área.[Abstract] The lake and valley of Metztilán is located in Sierra Madre Oriental range (Mexico). Its origin is due to the slope collapse after great rockslide. This paper exposes the firsts geomorphologic analysis of the feature, and includes and detailed geomorphologic map. A different evolution phases is determined

CONCENTRATION OF SOME ELEMENTS IN BLOOD SERUM OF NONLACTATING GOATS IN A SUBTROPICAL REGION OF SOUTHWEST OF MÉXICO STATE

The objective of this study was to determine the mineral levels in blood serum of nonlactating adult goats in the south of the State of México during the dry and rainy seasons. Eighty four multiparous (>2 calving and non-lactating) does were sampled (LW 39 ± 8 kg). Blood samples were collected by jugular vein punction, followed by separation of blood serum by adding 10% trichloroacetic acid for later laboratory analysis. Data were analyzed as a completely randomized factorial experiment. There was as effect (P<0.05) of season on serum concentrations of P, and there was an interaction (P<0.01) of season*region for Ca, Na, Cu and Zn. Mg was unaffected by treatments. Results suggest possible deficiencies in the diets of P, Ca, Cu and Zn

Las Bibliotecas universitarias mexicanas: apuntes para un diagnóstico

Some recent data about the situation of the Mexican university libraries, as well as the paper of the National Association of Universities and Institutions of Education in the promotion of the cooperation; among them, the creation of the National Network of Libraries of Institutions of High Education. Also, a brief description the services and the systems of integral automatization. In the end a general view of the librarian system of the Independent National University of Mexico

Las revistas electrónicas y el derecho sobre el documento

The main universities of the world maintain subscriptions of electronic journals and these have remained by almost one decade, in resistance, for example with the electronic book commercialization, that has evolved more slowly and with smaller acceptance

El sistema bibliotecario de la Universidad Nacional Autónoma de México: ¿un consorcio?

UNAM's acquired experience with the acquisition of print documents and cd-rom databases has allowed it to establish actions for carrying out centralised and shared electronic resource acquisition. Its goals are to rationalise spending and to avoid the duplicate subscriptions that occurred with print journals and cd-rom databases. In this article we explain how the UNAM's library system acquires electronic resources in ways similar to some library consortia, even though it does not constitute a consortium itself