J. Chico Ramos to James H. Meredith (2 October 1962)

https://egrove.olemiss.edu/mercorr_anti/1234/thumbnail.jp

The geology of the uranium-vanadium deposit of the Diamond No. 2 mine, near Gallup, New Mexico

This thesis deals with the geology of the Diamond No. 2 Mine east of Gallup, New Mexico. The sedimentary rocks ranging from Triassic to Cretaceous are described in relation to the local stratigraphic setting. The Dakota formation is the host rock of the ore deposit, and was therefore studied in detail with regard to its petrographic nature and the sedimentary structures such as slumping. Special emphasis is placed on the study of the relationships between the uranium and vanadium deposit and the host rock. Geometrical and geochemical criteria are offered in order to explain the local genesis of the ore deposit at the Diamond No. 2 Mine. The geometric (textural, structural) evidence such as the lack of crosscutting relationships on one hand, and the abundance of congruent features readily explained as depositional sedimentary structures on the other hand, suggest to an originally syngenetic origin. The presence of tuffaceous matter lends probability to a volcanic and thus hypogene source of the uranium and vanadium minerals. Geo chemically there is no objection for a syngenetic explanation since the only alteration ( silicification ) occurring adjacent to the ore bodies may be diagenetic and thus also syngenetic. Later epigenetic supergene processes redistributed some of the uranium in form of camotite (camotitization) and caused later alterations such as limonitization, jarositization, etc. The field observations are presented on 33 figures and 12 plates (mostly maps and cross sections)* A special, probably partly- new mapping method was used successfully for the mapping of 60,000 square feet of mine walls at the scale of 1 to 20V --Introduction, page 9

Interpretación de indicadores discursivos en situación de aprendizaje matemático en pareja

En este informe, presentamos el análisis de datos de una pareja de estudiantes durante la resolución de un problema de generalización en una clase de matemáticas de secundaria (15-16 años). De acuerdo con las teorías interaccionistas del aprendizaje matemático, asumimos que el discurso establecido en la interacción en pareja es un factor clave de influencia en los procesos de construcción de conocimiento matemático. Hasta ahora, los resultados ponen de relieve la relación entre el uso de ciertos indicadores discursivos y los avances en la "intención argumentativa" de las estudiantes. La mayoría de intercambios con intención argumentativa vienen precedidos o acompañados por refutación y cuestionamiento, y en menor grado, validación. La refinación del análisis actual se está realizando dentro del trabajo de tesis doctoral de la primera autora

Gate-controlled conductance through bilayer graphene ribbons

We study the conductance of a biased bilayer graphene flake with monolayer nanoribbon contacts. We find that the transmission through the bilayer ribbon strongly depends on the applied bias between the two layers and on the relative position of the monolayer contacts. Besides the opening of an energy gap on the bilayer, the bias allows to tune the electronic density on the bilayer flake, making possible the control of the electronic transmission by an external parameter.Comment: 5 pages, 5 figures include

Electronic transport through bilayer graphene flakes

We investigate the electronic transport properties of a bilayer graphene flake contacted by two monolayer nanoribbons. Such a finite-size bilayer flake can be built by overlapping two semiinfinite ribbons or by depositing a monolayer flake onto an infinite nanoribbon. These two structures have a complementary behavior, that we study and analyze by means of a tight-binding method and a continuum Dirac model. We have found that for certain energy ranges and geometries, the conductance of these systems oscillates markedly between zero and the maximum value of the conductance, allowing for the design of electromechanical switches. Our understanding of the electronic transmission through bilayer flakes may provide a way to measure the interlayer hopping in bilayer graphene.Comment: 11 pages, 8 figure