Exceptional river gorge formation from unexceptional floods

An understanding of rates and mechanisms of incision and knickpoint retreat in bedrock rivers is fundamental to perceptions of landscape response to external drivers, yet only sparse field data are available. Here we present eye witness accounts and quantitative surveys of rapid, amphitheatre-headed gorge formation in unweathered granite from the overtopping of a rock-cut dam spillway by small-moderate floods (B100–1,500m3 s�1). The amount of erosion demonstrates no relationship with flood magnitude or bedload availability. Instead, structural pattern of the bedrock through faults and joints appears to be the primary control on landscape change. These discontinuities facilitate rapid erosion (4270m headward retreat; B100m incision; and B160m widening over 6 years) principally through fluvial plucking and block topple. The example demonstrates the potential for extremely rapid transient bedrock erosion even when rocks are mechanically strong and flood discharges are moderate. These observations are relevant to perceived models of gorge formation and knickpoint retreat.

On continuous families of geometric Seifert conemanifold structures

In this paper, dedicated to Prof. Lou Kauffman, we determine the Thurston’s geometry possesed by any Seifert fibered conemanifold structure in a Seifert manifold with orbit space (Formula presented.) and no more than three exceptional fibers, whose singular set, composed by fibers, has at most three components which can include exceptional or general fibers (the total number of exceptional and singular fibers is less than or equal to three). We also give the method to obtain the holonomy of that structure. We apply these results to three families of Seifert manifolds, namely, spherical, Nil manifolds and manifolds obtained by Dehn surgery on a torus knot (Formula presented.). As a consequence we generalize to all torus knots the results obtained in [Geometric conemanifolds structures on (Formula presented.), the result of (Formula presented.) surgery in the left-handed trefoil knot (Formula presented.), J. Knot Theory Ramifications 24(12) (2015), Article ID: 1550057, 38pp., doi: 10.1142/S0218216515500571] for the case of the left handle trefoil knot. We associate a plot to each torus knot for the different geometries, in the spirit of Thurston.

Narrativa de tradición oral maya-tojolabal

For this research, a literary study of the oral tradition in the Maya-Tojolabal culture was carried out through an examination of a collection of 37 texts. The texts were audiovisually recorded through interviews with 17 Tojolabal informants from six communities in the state of Chiapas, Mexico. The Maya-Tojolabal people, found in the southeast of Chiapas, speak one of the Mayan languages of Mexico. One of their cultural expressions is traditional narrative, which is constituted by several versions of stories that men and women with expertise in traditional storytelling maintain alive. However, this oral tradition has been neglected by academia, and the very few studies on this tradition are primarily focused on either the historical, anthropological or linguistic aspects. The literary approach to this phenomenon has largely been relegated to articles that do not offer the possibility of any critical formalsemantic study of the stories that they publish. Nonetheless, there are some exceptional cases, which are considered in detail in this research. Like any collective art, the narrative in the Tojolabal oral tradition manifests in various forms, meanings, and mechanisms that are shared by all members of the community. In addition to being an artistic expression, the narratives are also a reflection of the values and beliefs shared by the group...