Nuevos chamanes en la Colombia accidentalizada

Este es un ensayo de una pequeña investigación de pregrado en donde se busca hacer una revisión bibliográfica de los temas asociados al chamanismo en la ciudad, o neochamanismo (como algunos lo llaman). Para este ensayo se muestra cómo puede estar funcionando la teoría en un caso etnografico concreto en un lugar de Bogotá. Este ensayo fue escogido para participar como ponencia , en 2009, en el Primer Foro Interno de Debate y Reflexión Escuela de Ciencias Humanas de la Universidad del Rosari

Detection of the old stellar component of the major Galactic bar

We present near-IR colour--magnitude diagrams and star counts for a number of regions along the Galactic plane. It is shown that along the l=27 b=0 line of sight there is a feature at 5.7 +-0.7kpc with a density of stars at least a factor two and probably more than a factor five times that of the disc at the same position. This feature forms a distinct clump on an H vs. J-H diagram and is seen at all longitudes from the bulge to about l=28, but at no longitude greater than this. The distance to the feature at l=20 is about 0.5kpc further than at l=27 and by l=10 it has merged with, or has become, the bulge. Given that at l=27 and l=21 there is also a clustering of very young stars, the only component that can reasonably explain what is seen is a bar with half length of around 4kpc and a position angle of about 43+-7.Comment: 5 pages, 5 figures accepted as a letter in MNRA

Coherent control of nanomagnet dynamics via ultrafast spin torque pulses

The magnetization orientation of a nanoscale ferromagnet can be manipulated using an electric current via the spin transfer effect. Time domain measurements of nanopillar devices at low temperatures have directly shown that magnetization dynamics and reversal occur coherently over a timescale of nanoseconds. By adjusting the shape of a spin torque waveform over a timescale comparable to the free precession period (100-400 ps), control of the magnetization dynamics in nanopillar devices should be possible. Here we report coherent control of the free layer magnetization in nanopillar devices using a pair of current pulses as narrow as 30 ps with adjustable amplitudes and delay. We show that the switching probability can be tuned over a broad range by timing the current pulses with the underlying free-precession orbits, and that the magnetization evolution remains coherent for more than 1 ns even at room temperature. Furthermore, we can selectively induce transitions along free-precession orbits and thereby manipulate the free magnetic moment motion. We expect this technique will be adopted for further elucidating the dynamics and dissipation processes in nanomagnets, and will provide an alternative for spin torque driven spintronic devices, such as resonantly pumping microwave oscillators, and ultimately, for efficient reversal of memory bits in magnetic random access memory (MRAM).Comment: 4 pages, 3 figures, submitted to Nature Physic