Evidence of Inverse Hall-Petch Behavior and Low Friction and Wear in High Entropy Alloys.

We present evidence of inverse Hall-Petch behavior for a single-phase high entropy alloy (CoCrFeMnNi) in ultra-high vacuum and show that it is associated with low friction coefficients (~0.3). Grain size measurements by STEM validate a recently proposed dynamic amorphization model that accurately predicts grain size-dependent shear strength in the inverse Hall-Petch regime. Wear rates in the initially soft (coarse grained) material were shown to be remarkably low (~10-6 mm3/N-m), the lowest for any HEA tested in an inert environment where oxidation and the formation of mixed metal-oxide films is mitigated. The combined high wear resistance and low friction are linked to the formation of an ultra-nanocrystalline near-surface layer. The dynamic amorphization model was also used to predict an average high angle grain boundary energy (0.87 J/m2). This value was used to explain cavitation-induced nanoporosity found in the highly deformed surface layer, a phenomenon that has been linked to superplasticity.

Absceso hepático amebiano

Se señala la relativa frecuencia con que se observa el absceso amebiano entre nosostros. Se muestran los porcentajes que aceptan diversos autores en cuanto a síntomas y signos. Se señala el valor de los exámenes complementarios en especial la radiología y la rectosigmoidoscopía. Se resalta el valor de la punción y se describe su técnica. Se demuestran los medicamentos que utilizamos y sus dosis. Se precisan las indicaciones del tratamiento quirúrgico. Se señalan los peligros de las vías transserosas. Se preconiza la utilización de las vías extraserosa anterior y posterior. Se recomienda el uso de la anestesia local infiltrativa. Se describe la técnica de abordaje y drenajes de los abscesos empleada. Se presentan los datos obtenidos en 16 casos tratados quirúrgicamente (AU)