Abstract Iso and non-iso architected TiN/Cr multilayers with constant composition were deposited by balanced magnetron sputtering aiming to investigate the influence of different architectures over coatings structures and properties. Glow discharge optical emission spectroscopy analyses were used to determine in-depth constituents and suggested that no diffusion of elements occurred between layers in room temperature. Field emission gun scanning electron microscopy analyses showed that all multilayers presented sharp interfaces and low porosity microstructures, with column-like grain growth influenced by layer sizes. Glancing angle X-ray diffraction analyses showed that multilayers consist of polycrystalline α-Cr and δ-TiN phases with a main peak in Cr(110) plane. The overlapping of TiN onto metallic layers led to the suppression of growth in the TiN(111) plane, although TiN layers thicker than 50 nm demonstrated a growth in plane TiN(200). Nanoindentation tests registered equal hardness values for all multilayers of around 16.2 GPa, on the other hand, a tendency to improve hardness has been identified for hierarchical multilayer. Oxidation tests revealed that architectures with thicker TiN top layers presented an improved oxidation resistance up to 600 ºC, probably due to growth in more compact TiN(200) plane. However, TiN/Cr coatings did not resist integrally to oxidation tests at 750 ºC.

Abstract: Mexican bay (Litsea glaucescens) is one of the most important non-timber forest species in México due to its use as a condiment and its medicinal properties. This has caused the overexploitation of the populations of the species, which, together with the degradation of its habitat, has put in danger of extinction. In this work the development of an in vitro regeneration system for this species through indirect somatic embryogenesis is reported. The initial explants were mature zygotic embryos, from which embryogenic callus was generated on Murashige & Skoog culture medium, pH 5.7, with 30 g L-1 sucrose and 8 g L-1 agar, added with 4 g L-1 activated charcoal or 1 mg L-1 benzyladenine. The later was the best treatment and 29 % of the inoculated explants generated embryogenic tissue. Differentiation of somatic embryos was observed on culture medium with 4 g L-1 of activated charcoal, showing an average production of 282 somatic embryos per gram of embryogenic tissue. Maturation and germination of somatic embryos was more efficient (27 %) on basal medium with 6 g L-1 of activated charcoal and 12 g L-1 agar. The conversion of germinated embryos int∫o seedlings was achieved on 50 % basal medium with 8 g L-1 agar, with an efficiency of 87 %. Finally, 76 % of the plants generated via somatic embryogenesis survived and resumed growth in soil.

Resumen: El laurel silvestre (Litsea glaucescens) es una de las especies forestales no maderables más importantes en México debido a su uso como condimento y a sus propiedades medicinales. Esto ha causado una sobreexplotación de muchas de las poblaciones de la especie, lo cual, junto a la degradación de su hábitat, la ha puesto en peligro de extinción. En este trabajo se reporta el desarrollo de un sistema de regeneración in vitro para esta especie a través de la embriogénesis somática indirecta. Los explantes iniciales fueron embriones cigóticos maduros, a partir de los cuales se generó tejido calloso embriogénico en medio de cultivo de Murashige y Skoog, a pH 5.7, con 30 g L-1 de sacarosa y 8 g L-1 de agar, adicionados con 4 g L-1 carbón activado o 1 mg L-1 de benciladenina. Este último fue el mejor tratamiento ya que 29 % de los explantes inoculados generó tejido embriogénico. La diferenciación de los embriones somáticos se observó en medio de cultivo con 4 g L-1 de carbón activado, con una producción promedio de 282 embriones somáticos por cada gramo de tejido embriogénico. La maduración y germinación de los embriones somáticos fue más eficiente (27 %) en medio basal con 6 g L-1 de carbón activado y 12 g L-1 de agar. La conversión de embriones germinados en plántulas se logró en medio basal a 50 % con 8 g L-1 de agar, esto con una eficiencia de 87 %. Finalmente, 76 % de las plantas generadas a través de la embriogénesis somática sobrevivieron y reiniciaron su crecimiento en suelo.