RESUMEN
The paper deals with the evolution of the microstructure of AlSi10Mg alloy obtained by laser powder bed fusion (LPBF), as a function of the post-processing heat treatment temperature. This was approached by complementary methods including FE-scanning electron microscopy, scanning Kelvin probe force microscopy and exo-electron emission techniques. The fast cooling rate of the LPBF process as compared to traditional casting produces a very fine microstructure with high mechanical properties and corrosion resistance. However, the LPBF-AlSi10Mg alloy can be susceptible to selective corrosion at the edge of the melt pools generated by the laser scan tracks. Post-process thermal treatments of the Al alloy induce a marked modification of the silicon network at melt pool edges, in particular at high temperature such as 400 °C. It was found that this is associated to a more homogeneous distribution of Volta potential. Analysis of exo-electron emission confirms the silicon diffusion during thermal treatment. The modification of the silicon network structure of the LPBF-AlSi10Mg during thermal treatment reduces the susceptibility to selective corrosion.
RESUMEN
Hydroalcoholic extracts (HE) and essential oils (EO) of branches, leaves and fruits of Rhus typhina L., were characterized by GC-MS. HE (yealds: branches 68.30 mg/g, leaves 35.82 mg/g and fruits 257.76 mg/g), showed different compositions dominated by gallic acid (33.46%) in branches, its precursor 1-cyclohexane-3,4,5-hydroxy-carboxylic acid (20.55%) in leaves and malic acid (89.15%) in fruits. EO yields were 210 µg/g for branches (main component δ-cadinene, 22.00%), followed by fruits with 132 µg/g (ß-pinene 32.2%) and by leaves with 54 µg/g and phenylacetaldehyde as major component (40.13%). Total phenolic content (TPC) was highest in branches HE (5.87 µg GAE/mL) and in EO leaves (17.71 µg GAE/mL). The highest value of radical scavenging activity (DPPH test) was detected in leaves HE and EO. The branches EO antimicrobial activity was strong against C. albicans and negligible against E. coli. Leaves and fruits EO showed strong activity against C. albicans and intermediate activity against Escherichia coli.
Asunto(s)
Anacardiaceae , Aceites Volátiles , Rhus , Antibacterianos , Antioxidantes , Escherichia coli , Frutas , Cromatografía de Gases y Espectrometría de Masas , Aceites Volátiles/farmacología , Extractos Vegetales/farmacología , Hojas de la Planta , MaderaRESUMEN
OBJECTIVE: Environmental bacterial contaminant microorganisms are an ongoing problem in hospitals. Essential oil vapours (EO) may help reducing this type of contamination. Aim of this study was to evaluate the efficacy of nebulized selected essential oils (EO) in reducing the microbial contamination in residential health care house rooms. DESIGN: The study was carried out in a two-story 112-bed tertiary care structure (approximately 1060 m(2)). Contamination in rooms and corridors was monitored for a total of n=5 months, including a starting baseline sampling and one end-study point, and without combined treatment (standard sanitization alone). Contact slides were collected for microbiological analysis. RESULTS: Reductions in both bacterial and fungal contamination were observed between rooms cleaned using standard sanitization alone or in combination with essential oils nebulization (average 90% decrease for total count, P<0.01; 90% for yeasts and molds, P<0.05). Decreases of antibiotic (70%), mucolytic (100%), bronchodilators (100%), and steroidal (67%) and non-steroidal anti-inflammatory drugs (33%) prescriptions were observed, with no adverse effects on patients. CONCLUSIONS: The selected EO composition is effective in reducing both the environmental microbial contamination and pharmaceutical drugs consumption in a nosocomial health care house. This study demonstrates that aerial EO diffusion combined with standard sanitization procedures, has great potential to reduce the microbial contamination in critical hospital environments such as hospitalization rooms.