RESUMEN
The Talbragar Fish Bed is one of Australia's most important Jurassic deposits for freshwater fishes, land plants and aquatic and terrestrial insects. The site has yielded many well preserved fossils, which has led to the formal description of numerous new species and higher taxa. The excellent preservation of many fossils has allowed detailed anatomical studies, e.g. of the early teleost fish Cavenderichthys talbragarensis (Woodward, 1895). Here we report on the fluorescent characteristics and mineral composition of a range of Talbragar fossils. Most specimens fluoresce under ultraviolet, blue and green light. Elemental and mineralogical analyses revealed that the Talbragar fossils consist predominantly of quartz (SiO2), a mineral that is likely to account for the observed fluorescence, with trace kaolinite (Al2Si2O5(OH)4) in some of the fish fossils. Rock matrices are predominantly composed of quartz and goethite (FeO(OH)). Closer inspection of a plant leaf (Pentoxylon australicum White, 1981) establishes fluorescence as a useful tool for the visualisation of anatomical details that are difficult to see under normal light conditions.
Asunto(s)
Peces/anatomía & histología , Fósiles , Insectos/anatomía & histología , Hojas de la Planta/anatomía & histología , Plantas/anatomía & histología , Animales , Australia , Evolución Biológica , Historia Antigua , Insectos/química , Compuestos de Hierro/análisis , Compuestos de Hierro/química , Compuestos de Hierro/historia , Caolín/análisis , Caolín/química , Caolín/historia , Mediciones Luminiscentes , Metales Pesados/análisis , Metales Pesados/química , Metales Pesados/historia , Minerales/análisis , Minerales/química , Minerales/historia , Hojas de la Planta/química , Plantas/química , Cuarzo/análisis , Cuarzo/química , Cuarzo/historia , Espectrometría de FluorescenciaAsunto(s)
Rendimiento Atlético/historia , Automóviles/historia , Béisbol/historia , Compuestos de Hierro/historia , Poliomielitis/historia , Rendimiento Atlético/fisiología , Béisbol/fisiología , Brotes de Enfermedades/historia , Historia del Siglo XX , Humanos , Compuestos de Hierro/farmacología , Masculino , Fuerza Muscular/efectos de los fármacos , Poliomielitis/epidemiología , Poliomielitis/etiologíaRESUMEN
Archaeological indicators of cognitively modern behaviour become increasingly prevalent during the African Middle Stone Age (MSA). Although the exploitation of ochre is viewed as a key feature of the emergence of modern human behaviour, the uses to which ochre and ochre-based mixtures were put remain ambiguous. Here we present the results of an experimental study exploring the efficacy of ochre as a topical photoprotective compound. This is achieved through the in vivo calculation of the sun protection factor (SPF) values of ochre samples obtained from Ovahimba women (Kunene Region, Northern Namibia) and the Palaeozoic Bokkeveld Group deposits of the Cape Supergroup (Western Cape Province, South Africa). We employ visible spectroscopy, energy-dispersive X-ray fluorescence (ED-XRF), X-ray diffraction (XRD) and granulometric analyses to characterise ochre samples. The capacity of ochre to inhibit the susceptibility of humans to the harmful effects of exposure to ultraviolet radiation (UVR) is confirmed and the mechanisms implicated in the efficacy of ochre as a sunscreen identified. It is posited that the habitual application of ochre may have represented a crucial innovation for MSA humans by limiting the adverse effects of ultraviolet exposure. This may have facilitated the colonisation of geographic regions largely unfavourable to the constitutive skin colour of newly arriving populations.
Asunto(s)
Compuestos Férricos/química , Migración Humana/historia , Compuestos de Hierro/química , Minerales/química , Suelo/química , Factor de Protección Solar , Protectores Solares/química , Silicatos de Aluminio/química , Animales , Mantequilla , Arcilla , Radiación Cósmica/efectos adversos , Planeta Tierra , Extinción Biológica , Femenino , Compuestos Férricos/historia , Historia del Siglo XXI , Historia Antigua , Hominidae , Humanos , Compuestos de Hierro/historia , Campos Magnéticos , Masculino , Minerales/historia , Namibia , Pomadas , Tamaño de la Partícula , Cuarzo , Selección Genética , Piel/efectos de la radiación , Pigmentación de la Piel , Espectrometría por Rayos X , Espectrofotometría , Luz Solar/efectos adversos , Protectores Solares/historia , Rayos Ultravioleta/efectos adversos , Difracción de Rayos XRESUMEN
Iron-arsenic alloys are described in many medieval chemical recipes as a means to "liquefy" iron. In fact, while such alloys have relatively low melting points, they are not the only examples of iron being known as a liquid metal. There is evidence from the analysis of swords, as well as from written references, that crucible steel, probably imported from the Middle East, was known in Western Europe from the Early Middle Ages. In addition, the "blast furnace", which produced liquid pig iron, is now known from archaeological evidence to have been operated from at least the thirteenth century in Scandinavia. The descriptions of iron-smelting and iron-working given in the accounts written by scholastic alchemists are in fact closely related to the contemporary practices of craftsmen operating iron furnaces.