Ancient DNA from lake sediments: Bridging the gap between paleoecology and genetics

<p>Abstract</p> <p>Background</p> <p>Quaternary plant ecology in much of the world has historically relied on morphological identification of macro- and microfossils from sediments of small freshwater lakes. Here, we report new protocols that reliably yield DNA sequence data from Holocene plant macrofossils and bulk lake sediment used to infer ecological change. This will allow changes in census populations, estimated from fossils and associated sediment, to be directly associated with population genetic changes.</p> <p>Results</p> <p>We successfully sequenced DNA from 64 samples (out of 126) comprised of bulk sediment and seeds, leaf fragments, budscales, and samaras extracted from Holocene lake sediments in the western Great Lakes region of North America. Overall, DNA yields were low. However, we were able to reliably amplify samples with as few as 10 copies of a short cpDNA fragment with little detectable PCR inhibition. Our success rate was highest for sediments < 2000 years old, but we were able to successfully amplify DNA from samples up to 4600 years old. DNA sequences matched the taxonomic identity of the macrofossil from which they were extracted 79% of the time. Exceptions suggest that DNA molecules from surrounding nearby sediments may permeate or adhere to macrofossils in sediments.</p> <p>Conclusions</p> <p>An ability to extract ancient DNA from Holocene sediments potentially allows exciting new insights into the genetic consequences of long-term environmental change. The low DNA copy numbers we found in fossil material and the discovery of multiple sequence variants from single macrofossil extractions highlight the need for careful experimental and laboratory protocols. Further application of these protocols should lead to better understanding of the ecological and evolutionary consequences of environmental change.</p

Quenching of TiO2 photo catalysis by silver nanoparticles

The plasmon resonance of metal nanostructures affects neighboring semiconductors, quenching or enhancing optical transitions depending on various parameters. These plasmonic properties are currently investigated with respect to topics such as photovoltaics and optical detection and could also have important consequences for photocatalysis. Here the effect of silver nanoparticles of a size up to 30 nm and at maximum 0.50 monolayers on the photocatalytic oxidation of ethylene on TiO2 is studied. Since the plasmon resonance energy of silver nanoparticles is comparable with the TiO2 band gap, dipole–dipole interaction converts excitons into heat at the silver nanoparticle. This indicates that plasmonic interaction with TiO2 semiconductor catalysts can reduce the photo catalytic activity considerably

Quenching of TiO2 photo catalysis by silver nanoparticles

The plasmon resonance of metal nanostructures affects neighboring semiconductors, quenching or enhancing optical transitions depending on various parameters. These plasmonic properties are currently investigated with respect to topics such as photovoltaics and optical detection and could also have important consequences for photocatalysis. Here the effect of silver nanoparticles of a size up to 30 nm and at maximum 0.50 monolayers on the photocatalytic oxidation of ethylene on TiO2 is studied. Since the plasmon resonance energy of silver nanoparticles is comparable with the TiO2 band gap, dipole–dipole interaction converts excitons into heat at the silver nanoparticle. This indicates that plasmonic interaction with TiO2 semiconductor catalysts can reduce the photo catalytic activity considerably

Piezoresistive effect in spin-coated polyaniline thin films

Polymeric materials have been replacing other materials in various applications, from structural to electronic components. In particular, since the discovery of conducting polymers, the use of these materials is growing up in the manufacture of electronic components, such as organic light-emitting diodes, organic electrodes, energy storage devices and artificial muscles, among many others. On the other hand, examples of sensors of conductive polymers based on the piezoresistive effect with large potential for applications are not sufficiently investigated. This investigation reports on the piezoresistive effect of an intrinsically conductive polymer, polyaniline, which was prepared in the form of thin films by spin coating on polyethylene terephthalate substrates. The relationship between the electrical response and mechanical solicitations is presented for different preparation conditions. The values of the gauge factor ranges from 10 to 22 for different samples and demonstrates the viability of these materials as piezoresistive sensors.This work is funded by FEDER funds through the "Programa Operacional Factores de Competitividade - COMPETE" and by national funds by FCT-Fundacao para a Ciencia e a Tecnologia, project references PTDC/CTM/69316/2006, PTDC/CTMNAN/112574/2009, and NANO/NMed-SD/0156/2007. J.N.P, A. F. and J. G. R. thank the FCT for Grants SFRH/BD/66930/2009, SFRH/BD/69796/2010 and SFRH/BSAB/1014/2010, respectively. The authors also than the support of the COST Action MP1003, 2010: The 'European Scientific Network for Artificial Muscles' (ESNAM)