692 research outputs found

    Cryo-FIB Machining: An Alternative to TEM Cryo-Sections Cut with Diamonds?

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    Extended abstract of a paper presented at Microscopy and Microanalysis 2011 in Nashville, Tennessee, USA, August 7-August 11, 201

    Biogeographic, Atmospheric, and Climatic Factors Influencing Tree Growth in Mediterranean Aleppo Pine Forests

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    There is a lack of knowledge on how tree species respond to climatic constraints like water shortages and related atmospheric patterns across broad spatial and temporal scales. These assessments are needed to project which populations will better tolerate or respond to global warming across the tree species distribution range. Warmer and drier conditions have been forecasted for the Mediterranean Basin, where Aleppo pine (Pinus halepensisMill.) is the most widely distributed conifer in dry sites. This species shows plastic growth responses to climate, being particularly sensitive to drought. We evaluated how 32 Aleppo pine forests responded to climate during the second half of the 20th century by using dendrochronology. Climatic constraints of radial growth were inferred by fitting the Vaganov-Shashkin (VS-Lite) growth model to ring-width data from our Aleppo pine forest network. Our findings reported that Aleppo pine growth decreased and showed the highest common coherence among trees in dry, continental sites located in southeastern and eastern inland Spain and Algeria. In contrast, growth increased in wetter sites located in northeastern Spain. Overall, across the Aleppo pine network tree growth was enhanced by prior wet winters and cool and wet springs, whilst warm summers were associated with less growth. The relationships between site ring-width chronologies were higher in nearby forests. This explains why Aleppo pine growth was distinctly linked to indices of atmospheric circulation patterns depending on the geographical location of the forests. The western forests were more influenced by moisture and temperature conditions driven by the Western Mediterranean Oscillation (WeMO) and the Northern Atlantic Oscillation (NAO), the southern forests by the East Atlantic (EA) and the august NAO, while the Balearic, Tunisian and northeastern sites by the Arctic Oscillation (AO) and the Scandinavian pattern (SCA). The climatic constraints for Aleppo pine tree growth and its biogeographical variability were well captured by the VS-Lite model. The model performed better in dry and continental sites, showing strong growth coherence between trees and climatic limitations of growth. Further research using similar broad-scale approaches to climate-growth relationships in drought-prone regions deserves more attention

    Bio-Inspired Nanostructured Ti-6Al-4V Alloy: The Role of Two Alkaline Etchants and the Hydrothermal Processing Duration on Antibacterial Activity

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    Inspired by observations that the natural topography observed on cicada and dragonfly wings may be lethal to bacteria, researchers have sought to reproduce these nanostructures on biomaterials with the goal of reducing implant-associated infections. Titanium and its alloys are widely employed biomaterials with excellent properties but are susceptible to bacterial colonisation. Hydrothermal etching is a simple, cost-effective procedure which fabricates nanoscale protrusions of various dimensions upon titanium, depending on the etching parameters used. We investigated the role of etching time and the choice of cation (sodium and potassium) in the alkaline heat treatment on the topographical, physical, and bactericidal properties of the resulting modified titanium surfaces. Optimal etching times were 4 h for sodium hydroxide (NaOH) and 5 h for potassium hydroxide (KOH). NaOH etching for 4 h produced dense, but somewhat ordered, surface nanofeatures with 75 nanospikes per µm2. In comparison, KOH etching for 5 h resulted sparser but nonetheless disordered surface morphology with only 8 spikes per µm2. The NaOH surface was more effective at eliminating Gram-negative pathogens, while the KOH surface was more effective against the Gram-positive strains. These findings may guide further research and development of bactericidal titanium surfaces which are optimised for the predominant pathogens associated with the intended application

    Biogeographic, atmospheric, and climatic factors influencing tree growth in Mediterranean Aleppo pine forests

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    There is a lack of knowledge on how tree species respond to climatic constraintslike water shortages and related atmospheric patterns across broad spatial and temporal scales.These assessments are needed to project which populations will better tolerate or respond to globalwarming across the tree species distribution range. Warmer and drier conditions have been forecastedfor the Mediterranean Basin, where Aleppo pine (Pinus halepensisMill.) is the most widely distributedconifer in dry sites. This species shows plastic growth responses to climate, being particularly sensitiveto drought. We evaluated how 32 Aleppo pine forests responded to climate during the second half ofthe 20th century by using dendrochronology. Climatic constraints of radial growth were inferred byfitting the Vaganov-Shashkin (VS-Lite) growth model to ring-width data from our Aleppo pine forestnetwork. Our findings reported that Aleppo pine growth decreased and showed the highest commoncoherence among trees in dry, continental sites located in southeastern and eastern inland Spain andAlgeria. In contrast, growth increased in wetter sites located in northeastern Spain. Overall, across theAleppo pine network tree growth was enhanced by prior wet winters and cool and wet springs,whilst warm summers were associated with less growth. The relationships between site ring-widthchronologies were higher in nearby forests. This explains why Aleppo pine growth was distinctlylinked to indices of atmospheric circulation patterns depending on the geographical location of theforests. The western forests were more influenced by moisture and temperature conditions drivenby the Western Mediterranean Oscillation (WeMO) and the Northern Atlantic Oscillation (NAO),the southern forests by the East Atlantic (EA) and the august NAO, while the Balearic, Tunisian andnortheastern sites by the Arctic Oscillation (AO) and the Scandinavian pattern (SCA). The climaticconstraints for Aleppo pine tree growth and its biogeographical variability were well captured by theVS-Lite model. The model performed better in dry and continental sites, showing strong growthcoherence between trees and climatic limitations of growth. Further research using similar broad-scaleapproaches to climate-growth relationships in drought-prone regions deserves more attention
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