The Role of Landscape Connectivity in Assembling Exotic Plant Communities: A Network Analysis

Landscape fragmentation and exotic species invasions are two modern-day forces that have strong and largely irreversible effects on native diversity worldwide. The spatial arrangement of habitat fragments is critical in affecting movement of individuals through a landscape, but little is known about how invasive species respond to landscape configuration relative to native species. This information is crucial for managing the global threat of invasive species spread. Using network analysis and partial Mantel tests to control for covarying environmental conditions, we show that forest plant communities in a fragmented landscape have spatial structure that is best captured by a network representation of landscape connectivity. This spatial structure is less pronounced in invasive species and exotic species dispersed by animals. Our research suggests that invasive species can spread more easily in fragmented landscapes than native species, which may. make communities more homogeneous over time

Helix vs. Sheet Formation in a Small Peptide

Segments with the amino acid sequence EKAYLRT appear in natural occurring proteins both in $\alpha$-helices and $\beta$-sheets. For this reason, we have use this peptide to study how secondary structure formation in proteins depends on the local environment. Our data rely on multicanonical Monte Carlo simulations where the interactions among all atoms are taken into account. Results in gas phase are compared with that in an implicit solvent. We find that both in gas phase and solvated EKAYLRT forms an $\alpha$-helix when not interacting with other molecules. However, in the vicinity of a $\beta$-strand, the peptide forms a $\beta$-strand. Because of this change in secondary structure our peptide may provide a simple model for the $\alpha \to \beta$ transition that is supposedly related to the outbreak of Prion diseases and similar illnesses.Comment: to appear in Physical Review

The Effects of Various Conductive Additive and Polymeric Binder Contents on the Performance of a Lithium-ion Composite

Fundamental electrochemical methods, cell performance tests, and physical characterization tests such as electron microscopy were used to study the effects of levels of the inert materials (acetylene black (AB), a nano-conductive additive, and polyvinylidene difluoride (PVDF), a polymer binder) on the power performance of lithium-ion composite cathodes. The electronic conductivity of the AB/PVDF composites at different compositions was measured with a four-point probe direct current method. The electronic conductivity was found to increase rapidly and plateau at a AB:PVDF ratio 0.2:1 (by weight), with 0.8:1 being the highest conductivity composition. AB:PVDF compositions along the plateau of 0.2:1, 0.4:1, 0.6:1 and 0.8:1 were investigated. Electrodes of each of those compositions were fabricated with different fractions of AB/PVDF to active material. It was found that at the 0.8:1 AB:PVDF, the rate performance improved with increases in the AB/PVDF loading, whereas at the 0.2:1 AB:PVDF, the rate performance improved with decreases in the AB/PVDF loading. The impedance of electrodes made with 0.6:1 AB:PVDF was low and relatively invariant

In situ TEM nanomechanics

cited By 22International audienceIn situ transmission electron microscopy (TEM) nanomechanical testing has benefited from a number of recent technical developments related to both how deformation is imaged and how deformation is induced and measured inside a TEM instrument. These developments have led to new insights into the deformation mechanisms of a wide range of metals and alloys, as well as measurements of the unusual mechanical properties of small-scale objects such as whiskers and nanocrystals. Herein, we describe this recent progress through selected highlights of recent findings on the dynamic behavior of defects such as dislocations, twins, and grain boundaries