APPLYING GEODESY TO MODEL POSTSEISMIC SLIP OF THE 2016 MW 6.4 MEINONG EARTHQUAKE

In regions of rapid convergence such as southwest Taiwan, unmapped active structures at multiple depths increase the uncertainty of seismic hazard estimates. The 2016 Mw 6.4 MeiNong earthquake occurred below the main Taiwan detachment, and may have illuminated some preexisting, but undocumented, fault structures. In this study, I use geodetic measurements to constrain afterslip on the main fault for 15 months following the MeiNong earthquake. The inverted afterslip is concentrated around the peak coseismic slip asperity without significant aftershock correlation, which implies heterogeneous frictional properties on the fault. Additionally, slip model misfit indicates shallower faults that are critically stressed before the earthquake creep due to the MeiNong coseismic stress. My results can help identify active faults located at shallower depth as well as their seismic potential in southwest Taiwan

An indole-containing dauer pheromone component with unusual dauer inhibitory activity at higher concentrations

In Caenorhabdltls elegans, the dauer pheromone, which consists of a number of derivatives of the 3,6-dideoxysugar ascarylose, is the primary cue for entry into the stress-resistant, nonaging dauer larval stage. Here, using activity-guided fractionation and NMR-based structure elucidation, a structurally novel, indole-3-carboxyl-modified ascaroside is identified that promotes dauer formation at low nanomolar concentrations but inhibits dauer formation at higher concentrations. © 2009 American Chemical Society

Synthesis and characterization of silica/silver multilayer nanoparticles and their application in surface enhanced spectroscopy

This research is focused on determining the most effective silver shell growth method formultilayered metallic nanoparticles, and determining the plausibility of using embedded[Ru(bpy)3]2+ as an internal standard for surface enhanced Raman spectroscopy. In the surfacestudy, silica particles were functionalized with (3-aminopropyl)trimethoxysilane followed by avariety of seeding techniques to complete the silver shell. This study revealed that the optimumsynthesis method prior to the hydrogen reduction of the silver shell utilized a tin treatmentfollowed by a silver (I) oxide soak, resulting in the best surface coverage. Likewise extinctionanalysis revealed that this type of particle absorbs the most light, which likely is important forsurface enhanced spectroscopy.In the second part of the study, a procedure is reported for the synthesis of multilayeredmetallic nanoparticles with a dye molecule ([Ru(bpy)3]2+) embedded in the dielectric layerseparating the two silver layers. Raman spectroscopy was used to prove the success ofembedding the dye molecule into the spacer layer. Fluorescence, extinction, absorption, andscattering data were used to determine that, as the shell is synthesized, it begins to absorb moreof the excitation light. This absorption is a problem because [Ru(bpy)3]2+ has a low quantumyield of only 7.2% and the signal is easily extinguished as the shell becomes thicker. Finally, the particles with the embedded dye molecule were used for a preliminary test to determine theirusefulness as an internal standard for surface enhanced Raman scattering. This preliminarystudy revealed that it is possible to detect [Ru(bpy)3]2+ using the 457.9 nm laser and use a632.8 nm laser line to detect a 500 nM crystal violet solution. 500 nM is below the detection ofcrystal violet only using Raman spectroscopy

A Sexually Conditioned Switch of Chemosensory Behavior in C. elegans

In sexually reproducing animals, mating is essential for transmitting genetic information to the next generation and therefore animals have evolved mechanisms for optimizing the chance of successful mate location. In the soil nematode C. elegans, males approach hermaphrodites via the ascaroside pheromones, recognize hermaphrodites when their tails contact the hermaphrodites' body, and eventually mate with them. These processes are mediated by sensory signals specialized for sexual communication, but other mechanisms may also be used to optimize mate location. Here we describe associative learning whereby males use sodium chloride as a cue for hermaphrodite location. Both males and hermaphrodites normally avoid sodium chloride after associative conditioning with salt and starvation. However, we found that males become attracted to sodium chloride after conditioning with salt and starvation if hermaphrodites are present during conditioning. For this conditioning, which we call sexual conditioning, hermaphrodites are detected by males through pheromonal signaling and additional cue(s). Sex transformation experiments suggest that neuronal sex of males is essential for sexual conditioning. Altogether, these results suggest that C. elegans males integrate environmental, internal and social signals to determine the optimal strategy for mate location

Sporulenes, Heptaprenyl Metabolites from Bacillus subtilis Spores

Sporulene, a C35-terpenoid hydrocarbon with an unusual pentacyclic structure, is produced by Bacillus subtilis during sporulation.Earth and Planetary SciencesMolecular and Cellular Biolog

A Novel ascaroside controls the parasitic life cycle of the entomopathogenic nematode heterorhabditis bacteriophora

Entomopathogenic nematodes survive in the soil as stress-resistant infective juveniles that seek out and infect insect hosts. Upon sensing internal host cues, the infective juveniles regurgitate bacterial pathogens from their gut that ultimately kill the host. Inside the host, the nematode develops into a reproductive adult and multiplies until unknown cues trigger the accumulation of infective juveniles. Here, we show that the entomopathogenic nematode Heterorhabditis bacteriophora uses a small-molecule pheromone to control infective juvenile development. The pheromone is structurally related to the dauer pheromone ascarosides that the free-living nematode Caenorhabditis elegans uses to control its development. However, none of the C. elegans ascarosides are effective in H. bacteriophora, suggesting that there is a high degree of species specificity. Our report is the first to show that ascarosides are important regulators of development in a parasitic nematode species. An understanding of chemical signaling in parasitic nematodes may enable the development of chemical tools to control these species. © 2012 American Chemical Society