37 research outputs found
Opportunity to Test non-Newtonian Gravity Using Interferometric Sensors with Dynamic Gravity Field Generators
We present an experimental opportunity for the future to measure possible
violations to Newton's 1/r^2 law in the 0.1-10 meter range using Dynamic
gravity Field Generators (DFG) and taking advantage of the exceptional
sensitivity of modern interferometric techniques. The placement of a DFG in
proximity to one of the interferometer's suspended test masses generates a
change in the local gravitational field that can be measured at a high signal
to noise ratio. The use of multiple DFGs in a null experiment configuration
allows to test composition independent non-Newtonian gravity significantly
beyond the present limits. Advanced and third-generation gravitational-wave
detectors are representing the state-of-the-art in interferometric distance
measurement today, therefore we illustrate the method through their sensitivity
to emphasize the possible scientific reach. Nevertheless, it is expected that
due to the technical details of gravitational-wave detectors, DFGs shall likely
require dedicated custom configured interferometry. However, the sensitivity
measure we derive is a solid baseline indicating that it is feasible to
consider probing orders of magnitude into the pristine parameter well beyond
the present experimental limits significantly cutting into the theoretical
parameter space.Comment: 9 pages, 6 figures; Physical Review D, vol. 84, Issue 8, id. 08200
Direct measurement of VOC diffusivities in tree tissues:Impacts on tree-based phytoremediation and plant contamination
Recent discoveries in the phytoremediation of volatile organic compounds (VOCs) show that vapor-phase transport into roots leads to VOC removal from the vadose zone and diffusion and volatilization out of plants is an important fate following uptake. Volatilization to the atmosphere constitutes one fundamental terminal fate processes for VOCs that have been translocated from contaminated soil or groundwater, and diffusion constitutes the mass transfer mechanism to the plantâatmosphere interface. Therefore, VOC diffusion through woody plant tissues, that is, xylem, has a direct impact on contaminant fate in numerous vegetationâVOC interactions, including the phytoremediation of soil vapors and dissolved aqueous-phase contaminants. The diffusion of VOCs through freshly excised tree tissue was directly measured for common groundwater contaminants, chlorinated compounds such as trichloroethylene, perchloroethene, and tetrachloroethane and aromatic hydrocarbons such as benzene, toluene, and methyl tert-butyl ether. All compounds tested are currently being treated at full scale with tree-based phytoremediation. Diffusivities were determined by modeling the diffusive transport data with a one-dimensional diffusive flux model, developed to mimic the experimental arrangement. Woodâwater partition coefficients were also determined as needed for the model application. Diffusivities in xylem tissues were found to be inversely related to molecular weight, and values determined herein were compared to previous modeling on the basis of a tortuous diffusion path in woody tissues. The comparison validates the predictive model for the first time and allows prediction for other compounds on the basis of chemical molecular weight and specific plant properties such as water, lignin, and gas contents. This research provides new insight into phytoremediation efforts and into potential fruit contamination for fruit-bearing trees, specifically establishing diffusion rates from the transpiration stream and modeling volatilization along the transpiration path, including the trunk and branches. This work also has importance in other plantâVOC interactions, such as potential uptake from the atmosphere for hydrophobic compounds and also uptake from vapor-phase soil contaminants