Application of a Numerical Model to Evaluate the Impact of Future Sea-level Change in Coastal Inundation around Chester and Delaware Counties

Coastal inundation caused by severe weather events such as hurricanes was investigated by applying a numerical simulation for the area of eastern Pennsylvania. The study area includes long extension of coastal low-lying lands by the Delaware River, including Philadelphia city as well as Chester and Delaware counties, which is under the risk of coastal inundation when hurricanes hit the mid-Atlantic regions. The SLOSH (Sea, Lake and Overland Surges from Hurricanes) model, initially developed by the National Weather Service (NWS), was implemented to the study area to evaluate the probability of inundation due to combined effect of Hurricane storm surge and the climate change and subsequent sea-level rise. Dr. Yong Hoon Kim and Ms. Dominica DeFelice, an undergraduate student in the Department of Earth and Space Science, collected coastline and topography data of the eastern Pennsylvania, digitized them into proper GIS format, and ran SLOSH simulation with these newly-collected data. The simulation results show that the low land areas around Chester, Philadelphia airport and Philadelphia Naval business area could be inundated even under category 3 hurricanes if we have a sea-level rise of 2.23 ft above the present level at year 2050 (based on IPCC 5th Assessment Report). With category 5 hurricanes, some residential areas in southwestern Philadelphia and oil storage tanks fields along Schuylkill river could also be under influence. This study shows high risk of inundation in lowland coastal areas in eastern Pennsylvania during severe Hurricanes when we have sea-level rise near future. The findings from this project will be used to teach Impact of Climate Change topic in Dr. Kim’s ESS 130 Our Coastal Ocean (Gen Ed) and other courses. This study was supported by Sustainability Research and Creative Activities Grant from Office of Sustainability, West Chester University of Pennsylvania

Object-oriented construction of a multigrid electronic-structure code with Fortran 90

We describe the object-oriented implementation of a higher-order finite-difference density-functional code in Fortran 90. Object-oriented models of grid and related objects are constructed and employed for the implementation of an efficient one-way multigrid method we have recently proposed for the density-functional electronic-structure calculations. Detailed analysis of performance and strategy of the one-way multigrid scheme will be presented.Comment: 24 pages, 6 figures, to appear in Comput. Phys. Com

A study on the turbulent transport of an advective nature in the fluid plasma

Advective nature of the electrostatic turbulent flux of plasma energy is studied numerically in a nearly adiabatic state. Such a state is represented by the Hasegawa-Mima equation that is driven by a noise that may model the destabilization due to the phase mismatch of the plasma density and the electric potential. The noise is assumed to be Gaussian and not to be invariant under reflection along a direction $\hat s$. It is found that the flux density induced by such noise is anisotropic: While it is random along $\hat s$, it is not along the perpendicular direction ${\hat s}_\perp$ and the flux is not diffusive. The renormalized response may be approximated as advective with the velocity being proportional to $(k\rho_s)^2$ in the Fourier space $\vec k$

Stretching-induced conductance variations as fingerprints of contact configurations in single-molecule junctions

Molecule-electrode contact atomic structures are a critical factor that characterizes molecular devices, but their precise understanding and control still remain elusive. Based on combined first-principles calculations and single-molecule break junction experiments, we herein establish that the conductance of alkanedithiolate junctions can both increase and decrease with mechanical stretching and the specific trend is determined by the S-Au linkage coordination number (CN) or the molecule-electrode contact atomic structure. Specifically, we find that the mechanical pulling results in the conductance increase for the junctions based on S-Au CN two and CN three contacts, while the conductance is minimally affected by stretching for junctions with the CN one contact and decreases upon the formation of Au monoatomic chains. Detailed analysis unravels the mechanisms involving the competition between the stretching-induced upshift of the highest occupied molecular orbital-related states toward the Fermi level of electrodes and the deterioration of molecule-electrode electronic couplings in different contact CN cases. Moreover, we experimentally find a higher chance to observe the conductance enhancement mode under a faster elongation speed, which is explained by ab initio molecular dynamics simulations that reveal an important role of thermal fluctuations in aiding deformations of contacts into low-coordination configurations that include monoatomic Au chains. Pointing out the insufficiency in previous notions of associating peak values in conductance histograms with specific contact atomic structures, this work resolves the controversy on the origins of ubiquitous multiple conductance peaks in S-Au-based single-molecule junctions.Comment: 11 pages, 4 figures; to be published in J. Am. Chem. So

Nitrogen doping of carbon nanoelectrodes for enhanced control of DNA translocation dynamics

Controlling the dynamics of DNA translocation is a central issue in the emerging nanopore-based DNA sequencing. To address the potential of heteroatom doping of carbon nanostructures to achieve this goal, herein we carry out atomistic molecular dynamics simulations for single-stranded DNAs translocating between two pristine or doped carbon nanotube (CNT) electrodes. Specifically, we consider the substitutional nitrogen doping of capped CNT (capCNT) electrodes and perform two types of molecular dynamics simulations for the entrapped and translocating single-stranded DNAs. We find that the substitutional nitrogen doping of capCNTs stabilizes the edge-on nucleobase configurations rather than the original face-on ones and slows down the DNA translocation speed by establishing hydrogen bonds between the N dopant atoms and nucleobases. Due to the enhanced interactions between DNAs and N-doped capCNTs, the duration time of nucleobases within the nanogap was extended by up to ~ 290 % and the fluctuation of the nucleobases was reduced by up to ~ 70 %. Given the possibility to be combined with extrinsic light or gate voltage modulation methods, the current work demonstrates that the substitutional nitrogen doping is a promising direction for the control of DNA translocation dynamics through a nanopore or nanogap based of carbon nanomaterials.Comment: 11 pages, 4 figure