Report on spectral wave modeling : extended study of the effects of sand mining on the wave regime at Sandbridge, Virginia - Comparison of results using a phase-revolving and a phase-averaging spectral wave model (REF/DIF S and SWAN)

In an earlier report (Boon, 1998), findings were presented from a wave modeling study whose purpose was to investigate the effects of sand mining on the nearshore wave regime at Sandbridge, Virginia (Fig . 1). Using a phase-resolving spectral wave model, REF/DIF S (Kirby and Ozkan, 1992), a representative set of hypothetical storm waves was propagated across a 20 km section of the inner shelf from approximately the 20 m depth contour offshore to the 11 m depth contour inshore . Subsequent simulations were then made that tested local effects of shoaling and refraction on wave heights within a fine-scale subgrid extending from Sandbridge Shoal near the 10 m depth contour to the surf zone immediately in front of Sand bridge (Fig. 1 ). Two test cases were used: Case 1 - Existing bottom configuration based on pre-1998 charted depths, Case 2- Bottom with uniform removal of bed material to a depth of3 meters below grade within a designated borrow area on Sandbridge Shoal

Investigation of Geant4 Simulation of Electron Backscattering

A test of Geant4 simulation of electron backscattering recently published in this journal prompted further investigation into the causes of the observed behaviour. An interplay between features of geometry and physics algorithms implemented in Geant4 is found to significantly affect the accuracy of backscattering simulation in some physics configurations

Porphyra-334, a mycosporine-like amino acid, attenuates UV-induced apoptosis in HaCaT cells

The main aim of the current research was to study the effect of porphyra-334, one of mycosporine-like amino acids (MAAs), well known as UV-absorbing compounds, on UV-induced apoptosis in human immortalized keratinocyte (HaCaT) cells. Due to their UV-screening capacity and ability to prevent UV-induced DNA damage, MAAs have recently attracted considerable attention in both industry and research in pharmacology. Herein, human HaCaT cells were used to determine the biological activities of porphyra-334 by various in vitro assays, including proliferation, apoptosis and Western blot assays. The proliferation rate of UV-irradiated HaCaT cells was significantly decreased compared to the control group. Pretreatment with porphyra-334 markedly attenuated the inhibitory effect of UV and induced a dramatic decrease in the apoptotic rate. Expression of active caspase-3 protein was increased in response to UV irradiation, while caspase-3 levels were similar between cells treated with porphyra-334 and the non-irradiated control group. Taken together, our data suggest that porphyra-334 inhibits UV-induced apoptosis in HaCaT cells through attenuation of the caspase pathway

Validation Test of Geant4 Simulation of Electron Backscattering

Backscattering is a sensitive probe of the accuracy of electron scattering algorithms implemented in Monte Carlo codes. The capability of the Geant4 toolkit to describe realistically the fraction of electrons backscattered from a target volume is extensively and quantitatively evaluated in comparison with experimental data retrieved from the literature. The validation test covers the energy range between approximately 100 eV and 20 MeV, and concerns a wide set of target elements. Multiple and single electron scattering models implemented in Geant4, as well as preassembled selections of physics models distributed within Geant4, are analyzed with statistical methods. The evaluations concern Geant4 versions from 9.1 to 10.1. Significant evolutions are observed over the range of Geant4 versions, not always in the direction of better compatibility with experiment. Goodness-of-fit tests complemented by categorical analysis tests identify a configuration based on Geant4 Urban multiple scattering model in Geant4 version 9.1 and a configuration based on single Coulomb scattering in Geant4 10.0 as the physics options best reproducing experimental data above a few tens of keV. At lower energies only single scattering demonstrates some capability to reproduce data down to a few keV. Recommended preassembled physics configurations appear incapable of describing electron backscattering compatible with experiment. With the support of statistical methods, a correlation is established between the validation of Geant4-based simulation of backscattering and of energy deposition

Quantitative Test of the Evolution of Geant4 Electron Backscattering Simulation

Evolutions of Geant4 code have affected the simulation of electron backscattering with respect to previously published results. Their effects are quantified by analyzing the compatibility of the simulated electron backscattering fraction with a large collection of experimental data for a wide set of physics configuration options available in Geant4. Special emphasis is placed on two electron scattering implementations first released in Geant4 version 10.2: the Goudsmit-Saunderson multiple scattering model and a single Coulomb scattering model based on Mott cross section calculation. The new Goudsmit-Saunderson multiple scattering model appears to perform equally or less accurately than the model implemented in previous Geant4 versions, depending on the electron energy. The new Coulomb scattering model was flawed from a physics point of view, but computationally fast in Geant4 version 10.2; the physics correction released in Geant4 version 10.2p01 severely degrades its computational performance. Evolutions in the Geant4 geometry domain have addressed physics problems observed in electron backscattering simulation in previous publications.Comment: To be published in IEEE Trans. Nucl. Sc

Development of Nanocomposite Powders for the SLS Process to Enhance Mechanical Properties

In an effort to fabricate prototypes with improved mechanical properties in the dual laser sintering process, functionalized graphite nanoplatelets were added to the PA-12 powder to produce a nanocomposite powder. The PA-12 powder was chosen as the matrix polymer because it has features conducive to laser sintering such as relatively low melting temperature and high mechanical properties. The GNPs were oxidized through a nitric acid treatment to improve the interfacial bonding. The resulting nanocomposite powder was layered and sintered by laser without any sign of agglomeration. Although the result is preliminary, it nevertheless shows the suitability of the nanocomposite powder for the laser sintering process.Mechanical Engineerin

Inner continental shelf benthic boundary layer dynamics and suspended sediment transport

An experiment conducted over the shoreface at Duck, North Carolina in 1985 embraced both fair-weather low energy and storm-related high energy conditions. to differentiate the diffusion and advection processes of suspended sediments under the high energy conditions from those under the low energy conditions, numerical modeling and the analysis of field data are exercised. A simple two-layer eddy viscosity wave-current combined boundary layer model is developed. The modeled characteristics of the boundary layer are incorporated with a diffusion equation to give suspended sediment concentration profiles. A velocity scale related to factors other than turbulent diffusion is formulated, representing the diffusion under varying energy conditions. With increasing bed friction, the vertical diffusion of sediment is reduced due to stratification, thus reducing velocity. From the measured suspended sediment concentration profiles, the resuspension coefficient, &\gamma&, shows a tendency to decrease with increased flow intensity, suggesting the role of the armoring effect. The coefficient, &\gamma&, varies between 0.0003 for high-energy conditions and 0.002 for low-energy conditions. The energetics approach to predicted sediment transport overestimates the role of wave transport for the low energy conditions. Cross-correlations between cross-shore velocity and sediment concentration show that the role of wave for the transport under low energy conditions is not substantial. The direction of transport under low energy conditions is governed by the mean current. Under high energy conditions, transport by waves is onshore but superseded by offshore transport by the mean current, resulting in net offshore transport. The energetics model based on the surfzone dynamics underestimates the transport rate by an order of magnitude compared to the depth integration of the average product of mean cross-shore velocity and mean concentration. This indicates that the calibration of the efficiency factors &\epsilon\sb{lcub}\rm s{rcub}& and &\epsilon\sb{lcub}\rm b{rcub}& in an energetics model is essential