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Articles 841 - 870 of 4602

Full-Text Articles in Physical Sciences and Mathematics

A 3d Unstructured-Grid Model For Chesapeake Bay: Importance Of Bathymetry, Fei Ye, Yinglong J. Zhang, Harry V. Wang, Marjorie A.M. Friedrichs, Isaac D. Irby, Eli Alteljevich, Arnaldo Valle-Levinson, Zhengui Wang, Hai Huang, Jian Shen, Jiabi Du Jul 2018

A 3d Unstructured-Grid Model For Chesapeake Bay: Importance Of Bathymetry, Fei Ye, Yinglong J. Zhang, Harry V. Wang, Marjorie A.M. Friedrichs, Isaac D. Irby, Eli Alteljevich, Arnaldo Valle-Levinson, Zhengui Wang, Hai Huang, Jian Shen, Jiabi Du

VIMS Articles

We extend the 3D unstructured-grid model previously developed for the Upper Chesapeake Bay to cover the entire Bay and its adjacent shelf, and assess its skill in simulating saltwater intrusion and the coastal plume. Recently developed techniques, including a flexible vertical grid system and a 2nd-order, monotone and implicit transport solver are critical in successfully capturing the baroclinic responses. Most importantly, good accuracy is achieved through an accurate representation of the underlying bathymetry, without any smoothing. The model in general exhibits a good skill for all hydrodynamic variables: the averaged root-mean-square errors (RMSE‟s) in the Bay are 9 cm for …

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Role Of Sediment Resuspension On Estuarine Suspended Particulate Mercury Dynamics, Ea Seelen, Grace M. Massey, Rp Mason Jul 2018

Role Of Sediment Resuspension On Estuarine Suspended Particulate Mercury Dynamics, Ea Seelen, Grace M. Massey, Rp Mason

VIMS Articles

Coastal sediments are an important site for transient and long-term mercury (Hg) storage, and they foster a geochemical environment optimal for Hg methylation. Therefore, efforts have been taken to constrain the role of sediments as a source of methylmercury (MeHg) to the estuarine water column. This study employed the Gust Microcosm Erosion Core system capable of quantifying particle removal from undisturbed cores under measurable shear stress conditions to assess particulate Hg and MeHg exchange between sediments and the water column. Samples were collected from organic-rich and organic-poor sediment types from the mid- and lower Delaware Bay. It was found that …

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Asymmetric Hillslope Erosion Following Wildfire In Fourmile Canyon, Colorado, Edward R. Abrahams, James M. Kaste, William Ouimet, David P. Dethier Jul 2018

Asymmetric Hillslope Erosion Following Wildfire In Fourmile Canyon, Colorado, Edward R. Abrahams, James M. Kaste, William Ouimet, David P. Dethier

Arts & Sciences Articles

Infrequent, high-magnitude events cause a disproportionate amount of sediment transport on steep hillslopes, but few quantitative data are available that capture these processes. Here we study the influence of wildfire and hillslope aspect on soil erosion in Fourmile Canyon, Colorado. This region experienced the Fourmile Fire of 2010, strong summer convective storms in 2011 and 2012, and extreme flooding in September 2013. We sampled soils shortly after these events and use fallout radionuclides to trace erosion on polar- and equatorial-facing burned slopes and on a polar-facing unburned slope. Because these radionuclides are concentrated in the upper decimeter of soil, soil …

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Forecasting Coastal Water Levels In Virginia, Center For Coastal Resources Management, Virginia Institute Of Marine Science Jul 2018

Forecasting Coastal Water Levels In Virginia, Center For Coastal Resources Management, Virginia Institute Of Marine Science

Reports

Rivers & Coast is a periodic publication of the Center for Coastal Resources Management, Virginia Institute of Marine Science. The goal of Rivers & Coast is to keep readers well informed of current scientific understanding behind key environmental issues related to watershed rivers and coastal ecosystems of the Chesapeake Bay.

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An Updated Model For Estimating The Tmdl-Related Benefits Of Oyster Reef Restoration Harris Creek, Maryland, Usa, M. Lisa Kellogg, Mark J. Brush, Jeff C. Cornwell Jun 2018

An Updated Model For Estimating The Tmdl-Related Benefits Of Oyster Reef Restoration Harris Creek, Maryland, Usa, M. Lisa Kellogg, Mark J. Brush, Jeff C. Cornwell

Reports

In 2014, a user-friendly, web-accessible model was developed that allowed restoration practitioners and resource managers to easily estimate the TMDLrelated benefits of oyster reef (Crassostrea virginica) restoration per unit area, run restoration scenarios in Harris Creek, MD to optimize restoration planning and implementation, and calculate the benefits of the chosen plan. The model was rooted in scientifically defensible data and was readily transferrable to systems throughout the Chesapeake Bay and Eastern Shore. The model operated in five vertically well-mixed boxes along the main axis of the creek. Exchanges among creeks were computed using a tidal prism approach and were compared …

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Usability, Efficiency And Security Of Personal Computing Technologies, Nancy Carter Jun 2018

Usability, Efficiency And Security Of Personal Computing Technologies, Nancy Carter

Dissertations, Theses, and Masters Projects

New personal computing technologies such as smartphones and personal fitness trackers are widely integrated into user lifestyles. Users possess a wide range of skills, attributes and backgrounds. It is important to understand user technology practices to ensure that new designs are usable and productive. Conversely, it is important to leverage our understanding of user characteristics to optimize new technology efficiency and effectiveness. Our work initially focused on studying older users, and personal fitness tracker users. We applied the insights from these investigations to develop new techniques improving user security protections, computational efficiency, and also enhancing the user experience. We offer …

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Topological Changes Of Wave Functions Associated With Hamiltonian Monodromy, C. Chen, John B. Delos Jun 2018

Topological Changes Of Wave Functions Associated With Hamiltonian Monodromy, C. Chen, John B. Delos

Arts & Sciences Articles

Almost everything that happens in classical mechanics also shows up in quantum mechanics when we know where to look for it. A phenomenon in classical mechanics involves topological changes in action-angle loops as a result of passage around a “monodromy circuit.” This phenomenon is known by the short name “Hamiltonian monodromy” (or, more ponderously, “nontrivial monodromy of action and angle variables in integrable Hamiltonian systems”). In this paper, we show a corresponding change in quantum wave functions: These wave functions change their topological structure in the same way that the corresponding classical action-angle loops change.

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Understanding And Enriching Randomness Within Resource-Constrained Devices, Kyle Wallace Jun 2018

Understanding And Enriching Randomness Within Resource-Constrained Devices, Kyle Wallace

Dissertations, Theses, and Masters Projects

Random Number Generators (RNG) find use throughout all applications of computing, from high level statistical modeling all the way down to essential security primitives. A significant amount of prior work has investigated this space, as a poorly performing generator can have significant impacts on algorithms that rely on it. However, recent explosive growth of the Internet of Things (IoT) has brought forth a class of devices for which common RNG algorithms may not provide an optimal solution. Furthermore, new hardware creates opportunities that have not yet been explored with these devices. in this Dissertation, we present research fostering deeper understanding …

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Role Of Baroclinic Processes On Flushing Characteristics In A Highly Stratified Estuarine System, Mobile Bay, Alabama, Jiabi Du, Kyeong Park, Jian Shen, Et Al Jun 2018

Role Of Baroclinic Processes On Flushing Characteristics In A Highly Stratified Estuarine System, Mobile Bay, Alabama, Jiabi Du, Kyeong Park, Jian Shen, Et Al

VIMS Articles

Flushing of an estuary quantifies the overall water exchange between the estuary and coastal ocean and is crucially important for water quality as well as biological and geochemical processes within the system. Flushing times and freshwater age in Mobile Bay were numerically calculated under realistic and various controlled forcing conditions. Their responses to external forcing were explained by the three‐dimensional characteristics of general circulation in the system. The flushing time ranges from 10 to 33 days under the 25th–75th percentile river discharges, nearly half of the previous estimates based on barotropic processes only, suggesting the important contribution of baroclinic processes. …

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Low-Cost Wave Characterization Modules For Oil Spill Response, E. D. Skinner, M. M. Rooney, Mark K. Hinders Jun 2018

Low-Cost Wave Characterization Modules For Oil Spill Response, E. D. Skinner, M. M. Rooney, Mark K. Hinders

Arts & Sciences Articles

Marine oil spills can be remediated by mechanical skimmers in calm waters, but performance degrades with increased wave height. We have developed and demonstrated a system that quantifies local wave characteristics with an uncertainty of four inches of heave. Our system is intended for the measurement of wave characteristics during oil spill recovery. It conveys this information to coordinators and responders in real time via WiFi and remote reporting through a satellite network. This information will allow for enhanced situational awareness during an oil spill response, assisting stakeholders and optimizing mechanical skimming operations. Our wave characterization module (WCM) uses accelerometer …

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Effects Of Marsh Edge Erosion In Coupled Barrier Island-Marsh Systems And Geometric Constraints On Marsh Evolution, Rebecca Lauzon, A Brad Murray, Laura J Moore, David C. Walters, Matthew L. Kirwan, Sergio Fagherazzi, Jun 2018

Effects Of Marsh Edge Erosion In Coupled Barrier Island-Marsh Systems And Geometric Constraints On Marsh Evolution, Rebecca Lauzon, A Brad Murray, Laura J Moore, David C. Walters, Matthew L. Kirwan, Sergio Fagherazzi,

VIMS Articles

Sand washed across barrier islands during storms (called overwash) provides sediment for salt marshes behind those islands, and can allow a marsh which otherwise would drown to grow vertically fast enough to keep up with sea level. We use a barrier island-marsh evolution model (GEOMBEST+) to see what effect marsh edge erosion by waves has on overwash-supported marshes. Consistent with previous research, we find that wave erosion can make marshes more resilient by freeing sediment that can be used elsewhere on the marsh surface. We add that horizontal erosion of the marsh edge provides more sediment per volume eroded than …

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A Terbium Chlorobismuthate(Iii) Double Salt: Synthesis, Structure, And Photophysical Properties, John C. Ahern, Aaron D. Nicholas, Andrew W. Kelly, Benny Chan, Robert D. Pike, Howard Patterson Jun 2018

A Terbium Chlorobismuthate(Iii) Double Salt: Synthesis, Structure, And Photophysical Properties, John C. Ahern, Aaron D. Nicholas, Andrew W. Kelly, Benny Chan, Robert D. Pike, Howard Patterson

Arts & Sciences Articles

We report on the structure and luminescence of a double salt trivalent rare earth ion acceptor, Tb3+, with octahedral [BiCl6]3– donor clusters. The novel TbBiCl6·14H2O (1) was prepared from aqueous BiOCl and TbCl3·6H2O. The crystal structure of compound 1 exhibits isolated [BiCl6]3– and [Tb(OH2)8]3+ clusters. Luminescence data show energy transfer from octahedral chlorobismuthate(III) clusters to rare earth metal ions. Density Functional Theory (DFT) calculations show distinctly different emission pathways at high and low excitation energies.

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Probing Molecular Dynamics With Hyperpolarized Ultrafast Laplace Nmr Using A Low-Field, Single-Sided Magnet, Jared N. King, Alfredo Fallorina, Justin Yu, Et Al., Tyler K. Meldrum Jun 2018

Probing Molecular Dynamics With Hyperpolarized Ultrafast Laplace Nmr Using A Low-Field, Single-Sided Magnet, Jared N. King, Alfredo Fallorina, Justin Yu, Et Al., Tyler K. Meldrum

Arts & Sciences Articles

Laplace NMR (LNMR) offers deep insights on diffusional and rotational motion of molecules. The so-called “ultrafast” approach, based on spatial data encoding, enables one to carry out a multidimensional LNMR experiment in a single scan, providing from 10 to 1000-fold acceleration of the experiment. Here, we demonstrate the feasibility of ultrafast diffusion–T2 relaxation correlation (D–T2) measurements with a mobile, low-field, relatively low-cost, single-sided NMR magnet. We show that the method can probe a broad range of diffusion coefficients (at least from 10−8 to 10−12 m2 s−1) and reveal multiple components of fluids in heterogeneous …

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Section: 01 Line Frame: 06, 27 August 2017: Aerial Imagery Acquired To Monitor The Distribution And Abundance Of Submerged Aquatic Vegetation In Chesapeake Bay And Coastal Bays, Robert J. Orth, David J. Wilcox, Jennifer R. Whiting, Anna K. Kenne, Erica R. Smith Jun 2018

Section: 01 Line Frame: 06, 27 August 2017: Aerial Imagery Acquired To Monitor The Distribution And Abundance Of Submerged Aquatic Vegetation In Chesapeake Bay And Coastal Bays, Robert J. Orth, David J. Wilcox, Jennifer R. Whiting, Anna K. Kenne, Erica R. Smith

Data

Multispectral aerial imagery acquired in 2017 to monitor the distribution and abundance of submerged aquatic vegetation in Chesapeake Bay and coastal bays

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Associated Dataset: Impacts Of Atmospheric Nitrogen Deposition And Coastal Nitrogen Fluxes On Oxygen Concentrations In Chesapeake Bay, Fei Da, Marjorie A.M. Friedrichs, Pierre St-Laurent Jun 2018

Associated Dataset: Impacts Of Atmospheric Nitrogen Deposition And Coastal Nitrogen Fluxes On Oxygen Concentrations In Chesapeake Bay, Fei Da, Marjorie A.M. Friedrichs, Pierre St-Laurent

Data

The dataset includes model outputs used in publication Da et al. (2018), which used the Estuarine-Carbon-Biogeochemistry model embedded in the Regional-Ocean-Modeling-System (ChesROMS-ECB) to examine the relative impact of direct atmospheric dissolved inorganic nitrogen (DIN) deposition and DIN from the continental shelf on the Chesapeake Bay dissolved oxygen. Model simulations highlight that DIN from the atmosphere has roughly the same impact on hypoxia as the same gram-for-gram change in riverine DIN loading. DIN concentrations on the continental shelf has a similar overall impact on hypoxia as DIN from the atmosphere.

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Section: 01 Line Frame: 01, 18 October 2017: Aerial Imagery Acquired To Monitor The Distribution And Abundance Of Submerged Aquatic Vegetation In Chesapeake Bay And Coastal Bays, Robert J. Orth, David J. Wilcox, Jennifer R. Whiting, Anna K. Kenne, Erica R. Smith Jun 2018

Section: 01 Line Frame: 01, 18 October 2017: Aerial Imagery Acquired To Monitor The Distribution And Abundance Of Submerged Aquatic Vegetation In Chesapeake Bay And Coastal Bays, Robert J. Orth, David J. Wilcox, Jennifer R. Whiting, Anna K. Kenne, Erica R. Smith

Data

Multispectral aerial imagery acquired in 2017 to monitor the distribution and abundance of submerged aquatic vegetation in Chesapeake Bay and coastal bays

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Antineutrino Charged-Current Reactions On Hydrocarbon With Low Momentum Transfer, Minerva Collaboration, L. Aliaga, Michael Kordosky, Jeffrey K. Nelson, A. Norrick, E. Valencia, Et Al. Jun 2018

Antineutrino Charged-Current Reactions On Hydrocarbon With Low Momentum Transfer, Minerva Collaboration, L. Aliaga, Michael Kordosky, Jeffrey K. Nelson, A. Norrick, E. Valencia, Et Al.

Arts & Sciences Articles

We report on multinucleon effects in low momentum transfer (< 0.8 GeV/c) antineutrino interactions on plastic (CH) scintillator. These data are from the 2010-2011 antineutrino phase of the MINERvA experiment at Fermilab. The hadronic energy spectrum of this inclusive sample is well described when a screening effect at a low energy transfer and a two-nucleon knockout process are added to a relativistic Fermi gas model of quasielastic, Delta resonance, and higher resonance processes. In this analysis, model elements introduced to describe previously published neutrino results have quantitatively similar benefits for this antineutrino sample. We present the results as a double-differential cross section to accelerate the investigation of alternate models for antineutrino scattering off nuclei.

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Host And Symbionts In Pocillopora Damicornis Larvae Display Different Transcriptomic Responses To Ocean Acidification And Warming, Emily B. Rivest, Morgan B. Kelly, Melissa B. Debiasse, Gretchen E. Hofmann May 2018

Host And Symbionts In Pocillopora Damicornis Larvae Display Different Transcriptomic Responses To Ocean Acidification And Warming, Emily B. Rivest, Morgan B. Kelly, Melissa B. Debiasse, Gretchen E. Hofmann

VIMS Articles

As global ocean change progresses, reef-building corals and their early life history stages will rely on physiological plasticity to tolerate new environmental conditions. Larvae from brooding coral species contain algal symbionts upon release, which assist with the energy requirements of dispersal and metamorphosis. Global ocean change threatens the success of larval dispersal and settlement by challenging the performance of the larvae and of the symbiosis. In this study, larvae of the reef-building coral Pocillopora damicornis were exposed to elevated pCO2 and temperature to examine the performance of the coral and its symbionts in situ and better understand the mechanisms of …

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Simple Parameterized Models For Predicting Mobility, Burial And Re-Exposure Of Underwater Munitions. Serdp Final Report Mr-2224, Carl Friedrichs, Sarah E. Rennie, Alan Brandt May 2018

Simple Parameterized Models For Predicting Mobility, Burial And Re-Exposure Of Underwater Munitions. Serdp Final Report Mr-2224, Carl Friedrichs, Sarah E. Rennie, Alan Brandt

Reports

A compilation of 761 observations of scour-induced burial and 406 observations of initiation of motion of UXO-like objects are presented. The main factors that increase the scour-induced burial-to-diameter ratio (B/D) under (i) currents and (ii) waves are the (i) Shields parameter (S) and (ii) Keulegan-Carpenter number. For cylinders under waves, B/D additionally increases as the current component parallel to wave orbitals decreases, as S increases, and as the angle between wave orbitals and a cylinder’s axis increases. Cylinders bury most, then spheres, and conical frustums bury least. Simple models dependent on these variables explain 85% of observed variance in B/D. …

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Projecting Shifts In Thermal Habitat For 686 Species On The North American Continental Shelf, J. W. Morley, R. L. Selden, Robert J. Latour, T. L. Frolicher, R. J. Seagraves, M. L. Pinsky May 2018

Projecting Shifts In Thermal Habitat For 686 Species On The North American Continental Shelf, J. W. Morley, R. L. Selden, Robert J. Latour, T. L. Frolicher, R. J. Seagraves, M. L. Pinsky

VIMS Articles

Recent shifts in the geographic distribution of marine species have been linked to shifts in preferred thermal habitats. These shifts in distribution have already posed challenges for living marine resource management, and there is a strong need for projections of how species might be impacted by future changes in ocean temperatures during the 21st century. We modeled thermal habitat for 686 marine species in the Atlantic and Pacific oceans using long-term ecological survey data from the North American continental shelves. These habitat models were coupled to output from sixteen general circulation models that were run under high (RCP 8.5) and …

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Virginia Game Fish Tagging Program Annual Report 2017, Susanna Musick, Lewis Gillingham May 2018

Virginia Game Fish Tagging Program Annual Report 2017, Susanna Musick, Lewis Gillingham

Reports

Through 2017, the Virginia Game Fish Tagging Program (VGFTP) has maintained a 22-year database of records for tagged and recaptured fish. The program is a cooperative project of the Virginia Saltwater Fishing Tournament (VSFT) under the Virginia Marine Resources Commission-(VMRC) and the Virginia Institute of Marine Science (VIMS) of the College of William and Mary (under the VIMS Marine Advisory Program).

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Evaluation Of Population Structure And The Interspecific Relationship Of Striped Marlin (Kajikia Audax) And White Marlin (K. Albida) Based On Traditional Or Genome-Wide Molecular Markers, Nadya Mamoozadeh Apr 2018

Evaluation Of Population Structure And The Interspecific Relationship Of Striped Marlin (Kajikia Audax) And White Marlin (K. Albida) Based On Traditional Or Genome-Wide Molecular Markers, Nadya Mamoozadeh

Dissertations, Theses, and Masters Projects

The istiophorid billfishes (marlins, spearfishes, and sailfish) are highly migratory pelagic fishes exhibiting broad and continuous spatial distributions in the Atlantic, Pacific, and Indian oceans. These species are targeted by a number of recreational, commercial, artisanal, and subsistence fisheries worldwide, and are also caught as bycatch in pelagic longline fisheries targeting tunas and swordfish. Though stock assessments have not been conducted for all istiophorids, assessments available for some species indicate that many istiophorid stocks are overfished and/or experiencing overfishing. However, the development of stock-specific recovery efforts is often impeded by a lack of information on basic species biology, including stock …

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Monitoring The Abundance Of American Shad And River Herring In Virginia's Rivers - 2017 Annual Report, Eric J. Hilton, Rob Latour, Patrick E. Mcgrath, Brian Watkins, Ashleigh Magee Apr 2018

Monitoring The Abundance Of American Shad And River Herring In Virginia's Rivers - 2017 Annual Report, Eric J. Hilton, Rob Latour, Patrick E. Mcgrath, Brian Watkins, Ashleigh Magee

Reports

This report describes the results of the twentieth year of a continuing study to estimate the relative abundance and assess the status of American shad (Alosa sapidissima) stocks in Virginia by monitoring the spawning runs in the James, York and Rappahannock rivers in spring 2017, evaluating hatchery programs, and contributing to coast-wide assessments (ASMFC 2007). We also report on two fishery-independent monitoring programs, one using staked gillnets in the Rappahannock River (year 2) and the other using anchor gillnets in the Chickahominy River (year 3; a major tributary of the James River),to determine relative abundance and stock structure for the …

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Iron Polypyridyl Catalysts Assembled On Metal Oxide Semiconductors For Heterogeneous Photocatalytic Hydrogen Generation, Nicholas Race Apr 2018

Iron Polypyridyl Catalysts Assembled On Metal Oxide Semiconductors For Heterogeneous Photocatalytic Hydrogen Generation, Nicholas Race

Dissertations, Theses, and Masters Projects

Artificial Photosynthesis (AP) provides a promising method for the conversion of solar energy to chemical fuel in the form of H2 and O2. Development of heterogeneous systems in which H2 evolution catalysts are immobilized on metal oxide semiconductors is imperative for the large-scale implementation of AP systems. This research focuses on the immobilization of an active H2 evolution catalyst on large band gap semiconductors for the development and optimization of a highly active photocatalytic H2 generation system.

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Surface-Enhanced Raman Spectroscopy Studies Of Organic Dyes For Art Conservation And Ph Sensing Applications, Shelle Nicholle Butler Apr 2018

Surface-Enhanced Raman Spectroscopy Studies Of Organic Dyes For Art Conservation And Ph Sensing Applications, Shelle Nicholle Butler

Dissertations, Theses, and Masters Projects

Surface-enhanced Raman scattering (SERS) spectroscopy is a powerful analytical technique with widespread applications. In this work, SERS applications in the realms of art conservation and biosensing are reviewed. First, the theory of this unambiguous and ultrasensitive technique is explained. Next, a review of the pedagogical journey in art conservation research through the lenses of undergraduates is offered in Chapter 2, a chapter recently submitted to the American Chemical Society. Finally, an investigation in biosensing SERS is explored with developing a SERS pH sensitive probe while offering new insight into SERS capabilities and the relationship between analyte and nanoparticle.

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Ratiometric Fluorescent Sensors In Aqueous Environments, Matthew August Mccarron Apr 2018

Ratiometric Fluorescent Sensors In Aqueous Environments, Matthew August Mccarron

Dissertations, Theses, and Masters Projects

Conjugated polymer nanoparticles (CPN) doped with a mercury sensitive dye are able to detect ion concentrations as low as a parts-per-billion within an aqueous environment. Select forms of spirolatam rhodamine dye are capable of selectively undergoing a ring-opening reaction in response to Hg2+ ions. The initial closed form presents as a colorless, non-fluorescent, compound while the opened form results in a colored and highly fluorescent form. The CPNs are also fluorescent, yet at a lower wavelength and can transfer of their energy into the dye molecules via Förster resonance energy transfer. The dye’s reaction with Hg2+ goes unhindered by the …

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Effect Of Pigment Volume Concentration On Physical And Chemical Properties Of Acrylic Emulsion Paints Assessed Using Single-Sided Nmr, Mary Therese Rooney Apr 2018

Effect Of Pigment Volume Concentration On Physical And Chemical Properties Of Acrylic Emulsion Paints Assessed Using Single-Sided Nmr, Mary Therese Rooney

Dissertations, Theses, and Masters Projects

Acrylic emulsion paint is one of the most common media employed by 20th century painters. Since early acrylic paintings have begun to require the attention of conservators, scientists are working to characterize the properties of these paints to facilitate conservation efforts. In this study, we report an investigation of the physical and chemical properties of acrylic emulsion paints using single-sided NMR in conjunction with gloss measurements and scanning electron microscopy coupled with energy dispersive spectrometry. Combining the data from these techniques gives insight into pigment-binder interactions and the acrylic curing process, showing that as pigment concentration is increased in paints, …

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Isotope Shifts In The 7 S → 8 S Transition Of Francium: Measurements And Comparison To Ab Initio Theory, M. R. Kalita, J. A. Behr, (...), Seth Aubin, Et Al. Apr 2018

Isotope Shifts In The 7 S → 8 S Transition Of Francium: Measurements And Comparison To Ab Initio Theory, M. R. Kalita, J. A. Behr, (...), Seth Aubin, Et Al.

Arts & Sciences Articles

We observe the electric-dipole forbidden 7s→8s transition in the francium isotopes 208−211Fr and 213Fr using a two-photon excitation scheme. We collect the atoms online from an accelerator and confine them in a magneto-optical trap for the measurements. In combination with previous measurements of the 7s→7p1/2 transition we perform a King plot analysis. We compare the thus-determined ratio of the field shift constants (1.228 ± 0.019) to results obtained from new ab initio calculations (1.234 ± 0.010).

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Associated Dataset: The Competing Impacts Of Climate Change And Nutrient Reductions On Dissolved Oxygen In Chesapeake Bay, Isaac D. Irby, Marjorie A.M. Friedrichs Apr 2018

Associated Dataset: The Competing Impacts Of Climate Change And Nutrient Reductions On Dissolved Oxygen In Chesapeake Bay, Isaac D. Irby, Marjorie A.M. Friedrichs

Data

This research uses an estuarine-watershed hydrodynamic–biogeochemical modeling system along with projected mid-21st-century changes in temperature, freshwater flow, and sea level rise to explore the impact climate change may have on future Chesapeake Bay dissolved-oxygen (DO) concentrations and the potential success of nutrient reductions in attaining mandated estuarine water quality improvements.

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Microwave Ac Zeeman Force For Ultracold Atoms, C. T. Fancher, A. J. Pyle, A. P. Rotunno, Seth Aubin Apr 2018

Microwave Ac Zeeman Force For Ultracold Atoms, C. T. Fancher, A. J. Pyle, A. P. Rotunno, Seth Aubin

Arts & Sciences Articles

We measure the ac Zeeman force on an ultracold gas of 87Rb due to a microwave magnetic field targeted to the 6.8 GHz hyperfine splitting of these atoms. An atom chip produces a microwave near field with a strong amplitude gradient, and we observe a force over three times the strength of gravity. Our measurements are consistent with a simple two-level theory for the ac Zeeman effect and demonstrate its resonant, bipolar, and spin-dependent nature. We observe that the dressed-atom eigenstates gradually mix over time and have mapped out this behavior as a function of magnetic field and detuning. We …

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