Papers by Randolph Larsen
Scientific Reports, May 1, 2018
Marine and Petroleum Geology, Aug 1, 2013
ABSTRACT The MITAS (Methane in the Arctic Shelf/Slope) expedition was conducted during September,... more ABSTRACT The MITAS (Methane in the Arctic Shelf/Slope) expedition was conducted during September, 2009 onboard the U.S. Coast Guard Cutter (USCGC) Polar Sea (WAGB-11), on the Alaskan Shelf/Slope of the Beaufort Sea. Expedition goals were to investigate spatial variations in methane source(s), vertical methane flux in shallow sediments (<10 mbsf), and methane contributions to shallow sediment carbon cycling. Three nearshore to offshore transects were conducted across the slope at locations approximately 200 km apart in water column depths from 20 to 2100 m. Shallow sediments were collected by piston cores and vibracores and samples were analyzed for sediment headspace methane (CH4), porewater sulfate (SO4 2�), chloride (Cl�), and dissolved inorganic carbon (DIC) concentrations, and CH4 and DIC stable carbon isotope ratios (d13C). Downward SO4 2� diffusion rates estimated from sediment porewater SO4 2� profiles were between �15.4 and �154.8 mmol m�2 a�1 and imply a large spatial variation in vertical CH4 flux between transects in the study region. Lowest inferred CH4 fluxes were estimated along the easternmost transect. Higher inferred CH4 flux rates were observed in the western transects. Sediment headspace d13CCH4 values ranged from �138 to �48&, suggesting strong differences in shallow sediment CH4 cycling within and among sample locations. Measured porewater DIC concentrations ranged from 2.53 mM to 79.39 mM with d13CDIC values ranging from �36.4& to 5.1&. Higher down-core DIC concentrations were observed to occur with lower d13C where an increase in d13CCH4 was measured, indicating locations with active anaerobic oxidation of methane. Shallow core CH4 production was inferred at the two western most transects (i.e. Thetis Island and Halkett) through observations of low d13CCH4 coupled with elevated DIC concentrations. At the easternmost Hammerhead transect and offshore locations, d13CCH4 and DIC concentrations were not coupled suggesting less rapid methane cycling. Results from the MITAS expedition represent one of the most comprehensive studies of methane source(s) and vertical methane flux in shallow sediments of the U.S. Alaskan Beaufort Shelf to date and show geospatially variable sediment methane flux that is highly influenced by the local geophysical environment.
Clinical assessment of breast cancer tumors has shown that androgen receptor (AR) is expressed in... more Clinical assessment of breast cancer tumors has shown that androgen receptor (AR) is expressed in more than 75% of cases, independent of molecular subtype. Specifically, clinical studies have shown that estrogen receptor (ER) and AR discordance correlates with endocrine resistance. Preclinical studies show that downregulation of ER results in a lack of estrogen mediated growth which is concurrent with upregulation of AR and its mediated gene targets. In addition, forced expression of AR was shown to induce resistance to tamoxifen, even when estrogen receptor was still expressed. Furthermore, ER positive breast cancer cells made resistant to tamoxifen express higher levels of AR and show sensitivity to abiraterone acetate. Together, these results implicate AR in endocrine resistance and suggest AR as a potential therapeutic target in a subset of these endocrine resistant cancers. The aim of this study was to better understand the role of AR in aromatase inhibitor (AI) resistance through the use of cell lines made resistant to AI through xenograft mouse modeling. In this study, MCF7 cells, MCF7 cells transfected with the human aromatase gene (MCF7Ca), and their aromatase inhibitor (AI) resistant counterparts, were analyzed for changes in AR and ER expression by qPCR and Western blot. Sensitivity of these cells to AR targeting agents was assessed by MTT assay. MCF7Ca cells displayed decreased expression of AR and increased expression of ER when compared to MCF7 cells. AI-resistant cell lines displayed modulation of ER and AR expression when compared to their AI-sensitive counterparts. Upregulation of AR was accompanied with increased AR transcriptional activity, as demonstrated by increased expression of PSA. Treatment of AI-resistant cells with AR targeting agents displayed increased sensitivity when compared to AI-sensitive cells. Together, these results suggest that upregulation of AR may contribute to AI-resistance, and that targeting AR in AI-resistant breast cancer may have therapeutic relevance. Citation Format: Caleb Hunt, Sarah E. Lock, Cynthia E. Shannon, Nichole M. Varela-Gonzalez, Randolph K. Larsen, Amanda J. Schech. Potential role of androgen receptor in aromatase inhibitor resistance. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 315.
... low concentrations of PAHs. Stream biota, such as insect larvae and crustaceans, are also aff... more ... low concentrations of PAHs. Stream biota, such as insect larvae and crustaceans, are also affected adversely, resulting in reduced species diversity in affected areas (Beasley and Kneale, 2002). Single-celled aquatic plants ...
Scientific Reports, Aug 18, 2017
Sulfate reduction plays an important role in altering dissolved organic matter (DOM) in estuarine... more Sulfate reduction plays an important role in altering dissolved organic matter (DOM) in estuarine and coastal sediments, although its role in the production of optically active chromophoric DOM (CDOM) and a subset of fluorescent DOM (FDOM) has not been previously investigated in detail. Freshwater sediment slurries were incubated anaerobically with added sulfate and acetate to promote sulfatereducing bacteria. Ultraviolet visible (UV-Vis) absorbance and 3-dimensional excitation emission matrix (EEM) fluorescence spectra were measured over a five weeks anaerobic dark incubation period. Parallel Factor Analysis (PARAFAC) of FDOM determined components that increased significantly during dark and anaerobic incubation matching three components previously considered of terrestrially-derived or humic-like origin published in the OpenFluor database. The observed FDOM increase was strongly correlated (R 2 = 0.96) with the reduction of sulfate. These results show a direct experimental link between sulfate reduction and FDOM production, which impacts our understanding of coastal FDOM sources and early sediment diagenesis. As 3D fluorescence techniques are commonly applied to diverse systems, these results provide increasing support that FDOM can have many diverse sources not consistently captured by common classifications such as "humic-like" fluorescence.
Environmental Science & Technology, Nov 8, 2001
Excess phytoplankton production, which contributes to hypoxic conditions, is nitrogen limited in ... more Excess phytoplankton production, which contributes to hypoxic conditions, is nitrogen limited in the Chesapeake Bay during the summer months. Therefore, understanding the flux of ammonia by direct deposition to the biologically active surface layer is critical to understanding the nutrient dynamics of the bay. This paper presents the results of a 2-yr study measuring gaseous ammonia (NH 3) and aerosol ammonium (NH 4 +) in Baltimore and Solomons, MD, from which direct atmospheric loading of total ammonia (N t) NH 3 + NH 4 +) to the Chesapeake Bay is estimated. Mean atmospheric concentrations of total ammonia for Baltimore and Solomons were 2.7 (1.7 and 1.0 (0.8 µg of N m-3 , respectively. Monte Carlo estimates of gross dry deposition ranged from <100 to 4900 µg of N m-2 d-1. However, based upon water quality parameters, Monte Carlo estimates of gross volatilization of NH 3 were calculated to range from <100 to 7700 µg of N m-2 d-1. The resulting net air-sea exchange flux varied seasonally from a net deposition into the water during the winter to a net volatilizing into the atmosphere during the summer. A total of 60% of the paired air-water samples had flux estimates that were not significantly different than equilibrium at the 90% confidence interval. The gross deposition, gross volatilization, and net air-sea fluxes were greater and more variable in Baltimore relative to the rural site. Atmospheric ammonia concentrations decrease during the winter at the rural site. However, the net exchange is still into the water due to an exponential decrease in [NH 3 ] eq with temperature. These results indicate that the nitrogen-limited Chesapeake Bay can act as a source of ammonia to the local atmosphere.
Environmental Science & Technology, Mar 22, 2003
Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous pollutants in urban atmospheres. Several P... more Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous pollutants in urban atmospheres. Several PAHs are known carcinogens or are the precursors to carcinogenic daughter compounds. Understanding the contributions of the various emission sources is critical to appropriately managing PAH levels in the environment. The sources of PAHs to ambient air in Baltimore, MD, were determined by using three source apportionment methods, principal component analysis with multiple linear regression, UNMIX, and positive matrix factorization. Determining the source apportionment through multiple techniques mitigates weaknesses in individual methods and strengthens the overlapping conclusions. Overall source contributions compare well among methods. Vehicles, both diesel and gasoline, contribute on average 16-26%, coal 28-36%, oil 15-23%, and wood/other having the greatest disparity of 23-35% of the total (gas- plus particle-phase) PAHs. Seasonal trends were found for both coal and oil. Coal was the dominate PAH source during the summer while oil dominated during the winter. Positive matrix factorization was the only method to segregate diesel from gasoline sources. These methods indicate the number and relative strength of PAH sources to the ambient urban atmosphere. As with all source apportionment techniques, these methods require the user to objectively interpret the resulting source profiles.
Standard Form 298 (Rev. 8-98) Prescribed by ANSI Std. Z39.18 Public reporting burden for this col... more Standard Form 298 (Rev. 8-98) Prescribed by ANSI Std. Z39.18 Public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing this collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden to Department of Defense, Washington Headquarters Services, Directorate for Information Operations and Reports (0704-0188), 1215 Jefferson Davis Highway, Suite 1204, Arlington, VA 22202-4302. Respondents should be aware that notwithstanding any other provision of law, no person shall be subject to any penalty for failing to comply with a collection of information if it does not display a currently valid OMB control number. PLEASE DO NOT RETURN YOUR FORM TO THE ABOVE ADDRESS. 5a. CONTRACT NUMBER a. REPORT 19a. NAME OF RESPONSIBLE PERSON 19b. TELEPHONE NUMBER
PhDT, 2002
This study combines long term measurements of precipitation, gas and aerosols at urban and rural ... more This study combines long term measurements of precipitation, gas and aerosols at urban and rural settings in the mid-Atlantic to provide a holistic analysis of the impact from direct transmission of semi-volatile compounds between the atmosphere and the Chesapeake Bay. Three groups of semi-volatile compounds were investigated, polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), and ammonia. Elevated levels of these contaminants contribute to impairing the Chesapeake Bay water quality. The geometric mean concentrations (and geometric standard deviation) of the total gas phase PAHs (sum of 32 PAHs) were 41 (1.9), 29 (2), and 5.6 (2.2) ng m-3 at Baltimore, Solomons, and Stillpond, respectively. The geometric mean concentrations (and geometric standard deviation) of the Sigma32 particle bound PAHs at Baltimore, Solomons, and Stillpond were 3.2 (1.9), 0.51 (2.1), and 0.74 (1.5) ng m-3, respectively. The geometric mean (and geometric standard deviation) at Baltimore and Stillpond for total PCB concentrations were 435 (2) and 95 (2) pg m-3 in the gas phase, respectively. Mean and arithmetic standard deviations of atmospheric total ammonia concentrations at Baltimore and Solomons were 2.7 +/- 1.7 and 1.0 +/- 0.8 mug N m-3, respectively. Results of three source apportionment models suggested that sources of atmospheric PAHs in Baltimore were vehicles (17 to 22%), coal (26 to 32%), oil (18 to 22%), and wood/other sources (17 to 40%). The net direct fluxes of these compounds to the Chesapeake Bay were calculated from these measurements. The primary mechanism for the transfer of most of these chemicals across the air-water interface was gas exchange. The degraded air and water quality of Baltimore with respect to these compounds resulted in significant fluxes both into and out of the water. For example, fluxes in Baltimore were +/-1000 mug N m-2 d-1 for ammonia, 114 mug m-2 y-1 for the SigmaPCB, and 780, mug m-2 y -1 for fluorene. The magnitude of the net air-water exchange in Baltimore Harbor was greater than in the Chesapeake mainstem. However, when the exchange is normalized to the water column contaminant inventory, it appears that the northern Chesapeake Bay is impacted to a greater degree by direct air-water fluxes.
hypotheses of the study were that PAHs washing off roads would retard the growth of aquatic
Aerosol Science and Technology, Oct 1, 2006
Page 1. Aerosol Science and Technology, 40:781787, 2006 Copyright c American Association for Aer... more Page 1. Aerosol Science and Technology, 40:781787, 2006 Copyright c American Association for Aerosol Research ISSN: 0278-6826 print / 1521-7388 online DOI: 10.1080/ 02786820600596909 Determination of Levoglucosan in Particulate Matter Reference Materials ...
Estuaries and Coasts, 2008
Multi-year nitrogen (N) and phosphorus (P) budgets were developed for the Patuxent River estuary,... more Multi-year nitrogen (N) and phosphorus (P) budgets were developed for the Patuxent River estuary, a seasonally stratified and moderately eutrophic tributary of Chesapeake Bay. Major inputs (point, diffuse, septic, and direct atmospheric) were measured for 13 years during which, large reductions in P and then lesser reductions in N-loading occurred due to wastewater treatment plant improvements. Internal nutrient losses (denitrification and long-term burial of particulate N and P) were measured in tidal marshes and sub-tidal sediments throughout the estuary as were nutrient storage in the water column, sediments, and biota. Nutrient transport between the oligohaline and mesohaline zones and between the Patuxent and Chesapeake Bay was estimated using a salt and water balance model. Several major nutrient recycling terms were directly and indirectly evaluated and compared to new N and P inputs on seasonal and annual timescales. Major findings included: (1) average terrestrial and atmospheric inputs of N and P were very close to the sum of internal losses plus export, suggesting that dominant processes are captured in these budgets; (2) both N and P export were a small fraction (13% and 28%, respectively) of inputs, about half of that expected for N based on water residence times, and almost all exported N and P were in organic forms; (3) the tidal marsh-oligohaline estuary, which by area com-prised~27% of the full estuarine system, removed about 46% and 74% of total annual upland N and P inputs, respectively; (4) recycled N and P were much larger sources of inorganic nutrients than new inputs during warm seasons and were similar in magnitude even during cold seasons; (5) there was clear evidence that major estuarine processes responded rapidly to inter-annual nutrient input variations; (6) historical nutrient input data and nutrient budget data from drought periods indicated that diffuse nutrient sources were dominant and that N loads need to be reduced by about 50% to restore water quality conditions to pre-eutrophic levels.
Pigments Checker is a collection of swatches of historical pigments that offers art professionals... more Pigments Checker is a collection of swatches of historical pigments that offers art professionals, conservation scientists, conservators and fine art photographers, a tool to evaluate and test their imaging and spectroscopic methodologies for pigment identification. "Pigments Checker Free Spectra Database" is an ongoing project that wants to thoroughly characterize each pigment in the collection with a series of spectroscopic and imaging techniques and to make the data open access. This paper presents the free and downloadable database of XRF spectra, adding to the reflectance spectral database already published. The XRF analysis is in agreement with the information provided by the pigments' manufacturers since all of the pigments have XRF spectra consistent with the expected elemental content reported in literature. In addition to elemental characterization by XRF, future analysis with Raman, FT-IR and XRD will be pursued in order to achieve a broader characterization...
Prescribed by ANSI Std. Z39.18 Public reporting burden for this collection of information is esti... more Prescribed by ANSI Std. Z39.18 Public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing this collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden to Department of Defense, Washington Headquarters Services, Directorate for Information Operations and Reports (0704-0188), 1215 Jefferson Davis Highway,
Journal of Chemical Education, 2021
This paper describes and assesses the impact of a new upper-level “scholarly” laboratory model th... more This paper describes and assesses the impact of a new upper-level “scholarly” laboratory model that is part of a four-year scaffolded research skills curriculum at a Carnegie Bachelor’s institution...
Pigments Checker is a collection of swatches of historical pigments that offers art professionals... more Pigments Checker is a collection of swatches of historical pigments that offers art professionals, conservation scientists, conservators and fine art photographers, a tool to evaluate and test their imaging and spectroscopic methodologies for pigment identification. “Pigments Checker Free Spectra Database” is an ongoing project that wants to thoroughly characterize each pigment in the collection with a series of spectroscopic and imaging techniques and to make the data open access. This paper presents the free and downloadable database of XRF spectra, adding to the reflectance spectral database already published. The XRF analysis is in agreement with the information provided by the pigments’ manufacturers since all of the pigments have XRF spectra consistent with the expected elemental content reported in literature. In addition to elemental characterization by XRF, future analysis with Raman, FT-IR and XRD will be pursued in order to achieve a broader characterization of the
: Compound-specific stable isotope analysis (CSIA) was applied to a pentaerythritol ester lubrica... more : Compound-specific stable isotope analysis (CSIA) was applied to a pentaerythritol ester lubricant to determine if predictable fractionation effects could be related to friction stress. A pin-on-disk tribometer was used to expose the lubricant to five doubly-increasing sliding distances (up to 36 km). PCA was used to ordinate multivariate data and test if significant isotopic shifts or FTIR spectral changes could be related to sliding cycles. 13C Isotope ratios only were found to be statistically different (P 0.05) between treatments. PCA gave a primary score (PC1) containing 44% of the 13C-isotopic variability, which correlated exponentially with sliding cycles (r2 = 0.96). A peak, not present in unexposed lubricant, became evident and showed increasing 13C depletion with increasing length of sliding exposure.
Polycyclic aromatic hydrocarbons (PAHs) are a class of chemical compounds that are mostly anthrop... more Polycyclic aromatic hydrocarbons (PAHs) are a class of chemical compounds that are mostly anthropogenic in nature, and they can become persistent organic contaminants in aquatic ecosystems. Runoff from impervious surfaces is one of the many ways contaminants enter the aquatic realm. Three different PAH concentrations were used to investigate the effects on oyster-egg fertilization, embryonic transformation to the D-shell veliger larva, and larvae settlement onto hard substrate. The three different concentrations of PAHs ranged from one that is environmentally relevant to the concentrations found in runoff from road surfaces, another that was tenfold more concentrated, and finally one that was one hundred times more concentrated. The extremely concentrated solution had negative effects on fertilization success after one hour of exposure, while the lesser concentrations showed significant deleterious effects after two hours of exposure. All of the three PAH solutions caused significan...
The hypothesis of the study was that polycyclic aromatic hydrocarbons (PAHs) washing off roads wo... more The hypothesis of the study was that polycyclic aromatic hydrocarbons (PAHs) washing off roads would retard the growth of aquatic life-supporting algae and promote the growth of harmful, toxin-producing algae in estuaries, such as the Chesapeake Bay. Runoff from various road surfaces was tested for PAH concentrations. The tests revealed PAHs but also heavy metals in various concentrations. The research results show that road surface runoff does not seem to affect algae detrimentally after a few days under normal summer conditions. Either the chemicals in the runoff degrade over time or bacteria in the runoff break down the chemical pollutants. In both cases, once the PAHs degrade, they seem to stimulate algal growth. The one exception is Chaetoceros, a beneficial algae, which was negatively affected by both 1 percent and full strength concentrations on newly paved and low traffic asphalt. Since PAH levels were relatively low for those two sites, it is possible that the response was ...
This study combines long term measurements of precipitation, gas and aerosols at urban and rural ... more This study combines long term measurements of precipitation, gas and aerosols at urban and rural settings in the mid-Atlantic to provide a holistic analysis of the impact from direct transmission of semi-volatile compounds between the atmosphere and the Chesapeake Bay. Three groups of semi-volatile compounds were investigated, polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), and ammonia. Elevated levels of these contaminants contribute to impairing the Chesapeake Bay water quality. The geometric mean concentrations (and geometric standard deviation) of the total gas phase PAHs (sum of 32 PAHs) were 41 (1.9), 29 (2), and 5.6 (2.2) ng m-3 at Baltimore, Solomons, and Stillpond, respectively. The geometric mean concentrations (and geometric standard deviation) of the Sigma32 particle bound PAHs at Baltimore, Solomons, and Stillpond were 3.2 (1.9), 0.51 (2.1), and 0.74 (1.5) ng m-3, respectively. The geometric mean (and geometric standard deviation) at Baltimore and Stillpond for total PCB concentrations were 435 (2) and 95 (2) pg m-3 in the gas phase, respectively. Mean and arithmetic standard deviations of atmospheric total ammonia concentrations at Baltimore and Solomons were 2.7 +/- 1.7 and 1.0 +/- 0.8 mug N m-3, respectively. Results of three source apportionment models suggested that sources of atmospheric PAHs in Baltimore were vehicles (17 to 22%), coal (26 to 32%), oil (18 to 22%), and wood/other sources (17 to 40%). The net direct fluxes of these compounds to the Chesapeake Bay were calculated from these measurements. The primary mechanism for the transfer of most of these chemicals across the air-water interface was gas exchange. The degraded air and water quality of Baltimore with respect to these compounds resulted in significant fluxes both into and out of the water. For example, fluxes in Baltimore were +/-1000 mug N m-2 d-1 for ammonia, 114 mug m-2 y-1 for the SigmaPCB, and 780, mug m-2 y -1 for fluorene. The magnitude of the net air-water exchange in Baltimore Harbor was greater than in the Chesapeake mainstem. However, when the exchange is normalized to the water column contaminant inventory, it appears that the northern Chesapeake Bay is impacted to a greater degree by direct air-water fluxes.
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Papers by Randolph Larsen