475 research outputs found
Reagan Brenneman
No full textPhotograph of Reagan Brenneman in office. Ms. Brenneman is a trustee of the S.J. Quinney College of Law and currently practices in San Diego
Reagan Brenneman and Leslie Morley
No full textPhotograph of Regan Brenneman (left) and Leslie Morley
Principal component analysis of MCG-06-30-15 with XMM-Newton
No full textWe analyse the spectral variability of MCG-06-30-15 with 600 k s of XMM-Newton data, including 300 k s of new data from the joint XMM-Newton and NuSTAR 2013 observational campaign. We use principal component analysis to find high-resolution, model-independent spectra of the different variable components of the spectrum. We find that over 99 per cent of the variability can be described by just three components, which are consistent with variations in the normalization of the power-law continuum (similar to 97 per cent), the photon index (similar to 2 per cent) and the normalization of a relativistically blurred reflection spectrum (similar to 0.5 per cent). We also find a fourth significant component but this is heavily diluted by noise, and we can attribute all the remaining spectral variability to noise. All three components are found to be variable on time-scales from 20 down to 1 k s, which corresponds to a distance from the central black hole of less than 70 gravitational radii. We compare these results with those derived from spectral fitting, and find them to be in very good agreement with our interpretation of the principal components. We conclude that the observed relatively weak variability in the reflected component of the spectrum of MCG-06-30-15 is due to the effects of light-bending close to the event horizon of the black hole, and demonstrate that principal component analysis is an effective tool for analysing spectral variability in this regime
The effect of beaver (Castor canadensis) dam removal on total phosphorus concentration in Taylor Creek and Wetland, South Lake Tahoe, California
No full textThesis (M.S.)--Humboldt State University, Natural Resources, 2007Taylor Creek is located in the Lake Tahoe basin and drains into Lake Tahoe. A beaver colony in Taylor Wetland has built 14 dams along Taylor Creek and in the wetland, creating nine beaver ponds upstream. All of the dams in the main channel of Taylor Creek are destroyed annually in early fall by United States Department of Agriculture Forest Service to allow kokanee salmon (Onchorynchus nerka) to spawn. In addition, flows from Fallen Leaf Dam, located upstream of Taylor Wetland, are increased to supply ample flows for spawning (United States Department of Agriculture 1981). To determine whether beaver activity, specifically the creation of beaver dams and ponds, improve water clarity by reducing the amount of total phosphorus entering Lake Tahoe, water samples were taken before and after beaver dam removal at sites upstream from beaver influence (control sites) and downstream from beaver pond sites (impacted sites). Results were analyzed using multiple linear regression models and mixed-effect models with site random effects for intercept and covariate coefficients. The mean total phosphorus concentration for control sites before and after dam removal was 51.0??g/l and 64.5??g/l, respectively. The impacted sites increased from 70.4 ??g/l to 170.5??g/l (p =\ud
0.1517). This study implies that the presence of beaver ponds in Taylor Creek could improve water quality by reducing the phosphorus load entering Lake Tahoe when flows are increased from Fallen Leaf Dam.City of Arcata grant number 1.22-4512\ud
US Forest Servic
Examination of physical, chemical, and microbiological water quality parameters in the Lower Van Duzen River Basin
No full textThesis (M.S.)--Humboldt State University, Natural Resources: Wastewater Utilization Program, 2009The purpose of this study is to provide chemical, physical, and microbiological water quality baseline data for the lower Van Duzen River Basin mandated by California Regional Water Quality Control Board. Water quality data were collected from October 2006 to April 2008, and included temperature, dissolved oxygen, pH, conductivity, total suspended solids, turbidity, and fecal coliforms. Data were collected from monitoring sites on five tributaries (Wolverton Gulch, Yager Creek, Cummings Creek, Hely Creek, and Grizzly Creek) and two sites on the mainstem Van Duzen River. All sampling parameters were measured using approved Environmental Protection Agency standard methods. Water temperature exceeded water quality standards during the warm summer months in Yager Creek and the Van Duzen River. Fecal coliform concentrations exceeded standards of less than 200 CFU/100 ml at Wolverton Gulch, Yager Creek, Grizzly Creek, and the Van Duzen River during significant rainstorms. However, levels were never exceeded during warm summer months when United States Environmental Protection Agency full body contact standards would most likely occur. Water quality standards for dissolved oxygen, pH, and conductivity levels were met at all sampling sites. The analysis of turbidity data will be used to assist the North Coast Regional Water Quality Control Board in determining baseline conditions required for development of water quality standards. Levels of total suspended solids exceeded water quality standards following rainstorms, but did not exceed standards during periods of no rainfall. Water quality monitoring in the lower Van Duzen River Basin should continue to focus on analysis of suspended sediment to determine the duration and frequency of events when levels are exceeded. Tributaries to the lower Van Duzen River should continue to be managed as coldwater refugia for aquatic species during the warm summer months
The effect of beaver (Castor canadensis) dam removal on total phosphorus concentration in Taylor Creek and Wetland, South Lake Tahoe, California
No full textTaylor Creek is located in the Lake Tahoe basin and drains into Lake Tahoe. A beaver colony in Taylor Wetland has built 14 dams along Taylor Creek and in the wetland, creating nine beaver ponds upstream. All of the dams in the main channel of Taylor Creek are destroyed annually in early fall by United States Department of Agriculture Forest Service to allow kokanee salmon (Onchorynchus nerka) to spawn. In addition, flows from Fallen Leaf Dam, located upstream of Taylor Wetland, are increased to supply ample flows for spawning (United States Department of Agriculture 1981). To determine whether beaver activity, specifically the creation of beaver dams and ponds, improve water clarity by reducing the amount of total phosphorus entering Lake Tahoe, water samples were taken before and after beaver dam removal at sites upstream from beaver influence (control sites) and downstream from beaver pond sites (impacted sites). Results were analyzed using multiple linear regression models and mixed-effect models with site random effects for intercept and covariate coefficients. The mean total phosphorus concentration for control sites before and after dam removal was 51.0μg/l and 64.5μg/l, respectively. The impacted sites increased from 70.4 μg/l to 170.5μg/l (p = 0.1517). This study implies that the presence of beaver ponds in Taylor Creek could improve water quality by reducing the phosphorus load entering Lake Tahoe when flows are increased from Fallen Leaf Dam.Thesis (M.S.)--Humboldt State University, Natural Resources, 2007application/pd
Long-term wind-driven X-ray spectral variability of NGC 1365 with Swift
No full textWe present long-term (months–years) X-ray spectral variability of the Seyfert 1.8 galaxy NGC 1365 as observed by Swift, which provides well-sampled observations over a much longer time-scale (six years) and a much larger flux range than is afforded by other observatories. At very low luminosities, the spectrum is very soft, becoming rapidly harder as the luminosity increases and then, above a particular luminosity, softening again. At a given flux level, the scatter in hardness ratio is not very large, meaning that the spectral shape is largely determined by the luminosity. The spectra were therefore summed in luminosity bins and fitted with a variety of models. The best-fitting model consists of two power laws, one unabsorbed and another, more luminous, which is absorbed. In this model, we find a range of intrinsic 0.5–10.0 keV luminosities of approximately 1.1–3.5 erg s?1, and a very large range of absorbing columns, of approximately 1022–1024 cm?2. Interestingly, we find that the absorbing column decreases with increasing luminosity, but that this result is not due to changes in ionization. We suggest that these observations might be interpreted in terms of a wind model in which the launch radius varies as a function of ionizing flux and disc temperature and therefore moves out with increasing accretion rate, i.e. increasing X-ray luminosity. Thus, depending on the inclination angle of the disc relative to the observer, the absorbing column may decrease as the accretion rate goes up. The weaker, unabsorbed, component may be a scattered component from the wind
The effects of selected antibiotics on nitrogen uptake by Spirodela punctata
No full textThesis (M.S.)--Humboldt State University, Natural Resources: Wastewater Utilization Program, 2010The purpose of this study was to determine the effects of nitrogenous compound removal by the aquatic macrophyte, Spirodela punctata, when exposed to three selected antibiotics. Recent research has shown that certain antibiotics target the chloroplasts of aquatic species such as Lemna and Myriophyllum. Studies have demonstrated antibiotic toxicity to Lemna gibba at concentrations as low as 10 ??g/L. Meanwhile, antibiotic concentrations in domestic wastewater lie in the nanogram to microgram range with an average of approximately 50 ??g/L.\ud
In this study, Spirodela punctata was grown in a mineral salts medium containing the antibiotics chlortetracycline, lomefloxacin, and sulfamethoxazole in concentrations ranging from 10 ??g/L to 300 ??g/L. Fronds were allowed to grow in the medium for seven, fourteen, and twenty-one day periods. Following the growth periods, the medium was analyzed for nitrate and total nitrogen concentrations. Dry weights of fronds were taken and the dried plant material was analyzed for Total Kjeldahl Nitrogen (TKN) content.\ud
Effective concentrations (EC25 and EC50) that impacted total nitrogen and nitrate removal from the growth medium as well as dry weights and Total Kjeldahl Nitrogen of the plant tissue were calculated. Of the antibiotics tested, chlortetracycline had the most \ud
significant responses. The antibiotic reduced nitrate and total nitrogen removal from the medium and decreased plant biomass. For nitrate removal chlortetracycline had an EC25 of 32 ??g/L after three weeks of exposure. Dry weight EC25 for chlortetracycline was 73 ??g/L after seven days of exposure to the antibiotic. Control treatments containing the antibiotic and no plant material had similar results indicating that the compounds added nitrogen.\ud
Conversely, other compounds tested resulted in very few significant responses. Lomefloxacin only showed significance for nitrate removal during week two and total nitrogen for week one. Surprisingly, the antibiotic seemed to stimulate the ability of Spirodela punctata to remove total nitrogen during the first week of exposure. Sulfamethoxazole had only one significant response during the test period. The combination of the three antibiotics resulted in only a reduction in nitrate removal during the first week after which there was no significant effect.\ud
Overall, selected antibiotics had little direct effect on ability of Spirodela punctata to remove nitrogenous compounds. However, with respect to chlortetracycline, the reduction in the production of biomass resulted in the reduction in nitrate and total nitrogen removal. This reduction in biomass is perhaps the greatest impact on S. punctata???s ability to remove nitrogenous compounds from wastewater
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