Scholarship & Research
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Item The interplay between the central engine and the circumnuclear environment in Compton-thin AGN(Montana State University - Bozeman, College of Letters & Science, 2022) Chalise, Sulov; Chairperson, Graduate Committee: Anne Lohfink; This is a manuscript style paper that includes co-authored chapters.All massive galaxies harbor a supermassive black hole (SMBH) at their galactic center. If these SMBH are actively feeding then they are called Active galactic nuclei (AGN). Their accretion system contains a corona, an accretion disk and an axisymmetric dusty torus. The torus can be connected physically and dynamically to the circumnuclear disk of the galaxy which acts as a molecular gas reservoir for material to be accreted onto the SMBH. Further, AGN can emit radiation from radio up to the gamma rays. The AGN accretion disk emits photons mostly in the optical/UV band which are Compton up-scattered in the corona to generate X-rays. If present, a jet can produce additional high-energy and Synchrotron emission. In some AGN, a huge amount of material can be stripped away from the accretion disk creating an outowing wind. These --radiation pressure, jet, wind etc.--inject energy back into the host galaxy, regulating the SMBH growth. There exist a complex interplay between the AGN feeding and feedback. Understanding this interaction between the central engine and its circumnuclear environment is vital in context of galaxy evolution. My work aims to study this interaction in low to moderately obscured (or Compton-thin) AGN using their broadband multi-epoch X-ray spectra plus other emission bands whenever appropriate. From the spectral analysis of broad-line radio galaxy 3C 109, I was able to constrain its high-energy cutoff for the first time. In another Seyfert galaxy Mrk 926, I was able to explore the origin of its soft excess, and found that a warm coronal origin was slightly preferred. Finally, I performed a joint multi-wavelength analysis with a physical torus model of a sample of Polar-scattered Seyfert 1 galaxies. I utilized their multi-epoch broadband X-ray spectra along with their infrared spectral/photometric data, and was able to constrain their torus properties. Despite being a sample of similar moderately-inclined Compton-thin AGN, I found a complex and varied distribution of gas and dust in their torus.Item Accuracy of saline seep mapping from color infrared aerial photographs(Montana State University - Bozeman, College of Agriculture, 1990) Beyrau, John ArthurItem A study of the polarized infrared spectrum of maleic anhydride(Montana State University - Bozeman, College of Letters & Science, 1963) Layman, Wilbur AllenItem Seasonal forage dry matter production and quality of 29 dryland grasses in Montana(Montana State University - Bozeman, College of Agriculture, 2001) Blunt, Kurtis Russell; Chairperson, Graduate Committee: Dennis CashProducers must have accurate and reliable measurements of both forage production and quality in their pastures. Previous studies with dryland grasses in Montana have mostly been limited to adaptation or yield performance of a few species at a single location. The first objective of this study was to document yield and forage quality characteristics of adapted dryland grass varieties over a three-year period at three separate locations. Another objective was to accurately predict forage quality constituents of numerous dryland forage grasses using near infrared spectroscopy (NIRS). A third objective was to generate predictive models for crude protein (CP), acid detergent fiber (ADF), neutral detergent fiber (NDF), and in vitro digestible dry matter (IVDDM) using date or growing degree days. And finally, the last objective of this study was to demonstrate how forage quality information generated in this study can be useful for future improvement of animal carrying capacity predictions. Twenty-nine dryland grass varieties were established at three Montana locations. Data were collected over a three-year period. Forage production and quality data were gathered under a wide range of climatic conditions. Interactions among years, varieties, and locations illustrated the variability of the climate in Montana and biological differences of varieties at different locations. This study makes a strong case for the use of NIRS technology in estimating forage quality of dryland grasses in Montana. Compared to traditional wet chemistry procedures, NIRS proved to be much faster and generated accurate results. Predictive models using date and growing degree days generated estimates of forage quality similar to NIRS but standard errors associated with model parameters limited statistical differences among varieties for season-long forage quality. However, it was determined that the rates of forage quality decline among many of the varieties studied were different (P < 0.01). The r^2 values for predicted forage quality ranged from 0.39 (Rosana, ADF) to 0.85 (Schwendimar, ADF) for the AGGD models and all were highly significant. Strong negative correlations between yield and quality were not found in this study (-0.3<0.3). ADF and NDF were highly correlated (r>0.79). It appears that with optimal management, both forage production and quality can be. optimized. Preliminary use of this data suggests that energy becomes limiting first as the growing season progresses, followed by intake and protein. Further studies should be devoted to modeling pasture carrying capacity with forage quality data.Item Parameters influencing infrared reflectance of a vegetational canopy(Montana State University - Bozeman, College of Agriculture, 1985) Hoard, Mark WilliamItem Detection and inventory of saline seep using color infrared aerial photographs and video image analysis(Montana State University - Bozeman, College of Agriculture, 1986) Long, Daniel SimpsonItem Diffuse reflectance spectroscopy for the characterization of calcareous glacial till soils from north central Montana(Montana State University - Bozeman, College of Agriculture, 2006) Steward, Genevieve Christine; Chairperson, Graduate Committee: David Brown.Diffuse reflective spectroscopy (DRS) is a method of soil carbon (C) quantification. In this study, the Vis-NIR (350 - 2500 nm) and MIR (2500-25000 nm) regions were evaluated to determine respective predictive accuracies of soil organic and inorganic carbon (SOC and SIC, respectively). The dataset included 315 soil samples of glacial till origin, obtained from six independent farm sites within the Golden Triangle region of Montana, with depths ranging from 0-100 cm. For Vis-NIR analysis, Local vs. Regional vs. Global calibration sets were compared by six-fold cross validation by site of C predictions developed by Partial Least Squares (PLS) regression and Boosted Regression Trees (BRT). First derivative spectral data was used along with four preparation methods: (i) field moist and (ii) dry cores, (iii) 2-mm sieved ("Sieved") and (iv) milled samples (<200-um, "Milled") were used to evaluate the potential application to in-situ analysis. The most accurate SOC predictions were from Milled samples using a Local calibration set. SOC predictions were a result of SOM electronic absorptions within the visible region.