In this thesis, we focus on obtaining and interpreting observational information on (i) the role of multiplicity on the properties of young stars; (ii) the early evolutionary influence of circumstellar disks; and (iii) the nature of accretion in young systems. To facilitate this research, we conducted an extensive multi-epoch high-resolution spectroscopic survey at optical wavelengths (3,200-10,000 A) of ~200 T Tauri stars in the ~2 Myr old Chamaeleon I, and Taurus-Auriga star-forming regions with the Magellan Inamori Kyocera Echelle (MIKE) spectrograph on the Magellan Clay 6.5 m telescope. From the spectroscopic data, we identify eight close binaries and four close triples, of which three and two, respectively, are new discoveries. We find that the multiplicity fraction for Cha I and Tau-Aur are similar to each other, and to the results of field star surveys. The frequency of systems with close companions in our sample is not seen to depend on primary mass or accretion. We probed for evidence of disk braking. We did not see a statistically significant difference between the distribution of rotational velocities with the presence of an inner disk. Also, our findings show that F-K stars in our sample have larger rotational velocities and specific angular momentum than M stars. We also analyzed accretion variability in our sample using the H\alpha 10% width and the CaII-8662 line flux as accretion diagnostics. We find that the maximum extent of accretion variability in our sample was reached on timescale of a few days, indicating that rotation could significantly contribute to the variability.

Graduation date: 1992

Mössbauer spectroscopy, X-ray spectroscopy, SEM, EDX, heat capacity and SQUID measurement were carried out in conjunction with a catalytic study on mixed Fe-Mo oxides, some of which have been used in selective oxidation of certain hydrocarbons. With the specific activity being sensitive to the catalytic particle size and morphology, an aerogel process was employed to prepare seven samples covering Fe/Mo ratios from 1/2 to 2/1and some of the samples were annealed at 300oC and 500oC . Mössbauer data have been analyzed, with each set well fitted to reflect one Fe3+ and two or more non-equivalent Fe2+ sites. There isomer shift, quadruple splitting and molar fraction are analyzed in terms of temperature and Fe/Mo-ratio dependence. The Fe-rich samples exhibit magnetic ordering at low temperatures, revealing multiple sextets corresponding to different magnetic hyperfine fields. Two samples with the Fe:Mo ratio 1:1 and 2:3 were study in more detail their X-ray diffraction pattern reveal that they crystallize with the β-FeMoO4 structure. SEM gives unusual morphology and the material form into hallow sphere with 2um in diameter. EDS confirms that the metal ion is fairly uniformly distributed and close to the nominal values. Finally heat capacity and SQUID measurements confirm the antiferromagnetic phase transition near 13K for the heat treated samples. / "December 2006."

Techniques have been developed for measuring the temperature, stable species concentrations, and atomic radical concentrations during a transient combustion event. They combine the features of direct sampling with two spectroscopic techniques to produce relatively simple diagnostic techniques to obtain time-resolved measurements. In this study, a transient event was provided by a propagating hydrogen/air flame. Stable species were detected downstream of the sampling orifice by electron impact fluorimetry, while temperatures and atomic hydrogen concentrations were measured by atomic resonance absorption spectroscopy. The calculation of stable species concentrations from time-varying fluorescence signals was straightforward, however conversion from absorption measurements to temperatures and atomic radical concentrations required the development of a computer model of the radiation source and the absorption by the sample. The model of the source was validated by comparing predicted and recorded spectra of hydrogen Lyman-α emissions, while the absorption model for the sampled gas was tested by comparing the temperatures predicted by absorption measurements with those recorded at a range of known temperatures. These direct sampling spectroscopic techniques minimize time-history distortions inherent in other direct sampling techniques, and are capable of tracking local temperatures and species concentrations during the passage of a propagating flame front. / Graduation date: 1990

This study was conducted to compare the speciation and behavior of P in soils receiving either different biosolids or inorganic fertilizer, as assessed by sequential chemical extractions, phosphate desorption, and synchrotron X-ray absorption near edge structure (XANES) spectroscopy. The objectives of this study were to i) measure the total amount of organic and inorganic phosphorus removed by chemical extraction method ii) investigate how P desorption kinetics are influenced in biosolids amended soils compared to inorganic fertilizer amended soils; and iii) perform solid state speciation of soil samples before and after chemical extraction and desorption with P K-edge XANES spectroscopy. Soil samples were analyzed that received three different rates of biosolids (16.8, 33.6, and 67.2 Mg ha-1 yr-1) and one inorganic fertilizer application (336 kg N, 224 kg P, and 112 kg K ha-1 yr-1) for 32 years. Both sequential chemical extraction and XANES analysis showed that total amount of P increased in biosolids amended soils (from 5292 to 10945 mg P kg-1) and that it increased with increasing application rate. Sequential chemical extractions showed that the labile portion of total P in inorganic fertilized soil (40 %) was larger than in biosolids applied soils (39 to 27 %). Results from both sequential chemical extraction and XANES analysis showed that NaOH extraction removed the highest amount of P from all biosolids applied soils (from 1857 to 2600 mg P kg-1). <p>The amount of desorbed P decreased as the soil:solution ratio increased from 0.005 to 100 g L-1 for both soils and the desorption was typically higher in inorganic fertilizer applied soil than in biosolids applied soil. The effect of pH on P desorption was pronounced, and desorption was higher at pH 5 than pH 7.5 for both soils. A continuous flow desorption method was also used to measure cumulative P desorption over time. Cumulative P desorption in inorganic fertilizer applied soil (894.5 mg P kg-1) was higher than in the biosolids amended soils (572.9 mg P kg-1) over 20 hr period time. First-order and parabolic diffusion kinetic equations were used to model the desorption data from the continuous flow technique. This revealed that the P desorption rate was faster (and chemically-controlled) at initial stages and slower (and diffusion-limited) at later stages. The desorption rate was much faster in inorganic fertilizer applied soil than in biosolids applied soil.<p>XANES analysis of the fractions removed in sequential chemical extractions suggested that the predominant form of P was poorly crystalline dicalcium phosphate in biosolids applied soils, and labile, sorbed forms as well as some apatite-type calcium phosphate was present in inorganic fertilizer applied soil. The combined results from sequential chemical extraction and XANES analysis indicate that P in inorganic fertilizer and biosolids-applied soils behave differently. There were larger amounts of low crystallinity phosphates in the biosolids samples, and much higher apatite content in the inorganic fertilizer amended soil.

Graduation date: 1991

Graduation date: 1991

In this thesis, we focus on obtaining and interpreting observational information on (i) the role of multiplicity on the properties of young stars; (ii) the early evolutionary influence of circumstellar disks; and (iii) the nature of accretion in young systems. To facilitate this research, we conducted an extensive multi-epoch high-resolution spectroscopic survey at optical wavelengths (3,200-10,000 A) of ~200 T Tauri stars in the ~2 Myr old Chamaeleon I, and Taurus-Auriga star-forming regions with the Magellan Inamori Kyocera Echelle (MIKE) spectrograph on the Magellan Clay 6.5 m telescope. From the spectroscopic data, we identify eight close binaries and four close triples, of which three and two, respectively, are new discoveries. We find that the multiplicity fraction for Cha I and Tau-Aur are similar to each other, and to the results of field star surveys. The frequency of systems with close companions in our sample is not seen to depend on primary mass or accretion. We probed for evidence of disk braking. We did not see a statistically significant difference between the distribution of rotational velocities with the presence of an inner disk. Also, our findings show that F-K stars in our sample have larger rotational velocities and specific angular momentum than M stars. We also analyzed accretion variability in our sample using the H\alpha 10% width and the CaII-8662 line flux as accretion diagnostics. We find that the maximum extent of accretion variability in our sample was reached on timescale of a few days, indicating that rotation could significantly contribute to the variability.

This research work focused on studying the emission spectroscopy produced from the high energy ion-molecule collision processes in mass spectrometry. The collision experiments are described and divided into 4 chapters (Chapter 3, 4, 5, 6).N2O+● is an ion of atmospheric importance. In chapter 3 the investigation of the collision between high translational energy (4-8 keV range) N2O+● ions and Helium target gas in mass spectrometry using collision induced emission (CIE) spectroscopy is described.In chapter 4, the collision-induced emission (CIE) spectra from 4-8 keV collisions between projectile He+● ions and CO2 target gas (He+●/CO2) were obtained. In Chapter 5, to probe the validity of this hypothesis, CIE experiments were carried out to observe the photon emissions from keV collisions of a selection of projectile ions with O2 target gas. By studying the resulting CIE spectra, a second potential mechanism came to light, one that involves the nearly isoenergetic O2+. A → X state transition. In chapter 6, neutral hydroxymethylene and formaldehyde were generated by charge exchange neutralization of their respective ionic counterparts and then were reionized and detected as recovery signals in neutralization-reionization mass spectrometry in the modified VG-ZAB mass spectrometer.

This study was conducted to compare the speciation and behavior of P in soils receiving either different biosolids or inorganic fertilizer, as assessed by sequential chemical extractions, phosphate desorption, and synchrotron X-ray absorption near edge structure (XANES) spectroscopy. The objectives of this study were to i) measure the total amount of organic and inorganic phosphorus removed by chemical extraction method ii) investigate how P desorption kinetics are influenced in biosolids amended soils compared to inorganic fertilizer amended soils; and iii) perform solid state speciation of soil samples before and after chemical extraction and desorption with P K-edge XANES spectroscopy. Soil samples were analyzed that received three different rates of biosolids (16.8, 33.6, and 67.2 Mg ha-1 yr-1) and one inorganic fertilizer application (336 kg N, 224 kg P, and 112 kg K ha-1 yr-1) for 32 years. Both sequential chemical extraction and XANES analysis showed that total amount of P increased in biosolids amended soils (from 5292 to 10945 mg P kg-1) and that it increased with increasing application rate. Sequential chemical extractions showed that the labile portion of total P in inorganic fertilized soil (40 %) was larger than in biosolids applied soils (39 to 27 %). Results from both sequential chemical extraction and XANES analysis showed that NaOH extraction removed the highest amount of P from all biosolids applied soils (from 1857 to 2600 mg P kg-1). <p>The amount of desorbed P decreased as the soil:solution ratio increased from 0.005 to 100 g L-1 for both soils and the desorption was typically higher in inorganic fertilizer applied soil than in biosolids applied soil. The effect of pH on P desorption was pronounced, and desorption was higher at pH 5 than pH 7.5 for both soils. A continuous flow desorption method was also used to measure cumulative P desorption over time. Cumulative P desorption in inorganic fertilizer applied soil (894.5 mg P kg-1) was higher than in the biosolids amended soils (572.9 mg P kg-1) over 20 hr period time. First-order and parabolic diffusion kinetic equations were used to model the desorption data from the continuous flow technique. This revealed that the P desorption rate was faster (and chemically-controlled) at initial stages and slower (and diffusion-limited) at later stages. The desorption rate was much faster in inorganic fertilizer applied soil than in biosolids applied soil.<p>XANES analysis of the fractions removed in sequential chemical extractions suggested that the predominant form of P was poorly crystalline dicalcium phosphate in biosolids applied soils, and labile, sorbed forms as well as some apatite-type calcium phosphate was present in inorganic fertilizer applied soil. The combined results from sequential chemical extraction and XANES analysis indicate that P in inorganic fertilizer and biosolids-applied soils behave differently. There were larger amounts of low crystallinity phosphates in the biosolids samples, and much higher apatite content in the inorganic fertilizer amended soil.