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Creators: School of Mathematical and Natural Sciences
Creators: Anbar, Ariel D

The chemical composition of exoplanet-hosting binary star systems

Description

A significant portion of stars occur as binary systems, in which two stellar components orbit a common center of mass. As the number of known exoplanet systems continues to grow, some binary systems are now known to harbor planets around one or both stellar components. As a first look into composition of these planetary systems, I investigate the chemical compositions of 4 binary star systems, each of which is known to contain at least one planet. Stars are known to vary significantly in their composition, and their overall metallicity (represented by iron abundance, [Fe/H]) has been shown to correlate with the likelihood of hosting a planetary system. Furthermore, the detailed chemical composition of a system can give insight into the possible properties of the system's known exoplanets. Using high-resolution spectra, I quantify the abundances of up to 28 elements in each stellar component of the binary systems 16 Cyg, 83 Leo, HD 109749, and HD 195019. A direct comparison is made between each star and its binary companion to give a differential composition for each system. For each star, a comparison of elemental abundance vs. condensation temperature is made, which may be a good diagnostic of refractory-rich terrestrial planets in a system. The elemental ratios C/O and Mg/Si, crucial in determining the atmospheric composition and mineralogy of planets, are calculated and discussed for each star. Finally, the compositions and diagnostics of each binary system are discussed in terms of the known planetary and stellar parameters for each system.

ContributorsCarande, Bryce (Author) / Young, Patrick (Thesis advisor) / Patience, Jennifer L (Thesis advisor) / Anbar, Ariel D (Committee member) / Arizona State University (Publisher)

Created2013

Seed Beetle Abundance and Diversity in Urban and Rural Sites

Description

The spread of urbanization leads to habitat fragmentation and deterioration and changes the composition of ecosystems for species all over the world. Different groups of organisms are impacted differently, and insects have experienced loss in diversity and abundance due to changing environmental factors. Here, I collected seed beetles across 12 urban and rural sites in Phoenix, Arizona, to analyze the effects of urbanization and habitat variation on beetle diversity and abundance. I found that urbanization, host tree origin, and environmental factors such as tree diversity and density had no impact on overall beetle diversity and abundance. Beetles were found to have higher density on hosts with a higher density of pods. In assessing individual beetle species, some beetles exhibited higher density in rural sites with native trees, and some were found more commonly on nonnative tree species. The observed differences in beetle density demonstrate the range of effects urbanization and environmental features can have on insect species. By studying ecosystem interactions alongside changing environments, we can better predict the role urbanization and human development can have on different organisms.

ContributorsPaduano, Gabrielle (Author) / Savalli, Udo (Thesis director) / Sweat, Ken (Committee member) / Division of Teacher Preparation (Contributor) / School of Mathematical and Natural Sciences (Contributor) / Barrett, The Honors College (Contributor)

Created2018-05

The Effect of the COVID-19 Pandemic on the Fertility of Women in Reproductive Ages: Cross-sectional Study

Description

Background: Recent studies have shown a decline in birth rates in large metropolitan areas (after accounting for population), which can be possibly explained by barriers to reproduction associated with the COVID-19 pandemic and related lockdowns. Objective: This study’s objective was to investigate the impact of the COVID-19 pandemic and related lockdowns on the fertility rates of women in reproductive ages living in Greater Phoenix. Methods: The total number of inpatient births and people in both Maricopa and Pinal Counties during pre-COVID-19 years (2017-2019) were compared with those during the COVID-19 years (2021) among women in reproductive ages (15-49 years). To make age-specific comparisons, women in reproductive years were divided into eight distinct age group categories (15-17, 18-20, and then five year age group categories to age 49) from which age-specific, general, and total fertility rates were calculated. Results: Using a two-sample z-test for difference in proportions, findings revealed that the general fertility rate in Greater Phoenix had significantly declined from 48 to 46 per 1,000 population from the pre-COVID-19 period to COVID-19 period (P<0.001). Two sample z-tests were also used to compare age-specific fertility rates, which revealed a significant decline in the fertility rate in women ages 15-17 (from 8.0/1000 to 5.0/1000) (P<0.001), 18-20 (from 43.0/1000 to 35.0/1000) (P<0.001), and 21-24 (from 79.0/1000 to 68.0/1000) (P<0.001) from the pre-COVID-19 period to COVID-19 period, while no significant change was observed in the fertility rate in women ages 25-49. Conclusions: The observed general fertility decline in Greater Phoenix as a result of the COVID-19 pandemic poses significant implications for further research on barriers to reproduction brought upon by the COVID-19 pandemic and related lockdown measures. Another direction for further research involves possibly continuing this study to include years 2022 and 2023 in the COVID-19 period, as well as calculating age-specific fertility rates by race.

ContributorsYoung, Macy (Author) / Biviji, Rizwana (Thesis director) / Ohri-Vachaspati, Punam (Committee member) / Acciai, Francesco (Committee member) / Barrett, The Honors College (Contributor) / School of Mathematical and Natural Sciences (Contributor) / College of Health Solutions (Contributor)

Created2023-05