Browsing by Author "McNamara, Brian"

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    An Analysis of Coffee Production, Food Security, and Child Nutrition in Ethiopia
    (2021-05) McNamara, Brian
    Arguably one of the most enduring legacies of COVID-19 will be the pandemic’s impact on global nutrition and food security. A recent report estimated that an additional 9.3 million children will become wasted, 2.6 million will become stunted, and 168,000 will die by 2022 as a result of the COVID19 pandemic and associated economic shock (Carducci et al., 2021). These statistics underscore a global problem that preceded the events of 2020. Malnutrition had been increasing gradually around the world for years so that 690 million people were already undernourished by 2019 (Pretorius et al., 2019) (Carducci et al., 2021). This trend has major implications for global poverty and well-being. Malnourished individuals have lower energy levels and are more likely to become sick. This can impede economic activity while also increasing healthcare costs for families (Schaible & Kaufmann, 2007) (Vorster, 2010). Furthermore, these effects can also lead to mental health issues and social isolation (Pretorius et al.,2019) (Huang et al., 2013). Malnutrition has even greater consequences for young children who may suffer impediments to their physical and mental development, which limit their future earning potential and shorten their life span (Martinez et al., 2018).
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    Thermal Instability in Low Entropy Gas Lifted behind Buoyantly-Rising X-ray Bubbles
    (2016-08-24) McNamara, Brian
    Precipitation models indicate that cooling instabilities form when the ratio of cooling time to free-fall in hot atmospheres surrounding massive galaxies falls below ~10, i.e., t_c/t_ff < 10. We show that this criterion is rarely met in central galaxies and is a statistically weaker indicator of cooling instabilities than cooling time alone. Hot atmospheres apparently do not experience large swings in gas density and cooling time in response to powerful AGN outbursts, which is an essential aspect of precipitation models. Based primarily on new ALMA observations, we show instead that molecular gas likely forms from low entropy gas caught in the updraft of rising X-ray bubbles. We suggest that thermal instabilities ensue when the ratio of the cooling time to the infall time of gas lifted to high altitudes falls below unity, i.e., t_c/t_I ~ 1.