The Impact of Radio AGN Bubble Composition on the Dynamics and Thermal Balance of the Intracluster Medium

Feeding and feedback of active galactic nuclei (AGN) are critical for understanding the dynamics and thermodynamics of the intracluster medium (ICM) within the cores of galaxy clusters. While radio bubbles inflated by AGN jets could be dynamically supported by cosmic rays (CRs), the impact of CR-dominated jets are not well understood. In this work, we perform three-dimensional simulations of CR-jet feedback in an isolated cluster atmosphere; we find that CR jets impact the multiphase gas differently than jets dominated by kinetic energy. In particular, CR bubbles can more efficiently uplift the cluster gas and cause an outward expansion of the hot ICM. Due to adiabatic cooling from the expansion and less efficient heating from CR bubbles by direct mixing, the ICM is more prone to local thermal instabilities, which will later enhance chaotic cold accretion onto the AGN. The amount of cold gas formed during the bubble formation and its late-time evolution sensitively depend on whether CR transport processes are included or not. We also find that low-level, subsonic driving of turbulence by AGN jets holds for both kinetic and CR jets; nevertheless, the kinematics is consistent with the Hitomi measurements. Finally, we carefully discuss the key observable signatures of each bubble model, focusing on gamma-ray emission (and related comparison with Fermi), as well as thermal Sunyaev-Zel'dovich constraints.Comment: accepted to Ap

Atmospheric Condensational Properties of Ultrafine Chain and Fractal Aerosol Particles

The purpose for the research sponsored by this grant was to lay the foundations for qualitative understanding and quantitative description of the equilibrium vapor pressure of water vapor over the irregularly shaped, carbonaceous particles that are present in the atmosphere. This work apparently was the first systematic treatment of the subject. Research was conducted in two complementary components: 1. Calculations were performed of the equilibrium vapor pressure of water over particles comprised of aggregates of spheres in the 50-200 nm radius range. The purposes of this work were two-fold. First, since no systematic treatment of this subject had previously been conducted, its availability would be directly useful for quantitative treatment for a limited range of atmospheric aerosols. Second, it would provide qualitative indications of the effects of highly irregular particle shape on equilibrium vapor pressure of aggregates comprised of smaller spheres

A Framework For Memory Performance Prediction From Brain Volume In Preterm-Born Adolescents

With advances in medical care, higher numbers of extremely preterm-born babies are now surviving, however the rate of neurodevelopmental and neurological complications has not improved at the same rate and the relative rate of disabilities and health problems is increasing, with associated high costs for health care systems and education. Understanding brain development after early birth is of great importance to be able to make informed decisions. Many studies have associated different areas of the preterm brain with poor cognitive performance, however it is less clear whether these associations persist into adult life. In this study, we investigate how well cortical volumes describe memory performance in 133 19 year-old adolescents, 61% of whom were born extremely preterm. We employ LASSO to identify brain regions that better explain memory performance. The brain regions identified by LASSO explained 27% and 32% of the variance in the visual working memory scores and the visual short term memory respectively. Furthermore, the correlation between the predicted scores and validation scores is statistically significant and it is 58% for the visual working memory task and 56% for the visual short term memory task

Brain Volume and Neuropsychological Differences in Extremely Preterm Adolescents

Although findings have revealed that preterm subjects are at higher risk of brain abnormalities and adverse cognitive outcome, very few studies have investigated the long-term effects of extreme prematurity on regional brain structures, especially in adolescence. The current study aims to investigate the volume of brain structures of 88 extremely preterm born 19-year old adolescents and 54 age- and socioeconomically-matched full-term born subjects. In addition, we examine the hypothesis that the volume of grey matter regions where a significant group or group-sex differences are found would be connected with the neurodevelopmental outcome. The results of the analysis show regional brain difference linked to extreme prematurity with reduced grey matter content in the subcortical regions and larger grey matter volumes distributed around the medial prefrontal cortex and anterior medial cortex. Premature birth and the volume of the left precuneus and the right posterior cingulate gyrus accounts for 34% of the variance in FSIQ. The outcome of this analysis reveals that structural brain differences persist into adolescence in extremely preterm subjects and that they correlate with cognitive functions