Epigenetic Effects of Polybrominated Diphenyl Ethers on Human Health.

Disruption of epigenetic regulation by environmental toxins is an emerging area of focus for understanding the latter's impact on human health. Polybrominated diphenyl ethers (PBDEs), one such group of toxins, are an environmentally pervasive class of brominated flame retardants that have been extensively used as coatings on a wide range of consumer products. Their environmental stability, propensity for bioaccumulation, and known links to adverse health effects have evoked extensive research to characterize underlying biological mechanisms of toxicity. Of particular concern is the growing body of evidence correlating human exposure levels to behavioral deficits related to neurodevelopmental disorders. The developing nervous system is particularly sensitive to influence by environmental signals, including dysregulation by toxins. Several major modes of actions have been identified, but a clear understanding of how observed effects relate to negative impacts on human health has not been established. Here, we review the current body of evidence for PBDE-induced epigenetic disruptions, including DNA methylation, chromatin dynamics, and non-coding RNA expression while discussing the potential relationship between PBDEs and neurodevelopmental disorders

Neurodevelopmental polybrominated diphenyl ether exposures

Humans around the world are exposed to many potentially toxic compounds of both natural and anthropogenic origin. Industrial chemicals represent a large fraction of such compounds, some of which are now considered widespread environmental pollutants. One such class of compounds is polybrominated diphenyl ethers (PBDEs), a widely prevalent persistent organic pollutant spread largely by anthropogenic production and use of these chemicals as flame retardants in consumer products. The lipophilic nature of PBDEs, which are small halogenated organic molecules, allows them to accumulate in lipid-rich bodily tissues, including the brain. Due to the exposure kinetics of these compounds (detailed in Chapter 4 of this dissertation), cortical astrocytes and neurons are likely exposed in a region-specific manner. Concerningly, there is now a growing body of evidence epidemiologically linking PBDE exposure levels and incidences of behavioral deficits related to neurodevelopmental disorders (NDDs) in human children. NDDs include intellectual disability, attention deficit disorders, and autism spectrum disorders that are estimated to affect up to 15% of children in the United States. This association is supported by evidence from non-human animal studies that has established that exposures to several PBDEs affect learning. In an effort to understand the effects of exposures to these compounds, several major molecular and cellular mechanisms have been identified, including: disruption of calcium homeostasis, interference with hormonal signaling, cellular toxicity resulting from mitochondrial disruption and the production of reactive oxygen species, and a more recently emerging focus, disruption of epigenetic mechanisms. Despite much progress, there is not a clear understanding of how these identified effects of PBDE exposure are related to observed impacts on behavior and learning. In this dissertation, I first tested the hypothesis that the effects of neurodevelopmental PBDE exposures intersect with epigenetic regulation in embryonic cortical neurons, leading to the development and testing of a mechanistic hypothesis of intracellular signaling disruption caused by ortho-hydroxylated PBDE metabolites. I close by detailing a model of neurodevelopmental PBDE exposures that I combine with novel data presented here to generate hypotheses for future study. This body of work aims to be of value in continuing to build an understanding of the effects of PBDE exposures in the developing nervous system, how these exposures are related to observed behavioral deficits in animals, and generating insight regarding the interplay between genetic and environmental risk factors in neurodevelopmental disorders

The Mid-IR Spectral Effects of Darkening Agents and Porosity on the Silicate Surface Features of Airless Bodies

We systematically measured the mid-IR spectra of different mixtures of three silicates (antigorite, lizardite, and pure silica) with varying effective porosities and amounts of darkening agent (iron oxide and carbon). These spectra have broad implications for interpretation of current and future mission data for airless bodies, as well as for testing the capabilities of new instruments. Serpentines, such as antigorite and lizardite, are common to airless surfaces, and their mid-IR spectra in the presence of darkening agents and different surface porosities would be typical for those measured by spacecraft. Silica has only been measured in the plumes of Enceladus and presents exciting possibilities for other Saturn-system surfaces due to long range transport of E-ring material. Results show that the addition of the IR-transparent salt, KBr, to simulate surface porosity affected silicate spectra in ways that were not predictable from linear mixing models. The strengthening of silicate bands with increasing pore space, even when only trace amounts of KBr were added, indicates that spectral features of porous surfaces are more detectable in the mid-IR. Combining iron oxide with the pure silicates seemed to flatten most of the silicate features, but strengthened the reststrahlen band of the silica. Incorporating carbon with the silicates weakened all silicate features, but the silica bands were more resistant to being diminished, indicating silica may be more detectable in the mid-IR than the serpentines. We show how incorporating darkening agents and porosity provides a more complete explanation of the mid-IR spectral features previously reported on worlds such as Iapetus

The Role of Accounting and Professional Associations in IT Security Auditing: An AMCIS Panel Report

Information systems security is a critical area of inquiry and closely allied with IT audit skills from the accounting discipline. While accounting scholars are well informed about IT audits, information systems scholars interested in the security aspects of IT audits sometimes lack knowledge about the process through which scholars and professionals become security and audit experts in order to assess the quality of information-security implementations. IT audit knowledge enriches cybersecurity professors for both teaching and research. Individuals skilled in accounting, such as graduates from combined accounting/information systems departments in business schools, are naturally oriented to industry certification groups and their professional certifications, but mainstream IT academics are not. In this paper, we report on a panel discussion at AMCIS 2017 that focused on how researchers and educators who seek professional certifications offered by organizations such as the Information Systems Audit and Control Association (ISACA) can gain much richer knowledge of and insights into IT security assurance, which they can use for both teaching and research purposes. Such certifications provide valuable perspectives for the classroom and for research and are useful for IT professors interested in all aspects of security

Surface Environmental Surveillance Procedures Manual, PNL-MA-580, Rev. 5

This manual contains the procedures that are used for the collection of routine Surface Environmental Surveillance Project environmental samples and field measurements on and around the Hanford Site. Specific responsibilities for project personnel are also defined

Visible Near-infrared Spectral Evolution of Irradiated Mixed Ices and Application to Kuiper Belt Objects and Jupiter Trojans

Understanding the history of Kuiper Belt Objects and Jupiter Trojans will help to constrain models of solar system formation and dynamical evolution. Laboratory simulations of a possible thermal and irradiation history of these bodies were conducted on ice mixtures while monitoring their spectral properties. These simulations tested the hypothesis that the presence or absence of sulfur explains the two distinct visible near-infrared spectral groups observed in each population and that Trojans and KBOs share a common formation location. Mixed ices consisting of water, methanol, and ammonia, in mixtures both with and without hydrogen sulfide, were deposited and irradiated with 10 keV electrons. Deposition and initial irradiation were performed at 50 K to simulate formation at 20 au in the early solar system, then heated to Trojan-like temperatures and irradiated further. Finally, irradiation was concluded and resulting samples were observed during heating to room temperature. Results indicated that the presence of sulfur resulted in steeper spectral slopes. Heating through the 140–200 K range decreased the slopes and total reflectance for both mixtures. In addition, absorption features at 410, 620, and 900 nm appeared under irradiation, but only in the H_2S-containing mixture. These features were lost with heating once irradiation was concluded. While the results reported here are consistent with the hypothesis, additional work is needed to address uncertainties and to simulate conditions not included in the present work

Electron Irradiation and Thermal Processing of Mixed-ices of Potential Relevance to Jupiter Trojan Asteroids

In this work we explore the chemistry that occurs during the irradiation of ice mixtures on planetary surfaces, with the goal of linking the presence of specific chemical compounds to their formation locations in the solar system and subsequent processing by later migration inward. We focus on the outer solar system and the chemical differences for ice mixtures inside and outside the stability line for H_2S. We perform a set of experiments to explore the hypothesis advanced by Wong & Brown that links the color bimodality in Jupiter's Trojans to the presence of H_2S in the surface of their precursors. Non-thermal (10 keV electron irradiation) and thermally driven chemistry of CH_3OH–NH_3–H_2O ("without H_2S") and H_2S–CH_3OH–NH_3–H_2O ("with H_2S") ices were examined. Mid-IR analyses of ice and mass spectrometry monitoring of the volatiles released during heating show a rich chemistry in both of the ice mixtures. The "with H_2S" mixture experiment shows a rapid consumption of H_2S molecules and production of OCS molecules after a few hours of irradiation. The heating of the irradiated "with H_2S" mixture to temperatures above 120 K leads to the appearance of new infrared bands that we provisionally assign to SO_2 and CS. We show that radiolysis products are stable under the temperature and irradiation conditions of Jupiter Trojan asteroids. This makes them suitable target molecules for potential future missions as well as telescope observations with a high signal-to-noise ratio. We also suggest the consideration of sulfur chemistry in the theoretical modeling aimed at understanding the chemical composition of Trojans and KOBs

Complex organosulfur molecules on comet 67P: Evidence from the ROSINA measurements and insights from laboratory simulations.

The ROSINA (Rosetta Orbiter Spectrometer for Ion and Neutral Analysis) instrument aboard the Rosetta mission revolutionized our understanding of cometary material composition. One of Rosetta's key findings is the complexity of the composition of comet 67P/Churyumov-Gerasimenko. Here, we used ROSINA data to analyze dust particles that were volatilized during a dust event in September 2016 and report the detection of large organosulfur species and an increase in the abundances of sulfurous species previously detected in the coma. Our data support the presence of complex sulfur-bearing organics on the surface of the comet. In addition, we conducted laboratory simulations that show that this material may have formed from chemical reactions that were initiated by the irradiation of mixed ices containing H2S. Our findings highlight the importance of sulfur chemistry in cometary and precometary materials and the possibility of characterizing organosulfur materials in other comets and small icy bodies using the James Webb Space Telescope