Phytoforensics: Applications in vapor intrusion assessment

Vapor intrusion (VI) occurs when contaminants in the vapor phase migrate in the shallow subsurface and enter buildings through cracks, seams, and gaps and has been recognized as a serious human-health threat as occupants are exposed to potentially harmful concentrations over long periods of time. The VI pathway has recently (2017) been identified as a primary exposure pathway and implemented into the Hazard Ranking System for inclusion on the Nation Priorities List. However, assessing VI and human exposure is not simple and current methods are time-, cost-, and labor-intensive; intrusive; and temporally and spatially variability. Trees are ideal candidates for environmental biomonitors because they are ubiquitous, active samplers of vapor and groundwater and because they are thought to sample over large spatial and temporal scales, effectively averaging variability. Sampling trees is noninvasive and does not require the construction of sampling ports in homes, increasing the likelihood of obtaining property access and VI data. Tree samples are representative of the shallow subsurface with a footprint similar to a residential building. Directional tree sampling can also be used to elucidate shallow subsurface contamination from a single tree, and tree sampling is shown to be correlated with VI samples, especially when environmental samples are averaged over months and years. However, non-uniform distributions of tree-core samples likely resulted in large interpolation error in areas where trees are sparse. Although these findings demonstrate that tree sampling can augment traditional VI assessment methods, tree sampling is best applied as a screening tool because of the many parameters, and their associate uncertainties, that control mass transfer of contaminants in the subsurface and entry into plants and the built environment --Abstract, page iv

Secondary Electron Yield Measurements of Carbon Nanotube Forests: Dependence on Morphology and Substrate

Total, secondary, and backscatter electron yield data were taken with beam energies between 15 eV and 30 keV, in conjunction with energy emission data, to determine the extent of suppression of yield caused by carbon nanotube (CNT) forest coatings on substrates. CNT forests can potentially lower substrate yield due to both its inherently low-yield, low-atomic number (Z) carbon composition, and its bundled, high-aspect ratio structure. Rough surfaces, and in particular, surfaces with deep high-aspect-ratio voids, can suppress yields, as the electrons emitted from lower lying surfaces are recaptured by surface protrusions rather than escaping the near-surface region. Yields of multilayered materials can be modeled essentially serially as a combination of the constituents. However, it is shown that suppression of yields due to CNT forest morphology is more significant than simple predicted contributions of homogeneous layered components. This effect is found to be most pronounced at low energies, where the incident electrons interact preferentially with the CNTs. CNT forests between 20 and 50 μm tall were grown on a thick silicon substrate capped with a 3-nm diffusion barrier of evaporated aluminum using a wet injection chemical vapor deposition (CVD) method. Yields of an annealed substrate and constituent bulk materials were also investigated. At incident electron energies above ~1200 eV, the substrate secondary yield dominated those of the CNT forests, as incident electrons penetrated through the low-density, low-Z CNT forests, and backscattered from the higher-Z substrate. At lower energies \u3c1200 \u3eeV, the CNT forests substantially reduced the overall yields of the substrate, and for \u3c500 eV CNT forest yields were \u3c1, well below the already low yields of bulk graphite. This suppressed yield at low energies is attributed to the porosity and preferred vertical alignment of the CNT forest. The yield’s dependence on the height and density of the CNT forest is also discussed

Influence of Vibrationally-Induced Structural Changes on Carbon Nanotube Forests Suppression of Electron Yield

Carbon nanotube (CNT) forest coatings have been found to lower electron yield from material surfaces. The suppressed yields have been attributed to both the lower inherent yields of low-atomic number carbon and the enhanced electron recapture resulting from the morphology of the carbon layer. To explore the relative contributions of these two causes of yield suppression, tests have been made on CNT forest-coated conducting substrate samples subjected to vibrationally-induced changes of the coating structure. The extent of vibrationally-induced structural changes—due, for example, to shear-force conditions during space-vehicle transit—are of interest, as CNT have been a frequent topic of scientific curiosity and space applications due to their high tensile strength, high aspect ratio geometry, and unique electromagnetic characteristics. Their use has also been beneficial for sensor equipment, both terrestrial and space-faring, due to their extremely low photon and electron reflectivity

Suppresion of Electron Yield With Carbon Nanotube Forests: A Case Study

Electron emission of carbon nanotube (CNT) forests grown on silicon substrates was measured to investigate possible electron yield suppression due to the composition and morphology of CNT forests. CNT forests are vertically-oriented tubular formations of graphitic carbon grown on a substrate; these have been widely investigated for their extreme properties in optical, electrical, and mechanical aspects of physics and material sciences. CNT coatings are good candidates for yield reduction, in analogy with the near-ideal blackbody optical properties of CNT forests. Carbon with its low atomic number has an inherent low yield due to its low density of bulk electrons. Furthermore, the large aspect ratio of this vertically-aligned CNT allows for easy penetration of the high energy incident electrons, but enhanced recapture of lower-energy secondary electrons due to their wider angular distribution of emission. Total (TEY), secondary (SEY) and backscattered (BSEY) yield curves using 15 eV to 30 keV electron beams, along with energy emission spectra, were acquired for three CNT forest samples to determine the extent of yield suppression of the substrate due to the CNT forests [Wood, 2018]

A Case for the Humanities

First proposed in 2020 and supported by UCL’s Grand Challenge of Cultural Understanding, the UCL Enquiry on a Case for the Humanities set out to articulate and celebrate the value of the Humanities. This Enquiry places its emphasis on asking questions: it is not an official inquiry or inquest, nor a process designed to come up with a specific, single answer. It is, instead, a thoughtful search for insights, conducted in the spirit of the approach Humanities scholars take to their subjects. Liberated from the burden of serving any particular purpose or interest, those involved in the Enquiry set themselves the task of examining and expressing the vital role of the Humanities in a rapidly changing world

Integrative analysis of genomic and exposomic influences on youth mental health

Background: Understanding complex influences on mental health problems in young people is needed to inform early prevention strategies. Both genetic and environmental factors are known to influence youth mental health, but a more comprehensive picture of their interplay, including wide-ranging environmental exposures – that is, the exposome – is needed. We perform an integrative analysis of genomic and exposomic data in relation to internalizing and externalizing symptoms in a cohort of 4,314 unrelated youth from the Adolescent Brain and Cognitive Development (ABCD) Study. / Methods: Using novel GREML-based approaches, we model the variance in internalizing and externalizing symptoms explained by additive and interactive influences from the genome (G) and modeled exposome (E) consisting of up to 133 variables at the family, peer, school, neighborhood, life event, and broader environmental levels, including genome-by-exposome (G × E) and exposome-by-exposome (E × E) effects. / Results: A best-fitting integrative model with G, E, and G × E components explained 35% and 63% of variance in youth internalizing and externalizing symptoms, respectively. Youth in the top quintile of model-predicted risk accounted for the majority of individuals with clinically elevated symptoms at follow-up (60% for internalizing; 72% for externalizing). Of note, different domains of environmental exposures were most impactful for internalizing (life events) and externalizing (contextual including family, school, and peer-level factors) symptoms. In addition, variance explained by G × E contributions was substantially larger for externalizing (33%) than internalizing (13%) symptoms. / Conclusions: Advanced statistical genetic methods in a longitudinal cohort of youth can be leveraged to address fundamental questions about the role of ‘nature and nurture’ in developmental psychopathology

Prospectus, October 2, 2002

https://spark.parkland.edu/prospectus_2002/1024/thumbnail.jp

Design Construction Networks

This visual essay diagrams a global design construction network that connects architects to migrant construction workers in a direct line. A hypothetical stadium construction site lies in the center; one side maps the movement of a steel truss from design to fabrication to a building site; the other side charts the path of migrant workers as they travel from villages to this construction site. Detailed scenarios outline the work of different actors on both sides, and additionally highlight challenges faced by migrant construction workers and where solutions might intervene. By connecting architects and workers the essay points to visible as well as sometimes hidden economies of architecture, and asks: What are the architects’ ethical responsibilities towards those who erect their buildings around the world? The essay further opens up a theoretical trajectory that seeks to understand the underlying and often unequal systems that structure today’s architecture and construction

Introducing Adaptive Flood Risk Management in England, New Zealand, and the Netherlands: The Impact of Administrative Traditions

Climate change adaptation creates significant challenges for decision makers in the flood risk-management policy domain. Given the complex characteristics of climate change, adaptive approaches(which can be adjusted as circumstances evolve) are deemed necessary to deal with a range of uncertainties around flood hazard and its impacts and associated risks. The question whether implementing adaptive approaches is successful highly depends upon how the administrative tradition of a country enable or hinder applying a more adaptive approach. In this article, we discern how the administrative tradition in the Netherlands, England, and New Zealand impact upon the introduction of adaptive flood risk management approaches. Using the concept of administrative traditions, we aim to explain the similarities and/or differences in how adaptive strategies are shaped and implemented in the three different state flood management regimes and furthermore, which aspects related to administrative traditions are enablers or barriers to innovation in these processe