Ariel - Volume 2 Number 4

Copyright 1969 Arie

Methane emissions: choosing the right climate metric and time horizon

Methane is a more potent greenhouse gas (GHG) than CO2, but it has a shorter atmospheric lifespan, thus its relative climate impact reduces significantly over time. Different GHGs are often conflated into a single metric to compare technologies and supply chains, such as the global warming potential (GWP). However, the use of GWP is criticised, regarding: (1) the need to select a timeframe; (2) its physical basis on radiative forcing; and (3) the fact that it measures the average forcing of a pulse over time rather than a sustained emission at a specific end-point in time. Many alternative metrics have been proposed which tackle different aspects of these limitations and this paper assesses them by their key attributes and limitations, with respect to methane emissions. A case study application of various metrics is produced and recommendations are made for the use of climate metrics for different categories of applications. Across metrics, CO2 equivalences for methane range from 4–199 gCO2eq./gCH4, although most estimates fall between 20 and 80 gCO2eq./gCH4. Therefore the selection of metric and time horizon for technology evaluations is likely to change the rank order of preference, as demonstrated herein with the use of natural gas as a shipping fuel versus alternatives. It is not advisable or conservative to use only a short time horizon, e.g. 20 years, which disregards the long-term impacts of CO2 emissions and is thus detrimental to achieving eventual climate stabilisation. Recommendations are made for the use of metrics in 3 categories of applications. Short-term emissions estimates of facilities or regions should be transparent and use a single metric and include the separated contribution from each GHG. Multi-year technology assessments should use both short and long term static metrics (e.g. GWP) to test robustness of results. Longer term energy assessments or decarbonisation pathways must use both short and long-term metrics and where this has a large impact on results, climate models should be incorporated. Dynamic metrics offer insight into the timing of emissions, but may be of only marginal benefit given uncertainties in methodological assumptions

Pathocenosis: A Holistic Approach to Disease Ecology

The History of medicine describes the emergence and recognition of infectious diseases, and human attempts to stem them. It also throws light on the role of changing environmental conditions on disease emergence/re-emergence, establishment and, sometimes, disappearance. However, the dynamics of infectious diseases is also influenced by the relationships between the community of interacting infectious agents present at a given time in a given territory, a concept that Mirko Grmek, an historian of medicine, conceptualized with the word “pathocenosis”. The spatial and temporal evolution of diseases, when observed at the appropriate scales, illustrates how a change in the pathocenosis, whether of “natural” or anthropic origin, can lead to the emergence and spread of diseases

Cholinergic Interneurons Mediate Fast VGluT3-Dependent Glutamatergic Transmission in the Striatum

The neurotransmitter glutamate is released by excitatory projection neurons throughout the brain. However, non-glutamatergic cells, including cholinergic and monoaminergic neurons, express markers that suggest that they are also capable of vesicular glutamate release. Striatal cholinergic interneurons (CINs) express the Type-3 vesicular glutamate transporter (VGluT3), although whether they form functional glutamatergic synapses is unclear. To examine this possibility, we utilized mice expressing Cre-recombinase under control of the endogenous choline acetyltransferase locus and conditionally expressed light-activated Channelrhodopsin2 in CINs. Optical stimulation evoked action potentials in CINs and produced postsynaptic responses in medium spiny neurons that were blocked by glutamate receptor antagonists. CIN-mediated glutamatergic responses exhibited a large contribution of NMDA-type glutamate receptors, distinguishing them from corticostriatal inputs. CIN-mediated glutamatergic responses were insensitive to antagonists of acetylcholine receptors and were not seen in mice lacking VGluT3. Our results indicate that CINs are capable of mediating fast glutamatergic transmission, suggesting a new role for these cells in regulating striatal activity

Proterozoic sedimentary exhalative (SEDEX) deposits and links to evolving global ocean chemistry

Sedimentary exhalative (SEDEX) Zn-Pb-sulfi de mineralization fi rst occurred on a large scale during the late Paleoproterozoic. Metal sulfi des in most Proterozoic deposits have yielded broad ranges of predominantly positive d34S values traditionally attributed to bacterial sulfate reduction. Heavy isotopic signatures are often ascribed to fractionation within closed or partly closed local reservoirs isolated from the global ocean by rifting before, during, and after the formation of Rodinia. Although such conditions likely played a central role, we argue here that the fi rst appearance of signifi cant SEDEX mineralization during the Proterozoic and the isotopic properties of those deposits are also strongly coupled to temporal evolution of the amount of sulfate in seawater. The ubiquity of 34S-enriched sulfi de in ore bodies and shales and the widespread stratigraphic patterns of rapid d34S variability expressed in both sulfate and sulfi de data are among the principal evidence for global seawater sulfate that was increasing during the Proterozoic but remained substantially lower than today. Because sulfate is produced mostly through weathering of the continents in the presence of oxygen, low Proterozoic concentrations imply that levels of atmospheric oxygen fell between the abundances of the Phanerozoic and the defi ciencies of the Archean, which are also indicated by the Precambrian sulfur isotope record. Given the limited availability of atmospheric oxygen, deep-water anoxia may have persisted well into the Proterozoic in the presence of a growing sulfate reservoir, which promoted prevalent euxinia. Collectively, these observations suggest that the mid-Proterozoic maximum in SEDEX mineralization and the absence of Archean deposits refl ect a critical threshold in the accumulation of oceanic sulfate and thus sulfi de within anoxic bottom waters and pore fluids-conditions that favored both the production and preservation of sulfi de mineralization at or just below the seafl oor. Consistent with these evolving global conditions, the appearance of voluminous SEDEX mineralization ca. 1800 Ma coincides generally with the disappearance of banded iron formations-marking the transition from an early iron-dominated ocean to one more strongly influenced by sulfi de availability. In further agreement with this conceptual model, Proterozoic SEDEX deposits in northern Australian formed from relatively oxidized fl uids that required reduced conditions at the site of mineralization. By contrast, the generally more oxygenated Phanerozoic ocean may have only locally and intermittently favored the formation and preservation of exhalative mineralization, and most Phanerozoic deposits formed from reduced fluids that carried some sulfide to the site of ore precipitation

Macrophage biology in development, homeostasis and disease

Macrophages the most plastic cells of the hematopoietic system are found in all tissues and exhibit great functional diversity. They have roles in development, homeostasis, tissue repair, and immunity. While anatomically distinct, resident tissue macrophages exhibit different transcriptional profiles, and functional capabilities, they are all required for the maintenance of homeostasis. However, these reparative and homeostatic functions can be subverted by chronic insults, resulting in a causal association of macrophages with disease states. In this review, we discuss how macrophages regulate normal physiology and development and provide several examples of their pathophysiologic roles in disease. We define the “hallmarks” of macrophages performing particular functions, taking into account novel insights into the diversity of their lineages, identity, and regulation. This diversity is essential to understand because macrophages have emerged as important therapeutic targets in many important human diseases

Iterations

For millennia, pottery has facilitated the communal activities of eating and drinking. I use pottery as a placeholder, a metaphor for human interaction. The central core, the initial inspiration, of my sculpture is the diminishing level of connection our culture actively pursues. I began to notice a trend of increasing disengagement in American culture after spending time abroad and observing the amount of time other cultures allotted for meals, coffee, etc. with companions. I make sculptures that comment on growing American disengagement using various formal principles of art (line, mass, scale, rhythm, and repetition). I am generally unsatisfied with a single solution to an idea, thus I create numerous iterations, a variety of ways to visually represent the inspiration. The resulting works move away from the initial concept to satisfy my aesthetic goals. While the idea that first inspired me is essential to my creative process, it is secondary to creating dynamic works to engage the viewer. Regardless, the pieces maintain enough of the original reference to be interpreted by individuals based on their own experiential references. This allows the viewer freedom to interpret and generate a personal narrative. I use a variety of utilitarian forms in my artistic investigation. Wheel throwing provides a means of producing similar sized elements with a degree of variation that adds richness to the composition. This dissimilarity in the repetition, albeit subtle, is an important factor in the success of my work, which will be referred to later. I use commercially produced objects, which have little to no variation, when a more consistent linear quality is desired for the specific iteration of the idea. The ceramic components of my work are chosen for the inherent qualities provided by the material. Porcelain offers a stark contrast against the aggregate of the concrete. The same porcelain against gypsum cement gives a far more subtle contrast; when coupled with components fired in varying (reduction or oxidation) atmospheres, the tonal qualities of the fired clay provide a warm and cool appearance that is desirable for creating repetition and rhythm in certain works. These ceramic objects, embedded in monolithic structures, are deliberately culturally ambiguous. The monoliths are memorials, fossils that symbolize the departure from shared communicative experience. Conceptually, I made the decision to deconstruct useful objects to evoke the idea of how shards of pottery are used by archeologists to gain insight into how a society functioned, its rituals, and how its society was structured. By grinding a portion of the vessel away, I deliberately create shards, pottery that is no longer able to fulfill its intended function. The purposeful denial of utility, created by erosion, is an additional reference to the initial foundation that began this work. Using line, mass, shape, and scale, I create visually dynamic pieces that pull the viewer in for closer investigation. The linear qualities generated by repetitive forms create visual movement that holds the viewer’s attention. In the pieces that include hand-made ceramic elements, the vessels themselves have subtle variations across the repeated forms that make up the composition. The variations within individual forms, a byproduct of the making process, add a very quiet human touch to an otherwise monumental work. While I generally look for balance, with a sense of calm throughout the work, I add a slight tension to create visual interest. The more successful pieces have a focal point of fragility or obvious dissonance. Areas that deliberately catch the eye, causing what would otherwise be an unassuming sculpture, make the viewer feel slight discomfort. I create more visually dynamic pieces by increasing the scale of my works. A larger context or “canvas” simply provides more space for compositions wrought from more numerous components. My sculptures are formal investigations that began by exploring the departure from utilitarian pottery’s role throughout human civilization. These works no longer rely strictly on that premise, but are growing in complexity through scale and subtle tensions built into every individual piece. The compositions rely on the similarities and differences within the pottery and the materials that encase them to emphasize line, shape, mass, rhythm, and repetition. My hope is that the subtle variations in the pottery components add texture to the overall composition in a way that sparks viewer interest and encourages investigation. Advisor: Peter J. Pinnel

Microfrabricated Acoustic and Thermal Field-Flow Fractionation Systems

Arguments for miniaturization of a thermal field-flow fractionation system ( and #956;-ThFFF) and fabrication of a micro-scale acoustic field-flow fractionation system ( and #956;-AcFFF) using similar methods was presented. Motivation for miniaturization of ThFFF systems was established by examining the geometrical scaling of the fundamental ThFFF theory. Miniaturization of conventional macro-scale ThFFF systems was made possible through utilization of micromachining technologies. Fabrication of the and #956;-ThFFF system was discussed in detail. The and #956;-ThFFF system was characterized for plate height versus flow rate, single component polystyrene retention, and multi-component polystyrene separations. Retention, thermal diffusion coefficients, and maximum diameter-based selectivity values were extracted from separation data and found comparable with macro-scale ThFFF system results. Retention values ranged from 0.33 to 0.46. Thermal diffusion coefficients were between 3.0ױ0-8 and 5.4ױ0-8 cm2/sec?? The maximum diameter-based selectivity was 1.40. While the concept of an acoustic FFF sub-technique has been around for decades, the fabrication methods have not been available until recently. The theory was developed in full including relating sample physical properties to retention time in the FFF system. In addition to the theory, the design and fabrication of the and #956;-AcFFF was presented. Design results from an acoustic modeling program were presented with the determination of the acoustic resonant frequency. The acoustic-based systems was designed around the model results and characterized by electrical input impedance, fluidic, plate height, polystyrene suspension retention, and polystyrene mixture separation studies. The and #956;-AcFFF system was able to retain a series of nanometer scale polystyrene samples. However, the retention data did not follow normal mode retention but did reveal the location of the steric inversion point for the power level used, around 200 nm. The results of the multiple component separation confirmed this results as the sample, which contained 110, 210, and 300 nm diameter samples, was not resolved but only broadened.Ph.D.Committee Chair: A. Bruno Frazier; Committee Member: F. Levent Degertekin; Committee Member: Faramarz Fekri; Committee Member: John Papapolymerou; Committee Member: Mark G. Alle