Multi-Objective Calibration For Agent-Based Models

Agent-based modelling is already proving to be an immensely useful tool for scientific and industrial modelling applications. Whilst the building of such models will always be something between an art and a science, once a detailed model has been built, the process of parameter calibration should be performed as precisely as possible. This task is often made difficult by the proliferation of model parameters with non-linear interactions. In addition to this, these models generate a large number of outputs, and their ‘accuracy’ can be measured by many different, often conflicting, criteria. In this paper we demonstrate the use of multi-objective optimisation tools to calibrate just such an agent-based model. We use an agent-based model of a financial market as an exemplar and calibrate the model using a multi-objective genetic algorithm. The technique is automated and requires no explicit weighting of criteria prior to calibration. The final choice of parameter set can be made after calibration with the additional input of the domain expert

Accuracy in Screening for Autism Spectrum Disorder in Children with Down Syndrome

There is a high variance in prevalence of Autism Spectrum Disorder in individuals with Down syndrome because of the absence in accurate screening measures for this specific population. Many professionals mistake a child’s deficits in social, language, linguistic, and adaptive skills as symptoms of an intellectual disability, which is a common characteristic found in individuals with DS, rather than as characteristics of co-occurring ASD. Due to this, appropriate interventions may be hindered or the child may be placed in an inappropriate educational placement, which could lead parents and/or caregivers to unnecessary hardship.https://griffinshare.fontbonne.edu/slp-posters/1000/thumbnail.jp

Organic carbon burial under greenhouse climate conditions: The regional expression of the Late Cretaceous Oceanic Anoxic Event 3 within the Western Interior Seaway.

The Cretaceous period (145−66 million years ago) was characterized by elevated atmospheric pCO2 and an equable, warm climate. High Cretaceous sea levels flooded continental areas producing extensive shallow seaways, including the Western Interior Seaway (WIS) in North America. The resulting sedimentary record of the WIS includes episodic deposition of organic carbon-rich black shales, during a series of Oceanic Anoxic Events (OAEs). Multiple processes control marine black shale deposition, including changes in primary productivity, organic matter preservation, and sedimentary dilution. OAEs offer an opportunity to evaluate the relative roles of these forcing factors on marine carbon burial. This dissertation centers on understanding the causes of enhanced organic carbon burial within the WIS during a particularly poorly studied OAE, the Coniacian-Santonian OAE 3 (~88−84 Ma). In Chapter 2, I use trace metal records from the USGS Portland core (drilled near Cañon City, Colorado) to reconstruct the degree of oxygenation before, during, and after OAE 3. These data are compared to bulk elemental and isotopic records of organic matter composition to demonstrate that oxygen depletion in pore and bottom waters provided a feedback to carbon burial, by triggering enhanced organic matter preservation within the WIS during OAE 3. In Chapter 3, I examine changes in organic carbon preservation in greater detail using biomarker and compound specific carbon isotope records. My results document distinct organic matter sources before, during, and after the OAE associated with varying degrees of bioturbation and therefore, oxygen exposure time. In Chapter 4, I explore the feedbacks associated with changing iron chemistry in the WIS. Sequential iron extractions, phosphorus, and sulfur results indicate that low reactive iron availability promoted phosphorus remineralization from sediments, illustrating the importance of internal nutrient recycling during and after OAE 3. In Chapter 5, trends and timing of organic carbon accumulation are examined on a larger spatial scale. Trace metal and foraminiferal records from western Alberta are compared to time equivalent records from the central seaway. The reconstructed seaway-wide patterns indicate that anoxic conditions and the resulting sedimentary elevated organic carbon accumulation closely follow the sea-level transgression and expanding influence of nutrient-rich Tethyan (equatorially-sourced) water.PhDGeologyUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/133431/1/atessin_1.pd

Lake Sediment Geochemical Changes in Response to Land Use Variations in the Catchments of Lakes Volvi and Koronia, Northern Greece

Lakes Koronia and Volvi, located within the Mygdonia Basin in northern Greece, comprise an internationally protected wetland. The lakes support major industrial and agricultural activities, and a population of 45,000. Consequently, both sites have been greatly impacted by the conversion of marshland to farmland, water losses to irrigation, and pollution discharges including raw sewage, agricultural run-off, and industrial wastes. Sediment chronology and accumulation rates have been determined in cores from multiple sites within the lakes using 210Pb dating techniques. Bulk sediment elemental composition (organic carbon content, C/N ratios, etc.) and trace metal concentrations have been measured to provide critical evidence for variations in land-use within watersheds. Stratigraphic variations in the carbon and nitrogen isotopic ratio of sedimented organic matter have been measured to determine changes in aquatic ecosystem productivity. The geochemical results will be compared to historical records to determine the relative importance of disturbances caused by urban, agricultural, and industrial activities

Iron limitation in the Western Interior Seaway during the Late Cretaceous OAE 3 and its role in phosphorus recycling and enhanced organic matter preservation

The sedimentary record of the Coniacian–Santonian Oceanic Anoxic Event 3 (OAE 3) in the North American Western Interior Seaway is characterized by a prolonged period of enhanced organic carbon (OC) burial. This study investigates the role of Fe in enhancing organic matter preservation and maintaining elevated primary productivity to sustain black shale deposition within the Coniacian–Santonian-aged Niobrara Formation in the USGS #1 Portland core. Iron speciation results indicate the development of a reactive Fe limitation coeval with reduced bioturbation and increased organic matter preservation, suggesting that decreased sulfide buffering by reactive Fe may have promoted enhanced organic matter preservation at the onset of OAE 3. An Fe limitation would also provide a feedback mechanism to sustain elevated primary productivity through enhanced phosphorus recycling. Additionally our results demonstrate inconsistencies between Fe-based and trace metal redox reconstructions. Iron indices from the Portland core indicate a single stepwise change, whereas the trace metal redox proxies indicate fluctuating redox conditions during and after OAE 3. Using Fe speciation to reconstruct past redox conditions may be complicated by a number of factors, including Fe sequestration in diagenetic carbonate phases and efficient sedimentary pyrite formation in a system with limited Fe supply and high levels of export production

Isotopically Depleted Carbon in the Mid-Depth South Atlantic During the Last Deglaciation

The initial rise in atmospheric CO2 during the last deglaciation was likely driven by input of carbon from a 13C-depleted reservoir (Schmitt et al., 2012). Here we show that high resolution benthic foraminiferal records from the mid‐depth Brazil Margin display an abrupt drop in δ13C during Heinrich Stadial 1 (HS1) that is similar to but larger than in the atmosphere. Comparing the Brazil Margin results to published records from the North Atlantic, we are unable to account for the South Atlantic δ13C data with conservative mixing between northern and southern component watermasses. Rapid input of abyssal water from the Southeast Atlantic could account for deglacial δ13C anomalies at the Brazil Margin but it would require a reversal in deep water flow direction compared to today. A new mid-depth watermass may explain similar HS1 δ13C values in both the North and South Atlantic, but contrasting oxygen isotopic values between the two basins do not support the presence of a single dominant watermass at mid‐depths. Instead, it appears that δ13C behaved non-conservatively during the deglaciation, possibly reflecting the input of carbon from an isotopically depleted source.NSFPeer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/98090/1/Tessin_Allyson_MS_2013.pdf1

Benthic phosphorus cycling within the Eurasian marginal sea ice zone

The Arctic Ocean region is currently undergoing dramatic changes, which will likely alter the nutrient cycles that underpin Arctic marine ecosystems. Phosphate is a key limiting nutrient for marine life but gaps in our understanding of the Arctic phosphorus (P) cycle persist. In this study, we investigate the benthic burial and recycling of phosphorus using sediments and pore waters from the Eurasian Arctic margin, including the Barents Sea slope and the Yermak Plateau. Our results highlight that P is generally lost from sediments with depth during organic matter respiration. On the Yermak Plateau, remobilization of P results in a diffusive flux of P to the seafloor of between 96 and 261 µmol m−2 yr−1. On the Barents Sea slope, diffusive fluxes of P are much larger (1736–2449 µmol m−2 yr−1), but these fluxes are into near-surface sediments rather than to the bottom waters. The difference in cycling on the Barents Sea slope is controlled by higher fluxes of fresh organic matter and active iron cycling. As changes in primary productivity, ocean circulation and glacial melt continue, benthic P cycling is likely to be altered with implications for P imported into the Arctic Ocean Basin

In vitro comparison of Ethanol Metabolism in Precision Cut Liver Slices from C57Bl/6, Balb/c, DBA/2J and 129S1/SvlmJ Mice and with the Aldeyra Product ADX-629

Alcoholic liver disease (ALD) is common consequence of excessive alcohol consumption [1]. When the liver is damaged by the intake of alcohol, repair mechanisms are deployed, which results in fibrosis or scarring of the liver. Development of this disease is due to the byproducts of ethanol metabolism. These byproducts include acetaldehyde from the metabolism of ethanol and malondialdehyde from the breakdown of cell membranes during injury. An Aldeyra product, ADX-629, is a small molecule that acts as a reactive aldehyde species (RASP) inhibitor. ADX-629 covalently binds free aldehydes, thus diminishing excessive RASP levels. To determine the aldehyde scavenging abilities of ADX-629 in attenuating fatty liver disease, precision cut liver slices (PCLS) were exposed to varying concentrations of ADX-629 as well as 25mM of ethanol. PCLS, which provide a novel in vitro/ex vivo experimental model, were then measured for triglyceride levels and supernatants were analyzed for acetaldehyde levels. It was found that ADX-629 reduced the acetaldehyde levels released from PCLS while also decreasing triglyceride levels. ADX-629 offers promising clinical uses such as in the prevention of fatty liver formation in patients with non-alcoholic steatohepatitis and in the treatment of alcoholic patients by preventing oxidative stress caused by the breakdown of ethanol thereby, preventing ALD.https://digitalcommons.unmc.edu/surp2021/1062/thumbnail.jp

A changing Arctic Ocean

The Arctic is the fastest changing region on the planet. It is also intrinsically tied to global processes, whether they are climatic, environmental or socio-economic. The impacts of climate change on the vast and multiple interacting Arctic systems are inherently complex, although can be broadly summarised as an increase in temperature and the subsequent loss of sea-ice cover. This will ultimately result in the emergence of new physical and ecological statesNon peer reviewe