Assimilation of trace gas retrievals with the Local Ensemble Transform Kalman Filter

Over the 50 year history of Numerical Weather Prediction (NWP), the focus has been on the modeling and prediction of meteorological parameters such as surface pressure, temperature, wind, and precipitation. However, due to concerns over pollution and to recent advancements in satellite technologies, an increasing number of NWP systems have been upgraded to include capabilities to analyze and predict the concentration of trace gases. This dissertation explores some of the specific issues that have to be addressed for an efficient modeling of the concentration of the trace gases. These issues include modeling the effects of convective mixing on the concentration of the trace gases and the multivariate assimilation of space-based observations of the concentration of the trace gases. In this dissertation, we assimilate observations of the concentration of trace gases with an implementation of the Local Ensemble Transform Kalman Filter (LETKF) data assimilation system on the National Centers for Environmental Prediction (NCEP) Global Forecast System (GFS) NWP model. We use a modified version of the NCEP GFS model that was operational in 2004 at resolution T62/L28. We modify the model by adding parameterization for the process of convective mixing of the trace gases. We consider two specific trace gases: ozone (O3) and carbon monoxide (CO). We incorporate these gases into the model by using 3-dimensional time-dependent O3 and CO production-loss values from the Real-time Air Quality Modeling System (RAQMS) global chemical model. The O3 observations we assimilate are from the Solar Backscatter UltraViolet generation 2 (SBUV/2) satellite instrument (version 8) flown on the NOAA 16 and 17 satellites. The CO observations we assimilate are from the Measurements Of Pollution In The Troposphere (MOPITT) instrument (version 3) flown on the NASA TERRA satellite. We also develop a new observation operator for the assimilation of retrievals with the LETKF. We carry out numerical experiment for the period between 000UTC 1 July 2004 to 000UTC 15 August in the summer of 2004. The analysis and forecast impact of the assimilation of trace gas observations on the meteorological fields is assessed by comparing the analyses and forecasts to the high resolution operational NCEP GFS analyses and to radiosonde observations. The analysis and forecast impact on the trace gas fields is assessed by comparing the analyzed and predicted fields to observations collected during the Intercontinental Chemical Transport Experiment (INTEX-A) field mission. The INTEX-A field mission was conducted to characterize composition of pollution over North America, thus providing us with ozonesonde and aircraft based verification data. We find that adding the process of convective mixing to the parameterization package of the model and the assimilation of observations of the trace gases improves the analysis and forecast of the concentration of the trace gases. In particular, our system is more accurate in quantifying the concentration of O3 in the troposphere than the original NCEP GFS. Also, our system is competitive with the state-of-the-art RAQMS atmospheric chemical model in analyzing the concentration of O3 and CO throughout the full atmospheric model column. The assimilation of O3 and CO observations has a mixed impact on the analysis and forecast of the meteorological fields. We find that most of the negative impact on the meteorological fields can be eliminated, without much reduction to the positive impact on the trace gas fields, by inflating the prescribed variance of the trace gas observations. The appendices of this dissertation reproduces two papers on related research. The first paper covers the northward front movement and rising surface temperatures in the great planes. The second paper covers the assessment of predictability with a Local Ensemble Kalman Filter

PET and P300 Relationships in Early Alzheimer\u27s Disease

The P300 (P3) wave of the auditory brain event-related potential was investigated in patients with probable Alzheimer\u27s disease to determine whether P300 latency discriminated these patients from controls and whether prolonged P300 latency correlated with rates of brain glucose metabolism as measured by Positron Emission Tomography. P300 latency was prolonged by more than 1.5 standard deviations from age expectancy in 14 of 18 patients, but none of 17 controls. In these subjects P300 latency was shown to be inversely correlated with relative metabolic rates of parietal and, to a lesser extent, temporal and frontal association areas, but not with subcortical areas

Clinical Characterization of Alzheimer's Disease: Reliability of 'Age at Onset' and a New Descriptor, 'Age at Shift'

To determine the interrater reliability of clinical descriptors for Alzheimer's disease (AD), we assessed the degree of agree ment among four clinicians who rated 21 patients during a longitudinal study. Despite variability in response patterns, degree of agreement for determining age at onset of dementia was statistically significant (P < 0.005). We also found significant agreement (P < 0.0001) among three clinicians for the clinical descriptor, "age at shift" from questionable to probable AD, according to the National Institutes of Health Consensus Criteria. These data demonstrate that both retro spective and prospective descriptors can be reliably determined in the clinical assessment of AD. (J Geriatr Psychiatry Neurol 1988;1:207-211).Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/68908/2/10.1177_089198878800100404.pd

INTIMATE PARTNER VIOLENCE RISK AMONG VICTIMS OF YOUTH VIOLENCE: ARE EARLY UNIONS BAD, BENEFICIAL, OR BENIGN?*

Youth violent victimization (YVV) is a risk factor for precocious exits from adolescence via early coresidential union formation. It remains unclear, however, whether these early unions 1) are associated with intimate partner violence (IPV) victimization, 2) interrupt victim continuity or victim–offender overlap through protective and prosocial bonds, or 3) are inconsequential. By using data from the National Longitudinal Study of Adolescent to Adult Health (N = 11,928; 18–34 years of age), we examine competing hypotheses for the effect of early union timing among victims of youth violence (n = 2,479)—differentiating across victimization only, perpetration only, and mutually combative relationships and considering variation by gender. The results from multinomial logistic regression models indicate that YVV increases the risk of IPV victimization in first unions, regardless of union timing; the null effect of timing indicates that delaying union formation would not reduce youth victims’ increased risk of continued victimization. Gender-stratified analyses reveal that earlier unions can protect women against IPV perpetration, but this is partly the result of an increased risk of IPV victimization. The findings suggest that YVV has significant transformative consequences, leading to subsequent victimization by coresidential partners, and this association might be exacerbated among female victims who form early unions. We conclude by discussing directions for future research

Improving the Timing Resolution of Positron Emission Tomography Detectors Using Boosted Learning -- A Residual Physics Approach

Artificial intelligence (AI) is entering medical imaging, mainly enhancing image reconstruction. Nevertheless, improvements throughout the entire processing, from signal detection to computation, potentially offer significant benefits. This work presents a novel and versatile approach to detector optimization using machine learning (ML) and residual physics. We apply the concept to positron emission tomography (PET), intending to improve the coincidence time resolution (CTR). PET visualizes metabolic processes in the body by detecting photons with scintillation detectors. Improved CTR performance offers the advantage of reducing radioactive dose exposure for patients. Modern PET detectors with sophisticated concepts and read-out topologies represent complex physical and electronic systems requiring dedicated calibration techniques. Traditional methods primarily depend on analytical formulations successfully describing the main detector characteristics. However, when accounting for higher-order effects, additional complexities arise matching theoretical models to experimental reality. Our work addresses this challenge by combining traditional calibration with AI and residual physics, presenting a highly promising approach. We present a residual physics-based strategy using gradient tree boosting and physics-guided data generation. The explainable AI framework SHapley Additive exPlanations (SHAP) was used to identify known physical effects with learned patterns. In addition, the models were tested against basic physical laws. We were able to improve the CTR significantly (more than 20%) for clinically relevant detectors of 19 mm height, reaching CTRs of 185 ps (450-550 keV)

Imaging butyrylcholinesterase activity in Alzheimer's disease

No abstract.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/55890/1/21023_ftp.pd

Huntingtin regulates Ca2+ chemotaxis and K+-facilitated cAMP chemotaxis, in conjunction with the monovalent cation/H+ exchanger Nhe1, in a model developmental system: Insights into its possible role in Huntington׳s disease

AbstractHuntington׳s disease is a neurodegenerative disorder, attributable to an expanded trinucleotide repeat in the coding region of the human HTT gene, which encodes the protein huntingtin. These mutations lead to huntingtin fragment inclusions in the striatum of the brain. However, the exact function of normal huntingtin and the defect causing the disease remain obscure. Because there are indications that huntingtin plays a role in Ca2+ homeostasis, we studied the deletion mutant of the HTT ortholog in the model developmental system Dictyostelium discoideum, in which Ca2+ plays a role in receptor-regulated behavior related to the aggregation process that leads to multicellular morphogenesis. The D. discoideum htt−-mutant failed to undergo both K+-facilitated chemotaxis in spatial gradients of the major chemoattractant cAMP, and chemotaxis up a spatial gradient of Ca2+, but behaved normally in Ca2+-facilitated cAMP chemotaxis and Ca2+-dependent flow-directed motility. This was the same phenotypic profile of the null mutant of Nhel, a monovalent cation/H+exchanger. The htt−-mutant also failed to orient correctly during natural aggregation, as was the case for the Nhel mutant. Moreover, in a K+-based buffer the normal localization of actin was similarly defective in both htt− and nhe1− cells in a K+-based buffer, and the normal localization of Nhe1 was disrupted in the htt− mutant. These observations demonstrate that Htt and Nhel play roles in the same specific cation-facilitated behaviors and that Nhel localization is directly or indirectly regulated by Htt. Similar cation-dependent behaviors and a similar relationship between Htt and Nhe1 have not been reported for mammalian neurons and deserves investigation, especially as it may relate to Huntington׳s disease

Posterior cingulate cortex in Alzheimer's disease

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/31318/1/0000227.pd