The Enrichment of Stable Cesium and Rubidium in Savannah River Site Soils

The following dissertation investigates the sequestration of Cs and Rb in the wedge zone regions of hydroxy-interlayered vermiculite (HIV), a clay mineral commonly found in the southeastern United States. Savannah River Site soils are studied from the highly contaminated Department of Energy Site. The soils are found to preferentially adsorb Cs and Rb (to a lesser extent) with respect to K and be highly enriched with respect to upper continental crust. Enrichment is found to be a function of weathering progression. Molecular modeling results support the hypothesis that Cs is the sterically favorable ion in the interlayer wedge zone of HIV

Coral records of radiocarbon variability in the central tropical pacific during the last millennium

Ocean circulation changes in the tropical Pacific strongly influence global climate, as demonstrated during El Niño-Southern Oscillation (ENSO) extremes. Understanding the causes of past variability in tropical Pacific circulation and their relationship to climate change will help to predict how future climate may evolve under anthropogenic radiative forcing. I measure fossil coral radiocarbon (Δ¹⁴C) from Palmyra (6°N, 162°W) and Christmas (2°N, 157°W) Islands in the central tropical Pacific to reconstruct high-resolution records of tropical Pacific ocean circulation variability over the last millennium. Variations in coral Δ¹⁴C from Palmyra and Christmas reflect a combination of the atmospheric concentration of ¹⁴C at the time of growth, Δ¹⁴C-depleted waters associated with equatorial upwelling, and Δ¹⁴C -enriched waters advected from the western tropical Pacific. Existing oxygen isotopic (δ ¹⁸O) records of the Palmyra and Christmas fossil corals reveal a rich history of interannual to centennial variability in sea-surface temperature (SST) and salinity over the last millennium [Cobb et al., 2003b]. My approach targets specific time intervals associated with strong interannual to centennial-scale coral δ ¹⁸O anomalies for high-resolution Δ¹⁴C analysis. Seasonally-resolved Δ¹⁴C measurements are used to compare interannual Δ¹⁴C variability across the 10th, 13th, 15th, 17th, and 20th centuries. Annually-resolved Δ¹⁴C measurements are used to compare decadal to centennial-scale Δ¹⁴C variations from the 10th, 12th - 15th and 17th centuries. SEM photos are used to assess the fidelity of the coral Δ¹⁴C records with respect to post-depositional alteration of the coral skeleton. I find evidence for minor dissolution and addition of secondary aragonite, but my results indicate that coral Δ¹⁴C is only compromised after moderate to severe diagenesis. Despite strong ENSO signals in modern and fossil coral δ ¹⁸O, our data show no statistically significant interannual variability in coral ¹⁴C. There is a centennial-scale increase in coral radiocarbon from the Medieval Climate Anomaly (MCA, ~900-1200AD) to the Little Ice Age (LIA, ~1500-1800). I use a box model of central tropical Pacific Δ¹⁴C contributions to show that this centennial-scale trend over the last millennium is largely explained by centennial-scale changes in atmospheric ¹⁴C. However, large 12th century depletions in Palmyra coral ∆¹⁴C data cannot be explained by atmospheric ¹⁴C variability and likely reflect a roughly two-fold increase in upwelling and/or a significant change in the ¹⁴C of higher-latitude source waters reaching the equatorial Pacific during this time. Conversely, significantly enriched Christmas coral ∆¹⁴C values during the 16th century are consistent with a two-fold reduction in upwelling strength and/or the advection of high-¹⁴C waters to the equatorial thermocline from higher latitudes.M.S.Committee Chair: Kim Cobb; Committee Member: Annalisa Bracco; Committee Member: Ellery Ingall; Committee Member: Jean Lynch-Stieglitz; Committee Member: Yuhang Wan

Cholinergic Pathway SNPs and Postural Control in 477 Older Adults

Objective: To determine whether single nucleotide polymorphisms (SNPs) of the cholinergic system and quantitative parameters of postural control are associated in healthy older adults. This is a cross-sectional analysis from the TREND study.Methods: All participants performed a static postural control task for 30 s on a foam pad in semitandem stance and eyes closed. We analyzed mean power frequency (MPF), area, acceleration, jerk, and velocity from a mobile sensor worn at the lower back using a validated algorithm. Genotypes of four SNPs in genes involved in the cholinergic system (SLC5A7, CHAT, BCHE, CHRNA4) were extracted from the NeuroX chip. All participants present a normal neurological examination and a Minimental state examination score >24.Results: Four hundred and seventy seven participants were included. Mean age was 69 years, 41% were female. One SNP of the cholinergic pathway was significantly associated with a quantitative postural control parameter. The minor allele of rs6542746 in SLC5A7 was associated with lower MPF (4.04 vs. 4.22 Hz; p = 3.91 × 10-4). Moreover, the following associations showed trends toward significance: minor allele of rs6542746 in SLC5A7 with higher anteroposterior acceleration (318 vs. 287 mG; p = 0.005), and minor allele of rs3810950 in CHAT with higher mediolateral acceleration [1.77 vs. 1.65 log(mG); p = 0.03] and velocity [1.83 vs. 1.74 log(mm/s); p = 0.019]. Intraindividual occurrence of rs6542746 and rs3810950 minor alleles was dose-dependently related with lower MPF (p = 0.004).Conclusion: This observational study suggests an influence of SNPs of the cholinergic pathway on postural control in older adults

Effect of Fear of Falling on Turning Performance in Parkinson's Disease in the Lab and at Home

Background: Parkinson's disease (PD) is a neurodegenerative movement disorder associated with gait and balance problems and a substantially increased risk of falling. Falls occur often during complex movements, such as turns. Both fear of falling (FOF) and previous falls are relevant risk factors for future falls. Based on recent studies indicating that lab-based and home assessment of similar movements show different results, we hypothesized that FOF and a positive fall history would influence the quantitative turning parameters differently in the laboratory and home. Methods: Fifty-five PD patients (43 underwent a standardized lab assessment; 40 were assessed over a mean of 12 days at home with approximately 10,000 turns per participant; and 28 contributed to both assessments) were classified regarding FOF and previous falls as "vigorous" (no FOF, negative fall history), "anxious" (FOF, negative fall history), "stoic" (no FOF, positive fall history) and "aware" (FOF, positive fall history). During the assessments, each participant wore a sensor on the lower back. Results: In the lab assessment, FOF was associated with a longer turning duration and lowered maximum and middle angular velocities of turns. In the home evaluations, a lack of FOF was associated with lowered maximum and average angular velocities of turns. Positive falls history was not significantly associated with turning parameters, neither in the lab nor in the home. Conclusion: FOF but not a positive fall history influences turning metrics in PD patients in both supervised and unsupervised environments, and this association is different between lab and home assessments. Our findings underline the relevance of comprehensive assessments including home-based data collection strategies for fall risk evaluation

Assoziation von subjektiv empfundener Schlafqualität und motorischen Bewegungsprofilen mit der Levodopa Nachtmedikation von Parkinsonpatienten : eine Querschnittsstudie unter Verwendung von tragbaren Bewegungssensoren und standardisierten Fragebögen

Diese Arbeit untersucht die Frage, inwieweit sich die Gabe von retardiertem L-3,4- Dihydroxyphenylalanin (Levodopa) zur Nacht auf die subjektive Wahrnehmung und die objektive Messung der Schlafqualität bei Patienten mit idiopathischen Parkinsonsyndrom (IPS) auswirkt. Des Weiteren soll geklärt werden, in welchen Parametern sich die objektiv gemessene Schlafqualität zwischen IPS-Patienten und gesunden Probanden unterscheide

Enrichment of Cesium and Rubidium in Weathered Micaceous Materials at the Savannah River Site, South Carolina

The enrichment of Cs and Rb relative to Ba, Sr, and K in three soils representing a range of soil maturities was determined to investigate the long-term sorption behavior of these elements in upland soils of the Savannah River Site (SRS). Elemental mass fractions normalized to upper continental crust (UCC) decreased in the order Cs > Rb > Ba > K > Sr in the soil fine fractions. Only the UCC-normalized amount of Cs was greater than unity. The UCC-normalized amounts in strong-acid extracts decreased as Cs > Rb > Ba > K ≈ Sr. In all three soil cores, the trends of the UCC-normalized amounts of acid-extractable metals were similar to trends of cation-exchange capacity (CEC) calculated from synchrotron-X-ray diffractometry measurements of soil mineralogy. Consequently, the relative enrichment of Cs and Rb is largely controlled by selective sorption to micaceous minerals, including hydroxy-interlayered vermiculite, that dominate the CEC. Where high clay content had caused retention of soil solution, amounts of acid extractable K, Sr, and Ba were enhanced. The retention of natural Cs by these three soils, which developed over many thousands of years, is a strong indicator that radiocesium will likewise be retained in SRS soils