The Use of Chemical Element Fingerprints to Investigate the Transformation of Lake Sediments to Land Soils in Drying Lakes: A Case Study at Lake Mead, Nevada

Drying lakes are a worldwide catastrophe. The goals of this dissertation research were (1) to investigate whether chemical fingerprints of lake sediments, and nearby land soils, could be established by the analysis of 44 chemical elements, moisture content, Eh, pH, and leachable anions and if so, (2) whether the fingerprints could help explain the process of physical and chemical changes in the lake sediments as they became soils when the lake\u27s water level fell and the anoxic sediments were exposed to the air and weather. Lake Mead was chosen to model drying lakes because its water level has fallen over 150 feet from full pool, stranding acres of former lake sediments to be transformed into land soils. Since the lake was formed, it has experienced three cycles of drying and refilling. This history complicates the chemical fingerprint, but has yielded a new sediment dating method. The research was conducted at Crawdad Cove in Lake Mead, Nevada, from 2012 to 2018. Six soil or sediment cores were collected at three locations along each of two transects on the east and west sides of Crawdad Cove Road at Lake Mead. One core was at the water’s edge and two spaced equidistant going inland from the water’s edge towards the historical full lake water elevation line. Each core was sliced vertically in up to 50 samples. Data were analyzed using ICPAES, ICPMS, XRF, alpha spectrometry, and ion chromatography to examine element concentrations, percent moisture, and anion concentrations and Principal Component Analysis (PCA) to process ten thousands of the experimental results. Most chemical elements, including Mg, Al, P, S, Ca, V, Cr, Ni, Cu, Zn, Rb, Sr, Y, Zr, Ba, La, Ce, Nd, Pb, Th, and U, had their highest concentrations in the submerged sediment core and lower concentrations in the inland soil cores. Higher concentrations of F-, Cl-, and SO42- are found in the water’s edge than the farthest inland and they are strongly correlated to each other. HCO2- and NO3 are higher in the farthest inland core than at the water’s edge. Sulfur by ICP and sulfate by ion chromatography have a strong correlation, as they should. The results of PCA showed that: (1) every cores had an unique fingerprint; and (2) rather than showing a consistent pattern of change in the cores along each transect based on distance from shoreline, the patterns of chemical fingerprint in the cores reflected changes in elevation. The change in chemical fingerprints in the cores is most closely associated with time the sediments have been out of the water. The elevation is the marker of lake sediments’ wetting/drying history due to the changes in lake level. The results of this analysis indicate that there is a clear change in chemical fingerprint as drying lake sediments become soils. The most likely explanation for the chemical fingerprint change is that it reflects changes in the redox conditions from reducing to oxidizing which creates soluble element species. Other explanations are possible if the sediment composition changes over time. This could occur due to factors such as wind erosion or deposition that would change surface material composition, water erosion or deposition of the surface material and vegetation growth in the mudflats after lake water recedes that affects uptake and cycling of chemical elements. Investigation of such factors would be an interesting future extension of this analysis. Core dating or calculating sedimentation rates was done by two methods: one by an established Pb-210 dating and a new method using the historical records of lake water levels and the ratios of the natural abundances of the elements divided by the concentrations of the elements in mid-inland cores from the two transects. Results of these two dating methods agree closely, 0.6 cm/year for the Pb-210 method and 0.7 cm/year for the natural abundance ratio method. This suggests that the historical records and ratio method can substitute well for the Pb-210 dating method. It also suggests that the historical record of sediment input to the lake is somewhat preserved since Lake Mead was created in 1935

Environmental impact of the Three Kids Mine tailings, Henderson, NV

This research focused on the distribution of the Three Kids Mine tailings in surface soils in and around the mine in Henderson, Nevada. It is situated next to the communities of Calico Ridge and Lake Las Vegas Resort, and, just the west of the Lake Mead Recreation area. Even though the mine has been inactive for almost 50 years (1917-1961), tailing piles and other sources of contamination on the mine are currently exposed to the atmosphere. In this study, surface soil samples were collected along eight transects emanating from the center of Three Kids Mine tailing piles up to five miles in one mile increments. The soil samples were analyzed for lead, manganese, arsenic, and 12 other elements using x-ray florescence spectroscopy (XRF). The results of this study show that there is transport of mine tailings to surface soils at locations adjacent to the mine. The majority of the elements (Mn, Cu, Zn, As, Sr, Mo, and Pb) at these sites have concentrations above the limit of detection; chromium, cobalt, mercury, nickel, and selenium are below the limit of detection in the soil samples; and, iron, rubidium, and zirconium stay fairly constant within a factor of three or four fold. Examination of the transect maps shows that the mining wastes are transported the farthest from the center of the waste piles along Transects 1 and 2, which go up to three miles the north east and east from the site, respectively. The concentrations of manganese, arsenic, and lead in Transects 1 and 2, at one mile from the mine, are also found to be significantly higher than the U.S. Environmental Protection Agency (EPA) Regional Screening Level (RSL). The topography (altitude) of these transects is initially increasing from the west to the mine, with mountains in the path of Transect 2, and subsequently decreasing toward the Las Vegas Wash and Lake Mead. Relatively low transport of the wastes occurs on Transects 3-8, in the direction of the River Mountains, the City of Henderson, the communities of Calico Ridge, and the western edge of the Lake Las Vegas Resort, going out to between a half mile and one mile from the mine. Overall, there is contamination of surface soils adjacent to the mine site, with manganese, arsenic, and lead contamination reaching up to between one and three miles. Further study is needed to show conclusively that the mine waste has reached the communities of Calico Ridge and Lake Las Vegas Resort

Stock Return Synchronicity and Analysts’ Forecast Properties

Using stock return synchronicity as a measure of a firm’s information environment, our research investigates how the firms’ stock return synchronicity affects analysts’ forecast properties for the accuracy and optimism of the analysts’ annual earnings forecasts. Stock return synchronicity represents the degree to which market and industry information explains firm-level stock return variations. A higher stock return synchronicity indicates the higher quality of a firm’s information environment, because a firm’s stock price reflects more market-level and industry-level information relative to firm-specific information. Our study shows that stock return synchronicity positively affects the forecast properties. Our finding shows that when stock return synchronicity is high, analysts’ annual earnings forecasts are more accurate and less optimistically biased

Stock Return Synchronicity and Analysts’ Forecast Properties

Using stock return synchronicity as a measure of a firm’s information environment, our research investigates how the firms’ stock return synchronicity affects analysts’ forecast properties for the accuracy and optimism of the analysts’ annual earnings forecasts. Stock return synchronicity represents the degree to which market and industry information explains firm-level stock return variations. A higher stock return synchronicity indicates the higher quality of a firm’s information environment, because a firm’s stock price reflects more market-level and industry-level information relative to firm-specific information. Our study shows that stock return synchronicity positively affects the forecast properties. Our finding shows that when stock return synchronicity is high, analysts’ annual earnings forecasts are more accurate and less optimistically biased

G-quadruplexes as versatile scaffolds for catalysis

DNA is receiving attention as a useful biomaterial in a broad range of research fields beyond its classical role as a biopolymer for storage and delivery of genetic information. Based on its chemical and thermal stability and easy accessibility, a series of DNA-based hybrid catalysts have been developed and successfully applied to various asymmetric reactions in water. Besides the canonical Watson–Crick duplex, the G-quadruplex structure has been actively exploited as horseradish-peroxidase (HRP)-mimicking DNAzymes via specific complexation with hemin. G-quadruplexes also provide a fascinating scaffold to develop a switchable catalytic system. This review summarizes the beginning, progress, and prospects of the noncanonical DNA-based hybrid catalysts, focusing on the G-quadruplexes as versatile scaffolds for catalysis

Parenthood, Professorship, and Librarianship: Are They Mutually Exclusive?

A survey of tenure-track and tenured librarians at ARL libraries provides data on the relationship between parenthood and professorship. Results analyze the impact of the promotion and tenure process on child-bearing and child-rearing decisions. Discrepancies are found based on gender, tenure status, and family status

Isolation and functional characterization of CE1 binding proteins

<p>Abstract</p> <p>Background</p> <p>Abscisic acid (ABA) is a plant hormone that controls seed germination, protective responses to various abiotic stresses and seed maturation. The ABA-dependent processes entail changes in gene expression. Numerous genes are regulated by ABA, and promoter analyses of the genes revealed that <it>cis</it>-elements sharing the ACGTGGC consensus sequence are ubiquitous among ABA-regulated gene promoters. The importance of the core sequence, which is generally known as ABA response element (ABRE), has been demonstrated by various experiments, and its cognate transcription factors known as ABFs/AREBs have been identified. Although necessary, ABRE alone is not sufficient, and another <it>cis</it>-element known as "coupling element (CE)" is required for full range ABA-regulation of gene expression. Several CEs are known. However, despite their importance, the cognate transcription factors mediating ABA response via CEs have not been reported to date. Here, we report the isolation of transcription factors that bind one of the coupling elements, CE1.</p> <p>Results</p> <p>To isolate CE1 binding proteins, we carried out yeast one-hybrid screens. Reporter genes containing a trimer of the CE1 element were prepared and introduced into a yeast strain. The yeast was transformed with library DNA that represents RNA isolated from ABA-treated Arabidopsis seedlings. From the screen of 3.6 million yeast transformants, we isolated 78 positive clones. Analysis of the clones revealed that a group of AP2/ERF domain proteins binds the CE1 element. We investigated their expression patterns and analyzed their overexpression lines to investigate the <it>in vivo </it>functions of the CE element binding factors (CEBFs). Here, we show that one of the CEBFs, AtERF13, confers ABA hypersensitivity in Arabidopsis, whereas two other CEBFs enhance sugar sensitivity.</p> <p>Conclusions</p> <p>Our results indicate that a group of AP2/ERF superfamily proteins interacts with CE1. Several CEBFs are known to mediate defense or abiotic stress response, but the physiological functions of other CEBFs remain to be determined. Our <it>in vivo </it>functional analysis of several CEBFs suggests that they are likely to be involved in ABA and/or sugar response. Together with previous results reported by others, our current data raise an interesting possibility that the coupling element CE1 may function not only as an ABRE but also as an element mediating biotic and abiotic stress responses.</p

Effects of Nonuniform Fiber Geometries on the Microstructural Fracture Behavior of Ceramic Matrix Composites

Microstructural fracture behavior of a ceramic matrix composite (CMC) with nonuniformly distributed fibers is studied in the presentation. A comprehensive numerical analysis package to study the effect of nonuniform fiber dimensions and locations on the microstructural fracture behavior is developed. The package starts with an optimization algorithm for generating representative volume element (RVE) models that are statistically equivalent to experimental measurements. Experimentally measured statistical data are used as constraints while the optimization algorithm is running. Virtual springs are utilized between any adjacent fibers to nonuniformly distribute the coated fibers in the RVE model. The virtual spring with the optimization algorithm can efficiently generate multiple RVEs that are statistically identical to each other. Smeared crack approach (SCA) is implemented to consider the fracture behavior of the CMC material in a mesh-objective manner. The RVEs are subjected to tension as well as the shear loading conditions. SCA is capable of predicting different fracture patterns, uniquely defined by not only the fiber arrangement but also the specific loading type. In addition, global stress-strain curves show that the microstructural fracture behavior of the RVEs is highly dependent on the fiber distributions