The Ecology of Signal Crayfish in Two Large Ultra-Oligotrophic Ecosystems: Crater Lake and Lake Tahoe

Invasive species have become an increasing problem in the Western United States particularly when there are multiple stressors (e.g., invasive species and eutrophication) occurring to ecosystems. Invasive omnivores can present unique problems for aquatic ecosystems by having both direct and indirect impacts on native benthic invertebrates and vertebrates. Omnivorous crayfish, for example, strongly influence littoral habitats and biota with their foraging habits, creating both direct and indirect effects on trophic interactions in aquatic systems. Once they invade, these crayfish can ultimately dominate freshwater ecosystems. This dissertation investigates the distribution, density changes, and the direct and indirect impacts of the invasive signal crayfish (Pacifastacus leniusculus) in two oligotrophic lentic ecosystems in the western United States; Lake Tahoe (CA-NV) and Crater Lake (OR). In chapter 1, I investigate the distribution, movement, and feeding behavior of invasive signal crayfish in Crater Lake. This lake population presents a unique opportunity to understand the movement of crayfish in a recently expanding population. I used minnow traps and snorkeling to determine crayfish distribution and stable isotope ratios of δ13C and δ15N to determine the flow of organic matter through the food web, trophic position, and percent benthic reliance. Depth gradient minnow traps demonstrate that crayfish densities can live as deep as 250 m. Trap and snorkel surveys from 2008 to 2013 indicate an expansion of crayfish from 44% to 78% of the littoral zone. Summer water temperature in Crater Lake has been warming, which may increase the recruitment of individuals and expand habitat availability for growth. Between 1965 and 2014 the nearshore surface temperature increased by 3.5°C. Principal component analysis revealed a positive relationship between crayfish occupation and cobble and boulder habitats of the lake. Crayfish in the littoral zone rely heavily (97.4%) on littoral-benthic carbon sources indicating their potential for impacting native invertebrate communities and the overall dynamics of Crater Lake’s ecosystem. Our findings indicate, however, that deeper water crayfish also may rely on littoral benthic energy resources. Crayfish movement to deeper waters may be subsidizing generally nutrient poor, deep-water habitats with littoral energy through excretion and egestion, where physical conditions are stable and natural perturbation is low.In Chapter 2, I quantify the influence of this early, expanding invasion in Crater Lake to littoral zone ecology by evaluating their influence on zoobenthic consumer biomass and basal algal biomass. Benthic invertebrate biomass was 77% lower in hard substrate and 78% lower in soft substrate areas with crayfish present than in crayfish-absent locations. Using Bayesian, stable isotope mixing models, dietary preferences of crayfish at three locations with varying crayfish densities were quantified. Only slight variations in crayfish diet were detected between the three locations where crayfish have been established, the outer boundary of crayfish expansion, and the middle of the crayfish population indicating that crayfish. Despite differing densities, crayfish are feeding on similar food sources, particularly benthic invertebrates. At low crayfish densities (0 to 10), benthic invertebrate numbers were 222.3±36.6 individuals m-2, while chlorophyll a was 16.8±5.8 mg m-2. At high densities of crayfish (>50), benthic invertebrates had low mean density 3.0±4.2 individuals m-2, while chlorophyll a biomass was high 226.7±48.1 mg m-2. Crayfish are impacting native invertebrate communities and periphyton biomass in Crater Lake by changing trophic interactions in the lake’s littoral zone and altering the lake’s food web.In Chapter 3, I focus on the benthic environment and biodiversity of Lake Tahoe and regional lakes (Donner Lake, Marlette Lake, and Fallen Leaf Lake. Signal crayfish were introduced into the Central Sierra Nevada region of the United States in the late 19th to early 20th century. I used a long-term data set to document highly variable crayfish densities in the littoral zone of Lake Tahoe, showing an increase during the summer months linked to an increase in water temperature (R2 = 0.69, P<0.001). Crayfish responded to site-specific characteristics of the nearshore rather than to lake-wide characteristics; local stream discharge was the only factor that explained a positive increase in lake densities (P< 0.04). Trophic niche models developed from stable isotope measurements of crayfish and nongame fish indicate that crayfish influence the dietary breadth (e.g. niche area) of nongame fish consumers. Crayfish feeding behavior may be forcing nongame fish to feed on a broader set of food resources when crayfish are present. Stable isotope analysis also indicates an overlap of crayfish niche area with other nongame fish and amphibians, indicating interspecific competition between organisms. Our study highlights that local factors influence cold-water crayfish movement and densities in large lakes, as well as potential direct and indirect influences on nongame fish consumers in the littoral region, potentially affecting native biota and ecosystem function. This research has significant implications for understanding the direct and indirect impacts of signal crayfish in oligotrophic food webs, particularly on benthic invertebrate densities. It expands on the current understanding of expansion of signal crayfish and the factors that influence crayfish density. Future research will need to focus on better understanding the life history and mechanisms controlling this species if they are to be controlled in lakes of the Western United States

Are commonly used self-report inventories suitable for screening postpartum depression and anxiety disorders?

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/66459/1/j.1600-0447.2000.102001071.x.pd

Discovering a taste for the unusual: exceptional models for preference mining

Exceptional preferences mining (EPM) is a crossover between two subfields of data mining: local pattern mining and preference learning. EPM can be seen as a local pattern mining task that finds subsets of observations where some preference relations between labels significantly deviate from the norm. It is a variant of subgroup discovery, with rankings of labels as the target concept. We employ several quality measures that highlight subgroups featuring exceptional preferences, where the focus of what constitutes exceptional' varies with the quality measure: two measures look for exceptional overall ranking behavior, one measure indicates whether a particular label stands out from the rest, and a fourth measure highlights subgroups with unusual pairwise label ranking behavior. We explore a few datasets and compare with existing techniques. The results confirm that the new task EPM can deliver interesting knowledge.This research has received funding from the ECSEL Joint Undertaking, the framework programme for research and innovation Horizon 2020 (2014-2020) under Grant Agreement Number 662189-MANTIS-2014-1

Synthesis, structure and magnetic properties ofβ-MnO2nanorods

We present synthesis, structure and magnetic properties of structurally well-ordered single-crystalline β-MnO2nanorods of 50–100 nm diameter and several µm length. Thorough structural characterization shows that the basic β-MnO2material is covered by a thin surface layer (∼2.5 nm) of α-Mn2O3phase with a reduced Mn valence that adds its own magnetic signal to the total magnetization of the β-MnO2nanorods. The relatively complicated temperature-dependent magnetism of the nanorods can be explained in terms of a superposition of bulk magnetic properties of spatially segregated β-MnO2and α-Mn2O3constituent phases and the soft ferromagnetism of the thin interface layer between these two phases

Exceptional Preferences Mining

Exceptional Preferences Mining (EPM) is a crossover between two subfields of datamining: local pattern mining and preference learning. EPM can be seen as a local pattern mining task that finds subsets of observations where the preference relations between subsets of the labels significantly deviate from the norm; a variant of Subgroup Discovery, with rankings as the (complex) target concept. We employ three quality measures that highlight subgroups featuring exceptional preferences, where the focus of what constitutes 'exceptional' varies with the quality measure: the first gauges exceptional overall ranking behavior, the second indicates whether a particular label stands out from the rest, and the third highlights subgroups featuring unusual pairwise label ranking behavior. As proof of concept, we explore five datasets. The results confirm that the new task EPM can deliver interesting knowledge. The results also illustrate how the visualization of the preferences in a Preference Matrix can aid in interpreting exceptional preference subgroups

Synthesis and Cathodoluminescence of Undoped and Cr^3^+-Doped Sodium Titanate Nanotubes and Nanoribbons

We report on the synthesis of Cr^3^+-doped sodium titanate nanotubes and nanoribbons by a hydrothermal method. The presence of dopant ions in these nanostructures was confirmed by high angle annular dark field scanning transmission electron microscopy in combination with electron energy loss spectroscopy measurements. Luminescence properties of undoped and Cr^3^+-doped sodium titanate nanotubes and nanoribbons were investigated by cathodoluminescence in the scanning electron microscope. A broad visible band in the range 1.7−2.7 eV is observed in these nanostructures. Such emission is similar to that observed in bulk anatase TiO_2 and titanate powders, and is related to TiO_6 octahedra, which is a common feature to all the samples investigated. Near-infrared emission, sometimes attributed to Ti^3^+ interstitials, is observed in bulk powders but is absent in the titanate nanotubes and nanoribbons. Incorporation of Cr^3^+ between the titanate layers of the nanostructures is revealed by the characteristic intraionic emission line at 1.791 eV. Sodium titanate nanoribbons appear to be an effective host for optically active Cr^3^+ ions, as compared with nanotubes or bulk powder

The over-representation of binary DNA tracts in seven sequenced chromosomes

BACKGROUND: DNA tracts composed of only two bases are possible in six combinations: A+G (purines, R), C+T (pyrimidines, Y), G+T (Keto, K), A+C (Imino, M), A+T (Weak, W) and G+C (Strong, S). It is long known that all-pyrimidine tracts, complemented by all-purines tracts ("R.Y tracts"), are excessively present in analyzed DNA. We have previously shown that R.Y tracts are in vast excess in yeast promoters, and brought evidence for their role in gene regulation. Here we report the systematic mapping of all six binary combinations on the level of complete sequenced chromosomes, as well as in their different subregions. RESULTS: DNA tracts composed of the above binary base combinations have been mapped in seven sequenced chromosomes: Human chromosomes 21 and 22 (the major contigs); Drosophila melanogaster chr. 2R; Caenorhabditis elegans chr. I; Arabidopsis thaliana chr. II; Saccharomyces cerevisiae chr. IV and M. jannaschii. A huge over-representation, reaching million-folds, has been found for very long tracts of all binary motifs except S, in each of the seven organisms. Long R.Y tracts are the most excessive, except in D. melanogaster, where the K.M motif predominates. S (G, C rich) tracts are in excess mainly in CpG islands; the W motif predominates in bacteria. Many excessively long W tracts are nevertheless found also in the archeon and in the eukaryotes. The survey of complete chromosomes enables us, for the first time, to map systematically the intergenic regions. In human and other chromosomes we find the highest over-representation of the binary DNA tracts in the intergenic regions. These over-representations are only partly explainable by the presence of interspersed elements. CONCLUSIONS: The over-representation of long DNA tracts composed of five of the above motifs is the largest deviation from randomness so far established for DNA, and this in a wide range of eukaryotic and archeal chromosomes. A propensity for ready DNA unwinding is proposed as the functional role, explaining the evolutionary conservation of the huge excesses observed

CCAAT/Enhancer Binding Protein alpha uses distinct domains to prolong pituitary cells in the Growth 1 and DNA Synthesis phases of the cell cycle

BACKGROUND: A number of transcription factors coordinate differentiation by simultaneously regulating gene expression and cell proliferation. CCAAT/enhancer binding protein alpha (C/EBPα) is a basic/leucine zipper transcription factor that integrates transcription with proliferation to regulate the differentiation of tissues involved in energy balance. In the pituitary, C/EBPα regulates the transcription of a key metabolic regulator, growth hormone. RESULTS: We examined the consequences of C/EBPα expression on proliferation of the transformed, mouse GHFT1-5 pituitary progenitor cell line. In contrast to mature pituitary cells, GHFT1-5 cells do not contain C/EBPα. Ectopic expression of C/EBPα in the progenitor cells resulted in prolongation of both growth 1 (G1) and the DNA synthesis (S) phases of the cell cycle. Transcription activation domain 1 and 2 of C/EBPα were required for prolongation of G1, but not of S. Some transcriptionally inactive derivatives of C/EBPα remained competent for G1 and S phase prolongation. C/EBPα deleted of its leucine zipper dimerization functions was as effective as full-length C/EBPα in prolonging G1 and S. CONCLUSION: We found that C/EBPα utilizes mechanistically distinct activities to prolong the cell cycle in G1 and S in pituitary progenitor cells. G1 and S phase prolongation did not require that C/EBPα remained transcriptionally active or retained the ability to dimerize via the leucine zipper. G1, but not S, arrest required a domain overlapping with C/EBPα transcription activation functions 1 and 2. Separation of mechanisms governing proliferation and transcription permits C/EBPα to regulate gene expression independently of its effects on proliferation

Guidelines For The Standardization Of Preanalytic Variables For Blood-based Biomarker Studies In Alzheimer\u27s Disease Research

The lack of readily available biomarkers is a significant hindrance toward progressing to effective therapeutic and preventative strategies for Alzheimer\u27s disease (AD). Blood-based biomarkers have potential to overcome access and cost barriers and greatly facilitate advanced neuroimaging and cerebrospinal fluid biomarker approaches. Despite the fact that preanalytical processing is the largest source of variability in laboratory testing, there are no currently available standardized preanalytical guidelines. The current international working group provides the initial starting point for such guidelines for standardized operating procedures (SOPs). It is anticipated that these guidelines will be updated as additional research findings become available. The statement provides (1) a synopsis of selected preanalytical methods utilized in many international AD cohort studies, (2) initial draft guidelines/SOPs for preanalytical methods, and (3) a list of required methodological information and protocols to be made available for publications in the field to foster cross-validation across cohorts and laboratorie

The genetic architecture of the human cerebral cortex

The cerebral cortex underlies our complex cognitive capabilities, yet little is known about the specific genetic loci that influence human cortical structure. To identify genetic variants that affect cortical structure, we conducted a genome-wide association meta-analysis of brain magnetic resonance imaging data from 51,665 individuals. We analyzed the surface area and average thickness of the whole cortex and 34 regions with known functional specializations. We identified 199 significant loci and found significant enrichment for loci influencing total surface area within regulatory elements that are active during prenatal cortical development, supporting the radial unit hypothesis. Loci that affect regional surface area cluster near genes in Wnt signaling pathways, which influence progenitor expansion and areal identity. Variation in cortical structure is genetically correlated with cognitive function, Parkinson's disease, insomnia, depression, neuroticism, and attention deficit hyperactivity disorder