The Influence Of Estuarine Habitats On Expression On Life History Characteristics Of Coho Salmon Smolts In South-Central Alaska

Thesis (Ph.D.) University of Alaska Fairbanks, 2012Expression of traits that lead to life history diversity in salmonids may provide population-level resilience and stability in dynamic environments. I examined habitat use and variability in life history trait expression in juvenile coho salmon Oncorhynchus kisutch occupying two contrasting estuary environments in south-central Alaska. My goal was two-fold: first, to determine if salmon were using estuaries as rearing environments and were therefore potentially vulnerable to selection pressures within; and second, to compare traits of salmon that reared in contrasting estuary environments to explore the potential for differential trait expression related to estuary size and habitat complexity differences. Juvenile coho salmon reared in estuaries for extended periods of time and patterns of use corresponded to environmental conditions within the estuaries. Populations using adjacent but contrasting estuary environments exhibited differential trait expression and were genetically distinct. My work highlights how pristine, functioning estuary habitats contribute to resilience of salmon populations to environmental changes in two ways: first, by providing habitats for individuals to increase in size and condition prior to ocean entry; and second, by providing for alternative life history tactics (providing quality habitat to delay marine entry times and increase body size). Management approaches for resilient salmon runs must therefore maintain both watershed and estuary function

Rapid Changes of Potassium Concentration at the Outer Surface of Exposed Single Neurons during Membrane Current Flow

K+-sensitive liquid ion-exchanger microelectrodes are shown to be capable of measuring concentration changes which occur on a millisecond time scale. However, some quaternary ammonium ions, such as tetraethylammonium and acetylcholine, are able to block electrode function when present in concentrations as low as 10-4 to 10-3 M. Changes in extracellular potassium concentration caused by spike activity or voltage clamp pulses of exposed single neurons of the snail Helix pomatia may be measured by these electrodes. Quantitative analysis shows that the total amount of excess potassium found in the vicinity of the cell a short time after a clamp pulse, is in relatively good agreement with the amount of potassium carried by the membrane current

Target search on a dynamic DNA molecule

We study a protein-DNA target search model with explicit DNA dynamics applicable to in vitro experiments. We show that the DNA dynamics plays a crucial role for the effectiveness of protein "jumps" between sites distant along the DNA contour but close in 3D space. A strongly binding protein that searches by 1D sliding and jumping alone, explores the search space less redundantly when the DNA dynamics is fast on the timescale of protein jumps than in the opposite "frozen DNA" limit. We characterize the crossover between these limits using simulations and scaling theory. We also rationalize the slow exploration in the frozen limit as a subtle interplay between long jumps and long trapping times of the protein in "islands" within random DNA configurations in solution.Comment: manuscript and supplementary material combined into a single documen

The nature of statistical fluctuations with applications to cosmic rays

I. The square of the mean deviation D of the combined effect of several random processes releasing an average of x, y, z ... particles per unit time and producing a, b, c ... ion pairs, respectively, per particle, is D2=a2x+b2y+c2z+..., regardless of whether the separate effects are added or subtracted by the experimental arrangement. For tube-counters, point-counters, scintillation screens and particle counting chambers, a=b=c=1; for ionization chambers a, b, c ... are unequal. II. From the standpoint of statistical fluctuations, the use of two identical instruments in a differential circuit is inferior to the use of a single instrument. III. The natural observational limit for the measurement of x particles against a background of y particles is x=0.67(y)1/2. IV. The statistical fluctuations in the ionization produced by cosmic rays in a spherical ionization chamber are treated rigorously and the fluctuations due to heterogeneity of range and to showers are derived. V. Application to existing data shows that the showers observed in cloud-chamber photographs of the cosmic radiation are also present in the ionization chamber in about the same frequency and multiplicity as indicated by the cloud-chamber results. The tube-counter investigations of the cosmic-ray flux are also in agreement with the deductions from the statistical fluctuations in the ionization chamber. An upper limit of 70±10 ion pairs per cm in air at 1 atmosphere is set for the total ionization along the path of an individual cosmic-ray secondary. The size and the relative frequency of occurrence of showers is appreciably greater at 14,700 feet elevation than at sea level. These showers are quite distinct from the ionization bursts or Stösse observed by Hoffmann, Steinke and others

Reduced tillage, but not organic matter input, increased nematode diversity and food web stability in European long‐term field experiments

Soil nematode communities and food web indices can inform about the complexity, nutrient flows and decomposition pathways of soil food webs, reflecting soil quality. Relative abundance of nematode feeding and life‐history groups are used for calculating food web indices, i.e., maturity index (MI), enrichment index (EI), structure index (SI) and channel index (CI). Molecular methods to study nematode communities potentially offer advantages compared to traditional methods in terms of resolution, throughput, cost and time. In spite of such advantages, molecular data have not often been adopted so far to assess the effects of soil management on nematode communities and to calculate these food web indices. Here, we used high‐throughput amplicon sequencing to investigate the effects of tillage (conventional vs. reduced) and organic matter addition (low vs. high) on nematode communities and food web indices in 10 European long‐term field experiments and we assessed the relationship between nematode communities and soil parameters. We found that nematode communities were more strongly affected by tillage than by organic matter addition. Compared to conventional tillage, reduced tillage increased nematode diversity (23% higher Shannon diversity index), nematode community stability (12% higher MI), structure (24% higher SI), and the fungal decomposition channel (59% higher CI), and also the number of herbivorous nematodes (70% higher). Total and labile organic carbon, available K and microbial parameters explained nematode community structure. Our findings show that nematode communities are sensitive indicators of soil quality and that molecular profiling of nematode communities has the potential to reveal the effects of soil management on soil quality

Poisson transition rates from time-domain measurements with finite bandwidth

In time-domain measurements of a Poisson two-level system, the observed transition rates are always smaller than those of the actual system, a general consequence of finite measurement bandwidth in an experiment. This underestimation of the rates is significant even when the measurement and detection apparatus is ten times faster than the process under study. We derive here a quantitative form for this correction using a straightforward state-transition model that includes the detection apparatus, and provide a method for determining a system's actual transition rates from bandwidth-limited measurements. We support our results with computer simulations and experimental data from time-domain measurements of quasiparticle tunneling in a single-Cooper-pair transistor.Comment: 4 pages, 5 figure

Alkylated-C-60 based soft materials: regulation of self-assembly and optoelectronic properties by chain branching

Derivatization of fullerene (C60) with branched aliphatic chains softens C60-based materials and enables the formation of thermotropic liquid crystals and room temperature nonvolatile liquids. This work demonstrates that by carefully tuning parameters such as type, number and substituent position of the branched chains, liquid crystalline C60 materials with mesophase temperatures suited for photovoltaic cell fabrication and room temperature nonvolatile liquid fullerenes with tunable viscosity can be obtained. In particular, compound 1, with branched chains, exhibits a smectic liquid crystalline phase extending from 84 °C to room temperature. Analysis of bulk heterojunction (BHJ) organic solar cells with a ca. 100 nm active layer of compound 1 and poly(3-hexylthiophene) (P3HT) as an electron acceptor and an electron donor, respectively, reveals an improved performance (power conversion efficiency, PCE: 1.6 ± 0.1%) in comparison with another compound, 10 (PCE: 0.5 ± 0.1%). The latter, in contrast to 1, carries linear aliphatic chains and thus forms a highly ordered solid lamellar phase at room temperature. The solar cell performance of 1 blended with P3HT approaches that of PCBM/P3HT for the same active layer thickness. This indicates that C60 derivatives bearing branched tails are a promising class of electron acceptors in soft (flexible) photovoltaic devices

The Effect of Nutrient Levels in Nutrient Cultures on the Translocation of Foliar Applied Nutrients

Since man first grew crops on calcareous soils he has probably been troubled with what we today call lime-induced chlorosis. This chlorosis has determined whether he grew certain desirable ornamentals or crops or whether he had to substitute others which were less desirable. Lime-induced chlorosis is spread world wide. It has been reported in the vine and fruit growing regions of Europe, in the chernozem soils of Russia, and many other areas where the rainfall is relatively low and the soil is relatively high in calcium carbonate. In the United States it most frequently occurs where the average annual rainfall is less than 30 inches. The conditions causing chlorosis are not stable, for it varies from year to year and even from week to week with changing conditions in climate and soil. An estimated 500,000 acres of crops grown in the western United States on calcareous soils are subject to moderate to severe chlorosis. This physiological malady has challenged the technical ingenuity of outstanding plant and soil scientists. The exact cause or causes have never been isolated; consequently no permanent preventative measures or cures can, as yet, be recommended

Identifying Factors Associated with Participation in T1D Support Program for Young Adults

Objective: Type 1 diabetes (T1D) has been shown to have a significant and stressful impact on an individual’s transition into young adulthood. Young adults are often experiencing new levels of independence and decision-making at this time. Insufficient research has been conducted on the use and impact of T1D support programs tailored to young adults in relation to the emotional impacts of the disease, access to programming, and desired outcomes of programs. his study assesses awareness, utilization, and emotional needs of T1D support programs tailored to young adults. Research Design and Methods: A cross-sectional analysis was performed on surveys collected through specific groups on Facebook (n=529). Logistic regression was used to assess factors associated with participation in T1D support programs. Results: Approximately 41% of participants had been involved in a program or activity for young adults. he average age was 24 (range 18-30) with females being overrepresented (85%). Individuals who attended a T1D support program for young adults were more likely to disagree that: 1) their T1D keeps them from having a normal life; 2) they feel their T1D controls their life; 3) they feel their T1D takes up too much mental/physical energy; or 4) they need more peer-to-peer support with T1D. Conclusion: The indings highlight the importance for T1D support programs for young adults and the unique needs of a population with T1D. T1D support programs should be considered in combination with clinical support to better prepare individuals as they transition into young adulthood