On the Curious Resemblance Between Fly Ash and Meteoritic Dust

This paper is a discussion of W. J. Thomsen\u27s prize-winning paper presented to the Geology Section of the Iowa Academy of Science in 1952 and entitled The Annual Contribution of Meteoritic Dust to the Mass of the Earth (1). The present paper presents evidence that Thomsen\u27s unusually high estimate for the annual deposition of meteoritic dust may be due to the presence of fly-ash in the magnetic dust samples he collected

Variation of Loess Thickness and Clay Content in Southern Iowa

This report summarizes two aspects of the Wisconsin loess in southern Iowa and presents some information on the sandy-silt immediately underlying the loess and overlying the till in southcentral Iowa. The data has originated from project work done over the last five year on the loess and glacial till of Iowa (Project 283-S) in .an attempt to solve the problem of stabilization of loess and till for roads. This paper incorporates data procured to date on the loess of southwest, southern and east-central Iowa and present studies in progress in south-central Iowa. (See references 1, 2, 3 and 4.

Eigenvalues of PT-symmetric oscillators with polynomial potentials

We study the eigenvalue problem $-u^{\prime\prime}(z)-[(iz)^m+P_{m-1}(iz)]u(z)=\lambda u(z)$ with the boundary conditions that $u(z)$ decays to zero as $z$ tends to infinity along the rays $\arg z=-\frac{\pi}{2}\pm \frac{2\pi}{m+2}$, where $P_{m-1}(z)=a_1 z^{m-1}+a_2 z^{m-2}+...+a_{m-1} z$ is a polynomial and integers $m\geq 3$. We provide an asymptotic expansion of the eigenvalues $\lambda_n$ as $n\to+\infty$, and prove that for each {\it real} polynomial $P_{m-1}$, the eigenvalues are all real and positive, with only finitely many exceptions.Comment: 23 pages, 1 figure. v2: equation (14) as well as a few subsequent equations has been changed. v3: typos correcte

Physiological modulation of iron metabolism in rainbow trout (Oncorhynchus mykiss) fed low and high iron diets

Iron (Fe) is an essential element, but Fe metabolism is poorly described in fish and the role of ferrireductase and transferrin in iron regulation by teleosts is unknown. The aim of the present study was to provide an overview of the strategy for Fe handling in rainbow trout, Oncorhynchus mykiss. Fish were fed Fe-deficient, normal and high-Fe diets (33, 175, 1975 mg Fe kg-1 food, respectively) for 8 weeks. Diets were chosen so that no changes in growth, food conversion ratio, haematology, or significant oxidative stress (TBARS) were observed. Elevation of dietary Fe caused Fe accumulation particularly in the stomach, intestine, liver and blood. The increase in total serum Fe from 10 to 49 μmol l-1 over 8 weeks was associated with elevated total Fe binding capacity and decreased unsaturated Fe binding capacity, so that in fish fed a high-Fe diet transferrin saturation increased from 15% at the start of the experiment to 37%. Fish on the high-Fe diet increased Fe accumulation in the liver, which was correlated with elevation of hepatic ferrireductase activity and serum transferrin saturation. Conversely, fish on the low-Fe diet did not show tissue Fe depletion compared with normal diet controls and did not change Fe binding to serum transferrin. Instead, these fish doubled intestinal ferrireductase activity which may have contributed to the maintenance of tissue Fe status. The absence of clear treatment-dependent changes in branchial Fe accumulation and ferrireductase activity indicated that the gills do not have a major role in Fe metabolism. Some transient changes in Cu, Zn and Mn status of tissues occurred.Facultad de Ciencias Naturales y Muse

Depth Studies of the Wisconsin Loess in Southwestern Iowa: I. Particle-Size and In-Place Density

The Soil Research Laboratory of the Iowa Engineering Experiment Station has been studying areal and stratigraphic variations in properties of the Wisconsin (Peorian) loess in southwestern Iowa since September, 1950. The information on loess properties is being utilized in soil stabilization studies now in progress. A paper presented before the Geology Section of the Iowa Academy of Science in 1952 (1) discussed the distribution of and some property variations in the Wisconsin loess in the southwestern Iowa area shown by Figure 1. While last year\u27s paper presented some depth data, the main emphasis was on areal property variations. More detailed studies of selected Wisconsin loess sections are now in progress to determine the variations in properties with depth. The present paper, Part I of two parts, presents particle-size, field moisture, and in-place density data. Part II will cover chemical, mineralogical, and additional physical property data

Exchangeable Potassium and Clay Minerals in Selected Iowa Soil Profiles

Exchangeable K values and X-ray diffraction patterns were obtained for soil samples from several modal profiles of nine different soil series in Iowa. Exchangeable K in moist subsoils was consistently low and almost always lower than in the moist surface soil. Drying increased exchangeable K in all the soils, but the increase due to drying varied between soil series and with depth in the profile of each series. Reversion of exchangeable K to a non-exchangeable form on rewetting the oven-dry samples generally increased with depth in the profile but the exchangeable K never decreased to the original moist level. X-ray diffraction analyses showed the presence of montmorillonite, chorlite, illite and/ or mica, and kaolinite in all the profiles, with mortmorillonite predominating. Vermiculite was present in some of the soil series. No relationship between the clay mineral content and the amount of exchangeable K could be established

Palytoxin Found in Palythoa sp. Zoanthids (Anthozoa, Hexacorallia) Sold in the Home Aquarium Trade

Zoanthids (Anthozoa, Hexacorallia) are colonial anemones that contain one of the deadliest toxins ever discovered, palytoxin (LD50 in mice 300 ng/kg), but it is generally believed that highly toxic species are not sold in the home aquarium trade. We previously showed that an unintentionally introduced zoanthid in a home aquarium contained high concentrations of palytoxin and was likely responsible for a severe respiratory reaction when an individual attempted to eliminate the contaminant colonies using boiling water. To assess the availability and potential exposure of palytoxin to marine aquarium hobbyists, we analyzed zoanthid samples collected from local aquarium stores for palytoxin using liquid chromatography and high resolution mass spectrometry and attempted to identify the specimens through genetic analysis of 16S and cytochrome c oxidase 1 (COI) markers. We found four specimens of the same apparent species of zoanthid, that we described previously to be responsible for a severe respiratory reaction in a home aquarium, to be available in three aquarium stores in the Washington D.C. area. We found all of these specimens (n = 4) to be highly toxic with palytoxin or palytoxin-like compounds (range 0.5–3.5 mg crude toxin/g zoanthid). One of the most potent non-protein compounds ever discovered is present in dangerous quantities in a select species of zoanthid commonly sold in the home aquarium trade

Dynamics of the solar chromosphere. V. High-frequency modulation in ultraviolet image sequences from TRACE

We search for signatures of high-frequency oscillations in the upper solar photosphere and low chromosphere in the context of acoustic heating of outer stellar atmospheres. We use ultraviolet image sequences of a quiet center-disk area from the Transition Region and Coronal Explorer (TRACE) mission which were taken with strict cadence regularity. The latter permits more reliable high-frequency diagnosis than in earlier work. Spatial Fourier power maps, spatially averaged coherence and phase-difference spectra, and spatio-temporal k-f decompositions all contain high-frequency features that at first sight seem of considerable intrinsic interest but actually are more likely to represent artifacts of different nature. Spatially averaged phase difference measurement provides the most sensitive diagnostic and indicates the presence of acoustic modulation up to f=20 mHz (periods down to 50 seconds) in internetwork areas.Comment: 9 pages, 8 figure

Distributed leadership, trust and online communities

This paper analyses the role of distributed leadership and trust in online communities. The team-based informal ethos of online collaboration requires a different kind of leadership from that in formal positional hierarchies. Such leadership may be more flexible and sophisticated, capable of encompassing ambiguity and rapid change. Online leaders need to be partially invisible, delegating power and distributing tasks. Yet, simultaneously, online communities are facilitated by the high visibility and subtle control of expert leaders. This paradox: that leaders need to be both highly visible and invisible as appropriate, was derived from prior research and tested in the analysis of online community discussions using a pattern-matching process. It is argued that both leader visibility and invisibility are important for the facilitation of trusting collaboration via distributed leadership. Advanced leadership responses to complex situations in online communities foster positive group interaction and decision-making, facilitated through active distribution of specific tasks