Preliminary Aspects of an Ecological Investigation of Lake East Okoboji, Iowa

A preliminary study of some ecological factors of Lake East Okoboji was made in the period June 1960- June 1961. Chemical analyses were conducted to determine phenolphthalein alkalinity, total alkalinity, calcium hardness, total hardness, chloride, sulfate, pH, dissolved oxygen, iron, phosphate, nitrate, and silica. Collections of diatoms were made concurrently with the chemical analyses. Lake East Okoboji was found to be an alkaline, shallow, non-stratified, moderately hard water lake. A large spring and fall bloom of diatoms occurred, with a dense blue-green algal bloom in mid-summer

A Microscope Lamp

9. a microscope The beginning student in biology is faced with a number of difficulties in laboratory work, and many of these problems are related to his use of the microscope. Some students, even after a year or more of biology, still confess they have rarely seen what they were supposed to see through the microscope

Frogs: Living Tools of Science

The lowly frog has long been the biologist\u27s friend. As a small vertebrate available in large numbers, this amphibian has been made the high point of every biology class across the country, since the turn of the century

A DNA Extract from \u3ci\u3eGrocericus storeii\u3c/i\u3e

A simple, but accurate DNA model can be constructed by students, working in groups of two, from common grocery store materials

Iowa Science Teacher\u27s Association Financial Report

Iowa Science Teacher’s Association Financial Report as presented at the Annual Meeting, October 16, 1964

Detection of Methyl Radicals in a Flat Flame by Degenerate Four-Wave Mixing

We report the spatially resolved detection of methyl radicals in a methane–air f lat flame, using degenerate four-wave mixing (DFWM). A frequency-tripled dye laser pumped with a frequency-doubled Nd:YAG laser was used to access the Herzberg b1 band of methyl near 216 nm. Using a nearly phase-conjugate geometry, we detected methyl with high spatial resolution [0.2 mm (0.3 mm) vertical (horizontal) and ,6 mm longitudinal] and with good signal-to-noise ratio in a rich sf _ 1.55d flame. Compared with laser absorption spectra, DFWM spectra were much less influenced by a broad featureless background. From the absorption data, we measured the peak methyl concentration to be 650 parts in 106, resulting in an estimated DFWM detection limit of 65 parts in 106.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/86762/1/Sick48.pd

Changes in the Aquatic Vascular Flora of Lake East Okoboji in Historic Times

The submerged, floating, and emergent vascular flora of Lake East Okoboji, Dickenson County, Iowa, was surveyed by the senior author in the summer of 1961, with collections made at 21 stations. Emergent species and one hybrid, and 7 submerged or floating species were found. A comparison is made with a 1915 survey in which a very rich flora of about 18 emergents and 26 submerged or floating species was reported. Pollution by sewage and by agricultural fertilizers and other factors that may have caused changes in the vascular flora are discussed

Robust optimal stopping

This paper studies the optimal stopping problem in the presence of model uncertainty (ambiguity). We develop a method to practically solve this problem in a general setting, allowing for general time-consistent ambiguity averse preferences and general payoff processes driven by jump-diffusions. Our method consists of three steps. First, we construct a suitable Doob martingale associated with the solution to the optimal stopping problem using backward stochastic calculus. Second, we employ this martingale to construct an approximated upper bound to the solution using duality. Third, we introduce backward-forward simulation to obtain a genuine upper bound to the solution, which converges to the true solution asymptotically. We analyze the asymptotic behavior and convergence properties of our method. We illustrate the generality and applicability of our method and the potentially significant impact of ambiguity to optimal stopping in a few examples