Electricity In the Farm Business

Electrical energy is an important source of power on Iowa farms- over 95 percent of our farms now receive central station electric service. And use of electricity per farm increased about 2.7 times between 1938 and 1947- from 812 to 2,174 kilowatt-hours each year. Electrical equipment used in farm production has increased too. But many possibilities for further expansion still remain

An Illustrated Key to the Ohio Cambarus and Fallicambarus (Decapoda: Cambaridae) with Comments and a New Subspecies Record

Author Institution: Department of Zoology, The Ohio State UniversityAn illustrated taxonomic key is presented using structures of the chela and carapace to identify the 4 species and 2 subspecies of Cambarus, and one species of Fallicambarus known to occur in Ohio. Those forms broadly distributed throughout the state are C. (Lacunicambarus) diogenes diogenes Girard, a primary or secondary burrower; and C. (Cambarus) bartonii cavatus Hay, a secondary or tertiary burrower; the latter crayfish has not been previously recorded from the state. Species with restricted distributions are C. (C.) ortmanni Williamson, a primary or secondary burrower confined to the Ordovician region of southwestern Ohio; C. (C.) sciotensis Rhoades, a stream dweller occurring in the Scioto River, Little Scioto River, and tributaries of the Ohio River in Scioto and Lawrence counties; C. (C.) b, carinirostris Hay, a secondary or tertiary burrower frequenting streams of the Flushing Escarpment, Mahoning River, and Grand River drainages in eastern and northeastern Ohio; C. (Puncticambarus) robustus Girard, a stream inhabitant occupying primarily tributaries to Lake Erie and central and northern tributaries to the Ohio River, and F. (Creaserinus) fodiens (Cottle), a primary burrower occurring chiefly in the glaciated regions of northern Ohio. Species with broad distributions generally have a larger number of species as associates than those with restricted distributions

Brief Note: Morphological Variations of Cambarus (Cambarus) bartonii cavatus (Decapoda: Cambaridae) from Ohio, With a Diagnosis of the Ohio Form

Author Institution: Department of Zoology, The Ohio State Universit

In-shock Cooling in Numerical Simulations

We model a one-dimensional shock-tube using smoothed particle hydrodynamics and investigate the consequences of having finite shock-width in numerical simulations. We investigate the cooling of gas during passage through the shock for different cooling regimes. For a shock temperature of 10^5K, the maximum temperature of the gas is much reduced and the cooling time was reduced by a factor of 2. At lower temperatures, we are especially interested in the production of molecular Hydrogen and so we follow the ionization level and H_2 abundance across the shock. This regime is particularly relevent to simulations of primordial galaxy formation for halos in which the virial temperature of the galaxy is sufficiently high to partially re-ionize the gas. The effect of in-shock cooling is substantial: the maximum temperature the gas reaches compared to the theoretical temperature was found to vary between 0.15 and 0.81 for the simulations performed. The downstream ionization level is reduced from the theoretical level by a factor of between 2.4 and 12.5, and the resulting H_2 abundance was found to be reduced to a fraction of 0.45 to 0.74 of its theoretical value. At temperatures above 10^5K, radiative shocks are unstable and will oscillate. We reproduce these oscillations and find good agreement with the previous work of Chevalier and Imamura (1982), and Imamura, Wolff and Durisen (1984). The effect of in-shock cooling in such shocks is difficult to quantify, but is undoubtedly present.Comment: 8 pages, LaTeX, 7 figure

Do Enhanced Compiler Error Messages Help Students? Results Inconclusive.

One common frustration students face when first learning to program in a compiled language is the difficulty in interpreting the compiler error messages they receive. Attempts to improve error messages have produced differing results. Two recently published papers showed conflicting results, with one showing measurable change in student behavior, and the other showing no measurable change. We conducted an experiment comparable to these two over the course of several semesters in a CS1 course. This paper presents our results in the context of previous work in this area. We improved the clarity of the compiler error messages the students receive, so that they may more readily understand their mistakes and be able to make effective corrections. Our goal was to help students better understand their syntax mistakes and, as a reasonable measure of our success, we expected to document a decrease in the number of times students made consecutive submissions with the same compilation error. By doing this, we could demonstrate that this enhancement is effective. After collecting and thoroughly analyzing our own experimental data, we found that—despite anecdotal stories, student survey responses, and instructor opinions testifying to the tool’s helpfulness— enhancing compiler error messages shows no measurable benefit to students. Our results validate one of the existing studies and contradict another. We discuss some of the reasons for these results and conclude with projections for future research

Non-Caucasian Recruiting and the Occupational Structure of the Navy

The inception of the all-volunteer armed force has placed the military service in competition with civilian employers for !he available portion of the Nation\u27s work force. While there are indications that the elimination of the draft has not severely hampered the services in meeting their immediate manpower needs, fears have been expressed that in time the racial composition of the services will deviate substantially from that of the civilian population.