Plasmas and space physics Progress report, 1 Aug. 1965 - 31 Jan. 1966

Theoretical plasma studies for space physics applicatio

Collective bremsstrahlung emission from plasmas containing energetic particle fluxes

Collective bremsstrahlung emission from plasmas containing energetic particle fluxe

Solitary versus Shock Wave Acceleration in Laser-Plasma Interactions

The excitation of nonlinear electrostatic waves, such as shock and solitons, by ultraintense laser interaction with overdense plasmas and related ion acceleration are investigated by numerical simulations. Stability of solitons and formation of shock waves is strongly dependent on the velocity distribution of ions. Monoenergetic components in ion spectra are produced by "pulsed" reflection from solitary waves. Possible relevance to recent experiments on "shock acceleration" is discussed.Comment: 4 pages, 4 figure

Hockey Skating Kinematics and the Effect of Skate Design and Technique Training

The purpose of this study was to investigate the effects of technique training and hockey skate design on hockey skating performance. Fourteen male subjects, aged 12-16 years, with no recent skate treadmill experience completed ten training sessions on a skating treadmill. Instruction emphasized maximizing stride width by pushing laterally with the skate pointed anteriorly. Subjects were randomly placed into one of two experimental groups based on initial skate type: traditional or Easton Mako. After completion of five sessions, skate type was switched so that skate design effects could be assessed. In contrast to a traditional hockey skate design, the Easton Mako skate incorporates a flexible tendon guard allowing greater ankle extension as well as a heat-moldable skate boot for greater conformity to the underlying anatomy. Kinematic data were acquired during submaximal constant speed trials and maximum speed tests, at the first (baseline, skate 1), fifth (post-training, skate 1), sixth (baseline, skate 2), and tenth (post-acclimation, skate 2) training sessions. Treadmill training effects were investigated by contrasting data from sessions 1 and 5, and session6 and 10. Design effects were investigated contrasting data from sessions 5 and 6, and sessions 5 and 10; significance was assessed using paired t-tests. Significant initial training effects included increased stride width and decreased anterior-posterior foot separation at foot off, with the foot less rotated out of the anterior-posterior direction as intended by the specific training program. Other effects included decreased stride rate at a constant speed and increased maximum speed. Initial training effects held through the latter training sessions suggesting five sessions were sufficient to adapt to the treadmill training. Significant skate design effects included decreased sagittal ankle range of motion (ROM), decreased stride rate at constant speed, increased stride width and increased maximum speed with the Mako skate. The decreased sagittal plane ankle ROM, perhaps counterintuitive with the more flexible skate design, may be indicative of a more natural ankle movement. As for treadmill training, the increased maximum speed in concert with decreased stride rate suggest potentially more efficient stride with the Mako skate

Phosphorus losses to surface water

Increased concentration of livestock and concerns for manure and fertilizer phosphorus (P) management present producers with the challenge of understanding P losses to surface waters. This article continues a series that aids producers with improving land and P management to reduce environmental concerns related to P transport and losses to surface waters. Phosphorus is a major nutrient for aquatic plant growth and is often a limiting nutrient in freshwater systems. P abundance in Iowa\u27s surface waters produces aquatic plant overgrowth, primarily of algae. Plants and algae use much of the oxygen in water as they die and decompose, resulting in oxygen shortages that are detrimental to many aquatic organisms

Erosion in northeastern Iowa

Over the last 2 years, the northeastern part of the state has been devastated by gully washers and torrential rains. The result has been significant storm damage and erosion. To make matters worse, areas that escaped hard rainfall last year were hit this year. Severe rill and sheet erosion is present in most producers\u27 fields and seems especially severe in fields with Kenyon and Fayette and Downs soils. It is a characteristic of the Fayette and Downs soils to have short slopes; however, the intensity of rainfall has lead to the severe damage in these fields

Phosphorus and swine feeding

This article focuses on developing a phosphorus (P) strategy for swine feeding operations and continues a series that provides producers with information on P management and environmental issues relating to P management