Ionospheric E-region Irregularities Produced by Non-linear Coupling of Unstable Plasma Waves

Ionospheric E region irregularities produced by nonlinear coupling of unstable plasma wave

Efficient Grazing Systems: Putting Pieces Together

Pros and cons of grazing systems are well-known to this audience. Efficient grazing systems, however, are a different story. What is an efficient grazing system? I think we could argue that topic until the cows come home and I do not believe we could come to any agreement. I am going to approach the subject of efficiency from several angles but you will probably see them differently. Economic efficiencies will not be covered

Grazing Alfalfa

Alfalfa (Medicaao sativa) is a native of an area south of the Black and Caspian seas and it still grows wild in Iran and eastern Anatolia. Alfalfa was the chosen forage for the fighting horses of ancient armies as long ago as 1800 B.C. when the Kassites conquered Babylon. The spread of alfalfa followed the pathway of armies through the Mediterranean, Europe, and the New World. For ages before man used alfalfa to fuel his fighting animals natural selection processes worked on the evolution of alfalfa and its predecessors. A scenario which would account for the morphology and physiology of alfalfa is as follows. Alfalfa evolved in a climate similar to that which it is best adapted. Under these conditions alfalfa would be subjected to periodic grazings as flocks or herds moved in migratory patterns. During stress periods plants which avoided drought or cold damage had an advantage and survived. Concurrently, possibly because of the low nitrogen status of the soils, symbiotic nitrogen fixation coevolved, This latter characteristic is often associated with plant colonizers. In more recent times the natural selection pressures were modified by man but the fact remains that evolution of alfalfa was primarily influenced by grazing herbivores, and was not affected by man until recently. Evidently the selection pressures under grazing were consistent with our modern management of alfalfa for hay or silage crops

Advances in Grazing Alfalfa

Many farmers are reluctant to develop a new enterprise based on the grazing of alfalfa if they have had no experience with grazing of this species. Their first negative reaction is usually based on their fear of legume bloat. Often their second reaction is that grazing will destroy the alfalfa stand in short order. Another response is that grazing is a wasteful and inefficient use of a valuable resource generating less income than conventional uses, such as hay and silage. Another reaction is based on the fear Alfalfa grazing, according to other sceptics, also requires lots of capital for fencing and water services, needs much more labor, demands complex managerial skills and the assumption of more risk. Still others believe that alfalfa does not provide a balanced diet for grazing livestock. In this paper I will discuss these points of concern about the grazing of alfalfa: whether they are real (and if they are the available options to avoid or minimize them) or imaginary. I will also discuss new technology and research activities that affect the grazing of alfalfa

Radio emission from the massive stars in the Galactic Super Star Cluster Westerlund 1

Current mass-loss rate estimates imply that main sequence winds are not sufficient to strip away the H-rich envelope to yield Wolf-Rayet (WR) stars. The rich transitional population of Westerlund 1 (Wd 1) provides an ideal laboratory to observe mass-loss processes throughout the transitional phase of stellar evolution. An analysis of deep radio continuum observations of Wd 1 is presented. We detect 18 cluster members. The radio properties of the sample are diverse, with thermal, non-thermal and composite thermal/non-thermal sources present. Mass-loss rates are ~10^{-5} solar mass/year across all spectral types, insufficient to form WRs during a massive star lifetime, and the stars must undergo a period of enhanced mass loss. The sgB[e] star W9 may provide an example, with a mass-loss rate an order of magnitude higher than the other cluster members, and an extended nebula of density ~3 times the current wind. This structure is reminiscent of luminous blue variables, and one with evidence of two eras of high, possibly eruptive, mass loss. Three OB supergiants are detected, implying unusually dense winds. They also may have composite spectra, suggesting binarity. Spatially resolved nebulae are associated with three of the four RSGs and three of the six YHGs in the cluster, which are due to quiescent mass loss rather than outbursts. For some of the cool star winds, the ionizing source may be a companion star though the cluster radiation density is sufficiently high to provide the necessary ionizing radiation. Five WR stars are detected with composite spectra, interpreted as arising in colliding-wind binaries.Comment: 15 pages, 6 figures. Accepted for publication in Astronomy and Astrophysic