Mechanical design of NASA Ames Research Center vertical motion simulator

NASA has designed and is constructing a new flight simulator with large vertical travel. Several aspects of the mechanical design of this Vertical Motion Simulator (VMS) are discussed, including the multiple rack and pinion vertical drive, a pneumatic equilibration system, and the friction-damped rigid link catenaries used as cable supports

Farm Sprayers for 2,4-D

Want to spray your own weeds? Homemade spray outfits can do the job. Lots of Iowa farmers are using them cheaply and effectively

The Control of Poison Ivy

Poison ivy (Rhus radicans L.) is a woody perennial, reproducing by seeds and creeping root stalks. It is found in rocky fields, pastures, fence rows, on roadsides, railroad embankments, under telephone lines, and in rich alluvial woodlands. Poison ivy is native in Iowa and widespread throughout the United States and Canada. Earliest mention of poison ivy was made by Captain John Smith in 1609. J. P. Cornut described the plant in his work on Canadian plants in 1635. It has been shown that as many as 26 different kinds of birds arc responsible for the wide dissemination of poison ivy

Another Year of 2,4-D

About a million acres of corn and 500,000 acres of small grain and flax were sprayed with 2,4-D in Iowa last season. County extension directors report an estimated 62,000 miles of fencerows were so treated. Chemical manufacturers sold between 500,000 and 800,000 pounds of actual 2,4-D last year

Resolution of the Klein Paradox

We present a resolution of the Klein paradox within the framework of one-particle relativistic quantum mechanics. Not only reflection becomes total but the vacuum remains neutral as well. This is accomplished by replacing the pair production process with virtual negative energy "incidence" within the barrier in a similar manner to what is done with image charges in electrostatic and virtual sources in optics.Comment: 9 pages, 8 figure

Seed Retention of Some Prairie Plants

There are still a number of native prairie areas in Iowa. One of these outstanding tracts belongs to the Steel family of Cherokee, Iowa. It consists of about half a section located in Cedar Township in Cherokee county (N. 1/2 Sec. 16) one and a half miles northwest of the town of Larabee. The area has never been plowed: as a matter of fact, it has never been fenced. The flora of this area, like most of the other generally treeless areas of the state consist largely of perennial plants of a distinctly xerophytic type (1.3.4.5). The Graminae are the most numerous, although exceeded in generic numbers by the Compositae, with the Leguminosae in third place. In the more highly developed soils, with better drainage and increased organic content, the dominant grasses include porcupine grass (Stipa spartea Trin.), little blue stem (Andropogon scoparius Michx.), Prairie drop seed (Sporobulus heterolepsis Gray), and numerous sub-dominant plants such as species of sunflower (Helianthus), golden rod (Solidago), blazing star (Liatris), tickseed (Coreopsis), and prairie clover (Petalostemum). Exposure to evaporation, as determined by temperature, wind and topography, is the primary cause of the treelessness according to Shimek (3.4)

Magnetic ground state and magnon-phonon interaction in multiferroic h-YMnO3_3

Inelastic neutron scattering has been used to study the magneto-elastic excitations in the multiferroic manganite hexagonal YMnO$_3$. An avoided crossing is found between magnon and phonon modes close to the Brillouin zone boundary in the $(a,b)$-plane. Neutron polarization analysis reveals that this mode has mixed magnon-phonon character. An external magnetic field along the $c$-axis is observed to cause a linear field-induced splitting of one of the spin wave branches. A theoretical description is performed, using a Heisenberg model of localized spins, acoustic phonon modes and a magneto-elastic coupling via the single-ion magnetostriction. The model quantitatively reproduces the dispersion and intensities of all modes in the full Brillouin zone, describes the observed magnon-phonon hybridized modes, and quantifies the magneto-elastic coupling. The combined information, including the field-induced magnon splitting, allows us to exclude several of the earlier proposed models and point to the correct magnetic ground state symmetry, and provides an effective dynamic model relevant for the multiferroic hexagonal manganites.Comment: 12 pages, 10 figure

Host-based identification is not supported by morphometrics in natural populations of Gyrodactylus salaris and G. thymalli (Platyhelminthes, Monogenea)

Gyrodactylus salaris is a serious pest of wild pre-smolt Atlantic salmon (Salmo salar) in Norway. The closely related G. thymalli, originally described from grayling (Thymallus thymallus), is assumed harmless to both grayling and salmon. The 2 species are difficult to distinguish using traditional, morphometric methods or molecular approaches. The aim of this study was to explore whether there is a consistent pattern of morphometrical variation between G. salaris and G. thymalli and to analyse the morphometric variation in the context of ‘diagnostic realism’ (in natural populations). Specimens from the type-material for the 2 species are also included. In total, 27 point-to-point measurements from the opisthaptoral hard parts were used and analysed by digital image processing and uni- and multivariate morphometry. All populations most closely resembled its respective type material, as expected from host species, with the exception of G. thymalli from the Norwegian river Trysilelva. We, therefore, did not find clear support in the morphometrical variation among G. salaris and G. thymalli for an a priori species delineation based on host. The present study also indicates an urgent need for more detailed knowledge on the influence of environmental factors on the phenotype of gyrodactylid populations