Critical slowing down near the multiferroic phase transition in MnWO4_4

By using broadband dielectric spectroscopy in the radiofrequency and microwave range we studied the magnetoelectric dynamics in the multiferroic chiral antiferromagnet MnWO$_4$. Above the multiferroic phase transition at $T_{N2} \approx 12.6$ K we observe a critical slowing down of the corresponding magnetoelectric fluctuations resembling the soft-mode behavior in canonical ferroelectrics. This electric field driven excitation carries much less spectral weight than ordinary phonon modes. Also the critical slowing down of this mode scales with an exponent larger than one which is expected for magnetic second order phase transition scenarios. Therefore the investigated dynamics have to be interpreted as the softening of an electrically active magnetic excitation, an electromagnon.Comment: 5 pages, 4 figures, appendi

Improved simulation of aerosol, cloud, and density measurements by shuttle lidar

Data retrievals are simulated for a Nd:YAG lidar suitable for early flight on the space shuttle. Maximum assumed vertical and horizontal resolutions are 0.1 and 100 km, respectively, in the boundary layer, increasing to 2 and 2000 km in the mesosphere. Aerosol and cloud retrievals are simulated using 1.06 and 0.53 microns wavelengths independently. Error sources include signal measurement, conventional density information, atmospheric transmission, and lidar calibration. By day, tenuous clouds and Saharan and boundary layer aerosols are retrieved at both wavelengths. By night, these constituents are retrieved, plus upper tropospheric, stratospheric, and mesospheric aerosols and noctilucent clouds. Density, temperature, and improved aerosol and cloud retrievals are simulated by combining signals at 0.35, 1.06, and 0.53 microns. Particlate contamination limits the technique to the cloud free upper troposphere and above. Error bars automatically show effect of this contamination, as well as errors in absolute density nonmalization, reference temperature or pressure, and the sources listed above. For nonvolcanic conditions, relative density profiles have rms errors of 0.54 to 2% in the upper troposphere and stratosphere. Temperature profiles have rms errors of 1.2 to 2.5 K and can define the tropopause to 0.5 km and higher wave structures to 1 or 2 km

Geophysical Research

Contains reports on two research projects.Joint Services Electronics Programs (U. S. Army, U. S. Navy, and U. S. Air Force) under Contract DA 36-039-AMC-03200(E)National Aeronautics and Space Administration (Grant NGR-22-009-131)National Aeronautics and Space Administration (Grant NGR-22-009-(114)

Remote terminal system evaluation

An Earth Resources Data Processing System was developed to evaluate the system for training, technology transfer, and data processing. In addition to the five sites included in this project two other sites were connected to the system under separate agreements. The experience of these two sites is discussed. The results of the remote terminal project are documented in seven reports: one from each of the five project sites, Purdue University, and an overview report summarizing the other six reports

Geophysical Research

Contains reports on two research projects.Joint Services Electronics Programs (U. S. Army, U. S. Navy, and U. S. Air Force) under Contract DA 28-043-AMC-02536(E)National Aeronautics and Space Administration (Grant NGR-22-009-131)National Aeronautics and Space Administration (Grant NGR-22-009-114)National Aeronautics and Space Administration (Contract NAS 12-436

Technical Note: A rotary seed processor for removing pubescence from seed of prairie grasses

Many of the perennial prairie grasses that are used in restoration plantings in the central Great Plains have seed appendages such as awns and pubescence that make seed flow through planters difficult. We have developed a rotary seed processor that efficiently processes small breeder or experimental lots of seed that can then be easily planted with small plot cone planters or conventional planters. The processor consists of a metal cylinder that is lined with corrugated rubber and a rotating center shaft with rubber paddles. Processing can be controlled by varying shaft rotation speed and processing time. A top-opening, full length trap door allows for easy loading and the cylinder can be inverted to dump out processed seed. The processor has been used successfully for several years on big bluestem [Andropogon gerardii Vitman], indiangrass [Sorghastrum nutans (L.) Nash], little bluestem [Schizachyrium scoparium (Michaux) Nash], prairie sandreed [Calamovilfa longifolia (Book.) Scribner], and blue grama [Boureloua gracilis (Willd. ex Kunth) Lagascaex Griffiths] seed. By removing seed appendages and pubescence, seed bulk is reduced and seed density and flow ability are improved. The processing operation is relatively gentle and seed germination per unit weight of seed is improved. Semillas de muchos pastos perennes que son usados en la restauracion de praderas en las Grandes Planicies centrales, poseen accesorios coma aristas y/o pubescencias que difcultan el paso de las semillas a traves de sembradoras convencionales. Para efectuar siembras con btas semillas, las semhradoras tendrian que estar especificamente diieiiadas para plantar material relativamente voluminoso y sin peso, al menos que las semillas scan procesadas para remover tales cuerpos accesorios. Nosotros hemos desarrollado un procesador de semilla que process eticientemente pequeiios lotes de semillas con fries de reproduction de germoplasma o experimentales. De &a manera, las semillas podran ser facilmente sembrados con un sembrador de cone para pequefias parcelas, o con sembradoras convencionales. El procesador consiste de un cilindro o tambor de metal forrado en su interior con hule corrugado. Paletas de hule adjuntas a un eje que atraviesa el cilindro y que son rotadas por polea, golpean las semillas. El proceso puede ser controlado variando el tamaiio de polea y la velocidad de rotacibn, y por el tiempo que la semilla permanece rotando dentro de la unidad. El cilindro cuenta con una puerta en la parte superior que permite el facil acceso de la semilla dentro de la unidad. Cuando la semilla ha sido procesada, el cilindro puede ser invertido para retirar la semilla de la unidad. El procesador ha sido exitosamente usado por varios aiios en big bluestem (Andropogon gerardii Vitman), indiangrass [Sorghastrum nutans (L.) Nash], little bluestem [Schizachyrium scoparium (Michx.) Nash], prairie sandreed [Calamovilfa longifolia (Hook.) Scribn.], and blue grama [Bouteloua gracilis (Wiid. ex Kunth) Lagasca ex Griffiths] seed. La remocion de las aristas y pubescencias disminuyen el volumen de la semi&, y la densidad y flujo dentro de la sembradora son entonces mejorados. El proceso de operation es relativamente suave para las semillas y la genninacion por unidad de peso es mejorada

Segregation of glutenins in wheat × maize-derived doubled haploid wheat populations

The segregation of both high and low molecular weight glutenin subunits across 7 F1 wheat (Triticum aestivum L.) × maize (Zea mays L.) derived doubled haploid populations was examined. The F1 wheats used in each population were produced from parents of interest to Australian wheat breeding programs. The parents varied by up to 5 glutenin subunit loci. Examination of subunits individually within each population using a chi-square analysis revealed that all but 2 of the 26 pairs of alleles analysed fitted the expected 1 : 1 segregation ratio. Glutenin profiles were examined for each cross individually and all but one (Sonalika/Hartog) fitted the expected Mendelian segregation pattern. The analysis of allele distribution of the 6 glutenin loci across all 7 crosses showed all falling well within expected segregation ratios. Closer examination of parental lines and populations revealed irregularities which conflict with original assumptions and provide a valid explanation for the few segregation distortions observed. It is concluded that wheat × maize-derived doubled haploid populations represent a unbiased assortment of parental gametes on both arms of Group 1 chromosomes

Geophysics

Contains reports on three research projects

Observations of mesoscale and boundary-layer circulations affecting dust uplift and transport in the Saharan boundary layer

International audienceObservations of the Saharan boundary layer, made during the GERBILS field campaign, show that mesoscale land surface temperature variations (which were related to albedo variations) induced mesoscale circulations, and that mesoscale and boundary-layer circulations affected dust uplift and transport. These processes are unrepresented in many climate models, but may have significant impacts on the vertical transport and uplift of desert dust. Mesoscale effects in particular tend to be difficult to parameterise. With weak winds along the aircraft track, land surface temperature anomalies with scales of greater than 10 km are shown to significantly affect boundary-layer temperatures and winds. Such anomalies are expected to affect the vertical mixing of the dusty and weakly stratified Saharan Air Layer (SAL). Mesoscale variations in winds are also shown to affect dust loadings in the boundary-layer. In a region of local uplift, with strong along-track winds, boundary-layer rolls are shown to lead to warm moist dusty updraughts in the boundary layer. Large eddy model (LEM) simulations suggest that these rolls increased uplift by approximately 30%. The modelled effects of boundary-layer convection on uplift is shown to be larger when the boundary-layer wind is decreased, and most significant when the mean wind is below the threshold for dust uplift and the boundary-layer convection leads to uplift which would not otherwise occur

Geophysics

Contains reports on four research projects.United States Air Force (Contract AF19(628)-500)Lincoln Laboratory (Purchase Order DDL BB-107