Hardware development for the surface tension driven convection experiment aboard the USML-1 spacelab mission

The Surface Tension Driven Convection Experiment is a Space Transportation System flight experiment to study both transient and steady thermocapillary fluid flows aboard the USML-1 Spacelab mission planned for March 1992. Hardware is under development to establish the experimental conditions and perform the specified measurements, for both ground based research and the flight experiment in a Spacelab single rack. Major development areas include an infrared thermal imaging system for surface temperature measurement, a CO2 laser and control system for surface heating, and for flow visualization, a He-Ne laser and optical system in conjunction with an intensified video camera. For ground based work the components of each system were purchased or designed, and tested individually. The three systems will be interfaced with the balance of the experimental hardware and will constitute a working engineering model. A description of the three systems and examples of the component performance is given along with the plans for the development of flight hardware

Efecto del glifosato sobre el crecimiento y acumulación de azúcares libres en dos biotipos de lolium perenne de distinta sensibilidad al herbicida

El movimiento sistémico del glifosato está determinado por el transporte de fotoasimilados. A su vez, la capacidad de un destino de consumir los asimilados está condicionada por su actividad metabólica. Pese a su importancia, la relación entre el glifosato y la síntesis de azúcares en hojas fuente ha sido poco abordada. El objetivo del presente trabajo fue evaluar los efectos del glifosato sobre el crecimiento y la acumulación de azúcares libres en dos biotipos de Lolium perenne de baja y alta sensibilidad al herbicida. Se trabajó con clones de ambos tipos de plantas, en macollaje, tratados con 1.440 g e.a. ha-1 de glifosato y sin tratamiento herbicida como controles. Se evaluó periódicamente el efecto del glifosato sobre el rebrote de hojas hasta las 50 horas post-aplicación y sobre los niveles de azúcares libres totales, reductores y no reductores en hojas a 1, 2, 3 y 5 días post-aplicación. A partir de las 25 horas post-aplicación, el glifosato provocó una disminución del crecimiento del 58% en el biotipo susceptible, con una acumulación de azúcares libres superior al 90% con relación al control, desde el primer día post-aplicación en adelante. La inhibición del crecimiento, inducida por el glifosato en plantas susceptibles, no depende de la limitación del traslado de fotoasimilados desde la parte aérea. Por tanto, la acumulación de azúcares libres en hojas podría explicarse por la caída en la tasa de crecimiento. En el biotipo de baja sensibilidad, en el que no se detectó inhibición del crecimiento, estos efectos fueron limitados.The systemic movement of glyphosate is determined by the transport of photoassimilates. In turn, the capacity of a destination to consume assimilates is conditioned by their metabolic activity. Despite its importance, the relationship between the glyphosate and the sugar synthesis from source leaves has been little studied. The aim of this work was to determine the effect of glyphosate on the growth and free sugar accumulation of two Lolium perenne biotypes of low and high glyphosate sensitivity. It was worked with clones of both types, in tillering, sprayed with 1,440 g a.e. ha-1 of glyphosate as treatments and without herbicide as controls. The glyphosate effects on the regrowth of leaves was studied until 50 hours post-application and on total free sugar, reducing free sugar and nonreducing free sugar from leaves to 1, 2, 3 and 5 days post-application were periodically evaluated. From 25 hours after glyphosate application, it caused on the susceptible biotype a growth decrease of 58% and an accumulation of free sugar above 90% compared to controls. In susceptible biotypes, growth inhibition does not depend on a reduced photoassimilate translocation from the overground part. Therefore, the free sugar accumulation in leaves could be explained by the fall in the rate of growth. These effects are limited in the low sensitivity biotype, where growth inhibition has not been detected

Experimental investigation of steady buoyant-thermocapillaryconvection near an evaporating meniscus

Micro-particle image velocimetry measurements of the 3D (three-dimensional) convection patterns generated near an evaporating meniscus in horizontally oriented capillary tubes are presented. Analysis of the vapor diffusion away from the meniscus reveals a zone of intense heat flux near the solid-liquid-vapor junction which creates a temperature gradient along the meniscus. This results in a surface tension gradient which, coupled with buoyancy effects, causes buoyant-thermocapillary convection in the liquid film. The relative influence of buoyancy and thermocapillarity on the flow was investigated for tube diameters ranging from 75 to 1575 µm. A transition from a pure 2D thermocapillary flow to a 3D buoyant-thermocapillary flow is observed with an increase in tube diameter. For the 75 µm tube, a symmetrical toroidal vortex is observed near the meniscus. For larger tubes, buoyancy effects become apparent as they dominate the flow field. The high mass fluxes in smaller-diameter tubes drive stronger vortices. Particle streaks and µPIV images obtained in multiple horizontal and vertical planes provide an understanding of this three-dimensional flow behavior. A scaling analysis shows the importance of thermocapillary convection in evaporating menisci