Preparation of anisotropic microparticles and their behaviour at liquid interfaces

Monolayers of solid particles at the liquid- fluid interface are of considerable interest in both academia and industry. Their behaviour during compression and expansion experiments in a Langmuir trough has important implications on particle stabilisation of foams and emulsions. This has been known for some time with regards to spherical particles. In this investigation, we have studied the role of non- spherical particles at the liquid- fluid interface. Particles have been fabricated using the technique of photolithography. The technique was modified in order to be able to apply it under normal laboratory conditions, thus making it more accessible for the fabrication of non- spherical particles of any size or shape. Flat plate- like particles with well controlled shape and size with disc, oval and rectangular geometry have been fabricated. Monolayers composed of such particles at both the air- water and oil- water interfaces exhibit important differences between each other and spherical particles. The geometry of the monolayers at the interface has been characterised, and preferential ordering of rectangular particles in domains consisting of side to side contacts has been discovered. A strong capillary attraction has been observed between the particles owing to the roughness and shape of the particles. It was found that during compression at the liquid- fluid interface, the surface pressure increases more slowly than that observed for spherical particles and this has been attributed to the tendency of the particles to undergo reorientation, tilting and flipping, the latter always occurred around the long axes of the particles. The thickness of the particles has significant implications on the stability of the monolayer; in addition the tendency for the particles to flip increases as the thickness of the particles is reduced. The non- spherical particles investigated here have been demonstrated to offer great potential as stabilisers of emulsion drops. The technique of photolithography has been utilised for the fabrication of Janus particles consisting of one face coated with metals, polyelectrolytes, silanes and colloidal particles

The Development of a Stepped Frequency Microwave Radiometer and Its Application to Remote Sensing of the Earth

The design, development, application, and capabilities of a variable frequency microwave radiometer are described. This radiometer has demonstrated the versatility, accuracy, and stability required to provide contributions to the geophysical understanding of ocean and ice processes. The design technique utilized a closed-loop feedback method, whereby noise pulses were added to the received electromagnetic radiation to achieve a null balance in a Dicke switched radiometer. Stability was achieved through the use of a constant temperature enclosure around the low loss microwave front end. The Dicke reference temperature was maintained to an absolute accuracy of 0.1 K using a closed-loop proportional temperature controller. Versatility was achieved by developing a microprocessor based digital controller which operates the radiometer and records the data on computer compatible tapes. Accuracy analysis has shown that this radiometer exhibits an absolute accuracy of better than 0.5 K when the sensitivity is 0.1 K. The sensitivity varies between 0.0125 K and 1.25 K depending upon the bandwidth and integration time selected by the digital controller. Computational techniques were developd to (1) predict the radiometric brightness temperature at the input to the radiometer antenna as a function of the geophysical parameters, (2) compute the required input radiometric brightness temperature as a function of the radiometer output using a mathematical model of the radiometer, (3) achieve computational efficiency through a simplified algorithm to determine the expected radiometric brightness temperature, and (4) calculate the emissivity of a layered dielectric media such as ice over water. The effects of atmospheric absorption due to oxygen, water vapor, nonprecipitating clouds have been included. Correction factors for the finite antenna beamwidth, surface roughness, and wind induced foam were employed in these computations. Remote sensing experiments were conducted from an aircraft platform using this radiometer. The purpose of these experiments was to demonstrate that the accuracy and versatility of this instrument had been achieved in actual field experiments. Four significant scientific observations were accomplished during these experiments. These observations consisted of the first radiometric mapping of an ocean polar front, exploratory experiments to measure the thickness of lake ice, first discrimination between first year and multiyear ice below 10 GHz, and the first known measurements of frequency sensitive characteristics of sea ice

Iowa 2008 Prediction for Stewart’s Disease of Corn

Following an Iowa winter of ice, snow and cold temperatures, the predicted risk for Stewart’s disease of corn in 2008 is negligible throughout most of Iowa, with only the southeastern-most counties having a low risk. Stewart’s disease (also known as Stewart’s wilt), is caused by the bacterium Pantoea stewartii. In addition to the pathogen, an insect vector, the corn flea beetle, plays a critical role in the spread of this microorganism from plant-to-plant

Field evaluations of the CropManage decision support tool for improving irrigation and nutrient use of cool season vegetables in California

Vegetable growers on the central coast of California are under regulatory pressure to reduce nitrate loading to ground and surface water supplies. California also implemented legislation that limits agricultural pumping in regions such as the central coast where the aquifers have been over-extracted for crop irrigation. Growers could potentially use less N fertilizer, address water quality concerns, and conserve water by improving water management and matching nitrogen applications to the N uptake pattern of their crops. Two tools available to growers, the soil nitrate quick test (SNQT) and reference evapotranspiration (ETo) data have been previously shown to improve the management of water and fertilizer nitrogen in vegetable production systems. However, adoption of these practices has not been widespread. These techniques can be time consuming to use, and vegetable growers often have many crops to manage. To address such time constraints, the CropManage online application (cropmanage.ucanr.edu) was developed to facilitate implementation of the SNQT and evapotranspiration-based irrigation scheduling. CropManage additionally helps growers account for plant available N from background levels of nitrate in irrigation water. Trials were conducted in commercial vegetable fields in the Salinas Valley during 2012–2019 to evaluate CropManage fertilizer and irrigation recommendations relative to the grower practice. Results demonstrated that in many cases fertilizer or irrigation reductions could be attained by following CropManage recommendations without jeopardizing yield. In lettuce, the total fertilizer N applied under CropManage guidance was reduced by an average of 31 % compared to the grower standard practice. Lettuce yield within the CropManage treatment averaged 107 % of the grower practice. CropManage guidance in broccoli reduced N and applied water by 24 % and 27 %, respectively, compared to the grower standard practice, while average yield was similar between treatments. Management tools such as CropManage can support operational efficiencies and compliance with regulatory targets designed to improve groundwater quality