Fusarium oxysporum f. sp. niveum Molecular Diagnostics Past, Present and Future

Watermelon is an important commercial crop in the Southeastern United States and around the world. However, production is significantly limited by biotic factors including fusarium wilt caused by the hemibiotrophic fungus Fusarium oxysporum forma specialis niveum (Fon). Unfortunately, this disease has increased significantly in its presence over the last several decades as races have emerged which can overcome the available commercial resistance. Management strategies include rotation, improved crop resistance, and chemical control, but early and accurate diagnostics are required for appropriate management. Accurate diagnostics require molecular and genomic strategies due to the near identical genomic sequences of the various races. Bioassays exist for evaluating both the pathogenicity and virulence of an isolate but are limited by the time and resources required. Molecular strategies are still imperfect but greatly reduce the time to complete the diagnosis. This article presents the current state of the research surrounding races, both how races have been detected and diagnosed in the past and future prospects for improving the system of differentiation. Additionally, the available Fon genomes were analyzed using a strategy previously described in separate formae speciales avirulence gene association studies in Fusarium oxysporum races.

Simultaneous Measurements of Temperature and Viscosity for Viscous Fluids Using an Ultrasonic Waveguide

The characterisation and monitoring of viscous fluids have many important applications. This paper reports a refined ‘dipstick’ method for ultrasonic measurement of the properties of viscous fluids. The presented method is based on the comparison of measurements of the ultrasonic properties of a waveguide that is immersed in a viscous liquid with the properties when it is immersed in a reference liquid. We can simultaneously determine the temperature and viscosity of a fluid based on the changes in the velocity and attenuation of the elastic shear waves in the waveguide. Attenuation is mainly dependent on the viscosity of the fluid that the waveguide is immersed in and the speed of the wave mainly depends on the surrounding fluid temperature. However, there is a small interdependency since the mass of the entrained viscous liquid adds to the inertia of the system and slows down the wave. The presented measurements have unprecedented precision so that the change due to the added viscous fluid mass becomes important and we propose a method to model such a ‘viscous effect’ on the wave propagation velocity. Furthermore, an algorithm to correct the velocity measurements is presented. With the proposed correction algorithm, the experimental results for kinematic viscosity and temperature show excellent agreement with measurements from a highly precise in-lab viscometer and a commercial resistance temperature detector (RTD) respectively. The measurement repeatability of the presented method is better than 2.0% in viscosity and 0.5% in temperature in the range from 8 to 300 cSt viscosity and 40 to 90 °C temperature.

A transformer model based on the Jiles-Atherton theory of ferromagnetic hysteresis

This paper presents a transformer model that is useful for lowfrequency applications. To describe the iron-core magnetic behavior, the Jiles Atherton hysteresis model is used, which is able to generate minor asymmetric loops and remanent flux. The obtained results are compared with those measured in the laboratory on a commercial resistance welding transformer.

Disposable Heater Strips for High Temperature Powder Diffractometer Furnaces

Commercial resistance heating and thermocouple materials specified for use in air at temperatures up to 1200°C were examined as possible alternatives to Pt-Rh for use as heater strips in high temperature x-ray diffractometer furnaces. Tests in air at 1150°C, showed that Chromel oxidized excessively, Nichrome oxidized moderately, while Kanthal was very slightly oxidized. Nichrome and Kanthal strips were sufficiently ductile to fabricate into strip heaters. The thickness of the Kanthal strip had to be reduced to 0.020 mm to match its resistance to the power and temperature control software of the high temperature diffractometer. Heater strips made from Nichrome proved effective, in terms of resistance to grain growth and surface degradation by adhesive liquid phases, at temperatures up to 1000°C, while Kanthal was effective up to 1150°C. The relatively low costs of these materials also make them viable as disposable heaters for use with chemically reactive or strongly adherent materials.