Organic phosphorus in the environment: solutions for phosphorus security

Before‐dinner speech by Guest of Honour A.F. Harrison, given Thursday 8th September 2016

EXPOSURE TO PHOSPHINE GAS DURING APPLICATION OF MAGNESIUM PHOSPHIDE IN STORED PRODUCT WAREHOUSES

The use of phosphine gas requires that respiratory protection be used if exposures exceed the OSHA permissible exposure limit. As with other chemical exposures limits many of the references used to establish occupational health guidelines date back to the 1930’s and 1940’s. This is quite common and is the case with phosphine gas. Initial planning for fumigations involving magnesium phosphide requires that a hazard assessment be performed. Expected worker exposures based on previous monitoring or test data was not readily available. Many current practices and procedures for fumigations are based on recommendations from applicators who used the product in the 1950’s and 60’s. Unfortunately, many of the recommendations were based on personal opinion and experience rather than actual exposure monitoring data. Not until the 1980\u27s were comprehensive applicator exposure assessments being conducted for different tasks involving magnesium phosphide. As a result, it is necessary to generate current applicator exposure data and compare the data to current occupational exposure limits for phosphine gas

The measurement of turbulent skin friction for smooth and rough plates.

An analysis of the measurement of turbulent skin friction on smooth and rough plates using a hot wire anemometer, and surface Pitot tubes is here presented. Emphasis is placed on the use of a modified form of Stanton tube for use on rough surfaces. In addition various parameters such as: Roughness Reynolds number, centre line average roughness value, grit size etc., are correlated to the law of the wall, and boundary layer momentum thickness and shape factor. Further investigations are made into the relationship between turbulence intensity and roughness parameters. The effect of a blunt-edged flat plate on the skin friction results is also considered, and a drag law taking into account free stream turbulence is presented. The experimental results were obtained using plates mounted in a vertical plane in the test section of a low speed wind tunnel at velocities up to a maximum of 21 m/s with a plate Reynolds number of 750,000

AN ELECTROMAGNETIC FIELD MODEL FOR THE DESIGN OF RF REED RELAYS

A model of the electromechanical characteristics, electrostatic characteristics and coil eddy current losses of a reed relay was developed. These characteristics were returned from reed and coil dimensions. The model was intended as an aid to the design of reed relays for Radio Frequency (RF) and high voltage applications. An electromechanical model of a reed switch and coil was developed using a combination of an axisymmetric finite element model and analytical methods. The characteristics returned from this model were operate, release and differential amp turns, contact gap and contact force. Inclusion of results for contact resistance against contact force yielded the contact resistance characteristics. Electrostatic force between reed contacts was calculated and a criteria for contact arcing in a vacuum applied to allow prediction of breakdown voltage in an evacuated reed switch. The above elements were incorporated in a "Reed Switch Design Program" in which operating, contact resistance and breakdown voltage characteristics were calculated from reed and coil dimensions. Results were found to be in agreement with measured values for three reed switch types. Eddy current losses in relay coils were investigated through experimental measurement of losses occurring in coils mounted around a copper conductor carrying a high frequency current. The losses occurring in the coil were found to present an effective resistance to the current in the conductor. The influence of coil dimensions and the magnetic properties of the conductor on losses were observed. An analytical model of eddy current losses was derived from first principals results and were found concordant with those measured. An "RF Reed Relay Design Program" embodying the eddy current loss model and preceding work was created to demonstrate how relay performance (and efficiency) can be enhanced by tuning reed and coil dimensions. An example of its successful application to product development at Crydom Magnetics Ltd is presented. Proposals for future work are included.Crydom Magnetics Limite

The Energy Dependence of Neutron Star Surface Modes and X-ray Burst Oscillations

We calculate the photon energy dependence of the pulsed amplitude of neutron star (NS) surface modes. Simple approximations demonstrate that it depends most strongly on the bursting NS surface temperature. This result compares well with full integrations that include Doppler shifts from rotation and general relativistic corrections to photon propagation. We show that the energy dependence of type I X-ray burst oscillations agrees with that of a surface mode, lending further support to the hypothesis that they originate from surface waves. The energy dependence of the pulsed emission is rather insensitive to the NS inclination, mass and radius, or type of mode, thus hindering constraints on these parameters. We also show that, for this energy-amplitude relation, the majority of the signal (relative to the noise) comes in the 2-25 keV band, so that the current burst oscillation searches with the Rossi X-Ray Timing Explorer are close to optimal. The critical test of the mode hypothesis for X-ray burst oscillations would be a measurement of the energy dependence of burst oscillations from an accreting millisecond pulsar.Comment: Accepted for publication in The Astrophysical Journal, 6 pages, 5 figures (revised version: no changes to text, just edited author list

Halogenation of A-frame µ-carbido complexes: synthesis of µ₂-halocarbynes

The reaction of [Rh2(μ-C)Cl2(PPh3)4] with bis(diphenylphosphino)methane (dppm) affords the A-frame μ-carbido complex [Rh2(μ-C)Cl2(μ-dppm)2], halide metathesis of which provides [Rh2(μ-C)Br2(μ-dppm)2]. The reactions of the former with PhICl2 or the latter with [pyH][Br3] provide rare examples of μ2-halocarbyne ligands in the complexes [Rh2(μ-CX)(μ-X)X4(μ-dppm)2] (X = Cl, Br). Graphical abstract: Halogenation of A-frame μ-carbido complexes: synthesis of μ2-halocarbynes Linear bimetallic μ-carbido complexes may be described by one of three distinct bonding modes (Chart 1) depending on the effective atomic number requirements of the metal termini. The simplest and oldest1 involve identical metal termini and are best described as dimetallacumulenic in nature (Class A, Chart 1) with two formal M[double bond, length as m-dash]C double bonds.We gratefully acknowledge the Australian Research Council (DP170102695 and DP190100723) for funding