Variation of manganese, dissolved oxygen and related chemical parameters in the bottom waters of Lake Mendota, Wisconsin

The increase of Mn concentration and the simultaneous depletion of dissolved oxygen in the bottom waters (hypolimnion) of Lake Mendota, Wisconsin were studied in situ. Considerably higher Mn concentrations were found in the hypolimnion compared to Fe, despite a sedimentary Fe/Mn weight ratio of 19 : 1. Laboratory equilibration studies under anoxic conditions indicated that pH was an important parameter involved in the release of Mn from the sediments. This was also implied by the Mn and pH data measured in situ. Possible mechanisms involved in the release of Mn from the sediments including desorption of Mn from oxide substrates, reduction of Mn oxides and dissolution of carbonates and sulfides are discussed.     

Internal alignment of the SLD vertex detector using a matrix singular value decomposition technique

The tracking resolution and vertex finding capabilities of the SLD experiment depend upon a precise knowledge of the location and orientation of the 96 elements of the SLD pixel vertex detector (VXD3) in 3D space. At the heart of the deterministic procedure described here to align the 96 CCDs is the matrix inversion technique of singular value decomposition (SVD). This tool is employed to unfold the detector geometry corrections from the track hit residual data in the VXD3. The algorithm is adapted to perform an optimal χ² minimization by careful treatment of the errors and correlations in the residual measurements. The general form of the problems that might be solved with this technique is discussed. The tracking resolution obtained with the aligned geometry is compared with the starting point, based on an optical survey of the CCDs, and is shown to achieve the design performance.     

A simplified approach to the analysis of geometrically imperfect cooling tower shells

A simplified method for analysing the elastic stresses in geometrically imperfect cooling tower shells is outlined. The method is based on the replacement of the imperfection by an appropriate additional normal pressure. Illustrations with respect to both axi-symmetric and non axi-symmetric imperfections are presented and the validity of the method is established by comparisons with the direct analysis for the axi-symmetric case. Further simplifications are considered and a possible basis for codefied tolerances on meridional imperfections is developed. Some extensions to the method are suggested, particularly for the case of non axi-symmetric geometric imperfections.     

C18 unsaturated fatty acid hydrogenation patterns of some rumen bacteria and their ability to hydrolyse exogenous phospholipid

The perforatorium of rat spermatozoa was isolated and its protein composition determined. SDS-polyacrylamide gel electrophoresis showed that the organelle is composed of a single polypeptide component with a molecular weight of 13,000. The perforatorium becomes more resistant to solubilization during epididymal transit due to an apparent increase in disulphide bond content. Amino acid analysis of the perforatorium polypeptide revealed a content of 6-5% cysteine.     

Small and moderate color differences. IV. Color-difference-perceptibility ellipses in surface-color space

Moderate (0.5–1.5 CIELAB units) color differences in surface colors were scaled visually to obtain color-dif-ference-perceptibility ellipses. The ellipse orientations appeared to be independent of the size of the color differences over the range indicated, and were consistent with literature results obtained with visual colorimeters. In the uivid greenish yellow region, the experimental ellipse orientation agreed with the Munsell spacing but not with the orientation of the CIELAB ellipse. In the deep greenish blue region, the experimental ellipse orientation agreed belter with the results of Wyszecki and Fielder than with the orientation of the MacAdam PGN ellipse.     

A room fire screening test procedure

Full-scale room fire economics necessitate a screening test procedure requiring only a small amount of material to quantitatively assess heat release rate. This test could determine which materials may justify full-scale testing and those which fail early. Such a procedure is described, sample results are given, and it is suggested that correlation of screening test results with full-room and bench-scale test methods could improve the evaluation of the pre-flashover fire spread characteristics of materials.     

Total WIP and WIP mix for a CONWIP controlled job shop

A planning procedure to set the constant level of Work-In-Process (WIP) for each product type in a job shop operated under CONWIP control is developed. We model the job shop as a single chain multiple class closed queuing network. Given a specified product mix and a total WIP, a nonlinear program bounds the throughput of the network and optimizes the WIP mix. We identify the minimum total WIP that is guaranteed to yield throughput near the maximum possible for the specified product mix and set individual WIP levels by multiplying the optimal WIP mix proportions by the minimum total WIP. Numerical examples illustrate how these individual product WIP levels achieve the goal of high throughput consistent with the specified product mix.     

Worldwide cryogenics — Australian National Measurement Laboratory and cryogenics

The National Measurement Laboratory in Sydney was opened in 1940 and its first hellium liquefier began to operate in 1950. Since then it has an active research programme at low temperatures on properties of matter including heat conduction and other transport properties, thermal expansion, calorimetry, magnetic susceptibility, and far infrared spectroscopy. Cryogenics has also become an essential part of programmes in thermometry and electric metrology.     

Neural-network analysis of irradiation hardening in low-activation steels

An artificial neural network has been used to model the irradiation hardening of low-activation ferritic/martensitic steels. The data used to create the model span a range of displacement damage of 0-90 dpa, within a temperature range of 273-973 K and contain 1800 points. The trained model has been able to capture the non-linear dependence of yield strength on the chemical composition and irradiation parameters. The ability of the model to generalise on unseen data has been tested and regions within the input domain that are sparsely populated have been identified. These are the regions where future experiments could be focused. It is shown that this method of analysis, because of its ability to capture complex relationships between the many variables, could help in the design of maximally informative experiments on materials in future irradiation test facilities. This will accelerate the acquisition of the key missing knowledge to assist the materials choices in a future fusion power plant.