A new method for handling flow problems with body forces

The solution of the Navier-Stokes equations by the numerical solution procedure of Patankar and Spalding has been found to be numerically unstable when applied to flows driven by body forces. A method (Pressure Reduction by Force Decomposition, PRFD) is outlined whereby such flows can be calculated without encountering numerical stability problems.The method is tested by calculating the laminar flow in a rotating square cavity with a moving lid. A stability limit is shown to exist when the numerical procedure in its usual form is applied to this problem. No limit is encountered when the PRFD technique is employed.     

Wave Climate and Potential Longshore Sediment Transport Patterns,Nottawasaga Bay,Ontario

A storm wave climate for Nottawasaga Bay, Ontario, is hindcast, using the SMB technique, from wind records at Cove Island for the period 1966-1970. Thirteen wave classes, defined on the basis of significant wave height, period, and direction, are identified and these are used as inputs into a computer model of wave refraction within the bay. The total and longshore component of wave energy flux are determined for each wave class. The total annual energy flux P₁ and the net longshore component P₁ are determined for 55 points spaced at one kilometre intervals by multiplying the value of energy flux at each point by the mean annual frequency for that wave class and summing the values for all relevant waves. A simple model of potential erosion, transport, and deposition patterns within the bay is then developed from the variation in the net P₁ values. The predicted model is compared with geomorphological evidence of sediment transport patterns visible in vertical aerial photographs and with measurements of erosion and accretion at selected points. It is concluded that the continued eastward growth of the Wasaga spit results primarily from deposition of sediments from the Nottawasaga River rather than littoral transport.     

Cocoa butter-like fat from cottonseed oil: Preliminary cost study

This paper includes a preliminary cost study for producing cocoa butter-like fat from hydrogenated cottonseed oil and triolein at an annual rate of 8.4 million lb in a hypothetical plant, employing interesterification and fractional crystallization as used in pilot plant studies at the Southern Utilization Research and Development Division. Equipment costs, total plant cost, manufacturing costs, and general expenses are given. Operating cost is estimated at 36.9ϕ/lb of product. This includes 31.8ϕ for manufacturing, 4.1ϕ for general expenses, and 1ϕ for refining of the recycled mixture of saturates and unsaturates. A laboratory of the Southern Utilization Research and Development Division, U.S.D.A.     

The calculation of some laminar flows using various discretisation schemes

For various laminar, two-dimensional flows, the upwind, hybrid and the quadratic finite-difference schemes are evaluated. The upwind and hybrid schemes are used in their normal forms. The quadratic formulation (Leonard's QUICK scheme) has in the past been found to be less stable than these two other schemes because it can, on occasion, generate both negative and positive influence coefficients. Two new forms of the quadratic formulation, both of which always generate positive influence coefficients, are presented for a uniform grid distribution and tested by reference to the results obtained from the upwind and hybrid schemes and data from other sources. These two new schemes are found to be stable, although one form seems to be sensitive to the size of the finite-difference grid. Furthermore, the solutions obtained using these new formulations are equal to or better than those obtained using the upwind and/or the hybrid schemes. It is concluded that these new formulations require further validation; and to this end, these new formulations are provided in a form that is easy to install into existing computer codes.     

Desaturation of positional and geometric isomers of monoenoic fatty acids by microsomal preparations from rat liver

A range ofcis- andtrans-monoenoic fatty acids was tested as substrates for desaturation in microsomal preparations from rat liver.Trans-monoenoic acids were generally desaturated in the Δ9 position to the same extent as stearic acid. Acids with Δ7-trans- and Δ11-trans-olefinic unsaturation produced Δ7-trans,9-cis- and Δ9-cis,11-trans-conjugated dienoic acids, respectively, but the Δ8-trans- and Δ10-trans-monoenoic acids did not give Δ8,9- or Δ9,10-allenes. Of thecis-monoenoic acids examined, only those with double bonds at or beyond the Δ14 position gave any measurable Δ9 desaturation. When Δ9 desaturation of long chain saturated acids was inhibited by adding sterculic acid, these saturated acids were desaturated at the Δ5 and Δ6 positions. Many of the monoenoic acids tested were also desaturated at the Δ5 and/or Δ6 positions, although the percentage conversions were always low. Δ9-cis,11-trans-, Δ9-cis,12-trans- and Δ9-cis,13-trans-dienoic acids, produced in situ by Δ9 desaturation of the corresponding monoenoic acids, were extensively desaturated in the Δ6 position. These results are discussed in terms of: (a) the various models proposed to explain the substrate specificities of the desaturases, and (b) the metabolism of unnatural fatty acids ingested from dietary sources.     

Studies on biosynthesis of waxes by developing jojoba seed. II. the demonstration of wax biosynthesis by cell-free homogenates

The following enzyme activities were demonstrated in cell-free homogenates from developing jojoba cotyledons: 1) elongation of long chain acyl-CoAs in the presence of malonyl-CoA and NADPH (or NADH), 2) NADPH-dependent reduction of long chain acyl-CoAs to the corresponding alcohols, 3) esterification of long chain acyl-CoAs and the alcohols produced from them into wax, 4) elongation of stearoyl-ACP to eicosanoate and docosanoate as well as reduction to stearyl alcohol, 5) desaturation of stearoyl-ACP to oleate in the presence of reduced ferredoxin, and 6) incorporation of malonyl-CoA into long chain fatty acids and alcohols in the presence of added acyl carrier protein. These activities were associated entirely with the floating wax pad after centrifugation of the cell-free homogenate at 12,000 g for 20 min. The relevance of the above reactions (1–6) to wax biosynthesis in vivo is discussed. Production of oleate from acetate by enzymes utilizing ACP-thioesters as substrates followed by conversion of oleyl-ACP to oleoyl-CoA (via free oleic acid) for subsequent elongation, reduction, and esterification, is presented as the most probable in vivo pathway, for wax biosynthesis. The substrate specificities of the elongation and reduction reactions utilizing acyl-CoAs as substrates are examined in terms of wax composition.     

Effect of glass-fibre reinforcement and annealing on microstructure and mechanical behaviour of nylon 6,6

The effects of glass fibres and annealing on the microstructures and spherulitic morphology of a glass fibre-reinforced nylon 6,6 were investigated. The annealing effects on matrix crystallinity of nylon 6,6 composites with varying glass fibre contents were measured and the morphology of the composites were examined using both the microtomed bulk samples and thin composite films prepared by melt crystallization. It was found that fibre breakage during injection moulding was significant for composites with glass content higher than 20 wt%, and the spherulite size as well as the crystallinity were reduced by the additions of glass fibres. Upon annealing, the start of a log time rate increase of matrix crystallinity was delayed by the addition of glass fibres. Glass fibre-induced transcrystallinity was not observed in injection-moulded composites; however, columnar spherulites were found to develop along the glass fibres in melt-crystallized thin composite films. Differences in morphological observations between the two sample preparation methods are also discussed.     

Exposure assessment of carcass disposal options in the event of a notifiable exotic animal disease: application to avian influenza virus

We present a generalized exposure assessment of 28 disposal options for poultry carcasses in the event of a highly pathogenic avian influenza (HPAI) outbreak. The analysis supports a hereto unverified disposal hierarchy for animal carcasses, placing waste processing (e.g., incineration and rendering) above controlled disposal (e.g., landfill), above uncontrolled disposal (e.g., burial on-farm). We illustrate that early stages of the disposal chain (on-farm) pose greater opportunities for exposure to hazardous agents than later stages, where agents are generally contained, wastes are treated, and residues are managed by regulated processes. In selecting carcass disposal options, practitioners are advised to consider the full range of hazards rather than focusing solely on the HPAI agent, and to give preference to technologies that (i) offer high destruction efficiencies for target pathogens; (ii) do not give rise to significant releases of other pathogenic organisms; and (iii) do not release unacceptable concentrations of toxic chemicals. The approach offers an exposure assessment perspective for carcass disposal, thus providing a risk-informed basis for contingency planning and operational intervention. The authors recognize that relevant legislation, public perception, available capacity, and cost also need to be considered when selecting disposal options in the event of HPAI.     

Fading Mechanisms and Voltage Hysteresis in FeF2–NiF2 Solid Solution Cathodes for Lithium and Lithium‐Ion Batteries

The rapid development of ultrahigh‐capacity alloying or conversion‐type anodes in rechargeable lithium (Li)‐ion batteries calls for matching cathodes for next‐generation energy storage devices. The high volumetric and gravimetric capacities, low cost, and abundance of iron (Fe) make conversion‐type iron fluoride (FeF₂ and FeF₃)‐based cathodes extremely promising candidates for high specific energy cells. Here, the substantial boost in the capacity of FeF₂ achieved with the addition of NiF₂ is reported. A systematic study of a series of FeF₂–NiF₂ solid solution cathodes with precisely controlled morphology and composition reveals that the presence of Ni may undesirably accelerate capacity fading. Using a powerful combination of state‐of‐the‐art analytical techniques in combination with the density functional theory calculations, fundamental mechanisms responsible for such a behavior are uncovered. The unique insights reported in this study highlight the importance of careful selection of metals and electrolytes for optimizing electrochemical properties of metal fluoride cathodes.