Reduction in Performance Due to Recirculation in Mechanical Draft Cooling Towers

Abstract

The influence of recirculating warm plume air on the performance of mechanical-draft cooling towers is investigated analytically, numerically, and experimentally. It is shown that the amount of recirculation that occurs is a function of the flow and the thermal and geometric characteristics of the tower. The presence of a wind wall tends to reduce the amount of recirculation. An equation is presented with which the performance effectiveness due to recirculation can be evaluated approximately for a mechanical-draft cooling tower.     

Progressive venous occlusion in a neonate with Sturge-Weber syndrome: demonstration with MR venography

Progressive cerebral sinovenous occlusion in a neonate with Sturge-Weber syndrome was documented by using two-dimensional time-of-flight MR venography. There was no evidence of intraluminal thrombus on routine spin-echo images obtained either before or after the onset of seizures, despite MR venographic evidence in both studies of venous abnormalities.     

The exchange of Arg-Gly-Asp (RGD) and Arg-Tyr-Asp (RYD) binding sequences in a recombinant murine Fab fragment specific for the integrin alpha IIb beta 3 does not alter integrin recognition

The murine monoclonal antibody OPG2 is an excellent paradigm of natural RGD ligands and binds specifically to alpha IIb beta 3 integrin. A reactive Arg103-Tyr104-Asp105 (RYD) tripeptide is located in an extended loop, the third complementarity-determining region of the heavy chain (H3). When compared to other RGD ligands, the RYD tripeptide of OPG2 is unique, in that the side chains are fixed in a stable orientation that we have defined by x-ray crystallography. In this study, we express OPG2 H chain segments (Fd) and kappa chains as components of active, Fab heterodimers by coinfection of Spodoptera frugiperda cell lines with recombinant baculoviruses containing cDNA specific for each protein. Recombinant AP7 Fd segments are generated from the parent OPG2 Fd segments by replacement of Tyr104 with Gly, while recombinant AP7E Fd segments are produced from AP7 Fd segments, by exchange of Asp105 with Glu. Neither the free Fd segments nor the free kappa chains of OPG2 or AP7 can bind to alpha IIb beta 3. The AP7 Fab fragment, like the parent OPG2 Fab, binds strongly to purified alpha IIb beta 3 but weakly, if at all, to purified alpha V beta 3. The affinity of OPG2 and AP7 Fab fragments for gel-filtered platelets, whether nonstimulated or activated by 0.2 microM phorbol 12-myristate 13-acetate, is identical. As with other natural RGD ligands, the binding of recombinant OPG2 Fab or AP7 Fab fragments to purified alpha IIb beta 3 or to gel-filtered platelets is completely inhibited by the peptide RGDW or by addition of EDTA, AP7E Fab fragments do not bind at all to either purified alpha IIb beta 3 or platelets. Our results demonstrate, for the first time within a natural protein ligand, that the tripeptides RGD and RYD exhibit equivalent binding capacity and specificity for the integrin alpha IIb beta 3.     

Biocompatibility of glass ionomer cements

Glass ionomer cements (GICs) are widely used in the dental field and are increasingly being considered as materials with potentially good osteogenic properties. This paper details a comprehensive biocompatibility evaluation of a number of GICs. These include conventional, commercially available materials, novel formulations and a new light cured material. The experimental programme entailed in vitro cell culture studies using direct contact and extraction tests and an in vitro rat model in which the GICs were in intimate contact with bone for periods up to 8 wk. The results demonstrate clear differences between the materials and in particular highlight the poor cellular response to the light cured material. Methylthiazolyldiphenyl tetrazolium assay demonstrates stimulation of cell growth by some GIC formulations and indicates that cytotoxic leachable agents can be removed from others. The results obtained following implantation into bone are comprehensively presented using photomicrographs. New bone formation with time is demonstrated with a number of formulations.     

Economic control of fertiliser in highly productive pastoral systems. V. Extending advice through the Mitscherlich-Liebig model

A general solution is proposed to the problem of extending economic fertilizer advice over a highly productive pastoral area. The scheme implies a subdivision of the area through objective information obtained from widely dispersed, long-term, 3 level field trials; within sub-areas advice appropriate to a particular farm, or part thereof, is specified by incorporating more or less subjective estimates concerning level of output from the current input of fertilizer and carry-over of fertility in the field from one year to the next. The mathematical model used to facilitate an economic evaluation has been termed ML because it combines two cardinal principles: Mitscherlich's Law of Diminishing Returns and Liebig's Law of the Minimum, and is thus in accord with both economic and physiological theory. The model has been used to assess the effectiveness of chemical soil testing as a means of estimating carryover of fertility and to study the sensitivity of economic advice to error in the vital ratio: cost of input/selling price of output. The concept of a common response curve for essential elements has been developed as a basis for calculating the composition of a complete physiologically balanced fertilizer.The articles I–IV appeared inFertilizer Research 4:4 (1984)