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A mathematical model of a catalytic converter for automobile diesel engines that contains zeolites for adsorption of hydrocarbons has been developed. The model includes a description of mass- and heat-transfer resistance at the external surface of the monolith washcoat and internal diffusion within the catalytic washcoat layer. Kinetic parameters for adsorption and oxidation of hydrocarbons [propene (C3H6), decane (C10H22), and toluene (C6H5CH3)], CO oxidation, and NOx adsorption and reduction were evaluated on the basis of dynamic experiments. Model simulations of dynamic operation regimes illustrate the effects of the inlet flow rate, temperature and adsorption capacity on the light-off, integral conversions, and spatiotemporal concentration patterns in the monolith. The effects of varying the transport properties of the washcoat layer (effective diffusion coefficient) and washcoat thickness are also investigated.

Two models of catalytic monolith reactor with diffusion in the washcoat are described, employing the nonstationary kinetics of CO and hydrocarbon oxidation, NOx reduction, and oxygen storage with 23 reaction steps. The first model describes the dynamic behavior in a short monolith (recirculation reactor or CSTR), and the second one is a spatially two-dimensional nonstationary model of the monolith with plug flow. The models are used to demonstrate the qualitative agreement between the observed nonlinear dynamics of CO oxidation, including hysteresis and periodic and period-doubled oscillations, and earlier experiments. The effects of transport parameters within the washcoat on the monolith lightoff and on the outlet conversions are simulated. Computed spatiotemporal concentration patterns of reaction intermediates within the washcoat layer are used to discuss the oxidation and reduction functions of the three-way-catalyst monolith.

The synthesis and enzyme inhibition data for a series of thiadiazole urea matrix metalloproteinase (MMP) inhibitors are described. A broad screening effort was utilized to identify several thiadiazoles which were weak inhibitors of stromelysin. Optimization of the thiadiazole leads to include an α-amino acid side chain with variable terminal amide substituents provided a series of ureas which were moderately effective stromelysin inhibitors, with Ki's between 0.3 and 1.0 μM. The most effective analogues utilized an l-phenylalanine as the amino acid component. In particular, unsubstituted 46 had a Ki of 710 nM, while the p-fluoro analogue 52 displayed increased potency (100 nM). Stromelysin inhibition was further improved using a pentafluorophenylalanine substituent which resulted in 70, a 14 nM inhibitor. While gelatinase inhibition was generally poor, the use of 1-(2-pyridyl)piperazine as the amide component usually provided for enhanced activity, with 71 inhibiting gelatinase with a Ki of 770 nM. The combination of this heterocycle with a p-fluorophenylalanine substituent provided the only analogue, 69, with collagenase activity (13 μM). The SAR for analogues described within this series can be rationalized through consideration of the X-ray structure recently attained for 70 complexed to stromelysin. Uniquely, this structure showed the inhibitor to be completely orientated on the left side of the enzyme cleft. These results suggest that thiadiazole urea heterocycles which incorporate a substituted phenylalanine can provide selective inhibitors of stromelysin. Careful selection of the amide substituent can also provide for analogues with modest gelatinase inhibition.

Antibodies contained in an A/J anti-B10 antiserum, when tested on lymphocytes from B10.A mice, were shown to bind to both B and T cells and to inhibit the binding of Ig complexes to the Fc receptors of B lymphocytes. These antibodies could be removed by absorption with B10.D2 lymphocytes. Similar results were obtained with lymphocytes from two to six (B6A)F1 x A/J backcross mice which had H-2a/a genotype. These data indicate that alloantigens determined by at least one non-H-2 locus are associated with or a part of Fc receptors. These antigens may be similar in structure and function to Ia antigens.

The model of Andrews and Graef (1974) was used as a basis of simulation of stationary and dynamic behaviour of an anaerobic digester. It was found, that multiple stable stationary states exist in the continuously operated digester. The feed-batch type of operation can give higher substrate conversion than the continuous operation. The introduction of the time-lag into the microorganism growth function causes appearance of both stable and unstable periodic states of the digester. The questions of controllability and the possibilities of multivariable control strategy has been discussed.

A mathematical description of a continuous adsorption process in the so-called “dessicant rotor” based on the assumption of a locally adiabatic operation is developed. The steady state of the cyclic process is formulated as a mixed boundary value problem for the governing spatially one-dimensional parabolic PDE's and solved by the shooting method. The efficiency of several quasi-Newton schemes is compared with that of the fixed-point iteration method. An algorithm for the determination of operational parameters satisfying given constraints and minimizing the amount of heat supplied to the process is demonstrated as an example.

The independent B lymphocyte surface membrane receptors IgM and Fc IgG receptors were evaluated for interactions using immunoflourescence. Ligand [F(ab')2 anti-mu]-induced capping of surface IgM resulted in capping of Fc IgG receptors only if the latter were occupied during the capping process by: (a) soluble antigen-antibody complexes that themselves provided insufficient cross-linking to result in capping; or (b) monomeric IgG at physiologic concentrations (or less) either purified or as normal serum. Ligand-induced capping of Fc IgG receptors did not result in capping of surface IgM occupied by monomeric F(ab') anti-mu. Control experiments showed that ligand binding to or capping of only one of these two receptors has no effect on the other, and that there were no cross-reactions. The interaction appears specific in that ligand-induced capping of surface IgM did not induce capping of ligand-occupied surface IgD or I-A antigens. Thus, there appears to be a specific interaction between ligand-bound surface IgM and ligand-bound Fc IgG receptors on the B lymphocyte surface. The results also indicate that binding of monomeric IgG produces a reversible alteration in the Fc IgG receptor leading to association with ligand-bound surface IgM. Because Fc IgG receptors are continuously exposed to monomeric IgG in vivo, these results suggest that whenever surface IgM is involved in a B lymphocyte response to an immunologic stimulus, the Fc IgG receptor is also involved.

The cultivation and characterization of a cell line derived from the foreskin of a fetal, rhesus monkey (rhfs2) are described. This cell line has proven satisfactory for isolation and assay of a variety of viral agents of human and simian origin. Virus titrations performed on foreskin cells yielded titers comparable to, or higher than, those obtained in rhesus monkey kidney cells (LLC-MK2). Replicate isolation attempts in our laboratory from simian clinical specimens have proven rhfs2 superior to LLC-MK2 for ease of detection and frequency of isolation.

Sr-doped lanthanum manganite (LSM) is a widely used cathode material in solid oxide fuel cells (SOFC). Despite being a poor ion conductor, LSM electrodes can reduce oxygen via two pathways: a “3PB surface path” which includes surface diffusion of oxygen species and oxide ion incorporation at the three phase boundary (3PB), and a “bulk path” based on oxygen diffusion in LSM. In this work, the kinetics of both paths and their dependence on temperature and electrode geometry is investigated by impedance spectroscopy on micropatterned LSM thin film electrodes. Differently shaped and sized macroscopic and microscopic LSM electrodes as well as LSM electrodes with oxygen blocking Pt capping layers are employed to identify two parallel reaction pathways of oxygen reduction. On circular microelectrodes the 3PB surface path carries most of the current in the lower temperature region (below ca. 700°C), while at high temperatures (above ca. 700°C) the bulk path is dominating. The significance of each reduction path also depends on the microstructure of the columnar LSM films which can be changed by varying pulsed laser deposition (PLD) parameters or by annealing. Moreover, relevance of a pseudo-3PB path across edges of the LSM electrodes is discussed.

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