Preliminary stability analysis

A key issue in studies of thermolysis kinetics in hitherto unexplored systems, including Hf-containing polymers, is the optimization of the experimental procedure. Preliminary thermodynamic analysis of the Hf-C-H-0 system offers the possibility of establishing the temperature stability limits of HfC and HfO. Earlier, thermodynamic studies of the Hf-C-H-O system were carried out in relation to hafnium acetylacetonate, which is used to prepare HfC [33]. The most convenient approach to producing hafnium-containing nanocomposites with the aim of... 

Accordingly, a hypothesis was formulated, which seeks the theoretical rationale of appearance of the specific flow structures inside the liquid layer. It is known, that under certain circumstances, the surface tension variations may lead to the flow instability and to the induction of convection cells [e.g., 5, 6]. Our preliminary theoretical analysis of the hydrodynamic stability of the system [7] indicated that it is possible, that for the Reynolds numbers exceeding the critical value, convection cells inside the hypophase can be formed. This should lead to the significant increase of the mass transfer rate. 

For the purpose of preliminary concepmal design of the Super LWR, first, it is important to determine whether the instability will be a problem, and how it can be avoided if it occurs. Thus, the first aim is to investigate what may cause the instability and when it can occur in the Super LWR. To achieve that aim, the approach is to use a simple model which can explain the essential features of the physical phenomena of the system without the requirement of much computing effort. Hence, the simple frequency domain linear stability analysis method is employed to investigate the onset of instability in the Super LWR. 

The analysis presented above for the effect of ceUobiose on CBH I thermal stability must be considered preliminary, in that equation 3, and therefore also equation 4, which is derived from equation 3, apply strictly only to single-transition processes. Equation 4 does, however, serve weU to illustrate the general type of peak-displacement being proposed here. Exact numerical appUcation of such an equation would require accurate estimates, not presently avaUable, for such quantities as the K. values for native CBH I and ceUobiose at pH values far remov from the activity optimum, and/or at temperatures at which the native enzyme, in the absence of the inhibitor, does not exist in measurable proportions. QuaUtatively, however, we beUeve that the analysis presented above can serve as a useful conceptual basis, or springboard, for further investigations of catalytic-domain structure and function. 

The sorbent materials that performed best in the capacity and desorption efficiency tests were investigated further with respect to the stability of the sorbed analyte. Preliminary tests of analyte stability were conducted by a procedure similar to that in the desorption efficiency tests the procedure differed in that samples were stored 7 d prior to analysis rather than Id. To be acceptable, a sorbent material had to exhibit no statistically significant loss of analyte at the 0.05 significance level by a two-tailed t test. 

In addition to the analysis of the thermal stability of the perchloric acid organic reaction media mixtures, a procedure was worked out to determine the fate of the perchloric acid by chlorine analysis of the batch, effluent streams, etc. Preliminary analyses on selected process samples showed no tendency for perchloric acid to concentrate in recycle material and therefore build up in the reactor. A total of less than 1% of the initial charge of perchloric acid (total chlorides calculated as perchloric acid) was found in the combined recovered acid-ester and olefin fractions. Less than 1 % of the initial charge of perchloric acid was found in the finished ester. The analytical method used was an oxygen bomb decomposition, followed by titration of chlorides with 0.0liV silver nitrate, using a recording automatic titrator. The eventual fate of the perchloric acid catalyst was... 

All these studies on bimolecular processes indirectly indicate the involvement of acz -nitromethane, but more detailed studies will be required to estimate the energy requirements for its formation. Our own preliminary analysis for the bimolecular transfer of hydrogen between carbon and oxygen shows this process to be spontaneous for the transfer from acz-nitromethane to the nitromethide anion, whereas that from nitromethane is 10 kcal/mol endothermic (Scheme VI). Thus, under gas phase conditions H-transfer from acz -nitromethane to the nitromethide anion should occur exclusively, but the reverse process may well occur in liquid and solid phases as the endothermicity is only modest. This is further supported by the 12 kcal/mol stabilization that results on the spontaneous carbon to oxygen transfer of hydrogen from protonated nitromethane to nitromethane [28]. 

The recent advances in NOS structure analysis have shed light on the roles of the pterin, the substrate, and the newly discovered zinc ion in dimer formation and stabilization as well as catalytic activity. Work by numerous groups on iNOS (murine and human) [100, 101, 105-107], and eNOS (human and bovine) [101, 102] provides an intimate view of the various interactions between cofactors and protein-protein interplay in dimer formation. Structural work on the neuronal isoform of NOS is presently ongoing, with preliminary results indicating high structural similarity to published structures of the other NOS isoforms (T.L. Poulos, personal communication). 

Phenylarsine oxide is used as a titrant for the direct and indirect determination of residual chlorine and ozone in water and wastewater. Preliminary investigations on the direct measurement of PAO by differential pulse polarography (DPP) indicate that this technique is a promising method for lowering the detection limits in the indirect measurement of these oxidants. The control of pH is a necessary consideration in free and combined chlorine analysis with as well as the stability and measurement of... 

---