Coaggregation between Acinetobacter johnsonii S35 and Microbacterium esteraromaticum strains isolated from sewage activated sludge

The extent and nature of intergeneric coaggregations among non-flocculating sludge bacteria were studied through examination of the coaggregation abilities of Acinetobacter johnsonii S35 with two other strains of non-flocculating sludge bacteria (Microbacterium esteraromaticum S38 and M. esteraromaticum S51). At first, the effect of electrolyte concentration as well as the addition of EDTA and proteases on coaggregation were studied. Changes in electrolyte concentration had little effect on the aggregation index (A.I.). However, the A.I. was reduced by 35-45% (addition of 2 mM EDTA) and 15-58% (addition of 0.2 mg/ml Actinase E) within 1 h depending upon the bacterial pair involved. Furthermore, the effect of pretreating either A. johnsonii S35 or its partners with Actinase E and periodate, respectively, was studied. The results indicate that these coaggregations involve a protein on the partner's surface that may interact with carbohydrate or a carbohydrate-containing moiety on the surface of A. johnsonii S35.     

Thermoreversible gelation of poly(vinylidene fluoride)/poly(methyl acrylate) blends in diethyl azelate: a thermodynamic investigation

The thermodynamic behaviour of poly(vinylidene fluoride) (PVF₂)/poly(methyl acrylate) (PMA) blend gels in diethyl azelate (DEAZ) was studied by differential scanning calorimetry at three different blend compositions (x (weight fraction of PVF₂ in the blend) = 0.75, 0.5 and 0.25). Transmission electron microscopy together with optical microscopy indicate the presence of fibrillar network morphology in the gels. The quasi‐binary phase diagrams drawn from both the heating and cooling processes are almost similar, with a hysteresis of 50–60 °C. The possibility of polymer–solvent compound formation in the blend gels have been explored from the composition dependency of enthalpy of gel fusion and enthalpy of gel formation data. Extending the procedure of the pure PVF₂/DEAZ gel systems to blend gels, it has been surmised that polymer–solvent compound formation also occurs in blend gels, but the stoichiometry of the complexes varies with blend composition. The shapes of the quasi‐binary phase diagrams of the blend gels are different in some cases from that of pure PVF₂/DEAZ, gel indicating that the polymer–solvent compounds are incongruent or singular type depending on the blend compositions. A possible explanation for this behaviour has been offered from entropic and enthalpic viewpoints. Copyright © 2003 Society of Chemical Industry     

A synthesis-based test generation and compaction algorithm for multifaults

Because of its inherent complexity, the problem of automatic test pattern generation for multiple stuck-at faults (multifaults) has been largely ignored. Recently, the observation that multifault testability is retained by algebraic factorization demonstrated that single fault (and therefore multifault) vector sets for two-level circuits could give complete multifault coverage for multilevel circuits constructed by algebraic factorization. Unfortunately, in using this method the vector set size can be much larger than what is really required to achieve multifault coverage, and the approach has some limitations in its applicability.In this article we first present a multifault test generation and compaction strategy for algebraically factored multilevel circuits, synthesized from two-level representations. We give a basic sufficiency condition for multifault testability of such networks.We next focus on the relationship between hazard-free robust path-delay-fault testability and multifault testability. We show that the former implies the latter for arbitrary multilevel circuits. This allows the use of previously developed composition rules that maintain path-delay-fault testability for the synthesis of multifault testable circuits.We identify a class of multiplexor-based networks and prove an interesting property of such networks—if the networks are fully single stuck-at fault testable, or made fully single stuck-at fault testable, they are completely multifault testable. We give a multifault test generation and compaction algorithm for such networks.We provide experimental results which indicate that a compacted multifault test set derived using the above strategies can be significantly smaller than the test set derived using previously proposed procedures. These results also indicate the substantially wider applicability of our procedures, as compared to previous techniques.     

Adaptive ground fault protection schemes for turbogenerator basedon third harmonic voltages

Equivalent circuits based on the actual connection of coil-groups of generators are used to study the characteristics of various generator stator ground fault protection schemes presented in the literature. The evaluation and the comparison of the characteristics of those schemes are given by means of protection coverage-critical resistance curves. Although these schemes are successful in practice, they suffer the disadvantage of low sensitivity, which is strongly related to generator operating conditions. To overcome this disadvantage, two adaptive stator ground fault protection schemes based on digital techniques are developed. Compared to conventional third-harmonic voltage schemes, they can automatically track the change of generator operating conditions before a ground fault occurs. Test results from a digital simulation show that they can keep high sensitivity during all operating conditions     

Analysis and performance characteristics of three-phase, thyrode ACvoltage controllers

A generalized approach based on numerical evaluation of the Fourier coefficients is used to determine the performance of three-phase phase-controlled thyrode AC voltage controllers. Balanced resistive and inductive loads of different power factors are considered. Various electrical properties are computed and compared graphically for different circuit configurations. It is found that although the branch-controlled delta-connected load gives the highest distortion and power factors, it offers limited control of input power. The line-controlled star-connected circuit offers full range of power control, a simple control scheme over a wider range of firing angle retardation, and good distortion and power factors. For applications where even harmonics can be tolerated in the line currents, such a controller has superior performance characteristics compared to that of the conventional thyristor voltage controller of similar configuration     

The growth of Görtler vortices in compressible boundary layers

The linear instability of Görtler vortices in compressible boundary layers is considered. Using asymptotic methods in the high-wavenumber regime, it is shown that a growth-rate estimate can be found by solving a sequence of linear equations. The growth rate obtained in this way takes non-parallel effects into account and can be found much more easily than by ordinary differential equation eigenvalue calculations associated with parallel-flow theories.     

Study of space-dependent fast-neutron spectra and tritium breeding ratio in different assemblies of Li, Li and natural Li

Using diffusion theory and the eigenfunction expansion method, a detailed space-dependent study of fast neutron spectra has been carried out in ⁷Li, ⁶Li and natural Li assemblies of dimensions 100 × 60 × 60 cm³ and 30 × 60 × 60 cm³. Values of total (space-averaged) tritium breeding ratio (TBR) have been obtained for these assemblies. BARC-892, a 27-group data-set was used for these calculations.

The results of TBR for the smaller assembly have been compared with the corresponding experimental and calculated values of Takahashi et al. (1984). We find that the present values of TBR are in reasonably good agreement with the above experimental results.