Levels of knowledge in distributed systems

We correlate thelevel of knowledge of certain formulas in agroup of individuals with certain regular, downward closed, sets of strings. We show that in suitable circumstances, all such sets can occur as levels of knowledge but that the lack of synchrony, or the lack of asynchrony when there are only two processors in the group, can create more or less severe restrictions.     

Parametric sensitivity of chain polymerization reactors exhibiting the trommsdorff effect

The recently developed mathematical technique for studying the parametric sensitivity of reactors is extended to include chain polymerization systems exhibiting the gel and glass effects, as well as physical property variations. The sensitivities of the two temperature maxima with respect to various parameters are computed. It is found that, for a sample system, poly(methyl methacrylate), all the sensitivities of the gel effect induced temperature peak attain their maxima at the same conditions—this leads to a generalized temperature sensitivity constraint applicable to reactor design or operation. This sensitivity boundary is associated with high conversions and high molecular weights. The analysis shows that the dimensionless propagation activation energy, ?_p, and the dimensionless initiation activation energy, ?_d, are the two most important parameters governing the system performance. Sensitivities of the gel effect-induced number average chain length peak with respect to various parameters are also obtained. Again, all of these chain length sensitivities show maxima at the same condition, leading to the concept of a generalized chain length sensitivity criterion of constraint. Most importantly, the temperature and chain length sensitivity boundaries are virtually identical.     

Kinetics of hydrogenation of D-glucose to sorbitol

The kinetics of the heterogeneous reaction between hydrogen and aqueous solutions of D -glucose to produce sorbitol were studied in a high pressure Parr reactor. Raney-Ni was used as catalyst. The reaction between hydrogen and D -glucose was found to be very slow. In the agitated slurry reactor the diffusional aspects were completely eliminated and the reaction followed homogeneous kinetics. It was found to be first order with respect to both hydrogen and D -glucose. The values of the pseudo-first-order rate constants were found to be 1.5 × 10^?4 and 6.4 × 10^?4s^?1 at 398 and 435 K, respectively. The activation energy was found to be 64.8 kJ mol^?1.     

Catalytic epoxidation of α-pinene over bifunctional mesoporous molecular sieves

Bifunctional titanium-mesoporous molecular sieves containing different trivalent ions, e.g. B³⁺, Al³⁺ or Fe³⁺, were synthesized and characterized. These catalysts, which contain both acid and oxidizing catalytic sites, are very active in epoxidation of bulky olefins and highly selective in diol formation. A reasonably good stability and re-usability are also observed. This revised version was published online in July 2006 with corrections to the Cover Date.     

Improving the calculation of interdiffusion coefficients

Least-squares spline interpolation techniques are reviewed and presented as a mathematical tool for noise reduction and interpolation of diffusion profiles. Numerically simulated diffusion profiles were interpolated using a sixth-order spline. The spline fit data were successfully used in conjunction with the Boltzmann-Matano treatment to compute the interdiffusion coefficient, demonstrating the usefulness of splines as a numerical tool for such calculations. Simulations conducted on noisy data indicate that the technique can extract the correct diffusivity data given compositional data that contain only three digits of information and are contaminated with a noise level of 0.001. Splines offer a reproducible and reliable alternative to graphical evaluation of the slope of a diffusion profile, which is used in the Boltzmann-Matano treatment. Hence, use of splines reduces the numerical errors associated with calculation of interdiffusion coefficients from raw diffusion profile data.     

Formation of ethanol from carbon monoxide via a new microbial catalyst

A recently discovered clostridial bacteria converts components of synthesis gas (CO, CO₂, H₂) into liquid products such as ethanol, butanol and acetic acid. Isolated from an agricultural lagoon, the stability and productivity characteristics of the bacteria were studied in a continuous 4.5 l bubble column bioreactor at 37°C using artificial blends of CO, CO₂, and N₂. Preliminary results on the rates of cell growth, substrate utilization, product formation, and yields of products and cells from CO are discussed. At steady state, apparent yields (mole C in products per mole CO consumed) of ethanol, butanol, and acetic acid were 0.15, 0.075 and 0.025, respectively, and the cell yield was 0.25 g/mol CO. The theoretical yield of ethanol is 0.33 if CO is only utilized for the production of ethanol. The experimental yield of CO₂ from CO was approximately 60% compared to the theoretical yield of 67% with ethanol as the sole product. As a comparison with another ethanol-producing bacteria, the results of a similar fermentation study using batch-grown Clostridium ljungdahlii showed yields of 0.062 for ethanol and 0.094 for acetic acid and a cell yield of 1.378 g/mol.     

Solar cell array parameters

A generalized method of combining non identical parameters like series and shunt resistance dependent photocurrents under open circuit conditions (I_phoa) and the loaded conditions (I_pha) have been deduced. It is found that in the case of series array, only I_pha is dependent upon shunt resistance, while in the case of parallel array both are dependent upon shunt resistance.     

Synthesis and characterization of 5,7-dimethyl-8-hydroxyquinoline and 2-(2-pyridyl)benzimidazole complexes of zinc(II) for optoelectronic application

Bis(5,7-dimethyl-8-hydroxyquinolinato)zinc(II) (Me₂q)₂Zn and 5,7-dimethyl-8-hydroxyquinolinato(2-(2-pyridyl)benzimidazole) zinc(II) Me₂q(pbi)Zn have been synthesized and characterized by various techniques. These metal complexes have high thermal stability (>300 °C) and high glass transition temperatures (>150 °C). The vacuum deposited films of these materials show good film forming property and are suitable for opto-electronic applications. Multilayered organic electroluminescent (EL) devices have been fabricated having structure ITO/α-NPD/zinc complex/BCP/Alq₃/LiF/Al, which produce emission with chromaticity having Commission Internationale d’Eclairage (CIE) coordinates x = 0.506 and y = 0.484 for (Me₂q)₂Zn; x = 0.47 and y = 0.52 for (Me₂q)(pbi)Zn complex. The electroluminescence spectra show peak emission centered at 572 and 561 nm respectively for these materials.     

Gate Current Modeling and Optimal Design of Nanoscale Non-Overlapped Gate to Source/Drain MOSFET

In this paper, novel nanoscale MOSFET with Source/Drain-to-Gate Non-overlapped and high-k spacer structure has been demonstrated to reduce the gate leakage current for the first time. The gate leakage behaviour of novel MOSFET structure has been investigated with help of compact analytical model and Sentaurus Simulation. Fringing gate electric field through the dielectric spacer induces inversion layer in the non-overlap region to act as extended S/D region. It is found that optimal Source/Drain-to-Gate Non-overlapped and high-k spacer structure has reduced the gate leakage current to great extent as compared to those of an overlapped structure. Further, the proposed structure had improved off current, subthreshold slope and DIBL characteristic. It is concluded that this structure solves the problem of high leakage current without introducing the extra series resistance.