Kinetics of the catalytic oxidation of carbon monoxide over oxide catalysts

The kinetics of the oxidation of carbon monoxide over five commercially available oxide catalysts have been determined at CO concentrations of 4–15 mol% and initial temperatures up to 170°C. The reaction showed a fractional dependence on the concentration of CO and was inhibited by CO₂. From an analysis of the data a Langmuir-Hinshelwood reaction scheme is proposed.     

Jojoba oil analysis by high pressure liquid chromatography and gas chromatography/mass spectrometry

Two analytical procedures for determining com-positions of jojoba liquid wax esters are described and compared. One, the more tedious, involves separation of wax ester homologs by high pressure liquid chro-matography followed by determination of the acid and alcohol moieties from each homolog. The second allows rapid determination of wax ester composition by gas Chromatographic separation of hydrogenated jojoba wax esters according to chain length, followed immediately by ancillary mass spectrometric identifi-cation of the acid and alcohol moieties. Double bonds in the alkyl chains in jojoba liquid waxes were almost exclusively (98%) ω-9, when examined by gas chro-matography/mass spectrometry (GC/MS) and ozonolysis/GC/MS. Presented in part at the 2nd International Conference on Jojoba and Its Uses, Ensenada, Mexico, February, 1976.     

Membership modification and level sets

We introduce the concept of a membership modification function and describe its role in transforming one fuzzy set into another. We discuss the related idea of a membership modification program consisting of a collection of related membership modification functions and show how the concept of level sets is an example of a membership modification program. Using this idea of membership modification allows us to consider other transformations of fuzzy sets that soften the idea of level sets. Using these ideas we provide an extension of the Jaccard similarity index.     

Invited article: A materials investigation of a phase-change micro-valve for greenhouse gas collection and other potential applications

The deleterious consequences of climate change are well documented. Future climate treaties might mandate greenhouse gas (GHG) emissions measurement from signatories in order to verify compliance. The acquisition of atmospheric chemistry would benefit from low cost, small size/weight/power of microsystems. In this paper, we investigated several key materials science aspects of a phase-change microvalve (PCμV) technology with low power/size/weight/cost for ubiquitous GHG sampling. The novel design, based on phase-change material low-melting-point eutectic metal alloys (indium-bismuth, InBi and tin-lead, SnPb), could be actuated at temperatures as low as 72 °C. Valve manufacturing was based on standard thick and thin-film processes and solder technologies that are commonly used in industry, enabling low-cost, high-volume fabrication. Aging studies showed that it was feasible to batch fabricate the PCμVs and store them for future use, especially in the case of SnPb alloys. Hermetic sealing of the valve prototypes was demonstrated through helium leak testing, and Mil spec leak rates less than 1 × 10(-9) atm cm(3)/s were achieved. This confirms that the sample capture and analysis interval can be greatly expanded, easing the logistical burdens of ubiquitous GHG monitoring. Highly conservative and hypothetical CO(2) bias due to valve actuation at altitude in 1 cm(3) microsamplers would be significantly below 1.0 and 2.2 ppmv for heat-treated InBi and SnPb solders, respectively. The CO(2) bias from the PCμV scales well, as a doubling of sampler volume halved the bias. We estimated the shelf life of the SnPb PCμVs to be at least 2.8 years. These efforts will enable the development of low cost, low dead volume, small size/weight microsystems for monitoring GHGs and volatile organic compounds.     

Investigation of Tibetian Plateau varnish: new findings at the nanoscale using focused ion beam and transmission electron microscopy techniques

Dual-beam focused ion beam microscopy (FIB/SEM) preparation of rock varnish for high-resolution transmission electron microscopy (HR-TEM) has enabled us to characterize unreported nanostructures. Fossils, unreported textures, and compositional variability were observed at the nanoscale. These techniques could provide a method for studying ancient terrestrial and extra-terrestrial environments to better understand geological processes at the nanoscale.     

The Thermal Distortion of a Funnel Mold

This article investigates the thermal distortion of a funnel mold for continuous casting of thin slabs and explores the implications on taper and solidification of the steel shell. The three-dimensional mold temperatures are calculated using shell-mold heat flux and cooling water profiles that were calibrated with plant measurements. The thermal stresses and distorted shape of the mold are calculated with a detailed finite-element model of a symmetric fourth of the entire mold and waterbox assembly, and they are validated with plant thermocouple data and measurements of the wear of the narrow-face copper mold plates. The narrow-face mold distorts into the typical parabolic arc, and the wide face distorts into a ??W?? shape owing to the large variation in bolt stiffnesses. The thermal expansion of the wide face works against the applied narrow-face taper and funnel effects, so the effect of thermal distortion must be considered to accurately predict the ideal mold taper.     

Selective Catalytic Oxidation of Alcohols,Aldehydes, Alkanes and Alkenes Employing Manganese Catalysts and Hydrogen Peroxide

The manganese‐containing catalytic system [Mn^IV,IV₂O₃(tmtacn)₂]²⁺ ( 1 )/carboxylic acid (where tmtacn=N,N′,N′′‐trimethyl‐1,4,7‐triazacyclononane), initially identified for the cis‐dihydroxylation and epoxidation of alkenes, is applied for a wide range of oxidative transformations, including oxidation of alkanes, alcohols and aldehydes employing H₂O₂ as oxidant. The substrate classes examined include primary and secondary aliphatic and aromatic alcohols, aldehydes, and alkenes. The emphasis is not primarily on identifying optimum conditions for each individual substrate, but understanding the various factors that affect the reactivity of the Mn‐tmtacn catalytic system and to explore which functional groups are oxidised preferentially. This catalytic system, of which the reactivity can be tuned by variation of the carboxylato ligands of the in situ formed [Mn^III,III₂(O)(RCO₂)₂(tmtacn)₂]²⁺ dimers, employs H₂O₂ in a highly atom efficient manner. In addition, several substrates containing more than one oxidation sensitive group could be oxidised selectively, in certain cases even in the absence of protecting groups.

     

Anomalous Quasi TE11 Mode Absorption in the Afterglow of a Positive Column Occupying a Long Guide Cylindrical Wave

Experimental observations of reflection and transmission of a cw wave propagating in the quasi TE11 mode in a cylindrical wave guide filled with a time decaying plasma are presented. The discharge column occupies, with the exception of a thin layer of quartz, the entire cross-section of the wave guide. The transmitted wave displays a series of optima whose relative amplitudes increase with decreasing electron density. With regard to phase separation, frequency and pressure variation the extrema seem to fit a simple theoretical model, which, however, fails to explain the absorption mechanism, the latter being also associated with a reversed cross-modulation not explainable by the Ramsauer effect.     

An attribute grammar approach to compiler optimization of intra-module interprocess communication

Earlier work has shown the effectiveness of hand-applied program transformations optimizing high-level interprocess communication mechanisms. This paper describes the static analysis techniques necessary to ensure correct compiler application of the optimizing transformations. These techniques include both dataflow analysis and interprocess analysis. This paper focuses on the analysis of communication mechanisms within program modules; however, the analysis techniques can be generalized to handle inter-module optimization analysis as well. The major contributions of this paper include the application of dataflow analysis and the extension of interprocedural analysis—interprocess analysis—to real concurrent programming languages and, more specifically, to the optimization of interprocess communication and synchronization mechanisms that use both static and dynamic channels. In addition, the use of attribute grammars to perform interprocess analysis is significant. This paper also describes an implementation of both intra-process dataflow and interprocess analysis techniques using attribute grammars.This work was supported by NSF under Grant Number CCR88-10617.