Ceramic-based chemical sensors, probes and field-tests in automobile engines

The monitoring and control of combustion-related emissions is a top priority in many industries. The major methods used to detect combustion gases fall short of practical applications for in-situ measurements in industrial environments involving high temperature and chemical contaminants. The real challenge is not only to develop highly sensitive and selective sensors, but to maintain long-term stability in such aggressive environments. This article presents an overview of a multidisciplinary research effort in ceramic-based chemical sensors, highlighting opportunities as well as challenges. The group of sensors (CO, NO _x , O₂, and CO₂) selected for this article can, in general, be used to determine the state of combustion in a wide variety of applications. Fabrication of sensor probes and their field-test results in automobile engines are also presented.     

Near-infrared spectroscopic method for real-time monitoring of pharmaceutical powders during voiding

A near-infrared (NIR) spectroscopic method has been developed to monitor flowing pharmaceutical powders during their voiding and detect post-blending segregation. The method is capable of providing both chemical and physical information (particle size differences) on the flowing pharmaceutical powders. Particle size differences are widely recognized as the predominant driver for segregation. Pharmaceutical powders may segregate following blending as they are voided down pipes to compressing machines, increasing the variability of the drug content and dissolution of the final product tablets because of segregation. NIR diffuse reflectance spectra of pharmaceutical powders were obtained following voiding through a six-foot pipe. Spectral subtraction was used to eliminate baseline differences but maintain particle size differences. The NIR spectra indicated differences in the particle size of the flowing powder. Particle size differences were also tracked throughout the voiding of pharmaceutical powders by plotting the absorbance at 1536 nm. The method was also applied to the voiding of two layers of lactose particles with different particle sizes. The system described in this report provides an approach to study post-blending segregation in pharmaceutical powders and other relevant materials.     

Evolutionary optimization for ranking how-to questions based on user-generated contents

In this work, a new evolutionary model is proposed for ranking answers to non-factoid (how-to) questions in community question-answering platforms. The approach combines evolutionary computation techniques and clustering methods to effectively rate best answers from web-based user-generated contents, so as to generate new rankings of answers. Discovered clusters contain semantically related triplets representing question–answers pairs in terms of subject-verb-object, which is hypothesized to improve the ranking of candidate answers. Experiments were conducted using our evolutionary model and concept clustering operating on large-scale data extracted from Yahoo! Answers. Results show the promise of the approach to effectively discovering semantically similar questions and improving the ranking as compared to state-of-the-art methods.     

Angina in the acute phase of myocardial infarct

Factor VIII (AHG) activity was assayed in the plasma specimens from 1016 regular and controlled blood donors. Age and ABO blood groups had highly significant effects on factor VIII concentrations, whereas the effect of sex was not significant. The median in the donors of blood group O rose from 87% at the age of 20 to 119% at the age of 60 years, and the median in blood groups A and B+AB of corresponding ages rose from 108 to 147%. An interaction effect of age and blood groups was present only at the 5% level of significance. The present data and the previous findings of others suggest the existence of an association between high factor VIII levels and thrombotic states.     

Compilation and evaluation of a Paso del Norte emission inventory

Emission inventories of ozone precursors are routinely used as input to comprehensive photochemical air quality models. Photochemical model performance and the development of effective control strategies rely on the accuracy and representativeness of an underlying emission inventory. This paper describes the tasks undertaken to compile and evaluate an ozone precursor emission inventory for the El Paso/Ciudad Juárez/Southern Do?a Ana region. Point, area and mobile source emission data were obtained from local government agencies and were spatially and temporally allocated to a gridded domain using region-specific demographic and land-cover information. The inventory was then processed using the US Environmental Protection Agency (EPA) recommended Emissions Preprocessor System 2.0 (UAM-EPS 2.0) which generates emissions files compatible with the Urban Airshed Model (UAM). A top down evaluation of the emission inventory was performed to examine how well the inventory represented ambient pollutant compositions. The top-down evaluation methodology employed in this study compares emission inventory ratios of non-methane hydrocarbon (NMHC)/nitrogen oxide (NOx) and carbon monoxide (CO)/NOx ratios to corresponding ambient ratios. Detailed NMHC species comparisons were made in order to investigate the relative composition of individual hydrocarbon species in the emission inventory and in the ambient data. The emission inventory compiled during this effort has since been used to model ozone in the Paso del Norte airshed (Emery et al., CAMx modeling of ozone and carbon monoxide in the Paso del Norte airshed. In: Proc of Ninety-Third Annual Meeting of Air & Waste Management Association, 18-22 June 2000, Air & Waste Management Association, Pittsburgh, PA, 2000).     

Ge-modified Pt/SiO2 catalysts used in preferential CO oxidation (CO-PROX)

A bimetallic PtGe catalyst was prepared by a controlled surface reaction and studied for the PROX reaction. The good activity of the bimetallic catalyst can be assigned to the presence of a “noble metal-oxidized metal promoter” ensemble site in close contact, the noble metal (Pt) being the CO adsorption site and the oxidized metal promoter (Ge) the O₂ adsorption site. The stability of the PtGe clusters is confirmed by the EXAFS spectra and activity measurements in the preferential oxidation reaction that show similar values for samples subjected to different oxidation–reduction cycles.     

The Oxidative Precipitation of Thallium at Alkaline pH for Treatment of Mining Influenced Water

Thallium (Tl) may exceed regulatory limits in mining-influenced water (MIW) associated with processing cadmium, copper, gold, lead, and zinc ores. It is a toxic metal that is soluble over a wide pH range, resulting in both persistence in the environment and poor removal by conventional lime precipitation. This study evaluated the effect of potassium permanganate (KMnO₄) at alkaline pH on Tl removal from MIW in batch experiments. The oxidation of Tl⁺ to Tl³⁺ by KMnO₄ and subsequent Tl removal was explored at Tl concentrations of ≤1 mg/L in synthetic and actual MIW. In addition to Tl, the synthetic MIW contained ≈5 mg/L of Mn, while the actual MIW contained >10 mg/L of Al, Cu, Fe, Mn, and Zn and had a pH ≈ 2.5. Dissolved Tl <2 μg/L in synthetic MIW was achieved at a pH ≈ 9 (CaO addition) and ≥5 mg/L of KMnO₄. In the actual MIW, dissolved Tl <2 μg/L was achieved at pH ≈ 9 and ≥12 mg/L of KMnO₄. The Tl removal mechanism is complicated due to the presence of reduced Mn in the synthetic MIW and multiple metals in the actual MIW. However, effective Tl removal was achieved by adding KMnO₄ to synthetic and actual MIW at alkaline pH.     

Hydraulic and purification behaviors and their interactions during wastewater treatment in soil infiltration systems

Four three-dimensional lysimeters were established in a pilot laboratory with the same medium sand and either an aggregate-laden (AL) or aggregate-free (AF) infiltration surface and a 60- or 90-cm soil vadose zone depth to ground water. During 48 weeks of operation, each lysimeter was dosed 4 times daily with septic tank effluent (STE) at 5 cm/d (AL) or 8.4 cm/d (AF). Weekly monitoring was done to characterize the STE, percolate flow and composition, and water content distributions within the lysimeters. Bromide tracer tests were completed at weeks 0, 8, and 45 and during the latter two times, ice nucleating active (INA) bacteria and MS-2 and PRD-1 bacteriophages were used as bacterial and viral surrogates. After 48 weeks, soil cores were collected and analyzed for chemical and microbial properties. The observations made during this study revealed a dynamic, interactive behavior for hydraulic and purification processes that were similar for all four lysimeters. Media utilization and bromide retention times increased during the first two months of operation with the median bromide breakthrough exceeding one day at start-up and increasing to two days or more. Purification processes were gradually established over four months or longer, after which there were high removal efficiencies (>90%) for organic constituents, microorganisms, and virus, but only limited removal of nutrients. Soil core analyses revealed high biogeochemical activity within the infiltrative zone from 0 to 15 cm depth. All four lysimeters exhibited comparable behavior and there were no significant differences in performance attributable to infiltrative surface character or soil depth. It is speculated that the comparable performance is due to a similar and sufficient degree of soil clogging genesis coupled with bioprocesses that effectively purified the wastewater effluent given the adequate retention times and high volumetric utilization's of the sand media.