A survey and analysis of commercially available hydrogen sensors

The performance requirements for hydrogen detection in aerospace applications often exceed those of more traditional applications. In order to ascertain the applicability of existing hydrogen sensors to aerospace applications, a survey was conducted of commercially available point-contact hydrogen sensors, and their operation was analyzed. The operation of the majority of commercial hydrogen sensors falls into four main categories: catalytic combustion, electrochemical, semiconducting oxide sensors, and thermal conductivity detectors. The physical mechanism involved in hydrogen detection for each main category is discussed in detail. From an understanding of the detection mechanism, each category of sensor is evaluated for use in a variety of space and propulsion environments. In order to meet the needs of aerospace applications, the development of point-contact hydrogen sensors that are based on concepts beyond those used in commercial sensors is necessary

Serpins : form, function and dysfunction

The serpin superfamily of serine protease inhibitors is one of the most ubiquitous and successful classes of inhibitors in the living world. Their unique mechanism of suicide inhibition has led to much research and several important discoveries. They function via rapid incorporation of a reactive centre loop (RCL) within a β-sheet following the former's proteolysis by the target protease: the serpin thus achieves a conformation which is more stable than the native form. Through this conformational change, the target protease structure is distorted and its function disrupted. Alpha-1-antitrypsin (AAT) has often been studied as an archetype for the serpin superfamily, and is discussed in more detail in this review. Of particular interest are the mutant variants of AAT, which have a tendency to polymerise, and thus offer insights into some mechanisms of serpin polymerisation.peer-reviewe

Long-Lived In-Situ Solar System Explorer (LLISSE): Potential Contributions to the Next Decade of Solar System Exploration

Venus, while having similar size, mass, and location in the solar system to Earth, varies from Earth in many ways and holds many scientific mysteries despite many missions that have focused on it in the past. Primary differences include Venus' climate, atmosphere, and perhaps most notably the extreme surface conditions. The layers of sulfuric acid clouds and high pressure CO2 laden atmosphere make remote sensing at Venus much less effective than at other solar system bodies. In addition, surface conditions present formidable engineering challenges due to the high temperature, pressure, and reactive chemistry. To date, landed missions have not been able to last more than about 2 hours on the surface [1]. This has resulted in significant knowledge gaps about the surface conditions of this important body in the solar system. The science community has effectively no in-situ temporal data at the Venus surface. These data are critical for the development of a thorough understanding of Venus' weather and the processes by which chemical species interact with each other and are transported throughout the atmospheric column. The LLISSE platform, and its variants, are a foundation for future mission concepts based on a core set of long-lived technologies providing significant new science as well as demonstrating new technical capabilities. After completion, LLISSE has the potential to be a complimentary element to missions going to Venus and would provide unique and important science to missions whether they be orbiters or short duration landers

The structure of protein molecules : in celebration of the International Year of Crystallography, 2014

Many people, including laymen, are aware of the double helical nature of the DNA molecule. A few may actually realise that it was the technique of X-ray crystallography that was the key to solving this structure. Even fewer will understand the uses and applications of crystallography to the most diverse of biological materials; proteins. In this review we discuss the application of a number of methodologies required to progress from a cloned gene to protein expression and purification, crystallisation conditions and eventually to X-ray structure determination. We provide our own experience in the field as examples of the procedures required. Protein crystallographers worldwide are contributing to our understanding of how enzymes work, how our immune system defends us against viruses and are using structural information to design novel pharmaceutical reagents.peer-reviewe

Summer Camp

Examinations for Spring Quarter 1972 ended on May 26, and hasty preparations began for Forestry Summer Camp in Harrington, Quebec at CIP Nature Center. The next five days were spent in our home twons with our girl friends, preparing ourselves for a rigorous six weeks in the bush

PDTI metal alloy as a hydrogen or hydrocarbon sensitive metal

A hydrogen sensitive metal alloy contains palladium and titanium to provide a larger change in electrical resistance when exposed to the presence of hydrogen. The alloy can be used for improved hydrogen detection

An analysis of contract broiler production in Tennessee

The purpose of this study was to (1) obtain a description of broiler growers and their enterprises in Tennessee, (2) to determine the provisions of the contracts being used, and (3) evaluate grower attitude toward, and degree of satisfaction with, existing conditions in Tennessee\u27s broiler industry. A random sample of 88 Tennessee broiler growers and the managers from all four of the agribusiness firms located in Tennessee which were involved in contract broiler production in the state were personally interviewed. The average broiler grower was almost 47 years old, had a ninth-grade education, and over 9 years\u27 experience producing broilers. He averaged starting into production about 74,663 chicks in 1976 and earned an income of about $6,100 from this production. Overall, the growers were not satisfied with their contract. Only about 45$ of the growers in the sample gave their contract a favorable rating. Almost 46% of them did not think they received an equitable payment. Almost 14% of the broiler growers interviewed indicated they planned to discontinue broiler production. Different perceptions of broiler production contract provisions by growers and contractors may lead to production and marketing ineffi-ciencies. Several broiler production contract provisions were identified in this study which growers and contractors perceived differently. These differences in grower and contractor perceptions of broiler production contract provisions indicate a need for improved communication between these two parties and for changes in contract provisions

Microfabricated Gas Sensors Demonstrated in Fire and Emission Applications

A range of microfabricated chemical sensors are being developed to meet the needs of fire detection and emission monitoring in aerospace applications. These sensors have the advantages over traditional technology of minimal size, weight, and power consumption as well as the ability to be placed closer to where the measurements need to be made. Sensor arrays are being developed to address detection needs in environments where multiple species need to be measured. For example, the monitoring of chemical species such as carbon monoxide (CO), carbon dioxide (CO2), hydrocarbons, and other species is important in the detection of fires on airplanes and spacecraft. In contrast, different sensors are necessary for characterizing some aircraft engine designs where the monitoring of nitrogen oxides (NO(x)) and CO is of high interest. Demonstration of both fire and emission microsensor technology was achieved this year in a collaborative effort undertaken by the NASA Glenn Research Center, Case Western Reserve University, and Makel Engineering, Inc

Slow dynamics in cylindrically confined colloidal suspensions

We study bidisperse colloidal suspensions confined within glass microcapillary tubes to model the glass transition in confined cylindrical geometries. We use high speed three-dimensional confocal microscopy to observe particle motions for a wide range of volume fractions and tube radii. Holding volume fraction constant, we find that particles move slower in thinner tubes. The tube walls induce a gradient in particle mobility: particles move substantially slower near the walls. This suggests that the confinement-induced glassiness may be due to an interfacial effect.Comment: Submitted to AIP conference proceedings for "Slow Dynamics in Complex Systems" (Sendai, Japan, Dec. 2012