Ambient-temperature co-oxidation catalysts

Oxidation catalysts which operate at ambient temperature were developed for the recombination of carbon monoxide (CO) and oxygen (O2) dissociation products which are formed during carbon dioxide (CO2) laser operation. Recombination of these products to regenerate CO2 allows continuous operation of CO2 lasers in a closed cycle mode. Development of these catalyst materials provides enabling technology for the operation of such lasers from space platforms or in ground based facilities without constant gas consumption required for continuous open cycle operation. Such catalysts also have other applications in various areas outside the laser community for removal of CO from other closed environments such as indoor air and as an ambient temperature catalytic converter for control of auto emissions

Catalyst for carbon monoxide oxidation

A catalyst is disclosed for the combination of CO and O2 to form CO2, which includes a platinum group metal (e.g., platinum); a reducable metal oxide having multiple valence states (e.g., SnO2); and a compound which can bind water to its structure (e.g., silica gel). This catalyst is ideally suited for application to high-powered pulsed, CO2 lasers operating in a sealed or closed-cycle condition

Chemisorption studies of Pt/SnO2 catalysts

The low temperature CO oxidation catalysts that are being developed and tested at NASA-Langley are fairly unique in their ability to efficiently oxidize CO at low temperatures (approx. 303 K). The bulk of the reaction data that has been collected in the laboratory has been determined using plug flow reactors with a low mass of Pt/SnO2/SiO2 catalyst (approx. 0.1 g) and a modest flow rate (5 to 10 sc sm). The researchers have previously characterized the surface solely in terms of N2 BET surface areas. These surface areas have not been that indicative of reaction rate. Indeed, some of the formulations with high BET surface area have yielded lower reaction rates than those with lower BET surface areas. As a result researchers began a program of determining the chemisorption of the various species involved in the reaction; CO, O2 and CO2. Such a determination of will lead to a better understanding of the mechanism and overall kinetics of the reaction. The pulsed-reactor technique, initially described by Freel, is used to determine the amount of a particular molecule that is adsorbed on the catalyst. Since there is some reaction of CO with the surface to produce CO2, the pulsed reactor had to be coupled with a gas chromatograph in order to distinguish between the loss of CO that is due to adsorption by the surface and the loss that is due to reaction with the surface

Newly detected data from Haestasaurus and review of sauropod skin morphology suggests Early Jurassic origin of skin papillae

Discovered in 1852, the scaly skin belonging to Haestasaurus becklesii was the first to be described in any non-avian dinosaur. Accordingly, it has played a crucial role in the reconstruction of sauropod integument and dinosaurs more broadly. Here, we reassess this historic specimen using Laser-Stimulated Fluorescence (LSF), revealing extensive, previously unknown regions of skin that augment prior interpretations of its integumentary morphology and taphonomy. Under white light, polygonal–subrounded, convex scales are visible on one side of the block (‘side A’), but LSF reveals extensive smaller and more flattened scales, which are diagenetically fragmented, on the reverse block surface (‘side B’). Contrary to the prior interpretation that the visible scales are the epidermal undersides, the presence of convex, intrascale papilliform textures on side A suggests that the external skin surface is exposed. We define intrascale papillae and provide a review of sauropod skin morphology, which clarifies that intrascale papillae are unique to and widespread across stem Neosauropoda, and likely have an evolutionary origin in the Early Jurassic. Intrascale papillae may ultimately have been integral to the evolution of gigantism in this charismatic clade

Pt/SnO2-based CO-oxidation catalysts for long-life closed-cycle CO2 lasers

Noble-metal/tin-oxide based catalysts such as Pt/SnO2 have been shown to be good catalysts for the efficient oxidation of CO at or near room temperature. These catalysts require a reductive pretreatment and traces of hydrogen or water to exhibit their full activity. Addition of Palladium enhances the activity of these catalysts with about 15 to 20 percent Pt, 4 percent Pd, and the balance SnO2 being an optimum composition. Unfortunately, these catalysts presently exhibit significant decay due in part to CO2 retention, probably as a bicarbonate. Research on minimizing the decay in activity of these catalysts is currently in progress. A proposed mechanism of CO oxidation on Pt/SnO2-based catalysts has been developed and is discussed

Postoperative fluid collection after hybrid debranching and endovascular repair of thoracoabdominal aortic aneurysms

ObjectiveHybrid thoracic endovascular aneurysm repair (H-TEVAR) to include visceral and renal debranching has emerged as a potential therapeutic option for thoracoabdominal aneurysms (TAAA). This study was performed to characterize the frequently noted development of postoperative fluid collections surrounding the bypass grafts.MethodsAll patients undergoing H-TEVAR from 2000-2010 (n = 39, 43.6% male) were identified. One hundred thirty-two bypasses were constructed (median 4 per patient) using either polyester (30), thin-walled polytetrafluoroethylene (ePTFE, 100) or saphenous vein (2). Follow-up computed tomography (CT) imaging was routinely performed at 1 and 6 months, and annually thereafter.ResultsOf the 37 patients with one follow-up CT, 20 (54.1%) were found to have fluid collections. The natural history of the 17 patients with collections and further follow-up imaging was variable, with 2 resolving, 6 stable, and 9 enlarging. Two patients with collections developed evidence of graft infection requiring reoperation. Two patients with enlarging sterile collections required evacuation for symptoms. By multivariate analysis, both preoperative creatinine (P = .005) and number of bypasses constructed (P = .04) independently correlated with the development of a fluid collection.ConclusionsPostoperative fluid collections following hybrid debranching procedures identified in this series represent a unique complication not previously described. The subsequent clinical course of these fluid collections is variable and ranges from benign to frank graft infection and relate both to patient factors, as well as specific operative strategies. Longer-term studies with more robust numbers of patient numbers are warranted to determine whether this complication may limit the long-term durability of this procedure

Postoperative fluid collection after hybrid debranching and endovascular repair of thoracoabdominal aortic aneurysms

ObjectiveHybrid thoracic endovascular aneurysm repair (H-TEVAR) to include visceral and renal debranching has emerged as a potential therapeutic option for thoracoabdominal aneurysms (TAAA). This study was performed to characterize the frequently noted development of postoperative fluid collections surrounding the bypass grafts.MethodsAll patients undergoing H-TEVAR from 2000-2010 (n = 39, 43.6% male) were identified. One hundred thirty-two bypasses were constructed (median 4 per patient) using either polyester (30), thin-walled polytetrafluoroethylene (ePTFE, 100) or saphenous vein (2). Follow-up computed tomography (CT) imaging was routinely performed at 1 and 6 months, and annually thereafter.ResultsOf the 37 patients with one follow-up CT, 20 (54.1%) were found to have fluid collections. The natural history of the 17 patients with collections and further follow-up imaging was variable, with 2 resolving, 6 stable, and 9 enlarging. Two patients with collections developed evidence of graft infection requiring reoperation. Two patients with enlarging sterile collections required evacuation for symptoms. By multivariate analysis, both preoperative creatinine (P = .005) and number of bypasses constructed (P = .04) independently correlated with the development of a fluid collection.ConclusionsPostoperative fluid collections following hybrid debranching procedures identified in this series represent a unique complication not previously described. The subsequent clinical course of these fluid collections is variable and ranges from benign to frank graft infection and relate both to patient factors, as well as specific operative strategies. Longer-term studies with more robust numbers of patient numbers are warranted to determine whether this complication may limit the long-term durability of this procedure

Device and method for measuring thermal conductivity of thin films

A device and method are provided for measuring the thermal conductivity of rigid or flexible, homogeneous or heterogeneous, thin films between 50 .mu.m and 150 .mu.m thick with relative standard deviations of less than five percent. The specimen is sandwiched between like material, highly conductive upper and lower slabs. Each slab is instrumented with six thermocouples embedded within the slab and flush with their corresponding surfaces. A heat source heats the lower slab and a heat sink cools the upper slab. The heat sink also provides sufficient contact pressure onto the specimen. Testing is performed within a vacuum environment (bell-jar) between 10.sup.-3 to 10.sup.-6 Torr. An anti-radiant shield on the interior surface of the bell-jar is used to avoid radiation heat losses. Insulation is placed adjacent to the heat source and adjacent to the heat sink to prevent conduction losses. A temperature controlled water circulator circulates water from a constant temperature bath through the heat sink. Fourier's one-dimensional law of heat conduction is the governing equation. Data, including temperatures, are measured with a multi-channel data acquisition system. On-line computer processing is used for thermal conductivity calculations

The state of workplace union reps organisation in Britain today

This article provides a brief evaluation of the state of workplace union reps’ organization in Britain as we approach the second decade of the 2000s. It documents the severe weakening of workplace union organization over the last 25 years, which is reflected in the declining number of reps, reduced bargaining power and the problem of bureaucratization. But it also provides evidence of the continuing resilience, and even combativity in certain areas of employment, of workplace union reps organization, and considers the future potential for a revival of fortunes

Reactivation of a tin oxide-containing catalyst

A method for the reactivation of a tin oxide-containing catalyst of a CO.sub.2 laser is provided. First, the catalyst is pretreated by a standard procedure. When the catalyst experiences diminished activity during usage, the heated zone surrounding the catalyst is raised to a temperature which is the operating temperature of the laser and 400.degree. C. for approximately one hour. The catalyst is exposed to the same laser gas mixture during this period. The temperature of the heated zone is then lowered to the operating temperature of the CO.sub.2 laser