The Development of Methodologies and Solvent Systems to Replace CFC-113 in the Validation of Large-Scale Spacecraft Hardware

Liquid oxygen is used as the oxidizer for the liquid fueled main engines during the launch of the space shuttle. Any hardware that comes into contact with pure oxygen either during servicing of the shuttle or in the operation of the shuttle must be validated as being free of nonvolatile residue (NVR). This is a safety requirement to prevent spontaneous combustion of carbonaceous NVR if it was to come into contact with pure oxygen. Previous NVR validation testing of space hardware used Freon (CFC-113) as the test solvent. Because CFC-113 no longer can be used, a program was conducted to develop a NVR test procedure that uses a safe environmentally friendly solvent. The solvent that has been used in the new NVR test procedure is water. Work that has been conducted over the past three years has served to demonstrate that when small parts are subjected to ultrasound in a water bath and NVR is present a sufficient quantity is dispersed into the water to analyze for its concentration by the TOC method. The work that is described in this report extends the water wash NVR validation test to large-scale parts; that is, parts too large to be subjected to ultrasound. The method consists of concentrating the NVR in the water wash onto a bed of silica gel. The total adsorbent bed is then analyzed for TOC content by using a solid sample probe. Work that has been completed thus far has demonstrated that hydrocarbon based NVR's can be detected at levels of less than 0.1 mg per square foot of part's surface area by using a simple water wash

Method for removal of nitrogen oxides from stationary combustion sources

A method for removing NO.sub.X from gas streams emanating from stationary combustion sources and manufacturing plants utilizes the injection of hydrogen peroxide into the gas stream for rapid gas-phase oxidation of NO to NO.sub.2 and water-soluble nitrogen acids HNO.sub.2 and HNO.sub.3. The nitrogen acids may be removed from the oxidized gas stream by wet scrubbing or by contact with a particulate alkaline material to form a nitrite/nitrate salt

Chronostratigraphic terminology at the Paleocene/Eocene boundary.

Integrated research over the past decade has led to the recognition of a short (150-200 k.y.) interval of Paleogene time within Chron C24r at ~55.5 Ma, formerly termed the late Paleocene Thermal Maximum (LPTM) but more recently the Paleocene-Eocene Thermal Maximum (PETM), that was crucial in the climatic, paleoceanographic, and biotic evolution of our planet. Stable isotope analysis of marine carbonates indicates that there were transient changes in surface and deep-water temperatures. These climatic changes coincided with a negative 3%-4% carbon isotope excursion (CIE), which is recorded in both marine and terrestrial deposits. It was soon realized that the CIE not only constitutes a powerful tool for long distance ("global") isochronous correlation, but even more importantly that it is coeval with notable biotic events in both marine and continental fossil records that have long been taken as criteria for the beginning of the Eocene in North America and more recently in deep sea cores. On the other hand, the conventional Paleocene/Eocene boundary level at the Thanetian/Ypresian boundary in Belgium and the London Basin has been found to be ~1 m.y. younger than the CIE, based on the association of the First Appearance Datum (FAD) of the (calcareous nannoplankton) Tribrachiatus digitalis (at ~54.4 Ma) with the base of the Ypresian in the London Basin. Although the Ypresian definition would take priority under normal circumstances, a consensus has been reached to redefine the Eocene in recognition of the worldwide significance and correlatibility of stratigraphic features associated with the PETM. Redefinition of the Eocene, however desirable, nevertheless cannot proceed in a stratigraphic vacuum, and this paper is concerned with resolving the consequences of this action. To be made coincident with the CIE at ~55.5 Ma, the Ypresian/Thanetian boundary would have to be lowered by ~1 m.y., resulting in the inflation of the span of the Ypresian by 20% and a reduction of the span of the Thanetian by 30%. At the same time, the terminology of the strata in the leapfrogged interval would be thrown into total conflict with the literature, with the substitution of one widely used stage name for the other in the conflicted interval. On the other hand, to relocate the Paleocene/Eocene boundary without moving the stage boundaries would result in the upper third of the Thanetian falling within the Eocene, demolishing a century-old consensus. We propose that the destabilizing effect of the new boundary in the classic chronostratigraphy of western Europe can best be minimized with the introduction of a pre-Ypresian Stage, to encompass the orphaned upper Thanetian interval as the basal unit of the Eocene under a separate name. To this end, we suggest the reintroduction of the Sparnacian Stage, now that its original concept has been shown to correlate essentially with the interval between the CIE and the FAD of T. digitalis

AhR sensing of bacterial pigments regulates antibacterial defence

The aryl hydrocarbon receptor (AhR) is a highly conserved ligand-dependent transcription factor that senses environmental toxins and endogenous ligands, thereby inducing detoxifying enzymes and modulating immune cell differentiation and responses. We hypothesized that AhR evolved to sense not only environmental pollutants but also microbial insults. We characterized bacterial pigmented virulence factors, namely the phenazines from Pseudomonas aeruginosa and the naphthoquinone phthiocol from Mycobacterium tuberculosis, as ligands of AhR. Upon ligand binding, AhR activation leads to virulence factor degradation and regulated cytokine and chemokine production. The relevance of AhR to host defence is underlined by heightened susceptibility of AhR-deficient mice to both P. aeruginosa and M. tuberculosis. Thus, we demonstrate that AhR senses distinct bacterial virulence factors and controls antibacterial responses, supporting a previously unidentified role for AhR as an intracellular pattern recognition receptor, and identify bacterial pigments as a new class of pathogen-associated molecular patterns