Lessons learned from the development and manufacture of ceramic reusable surface insulation materials for the space shuttle orbiters

Three ceramic, reusable surface insulation materials and two borosilicate glass coatings were used in the fabrication of tiles for the Space Shuttle orbiters. Approximately 77,000 tiles were made from these materials for the first three orbiters, Columbia, Challenger, and Discovery. Lessons learned in the development, scale up to production and manufacturing phases of these materials will benefit future production of ceramic reusable surface insulation materials. Processing of raw materials into tile blanks and coating slurries; programming and machining of tiles using numerical controlled milling machines; preparing and spraying tiles with the two coatings; and controlling material shrinkage during the high temperature (2100-2275 F) coating glazing cycles are among the topics discussed

Photometric analysis of a space shuttle water venting

Presented here is a preliminary interpretation of a recent experiment conducted on Space Shuttle Discovery (Mission STS 29) in which a stream of liquid supply water was vented into space at twilight. The data consist of video images of the sunlight-scattering water/ice particle cloud that formed, taken by visible light-sensitive intensified cameras both onboard the spacecraft and at the AMOS ground station near the trajectory's nadir. This experiment was undertaken to study the phenomenology of water columns injected into the low-Earth orbital environment, and to provide information about the lifetime of ice particles that may recontact Space Shuttle orbits later. The findings about the composition of the cloud have relevance to ionospheric plasma depletion experiments and to the dynamics of the interaction of orbiting spacecraft with the environment

Ground state of the helium-atom-graphite-surface system

We report the first results of a thermodynamic analysis of data for 3He adsorbed on Grafoil. The 3He-graphite binding energy is in excellent agreement with a prediction made on the basis of 4He-graphite atomic scattering data

Promoter sequence containing (CT)n.(GA)n repeats is critical for the formation of the DNase I hypersensitive sites in the Drosophila hsp26 gene

We have analyzed P-element-transformed lines carrying hsp26/lacZ transgenes with various deletions and substitutions within the Drosophila melanogaster hsp26 promoter region in order to identify the sequences required for the formation of the DNase I hypersensitive sites (DH sites). DH sites are generally found associated with promoters and enhancer elements of active and inducible eukaryotic genes, and are thought to be nucleosome-free regions of DNA that interact with regulatory proteins and the transcriptional machinery. There are two major DH sites located within the promoter region of the hsp26 gene, centered at -50 and at -350 (relative to the hsp26 transcription start site). The sequences from -135 to -85, which contain (CT)n.(GA)n repeats, contribute significantly to the formation of the DH sites in the hsp26 promoter region. Deletion or substitution of this (CT)n region drastically reduces the accessibility of the DNA at these sites to DNase I. This reduction in accessibility was quantified by measuring the susceptibility of the DNA within nuclei to cleavage at a restriction site within the DH site. In addition to the (CT)n region and the promoter at -85 to +11 (region P), one of two other regions must be present for effective creation of the DH sites: sequences between -351 and -135 (region A), or sequences between +11 and +632 (region D). Disruption of the wild-type chromatin structure, as assayed by the loss of accessibility to the DH sites, is correlated with a decrease in inducible transcriptional activity, even when the TATA box and heat shock regulatory elements are present in their normal positions

Loss of murine Paneth cell function alters the immature intestinal microbiome and mimics changes seen in neonatal necrotizing enterocolitis

Necrotizing enterocolitis (NEC) remains the leading cause of gastrointestinal morbidity and mortality in premature infants. Human and animal studies suggest a role for Paneth cells in NEC pathogenesis. Paneth cells play critical roles in host-microbial interactions and epithelial homeostasis. The ramifications of eliminating Paneth cell function on the immature host-microbial axis remains incomplete. Paneth cell function was depleted in the immature murine intestine using chemical and genetic models, which resulted in intestinal injury consistent with NEC. Paneth cell depletion was confirmed using histology, electron microscopy, flow cytometry, and real time RT-PCR. Cecal samples were analyzed at various time points to determine the effects of Paneth cell depletion with and without Klebsiella gavage on the microbiome. Deficient Paneth cell function induced significant compositional changes in the cecal microbiome with a significant increase in Enterobacteriacae species. Further, the bloom of Enterobacteriaceae species that occurs is phenotypically similar to what is seen in human NEC. This further strengthens our understanding of the importance of Paneth cells to intestinal homeostasis in the immature intestine

Targeting of P-Element Reporters to Heterochromatic Domains by Transposable Element 1360 in Drosophila melanogaster

Heterochromatin is a common DNA packaging form employed by eukaryotes to constitutively silence transposable elements. Determining which sequences to package as heterochromatin is vital for an organism. Here, we use Drosophila melanogaster to study heterochromatin formation, exploiting position-effect variegation, a process whereby a transgene is silenced stochastically if inserted in proximity to heterochromatin, leading to a variegating phenotype. Previous studies identified the transposable element 1360 as a target for heterochromatin formation. We use transgene reporters with either one or four copies of 1360 to determine if increasing local repeat density can alter the fraction of the genome supporting heterochromatin formation. We find that including 1360 in the reporter increases the frequency with which variegating phenotypes are observed. This increase is due to a greater recovery of insertions at the telomere-associated sequences (∼50% of variegating inserts). In contrast to variegating insertions elsewhere, the phenotype of telomere-associated sequence insertions is largely independent of the presence of 1360 in the reporter. We find that variegating and fully expressed transgenes are located in different types of chromatin and that variegating reporters in the telomere-associated sequences differ from those in pericentric heterochromatin. Indeed, chromatin marks at the transgene insertion site can be used to predict the eye phenotype. Our analysis reveals that increasing the local repeat density (via the transgene reporter) does not enlarge the fraction of the genome supporting heterochromatin formation. Rather, additional copies of 1360 appear to target the reporter to the telomere-associated sequences with greater efficiency, thus leading to an increased recovery of variegating insertions

Farming on the edge: farmer attitudes to bovine tuberculosis in newly endemic areas

Defra's recent strategy to eradicate bovine tuberculosis (bTB) establishes three spatial zones: high-risk areas (HRAs) and low-risk areas, and an area referred to as ‘the edge’, which marks the areas where infection is spreading outwards from the HRA. Little is known about farmers in the edge area, their attitudes towards bTB and their farming practices. This paper examines farmers’ practices and attitudes towards bTB in standardised epidemiologically defined areas. A survey was developed to collect data on farmer attitudes, behaviours, practices and environmental conditions as part of an interdisciplinary analysis of bTB risk factors. Survey items were developed from a literature review and focus groups with vets and farmers in different locations within the edge area. A case-control sampling framework was adopted with farms sampled from areas identified as recently endemic for bTB. 347 farmers participated in the survey including 117 with bTB, representing a 70 percent response rate. Results show that farmers believe they are unable to do anything about bTB but are keen for the government intervention to help control the spread of bTB

Quantum virial expansion approach to thermodynamics of 4^4He adsorbates in carbon nanotube materials: Interacting Bose gas in one dimension

I demonstrate that $^4$He adsorbates in carbon nanotube materials can be treated as one-dimensional interacting gas of spinless bosons for temperatures below 8 K and for coverages such that all the adsorbates are in the groove positions of the carbon nanotube bundles. The effects of adsorbate-adsorbate interactions are studied within the scheme of virial expansion approach. The theoretical predictions for the specific heat of the interacting adsorbed gas are given.Comment: 5 PS figure