LDEF Materials Workshop 1991, part 2

The LDEF Materials Workshop 1991 was a follow-on to the Materials Sessions at the First LDEF Post-Retrieval Symposium held in Kissimmee, Florida, June 1991. The workshop comprised a series of technical sessions on materials themes, followed by theme panel meetings. Themes included materials, environmental parameters, and data bases; contamination; thermal control and protective coating and surface treatments; polymers and films; polymer matrix composites; metals, ceramics, and optical materials; lubricants adhesives, seals, fasteners, solar cells, and batteries. This document continues the LDEF Space Environmental Effects on Materials Special Investigation Group (MSIG) pursuit to investigate the effects of LEO exposure on materials which were not originally planned to be test specimens. Papers from the technical sessions are presented

Photographic Observations of the Hayabusa Re-entry

We analyzed photographic observations of the re-entry of the Hayabusa spacecraft and capsule over Southern Australia on June 13, 2010, 13:52 UT. Radiometric measurements of the brightness of the associated fireball were obtained as well. We derived the trajectories and velocities of the spacecraft, its four fragments and the capsule. The capsule trajectory was within a few hundred meters of the trajectory predicted by JAXA prior the re-entry. The spacecraft trajectory was about 1 km higher than the capsule trajectory. Two major fragments separated from the spacecraft at a height of about 62 km with mutual lateral velocity of 250 m/s. The maximum absolute magnitude of the fireball of -12.6 was reached at a height of 67 km. The dynamic pressures acting on the spacecraft at the fragmentation points were only 1 - 50 kPa. No spacecraft fragment was seen to survive below the height of 47 km. The integral luminous efficiency of the event was 1.3%. As expected, the capsule had a very low luminous efficiency and very low ablation coefficient. The ablation coefficients and masses of the major spacecraft fragments are discussed.Comment: Accepted for publication in PASJ, 16 pages, 8 figures, 5 table

Proceedings of the LDEF Materials Data Analysis Workshop

The 5-year, 10-month flight of the Long Duration Exposure Facility (LDEF) greatly enhanced the potential value of most LDEF materials, compared to the original 1-year flight plan. NASA recognized this potential by forming the LDEF Space Environmental Effects on Materials Special Investigation Group in early 1989 to address the expanded opportunities available in the LDEF structure and on experimental trays, so that the value of all LDEF materials to current and future space missions would be assessed and documented. The LDEF Materials Data Analysis Workshop served as one step toward the realization of that responsibility and ran concurrently with activities surrounding the successful return of the spacecraft to the NASA Kennedy Space Center. A compilation of visual aids utilized by speakers at the workshop is presented. Session 1 summarized current information on analysis responsibilities and plans and was aimed at updating the workshop attendees: the LDEF Advisory Committee, Principle Investigators, Special Investigation Group Members, and others involved in LDEF analyses or management. Sessions 2 and 3 addressed materials data analysis methodology, specimen preparation, shipment and archival, and initial plans for the LDEF Materials Data Base. A complementary objective of the workshop was to stimulate interest and awareness of opportunities to vastly expand the overall data base by considering the entire spacecraft as a materials experiment

LDEF Materials Workshop 1991, part 1

The workshop comprised a series of technical sessions on materials themes, followed by theme panel meetings. Themes included materials, environmental parameters, and data bases; contamination; thermal control and protective coatings and surface treatments; polymers and films; polymer matrix composites; metals, ceramics, and optical materials; lubricants adhesives, seals, fasteners, solar cells, and batteries. This report contains most of the papers presented at the technical sessions. It also contains theme panel reports and visual aids. This document continues the LDEF Space Environmental Effects on Materials Special Investigation Group (MSIG) pursuit of its charter to investigate the effects of LEO exposure on materials which where not originally planned to be test specimens and to integrate this information with data generated by principal investigators into an LDEF materials data base

Ionizing Photons and EUV Excesses in Clusters of Galaxies

Observations with the Extreme Ultraviolet Explorer satellite are purported to show extreme ultraviolet (EUV) and soft X-ray excesses in several clusters of galaxies (Bonamente, Lieu & Mittaz 2001). If interpreted as thermal emission, this would imply the presence of warm (T\sim 10^6 K) gas in these clusters with a mass comparable to that of gas at coronal temperatures. If true, this would have profound implications for our understanding of galaxy clusters and the distribution of baryons in the universe. Here we show that because of the large ionizing photon emissivities of gas at such low temperatures, the ionizing photon fluxes seen by disk galaxies in the observed clusters can be very large, resulting in minimum emission measures from neutral gas in such disks as high as 100 cm^(-6) pc. This result is essentially independent of the mechanism actually responsible for producing the alleged EUV excesses. The predicted emission measures in Abell 1795 (z=0.063) are about an order of magnitude larger than seen in the Reynolds layer of the Galaxy, providing a straightforward observational test of the reality of the EUV excess. New tunable filter H alpha images and WFPC images from the Hubble Space Telescope archive do not support the existence of the claimed EUV excess.Comment: To appear in ApJ Letters; 11 pages, 3 figure

A geochemical study of the winonaites: Evidence for limited partial melting and constraints on the precursor composition

The winonaites are primitive achondrites which are associated with the IAB iron meteorites. Textural evidence implies heating to at least the Fe, Ni–FeS cotectic, but previous geochemical studies are ambiguous about the extent of silicate melting in these samples. Oxygen isotope evidence indicates that the precursor material may be related to the carbonaceous chondrites. Here we analysed a suite of winonaites for modal mineralogy and bulk major- and trace-element chemistry in order to assess the extent of thermal processing as well as constrain the precursor composition of the winonaite-IAB parent asteroid. Modal mineralogy and geochemical data are presented for eight winonaites. Textural analysis reveals that, for our sub-set of samples, all except the most primitive winonaite (Northwest Africa 1463) reached the Fe, Ni–FeS cotectic. However, only one (Tierra Blanca) shows geochemical evidence for silicate melting processes. Tierra Blanca is interpreted as a residue of small-degree silicate melting. Our sample of Winona shows geochemical evidence for extensive terrestrial weathering. All other winonaites studied here (Fortuna, Queen Alexander Range 94535, Hammadah al Hamra 193, Pontlyfni and NWA 1463) have chondritic major-element ratios and flat CI-normalised bulk rare-earth element patterns, suggesting that most of the winonaites did not reach the silicate melting temperature. The majority of winonaites were therefore heated to a narrow temperature range of between ∼1220 (the Fe, Ni–FeS cotectic temperature) and ∼1370 K (the basaltic partial melting temperature). Silicate inclusions in the IAB irons demonstrate partial melting did occur in some parts of the parent body (Ruzicka and Hutson, 2010), thereby implying heterogeneous heat distribution within this asteroid. Together, this indicates that melting was the result of internal heating by short-lived radionuclides. The brecciated nature of the winonaites suggests that the parent body was later disrupted by a catastrophic impact, which allowed the preservation of the largely unmelted winonaites. Despite major-element similarities to both ordinary and enstatite chondrites, trace-element analysis suggests the winonaite parent body had a carbonaceous chondrite-like precursor composition. The parent body of the winonaites was volatile-depleted relative to CI, but enriched compared to the other carbonaceous classes. The closest match are the CM chondrites; however, the specific precursor is not sampled in current meteorite collections

The Influence of a KDT501, a Novel Isohumulone, on Adipocyte Function in Humans

Objective: In a phase II clinical trial in nine obese, insulin-resistant humans, we observed that treatment with KDT501, a novel isohumulone drug, increased total and high-molecular weight (HMW) adiponectin in plasma. The objective was to determine whether KDT501 increased adiponectin secretion from subcutaneous white adipose tissue (SC WAT) and the underlying mechanism(s). Methods: Nine obese participants with either prediabetes or with normal glucose tolerance plus three features of metabolic syndrome were part of the study. SC WAT biopsies were performed before and after 28 days of KDT501 treatment in a clinical research setting. In addition, a cold stimulus was used to induce thermogenic gene expression. Adiponectin secretion was measured, and gene expression of 130 genes involved in adipose tissue function was determined. The effect of KDT501 on adipocyte mitochondrial function was analyzed in vitro. Results: SC WAT explants secreted more total and HMW adiponectin after KDT501 treatment (P \u3c 0.05). After KDT501 treatment, a number of genes involved in thermogenesis and lipolysis were induced by cold (P \u3c 0.05). KDT501 also potentiated β-adrenergic signaling (P \u3c 0.001) and enhanced mitochondrial function in adipocytes (P \u3c 0.001). Conclusion: KDT501 induced adiponectin secretion posttranscriptionally and increased gene expression of thermogenic and lipolytic genes in response to cold stimulation. These beneficial effects on SC WAT may be explained by the ability of KDT501 to potentiate β-adrenergic signaling and enhance mitochondrial function in adipocytes. Clinical Trial Registration: https://www.ClinicalTrials.gov, ID number: NCT02444910

Effects of KDT501 on Metabolic Parameters in Insulin-Resistant Prediabetic Humans

Context: KDT501 is an isohumulone drug that has demonstrated beneficial effects on metabolic parameters in mice. Objective: This study was intended to examine potential improvements in metabolism in humans. Design and Setting: Changes in carbohydrate and lipid metabolism, along with inflammatory markers, were evaluated in prediabetic humans in a clinical research center. Participants: Nine obese patients participated. All had prediabetes or normal glucose tolerance plus three features of metabolic syndrome. Intervention: All participants were treated with escalating doses of KDT501 to a maximum dose of 1000 mg every 12 hours for a total of 28 days. Outcome Measures: Changes in carbohydrate metabolism were measured with oral glucose tolerance, homeostatic model of insulin resistance, and euglycemic clamp; changes in plasma lipids and response to a lipid tolerance test; and changes in plasma inflammatory markers. Results: The drug was well tolerated. After KDT501 treatment, plasma triglycerides were reduced at 4 hours during a lipid tolerance test. Furthermore, plasma adiponectin and high-molecular-weight adiponectin increased significantly, and plasma tumor necrosis factor-α decreased significantly. There were no significant changes in oral glucose tolerance test results or insulin sensitivity measures. Conclusions: Despite the small sample size and the short duration of therapy, KDT501 administration reduced measures of systemic inflammation and improved postmeal plasma triglyceride levels, which may be beneficial in participants with insulin resistance or metabolic syndrome