Finite-element reentry heat-transfer analysis of space shuttle Orbiter

A structural performance and resizing (SPAR) finite-element thermal analysis computer program was used in the heat-transfer analysis of the space shuttle orbiter subjected to reentry aerodynamic heating. Three wing cross sections and one midfuselage cross section were selected for the thermal analysis. The predicted thermal protection system temperatures were found to agree well with flight-measured temperatures. The calculated aluminum structural temperatures also agreed reasonably well with the flight data from reentry to touchdown. The effects of internal radiation and of internal convection were found to be significant. The SPAR finite-element solutions agreed reasonably well with those obtained from the conventional finite-difference method

Comparison of flight-measured and calculated temperatures on the space shuttle orbiter

Structural temperatures and thermal protection system surface temperatures were measured on the space shuttle during the flight of STS 5. The measured data are compared with values calculated at wing stations 134, 240, and 328 and at fuselage station 877. The theoretical temperatures were calculated using the structural performance and resizing finite element thermal analysis program. The comparisons show that the calculated temperatures are, generally, in good agreement with the measured data

Selection of gonadotrophin surge attenuating factor phage antibodies by bioassay

Peer reviewedPublisher PD

Study of DXA-derived lateral–medial cortical bone thickness in assessing hip fracture risk

AbstractThe currently available clinical tools have limited accuracy in predicting hip fracture risk in individuals. We investigated the possibility of using normalized cortical bone thickness (NCBT) estimated from the patient's hip DXA (dual energy X-ray absorptiometry) as an alternative predictor of hip fracture risk. Hip fracture risk index (HFRI) derived from subject-specific DXA-based finite element model was used as a guideline in constructing the mathematical expression of NCBT. We hypothesized that if NCBT has stronger correlations with HFRI than the single risk factors such as areal BMD (aBMD), then NCBT can be a better predictor. The hypothesis was studied using 210 clinical cases, including 60 hip fracture cases, obtained from the Manitoba Bone Mineral Density Database. The results showed that, in general HFRI has much stronger correlations with NCBT than any of the single risk factors; the strongest correlation was observed at the superior side of the narrowest femoral neck with r2=0.81 (p<0.001), which is much higher than the correlation with femoral aBMD, r2=0.50 (p<0.001). The capability of aBMD, NCBT, and HFRI in discriminating the hip fracture cases from the non-fracture ones, expressed as the area under the curve with 95% confidence interval, AUC (95% CI), is respectively 0.627 (0.593–0.657), 0.714 (0.644–0.784) and 0.839 (0.787–0.892). The short-term repeatability of aBMD, NCBT, and HFRI, measured by the coefficient of variation (CV, %), was found to be in the range of (0.64–1.22), (1.93–3.41), (3.10–4.16), respectively. We thus concluded that NCBT is potentially a better predictor of hip fracture risk

Taxonomomy of Disinformation

Disinformation permeates science through individuals, organizations, and governments that manipulate scholarly communication, media, and institutions. This new taxonomy provides a framework and language to explain the actors, outlets, and methods. For example, scholars recently published misinformation about COVID-19 vaccines in a peer-reviewed journal. Now retracted, an author reposted the debunked claims as legitimate research on their website. This case demonstrates how the credibility of a professor's website can be exploited to introduce falsehoods, and how bad actors circumvent corrections. With clarity on the nature and flow of scientific disinformation, journalists and policymakers can better identify and respond.Comment: 10 pages, 3 table

Variation in heart rate influences the assessment of transient ischemic dilation in myocardial perfusion scintigraphy

BACKGROUND: Transient arrhythmias can affect transient ischemic dilation (TID) ratios. This study was initiated to evaluate the frequency and effect of normal heart rate change on TID measures in routine clinical practice. METHODS: Consecutive patients undergoing stress/rest sestamibi gated myocardial perfusion scintigraphy were studied (N = 407). Heart rate at the time of stress and rest imaging were recorded. TID ratios were analyzed in relation to absolute change in heart rate (stress minus rest) for subjects with normal perfusion and systolic function (Group 1, N = 169) and those with abnormalities in perfusion and/or function (Group 2, N = 238). RESULTS: In Group 1, mean TID ratio was inversely correlated with the change in heart rate (r = -0.47, P < 0.0001). For every increase of 10 BPM in heart rate change, the TID ratio decreased by approximately 0.06 (95% confidence interval 0.04–0.07). In Group 2, multiple linear regression demonstrated that the change in heart rate (beta = -0.25, P < 0.0001) and the summed difference score (beta = 0.36, P < 0.0001) were independent predictors of the TID ratio. CONCLUSION: Normal variation in heart rate between the stress and rest components of myocardial perfusion scans is common and can influence TID ratios in patients with normal and abnormal cardiac scans

Backyard effect : is the grass really greener?

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Urban Studies and Planning, 2001.Includes bibliographical references (leaf 53).For many reasons outlined in this thesis, line of credit facilities have become an integral part of a REITs capital structure. During this evolution, a possible pricing discrepancy for REIT lines of credit has emerged whereby certain REITs appear to obtain advantageous pricing (as indicated by LIBOR spread) on their lines of credit based on the location of their headquarters or the geographic focus of their operations. We have defined the potential existence of this phenomenon as the "Backyard Effect". While there are several possible explanations for the existence of such an occurrence, it nonetheless represents a potential market effect that impacts REIT line of credit costs. Through this thesis, we present market evidence supported by rigorous data and statistical analysis to conclude that the Backyard Effect is apparently present in the market for REIT lines of credit. In addition, we present the following line of credit market background and information: a historical perspective regarding the evolution of REITs and the LOC market, including current and past trends; basic contractual elements and terms as to how these LOC facilities function; and a discussion as to why REITs utilize LOCs and what are the main advantages and disadvantages of this form of financing. We hope that through this thesis, the reader is provided with a much greater awareness and understanding of the market for REIT lines of credit. Further, and most importantly, by identifying and providing statistical evidence of the existence of a possible pricing effect in the market for REIT lines of credit, we hopefully uncover an issue that will be of value to the multiple market participants.by Adrian L. Watkins [and] William D. Dobbins, IV.S.M

Reentry Thermal Analysis of a Generic Crew Exploration Vehicle Structure

Comparative studies were performed on the heat-shielding characteristics of honeycomb-core sandwich panels fabricated with different materials for possible use as wall panels for the proposed crew exploration vehicle. Graphite/epoxy sandwich panel was found to outperform aluminum sandwich panel under the same geometry due to superior heat-shielding qualities and lower material density. Also, representative reentry heat-transfer analysis was performed on the windward wall structures of a generic crew exploration vehicle. The Apollo low Earth orbit reentry trajectory was used to calculate the reentry heating rates. The generic crew exploration vehicle has a graphite/epoxy composite honeycomb sandwich exterior wall and an aluminum honeycomb sandwich interior wall, and is protected with the Apollo thermal protection system ablative material. In the thermal analysis computer program used, the TPS ablation effect was not yet included; however, the results from the nonablation heat-transfer analyses were used to develop a "virtual ablation" method to estimate the ablation heat loads and the thermal protection system recession thicknesses. Depending on the severity of the heating-rate time history, the virtual ablation period was found to last for 87 to 107 seconds and the ablation heat load was estimated to be in the range of 86 to 88 percent of the total heat load for the ablation time period. The thermal protection system recession thickness was estimated to be in the range of 0.08 to 0.11 inches. For the crew exploration vehicle zero-tilt and 18-degree-tilt stagnation points, thermal protection system thicknesses of h = {0.717, 0.733} inches were found to be adequate to keep the substructural composite sandwich temperature below the limit of 300 F

Effect of internal convection and internal radiation on the structural temperatures of Space Shuttle Orbiter

Structural performance and resizing of the finite-element thermal analysis computer program was used in the reentry heat transfer analysis of the space shuttle orbiter. One midfuselage cross section and one midspan wing segment were selected to study the effects of internal convection and internal radiation on the structural temperatures. The effect of internal convection was found to be more prominent than that of internal radiation in the orbiter thermal analysis. Without these two effects, the calculated structural temperatures at certain stations could be as much as 45 to 90 percent higher than the measured values. By considering internal convection as free convection, the correlation between the predicted and measured structural temperatures could be improved greatly

Tregitope: Immunomodulation Powerhouse

IVIG is frequently used in the ‘pre-conditioning’ regimens for higher risk transplants; its effects are attributed in part to induction of Tregs. We have identified regulatory T cell (Treg) epitopes, now known as Tregitopes, in IgG, the main component of intravenous immunoglobulin therapy (IVIg). Tregitopes provide one explanation for the expansion and activation of Treg cells following IVIg treatment. Tregitopes are peptides that exhibit high affinity binding to multiple human HLA Class II DR; they are conserved across IgG isotypes and mammalian species. In vitro and in vivo, for human PBMC and in animal models, Tregitopes activate Tregs. Studies to delineate the mechanism of action have shown that Tregitopes’ effects are very similar to IVIg in vitro. Here we demonstrate that Tregitopes induce Tregs to produce IL-10, leading to modulation of dendritic cell phenotype (down-regulation of Class II, CD80 and CD86 and up-regulation of ILT3), and describe the effects of Tregitopes in the ABM-TCR-transgenic skin transplantation model. The discovery of Tregitopes in IgG and other autologous proteins may contribute to improved understanding of the mechanism of action of IVIg and lead to the application of these powerful immunomodulators to improve transplantation success and suppress autoimmune disease, in the future