Flutter suppression control law synthesis for the Active Flexible Wing model

The Active Flexible Wing Project is a collaborative effort between the NASA Langley Research Center and Rockwell International. The objectives are the validation of methodologies associated with mathematical modeling, flutter suppression control law development and digital implementation of the control system for application to flexible aircraft. A flutter suppression control law synthesis for this project is described. The state-space mathematical model used for the synthesis included ten flexible modes, four control surface modes and rational function approximation of the doublet-lattice unsteady aerodynamics. The design steps involved developing the full-order optimal control laws, reducing the order of the control law, and optimizing the reduced-order control law in both the continuous and the discrete domains to minimize stochastic response. System robustness was improved using singular value constraints. An 8th order robust control law was designed to increase the symmetric flutter dynamic pressure by 100 percent. Preliminary results are provided and experiences gained are discussed

Pesticide effects on body temperature of torpid/hibernating rodents (Peromyscus leucopus and Spermophilus tridecemlineatus)

Environmental contaminants have been shown in the lab to alter thyroid hormone concentrations. Despite the role these hormones play in the physiological ecology of small mammals, no one has investigated the possible effects of thyroid-disrupting chemicals on mammalian thermal ecology and thermoregulatory ability. Because the energetic impact of such a disruption is likely to be most dramatic during times already energetically stressful, we investigated the effects of two common pesticides (atrazine and lindane) on the use of daily torpor in white-footed mice, and the use of hibernation in 13-lined ground squirrels. Fortunately, we found that these strategies for over-wintering success were not impaired

Recent activities within the Aeroservoelasticity Branch at the NASA Langley Research Center

The objective of research in aeroservoelasticity at the NASA Langley Research Center is to enhance the modeling, analysis, and multidisciplinary design methodologies for obtaining multifunction digital control systems for application to flexible flight vehicles. Recent accomplishments are discussed, and a status report on current activities within the Aeroservoelasticity Branch is presented. In the area of modeling, improvements to the Minimum-State Method of approximating unsteady aerodynamics are shown to provide precise, low-order aeroservoelastic models for design and simulation activities. Analytical methods based on Matched Filter Theory and Random Process Theory to provide efficient and direct predictions of the critical gust profile and the time-correlated gust loads for linear structural design considerations are also discussed. Two research projects leading towards improved design methodology are summarized. The first program is developing an integrated structure/control design capability based on hierarchical problem decomposition, multilevel optimization and analytical sensitivities. The second program provides procedures for obtaining low-order, robust digital control laws for aeroelastic applications. In terms of methodology validation and application the current activities associated with the Active Flexible Wing project are reviewed

NASA Applications for Computational Electromagnetic Analysis

Computational Electromagnetic Software is used by NASA to analyze the compatibility of systems too large or too complex for testing. Recent advances in software packages and computer capabilities have made it possible to determine the effects of a transmitter inside a launch vehicle fairing, better analyze the environment threats, and perform on-orbit replacements with assured electromagnetic compatibility

Clinical utility of the 2-minute walk test for older adults living in long-term care

Purpose: This study\u27s purposes were to examine the measurement properties of the 2-minute walk test (2MWT), to illustrate the use of reliability coefficients in clinical practice, and to estimate sample size for a subsequent validity study. Method: Sixteen residents of long-term care (LTC; mean age = 87 years) completed two 2MWTs with Rater A and two 2MWTs with Rater B on test days 1 and 2, approximately 1 week apart. On a third test day, subjects completed one trial of the Berg Balance Scale (BBS), timed up-and-go (TUG) test, and 6-minute walk test (6MWT) with Rater A. On 2 other test days, approximately 1 week apart, Rater A administered the 2MWT to five older adults living in a retirement facility. Absolute and relative reliability and concurrent and known-groups validity coefficients were calculated. Results: No main effect for rater, trial, or occasion was found. Test-retest reliability estimates of 0.94 and 0.95 were obtained. The 2MWT demonstrated concurrent validity (r\u3e0.84) with the BBS, TUG, and 6MWT. Comparison of distance walked by LTC and retirement residents showed a difference of 72.9m (95% CI: 44.2, 101.6). The results suggest that 90% of truly stable older adults will display random fluctuations in 2MWT performance within a boundary of 15 m. Conclusion: The 2MWT had sound measurement properties in this sample of LTC residents. Based on our results, 24 subjects would be required for a subsequent hypothesis-testing validity study

Aeroservoelastic wind-tunnel investigations using the Active Flexible Wing Model: Status and recent accomplishments

The status of the joint NASA/Rockwell Active Flexible Wing Wind-Tunnel Test Program is described. The objectives are to develop and validate the analysis, design, and test methodologies required to apply multifunction active control technology for improving aircraft performance and stability. Major tasks include designing digital multi-input/multi-output flutter-suppression and rolling-maneuver-load alleviation concepts for a flexible full-span wind-tunnel model, obtaining an experimental data base for the basic model and each control concept and providing comparisons between experimental and analytical results to validate the methodologies. The opportunity is provided to improve real-time simulation techniques and to gain practical experience with digital control law implementation procedures

Morphometric analysis of structural MRI using schizophrenia meta-analytic priors distinguish patients from controls in two independent samples and in a sample of individuals with high polygenic risk

Schizophrenia (SCZ) is associated with structural brain changes, with considerable variation in the extent to which these cortical regions are influenced. We present a novel metric that summarises individual structural variation across the brain, while considering prior effect sizes, established via meta-analysis. We determine individual participant deviation from a within-sample-norm across structural MRI regions of interest (ROIs). For each participant, we weight the normalised deviation of each ROI by the effect size (Cohen’s d) of the difference between SCZ/control for the corresponding ROI from the SCZ Enhancing Neuroimaging Genomics through Meta-Analysis working group. We generate a morphometric risk score (MRS) representing the average of these weighted deviations. We investigate if SCZ-MRS is elevated in a SCZ case/control sample (N(CASE) = 50; N(CONTROL) = 125), a replication sample (N(CASE) = 23; N(CONTROL) = 20) and a sample of asymptomatic young adults with extreme SCZ polygenic risk (N(HIGH-SCZ-PRS) = 95; N(LOW-SCZ-PRS) = 94). SCZ cases had higher SCZ-MRS than healthy controls in both samples (Study 1: β = 0.62, P < 0.001; Study 2: β = 0.81, P = 0.018). The high liability SCZ-PRS group also had a higher SCZ-MRS (Study 3: β = 0.29, P = 0.044). Furthermore, the SCZ-MRS was uniquely associated with SCZ status, but not attention-deficit hyperactivity disorder (ADHD), whereas an ADHD-MRS was linked to ADHD status, but not SCZ. This approach provides a promising solution when considering individual heterogeneity in SCZ-related brain alterations by identifying individual’s patterns of structural brain-wide alterations

Bcl-2 antagonizes apoptotic cell death induced by two new ceramide analogues

AbstractCeramides which arise in part from the breakdown of sphingomyelin comprise a class of antiproliferative lipids and have been implicated in the regulation of programmed cell death better known as apoptosis. In the present study, two new synthetic ceramide analogues, N-thioacetylsphingosine and FS-5, were used in Molt4 cells to induce cell death. Besides their cytotoxic effects at concentrations ≥14 μM the data obtained clearly show that both analogues induced apoptosis at concentrations below this critical concentration as assessed by trypan blue exclusion and cleavage of the death substrate poly-(ADP-ribose) polymerase (PARP). Additional experiments in bcl-2-transfected Molt4 cells revealed that the apoptotic but not the lytic effects of the analogues were antagonized by the apoptosis inhibitor Bcl-2. Furthermore, neither N-thio-acetylsphingosine nor FS-5 induced PARP cleavage in bcl-2-transfected Molt4 cells indicating that the induction of apoptotic cell death by cell permeable ceramides is not due to unspecific disturbance of the cell membrane