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NASA NTRS2003

A Step Beyond Simple Keyword Searches: Services Enabled by a Full Content Digital Journal Archive

The problems of managing and searching large archives of scientific journal articles can potentially be addressed through data mining and statistical techniques matured primarily for quantitative scientific data analysis. A journal paper could be represented by a multivariate descriptor, e.g., the occurrence counts of a number key technical terms or phrases (keywords), perhaps derived from a controlled vocabulary ( e . g . , the American Meteorological Society's Glossary of Meteorology) or bootstrapped from the journal archive itself. With this technique, conventional statistical classification tools can be leveraged to address challenges faced by both scientists and professional societies in knowledge management. For example, cluster analyses can be used to find bundles of "most-related" papers, and address the issue of journal bifurcation (when is a new journal necessary, and what topics should it encompass). Similarly, neural networks can be trained to predict the optimal journal (within a society's collection) in which a newly submitted paper should be published. Comparable techniques could enable very powerful end-user tools for journal searches, all premised on the view of a paper as a data point in a multidimensional descriptor space, e.g.: "find papers most similar to the one I am reading", "build a personalized subscription service, based on the content of the papers I am interested in, rather than preselected keywords", "find suitable reviewers, based on the content of their own published works", etc. Such services may represent the next "quantum leap" beyond the rudimentary search interfaces currently provided to end-users, as well as a compelling value-added component needed to bridge the print-to-digital-medium gap, and help stabilize professional societies' revenue stream during the print-to-digital transition.

Boccippio, Dennis J.↗
NASA NTRS2003

Numerical Models of Human Circulatory System under Altered Gravity: Brain Circulation

A computational fluid dynamics (CFD) approach is presented to model the blood flow through the human circulatory system under altered gravity conditions. Models required for CFD simulation relevant to major hemodynamic issues are introduced such as non-Newtonian flow models governed by red blood cells, a model for arterial wall motion due to fluid-wall interactions, a vascular bed model for outflow boundary conditions, and a model for auto-regulation mechanism. The three-dimensional unsteady incompressible Navier-Stokes equations coupled with these models are solved iteratively using the pseudocompressibility method and dual time stepping. Moving wall boundary conditions from the first-order fluid-wall interaction model are used to study the influence of arterial wall distensibility on flow patterns and wall shear stresses during the heart pulse. A vascular bed modeling utilizing the analogy with electric circuits is coupled with an auto-regulation algorithm for multiple outflow boundaries. For the treatment of complex geometry, a chimera overset grid technique is adopted to obtain connectivity between arterial branches. For code validation, computed results are compared with experimental data for steady and unsteady non-Newtonian flows. Good agreement is obtained for both cases. In sin-type Gravity Benchmark Problems, gravity source terms are added to the Navier-Stokes equations to study the effect of gravitational variation on the human circulatory system. This computational approach is then applied to localized blood flows through a realistic carotid bifurcation and two Circle of Willis models, one using an idealized geometry and the other model using an anatomical data set. A three- dimensional anatomical Circle of Willis configuration is reconstructed from human-specific magnetic resonance images using an image segmentation method. The blood flow through these Circle of Willis models is simulated to provide means for studying gravitational effects on the brain circulation under auto-regulation.

Kim, Chang Sung↗
NASA NTRS2003

Structure of the Outer Cusp and Sources of the Cusp Precipitation during Intervals of a Horizontal IMF

The cusp represents a place where the magnetosheath plasma can directly penetrate into the magnetosphere. Since the main transport processes are connected with merging of the interplanetary and magnetospheric field lines: the interplanetary magnetic field (IMF) Orientation plays a decisive role in the formation of the high-altitude cusp. The importance of the sign of the IMF B(sub Z) component for this process was suggested about 40 years ago and later it was documented by many experimental investigations. However, situations when IMF Bz is the major IMF component are rather rare. The structure of the cusp during periods of a small IMF B(sub Z) is generally unknown, probably due to the fully 3-D nature of the interaction. The present case study reveals the importance of horizontal IMF components on the global magnetospheric configuration as well as on small-scale processes at the cusp-magnetosheath interface. We have used simultaneous measurements of several spacecraft (ISTP program) operating in different regions of interplanetary space and two closely spaced satellites (INTERBALL-1/MAGION-4) crossing the cusp-magnetosheath boundary to show the connection between the short- and large-scale phenomena. In the northern hemisphere, observations suggest a presence of two spots of cusp-like precipitation supplied by reconnection occurring simultaneously in both hemispheres. A source of this bifurcation is the positive IMF B(sub y) component further enhanced by the field draping in the magnetosheath. This magnetic field component shifts the entry point far away from the local noon but in opposite sense in either hemisphere. The cusp represents a place where the magnetosheath plasma can directly

Berchem, Jean↗
NASA NTRS2004

Mechanisms for Antagonistic Regulation of AMPA and NMDA-D1 Receptor Complexes at Postsynaptic Sites

From the analysis of these pathways we conclude that postsynaptic processes that regulate synaptic transmission undergo significant cross-talk with respect to glutamatergic and neuromodulatory (dopamine) signals. The main hypothesis is that of a compensatory regulation, a competitive switch between the induction of increased AMPA conductance by CaMKII-dependent phosphorylation and reduced expression of PP2A, and increased D1 receptor sensitivity and expression by increased PKA, PP2A and decreased PP-1/calcineurin expression. Both types of plasticity are induced by NMDA receptor activation and increased internal calcium, they require different internal conditions to become expressed. Specifically we propose that AMPA regulation and D1 regulation are inversely coupled;The net result may be a bifurcation of synaptic state into predominantly AMPA or NMDA-D1 synapses. This could have functional consequences: stable connections for AMPA and conditional gating for NMDA-D1 synapses.

Schumann, Johann↗
NASA NTRS2002

Deformation Response of Unsymmetrically Laminated Plates Subjected to Inplane Loading

This paper discusses the out-of-plane deformation behavior of unsymmetric cross-ply composite plates compressed inplane by displacing one edge of the plate a known amount. The plates are assumed to be initially flat and several boundary conditions are considered. Geometrically nonlinear behavior is assumed. The primary objectives are to study the out-of-plane behavior as a function of increasing inplane compression and to determine if bifurcation behavior and secondary buckling can occur. It is shown that, depending on the boundary conditions, both can occur, though the characteristics are different than the pre and post-buckling behavior of a companion symmetric cross-ply plate. Furthermore, while a symmetric cross-ply plate can postbuckle with either a positive or negative out-of-plane displacement, the unsymmetric cross-ply plates studied deflect out-of-plane only in one direction throughout the range of inplane compression, the direction again depending on the boundary conditions

Ochinero, Tomoya T.↗
NASA NTRS2004

Deformations of Flat Unsymmetric Laminates Subjected to Inplane Loads

The geometrically nonlinear deformation response of initially flat unsymmetric cross-ply laminates subjected to an inplane compressive load and two sets of boundary conditions is studied. Stability of the deformations is considered. At issue is whether or not the plate remains flat with increased compressive loading, and whether it buckles. A semi-infinite unsymmetric cross-ply laminate is used to show the combined effects of geometric nonlinearities and bending-stretch coupling. Finite element results for finite laminates are then presented, and it is shown that to a large degree the boundary conditions control the character of the deformation response. It appears that clamped boundary conditions support buckling behavior, in the classic sense of bifurcation, whereas simply-supported conditions do not.

Hyer, Michael W.↗
NASA NTRS2003

Mode Jumping of an Isogrid Panel Under Quasi-Static Compression

A wide column test of a composite isogrid panel subjected to quasi-static, axial compression is modeled with a hybrid-static dynamic computational method. The data from the test panel exhibited discontinuous responses in the compressive load for slowly increased end-shortening. The computational model was developed to corroborate these discontinuities with the phenomenon of mode jumping. Mode jumping refers to the transient response of the panel from an unstable bifurcation point on a postbuckled equilibrium path to a second stable equilibrium state on a new equilibrium path. On the new equilibrium path, both the analysis and test show that the panel can resist increased endshortening beyond that of the unstable critical point. Fair agreement is achieved between the analysis and test.

Muheim, Danniella M.↗
NASA NTRS1988

Nonlinear dynamics in cardiac conduction

Electrical conduction in the heart shows many phenomena familiar from nonlinear dynamics. Among these phenomena are multiple basins of attraction, phase locking, and perhaps period-doubling bifurcations and chaos. We describe a simple cellular-automation model of electrical conduction which simulates normal conduction patterns in the heart as well as a wide range of disturbances of heart rhythm. In addition, we review the application of percolation theory to the analysis of the development of complex, self-sustaining conduction patterns.

NASA Discipline Cardiopulmonary↗
NASA NTRS2004

Continuation Methods for Qualitative Analysis of Aircraft Dynamics

A class of numerical methods for constructing bifurcation curves for systems of coupled, non-linear ordinary differential equations is presented. Foundations are discussed, and several variations are outlined along with their respective capabilities. Appropriate background material from dynamical systems theory is presented.

Cummings, Peter A.↗
NASA NTRS2001

Anatomical and functional characteristics of carotid sinus stimulation in humans

Transmission characteristics of pneumatic pressure to the carotid sinus were evaluated in 19 subjects at rest and during exercise. Either a percutaneous fluid-filled (n = 12) or balloon-tipped catheter (n = 7) was placed at the carotid bifurcation to record internal transmission of external neck pressure/neck suction (NP/NS). Sustained, 5-s pulses, and rapid ramping pulse protocols (+40 to -80 Torr) were recorded. Transmission of pressure stimuli was less with the fluid-filled catheter compared with that of the balloon-tipped catheter (65% vs. 82% negative pressure, 83% vs. 89% positive pressure; P < 0.05). Anatomical location of the carotid sinus averaged 3.2 cm (left) and 3.6 cm (right) from the gonion of the mandible with a range of 0-7.5 cm. Transmission was not altered by exercise or Valsalva maneuver, but did vary depending on the position of the carotid sinus locus beneath the sealed chamber. These data indicate that transmission of external NP/NS was higher than previously recorded in humans, and anatomical variation of carotid sinus location and equipment design can affect transmission results.

Randomized Controlled Trial↗
NASA NTRS1997

Three-dimensional analysis of vestibular efferent neurons innervating semicircular canals of the gerbil

Anterograde labeling techniques were used to examine peripheral innervation patterns of vestibular efferent neurons in the crista ampullares of the gerbil. Vestibular efferent neurons were labeled by extracellular injections of biocytin or biotinylated dextran amine into the contralateral or ipsilateral dorsal subgroup of efferent cell bodies (group e) located dorsolateral to the facial nerve genu. Anterogradely labeled efferent terminal field varicosities consist mainly of boutons en passant with fewer of the terminal type. The bouton swellings are located predominately in apposition to the basolateral borders of the afferent calyces and type II hair cells, but several boutons were identified close to the hair cell apical border on both types. Three-dimensional reconstruction and morphological analysis of the terminal fields from these cells located in the sensory neuroepithelium of the anterior, horizontal, and posterior cristae were performed. We show that efferent neurons densely innervate each end organ in widespread terminal fields. Subepithelial bifurcations of parent axons were minimal, with extensive collateralization occurring after the axons penetrated the basement membrane of the neuroepithelium. Axonal branching ranged between the 6th and 27th orders and terminal field collecting area far exceeds that of the peripheral terminals of primary afferent neurons. The terminal fields of the efferent neurons display three morphologically heterogeneous types: central, peripheral, and planum. All cell types possess terminal fields displaying a high degree of anisotropy with orientations typically parallel to or within +/-45 degrees of the longitudinal axis if the crista. Terminal fields of the central and planum zones predominately project medially toward the transverse axis from the more laterally located penetration of the basement membrane by the parent axon. Peripheral zone terminal fields extend predominately toward the planum semilunatum. The innervation areas of efferent terminal fields display a trend from smallest to largest for the central, peripheral, and planum types, respectively. Neurons that innervate the central zone of the crista do not extend into the peripheral or planum regions. Conversely, those neurons with terminal fields in the peripheral or planum regions do not innervate the central zone of the sensory neuroepithelium. The central zone of the crista is innervated preferentially by efferent neurons with cell bodies located in the ipsilateral group e. The peripheral and planum zones of the crista are innervated preferentially by efferent neurons with cell bodies located in the contralateral group e. A model incorporating our anatomic observations is presented describing an ipsilateral closed-loop feedback between ipsilateral efferent neurons and the periphery and an open-loop feed-forward innervation from contralateral efferent neurons. A possible role for the vestibular efferent neurons in the modulation of semicircular canal afferent response dynamics is proposed.

Non-NASA Center↗
NASA NTRS2004

Far-Field Acoustic Characteristics of Multiple Blade-Vane Configurations for a High Tip Speed Fan

The acoustic characteristics of a model high-speed fan stage were measured in the NASA Glenn 9- by 15-Foot Low Speed Wind Tunnel at takeoff and approach flight conditions. The fan was designed for a corrected rotor tip speed of 442 m/s (1450 ft/s), and had a powered core, or booster stage, giving the model a nominal bypass ratio of 5. A simulated engine pylon and nozzle bifurcation was contained within the bypass duct. The fan stage consisted of all combinations of 3 possible rotors, and 3 stator vane sets. The 3 rotors were (1) wide chord, (2) forward swept, and (3) shrouded. The 3 stator sets were (1) baseline, moderately swept, (2) swept and leaned, and (3) swept integral vane/frame which incorporated some of the swept and leaned features as well as eliminated the downstream support structure. The baseline configuration is considered to be the wide chord rotor with the radial vane stator. A flyover Effective Perceived Noise Level (EPNL) code was used to generate relative EPNL values for the various configurations. The swept and leaned stator showed a 3 EPNdB reduction at lower fan speeds relative to the baseline stator; while the swept integral vane/frame stator showed lowest noise levels at high fan speeds. The baseline, wide chord rotor was typically the quietest of the three rotors. A tone removal study was performed to assess the acoustic benefits of removing the fundamental rotor interaction tone and its harmonics. Reprocessing the acoustic results with the bypass tone removed had the most impact on reducing fan noise at transonic rotor speeds. Removal of the bypass rotor interaction tones (BPF and nBPF) showed up to a 6 EPNdB noise reduction at transonic rotor speeds relative to noise levels for the baseline (wide chord rotor and radial stator; all tones present) configuration.

Woodward, Richard P.↗
NASA NTRS1995

Hair-cell counts and afferent innervation patterns in the cristae ampullares of the squirrel monkey with a comparison to the chinchilla

1. The numbers of type I and type II hair cells were estimated by dissector techniques applied to semithin, stained sections of the horizontal, superior, and posterior cristae in the squirrel monkey and the chinchilla. 2. The crista in each species was divided into concentrically arranged central, intermediate, and peripheral zones of equal areas. The three zones can be distinguished by the sizes of individual hair cells and calyx endings, by the density of hair cells, and by the relative frequency of calyx endings innervating single or multiple type I hair cells. 3. In the monkey crista, type I hair cells outnumber type II hair cells by a ratio of almost 3:1. The ratio decreases from 4-5:1 in the central and intermediate zones to under 2:1 in the peripheral zone. For the chinchilla, the ratio is near 1:1 for the entire crista and decreases only slightly between the central and peripheral zones. 4. Nerve fibers supplying the cristae in the squirrel monkey were labeled by extracellular injections of horseradish peroxidase (HRP) into the vestibular nerve. Peripheral terminations of individual fibers were reconstructed and related to the zones of the cristae they innervated and to the sizes of their parent axons. Results were similar for the horizontal, superior, and posterior cristae. 5. Axons seldom bifurcate below the neuroepithelium. Most fibers begin branching shortly after crossing the basement membrane. Their terminal arbors are compact, usually extending no more than 50-100 microns from the parent exon. A small number of long intraepithelial fibers enter the intermediate and peripheral zones of the cristae near its base, then run unbranched for long distances through the neuroepithelium to reach the central zone. 6. There are three classes of afferent fibers innervating the monkey crista. Calyx fibers terminate exclusively on type I hair cells, and bouton fibers end only on type II hair cells. Dimorphic fibers provide a mixed innervation, including calyx endings to type I hair cells and bouton endings to type II hair cells. Long intraepithelial fibers are calyx and dimorphic units, whose terminal fields are similar to those of other fibers. The central zone is innervated by calyx and dimorphic fibers; the peripheral zone, by bouton and dimorphic fibers; and the intermediate zone, by all three kinds of fibers. Internal (axon) diameters are largest for calyx fibers and smallest for bouton fibers. Of the entire sample of 286 labeled fibers, 52% were dimorphic units, 40% were calyx units, and 8% were bouton units.(ABSTRACT TRUNCATED AT 400 WORDS).

Non-NASA Center↗
NASA NTRS2000

Svalbard: A Window for Understanding Temporal/Spatial Aspects of Solar Wind Coupling to the Magnetosphere and Ionosphere

The research facilities on the Svalbard archepelego provide a unique opportunity for observing the temporal and spatial characteristics of the interaction of the solar wind with the magnetosphere-ionosphere system. The first sounding rockets from the SvdRak range at Ny-Alesund have opened a new perspective for separating temporal and spatial effects. Finding a correlation between observations from the rockets and the Wind satellite located nearly 200 R(sub E) upstream in the solar wind that had a lag time less than the advection time forced consideration of tilted phase planes of the interp1anetary electric field. From this it was deduced that the interaction process has to involve high latitude merging, the interplanetary magnetic field (IMF) B(sub Y) bifurcates the cusp relative to the high latitude source regions in the Northern and Southern Hemispheres, IMF B(sub X) controls the interaction time in each hemisphere, and the small convection cell is driven by opposite hemisphere merging. Studies with 4 satellites in the solar wind have shown that the tilt of the phase plane varies on a minute-by-minute basis and change significantly on time scales of tens of minutes. Images of the cusp at 557.7 nm provide a nearly instantaneous picture of the temporal and spatial characteristics of merging at the magnetopause and show that the process can occur at multiple locations. The rate and location vary with time.

Maynard, Nelson C.↗
NASA NTRS2003

Coupling the Solar-Wind/IMF to the Ionosphere through the High Latitude Cusps

Magnetic merging is a primary means for coupling energy from the solar wind into the magnetosphere-ionosphere system. The location and nature of the process remain as open questions. By correlating measurements form diverse locations and using large-scale MHD models to put the measurements in context, it is possible to constrain out interpretations of the global and meso-scale dynamics of magnetic merging. Recent evidence demonstrates that merging often occurs at high latitudes in the vicinity of the cusps. The location is in part controlled by the clock angle in the interplanetary magnetic field (IMF) Y-Z plane. In fact, B(sub Y) bifurcated the cusp relative to source regions. The newly opened field lines may couple to the ionosphere at MLT locations of as much as 3 hr away from local noon. On the other side of noon the cusp may be connected to merging sites in the opposite hemisphere. In face, the small convection cell is generally driven by opposite hemisphere merging. B(sub X) controls the timing of the interaction and merging sites in each hemisphere, which may respond to planar features in the IMF at different times. Correlation times are variable and are controlled by the dynamics of the tilt of the interplanetary electric field phase plane. The orientation of the phase plane may change significantly on time scales of tens of minutes. Merging is temporally variable and may be occurring at multiple sites simultaneously. Accelerated electrons from the merging process excite optical signatures at the foot of the newly opened field lines. All-sky photometer observations of 557.7 nm emissions in the cusp region provide a "television picture" of the merging process and may be used to infer the temporal and spatial variability of merging, tied to variations in the IMF.

Maynard, Nelson C.↗
NASA NTRS2000

Inlet Unstart Propulsion Integration Wind Tunnel Test Program Completed for High-Speed Civil Transport

One of the propulsion system concepts to be considered for the High-Speed Civil Transport (HSCT) is an underwing, dual-propulsion, pod-per-wing installation. Adverse transient phenomena such as engine compressor stall and inlet unstart could severely degrade the performance of one of these propulsion pods. The subsequent loss of thrust and increased drag could cause aircraft stability and control problems that could lead to a catastrophic accident if countermeasures are not in place to anticipate and control these detrimental transient events. Aircraft system engineers must understand what happens during an engine compressor stall and inlet unstart so that they can design effective control systems to avoid and/or alleviate the effects of a propulsion pod engine compressor stall and inlet unstart. The objective of the Inlet Unstart Propulsion Airframe Integration test program was to assess the underwing flow field of a High-Speed Civil Transport propulsion system during an engine compressor stall and subsequent inlet unstart. Experimental research testing was conducted in the 10- by 10-Foot Supersonic Wind Tunnel at the NASA Glenn Research Center at Lewis Field. The representative propulsion pod consisted of a two-dimensional, bifurcated inlet mated to a live turbojet engine. The propulsion pod was mounted below a large flat plate that acted as a wing simulator. Because of the plate s long length (nominally 10-ft wide by 18-ft long), realistic boundary layers could form at the inlet cowl plane. Transient instrumentation was used to document the aerodynamic flow-field conditions during an unstart sequence. Acquiring these data was a significant technical challenge because a typical unstart sequence disrupts the local flow field for about only 50 msec. Flow surface information was acquired via static pressure taps installed in the wing simulator, and intrusive pressure probes were used to acquire flow-field information. These data were extensively analyzed to determine the impact of the unstart transient on the surrounding flow field. This wind tunnel test program was a success, and for the first time, researchers acquired flow-field aerodynamic data during a supersonic propulsion system engine compressor stall and inlet unstart sequence. In addition to obtaining flow-field pressure data, Glenn researchers determined other properties such as the transient flow angle and Mach number. Data are still being reduced, and a comprehensive final report will be released during calendar year 2000.

Porro, A. Robert↗
NASA NTRS2004

Image-Based Computational Fluid Dynamics in Blood Vessel Models: Toward Developing a Prognostic Tool to Assess Cardiovascular Function Changes in Prolonged Space Flights

One of NASA's objectives is to be able to perform a complete, pre-flight, evaluation of cardiovascular changes in astronauts scheduled for prolonged space missions. Computational fluid dynamics (CFD) has shown promise as a method for estimating cardiovascular function during reduced gravity conditions. For this purpose, MRI can provide geometrical information, to reconstruct vessel geometries, and measure all spatial velocity components, providing location specific boundary conditions. The objective of this study was to investigate the reliability of MRI-based model reconstruction and measured boundary conditions for CFD simulations. An aortic arch model and a carotid bifurcation model were scanned in a 1.5T Siemens MRI scanner. Axial MRI acquisitions provided images for geometry reconstruction (slice thickness 3 and 5 mm; pixel size 1x1 and 0.5x0.5 square millimeters). Velocity acquisitions provided measured inlet boundary conditions and localized three-directional steady-flow velocity data (0.7-3.0 L/min). The vessel walls were isolated using NIH provided software (ImageJ) and lofted to form the geometric surface. Constructed and idealized geometries were imported into a commercial CFD code for meshing and simulation. Contour and vector plots of the velocity showed identical features between the MRI velocity data, the MRI-based CFD data, and the idealized-geometry CFD data, with less than 10% differences in the local velocity values. CFD results on models reconstructed from different MRI resolution settings showed insignificant differences (less than 5%). This study illustrated, quantitatively, that reliable CFD simulations can be performed with MRI reconstructed models and gives evidence that a future, subject-specific, computational evaluation of the cardiovascular system alteration during space travel is feasible.

Chatzimavroudis, George P.↗
NASA NTRS2006

A Numerical and Experimental Study of Compression-Loaded Composite Panels With Cutouts

Results from a numerical and experimental study on the effects of laminate orthotropy and circular cutout size on the response of compression-loaded composite curved panels are presented. Several 60-in-radius composite panels with four different laminate configurations were tested with cutout diameters that range from 10% to 60% of the panel width. Finite-element analyses were performed for each panel in order to identify the effects boundary conditions, measured initial geometric imperfections and thickness variations had on the nonlinear and buckling behavior of the panels. The compression-loaded panels considered herein exhibited two separate types of behavior depending on the laminate stacking sequence and cutout size. More specifically, some of the panels exhibited the classical snap-through type buckling response; however, some of the panels exhibited a monotonically increasing stable response and achieved compressive loads in excess of twice the predicted linear bifurcation buckling load. In general, the finite-element analyses were able to predict accurately the nonlinear response and buckling loads of the panels and the prebuckling and postbuckling out-of-plane deformations and strains.

Thornburgh, Robert P.↗