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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
NASA NTRS2001

Clinical and echocardiographic characteristics of papillary fibroelastomas: a retrospective and prospective study in 162 patients

BACKGROUND: Cardiac papillary fibroelastoma (CPF) is a primary cardiac neoplasm that is increasingly detected by echocardiography. The clinical manifestations of this entity are not well described. METHODS AND RESULTS: In a 16-year period, we identified patients with CPF from our pathology and echocardiography databases. A total of 162 patients had pathologically confirmed CPF. Echocardiography was performed in 141 patients with 158 CPFs, and 48 patients had CPFs that were not visible by echocardiography (<0.2 cm), leaving an echocardiographic subgroup of 93 patients with 110 CPFs. An additional 45 patients with a presumed diagnosis of CPF were identified. The mean age of the patients was 60+/-16 years of age, and 46.1% were male. Echocardiographically, the mean size of the CPFs was 9+/-4.6 mm; 82.7% occurred on valves (aortic more than mitral), 43.6% were mobile, and 91.4% were single. During a follow-up period of 11+/-22 months, 23 of 26 patients with a prospective diagnosis of CPF that was confirmed by pathological examination had symptoms that could be attributable to embolization. In the group of 45 patients with a presumed diagnosis of CPF, 3 patients had symptoms that were likely due to embolization (incidence, 6.6%) during a follow-up period of 552+/-706 days. CONCLUSIONS: CPFs are generally small and single, occur most often on valvular surfaces, and may be mobile, resulting in embolization. Because of the potential for embolic events, symptomatic patients, patients undergoing cardiac surgery for other lesions, and those with highly mobile and large CPFs should be considered for surgical excision.

NASA Discipline Cardiopulmonary↗
NASA NTRS2000

Noninvasive estimation of transmitral pressure drop across the normal mitral valve in humans: importance of convective and inertial forces during left ventricular filling

OBJECTIVES: We hypothesized that color M-mode (CMM) images could be used to solve the Euler equation, yielding regional pressure gradients along the scanline, which could then be integrated to yield the unsteady Bernoulli equation and estimate noninvasively both the convective and inertial components of the transmitral pressure difference. BACKGROUND: Pulsed and continuous wave Doppler velocity measurements are routinely used clinically to assess severity of stenotic and regurgitant valves. However, only the convective component of the pressure gradient is measured, thereby neglecting the contribution of inertial forces, which may be significant, particularly for nonstenotic valves. Color M-mode provides a spatiotemporal representation of flow across the mitral valve. METHODS: In eight patients undergoing coronary artery bypass grafting, high-fidelity left atrial and ventricular pressure measurements were obtained synchronously with transmitral CMM digital recordings. The instantaneous diastolic transmitral pressure difference was computed from the M-mode spatiotemporal velocity distribution using the unsteady flow form of the Bernoulli equation and was compared to the catheter measurements. RESULTS: From 56 beats in 16 hemodynamic stages, inclusion of the inertial term ([deltapI]max = 1.78+/-1.30 mm Hg) in the noninvasive pressure difference calculation significantly increased the temporal correlation with catheter-based measurement (r = 0.35+/-0.24 vs. 0.81+/-0.15, p< 0.0001). It also allowed an accurate approximation of the peak pressure difference ([deltapc+I]max = 0.95 [delta(p)cathh]max + 0.24, r = 0.96, p<0.001, error = 0.08+/-0.54 mm Hg). CONCLUSIONS: Inertial forces are significant components of the maximal pressure drop across the normal mitral valve. These can be accurately estimated noninvasively using CMM recordings of transmitral flow, which should improve the understanding of diastolic filling and function of the heart.

Non-NASA Center↗
NASA NTRS2000

Resistance of extraocular motoneuron terminals to effects of amyotrophic lateral sclerosis sera

In sporadic ALS (s-ALS), axon terminals contain increased intracellular calcium. Passively transferred sera from patients with s-ALS increase intracellular calcium in spinal motoneuron terminals in vivo and enhance spontaneous transmitter release, a calcium-dependent process. In this study, passive transfer of s-ALS sera increased spontaneous release from spinal but not extraocular motoneuron terminals, suggesting that the resistance to physiologic abnormalities induced by s-ALS sera in mice parallels the resistance of extraocular motoneurons to dysfunction and degeneration in ALS.

NASA Program Biomedical Research and Countermeasur↗
NASA NTRS1999

Neocytolysis contributes to the anemia of renal disease

Neocytolysis is a recently described physiological process affecting the selective hemolysis of young red blood cells in circumstances of plethora. Erythropoietin (EPO) depression appears to initiate the process, providing the rationale to investigate its contributions to the anemia of renal disease. When EPO therapy was withheld, four of five stable hemodialysis patients showed chromium 51 (51Cr)-red cell survival patterns indicative of neocytolysis; red cell survival was short in the first 9 days, then normalized. Two of these four patients received oral 13C-glycine and 15N-glycine, and there was a suggestion of pathological isotope enrichment of stool porphyrins when EPO therapy was held, again supporting selective hemolysis of newly released red cells that take up the isotope (one patient had chronic hemolysis indicated by isotope studies of blood and stool). Thus, neocytolysis can contribute to the anemia of renal disease and explain some unresolved issues about such anemia. One implication is the prediction that intravenous bolus EPO therapy is metabolically and economically inefficient compared with lower doses administered more frequently subcutaneously.

Non-NASA Center↗
NASA NTRS1998

Normative data on phases of the Valsalva maneuver

The phases of the Valsalva maneuver have well-known pathophysiology, and are used in the evaluation of adrenergic function. Because scant normative data is available, we have evaluated normative data for the Valsalva maneuver in control subjects. The patient, supine, performed the Valsalva maneuver maintaining an expiratory pressure of 40 mm Hg for 15 seconds. We reviewed 188 Valsalva maneuver recordings of normal control subjects, and recordings were excluded if two reproducible recordings were not obtained, or if expiratory pressure was <30 mm Hg or < 10 seconds. One hundred and three recordings were acceptable for analysis; 47 female and 56 male subjects, age in years (mean +/- SD) was 52.2+/-17.3 and 44.8+/-17.3, respectively. The association of expiratory pressure with age (P < 0.001) and gender ( P < 0.001) was complex, expressed as a parabola in both men and women, but resulted in phases I and III that were not significantly different. An increase in age resulted in a progressively more negative phase II_E (P < 0.05) and attenuation of phase II_L (P < 0.01). An increase in supine blood pressure resulted in a significantly more negative phase II_E (P < 0.001) and a lower phase IV. Phase IV is unaffected by age and gender.

NASA Discipline Cardiopulmonary↗
NASA NTRS1998

T wave alternans as a predictor of recurrent ventricular tachyarrhythmias in ICD recipients: prospective comparison with conventional risk markers

INTRODUCTION: The current standard for arrhythmic risk stratification is electrophysiologic (EP) testing, which, due to its invasive nature, is limited to patients already known to be at high risk. A number of noninvasive tests, such as determination of left ventricular ejection fraction (LVEF) or heart rate variability, have been evaluated as additional risk stratifiers. Microvolt T wave alternans (TWA) is a promising new risk marker. Prospective evaluation of noninvasive risk markers in low- or moderate-risk populations requires studies involving very large numbers of patients, and in such studies, documentation of the occurrence of ventricular tachyarrhythmias is difficult. In the present study, we identified a high-risk population, recipients of an implantable cardioverter defibrillator (ICD), and prospectively compared microvolt TWA with invasive EP testing and other risk markers with respect to their ability to predict recurrence of ventricular tachyarrhythmias as documented by ICD electrograms. METHODS AND RESULTS: Ninety-five patients with a history of ventricular tachyarrhythmias undergoing implantation of an ICD underwent EP testing, assessment of TWA, as well as determination of LVEF, baroreflex sensitivity, signal-averaged ECG, analysis of 24-hour Holter monitoring, and QT dispersion from the 12-lead surface ECG. The endpoint of the study was first appropriate ICD therapy for electrogram-documented ventricular fibrillation or tachycardia during follow-up. Kaplan-Meier survival analysis revealed that TWA (P < 0.006) and LVEF (P < 0.04) were the only significant univariate risk stratifiers. EP testing was not statistically significant (P < 0.2). Multivariate Cox regression analysis revealed that TWA was the only statistically significant independent risk factor. CONCLUSIONS: Measurement of microvolt TWA compared favorably with both invasive EP testing and other currently used noninvasive risk assessment methods in predicting recurrence of ventricular tachyarrhythmias in ICD recipients. This study suggests that TWA might also be a powerful tool for risk stratification in low- or moderate-risk patients, and needs to be prospectively evaluated in such populations.

Non-NASA Center↗
NASA NTRS1992

Rotating shift work, sleep, and accidents related to sleepiness in hospital nurses

A hospital-based survey on shift work, sleep, and accidents was carried out among 635 Massachusetts nurses. In comparison to nurses who worked only day/evening shifts, rotators had more sleep/wake cycle disruption and nodded off more at work. Rotators had twice the odds of nodding off while driving to or from work and twice the odds of a reported accident or error related to sleepiness. Application of circadian principles to the design of hospital work schedules may result in improved health and safety for nurses and patients.

Non-NASA Center↗
NASA NTRS2002

X-ray synchronization emitting Fe-rich ejecta in SNR RCW 86

Supernova remnants may exhibit both thermal and nonthermal X-ray emission. In a previous study with ASCA data, we found that the middle-aged supernova remnant RCW 86 showed evidence for both processes, and predicted that observations with much higher spatial resolution would distinguish harder X-rays, which we proposed were primarily synchrotron emission, from softer, thermal X-rays. Here we describe Chandra observations which amply confirm our predictions.

ISM individual (RCW86) supernova remnants↗
NASA NTRS2007

Aerospace Toxicology and Microbiology

Toxicology dates to the very earliest history of humanity with various poisons and venom being recognized as a method of hunting or waging war with the earliest documentation in the Evers papyrus (circa 1500 BCE). The Greeks identified specific poisons such as hemlock, a method of state execution, and the Greek word toxos (arrow) became the root of our modern science. The first scientific approach to the understanding of poisons and toxicology was the work during the late middle ages of Paracelsus. He formulated what were then revolutionary views that a specific toxic agent or "toxicon" caused specific dose-related effects. His principles have established the basis of modern pharmacology and toxicology. In 1700, Bernardo Ramazzini published the book De Morbis Artificum Diatriba (The Diseases of Workers) describing specific illnesses associated with certain labor, particularly metal workers exposed to mercury, lead, arsenic, and rock dust. Modern toxicology dates from development of the modern industrial chemical processes, the earliest involving an analytical method for arsenic by Marsh in 1836. Industrial organic chemicals were synthesized in the late 1800 s along with anesthetics and disinfectants. In 1908, Hamilton began the long study of occupational toxicology issues, and by WW I the scientific use of toxicants saw Haber creating war gases and defining time-dosage relationships that are used even today.

James, John T.↗
NASA NTRS2008

Space Weather: What is it, and Why Should a Meteorologist Care?

"Space weather" is a term coined almost 15 years ago to describe environmental conditions ABOVE Earth's atmosphere that affect satellites and astronauts. As society has become more dependent on technology, we nave found that space weather conditions increasingly affect numerous commercial and infrastructure sectors: airline operations, the precision positioning industry, and the electric power grid, to name a few. Similar to meteorology where "weather" often refers to severe conditions, "space weather" includes geomagnetic storms, radiation storms, and radio blackouts. But almost all space weather conditions begin at the Sun--our middle-age, magnetically-variable star. At NASA, the science behind space weather takes place in the Heliophysics Division. The Space Weather Prediction Center in Boulder, Colorado, is manned jointly by NCAA and US Air Force personnel, and it provides space weather alerts and warnings for disturbances that can affect people and equipment working in space and on Earth. Organizationally, it resides in NOAA's National Weather Service as one of the National Centers for Environmental Prediction. In this seminar we hope to give the audience a brief introduction to the causes of space weather, discuss some of the effects, and describe the state of the art in forecasting. Our goal is to highlight that meteorologists are increasingly becoming the "first responders" to questions about space weather causes and effects.

SaintCyr, Chris↗
NASA NTRS2010

Discovery of X-Ray-Emitting O-Ne-Mg-Rich Ejecta in the Galactic Supernova Remnant Puppis A

We report on the discovery of X-ray-emitting O-Ne-Mg-rich ejecta in the middle-aged Galactic O-rich supernova remnant Puppis A with Chandra and XMM-Newton. We use line ratios to identify a low-ionization filament running parallel to the northeastern edge of the remnant that requires super-solar abundances, particularly for O, Ne, and Mg, which we interpret to be from O-Ne-Mg-rich ejecta. Abundance ratios of Ne/O, Mg/O, and Fe/O are measured to be [approx]2, [approx]2, and <0.3 times the solar values. Our spatially resolved spectral analysis from the northeastern rim to the western rim otherwise reveals sub-solar abundances consistent with those in the interstellar medium. The filament is coincident with several optically emitting O-rich knots with high velocities. If these are physically related, the filament would be a peculiar fragment of ejecta. On the other hand, the morphology of the filament suggests that it may trace ejecta heated by a shock reflected strongly off the dense ambient clouds near the northeastern rim.

Katsuda, Satoru↗
NASA NTRS2013

The VELA-X-Pulsar Wind Nebula Revisited with Four Years of Fermi Large Area Telescope Observations

The Vela supernova remnant (SNR) is the closest SNR to Earth containing an active pulsar, the Vela pulsar (PSR B0833-45). This pulsar is an archetype of the middle-aged pulsar class and powers a bright pulsar wind nebula (PWN), Vela-X, spanning a region of 2deg × 3deg south of the pulsar and observed in the radio, X-ray, and very high energy γ-ray domains. The detection of the Vela-X PWN by the Fermi Large Area Telescope (LAT) was reported in the first year of the mission. Subsequently, we have reinvestigated this complex region and performed a detailed morphological and spectral analysis of this source using 4 yr of Fermi-LAT observations. This study lowers the threshold for morphological analysis of the nebula from 0.8 GeV to 0.3 GeV, allowing for the inspection of distinct energy bands by the LAT for the first time. We describe the recent results obtained on this PWN and discuss the origin of the newly detected spatial features.

Vela-X↗
NASA NTRS2023

XMM-Newton and Chandra Observations of the Candidate Fermi-LAT Pulsar 4FGL J1015.5-6030

4FGL J1015.5-6030 is an unidentified Fermi-LAT source hosting a bright, extended X-ray source whose X-ray spectrum is consistent with that of a young pulsar, yet no pulsations have been found. Here we report on XMM-Newton timing and Chandra imaging observations of the X-ray counterpart of 4FGL J1015.5-6030. We find no significant periodicity from the source and place a 3σ upper limit on its pulsed fraction of 34%. The Chandra observations resolve the point source from the extended emission. We find that the point source's spectrum is well fit by a blackbody model, with temperature kT = 0.205 ± 0.009 keV, plus a weak power-law component, which is consistent with a thermally emitting neutron star with a magnetospheric component. The extended emission spans angular scales of a few arcseconds up to about 30'' from the point source and its spectrum is well fit by a power-law model with a photon index Γ = 1.70 ± 0.05. The extended emission's spectrum and 0.5–10 keV luminosity of 4 × 10 32 erg s −1 (at a plausible distance of 2 kpc) are consistent with that of a pulsar wind nebula. Based on a comparison to other GeV and X-ray pulsars, we find that this putative pulsar is likely a middle-aged (i.e., τ ∼ 0.1–1 Myr) radio-quiet pulsar with Ė~10 34 -10 35 erg s −1 .

Pulsars↗
NASA NTRS2001

The effects of age and gender on sleep EEG power spectral density in the middle years of life (ages 20-60 years old)

The effects of age and gender on sleep EEG power spectral density were assessed in a group of 100 subjects aged 20 to 60 years. We propose a new statistical strategy (mixed-model using fixed-knot regression splines) to analyze quantitative EEG measures. The effect of gender varied according to frequency, but no interactions emerged between age and gender, suggesting that the aging process does not differentially influence men and women. Women had higher power density than men in delta, theta, low alpha, and high spindle frequency range. The effect of age varied according to frequency and across the night. The decrease in power with age was not restricted to slow-wave activity, but also included theta and sigma activity. With increasing age, the attenuation over the night in power density between 1.25 and 8.00 Hz diminished, and the rise in power between 12.25 and 14.00 Hz across the night decreased. Increasing age was associated with higher power in the beta range. These results suggest that increasing age may be related to an attenuation of homeostatic sleep pressure and to an increase in cortical activation during sleep.

NASA Discipline Regulatory Physiology↗
NASA NTRS2003

The dynamics of herpesvirus and polyomavirus reactivation and shedding in healthy adults: a 14-month longitudinal study

Humans are infected with viruses that establish long-term persistent infections. To address whether immunocompetent individuals control virus reactivation globally or independently and to identify patterns of sporadic reactivation, we monitored herpesviruses and polyomaviruses in 30 adults, over 14 months. Epstein-Barr virus (EBV) DNA was quantitated in saliva and peripheral blood mononuclear cells (PBMCs), cytomegalovirus (CMV) was assayed in urine, and JC virus (JCV) and BK virus (BKV) DNAs were assayed in urine and PBMCs. All individuals shed EBV in saliva, whereas 67% had >or=1 blood sample positive for EBV. Levels of EBV varied widely. CMV shedding occurred infrequently but occurred more commonly in younger individuals (P<.03). JCV and BKV virurias were 46.7% and 0%, respectively. JCV shedding was age dependent and occurred commonly in individuals >or=40 years old (P<.03). Seasonal variation was observed in shedding of EBV and JCV, but there was no correlation among shedding of EBV, CMV, and JCV (P>.50). Thus, adults independently control persistent viruses, which display discordant, sporadic reactivations.

Non-NASA Center↗
NASA NTRS1997

Deviations from uniform power law scaling in nonstationary time series

A classic problem in physics is the analysis of highly nonstationary time series that typically exhibit long-range correlations. Here we test the hypothesis that the scaling properties of the dynamics of healthy physiological systems are more stable than those of pathological systems by studying beat-to-beat fluctuations in the human heart rate. We develop techniques based on the Fano factor and Allan factor functions, as well as on detrended fluctuation analysis, for quantifying deviations from uniform power-law scaling in nonstationary time series. By analyzing extremely long data sets of up to N = 10(5) beats for 11 healthy subjects, we find that the fluctuations in the heart rate scale approximately uniformly over several temporal orders of magnitude. By contrast, we find that in data sets of comparable length for 14 subjects with heart disease, the fluctuations grow erratically, indicating a loss of scaling stability.

Non-NASA Center↗
NASA NTRS2001

Visually induced reorientation illusions

It is known that rotation of a furnished room around the roll axis of erect subjects produces an illusion of 360 degrees self-rotation in many subjects. Exposure of erect subjects to stationary tilted visual frames or rooms produces only up to 20 degrees of illusory tilt. But, in studies using static tilted rooms, subjects remained erect and the body axis was not aligned with the room. We have revealed a new class of disorientation illusions that occur in many subjects when placed in a 90 degrees or 180 degrees tilted room containing polarised objects (familiar objects with tops and bottoms). For example, supine subjects looking up at a wall of the room feel upright in an upright room and their arms feel weightless when held out from the body. We call this the levitation illusion. We measured the incidence of 90 degrees or 180 degrees reorientation illusions in erect, supine, recumbent, and inverted subjects in a room tilted 90 degrees or 180 degrees. We report that reorientation illusions depend on the displacement of the visual scene rather than of the body. However, illusions are most likely to occur when the visual and body axes are congruent. When the axes are congruent, illusions are least likely to occur when subjects are prone rather than supine, recumbent, or inverted.

Non-NASA Center↗
NASA NTRS2001

Mitral inertance in humans: critical factor in Doppler estimation of transvalvular pressure gradients

The pressure-velocity relationship across the normal mitral valve is approximated by the Bernoulli equation DeltaP = 1/2 rhoDeltav(2) + M. dv/dt, where DeltaP is the atrioventricular pressure difference, rho is blood density, v is transmitral flow velocity, and M is mitral inertance. Although M is indispensable in assessing transvalvular pressure differences from transmitral flow, this term is poorly understood. We measured intraoperative high-fidelity left atrial and ventricular pressures and simultaneous transmitral flow velocities by using transesophageal echocardiography in 100 beats (8 patients). We computed mean mitral inertance (M) by M = integral((DeltaP)-(1/2 x rho v(2))dt/integral(dv/dt)dt and we assessed the effect of the inertial term on the transmitral pressure-flow relation. ranged from 1.03 to 5.96 g/cm(2) (mean = 3.82 +/- 1.22 g/cm(2)). DeltaP calculated from the simplified Bernoulli equation (DeltaP = 1/2. rhov(2)) lagged behind (44 +/- 11 ms) and underestimated the actual peak pressures (2.3 +/- 1.1 mmHg). correlated with left ventricular systolic pressure (r = -0.68, P < 0.0001) and transmitral pressure gradients (r = 0.65, P < 0.0001). Because mitral inertance causes the velocity to lag significantly behind the actual pressure gradient, it needs to be considered when assessing diastolic filling and the pressure difference across normal mitral valves.

NASA Discipline Cardiopulmonary↗