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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 163 records · Page 9
All sourcesNASA NTRSDOE OSTI
NASA NTRS1998

Changes in gravitational state cause changes in ocular torsion

Gravity-responsive eye torsion was studied simultaneously in both eyes during parabolic flight to determine the effects of weightlessness. Observed effects were that torsional position of eyes in the 1G states between parabolas was offset from the baseline positions obtained prior to the onset of parabolas, responses to hyper- and hypogravity were seen in most subjects, and responses were consistent within subjects but varied between subjects.

NASA Discipline Neuroscience↗
NASA NTRS2019

The Changing Changing-Look AGN 1ES 1927+654

We report on X-ray follow-up observations of the March 2018 nuclear transient event AT2018zf (ASASSN-18el) from an ongoing campaign that includes XMM-Newton, NuSTAR, Swift, and high cadence (daily-to-weekly) NICER observations. The event was associated with the Seyfert galaxy 1ES 1927+654, a "True Type-2" that, nevertheless, showed an X-ray spectrum typical of an unobscured Type 1 AGN. Optical monitoring revealed the emergence of broad Balmer emission lines following the outburst, suggesting a transition from a Type 2 to a Type 1 AGN on timescales consistent with the light-travel time between the central black hole and the broad line region. The optical outburst was followed by a dramatic shift in the X-ray spectrum as the hard X-ray luminosity of the corona plunged by >2 orders of magnitude and the spectrum became dominated by a 10^6 K thermal component. The subsequent X-ray evolution of 1ES 1927+654 includes an additional two-order of magnitude decline in overall luminosity, followed by an extended period of quiescence, and re-brightening to levels that make it the brightest AGN currently in the X-ray sky. Throughout its evolution, the source has displayed X-ray flux variability of factors of several on timescales less than hour, and of ~100 on timescales less than a day. The X-ray spectrum varies along a consistent luminosity-dependent track, wherein increases in flux are accompanied by a spectral hardening. We seem to be witnessing the onset of an instability in the pre-existing AGN disc and corona, followed by a still-continuing re-emergence of the corona. If the initial transient is identified as the tidal disruption of a star, it is possible that this was the instigator of this unique behavior.

Loewenstein, M.↗
NASA NTRSDate not supplied

Decadal Changes in the Antarctic Sea Ice Response to the Changing ENSO in the Last Four Decades

The Antarctic Dipole (AD) structure, resulting from the Pacific South American pattern triggered by the El Niño-Southern Oscillation (ENSO), leads to a reduction in sea ice over the Ross and Amundsen Sea in the Pacific sector and an increase over the Weddell Sea in the Atlantic sector during El Niño, with the opposite occurring during La Niña. In the initial two decades of the 21st century, there is a notable weakening of the AD pattern compared to the late 20th century. This research provides evidence that the weakened AD pattern and the associated sea ice response are connected to a higher frequency of weaker and central Pacific type ENSO events, on average, in the early 21st century as opposed to the late 20th century.

Young-Kwon Lim↗
DOE OSTI2023

Changing Temperatures, Changing Risks

Imagine what life with dengue fever would be like in the U.S. during the year 2050. You live with your family in Houston, Texas, and enjoy frequent fishing excursions at the nearby nature reserve. On average, days are about 5° Fahrenheit warmer than in the previous decade, and a summer dengue outbreak is underway. The local public health agency recommends using insect repellent, wearing long sleeves and pants, covering strollers with mosquito netting, and installing screens on windows and doors. It also suggests eliminating mosquito habitats near homes by emptying water-holding containers like planters, toys, tires, and trash receptacles.

59 BASIC BIOLOGICAL SCIENCES↗
NASA NTRS2006

Relative Contribution of Greenhouse Gases and Ozone Change to Temperature Trends in the Stratosphere: A Chemistry/Climate Model Study

Long-term changes in greenhouse gases, primarily carbon dioxide, are expected to lead to a warming of the troposphere and a cooling of the stratosphere. We examine the cooling of the stratosphere and compare the contributions greenhouse gases and ozone change for the decades between 1980 and 2000. We use 150 years of simulation done with our coupled chemistry/climate model (GEOS 4 GCM with GSFC CTM chemistry) to calculate temperatures and constituents fiom,1950 through 2100. The contributions of greenhouse gases and ozone to temperature change are separated by a time-series analysis using a linear trend term throughout the period to represent the effects of greenhouse gases and an equivalent effective stratospheric chlorine (EESC) term to represent the effects of ozone change. The temperature changes over the 150 years of the simulation are dominated by the changes in greenhouse gases. Over the relatively short period (approx. 20 years) of ozone decline between 1980 and 2000 changes in ozone are competitive with changes in greenhouse gases. The changes in temperature induced by the ozone change are comparable to, but smaller than, those of greenhouse gases in the upper stratosphere (1-3 hPa) at mid latitudes. The ozone term dominates the temperature change near both poles with a negative temperature change below about 3-5 hPa and a positive change above. At mid latitudes in the upper stratosphere and mesosphere (above about 1 hPa) and in the middle stratosphere (3 to 70 ma), the greenhouse has term dominates. From about 70 hPa down to the tropopause at mid latitudes, cooling due to ozone changes is the largest influence on temperature. Over the 150 years of the simulation, the change in greenhouse gases is the most important contributor to temperature change. Ozone caused a perturbation that is expected to reverse over the coming decades. We show a model simulation of the expected temperature change over the next two decades (2006-2026). The simulation shows a crossover between lower atmospheric heating and upper atmospheric cooling that is located at about 90 hPa in the tropics and 30-40 hPa in the polar regions. This results from the combination of continuing increases in greehouse gases and recovery from ozone depletion.

Stolarski, Richard S.↗