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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 1,405 records · Page 78
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Carbonated apatite lattice parameter variation across incremental growth lines in teeth

Here, results of microbeam mapping (x-ray excited x-ray fluorescence and transmission x-ray diffraction) of Beluga whale cementum and of beaver dentin reveal growth bands are defined by variation in mineral content (carbonated hydroxyapatite, cAp), by variation in Zn content and by variation in cAp lattice parameter a. For both tissues, diffraction and fluorescence data show that Zn signal and a are anti-correlated, that is high Zn signal is co-located with low a, and vice versa. In cementum and bone, treatment with acid removes Ca, Zn and cAp. The data are strong evidence that Zn is incorporated into the cAp lattice in these tissues and that the amount of Zn incorporated varies across two very different types of growth bands, annual bands in Beluga cementum and daily incremental bands in beaver dentin. To the best of the authors’ knowledge, this is the first observation of spatial variation of lattice parameter within growth bands.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Conserved and reproducible bacterial communities associate with extraradical hyphae of arbuscular mycorrhizal fungi

Abstract Extraradical hyphae (ERH) of arbuscular mycorrhizal fungi (AMF) extend from plant roots into the soil environment and interact with soil microbial communities. Evidence of positive and negative interactions between AMF and soil bacteria point to functionally important ERH-associated communities. To characterize communities associated with ERH and test controls on their establishment and composition, we utilized an in-growth core system containing a live soil–sand mixture that allowed manual extraction of ERH for 16S rRNA gene amplicon profiling. Across experiments and soils, consistent enrichment of members of the Betaproteobacteriales, Myxococcales, Fibrobacterales, Cytophagales, Chloroflexales, and Cellvibrionales was observed on ERH samples, while variation among samples from different soils was observed primarily at lower taxonomic ranks. The ERH-associated community was conserved between two fungal species assayed, Glomus versiforme and Rhizophagus irregularis, though R. irregularis exerted a stronger selection and showed greater enrichment for taxa in the Alphaproteobacteria and Gammaproteobacteria. A distinct community established within 14 days of hyphal access to the soil, while temporal patterns of establishment and turnover varied between taxonomic groups. Identification of a conserved ERH-associated community is consistent with the concept of an AMF microbiome and can aid the characterization of facilitative and antagonistic interactions influencing the plant-fungal symbiosis.

59 BASIC BIOLOGICAL SCIENCES↗
NASA NTRS1984

H-beta line variability in magnetic Ap stars. I

Preliminary results of photometric measurements of H-beta in several Ap stars are presented. Periodic variations are found certainly in Theta Aur and Alpha (2) CVn, and possibly in Phi Dra. For the other stars upper limits for variations of H-beta are determined. Observed amplitudes are transformed into variations of equivalent width assuming specific profile variations. The results show that variations of equivalent width of H-beta in the stars investigated are of the order of 10 percent or less.

Madej, J.↗
NASA NTRS1994

Near-global survey of effective droplet radii in liquid water clouds using ISCCP data

A global survey of cloud particle size variations can provide crucial constraints on how cloud processes determine cloud liquid water contents and their variation with temperature, and further, may indicate the magnitude of aerosol effects on clouds. A method, based on a complete radiative transfer model for Advanced Very High Resolution Radiometer (AVHRR)-measured radiances, is described for retrieving cloud particle radii in liquid water clouds from satellite data currently available from the International Satellite Cloud Climatology Project. Results of sensitivity tests and validation studies provide error estimates. AVHRR data from NOAA-9 and NOAA-10 have been analyzed for January, April, July and October in 1987 and 1988. The results of this first survey reveal systematic continental and maritime differences and hemispheric contrasts that are indicative of the effects of associated aerosol concentration differences: cloud droplet radii in continental water clouds are about 2-3 micrometers smaller than in marine clouds, and droplet radii are about 1 micrometer smaller in marine clouds of the Northern Hemisphere than in the Southern Hemisphere. The height dependencies of cloud droplet radii in continental and marine clouds are also consistent with differences in the vertical profiles of aerosol concentration. Significant seasonal and diurnal variations of effective droplet radii are also observed, particularly at lower latitudes. Variations of the relationship between cloud optical thickness and droplet radii may indicate variations in cloud microphysical regimes.

Han, Qingyan↗
NASA NTRS2000

Precision Solar Disk Photometry - A Tool for Understanding Changes in the Sun's Luminosity

The principal scientific aim of this project is to better understand the observed long-term temporal variations in the Sun's luminosity. Satellite observations have revealed that the flux of solar radiation striking the Earth is modulated by the solar magnetic cycle, being approximately 0.1 percent larger during solar maximum. The impact of this irradiance modulation on terrestrial climate is difficult to model. However, the correlation between the Maunder minimum (a period of low solar magnetic activity in the late 1600s) and the 'Little Ice Age' in Europe during the same period does suggest that small changes in the solar luminosity can profoundly affect the Earth's climate.

Source record↗
NASA NTRS2017

Climatic History of the Northeastern United States During the Past 3000 Years

Many ecosystem processes that influence Earth system feedbacks - vegetation growth, water and nutrient cycling, disturbance regimes - are strongly influenced by multidecadal- to millennial-scale climate variations that cannot be directly observed. Paleoclimate records provide information about these variations, forming the basis of our understanding and modeling of them. Fossil pollen records are abundant in the NE US, but cannot simultaneously provide information about paleoclimate and past vegetation in a modeling context because this leads to circular logic. If pollen data are used to constrain past vegetation changes, then the remaining paleoclimate archives in the northeastern US (NE US) are quite limited. Nonetheless, a growing number of diverse reconstructions have been developed but have not yet been examined together. Here we conduct a systematic review, assessment, and comparison of paleotemperature and paleohydrological proxies from the NE US for the last 3000 years. Regional temperature reconstructions (primarily summer) show a long-term cooling trend (1000BCE - 1700CE) consistent with hemispheric-scale reconstructions, while hydroclimate data show gradually wetter conditions through the present day. Multiple proxies suggest that a prolonged, widespread drought occurred between 550 and 750CE. Dry conditions are also evident during the Medieval Climate Anomaly, which was warmer and drier than the Little Ice Age and drier than today. There is some evidence for an acceleration of the longer-term wetting trend in the NE US during the past century; coupled with an abrupt shift from decreasing to increasing temperatures in the past century, these changes could have wide-ranging implications for species distributions, ecosystem dynamics, and extreme weather events. More work is needed to gather paleoclimate data in the NE US to make inter-proxy comparisons and to improve estimates of uncertainty in reconstructions.

Marlon, Jennifer R.↗
DOE OSTI2019

Neptune's Latitudinal Variations as Viewed with ALMA

We present spatially resolved millimeter maps of Neptune between 95 and 242 GHz taken with the Atacama Large Millimeter/submillimeter Array (ALMA) in 2016–2017. The millimeter weighting functions peak between 1 and 10 bar on Neptune, lying in between the altitudes probed at visible/infrared and centimeter wavelengths. Thus, these observations provide important constraints on the atmospheric structure and dynamics of Neptune. We identify seven well-resolved latitudinal bands of discrete brightness temperature variations, on the order of 0.5–3 K in all three observed ALMA spectral bands. We model Neptune’s brightness temperature using the radiative-transfer code Radio-BEAR and compare how various H{sub 2}S, CH{sub 4}, and ortho-/para-H{sub 2} abundance profiles can fit the observed temperature variations across the disk. We find that observed variations in brightness temperature with latitude can be explained by variations in the H{sub 2}S profile that range from sub- to supersaturations at altitudes above the 10 bar pressure level, while variations in CH{sub 4} improve the quality of fit near the equator. At the south polar cap, our best-fit model has a depleted deep atmospheric abundance of H{sub 2}S from 30 to only 1.5 times the protosolar value, while simultaneously depleting the CH{sub 4} abundance. This pattern of enhancement and depletion of condensible species is consistent with a global circulation structure where enriched air rises at the midlatitudes (32°–12°S) and north of the equator (2°–20°N), and dry air descends at the poles (90°–66°S) and just south of the equator (12°S–2°N). Our analysis finds more complex structure near the equator than accounted for in previous circulation models.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS2001

Some Impacts of Solar Irradiance Variation on Terrestrial Climate

As chairman of the Special Session addressing the above topic, a brief overview of the problem will be offered, after which 20-minute talks will be given on the determination of solar irradiance variations from space observations (Dr. Judit Pap) and from groundbased measurements of solar magnetic fields (Dr. Harrison Jones). The chairman will then introduce four panel members representing different areas of expertise bearing on the topic. Each panel member will offer a brief 5-minute summary of his views. Panel members are: Chick Keller, Los Alamos National Laboratory; Drew Shindell, Goddard Institute for Space Science, Columbia University; Michael Schlesinger, University of Illinois; Sabatino Sofia, Yale University. General Circulation Models of the terrestrial atmosphere, the possible impact on this atmosphere of large percentage changes in the solar EUV over a solar cycle, and the role of strong magnetic field in the solar convection zone on irradiance variation will all be considered in brief summaries. The chairman will conclude the session by facilitating a discussion between the audience, the main speakers, and the panel members.

Jordan, Stuart D.↗
NASA NTRS1993

The continuum slope of Mars - Bidirectional reflectance investigations and applications to Olympus Mons

Two primary causes of near-IR continuum slope variations have been observed in an investigation of the bidirectional reflectance characteristics of ferric coatings on the continuum slope of Mars. First, the presence of a thin ferric coating on a dark substrate produces a negative continuum slope due to the wavelength-dependent transparency of the ferric coating. Second, wavelength-dependent directional reflectance occurs when the surface particles are tightly packed, particle sizes are on the order of or smaller than the wavelength of light, or the surface is otherwise smooth on the order of the wavelength of light. Based on these results, the annuli on the flanks of Olympus Mons which are defined by reflectance and continuum slope are consistent with spatial variations in surface texture and possibly with spatial variations in the thickness of a ferric dust coating or rind.

Fischer, Erich M.↗
NASA NTRS2004

MODIS Solar Calibration Simulation Assisted Refinement

A detailed optical radiometric model has been created of the MODIS instruments solar calibration process. This model takes into account the orientation and distance of the spacecraft with respect to the sun, the correlated motions of the scan mirror and the sun, all of the optical elements, the detector locations on the visible and near IR focal planes, the solar diffuser and the attenuation screen with all of its hundreds of pinholes. An efficient computational scheme, takes into account all of these factors and has produced results which reproduce the observed time dependent intensity variations on the two focal planes with considerable fidelity. This agreement between predictions and observations, has given insight to the causes of some small time dependent variations and how to incorporate them into the overall calibration scheme. The radiometric model is described and modeled and actual measurements are presented and compared.

Waluschka, Eugene↗
NASA NTRS1988

Seasonal variation of the semiannual oscillation

Observations of zonally average temperature from the Nimbus-7 Stratospheric and Mesospheric Sounder in 1979-82 show the existence of a significant season variation in the equatorial semiannual oscillation. The first semiannual cycle, beginning in the Northern Hemisphere winter (December-May), is much stronger than the second (June-November) cycle. The balanced winds are calculated from satellite data, showing corresponding seasonality in the semiannual oscillation wind regimes. Strong coupling is observed during the first cycle between equatorial and North Polar temperature. A model of this coupling suggests that planetary Rossby wave momentum deposition in the northern winter is the cause of the seasonal variation in the easterly phase of the semiannual oscillation.

Delisi, Donald P.↗
DOE OSTI2017

Spectroscopic Observation and Analysis of H ii Regions in M33 with MMT: Temperatures and Oxygen Abundances

The spectra of 413 star-forming (or H ii) regions in M33 (NGC 598) were observed using the multifiber spectrograph of Hectospec at the 6.5 m Multiple Mirror Telescope. Using this homogeneous spectra sample, we measured the intensities of emission lines and some physical parameters, such as electron temperatures, electron densities, and metallicities. Oxygen abundances were derived via the direct method (when available) and two empirical strong-line methods, namely, O3N2 and N2. At the high-metallicity end, oxygen abundances derived from the O3N2 calibration were higher than those derived from the N2 index, indicating an inconsistency between O3N2 and N2 calibrations. We present a detailed analysis of the spatial distribution of gas-phase oxygen abundances in M33 and confirm the existence of the axisymmetric global metallicity distribution that is widely assumed in the literature. Local variations were also observed and subsequently associated with spiral structures to provide evidence of radial migration driven by arms. Our O/H gradient fitted out to 1.1 R {sub 25} resulted in slopes of −0.17 ± 0.03, −0.19 ± 0.01, and −0.16 ± 0.17 dex R{sub 25}{sup −1}, utilizing abundances from O3N2, N2 diagnostics, and a direct method, respectively.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2020

Host phylogeny matters: Examining sources of variation in infection risk by blood parasites across a tropical montane bird community in India

Abstract Background Identifying patterns and drivers of infection risk among host communities is crucial to elucidate disease dynamics and predict infectious disease risk in wildlife populations. Blood parasites of the genera Plasmodium and Haemoproteus are a diverse group of vector-borne protozoan parasites that affect bird populations globally. Despite their widespread distribution and exceptional diversity, factors underlying haemosporidian infection risk in wild bird communities remain poorly understood. While some studies have examined variation in avian haemosporidian risk, researchers have primarily focused on host ecological traits without considering host phylogenetic relationships. In this study, we employ a phylogenetically informed approach to examine the association between host ecological traits and haemosporidian infection risk in endemic bird communities in the Western Ghats Sky Islands. Methods We used parasite sequence data based on partial mitochondrial cytochrome b gene, that was amplified from genomic DNA extracted from 1177 birds (28 species) across the Western Ghats to assess infection of birds with haemosporidian parasites. We employed a Bayesian phylogenetic mixed effect modelling approach to test whether haemosporidian infection risk was affected by seven species-specific and four individual-level ecological predictors. We also examined the effect of host phylogenetic relationships on the observed patterns of variation in haemosporidian infection risk by estimating phylogenetic signal. Results Our study shows that host ecological traits and host phylogeny differentially influence infection risk by Plasmodium (generalist parasite) and Haemoproteus (specialist parasite). For Plasmodium , we found that sociality, sexual dimorphism and foraging strata were important ecological predictors. For Haemoproteus , patterns of infection risk among host species were associated with sociality, species elevation and individual body condition. Interestingly, variance in infection risk explained by host phylogeny was higher for Haemoproteus parasites compared to Plasmodium . Conclusions Our study highlights that while host ecological traits promoting parasite exposure and host susceptibility are important determinants of infection risk, host phylogeny also contributes substantially to predicting patterns of haemosporidian infection risk in multi-host communities. Importantly, infection risk is driven by joint contributions of host ecology and host phylogeny and studying these effects together could increase our ability to better understand the drivers of infection risk and predict future disease threats. Graphical abstract

59 BASIC BIOLOGICAL SCIENCES↗
NASA NTRS1993

Controls on the CO2 seasonal cycle

Surface pressure measurement performed by the Viking landers show substantial variations in pressure on seasonal timescales that are characterized by two local minima and two local maxima. These variations have widely been attributed to the seasonal condensation and sublimation of CO2 in the two polar regions. It has been somewhat of a surprise that the amplitude of the minimum and maximum that is dominated by the CO2 cycle in the north was much weaker than the corresponding amplitude of the south-dominated extrema. Another surprise was that the seasonal pressure cycle during years 2 and 3 of the Viking mission was so similar to that for year 1, despite the occurrence of two global dust storms during year 1 and none during years 2 and 3. An energy balance model that incorporates dynamical factors from general circulation model (GCM) runs in which the atmospheric dust opacity and seasonal date were systematically varied was used to model the observed seasonal pressure variations. The energy balance takes account of the following processes in determining the rates of CO2 condensation and sublimation at each longitudinal and latitudinal grid point: solar radiation, infrared radiation from the atmosphere and surface, subsurface heat conduction, and atmospheric heat advection. Condensation rates are calculated both at the surface and in the atmosphere. In addition, the energy balance model also incorporates information from the GCM runs on seasonal redistribution of surface pressure across the globe. Estimates of surface temperature of the seasonal CO2 caps were used to define the infrared radiative losses from the seasonal polar caps. The seasonal pressure variations measured at the Viking lander sites were closely reproduced.

Pollack, J. B.↗
DOE OSTI2020

Further Investigation on Chromospheric and Prominence Activity of the RS Canum Venaticorum Star SZ Piscium

To continue our study on chromospheric activity and detection for possible prominence events of the very active RS Canum Venaticorum star SZ Piscium (SZ Psc), long-term high-resolution spectroscopic observations were obtained during several observing runs from 2014 to 2018. Based on the spectral subtraction technique, the chromospheric emission of the Ca ii IRT (λ8662, λ8542, and λ8498), H{sub α}, Na i D{sub 1}, D{sub 2} doublet, H{sub β}, and Ca ii H & K lines is mainly associated with the K1 IV primary star of the SZ Psc system, in good agreement with the previous studies, and the F8 V secondary star also shows some chromospheric emission, implying its active chromosphere. Moreover, an optical flare characterized by the He i D{sub 3} line emission together with stronger emission in the other indicators was detected. Furthermore, two chromospheric active longitudes around the two quadratures of the system were identified for most of the time, and the chromospheric activity shows significant changes during a few orbital cycles. The chromospheric activity level seems to show a long-term variation during our observations. There were some excess absorption features in the subtracted H{sub α} line and the other activity indicators, which would be caused by prominence-like materials associated with the K1 IV primary star of the system. Prominence materials could absorb the chromospheric emission and continuum from the K1 IV primary star and even the F8 V secondary one.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2024

Hierarchical Conditioning of Diffusion Models Using Tree-of-Life for Studying Species Evolution

A central problem in biology is to understand how organisms evolve and adapt to their environment by acquiring variations in the observable characteristics or traits of species across the tree of life. With the growing availability of large-scale image repositories in biology and recent advances in generative modeling, there is an opportunity to accelerate the discovery of evolutionary traits automatically from images. Toward this goal, we introduce Phylo-Diffusion, a novel framework for conditioning diffusion models with phylogenetic knowledge represented in the form of HIERarchical Embeddings (HIER-Embeds). We also propose two new experiments for perturbing the embedding space of Phylo-Diffusion: trait masking and trait swapping, inspired by counterpart experiments of gene knockout and gene editing/swapping. Our work represents a novel methodological advance in generative modeling to structure the embedding space of diffusion models using tree-based knowledge. Our work also opens a new chapter of research in evolutionary biology by using generative models to visualize evolutionary changes directly from images. We empirically demonstrate the usefulness of Phylo-Diffusion in capturing meaningful trait variations for fishes and birds, revealing novel insights about the biological mechanisms of their evolution. (Model and code can be found at imageomics.github.io/phylo-diffusion)

Khurana, Mridul↗
NASA NTRS1986

Tidal decomposition of zonal neutral and ion flows in the earth's upper equatorial thermosphere

Evidence is presented for strong coupling between the diurnal components of zonal neutral winds and ion drifts, suggesting that the relative importance of the E- and F-region dynamos be reevaluated. Measurements of zonal neutral winds in the equatorial region of the earth's thermosphere at an average altitude of about 350 km show that the nighttime zonal winds are very similar to the zonal ion-drifts. That similarity is examined, comparing the corresponding tidal components of the 24 hr variations of these two parameters. The amplitude spectrum of the neutral winds exhibits primary and secondary maxima at the diurnal and ter-diurnal frequencies respectively, while the ion-drift spectrum shows only the diurnal maximum. It is found that the simularity between neutral winds and ion-drifts is strongest in the diurnal mode where the phases differ by less than one half hour, the amplitude of the ion-drift being between 70 percent and 80 percent that of the neutral wind, suggesting a first-order relation between the two quantities. The largest difference is found in the steady component representing superrotation; under similar conditions of solar activity, the ions superrotate with a velocity of about 30 m/s and the neutrals with 10 m/s. For the ions, the steady component, the phase of the semi-diurnal component and the amplitude of the ter-diurnal component appear to be sensitive to solar activity and are responsible for the observed solar cycle variations in the times of eastward-to-westward reversals between 0400 and 0700 LT. The ion-drift diurnal amplitude and phase are relatively insensitive to changes in solar activity.

Herrero, F. A.↗
NASA NTRS2015

Daily Global Mapping of Mars Ozone Column Abundances with MARCI UV Band Imaging

Since November of 2006, The Mars Color Imager (MARCI) onboard the Mars Reconnaissance Orbiter (MRO) has obtained multiple-filter daily global images of Mars centered upon a local time (LT) of 3 pm. Ultraviolet imaging bands placed within (260 nm) and longward (320 nm) of Hartley band (240-300 nm) ozone (O3) absorption support retrievals of atmospheric ozone columns, with detection limits (approximately 1 micrometer-atm) appropriate to mapping elevated O3 abundances at low latitudes around Mars aphelion, and over mid-to-high latitudes during fall/winter/spring seasons. MARCI O3 maps for these regions reveal the detailed spatial (approximately 1 deg lat/long, for 8 x 8 pixel binned resolution) and temporal (daily, with substantial LT coverage at pole) behaviors of water vapor saturation conditions that force large variations in water vapor photolysis products (HOx-OH, HO2, and H) responsible for the catalytic destruction of O3 in the Mars atmosphere. A detailed description of the MARCI O3 data set, including measurement and retrieval characteristics, is provided in conjunction with comparisons to Mars Express SPICAM ozone measurements (Perrier, S. et al. [2006]. J. Geophys. Res. (Planets) 111) and LMD GCM simulated O3 abundances (Lefevre, F. [2004]. J. Geophys. Res. (Planets) 109). Presented aspects of the MARCI ozone mapping data set include aphelion increases in low latitude O3, dynamically evolving high latitude O3 maxima associated with planetary waves and weather fronts during northern early spring, and distinctive winter/spring O3 and CO increases within the Hellas Basin associated with transport of condensation enhanced south polar air mass. Comparisons of coincident MARCI measurements and LMD simulations for ice cloud and O3 columns are considered in the context of potential heterogeneous photochemical processes (Lefevre, F. [2008]. Nature 454, 971-975), which are not strongly evidenced in the MARCI observations. Modest interannual variations are exhibited, most notably a 20% reduction in aphelion low latitude O3 columns following the 2007 perihelic global dust storm.

Clancy, R. Todd↗