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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 739 records · Page 41
All sourcesNASA NTRSDOE OSTI
DOE OSTI2018

Superlubricity: Friction’s vanishing act

Friction and wear affect almost all moving mechanical systems. By some estimates, nearly a quarter of the world's energy output is spent in overcoming friction.(1) About 70% of equipment failures are in some way attributable to wear and fatigue. Granted, strong friction forces are sometimes needed; brakes, tires, and continuously variable transmissions, for example, couldn't operate without them. But in many cases, alleviating friction would save energy, help the environment, and boost productivity.

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2014

Electron Flow in Multiheme Bacterial Cytochromes is a Balancing Act Between Heme Electronic Interaction and Redox Potentials

The naturally widespread process of electron transfer from metal reducing bacteria to extracellular solid metal oxides entails unique biomolecular machinery optimized for long-range electron transport. To perform this function efficiently microorganisms have adapted multi-heme c-type cytochromes to arrange heme cofactors into wires that cooperatively span the cellular envelope, transmitting electrons along distances greater than 100 Angstroms. Implications and opportunities for bionanotechnological device design are self-evident. However, at the molecular level how these proteins shuttle electrons along their heme wires, navigating intraprotein intersections and interprotein interfaces effciently, remains a mystery so far inaccessible to experiment. To shed light on this critical topic, we carried out extensive computer simulations to calculate Marcus theory quantities for electron transfer along the ten heme cofactors in the recently crystallized outer membrane cytochrome MtrF. The combination of electronic coupling matrix elements with free energy calculations of heme redox potentials and reorganization energies for heme-to-heme electron transfer allows the step-wise and overall electron transfer rate to be estimated and understood in terms of structural and dynamical characteristics of the protein. By solving a master equation for electron hopping, we estimate an intrinsic, maximum possible electron flux through solvated MtrF of 104-105 s-1, consistent with recently measured rates for the related MtrCAB protein complex. Intriguingly, this flux must navigate thermodynamically uphill steps past low potential hemes. Our calculations show that the rapid electron transport through MtrF is the result of a clear correlation between heme redox potential and the strength of electronic coupling along the wire: Thermodynamically uphill steps occur only between electronically well connected stacked heme pairs. This suggests that the protein evolved to harbor low potential hemes, presumably necessary for reduction of certain soluble substrates, without slowing down electron ow. These findings are particularly profound in light of the apparently well conserved staggered cross heme wire structural motif in functionally related outer-membrane proteins.

Environmental Molecular Sciences Laboratory↗
DOE OSTI2016

Cellulose synthase complexes act in a concerted fashion to synthesize highly aggregated cellulose in secondary cell walls of plants

Significance Plant cell walls are important in plant development and for textiles, wood products, and bioenergy. Cellulose, the microfibrillar component of primary cell walls (PCWs) and secondary cell walls (SCWs), is formed by cellulose synthase complexes (CSCs) at the plasma membrane. Here, we show that CSCs behave differently during PCW and SCW synthesis and form microfibrils with different organization. During PCW synthesis, dispersed CSCs synthesize cellulose microfibrils with low aggregation, whereas during SCW synthesis, densely arranged groups of CSCs move coherently to synthesize highly aggregated microfibrils. Our study suggests that controlled alterations in CSC distribution and orchestrated movements contribute to the high density and bundling of cellulose microfibrils in SCWs.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2010

A DOZEN NEW GALAXIES CAUGHT IN THE ACT: GAS STRIPPING AND EXTENDED EMISSION LINE REGIONS IN THE COMA CLUSTER

We present images of extended H{alpha} clouds associated with 14 member galaxies in the Coma cluster obtained from deep narrowband imaging observations with the Suprime-Cam at the Subaru Telescope. The parent galaxies of the extended H{alpha} clouds are distributed farther than 0.2 Mpc from the peak of the X-ray emission of the cluster. Most of the galaxies are bluer than g - r {approx} 0.5 and they account for 57% of the blue (g - r < 0.5) bright (r < 17.8 mag) galaxies in the central region of the Coma cluster. They reside near the red- and blueshifted edges of the radial velocity distribution of Coma cluster member galaxies. Our findings suggest that most of the parent galaxies were recently captured by the Coma cluster potential and are now infalling toward the cluster center with their disk gas being stripped off and producing the observed H{alpha} clouds.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2011

CAUGHT IN THE ACT: STRONG, ACTIVE RAM PRESSURE STRIPPING IN VIRGO CLUSTER SPIRAL NGC 4330

We present a multi-wavelength study of NGC 4330, a highly inclined spiral galaxy in the Virgo Cluster which is a clear example of strong, ongoing intracluster medium-interstellar medium (ICM-ISM) ram pressure stripping. The H I has been removed from well within the undisturbed old stellar disk, to 50%-65% of R{sub 25}. Multi-wavelength data (WIYN BVR-H{alpha}, Very Large Array 21 cm H I and radio continuum, and Galaxy Evolution Explorer NUV and FUV) reveal several one-sided extraplanar features likely caused by ram pressure at an intermediate disk-wind angle. At the leading edge of the interaction, the H{alpha} and dust extinction curve sharply out of the disk in a remarkable and distinctive 'upturn' feature that may be generally useful as a diagnostic indicator of active ram pressure. On the trailing side, the ISM is stretched out in a long tail which contains 10% of the galaxy's total H I emission, 6%-9% of its NUV-FUV emission, but only 2% of the H{alpha}. The centroid of the H I tail is downwind of the UV/H{alpha} tail, suggesting that the ICM wind has shifted most of the ISM downwind over the course of the past 10-300 Myr. Along the major axis, the disk is highly asymmetric in the UV, but more symmetric in H{alpha} and H I, also implying recent changes in the distributions of gas and star formation. The UV-optical colors indicate very different star formation histories for the leading and trailing sides of the galaxy. On the leading side, a strong gradient in the UV-optical colors of the gas-stripped disk suggests that it has taken 200-400 Myr to strip the gas from a radius of >8 to 5 kpc, but on the trailing side there is no age gradient. All our data suggest a scenario in which NGC 4330 is falling into the cluster center for the first time and has experienced a significant increase in ram pressure over the last 200-400 Myr. Many of the UV-bright stars that form outside the thin disk due to ram pressure will ultimately produce stellar thick disk and halo components with characteristic morphologies and age distributions distinct from those produced by gravitational interactions.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2013

A NEW POPULATION OF HIGH-z, DUSTY Ly{alpha} EMITTERS AND BLOBS DISCOVERED BY WISE: FEEDBACK CAUGHT IN THE ACT?

By combining data from the NASA Wide-field Infrared Survey Explorer (WISE) mission with optical spectroscopy from the W. M. Keck telescope, we discover a mid-IR color criterion that yields a 78% success rate in identifying rare, typically radio-quiet, 1.6 {approx}< z {approx}< 4.6 dusty Ly{alpha} emitters (LAEs). Of these, at least 37% have emission extended on scales of 30-100 kpc and are considered Ly{alpha} ''blobs'' (LABs). The objects have a surface density of only {approx}0.1 deg{sup -2}, making them rare enough that they have been largely missed in deep, small area surveys. We measured spectroscopic redshifts for 92 of these galaxies, and find that the LAEs (LABs) have a median redshift of 2.3 (2.5). The WISE photometry coupled with data from Herschel (Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA) reveals that these galaxies are in the Hyper Luminous IR galaxy regime (L{sub IR} {approx}> 10{sup 13}-10{sup 14} L{sub Sun }) and have warm colors. They are typically more luminous and warmer than other dusty, z {approx} 2 populations such as submillimeter-selected galaxies and dust-obscured galaxies. These traits are commonly associated with the dust being illuminated by intense active galactic nucleus activity. We hypothesize that the combination of spatially extended Ly{alpha}, large amounts of warm IR-luminous dust, and rarity (implying a short-lived phase) can be explained if the galaxies are undergoing brief, intense ''feedback'' transforming them from an extreme dusty starburst/QSO into a mature galaxy.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2013

CAUGHT IN THE ACT: THE ASSEMBLY OF MASSIVE CLUSTER GALAXIES AT z = 1.62

We present the recent merger history of massive galaxies in a spectroscopically confirmed proto-cluster at z = 1.62. Using Hubble Space Telescope WFC3 near-infrared imaging from the Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey, we select cluster and z {approx} 1.6 field galaxies with M{sub star} {>=} 3 Multiplication-Sign 10{sup 10} M{sub Sun }, to determine the frequency of double nuclei or close companions within projected separations less than 20 kpc co-moving. We find that four out of five spectroscopically confirmed massive proto-cluster galaxies have double nuclei, and 57 {sup +13}{sub -14}% of all M{sub star} {>=} 3 Multiplication-Sign 10{sup 10} M{sub Sun} cluster candidates are observed in either close pair systems or have double nuclei. In contrast, only 11% {+-} 3% of the field galaxies are observed in close pair/double nuclei systems. After correcting for the contribution from random projections, the implied merger rate per massive galaxy in the proto-cluster is {approx}3-10 times higher than the merger rate of massive field galaxies at z {approx} 1.6. Close pairs in the cluster have minor merger stellar mass ratios (M{sub primary}: M{sub satellite} {>=} 4), while the field pairs consist of both major and minor mergers. At least half of the cluster mergers are gas-poor, as indicated by their red colors and low 24 {mu}m fluxes. Two of the double-nucleated cluster members have X-ray detected active galactic nuclei with L{sub x} > 10{sup 43} erg s{sup -1}, and are strong candidates for dual or offset super-massive black holes. We conclude that the massive z = 1.62 proto-cluster galaxies are undergoing accelerated assembly via minor mergers, and discuss the implications for galaxy evolution in proto-cluster environments.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2015

NUSTAR AND XMM-NEWTON OBSERVATIONS OF THE EXTREME ULTRALUMINOUS X-RAY SOURCE NGC 5907 ULX1: A VANISHING ACT

We present results obtained from two broadband X-ray observations of the extreme ultraluminous X-ray source (ULX) NGC 5907 ULX1, known to have a peak X-ray luminosity of ∼5 × 10{sup 40} erg s{sup –1}. These XMM-Newton and NuSTAR observations, separated by only ∼4 days, revealed an extreme level of short-term flux variability. In the first epoch, NGC 5907 ULX1 was undetected by NuSTAR, and only weakly detected (if at all) with XMM-Newton, while in the second NGC 5907 ULX1 was clearly detected at high luminosity by both missions. This implies an increase in flux of ∼2 orders of magnitude or more during this ∼4 day window. We argue that this is likely due to a rapid rise in the mass accretion rate, rather than to a transition from an extremely obscured to an unobscured state. During the second epoch we observed the broadband 0.3-20.0 keV X-ray luminosity to be (1.55 ± 0.06) × 10{sup 40} erg s{sup –1}, similar to the majority of the archival X-ray observations. The broadband X-ray spectrum obtained from the second epoch is inconsistent with the low/hard accretion state observed in Galactic black hole binaries, but is well modeled with a simple accretion disk model incorporating the effects of photon advection. This strongly suggests that when bright, NGC 5907 ULX1 is a high-Eddington accretor.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2015

A MINOR MERGER CAUGHT IN THE ACT OF FUELING THE ACTIVE GALACTIC NUCLEUS IN Mrk 509

In recent observations by the Hubble Space Telescope (HST) as part of a campaign to discover locations and kinematics of AGN outflows, we found that Mrk 509 contains a 3'' (∼2100 pc) linear filament in its central region. Visible in both optical continuum and [O III] imaging, this feature resembles a ''check mark'' of several knots of emission that travel northwest to southeast before jutting toward the nucleus from the southwest. Space Telescope Imaging Spectrograph (STIS/HST) observations along the inner portion of the filament reveal redshifted velocities, indicating that the filament is inflowing. We present further observations of the nucleus in Mrk 509 using the Gemini Near-Infrared Integral Field Spectrograph, from which we conclude that this structure cannot be related to previously studied, typical narrow line region outflows and instead embodies the remains of an ongoing minor merger with a gas-rich dwarf galaxy, therefore providing a great opportunity to study the fueling of an AGN by a minor merger in progress.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2015

DISCOVERY OF LOW DM FAST RADIO TRANSIENTS: GEMINGA PULSAR CAUGHT IN THE ACT

We report the discovery of several energetic radio bursts at 34 MHz, using the Gauribidanur radio telescope. The radio bursts exhibit two important properties associated with the propagation of astronomical signals through the interstellar medium: (i) frequency dependent dispersive delays across the observing bandwidth and (ii) Faraday rotation of the plane of linear polarization. These bursts sample a range of dispersion measures (DM; 1.4–3.6 pc cm{sup −3}) and show DM-variation at timescales of the order of a minute. Using groups of bursts having a consistent DM, we show that the bursts have originated from the radio-quiet gamma-ray pulsar Geminga. Detection of these bursts supports the existence of occasional radio emission from Geminga. The rare occurrence of these bursts, and the short timescale variation in their DM (if really caused by the intervening medium or the pulsar magnetosphere), might provide clues as to why the pulsar has not been detected in earlier sensitive searches. We present details of the observations and search procedure used to discover these bursts, a detailed analysis of their properties, and evidences of these bursts being associated with Geminga pulsar, and briefly discuss the possible emission mechanism of these bursts.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2013

BLUE STRAGGLER EVOLUTION CAUGHT IN THE ACT IN THE LARGE MAGELLANIC CLOUD GLOBULAR CLUSTER HODGE 11

High-resolution Hubble Space Telescope imaging observations show that the radial distribution of the field-decontaminated sample of 162 'blue straggler' stars (BSs) in the 11.7{sup +0.2}{sub -0.1} Gyr old Large Magellanic Cloud cluster Hodge 11 exhibits a clear bimodality. In combination with their distinct loci in color-magnitude space, this offers new evidence in support of theoretical expectations that suggest different BS formation channels as a function of stellar density. In the cluster's color-magnitude diagram, the BSs in the inner 15'' (roughly corresponding to the cluster's core radius) are located more closely to the theoretical sequence resulting from stellar collisions, while those in the periphery (at radii between 85'' and 100'') are preferentially found in the region expected to contain objects formed through binary mass transfer or coalescence. In addition, the objects' distribution in color-magnitude space provides us with the rare opportunity in an extragalactic environment to quantify the evolution of the cluster's collisionally induced BS population and the likely period that has elapsed since their formation epoch, which we estimate to have occurred {approx}4-5 Gyr ago.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2011

Health Insurance Portability and Accountability Act-Compliant Ocular Telehealth Network for the Remote Diagnosis and Management of Diabetic Retinopathy

In this article, we present the design and implementation of a regional ocular telehealth network for remote assessment and management of diabetic retinopathy (DR), including the design requirements, network topology, protocol design, system work flow, graphics user interfaces, and performance evaluation. The Telemedical Retinal Image Analysis and Diagnosis Network is a computer-aided, image analysis telehealth paradigm for the diagnosis of DR and other retinal diseases using fundus images acquired from primary care end users delivering care to underserved patient populations in the mid-South and southeastern United States.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2025

Seismic imaging of the Ecuadorian forearc and arc from joint ambient noise, local, and teleseismic tomography: catching the Nazca slab in the act of flattening

SUMMARY The Ecuadorian Andes are a complex region characterized by accreted oceanic terranes driven by the ongoing subduction of the oceanic Nazca plate beneath South America. Present-day tectonics in Ecuador are linked to the downgoing plate geometry featuring the subduction of the aseismic, oceanic Carnegie Ridge, which is currently entering the trench. Using seismic tomography, we jointly invert arrival times of P and S waves from local and teleseismic earthquakes with surface wave dispersion curves to image the structure of the forearc and magmatic arc of the Ecuadorian Andes. Our data set includes > 100 000 traveltimes recorded at 294 stations across Ecuador. Our images show the basement of the central forearc is composed of accreted oceanic terranes with high elastic wave speeds. Inboard of the Carnegie Ridge, the westernmost forearc and coastal cordilleras display relatively low Vp and Vs and high Vp/Vs values, which we attribute to the increased hydration and fracturing of the overriding plate due to the subduction of the thick oceanic crust of the Carnegie Ridge. We additionally image across-arc differences in magmatic architecture. The frontal volcanic arc overlies accreted terranes and is characterized by low velocities and high Vp/Vs indicative of partial melt reservoirs which are limited to the upper crust. In contrast, the main arc displays regions of partial melt across a wider range of depths. The Subandean zone of Ecuador has two active volcanoes built on continental crust suggesting the arc is expanding eastwards. The mid to lower crust does not show indications of being modified from the magmatic process. We infer that the slab is in the process of flattening as a consequence of early-stage subduction of the buoyant Carnegie Ridge.

58 GEOSCIENCES↗
DOE OSTI2023

The Efficacy and Safety of an Intra-articular Dual-Acting Antibacterial Agent (TNP-2092) for Implant Infection–Associated Methicillin-Resistant Staphylococcus aureus

Abstract Owing to the presence of microbial biofilm on the implant, the eradication of biofilm-associated infections poses a challenge for antibiotic therapies. The study aimed to investigate the efficacy and safety of the novel antibiotic agent TNP-2092 in the context of implant infections. In vivo, rats with periprosthetic joint infection (PJI) treated with antibiotics showed an increase in body weight and decrease in swelling, temperature, and width of knee, compared with the control group. Meanwhile, inflammatory markers in synovium and serum were decreased in the TNP-2092 group, consistent with the pathological results. Moreover, TNP-2092 was effective in eliminating bacteria and disruption biofilm formation, and further alleviated the abnormal bone absorption and reactive bone changes around the prosthesis. In conclusion, intra-articular injection of TNP-2092 is safe and effective in treating knee PJI in a rat model. The study provides a foundation for the future utilization of TNP-2092 in the management of implant-related infections.

Dai, Tianyu↗