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DOE OSTI2013

GAS MOTION STUDY OF Ly{alpha} EMITTERS AT z {approx} 2 USING FUV AND OPTICAL SPECTRAL LINES {sup ,}

We present the results of Magellan/MMIRS and Keck/NIRSPEC spectroscopy for five Ly{alpha} emitters (LAEs) at z {approx_equal} 2.2 for which high-resolution FUV spectra from Magellan/MagE are available. We detect nebular emission lines including H{alpha} on the individual basis and low-ionization interstellar (LIS) absorption lines in a stacked FUV spectrum, and measure average offset velocities of the Ly{alpha} line, {Delta}v {sub Ly{alpha}}, and LIS absorption lines, {Delta}v {sub abs}, with respect to the systemic velocity defined by the nebular lines. For a sample of eight z {approx} 2-3 LAEs without active galactic nucleus from our study and the literature, we obtain {Delta}v {sub Ly{alpha}} = 175 {+-} 35 km s{sup -1}, which is significantly smaller than that of Lyman-break Galaxies (LBGs), {Delta}v {sub Ly{alpha}} {approx_equal} 400 km s{sup -1}. The stacked FUV spectrum gives {Delta}v {sub abs} = -179 {+-} 73 km s{sup -1}, comparable to that of LBGs. These positive {Delta}v {sub Ly{alpha}} and negative {Delta}v {sub abs} suggest that LAEs also have outflows. In contrast to LBGs, however, the LAEs' {Delta}v {sub Ly{alpha}} is as small as |{Delta}v {sub abs}|, suggesting low neutral hydrogen column densities. Such a low column density with a small number of resonant scattering may cause the observed strong Ly{alpha} emission of LAEs. We find an anti-correlation between Ly{alpha} equivalent width (EW) and {Delta}v {sub Ly{alpha}} in a compilation of LAE and LBG samples. Although its physical origin is not clear, this anti-correlation result appears to challenge the hypothesis that a strong outflow, by means of a reduced number of resonant scattering, produces a large EW. If LAEs at z > 6 have similarly small {Delta}v {sub Ly{alpha}} values, constraints on the reionization history derived from the Ly{alpha} transmissivity may need to be revised.

79 ASTRONOMY AND ASTROPHYSICS↗

DOE OSTI2013

CAN WE REPRODUCE THE X-RAY BACKGROUND SPECTRAL SHAPE USING LOCAL ACTIVE GALACTIC NUCLEI?

The X-ray background (XRB) is due to the aggregate of active galactic nuclei (AGNs), which peak in activity at z {approx} 1 and is often modeled as the sum of different proportions of unabsorbed, moderately, and heavily absorbed AGN. We present the summed spectrum of a complete sample of local AGN (the Northern Galactic Cap of the 58 month Swift/BAT catalog, z < 0.2) using 0.4-200 keV data and directly determine the different proportions of unabsorbed, moderately and heavily absorbed AGN that make up the summed spectrum. This stacked low redshift AGN spectrum is remarkably similar in shape to the XRB spectrum (when shifted to z {approx} 1), but the observed proportions of different absorption populations differ from most XRB synthesis models. AGN with Compton-thick absorption account for only {approx}12% of the sample, but produce a significant contribution to the overall spectrum. We confirm that Compton reflection is more prominent in moderately absorbed AGN and that the photon index differs intrinsically between unabsorbed and absorbed AGN. The AGN in our sample account for only {approx}1% of the XRB intensity. The reproduction of the XRB spectral shape suggests that strong evolution in individual AGN properties is not required between z {approx} 0 and 1.

79 ASTRONOMY AND ASTROPHYSICS↗

DOE OSTI2016

Measurements of structures and concentrations of carbon particle species in premixed flames by the use of in-situ wide angle X-ray scattering

In-situ wide-angle X-ray scattering (WAXS) measurements have been conducted on atmospheric-pressure fuel-rich premixed freely propagating ethylene/oxygen flames with argon and nitrogen dilution. In this work, a novel analysis methodology able to provide quantitative information on soot/carbon particle species and concentrations was tested under heavy sooting conditions. The particle composition and concentrations were retrieved by fitting theoretical calculations of structural components from major molecular and nanometric species to the experimental WAXS data. The results show that argon dilution yields predominantly graphenelike components that are less stacked and amorphous carbon that is less structured than under nitrogen dilution. This finding was later confirmed by electron microscopy analysis on samples extracted from similar flames. In addition, the WAXS showed that most of the carbon present in the flames was bound as particles. These results constitute some of the first in-situ observations on structures and concentrations of carbon species in laboratory burner flames operating without stabilization plates.

Concentrations↗

DOE OSTI2018

The shape recovery conditions for Fe–Mn–Si alloys: An interplay between martensitic transformation and plasticity

Highlights: • Fe15Mn5Si9Cr5Ni samples were rolled at 800 °C and annealed at 650 (C1) and 1000 °C (C2). • TEM analysis was performed. • High density of stacking faults and appropriate density of dislocation appears in C1. • Complex dislocation arrays due to plastic deformation are observed in C2. • Shape memory properties depend on the thermomechanical treatment. - Abstract: This work analyses the improvement of the shape memory properties of Fe-Mn-Si based alloys, and expands upon and deepens recently published developments concerning this topic. We prepared TEM specimens from a Fe-15Mn-5Si-9Cr-5Ni sheet rolled at 800 °C and annealed at 650 °C–92% shape recovery – and from another sheet annealed at 1000 °C–45% shape recovery. Here, we analyse the development of microstructure during the γ ↔ ε martensitic transformation and correlate it with the shape memory behaviour. Among the observed microstructural features, the introduction of complex dislocation arrays due to plastic deformation appears to be critical for shape memory development, since they can arrest the backward movement of Shockley partial dislocations over the original path. Tailoring the microstructure in order to introduce a high stacking-fault density accompanied by an appropriate dislocation density remains a key issue in the design of these kinds of functional materials.

36 MATERIALS SCIENCE↗

DOE OSTI2022

Non-Gaussianity of optical emission lines in SDSS star-forming galaxies and its implications on galactic outflows

The shape of emission lines in the optical spectra of star-forming galaxies reveals the kinematics of the diffuse gaseous component. We analyse the shape of prominent emission lines in a sample of ~ 53000 star-forming galaxies from the Sloan Digital Sky Survey, focusing on departures from gaussianity. Departures from a single gaussian profile allow us to probe the motion of gas and to assess the role of outflows. The sample is divided into groups according to their stellar velocity dispersion and star formation rate (SFR). The spectra within each group are stacked to improve the signal-to-noise ratio of the emission lines, to remove individual signatures, and to enhance the effect of SFR on the shapes of the emission lines. The moments of the emission lines, including kurtosis and skewness, are determined. We find that most of the emission lines in strong star-forming systems unequivocally feature negative kurtosis. This signature is present in Hβ, Hα, [N ii], and [S ii] in massive galaxies with high SFRs. We attribute it as evidence of radial outflows of ionised gas driven by the star formation of the galaxies. Also, most of the emission lines in low-mass systems with high SFRs feature negative skewness, and we interpret it as evidence of dust obscuration in the galactic disk. These signatures are however absent in the [O iii] line, which is believed to trace a different gas component. The observed trend is significantly stronger in face-on galaxies, indicating that star formation drives the outflows along the galactic rotation axis, presumably the path of least resistance. The data suggest that outflows driven by star formation exert accumulated impacts on the interstellar medium, and the outflow signature is more evident in older galaxies as they have experienced a longer total duration of star formation.

79 ASTRONOMY AND ASTROPHYSICS↗

DOE OSTI2014

Plasma-beam traps and radiofrequency quadrupole beam coolers

Two linear trap devices for particle beam manipulation (including emittance reduction, cooling, control of instabilities, dust dynamics, and non-neutral plasmas) are here presented, namely, a radiofrequency quadrupole (RFQ) beam cooler and a compact Penning trap with a dust injector. Both beam dynamics studies by means of dedicated codes including the interaction of the ions with a buffer gas (up to 3 Pa pressure), and the electromagnetic design of the RFQ beam cooler are reported. The compact multipurpose Penning trap is aimed to the study of multispecies charged particle samples, primarily electron beams interacting with a background gas and/or a micrometric dust contaminant. Using a 0.9 T solenoid and an electrode stack where both static and RF electric fields can be applied, both beam transport and confinement operations will be available. The design of the apparatus is presented.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗

DOE OSTI2014

Star formation rate and extinction in faint z ∼ 4 Lyman break galaxies

We present a statistical detection of 1.5 GHz radio continuum emission from a sample of faint z ∼ 4 Lyman break galaxies (LBGs). To constrain their extinction and intrinsic star formation rate (SFR), we combine the latest ultradeep Very Large Array 1.5 GHz radio image and the Hubble Space Telescope Advanced Camera for Surveys (ACS) optical images in the GOODS-N. We select a large sample of 1771 z ∼ 4 LBGs from the ACS catalog using B {sub F435W}-dropout color criteria. Our LBG samples have I {sub F775W} ∼ 25-28 (AB), ∼0-3 mag fainter than M{sub UV}{sup ⋆} at z ∼ 4. In our stacked radio images, we find the LBGs to be point-like under our 2'' angular resolution. We measure their mean 1.5 GHz flux by stacking the measurements on the individual objects. We achieve a statistical detection of S {sub 1.5} {sub GHz} = 0.210 ± 0.075 μJy at ∼3σ for the first time on such a faint LBG population at z ∼ 4. The measurement takes into account the effects of source size and blending of multiple objects. The detection is visually confirmed by stacking the radio images of the LBGs, and the uncertainty is quantified with Monte Carlo simulations on the radio image. The stacked radio flux corresponds to an obscured SFR of 16.0 ± 5.7 M {sub ☉} yr{sup –1}, and implies a rest-frame UV extinction correction factor of 3.8. This extinction correction is in excellent agreement with that derived from the observed UV continuum spectral slope, using the local calibration of Meurer et al. This result supports the use of the local calibration on high-redshift LBGs to derive the extinction correction and SFR, and also disfavors a steep reddening curve such as that of the Small Magellanic Cloud.

79 ASTRONOMY AND ASTROPHYSICS↗

DOE OSTI2015

The massive survey. II. Stellar population trends out to large radius in massive early-type galaxies

We examine stellar population gradients in ∼100 massive early-type galaxies spanning 180<σ{sub ∗}<370 km s{sup −1} and M{sub K} of −22.5 to −26.5 mag, observed as part of the MASSIVE survey. Using integral-field spectroscopy from the Mitchell Spectrograph on the 2.7 m telescope at McDonald Observatory, we create stacked spectra as a function of radius for galaxies binned by their stellar velocity dispersion, stellar mass, and group richness. With excellent sampling at the highest stellar mass, we examine radial trends in stellar population properties extending to beyond twice the effective radius (∼2.5 R{sub e}). Specifically, we examine trends in age, metallicity, and abundance ratios of Mg, C, N, and Ca, and discuss the implications for star formation histories and elemental yields. At a fixed physical radius of 3–6 kpc (the likely size of the galaxy cores formed at high redshift), stellar age and [α/Fe] increase with increasing σ{sub ∗} and depend only weakly on stellar mass, as we might expect if denser galaxies form their central cores earlier and faster. If we instead focus on 1−1.5 R{sub e}, the trends in abundance and abundance ratio are washed out, as might be expected if the stars at large radius were accreted by smaller galaxies. Finally, we show that when controlling for σ{sub ∗}, there are only very subtle differences in stellar population properties or gradients as a function of group richness; even at large radius, internal properties matter more than environment in determining star formation history.

79 ASTRONOMY AND ASTROPHYSICS↗

DOE OSTI2022

The ultraviolet upturn in field luminous red galaxies at 0.3 < z < 0.7

ABSTRACT We derive the evolution of the ultraviolet upturn colour from a sample of field luminous red galaxies at 0.3 < z < 0.7 with −24 < Mr < −21.5. No individual objects are securely detected, so we stack several hundred galaxies within absolute magnitude and redshift intervals. We find that the colour of the ultraviolet upturn (in observed NUV − i which is approximately equivalent to the classical FUV − V at the redshifts of our targets) does not change strongly with redshift to z = 0.7. This behaviour is similar to that observed in cluster ellipticals over this same mass range and at similar redshifts, and we speculate that the processes involved in the origin of the UV upturn are the same. The observations are most consistent with spectral synthesis models containing a fraction of a helium rich stellar population with abundances between 37 per cent and 42 per cent, although we cannot formally exclude a contribution due to residual star formation at the $\sim 0.5\, \mathrm{ per\,cent}$ level (however, this appears unlikely for cluster galaxies that are believed to be more quenched). This suggests that the ultraviolet upturn is a primordial characteristic of early-type galaxies at all redshifts and that an unexpected nucleosynthesis channel may lead to nearly complete chemical evolution at early times.

79 ASTRONOMY AND ASTROPHYSICS↗

DOE OSTI2026

Unraveling design principles of protein landscapes in photosynthetic membranes in plant chloroplasts

The supramolecular organization of proteins within photosynthetic membranes is crucial for energy conversion in plants. Here, we introduce an analytical and computational pipeline that integrates high-resolution cryo–scanning electron microscopy, biochemical quantification, advanced Monte Carlo computer simulations, and statistical methods to elucidate the elusive protein landscapes of grana membranes in intact Arabidopsis leaves. Our integrated analysis challenges the prevailing view that particles on the exoplasmic fracture faces in freeze-fracture samples represent photosystem II exclusively. Instead, these particles also include cytochrome b 6 f complexes. Furthermore, our steric clash analysis demonstrates that stacked membranes contain a mixture of larger PSII supercomplexes (C 2 S 2 M 2 and C 2 S 2 ) in addition to a smaller complex (C 2 ). This suggests that in vivo PSII supercomplexes exist in an equilibrium distribution of differing sizes. Furthermore, we discovered that, although size exclusion effects govern the global protein arrangement, local packing exhibits orientational order indicative of lateral attractive protein-protein interactions.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2013

Barriers to Developing Sustainable Supply of Lignocellulosic Feedstock for Production of Biofuels

Thirteen unique storage conditions of baled corn stover biomass were studied to examine the impact of bale type, baling technique, and storage practice on moisture control and product degradation over time. Square bales were found to outperform round bales in terms of moisture regulation and physical stability across all treatment types and at all sampling times. Within square bales, the control of moisture content in short term storage (3 months) is comparable between tarped and untarped stacks. In long term storage (9 months), bale wrapping outperforms both tarped and open stacks. In terms of overall moisture control, stack tarping allows moisture to leave initially wet bales, but allows dry bales to gain large amounts of moisture over time. Initial moisture content was found to drive self-heating and depend heavily on storage practice. While differences in dry matter loss over time are unclear, bale stability was lowest in the untarped stack, moderate in tarped stacks, and greatest in wrapped stacks. Overall, bale storage has been shown to be a dynamic system which requires special judgment to be made depending on the state of inbound material and the desired storage duration.

Feedstock↗

DOE OSTI2016

Stellar populations of early-type galaxies with mid-infrared excess emission

We present a stellar population analysis of quiescent (without Hα emission) and bright (M{sub r} < −21.5) early-type galaxies (ETGs) with recent star formation. The ETGs are selected from a spectroscopic sample of SDSS galaxies at 0.04 < z < 0.11 with WISE mid-infrared (IR) and GALEX near-ultraviolet (UV) emissions. We stack the optical spectra of ETGs with different amounts of mid-IR and near-UV excess emissions to measure the strength of 4000 Å break D{sub n}4000 and the width of Balmer absorption line Hδ{sub A} that are indicative of recent (∼1 Gyr) star formation activity. The WISE [3.4]–[12] colors show stronger correlations with the spectral features than NUV–r colors. We fit to the stacked spectra with a spectral fitting code, STARLIGHT, and find that the mass fraction of young (⩽1 Gyr) and intermediate-age (∼1–5 Gyr) stars in the ETGs with mid-IR excess emission is ∼4%–11%, depending on the template spectrum used for the fit. These results show that the ETGs with mid-IR excess emission have experienced star formation within the last 1–5 Gyr and that the mid-IR emission is a useful diagnostic tool for probing recent star formation activity in ETGs.

79 ASTRONOMY AND ASTROPHYSICS↗

DOE OSTI2022

Aerodynamic diameter particle size distributions for the AGINSGP experiment

Aerodynamic size distributions were collected by the APS 3321 (TSI Inc.) in the guest instrument facility at ARM’s Southern Great Plains site, during the AGINSGP field campaign. The APS accelerates particle through an orifice and uses two overlapping laser beams to measure the time-of-flights for particles. The aerodynamic diameter controls how quickly a particle will accelerate, with larger particles accelerating more slowly due to their greater inertia. The APS measures particle size distributions from 0.542 to 19.81 µm. Size distributions are averaged to their 1 minute averages. Air was drawn into the GIF through custom aluminum stack inlets (6” inner diameter) attached vertically to the outer GIF wall and the GIF outside platform. A blower pulled air through the stacks at a velocity of 1 m/s. Aerosol instruments subsampled via wall ports, through either 3/8” or 1/4" copper lines, depending on sample flow of the instrument.

54 ENVIRONMENTAL SCIENCES↗

DOE OSTI2022

Ice nucleating particle concentrations measured by the PNNL-CFDC during the AGINSGP field experiment

54 ENVIRONMENTAL SCIENCES↗

DOE OSTI2022

Ice nucleating particle concentrations measured by the CSU-CFDC during the AGINSGP field experiment

Real-time, immersion mode ambient ice nucleating particle (INP) concentrations were measured at ARM’s Southern Great Plains (SGP) site during the AGINSGP field experiment using a continuous flow diffusion chamber (CFDC) from Colorado State University (CSU). The CSU-CFDC is an ice-thermal gradient diffusion chamber that optically detects the freezing of single aerosol particles (Rogers 1988; Rogers et al. 2001; and Eidhammer et al. 2010). The instrument was located in the guest instrument facility (GIF) and measured INP concentrations from April 8th to April 29th. Air was drawn into the GIF through custom aluminum stack inlets (6” inner diameter) attached vertically to the outer GIF wall and the GIF outside platform. A blower pulled air through the stacks at a velocity of 1 m/s. Aerosol instruments subsampled via wall ports, through either 3/8” or 1/4" copper lines, depending on sample flow of the instrument. Rogers, D. C., Development of a continuous flow thermal gradient diffusion chamber for ice nucleation studies, Atmospheric Research, 22(2), 149-181, doi:10.1016/0169-8095(88)90005-1, 1988. Rogers, D. C., P. J. DeMott, S. M. Kreidenweis and Y. Chen, A continuous flow diffusion chamber for airborne measurements of ice nuclei, J. Atmos. Oceanic Technol., 18, 725-741, doi:10.1175/1520-0426(2001)018<0725:ACFDCF>2.0.CO;2, 2001. Eidhammer, T., DeMott, P. J., Prenni, A. J., Petters, M. D., Twohy, C. H., Rogers, D. C., Stith, J., Heymsfield, A., Wang, Z., Haimov, S., French, J., Pratt, K., Prather, K., Murphy, S., Seinfeld, J., Subramanian, R., and Kreidenweis, S. M., Ice initiation by aerosol particles: Measured and predicted ice nuclei concentrations versus measured ice crystal concentrations in an orographic wave cloud, J. Atmos. Sci., 67, 2417-2436, doi:10.1175/2010JAS3266.1, 2010

54 ENVIRONMENTAL SCIENCES↗

DOE OSTI2023

Fluorescent bioaerosol particle concentrations measured by the DU WIBS during the AGINSGP field experiment

Real-time, immersion mode ambient fluorescent bioaerosol concentrations were measured at ARM’s Southern Great Plains (SGP) site during the AGINSGP field experiment using a Wideband Integrated Bioaerosol Sensor (DMT Inc.; WIBS-4A). The WIBS-4A is an optical particle counter that also measures single particle fluorescence in three channels, along with particle asymmetry. Particles are grouped into different types depending on which channels they fluoresce in. The instrument was located in the guest instrument facility (GIF) and measured fluorescent particle concentrations from April 7th to April 29th. Data presented here are the concentrations for each particle type, binned in 5 minute increments. Air was drawn into the GIF through custom aluminum stack inlets (6” inner diameter) attached vertically to the outer GIF wall and the GIF outside platform. A blower pulled air through the stacks at a velocity of 1 m/s. Aerosol instruments subsampled via wall ports, through either 3/8” or 1/4" copper lines, depending on sample flow of the instrument. Particles were dried using a silica diffusion dryer prior to analysis.

54 ENVIRONMENTAL SCIENCES↗

DOE OSTI2018

Preparation and characterization of microwave absorbing composite materials with GSs or FeCo/GS composites

Highlights: • It is found that adding GSs or FeCo/GSs composite into the sample SiC/NR can greatly increase RL and the absorbing peak shifts to low-frequency with increasing the adding amount. • The optimum adding amount of GSs is 2%. The sample GS-200-2% possesses the lowest RL value of −31.27 dB at 7.6 GHz. • The optimum adding amount of FeCo/GSs composite is 3%. The sample AGS-450-3% possesses the lowest RL value of −20.67 dB at 7.8 GHz. - Abstract: This study mainly explored the synthesis method of graphene sheets (GSs) and FeCo/graphene sheet (FeCo/GS) composites and evaluated the microwave absorbing characteristics of composite materials containing GSs or FeCo/GS composites. First, graphite oxide (GO) was synthesized by the modified Hummers method. The synthesized GO was further used to synthesize GSs and FeCo/GS composites. Afterward, GSs or FeCo/GS composites were mixed with silicon carbide (SiC) and natural rubber (NR) to prepare microwave absorbing materials with thicknesses of 2 mm. Finally, identification and characterization of these samples were performed by XRD, FE-SEM, TEM, TGA, ESCA, RS, AFM and VNA. GSs were synthesized successfully at a low annealing temperature of 200 °C, and their thicknesses were between 0.848 nm and 2.115 nm, which corresponds to 2–6 stacked layers of graphene. FeCo/GS composites were also synthesized successfully at three different annealing temperatures. The nanoparticles of metals and metal oxides were well-dispersed on the surfaces of and the spaces between GSs. It was found that adding GSs or FeCo/GS composites into the SiC/NR sample can greatly increase reflection loss (RL) and that the absorbing peak shifts to lower frequencies as the concentration of added particles increases. The optimum concentration of added GSs was 2 wt.%. The GS-200-2% sample possessed the lowest RL value of −31.27 dB at 7.6 GHz. The optimum concentration of added FeCo/GS composites was 3 wt.%. The AGS-450-3% sample possessed the lowest RL value of −20.67 dB at 7.8 GHz.

36 MATERIALS SCIENCE↗

DOE OSTI2018

Direct observations of crystal defects in polycrystalline diamond

Highlights: • Electron channeling contrast imaging of crystal defects in polycrystalline diamond • Introducing acid etching as a novel protocol for diamond surface preparation • Characterization of {111} twins, {111} stacking faults and {111} helical dislocations in diamond using ECCI and EBSD - Abstract: Crystal defects are abundant in synthetic diamond produced by chemical vapor deposition (CVD). We present the first images of crystal defects in a bulk polycrystalline CVD diamond sample using general electron channeling contrast imaging (ECCI) in a field emission scanning electron microscope (FE-SEM). For enhancement of channeling contrast of this material, we introduce a novel protocol for diamond surface preparation that involves acid etching. Using this protocol, we imaged three types of crystal defects including twins, stacking faults and dislocations. Each defect was identified based on its appearance in electron channeling contrast (ECC) micrographs. We analyzed grains containing twins and dislocations using electron backscatter diffraction (EBSD) crystal orientation mapping. We found a large population of grains that contained Σ3 type twins on {111} planes with a 60°<111> angle–axis pair of misorientation for twin boundaries. In addition, we identified {111} stacking faults and {111} helical dislocations. These observations are in agreement with reports of crystal defects in CVD diamond thin foils studied by a transmission electron microscope (TEM).

36 MATERIALS SCIENCE↗