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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 433 records · Page 24
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DOE OSTI2016

Planck 2015 results: XXIII. The thermal Sunyaev-Zeldovich effect-cosmic infrared background correlation

In this paper, we use Planck data to detect the cross-correlation between the thermal Sunyaev-Zeldovich (tSZ) effect and the infrared emission from the galaxies that make up the the cosmic infrared background (CIB). We first perform a stacking analysis towards Planck-confirmed galaxy clusters. We detect infrared emission produced by dusty galaxies inside these clusters and demonstrate that the infrared emission is about 50% more extended than the tSZ effect. Modelling the emission with a Navarro-Frenk-White profile, we find that the radial profile concentration parameter is c 500 = 1.00 +0.18 -0.15 . This indicates that infrared galaxies in the outskirts of clusters have higher infrared flux than cluster-core galaxies. We also study the cross-correlation between tSZ and CIB anisotropies, following three alternative approaches based on power spectrum analyses: (i) using a catalogue of confirmed clusters detected in Planck data; (ii) using an all-sky tSZ map built from Planck frequency maps; and (iii) using cross-spectra between Planck frequency maps. With the three different methods, we detect the tSZ-CIB cross-power spectrum at significance levels of (i) 6σ; (ii) 3σ; and (iii) 4σ. We model the tSZ-CIB cross-correlation signature and compare predictions with the measurements. The amplitude of the cross-correlation relative to the fiducial model is A tSZ-CIB = 1.2 ± 0.3. Finally, this result is consistent with predictions for the tSZ-CIB cross-correlation assuming the best-fit cosmological model from Planck 2015 results along with the tSZ and CIB scaling relations.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2016

Comment on “Early stage time evolution of a dense nanosecond microdischarge used in fast optical switching applications” [Phys. Plasmas 22, 123518 (2015)]

In an effort to understand the opaque nature of high-voltage nanosecond microdischarges and their ability to block 532 nm nanosecond laser pulses, as demonstrated by Bataller et al. [Appl. Phys. Lett. 105, 223501 (2014)], Levko and Raja have published a paper [Phys. Plasmas 22, 123518 (2015)] which simulates spark discharges in 1 bar of xenon gas. At this ambient pressure, Levko and Raja simulate final electron densities much too low to explain the observed opacity and conclude the probing laser generates the requisite ionization for self-blocking. However, the experimental findings of Bataller et al. showed opacity being reached at 10 bar, an order of magnitude larger than the pressure simulated by Levko and Raja. Furthermore, Bataller et al. showed the spark remained opaque for very low laser intensities, insufficient to cause any significant ionization. Although the simulation performed by Levko and Raja could have merit at 1 bar, it is not an appropriate comparison to the regime studied by Bataller et al.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2016

Phase Transition Enthalpy Measurements of Organic and Organometallic Compounds. Sublimation, Vaporization and Fusion Enthalpies From 1880 to 2015. Part 1. C{sub 1} − C{sub 10}

A compendium of phase change enthalpies published in 2010 is updated to include the period 1880–2015. Phase change enthalpies including fusion, vaporization, and sublimation enthalpies are included for organic, organometallic, and a few inorganic compounds. Part 1 of this compendium includes organic compounds from C{sub 1} to C{sub 10}. Part 2 of this compendium, to be published separately, will include organic and organometallic compounds from C{sub 11} to C{sub 192}. Sufficient data are presently available to permit thermodynamic cycles to be constructed as an independent means of evaluating the reliability of the data. Temperature adjustments of phase change enthalpies from the temperature of measurement to the standard reference temperature, T = 298.15 K, and a protocol for doing so are briefly discussed.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2016

Comment on “Existence domains of slow and fast ion-acoustic solitons in two-ion space plasmas” [Phys. Plasmas 22, 032313 (2015)]

In a series of papers by Maharaj et al., including “Existence domains of slow and fast ion-acoustic solitons in two-ion space plasmas” [Phys. Plasmas 22, 032313 (2015)], incorrect expressions for the Sagdeev potential are presented. In this paper, we provide the correct expression of the Sagdeev potential. The correct expression was used to generate the numerical results for the above-mentioned series of papers, so that all results and conclusions are correct, despite the wrong Sagdeev potential expressions printed in the papers. The correct expression of the Sagdeev potential presented here is a very useful generic expression in the sense that a single expression can be used to study nonlinear structures associated with any acoustic mode, despite the fact that the supersonic and subsonic species would vary if solitons associated with different linear modes are studied.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2016

Richard Freeman Post (14 November 1918–7 April 2015)

Richard Freeman Post, a member of the Nuclear Fusion Board of Editors in 1976 and again in the 1990s, passed away April 7, 2015 [1]. He was 96. Dick Post initiated magnetic mirror research in the US and served as Deputy Associate Director for Magnetic Fusion Energy at the Lawrence Livermore National Laboratory. Dick contributed three seminal ideas— yin-yang mirrors, high current neutral beams and a way to stabilize mirror plasmas—that culminated in the first demonstration of a plasma at thermonuclear temperatures, in the 2XIIB experiment in 1976. He also invented a method for direct conversion of plasma energy to electricity as a way to improve the efficiency of mirror fusion reactors. His review papers published in 1956 in Reviews of Modern Physics and in 1959 in Annual Review of Nuclear Science were among the first consistent reviews of hot plasmas for controlled fusion. These influential papers were immediately translated into Russian and published in Russia; the 1959 paper as a separate book. In 1987, Dick published a comprehensive review of mirror research that filled the whole October issue of Nuclear Fusion [2]. Dick also pioneered research on high-speed flywheel energy storage employing novel magnetic bearings that presaged a new approach to magnetically levitated trains. He remained actively engaged in mirror research and in early 2000 came up with an idea of a 'kinetic stabilizer' for axisymmetric tandem mirrors.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2015

The morphology of the Anomalous Microwave Emission in the Planck 2015 data release

We calculate weighted mosaic correlations between the recently published Planck 2015 foreground maps— both anomalous microwave emission (AME) maps, free-free emission, synchrotron radiation and thermal dust emission. The weighting coefficients are constructed taking account of the signal-to-error ratio given by the data product. Positive correlation is found for AME compared with thermal dust emission as well as synchrotron radiation. We find AME and free-free emission tending to be anti-correlated, however, when investigating different scales, their relationship appears to be more complex. We argue that dust particles responsible for AME are pushed out of hot zones in the interstellar medium (ISM)

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2015

Distance priors from Planck 2015 data

We update the distance priors by adopting Planck TT,TE,EE+lowP data released in 2015, and our results impose at least 30% tighter constraints than those from Planck TT+lowP. Combining the distance priors with the combination of supernova Union 2.1 compilation of 580 SNe (Union 2.1) and low redshift Baryon Acoustic Oscillation (BAO) data, we constrain the cosmological parameters in the freely binned dark energy (FBDE) and FBDE+Ω{sub k} models respectively, and find that the equations of state of dark energy in both models are consistent with w=−1. Furthermore, we show that the tension with the BAO data at z=2.34 from Lyα forest (LyαF) auto-correlation and Combined LyαF cannot be relaxed in the FBDE and FBDE+Ω{sub k} models.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2016

The present and future of the most favoured inflationary models after Planck 2015

The value of the tensor-to-scalar ratio r in the region allowed by the latest Planck 2015 measurements can be associated to a large variety of inflationary models. We discuss here the potential of future Cosmic Microwave Background cosmological observations in disentangling among the possible theoretical scenarios allowed by our analyses of current Planck temperature and polarization data. Rather than focusing only on r, we focus as well on the running of the primordial power spectrum, α{sub s} and the running thereof, β{sub s}. If future cosmological measurements, as those from the COrE mission, confirm the current best-fit value for β{sub s} ∼> 10{sup −2} as the preferred one, it will be possible to rule-out the most favoured inflationary models.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2016

DBI Galileon inflation in the light of Planck 2015

In this work we consider a DBI Galileon (DBIG) inflationary model and constrain its parameter space with the Planck 2015 and BICEP2/Keck array and Planck (BKP) joint analysis data by means of a potential independent analysis. We focus our attention on inflationary solutions characterized by a constant or varying sound speed as well as warp factor. We impose bounds on stringy aspects of the model, such as the warp factor (f) and the induced gravity parameter ( m-tilde ). We study the parameter space of the model and find that the tensor-to-scalar ratio can be as low as r ≅ 6 × 10{sup −4} and inflation happens to be at GUT scale. In addition, we obtain the tilt of the tensor power spectrum and test the standard inflationary consistency relation (r = −8n{sub t}) against the latest bounds from the combined results of BKP+Laser Interferometer Gravitational-Waves Observatory (LIGO), and find that DBIG inflation predicts a red spectral index for the tensor power spectrum.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2016

Inflationary spectra with inverse-volume corrections in loop quantum cosmology and their observational constraints from Planck 2015 data

We first derive the primordial power spectra, spectral indices and runnings of both scalar and tensor perturbations of a flat inflationary universe to the second-order approximations of the slow-roll parameters, in the framework of loop quantum cosmology with the inverse-volume quantum corrections. This represents an extension of our previous work in which the parameter σ was assumed to be an integer, where σ characterizes the quantum corrections and in general can take any of values from the range σ element of (0, 6]. Restricting to the first-order approximations of the slow-roll parameters, we find corrections to the results obtained previously in the literature, and point out the causes for such errors. To our best knowledge, these represent the most accurate calculations of scalar and tensor perturbations given so far in the literature. Then, fitting the perturbations to the recently released data by Planck (2015), we obtain the most severe constraints for various values of σ. Using these constraints as our referring point, we discuss whether these quantum gravitational corrections can lead to measurable signatures in the future cosmological observations. We show that, depending on the value of σ, the scale-dependent contributions to the relativistic inflationary spectra due to the inverse-volume corrections could be well within the range of the detectability of the forthcoming generations of experiments, such as the Stage IV experiments.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2016

Revisit of the interacting holographic dark energy model after Planck 2015

We investigate the observational constraints on the interacting holographic dark energy model. We consider five typical interacting models with the interaction terms Q = 3β H ρ{sub de}, Q = 3β H ρ{sub c}, Q = 3β H (ρ{sub de}+ρ{sub c}), Q = 3β H √ρ{sub de}ρ{sub c}, and Q = 3β H ρ{sub de}ρ {sub c} /ρ{sub de}+ρ{sub c}, respectively, where β is a dimensionless coupling constant. The observational data we use in this paper include the JLA compilation of type Ia supernovae data, the Planck 2015 distance priors data of cosmic microwave background observation, the baryon acoustic oscillations measurements, and the Hubble constant direct measurement. We make a comparison for these five interacting holographic dark energy models by employing the information criteria, and we find that, within the framework of holographic dark energy, the Q = 3β H ρ{sub de}ρ{sub c}/ρ{sub de}+ρ{sub c} model is most favored by current data, and the Q = 3β H ρ{sub c} model is relatively not favored by current data. For the Q = 3β H ρ{sub de} and Q = 3β H ρ{sub de}ρ{sub c}/ρ{sub de}+ρ{sub c} models, a positive coupling β can be detected at more than 2σ significance.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2016

Constraints on modified gravity from Planck 2015: when the health of your theory makes the difference

We use the effective field theory of dark energy (EFT of DE) formalism to constrain dark energy models belonging to the Horndeski class with the recent Planck 2015 CMB data. The space of theories is spanned by a certain number of parameters determining the linear cosmological perturbations, while the expansion history is set to that of a standard ΛCDM model. We always demand that the theories be free of fatal instabilities. Additionally, we consider two optional conditions, namely that scalar and tensor perturbations propagate with subliminal speed. Such criteria severely restrict the allowed parameter space and are thus very effective in shaping the posteriors. As a result, we confirm that no theory performs better than ΛCDM when CMB data alone are analysed. Indeed, the healthy dark energy models considered here are not able to reproduce those phenomenological behaviours of the effective Newton constant and gravitational slip parameters that, according to previous studies, best fit the data.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2017

Constraints on interacting dark energy models from Planck 2015 and redshift-space distortion data

We investigate phenomenological interactions between dark matter and dark energy and constrain these models by employing the most recent cosmological data including the cosmic microwave background radiation anisotropies from Planck 2015, Type Ia supernovae, baryon acoustic oscillations, the Hubble constant and redshift-space distortions. We find that the interaction in the dark sector parameterized as an energy transfer from dark matter to dark energy is strongly suppressed by the whole updated cosmological data. On the other hand, an interaction between dark sectors with the energy flow from dark energy to dark matter is proved in better agreement with the available cosmological observations. This coupling between dark sectors is needed to alleviate the coincidence problem.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2019

Results from 2015 and the 2016 upgrade of the CONNIE experiment for detecting coherent neutrino nucleus scattering

The CONNIE Experiment (Coherent Neutrino Nucleus Interaction Experiment) is currently collecting reactor neutrino data to search for the undiscovered standard model process of coherent neutrino-nucleus scattering (CNNS). The detector is composed of a silicon target of thick, fully-depleted, low-noise CCD detectors. Results from data collected in 2015 indicate backgrounds are controlled, and allow an estimate of sensitivity to be presented for a larger scale detector. A 2016 upgrade, adding additional target mass, and reducing readout noise, has been performed, increasing the total yield of signal events by a factor of 30, and already yielding science-quality data. Low-energy nuclear calibrations have been performed, enabling calibration down to the device energy threshold. An estimate of the sensitivity expected for measuring the coherent neutrino process is presented. Future prospects with improved detector energy thresholds are estimated.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2018

Anthropogenic influence on the drivers of the Western Cape drought 2015–2017

In the period 2015–2017, the Western Cape region has suffered from three consecutive years of below average rainfall—leading to a prolonged drought and acute water shortages, most prominently in the city of Cape Town. After testing that the precipitation deficit is the primary driver behind the reduced surface water availability, we undertake a multi-method attribution analysis for the meteorological drought, defined in terms of a deficit in the 3 years running mean precipitation averaged over the Western Cape area. The exact estimate of the return time of the event is sensitive to the number of stations whose data is incorporated in the analysis but the rarity of the event is unquestionable, with a return time of more than a hundred years. Synthesising the results from five different large model ensembles as well as observed data gives a significant increase by a factor of three (95% confidence interval 1.5–6) of such a drought to occur because of anthropogenic climate change. All the model results further suggest that this trend will continue with future global warming. These results are in line with physical understanding of the effect of climate change at these latitudes and highlights that measures to improve Cape Town's resilience to future droughts are an adaptation priority.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2015

FIRST INTEGRAL OBSERVATIONS OF V404 CYGNI DURING THE 2015 OUTBURST: SPECTRAL BEHAVIOR IN THE 20–650 KeV ENERGY RANGE

In 2015 June, the source V404 Cygni (= GS2023+38) underwent an extraordinary outburst. We present the results obtained during the first revolution dedicated to this target by the INTEGRAL mission and focus on the spectral behavior in the hard X-ray domain, using both SPI and IBIS instruments. The source exhibits extreme variability and reaches fluxes of several tens of Crab. However, the emission between 20 and 650 keV can be understood in terms of two main components, varying on all the observable timescales, similar to what is observed in the persistent black hole system Cyg X-1. The low-energy component (up to ∼200 keV) presents a rather unusual shape, probably due to the intrinsic source variability. Nonetheless, a satisfactory description is obtained with a Comptonization model, if an unusually hot population of seed photons (kT{sub 0} ∼ 7 keV) is introduced. Above this first component, a clear excess extending up to 400–600 keV leads us to investigate a scenario where an additional (cutoff) power law could correspond to the contribution of the jet synchrotron emission, as proposed in Cyg X-1. A search for an annihilation feature did not provide any firm detection, with an upper limit of 2 × 10{sup −4} ph cm{sup −2} s{sup −1} (2σ) for a narrow line centered at 511 keV, on the averaged obtained spectrum.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2017

CMB signatures of metal-free star formation and Planck 2015 polarization data

Standard analyses of the reionization history of the Universe from Planck cosmic microwave background (CMB) polarization measurements consider only the overall optical depth to electron scattering (τ), and further assume a step-like reionization history. However, the polarization data contain information beyond the overall optical depth, and the assumption of a step-like function may miss high redshift contributions to the optical depth and leads to biased τ constraints. Accounting for its full reionization information content, we reconsider the interpretation of Planck 2015 Low-Frequency Instrument (LFI) polarization data using simple, yet physically motivated reionization models. We show that these measurements still, in fact, allow a non-negligible contribution from metal-free (Pop-III) stars forming in mini-haloes of mass M ~ 10 5 –10 6 M ⊙ at z ≳ 15, provided this mode of star formation is fairly inefficient. We find that an early, self-regulated phase of Pop-III star formation with a gradual, plateau feature in the ionization history provides a good match to the Planck LFI measurements. In this case, as much as 20 percent of the volume of the Universe is ionized by z ~ 20. Although preferred when the full information content of the data is incorporated, this model would spuriously be disfavoured in the standard analysis. This preference is driven mostly by excess power from E-mode polarization at multipoles of 10 ≲ ℓ ≲ 20, which may reflect remaining systematic errors in the data, a statistical fluctuation or signatures of the first stars. Measurements from the Planck High-Frequency Instrument should be able to confirm or refute this hint and future cosmic-variance-limited E-mode polarization surveys can provide substantially more information on these signatures.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2018

First study of reionization in the Planck 2015 normalized closed ΛCDM inflation model

We study reionization in two non-flat ΛCDM inflation models that best fit the Planck 2015 cosmic microwave background (CMB) anisotropy observations, ignoring or in conjunction with baryon acoustic oscillation distance measurements. We implement a principal component analysis (PCA) to estimate the uncertainties in the reionization history from a joint quasar–CMB data set. A thorough Markov Chain Monte Carlo analysis is done over the parameter space of the PCA modes for both non-flat ΛCDM inflation models as well as the original Planck 2016 tilted, spatially flat ΛCDM inflation model. Although both flat and non-flat models can closely match the low-redshift ( z ≲ 6) observations, we notice a possible tension between high-redshift ( z ~ 8) Lyman α emitter data and the non-flat models. This is solely due to the fact that the closed models have a relatively higher reionization optical depth compared to the flat one, which in turn demands more high-redshift ionizing sources and favours an extended reionization starting as early as z ≈ 14. We conclude that as opposed to flat cosmology, for the non-flat cosmology models (i) the escape fraction needs steep redshift evolution and even unrealistically high values at some redshifts and (ii) most of the physical parameters require to have non-monotonic redshift evolution, especially apparent when Lyman α emitter data are included in the analysis.

79 ASTRONOMY AND ASTROPHYSICS↗