PIM-1 as a Solution-Processable “Molecular Basket” for CO 2 Capture from Dilute Sources
Not Available
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
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Acceleration of Oxygen Ions In Dipolarization Events: 2. PSBL Distributions
Abstract This paper represents the second part of an investigation of the acceleration of energetic oxygen ions from encounters with a dipolarization front (DF), based on test particle tracing in the fields of an MHD simulation. In this paper, we focus on distributions in the plasma sheet boundary layer (PSBL). O + beams close to the plasma sheet boundary are found to be less pronounced and/or delayed against the H + beams. The reason is that these particles are accelerated by nonadiabatic motion in the duskward electric field such that O + ions gain the same amount of energy, but only 1/4 of the speed of protons. This causes a delay and larger equatorward displacement by the E × B drift. In contrast, the O + beams somewhat deeper inside the plasma sheet, where previously multiple proton beams were found, are accelerated at an earthward propagating DF just like H + , forming a field‐aligned beam at a similar speed as the lowest‐energy H + beam. We found that the source location depends on the adiabaticity of the orbit. For larger adiabaticity, the beam ions originate initially from the outer plasma sheet, but later from the opposite PSBL or lobe, but for low adiabaticity, sources are well inside the plasma sheet. The energy gained from a single encounter of a DF is comparable to the kinetic energy associated with the front speed. Assuming maximum speeds of 500–1,000 km/s, this yields a mass dependent acceleration of about 1–5 keV for protons and 20–80 keV for oxygen ions, independent of their charge state.
Birn, J.↗
In situ observation of thermal-driven degradation and safety concerns of lithiated graphite anode
Abstract Graphite, a robust host for reversible lithium storage, enabled the first commercially viable lithium-ion batteries. However, the thermal degradation pathway and the safety hazards of lithiated graphite remain elusive. Here, solid-electrolyte interphase (SEI) decomposition, lithium leaching, and gas release of the lithiated graphite anode during heating were examined by in situ synchrotron X-ray techniques and in situ mass spectroscopy. The source of flammable gas such as H 2 was identified and quantitively analyzed. Also, the existence of highly reactive residual lithium on the graphite surface was identified at high temperatures. Our results emphasized the critical role of the SEI in anode thermal stability and uncovered the potential safety hazards of the flammable gases and leached lithium. The anode thermal degradation mechanism revealed in the present work will stimulate more efforts in the rational design of anodes to enable safe energy storage.
25 ENERGY STORAGE↗
A cyanide-bridged di-manganese carbonyl complex that photochemically reduces CO 2 to CO
Manganese(I) tricarbonyl complexes such as [Mn(bpy)(CO) 3 L] (L = Br, or CN) are known to be electrocatalysts for CO 2 reduction to CO. However, due to their rapid photodegradation under UV and visible light, these monomeric manganese complexes have not been considered as photocatalysts for CO 2 reduction without the use of a photosensitizer. We report a cyanide-bridged di-manganese complex, {[Mn(bpy)(CO) 3 ] 2 (μ-CN)}ClO 4 , which is both electrocatalytic and photochemically active for CO 2 reduction to CO. Compared to the [Mn(bpy)(CO) 3 CN] electrocatalyst, our CN-bridged binuclear complex is a more efficient electrocatalyst for CO 2 reduction using H 2 O as a proton source. In addition, we report a photochemical CO 2 reduction to CO using the dimanganese complex under 395 nm irradiation.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Growth of polyaromatic molecules via ion-molecule reactions: An experimental and theoretical mechanistic study
The reactivity of naphthyl cations with benzene is investigated in a joint experimental and theoretical approach. Experiments are performed by using guided ion beam tandem mass spectrometers equipped with electron impact or atmospheric pressure chemical ion sources to generate C{sub 10}H{sub 7}{sup +} with different amounts of internal excitation. Under single collision conditions, C-C coupling reactions leading to hydrocarbon growth are observed. The most abundant ionic products are C{sub 16}H{sub 13}{sup +}, C{sub 16}H{sub n}{sup +} (with n=10-12), and C{sub 15}H{sub 10}{sup +}. From pressure-dependent measurements, absolute cross sections of 1.0{+-}0.3 and 2{+-}0.6 A{sup 2} (at a collision energy of about 0.2 eV in the center of mass frame) are derived for channels leading to the formation of C{sub 16}H{sub 12}{sup +} and C{sub 15}H{sub 10}{sup +} ions, respectively. From cross section values a phenomenological total rate constant k=(5.8{+-}1.9)x10{sup -11} cm{sup 3} s{sup -1} at an average collision energy of about 0.27 eV can be estimated for the process C{sub 10}H{sub 7}{sup +}+C{sub 6}H{sub 6}{yields} all products. The energy behavior of the reactive cross sections, as well as further experiments performed using partial isotopic labeling of reagents, support the idea that the reaction proceeds via a long lived association product, presumably the covalently bound protonated phenylnaphthalene, from which lighter species are generated by elimination of neutral fragments (H, H{sub 2}, CH{sub 3}). A major signal relevant to the fragmentation of the initial adduct C{sub 16}H{sub 13}{sup +} belongs to C{sub 15}H{sub 10}{sup +}. Since it is not obvious how CH{sub 3} loss from C{sub 16}H{sub 13}{sup +} can take place to form the C{sub 15}H{sub 10}{sup +} radical cation, a theoretical investigation focuses on possible unimolecular transformations apt to produce it. Naphthylium can act as an electrophile and add to the {pi} system of benzene, leading to a barrierless formation of the ionic adduct with an exothermicity of about 53 kcal mol{sup -1}. From this structure, an intramolecular electrophilic addition followed by H shifts and ring opening steps leads to an overall exothermic loss (-7.1 kcal mol{sup -1} with respect to reagents) of the methyl radical from that part of the system which comes from benzene. Methyl loss can take place also from the ''naphthyl'' part, though via an endoergic route. Experimental and theoretical results show that an ionic route is viable for the growth of polycyclic aromatic species by association of smaller building blocks (naphthyl and phenyl rings) and this may be of particular relevance for understanding the formation of large molecules in ionized gases.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Tokamak equilibria with non field-aligned axisymmetric divergence-free rotational flows
Rotational ideal divergence-free magnetohydrodynamic (MHD) equations are expressed in terms of transformed variables w-vector{sub *}=({mu}{rho}){sup 1/2}v-vector and {mu}p{sub *} = ({mu}p + w{sub *}{sup 2}/2), where v-vector, p, and {rho} are plasma velocity, pressure, and mass density, respectively. With divergence-free flows, {nabla}{center_dot}v-vector=0, the plasma density {rho} does not appear in the MHD equations written in terms of w-vector{sub *} and {mu}p{sub *}. The non field-aligned rotational Grad-Shafranov equation is represented in spherical coordinates. Tokamak-like axisymmetric equilibria with v-vector perpendicular {nabla}{rho} are obtained analytically by solving for torus solutions under only three source functions.
70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
Dual radio frequency plasma source: Understanding via electrical asymmetry effect
On the basis of the global model, the influences of driving voltage and frequency on electron heating in geometrically symmetrical dual capacitively coupled radio frequency plasma have been investigated. Consistent with the experimental and simulation results, non-monotonic behavior of dc self bias and plasma heating with increasing high frequency is observed. In addition to the local maxima of plasma parameters for the integer values of the ratio between the frequencies ({xi}), ourstudies also predict local maxima for odd integer values of 2{xi} as a consequence of the electrical asymmetry effect produced by dual frequency voltage sources.
70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
BiPo: A dedicated radiopurity detector for the SuperNEMO experiment
New generation experiments in Astroparticle Physics need to operate in really restrictive background conditions, which implies the use of high radiopure materials for the experimental setup construction. For this reason the screening of the materials with enough sensitivity has become a challenge that sometimes cannot be afforded with standard techniques like Germanium detector spectroscopy. BiPo is a dedicated detector, that operates in the Canfranc Underground Laboratory, designed to measure the radiopurity, mainly of the ββ sources of the SuperNEMO experiment, by the detection of BiPo events. It is composed of two modules with 40 optical lines each one, registering the energy and the time of the emitted particles. The well known features of the BiPo events (delayed coincidence between an electron and an alpha particle) facilitate the discrimination of other background events that could entangle the expected signal. In addition, the geometry of the detector, with an active area of around 3.6 m{sup 2}, has been optimized to reach the necessary sensitivity levels for the SuperNEMO source foils in the shortest time possible. Preliminary results of background measurements and calibrations taken since summer 2012 shows that the required sensitivity for the measurements of the source foils could be reached in few months. Routine measurements of samples are already started being an important point for the SuperNEMO source foils construction.
46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
Realization of highly efficient hexagonal boron nitride neutron detectors
Here, we report the achievement of highly efficient 10 B enriched hexagonal boron nitride (h- 10 BN) direct conversion neutron detectors. These detectors were realized from freestanding 4-in. diameter h- 10 BN wafers 43 μm in thickness obtained from epitaxy growth and subsequent mechanical separation from sapphire substrates. Both sides of the film were subjected to ohmic contact deposition to form a simple vertical “photoconductor-type” detector. Transport measurements revealed excellent vertical transport properties including high electrical resistivity (>10 13 Ω cm) and mobility-lifetime (μτ) products. A much larger μτ product for holes compared to that of electrons along the c-axis of h- BN was observed, implying that holes (electrons) behave like majority (minority) carriers in undoped h- BN. Exposure to thermal neutrons from a californium-252 ( 252 Cf) source moderated by a high density polyethylene moderator reveals that 43 μm h- 10 BN detectors possess 51.4% detection efficiency at a bias voltage of 400 V, which is the highest reported efficiency for any semiconductor-based neutron detector. The results point to the possibility of obtaining highly efficient, compact solid-state neutron detectors with high gamma rejection and low manufacturing and maintenance costs.
36 MATERIALS SCIENCE↗
Materials representation and transfer learning for multi-property prediction
The adoption of machine learning in materials science has rapidly transformed materials property prediction. Hurdles limiting full capitalization of recent advancements in machine learning include the limited development of methods to learn the underlying interactions of multiple elements as well as the relationships among multiple properties to facilitate property prediction in new composition spaces. To address these issues, we introduce the Hierarchical Correlation Learning for Multi-property Prediction (H-CLMP) framework that seamlessly integrates: (i) prediction using only a material's composition, (ii) learning and exploitation of correlations among target properties in multi-target regression, and (iii) leveraging training data from tangential domains via generative transfer learning. The model is demonstrated for prediction of spectral optical absorption of complex metal oxides spanning 69 three-cation metal oxide composition spaces. H-CLMP accurately predicts non-linear composition-property relationships in composition spaces for which no training data are available, which broadens the purview of machine learning to the discovery of materials with exceptional properties. This achievement results from the principled integration of latent embedding learning, property correlation learning, generative transfer learning, and attention models. The best performance is obtained using H-CLMP with transfer learning [H-CLMP(T)] wherein a generative adversarial network is trained on computational density of states data and deployed in the target domain to augment prediction of optical absorption from composition. H-CLMP(T) aggregates multiple knowledge sources with a framework that is well suited for multi-target regression across the physical sciences.
36 MATERIALS SCIENCE↗
CADIS and FW-CADIS Variance Reduction in Gamma Transport for Predicting Prompt Forensics Signatures
The goal of prompt nuclear forensics is to determine the characteristics of a nuclear detonation based on the signatures available almost immediately after the explosion. An important characteristic is the reaction time history (RTH), a measure of the device’s rate of neutron multiplication. The RTH can be estimated by observation of the gamma radiation emitted from the detonation, which can be detected directly or observed indirectly as Teller light. Gamma transport simulations used to predict these radiation fields are often modeled stochastically using the Monte Carlo N-Particle (MCNP) code, which can be a computationally demanding task due to the number of particle histories needed to achieve statistical convergence. In an attempt to improve the efficiency of these calculations, we evaluate two variance reduction techniques: Consistent Adjoint-Driven Importance Sampling (CADIS) and Forward-Weighted Consistent Adjoint-Driven Importance Sampling (FW-CADIS). These methods use a deterministically calculated adjoint flux to create weight windows and source biasing that guide MCNP sampling. We study the utility of CADIS and FW-CADIS for their use in MCNP gamma transport for nuclear forensics prediction simulations. Furthermore, the results demonstrate that both CADIS and FW-CADIS improve the accuracy for forensics-focused simulations, with CADIS being most beneficial in direct detection and FW-CADIS being ideal for computing a global Teller light source.
CADIS↗
IONIZED GAS KINEMATICS AND MORPHOLOGY IN Sgr B2 Main ON 1000 AU SCALES
We have imaged the Sgr B2 Main region with the Very Large Array in the BnA configuration ({theta}{sub beam} = 0.''13) in both the H52{alpha} (45.453 GHz) radio recombination line and 7 mm continuum emission. At a distance of 8500 pc, this spatial resolution corresponds to a physical scale of 0.005 pc ({approx}1100 AU). The current observations detect H52{alpha} emission in 12 individual ultracompact and hypercompact H II regions. Two of the sources with detected H52{alpha} emission have broad ({Delta}V{sub FWHM} {approx} 50 km s{sup -1}) recombination lines, and two of the sources show lines with peaks at more than one velocity. We use line parameters from the H52{alpha} lines and our previous H66{alpha} line observations to determine the relative contribution of thermal, pressure, and kinematic broadening, and electron density. These new observations suggest that pressure broadening can account for the broad lines in some of the sources, but that gas motions (e.g., turbulence, accretion, or outflow) contribute significantly to the broad lines in at least one of the sources (Sgr B2 F3).
79 ASTRONOMY AND ASTROPHYSICS↗
PROPERTIES AND KEPLERIAN ROTATION OF THE HOT CORE IRAS 20126+4104
We present Submillimeter Array (SMA) observations of the massive star-forming region IRAS 20126+4104 in the millimeter continuum and in several molecular line transitions. With the SMA data, we have detected nine molecular transitions, including deuterated hydrogen cyanide, CH{sub 3}OH, H{sub 2}CO, and HC{sub 3}N molecules, and imaged each molecular line. From the 1.3 mm continuum emission a compact millimeter source is revealed, which is also associated with H{sub 2}O, OH, and CH{sub 3}OH masers. Using a rotation temperature diagram, we derive that the rotational temperature and the column density of CH{sub 3}OH are 200 K and 3.7 Multiplication-Sign 10{sup 17} cm{sup -2}, respectively. The calculated results and analysis further indicate that a hot core coincides with IRAS 20126+4104. The position-velocity diagrams of H{sub 2}CO (3{sub 0,3}-2{sub 0,2}) and HC{sub 3}N (25-24) clearly present Keplerian rotation. Moreover, H{sub 2}CO (3{sub 0,3}-2{sub 0,2}) is found to trace the disk rotation for the first time.
79 ASTRONOMY AND ASTROPHYSICS↗
DIFFERENT EVOLUTIONARY STAGES IN THE MASSIVE STAR-FORMING REGION W3 MAIN COMPLEX
We observed three high-mass star-forming regions in the W3 high-mass star formation complex with the Submillimeter Array and IRAM 30 m telescope. These regions, i.e., W3 SMS1 (W3 IRS5), SMS2 (W3 IRS4) and SMS3, are in different evolutionary stages and are located within the same large-scale environment, which allows us to study rotation and outflows as well as chemical properties in an evolutionary sense. While we find multiple millimeter continuum sources toward all regions, these three subregions exhibit different dynamical and chemical properties, which indicate that they are in different evolutionary stages. Even within each subregion, massive cores of different ages are found, e.g., in SMS2, sub-sources from the most evolved ultracompact H II region to potential starless cores exist within 30,000 AU of each other. Outflows and rotational structures are found in SMS1 and SMS2. Evidence for interactions between the molecular cloud and the H II regions is found in the {sup 13}CO channel maps, which may indicate triggered star formation.
79 ASTRONOMY AND ASTROPHYSICS↗
EMISSION HEIGHT AND TEMPERATURE DISTRIBUTION OF WHITE-LIGHT EMISSION OBSERVED BY HINODE/SOT FROM THE 2012 JANUARY 27 X-CLASS SOLAR FLARE
White-light emissions were observed from an X1.7 class solar flare on 2012 January 27, using three continuum bands (red, green, and blue) of the Solar Optical Telescope on board the Hinode satellite. This event occurred near the solar limb, and so differences in the locations of the various emissions are consistent with differences in heights above the photosphere of the various emission sources. Under this interpretation, our observations are consistent with the white-light emissions occurring at the lowest levels of where the Ca II H emission occurs. Moreover, the centers of the source regions of the red, green, and blue wavelengths of the white-light emissions are significantly displaced from each other, suggesting that those respective emissions are emanating from progressively lower heights in the solar atmosphere. The temperature distribution was also calculated from the white-light data, and we found the lower-layer emission to have a higher temperature. This indicates that high-energy particles penetrated down to near the photosphere, and deposited heat into the ambient lower layers of the atmosphere.
79 ASTRONOMY AND ASTROPHYSICS↗
Matter under extreme conditions experiments at the Linac Coherent Light Source
Not Available
43 PARTICLE ACCELERATORS↗
OzDES Reverberation Mapping Programme: the first Mg ii lags from 5 yr of monitoring
ABSTRACT Reverberation mapping is a robust method to measure the masses of supermassive black holes outside of the local Universe. Measurements of the radius–luminosity (R−L) relation using the Mg ii emission line are critical for determining these masses near the peak of quasar activity at z ≈ 1−2, and for calibrating secondary mass estimators based on Mg ii that can be applied to large samples with only single-epoch spectroscopy. We present the first nine Mg ii lags from our 5-yr Australian Dark Energy Survey reverberation mapping programme, which substantially improves the number and quality of Mg ii lag measurements. As the Mg ii feature is somewhat blended with iron emission, we model and subtract both the continuum and iron contamination from the multiepoch spectra before analysing the Mg ii line. We also develop a new method of quantifying correlated spectroscopic calibration errors based on our numerous, contemporaneous observations of F-stars. The lag measurements for seven of our nine sources are consistent with both the H β and Mg ii R−L relations reported by previous studies. Our simulations verify the lag reliability of our nine measurements, and we estimate that the median false positive rate of the lag measurements is $4{{\ \rm per\ cent}}$.
79 ASTRONOMY AND ASTROPHYSICS↗
BAT AGN Spectroscopic Survey – XIII. The nature of the most luminous obscured AGN in the low-redshift universe
In this paper, we present a multiwavelength analysis of 28 of the most luminous low-redshift narrow-line, ultra-hard X-ray-selected active galactic nuclei (AGN) drawn from the 70-month Swift /BAT all-sky survey, with bolometric luminosities of $\log (L_{\rm bol} /{\rm erg\, s}^{-1}) \gtrsim 45.25$. The broad goal of our study is to determine whether these objects have any distinctive properties, potentially setting them aside from lower luminosity obscured AGN in the local Universe. Our analysis relies on the first data release of the BAT AGN Spectroscopic Survey (BASS/DR1) and on dedicated observations with the VLT, Palomar, and Keck observatories. We find that the vast majority of our sources agree with commonly used AGN selection criteria which are based on emission line ratios and on mid-infrared colours. Our AGN are pre-dominantly hosted in massive galaxies (9.8 ≲ log (M*/M ⊙ ) ≲ 11.7); based on visual inspection of archival optical images, they appear to be mostly ellipticals. Otherwise, they do not have distinctive properties. Their radio luminosities, determined from publicly available survey data, show a large spread of almost four orders of magnitude – much broader than what is found for lower X-ray luminosity obscured AGN in BASS. Moreover, our sample shows no preferred combination of black hole masses ( M BH ) and/or Eddington ratio (λ Edd , covering 7.5 ≲ log ( M BH /M ⊙ ) ≲ 10.3 and 0.01 ≲ λ Edd ≲ 1. Based on the distribution of our sources in the λ Edd - N H plane, we conclude that our sample is consistent with a scenario where the amount of obscuring material along the line of sight is determined by radiation pressure exerted by the AGN on the dusty circumnuclear gas.
79 ASTRONOMY AND ASTROPHYSICS↗