Probing quasar winds using intrinsic narrow absorption lines

ABSTRACT We use the spectra of 73 quasars (1.5 ≲ z ≲ 5) from the VLT UVES archive to catalogue and study narrow absorption lines (NALs) that are physically associated with (intrinsic to) the quasars. We identify 410 NAL systems containing C iv, N v, and/or Si iv doublets. Based on the assumption that only systems intrinsic to the quasar can exhibit partial coverage of the background source(s), we identify 34 reliably intrinsic NAL systems and 11 systems that are potentially intrinsic, as well as 4 mini-broad absorption lines (BALs) and 1 BAL. The minimum fraction of quasars with at least one intrinsic system is shown to be 38 per cent. We identify intrinsic NALs with a wide range of properties, including apparent ejection velocity, coverage fraction, and ionization level. There is a continuous distribution of properties, rather than discrete families, ranging from partially covered C iv systems with black Ly α and with a separate low-ionization gas phase to partially covered N v systems with partially covered Ly α and without detected low-ionization gas. Even more highly ionized associated and intrinsic absorption systems (O vi, Ne viii, and Mg x doublets) have been presented in separate studies; these may represent an extension of the above sequence. We also use the properties of the NALs in conjunction with recent models of accretion disc winds that predict the origins of the absorbing gas in order to determine the model that best characterizes our sample. Additionally, we construct a model describing the spatial distributions, geometries, and varied ionization structures of intrinsic NALs.

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Accretion disc winds in tidal disruption events: ultraviolet spectral lines as orientation indicators

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa1060 ◽

2020 ◽

Vol 494 (4) ◽

pp. 4914-4929 ◽

Cited By ~ 2

Author(s):

Edward J Parkinson ◽

Christian Knigge ◽

Knox S Long ◽

James H Matthews ◽

Nick Higginbottom ◽

...

Keyword(s):

Emission Measure ◽

Relative Number ◽

Uv Spectra ◽

Accretion Disc ◽

Spectral Lines ◽

Absorption Lines ◽

Line Formation ◽

Ionization State ◽

Tidal Disruption ◽

Wide Range

ABSTRACT Some tidal disruption events (TDEs) exhibit blueshifted broad absorption lines (BALs) in their rest-frame ultraviolet (UV) spectra, while others display broad emission lines (BELs). Similar phenomenology is observed in quasars and accreting white dwarfs, where it can be interpreted as an orientation effect associated with line formation in an accretion disc wind. We propose and explore a similar unification scheme for TDEs. We present synthetic UV spectra for disc and wind-hosting TDEs, produced by a state-of-the-art Monte Carlo ionization and radiative transfer code. Our models cover a wide range of disc wind geometries and kinematics. Such winds naturally reproduce both BALs and BELs. In general, sightlines looking into the wind cone preferentially produce BALs, while other orientations preferentially produce BELs. We also study the effect of wind clumping and CNO-processed abundances on the observed spectra. Clumpy winds tend to produce stronger UV emission and absorption lines, because clumping increases both the emission measure and the abundances of the relevant ionic species, the latter by reducing the ionization state of the outflow. The main effect of adopting CNO-processed abundances is a weakening of C iv 1550 Å and an enhancement of N v 1240 Å in the spectra. We conclude that line formation in an accretion disc wind is a promising mechanism for explaining the diverse UV spectra of TDEs. If this is correct, the relative number of BAL and BEL TDEs can be used to estimate the covering factor of the outflow. The models in this work are publicly available online and upon request.

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Intrinsic Stacking Interactions of Natural and Artificial Nucleobases

10.26434/chemrxiv.11400405 ◽

2019 ◽

Author(s):

Drew P. Harding ◽

Laura J. Kingsley ◽

Glen Spraggon ◽

Steven Wheeler

Keyword(s):

Gas Phase ◽

Electrostatic Interactions ◽

Density Functional ◽

Molecular Descriptors ◽

Stacking Interactions ◽

Interaction Energies ◽

Functional Theory ◽

Binding Partner ◽

Heavy Atoms ◽

Wide Range

The intrinsic (gas-phase) stacking energies of natural and artificial nucleobases were explored using density functional theory (DFT) and correlated ab initio methods. Ranking the stacking strength of natural nucleobase dimers revealed a preference in binding partner similar to that seen from experiments, namely G > C > A > T > U. Decomposition of these interaction energies using symmetry-adapted perturbation theory (SAPT) showed that these dispersion dominated interactions are modulated by electrostatics. Artificial nucleobases showed a similar stacking preference for natural nucleobases and were also modulated by electrostatic interactions. A robust predictive multivariate model was developed that quantitively predicts the maximum stacking interaction between natural and a wide range of artificial nucleobases using molecular descriptors based on computed electrostatic potentials (ESPs) and the number of heavy atoms. This model should find utility in designing artificial nucleobase analogs that exhibit stacking interactions comparable to those of natural nucleobases. Further analysis of the descriptors in this model unveil the origin of superior stacking abilities of certain nucleobases, including cytosine and guanine.

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NOHSO4/HF – A Novel Etching System for Crystalline Silicon

Zeitschrift für Naturforschung B ◽

10.1515/znb-2007-1110 ◽

2007 ◽

Vol 62 (11) ◽

pp. 1411-1421 ◽

Cited By ~ 12

Author(s):

Sebastian Patzig ◽

Gerhard Roewer ◽

Edwin Kroke ◽

Ingo över

Keyword(s):

Gas Phase ◽

Chemical Etching ◽

Silicon Surface ◽

Crystalline Silicon ◽

Etching Solution ◽

Wide Range ◽

Ft Ir ◽

Wet Chemical ◽

Wet Chemical Etching ◽

Etching System

Solutions consisting of HF - NOHSO4 - H2SO4 exhibit a strong reactivity towards crystalline silicon which is controlled by the concentrations of the reactive species HF and NO+. Selective isotropic and anisotropic wet chemical etching with these solutions allows to generate a wide range of silicon surface morphology patterns. Traces of Ag+ ions stimulate the reactivity and lead to the formation of planarized (polished) silicon surfaces. Analyses of the silicon surface, the etching solution and the gas phase were performed with scanning electron microscopy (SEM), DR/FT-IR (diffusive reflection Fourier transform infra-red), FT-IR, Raman and NMR spectroscopy, respectively. It was found that the resulting silicon surface is hydrogen-terminated. The gas phase contains predominantly SiF4, NO and N2O. Furthermore, NH4+ is produced in solution. The study has confirmed the crucial role of nitrosyl ions for isotropic wet chemical etching processes. The novel etching system is proposed as an effective new way for selective surface texturing of multi- and monocrystalline silicon. A high etching bath service lifetime, besides a low contamination of the etching solution with reaction products, provides ecological and economical advantages for the semiconductor and solar industry.

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Bubble dynamics and oxygen transfer in a hypolimnetic aerator

Water Science & Technology ◽

10.2166/wst.1998.0152 ◽

1998 ◽

Vol 37 (2) ◽

pp. 293-300 ◽

Cited By ~ 7

Author(s):

Vickie L. Burris ◽

John C. Little

Keyword(s):

Gas Phase ◽

Bubble Size ◽

Oxygen Transfer ◽

Bubble Dynamics ◽

Water Flow Rate ◽

Flow Rates ◽

Wide Range ◽

The City ◽

Close Fit ◽

Water Supply Reservoirs

A hypolimnetic aerator operating in one of the City of Norfolk's water supply reservoirs was tested. Dissolved oxygen (DO) profiles, water flow rate, and gas-phase holdup were measured over a wide range of applied air flow rates. A model that was developed to predict oxygen transfer in a Speece Cone was modified to conform to the conditions of the hypolimnetic aerator. By varying a single parameter (the initial bubble size) the model was found to provide a close fit to the experimental DO profiles as well as the observed gas-phase holdup. The model was used to show that a doubling in oxygen transfer may be achieved if initial bubble size is reduced from 5 mm to 2.5 mm. Knowing the initial bubble size, it should be possible to predict water velocity by incorporating the effect of momentum. Further work is now underway to test this approach and to examine the possibility of extending this generalized model to cover the range of hypolimnetic aeration and oxygenation devices.

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Emissions of organic carbon and methane from petroleum and dairy operations in California's San Joaquin Valley

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-13-28225-2013 ◽

2013 ◽

Vol 13 (10) ◽

pp. 28225-28278 ◽

Cited By ~ 4

Author(s):

D. R. Gentner ◽

T. B. Ford ◽

A. Guha ◽

K. Boulanger ◽

J. Brioude ◽

...

Keyword(s):

Spatial Distribution ◽

Organic Carbon ◽

Gas Phase ◽

Organic Compounds ◽

Methane Emissions ◽

San Joaquin Valley ◽

Motor Vehicles ◽

Meteorological Model ◽

Wide Range ◽

Petroleum Extraction

Abstract. Petroleum and dairy operations are prominent sources of gas-phase organic compounds in California's San Joaquin Valley. Ground site measurements in Bakersfield and aircraft measurements of reactive gas-phase organic compounds were made in this region as part of the CalNex (California Research at the Nexus of Air Quality and Climate Change) project to determine the sources contributing to regional gas-phase organic carbon emissions. Using a combination of near-source and downwind data, we assess the composition and magnitude of emissions from these prominent sources that are relatively understudied compared to motor vehicles We also developed a statistical modeling method with the FLEXPART-WRF transport and meteorological model using ground-based data to assess the spatial distribution of emissions in the San Joaquin Valley. We present evidence for large sources of paraffinic hydrocarbons from petroleum extraction/processing operations and oxygenated compounds from dairy (and other cattle) operations. In addition to the small straight-chain alkanes typically associated with petroleum operations, we observed a wide range of branched and cyclic alkanes that have limited previous in situ measurements or characterization in emissions from petroleum operations. Observed dairy emissions were dominated by ethanol, methanol, and acetic acid, and methane. Dairy operations were responsible for the vast majority of methane emissions in the San Joaquin Valley; observations of methane were well-correlated with non-vehicular ethanol, and multiple assessments of the spatial distribution of emissions in the San Joaquin Valley highlight the dominance of dairy operations for methane emissions. The good agreement of the observed petroleum operations source profile with the measured composition of non-methane hydrocarbons in unrefined natural gas associated with crude oil suggests a fugitive emissions pathway during petroleum extraction, storage, or processing with negligible coincident methane emissions Aircraft observations of emission hotspots from operations at oil wells and dairies are consistent with the statistical source footprint determined via transport modeling and ground-based data. At Bakersfield, petroleum and dairy operations each comprised 22–23% of anthropogenic non-methane organic carbon and were each responsible for ~12% of potential precursors to ozone, but their direct impacts as potential SOA precursors were estimated to be minor. A comparison with the California Air Resources Board emission inventory supports the current relative emission rates of reactive organic gases from these sources in the region.

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Formamide reaction network in gas phase and solution via a unified theoretical approach: Toward a reconciliation of different prebiotic scenarios

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1512486112 ◽

2015 ◽

Vol 112 (49) ◽

pp. 15030-15035 ◽

Cited By ~ 60

Author(s):

Fabio Pietrucci ◽

Antonino Marco Saitta

Keyword(s):

Gas Phase ◽

Computational Study ◽

Reaction Network ◽

Theoretical Method ◽

Active Role ◽

Decomposition Reaction ◽

Ab Initio Molecular Dynamics ◽

Collective Variables ◽

Wide Range ◽

Reaction Channels

Increasing experimental and theoretical evidence points to formamide as a possible hub in the complex network of prebiotic chemical reactions leading from simple precursors like H2, H2O, N2, NH3, CO, and CO2 to key biological molecules like proteins, nucleic acids, and sugars. We present an in-depth computational study of the formation and decomposition reaction channels of formamide by means of ab initio molecular dynamics. To this aim we introduce a new theoretical method combining the metadynamics sampling scheme with a general purpose topological formulation of collective variables able to track a wide range of different reaction mechanisms. Our approach is flexible enough to discover multiple pathways and intermediates starting from minimal insight on the systems, and it allows passing in a seamless way from reactions in gas phase to reactions in liquid phase, with the solvent active role fully taken into account. We obtain crucial new insight into the interplay of the different formamide reaction channels and into environment effects on pathways and barriers. In particular, our results indicate a similar stability of formamide and hydrogen cyanide in solution as well as their relatively facile interconversion, thus reconciling experiments and theory and, possibly, two different and competing prebiotic scenarios. Moreover, although not explicitly sought, formic acid/ammonium formate is produced as an important formamide decomposition byproduct in solution.

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Applied Novel Quality Check Method for PVT Data with High Impurities Using Various Samples from Malaysian Fields

10.2118/207220-ms ◽

2021 ◽

Author(s):

Luky Hendraningrat ◽

Intan Khalida Salleh

Keyword(s):

Molecular Weight ◽

Equation Of State ◽

Gas Phase ◽

Oil And Gas ◽

Comprehensive Evaluation ◽

Gas Condensate ◽

Fluid Composition ◽

Essential Information ◽

Pvt Data ◽

Wide Range

Abstract PVT analysis of reservoir fluid samples provides essential information for determining hydrocarbon in place, depletion strategy, and hydrocarbon flowability. Hence, quality checking (QC) is necessary to ensure the best representative sample for further analysis. Recently, a novel tool based on Equation of State (EOS) was introduced to tackle the limitation of the Hoffmann method for surface samples with high impurities and heavier components. This paper presents comprehensively evaluating a novel EOS-based method using various PVT data from Malaysian fields. Numerous PVT separator samples from 30 fields with various reservoir fluids (Black Oil, Volatile, and Gas Condensate) were carried out and evaluated. The impurities contain a wide range of up to 60%. The 2-phase P-T (pressure and temperature) diagram of each oil and gas phase before recombination was calculated using PVT software based on Equation of State (EOS). The 2-phase P-T diagram was created and observed the intersection point as calculated equilibrium at separator conditions. Once it is observed and compared with written separator condition in the laboratory report and observed its deviation. Eventually, the result will be compared with the Hoffmann method. The Hoffmann method is well-known as a traditional QC method that was initially developed using gas condensate PVT data to identify possible errors in measured separator samples. If the sample has high impurities and/or heavier components, the Hoffmann method will only show a straight line to the lighter components and those impurities and heavier components will be an outlier that engineers will misinterpret that it has errors and cannot be used for further analysis such PVT characterization. The QC using EOS-based were conducted using actual fields data. It shows potential as novel QC tools but observed only less than 10% of data with complete information that can meet intersection points located precisely similar with reported in the laboratory. There is some investigation and evaluation of the EOS-based QC method. First, most of the molecular weight of the heavier fluid composition of gas and oil phase was not reported or used assumptions especially when its mole fraction is not zero. Second, properties of heavier components of the oil phase (molecular weight and specific gravity) were not measured and assumed similar as wellstream. Third, pressure and temperature data are inconsistent between the oil and gas phase at the separator condition. This study can provide improvement in laboratory measurement quality and help engineers to have a better understanding of PVT Report, essential data requirements, and assumptions used in the laboratory. Nevertheless, the Hoffmann method can be used as an inexpensive QC tool because it can be generated in a spreadsheet without a PVT software license. Both combination techniques can provide a comprehensive evaluation for separator samples with high impurities before identifying representative fluid for further analysis.

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A Gas-Phase Reaction Cell for Modern Atom Probe Systems

Microscopy and Microanalysis ◽

10.1017/s1431927618016240 ◽

2019 ◽

Vol 25 (2) ◽

pp. 410-417 ◽

Cited By ~ 1

Author(s):

Daniel Haley ◽

Ingrid McCarroll ◽

Paul A. J. Bagot ◽

Julie M. Cairney ◽

Michael P. Moody

Keyword(s):

Gas Phase ◽

Atom Probe Tomography ◽

Atom Probe ◽

Phase Reaction ◽

Reaction Cell ◽

Current Form ◽

Gas Phase Reaction ◽

Wide Range ◽

Gas Interactions ◽

Selection Of

AbstractIn this work, we demonstrate a new system for the examination of gas interactions with surfaces via atom probe tomography. This system provides capability of examining the surface and subsurface interactions of gases with a wide range of specimens, as well as a selection of input gas types. This system has been primarily developed to aid the investigation of hydrogen interactions with metallurgical samples, to better understand the phenomenon of hydrogen embrittlement. In its current form, it is able to operate at pressures from 10−6 to 1000 mbar (abs), can use a variety of gasses, and is equipped with heating and cryogenic quenching capabilities. We use this system to examine the interaction of hydrogen with Pd, as well as the interaction of water vapor and oxygen in Mg samples.

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The Absorption Line Systems of the Supershell LMC2 in the Large Magellanic Cloud

Symposium - International Astronomical Union ◽

10.1017/s0074180900117735 ◽

1999 ◽

Vol 190 ◽

pp. 154-155

Author(s):

Adeline Caulet

Keyword(s):

Optical Absorption ◽

Interstellar Medium ◽

Gas Phase ◽

Absorption Line ◽

Large Magellanic Cloud ◽

Magellanic Cloud ◽

Absorption Lines

The interstellar medium of LMC2, a well studied supershell in the Large Magellanic Cloud, has been probed in UV and optical absorption lines. The data allow to derive the kinematics, abundances and depletions of gas clouds in this supershell. The relative gas-phase abundances of observed elements with respect to sulphur are useful to determine the origins of the supershell absorption-line clouds.

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