Nuclei In Gas Research Articles

Quenching factor measurements of neon nuclei in neon gas

The NEWS-G collaboration uses spherical proportional counters (SPCs) to search for weakly interacting massive particles (WIMPs). In this paper, we report the first measurements of the nuclear quenching factor in neon gas at 2 bar using an SPC deployed in a neutron beam at the TUNL facility. The energy-dependence of the nuclear quenching factor is modeled using a simple power law: αEnrβ; we determine its parameters by simultaneously fitting the data collected with the detector over a range of energies. We measured the following parameters in Ne:CH4 at 2 bar: α=0.2801±0.0050 (fit) ±0.0045 (sys) and β=0.0867±0.020 (fit) ±0.006 (sys). Our measurements do not agree with expected values from SRIM or Lindhard theory. We demonstrated the feasibility of performing quenching factor measurements at sub-keV energies in gases using SPCs and a neutron beam.11 MoreReceived 8 September 2021Accepted 24 December 2021DOI:https://doi.org/10.1103/PhysRevD.105.052004© 2022 American Physical SocietyPhysics Subject Headings (PhySH)Research AreasParticle dark matterTechniquesDark matter detectorsGravitation, Cosmology & Astrophysics

Aerosol Emissions of Amine-Based CO2 Absorption System: Effects of Condensation Nuclei and Operating Conditions.

Amine emissions from a post-combustion CO2 capture process can lead to solvent loss and serious environmental issues. The emission characteristics of amine mixtures and influencing factors are seldom reported. This work comprehensively investigated emissions of AMP (2-amino-2-methyl-1-propanol)/MEA (monoethanolamine) from a 3.6 Nm3/h flue gas CO2 capture platform. The condensation nuclei in flue gas dominated the generation of amine aerosols and resulted in a heavy total amine loss of over 1400 mg/Nm3, which is equivalent to 5.88 kg/t CO2 captured under the high nuclei concentration scenario. Inside the absorber, a higher CO2 concentration and lower lean solvent CO2 loading can significantly promote the growth of aerosols due to the intensive reaction of CO2 absorption. The maximum amine emissions were observed at 8-12 vol % CO2. The flue gas temperature and liquid/gas ratio had insignificant effects on aerosol emissions, while amine emissions after the absorber increased 340-500% as the lean solvent temperature increased from 30 to 50 °C. A synergistic control strategy of nuclei pretreatment, operating optimization, and water scrubbing can effectively reduce amine emissions to 4.0 mg/Nm3 MEA and 8.3 mg/Nm3 AMP.

Light nuclei in the hadron resonance gas

The description of the production of light (anti-)(hyper-)nuclei in a hadron resonance gas, or statistical-thermal model approach, has proven to be rather successful, despite the fact that the binding energies of these compound objects are small compared to the emitting fireball temperature. We summarize some recent developments and findings in this approach.

Trichostatin A inhibits skeletal muscle atrophy induced by cigarette smoke exposure in mice

AimsIt is well known that cigarette smoke (CS) is the main risk factor for chronic obstructive pulmonary disease (COPD) accompanied by skeletal muscle atrophy. Histone deacetylases (HDACs) that remove acetyl groups from target proteins are necessary for the muscle atrophy associated with skeletal muscle disuse. However, the role of HDACs and trichostatin A (TSA), a HDAC inhibitor, in skeletal muscle atrophy caused by CS exposure remains poorly understood. Main methodsFemale mice were exposed to CS twice daily for 40 days and TSA injected intraperitoneally into CS-exposed mice on alternate days. Skeletal muscles were weighed and gastrocnemius (Gas) muscle histomorphology examined by hematoxylin and eosin staining. Histone deacetylases 1 and 2 (HDAC1/2), and markers of ubiquitin degradation, muscle differentiation, apoptosis, pyroptosis, and the cytoskeletal proteins were assessed by western blot and immunohistochemistry in Gas. KeyfindingsCS exposure decreased body and skeletal muscle weights and triggered an increase in the percentage of fiber with centralized nuclei in Gas. HDAC1/2 proteins were upregulated in the Gas of mice exposed to CS, while TSA effectively inhibited HDAC1/2 protein levels and attenuated the loss of body weight and skeletal muscle wet weight induced by CS exposure. Markers for ubiquitin degradation, muscle differentiation, cytoskeletal proteins, apoptosis and pyroptosis were all upregulated following CS exposure and effectively restored by TSA. SignificanceTSA may inhibit skeletal muscle atrophy and histomorphological alterations induced by CS exposure by downregulating markers of ubiquitin degradation, muscle fiber differentiation, cytoskeletal proteins, apoptosis and pyroptosis via HDAC1/2 inhibition.

EVAPORATION OF GRAIN-SURFACE SPECIES BY SHOCK WAVES IN A PROTOPLANETARY DISK

Recent ALMA (Atacama Large Millimeter/submillimeter Array) observations of young protostellar objects detected warm SO emission, which could be associated with a forming protostellar disk. In order to investigate if such warm gas can be produced by accretion shock onto the forming disk, we calculate the sputtering and thermal desorption of various grain surface species in one dimensional shock waves. We find that thermal desorption is much more efficient than the sputtering in the post-shock region. While H$_{2}$O can be thermally desorbed, if the accretion velocity is larger than 8 km s$^{-1}$ with the pre-shock gas number density of 10$^{9}$ cm$^{-3}$, SO is desorbed, if the accretion velocity $\gtrsim$ 2 km s$^{-1}$ and $\gtrsim$ 4km s$^{-1}$, with the pre-shock density of 10$^{9}$ cm$^{-3}$ and 10$^{8}$ cm$^{-3}$, respectively. We also find that the column density of hydrogen nuclei in warm post-shock gas is $N_{{\rm warm}} \sim 10^{21}$ cm$^{-2}$.

Molecular dynamics simulations of gas–liquid nucleation of Lennard-Jones fluid

Grand canonical molecular dynamics simulations have been performed to determine the sizes of critical nuclei in gas–liquid nucleation. The studied system consists of Lennard-Jones (LJ) argon atoms with a potential cutoff of 4.9σ at a reduced temperature of 0.694 and at vapor supersaturations between 3.5 and 6.2. To facilitate comparison with nucleation theories, we have also determined the equilibrium vapor pressure of LJ argon as a function of temperature. The results are compared with other simulation studies, and with predictions of the classical (CNT) and density functional (DFT) nucleation theories. We find that the semiempirical version of the DFT is in excellent agreement with the simulation results, and that the CNT underestimates the number of LJ atoms in the nuclei only very slightly.

Green’s-function calculation of electron screening in a plasma

Extensions to the finite temperature Green's-function method for the calculation of equilibrium densities within the Kohn-Sham formulation of density functional theory are presented. In particular, an expression for the density in terms of single-particle Green's-function differences summed over all Matsubara poles is utilized. Numerical methods for the evaluation of this infinite sum are given. This formulation automatically includes discrete as well as continuum states, is valid for finite temperatures, and is especially well suited for high temperatures. Techniques are also presented for the calculation of single-particle Green's functions for spherically symmetric systems and arbitrary complex energies. The usefulness of these methods is demonstrated by their application to the problem of electron screening of nuclei in a plasma. Direct comparison is made with previous finite temperature, Kohn-Sham, wave function type calculations for protons and for neon nuclei in an electron gas.

Interaction between the W51C Supernova Remnant and a Molecular Cloud. II. Discovery of Shocked CO and HCO+

We carried out 12CO J = 1-0, J = 2-1,13CO J = 1-0, and HCO+ J = 1-0 line observations of the supernova remnant W51C in order to search for shocked molecules associated with the shocked H I reported in a companion paper. We discovered shocked CO distributed along an ~8' (or ~14 pc at a distance of 6 kpc) long arc structure. The position and morphology of the CO distribution coincide with the shocked H I. The shocked CO has line-of-sight velocities between +20 and +50 km s-1 with respect to the ambient cloud and velocity widths of 8-21 km s-1. The CO emission is optically thin, and Tex 10 K. The shocked CO is clumpy, and we have identified five clumps. Their column densities are in the range N(CO) = 1.2-4.0 × 1016 cm-2. Total mass of the shocked CO is 0.16 M☉. The HCO+/CO abundance ratio is 1.2-1.3 × 10-4, typical of quiescent molecular clouds. The fast-moving CO and HCO+ are probably the molecules that had been destroyed by a fast, dissociative J-type shock and re-formed behind the shock front. We find that the CO/H I abundance ratio is generally less than 4 × 10-5, except for some weak features. The upper limit implies that almost all the hydrogen nuclei in the shocked gas is atomic, not molecular. We conclude that the shock is old enough to re-form CO and HCO+ molecules but not old enough to completely re-form H2 molecules. We discuss the variation of the CO content of the shocked gas.

High nuclear polarization in3He and3He-4He gas mixtures by optical pumping with a laser diode

New diode lasers delivering 50 mW output power at 1083 nm are shown to be efficient sources for optical pumping of helium. They can polarize nuclei in a3He gas up toM = 50% over the pressure range 0.4–1.6 torr. Larger nuclear polarizationsM of3He nuclei, of order 80%, can be obtained in3He-4He mixtures when the laser frequency is tuned to a4He line. A standard optical measurement of nuclear polarizationM has been extended to the case of3He-4He mixtures. The effect of various parameters on the steady-state polarizationM and on the pumping timeTp is discussed.

Optical pumping magnetic resonance in high magnetic fields: characterization of the optical properties of Rb-Xe mixtures

The spectroscopic characteristics of the polarization of 129Xe nuclei in Xe gas by spin exchange with optically pumped Rb atoms is examined in high magnetic field. The high field Zeeman effect provides the spectral dispersion necessary to separate the effects of different light polarizations and incident wavelengths on the pumping cycle. Indirect detection of the D1 line in Rb using 129Xe nuclear magnetic resonance in combination with direct optical detection indicates that conventional container construction significantly decreases the efficiency of the 129Xe polarization. The decreased pumping efficiency is due to randomly polarized photons that can be eliminated by using containers with good optical quality windows. Study of these effects is facilitated by the large Zeeman shifts obtained with multi-tesla fields which resolve the D1 multiplet structure even in the presence of the significant pressure-broadening incells with typical gas pressures of 0⋅1-1 atm.

ORFEUS Observations of G191-B2B: Neutral and Ionized Gas in the Local Interstellar Medium

view Abstract Citations (34) References (39) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS ORFEUS Observations of G191-B2B: Neutral and Ionized Gas in the Local Interstellar Medium Hurwitz, M. ; Bowyer, S. Abstract We present high-resolution (λ/δλ = 3000) observations of far-ultraviolet (900-1170 Å) absorption lines in the spectrum of the hot DA white dwarf G191-B2B, collected with the Berkeley EUV/FUV spectrometer in the ORFEUS telescope aboard the space platform Astro-SPAS during the mission of space shuttle Discovery flown in 1993 September. Lines of H I, C II, C* II, C III, N I, N II, N III, and O I are detected, and useful upper limits are set on C I and O VI. The apparent position of the H I "Lyman edge," actually the convergence of many lines approaching the H I ionization potential, determines a narrow range of allowed values for the broadening parameter b for H I; equivalent widths of discrete H I features in combination with the column density of H I determined from Extreme Ultraviolet Explorer observations (Dupuis et al. 1995) confirm this range. We find bH I = 11.0±1.0 km s-1. Features of O I allow us to estimate the temperature and turbulence (ζ) in the gas containing the neutral species; we find 6200 < T < 8700 K and ζ < 4.3 km s-1. If the temperature and turbulence are similar to those found by Linsky et al. (1993) for the nearby line of sight to Capella, the column densities of the neutral species O I and N I are consistent with the column of H I and cosmic elemental abundances, suggesting similar ionization fractions for all three elements in the local cloud, and low depletion. The equivalent widths of the C II and N II features are significantly larger than would be expected from the local cloud gas unless hydrogen in the local cloud is very highly ionized. We rule out this possibility on the grounds that the resulting high electron density would overproduce the population of excited-state C* II, whose column density is constrained by our data, and requires χH < 0.75 in the local cloud. We conclude that one or more additional clouds exist along the line of sight. The column density of hydrogen nuclei in gas beyond the local cloud could be as low as 4 × 1017 cm-2, if the local cloud ionization is at its upper limit and the region is well separated in velocity from the local cloud, or as high as 2 × 1018 cm-2, adopting Doppler b-values for carbon and nitrogen that reconcile their column densities with cosmic abundances in each case. Regardless of how the ionized gas is distributed between the local cloud and other regions, NH II is comparable to or significantly greater than NH I along the line of sight. Our upper limit to NO VI requires that there be no more than two conductive interfaces along the line of sight. Publication: The Astrophysical Journal Pub Date: June 1995 DOI: 10.1086/175838 Bibcode: 1995ApJ...446..812H Keywords: ISM: GENERAL; STARS: ATMOSPHERES; STARS: INDIVIDUAL ALPHANUMERIC: G191-B2B; STARS: WHITE DWARFS; ULTRAVIOLET: STARS full text sources ADS | data products SIMBAD (8) MAST (1)

Production and Electrostatic Precipitation of Combustion Nuclei by an Electrified Propane--Air Flame

The results are given of an investigation into the production and electrostatic precipitation of combustion nuclei by an electrified propane-air flame. The apparatus consisted of a burner with a dc potential applied which was supported inside a grounded metal combustion chamber where the generation and removal of particles could be studied. A mathematical and experimental analysis of transient combustion nuclei concentrations inside the combustion chamber was carried out to evaluate the nuclei precipitation and production rates as a function of flame potentials and air flow rates. Two new theoretical equations containing production, precipitation, and flow parameters are derived to describe these transient concentrations. The constants of the equations were determined by experiment. These lead directly to the important parameters of nuclei production and precipitation rates, which are difficult to assess individually using previously known techniques. The experiments show that the concentration of combustion nuclei in the exhaust gas can be significantly decreased by the simple electrification of the flame. For combustion processes that generate aerosols, the method has the advantage of using the flame itself to affect the removal of the particles from the exhaust gases. Since combustion nuclei are receiving increased attention as air pollutants, this study could have important practical applications.

Disintegration threshold for nuclei in a degenerate electron-neutron gas

Disintegration threshold for nuclei in a degenerate electron-neutron gas

Internal structure of neutron stars

The equation of state and the structure and composition of neutron star matter are investigated in the density region 3.1 × 10 11−2 × 10 15g/cm 3. Below the density 3.1 × 10 11 g/cm 3 the matter is a solid consisting of neutron-rich nuclei in a degenerate electron gas. At 3.1 × 10 11g/cm 3 neutrons start to drip out of the nuclei; as the density increases, the lattice spacing continuously decreases while the geometrical size of the nuclei only slightly increases, until at about 15 × 10 13g/cm 3 the nuclei disappear by coalescing into a homogeneous liquid in an almost continuous phase transition. The maximum proton number per nucleus is 40, which is obtained between the densities 1−2.5 × 10 13g/cm 3; after that the proton number decreases until at the solid-to-liquid phase boundary it is about 20. In the liquid-core region, muons appear at the density 20.5 × 10 13g/cm 3. The calculations use the differential Thomas-Fermi theory in connection with a new model for the nuclear matter energy. The model is based on the parametrization of the Brueckner G-matrix in conjunction with a few empirical requirements concerning the saturation of the symmetric nuclear matter. It is shown that very small modifications in the details of the nuclear matter energy may lead to considerable differences in the resulting neutron star structure; for example the density of matter at the solid-to-liquid phase boundary is found to be very sensitive to such details. One of the main reasons for this is that the stability of the liquid against clustering into separate nuclei depends mainly on the second derivatives of the nuclear matter energy with respect to neutron and proton densities; for these second derivatives there exist no very reliable theoretical or phenomenological predictions so far. To check that the Thomas-Fermi theory together with the model for the nuclear matter energy works satisfactorily, a test calculation is made about finite nuclei of different sizes between A = 16 and 400.

Nuclear Magnetic Relaxation of 11B and F in BF3 Gas

The longitudinal nuclear magnetic relaxations of the 11B and F nuclei in BF3 gas have been measured as a function of pressure at temperatures of 270, 300, and 350°K, and the relaxation times T1 have been determined as a function of density. The purpose of the investigation was to determine whether or not there is a steplike dependence of T1 or T1 / ρ on density ρ for nuclei relaxed by quadrupole interactions in gas molecules. The T1 of 11B was found to increase linearly with density at low densities, and less rapidly than linearly at high densities, but no evidence of a steplike dependence on density was found.

Quadrupolar Relaxation ofXe131in Xenon Gas

A theoretical study is made of the spin-lattice relaxation of ${\mathrm{Xe}}^{131}$ ($I=\frac{3}{2}$) nuclei in pure xenon gas due to collision-induced nuclear electric quadrupole interactions. The calculation treats a pair of colliding Xe atoms as a rotating diatomic molecule, whose nuclear electric quadrupole interaction couples the nuclear spin and rotational angular momenta. This interaction permits the nuclei to relax by exchanging energy with the rotational motion of the colliding atoms. The quadrupole interaction in such a diatomic molecule is computed by considering the effects of exchange and Van der Waals interactions in deforming the spherical electronic charge clouds of the free atoms. It is found that the exchange interaction makes the dominant contribution to the quadrupole interaction. Averaging the single-collision transition probabilities over all types of collisions gives the following result for the spin-lattice relaxation time ${T}_{1}:\frac{1}{{T}_{1}}=0.046\ensuremath{\rho}$ ${\mathrm{sec}}^{\ensuremath{-}1}$, where $\ensuremath{\rho}$ is the density in amagats. This is in good agreement with the observed result: $\frac{1}{{T}_{1}}=0.039\ensuremath{\rho}$ ${\mathrm{sec}}^{\ensuremath{-}1}$.

On the theory of diffusion and sedimentation of condensation nuclei in cylindrical containers

The theory is given of a method for determining the diffusion coefficientD and the sedimentation velocityV of a suspension of uniform nuclei in a stationary gas contained in a cylindrical vessel with vertical axis and adsorbing walls. It is shown howD andV can be calculated from measurements of the total numberN of particles in the container or the relative loss per unit time $$\Lambda = - \frac{1}{N}\frac{{dN}}{{dt}}$$ of this number for two different time intervals. FromD andV the size, density and mass of the nuclei can be deduced.