Atomic Mass Fractions Research Articles

Enhancing sludge conditioning and dewatering characteristics by active surfaces modified with fast recombining immobilized nanoparticles

Nichrome is a composite of nickel chromium alloys and commonly used as resistance wire for heating equipment. In this study, ability of multilayered heterojunctions between Cr+3-TiO2 and Ni2+-TiO2 nanoparticles to disintegrate acidified slurry sludge was investigated experimentally. Recombination and photoactivity of the Cr3+ and Ni2+ nanoparticles were optimized alternating their atomic mass fractions in the nanocomposites by their heating ability, using a central composite statistical design approach. Effects of the applied method on sludge conditioning, stabilization, and drying behaviors were systematically investigated. Temperature increase (ΔT) at the highest volatile suspended solids (VSS) oxidation level in the treated sludge samples were 2 ± 1 °C, 5 ± 1 °C, and 20 ± 1 °C for “UV C + H2O2-no catalyst,” pure and Cr-Ni-TiO2 thin films (TFs), respectively. Obtained results also indicated that the modified TiO2 nanoparticles were able to decrease sludge bound water content by 45 ± 1% efficiency. Cr3+ and Ni+2 co-doped TF functioned to decrease the unit drying energy from 236 ± 10 kJ kg−1 H2Oevaporated to 140 ± 10 kJ kg−1 H2Oevaporated. Drying profiles of raw and treated the sludge samples were fitted to Henderson and Pabis Model. Drying constants (k) for raw and treated sludge samples by pure TiO2 and Cr-Ni-TiO2 TFs were found to be 0.11 ± 0.01 min−1, 0.12 ± 0.01 min−1, and 0.19 ± 0.01 min−1, respectively. VSS degradation followed pseudo-first-order reaction kinetics in the all assayed conditions and pseudo-first-order reaction rates (k obs) for pure and the modified TFs were determined as 6 × 10−4 min−1 and 4 × 10−3 min−1, respectively. 2,2′,5-Trichlorobphennyl, 2,2′,5,5′-Tetrachlorobiphenyl, 2,3′,4,4′,5-Pentachlorobiphenyl, and 2,2′,3,4,4,5,5′-Heptachlorobiphenyl were detected in raw sludge and after the photocatalytic oxidation through Cr3+ and Ni2+ co-doped TiO2 TF reactor, their total concentration was reduced from 4.36 mg kg−1 to 9.76 × 10−3 mg kg−1.

Relative Atomic Solar System Abundances, Mass Fractions, and Atomic Masses of the Elements and Their Isotopes, Composition of the Solar Photosphere, and Compositions of the Major Chondritic Meteorite Groups

This brief special communications article gives data for atomic abundances and mass fractions for the elemental and isotopic solar system composition, the atomic masses of the elements and their isotopes, the composition of the solar photosphere, and the compositions of the major chondritic meteorite groups. This additional material is relevant for researchers who are interested in this Topical Collection on planetary evolution.

Molecular and atomic gas along and across the main sequence of star-forming galaxies

We use spectra from the ALFALFA, GASS and COLD GASS surveys to quantify variations in the mean atomic and molecular gas mass fractions throughout the SFR-M* plane and along the main sequence (MS) of star-forming galaxies. Although galaxies well below the MS tend to be undetected in the Arecibo and IRAM observations, reliable mean atomic and molecular gas fractions can be obtained through a spectral stacking technique. We find that the position of galaxies in the SFR-M* plane can be explained mostly by their global cold gas reservoirs as observed in the HI line, with in addition systematic variations in the molecular-to-atomic ratio and star formation efficiency. When looking at galaxies within +/-0.4 dex of the MS, we find that as stellar mass increases, both atomic and molecular gas mass fractions decrease, stellar bulges become more prominent, and the mean stellar ages increase. Both star formation efficiency and molecular-to-atomic ratios vary little for massive main sequence galaxies, indicating that the flattening of the MS is due to the global decrease of the cold gas reservoirs of galaxies rather than to bottlenecks in the process of converting cold atomic gas to stars.

Micro-X-Ray Fluorescence Spectrometry of the Surface Elemental Composition of Vegetative Parts and Fruiting Bodies of Lichenized Teloschistaceae Fungi

The elemental composition and atomic mass ratios (%) on the surface of vegetative and generative parts of crustose Caloplaca cerina and foliose Xanthoria parietina lichen thalli collected from the same tree trunk were measured using micro-x-ray fluorescence spectrometry. The atomic mass fractions for half of the elements (of 21 identified) were significantly higher on the surfaces of fruiting bodies (apothecia) than on vegetative parts of thalli of both species. The atomic mass fractions of most elements were much greater on the surfaces of fruiting bodies and vegetative parts of the foliose species than on the crustose species.

A systematic study of the inner rotation curves of galaxies observed as part of the GASS and COLD GASS surveys

We present a systematic analysis of the rotation curves of 187 galaxies with masses greater than 10^10 M_sol, with atomic gas masses from the GALEX Arecibo Sloan Survey (GASS), and with follow-up long-slit spectroscopy from the MMT. Our analysis focuses on stellar rotation curves derived by fitting stellar template spectra to the galaxy spectra binned along the slit. In this way, we are able to obtain accurate rotation velocity measurements for a factor of 2 more galaxies than possible with the Halpha line. Galaxies with high atomic gas mass fractions are the most dark-matter dominated galaxies in our sample and have dark matter halo density profiles that are well fit by Navarro, Frenk & White profiles with an average concentration parameter of 10. The inner slopes and of the rotation curves correlate more strongly with stellar population age than with galaxy mass or structural parameters. At fixed stellar mass, the rotation curves of more actively star-forming galaxies have steeper inner slopes than less actively star-forming galaxies. The ratio between the galaxy specific angular momentum and the total specific angular momentum of its dark matter halo, R_j, correlates strongly with galaxy mass, structure and gas content. Low mass, disk-dominated galaxies with atomic gas mass fractions greater than 20% have median values of R_j of around 1, but massive, bulge-dominated galaxies have R_j=0.2-0.3. We argue that these trends can be understood in a picture where gas inflows triggered by disk instabilities lead to the formation of passive, bulge-dominated galaxies with low specific angular momentum.

Numerical analysis of the Cambridge stratified flame series using artificial thickened flame LES with tabulated premixed flame chemistry

Detailed comparisons of LES results against measurement data are presented for the turbulent lean and rich stratified Cambridge flame series. The co-annular methane/air burner with a central bluff body for flame stabilization has been investigated experimentally by Sweeney et al. [1,2]. Three cases with varying levels of stratification in the lean and rich combustion regime are taken into account. Turbulent combustion is modeled by using the artificial thickened flame (ATF) approach in combination with flamelet generated manifolds (FGM) lookup tables. The model is adapted for stratified combustion and an alternative formulation for the flame sensor is presented. Three different grids are used to investigate the influence of the filter width and the sub-filter modeling on the overall results. Velocities, temperatures, equivalence ratios, and major species mass fractions predictions are compared with measurements for three different stratification rates and an overall good overall agreement was found between simulation and experiment. Some deviations occur near the bluff body, which are analyzed further by evaluation of atomic and species mass fractions. The stratified combustion process was further investigated and characterized by probability density functions extracted from the simulation results.

ALFALFA H I data stacking - III. Comparison of environmental trends in H I gas mass fraction and specific star formation rate

It is well known that both the star formation rate and the cold gas content of a galaxy depend on the local density out to distances of a few Megaparsecs. In this paper, we compare the environmental density dependence of the atomic gas mass fractions of nearby galaxies with the density dependence of their central and global specific star formation rates. We stack HI line spectra extracted from the Arecibo Legacy Fast ALFA survey centered on galaxies with UV imaging from GALEX and optical imaging/spectroscopy from SDSS. We use these stacked spectra to evaluate the mean atomic gas mass fraction of galaxies in bins of stellar mass and local density. For galaxies with stellar masses less than 10^10.5 M_sun, the decline in mean atomic gas mass fraction with density is stronger than the decline in mean global and central specific star formation rate. The same conclusion does not hold for more massive galaxies. We interpret our results as evidence for ram-pressure stripping of atomic gas from the outer disks of low mass satellite galaxies. We compare our results with the semi-analytic recipes of Guo et al. (2011) implemented on the Millennium II simulation. These models assume that only the diffuse gas surrounding satellite galaxies is stripped, a process that is often termed "strangulation". We show that these models predict relative trends in atomic gas and star formation that are in disagreement with observations. We use mock catalogues generated from the simulation to predict the halo masses of the HI-deficient galaxies in our sample. We conclude that ram-pressure stripping is likely to become effective in dark matter halos with masses greater than 10^13 M_sun.

Effects of preferential transport in turbulent bluff-body-stabilized lean premixed CH4/air flames

Preferential species diffusion is known to have important effects on local flame structure in turbulent premixed flames, and differential diffusion of heat and mass can have significant effects on both local flame structure and global flame parameters, such as turbulent flame speed. However, models for turbulent premixed combustion normally assume that atomic mass fractions are conserved from reactants to fully burnt products. Experiments reported here indicate that this basic assumption may be incorrect for an important class of turbulent flames. Measurements of major species and temperature in the near field of turbulent, bluff-body stabilized, lean premixed methane–air flames (Le=0.98) reveal significant departures from expected conditional mean compositional structure in the combustion products as well as within the flame. Net increases exceeding 10% in the equivalence ratio and the carbon-to-hydrogen atom ratio are observed across the turbulent flame brush. Corresponding measurements across an unstrained laminar flame at similar equivalence ratio are in close agreement with calculations performed using Chemkin with the GRI 3.0 mechanism and multi-component transport, confirming accuracy of experimental techniques. Results suggest that the large effects observed in the turbulent bluff-body burner are cause by preferential transport of H2 and H2O through the preheat zone ahead of CO2 and CO, followed by convective transport downstream and away from the local flame brush. This preferential transport effect increases with increasing velocity of reactants past the bluff body and is apparently amplified by the presence of a strong recirculation zone where excess CO2 is accumulated.

SU‐GG‐I‐33: A General Three‐Material Quantification Method Using Dual‐Energy CT Imaging

Purpose: To propose a general method to quantify the density, atomic number, and mass fraction of three materials using only two energies levels (kVp settings), and evaluate its performance with quantitative simulations. Method and Materials: It is well known that dual‐energy CT can accurately quantify the density and atomic number for two materials in a two‐material object. This is possible because the dual‐energy CT technique provides two spectrally different measurements. For an object with three constituents, an additional measurement is required to solve the dual‐energy equations that now have three unknown values. Under certain conditions, a third physical measurement is not needed to solve for the three unknowns. One such solution is to assume that each material has a constant volume when mixed together, which provides an additional equation regarding the mixture's density. However, the constant volume assumption is not always true. Here, we calculate the mixture's density based on the mass attenuation coefficient, which can be expressed using the effective atomic number and density of the mixture. Then, we use the calculated density of the mixture to solve for the mass fractions of the three materials. To evaluate this method, we made numerical simulations using different densities of hydroxyapatite (HA: ). The developed algorithm is applied to the images and the chemical elements Ca, P, and are quantified. Results: The numerical simulation results indicate that the proposed method can accurately calculate the effective atomic number, density, and mass fractions of the constituents of a mixture for up to three different materials. Conclusion: The proposed algorithm is a general material‐decomposition method for dual‐energy CT. The number of materials which can be quantified is up to three. Conflict of Interest: CHM and ANP: Research grants from Siemens Medical Solutions.

The uncertainty of atomic mass fractions in a molecule.

The mass fraction of a certain atom species in a molecule is needed for the calculation of the result of some chemical analyses. Common examples are gravimetric determinations (e.g., the sulfur concentration in a sample that can be obtained from the mass of precipitated barium sulfate). A similar problem is encountered when a reference solution of an ion is prepared by dissolution of a salt. This paper presents how the uncertainty of the mass fraction is calculated from the uncertainties of the atomic weights as published by IUPAC. The value is needed for the determination of the combined standard uncertainty of the analysis. Some calculated examples illustrate the mathematical considerations presented in the paper.

3D modeling of a microwave post-discharge nitriding reactor

A 3D model has been developed for a post-discharge microwave nitriding reactor. It enables prediction of the hydrodynamics of the gas, together with the distribution of atomic nitrogen mass fractions, representing the map of the active nitriding species, and the temperature distribution inside the reactor. The coupled transport equations are solved using the PHOENICS calculation code. The model has been used to simulate the phenomena occurring in the gas phase during the nitriding of three pure iron rods placed in the reactor. The optimum nitriding conditions were determined by optical emission spectroscopy and N atoms titration by NO. Under these conditions, numerical validation of the model was performed by comparison with experiments, using a second solid-state diffusion model to evaluate the interaction between the solid and gas phases.

The ratio of molecular to atomic gas in infrared luminous galaxies

In infrared luminous galaxies the ratio of the CO(1 - 0) to H I integrated fluxes increases with the far-infrared excess, f(fir)/f(b). All infrared active galaxies with f(fir)/f(b) greater than 2 have molecular to atomic gas mass fractions greater than 0.5. Among the galaxies with the higher infrared excesses there are systems with strikingly small atomic mass fractions, where less than 15 percent of the total mass of interstellar gas is in atomic form. The optical morphology of luminous infrared galaxies indicates that the majority, if not all, of these objects are interacting systems. These observations suggest that the overall mass fraction of molecular to atomic gas, and the infrared luminosities per nucleon of interstellar gas are enhanced during galaxy-galaxy interactions.

The Ratio of H2 to HI Gas in Infrared Luminous Galaxies

AbstractThe majority of infrared active galaxies (ffir/fb ≥ 2) have molecular to atomic mass fractions in the range of 0.5 to 2.0. Among the galaxies with the higher infrared excesses there are spectacular cases of HI deficient systems, where less than 15% of the total mass of interstellar gas is in atomic form. The optical morphology of luminous infrared galaxies suggest that the overall mass fractions of molecular to atomic gas, and the infrared luminosities per nucleon of interstellar gas are enhanced during galaxy-galaxy interactions.