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Sequential density fractionation separated soil particles into “light” predominantly mineral-free organic matter vs. increasingly “heavy” organo-mineral particles in four soils of widely differing mineralogy. With increasing particle density C concentration decreased, implying that the soil organic matter (OM) accumulations were thinner. With thinner accumulations we saw evidence for both an increase in ¹⁴C-based mean residence time (MRT) of the OM and a shift from plant to microbial origin.Evidence for the latter included: (1) a decrease in C/N, (2) a decrease in lignin phenols and an increase in their oxidation state, and (3) an increase in δ¹³C and δ¹⁵N. Although bulk-soil OM levels varied substantially across the four soils, trends in OM composition and MRT across the density fractions were similar. In the intermediate density fractions (~1.8-2.6 g cm⁻³), most of the reactive sites available for interaction with organic molecules were provided by aluminosilicate clays, and OM characteristics were consistent with a layered mode of OM accumulation. With increasing density (lower OM loading) within this range, OM showed evidence of an increasingly microbial origin. We hypothesize that this microbially derived OM was young at the time of attachment to the mineral surfaces but that it persisted due to both binding with mineral surfaces and protection beneath layers of younger, less microbially processed C. As a result of these processes, the OM increased in MRT, oxidation state, and degree of microbial processing in the sequentially denser intermediate fractions. Thus mineral surface chemistry is assumed to play little role in determining OM composition in these intermediate fractions. As the separation density was increased beyond ~2.6 g cm⁻³, mineralogy shifted markedly: aluminosilicate clays gave way first to light primary minerals including quartz, then at even higher densities to various Fe-bearing primary minerals. Correspondingly, we observed a marked drop in δ¹⁵N, a weaker decrease in extent of microbial processing of lignin phenols, and some evidence of a rise in C/N ratio. At the same time, however, ¹⁴C-based MRT time continued its increase. The increase in MRT, despite decreases in degree of microbial alteration, suggests that mineral surface composition (especially Fe concentration) plays a strong role in determining OM composition across these two densest fractions.

The state of a suspension is crucial with regard to processing pathways, functionality and performance of the end product. In the past decade, substantial progress has been made in designing highly specialized and functionalized particles. In current particle technology, besides classic particle properties such as particle size distribution, shape and density, surface properties play an essential role for processing, product specification and use. For example, in medical therapy, analytical diagnostic applications, as well as in separation processing and harvesting of high-valued materials, magnetic micro- and nanoparticles play an increasing role. In addition to traditional parameters such as size, the particle magnetization has to be quantified here.Sedimentation techniques have been used for hundreds of years to determine the geometrical characteristics of dispersed particles. Numerous national and international standards regarding these techniques have been published. Mainly due to the fast growing market share of laser scattering techniques over the past two decades, most customers these days are not aware of some advantageous features of particle characterization via a first-principle fractionating approach such as sedimentation. This is unfortunate as sedimentation techniques have made huge technological leaps forward regarding electronics, sensors and computing abilities.This paper aims to give a short review about different cumulative and incremental sedimentation approaches to measure the particle size distribution. It focuses mainly on the in-situ visualization (STEP-Technology®) of particle migration in gravitational and centrifugal fields. It describes the basics of the new multi-sample measuring approaches to quantify the separation kinetics by spatial and time-resolved particle concentration over the entire sample height. Based on these data, the sedimentation velocity and particle size distribution are elucidated and estimates of accuracy, precision and experimental uncertainties are discussed. Multi-wavelength approaches, correction of higher concentration, and the influence of rheological behavior of continuous phase will also be discussed. Applications beyond the traditional scope of sedimentation analysis are presented. This concerns the in-situ determination of hydrodynamic particle density and of magnetophoretic velocity distributions for magnetic particulate objects.

This paper presents a photogrammetry-based volume measurement framework for the particle density estimation of Lightweight expanded clay aggregate (LECA). The results are compared with computed tomography (CT) and Archimedes’ method measurements. All of the steps required in order to apply the proposed approach are explained. Next, we discuss how the interpretation of open pores affects the results of volume measurements. We propose to process the shapes obtained from different methods by applying an Ambient Occlusion algorithm with the same threshold, t = 0.175. The difference between the CT and SfM methods is less than 0.006 g/cm3, proving that the photogrammetry-based approach is accurate enough. The Archimedes’ method significantly overestimates the density of the particles. Nevertheless, its accuracy is acceptable for most engineering purposes. Additionally, we evaluate the accuracy of shape reconstruction (in terms of the Hausdorff distance). For 95% of the grain’s surface, the maximum error is between 0.073 mm and 0.129 mm (depending on the grain shape). The presented approach is helpful for measuring the particle density of porous aggregates. The proposed methodology can be utilized in order to estimate intergranular porosity, which is valuable information for the calibration of DEM models.

We investigate a single-particle density of states in the three-dimensional system described by effective two-band Hamiltonian, which describes a ground state in two distant electronic phases: the semimetalic nodal-loop phase and the insulating gapped phase. An analysis of valence bands and Fermi surfaces in both phases indicates that the density of states crucially depends on the parameter in the Hamiltonian of the system that controls a topological alternation of the Fermi surface. The signature of that alternation is expected to play an important role in all quantities closely related to the density of electronic states, such as charge transport and the optical conductivity of the system for example.

We study the action of Bogoliubov transformations on admissible generalized one-particle density matrices arising in Hartree–Fock–Bogoliubov theory. We show that the orbits of this action are reductive homogeneous spaces, and we give several equivalences that characterize when they are embedded submanifolds of natural ambient spaces. We use Lie theoretic arguments to prove that these orbits admit an invariant symplectic form. If, in addition, the operators in the orbits have finite spectrum, then we obtain that the orbits are actually Kähler homogeneous spaces.

Effective particle density is a key parameter for assessing inhalation exposure of engineered NPs in occupational environments. In this paper, particle density measurements were carried out using two different techniques: one based on the ratio between mass and volumetric particle concentrations; the other one based on the ratio between aerodynamic and geometric particle diameter. These different approaches were applied to both field- and laboratory-scale atomization processes where the two target NPs (N-doped TiO2, TiO2N and AgNPs capped with a quaternized hydroxyethylcellulose, AgHEC) were generated. Spray tests using TiO2N were observed to release more and bigger particles than tests with AgHEC, as indicated by the measured particle mass concentrations and volumes. Our findings give an effective density of TiO2N particle to be in a similar range between field and laboratory measurements (1.8 ± 0.5 g/cm3); while AgHEC particle density showed wide variations (3.0 ± 0.5 g/cm3 and 1.2 + 0.1 g/cm3 for field and laboratory campaigns, respectively). This finding leads to speculation regarding the composition of particles emitted because atomized particle fragments may contain different Ag-to-HEC ratios, leading to different density values. A further uncertainty factor is probably related to low process emissions, making the subtraction of background concentrations from AgHEC process emissions unreliable.

String cosmology has been investigated in a spatially symmetric Bianchi-IX line element under consideration of flat potential. To illustrate the nonlinear system of field equations an appropriate relation between the metric coefficient and the hybrid expansion law (HEL) for the scalar factor a (t) is considered i.e. a ( t ) = a 0 t γ 1 e γ 2 t where γ 1 and γ 2 are the non-negative constants and a 0 denotes current value of a(t) . It has been observed that the energy density and particle density diverge initially and become finite for large t. The tension in string clouds tends to infinite when t = 0 and constant value at a large value of t for m>1. The proper volume is also increases with time in exponentially way favorable to inflationary criteria. Expansion and shear infinite large initially and approach to finite value at late time. Some structural aspects of the model and their importance are pointed.

To evaluate the neurotoxic effects from exposure to airborne tungsten, we developed a method of generating mass concentrations of this element between 5 and 10 mg m −3 , the time-weighted average occupational exposure limits. We then conducted measurements of the aerosol—a challenge due to the high particle density—that enabled us to calculate the deposition in the upper airway and lungs. First, we fed a mixture of coarse tungsten bead powder and aerosolizable tungsten powder, which had been combined in specific mass proportions, to an RBG 1000 (Palas®) equipped with a cyclone at the outlet that filtered out the coarse particles. Then, we simultaneously measured the resultant aerosol, which was generated in an inhalation chamber, using three pairs of instruments—a Dekati® Low Pressure Impactor (DLPI; 30 L min − ) and a gravimetric filter holder, a DLPI and a TSI® Aerodynamic Particle Sizer (APS; Model 3321), a TSI Engine Exhaust Particle Sizer (EEPS; Model 3090) and an APS—and symmetrical sampling lines. The mass concentrations obtained with the DLPI and the filter holder were extremely consistent with each other, and the mass median aerodynamic diameters based on the DLPI and the APS data (with the Stokes correction applied to the latter) were also fairly close (1.77 and 1.89 µm, respectively). Additionally, the count median diameter determined from the electrical mobility measured by the EEPS equaled 0.17 µm, which falls beyond both the intended range of the instrument and the range of previously studied aerodynamic sizes. Overall, the results from the DLPI, the APS, and the EEPS showed very good agreement. Computational fluid dynamics (CFD) simulations of the airflows and aerosol dispersion in the inhalation chamber verified that the test aerosol was homogeneous and representative.

A measurement method of the apparent particle density of the carbon nanotube (CNT) particles, characterized by enveloped volume formed by loosely entangled nanotubes, has been proposed for the CNT fluidized bed application. The method is characterized by obtaining the enveloped volume from the CNTs imaging under the free falling condition similar to the fluidized bed. The shape of the falling CNT particles in a column (0.1 m long × 0.012 m wide × 0.60 m high) was photographed using a high-speed camera under the sedimentation condition, and the apparent CNT particle density was calculated from the enveloped volume obtained by image-processing for the particles images. The apparent densities and solid holdups by the imaging method at various conditions were compared with those by the previous Hg-porosimetry method for the two types of CNTs (a vertically aligned CNT and two entangle CNTs) and the nonporous polycarbonate particle (a reference particle). The imaging method reflects well the packed bed and fluidized bed phenomena observed in the experiments with reasonable solid holdups, compared with the Hg-porosimetry method showing high densities and low holdups. The sizes of CNT particles predicted with the density by the imaging method were in good agreement with the measured mean particle sizes when calculated based on the Richardson–Zaki equation, indicating the imaging method represented well the enveloped volume and shape formed by entangled nanotubes on the CNTs.

This work offers a vision of physicochemical properties of the soils of Caleta Vítor, Northern Chile, such as: organic matter content, pH, porosity, apparent density, particle density and contamination by the presence of Cu, Pb and Zn in the soils where the abandoned mine Compañía Minera San Carlos is located, areas surrounding the river and the beach. The environmental impact of this abandoned mine is analyzed by evaluating the enrichment factor of the metals and the corresponding geo-accumulation index. The information obtained in this study is compared with those reported by SERNAGEOMIN five years earlier. The results of the enrichment factors based on PEC reach values of up to 664 times above the probable effects of their concentration can be observed and, based on TEC, 3037 times above harmful effects due to the presence of Cu can be observed. The Igeo index calculation shows that the abandoned mine area and samples located in the river area and the beach closest to the mining area can be classified as extremely to highly contaminated with Cu and Pb, while they are not contaminated with Zn. It is also shown that almost all sites in the abandoned mining area have increased after five years their Cu concentration between 2 and 54 times; a similar situation is observed with Pb and to a lesser extent with Zn.