Achieving a representative elementary volume (REV) has become a de facto criterion for demonstrating the quality of CT measurements in porous media systems. However, the data quality implications of ...an REV requirement have not been previously examined. In this work, deterministic REVs for porosity, moisture saturation (SW), and air‐water interfacial area (AI) were estimated using a set of 49 CT images of eight unsaturated homogeneous porous media with heterogeneity in moisture distributions present in varying degrees. Estimated porosity REVs were <8 mm3 for all cases, smaller than typical CT image sizes (∼100 mm3). Estimated SW and AI REVs were <55 mm3 for cases with homogeneous moisture distributions but could not be estimated for cases with heterogeneous moisture distributions, due to the absence of a distinct “REV plateau” within the maximum imaged volume. Conventionally, SW and AI data from such non‐REV cases would be excluded. The implications of excluding data on the basis of REV were examined by comparing AI‐SW data measured on image windows of increasing size against the expected linear AI‐SW relationship. At measurement scales exceeding porosity REV, random fluctuations in AI‐SW data were excluded, even for cases containing heterogeneous moisture distributions. In contrast, requiring measurement scales to exceed SW and AI REV appeared overly restrictive and resulted in visible loss of reliable AI‐SW data. We attribute these findings to overestimation of REVs due to inherently problematic estimation of deterministic REVs in real systems. Implications of these findings for ensuring CT data quality and the efficient use of CT data are discussed.
Key Points
REVs are achieved within the size of typical µCT images for homogeneous systems
REVs may be routinely overestimated for real systems
Higher µCT spatial resolution and increased data efficiency may be possible
Microalgae have been investigated as a promising biodiesel feedstock; however, large-scale production is not currently cost-competitive with petroleum diesel, and its environmental impacts have ...received little attention. Using wastewater to supply nutrients for algal growth obviates synthetic fertilizer use, provides on-site nutrient removal, and reduces greenhouse gas emissions. In this work, anaerobically digested dairy manure was used to grow the oleaginous green alga
Neochloris oleoabundans. In batch culture experiments with both synthetic media and anaerobic digester effluent,
N. oleoabundans assimilated 90–95% of the initial nitrate and ammonium after 6 d and yielded 10–30% fatty acid methyl esters on a dry weight basis. Cellular lipid content and the N concentration in the growth media were inversely correlated. In addition, the proportion of polyunsaturated fatty acids (i.e. C16:3, C18:2, and C18:3) decreased with N concentration over time while the proportion of C18:1 fatty acid increased. Although N deficiency is likely the primary driver behind lipid accumulation, the influence of culture pH confounded results and requires further study. Other living microorganisms in the digester effluent were not observed to affect algal growth and lipid productivity, though the breakdown of organic nitrogen may have hindered lipid accumulation traditionally achieved through the manipulation of synthetic media. This work highlights the potential for waste-grown mono-algal cultures to produce high quality biodiesel while accomplishing simultaneous wastewater treatment.
The reactions γp→ηp and γp→η^{'}p are measured from their thresholds up to the center-of-mass energy W=1.96 GeV with the tagged-photon facilities at the Mainz Microtron, MAMI. Differential cross ...sections are obtained with unprecedented statistical accuracy, providing fine energy binning and full production-angle coverage. A strong cusp is observed in the total cross section for η photoproduction at the energies in the vicinity of the η^{'} threshold, W=1896 MeV (E_{γ}=1447 MeV). Within the framework of a revised ηMAID isobar model, the cusp, in connection with a steep rise of the η^{'} total cross section from its threshold, can only be explained by a strong coupling of the poorly known N(1895)1/2^{-} state to both ηp and η^{'}p. Including the new high-accuracy results in the ηMAID fit to available η and η^{'} photoproduction data allows the determination of the N(1895)1/2^{-} properties.
Objectives
To assess the extent to which crime, Hispanic‐to‐white population changes, black‐to‐white population changes, and conservative political appeals affect gun permit application rates across ...Texas counties.
Methods
This article uses spatial lag regression and robust regression with county‐level data to assess structural sources of variation in handgun permitting across Texas counties in 2016.
Conclusions
Spatial and robust regression model results confirm that median incomes, Republican votes, and rising rates of Hispanic‐to‐white populations are significant predictors of handgun permit application rates. The results call attention to the centrality of Hispanic threat and the prevalence of partisan politics in aggregate permit‐seeking processes.
A precise measurement of the differential cross sections dσ/dΩ and the linearly polarized photon beam asymmetry Σ_{3} for Compton scattering on the proton below pion threshold has been performed with ...a tagged photon beam and almost 4π detector at the Mainz Microtron. The incident photons were produced by the recently upgraded Glasgow-Mainz photon tagging facility and impinged on a cryogenic liquid hydrogen target, with the scattered photons detected in the Crystal Ball/TAPS setup. Using the highest statistics Compton scattering data ever measured on the proton along with two effective field theories (both covariant baryon and heavy-baryon) and one fixed-t dispersion relation model, constraining the fits with the Baldin sum rule, we have obtained the proton electric and magnetic polarizabilities with unprecedented precision: α_{E1}=10.99±0.16±0.47±0.17±0.34, β_{M1}=3.14±0.21±0.24±0.20±0.35; in units of 10^{-4} fm^{3} where the errors are statistical, systematic, spin polarizability dependent, and model dependent.
We report a measurement of the spin polarization of the recoiling neutron in deuterium photodisintegration, utilizing a new large acceptance polarimeter within the Crystal Ball at MAMI. The measured ...photon energy range of 300-700 MeV provides the first measurement of recoil neutron polarization at photon energies where the quark substructure of the deuteron plays a role, thereby providing important new constraints on photodisintegration mechanisms. A very high neutron polarization in a narrow structure centered around E_{γ}∼570 MeV is observed, which is inconsistent with current theoretical predictions employing nucleon resonance degrees of freedom. A Legendre polynomial decomposition suggests this behavior could be related to the excitation of the d^{*}(2380) hexaquark.
The relationships among air-water interfacial area, capillary pressure, and water saturation were investigated for a sandy, natural porous medium. Air-water interfacial areas as a function of water ...saturation were measured using two methods, gas phase partitioning tracer tests and synchrotron X-ray microtomography. The tracer test method provides a measure of effective total (capillary and film) interfacial area, whereas microtomography can be used to determine both capillary-associated and total areas (the latter is the focus of this study). Air-water interfacial areas determined with both methods increased continuously with decreasing water saturation. The areas measured with the tracer test method were significantly larger than those obtained from microtomography. The maximum values measured with the tracer test method approached the N2/BET-measured specific solid surface area, whereas the maximum values measured by microtomography approached the smooth-sphere-calculated specific solid surface area. The interfacial area-saturation data were combined with capillary pressure-saturation data obtained from water drainage experiments to examine the relationship between total air-water interfacial area and capillary pressure. Air-water interfacial area was observed to increase monotonically with increasing capillary pressure and then to plateau at values that correspond to areas associated with residual water saturation. These results are consistent with previously reported theoretically and computationally based analyses of functional relationships between total nonwetting-wetting interfacial area and capillary pressure.
The double polarization observable E and the helicity dependent cross sections σ_{1/2} and σ_{3/2} were measured for η photoproduction from quasifree protons and neutrons. The circularly polarized ...tagged photon beam of the A2 experiment at the Mainz MAMI accelerator was used in combination with a longitudinally polarized deuterated butanol target. The almost 4π detector setup of the Crystal Ball and TAPS is ideally suited to detect the recoil nucleons and the decay photons from η→2γ and η→3π^{0}. The results show that the narrow structure previously observed in η photoproduction from the neutron is only apparent in σ_{1/2} and hence, most likely related to a spin-1/2 amplitude. Nucleon resonances that contribute to this partial wave in η production are only N 1/2^{-} (S_{11}) and N 1/2^{+} (P_{11}). Furthermore, the extracted Legendre coefficients of the angular distributions for σ_{1/2} are in good agreement with recent reaction model predictions assuming a narrow resonance in the P_{11} wave as the origin of this structure.
The spin polarizabilities of the nucleon describe how the spin of the nucleon responds to an incident polarized photon. The most model-independent way to extract the nucleon spin polarizabilities is ...through polarized Compton scattering. Double-polarized Compton scattering asymmetries on the proton were measured in the Δ(1232) region using circularly polarized incident photons and a transversely polarized proton target at the Mainz Microtron. Fits to asymmetry data were performed using a dispersion model calculation and a baryon chiral perturbation theory calculation, and a separation of all four proton spin polarizabilities in the multipole basis was achieved. The analysis based on a dispersion model calculation yields γ(E1E1)=-3.5±1.2, γ(M1M1)=3.16±0.85, γ(E1M2)=-0.7±1.2, and γ(M1E2)=1.99±0.29, in units of 10(-4) fm(4).
This article uses multi-level analysis to model the effects of both institutional and state characteristics on juvenile reported sexual behavior (both consensual and forced) in 118 juvenile ...correctional facilities across 36 states. Data are taken from the 2012 National Survey of Youth in Custody (NSYC). We examine three dimensions of reported sexual contact including: forced sexual contact between juveniles and other institutionalized juveniles; forced sexual contact between juveniles and staff; and alleged consensual contact between juveniles and staff. At the institutional-level, facility capacity is the most consistent significant predictor of reported sexual contact. Findings also indicate that state-level variables such as median income and state-level violent crime rates are significantly associated with some types of reported incidents. Privacy protections of the available data make it impossible to look at individual level factors; however, we suggest this as a future step in important research.
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