Laboratory measurements of light scattering properties of kaolinite dust at 532 nm

Light scattering by kaolinite dust samples at 532 nm is studied using a newly developed laboratory apparatus. During the experiments, dust samples are suspended in water, aerosolized by a nebulizer, and then injected into the scattering zone, with or without going through a diffusion drier, to generate either dried dust particles or water droplets with dust inclusions. The light source is a dual wavelength (532 and 1064 nm) diode-pumped solid state laser. Light scattered by an ensemble of particles is collected by a charge-coupled device (CCD) camera, which is mounted on the rotating arm of a stepper motor. The stepper motor rotates the CCD to cover the scattering angle range from 3° to 177°. Polarized scattering light is measured for the horizontally and vertically polarized incident light. The apparatus is calibrated, using pure water droplets as the scattering media. The response function with respect to the scattering angle is obtained by comparing the measurements with Lorenz–Mie calculations and then used in the later data analysis. Measurements show that the backward scattering features of the water droplets are smoothened due to their dust inclusions. Numerical simulations and measurements are extensively compared and discussed. It is found that the Lorenz–Mie theory is inadequate to reproduce the scattering phase functions of either dust particles or water droplets with dust inclusions. A nonspherical aggregate model is applied to simulate the scattering phase functions. The simulation is able to reproduce the overall scattering features; however, substantial discrepancies still exist due to uncertainties in particle shape and refractive index.

Copyright © 2018 American Association for Aerosol Research     

Isolation of Ambient Particles of Known Critical Supersaturation: The Differential Activation Separator (DAS)

A field-deployable instrument has been developed that isolates from an ambient aerosol those particles that have critical supersaturations, S_c, within a narrow, user-specified, range. This Differential Activation Separator (DAS) consists of two continuous flow diffusion chambers housed within a single enclosure. Particles are introduced into the upstream chamber referred to as the CCN remover (CCNR) near the centerline between a warm, water-soaked, plate and a cool, continuously circulated, water bath. Those particles that activate at the resulting peak supersaturation, S_p, grow quickly and fall into the water bath. The remaining aerosol enters the second chamber referred to as the CCN separator (CCNS), which differs from the CCNR primarily in the use of a salt solution in the lower bath. The imposed temperature differential establishes an S_p slightly higher than that maintained in the upstream chamber, while the presence of a salt solution at the lower boundary results in a subsaturated region in roughly the lower half of the chamber. Those particles having (S_p)_CCNR < S _c < (S_p)_CCNS activate in this chamber and begin to fall due to gravitational settling. Before reaching the lower bath, the droplets evaporate in the subsaturated environment and continue to travel towards the chamber exit. The previously activated particles in the lower half of the chamber and the unactivated particles in the upper half are extracted in separate flows that are subsequently dried. Calibration of the DAS was achieved by measuring the size distribution of separated particles when a polydisperse ammonium sulfate aerosol was introduced.     

Starting up the Sherritt Zinc Pressure Leach Process at Hudson Bay

The first commercial application of the Sherritt two-stage zinc pressure leach process commenced operation at the Hudson Bay Mining and Smelting Company metallurgical complex in Flin Flon, Manitoba (Canada), on July 2, 1993. The start-up was relatively smooth, and full design rate for the plant was achieved by September 12, 1993. Since that time, zinc extraction in the zinc pressure leach plant has consistently been in excess of 98%, and production has continued to exceed expectations. The successful operation of the Hudson Bay plant represents a significant advancement of zinc processing technology, especially with respect to meeting the environmental challenge faced by zinc plants today.     

Efficient Synthesis of Highly Active Phospha‐Isosteres of the Influenza Neuraminidase Inhibitor Oseltamivir

With a Hunsdiecker–Barton iododecarboxylation strategy, we converted the carboxylate group of the oseltamivir precursor into exemplary phosphonate monoesters. In all cases, K_i values towards influenza virus sialidase remained in the sub‐nanomolar range. We have thus made valuable structural space available for the design of novel oseltamivir‐based tools for influenza virus research.

     

Cardiac Oxidative Signaling and Physiological Hypertrophy in the Na/K-ATPase α1s/sα2s/s Mouse Model of High Affinity for Cardiotonic Steroids

The Na/K-ATPase is the specific receptor for cardiotonic steroids (CTS) such as ouabain and digoxin. At pharmacological concentrations used in the treatment of cardiac conditions, CTS inhibit the ion-pumping function of Na/K-ATPase. At much lower concentrations, in the range of those reported for endogenous CTS in the blood, they stimulate hypertrophic growth of cultured cardiac myocytes through initiation of a Na/K-ATPase-mediated and reactive oxygen species (ROS)-dependent signaling. To examine a possible effect of endogenous concentrations of CTS on cardiac structure and function in vivo, we compared mice expressing the naturally resistant Na/K-ATPase α1 and age-matched mice genetically engineered to express a mutated Na/K-ATPase α1 with high affinity for CTS. In this model, total cardiac Na/K-ATPase activity, α1, α2, and β1 protein content remained unchanged, and the cardiac Na/K-ATPase dose–response curve to ouabain shifted to the left as expected. In males aged 3–6 months, increased α1 sensitivity to CTS resulted in a significant increase in cardiac carbonylated protein content, suggesting that ROS production was elevated. A moderate but significant increase of about 15% of the heart-weight-to-tibia-length ratio accompanied by an increase in the myocyte cross-sectional area was detected. Echocardiographic analyses did not reveal any change in cardiac function, and there was no fibrosis or re-expression of the fetal gene program. RNA sequencing analysis indicated that pathways related to energy metabolism were upregulated, while those related to extracellular matrix organization were downregulated. Consistent with a functional role of the latter, an angiotensin-II challenge that triggered fibrosis in the α1^r/rα2^s/s mouse failed to do so in the α1^s/sα2^s/s. Taken together, these results are indicative of a link between circulating CTS, Na/K-ATPase α1, ROS, and physiological cardiac hypertrophy in mice under baseline laboratory conditions.     

Lattice misfit during ageing of a polycrystalline nickel-base superalloy

The temporal evolution of the lattice parameters and lattice misfit of an advanced polycrystalline nickel-base superalloy have been studied in situ during an ageing heat treatment using synchrotron X-ray diffraction. During ageing, the γ and γ′ lattice parameters were both observed to decrease, a trend that cannot be attributed to a loss of coherency alone. Phase-extracted γ′ replicated this behaviour. Atom probe tomography was used to measure the compositional changes between the start and end of the ageing heat treatment. Using these data, a thermodynamic assessment was made using the software ThermoCalc of the structural change across the interface between γ and γ′. Subsequently, the unconstrained lattice parameters were estimated and were shown to be in good agreement with the X-ray diffraction measurements. Thus, the observed anomalous lattice misfit behaviour was concluded to be dominated by elemental exchange between the γ and γ′ phases during ageing.     

Sensitivity Analysis of Corrosion Rate Prediction Models Utilized for Reinforced Concrete Affected by Chloride

Chloride-induced reinforcement corrosion is one of the major causes of premature deterioration in reinforced concrete (RC) structures. Given the high maintenance and replacement costs, accurate modeling of RC deterioration is indispensable for ensuring the optimal allocation of limited economic resources. Since corrosion rate is one of the major factors influencing the rate of deterioration, many predictive models exist. However, because the existing models use very different sets of input parameters, the choice of model for RC deterioration is made difficult. Although the factors affecting corrosion rate are frequently reported in the literature, there is no published quantitative study on the sensitivity of predicted corrosion rate to the various input parameters. This paper presents the results of the sensitivity analysis of the input parameters for nine selected corrosion rate prediction models. Three different methods of analysis are used to determine and compare the sensitivity of corrosion rate to various input parameters: (i) univariate regression analysis, (ii) multivariate regression analysis, and (iii) sensitivity index. The results from the analysis have quantitatively verified that the corrosion rate of steel reinforcement bars in RC structures is highly sensitive to corrosion duration time, concrete resistivity, and concrete chloride content. These important findings establish that future empirical models for predicting corrosion rate of RC should carefully consider and incorporate these input parameters.     

Corrosion under mixed flowing gas conditions of various connector coatings

This paper presents an investigation on the corrosion performance of Ni/Au, NiP/Au, Ni/NiP/Au and Ni/NiPd/Au electrical connector coating systems. The coating systems were exposed to 10 days Class III mixed flowing gas and were subsequently examined by X‐ray diffraction, focused ion beam microscopy, scanning electron microscopy and energy dispersive spectroscopy to evaluate the performance of each coating system. The Ni/Au coating system showed the worst performance followed by NiP/Au and Ni/NiP/Au. The Ni/NiPd/Au coated connector materials exhibited the least surface corrosion and this was attributed to a number of factors including a thicker coating system, more compact gold layer with fewer defects and a reduction in the electrochemical potential difference between layers reducing the local cell effect.     

EVALUATION OF THE SOUNDING ROD METHOD FOR SAMPLING COARSE RIVERBED SEDIMENTS IN NON‐WADEABLE STREAMS AND RIVERS

The substrate of fluvial systems is regularly characterized as part of a larger physical habitat assessment. These measures are instrumental in meeting the regulatory responsibilities of bioassessment and monitoring programs, and essential to monitoring restoration and rehabilitation success. We describe and validate a commonly used technique for broadly categorizing, and thus characterizing, the substrate in non‐wadeable streams and rivers called the sounding rod method. In brief, a rod, often hollow, is used to probe the substrate of non‐wadeable systems to characterize the substrate. We tested the viability of this method on three different systems by comparing estimated particle class and direct particle measurements. Our results indicate that substrates can adequately be defined into six broad classes (fine‐particle sediment, sand, gravel, cobble, boulder and bedrock) based on size using the sounding rod. Estimated classes were significantly positively correlated to measured classes (τ = 0.83, p < 0.001), and estimates of size class and direct measurements of size were not from significantly different distributions (χ² _0.05,9 = 569.51, p < 0.001). Further, there were significant differences between each category (H = 243.5, 3 d.f., p < 0.001). Although our results affirm that actual substrate class size can be directly inferred from estimated data, it should be noted that soft sediments <200 mm were not always detected. This finding should be carefully considered with individual study objective. Overall, the sounding rod method can be learned quickly, and it is a low‐cost and time‐efficient method for substrate classification. Published 2013. This article is a U.S. Government work and is in the public domain in the USA.     

Determinants of temperature in small coastal embayments of Lake Ontario

Along 25 km of the Lake Ontario shoreline near Toronto, Ontario, small coastal embayments (0.4–32 ha) have been constructed or modified by lake-infilling to restore warmwater fish habitat. The variation in thermal habitat quality for warmwater fishes among these embayments is very high; temperatures range from those found within a small pond to those of much cooler Lake Ontario. Since meteorological conditions and surface heat fluxes are almost identical, the temperature variation among embayments must be caused by differences in bathymetry or exchange with Lake Ontario. However, a previous study on these embayments found paradoxically that temperatures were not strongly associated with channel size or embayment bathymetry. This paper resolves the paradox by showing that flushing times for almost all of the constructed embayments were less than 1 day, and often less than 12 h. With so little time to warm within the embayments, water temperatures of almost all embayments remained very close to the temperatures of the adjacent lake waters. The coldest embayments connected directly to open Lake Ontario and warmer embayments connected to Lake Ontario through other embayments or protected harbors, where the inflowing water from Lake Ontario had already substantially warmed. To allow embayments along the exposed shoreline of Toronto to reach acceptable temperatures for warmwater fish, we use heat budgets to calculate that average summer flushing times must be increased from their current length of 1.5 to 5.5 h to approximately 30 h. Such changes could be achieved through large reductions in the channel cross section.