Complex refractive index, single scattering albedo, and mass absorption coefficient of secondary organic aerosols generated from oxidation of biogenic and anthropogenic precursors

Refractive index and optical properties of biogenic and anthropogenic secondary organic aerosol (SOA) particles were investigated. Aerosol precursors, namely longifolene, α-pinene, 1-methylnaphthalene, phenol, and toluene were oxidized in a Teflon chamber to produce SOA particles under different initial hydrocarbon concentrations and hydroxyl radical sources, reflecting exposures to different levels of nitrogen oxides (NOx). The real and imaginary components (n and k, respectively) of the refractive index at 375 nm and 632 nm were determined by Mie theory calculations through an iterative process, using the χ2 function to evaluate the fitness of the predicted optical parameters with the measured scattering, absorption, and extinction coefficients from a Photoacoustic Extinctiometer and Cavity Attenuated Phase Shift Spectrometer. Single scattering albedo (SSA) and bulk mass absorption coefficient (MAC) at 375 nm were calculated. SSA values of SOA particles from biogenic precursors (longifolene and α-pinene) were ∼0.98–0.99 (∼6.3% uncertainty), reflecting purely scattering aerosols regardless of the NOx regime. However, SOA particles from aromatic precursors were more absorbing and displayed NOx-dependent SSA values. For 1-methylnaphthalene SOA particles, SSA values of 0.92–0.95 and ∼0.75–0.90 (∼6.1% uncertainty) were observed under intermediate- and high-NOx conditions, respectively, reflecting the absorbing effects of SOA particles and NOx chemistry for this aromatic system. In mixtures of longifolene and phenol or longifolene and toluene SOA under intermediate- and high-NOx conditions, k values of the aromatic-related component of the SOA mixture were higher than that of 1-methylnaphthalene SOA particles. With the increase in OH exposure, kphenol decreased from 0.10 to 0.02 and 0.22 to 0.05 for intermediate- and high-NOx conditions, respectively. A simple relative radiative forcing calculation for urban environments at λ = 375 nm suggests the influence of absorbing SOA particles on relative radiative forcing at this wavelength is most significant for aerosol sizes greater than 0.4 µm. Copyright © 2019 American Association for Aerosol Research</p

Coal-shale interface detection system

A coal-shale interface detection system for use with coal cutting equipment consists of a reciprocating hammer on which an accelerometer is mounted to measure the impact of the hammer as it penetrates the ceiling or floor surface of a mine. A pair of reflectometers simultaneously view the same surface. The outputs of the accelerometer and reflectometers are detected and jointly registered to determine when an interface between coal and shale is being cut through

Self-Regulation in a Web-Based Course: A Case Study

Little is known about how successful students in Web-based courses self-regulate their learning. This descriptive case study used a social cognitive model of self-regulated learning (SRL) to investigate how six graduate students used and adapted traditional SRL strategies to complete tasks and cope with challenges in a Web-based technology course; it also explored motivational and environmental influences on strategy use. Primary data sources were three transcribed interviews with each of the students over the course of the semester, a transcribed interview with the course instructor, and the students’ reflective journals. Archived course documents, including transcripts of threaded discussions and student Web pages, were secondary data sources. Content analysis of the data indicated that these students used many traditional SRL strategies, but they also adapted planning, organization, environmental structuring, help seeking, monitoring, record keeping, and self-reflection strategies in ways that were unique to the Web-based learning environment. The data also suggested that important motivational influences on SRL strategy use—self-efficacy, goal orientation, interest, and attributions—were shaped largely by student successes in managing the technical and social environment of the course. Important environmental influences on SRL strategy use included instructor support, peer support, and course design. Implications for online course instructors and designers, and suggestions for future research are offered

Forever Chemicals Needing Immediate Solutions: Mainers’ Preferences for Addressing PFAS Contamination

Per- and poly-fluoroalkyl substances (PFAS) are a diverse class of synthetic fluorinated chemicals also referred to as “forever chemicals.” The release of these chemicals into the environment presents an urgent, emerging threat to human and environmental health. Decision-makers seeking to address a variety of PFAS-related issues need better understanding of citizens’ knowledge of PFAS contamination and their preferences for managing the issue. To provide this vital information, we analyze data from a survey of Maine citizens. We assess Maine residents’ baseline knowledge of PFAS contamination, as well as their preferences for generation and allocation of funds to address PFAS contamination in Maine. Per- and poly-fluoroalkyl substances (PFAS) are a diverse class of synthetic fluorinated chemicals also referred to as “forever chemicals.” The release of these chemicals into the environment presents an urgent, emerging threat to human and environmental health. Decision-makers seeking to address a variety of PFAS-related issues need better understanding of citizens’ knowledge of PFAS contamination and their preferences for managing the issue. To provide this vital information, we analyze data from a survey of Maine citizens. We assess Maine residents’ baseline knowledge of PFAS contamination, as well as their preferences for generation and allocation of funds to address PFAS contamination in Maine

Failure mechanisms and surface roughness statistics of fractured Fontainebleau sandstone

In an effort to investigate the link between failure mechanisms and the geometry of fractures of compacted grains materials, a detailed statistical analysis of the surfaces of fractured Fontainebleau sandstones has been achieved. The roughness of samples of different widths W is shown to be self affine with an exponent zeta=0.46 +- 0.05 over a range of length scales ranging from the grain size d up to an upper cut-off length \xi = 0.15 W. This low zeta value is in agreement with measurements on other sandstones and on sintered materials. The probability distributions P(delta z,delta h) of the variations of height over different distances delta z > d can be collapsed onto a single Gaussian distribution with a suitable normalisation and do not display multifractal features. The roughness amplitude, as characterized by the height-height correlation over fixed distances delta z, does not depend on the sample width, implying that no anomalous scaling of the type reported for other materials is present. It is suggested, in agreement with recent theoretical work, to explain these results by the occurence of brittle fracture (instead of damage failure in materials displaying a higher value of zeta = 0.8).Comment: 7 page

Rate of Meander Development as Exhibited by Two Streams in Story County, Iowa

During the winter of 1950 Mr. Zimmerman undertook the study of the drainage of western Story County. His first concern was that of an adequate base-map. This problem he solved by tracing the drainage from air photos of the area involved in the study. It was during this phase of the research that we discovered the full-scale working-model of some of the very experiments conducted by the Army Engineers at Vicksburg, Mississippi. The experiments were in effect detailed studies of the causation of meandering in rivers. Scale models of various situations were carefully constructed, then tested and the results noted and discussed in a report written by Captain J. F. Friedkin. Among the factors so tested was the effect of the initial angle of attack, or alignment of the flow of water into a straight channel, on the size of meanders (bends) developed. It was found that as the angle of attack increased, the length of the meander (bend) decreased and its width increased; that is, the greater the angle of attack the shorter were the radii of the meanders (bends) which developed