Elucidation and quantification of the decomposition products of sodium dithionite and the detection of peroxide vapors with thin films

Sodium dithionite (Na2S2O4) is an oxidizable sulfur oxyanion often employed as a reducing agent in environmental and synthetic chemistry. When exposed to the atmosphere, dithionite degrades through a series of decomposition reactions to form a number of compounds, with the primary two being bisulfite (HSO32-) and thiosulfate (S2O32-). Ten samples of sodium dithionite ranging from brand new to nearly fifty years old were analyzed using ion chromatography; from this, a new quantification method for dithionite and thiosulfate was achieved and statistically validated against the current three iodometric titration method used industrially. Additional sample analysis with Raman spectroscopy of solid and dissolved samples identified unique compounds in the oldest samples, including dithionate (S2O62-) and tetrathionate (S4O62-).Additionally, titania nanoparticles in a hydroxypropyl cellulose matrix were used to prepare films on polycarbonate slides and coatings on cellulose papers. The exposure of these materials to hydrogen peroxide gas led to the development of an intense yellow color. Using an inexpensive web camera and a tungsten lamp to measure the reflected light, first-order behavior in the color change was observed when exposed to peroxide vapor of less than 50 ppm. For 50 mass percent titania nanoparticles in hydroxypropyl cellulose films on polycarbonate, the detection limit was estimated to be 90 ppm after a 1-minute measurement and 1.5 ppm after a 1-hour integration. The coatings on the filter paper had a threefold higher sensitivity compared to the films, with a detection limit of 5.4 ppm peroxide for a 1-minute measurement and 0.09 ppm peroxide for a 1-hour integration period. Further experimentation with the effects of acid loading on the filter paper coatings identified these as possible sensors for organic peroxides. With the addition of sulfuric acid, the support was changed from cellulose to glass microfiber or silica. This coatings showing increased sensitivity when compared to coatings with hydrochloric acid. Finally, coatings containing an ionic liquid solvent and trifluoromethanesulfonic acid were produced and found to have increased longevity. These coatings have potential as peroxide vapor sensors for both industrial and security applications

Visual Acuity does not Moderate Effect Sizes of Higher-Level Cognitive Tasks.

Background/study contextDeclining visual capacities in older adults have been posited as a driving force behind adult age differences in higher-order cognitive functions (e.g., the "common cause" hypothesis of Lindenberger & Baltes, 1994, Psychology and Aging, 9, 339-355). McGowan, Patterson, and Jordan (2013, Experimental Aging Research, 39, 70-79) also found that a surprisingly large number of published cognitive aging studies failed to include adequate measures of visual acuity. However, a recent meta-analysis of three studies (La Fleur and Salthouse, 2014, Psychonomic Bulletin & Review, 21, 1202-1208) failed to find evidence that visual acuity moderated or mediated age differences in higher-level cognitive processes. In order to provide a more extensive test of whether visual acuity moderates age differences in higher-level cognitive processes, we conducted a more extensive meta-analysis of topic.MethodsUsing results from 456 studies, we calculated effect sizes for the main effect of age across four cognitive domains (attention, executive function, memory, and perception/language) separately for five levels of visual acuity criteria (no criteria, undisclosed criteria, self-reported acuity, 20/80-20/31, and 20/30 or better).ResultsAs expected, age had a significant effect on each cognitive domain. However, these age effects did not further differ as a function of visual acuity criteria.ConclusionThe current meta-analytic, cross-sectional results suggest that visual acuity is not significantly related to age group differences in higher-level cognitive performance-thereby replicating La Fleur and Salthouse (2014). Further efforts are needed to determine whether other measures of visual functioning (e.g., contrast sensitivity, luminance) affect age differences in cognitive functioning

Organic Price Premiums Paid for Fresh Tomatoes and Apples by U.S. Households: Evidence from Nielsen Homescan Data

Using multivariate regression on data composed of prices, produce characteristics, demographics, and interactions, this study investigates organic price premiums paid by U.S. consumers for fresh tomatoes and apples, two of the top organic produce sellers, and identifies factors explaining variation in price premiums. The econometric problem of each buyer having multiple records in the purchase data is addressed in the estimation procedure.Consumer/Household Economics, Food Consumption/Nutrition/Food Safety,

Blending Formative and Summative Assessment in a Capstone Subject: ‘It’s not your tools, it’s how you use them’

Discussions about the relationships between formative and summative assessment have come full circle after decades of debate. For some time formative assessment with its emphasis on feedback to students was promoted as better practice than traditional summative assessment. Summative assessment practices were broadly criticised as distanced from the learning process. More recently discussions have refocused on the potential complementary characteristics of formative and summative purposes of assessment. However studies on practical designs to link formative and summative assessment in constructive ways are rare. In paramedic education, like many other professional disciplines, strong traditions of summative assessment - assessment ‘of’ learning - have long dominated. Communities require that a graduate has been judged fit to practice. The assessment redesign described and evaluated in this paper sought to rebalance assessment relationships in a capstone paramedic subject to integrate formative assessment for learning with summative assessment of learning. Assessment was repositioned as a communication process about learning. Through a variety of frequent assessment events, judgement of student performance is accompanied with rich feedback. Each assessment event provides information about learning, unique to each student’s needs. Each assessment event shaped subsequent assessment events. Student participants in the formal evaluation of the subject indicated high levels of perceived value and effectiveness on learning across each of the assessment events, with broad agreement also demonstrated relating to student perceptions for preparedness: ‘readiness to practice’. Our approach focused on linking assessment events, resulted in assessments providing formative communication to students and summative outcome information to others simultaneously. The formative-summative dichotomy disappeared: all assessment became part of communication about learning

A Limnological Study of Ricks Pond and the Gulpha Creek Drainage in Garland County, Arkansas

A limnological investigation of Ricks Pond and the Gulpha Creek drainage of Garland County, Arkansas was conducted between 1 June 1978, and 21 August 1978. Water samples taken from ten stations on three different dates indicated that the stream and pond systems were typical in water quality characteristics of other small, high gradient streams and impoundments in the Ouachita Mountains of Arkansas. In Ricks Pond, thermal stratification occurred along with the development of an oxygen deficient zone below a depth of one meter. Other water quality parameters indicated that Ricks Pond is a moderately productive ecosystem, with the productivity limited by the nitrogen species. The fecal coliform bacterial counts were very low, indicating no direct input of excessive amounts of fecal matter into the system during the present study. However, a Hot Springs city sewer line runs through the pond, and two manholes emerge from the pond\u27s surface. The possibility exists that this sewer line could discharge raw sewage into Ricks Pond during periods of high water. A biological investigation was also conducted in the study area, and lists of the phytoplankton, periphyton, higher aquatic vegetation, zooplankton, benthic macroinvertebrates, and fishes are presented. Twenty-seven species of fishes were collected from the Gulpha Creek drainage, and no rare or endangered forms were found. Ricks Pond is best-suited for the establishment of a put- and-take fishery for channel catfish, Ictalurus punctatus. The following recommendations were made for the establishment of such a fishery: (1) Renovation of the pond by draining and deepening it; (2) Removal of the sewer line from the pond; (3) Stocking of catchable size channel catfish at the rate of approximately 300-400 pounds per acre; (4) Periodic monitoring of the water quality

Alternative AMTA and Loan Rate Options for Program Crops With Counter Cyclical Payments Triggered at the National and State Level

This analysis focuses on four policy options, based on national formulas where implications are examined for varying levels of loan rates and base AMTA payment rates.Agricultural and Food Policy,

Method for Calculation of Counter Cyclical Payments Using State and National Trigger Levels (Major Crops)

Agricultural and Food Policy,

Practical Implications of Learning from Unsuccessful Retrieval Attempts

Recent findings suggest that retesting oneself facilitates better learning than studying alone. Building off previous experiments where correcting participants has significantly increased correctness, the current study furthers our understanding about learning from unsuccessful retrieval attempts by manipulating the frequency of correction. Using a set of 42 associated word pairings, each participant was exposed to two blocks where they would memorize the word pairs. This was followed by two quizzing blocks and a final exam block where participants were asked to write down the associate to the stimulus presented on screen. Frequency of correction was manipulated during the quizzing blocks where the participant had their answers checked and corrected by the proctor after every word pair, every third, or every seventh, depending on their condition. There was no correction during the final exam block. After completing the experiment, each participant completed both the Mill-Hill vocabulary scale and the OSPAN task for baseline comparison. Results indicated no significant difference between any of the correction frequency groups but did find that participant’s second quizzing and final exam scores increased significantly from the initial quiz score