Rotation of Coulomb crystals in a magnetized inductively coupled complex plasma

Under suitable conditions, micron-sized dust particles introduced into inductively coupled argon plasma form a stable microscopic crystal lattice, known as a Coulomb (or plasma) crystal. In the experiment described, an external axial magnetic field was applied to various configurations of Coulomb crystal, including small crystal lattices consisting of one to several particles, and large crystal lattices with many hundreds of particles. The crystals were observed to rotate collectively under the influence of the magnetic field. This paper describes the experimental procedures and the preliminary results of this investigation

A Cognitive Analysis of the Task Demands of Early Algebra

Mathematical problems presenting themselves in the workplace and in academia are often solved by informal strategies in addition to or instead of the normative formal strategies typically taught in school. By itself this observation does little to tell us whether, when and how much these techniques should be taught. To ground arguments about the appropriate role of altemative problem-solving techniques in education, we need to first understand the demands of the tasks they address. Our focus here is on algebra and pre?algebra, or, more specifically, on the set of problems that resist solution by more elementary arithmetic methods. W e present a task analysis of this set of problems that is based on the identification of mathematical and situational problem difficulty factors. These factors provide a framework for comparing the candidate representations and strategies to meet the demands of more complex problems. W e summarize the altemative techniques that have been observed in effective problem solving and discuss their relative strengths and weaknesses. The task analysis along with this comparative analysis provides a basis for hypothesizing developmental sequences and for informing instmctional design

First IBEX observations of the terrestrial plasma sheet and a possible disconnection event

The Interstellar Boundary Explorer (IBEX) mission has recently provided the first all-sky maps of energetic neutral atoms (ENAs) emitted from the edge of the heliosphere as well as the first observations of ENAs from the Moon and from the magnetosheath stagnation region at the nose of the magnetosphere. This study provides the first IBEX images of the ENA emissions from the nightside magnetosphere and plasma sheet. We show images from two IBEX orbits: one that displays typical plasma sheet emissions, which correlate reasonably well with a model magnetic field, and a second that shows a significant intensification that may indicate a near-Earth (similar to 10 R(E) behind the Earth) disconnection event. IBEX observations from similar to 0.5-6 keV indicate the simultaneous addition of both a hot (several keV) and colder (similar to 700 eV) component during the intensification; if IBEX directly observed magnetic reconnection in the magnetotail, the hot component may signify the plasma energization

Adenosine Triphosphate and Carbon Efficient Route to Second Generation Biofuel Isopentanol.

Climate change necessitates the development of CO2 neutral or negative routes to chemicals currently produced from fossil carbon. In this paper we demonstrate a pathway from the renewable resource glucose to next generation biofuel isopentanol by pairing the isovaleryl-CoA biosynthesis pathway from Myxococcus xanthus and a butyryl-CoA reductase from Clostridium acetobutylicum. The best plasmid and Escherichia coli strain combination makes 80.50 ± 8.08 (SD) mg/L of isopentanol after 36 h under microaerobic conditions with an oleyl alcohol overlay. In addition, the system also shows a strong preference for isopentanol production over prenol in microaerobic conditions. Finally, the pathway requires zero adenosine triphosphate and can be paired theoretically with nonoxidative glycolysis, the combination being redox balanced from glucose thus avoiding unnecessary carbon loss as CO2. These pathway properties make the isovaleryl-CoA pathway an attractive isopentanol production route for further optimization

Middle School Students’ Conceptual Understanding of Equations: Evidence from Writing Story Problems

This study investigated middle school students’ conceptual understanding of algebraic equations. 257 sixth- and seventh-grade students solved algebraic equations and generated story problems to correspond with given equations. Aspects of the equations’ structures, including number of operations and position of the unknown, influenced students’ performance on both tasks. On the story-writing task, students’ performance on two-operator equations was poorer than would be expected on the basis of their performance on one-operator equations. Students made a wide variety of errors on the story-writing task, including (1) generating story contexts that reflect operations different from the operations in the given equations, (2) failing to provide a story context for some element of the given equations, (3) failing to include mathematical content from the given equations in their stories, and (4) including mathematical content in their stories that was not present in the given equations. The nature of students’ story-writing errors suggests two main gaps in students’ conceptual understanding. First, students lacked a robust understanding of the connection between the operation of multiplication and its symbolic representation. Second, students demonstrated difficulty combining multiple mathematical operations into coherent stories. The findings highlight the importance of fostering connections between symbols and their referents

Work hours, weight status, and weight-related behaviors: a study of metro transit workers

<p>Abstract</p> <p>Background</p> <p>Associations between hours worked per week and Body Mass Index (BMI), food intake, physical activity, and perceptions of eating healthy at work were examined in a sample of transit workers.</p> <p>Methods</p> <p>Survey data were collected from 1086 transit workers. Participants reported hours worked per week, food choices, leisure-time physical activity and perceptions of the work environment with regard to healthy eating. Height and weight were measured for each participant. Multivariate linear and logistic regressions were conducted to examine associations between work hours and behavioral variables. Associations were examined in the full sample and stratified by gender.</p> <p>Results</p> <p>Transit workers working in the highest work hour categories had higher BMI and poorer dietary habits, with results differing by gender. Working 50 or more hours per week was associated with higher BMI among men but not women. Additionally, working 50 or more hours per week was significantly associated with higher frequency of accessing cold beverage, cold food, and snack vending machines among men. Working 40 or more hours per week was associated with higher frequency of accessing cold food vending machines among women. Reported frequency of fruit and vegetable intake was highest among women working 50 or more hours per week. Intake of sweets, sugar sweetened beverages, and fast food did not vary with work hours in men or women. Physical activity and perception of ease of eating healthy at work were not associated with work hours in men or women.</p> <p>Conclusions</p> <p>Long work hours were associated with more frequent use of garage vending machines and higher BMI in transit workers, with associations found primarily among men. Long work hours may increase dependence upon food availability at the worksite, which highlights the importance of availability of healthy food choices.</p

Embodied truths: How dynamic gestures and speech contribute to mathematical proof practices

Grounded and embodied theories of cognition suggest that both language and the body play crucial roles in grounding higher-order thought. This paper investigates how particular forms of speech and gesture function together to support abstract thought in mathematical proof construction. We use computerized text analysis software to evaluate how speech patterns support valid proof construction for two different tasks, and we use gesture analysis to investigate how dynamic gestures—those gestures that depict and transform mathematical objects—further support proof practices above and beyond speech patterns. We also evaluate the degree to which speech and gesture convey distinct information about mathematical reasoning during proving. Dynamic gestures and speech indicating logical inference support valid proof construction, and both dynamic gestures and speech uniquely predict variance in valid proof construction. Thus, dynamic gestures and speech each make separate and important contributions to the formulation of mathematical arguments, and both modalities can convey elements of students’ understanding to teachers and researchers

Structural elucidation of hydroxy fatty acids by photodissociation mass spectrometry with photolabile derivatives

© 2020 John Wiley & Sons, Ltd. Rationale: Eicosanoids are short-lived bio-responsive lipids produced locally from oxidation of polyunsaturated fatty acids (FAs) via a cascade of enzymatic or free radical reactions. Alterations in the composition and concentration of eicosanoids are indicative of inflammation responses and there is strong interest in developing analytical methods for the sensitive and selective detection of these lipids in biological mixtures. Most eicosanoids are hydroxy FAs (HFAs), which present a particular analytical challenge due to the presence of regioisomers arising from differing locations of hydroxylation and unsaturation within their structures. Methods: In this study, the recently developed derivatization reagent 1-(3-(aminomethyl)-4-iodophenyl)pyridin-1-ium (4-I-AMPP+) was applied to a representative set of HFAs including bioactive eicosanoids. Photodissociation (PD) mass spectra obtained at 266 nm of 4-I-AMPP+-modified HFAs exhibit abundant product ions arising from photolysis of the aryl–iodide bond within the derivative with subsequent migration of the radical to the hydroxyl group promoting fragmentation of the FA chain and facilitating structural assignment. Results: Representative polyunsaturated HFAs (from the hydroxyeicosatetraenoic acid and hydroxyeicosapentaenoic acid families) were derivatized with 4-I-AMPP+ and subjected to a reversed-phase liquid chromatography workflow that afforded chromatographic resolution of isomers in conjunction with structurally diagnostic PD mass spectra. Conclusions: PD of these complex HFAs was found to be sensitive to the locations of hydroxyl groups and carbon–carbon double bonds, which are structural properties strongly associated with the biosynthetic origins of these lipid mediators

Global change and conservation triage on National Wildlife Refuges

National Wildlife Refuges (NWRs) in the United States play an important role in the adaptation of social-ecological systems to climate change, land-use change, and other global-change processes. Coastal refuges are already experiencing threats from sea-level rise and other change processes that are largely beyond their ability to influence, while at the same time facing tighter budgets and reduced staff. We engaged in workshops with NWR managers along the U.S. Atlantic coast to understand the problems they face from global-change processes and began a multidisciplinary collaboration to use decision science to help address them. We are applying a values-focused approach to base management decisions on the resource objectives of land managers, as well as those of stakeholders who may benefit from the goods and services produced by a refuge. Two insights that emerged from our workshops were a conspicuous mismatch between the scale at which management can influence outcomes and the scale of environmental processes, and the need to consider objectives related to ecosystem goods and services that traditionally have not been explicitly considered by refuges (e.g., protection from storm surge). The broadening of objectives complicates the decision-making process, but also provides opportunities for collaboration with stakeholders who may have agendas different from those of the refuge, as well as an opportunity for addressing problems across scales. From a practical perspective, we recognized the need to (1) efficiently allocate limited staff time and budgets for short-term management of existing programs and resources under the current refuge design and (2) develop long-term priorities for acquiring or protecting new land/habitat to supplement or replace the existing refuge footprint and thus sustain refuge values as the system evolves over time. Structuring the decision-making problem in this manner facilitated a better understanding of the issues of scale and suggested that a long-term solution will require a significant reassessment of objectives to better reflect the comprehensive values of refuges to society. We discuss some future considerations to integrate these two problems into a single framework by developing novel optimization approaches for dynamic problems that account for uncertainty in future conditions

Genetic (co)variation and accuracy of selection for resistance to viral mosaic disease and production traits in an inter-ecotypic switchgrass breeding population

Obtaining good accuracy and reliability of estimated breeding values is essential to increase the efficiency of a plant breeding program. Genetic variation was assessed for categorical (Virc) and binary (Virb) mosaic (caused by Panicum mosaic virus), dry matter (DMY) and predicted ethanol (Etoh) yields, and lignin content (Klason or KL, and acid-detergent or ADL) in a Summer–Kanlow switchgrass (Panicum virgatum L.) population. Breeding values were predicted with the restricted maximum likelihood–best linear unbiased prediction (REML-BLUP) approaches using a multivariate phenotypic (PBLUP) and animal (ABLUP) models, integrating a three-generation pedigree (1,622 half-sibs) in ABLUP and not in PBLUP. Models were compared in their precision (accuracy and reliability) in assessing genetic parameters and estimating breeding values. The models were similar in most aspects, allocating the highest heritability (ℎ2i) values to DMY (.38 ± .035 vs. .41 ± .035), Etoh (.46 ± .031 vs. .42 ± .033), and Virc (.43 ± .046 vs. .37 ± .047) and the lowest (.17 ± .032 to .30 ± .044) to KL, ADL, and Virb. Genetic correlations were always larger than residual and phenotypic correlations. Intermediate or strong additive genetic control suggest that selecting for high-biomass genotypes will slightly increase lignin content and simultaneously impart mosaic tolerance. Mitigating an increase in lignin content will require including Etoh in a selection index based on its much stronger negative correlation (rG = −.63) with lignin. In this population, accuracy values ranged from .06 to .94 (PBLUP) and from .26 to .92 (ABLUP) and corresponding reliability ranged from .004 to .89 and from .07 to .87. However, ABLUP improved average reliability of DMY and Etoh by 11% and of other traits by 4–5% over the PBLUP model. The ABLUP was a better model over PBLUP, which is a valid analysis in the absence of a pedigree