1,021 research outputs found

    Shocks and jets from the laboratory environment to the astrophysical regime: Transforming AstroBEAR into an all purpose MHD simulation package

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    Supersonic jets and shocks play an important role in numerous astrophysical phenomena, ranging from stellar formation to active galactic nebulae (AGN). Laboratory astrophysics opens up new avenues for research into these jets and shocks, and computer simulations show great promise in linking laboratory and astronomical data. To date, the most effective codes for the laboratory environment are not readily available and lack magnetic fields, a key component in astrophysical jets and future magnetized laboratory experiments. Also no 3D simulation code has had its non-local thermodynamic equilibrium (LTE) cooling, essential for generating emission maps for comparison with astronomical observations, rigorously tested against an accepted baseline. The focus of this dissertation research was to improve an existing magneto-hydrodynamic code, AstroBEAR, to better model jets and shocks in laboratory and astrophysical environments, with the ultimate goal of developing a code that can link astronomical and laboratory data. The work outlined in this dissertation facilitates the connection between astronomical and laboratory data in two areas. First, we added a multiple material and non-ideal equation of state capability into AstroBEAR to handle the high density ionized plasmas that characterize laboratory astrophysics experiments and now have the first working 3D MHD code capable of simulating the laboratory environment. We used AstroBEAR in 2.5 D hydrodynamic mode to simulate a series of experiments carried out on the OMEGA laser, and compared the simulations with experimental data. Secondly, we improved AstroBEAR's handling of radiative cooling, specifically in the post-shock cooling zones prevalent in many astrophysical jets. The first ever validation tests of a 3D code against a fully non-LTE 1D radiative cooling atomic code show explicitly that AstroBEAR correctly models post-shock radiative cooling down to the resolution and micro-physics limits. We used this improved cooling to simulate the HH 110 jet and conclude from these simulations that any model of stellar jet formation must be able to produce processing and pulsing outflow. Overall the improvements of AstroBEAR's ability to handle jets and shocks in the laboratory and astrophysical environments position it to potentially link observational data with magnetized laboratory experiments

    Association analysis of stem rust resistance in U.S. winter wheat

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    Citation: Zhang D, Bowden RL, Yu J, Carver BF, Bai G (2014) Association Analysis of Stem Rust Resistance in U.S. Winter Wheat. PLoS ONE 9(7): e103747. https://doi.org/10.1371/journal.pone.0103747Stem rust has become a renewed threat to global wheat production after the emergence and spread of race TTKSK (also known as Ug99) and related races from Africa. To elucidate U.S. winter wheat resistance genes to stem rust, association mapping was conducted using a panel of 137 lines from cooperative U.S. winter wheat nurseries from 2008 and simple sequence repeat (SSR) and sequence tagged site (STS) markers across the wheat genome. Seedling infection types were evaluated in a greenhouse experiment using six U.S. stem rust races (QFCSC, QTHJC, RCRSC, RKQQC, TPMKC and TTTTF) and TTKSK, and adult plant responses to bulked U.S. races were evaluated in a field experiment. A linearization algorithm was used to convert the qualitative Stakman scale seedling infection types for quantitative analysis. Association mapping successfully detected six known stem rust seedling resistance genes in U.S. winter wheat lines with frequencies: Sr6 (12%), Sr24 (9%), Sr31 (15%), Sr36 (9%), Sr38 (19%), and Sr1RS[superscript Amigo] (8%). Adult plant resistance gene Sr2 was present in 4% of lines. SrTmp was postulated to be present in several hard winter wheat lines, but the frequency could not be accurately determined. Sr38 was the most prevalent Sr gene in both hard and soft winter wheat and was the most effective Sr gene in the adult plant field test. Resistance to TTKSK was associated with nine markers on chromosome 2B that were in linkage disequilibrium and all of the resistance was attributed to the Triticum timopheevii chromosome segment carrying Sr36. Potential novel rust resistance alleles were associated with markers Xwmc326-203 on 3BL, Xgwm160-195 and Xwmc313-225 on 4AL near Sr7, Xgwm495-182 on 4BL, Xwmc622-147 and Xgwm624-146 on 4DL, and Xgwm334-123 on 6AS near Sr8. Xwmc326-203 was associated with adult plant resistance to bulked U.S. races and Xgwm495-182 was associated with seedling resistance to TTKSK

    Planning and delivery of intensity modulated bolus electron conformal therapy

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    PURPOSE: Bolus electron conformal therapy (BECT) is a clinically useful, well-documented, and available technology. The addition of intensity modulation (IM) to BECT reduces volumes of high dose and dose spread in the planning target volume (PTV). This paper demonstrates new techniques for a process that should be suitable for planning and delivering IM-BECT using passive radiotherapy intensity modulation for electrons (PRIME) devices. METHODS: The IM-BECT planning and delivery process is an addition to the BECT process that includes intensity modulator design, fabrication, and quality assurance. The intensity modulator (PRIME device) is a hexagonal matrix of small island blocks (tungsten pins of varying diameter) placed inside the patient beam-defining collimator (cutout). Its design process determines a desirable intensity-modulated electron beam during the planning process, then determines the island block configuration to deliver that intensity distribution (segmentation). The intensity modulator is fabricated and quality assurance performed at the factory (.decimal, LLC, Sanford, FL). Clinical quality assurance consists of measuring a fluence distribution in a plane perpendicular to the beam in a water or water-equivalent phantom. This IM-BECT process is described and demonstrated for two sites, postmastectomy chest wall and temple. Dose plans, intensity distributions, fabricated intensity modulators, and quality assurance results are presented. RESULTS: IM-BECT plans showed improved D CONCLUSION: These results demonstrated the feasibility of translating IM-BECT to the clinic using the techniques presented for treatment planning, intensity modulator design and fabrication, and quality assurance processes

    Agronomic performace in acid soils of wheat lines selected for hematoxylin staining pattern

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    Laboratory screening techniques enable detection of varying degrees of A1 tolerance during seedling development, but their application to crop improvement programs must be verified in the field. The objective of this study was to compare agronomic responses of wheat (Triticum aestivum L. emend. Thell.) lines differing in hematoxylin- staining pattern under naturally acidic and limed field conditions. Experiments were conducted on Bethany-Kirkland (fine, mixed, thermic Pachic-Udertic Paleustolls) or Grant-Pond Creek (fine-silty, mixed thermic Udic-Pachic Argiustolls) silt loam soil complexes. Four sets of three experimental lines were classified as very susceptible (VS), moderately susceptible (MS), intermediate (I), or tolerant based on hematoxylin staining pattern, and evaluated in limed and unlimed plots as separate experiments in 1988 and 1989. The VS group produced the fewest spikes per square meter and the lowest above-ground biomass and grain yield in the unlimed treatments; no such reductions occurred in the limed treatments. Differences in agronomic performance were found between groups of VS and MS lines, with relatively little differentiation among MS, I, and T groups. Comparison of two sister lines from the VS and T groups revealed a 12% increase in spike density, 11% increase in biomass, and a 14% increase in grain yield of the tolerant sib under acidic conditions. The two sibs performed similarly under limed conditions, except the VS line was superior in grain yield. The hematoxylin staining procedure shows promise for identifying wheat genotypes with potentially high sensitivity to acidic soils in the southern Great Plains.Peer reviewedAgronom

    Distributions, conservation status, and abiotic stress tolerance potential of wild cucurbits (Cucurbita L.)

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    Societal Impact Statement Crop wild relatives—wild species closely related to cultivated plants—are valuable genetic resources for crop improvement, but gaps in knowledge constrain their conservation and limit their further use. We develop new information on the distributions, potential breeding value, and conservation status of the 16 known wild relatives of cultivated pumpkins, squashes, zucchini, and gourds (Cucurbita L.). The taxa occur from the central USA to Central America, plus two South American species, with the greatest richness in central Mexico and the western borderlands between Mexico and the USA. We determine the majority of species are of medium priority for conservation, both with regard to collecting for ex situ maintenance, and for enhanced habitat protection. Summary Crop wild relatives are valuable genetic resources for crop improvement. Knowledge gaps, including with regard to taxonomy, distributions, and characterization for traits of interest constrain their use in plant breeding. These deficiencies also affect conservation planning, both with regard to in situ habitat protection, and further collection of novel diversity for ex situ maintenance. Here we model the potential ranges of all 16 known wild cucurbit taxa (Cucurbita L.), use ecogeographic information to infer their potential adaptations to abiotic stresses, and assess their ex situ and in situ conservation status. The taxa occur from the central USA to Central America, plus two South American species. Predicted taxon richness was highest in central Mexico and in the western borderlands between Mexico and the USA. We find substantial ecogeographic variation both across taxa and among populations within taxa, with regard to low temperatures, high and low precipitation, and other adaptations of potential interest for crop breeding. We categorize 13 of the taxa medium priority for further conservation as a combination of the ex situ and in situ assessments, two low priority, and one sufficiently conserved. Further action across the distributions of the taxa, with emphasis on taxonomic richness hotspots, is needed to comprehensively conserve wild Cucurbita populations

    Audible Image Description as an Accommodation in Statewide Assessments for Students with Visual and Print Disabilities.

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    Introduction:Although image description has been identified as an accommodation for presentations conducted in the classroom, only a few U.S. states have approved it for use in high-stakes assessments. This study examined the use of audible image description as an assessment accommodation for students with visual and print disabilities by investigating student comprehension under multiple conditions. Methods: Students in three western states in grades three through eight who had visual (n= 117) or print (n= 178) disabilities participated in an abbreviated test constructed of retired assessment questions in English language arts, mathematics, and science, that were aligned with each state's instructional standards, under conditions with and without standardized description of graphic images. The study used a within-subjects block design to collect and compare comprehension data under conditions where audible image description was both used and not used in an abbreviated test. Results: Results indicated that students who read braille were more likely to respond correctly under the audible image description condition, and students with visual and print disabilities who used print were equally likely to respond correctly regardless of condition. Discussion: Braille readers were more likely to obtain a correct answer when audible image description accompanied the question. Audible image description did not affect the likelihood of a correct response from students with print disabilities or students with visual disabilities who read print. Implications for practitioners: Audible image description is an accommodation that may help braille readers perform better on tests. Although the Partnership for Assessment of Readiness for College and Careers (PARCC) and Smarter Balanced consortia are taking steps to include image (or picture) descriptions in their assessment accommodations, teachers may want to develop a standard method for describing images and familiarize their braille readers to the strategy by including it in instruction and in classroom tests. Readers are referred to the National Center on Accessible Media’s online guidelines for image description

    Neutral and Cationic Rare Earth Metal Alkyl and Benzyl Compounds with the 1,4,6-Trimethyl-6-pyrrolidin-1-yl-1,4-diazepane Ligand and Their Performance in the Catalytic Hydroamination/Cyclization of Aminoalkenes

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    A new neutral tridentate 1,4,6-trimethyl-6-pyrrolidin-1-yl-1,4-diazepane (L) was prepared. Reacting L with trialkyls M(CH2SiMe3)3(THF)2 (M = Sc, Y) and tribenzyls M(CH2Ph)3(THF)3 (M = Sc, La) yielded trialkyl complexes (L)M(CH2SiMe3)3 (M = Sc, 1; M = Y, 2) and tribenzyl complexes (L)M(CH2Ph)3 (M = Sc, 3; M = La, 4). Complexes 1 and 2 can be converted to their corresponding ionic compounds [(L)M(CH2SiMe3)2(THF)][B(C6H5)4] (M = Sc, Y) by reaction with [PhNMe2H][B(C6H5)4] in THF. Complexes 3 and 4 can be converted to cationic species [(L)M(CH2Ph)2]+ by reaction with [PhNMe2H][B(C6F5)4] in C6D5Br in the absence of THF. The neutral complexes 1-4 and their cationic derivatives were studied as catalysts for the hydroamination/cyclization of 2,2-diphenylpent-4-en-1-amine and N-methylpent-4-en-1-amine reference substrates and compared with ligand-free Sc, Y, and La neutral and cationic catalysts. The most effective catalysts in the series were the cationic L-yttrium catalyst (for 2,2-diphenylpent-4-en-1-amine) and the cationic lanthanum systems (for N-methylpent-4-en-1-amine). For the La catalysts, evidence was obtained for release of L from the metal during catalysis.

    On passion and moral behavior in achievement settings: The mediating role of pride

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    The Dualistic Model of Passion (Vallerand et al., 2003) distinguishes two types of passion: harmonious passion (HP) and obsessive passion (OP) that predict adaptive and less adaptive outcomes, respectively. In the present research, we were interested in understanding the role of passion in the adoption of moral behavior in achievement settings. It was predicted that the two facets of pride (authentic and hubristic; Tracy & Robins, 2007) would mediate the passion-moral behavior relationship. Specifically, because people who are passionate about a given activity are highly involved in it, it was postulated that they should typically do well and thus experience high levels of pride when engaged in the activity. However, it was also hypothesized that while both types of passion should be conducive to authentic pride, only OP should lead to hubristic pride. Finally, in line with past research on pride (Carver, Sinclair, & Johnson, 2010; Tracy et al., 2009), only hubristic pride was expected to negatively predict moral behavior, while authentic pride was expected to positively predict moral behavior. Results of two studies conducted with paintball players (N=163, Study 1) and athletes (N=296, Study 2) supported the proposed model. Future research directions are discussed in light of the Dualistic Model of Passion
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