378 research outputs found
Exploring young students creativity: The effect of model eliciting activities
No full textThe aim of this paper is to show how engaging students in real-life mathematical situations can stimulate their mathematical creative thinking. We analyzed the mathematical modeling of two girls, aged 10 and 13 years, as they worked on an authentic task involving the selection of a track team. The girls displayed several modeling cycles that revealed their thinking processes, as well as cognitive and affective features that may serve as the foundation for a methodology that uses model-eliciting activities to promote the mathematical creative process
Control of glyphosate-resistant giant ragweed (Ambrosia trifida L.) with premix of iodosulfuron /thiencarbazone applied alone or in tank-mixtures in no-till corn (Zea mays L.)
No full textThe objectives of this study were to evaluate the efficacy of a new premix of iodosulfuron (6%) /thiencarbazone (45%) applied alone or tank-mixed with 2,4-D, dicamba, glyphosate, or metribuzin in fall and/or early spring followed by pre-emergence (PRE) and post-emergence (POST) herbicide applications for control of glyphosate-resistant giant ragweed and their effect on corn yield. Field experiments were conducted in no-till corn fields infested with glyphosate-resistant giant ragweed (20 to 30 plants m─2) near Clay Center and McCool Junction, Nebraska, USA in 2013 and 2014, respectively. A premix of iodosulfuron /thiencarbazone applied alone or in split applications in fall and early spring controlled glyphosate-resistant giant ragweedThe accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author
Biologically effective rates of a new premix (atrazine, bicyclopyrone, mesotrione, and S-metolachlor) for pre-emergence or post-emergence control of common waterhemp (Amaranthus rudis Sauer) in corn
No full textA premix of atrazine, bicyclopyrone, mesotrione, and S-metolachlor was recently approved for broad-spectrum weed control in corn in the United States. Greenhouse and field experiments were conducted in 2015 and 2016 to evaluate the response of common waterhemp to various rates of the premix applied pre-emergence or post-emergence in corn. In greenhouse dose-response bioassays, pre-emergence application of the premix at 975 g ai ha─1 provided 90% control (visual estimates) of common waterhemp at 28 DAT. The ED90 values for post-emergence applications were 1,157 and 1,838 g ai ha─1 at 21 DAT when applied to 8 to 10, and 15 to 18 cm tall common waterhemp, respectively. Under field conditions, the premix applied pre-emergence at the labeled rate (2,900 g ai ha─1) provided 98 and 91% control of common waterhemp at 14 and 63 d after treatment (DAT), respectively. The ED90 values for the in-field post-emergence dose-response bioassay were 680 and 2,302 g ai ha─1 at 14 DAT for the 8 to 10 and 15 to 18 cm tall common waterhemp, respectively. The root mean square error (RMSE) and the model efficiency coefficient (EF) values indicated a good fit for the prediction models. Spearman’s correlation coefficient (rs) showed that corn yield was positively correlated (rs ≥ 0.55; PThe accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author
An Adaptive Self-modeling Network Model for Multilevel Organizational Learning
No full textMultilevel organizational learning concerns an interplay of different types of learning at individual, team, and organizational levels. These processes use complex dynamic and adaptive mechanisms. A second-order adaptive network model for this is introduced here and illustrated.Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Safety and Security Scienc
Embedding Approximately Low-Dimensional l_2^2 Metrics into l_1
No full textGoemans showed that any n points x_1,..., x_n in d-dimensions satisfying l_2^2 triangle inequalities can be embedded into l_{1}, with worst-case distortion at most sqrt{d}. We consider an extension of this theorem to the case when the points are approximately low-dimensional as opposed to exactly low-dimensional, and prove the following analogous theorem, albeit with average distortion guarantees: There exists an l_{2}^{2}-to-l_{1} embedding with average distortion at most the stable rank, sr(M), of the matrix M consisting of columns {x_i-x_j}_{i<j}. Average distortion embedding suffices for applications such as the SPARSEST CUT problem. Our embedding gives an approximation algorithm for the SPARSEST CUT problem on low threshold-rank graphs, where earlier work was inspired by Lasserre SDP hierarchy, and improves on a previous result of the first and third author [Deshpande and Venkat, in Proc. 17th APPROX, 2014]. Our ideas give a new perspective on l_{2}^{2} metric, an alternate proof of Goemans' theorem, and a simpler proof for average distortion sqrt{d}
Mechanism of atrazine resistance in atrazine- and HPPD inhibitor-resistant Palmer amaranth (Amaranthus palmeri S. Watson) from Nebraska
No full textPalmer amaranth (Amaranthus palmeri S. Watson) is the most problematic weed species in the US agriculture. A Palmer amaranth biotype multiple resistant to atrazine and 4-hydroxyphenylpyruvate dioxygenase (HPPD) inhibitors was reported in a seed corn production field in Nebraska, USA. Rapid detoxification mediated by cytochrome P450 monooxygenases and increased HPPD gene expression were reported as the mechanisms of mesotrione resistance in atrazine- and HPPD inhibitor-resistant Palmer amaranth biotype from Nebraska; however, the mechanism of atrazine resistance is unknown. The objectives of this study were to investigate any target- or nontarget-site based mechanisms conferring atrazine resistance in resistant Palmer amaranth from Nebraska, USA. 14C-atrazine absorption and translocation studies revealed that reduced atrazine absorption or translocation were not involved as one of the mechanisms of atrazine resistance. Instead, greater 14C-atrazine absorption and recovery in treated leaves were observed in resistant compared to susceptible Palmer amaranth. No known mutations including Ser264Gly substitution in the psbA gene causing target-site based atrazine resistance were observed. However, parent 14C-atrazine was metabolized rapidly in less than 4 h after treatment in resistant plants, conferring enhanced atrazine metabolism as the mechanism of resistance.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author
Weed control and crop safety in sulfonylurea/glyphosate-resistant soybean
No full textA soybean trait resistant to sulfonylurea herbicides along with glyphosate (Bolt™ soybean) has been developed. Information is needed to determine herbicide programs for weed control and crop safety in this new multiple herbicide–resistant soybean trait. The objectives of this study were to evaluate weed control and crop safety in sulfonylurea/glyphosate-resistant soybean with herbicide programs, including but not limited to acetolactate synthase (ALS) inhibitors. Field experiments were conducted near Clay Center, NE, USA, in 2016 and 2017. Herbicide programs with multiple sites-of-action including rimsulfuron/thifensulfuron in mixture with flumioxazin, flumioxazin/chlorimuron, pyroxasulfone, chlorimuron/metribuzin, or saflufenacil/imazethapyr plus dimethenamid-P provided 91%–97% control of common waterhemp, velvetleaf, and common lambsquarters. Rimsulfuron and (or) thifensulfuron resulted in 92%–97% control of velvetleaf and common lambsquarters and 81%–87% common waterhemp control at 21 d after pre-emergence (PRE) (DAPRE) herbicide application. Soybean injury was transient and varied from 3% to 11% at 21 DAPRE and 14 d after post-emergence (POST) (DAPOST) herbicide application without causing yield loss. At 30 and 60 DAPOST, 87%–97% velvetleaf control and 92%–98% common lambsquarters control was achieved with herbicide programs tested (PRE, POST, or PRE followed by POST). Common waterhemp control at 30 and 60 DAPOST was not consistent between years. Weed density and biomass reduction were mostly similar to weed control achieved. Untreated control resulted in the lowest soybean yield (1811 kg ha−1) in 2016 compared with 3406–4611 kg ha−1 in herbicide programs.The presentation of the authors' names and (or) special characters in the title of the pdf file of the accepted manuscript may differ slightly from what is displayed on the item page. The information in the pdf file of the accepted manuscript reflects the original submission by the author
Control of glufosinate/glyphosate-resistant corn volunteers in imazamox- and quizalofop-resistant sorghum
No full textVolunteer corn is a problem weed in sorghum fields rotated with corn. The commercial availability of imazamox-resistant (igrowth®) and quizalofop-resistant (Double Team™) sorghum allows the use of imazamox and quizalofop, respectively, for controlling grass weeds; however, information is not available regarding their efficacy for control of volunteer corn. The objective of this study was to evaluate the efficacy of imazamox and quizalofop for control, density and biomass reduction of glufosinate/glyphosate-resistant corn volunteers in imazamox- and quizalofop-resistant sorghum. Two separate field experiments were conducted near Clay Center, NE, in 2023 and 2024. Imazamox applied early postemergence (E-POST) and late postemergence (L-POST) (53 and 79 g ai ha–1) controlled up to 98% and 89% of corn volunteers 28 d after application (DAA) in 2023 and 2024, respectively, in igrowth® sorghum. Similarly, quizalofop applied E-POST and L-POST (58 and 73 g ai ha–1) provided 98% and 99% control of volunteer corn in 2023 and 2024, respectively, in Double Team™ sorghum. Quizalofop reduced volunteer corn density (0 to 0.2 plants m–1) and biomass (0 to 13 g m–2) compared to nontreated control in both years. The results suggest that imazamox and quizalofop could be used as POST herbicides for control of glufosinate/glyphosate-resistant corn volunteers in imazamox- and quizalofop-resistant sorghum, respectively
Securitization and mortgage default
No full textThe academic literature, the popular press, and policymakers have all debated securitization's contribution to the poor performance of mortgages originated in the run-up to the recent crisis. Theoretical arguments have been advanced on both sides, but the lack of suitable data has made it difficult to assess them empirically. The author examines this issue by using a loan-level data set from LPS Analytics, covering approximately two-thirds of the mortgages originated in 2005 and 2006, and including both securitized and nonsecuritized loans. ; The author finds evidence that privately securitized loans do indeed perform worse than observably similar, nonsecuritized loans. Moreover, this effect is strongest in prime mortgage markets, which have not been studied in the previous literature. For example, a typical prime loan becomes delinquent at a 20 percent higher rate if it is privately securitized, ceteris paribus. This is consistent with the existence of adverse selection; that is, that lenders used information not available to investors to securitize loans that were riskier than they otherwise appeared. By contrast, for subprime mortgages, the impact of private securitization is concentrated in low or no-documentation loans; this latter result is consistent with previous work such as Keys et al. (2009).Mortgage-backed securities ; Default (Finance)
Comparison of a premix of atrazine, bicyclopyrone, mesotrione, and S-metolachlor with other preemergence herbicides for weed control and corn yield in no-tillage and reduced-tillage production systems in Nebraska, USA
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