Showing 1671 - 1680 of 2039 Items
Convergence of successive approximation methods with parameter target sets
Date: 2005-01-01
Creator: A.B. Levy
Access: Open access
Symmetric-group decomposition of SU(N) group-theory constraints on four-, five-, and six-point color-ordered amplitudes at all loop orders
Date: 2012-01-01
Creator: Alexander C. Edison
Stephen G. Naculich
Access: Open access
- Color-ordered amplitudes for the scattering of n particles in the adjoint representation of SU(N) gauge theory satisfy constraints that arise from group theory alone. These constraints break into subsets associated with irreducible representations of the symmetric group Sn, which allows them to be presented in a compact and natural way. Using an iterative approach, we derive the constraints for six-point amplitudes at all loop orders, extending earlier results for n = 4 and n = 5. We then decompose the four-, five-, and six-point group-theory constraints into their irreducible Sn subspaces. We comment briefly on higher-point two-loop amplitudes. © SISSA 2012.
Attention training for reducing spider fear in spider-fearful individuals
Date: 2010-10-01
Creator: Hannah E. Reese
Richard J. McNally
Sadia Najmi
Nader Amir
Access: Open access
- Cognitive theorists propose that attentional biases for threatening information play an important role in the development and maintenance of anxiety disorders. If attentional biases for threat figure in the maintenance of anxiety, then the experimental reduction of the bias for threat (attention training) should reduce anxiety. We randomly assigned 41 spider-fearful individuals to receive either attention training (n=20) or control procedures (n=21). We used a modified dot-probe discrimination paradigm with photographs of spiders and cows to train attention. Training reduced attentional bias for spiders, but only temporarily. Although both groups declined in spider fear and avoidance, reduction in attentional bias did not produce significantly greater symptom reduction in the training group than in the control group. However, reduction in attentional bias predicted reduction in self-reported fear for the training group. The reduction in attentional bias for threat may have been insufficiently robust to produce symptom reduction greater than that produced by exposure to a live spider and spider photographs alone. Alternatively, attention training may be an unsuitable intervention for spider fear. © 2010 Elsevier Ltd.
Information-Processing Approaches to Understanding Anxiety Disorders
Date: 2008-09-04
Creator: Richard J. McNally
Hannah E. Reese
Access: Open access
- Experimental psychopathologists have used cognitive psychology paradigms to elucidate information-processing biases in the anxiety disorders. A vast literature now suggests that patients with anxiety disorders are characterized by an attentional bias for threatening information and a bias toward threatening interpretations of ambiguous information. A memory bias favoring recall of threatening information occurs in panic disorder, but rarely in other anxiety disorders. New treatments involving the experimental modification of cognitive biases are promising.
Design and Impact of the National Workshop for Early Career Geoscience Faculty
Date: 2020-02-12
Creator: Rachel J. Beane
Ellen R. Altermatt
Ellen R. Iverson
R. Heather Macdonald
Access: Open access
- The National Association of Geoscience Teachers’ Workshop for Early Career Geoscience Faculty: Teaching, Research, and Managing One’s Career has been offered annually since 1999. The five-day workshop with accompanying web resources employs a “whole faculty” approach to support geoscience faculty members during their transition into academic careers. More than 1,000 faculty members (53% female, 47% male) have attended the national workshop; 52% from doctoral-granting institutions, 15% master’s, 28% bachelor’s, and 5% associates. Evidence-based instructional practices are shared and modeled during workshop sessions. Situated learning theory grounds the workshop design and promotes the development of a community of practice. Examination of the 2016 National Geoscience Faculty Survey data using univariate analyses of covariance (ANCOVAs) showed that workshop alumni report spending more class time on student activities, questions, and discussion than faculty members who did not participate in the workshop, particularly on small group discussions or think-pair-share and in-class exercises (for introductory courses p < .05; for majors courses p < .001). Workshop alumni also were more likely than faculty who did not participate to report feeling part of a geoscience community that shares their goals, philosophy, and values for geoscience education (p < .01), more likely to report that interactions with this community help them to become better educators (p < .001), and more likely to attend talks on teaching methods or science education (p < .001). Although causality cannot be established without random assignment, these findings are consistent with the hypothesis that this discipline-based workshop with its holistic approach is effective at promoting evidence-based teaching strategies and a community of practice.
Walking versus breathing: Mechanical differentiation of sea urchin podia corresponds to functional specialization
Date: 2000-01-01
Creator: Holly A. Leddy
Amy S. Johnson
Access: Open access
- The podia of sea urchins function in locomotion, adhesion, feeding, and respiration; but different podia on a single urchin are often specialized to one or more of these tasks. We examined the morphology and material properties of podia of the green sea urchin, Strongylocentrotus droebachiensis, to determine whether, despite apparent similarities, they achieve functional specialization along the oral-aboral axis through the differentiation of distinct mechanical properties. We found that oral podia, which are used primarily for locomotion and adhesion, are stronger and thicker than aboral podia, which are used primarily for capturing drift material and as a respiratory surface. The functional role of ambital podia is more ambiguous; however, they are longer and are extended at a lower strain rate than other podial types. They are also stronger and stiffer than aboral podia. In addition, all podia become stronger and stiffer when extended at faster strain rates, in some cases by nearly an order of magnitude for an order of magnitude change in strain rate. This strain-rate dependence implies that resistance to rapid loading such as that imposed by waves is high compared to resistance to slower, self-imposed loads. Thus, the serially arranged podia of S. droebachiensis are functionally specialized along an oral-aboral axis by differences in their morphology and mechanical properties.
Probing the National Geoscience Faculty Survey for Reported Use of Practices that Support Inclusive Learning Environments in Undergraduate Courses
Date: 2019-07-17
Creator: Rachel J. Beane
Karen S. McNeal
R. Heather Macdonald
Access: Open access
- What is the extent to which college and university geoscience faculty report using education practices that contribute to more inclusive learning environments and engage a diverse population of students? In the 2016 National Geoscience Faculty Survey, faculty answered questions about their practices in a specific introductory or major course they had taught in the previous two years, and about how they share and learn about the content and methods used in their teaching. Based on factor analysis, 22 of the survey questions divided into four categories associated with inclusive teaching practices: geoscientist representations, curricular choices, learning strategies, and career pathways. The self-reported use of practices across these four categories varies greatly, with some used by as many as 71% of faculty respondents whereas others by only 8%. These data provide new information on the current state of teaching practices in the geosciences with regard to inclusive practices, and establish a baseline to which responses from future surveys may be compared. Univariate general modeling combined with ANOVA tests on the responses to the questions shows that education practices differ based on variables such as teaching style, communication with colleagues, years of teaching experience, faculty type, institution type, class size, and course type (introductory or major). These differences suggest opportunities for focused geoscience faculty development around education practices that support the success of a diverse population of undergraduate students and the enhancement of inclusive learning environments in the geosciences.
Maintenance of dynamic strain similarity and environmental stres factor in different flow habitats: Thallus allometry and material properties of a giant kelp
Date: 1994-01-01
Creator: A. S. Johnson
M. A.R. Koehl
Access: Open access
Module structure of cells in unequal-parameter Hecke algebras
Date: 2010-09-06
Creator: Thomas Pietraho
Access: Open access
- A conjecture of Bonnafé, Geck, Iancu, and Lam parametrizes Kazhdan-Lusztig left cells for unequal-parameter Hecke algebras in type Bn by families of standard domino tableaux of arbitrary rank. Relying on a family of properties outlined by Lusztig and the recent work of Bonnafé, we verify the conjecture and describe the structure of each cell as a module for the underlying Weyl group. © 2010 by The Editorial Board of the Nagoya Mathematical Journal.
Climate change and health costs of air emissions from biofuels and gasoline
Date: 2009-02-10
Creator: Jason Hill
Stephen Polasky
Erik Nelson
David Tilman
Hong, Huo
Lindsay Ludwig
James Neumann
Haochi Zheng
Diego Bonta
Access: Open access
- Environmental impacts of energy use can impose large costs on society. We quantify and monetize the life-cycle climate-change and health effects of greenhouse gas (GHG) and fine particulate matter (PM2.5) emissions from gasoline, corn ethanol, and cellulosic ethanol. For each billion ethanol-equivalent gallons of fuel produced and combusted in the US, the combined climate-change and health costs are $469 million for gasoline, $472-952 million for corn ethanol depending on biorefinery heat source (natural gas, corn stover, or coal) and technology, but only $123-208 million for cellulosic ethanol depending on feedstock (prairie biomass, Miscanthus, corn stover, or switchgrass). Moreover, a geographically explicit life-cycle analysis that tracks PM2.5 emissions and exposure relative to U.S. population shows regional shifts in health costs dependent on fuel production systems. Because cellulosic ethanol can offer health benefits from PM2.5 reduction that are of comparable importance to its climate-change benefits from GHG reduction, a shift from gasoline to cellulosic ethanol has greater advantages than previously recognized. These advantages are critically dependent on the source of land used to produce biomass for biofuels, on the magnitude of any indirect land use that may result, and on other as yet unmeasured environmental impacts of biofuels. © 2009 by The National Academy of Sciences of the USA.