Bulletin 85 - Teaching Children to Read

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A raising operator formula for Macdonald polynomials

We give an explicit raising operator formula for the modified Macdonald polynomials $\tilde{H}_{\mu }(X;q,t)$, which follows from our recent formula for $\nabla$ on an LLT polynomial and the Haglund-Haiman-Loehr formula expressing modified Macdonald polynomials as sums of LLT polynomials. Our method just as easily yields a formula for a family of symmetric functions $\tilde{H}^{1,n}(X;q,t)$ that we call $1,n$-Macdonald polynomials, which reduce to a scalar multiple of $\tilde{H}_{\mu}(X;q,t)$ when $n=1$. We conjecture that the coefficients of $1,n$-Macdonald polynomials in terms of Schur functions belong to $\mathbb{N}[q,t]$, generalizing Macdonald positivity.Comment: 20 page

EVALUATION OF STUDENT REFLECTIVE DOCUMENTS IN AGROECOLOGY EDUCATION: A QUALITATIVE ANALYSIS OF EXPERIENTAL LEARNING

This paper describes an evaluation of experiential learning in agroecology, based on analysis of learning outcomes as described by students in their individual Learner (Reflection) Documents. Galt et al. (2013) highlighted the importance of reflective essays in reinforcing experiential learning. Each fall semester since 2000, students in an agroecology course in farming and food systems at the Norwegian University of Life Sciences (UMB) have submitted a self-evaluation of their learning as well as the teaching process. Their Learner Document is based on a log the students write about their experiences in the field, including interactions with stakeholders on farms and in communities, and lectures and discussion sessions with students and facilitators in and out of the classroom. Together with practical aspects described in the log is an in-depth reflection by each student on the learning process. While the students work in teams of four to six people to produce a Client (Stakeholder) Document, in cooperation with their stakeholders in the farming and food system, the Learner Document is written individually and reflects their personal learning experience

Educational innovations in agroecology: Learning-centred open-ended cases

Open-ended cases present students with learning situations where a particular dilemma on the farm or in the community food system has not been resolved. With minimal but focused prior preparations, students interview farmers and food system stakeholders to build context for the case and to discover the philosophy, goals, and major challenges faced by clients. Student teams build a rich picture of the current reality, including major elements, interactions, and driving forces both internal and external. Instead of reaching prescriptive recommendations, students develop multiple potential future scenarios that could be used by stakeholders to resolve the situation, and evaluate a priori the most likely outcomes of following each scenario. These are presented back to the farmer or community, and a visioning session is held to bring all the players to the table and decide on the most constructive future course of action. We have found this method to be highly stimulating to students, as they work in a team with instructors and clients to plan a desirable future. Students report that the learning experience has been valuable to their subsequent thesis research as well as contributing to their effectiveness on jobs after the university.Keywords: agroecology, systems learning, action learning, education for responsible action, organic farming system

Cultivating multi-cultural teams: lessons learned in the "milpa" of an Agroecology MSc course

Traditional milpa polycultures of maize-bean-squash consistently have higher yields and are more resilient to stresses than monocultures. This synergistic outcome builds on species differences in physiology and morphology. In our agroecology program, the faculty work as milperos, intentionally developing multi-cultural teams that are capable of building upon their differences

Penrose type inequalities for asymptotically hyperbolic graphs

In this paper we study asymptotically hyperbolic manifolds given as graphs of asymptotically constant functions over hyperbolic space \bH^n. The graphs are considered as subsets of \bH^{n+1} and carry the induced metric. For such manifolds the scalar curvature appears in the divergence of a 1-form involving the integrand for the asymptotically hyperbolic mass. Integrating this divergence we estimate the mass by an integral over an inner boundary. In case the inner boundary satisfies a convexity condition this can in turn be estimated in terms of the area of the inner boundary. The resulting estimates are similar to the conjectured Penrose inequality for asymptotically hyperbolic manifolds. The work presented here is inspired by Lam's article concerning the asymptotically Euclidean case.Comment: 29 pages, no figure, includes a proof of the equality cas

Environmental Risk and Meningitis Epidemics in Africa

Epidemics of meningococcal meningitis occur in areas with particular environmental characteristics. We present evidence that the relationship between the environment and the location of these epidemics is quantifiable and propose a model based on environmental variables to identify regions at risk for meningitis epidemics. These findings, which have substantial implications for directing surveillance activities and health policy, provide a basis for monitoring the impact of climate variability and environmental change on epidemic occurrence in Africa

Structure of a putative NTP pyrophosphohydrolase: YP_001813558.1 from Exiguobacterium sibiricum 255-15.

The crystal structure of a putative NTPase, YP_001813558.1 from Exiguobacterium sibiricum 255-15 (PF09934, DUF2166) was determined to 1.78 Å resolution. YP_001813558.1 and its homologs (dimeric dUTPases, MazG proteins and HisE-encoded phosphoribosyl ATP pyrophosphohydrolases) form a superfamily of all-α-helical NTP pyrophosphatases. In dimeric dUTPase-like proteins, a central four-helix bundle forms the active site. However, in YP_001813558.1, an unexpected intertwined swapping of two of the helices that compose the conserved helix bundle results in a `linked dimer' that has not previously been observed for this family. Interestingly, despite this novel mode of dimerization, the metal-binding site for divalent cations, such as magnesium, that are essential for NTPase activity is still conserved. Furthermore, the active-site residues that are involved in sugar binding of the NTPs are also conserved when compared with other α-helical NTPases, but those that recognize the nucleotide bases are not conserved, suggesting a different substrate specificity