International Collaboration in Crop Improvement Research: Current Status and Future Prospects

Investments over the past 35 years have created a system of national and international research centers that has revolutionized the supply of improved cereal varieties to developing country farmers. The newly created scientific ability to exploit genetic resources has been the engine of productivity growth in much of world agriculture. But the success that has been attained in building research institutions has not touched all countries or farmers, nor can it be considered permanent. The financial and political environment of the past decade has halted the expansion of agricultural research capacity and the scarcity of research resources and evolving world intellectual property rights (IPR) regimes complicates the search for stable arrangements for cooperation. This paper examines the current structure and institutional capacity of the international crop breeding systems for rice and wheat. Discussions are presented within the context of a system composed of research functions spanning the basic to applied research spectrum. The model emphasizes that an efficient and stable international system may be comprised of many partner institutions, each with a limited breadth of research activities, particularly when research budgets are fixed or declining. The paper concludes with a review of some of the trends that will influence the future direction of research cooperation.Crop Production/Industries, Research and Development/Tech Change/Emerging Technologies,

A new model for mixing by double-diffusive convection (semi-convection): I. The conditions for layer formation

The process referred to as "semi-convection" in astrophysics and "double-diffusive convection in the diffusive regime" in Earth and planetary sciences, occurs in stellar and planetary interiors in regions which are stable according to the Ledoux criterion but unstable according to the Schwarzschild criterion. In this series of papers, we analyze the results of an extensive suite of 3D numerical simulations of the process, and ultimately propose a new 1D prescription for heat and compositional transport in this regime which can be used in stellar or planetary structure and evolution models. In a preliminary study of the phenomenon, Rosenblum et al. (2011) showed that, after saturation of the primary instability, a system can evolve in one of two possible ways: the induced turbulence either remains homogeneous, with very weak transport properties, or transitions into a thermo-compositional staircase where the transport rate is much larger (albeit still smaller than in standard convection). In this paper, we show that this dichotomous behavior is a robust property of semi-convection across a wide region of parameter space. We propose a simple semi-analytical criterion to determine whether layer formation is expected or not, and at what rate it proceeds, as a function of the background stratification and of the diffusion parameters (viscosity, thermal diffusivity and compositional diffusivity) only. The theoretical criterion matches the outcome of our numerical simulations very adequately in the numerically accessible "planetary" parameter regime, and can easily be extrapolated to the stellar parameter regime. Subsequent papers will address more specifically the question of quantifying transport in the layered case and in the non-layered case.Comment: Submitted to Ap

1970’s Japanese Women’s Liberation Movement: Its Issues and Successes

The post-war period saw many economic, political, and social changes in Japan—one of which was the expansion of women’s roles in society and presence outside the home. During the 1970s in particular, the Japanese feminist movement critiqued traditional ideals of women’s sexuality, motherhood, and femininity, similar to the women’s liberation movement occurring in the Western world at the time. This Japanese-language presentation looks at various factors in Japan that allowed for the emergence and growth of the Japanese women’s liberation movement, as well as some of the issues it faced and successes it achieved

Comparing Network Centrality Measures of Non-Traditional Students in an Introductory Physics Class

The goal of this research was to compare different models of network influence for students. Two research questions were composed: 1. How do common centrality measures compare when ranking students\u27 network influence? 2. Do centrality values of non-traditional students show different trend than traditional students?https://corescholar.libraries.wright.edu/urop_celebration/1016/thumbnail.jp

Students’ Use of Symmetry with Gauss’s Law

To study introductory student difficulties with electrostatics, we compared student techniques when finding the electric field for spherically symmetric and non-spherically symmetric charged conductors. We used short interviews to design a free-response and multiple-choice-multiple-response survey that was administered to students in introductory calculus-based courses. We present the survey results and discuss them in light of Singh\u27s results for Gauss\u27s Law, Collins and Ferguson\u27s epistemic forms and games, and Tuminaro\u27s extension of games and frames

Network positions in active learning environments in physics

This study uses positional analysis to describe the student interaction networks in four research-based introductory physics curricula. Positional analysis is a technique for simplifying the structure of a network into blocks of actors whose connections are more similar to each other than to the rest of the network. This method describes social structure in a way that is comparable between networks of different sizes and densities and can show large-scale patterns such as hierarchy or brokering among actors. We detail the method and apply it to class sections using Peer Instruction, SCALE-UP, ISLE, and context-rich problems. At the level of detail shown in the blockmodels, most of the curricula are more alike than different, showing a late-term tendency to form coherent subgroups that communicate actively among themselves but have few inter-position links. This pattern may be a network signature of active learning classes, but wider data collection is needed to investigate.Comment: 17 pages, 10 figures; supplemental 10 pages, 9 figure

Turbulent Mixing and Layer Formation in Double-Diffusive Convection: 3D Numerical Simulations and Theory

Double-diffusive convection, often referred to as semi-convection in astrophysics, occurs in thermally and compositionally stratified systems which are stable according to the Ledoux criterion but unstable according to the Schwarzschild criterion. This process has been given relatively little attention so far, and its properties remain poorly constrained. In this paper, we present and analyze a set of three-dimensional simulations of this phenomenon in a Cartesian domain under the Boussinesq approximation. We find that in some cases the double-diffusive convection saturates into a state of homogeneous turbulence, but with turbulent fluxes several orders of magnitude smaller than those expected from direct overturning convection. In other cases, the system rapidly and spontaneously develops closely packed thermo-compositional layers, which later successively merge until a single layer is left. We compare the output of our simulations with an existing theory of layer formation in the oceanographic context and find very good agreement between the model and our results. The thermal and compositional mixing rates increase significantly during layer formation and increase even further with each merger. We find that the heat flux through the staircase is a simple function of the layer height. We conclude by proposing a new approach to studying transport by double-diffusive convection in astrophysics

Enriching gender in PER: A binary past and a complex future

In this article, we draw on previous reports from physics, science education, and women's studies to propose a more nuanced treatment of gender in physics education research (PER). A growing body of PER examines gender differences in participation, performance, and attitudes toward physics. We have three critiques of this work: (1) it does not question whether the achievements of men are the most appropriate standard, (2) individual experiences and student identities are undervalued, and (3) the binary model of gender is not questioned. Driven by these critiques, we propose a conception of gender that is more up-to-date with other fields and discuss gender-as-performance as an extended example. We also discuss work on the intersection of identities [e.g., gender with race and ethnicity, socioeconomic status, lesbian, gay, bisexual, and transgender (LGBT) status], much of which has been conducted outside of physics. Within PER, some studies examine the intersection of gender and race, and identify the lack of a single identity as a key challenge of "belonging" in physics. Acknowledging this complexity enables us to further critique what we term a binary gender deficit model. This framework, which is implicit in much of the gender-based PER, casts gender as a fixed binary trait and suggests that women are deficient in characteristics necessary to succeed. Alternative models of gender allow a greater range and fluidity of gender identities, and highlight deficiencies in data that exclude women's experiences. We suggest new investigations that diverge from this expanded gender framework in PER.Comment: 27 pages, accepted to Phys. Rev. Special Topics - PE

Individual Differences in Eye-Movements During Reading: Working Memory and Speed-of-Processing Effects

Mathematical models of eye-movement control do not yet incorporate individual differences as a source of variation in reading. These models nonetheless provide an excellent foundation for describing and explaining how and why patterns of eye-movements differ across readers (e.g., Rayner et al., 2006). We focus in this article on two aspects of individual variation: global processing speed (e.g., Salthouse, 1996) and working-memory capacity (e.g., Just & Carpenter, 1992). Using Hierarchical Linear Modeling (HLM) (Raudenbush & Bryk, 2001), we tested the extent to which overall reading speed and working-memory capacity moderate the degree to which syntactic and semantic information affect fixation times. We found that working-memory capacity interacted with sentence-characteristic variables only when processing speed was not included in the model