Microgravity: a Teacher's Guide with Activities, Secondary Level

This NASA Educational Publication is a teacher's guide that focuses on microgravity for the secondary level student. The introduction answers the question 'What is microgravity?', as well as describing gravity and creating microgravity. Following the introduction is a microgravity primer which covers such topics as the fluid state, combustion science, materials science, biotechnology, as well as microgravity and space flight. Seven different activities are described in the activities section and are written by authors prominent in the field. The concluding sections of the book include a glossary, microgravity references, and NASA educational resources

Estimates of random walk exit probabilities and application to loop-erased random walk

We prove an estimate for the probability that a simple random walk in a simply connected subset A of Z^2 starting on the boundary exits A at another specified boundary point. The estimates are uniform over all domains of a given inradius. We apply these estimates to prove a conjecture of S. Fomin in 2001 concerning a relationship between crossing probabilities of loop-erased random walk and Brownian motion.Comment: 26 pages, 0 figure

Topological censorship from the initial data point of view

We introduce a natural generalization of marginally outer trapped surfaces, called immersed marginally outer trapped surfaces, and prove that three dimensional asymptotically flat initial data sets either contain such surfaces or are diffeomorphic to R^3. We establish a generalization of the Penrose singularity theorem which shows that the presence of an immersed marginally outer trapped surface generically implies the null geodesic incompleteness of any spacetime that satisfies the null energy condition and which admits a non-compact Cauchy surface. Taken together, these results can be viewed as an initial data version of the Gannon-Lee singularity theorem. The first result is a non-time-symmetric version of a theorem of Meeks-Simon-Yau which implies that every asymptotically flat Riemannian 3-manifold that is not diffeomorphic to R^3 contains an embedded stable minimal surface. We also obtain an initial data version of the spacetime principle of topological censorship. Under physically natural assumptions, a 3-dimensional asymptotically flat initial data set with marginally outer trapped boundary and no immersed marginally outer trapped surfaces in its interior is diffeomorphic to R^3 minus a finite number of open balls. An extension to higher dimensions is also discussed.Comment: v2: Appendix added, Theorem 5.1 improved, other minor changes. To appear in J. Diff. Geo

Method for controlling the shift invariance of optical correlators

Holographic correlators can implement many correlations in parallel. For most systems shift invariance limits the number of correlation templates that can be stored in one correlator. This is because the output plane must be divided among the individual templates in the system. When the system is completely shift invariant, the correlation peak from one correlator can shift into an area that has been reserved for a different template; in this case a shifted version of one object might be mistaken for a well-centered version of a different object. We describe a technique for controlling the shift invariance of a correlator system by moving the holographic material away from the Fourier plane

North American Bison Cooperative and North Dakota Natural Beef LLC: Governance of a Contractual Alliance

In 2005, North American Bison Cooperative formed a contractual alliance with North Dakota Natural Beef, LLC. The alliance was formed in order to enable the cooperative to enhance returns from its physical and managerial assets by entering the natural beef market. This case describes the resources shared by the cooperative and LLC, how the alliance was governed, the risk of opportunism by the CEO and associated trust building and control mechanisms, and the benefits cooperative members received. Although the two companies operate under different business principles, cooperative members exercise indirect control over the resources they contribute to the venture.Agribusiness, Livestock Production/Industries,

Cass-Clay Creamery: A New Direction for an Old Brand

Consolidation and industrialization are increasingly important factors affecting the level of membership in cooperative businesses. This article presents information about the development of the dairy industry in North Dakota and its effect on Cass- Clay Creamery, a farmer-owned dairy cooperative. Students are asked to analyze decisions about branding and being acquired by another larger cooperative.Dairy, cooperative, acquisition, North Dakota, Cass-Clay, AMPI, Agribusiness,

Microgravity: A Teacher's Guide With Activities in Science, Mathematics, and Technology

The purpose of this curriculum supplement guide is to define and explain microgravity and show how microgravity can help us learn about the phenomena of our world. The front section of the guide is designed to provide teachers of science, mathematics, and technology at many levels with a foundation in microgravity science and applications. It begins with background information for the teacher on what microgravity is and how it is created. This is followed with information on the domains of microgravity science research; biotechnology, combustion science, fluid physics, fundamental physics, materials science, and microgravity research geared toward exploration. The background section concludes with a history of microgravity research and the expectations microgravity scientists have for research on the International Space Station. Finally, the guide concludes with a suggested reading list, NASA educational resources including electronic resources, and an evaluation questionnaire