AGRICULTURAL, FOOD AND HUMAN RESOURCE POLICIES: IMPLICATIONS FOR RURAL AFRICAN-AMERICANS

Agricultural and Food Policy,

Constructing compact 8-manifolds with holonomy Spin(7) from Calabi-Yau orbifolds

Compact Riemannian 7- and 8-manifolds with holonomy G(2) arid Spin(7) were first constructed by the author in 1994-5, by resolving orbifolds T-7/Gamma and T-8/Gamma. This paper describes a new construction of compact 8-manifolds with holonomy Spin(7). We start with a Calabi-Yau 4-orbifold Y with isolated singularities of a special kind. We divide by an antiholomorphic involution a of Y to get a real 8-orbifold Z = Y/. Then we resolve tire singularities of Z to get a compact 8-manifold M, which has metrics with holonomy Spin(7). Manifolds constructed in this way typically have large fourth Betti number b(4)(M).</sigma

Moduli spaces of G2 manifolds

This paper is a review of current developments in the study of moduli spaces of G2 manifolds. G2 manifolds are 7-dimensional manifolds with the exceptional holonomy group G2. Although they are odd-dimensional, in many ways they can be considered as an analogue of Calabi-Yau manifolds in 7 dimensions. They play an important role in physics as natural candidates for supersymmetric vacuum solutions of M-theory compactifications. Despite the physical motivation, many of the results are of purely mathematical interest. Here we cover the basics of G2 manifolds, local deformation theory of G2 structures and the local geometry of the moduli spaces of G2 structures.Comment: 31 pages, 2 figure

On the geometry of closed G2-structure

We give an answer to a question posed recently by R.Bryant, namely we show that a compact 7-dimensional manifold equipped with a G2-structure with closed fundamental form is Einstein if and only if the Riemannian holonomy of the induced metric is contained in G2. This could be considered to be a G2 analogue of the Goldberg conjecture in almost Kahler geometry. The result was generalized by R.L.Bryant to closed G2-structures with too tightly pinched Ricci tensor. We extend it in another direction proving that a compact G2-manifold with closed fundamental form and divergence-free Weyl tensor is a G2-manifold with parallel fundamental form. We introduce a second symmetric Ricci-type tensor and show that Einstein conditions applied to the two Ricci tensors on a closed G2-structure again imply that the induced metric has holonomy group contained in G2.Comment: 14 pages, the Einstein condition in the assumptions of the Main theorem is generalized to the assumption that the Weyl tensor is divergence-free, clarity improved, typos correcte

An Analysis of Children\u27s Responses to Storybook Characters in Non-Traditional Roles

Sex role stereotypes have been investigated in text materials (Rupley, Garcia and Longnion, 1981; Scott and Feldman-Summers, 1979; Taylor, 1973) and in children\u27s literature (Ashby and Wittmaier, 1978; DeLisi and Johns, 1984; Donlan, 1972; Key, 1971; Kropp and Halverson, 1983; Styer, 1975; Weitzman, 1972; Winkeljohann and Gallant, 1980). These studies have examined the stereotypical roles portrayed by male and female characters, in terms of the way the males and females are presented in the material. Findings indicate change in sex roles to be slow; males still tend to be viewed as active and achieving while girls are passive and emotional (Weitzman, 1972, p. 1125). According to social learning theory perspective, such stereotyped views of sex roles are incorporated into a child\u27s repertoire of behaviors. Children selectively imitate what they perceive as culturally designated appropriate sex role behavior (Hartley, 1959; Weitzman, 1972). In support of this theory researchers have also found children exposed to material containing non-traditional roles have been influenced by the stories that they hear (Berg-Cross and Berg-Cross, 1978; Kropp and Halverson, 1983; Litcher and Johnson, 1969; Styer, 1975). In these studies, hearing socially relevant stories containing sex equitable roles, roles which reflect the changing roles for men and women, changed children\u27s attitudes and values toward the character in the non-traditional role. If society has indeed reacted to findings such as these by exposing students to more sexequitable literature and ideas, it may mean that children to day have less sex-typed attitudes and are less likely to find such roles novel. One way of determining if this is the case would be to examine the ways in which children freely respond to such literature

Developing a Sense of Audience: An Examination of One School\u27s Instructional Contexts

The purpose of this naturalistic study was to extend our understanding of the ways in which consideration of audience may be salient in diverse students\u27 and teachers\u27 approaches to literacy. Data related to literacy interactions in one school were collected from the preschool class and three multiage elementary classrooms. Findings indicated that the school\u27s curriculum was developed through a socio-cultural approach with the students involved in constructing meaning of their world through interaction with others, through dialogue about texts, and through involvement in the arts. Within these experiences, students developed a sense of audience awareness and participated as audience members. In the upper grades, two specific instructional contexts, literature circles and project work, involved students in preparing for and communicating to (or communicating with) an audience

Unusual nanostructures of "lattice matched" InP on AlInAs

We show that the morphology of the initial monolayers of InP on Al0.48In0.52As grown by metalorganic vapor-phase epitaxy does not follow the expected layer-by-layer growth mode of lattice-matched systems, but instead develops a number of low-dimensional structures, e.g., quantum dots and wires. We discuss how the macroscopically strain-free heteroepitaxy might be strongly affected by local phase separation/alloying-induced strain and that the preferred aggregation of adatom species on the substrate surface and reduced wettability of InP on AlInAs surfaces might be the cause of the unusual (step) organization and morpholog

A Rare Cause of Low Back Pain: Report of a Tailgut Cyst

Tailgut cysts, also known as retrorectal cystic hamartomas, are rare developmental abnormalities that typically occur in the retrorectal space. They are believed to arise from remnants of the embryonic hindgut (Hjermstad and Helwig, 1988). They can present as incidental findings during routine examination but over half of patients are thought to present with symptoms. MRI has become the modality of choice to image these frequently misdiagnosed cysts. Biopsy is not recommended. Complete intact surgical excision is advised to avoid the potential complications of these cysts which include infection, fistula formation, and the possibility of malignant transformation (Hjermstad and Helwig (1988), Mathis et al. (2010)). We describe the case of a 46-year-old female who presented with a 6-month history of low back pain. CT and MRI imaging demonstrated a complex retrorectal lesion with supralevator and infralevator components. This was removed using a combined transperineal and transabdominal approach. Histology confirmed a tailgut cyst

Stability conditions and Stokes factors

Let A be the category of modules over a complex, finite-dimensional algebra. We show that the space of stability conditions on A parametrises an isomonodromic family of irregular connections on P^1 with values in the Hall algebra of A. The residues of these connections are given by the holomorphic generating function for counting invariants in A constructed by D. Joyce.Comment: Very minor changes. Final version. To appear in Inventione

Discrete versions of some Dirac type equations and plane wave solutions

A discrete version of the plane wave solution to some discrete Dirac type equations in the spacetime algebra is established. The conditions under which a discrete analogue of the plane wave solution satisfies the discrete Hestenes equation are briefly discussed.Comment: 12 pages. arXiv admin note: text overlap with arXiv:1609.0459