Universal graphs with a forbidden subtree

We show that the problem of the existence of universal graphs with specified forbidden subgraphs can be systematically reduced to certain critical cases by a simple pruning technique which simplifies the underlying structure of the forbidden graphs, viewed as trees of blocks. As an application, we characterize the trees T for which a universal countable T-free graph exists

Invariant measures concentrated on countable structures

Let L be a countable language. We say that a countable infinite L-structure M admits an invariant measure when there is a probability measure on the space of L-structures with the same underlying set as M that is invariant under permutations of that set, and that assigns measure one to the isomorphism class of M. We show that M admits an invariant measure if and only if it has trivial definable closure, i.e., the pointwise stabilizer in Aut(M) of an arbitrary finite tuple of M fixes no additional points. When M is a Fraisse limit in a relational language, this amounts to requiring that the age of M have strong amalgamation. Our results give rise to new instances of structures that admit invariant measures and structures that do not.Comment: 46 pages, 2 figures. Small changes following referee suggestion

Universal graphs with forbidden subgraphs and algebraic closure

We apply model theoretic methods to the problem of existence of countable universal graphs with finitely many forbidden connected subgraphs. We show that to a large extent the question reduces to one of local finiteness of an associated''algebraic closure'' operator. The main applications are new examples of universal graphs with forbidden subgraphs and simplified treatments of some previously known cases

From Sydney to Syracuse a Transcontinental Exploration of Women’s Health in Karen Refugee Communities

From Sydney to Syracuse a Transcontinental Exploration of Women’s Health in Karen Refugee Communities. There are many impediments to refugee women’s access to health care and sexual and reproductive services in their countries of resettlement, including language difference, transportation, and absence of culturally appropriate support. Through focus groups and participatory observation this paper identifies some major challenges that Karen (an ethnic group from Burma) women face accessing health care in their respective cities of resettlement (Syracuse, New York or Sydney, Australia). It is through such documentation and analysis that policies and services can be improved and any harm they inadvertently produced can be alleviated

Germline Cyst Formation and Development in Zebrafish

In developing pre-natal mice, germline cysts are clusters or packages of cells consisting of individual oocytes. They are formed after the primordial germ cells move to the ovary during embryogenesis. The primordial germ cells divide, but do not completely separate. The cells within the cysts are linked by intercellular bridges, which end up breaking down leading to the formation of primordial follicles. The primordial follicles are oocytes surrounded by somatic cells called granulosa cells. Only one third of the original oocytes survive cyst breakdown and become the eggs that will be used by the mouse for her reproduction. This developmental process is conserved in many organisms including Drosophila and humans. Infertility is a disorder that affects 330 million women in the United States alone. This striking statistic has led to much research on oocyte development. The developmental of cysts and cyst breakdown are vital to reproductive success as infertility arises when this process is hindered. Many factors can inhibit cyst breakdown, such as fetal exposure to estrogenic compounds found in the environment. By studying model organisms we hope to elucidate the mechanisms of cyst formation and regulation and bring this knowledge to the human scale. Cyst formation has already been well studied in fruit flies and in mice. My research will focus on oocyte development specifically cyst formation in zebrafish and how it compares to that of mice and fruit flies. Germline cysts have not been well studied in zebrafish so this research is relatively uncharted territory. To date there is some evidence to suggest the existence of germline cysts in other teleosts (bony fishes) such as the Medaka. By using the knowledge of what is known about cyst formation in Drosophila and mice, as well as literature on oogenesis in a wide range of organisms, I have conducted research to identify germline cysts in zebrafish. Zebrafish were sacrificed at different ages: from two weeks to adult, and their ovaries were stained with oocyte specific antibodies as well as antibodies that have been shown to mark intercellular bridges in Drosophila and mice. The ovary tissues were then imaged using confocal microscopy. My findings show preliminary data that supports the existence of germline cysts in zebrafish