A strong geometric hyperbolicity property for directed graphs and monoids

We introduce and study a strong "thin triangle"' condition for directed graphs, which generalises the usual notion of hyperbolicity for a metric space. We prove that finitely generated left cancellative monoids whose right Cayley graphs satisfy this condition must be finitely presented with polynomial Dehn functions, and hence word problems in NP. Under the additional assumption of right cancellativity (or in some cases the weaker condition of bounded indegree), they also admit algorithms for more fundamentally semigroup-theoretic decision problems such as Green's relations L, R, J, D and the corresponding pre-orders. In contrast, we exhibit a right cancellative (but not left cancellative) finitely generated monoid (in fact, an infinite class of them) whose Cayley graph is a essentially a tree (hence hyperbolic in our sense and probably any reasonable sense), but which is not even recursively presentable. This seems to be strong evidence that no geometric notion of hyperbolicity will be strong enough to yield much information about finitely generated monoids in absolute generality.Comment: Exposition improved. Results unchange

Amenability and geometry of semigroups

We study the connection between amenability, Følner conditions and the geometry of finitely generated semigroups. Using results of Klawe, we show that within an extremely broad class of semigroups (encompassing all groups, left cancellative semigroups, finite semigroups, compact topological semigroups, inverse semigroups, regular semigroups, commutative semigroups and semigroups with a left, right or two-sided zero element), left amenability coincides with the strong Følner condition. Within the same class, we show that a finitely generated semigroup of subexponential growth is left amenable if and only if it is left reversible. We show that the (weak) Følner condition is a left quasi-isometry invariant of finitely generated semigroups, and hence that left amenability is a left quasi-isometry invariant of left cancellative semigroups. We also give a new characterisation of the strong Følner condition in terms of the existence of weak Følner sets satisfying a local injectivity condition on the relevant translation action of the semigroup

The Convention on the Future of the EU: The European Commission and Treaty Reform

Treaty reform has become an almost constant feature in the European Union. This article challenges the traditional intergovernmentalist assumption that state representatives are the only significant actors in this process by looking in some detail at the role played by the European Commission. The article first sets out the institutional framework within which the Commission participates in the negotiations. It then demonstrates that the Commission's influence – even though limited in the actual decision-making – is evident with respect to agenda-setting and legitimation of treaty reform. Finally, we look at the impact of the convention method on the nature of treaty reform

the Growth Potential for the Indiana Livestock Industries

Feed, processing capacity, population density versus animal density, and environmental capacities are the four different dimensions of livestock location and growth potential analyzed for Indiana. These four dimensions provide livestock producers, government officials, and livestock associations a valuable perspective on the constraints that could limit Indiana’s livestock growth potential. Comparisons among 21 states on these dimensions indicated that Indiana is a second choice of states for livestock growth; Kansas and Iowa are the only first choices. Indiana’s strength in the state comparison is its ability to assimilate the phosphorus produced by livestock and commercial phosphorus. As environmental regulations continue to tighten and shift from nitrogen to phosphorus based application standards for manure, the ability to assimilate phosphorus will continue to be one of Indiana’s strengths, along with its abundance of feed and swine processing capacity. Population density is the key dimension that is a disadvantage for Indiana. Within the state of Indiana, the West Central district has key advantages compared to other districts of the state. This district has an abundance of feed, the second lowest population density in the state, and excess phosphorus assimilation capacity. This district does not have processing capacity for any species, but the adjoining districts do have adequate processing capacity. Overall, the results show that Indiana has the potential to grow the livestock sector. However, there will be constraints such as population density that require more in-depth study to determine how to address this potential limitation on growth.Livestock Growth, Animal Waste, Feed Capacity, Livestock Processing Capacity, Animal Density, Population Density

Human Development Trends since 1970: A Social Convergence Story

This paper uses a unique data set of the Human Development Index to describe long-run human development trends for 111 countries, from 1970 to 2005. The first part of the paper shows trends by region, period and index subcomponent. We find that 110 of the 111 countries show progress in their HDI levels over a 35-year period. HDI growth is fastest for low-HDI and middle-HDI countries in the pre-1990 period. The life-expectancy and education subcomponents grow faster than income. The assessment of HDI progress is sensitive to choice of measurement. The second part of the paper focuses on the differences between income and non-income determinants of human development. First, HDI growth converges, both absolutely and conditionally, when running HDI growth rates on initial levels of HD. Second, we find that the income and non-income components of HDI change have a near-zero correlation. Third, we look at determinants of the non-income components of the HDI. We find that income is not a significant determinant of HDI change once we include urbanization, fertility and female schooling. Fourth, we test the effects of institutions, geography and gender on HDI growth. We find that the most robust predictors of HDI growth are fertility and female schooling. We check this result using years of women’s suffrage as an instrument for changes in gender relations, and find that it is a significant predictor of HDI progress for the whole sample.human development, education, health and demographic trends, cross-country comparisons, measurement and analysis of poverty

Deactivation of biacetyl triplets by cyanocobaltate(III) complexes

The rate of electronic energy transfer from biacetyl triplets to Co(CN)_(5)(X)^(n–)(X = CN^–, MeCN, pyridine, N_(3)^–, H_(2)O, or SCN^–) is strongly dependent on the energy of the first spin-allowed d–d transition of Co(CN)_(5)(X)^(n–), and (for X = CN^–, N_(3)^–, and SCN^–) the direct and sensitized photosubstitution yields are the same, implying a common reactive state

An approach for developing a preliminary cost estimating methodology for USCG vessels

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Ocean Engineering, 1987.Bibliography: v. 2, leaves 287-291.by Mark James Gray.M.S

A Dynamin-3 Spliced Variant Modulates the Actin/Cortactin-Dependent Morphogenesis of Dendritic Spines

Immature dendrites extend many actin-rich filopodial structures that can be replaced by synapse-containing dendritic spines as the neuron matures. The large GTPase dynamin-3 (Dyn3) is a component of the postsynapse in hippocampal neurons but its function is undefined. Here, we demonstrate that a specific Dyn3 variant (Dyn3baa) promotes the formation of immature dendritic filopodia in cultured neurons. This effect is dependent upon Dyn3 GTPase activity and a direct interaction with the F-actin-binding protein cortactin. Consistent with these findings, Dyn3baa binds to cortactin with a 200% higher affinity than Dyn3aaa, a near identical isoform that does not induce dendritic filopodia when expressed in cultured neurons. Finally, levels of Dyn3baa-encoding mRNA are tightly regulated during neuronal maturation and are markedly upregulated during synaptogenesis. Together, these findings provide the first evidence that an enhanced interaction between a specific Dyn3 splice variant and cortactin modulate actin-membrane dynamics in developing neurons to regulate the morphogenesis of dendritic spines. Supplementary material available online at http://jcs.biologists.org/cgi/content/full/118/6/1279/DC