Approximation of the potential in scalar field dark energy models

We study the nature of potentials in scalar field based models for dark energy - with both canonical and noncanonical kinetic terms. We calculate numerically, and using an analytic approximation around $a\approx 1$, potentials for models with constant equation-of-state parameter, $w_{\phi}$. We find that for a wide range of models with canonical and noncanonical kinetic terms there is a simple approximation for the potential that holds when the scale factor is in the range $0.6\lesssim a\lesssim 1.4$. We discuss how this form of the potential can also be used to represent models with non-constant $w_{\phi}$ and, hence, how it could be used in reconstruction from cosmological data.Comment: 17 pages, 6 figures. Accepted by Phys. Rev.

Cosmological perturbation theory in Generalized Einstein-Aether models

We investigate the evolution of cosmological perturbations in models of dark energy described by a time-like unit normalized vector field specified by a general function $\mathcal{F}(\mathcal{K})$, so-called Generalized Einstein-Aether models. First we study the background dynamics of such models via a designer approach in an attempt to model this theory as dark energy. We find that only one specific form of this designer approach matches $\Lambda$CDM at background order and we also obtain a differential equation which $\mathcal{F}(\mathcal{K})$ must satisfy for general $w$CDM cosmologies. We also present the equations of state for perturbations in Generalized Einstein-Aether models, which completely parametrize these models at the level of linear perturbations. A generic feature of modified gravity models is that they introduce new degrees of freedom. By fully eliminating these we are able to express the gauge invariant entropy perturbation and the scalar, vector, and tensor anisotropic stresses in terms of the perturbed fluid variables and metric perturbations only. These can then be used to study the evolution of perturbations in the scalar, vector, and tensor sectors and we use these to evolve the Newtonian gravitational potentials.Comment: 26 pages, 4 figures, 3 tables, submitted to PR

Gravitational wave constraints on dark sector models

We explore the constraints on dark sector models imposed by the recent observation of coincident gravitational waves and gamma rays from a binary neutron star merger, GW170817. Rather than focusing on specific models as has been considered by other authors, we explore this in the context of the equation of state approach of which the specific models are special cases. After confirming the strong constraints found by others for Horndeski, Einstein-Aether and massive gravity models, we discuss how it is possible to construct models which might evade the constraints from GW170817 but still leading to cosmologically interesting modifications to gravity. Possible examples are ``miracle cancellations" such as in $f(R)$ models, nonlocal models and higher-order derivatives. The latter two rely on the dimensionless ratio of the wave number of the observed gravitational waves to the Hubble expansion rate being very large ($\sim10^{19}$) which is used to suppress modifications to the speed of gravitational waves.Comment: 10 page

The Singing Insects of Michigan

Excerpt: The so-called singing insects are all those that make loud, rhythmical noises. They include members of three groups of Orthoptera (Gryllidae, Tettigoniidae, and Acridoidea) and one family of Homoptera (Cicadidae). There are about 300 noisy species in these four groups in eastern North America, perhaps a thousand in all of North America, and 25-30 thousand in the entire world. Only about 1000 of the world species have been studied in any detail, mostly in North America, Europe, Japan, and Australia

The Potential of Exogenous Fatty Acids in Breast Tissue Engineering

More than 200,000 women are diagnosed with breast cancer each year in the United States, where the majority will undergo a lumpectomy procedure and then radiotherapy as preventative treatment. Both artificial and tissue transplants may obscure the detection of cancer recurrence or limit the effectiveness of radiation treatment. Previous research in our laboratory has been performed to develop injectable lumpectomy void fillers. This body of work seeks to continue and further develop the technology of the void fillers and further investigate the potential of fatty acids in breast tissue engineering. Literature suggests that lipid peroxidation products from free fatty acids may have anti-cancerous effects. Linoleic acid is in the family of fatty acids associated with lipid peroxidation; however, linoleic acid is also associated with growth promoting eicosanoids which has caused linoleic acid to be considered a cancer promoting agent. Studies shown here suggest that a high concentration, 100 µM, of linoleic acid was effective at limiting cancerous proliferation by day 6, and suggest a complete removal of the cancerous population by day 8, while control cells remained largely unaffected. Further studies confirmed the elevated presence of lipid peroxide products in the inhibited cancerous cell cultures. When linoleic acid was tested in culture with tamoxifen, the observed inhibition of cancerous proliferation was greater than either of the treatments alone. This finding supports the use of linoleic acid in tissue engineered scaffolding. Additional work was performed to advance the development of a lumpectomy scaffolding. An injectable chitosan scaffolding has previously been developed through the use of a pH shifting technique; however, work described here continued the scaffolding development by adding gelatin, hyaluronic acid, and an acid washing step which resulted in the formation of a distinct bilayer. Cells cultured on the bilayered scaffolding were found to migrate to the boundary between layers where they proliferated at an accelerated rate compared to uniform hydrogels. Fatty acids were able to be incorporated into the production of the hydrogels at a concentration of 400 µM. Previous researchers in the laboratory had reported adipogenic effects from linoleic acid. These results were not observed upon further investigation. Linoleic acid did result in the swelling of human stem cells but did not otherwise morphologically change the cells. A mixture of conjugated linoleic acid however, was tested and found to upregulate adipogenic specific markers to a level indistinguishable from adipogenic controls. Through the course of this body of research, several advances were made in the field of test methods for tissue engineering. Work was done towards the improvement of procedures of multiwell plate readers to allow sterile sampling, the cytotoxicity of alamarBlue was found and investigated, improvements to previous lab gas chromatography procedures were made, and analyses of experimental results indicated the importance of recovery periods in cytotoxicity studies

L'UE et ses voisinages : acteurs et espaces d'un discours

International audienceIn this communication, we provide an analysis of the European Neighbourhood Policy (ENP), based on 7 texts published by the European Commission and then by the European External Action Service between 2003 and 2013. The analysis of this corpus of texts by the methods of textual statistics brings a complementary perspective to the research works in the field of critical discourse analysis. Without formulating any hypothesis, we let emerge the contents of texts by a quantitative analysis of the vocabulary and the lexical fields which take shape during the studied decade. We paid a particular attention on the naming of the geographical entities in the manner of writing the policies of neighbourhood. This lexical analysis of the “official” speech of the politics (policy) of neighbourhood gives a significant contribution to the debates on regional integration at the macrogeographical level.Cette communication propose une analyse de la politique européenne de voisinage à partir des sept communications-cadres publiées par la Commission européenne et le Service européen d’Action extérieure entre 2003 et 2013. L’analyse de ce corpus de textes par les méthodes de la statistique textuelle apporte un éclairage complémentaire aux travaux qui s’inscrivent dans le champ de la critical discourse analysis. Le contenu des textes a été exploré par une analyse quantitative du vocabulaire et des champs lexicaux qui se dessinent au cours de la décennie étudiée. Nous avons porté une attention particulière à la désignation des entités géographiques dans la manière d’écrire la politique de voisinage. Cette analyse lexicale du discours « officiel » de la politique européenne de voisinage permet d’apporter une contribution significative aux débats sur l’intégration régionale à l’échelle macroscopique en décryptant le regard porté par les institutions européennes

Tributes to Peter Homans

Peter Homans, Professor Emeritus at the University of Chicago Divinity School, died on Saturday, May 30, 2009, in Evanston, Illinois. The cause of death was complications from a recent stroke. Professor of Psychology and Religious Studies in the Divinity School, Professor Homans also held appointments in the Committee on Human Development and on the Committee on the History of Culture, as well as in the Social Sciences Collegiate Division. He joined the Divinity School faculty in 1965