Many-body theory for positronium-atom interactions

A many-body-theory approach has been developed to study positronium-atom interactions. As first applications, we calculate the elastic scattering and momentum-transfer cross sections and the pickoff annihilation rate $^1Z_\text{eff}$ for Ps collisions with He and Ne. The cross section for He is in agreement with previous coupled-state calculations, and the momentum-transfer cross section for Ne agrees with available experimental data. $^1Z_\text{eff}$ is found to be 0.13 and 0.26 for He and Ne, respectively, in excellent agreement with the measured values.Comment: Accepted by Phys. Rev. Lett. (V2 contains update to text and Figs. 3 and 5. V3 contains further discussion on the calculation of pickoff annihilation rates.

There\u27s Nothing Like Dancing, After All Gender as Performance in Jane Austen\u27s Dance Scenes

This thesis examines the elaborate and intricate dance scenes in many of Jane Austen’s novels as representations of marriage and the performance of gender. Along with looking at the successful marriages in Austen’s novels which result from the social convention of English country dancing, this thesis also analyzes the failed relationships and broken hearts that result from Austenian dancing and discusses the role of gender in finding both a good dance partner and a good spouse

Effect of composition and density on the ablative performance of phenolic-nylon

Composition and density effects on ablative performance of phenolic-nylo

Potentials for hyper-Kahler metrics with torsion

We prove that locally any hyper-K\"ahler metric with torsion admits an HKT potential.Comment: 9 page

Holonomy groups of pseudo-quaternionic-K\"ahlerian manifolds of non-zero scalar curvature

The holonomy group $G$ of a pseudo-quaternionic-K\"ahlerian manifold of signature $(4r,4s)$ with non-zero scalar curvature is contained in \Sp(1)\cdot\Sp(r,s) and it contains \Sp(1). It is proved that either $G$ is irreducible, or $s=r$ and $G$ preserves an isotropic subspace of dimension $4r$, in the last case, there are only two possibilities for the connected component of the identity of such $G$. This gives the classification of possible connected holonomy groups of pseudo-quaternionic-K\"ahlerian manifolds of non-zero scalar curvature.Comment: 7 pages; Dedicated to Dmitri Vladimirovich Alekseevsky at the occasion of his 70th birthda

Design and application of nanoscale actuators using block-copolymers

Block copolymers are versatile designer macromolecules where a “bottom-up” approach can be used to create tailored materials with unique properties. These simple building blocks allow us to create actuators that convert energy from a variety of sources (such as chemical, electrical and heat) into mechanical energy. In this review we will discuss the advantages and potential pitfalls of using block copolymers to create actuators, putting emphasis on the ways in which these materials can be synthesised and processed. Particular attention will be given to the theoretical background of microphase separation and how the phase diagram can be used during the design process of actuators. Different types of actuation will be discussed throughout

Autoimmunity associated with chemically induced thymic dysplasia

Thymopoiesis strictly depends on the function of the Foxn1 transcription factor that is expressed in the thymic epithelium. During embryonic development, initial expression of the Foxn1 gene is induced in the pharyngeal endoderm by mesenchyme-derived BMP4 signals. Here, by engineering a time-delayed feedback system of BMP inhibition in mouse embryos, we demonstrate that thymopoiesis irreversibly fails if Foxn1 gene expression does not occur during a defining time span in mid-gestation. We also reveal an epistatic interaction between the extent of BMP signalling and the gene dosage of Foxn1. Our findings illustrate the complexities of the early steps of thymopoiesis and indicate that sporadic forms of thymic hypoplasia in humans may result from the interaction of genes affecting the magnitude of BMP signalling and Foxn1 expressio