Analytic calculation of the 1-loop effective action for the O(N+1)-symmetric 2-dimensional nonlinear sigma-model

Polyakov's calculation of the effective action for the 2d nonlinear sigma-Model is generalized by purely analytic means to include contributions which are not UV-divergent and which depend on the choice of block spin. An analytic approximation to the background field which determines the classical perfect action is given, and approximations to the 1-loop correction are found. The results should be useful for numerical simulations.Comment: 38 p, 1 figur

Self-consistent Calculation of Real Space Renormalization Group Flows and Effective Potentials

We show how to compute real space renormalization group flows in lattice field theory by a self-consistent method. In each step, the integration over the fluctuation field (high frequency components of the field) is performed by a saddle point method. The saddle point depends on the block-spin. Higher powers of derivatives of the field are neglected in the actions, but no polynomial approximation in the field is made. The flow preserves a simple parameterization of the action. In this paper we treat scalar field theories as an example.Comment: 52 pages, uses pstricks macro, three ps-figure

Nanopatterning of a Covalent Organic Framework Host-Guest System

We have used a boroxine-based COF as a template for C60-fullerene self-assembly on graphite. Local removal of the COF by STM based nanomanipulation creates nanocorrals that may host other species

Polling, Power and Legitimacy: The Politics of Representation and the Making of Publics

This dissertation is situated at the cross-section of Science and Technology Studies (STS), philosophy and sociology of science, and social theories of knowledge and ignorance. Building on historical literature on statistical thought and qualitative interviews, this research explores the history and sociology of survey research and polling. The central aim is to trace the emergence and potential dissolution of what is seen as the established scientific criteria governing survey research and polling, with particular attention to a longstanding, contentious controversy surrounding probability and non-probability sampling. Methodologically, the thesis draws on semi-structured interviews with polling experts based in industry and the academy, juxtaposed with a genealogical analysis of the history of different ontological and epistemological assumptions surrounding the validity of different polling techniques. The thesis explores competing paradigms throughout modern history for understanding the representativeness of polls. Drawing on the concept of boundary work, I analyse how proponents of competing polling programmes seek to legitimize their own approach while simultaneously delegitimizing the opposing viewpoint. In looking at different polling controversies and developing the new notion of ‘forging stable statistical chains’, the thesis explores questions around ontological politics, examining the formation and sustenance of publics through surveys and polls. The research presented in this thesis seeks to provide a sociological analysis of the making of social scientific knowledge. In so doing, I make novel conceptual contributions to sociological understandings of survey research and polling

Broken symmetry and the variation of critical properties in the phase behaviour of supramolecular rhombus tilings

The degree of randomness, or partial order, present in two-dimensional supramolecular arrays of isophthalate tetracarboxylic acids is shown to vary due to subtle chemical changes such as the choice of solvent or small differences in molecular dimensions. This variation may be quantified using an order parameter and reveals a novel phase behaviour including random tiling with varying critical properties as well as ordered phases dominated by either parallel or non-parallel alignment of neighbouring molecules, consistent with long-standing theoretical studies. The balance between order and randomness is driven by small differences in the intermolecular interaction energies, which we show, using numerical simulations, can be related to the measured order parameter. Significant variations occur even when the energy difference is much less than the thermal energy highlighting the delicate balance between entropic and energetic effects in complex self-assembly processes

Nonperturbative Evolution Equation for Quantum Gravity

A scale--dependent effective action for gravity is introduced and an exact nonperturbative evolution equation is derived which governs its renormalization group flow. It is invariant under general coordinate transformations and satisfies modified BRS Ward--Identities. The evolution equation is solved for a simple truncation of the space of actions. In 2+epsilon dimensions, nonperturbative corrections to the beta--function of Newton's constant are derived and its dependence on the cosmological constant is investigated. In 4 dimensions, Einstein gravity is found to be ``antiscreening'', i.e., Newton's constant increases at large distances.Comment: 35 pages, late

Oncogenic role of miR-155 in anaplastic large cell lymphoma lacking the t(2;5) translocation.

Anaplastic large cell lymphoma (ALCL) is a rare, aggressive, non-Hodgkin's lymphoma that is characterized by CD30 expression and disease onset in young patients. About half of ALCL patients bear the t(2;5)(p23;q35) translocation, which results in the formation of the nucleophosmin-anaplastic lymphoma tyrosine kinase (NPM-ALK) fusion protein (ALCL ALK(+)). However, little is known about the molecular features and tumour drivers in ALK-negative ALCL (ALCL ALK(-)), which is characterized by a worse prognosis. We found that ALCL ALK(-), in contrast to ALCL ALK(+), lymphomas display high miR-155 expression. Consistent with this, we observed an inverse correlation between miR-155 promoter methylation and miR-155 expression in ALCL. However, no direct effect of the ALK kinase on miR-155 levels was observed. Ago2 immunoprecipitation revealed miR-155 as the most abundant miRNA, and enrichment of target mRNAs C/EBPβ and SOCS1. To investigate its function, we over-expressed miR-155 in ALCL ALK(+) cell lines and demonstrated reduced levels of C/EBPβ and SOCS1. In murine engraftment models of ALCL ALK(-), we showed that anti-miR-155 mimics are able to reduce tumour growth. This goes hand-in-hand with increased levels of cleaved caspase-3 and high SOCS1 in these tumours, which leads to suppression of STAT3 signalling. Moreover, miR-155 induces IL-22 expression and suppresses the C/EBPβ target IL-8. These data suggest that miR-155 can act as a tumour driver in ALCL ALK(-) and blocking miR-155 could be therapeutically relevant. Original miRNA array data are to be found in the supplementary material (Table S1).This work was supported by the SCRI-LIMCR GmbH, the “Jubiläumsfond der Österreichischen Nationalbank” (grant-no. 14856 to O.M.), R.G. was supported by grant SFB P021 from the Austrian Science Funds (FWF), L.K. was supported by grant FWF, P26011, R.M. was supported by FWF grants SFB F28 and SFB F47. S.D.T. is a Senior Lecturer supported with funding from Leukemia and Lymphoma Research.This is the final version of the article. It first appeared from Wiley via http://dx.doi.org/10.1002/path.453

Zweidimensionale Architekturen organischer Adsorbate: Untersuchung mittels STM, LEED, TDS und Kraftfeldsimulationen

Die vorliegende Arbeit beschreibt die experimentelle Untersuchung organischer Adsorbate mit Hilfe der Raster-Tunnel-Mikroskopie im Ultrahochvakuum (UHV) und an ambienten Bedingungen. Im Zentrum dieser Arbeit stehen Untersuchun-gen an selbstassemblierten Monolagen von Trimesinsäure. Eine vorgeschlagene Gast-Wirt-Struktur aus Trimesinsäure wurde erzeugt und mit submolekularer Auf-lösung abgebildet. Ferner ist es gelungen gezielt Gäste in die Wirtstruktur einzu-lagern und zu manipulieren. Als Gäste konnten, neben Trimesinsäure selbst, Coronen, Fullerene und Gold-Cluster gezeigt werden

Bimolecular porous supramolecular networks deposited from solution on layered materials: graphite, boron nitride and molybdenum disulphide

A two-dimensional porous network formed from perylene tetracarboxylic diimide (PTCDI) and melamine may be deposited from solution on the surfaces of highly oriented pyrolytic graphite (HOPG), hexagonal boron nitride (hBN) and molybdenum disulphide (MoS2). Images acquired using high resolution atomic force microscopy (AFM) operating under ambient conditions have revealed that the network forms extended orderedmonolayers (41 lm2) on HOPG and hBN whereas on MoS2 much smaller islands are observed