N-flation from multiple DBI type actions

In this letter we present a new N-flation model constructed by making use of multiple scalar fields which are being described by their own DBI action. We show that the dependence of the e-folding number and of the curvature perturbation on the number of fields changes compared with the normal N-flation model. Our model is also quite different from the usual DBI N-flation which is still based on one DBI action but involves many moduli components. Some specific examples of our model have been analyzed.Comment: 4 pages, 1 figur

Functionally selective activation of the dopamine receptor D2 is mirrored by the protein expression profiles

The development of functionally selective or biased ligands is a promising approach towards drugs with less side effects. Biased ligands for G protein-coupled receptors can selectively induce G protein activation or β-arrestin recruitment. The consequences of this selective action on cellular functions, however, are not fully understood. Here, we investigated the impact of five biased and balanced dopamine D2 receptor agonists and antagonists on the global protein expression in HEK293T cells by untargeted nanoscale liquid chromatography–tandem mass spectrometry. The proteome analysis detected 5290 protein groups. Hierarchical clustering and principal component analysis based on the expression levels of 1462 differential proteins led to a separation of antagonists and balanced agonist from the control treatment, while the biased ligands demonstrated larger similarities to the control. Functional analysis of affected proteins revealed that the antagonists haloperidol and sulpiride regulated exocytosis and peroxisome function. The balanced agonist quinpirole, but not the functionally selective agonists induced a downregulation of proteins involved in synaptic signaling. The β-arrestin-preferring agonist BM138, however, regulated several proteins related to neuron function and the dopamine receptor-mediated signaling pathway itself. The G protein-selective partial agonist MS308 influenced rather broad functional terms such as DNA processing and mitochondrial translation

Deformations of calibrated D-branes in flux generalized complex manifolds

We study massless deformations of generalized calibrated cycles, which describe, in the language of generalized complex geometry, supersymmetric D-branes in N=1 supersymmetric compactifications with fluxes. We find that the deformations are classified by the first cohomology group of a Lie algebroid canonically associated to the generalized calibrated cycle, seen as a generalized complex submanifold with respect to the integrable generalized complex structure of the bulk. We provide examples in the SU(3) structure case and in a `genuine' generalized complex structure case. We discuss cases of lifting of massless modes due to world-volume fluxes, background fluxes and a generalized complex structure that changes type.Comment: 52 pages, added references, added comment on ellipticity in appendix B, made minor changes according to instructions referee JHE

GUTs in Type IIB Orientifold Compactifications

We systematically analyse globally consistent SU(5) GUT models on intersecting D7-branes in genuine Calabi-Yau orientifolds with O3- and O7-planes. Beyond the well-known tadpole and K-theory cancellation conditions there exist a number of additional subtle but quite restrictive constraints. For the realisation of SU(5) GUTs with gauge symmetry breaking via U(1)_Y flux we present two classes of suitable Calabi-Yau manifolds defined via del Pezzo transitions of the elliptically fibred hypersurface P_{1,1,1,6,9}[18] and of the Quintic P_{1,1,1,1,1}[5], respectively. To define an orientifold projection we classify all involutions on del Pezzo surfaces. We work out the model building prospects of these geometries and present five globally consistent string GUT models in detail, including a 3-generation SU(5) model with no exotics whatsoever. We also realise other phenomenological features such as the 10 10 5 Yukawa coupling and comment on the possibility of moduli stabilisation, where we find an entire new set of so-called swiss-cheese type Calabi-Yau manifolds. It is expected that both the general constrained structure and the concrete models lift to F-theory vacua on compact Calabi-Yau fourfolds.Comment: 138 pages, 9 figures; v2, v3: typos corrected, one reference adde

Progress in D-brane model building

The state of the art in D-brane model building is briefly reviewed, focusing on recent achievements in the construction of D=4 N = 1 type II string vacua with semi-realistic gauge sectors. Such progress relies on a better understanding of the spectrum of BPS D-branes, the effective field theory obtained from them and the explicit construction of vacua. We first consider D-branes in standard Calabi-Yau compactifications, and then the more involved case of compactifications with fluxes. We discuss how the non-trivial interplay between D-branes and fluxes modifies the previous model-building rules, as well as provides new possibilities to connect string theory to particle physics.Comment: Using w-art.cls, 27 pages, 6 figures. Based on a talk given at the RTN `Constituents, Fundamental Forces and Symmetries of the Universe' Workshop and Midterm meeting in Napoli, October 2006. v2: typos corrected and references adde

Automatischer Entwurf von Spannvorrichtungen auf Basis einer formellen Wissensrepräsentation, Konstruktionssynthese und –verifikation

Automating the design and configuration processes of fixture devices can increase the flexibility and degree of automation of manufacturing systems. This thesis presents an automatic fixture design system integrated with a reconfigurable fixture device that addresses shortcomings of existing solutions. The system is based on a formal ontology for knowledge representation and semantic reasoning, a spatial grammar for the synthesis of new fixture candidates, a tool-fixture interference analysis for design verification and a deformation analysis for design evaluation. Implementations for all methods are developed and their ability to automate the design and drive the reconfiguration of a flexible fixture is evaluated by processing a set of case-study parts.Die Flexibilität und der Automationsgrad von Fertigungssystemen kann durch die Automatisierung des Entwurfes und der Konstruktion von Spannvorrichtungen gesteigert werden. Ein Ansatz der die Defizite existierender Lösungen adressiert, bestehend aus einem System für den Entwurf und die Anpassung einer flexiblen Spannvorrichtung, wird präsentiert. Das System basiert auf einer formellen Ontologie für die Wissensrepräsentation und Ableitung logischer Schlussfolgerungen, einer räumlichen Grammatik für die Synthese neuer Kandidaten sowie einer Interferenz- und Deformationsanalyse zur Verifikation und Evaluation von Entwürfen. Softwareumsetzungen für alle Methoden werden zur Evaluation des Systems auf eine Reihe von Beispielwerkstücken angewandt

A Spatial Grammar for the Computational Design Synthesis of Vise Jaws

For the machining and assembly of mechanical parts, their secure fixation in a defined position is crucial. To achieve this task, flexible fixture devices (FFDs) are the industry standard for small and medium batch-sizes. Unlike dedicated fixtures, FFDs allow for the fixation of different part shapes, increasing their applicability and economic efficiency. Aiming to create a low-cost and autonomous FFD, a reconfigurable vise with adaptable jaws was developed. The jaws can be machined to a variety of shapes to securely hold prismatic and cylindrical parts. In this paper, a spatial grammar approach for the computational design synthesis of these customizable jaws is presented. Different sets of rules for the generation of 3D solid models of vise jaws based on the model of the workpiece to be held are developed and realized in a CAD environment. The approach is verified by generating jaw designs for example parts