Multi-instanton and string loop corrections in toroidal orbifold models

We analyze N=2 (perturbative and non-perturbative) corrections to the effective theory in type I orbifold models where a dual heterotic description is available. These corrections may play an important role in phenomenological scenarios. More precisely, we consider two particular compactifications: the Bianchi-Sagnotti-Gimon-Polchinski orbifold and a freely-acting Z_2 x Z_2 orbifold with N=1 supersymmetry and gauge group SO(q) x SO(32-q). By exploiting perturbative calculations of the physical gauge couplings on the heterotic side, we obtain multi-instanton and one-loop string corrections to the K\"ahler potential and the gauge kinetic function for these models. The non-perturbative corrections appear as sums over relevant Hecke operators, whereas the one-loop correction to the K\"ahler potential matches the expression proposed in [1,2]. We argue that these corrections are universal in a given class of models where target-space modular invariance (or a subgroup of it) holds.Comment: 37 pages, 3 figure

Flux-induced Soft Terms on Type IIB/F-theory Matter Curves and Hypercharge Dependent Scalar Masses

Closed string fluxes induce generically SUSY-breaking soft terms on supersymmetric type IIB orientifold compactifications with D3/D7 branes. This was studied in the past by inserting those fluxes on the DBI+CS actions for adjoint D3/D7 fields, where D7-branes had no magnetic fluxes. In the present work we generalise those computations to the phenomenologically more relevant case of chiral bi-fundamental fields laying at 7-brane intersections and F-theory local matter curves. We also include the effect of 7-brane magnetic flux as well as more general closed string backgrounds, including the effect of distant (anti-)D3-branes. We discuss several applications of our results. We find that squark/slepton masses become in general flux-dependent in F-theory GUT's. Hypercharge-dependent non-universal scalar masses with a characteristic sfermion hierarchy m_E^2 < m_L^2 < m_Q^2 < m_D^2 < m_U^2 are obtained. There are also flavor-violating soft terms both for matter fields living at intersecting 7-branes or on D3-branes at singularities. They point at a very heavy sfermion spectrum to avoid FCNC constraints. We also discuss the possible microscopic description of the fine-tuning of the EW Higgs boson in compactifications with a MSSM spectrum.Comment: 67 pages, 2 figures, 2 table

Virtual reality: applications in medicine and psychiatry.

Virtual reality (VR) is a coined description of a new computer-based technology that allows the user to enter a 3-D artificial world. Inside this world, the user can look around, move around and interact within computer worlds. The user can fly, visit exotic lands, play with molecules, "enter" cardiac chambers and watch blood swirl or do simulated surgery. The possibilities are staggering and it is important that physicians become literate in this visual experience. In this article I will introduce the technology in the field, discuss some medical applications already in use, and speculate on some potential uses in my field of interest: psychiatry

Deck-tower interaction in the transverse seismic response of cable-stayed bridges and optimum con figurations

Modern design solutions in cable-stayed bridges give a significant importance to the seismic response in the transverse direction. This work is focused on the dynamic interaction between the deck and the towers, exploring the key role of different vibration modes. An extensive parametric analysis is proposed to address the influence of the main span length, the tower geometry, the cable-system arrangement, the width and height of the deck and the soil conditions. It is demonstrated that the vibration modes that govern the seismic response of cable-stayed bridges in the transverse direction involve the interaction between the tower and the deck, but the order of these modes and the parts of the deck that are affected change with the main span length. It is also observed that the interaction between the deck and the towers during the earthquake is maximised if their isolated vibration frequencies are close to each other, leading to a significantly large seismic demand. Analytical expressions are proposed to obtain the critical frequencies of the towers for which these interactions arise, and recommendations are given to define the tower geometry in order to avoid such problematic scenarios

Effect of spatial variability of earthquakes on cable-stayed bridges

This paper focuses on the effect of spatially variable ground motions on the towers of cable-stayed bridges with 200, 400 and 600m main spans. Seismic analysis of the bridges is performed, taking account of different sources of the spatial variability, namely; incoherence and wave passage effects. To address these effects, the response of the towers is assessed under the effect of different propagation velocities of the seismic waves and different assumptions on the coherency of the ground motion, to conclude that the effect of spatially variable motions on the seismic response of cable-stayed bridges is dependent on the assumed wave propagation velocity and rate of coherency

Advanced onboard storage concepts for natural gas-fueled automotive vehicles

The evaluation of several advanced concepts for storing natural gas at reduced pressure is presented. The advanced concepts include adsorption on high surface area carbon, adsorption in high porosity zeolite, storage in clathration compounds, and storage by dissolution in liquid solvents. High surface area carbons with high packing density are the best low pressure storage mediums. A simple mathematical model is used to compare adsorption storage on a state of the art carbon with compression storage. The model indicates that a vehicle using adsorption storage of natural gas at 3.6 MPa will have 36 percent of the range, on the EPA city cycle, of a vehicle operating on a compression storage system having the same physical size and a peak storage pressure of 21 MPa. Preliminary experiments and current literature suggest that the storage capacity of state of the art carbons could be improved by as much as 50 percent, and that adsorption systems having a capacity equal to compression storage at 14 MPa are possible without exceeding a maximum pressure of 3.6 MPa

Damage to Mitochondrial Complex I During Cardiac Ischemia Reperfusion Injury is Reduced Indirectly by Anti-anginal Drug Ranolazine

Ranolazine, an anti-anginal drug, is a late Na+ channel current blocker that is also believed to attenuate fatty acid oxidation and mitochondrial respiratory complex I activity, especially during ischemia. In this study, we investigated if ranolazine\u27s protective effect against cardiac ischemia/reperfusion (IR) injury is mediated at the mitochondrial level and specifically if respiratory complex I (NADH Ubiquinone oxidoreductase) function is protected. We treated isolated and perfused guinea pig hearts with ranolazine just before 30 min ischemia and then isolated cardiac mitochondria at the end of 30 min ischemia and/or 30 min ischemia followed by 10 min reperfusion. We utilized spectrophotometric and histochemical techniques to assay complex I activity, Western blot analysis for complex I subunit NDUFA9, electron paramagnetic resonance for activity of complex I Fe–S clusters, enzyme linked immuno sorbent assay (ELISA) for determination of protein acetylation, native gel histochemical staining for respiratory supercomplex assemblies, and high pressure liquid chromatography for cardiolipin integrity; cardiac function was measured during IR. Ranolazine treated hearts showed higher complex I activity and greater detectable complex I protein levels compared to untreated IR hearts. Ranolazine treatment also led to more normalized electron transfer via Fe–S centers, supercomplex assembly and cardiolipin integrity. These improvements in complex I structure and function with ranolazine were associated with improved cardiac function after IR. However, these protective effects of ranolazine are not mediated by a direct action on mitochondria, but rather indirectly via cytosolic mechanisms that lead to less oxidation and better structural integrity of complex I