Effective Actions near Singularities

We study the heterotic string compactified on K3 x T^2 near the line T=U, where the effective action becomes singular due to an SU(2) gauge symmetry enhancement. By `integrating in' the light W^\pm vector multiplets we derive a quantum corrected effective action which is manifestly SU(2) invariant and non-singular. This effective action is found to be consistent with a residual SL(2,Z) quantum symmetry on the line T=U. In an appropriate decompactification limit, we recover the known SU(2) invariant action in five dimensions.Comment: 33 pages, LaTeX. v2: cosmetic correction on titlepage. v3: references and note adde

Global Sensitivity Analysis of Parameter Uncertainty in Landscape Evolution Models

The evaluation and verification of landscape evolution models (LEMs) has long been limited by a lack of suitable observational data and statistical measures which can fully capture the complexity of landscape changes. This lack of data limits the use of objective function based evaluation prolific in other modelling fields, and restricts the application of sensitivity analyses in the models and the consequent assessment of model uncertainties. To overcome this deficiency, a novel model function approach has been developed, with each model function representing an aspect of model behaviour, which allows for the application of sensitivity analyses. The model function approach is used to assess the relative sensitivity of the CAESAR-Lisflood LEM to a set of model parameters by applying the Morris method sensitivity analysis for two contrasting catchments. The test revealed that the model was most sensitive to the choice of the sediment transport formula for both catchments, and that each parameter influenced model behaviours differently, with model functions relating to internal geomorphic changes responding in a different way to those relating to the sediment yields from the catchment outlet. The model functions proved useful for providing a way of evaluating the sensitivity of LEMs in the absence of data and methods for an objective function approach.</p

Discovery of magnetic fields in central stars of planetary nebulae

For the first time we have directly detected magnetic fields in central stars of planetary nebulae by means of spectro-polarimetry with FORS1 at the VLT. In all four objects of our sample we found kilogauss magnetic fields, in NGC1360 and LSS1362 with very high significance, while in EGB5 and Abell36 the existence of a magnetic field is probable but with less certainty. This discovery supports the hypothesis that the non-spherical symmetry of most planetary nebulae is caused by magnetic fields in AGB stars. Our high discovery rate demands mechanisms to prevent full conservation of magnetic flux during the transition to white dwarfs.Comment: 8 pages, 4 figures, Accepted for Publication by Astronomy & Astrophysics See also press release by A&A on their homepage www.edpsiences.or

A modulator-free quantum key distribution transmitter chip

Quantum key distribution (QKD) has convincingly been proven compatible with real life applications. Its wide-scale deployment in optical networks will benefit from an optical platform that allows miniature devices capable of encoding the necessarily complex signals at high rates and with low power consumption. While photonic integration is the ideal route toward miniaturisation, an efficient route to high-speed encoding of the quantum phase states on chip is still missing. Consequently, current devices rely on bulky and high power demanding phase modulation elements which hinder the sought-after scalability and energy efficiency. Here we exploit a novel approach to high-speed phase encoding and demonstrate a compact, scalable and power efficient integrated quantum transmitter. We encode cryptographic keys on-demand in high repetition rate pulse streams using injection-locking with deterministic phase control at the seed laser. We demonstrate record secure-key-rates under multi-protocol operation. Our modulator-free transmitters enable the development of high-bit rate quantum communications devices, which will be essential for the practical integration of quantum key distribution in high connectivity networks

Fuel Cell Testing Protocols: An International Perspective

An overview of international polymer-electrolyte fuel cell (PEMFC) test procedures is presented. This overview is the first step in the global harmonization of testing methods. Many techniques and procedures determining stack performance and durability are discussed. Each approach has differences that may or may not impact the data and data quality. Through experiments, it was found that differences in the results from two methods for measuring sequential polarization curves are minimal. Answers to questions regarding differences in the aging duty cycles need to be determined experimentally. The results of these experiments are expected to help the harmonization process, to facilitate the understanding of test results, and, possibly, to accelerate the commercialization of PEMFCs.JRC.F.2-Cleaner energ

Construction of an adult barnacle (Balanus amphitrite) cDNA library and selection of reference genes for quantitative RT-PCR studies

De Gregoris TB, Borra M, Biffali E, et al. Construction of an adult barnacle (Balanus amphitrite) cDNA library and selection of reference genes for quantitative RT-PCR studies. BMC Molecular Biology. 2009;10(1):62.BACKGROUND: Balanus amphitrite is a barnacle commonly used in biofouling research. Although many aspects of its biology have been elucidated, the lack of genetic information is impeding a molecular understanding of its life cycle. As part of a wider multidisciplinary approach to reveal the biogenic cues influencing barnacle settlement and metamorphosis, we have sequenced and annotated the first cDNA library for B. amphitrite. We also present a systematic validation of potential reference genes for normalization of quantitative real-time PCR (qRT-PCR) data obtained from different developmental stages of this animal. RESULTS: We generated a cDNA library containing expressed sequence tags (ESTs) from adult B. amphitrite. A total of 609 unique sequences (comprising 79 assembled clusters and 530 singlets) were derived from 905 reliable unidirectionally sequenced ESTs. Bioinformatics tools such as BLAST, HMMer and InterPro were employed to allow functional annotation of the ESTs. Based on these analyses, we selected 11 genes to study their ability to normalize qRT-PCR data. Total RNA extracted from 7 developmental stages was reverse transcribed and the expression stability of the selected genes was compared using geNorm, BestKeeper and NormFinder. These software programs produced highly comparable results, with the most stable gene being mt-cyb, while tuba, tubb and cp1 were clearly unsuitable for data normalization. CONCLUSION: The collection of B. amphitrite ESTs and their annotation has been made publically available representing an important resource for both basic and applied research on this species. We developed a qRT-PCR assay to determine the most reliable reference genes. Transcripts encoding cytochrome b and NADH dehydrogenase subunit 1 were expressed most stably, although other genes also performed well and could prove useful to normalize gene expression studies

Human Engineered Heart Tissue as a Versatile Tool in Basic Research and Preclinical Toxicology

Human embryonic stem cell (hESC) progenies hold great promise as surrogates for human primary cells, particularly if the latter are not available as in the case of cardiomyocytes. However, high content experimental platforms are lacking that allow the function of hESC-derived cardiomyocytes to be studied under relatively physiological and standardized conditions. Here we describe a simple and robust protocol for the generation of fibrin-based human engineered heart tissue (hEHT) in a 24-well format using an unselected population of differentiated human embryonic stem cells containing 30–40% α-actinin-positive cardiac myocytes. Human EHTs started to show coherent contractions 5–10 days after casting, reached regular (mean 0.5 Hz) and strong (mean 100 µN) contractions for up to 8 weeks. They displayed a dense network of longitudinally oriented, interconnected and cross-striated cardiomyocytes. Spontaneous hEHT contractions were analyzed by automated video-optical recording and showed chronotropic responses to calcium and the β-adrenergic agonist isoprenaline. The proarrhythmic compounds E-4031, quinidine, procainamide, cisapride, and sertindole exerted robust, concentration-dependent and reversible decreases in relaxation velocity and irregular beating at concentrations that recapitulate findings in hERG channel assays. In conclusion this study establishes hEHT as a simple in vitro model for heart research

Summary report of MINSIS workshop in Madrid

Recent developments on tau detection technologies and the construction of high intensity neutrino beams open the possibility of a high precision search for non-standard {\mu} - {\tau} flavour transition with neutrinos at short distances. The MINSIS - Main Injector Non-Standard Interaction Search- is a proposal under discussion to realize such precision measurement. This document contains the proceedings of the workshop which took place on 10-11 December 2009 in Madrid to discuss both the physics reach as well as the experimental requirements for this proposal.Comment: Proceedings of the MINSIS Workshop, Dec 10-11, 2009 in Madrid. 15 pages late

Low-Mass Binary Induced Outflows from Asymptotic Giant Branch Stars

A significant fraction of planetary nebulae (PNe) and proto-planetary nebulae (PPNe) exhibit aspherical, axisymmetric structures, many of which are highly collimated. The origin of these structures is not entirely understood, however recent evidence suggests that many observed PNe harbor binary systems, which may play a role in their shaping. In an effort to understand how binaries may produce such asymmetries, we study the effect of low-mass (< 0.3 M_sun) companions (planets, brown dwarfs and low-mass main sequence stars) embedded into the envelope of a 3.0 M_sun star during three epochs of its evolution (Red Giant Branch, Asymptotic Giant Branch (AGB), interpulse AGB). We find that common envelope evolution can lead to three qualitatively different consequences: (i) direct ejection of envelope material resulting in a predominately equatorial outflow, (ii) spin-up of the envelope resulting in the possibility of powering an explosive dynamo driven jet and (iii) tidal shredding of the companion into a disc which facilitates a disc driven jet. We study how these features depend on the secondary's mass and discuss observational consequences.Comment: 24 pages, 6 figures, submitted to MNRA