2,514 research outputs found

    In-situ comparison of the NOy instruments flown

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    Abstract Two aircraft instruments for the measurement of total odd nitrogen (NO y ) were compared side by side aboard a Learjet A35 in April 2003 during a campaign of the AFO2000 project SPURT (Spurengastransport in der Tropopausenregion). The instruments albeit employing the same measurement principle (gold converter and chemilu-5 minescence) had different inlet configurations. The ECO-Physics instrument operated by ETH-Zürich in SPURT had the gold converter mounted outside the aircraft, whereas the instrument operated by FZ-Jülich in the European project MOZAIC III (Measurements of ozone, water vapour, carbon monoxide and nitrogen oxides aboard Airbus A340 in-service aircraft) employed a Rosemount probe with 80 cm of FEP-tubing con-10 necting the inlet to the gold converter. The NO y concentrations during the flight ranged between 0.3 and 3 ppb. The two data sets were compared in a blind fashion and each team followed its normal operating procedures. On average, the measurements agreed within 6%, i.e. within the combined uncertainty of the two instruments. This puts an upper limit on potential losses of HNO 3 in the Rosemount inlet of the MOZAIC instrument. 15 Larger transient deviations were observed during periods after calibrations and when the aircraft entered the stratosphere. The time lag of the MOZAIC instrument observed in these instances is in accordance with the time constant of the MOZAIC inlet line determined in the laboratory for HNO 3

    The spectrum of BPS branes on a noncompact Calabi-Yau

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    We begin the study of the spectrum of BPS branes and its variation on lines of marginal stability on O_P^2(-3), a Calabi-Yau ALE space asymptotic to C^3/Z_3. We show how to get the complete spectrum near the large volume limit and near the orbifold point, and find a striking similarity between the descriptions of holomorphic bundles and BPS branes in these two limits. We use these results to develop a general picture of the spectrum. We also suggest a generalization of some of the ideas to the quintic Calabi-Yau.Comment: harvmac, 45 pp. (v2: added references

    Non-Perturbative Corrections and Modularity in N=1 Type IIB Compactifications

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    Non-perturbative corrections and modular properties of four-dimensional type IIB Calabi-Yau orientifolds are discussed. It is shown that certain non-perturbative alpha' corrections survive in the large volume limit of the orientifold and periodically correct the Kahler potential. These corrections depend on the NS-NS two form and have to be completed by D-instanton contributions to transform covariantely under symmetries of the type IIB orientifold background. It is shown that generically also the D-instanton superpotential depends on the two-form moduli as well as on the complex dilaton. These contributions can arise through theta-functions with the dilaton as modular parameter. An orientifold of the Enriques Calabi-Yau allows to illustrate these general considerations. It is shown that this compactification leads to a controlled four-dimensional N=1 effective theory due to the absence of various quantum corrections. Making contact to the underlying topological string theory the D-instanton superpotential is proposed to be related to a specific modular form counting D3, D1, D(-1) degeneracies on the Enriques Calabi-Yau.Comment: 35 page

    The effective action of N=1 Calabi-Yau orientifolds

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    We determine the N=1 low energy effective action for compactifications of type IIB string theory on compact Calabi-Yau orientifolds in the presence of background fluxes from a Kaluza-Klein reduction. The analysis is performed for Calabi-Yau threefolds which admit an isometric and holomorphic involution. We explicitly compute the Kahler potential, the superpotential and the gauge kinetic functions and check the consistency with N=1 supergravity. We find a new class of no-scale Kahler potentials and show that their structure can be best understood in terms of a dual formulation where some of the chiral multiplets are replaced by linear multiplets. For O3- and O7-planes the scalar potential is expressed in terms of a superpotential while for O5- and O9-planes also a D-term and a massive linear multiplet can be present. The relation with the associated F-theory compactifications is briefly discussed.Comment: 40 pages, typos corrected, discussion of no-scale property improve

    The effective action of Type IIA Calabi-Yau orientifolds

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    The N=1 effective action for generic type IIA Calabi-Yau orientifolds in the presence of background fluxes is computed from a Kaluza-Klein reduction. The Kahler potential, the gauge kinetic functions and the flux-induced superpotential are determined in terms of geometrical data of the Calabi-Yau orientifold and the background fluxes. The moduli space is found to be a Kahler subspace of the N=2 moduli space and shown to coincide with the moduli space arising in compactification of M-theory on a specific class of G_2 manifolds. The superpotential depends on all geometrical moduli and vanishes at leading order when background fluxes are turned off. The N=1 chiral coordinates linearize the appropriate instanton actions such that instanton effects can lead to holomorphic corrections of the superpotential. Mirror symmetry between type IIA and type IIB orientifolds is shown to hold at the level of the effective action in the large volume - large complex structure limit.Comment: 51 pages, typos correcte

    Soft Supersymmetry Breaking in Calabi-Yau Orientifolds with D-branes and Fluxes

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    In this paper we compute the N=1 effective low energy action for a stack of N space-time filling D3-branes in generic type IIB Calabi-Yau orientifolds with non-trivial background fluxes by reducing the Dirac-Born-Infeld and Chern-Simons actions. Specifically, we determine the Kahler potential for the excitations of the D-brane including their couplings to all bulk moduli fields. In the effective theory, N=1 supergravity is spontaneously broken by the presence of fluxes and we compute the induced soft supersymmetry breaking terms. We find an interesting structure in the resulting soft terms with generically universal soft scalar masses.Comment: LaTeX, 41 pages, minor corrections and references adde

    Primary resection versus neoadjuvant chemoradiation followed by resection for locally resectable or potentially resectable pancreatic carcinoma without distant metastasis. A multi-centre prospectively randomised phase II-study of the Interdisciplinary Working Group Gastrointestinal Tumours (AIO, ARO, and CAO)

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    BACKGROUND: The disappointing results of surgical therapy alone of ductal pancreatic cancer can only be improved using multimodal approaches. In contrast to adjuvant therapy, neoadjuvant chemoradiation is able to facilitate resectability with free margins and to lower lymphatic spread. Another advantage is better tolerability which consecutively allows applying multimodal treatment in a higher number of patients. Furthermore, the synopsis of the overall survival results of neoadjuvant trials suggests a higher rate compared to adjuvant trials. METHODS/DESIGN: As there are no prospectively randomised studies for neoadjuvant therapy, the Interdisciplinary Study Group of Gastrointestinal Tumours of the German Cancer Aid has started such a trial. The study investigates the effect of neoadjuvant chemoradiation in locally resectable or probably resectable cancer of the pancreatic head without distant metastasis on median overall survival time compared to primary surgery. Adjuvant chemotherapy is integrated into both arms. DISCUSSION: The protocol of the study is presented in condensed form after an introducing survey on adjuvant and neoadjuvant therapy in pancreatic cancer

    Generalized N=1 Orientifold Compactifications and the Hitchin functionals

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    The four-dimensional N=1 supergravity theories arising in compactifications of type IIA and type IIB on generalized orientifold backgrounds with background fluxes are discussed. The Kahler potentials are derived for reductions on SU(3) structure orientifolds and shown to consist of the logarithm of the two Hitchin functionals. These are functions of even and odd forms parameterizing the geometry of the internal manifold, the B-field and the dilaton. The superpotentials induced by background fluxes and the non-Calabi-Yau geometry are determined by a reduction of the type IIA and type IIB fermionic actions on SU(3) and generalized SU(3) x SU(3) manifolds. Mirror spaces of Calabi-Yau orientifolds with electric and part of the magnetic NS-NS fluxes are conjectured to be certain SU(3) x SU(3) structure manifolds. Evidence for this identification is provided by comparing the generalized type IIA and type IIB superpotentials.Comment: 57 pages, references adde

    Symmetry Breaking Boundary States and Defect Lines

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    We present a large and universal class of new boundary states which break part of the chiral symmetry in the underlying bulk theory. Our formulas are based on coset constructions and they can be regarded as a non-abelian generalization of the ideas that were used by Maldacena, Moore and Seiberg to build new boundary states for SU(N). We apply our expressions to construct defect lines joining two conformal field theories with possibly different central charge. Such defects can occur e.g. in the AdS/CFT correspondence when branes extend to the boundary of the AdS-space.Comment: 36 pages, LaTeX, 1 figure, V1: typos corrected and references added, v2: we added a short remark concerning the geometry of symmetry breaking D-branes in group manifold

    Mapping gene associations in human mitochondria using clinical disease phenotypes

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    Nuclear genes encode most mitochondrial proteins, and their mutations cause diverse and debilitating clinical disorders. To date, 1,200 of these mitochondrial genes have been recorded, while no standardized catalog exists of the associated clinical phenotypes. Such a catalog would be useful to develop methods to analyze human phenotypic data, to determine genotype-phenotype relations among many genes and diseases, and to support the clinical diagnosis of mitochondrial disorders. Here we establish a clinical phenotype catalog of 174 mitochondrial disease genes and study associations of diseases and genes. Phenotypic features such as clinical signs and symptoms were manually annotated from full-text medical articles and classified based on the hierarchical MeSH ontology. This classification of phenotypic features of each gene allowed for the comparison of diseases between different genes. In turn, we were then able to measure the phenotypic associations of disease genes for which we calculated a quantitative value that is based on their shared phenotypic features. The results showed that genes sharing more similar phenotypes have a stronger tendency for functional interactions, proving the usefulness of phenotype similarity values in disease gene network analysis. We then constructed a functional network of mitochondrial genes and discovered a higher connectivity for non-disease than for disease genes, and a tendency of disease genes to interact with each other. Utilizing these differences, we propose 168 candidate genes that resemble the characteristic interaction patterns of mitochondrial disease genes. Through their network associations, the candidates are further prioritized for the study of specific disorders such as optic neuropathies and Parkinson disease. Most mitochondrial disease phenotypes involve several clinical categories including neurologic, metabolic, and gastrointestinal disorders, which might indicate the effects of gene defects within the mitochondrial system. The accompanying knowledgebase (http://www.mitophenome.org/) supports the study of clinical diseases and associated genes
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