2,514 research outputs found
In-situ comparison of the NOy instruments flown
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
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
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
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
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
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)
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
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
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
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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