6,279 research outputs found
Effective Action of Matter Fields in Four-Dimensional String Orientifolds
We study various aspects of the Kahler metric for matter fields in N=1,2
orientifold compactifications of type IIB string theory. The result has an
infrared-divergent part which reproduces the field- theoretical anomalous
dimensions, and a moduli-dependent part which comes from N=2 sectors of the
orientifold. For the N=2 orientifolds, we also compute the disk amplitude for
two matter fields on the boundary and a twisted closed string modulus in the
bulk. Our results are in agreement with supersymmetry: the singlet under the
SU(2)_R R-symmetry has vanishing coupling, while the coupling of the SU(2)_R
triplet does not vanish.Comment: 24 pages, JHEP LaTex, no figures, v2: references added, typos
correcte
Curvature terms in D-brane actions and their M-theory origin
We derive the complete terms of effective D-brane actions,
for arbitrary ambient geometries and world-volume embeddings, at lowest order
(disk-level) in the string-loop expansion. These terms reproduce the
corrections to string scattering amplitudes, and are consistent
with duality conjectures. In the particular case of the D3-brane with trivial
normal bundle, considerations of invariance lead to a
complete sum of D-instanton corrections for both the parity-conserving and the
parity-violating parts of the effective action. These corrections are required
for the cancellation of the modular anomalies of massless modes, and are
consistent with the absence of chiral anomalies in the intersection domain of
pairs of D-branes. We also show that the parity-conserving part of the
non-perturbative R^2 action follows from a one-loop quantum calculation in the
six-dimensional world-volume of the M5-brane compactified on a two-torus.Comment: tex file, 31 pages, uses harvmac. Some rewriting of section 2,
conclusions and appendix B, in particular in what concerns the discussion of
seven-branes in the conclusions and the structure of terms in
appendix B. Other minor corrections plus added reference
Clinical and biochemical improvements in a patient with MNGIE following enzyme replacement.
Mitochondrial neurogastrointestinal encephalomyopathy (MNGIE) is a rare autosomal recessive metabolic disorder caused by a deficiency of thymidine phosphorylase (TP, EC2.4.2.4) due to mutations in the nuclear gene TYMP. TP deficiency leads to plasma and tissue accumulations of thymidine and deoxyuridine which generate imbalances within the mitochondrial nucleotide pools, ultimately leading to mitochondrial dysfunction.1 MNGIE is characterized clinically by leukoencephalopathy, external ophthalmoplegia, peripheral polyneuropathy, cachexia, and enteric neuromyopathy manifesting as gastrointestinal dysmotility. The condition is relentlessly progressive, with patients usually dying from a combination of nutritional and neuromuscular failure at an average age of 37 years.2 Allogeneic hematopoietic stem cell transplantation (AHSCT) offers a permanent cure. Clinical and biochemical improvements following AHSCT have been reported but it carries a high mortality risk and is limited by matched donor availability.3 A consensus proposal for standardizing AHSCT recommends treatment of patients without irreversible end-stage disease and with an optimally matched donor; a majority of patients are ineligible and thus there is a critical requirement for an alternative treatment
Macrophage Migration Is Impaired within Candida albicans Biofilms
Acknowledgments: We thank the Microscopy and Histology Core Facility at the University of Aberdeen. This work was funded by NHS Grampian Endowments (grant RG10191); the Wellcome Trust Strategic Award in Medical Mycology and Fungal Immunology (grant 097377); the Wellcome Trust Investigator award (grants 101873, 086827, 075470, & 200208) and the Medical Research Council Centre for Medical Mycology (grant MR/N006364/1).Peer reviewedPublisher PD
Hyphal growth of phagocytosed fusarium oxysporum causes cell lysis and death of murine macrophages
Peer reviewedPublisher PD
On the predictions and limitations of the BeckerDoring model for reaction kinetics in micellar surfactant solutions
We investigate the breakdown of a system of micellar aggregates in a surfactant solution following an order-one dilution. We derive a mathematical model based on the BeckerâDöring system of equations, using realistic expressions for the reaction constants fit to Molecular Dynamics simulations. We exploit the largeness of typical aggregation numbers to derive a continuum model, substituting a large system of ordinary differential equations for a partial differential equation in two independent variables: time and aggregate size. Numerical solutions demonstrate that re-equilibration occurs in two distinct stages over well-separated time-scales, in agreement with experiment and with previous theories. We conclude by exposing a limitation in the BeckerâDöring theory for re-equilibration and discuss potential resolutions
An asymptotic theory for the re-equilibration of a micellar surfactant solution
Micellar surfactant solutions are characterized by a distribution of aggregates comprised predominantly of pre-micellar aggregates (monomers, dimers, trimers, etc.) and a region of proper micelles close to the peak aggregation number, connected by an intermediate region containing a very low concentration of aggregates. Such a distribution gives rise to a distinct two-timescale re-equilibration following a system dilution, known as the 1 and 2 processes, whose dynamics may be described by the BeckerâDöring equations. We use a continuum version of these equations to develop a reduced asymptotic description that elucidates the behavior during each of these processes
The Occurrence of Autoimmune Diseases in Patients with Multiple Sclerosis and Their Families
The aims of this study were to determine whether the occurrence of autoimmune diseases is increased in patients with multiple sclerosis (MS) and their families and whether this is influenced by the type of MS. We conducted a case-control study using a questionnaire design to determine whether the prevalence of 11 autoimmune diseases is increased in patients with MS and their first-degree relatives compared to a random population control group and their first-degree relatives. We found that the total combined prevalence of the 11autoimmune diseases was higher in the MS patients than in the controls, with an odds ratio of 1.7 (95% confidence interval 0.9-3.2; P= 0.10) increasing to 1.9 (1.0-3.5; P= 0.05) after adjusting for age. For persons aged under 60 years, the odds ratio was 2.3 (1.1-4.6). We also found that there was a significant increase in the total combined prevalence of the autoimmune diseases in the first-degree relatives of MS patients compared to the first-degree relatives of the control group (P= 0.003, odds ratio 2.2, confidence interval 1.3-3.7). Patients with primary progressive MS did not differ from patients with relapsing-remitting or secondary progressive MS in the personal or familial occurrence of autoimmune disease. In conclusion, although there were sources of possible bias, this study suggests that individuals with MS have a genetic predisposition to autoimmunity in general
String Loop Corrections to Kahler Potentials in Orientifolds
We determine one-loop string corrections to Kahler potentials in type IIB
orientifold compactifications with either N=1 or N=2 supersymmetry, including
D-brane moduli, by evaluating string scattering amplitudes.Comment: 80 pages, 4 figure
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