4,703 research outputs found
Stationary disks and Green functions in almost complex domains
Using generalized Riemann maps, normal forms for almost complex domains (D,
J) with singular foliations by stationary disks are defined. Such normal forms
are used to construct counterexamples and to determine intrinsic conditions,
under which the stationary disks are extremal disks for the Kobayashi metric or
determine solutions to almost complex Monge-Ampere equation.Comment: 25 page
Hyperkähler cones and instantons on quaternionic Kähler manifolds
We present a novel approach to the study of Yang-Mills instantons on quaternionic Kähler manifolds, based on an extension of the harmonic space method of constructing instantons on hyperk\"ahler manifolds. Our results establish a bijection between local equivalence classes of instantons on quaternionic Kähler manifolds M and equivalence classes of certain holomorphic maps on an appropriate SL_2(C)-bundle over the Swann bundle of M
Drug-therapy networks and the predictions of novel drug targets
Recently, a number of drug-therapy, disease, drug, and drug-target networks
have been introduced. Here we suggest novel methods for network-based
prediction of novel drug targets and for improvement of drug efficiency by
analysing the effects of drugs on the robustness of cellular networks.Comment: This is an extended version of the Journal of Biology paper
containing 2 Figures, 1 Table and 44 reference
Numerical simulation of solar coronal magnetic fields
Many aspects of solar activity are believed to be due to the stressing of the coronal magnetic field by footpoint motions at the photosphere. The results are presented of a fully spectral numerical simulation which is the first 3-D time dependent simulation of footpoint stressing in a geometry appropriate for the corona. An arcade is considered that is initially current-free and impose a smooth footpoint motion that produces a twist in the field of approx 2 pi. The footprints were fixed and the evolution was followed until the field relaxes to another current-free state. No evidence was seen for any instability, either ideal or resistive and no evidence for current sheet formation. The most striking feature of the evolution is that in response to photospheric motions, the field expands rapidly upward to minimize the stress. The expansion has two important effects. First, it suppresses the development of dips in the field that could support dense, cool material. For the motions assumed, the magnetic field does not develop a geometry suitable for prominence formation. Second, the expansion inhibits ideal instabilities such as kinking. The results indicate that simple stearing of a single arcade is unlikely to lead to solar activity such as flares or prominences. Effects are discussed that might possibly lead to such activity
Research in progress—LungSEARCH: a randomised controlled trial of surveillance for the early detection of lung cancer in a high-risk group
Abstract
Low-dose CT screening for lung cancer is effective but expensive. Therefore, cheaper or more focused screening strategies may be required. LungSEARCH is a randomised prospective trial of 1568 high-risk individuals (ie, current or former moderate to heavy smokers with mild/moderate COPD) who undergo either annual sputum cytology/cytometry testing or no screening. Those with abnormal sputum then receive annual CT and fluorescent bronchoscopy for the remainder of 5 years, to identify early stage lung cancer. It is hoped that these simple initial tests could identify those requiring expensive CT scans, and the aim is to demonstrate a stage shift towards early stage cancers.
Trial registration numbers ISRCTN: ISRCTN80745975, clinicaltrials.gov: NCT00512746
On pseudo-hyperk\"ahler prepotentials
An explicit surjection from a set of (locally defined) unconstrained
holomorphic functions on a certain submanifold of (Sp_1(C) \times C^{4n}) onto
the set HK_{p,q} of local isometry classes of real analytic
pseudo-hyperk\"ahler metrics of signature (4p,4q) in dimension 4n is
constructed. The holomorphic functions, called prepotentials, are analogues of
K\"ahler potentials for K\"ahler metrics and provide a complete
parameterisation of HK_{p,q}. In particular, there exists a bijection between
HK_{p,q} and the set of equivalence classes of prepotentials. This affords the
explicit construction of pseudo-hyperk\"ahler metrics from specified
prepotentials. The construction generalises one due to Galperin, Ivanov,
Ogievetsky and Sokatchev. Their work is given a coordinate-free formulation and
complete, self-contained proofs are provided. An appendix provides a vital tool
for this construction: a reformulation of real analytic G-structures in terms
of holomorphic frame fields on complex manifolds.Comment: 53 pages; v2: minor amendments to Def.4.1 and Theorem 4.5; a
paragraph inserted in the proof of the latter; V3: minor changes; V4: minor
changes/ typos corrected for journal versio
Neutrino oscillations in low density medium
For the case of small matter effects: , where is the
matter potential, we develop the perturbation theory using as the expansion parameter. We derive simple and physically
transparent formulas for the oscillation probabilities in the lowest order in
which are valid for arbitrary density profile. The formulas can be
applied for propagation of the solar and supernova neutrinos in matter of the
Earth, substantially simplifying numerical calculations. Using these formulas
we study sensitivity of the oscillation effects to structures of the density
profile situated at different distances from the detector . We show that for
the mass-to-flavor state transitions, {\it e.g.}, , the
sensitivity is suppressed for remote structures: ,
where is the oscillation length and is the energy
resolution of detector.Comment: discussion simplified, clarifications adde
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