28,197 research outputs found
On the susceptibility function of piecewise expanding interval maps
We study the susceptibility function Psi(z) associated to the perturbation
f_t=f+tX of a piecewise expanding interval map f. The analysis is based on a
spectral description of transfer operators. It gives in particular sufficient
conditions which guarantee that Psi(z) is holomorphic in a disc of larger than
one. Although Psi(1) is the formal derivative of the SRB measure of f_t with
respect to t, we present examples satisfying our conditions so that the SRB
measure is not Lipschitz.*We propose a new version of Ruelle's conjectures.* In
v2, we corrected a few minor mistakes and added Conjectures A-B and Remark 4.5.
In v3, we corrected the perturbation (X(f(x)) instead of X(x)), in particular
in the examples from Section 6. As a consequence, Psi(z) has a pole at z=1 for
these examples.Comment: To appear Comm. Math. Phy
Eigenfunctions for smooth expanding circle maps
We construct a real-analytic circle map for which the corresponding
Perron-Frobenius operator has a real-analytic eigenfunction with an eigenvalue
outside the essential spectral radius when acting upon -functions.Comment: 10 pages, 2 figure
Recurrence spectrum in smooth dynamical systems
We prove that for conformal expanding maps the return time does have constant
multifractal spectrum. This is the counterpart of the result by Feng and Wu in
the symbolic setting
The Flow of a Viscous Compressible Fluid Through a Very Narrow Gap
The effect of compressibility on the pressure distribution
in the narrow gap between a rotating cylinder and a plane in a viscous fluid was studied by Taylor and Saffman [1] during an investigation of the centripetal pump effect discovered by Reiner [2]
Planetary nebulae after common-envelope phases initiated by low-mass red giants
It is likely that at least some planetary nebulae are composed of matter
which was ejected from a binary star system during common-envelope (CE)
evolution. For these planetary nebulae the ionizing component is the hot and
luminous remnant of a giant which had its envelope ejected by a companion in
the process of spiralling-in to its current short-period orbit. A large
fraction of CE phases which end with ejection of the envelope are thought to be
initiated by low-mass red giants, giants with inert, degenerate helium cores.
We discuss the possible end-of-CE structures of such stars and their subsequent
evolution to investigate for which structures planetary nebulae are formed. We
assume that a planetary nebula forms if the remnant reaches an effective
temperature greater than 30 kK within 10^4 yr of ejecting its envelope. We
assume that the composition profile is unchanged during the CE phase so that
possible remnant structures are parametrized by the end-of-CE core mass,
envelope mass and entropy profile. We find that planetary nebulae are expected
in post-CE systems with core masses greater than about 0.3 solar masses if
remnants end the CE phase in thermal equilibrium. We show that whether the
remnant undergoes a pre-white dwarf plateau phase depends on the prescribed
end-of-CE envelope mass. Thus, observing a young post-CE system would constrain
the end-of CE envelope mass and post-CE evolution.Comment: Published in MNRAS. 12 pages, 12 figures. Minor changes to match
published versio
Rare events, escape rates and quasistationarity: some exact formulae
We present a common framework to study decay and exchanges rates in a wide
class of dynamical systems. Several applications, ranging form the metric
theory of continuons fractions and the Shannon capacity of contrained systems
to the decay rate of metastable states, are given
On Urabe's criteria of isochronicity
We give a short proof of Urabe's criteria for the isochronicity of periodical
solutions of the equation . We show that apart from the
harmonic oscillator there exists a large family of isochronous potentials which
must all be non-polynomial and not symmetric (an even function of the
coordinate x).Comment: 8 page
De-novo design of complementary (antisense) peptide mini-receptor inhibitor of interleukin 18 (IL-18).
Complementary (antisense) peptide mini-receptor inhibitors are complementary peptides designed to be receptor-surrogates that act by binding to selected surface features of biologically important proteins thereby inhibiting protein-cognate receptor interactions and subsequent biological effects. Previously, we described a complementary peptide mini-receptor inhibitor of interleukin-1beta (IL-1beta) that was designed to bind to an external surface loop (beta-bulge) of IL-1beta (Boraschi loop) clearly identified in the X-ray crystal structure of this cytokine. Here, we report the de-novo design and rational development of a complementary peptide mini-receptor inhibitor of cytokine interleukin-18 (IL-18), a protein for which there is no known X-ray crystal structure. Using sequence homology comparisons with IL-1beta, putative IL-18 surface loops are identified and used as a starting point for design, including a loop region 1 thought to be equivalent with the Boraschi loop of IL-1beta. Only loop region 1 complementary peptides are found to be promising leads as mini-receptor inhibitors of IL-18 but these are prevented from being properly successful owing to solubility problems. The application of "M-I pair mutagenesis" and inclusion of a C-terminal arginine residue are then sufficient to solve this problem and convert one lead peptide into a functional complementary peptide mini-receptor inhibitor of IL-18. This suggests that the biophysical and biological properties of complementary peptides can be improved in a rational and logical manner where appropriate, further strengthening the potential importance of complementary peptides as inhibitors of protein-protein interactions, even when X-ray crystal structural information is not readily available
Muon-Spin-Rotation Measurements of the Penetration Depth in the Infinite-Layer Electron-Doped Cuprate Superconductor Sr0.9La0.1CuO2
Muon spin rotation (mSR) measurements of the in-plane penetration depth
lambda_ab have been performed in the electron-doped infinite layer high-Tc
superconductor (HTS) Sr0.9La0.1CuO2. Absence of the magnetic rare-earth ions in
this compound allowed to measure for the first time the absolute value of
lambda_ab(0) in electron-doped HTS using mSR. We found lambda_ab(0)=116(2) nm.
The zero-temperature depolarization rate sigma(0)?1/lambda_ab(0)^2=4.6(1) MHz
is more than four times higher than expected from the Uemura line. Therefore
this electron-doped HTS does not follow the Uemura relation found for
hole-doped HTS.Comment: to be published in Physical Review Letter
Irrelevant Interactions without Composite Operators - A Remark on the Universality of Second Order Phase Transitions
We study the critical behaviour of symmetric theory including
irrelevant terms of the form in the bare action,
where is the UV cutoff (corresponding e.g. to the inverse lattice
spacing for a spin system). The main technical tool is renormalization theory
based on the flow equations of the renormalization group which permits to
establish the required convergence statements in generality and rigour. As a
consequence the effect of irrelevant terms on the critical behaviour may be
studied to any order without using renormalization theory for composite
operators. This is a technical simplification and seems preferable from the
physical point of view. In this short note we restrict for simplicity to the
symmetry class of the Ising model, i.e. one component theory. The
method is general, however.Comment: 13 page
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