10,802 research outputs found
Rotating 5D-Kaluza-Klein Space-Times from Invariant Transformations
Using invariant transformations of the five-dimensional Kaluza-Klein (KK)
field equations, we find a series of formulae to derive axial symmetric
stationary exact solutions of the KK theory starting from static ones. The
procedure presented in this work allows to derive new exact solutions up to
very simple integrations. Among other results, we find exact rotating solutions
containing magnetic monopoles, dipoles, quadripoles, etc., coupled to scalar
and to gravitational multipole fields.Comment: 24 pages, latex, no figures. To appear in Gen. Rel. Grav., 32,
(2000), in pres
Axisymmetric Stationary Solutions as Harmonic Maps
We present a method for generating exact solutions of Einstein equations in
vacuum using harmonic maps, when the spacetime possesses two commutating
Killing vectors. This method consists in writing the axisymmetric stationry
Einstein equations in vacuum as a harmonic map which belongs to the group
SL(2,R), and decomposing it in its harmonic "submaps". This method provides a
natural classification of the solutions in classes (Weil's class, Lewis' class
etc).Comment: 17 TeX pages, one table,( CINVESTAV- preprint 12/93
Plasma membrane-specific interactome analysis reveals calpain 1 as a druggable modulator of rescued Phe508del-CFTR cell surface stability
Cystic fibrosis (CF) is a genetic disease caused by mutations in the gene encoding CF transmembrane conductance regulator (CFTR), a chloride channel normally expressed at the surface of epithelial cells. The most frequent mutation, resulting in Phe-508 deletion, causes CFTR misfolding and its premature degradation. Low temperature or pharmacological correctors can partly rescue the Phe508del-CFTR processing defect and enhance trafficking of this channel variant to the plasma membrane (PM). Nevertheless, the rescued channels have an increased endocytosis rate, being quickly removed from the PM by the peripheral protein quality-control pathway. We previously reported that rescued Phe508del-CFTR (rPhe508del) can be retained at the cell surface by stimulating signaling pathways that coax the adaptor molecule ezrin (EZR) to tether rPhe508delâNa+/H+-exchange regulatory factor-1 (NHERF1) complexes to the actin cytoskeleton, thereby averting the rapid internalization of this channel variant. However, the molecular basis for why rPhe508del fails to recruit active EZR to the PM remains elusive. Here, using a proteomics approach, we characterized and compared the core components of wt-CFTRâ or rPhe508delâcontaining macromolecular complexes at the surface of human bronchial epithelial cells. We identified calpain 1 (CAPN1) as an exclusive rPhe508del interactor that prevents active EZR recruitment, impairs rPhe508del anchoring to actin, and reduces its stability in the PM. We show that either CAPN1 downregulation or its chemical inhibition dramatically improves the functional rescue of Phe508del-CFTR in airway cells. These observations suggest that CAPN1 constitutes an attractive target for pharmacological intervention, as part of CF combination therapies restoring Phe508del-CFTR function.This work was supported by a center grant UID/MULTI/04046/2019
to BioISI and project PTDC/BIA-CEL/28408/2017 and IF2012 to PM,
both from FCT, Portugal. AMM was recipient of fellowship
SFRH/BD/52490/2014 from BioSYS PhD programme PD65-2012,
and PB of fellowship SFRH/BPD/94322/2013.N/
Class of Einstein--Maxwell Dilatons
Three different classes of static solutions of the Einstein--Maxwell
equations non--minimally coupled to a dilaton field are presented. The
solutions are given in general in terms of two arbitrary harmonic functions and
involve among others an arbitrary parameter which determines their
applicability as charged black holes, dilaton black holes or strings. Most of
the known solutions are contained as special cases and can be non--trivially
generalized in different ways.Comment: Published in Physical Review D, R310 (1995
Gravitoelectromagnetism and Dark Energy in Superconductors
A gravitomagnetic analogue of the London moment in superconductors can
explain the anomalous Cooper pair mass excess reported by Janet Tate.
Ultimately the gravitomagnetic London moment is attributed to the breaking of
the principle of general covariance in superconductors. This naturally implies
non-conservation of classical energy-momentum. Possible relation with the
manifestation of dark energy in superconductors is questioned.Comment: 10 pages. Poster presented at "From Quantum to Cosmos - Fundamental
Physics Research in Space" 22-24 May 2006, To Appear in Int. J. Mod. Phys.
Oscillatons revisited
In this paper, we study some interesting properties of a spherically
symmetric oscillating soliton star made of a real time-dependent scalar field
which is called an oscillaton. The known final configuration of an oscillaton
consists of a stationary stage in which the scalar field and the metric
coefficients oscillate in time if the scalar potential is quadratic. The
differential equations that arise in the simplest approximation, that of
coherent scalar oscillations, are presented for a quadratic scalar potential.
This allows us to take a closer look at the interesting properties of these
oscillating objects. The leading terms of the solutions considering a quartic
and a cosh scalar potentials are worked in the so called stationary limit
procedure. This procedure reveals the form in which oscillatons and boson stars
may be related and useful information about oscillatons is obtained from the
known results of boson stars. Oscillatons could compete with boson stars as
interesting astrophysical objects, since they would be predicted by scalar
field dark matter models.Comment: 10 pages REVTeX, 10 eps figures. Updated files to match version
published in Classical and Quantum Gravit
Identification of a spatio-temporal model of crystal growth based on boundary curvature
A new method of identifying the spatio-temporal transition rule of crystal growth is introduced based on the connection between growth kinetics and dentritic
morphology. Using a modified three-point-method, curvatures of the considered crystal branch are calculated and curvature direction is used to measure growth
velocity. A polynomial model is then produced based on a curvature-velocity relationship to represent the spatio-temporal growth process. A very simple simulation
example is used initially to clearly explain the methodology. The results of identifying a model from a real crystal growth experiment show that the proposed
method can produce a good representation of crystal growth
Generation of Closed Timelike Curves with Rotating Superconductors
The spacetime metric around a rotating SuperConductive Ring (SCR) is deduced
from the gravitomagnetic London moment in rotating superconductors. It is shown
that theoretically it is possible to generate Closed Timelike Curves (CTC) with
rotating SCRs. The possibility to use these CTC's to travel in time as
initially idealized by G\"{o}del is investigated. It is shown however, that
from a technology and experimental point of view these ideas are impossible to
implement in the present context.Comment: 9 pages. Submitted to Classical and Quantum Gravit
Identification of geometrical models of interface evolution for dendritic crystal growth
This paper introduces a method for identifying geometrical models of interface evolution, directly from experimental imaging data. These local growth models relate
normal growth velocity to curvature and its derivatives estimated along the growing interface. Such models can reproduce many qualitative features of dendritic crystal
growth as well as predict quantitatively its early stages of evolution. Numerical simulations and experimental crystal growth data are used to demonstrate the applicability of this approach
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