9,964 research outputs found
M51 ULX-7: superorbital periodicity and constraints on the neutron star magnetic field
In this work, we explore the applicability of standard theoretical models of accretion to the observed properties of M51 ULX-7. The spin-up rate and observed X-ray luminosity are evidence of a neutron star with a surface magnetic field of 2-7 x 10(13) G, rotating near equilibrium. Analysis of the X-ray light curve of the system (Swift/XRT data) reveals the presence of a similar to 39 d superorbital period. We argue that the superorbital periodicity is due to disc precession, and that material is accreted on to the neutron star at a constant rate throughout it. Moreover, by attributing this modulation to the free precession of the neutron star we estimate a surface magnetic field strength of 3-4 x 10(13) G. The agreement of these two independent estimates provide strong constraints on the surface polar magnetic field strength of the NS
La encrucijada de Manuela Sáenz en el imaginario cultural latinoamericano del siglo XXI
Este trabajo analiza tres textos creativos de distintos gĂ©neros que recrean en el siglo xxi la imagen de Manuela Sáenz, la famosa amante del Libertador suramericano SimĂłn BolĂvar. Se arguye que en la Ăłpera, la novela y la pelĂcula examinadas se invita alThis essay analyzes three works from different genres - all produced in the xxi century - that recreate the image of Manuela Sáenz, famous lover of the South American liberator SimĂłn BolĂvar. In this work I contend that the opera, the novel and the film
Tagged particle in a sheared suspension: effective temperature determines density distribution in a slowly varying external potential beyond linear response
We consider a sheared colloidal suspension under the influence of an external
potential that varies slowly in space in the plane perpendicular to the flow
and acts on one selected (tagged) particle of the suspension. Using a
Chapman-Enskog type expansion we derive a steady state equation for the tagged
particle density distribution. We show that for potentials varying along one
direction only, the tagged particle distribution is the same as the equilibrium
distribution with the temperature equal to the effective temperature obtained
from the violation of the Einstein relation between the self-diffusion and
tagged particle mobility coefficients. We thus prove the usefulness of this
effective temperature for the description of the tagged particle behavior
beyond the realm of linear response. We illustrate our theoretical predictions
with Brownian dynamics computer simulations.Comment: Accepted for publication in Europhys. Let
Magnetic Excitations in NpCoGa5
We report the results of inelastic neutron scattering experiments on
NpCoGa, an isostructural analogue of the PuCoGa superconductor. Two
energy scales characterize the magnetic response in the antiferromagnetic
phase. One is related to a non-dispersive excitation between two crystal field
levels. The other at lower energies corresponds to dispersive fluctuations
emanating from the magnetic zone center. The fluctuations persist in the
paramagnetic phase also, although weaker in intensity. This supports the
possibility that magnetic fluctuations are present in PuCoGa, where
unconventional d-wave superconductivity is achieved in the absence of magnetic
order.Comment: 4 pages, 5 figure
Challenges for orchestration and instance selection of composite services in distributed edge clouds
Today's centralized cloud-computing infrastructures have not been designed with geo-localized, personalized, bandwidth/processing-intensive, real-time applications in mind. High network delay and low throughput can have a significant impact on the user experience. Instead, such services could be deployed in distributed service nodes at the edge of the network, closer to the user. In this paper we focus on composite services of which the components are running in different service nodes. We present a two-layer framework that provides service orchestration and instance selection. We present the orchestration mechanisms to enable the flexible re-use of components across different composite services. For the resolution layer of our framework, we present two modes of operation that combine network and service availability information for efficient per-request instance selection among a multitude of service replicas
Robust formation of morphogen gradients
We discuss the formation of graded morphogen profiles in a cell layer by
nonlinear transport phenomena, important for patterning developing organisms.
We focus on a process termed transcytosis, where morphogen transport results
from binding of ligands to receptors on the cell surface, incorporation into
the cell and subsequent externalization. Starting from a microscopic model, we
derive effective transport equations. We show that, in contrast to morphogen
transport by extracellular diffusion, transcytosis leads to robust ligand
profiles which are insensitive to the rate of ligand production
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