2,370 research outputs found
Reversible Dynamics in Strongly Non-Local Boxworld Systems
In order to better understand the structure of quantum theory, or speculate
about theories that may supercede it, it can be helpful to consider alternative
physical theories. ``Boxworld'' describes one such theory, in which all
non-signaling correlations are achievable. In a limited class of multipartite
Boxworld systems - wherein all subsystems are identical and all measurements
have the same number of outcomes - it has been demonstrated that the set of
reversible dynamics is `trivial', generated solely by local relabellings and
permutations of subsystems. We develop the convex formalism of Boxworld to give
an alternative proof of this result, then extend this proof to all multipartite
Boxworld systems, and discuss the potential relevance to other theories. These
results lend further support to the idea that the rich reversible dynamics in
quantum theory may be the key to understanding its structure and its
informational capabilities.Comment: 5 pages + appendice
Information causality from an entropic and a probabilistic perspective
The information causality principle is a generalisation of the no-signalling
principle which implies some of the known restrictions on quantum correlations.
But despite its clear physical motivation, information causality is formulated
in terms of a rather specialised game and figure of merit. We explore different
perspectives on information causality, discussing the probability of success as
the figure of merit, a relation between information causality and the non-local
`inner-product game', and the derivation of a quadratic bound for these games.
We then examine an entropic formulation of information causality with which one
can obtain the same results, arguably in a simpler fashion.Comment: 7 pages, v2: some references added and minor improvement
Simulating all non-signalling correlations via classical or quantum theory with negative probabilities
Many-party correlations between measurement outcomes in general probabilistic
theories are given by conditional probability distributions obeying the
non-signalling condition. We show that any such distribution can be obtained
from classical or quantum theory, by relaxing positivity constraints on either
the mixed state shared by the parties, or the local functions which generate
measurement outcomes. Our results apply to generic non-signalling correlations,
but in particular they yield two distinct quasi-classical models for quantum
correlations.Comment: 6 page
The effects of aggregation and protein corona on the cellular internalization of iron oxide nanoparticles
Engineered inorganic nanoparticles are essential components in the
development of nanotechnologies. For applications in nanomedicine, particles
need to be functionalized to ensure a good dispersibility in biological fluids.
In many cases however, functionalization is not sufficient : the particles
become either coated by a corona of serum proteins or precipitate out of the
solvent. In the present paper, we show that by changing the coating of iron
oxide nanoparticles from a low-molecular weight ligand (citrate ions) to small
carboxylated polymers (poly(acrylic acid)), the colloidal stability of the
dispersion is improved and the adsorption/internalization of iron towards
living mammalian cells is profoundly affected. Citrate-coated particles are
shown to destabilize in all fetal-calf-serum based physiological conditions
tested, whereas the polymer coated particles exhibit an outstanding
dispersibility as well as a structure devoid of protein corona. The
interactions between nanoparticles and human lymphoblastoid cells are
investigated by transmission electron microscopy and flow cytometry. Two types
of nanoparticle/cell interactions are underlined. Iron oxides are found either
adsorbed on the cellular membranes, or internalized into membrane-bound
endocytosis compartments. For the precipitating citrate-coated particles, the
kinetics of interactions reveal a massive and rapid adsorption of iron oxide on
the cell surfaces. The quantification of the partition between adsorbed and
internalized iron was performed from the cytometry data. The results highlight
the importance of resilient adsorbed nanomaterials at the cytoplasmic membrane.Comment: 21 pages, 11 figures, accepted at Biomaterials (2011
Spatial Distribution of Metal Emissions in SNR 3C 397 Viewed with Chandra and XMM
We present X-ray equivalent width imaging of the supernova remnant (SNR) 3C
397 for Mg He\alpha, Si He\alpha, S He\alpha, and Fe K\alpha complex lines with
the Chandra and XMM-Newton observations. The images reveal that the heavier the
element is, the smaller the extent of the element distribution is. The Mg
emission is evidently enhanced in the southeastern blow-out region, well along
the radio boundary there, and appears to partially envelope the eastern Fe
knot. Two bilateral hat-like Si line-emitting structures are along the northern
and southern borders, roughly symmetric with respect to the southeast-northwest
elongation axis. An S line-emitting shell is located just inner to the northern
radio and IR shell, indicating of a layer of reversely shocked sulphur in the
ejecta. A few enhanced Fe features are basically aligned along the diagonal of
the rectangular shape of the SNR, which implicates an early asymmetric SN
explosion.Comment: 4 pages, 4 figures, appears in Science China Physics, Mechanics &
Astronomy, 2010, 53 (Suppl.1), 267-27
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