79,265 research outputs found
Redistribution of particle and anti-particle entanglement in non-inertial frames
We analyse the entanglement tradeoff between particle and anti-particle modes
of a Dirac field from the perspective of inertial and uniformly accelerated
observers. Our results show that a redistribution of entanglement between
particle and anti-particle modes plays a key role in the survival of fermionic
field entanglement in the infinite acceleration limit.Comment: 10 pages, 5 figures, revtex4. Added journal referenc
Ceramic materials lead to underestimated DNA quantifications : a method for reliable measurements
In the context of investigating cell-material interactions or of material-guided generation of tissues, DNA quantification represents an elective method to precisely assess the number of cells attached or embedded within different substrates. Nonetheless, nucleic acids are known to electrostatically bind to ceramics, a class of materials commonly employed in orthopaedic implants and bone tissue engineering scaffolds. This phenomenon is expected to lead to a relevant underestimation of the DNA amount, resulting in erroneous experimental readouts. The present work aims at *lpar;i) investigating the effects of DNA-ceramic bond occurrence on DNA quantification, and (ii) developing a method to reliably extract and accurately quantify DNA in ceramic-containing specimens. A cell-free model was adopted to study DNA-ceramic binding, highlighting an evident DNA loss (up to 90%) over a wide range of DNA/ceramic ratios (w/w). A phosphate buffer-based (800 mM) enzymatic extraction protocol was developed and its efficacy in terms of reliable DNA extraction and measurement was confirmed with commonly used fluorometric assays, for various ceramic substrates. The proposed buffered DNA extraction technique was validated in a cell-based experiment showing 95% DNA retrieval in a cell seeding experiment, demonstrating a 3.5-fold increase in measured DNA amount as compared to a conventional enzymatic extraction protocol. In conclusion, the proposed phosphate buffer method consistently improves the DNA extraction process assuring unbiased analysis of samples and allowing accurate and sensitive cell number quantification on ceramic containing substrates
Coherent macroscopic quantum tunneling in boson-fermion mixtures
We show that the cold atom systems of simultaneously trapped Bose-Einstein
condensates (BEC's) and quantum degenerate fermionic atoms provide promising
laboratories for the study of macroscopic quantum tunneling. Our theoretical
studies reveal that the spatial extent of a small trapped BEC immersed in a
Fermi sea can tunnel and coherently oscillate between the values of the
separated and mixed configurations (the phases of the phase separation
transition of BEC-fermion systems). We evaluate the period, amplitude and
dissipation rate for Na and K-atoms and we discuss the
experimental prospects for observing this phenomenon.Comment: 4 pages, 3 figure
A Center-Symmetric 1/N Expansion
The free energy of U(N) gauge theory is expanded about a center-symmetric
topological background configuration with vanishing action and vanishing
Polyakov loops. We construct this background for SU(N) lattice gauge theory and
show that it uniquely describes center-symmetric minimal action orbits in the
limit of infinite lattice volume. The leading contribution to the free energy
in the 1/N expansion about this background is of O(N^0) rather than O(N^2) as
one finds when the center symmetry is spontaneously broken. The contribution of
planar 't Hooft diagrams to the free energy is O(1/N^2) and sub-leading in this
case. The change in behavior of the diagrammatic expansion is traced to Linde's
observation that the usual perturbation series of non-Abelian gauge theories
suffers from severe infrared divergences. This infrared problem does not arise
in a center-symmetric expansion. The 't Hooft coupling \lambda=g^2 N is found
to decrease proportional to 1/\ln(N) for large N. There is evidence of a
vector-ghost in the planar truncation of the model.Comment: 27 pages, 2 figures; extended and corrected version with additional
material and reference
Topological confinement in bilayer graphene
We study a new type of one-dimensional chiral states that can be created in
bilayer graphene (BLG) by electrostatic lateral confinement. These states
appear on the domain walls separating insulating regions experiencing the
opposite gating polarity. While the states are similar to conventional
solitonic zero-modes, their properties are defined by the unusual chiral BLG
quasiparticles, from which they derive. The number of zero-mode branches is
fixed by the topological vacuum charge of the insulating BLG state. We discuss
how these chiral states can manifest experimentally, and emphasize their
relevance for valleytronics.Comment: 4 pages, 3 figure
A Variational Approach to the Spinless Relativistic Coulomb Problem
By application of a straightforward variational procedure we derive a simple,
analytic upper bound on the ground-state energy eigenvalue of a
semirelativistic Hamiltonian for (one or two) spinless particles which
experience some Coulomb-type interaction.Comment: 7 pages, HEPHY-PUB 606/9
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