312 research outputs found
Does postoperative radiation therapy represent a contraindication to expander-implant based immediate breast reconstruction? An update 2012-2014
Post-mastectomy radiotherapy (PMRT) is well known in the plastic surgery community for having a negative impact on expander-implant based immediate breast reconstruction (IBBR), although recently some technical improvements allow better results. Very recent papers would suggest that there is no difference in postoperative complications in patients receiving post-mastectomy radiotherapy using modern techniques. However, study results are often biased by small groups of patients and by heterogeneity of radiotherapy timing, different surgical techniques and measured outcomes
Dynamical Couplings, Dynamical Vacuum Energy and Confinement/Deconfinement from R^2-Gravity
We study within Palatini formalism an f(R)-gravity with f(R)= R + \alpha R^2
interacting with a dilaton and a special kind of nonlinear gauge field system
containing a square-root of the standard Maxwell term, which is known to
produce confinement in flat space-time. Reformulating the model in the physical
Einstein frame we find scalar field effective potential with a flat region
where the confinement dynamics disappears, while in other regions it remains
intact. The effective gauge couplings as well as the induced cosmological
constant become dynamical. In particular, a conventional Maxwell kinetic term
for the gauge field is dynamically generated even if absent in the original
theory. We find few interesting classes of explicit solutions: (i)
asymptotically (anti-)de Sitter black holes of non-standard type with
additional confining vacuum electric potential even for the electrically
neutral ones; (ii) non-standard Reissner-Nordstroem black holes with additional
constant vacuum electric field and having non-flat-spacetime "hedgehog"
asymptotics; (iii) generalized Levi-Civitta-Bertotti-Robinson "tube-like"
space-times.Comment: 16 page
Spin-Nematic Squeezed Vacuum in a Quantum Gas
Using squeezed states it is possible to surpass the standard quantum limit of
measurement uncertainty by reducing the measurement uncertainty of one property
at the expense of another complementary property. Squeezed states were first
demonstrated in optical fields and later with ensembles of pseudo spin-1/2
atoms using non-linear atom-light interactions. Recently, collisional
interactions in ultracold atomic gases have been used to generate a large
degree of quadrature spin squeezing in two-component Bose condensates. For
pseudo spin-1/2 systems, the complementary properties are the different
components of the total spin vector , which fully characterize the state on
an SU(2) Bloch sphere. Here, we measure squeezing in a spin-1 Bose condensate,
an SU(3) system, which requires measurement of the rank-2 nematic or quadrupole
tensor as well to fully characterize the state. Following a quench
through a nematic to ferromagnetic quantum phase transition, squeezing is
observed in the variance of the quadratures up to -8.3(-0.7 +0.6) dB
(-10.3(-0.9 +0.7) dB corrected for detection noise) below the standard quantum
limit. This spin-nematic squeezing is observed for negligible occupation of the
squeezed modes and is analogous to optical two-mode vacuum squeezing. This work
has potential applications to continuous variable quantum information and
quantum-enhanced magnetometry
Cosmological Model-independent Gamma-ray Bursts Calibration and its Cosmological Constraint to Dark Energy
As so far, the redshift of Gamma-ray bursts (GRBs) can extend to
which makes it as a complementary probe of dark energy to supernova Ia (SN Ia).
However, the calibration of GRBs is still a big challenge when they are used to
constrain cosmological models. Though, the absolute magnitude of GRBs is still
unknown, the slopes of GRBs correlations can be used as a useful constraint to
dark energy in a completely cosmological model independent way. In this paper,
we follow Wang's model-independent distance measurement method and calculate
their values by using 109 GRBs events via the so-called Amati relation. Then,
we use the obtained model-independent distances to constrain CDM model
as an example.Comment: 16 pages, 5 figure
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