312 research outputs found

    Does postoperative radiation therapy represent a contraindication to expander-implant based immediate breast reconstruction? An update 2012-2014

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    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

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    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

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    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

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    As so far, the redshift of Gamma-ray bursts (GRBs) can extend to z8z\sim 8 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 Λ\LambdaCDM model as an example.Comment: 16 pages, 5 figure
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