6,571 research outputs found
Self-dual formulations of d=3 gravity theories in the path-integral framework
We study the connection, at the quantum level, between d=2+1 dimensional
self-dual models with actions of growing (from first to fourth) order,
governing the dynamics of helicity +2 (or -2) massive excitations. We obtain
identities between generating functionals of the different models using the
path-integral framework, this allowing to establish dual maps among relevant
vacuum expectation values. We check consistency of these v.e.v.'s with the
gauge invariance gained in each mapping.Comment: 26 pages. LaTeX. Minor changes. Published in Int. J Modern Phys. A;
http://www.worldscinet.com/ijmp
Effect of Contrast-Enhanced Echocardiograms on the Prognosis of Infective Endocarditis
Objective - Infective endocarditis (IE) is an infectious disease of the cardiac valves where bacteria colonize the valves; typically, via the formation of vegetations. Recent research has shown that the microbubbles in a contrast-enhanced ultrasound (CEUS) examination can move and dislodge bacterial vegetations in vitro. This study investigated whether CEUS resulted in faster resolution of IE in vivo by dislodging the vegetations.
Methods - This IRB approved retrospective study reviewed 36 patients who were diagnosed with IE via echocardiography. Data was sourced from patients within the Jefferson University Hospital’s Cardiology EMR system by searching for contrast and vegetation from January 1st, 2013 – January 1st, 2018. Fifteen patients were not given contrast, whereas 21 patients were given contrast via agitated saline (n=16) or an ultrasound contrast agent (n=5). All patients received an echocardiogram after blood cultures confirmed an infection, but before resolution of infection (defined by negative blood cultures). A student’s t-test was used for analyses.
Results - The study population was heterogeneous in terms of sex (67.5% male) and race (70% Caucasian, 25% African American, and 5% Asian), with an average age of 51±20 years, and an average BMI of 29.65±7.43 in the contrast group and 27.67±3.16 in the non-contrast group (p=0.37). Following ultrasound, no patients had documented stroke, pulmonary embolism, or systemic blood clot, which physicians could have attributed to a thrombus resulting from dislodging of bacterial vegetation. Overall, blood cultures did not clear faster in patients receiving CEUS compared to those undergoing standard echocardiography, (2.63±2.69 days vs. 1.34 ±1.11 days, p=0.09). CEUS also did not shorten the admission length in patients with IE, (16.9±7.7 days vs. 19.9±12.1 days; p=0.36).
Conclusion - Based on this limited sample size, patients who underwent CEUS did not have a different prognosis when compared to patients who received a non-contrast echocardiogram
Critical point symmetries in boson-fermion systems. The case of shape transition in odd nuclei in a multi-orbit model
We investigate phase transitions in boson-fermion systems. We propose an
analytically solvable model (E(5/12)) to describe odd nuclei at the critical
point in the transition from the spherical to -unstable behaviour. In
the model, a boson core described within the Bohr Hamiltonian interacts with an
unpaired particle assumed to be moving in the three single particle orbitals
j=1/2,3/2,5/2. Energy spectra and electromagnetic transitions at the critical
point compare well with the results obtained within the Interacting Boson
Fermion Model, with a boson-fermion Hamiltonian that describes the same
physical situation.Comment: Phys. Rev. Lett. (in press
Quantum Phase Transitions in the Interacting Boson Model: Integrability, level repulsion and level crossing
We study the quantum phase transition mechanisms that arise in the
Interacting Boson Model. We show that the second-order nature of the phase
transition from U(5) to O(6) may be attributed to quantum integrability,
whereas all the first-order phase transitions of the model are due to level
repulsion with one singular point of level crossing. We propose a model
Hamiltonian with a true first-order phase transition for finite systems due to
level crossings.Comment: Accepted in PR
Boundary effects on radiative processes of two entangled atoms
We analyze radiative processes of a quantum system composed by two identical
two-level atoms interacting with a massless scalar field prepared in the vacuum
state in the presence of perfect reflecting flat mirrors. We consider that the
atoms are prepared in a stationary maximally entangled state. We investigate
the spontaneous transitions rates from the entangled states to the collective
ground state induced by vacuum fluctuations. In the empty-space case, the
spontaneous decay rates can be enhanced or inhibited depending on the specific
entangled state and changes with the distance between the atoms. Next, we
consider the presence of perfect mirrors and impose Dirichlet boundary
conditions on such surfaces. In the presence of a single mirror the transition
rate for the symmetric state undergoes a slight reduction, whereas for the
antisymmetric state our results indicate a slightly enhancement. Finally, we
investigate the effect of multiple reflections by two perfect mirrors on the
transition rates.Comment: submitted version to the journa
Chiral Anomaly Beyond Lorentz Invariance
The chiral anomaly in the context of an extended standard model with minimal
Lorentz invariance violation is studied. Taking into account bounds from
measurements of the speed of light, we argue that the chiral anomaly and its
consequences are general results valid even beyond the relativistic symmetry.Comment: Final version. To be published in PR
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