11,187 research outputs found
Hydrodynamic Modes of a holographic wave superfluid
In this work we analyze the hydrodynamics of a wave superfluid on its
strongly coupled regime by considering its holographic description. We obtain
the poles of the retarded Green function through the computation of the
quasi-normal modes of the dual AdS black hole background finding diffusive,
pseudo-diffusive and sound modes. For the sound modes we compute the speed of
sound and its attenuation as function of the temperature. For the diffusive and
pseudo-diffusive modes we find that they acquire a non-zero real part at
certain finite momentum.Comment: 16 pag., 6 fig. Reference added. Minor corrections. Version accepted
for publication in JHE
Backreacting p-wave Superconductors
We study the gravitational backreaction of the non-abelian gauge field on the
gravity dual to a 2+1 p-wave superconductor. We observe that as in the
system a second order phase transition exists between a superconducting and a
normal state. Moreover, we conclude that, below the phase transition
temperature the lowest free energy is achieved by the p-wave solution. In
order to probe the solution, we compute the holographic entanglement entropy.
For both and systems the entanglement entropy satisfies an area law.
For any given entangling surface, the p-wave superconductor has lower
entanglement entropy.Comment: Minor Typos corrected, version published in JHE
Thermal Radiation from a Fluctuating Event Horizon
We consider a pointlike two-level system undergoing uniformly accelerated
motion. We evaluate the transition probability for a finite time interval of
this system coupled to a massless scalar field near a fluctuating event
horizon. Horizon fluctuations are modeled using a random noise which generates
light-cone fluctuations. We study the case of centered, stationary and Gaussian
random processes. The transition probability of the system is obtained from the
positive-frequency Wightman function calculated to one loop order in the noise
averaging process. Our results show that the fluctuating horizon modifies the
thermal radiation but leaves unchanged the temperature associated with the
acceleration.Comment: 8 pages, 3 figure
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
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