132 research outputs found
Multiple Reentrant Phase Transitions and Triple Points in Lovelock Thermodynamics
We investigate the effects of higher curvature corrections from Lovelock
gravity on the phase structure of asymptotically AdS black holes, treating the
cosmological constant as a thermodynamic pressure. We examine how various
thermodynamic phenomena, such as Van der Waals behaviour, reentrant phase
transitions (RPT), and tricritical points are manifest for U(1) charged black
holes in Gauss-Bonnet and 3rd-order Lovelock gravities. We furthermore observe
a new phenomenon of "multiple RPT" behaviour, in which for fixed pressure the
small/large/small/large black hole phase transition occurs as the temperature
of the system increases. We also find that when the higher-order Lovelock
couplings are related in a particular way, a peculiar isolated critical point
emerges for hyperbolic black holes and is characterized by non-standard
critical exponents.Comment: 50 pages, 28 Figures v2: minor corrections, references adde
The use of remote monitoring of cardiac implantable devices during the COVID-19 pandemic: an EHRA physician survey
It is unclear to what extent the COVID-19 pandemic has influenced the use of remote monitoring (RM) of cardiac implantable electronic devices (CIEDs). The present physician-based European Heart Rhythm Association (EHRA) survey aimed to assess the influence of the COVID-19 pandemic on RM of CIEDs among EHRA members and how it changed the current practice. The survey comprised 27 questions focusing on RM use before and during the pandemic. Questions focused on the impact of COVID-19 on the frequency of in-office visits, data filtering, reasons for initiating in-person visits, underutilization of RM during COVID-19, and RM reimbursement. A total of 160 participants from 28 countries completed the survey. Compared to the pre-pandemic period, there was a significant increase in the use of RM in patients with pacemakers (PMs) and implantable loop recorders (ILRs) during the COVID-19 pandemic (PM 24.2 vs. 39.9%, P = 0.002; ILRs 61.5 vs. 73.5%, P = 0.028), while there was a trend towards higher utilization of RM for cardiac resynchronization therapy-pacemaker (CRT-P) devices during the pandemic (44.5 vs. 55%, P = 0.063). The use of RM with implantable cardioverter-defibrillators (ICDs) and CRT-defibrillator (CRT-D) did not significantly change during the pandemic (ICD 65.2 vs. 69.6%, P = 0.408; CRT-D 65.2 vs. 68.8%, P = 0.513). The frequency of in-office visits was significantly lower during the pandemic (P < 0.001). Nearly two-thirds of participants (57 out of 87 respondents), established new RM connections for CIEDs implanted before the pandemic with 33.3% (n = 29) delivering RM transmitters to the patient's home address, and the remaining 32.1% (n = 28) activating RM connections during an in-office visit. The results of this survey suggest that the crisis caused by COVID-19 has led to a significant increase in the use of RM of CIEDs
Anomalous NMR Magnetic Shifts in CeCoIn_5
We report ^{115}In and ^{59}Co Nuclear Magnetic Resonance (NMR) measurements
in the heavy fermion superconductor CeCoIn_5 above and below T_c. The hyperfine
couplings of the In and Co are anisotropic and exhibit dramatic changes below
50K due to changes in the crystal field level populations of the Ce ions. Below
T_c the spin susceptibility is suppressed, indicating singlet pairing.Comment: 4 pages, 4 figure
Evidence for distinct polymer chain orientations in KC60 and RbC60
The KC60 and RbC60 polymer phases exhibit contrasting electronic properties
while powder diffraction studies have revealed no definite structural
difference. We have performed single crystal X-ray diffraction and diffuse
scattering studies of these compounds. It is found that KC60 and RbC60 possess
different chain orientations about their axes, which are described by distinct
space groups Pmnn and I2/m, respectively. Such a structural difference will be
of great importance to a complete understanding of the physical properties.Comment: To be published in Phys. Rev. Let
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