117 research outputs found
Quantum Interference in Superconducting Wire Networks and Josephson Junction Arrays: Analytical Approach based on Multiple-Loop Aharonov-Bohm Feynman Path-Integrals
We investigate analytically and numerically the mean-field
superconducting-normal phase boundaries of two-dimensional superconducting wire
networks and Josephson junction arrays immersed in a transverse magnetic field.
The geometries we consider include square, honeycomb, triangular, and kagome'
lattices. Our approach is based on an analytical study of multiple-loop
Aharonov-Bohm effects: the quantum interference between different electron
closed paths where each one of them encloses a net magnetic flux. Specifically,
we compute exactly the sums of magnetic phase factors, i.e., the lattice path
integrals, on all closed lattice paths of different lengths. A very large
number, e.g., up to for the square lattice, exact lattice path
integrals are obtained. Analytic results of these lattice path integrals then
enable us to obtain the resistive transition temperature as a continuous
function of the field. In particular, we can analyze measurable effects on the
superconducting transition temperature, , as a function of the magnetic
filed , originating from electron trajectories over loops of various
lengths. In addition to systematically deriving previously observed features,
and understanding the physical origin of the dips in as a result of
multiple-loop quantum interference effects, we also find novel results. In
particular, we explicitly derive the self-similarity in the phase diagram of
square networks. Our approach allows us to analyze the complex structure
present in the phase boundaries from the viewpoint of quantum interference
effects due to the electron motion on the underlying lattices.Comment: 18 PRB-type pages, plus 8 large figure
Improved Holographic QCD
We provide a review to holographic models based on Einstein-dilaton gravity
with a potential in 5 dimensions. Such theories, for a judicious choice of
potential are very close to the physics of large-N YM theory both at zero and
finite temperature. The zero temperature glueball spectra as well as their
finite temperature thermodynamic functions compare well with lattice data. The
model can be used to calculate transport coefficients, like bulk viscosity, the
drag force and jet quenching parameters, relevant for the physics of the
Quark-Gluon Plasma.Comment: LatEX, 65 pages, 28 figures, 9 Tables. Based on lectures given at
several Schools. To appear in the proceedinds of the 5th Aegean School
(Milos, Greece
Resuscitators' opinions on using a respiratory function monitor during neonatal resuscitation
Aim The aim of this study was to assess the resuscitators' opinions of the usefulness and clinical value of using a respiratory function monitor (RFM) when resuscitating extremely preterm infants with positive pressure ventilation. Methods The link to an online survey was sent to 106 resuscitators from six countries who were involved in a multicentre trial that compared the percentage of inflations within a predefined target range with and without the RFM. The resuscitators were asked to assess the usefulness and clinical value of the RFM. The survey was online for 4 months after the trial ended in May 2019. Results The survey was completed by 74 (70%) resuscitators of which 99% considered the RFM to be helpful during neonatal resuscitation and 92% indicated that it influenced their decision-making. The majority (76%) indicated that using the RFM improved their practice and made resuscitation more effective, even when the RFM was not available. Inadequate training was the key issue that limited the effectiveness of the RFM: 45% felt insufficiently trained, and 78% felt more training in using and interpreting the RFM would have been beneficial. Conclusion Resuscitators considered the RFM to be helpful to guide neonatal resuscitation, but sufficient training was required to achieve the maximum benefit.Developmen
Global extent and drivers of mammal population declines in protected areas under illegal hunting pressure
Illegal hunting is a persistent problem in many protected areas, but an overview of the extent of this problem and its impact on wildlife is lacking. We reviewed 40 years (1980–2020) of global research to examine the spatial distribution of research and socio-ecological factors influencing population decline within protected areas under illegal hunting pressure. From 81 papers reporting 988 species/site combinations, 294 mammal species were reported to have been illegally hunted from 155 protected areas across 48 countries. Research in illegal hunting has increased substantially during the review period and showed biases towards strictly protected areas and the African continent. Population declines were most frequent in countries with a low human development index, particularly in strict protected areas and for species with a body mass over 100 kg. Our results provide evidence that illegal hunting is most likely to cause declines of large-bodied species in protected areas of resource-poor countries regardless of protected area conservation status. Given the growing pressures of illegal hunting, increased investments in people’s development and additional conservation efforts such as improving anti-poaching strategies and conservation resources in terms of improving funding and personnel directed at this problem are a growing priority
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