16,065 research outputs found
Entropy production in the early-cosmology pionic phase
We point out that in the early universe, for temperatures in the approximate
interval 175-80 MeV (after the quark-gluon plasma), pions carried a large share
of the entropy and supported the largest inhomogeneities. Thus, we examine the
production of entropy in a pion gas, particularizing to inhomogeneities of the
temperature, for which we benefit from the known thermal conductivity. We
finally put that entropy produced in relaxing such thermal inhomogeneities in
the broad context of this relatively unexplored phase of early-universe
cosmology.Comment: 10 pages, 10 figures
Monetary policy and inflation persistence in the Eurozone
The primary goal of the European Central Bankâs (ECB) monetary policy is to achieve price stability. Whereas during the 1980s and 1990s there was a rapid and strong convergence in terms of price differential among the Euro countries, particularly in those countries with higher inflation rates in the past, single monetary policy has proved to be quite inefficient in continuing this trend and has not achieved further reductions in inflation rate differentials within the euro zone. Since the ECB sets the official interest rate according to the average inflation of the euro area, the persistence of such price differentials within the area would mean that the âone size interest rate policyâ would not fit all. This paper studies empirically the inflation rate differentials and their persistence in some currency unions with the aim to draw some conclusions for the working of the ECB monetary policy. KEYWORDS: monetary policy; inflation persistence; currency unions
Degenerate four-wave mixing in triply-resonant Kerr cavities
We demonstrate theoretical conditions for highly-efficient degenerate
four-wave mixing in triply-resonant nonlinear (Kerr) cavities. We employ a
general and accurate temporal coupled-mode analysis in which the interaction of
light in arbitrary microcavities is expressed in terms a set of coupling
coefficients that we rigorously derive from the full Maxwell equations. Using
the coupled-mode theory, we show that light consisting of an input signal of
frequency can, in the presence of pump light at
, be converted with quantum-limited efficiency into an output shifted
signal of frequency , and we derive expressions for
the critical input powers at which this occurs. We find that critical powers in
the order of 10mW assuming very conservative cavity parameters (modal volumes
cubic wavelengths and quality factors . The standard
Manley-Rowe efficiency limits are obtained from the solution of the classical
coupled-mode equations, although we also derive them from simple
photon-counting "quantum" arguments. Finally, using a linear stability
analysis, we demonstrate that maximal conversion efficiency can be retained
even in the presence of self- and cross-phase modulation effects that generally
act to disrupt the resonance condition.Comment: 13 pages, 8 figures. To appear in Physical Review
Correction of Optical Aberrations in Elliptic Neutron Guides
Modern, nonlinear ballistic neutron guides are an attractive concept in
neutron beam delivery and instrumentation, because they offer increased
performance over straight or linearly tapered guides. However, like other
ballistic geometries they have the potential to create significantly
non-trivial instrumental resolution functions. We address the source of the
most prominent optical aberration, namely coma, and we show that for extended
sources the off-axis rays have a different focal length from on-axis rays,
leading to multiple reflections in the guide system. We illustrate how the
interplay between coma, sources of finite size, and mirrors with non-perfect
reflectivity can therefore conspire to produce uneven distributions in the
neutron beam divergence, the source of complicated resolution functions. To
solve these problems, we propose a hybrid elliptic-parabolic guide geometry.
Using this new kind of neutron guide shape, it is possible to condition the
neutron beam and remove almost all of the aberrations, whilst providing the
same performance in beam current as a standard elliptic neutron guide. We
highlight the positive implications for a number of neutron scattering
instrument types that this new shape can bring.Comment: Presented at NOP2010 Conference in Alpe d'Huez, France, in March 201
Spatial and temporal variation in the diet of the California sea lion (Zalophus californianus) in the Gulf of California, Mexico
Between June 1995 and May 1996 seven rookeries in the Gulf of California were visited four times in order to collect scat samples for studying spatial and seasonal variability California sea lion prey. The rookeries studied were San Pedro MĂĄrtir, San Esteban, El Rasito, Los Machos, Los Cantiles, Isla Granito, and Isla Lobos. The 1273 scat samples collected yielded 4995 otoliths (95.3%) and 247 (4.7%) cephalopod beaks. Fish were found in 97.4% of scat samples collected, cephalopods in 11.2%, and crustaceans in 12.7%. We identified 92 prey taxa to the species level, 11 to genus level, and 10 to family level, of which the most important were Pacific cutlassfish (Trichiurus lepturus),
Pacific sardine (Sardinops caeruleus), plainfin midshipman (Porichthys spp.), myctophid no. 1, northern anchovy
(Engraulis mordax), Pacific mackerel (Scomber japonicus), anchoveta (Cetengraulis mysticetus), and jack mackerel
(Trachurus symmetricus). Significant differences were found among rookeries in the occurrence of all main prey
(Pâ€0.04), except for myctophid no. 1 (P>0.05). Temporally, significant differences were found in the occurrence
of Pacific cutlassfish, Pacific sardine, plainfin midshipman, northern anchovy, and Pacific mackerel (P<0.05),
but not in jack mackerel (Ï 2=2.94, df=3, P=0.40), myctophid no. 1 (Ï 2=1.67, df= 3, P=0.64), or lanternfishes (Ï 2=2.08, df=3, P=0.56). Differences were observed in
the diet and in trophic diversity among seasons and rookeries. More evident was the variation in diet in relation to availability of Pacific sardine
A Comprehensive Study on Pain Assessment from Multimodal Sensor Data
Pain assessment is a critical aspect of healthcare, influencing timely interventions and patient well-being. Traditional pain evaluation methods often rely on subjective patient reports, leading to inaccuracies and disparities in treatment, especially for patients who present difficulties to communicate due to cognitive impairments. Our contributions are three-fold. Firstly, we analyze the correlations of the data extracted from biomedical sensors. Then, we use state-of-the-art computer vision techniques to analyze videos focusing on the facial expressions of the patients, both per-frame and using the temporal context. We compare them and provide a baseline for pain assessment methods using two popular benchmarks: UNBC-McMaster Shoulder Pain Expression Archive Database and BioVid Heat Pain Database. We achieved an accuracy of over 96% and over 94% for the F1 Score, recall and precision metrics in pain estimation using single frames with the UNBC-McMaster dataset, employing state-of-the-art computer vision techniques such as Transformer-based architectures for vision tasks. In addition, from the conclusions drawn from the study, future lines of work in this area are discussed
Complex Methods Applied to Data Analysis, Processing, and Visualisation
The amount of data available every day is not only enormous but growing at an exponential rate. Over the last ten years there has been an increasing interest in using complex methods to analyse and visualise massive datasets, gathered from very different sources and including many different features: social networks, surveillance systems, smart cities, medical diagnosis systems, business information, cyberphysical systems, and digital media data. Nowadays, there are a large number of researchers working in complex methods to process, analyse, and visualise all this information, which can be applied to a wide variety of open problems in different domains. This special issue presents a collection of research papers addressing theoretical, methodological, and practical aspects of data processing, focusing on algorithms that use complex methods (e.g., chaos, genetic algorithms, cellular automata, neural networks, and evolutionary game theory) in a variety of domains (e.g., software engineering, digital media data, bioinformatics, health care, imaging and video, social networks, and natural language processing). A total of 27 papers were received from different research fields, but sharing a common feature: they presented complex systems that process, analyse, and visualise large amounts of data. After the review process, 8 papers were accepted for publication (around 30% of acceptance ratio)
- âŠ