Comparison between five stochastic global search algorithms for optimizing thermoelectric generator designs

In this study, the best settings of five heuristics are determined for solving a mixed-integer non-linear multi-objective optimization problem. The algorithms treated in the article are: ant colony optimization, genetic algorithm, particle swarm optimization, differential evolution, and teaching-learning basic algorithm. The optimization problem consists in optimizing the design of a thermoelectric device, based on a model available in literature. Results showed that the inner settings can have different effects on the algorithm performance criteria depending on the algorithm. A formulation based on the weighted sum method is introduced for solving the multiobjective optimization problem with optimal settings. It was found that the five heuristic algorithms have comparable performances. Differential evolution generated the highest number of non-dominated solutions in comparison with the other algorithms

Obsessive and Compulsive Characteristics of Craving for Alcohol in Alcohol Abuse and Dependence

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/65211/1/j.1530-0277.1992.tb01375.x.pd

Two types of nematicity in the phase diagram of the cuprate superconductor YBa2_2Cu3_3Oy_y

Nematicity has emerged as a key feature of cuprate superconductors, but its link to other fundamental properties such as superconductivity, charge order and the pseudogap remains unclear. Here we use measurements of transport anisotropy in YBa$_2$Cu$_3$O$_y$ to distinguish two types of nematicity. The first is associated with short-range charge-density-wave modulations in a doping region near $p = 0.12$. It is detected in the Nernst coefficient, but not in the resistivity. The second type prevails at lower doping, where there are spin modulations but no charge modulations. In this case, the onset of in-plane anisotropy - detected in both the Nernst coefficient and the resistivity - follows a line in the temperature-doping phase diagram that tracks the pseudogap energy. We discuss two possible scenarios for the latter nematicity.Comment: 8 pages and 7 figures. Main text and supplementary material now combined into single articl

Strong water stratification provides a refuge for rainbow smelt larvae Osmerus mordax in a sub-arctic estuary (Lake Melville, Labrador)

Estuaries provide nurseries for early life stages of fish that rely on the interaction between fresh- and saltwater. The 250 km long Lake Melville spans 2100 km2 and is the largest estuary of Labrador (northeastern Canada). This sub-arctic fjard hosts freshwater, anadromous, and marine fishes on which depend marine mammals and seabirds, but also coastal communities. Yet, how different fish species and life stages use the estuary as a habitat, in particular the importance of the low salinity surface layer for the development of fish larvae, remains unknown. By pairing seasonal hydroacoustic surveys conducted in summers 2018–2019 and winters 2019–2020 with net sampling and environmental DNA (eDNA) analyses, we test the hypothesis that the strong water stratification prevailing in upper Lake Melville provides a nursery for early life stages of fish, where they are protected from their predators. Ichthyoplankton aggregated just above and at the pycnocline, in the low salinity surface layer down to 25 m. Most adult pelagic fish occupied the bottom waters below the sharp pycnocline, although some ventured in the low salinity surface layer. Ten species of adult fish were captured in gill and fyke nets and 53 species were detected with eDNA. Larvae of rainbow smelt (Osmerus mordax) were ubiquitous in the surface layer in July and August and represented 100% of the ichthyoplankton assemblage sampled during these months. No fish larvae were detected in winter (February). We conclude that the low salinity surface layer provides a refuge for rainbow smelt larvae, a key forage species in the estuary. This study provides baseline information from which to assess future changes in biodiversity and distribution of fish in the Lake Melville estuary. It further supports the use of eDNA as a complementary tool for monitoring fish diversity in sub-arctic estuaries

Fermi-surface transformation across the pseudogap critical point of the cuprate superconductor La1.6−x_{1.6-x}Nd0.4_{0.4}Srx_{x}CuO4_4

The electrical resistivity $\rho$ and Hall coefficient R$_H$ of the tetragonal single-layer cuprate Nd-LSCO were measured in magnetic fields up to $H = 37.5$ T, large enough to access the normal state at $T \to 0$, for closely spaced dopings $p$ across the pseudogap critical point at $p^\star = 0.235$. Below $p^\star$, both coefficients exhibit an upturn at low temperature, which gets more pronounced with decreasing $p$. Taken together, these upturns show that the normal-state carrier density $n$ at $T = 0$ drops upon entering the pseudogap phase. Quantitatively, it goes from $n = 1 + p$ at $p = 0.24$ to $n = p$ at $p = 0.20$. By contrast, the mobility does not change appreciably, as revealed by the magneto-resistance. The transition has a width in doping and some internal structure, whereby R$_H$ responds more slowly than $\rho$ to the opening of the pseudogap. We attribute this difference to a Fermi surface that supports both hole-like and electron-like carriers in the interval $0.2 < p < p^\star$, with compensating contributions to R$_H$. Our data are in excellent agreement with recent high-field data on YBCO and LSCO. The quantitative consistency across three different cuprates shows that a drop in carrier density from $1 + p$ to $p$ is a universal signature of the pseudogap transition at $T=0$. We discuss the implication of these findings for the nature of the pseudogap phase.Comment: 11 pages, 12 figure

Anisotropy of the Seebeck Coefficient in the Cuprate Superconductor YBa2_{2}Cu3_{3}Oy_{y}: Fermi-Surface Reconstruction by Bidirectional Charge Order

The Seebeck coefficient $S$ of the cuprate YBa$_{2}$Cu$_{3}$O$_{y}$ was measured in magnetic fields large enough to suppress superconductivity, at hole dopings $p = 0.11$ and $p = 0.12$, for heat currents along the $a$ and $b$ directions of the orthorhombic crystal structure. For both directions, $S/T$ decreases and becomes negative at low temperature, a signature that the Fermi surface undergoes a reconstruction due to broken translational symmetry. Above a clear threshold field, a strong new feature appears in $S_{\rm b}$, for conduction along the $b$ axis only. We attribute this feature to the onset of 3D-coherent unidirectional charge-density-wave modulations seen by x-ray diffraction, also along the $b$ axis only. Because these modulations have a sharp onset temperature well below the temperature where $S/T$ starts to drop towards negative values, we infer that they are not the cause of Fermi-surface reconstruction. Instead, the reconstruction must be caused by the quasi-2D bidirectional modulations that develop at significantly higher temperature.Comment: 7 pages, 5 figure

Leisure practice and its relations to cognitive vitality for seniors attending community organizations

The purpose of this study was to explore the relations between certain dimensions of leisure practice and cognitive vitality in seniors and identify which of their sociodemographic and health characteristics (SHC) are related to leisure practice. A cross-sectional analysis of leisure practice, cognitive performance, self-perceived memory and SHC was performed among 294 French-speaking Canadian seniors attending community centres (255 women, average age: 71), by multiple linear regressions and partial correlations controlled for SHC. Outcomes from the project show that the diversity of leisure was related to the Montreal Cognitive Assessment and the California Verbal Learning Test, the frequency of cognitive leisure was associated to the Stroop Test, and the frequency of social leisure showed no significant association. “Paper and pencil games”, “computer use” and “helping a sibling” were related to various cognitive tests. Frequency of leisure (total) was related to gender and education, and diversity of leisure was related to education, age and depression. Study outcomes indicate that diversity of leisure was more related to cognitive vitality than frequency. Future studies should address leisure diversity as a way to promote cognitive vitality among seniors. Moreover, seniors’ characteristics should be considered when seeking to facilitate their participation in leisure activities.Le but de cette étude était d’explorer les relations entre certaines dimensions de la pratique de loisirs et la vitalité cognitive chez des aînés et d’identifier leurs caractéristiques sociodémographiques et de santé (CSS) qui étaient liées à leur pratique de loisirs. Une analyse transversale de la pratique de loisirs, de la performance cognitive, du niveau perçu de la mémoire et des CSS a été réalisée auprès de 294 aînés canadiens parlant français et qui participaient aux activités d’un centre communautaire (255 femmes, âge moyen : 71 ans), par des régressions linéaires multiples et des corrélations partielles contrôlées pour les CSS. Les résultats montrent que la variété des loisirs était liée au Montreal Cognitive Assessment et au California Verbal Learning Test, que la fréquence des loisirs cognitifs était associée au test de Stroop et que la fréquence des loisirs sociaux ne montrait aucune association. Les « jeux papier-crayon », « l’utilisation de l’ordinateur » et « prendre soin d’un proche » étaient reliés à plusieurs tests cognitifs. La fréquence totale des loisirs était liée au sexe et à l’éducation et la variété des loisirs était liée à l’éducation, à l’âge et à la dépression. Les résultats de cette étude montrent que la variété des loisirs était davantage liée à la vitalité comparée à la fréquence des loisirs. De futures études devraient aborder la variété des loisirs comme une manière de promouvoir la vitalité cognitive chez les aînées. De plus, les caractéristiques des aînés devraient être considérées afin de favoriser leur participation aux activités de loisirs dans les centres communautaires

Lifshitz critical point in the cuprate superconductor YBa2Cu3Oy from high-field Hall effect measurements

The Hall coefficient R_H of the cuprate superconductor YBa2Cu3Oy was measured in magnetic fields up to 60 T for a hole concentration p from 0.078 to 0.152, in the underdoped regime. In fields large enough to suppress superconductivity, R_H(T) is seen to go from positive at high temperature to negative at low temperature, for p > 0.08. This change of sign is attributed to the emergence of an electron pocket in the Fermi surface at low temperature. At p < 0.08, the normal-state R_H(T) remains positive at all temperatures, increasing monotonically as T \to 0. We attribute the change of behaviour across p = 0.08 to a Lifshitz transition, namely a change in Fermi-surface topology occurring at a critical concentration p_L = 0.08, where the electron pocket vanishes. The loss of the high-mobility electron pocket across p_L coincides with a ten-fold drop in the conductivity at low temperature, revealed in measurements of the electrical resistivity $\rho$ at high fields, showing that the so-called metal-insulator crossover of cuprates is in fact driven by a Lifshitz transition. It also coincides with a jump in the in-plane anisotropy of $\rho$, showing that without its electron pocket the Fermi surface must have strong two-fold in-plane anisotropy. These findings are consistent with a Fermi-surface reconstruction caused by a unidirectional spin-density wave or stripe order.Comment: 16 pages, 13 figures, see associated Viewpoint: M. Vojta, Physics 4, 12 (2011

Pseudogap phase of cuprate superconductors confined by Fermi surface topology

The properties of cuprate high-temperature superconductors are largely shaped by competing phases whose nature is often a mystery. Chiefly among them is the pseudogap phase, which sets in at a doping $p^*$ that is material-dependent. What determines $p^*$ is currently an open question. Here we show that the pseudogap cannot open on an electron-like Fermi surface, and can only exist below the doping $p_{FS}$ at which the large Fermi surface goes from hole-like to electron-like, so that $p^*$ $\leq$ $p_{FS}$. We derive this result from high-magnetic-field transport measurements in La$_{1.6-x}$Nd$_{0.4}$Sr$_x$CuO$_4$ under pressure, which reveal a large and unexpected shift of $p^*$ with pressure, driven by a corresponding shift in $p_{FS}$. This necessary condition for pseudogap formation, imposed by details of the Fermi surface, is a strong constraint for theories of the pseudogap phase. Our finding that $p^*$ can be tuned with a modest pressure opens a new route for experimental studies of the pseudogap.Comment: 15 pages, 5 figures, 7 supplemental figure