Phase-coherence transition in granular superconductors with π\pi junctions

We study the three-dimensional XY-spin glass as a model for the resistive behavior of granular superconductors containing a random distribution of $\pi$ junctions, as in high-$T_c$ superconducting materials with d-wave symmetry. The $\pi$ junctions leads to quenched in circulating currents (chiralities) and to a chiral-glass state at low temperatures, even in the absence of an external magnetic field. Dynamical simulations in the phase representation are used to determine the nonlinear current-voltage characteristics as a function of temperature. Based on dynamic scaling analysis, we find a phase-coherence transition at finite temperature below which the linear resistivity should vanish and determine the corresponding critical exponents. The results suggest that the phase and chiralities may order simultaneously for decreasing temperatures into a superconducting chiral-glass state.Comment: 5 pages, 1 figure, Proc. of ICM 2000, to appear in J. Magn. Magn. Mate

Optimisation de la production de nucléi d'abeilles (Apis mellifera L.) au Québec

La production de paquets d’abeilles (abeilles adultes et une jeune reine) et de nucléi (petite colonie avec du couvain, des abeilles adultes et une jeune reine) assure la création de nouvelles colonies et le remplacement des colonies faibles ou mortes. Bien que ce travail soit réalisé par les apiculteurs à l’aide de diverses méthodes à travers le monde entier, les études scientifiques sur ce sujet sont rares. Au Canada, il y a besoin croissant de colonies pour remplacer et agrandir les cheptels afin de satisfaire la demande en service de pollinisation et combler les importantes pertes hivernales de colonies. L’objectif principal de notre étude était de développer une méthodologie pour produire de nouvelles colonies à la fois plus structurée et plus adaptée pour répondre au défi actuel de l’industrie apicole canadienne. Une technique de paquet d’abeilles et deux techniques de nucléi sur cadres ont été testées au Centre de Recherche en Sciences Animales de Deschambault en 2014: A) 1kg d’abeilles adultes + une jeune reine fécondée; B) un cadre de couvain + les abeilles adultes adhérentes à ce cadre + une jeune reine fécondée; et C) deux cadres de couvain + les abeilles adultes adhérentes à ces cadres + une jeune reine fécondée. Au total, 38 nouvelles colonies ont été produites. Ces colonies ont été évaluées de juillet 2014 à juin 2015, selon un ensemble de paramètres pour estimer leur force et l’infestation en varroa et nosémose. Les résultats démontrent que le développement des colonies était similaire peu importe la technique employée. Cependant, c’est la technique à un cadre de couvain (B) qui présente le meilleur potentiel de multiplication. Ce projet a également permit de confirmer que le prélèvement d’abeilles ou de couvain assure un meilleur contrôle du parasite varroa et réduit l’essaimage chez les colonies mères.Producing package bees (adult bees and a young queen) and nuclei (small colonies, each with brood, adult bees and a young queen) is one strategy for establishing new colonies and replacing those that are weak or dead. Although beekeepers around the world commonly engage in this work using various methods, scientific literature on the subject is scarce. In Canada, there is a growing need to replace and increase colony numbers to satisfy the demand for pollination services and compensate for high winter colony mortality. The main objective of our study was to develop a methodology for producing new colonies that is both more structured and better adapted to the challenges facing today’s Canadian beekeeping industry. One package bee and two nuclei-making techniques were compared at the Deschambault Research Center for Animal Sciences in 2014: A) 1 kg of adult bees + young mated queen, B) one brood frame + adult bees covering frames + young mated queen, C) two brood frames + adult bees to covering frames + young mated queen. In total, 38 new colonies were produced. These colonies were monitored from July 2014 to June 2015, measuring a set of parameters designed to evaluate their strength as well as levels of varroa mite infestation and nosema disease infection. Results showed no significant statistical differences in the development of these colonies. However, the findings confirm that technique B) represents the best multiplication potential and that retrieving bees or brood in hives for making nuclei controls both varroa mite infestations and swarming

Metabolite modifications in Solanum lycopersicum roots and leaves under cadmium stress

The effects of cadmium (Cd) were investigated on growth and metabolite profiling in roots and leaves of tomato (Solanum lycopersicum L., Var. Ibiza F1) plants exposed for 3 and 10 days to various CdCl2 concentrations (0 - 300 ìM). The aim of this study was to describe metabolite modifications in response to Cd stress and to identify Cd stress markers in the roots and leaves of tomato plants. During the treatment, Cd accumulated  significantly in the roots compared to stems and leaves. Plant growth (root, stem and leaf) decreased when Cd concentration increased. The analysis of 1H-NMR spectra of polar extracts showed clear differences between metabolites amounts (soluble sugars, organic and amino acids) in 30 and 300 ìM Cd-treated plants versus control ones. Among soluble sugars and organic acids, glucose, fructose and citrate contents significantly increased, by a factor 2 to 5 in both leaves and roots of Cd treated plants during the first three days of the treatment and then only in roots. In addition, Cd induced qualitative and quantitative changes in amino acid contents in the roots. Asparagine, glutamine and branched chain amino acids (valine, isoleucine, phenylalanine and tryptophane) significantly accumulated after 10 days of Cd exposure. Asparagine content which increased by 26 fold in the roots of 300 ìM Cd treated plants when compared with control ones, was found to be a good marker for Cd stress. In contrast, few modifications occurred in the leaves in response to Cd, except for tyrosine which content was highly increased (by 10 fold) after three days of treatment with 30 ìM. Taken together, our results show that, the exposure of tomato plants to various Cd concentrations results in significant changes in primary metabolism compounds, especially in the accumulation of some amino and organic acids involved in cellular compartmentation and detoxification of Cd.Key words: Cadmium, sugars, organic acids, amino acids, tomato (Solanum lycopersicum)

MSPB: a longitudinal multi-sensor dataset with phenotypic trait measurements from honey bees

We present a longitudinal multi-sensor dataset collected from honey bee colonies (Apis mellifera) with rich phenotypic measurements. Data were continuously collected between May-2020 and April-2021 from 53 hives located at two apiaries in Qu\'ebec, Canada. The sensor data included audio features, temperature, and relative humidity. The phenotypic measurements contained beehive population, number of brood cells (eggs, larva and pupa), Varroa destructor infestation levels, defensive and hygienic behaviors, honey yield, and winter mortality. Our study is amongst the first to provide a wide variety of phenotypic trait measurements annotated by apicultural science experts, which facilitate a broader scope of analysis. We first summarize the data collection procedure, sensor data pre-processing steps, and data composition. We then provide an overview of the phenotypic data distribution as well as a visualization of the sensor data patterns. Lastly, we showcase several hive monitoring applications based on sensor data analysis and machine learning, such as winter mortality prediction, hive population estimation, and the presence of an active and laying queen.Comment: Under review; project webpage: https://zhu00121.github.io/MSPB-webpage

Correlation Network Analysis reveals a sequential reorganization of metabolic and transcriptional states during germination and gene-metabolite relationships in developing seedlings of Arabidopsis

<p>Abstract</p> <p>Background</p> <p>Holistic profiling and systems biology studies of nutrient availability are providing more and more insight into the mechanisms by which gene expression responds to diverse nutrients and metabolites. Less is known about the mechanisms by which gene expression is affected by endogenous metabolites, which can change dramatically during development. Multivariate statistics and correlation network analysis approaches were applied to non-targeted profiling data to investigate transcriptional and metabolic states and to identify metabolites potentially influencing gene expression during the heterotrophic to autotrophic transition of seedling establishment.</p> <p>Results</p> <p>Microarray-based transcript profiles were obtained from extracts of Arabidopsis seeds or seedlings harvested from imbibition to eight days-old. ¹H-NMR metabolite profiles were obtained for corresponding samples. Analysis of transcript data revealed high differential gene expression through seedling emergence followed by a period of less change. Differential gene expression increased gradually to day 8, and showed two days, 5 and 7, with a very high proportion of up-regulated genes, including transcription factor/signaling genes. Network cartography using spring embedding revealed two primary clusters of highly correlated metabolites, which appear to reflect temporally distinct metabolic states. Principle Component Analyses of both sets of profiling data produced a chronological spread of time points, which would be expected of a developmental series. The network cartography of the transcript data produced two distinct clusters comprising days 0 to 2 and days 3 to 8, whereas the corresponding analysis of metabolite data revealed a shift of day 2 into the day 3 to 8 group. A metabolite and transcript pair-wise correlation analysis encompassing all time points gave a set of 237 highly significant correlations. Of 129 genes correlated to sucrose, 44 of them were known to be sucrose responsive including a number of transcription factors.</p> <p>Conclusions</p> <p>Microarray analysis during germination and establishment revealed major transitions in transcriptional activity at time points potentially associated with developmental transitions. Network cartography using spring-embedding indicate that a shift in the state of nutritionally important metabolites precedes a major shift in the transcriptional state going from germination to seedling emergence. Pair-wise linear correlations of transcript and metabolite levels identified many genes known to be influenced by metabolites, and provided other targets to investigate metabolite regulation of gene expression during seedling establishment.</p

Numerical studies of the 2 and 3D gauge glass at low temperature

We report results from Monte Carlo simulations of the two- and three-dimensional gauge glass at low temperature using parallel tempering Monte Carlo. In two dimensions, we find strong evidence for a zero-temperature transition. By means of finite-size scaling, we determine the stiffness exponent theta = -0.39 +/- 0.03. In three dimensions, where a finite-temperature transition is well established, we find theta = 0.27 +/- 0.01, compatible with recent results from domain-wall renormalization group studies.Comment: 3 pages, 3 figures. Proceedings of "2002 MMM Conference", Tampa, F

Ordering of the three-dimensional Heisenberg spin glass in magnetic fields

Spin and chirality orderings of the three-dimensional Heisenberg spin glass are studied under magnetic fields in light of the recently developed spin-chirality decoupling-recoupling scenario. It is found by Monte Carlo simulations that the chiral-glass transition and the chiral-glass ordered state, which are essentially of the same character as their zero-field counterparts, occur under magnetic fields. Implication to experimental phase diagram is discussed.Comment: 5 pages, 3 figure

Phase Transitions in the Two-Dimensional XY Model with Random Phases: a Monte Carlo Study

We study the two-dimensional XY model with quenched random phases by Monte Carlo simulation and finite-size scaling analysis. We determine the phase diagram of the model and study its critical behavior as a function of disorder and temperature. If the strength of the randomness is less than a critical value, $\sigma_{c}$, the system has a Kosterlitz-Thouless (KT) phase transition from the paramagnetic phase to a state with quasi-long-range order. Our data suggest that the latter exists down to T=0 in contradiction with theories that predict the appearance of a low-temperature reentrant phase. At the critical disorder $T_{KT}\rightarrow 0$ and for $\sigma > \sigma_{c}$ there is no quasi-ordered phase. At zero temperature there is a phase transition between two different glassy states at $\sigma_{c}$. The functional dependence of the correlation length on $\sigma$ suggests that this transition corresponds to the disorder-driven unbinding of vortex pairs.Comment: LaTex file and 18 figure