Lemming–Food Plant Interactions, Density Effects, and Cyclic Dynamics on the Siberian Tundra

Theory predicts that trophic interactions can produce cyclic dynamics of microtine rodents, but that in addition, social interactions are necessary to create the cyclicity. We tested the induced defence hypothesis as a component driving multi-annual cycles by analyzing data on Siberian lemming (Lemmus sibiricus Kerr) populations and the levels of trypsin inhibitors (TI) and free proteins (SPP) in their food plants. We collected data at 12 sites along the Palaearctic tundra coast in 1994 and correlated these measures with lemming density and cycle phase. A negative correlation between lemming density and TI/SPP in Carex was found at the 12 sites. Cycle phase tended to correlate significantly with TI/SPP, and plants being grazed by lemmings respond with some delay. Mass of pancreas, the organ producing proteolytic enzymes, co-varied negatively with TI/SPP. These findings are in accord with predictions from the induced defence hypothesis. In contrast, reproductive effort did not conform to the predictions but co-varied strongly with density. Data are in accord with theory predicting that, in addition to trophic interactions, some self-regulation is necessary to create cyclic dynamics. Our data show that the plant defence hypothesis alone is not a sufficient explanation for the cyclicity. Several factors interact, including predation, food quality (including induced defence chemicals), and intra-specific competition.En théorie, les interactions trophiques peuvent produire une dynamique cyclique de rongeurs microtinés, mais en plus de cela, il faut des interactions sociales pour donner lieu à la cyclicité. Nous avons mis à l’épreuve l’hypothèse induite de défense en tant que composante intégrale des cycles multi-annuels en analysant les données relatives aux populations de lemming brun (Lemmus sibiricus Kerr) et les taux d’inhibiteurs de la trypsine (TI) et de protéines libres (SPP) se trouvant dans leur nourriture végétale. Nous avons recueilli des données à 12 emplacements le long de la côte paléarctique des toundras en 1994 et avons corrélé ces mesures à la densité des lemmings ainsi qu’à la phase du cycle. Une corrélation négative entre la densité des lemmings et TI/SPP dans Carex a été trouvée à 12 emplacements. La phase du cycle avait tendance à donner une corrélation significative avec TI/SPP, et les végétaux faisant l’objet d’un pâturage par les lemmings réagissaient avec un certain retard. Les masses de pancréas, soit l’organe producteur des enzymes protéolytiques, co-variait négativement avec TI/SPP. Ces constatations cadrent avec les prédictions émanant de l’hypothèse induite de défense. Par contre, les efforts de reproduction ne se conformaient pas aux prédictions mais co-variaient fortement en fonction de la densité. Les données sont en accord avec la théorie prédisant qu’en plus des interactions trophiques, il faut une certaine autorégulation pour créer une dynamique cyclique. Nos données montrent qu’à elle seule, l’hypothèse de défense des végétaux ne constitue pas une explication suffisante à la cyclicité. Plusieurs facteurs entrent en interaction, dont la prédation, la qualité de la nourriture (ce qui comprend les produits chimiques induits de la défense) et la compétition intraspécifique

Soft Magnetorotons and Broken-Symmetry States in Bilayer Quantum Hall Ferromagnets

The recent report on the observation of soft magnetorotons in the dispersion of charge-density excitations across the tunneling gap in coupled bilayers at total Landau level filling factor $\nu_T=1$ is reviewed. The inelastic light scattering experiments take advantage of the breakdown of wave-vector conservation that occurs under resonant excitation. The results offer evidence that in the quantum Hall state there is a roton that softens and sharpens markedly when the phase boundary for transitions to highly-correlated compressible states is approached. These findings are interpreted with Hartree-Fock evaluations of the dynamic structure factor. The model includes the effect of disorder in the breakdown of wave-vector conservation and resonance enhancement profiles within a phenomenological approach. These results link the softening of magnetorotons to enhanced excitonic Coulomb interactions in the ferromagnetic bilayers.Comment: 6 pages, 5 figures; conference: EP2DS-1

Benchmarking Advantage and D-Wave 2000Q quantum annealers with exact cover problems

We benchmark the quantum processing units of the largest quantum annealers to date, the 5000+ qubit quantum annealer Advantage and its 2000+ qubit predecessor D-Wave 2000Q, using tail assignment and exact cover problems from aircraft scheduling scenarios. The benchmark set contains small, intermediate, and large problems with both sparsely connected and almost fully connected instances. We find that Advantage outperforms D-Wave 2000Q for almost all problems, with a notable increase in success rate and problem size. In particular, Advantage is also able to solve the largest problems with 120 logical qubits that D-Wave 2000Q cannot solve anymore. Furthermore, problems that can still be solved by D-Wave 2000Q are solved faster by Advantage. We find, however, that D-Wave 2000Q can achieve better success rates for sparsely connected problems that do not require the many new couplers present on Advantage, so improving the connectivity of a quantum annealer does not per se improve its performance.Comment: new experiments to test the conjecture about unused couplers (appendix B

A 1-acetamido derivative of 6-epi-valienamine: an inhibitor of a diverse group of β-N-acetylglucosaminidases

The synthesis of an analogue of 6-epi-valienamine bearing an acetamido group and its characterisation as an inhibitor of β-N-acetylglucosaminidases are described. The compound is a good inhibitor of both human O-GlcNAcase and human β-hexosaminidase, as well as two bacterial β-N-acetylglucosaminidases. A 3-D structure of the complex of Bacteroides thetaiotaomicron BtGH84 with the inhibitor shows the unsaturated ring is surprisingly distorted away from its favoured solution phase conformation and reveals potential for improved inhibitor potency

Campylobacter jejuni Colonization in Wild Birds: Results from an Infection Experiment

Campylobacter jejuni is a common cause of bacterial gastroenteritis in most parts of the world. The bacterium has a broad host range and has been isolated from many animals and environments. To investigate shedding patterns and putative effects on an avian host, we developed a colonization model in which a wild bird species, the European Robin Erithacus rubecula, was inoculated orally with C. jejuni from either a human patient or from another wild bird species, the Song Thrush Turdus philomelos. These two isolates were genetically distinct from each other and provoked very different host responses. The Song Thrush isolate colonized all challenged birds and colonization lasted 6.8 days on average. Birds infected with this isolate also showed a transient but significant decrease in body mass. The human isolate did not colonize the birds and could be detected only in the feces of the birds shortly after inoculation. European Robins infected with the wild bird isolate generated a specific antibody response to C. jejuni membrane proteins from the avian isolate, which also was cross-reactive to membrane proteins of the human isolate. In contrast, European Robins infected with the human isolate did not mount a significant response to bacterial membrane proteins from either of the two isolates. The difference in colonization ability could indicate host adaptations

Testing for Optimal Monetary Policy via Moment Inequalities

The specification of an optimizing model of the monetary transmission mechanism requires selecting a policy regime: commonly, commitment or discretion. In this paper we propose a new procedure for testing optimal monetary policy, relying on moment inequalities that nest commitment and discretion as two special cases. The approach is based on the derivation of bounds for inflation that are consistent with optimal policy under either policy regime. We derive testable implications that allow for specification tests and discrimination between the two alternative regimes. The proposed procedure is implemented to examine the conduct of monetary policy in the US economy

Landscape Epidemiology of Tularemia Outbreaks in Sweden

Transmission sites of specific Francisella tularensis genotypes were highly localized during natural outbreaks of human tularemia

Epidemiologic and Molecular Analysis of Human Tularemia, United States, 1964–2004

Distinct subpopulations of F. tularensis differ in their clinical manifestations, geographic distribution, and likely modes of transmission

Canonical Insertion-Deletion Markers for Rapid DNA Typing of Francisella tularensis

By combining analysis of indel markers with multiple-locus variable-number tandem repeat analysis, individual strains were identified