BMC Microbiol

BackgroundCryptococcus gattii has been the cause of an ongoing outbreak starting in 1999 on Vancouver Island, British Columbia and spreading to mainland Canada and the US Pacific Northwest. In the course of the outbreak, C. gattii has been identified outside of its previously documented climate, habitat, and host disease. Genotyping of C. gattii is essential to understand the ecological and geographical expansion of this emerging pathogen.MethodsWe developed and validated a mismatch amplification mutation assay (MAMA) real-time PCR panel for genotyping C. gattii molecular types VGI-VGIV and VGII subtypes a,b,c. Subtype assays were designed based on whole-genome sequence of 20 C. gattii strains. Publically available multilocus sequence typing (MLST) data from a study of 202 strains was used for the molecular type (VGI-VGIV) assay design. All assays were validated across DNA from 112 strains of diverse international origin and sample types, including animal, environmental and human.ResultsValidation revealed each assay on the panel is 100% sensitive, specific and concordant with MLST. The assay panel can detect down to 0.5 picograms of template DNA.ConclusionsThe (MAMA) real-time PCR panel for C. gattii accurately typed a collection of 112 diverse strains and demonstrated high sensitivity. This is a time and cost efficient method of genotyping C. gattii best suited for application in large-scale epidemiological studies.R21AI098059/AI/NIAID NIH HHS/United State

Exploring the Role of Interdisciplinarity in Physics: Success, Talent and Luck

Although interdisciplinarity is often touted as a necessity for modern research, the evidence on the relative impact of sectorial versus to interdisciplinary science is qualitative at best. In this paper we leverage the bibliographic data set of the American Physical Society to quantify the role of interdisciplinarity in physics, and that of talent and luck in achieving success in scientific careers. We analyze a period of 30 years (1980-2009) tagging papers and their authors by means of the Physics and Astronomy Classification Scheme (PACS), to show that some degree of interdisciplinarity is quite helpful to reach success, measured as a proxy of either the number of articles or the citations score. We also propose an agent-based model of the publication-reputation-citation dynamics reproduces the trends observed in the APS data set. On the one hand, the results highlight the crucial role of randomness and serendipity in real scientific research; on the other, they shed light on a counter-intuitive effect indicating that the most talented authors are not necessarily the most successful ones.Comment: 21 pages, 19 figure

Frequencies and resonances around L4L_4 in the elliptic restricted three-body problem

The stability of the Lagrangian point $L_4$ is investigated in the elliptic restricted three-body problem by using Floquet's theory. Stable and unstable domains are determined in the parameter plane of the mass parameter and the eccentricity by computing the characteristic exponents. Frequencies of motion around $L_4$ have been determined both in the stable and unstable domains and fitting functions for the frequencies are derived depending on the mass parameter and the eccentricity. Resonances between the frequencies are studied in the whole parameter plane. It is shown that the 1:1 resonances are not restricted only to single curves but extend to the whole unstable domain. In the unstable domains longer escape times of the test particle from the neighbourhood of $L_4$ are related to certain resonances, but changing the parameters the same resonances may lead to faster escape

Trade and synchronization in a multi-country economy

Substantial evidence suggests that countries with stronger trade linkages have more synchro- nized business cycles. The standard international business cycle framework cannot replicate this finding, uncovering the trade-comovement puzzle. We show that under certain macro-level conditions but irrespective of the micro-level assumptions concerning trade the puzzle arises because trade fails to substantially increase the correlation between each country's import penetration ratio and the trade partner's technology shock. Within a large class of trade models, there are three channels through which bilateral trade may increase business cycle synchronization. Specifically, increased bilateral trade may (i) raise the correlation between each country's tech- nology shocks, (ii) raise the correlation between each country's share of expenditure on domestic goods, and (iii) raise the response of the domestic import penetration ratio to foreign technology shocks. Empirical evidence strongly supports the first and second channels. We show that the trade-comovement puzzle can be resolved if productivity shocks are more correlated between country-pairs that trade more

How does an interacting many-body system tunnel through a potential barrier to open space?

The tunneling process in a many-body system is a phenomenon which lies at the very heart of quantum mechanics. It appears in nature in the form of alpha-decay, fusion and fission in nuclear physics, photoassociation and photodissociation in biology and chemistry. A detailed theoretical description of the decay process in these systems is a very cumbersome problem, either because of very complicated or even unknown interparticle interactions or due to a large number of constitutent particles. In this work, we theoretically study the phenomenon of quantum many-body tunneling in a more transparent and controllable physical system, in an ultracold atomic gas. We analyze a full, numerically exact many-body solution of the Schr\"odinger equation of a one-dimensional system with repulsive interactions tunneling to open space. We show how the emitted particles dissociate or fragment from the trapped and coherent source of bosons: the overall many-particle decay process is a quantum interference of single-particle tunneling processes emerging from sources with different particle numbers taking place simultaneously. The close relation to atom lasers and ionization processes allows us to unveil the great relevance of many-body correlations between the emitted and trapped fractions of the wavefunction in the respective processes.Comment: 18 pages, 4 figures (7 pages, 2 figures supplementary information

Balanced gain and loss in Bose-Einstein condensates without PT symmetry

Balanced gain and loss renders the mean-field description of Bose-Einstein condensates PT symmetric. However, any experimental realization has to deal with unbalancing in the gain and loss contributions breaking the PT symmetry. We will show that such an asymmetry does not necessarily lead to a system without a stable mean-field ground state. Indeed, by exploiting the nonlinear properties of the condensate, a small asymmetry can stabilize the system even further due to a self-regulation of the particle number.Comment: 7 pages, 6 figure

International investment positions and exchange rate dynamics : a dynamic panel analysis

In this paper we revisit medium- to long-run exchange rate determination, focusing on the role of international investment positions. To do so, we develop a new econometric framework accounting for conditional long-run homogeneity in heterogeneous dynamic panel data models. In particular, in our model the long-run relationship between effective exchange rates and domestic as well as weighted foreign prices is a homogeneous function of a country’s international investment position. We find rather strong support for purchasing power parity in environments of limited negative net foreign asset to GDP positions, but not outside such environments. We thus argue that the purchasing power parity hypothesis holds conditionally, but not unconditionally, and that international investment positions are an essential component to characterizing this conditionality. Finally, we adduce evidence that whether deterioration of a country’s net foreign asset to GDP position leads to a depreciation of that country’s effective exchange rate depends on its rate of inflation relative to the rate of inflation abroad as well as its exposure to global shocks. JEL Classification: F31, F37, C2