Classical bifurcation at the transition from Rabi to Josephson dynamics

We report on the experimental realization of an internal bosonic Josephson junction in a Rubidium spinor Bose-Einstein condensate. The measurement of the full time dynamics in phase space allows the characterization of the theoretically predicted $\pi$-phase modes and quantitatively confirms analytical predictions, revealing a classical bifurcation. Our results suggest that this system is a model system which can be tuned from classical to the quantum regime and thus is an important step towards the experimental investigation of entanglement generation close to critical points

The mode of host-parasite interaction shapes coevolutionary dynamics and the fate of host cooperation

Antagonistic coevolution between hosts and parasites can have a major impact on host population structures, and hence on the evolution of social traits. Using stochastic modelling techniques in the context of bacteria-virus interactions, we investigate the impact of coevolution across a continuum of host-parasite genetic specificity (specifically, where genotypes have the same infectivity/resistance ranges (matching alleles, MA) to highly variable ranges (gene-for-gene, GFG)) on population genetic structure, and on the social behaviour of the host. We find that host cooperation is more likely to be maintained towards the MA end of the continuum, as the more frequent bottlenecks associated with an MA-like interaction can prevent defector invasion, and can even allow migrant cooperators to invade populations of defectors.Comment: 8 pages, 4 figures, 1 Supplementary Material file attached (to view it, please download the source file listed under "Other formats"

A graphical theory of competition on spatial resource gradients

Resource competition is a fundamental interaction in natural communities.However little is known about competition in spatial environments where organisms are able to regulate resource distributions. Here, we analyze the competition of two consumers for two resources in a one-dimensional habitat in which the resources are supplied from opposite sides. We show that the success of an invading species crucially depends on the slope of the resource gradients shaped by the resident. Our analysis reveals that parameter combinations which lead to coexistence in a uniform environment may favor alternative stable states in a spatial system, and vice versa. Furthermore, differences in growth rate, mortality or dispersal abilities allow a consumer to coexist stationarily with - or even outcompete - a competitor with lower resource requirements. Applying our theory to a phytoplankton model, we explain shifts in the community structure that are induced by environmental changes

Bose-Einstein condensation with magnetic dipole-dipole forces

Ground-state solutions in a dilute gas interacting via contact and magnetic dipole-dipole forces are investigated. To the best of our knowledge, it is the first example of studies of the Bose-Einstein condensation in a system with realistic long-range interactions. We find that for the magnetic moment of e.g. chromium and a typical value of the scattering length all solutions are stable and only differ in size from condensates without long-range interactions. By lowering the value of the scattering length we find a region of unstable solutions. In the neighborhood of this region the ground state wavefunctions show internal structures not seen before in condensates. Finally, we find an analytic estimate for the characteristic length appearing in these solutions.Comment: final version, 4 pages, 4 figure

Rab27a Contributes to the Processing of Inflammatory Pain in Mice

Tissue injury and inflammation may result in chronic pain, a severe debilitating disease that is associated with great impairment of quality of life. An increasing body of evidence indicates that members of the Rab family of small GTPases contribute to pain processing; however, their specific functions remain poorly understood. Here, we found using immunofluorescence staining and in situ hybridization that the small GTPase Rab27a is highly expressed in sensory neurons and in the superficial dorsal horn of the spinal cord of mice. Rab27a mutant mice, which carry a single-nucleotide missense mutation of Rab27a leading to the expression of a nonfunctional protein, show reduced mechanical hyperalgesia and spontaneous pain behavior in inflammatory pain models, while their responses to acute noxious mechanical and thermal stimuli is not affected. Our study uncovers a previously unrecognized function of Rab27a in the processing of persistent inflammatory pain in mice.publishersversionpublishe

Evaluating the RIST Molecular-Targeted Regimen in a Three-Dimensional Neuroblastoma Spheroid Cell Culture Model

Abstract Background: The outcome for patients with high-risk neuroblastoma remains poor and novel treatment strategies are urgently needed. The RIST protocol represents a novel metronomic and multimodal treatment strategy for high-risk neuroblastoma combining molecular-targeted drugs as ‘pre-treatment’ with a conventional chemotherapy backbone, currently evaluated in a phase II clinical trial. For preclinical drug testing, cancer cell growth as spheroid compared to mo-nolayer cultures is of advantage since it reproduces a wide range of tumor characteristics, including the three-dimensional architecture and cancer stem cell (CSC) properties. The objective of this study was to establish a neuroblastoma spheroid model for the rigorous assessment of the RIST treatment protocol. Methods: Evaluation of CSC marker expression was performed by mRNA and protein analysis and spheroid viability by luminescence-based assays. Aberrant expression of RNA-binding protein La in neuroblastoma was assessed by tissue microarray analysis and patients’ data mining. Results: Spheroid cultures showed increased expression of a subgroup of CSC-like markers (CXCR4, NANOG and BMI) and higher Thr389 phosphorylation of the neuroblastoma-associated RNA-binding protein La when compared to monolayer cultures. Molecular-targeted ‘pre-treatment’ of spheroids decreased neoplastic signaling and CSC marker expression. Conclusions: The RIST treatment protocol efficiently reduced the viability of neuroblastoma spheroids characterized by advanced CSC properties

Species richness, but not phylogenetic diversity, influences community biomass production and temporal stability in a re‐examination of 16 grassland biodiversity studies

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/111813/1/fec12432.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/111813/2/fec12432-sup-0002-Suppinfo.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/111813/3/fec12432-sup-0001-LaySummary.pd

Traits of neighbouring plants and space limitation determine intraspecific trait variability in semi-arid shrublands

Understanding how intraspecific trait variability (ITV) responds to both abiotic and biotic constraints is crucial to predict how individuals are assembled in plant communities, and how they will be impacted by ongoing global environmental change.Three key functional traits [plant height, leaf area (LA) and specific leaf area (SLA)] were assessed to quantify the range of ITV of four dominant plant species along a rainfall gradient in semi-arid Mediterranean shrublands. Variance partitioning and confirmatory multilevel path analyses were used to assess the direct and indirect effects of rainfall, space limitation (crowding) and neighbouring plant traits on ITV.The direct effect of the local neighbourhood on the trait values of subordinate individuals was as strong as the effect of rainfall. The indirect effect of rainfall, however, mediated by the effect of the local neighbourhood on the trait values of subordinate individuals, was weak. Rainfall decreased the height and SLA of subordinate individuals, but increased their LA. Neighbouring plant traits were just as strong predictors as crowding in explaining changes in ITV.Synthesis. Our study provides a framework to disentangle the direct effects of abiotic factors and their indirect effects on ITV mediated by the local neighbourhood. Our results highlight that abiotic and biotic constraints are both substantial sources of trait variations at the individual level, and can blur processes underlying changes in ITV. Considering and disentangling combined sources with an individual perspective would help to refine our predictions for community assembly and functional ecology

Environmental variation has stronger effects than plant genotype on competition among plant species

1.  Competition is a key factor affecting the performance and co-existence of species. Most ecological research on competition treats species’ populations as phenotypically homogenous. However, plant populations typically contain genetic variation for multiple traits and have the potential to rapidly adapt to changing environments. 2.  Recent theoretical and empirical research suggests that such variation and evolution may affect the ecological outcome of competitive interactions. We conducted a series of experiments to test the hypothesis whether genetic variation for competitive traits in a native plant ( Oenothera biennis ) affects the performance and diversity of competing plant species. 3.  In greenhouse and field experiments, the presence of O. biennis reduced the performance and diversity of neighbouring plant species. 4.  In greenhouse experiments, we detected heritable variation in O. biennis for above-ground and below-ground growth, and O. biennis varied genetically in response to competition, indicating the potential for adaptive evolution in response to selection by competitors. 5.  Variation among O. biennis genotypes also affected the performance of neighbouring plants in the greenhouse, whereby genetic variation in O. biennis shoot : root ratio explained up to 41% of the variation in the performance of an exotic grass ( Bromus inermis ). 6.  Despite effects of O. biennis genotype on B. inermis in the greenhouse, variable soil fertility had a much stronger effect on the grass's performance, and there were no effects of O. biennis genotype on neighbouring plants in the field. 7.  Synthesis . Our results show that interspecific competition affected the biomass and diversity of plants, but heritable variation in competitive ability of O. biennis is not expected to affect short-term ecological dynamics in this system. Nevertheless, O. biennis has the potential to influence co-existence over longer timescales by adapting to competitors.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/74631/1/j.1365-2745.2008.01410.x.pd