Phenotypic Diversity as a Mechanism to Exit Cellular Dormancy

SummaryMicroorganisms can facilitate their survival in stressful environments by entering a state of metabolic inactivity or dormancy [1]. However, this state impairs the function of the very sensory systems necessary to detect favorable growth conditions. Thus, how can a metabolically quiescent cell accurately monitor environmental conditions in order to best decide when to exit dormancy? One strategy employed by microbes to deal with changing environments is the generation of phenotypes that may be less well adapted to a current condition but might confer an advantage in the future [2, 3]. This bet-hedging depends on phenotypic diversity in the population [4], which itself can derive from naturally occurring stochastic differences in gene expression [5, 6]. In the case of metabolic dormancy, a bet-hedging strategy that has been proposed is the “scout model” where cells comprising a fraction of the dormant population reinitiate growth stochastically, independent of environmental cues [7, 8]. Here, we provide experimental evidence that such a mechanism exists in dormant spores produced by the ubiquitous soil bacterium Bacillus subtilis. We observe that these spores reinitiate growth at a low but measureable frequency even in the absence of an inducing signal. This phenomenon is the result of phenotypic variation in the propensity of individual spores to reinitiate growth spontaneously. Since this bet-hedging mechanism produces individuals that will either grow under favorable conditions or die under unfavorable conditions, a population can properly respond to environmental changes despite the impaired sensory ability of individual cells

Epidemiology and Etiology of Young Stroke

Introduction. Stroke in people under 45 years of age is less frequent than in older populations but has a major impact on the individual and society. In this article we provide an overview of the epidemiology and etiology of young stroke. Methods. This paper is based on a review of population-based studies on stroke incidence that have included subgroup analyses for patients under 45 years of age, as well as smaller community-based studies and case-series specifically examining the incidence of stroke in the young. Trends are discussed along with the relative frequencies of various etiologies. Discussion. Stroke in the young requires a different approach to investigation and management than stroke in the elderly given differences in the relative frequencies of possible underlying causes. It remains the case, however, that atherosclerosis contributes to a large proportion of stroke in young patients, thus, conventional risk factors must be targeted aggressively

Ground state topology of a four-terminal superconducting double quantum dot

In recent years, various classes of systems were proposed to realize topological states of matter. One of them are multiterminal Josephson junctions where topological Andreev bound states are constructed in the synthetic space of superconducting phases. Crucially, the topology in these systems results in a quantized transconductance between two of its terminals comparable to the quantum Hall effect. In this work, we study a double quantum dot with four superconducting terminals and show that it has an experimentally accessible topological regime in which the non-trivial topology can be measured. We also include Coulomb repulsion between electrons which is usually present in experiments and show how the topological region can be maximized in parameter space.Comment: 18 pages, 9 figures, submitted to SciPost Physic

Microwave plasma-assisted reactive HiPIMS of InN films: Plasma environment and material characterisation

This work focuses on the low temperature fabrication process of InN thin films via microwave plasma-assisted reactive high power impulse magnetron sputtering (MAR-HiPIMS). The influence of microwave plasma on the HiPIMS discharge process at various nitrogen flows and microwave powers was monitored and characterised through in situ diagnostics, including following HiPIMS I(V,t) curves, optical emission spectroscopy (OES), as well as performing time-resolved Langmuir probe and time-of-flight mass spectroscopy (ToF-MS) measurements. This was followed by the deposition of InN films via standard reactive HiPIMS (reference sample) and MAR-HiPIMS and their characterisation via X-ray diffraction (XRD), reflectometry (XRR), as well as scanning and transmission electron microscopy (SEM, TEM). It was found that the microwave plasma facilitates the dissociation/activation of nitrogen species and supplies seed electrons to the magnetron discharge plasma. Furthermore, the energy of the incoming ions was determined via ToF-MS, and it was possible to identify their plasma origin and temporal behaviour. The produced R-HiPIMS sample was highly metallic, with no nitride phase detected. The MAR-HiPMS film, however, was stoichiometric and exhibited (0002) direction texturing, with an optical bandgap of approx. 1.5 eV, electron concentration of 2.72 × 1020 cm−3 and electron mobility of 7.16 cm2V−1 s−1 (in the range for polycrystalline InN)