1,317 research outputs found
Mutation supply and the repeatability of selection for antibiotic resistance
Whether evolution can be predicted is a key question in evolutionary biology.
Here we set out to better understand the repeatability of evolution. We
explored experimentally the effect of mutation supply and the strength of
selective pressure on the repeatability of selection from standing genetic
variation. Different sizes of mutant libraries of an antibiotic resistance
gene, TEM-1 -lactamase in Escherichia coli, were subjected to different
antibiotic concentrations. We determined whether populations went extinct or
survived, and sequenced the TEM gene of the surviving populations. The
distribution of mutations per allele in our mutant libraries- generated by
error-prone PCR- followed a Poisson distribution. Extinction patterns could be
explained by a simple stochastic model that assumed the sampling of beneficial
mutations was key for survival. In most surviving populations, alleles
containing at least one known large-effect beneficial mutation were present.
These genotype data also support a model which only invokes sampling effects to
describe the occurrence of alleles containing large-effect driver mutations.
Hence, evolution is largely predictable given cursory knowledge of mutational
fitness effects, the mutation rate and population size. There were no clear
trends in the repeatability of selected mutants when we considered all
mutations present. However, when only known large-effect mutations were
considered, the outcome of selection is less repeatable for large libraries, in
contrast to expectations. Furthermore, we show experimentally that alleles
carrying multiple mutations selected from large libraries confer higher
resistance levels relative to alleles with only a known large-effect mutation,
suggesting that the scarcity of high-resistance alleles carrying multiple
mutations may contribute to the decrease in repeatability at large library
sizes.Comment: 31pages, 9 figure
LOAD EFFECTS OF FAST LONGITUDINAL ROTATIONS
Pirouettes, jumps in figure skating and twisting somersaults are fascinating movements in sports. But there is a lack of investigations in the field of motor control and load effects of fast longitudinal rotations. The purpose of the present study was to analyze load effects during and after longitudinal rotations. A "Longitudinal Rotation Simulator", posturography, and video nystagmography were used to analyze the rotational load. Six gymnasts, eleven figure skaters, and nineteen non-athletes were investigated. There were significant differences in the postural control between gymnasts and non-athletes. Per-rotatory nystagmus amplitude was significantly lower after three rotations than after ten rotations. The posturography and the video nystagmography are valid methods to characterize the rotational load
Spiral Growth and Step Edge Barriers
The growth of spiral mounds containing a screw dislocation is compared to the
growth of wedding cakes by two-dimensional nucleation. Using phase field
simulations and homoepitaxial growth experiments on the Pt(111) surface we show
that both structures attain the same characteristic large scale shape when a
significant step edge barrier suppresses interlayer transport. The higher
vertical growth rate observed for the spiral mounds on Pt(111) reflects the
different incorporation mechanisms for atoms in the top region and can be
formally represented by an enhanced apparent step edge barrier.Comment: 11 pages, 4 figures, partly in colo
Towards Digital Twin-enabled DevOps for CPS providing Architecture-Based Service Adaptation & Verification at Runtime
Industrial Product-Service Systems (IPSS) denote a service-oriented (SO) way
of providing access to CPS capabilities. The design of such systems bears high
risk due to uncertainty in requirements related to service function and
behavior, operation environments, and evolving customer needs. Such risks and
uncertainties are well known in the IT sector, where DevOps principles ensure
continuous system improvement through reliable and frequent delivery processes.
A modular and SO system architecture complements these processes to facilitate
IT system adaptation and evolution. This work proposes a method to use and
extend the Digital Twins (DTs) of IPSS assets for enabling the continuous
optimization of CPS service delivery and the latter's adaptation to changing
needs and environments. This reduces uncertainty during design and operations
by assuring IPSS integrity and availability, especially for design and service
adaptations at CPS runtime. The method builds on transferring IT DevOps
principles to DT-enabled CPS IPSS. The chosen design approach integrates,
reuses, and aligns the DT processing and communication resources with DevOps
requirements derived from literature. We use these requirements to propose a
DT-enabled self-adaptive CPS model, which guides the realization of DT-enabled
DevOps in CPS IPSS. We further propose detailed design models for
operation-critical DTs that integrate CPS closed-loop control and
architecture-based CPS adaptation. This integrated approach enables the
implementation of A/B testing as a use case and central concept to enable CPS
IPSS service adaptation and reconfiguration. The self-adaptive CPS model and DT
design concept have been validated in an evaluation environment for
operation-critical CPS IPSS. The demonstrator achieved sub-millisecond cycle
times during service A/B testing at runtime without causing CPS operation
interferences and downtime.Comment: Final published version appearing in 17th Symposium on Software
Engineering for Adaptive and Self-Managing Systems (SEAMS 2022
Options for accounting carbon sequestration in German forests
<p>Abstract</p> <p>Background</p> <p>The Accra climate change talks held from 21–27 August 2008 in Accra, Ghana, were part of an ongoing series of meetings leading up to the Copenhagen meeting in December 2009. During the meeting a set of options for accounting carbon sequestration in forestry on a post-2012 framework was presented. The options include gross-net and net-net accounting and approaches for establishing baselines.</p> <p>Results</p> <p>This article demonstrates the embedded consequences of Accra Accounting Options for the case study of German national GHG accounting. It presents the most current assessment of sequestration rates by forest management for the period 1990 – 2007, provides an outlook of future emissions and removals (up to the year 2042) as related to three different management scenarios, and shows that implementation of some Accra options may reverse sources to sinks, or sinks to sources.</p> <p>Conclusion</p> <p>The results of the study highlight the importance of elaborating an accounting system that would prioritize the climate convention goals, not national preferences.</p
Erratum to: Metal artifact suppression at the hip: diagnostic performance at 3.0Â T versus 1.5 Tesla
Magnetron sputtering fabrication of α-Al2O3:Cr powders and their T thermoluminescence properties
The authors gratefully acknowledge the financial support for this work from research grant ERA.NET RUS Plus Nr.609556.For many years doped α-Al2O3 has attracted interest as a dosimeter for personal, environment monitoring and food control. The alumina single crystal growth is a difficult process; however, materials in form of powders, ceramics and coating are possible to obtain. In this study for the first time Cr doped α-Al2O3 powders were prepared by DC reactive magnetron sputtering followed by milling and oxidation. The morphology and phase analysis was performed; content of residual impurities was determined and thermostimulated glow curves were measured after different x-ray irradiation times (radiation doses). The prepared powder shows the dosimetry properties up to 20 kGy dose.ERA.NET RUS Plus Nr.609556; Institute of Solid State Physics, University of Latvia as the Center of Excellence has received funding from the European Union’s Horizon 2020 Framework Programme H2020-WIDESPREAD-01-2016-2017-TeamingPhase2 under grant agreement No. 739508, project CAMART
Nonequilibrium wetting of finite samples
As a canonical model for wetting far from thermal equilibrium we study a
Kardar-Parisi-Zhang interface growing on top of a hard-core substrate.
Depending on the average growth velocity the model exhibits a non-equilibrium
wetting transition which is characterized by an additional surface critical
exponent theta. Simulating the single-step model in one spatial dimension we
provide accurate numerical estimates for theta and investigate the distribution
of contact points between the substrate and the interface as a function of
time. Moreover, we study the influence of finite-size effects, in particular
the time needed until a finite substrate is completely covered by the wetting
layer for the first time.Comment: 17 pages, 8 figures, revisio
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