13,746 research outputs found
Dynamic fitness landscapes: Expansions for small mutation rates
We study the evolution of asexual microorganisms with small mutation rate in
fluctuating environments, and develop techniques that allow us to expand the
formal solution of the evolution equations to first order in the mutation rate.
Our method can be applied to both discrete time and continuous time systems.
While the behavior of continuous time systems is dominated by the average
fitness landscape for small mutation rates, in discrete time systems it is
instead the geometric mean fitness that determines the system's properties. In
both cases, we find that in situations in which the arithmetic (resp.
geometric) mean of the fitness landscape is degenerate, regions in which the
fitness fluctuates around the mean value present a selective advantage over
regions in which the fitness stays at the mean. This effect is caused by the
vanishing genetic diffusion at low mutation rates. In the absence of strong
diffusion, a population can stay close to a fluctuating peak when the peak's
height is below average, and take advantage of the peak when its height is
above average.Comment: 19 pages Latex, elsart style, 4 eps figure
Detectors as a Function of Luminosity at e+ e- Machines
The performance of present multipurpose detectors at high luminosities is
discussed.Comment: 4 pages, 6 Figues, Latex, Invited talk at BCP
Gain Stablization of SiPMs
The gain of silicon photomultipliers (SiPMs) increases with bias voltage and
decreases with temperature. To operate SiPMs at stable gain, the bias voltage
can be adjusted to compensate temperature changes. We have tested this concept
with 30 SiPMs from three manufacturers (Hamamatsu, KETEK, CPTA) in a climate
chamber at CERN varying the temperature from to . We built an adaptive power supply that used a linear temperature dependence
of the bias voltage readjustment. With one selected bias voltage readjustment,
we stabilized four SiPMs simultaneously. We fulfilled our goal of limiting the
deviation from gain stability in the temperature
range to less than for most of the tested SiPMs. We have studied
afterpulsing of SiPMs for different temperatures and bias voltages.Comment: 20 pages, 18 figures, Talk presented at the APS Division of Particles
and Fields Meeting (DPF 2017), July 31-August 4, 2017, Fermilab. C17073
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