3,365 research outputs found
Limit theorems for discounted convergent perpetuities II
Let , be independent identically
distributed -valued random vectors. Assuming that has
zero mean and finite variance and imposing three distinct groups of assumptions
on the distribution of we prove three functional limit theorems for
the logarithm of convergent discounted perpetuities as . Also, we prove a law of
the iterated logarithm which corresponds to one of the aforementioned
functional limit theorems. The present paper continues a line of research
initiated in the paper Iksanov, Nikitin and Samoillenko (2022), which focused
on limit theorems for a different type of convergent discounted perpetuities.Comment: 23 page
Adaptation of NEMO-LIM3 model for multigrid high resolution Arctic simulation
High-resolution regional hindcasting of ocean and sea ice plays an important
role in the assessment of shipping and operational risks in the Arctic Ocean.
The ice-ocean model NEMO-LIM3 was modified to improve its simulation quality
for appropriate spatio-temporal resolutions. A multigrid model setup with
connected coarse- (14 km) and fine-resolution (5 km) model configurations was
devised. These two configurations were implemented and run separately. The
resulting computational cost was lower when compared to that of the built-in
AGRIF nesting system. Ice and tracer boundary-condition schemes were modified
to achieve the correct interaction between coarse- and fine grids through a
long ice-covered open boundary. An ice-restoring scheme was implemented to
reduce spin-up time. The NEMO-LIM3 configuration described in this article
provides more flexible and customisable tools for high-resolution regional
Arctic simulations
Complex partial synchronization patterns in networks of delay-coupled neurons
We study the spatio-temporal dynamics of a multiplex network of delay-coupled FitzHugh–Nagumo oscillators with non-local and fractal connectivities. Apart from chimera states, a new regime of coexistence of slow and fast oscillations is found. An analytical explanation for the emergence of such coexisting partial synchronization patterns is given. Furthermore, we propose a control scheme for the number of fast and slow neurons in each layer.DFG, 163436311, SFB 910: Kontrolle selbstorganisierender nichtlinearer Systeme: Theoretische Methoden und Anwendungskonzept
Injection locking in self-oscillating magnetometers
Injection locking (IL) is a well-known phenomenon that occurs in nonlinear oscillators subject to external periodic or non-periodic signals. It is a phenomenon of induced synchronization that occurs when an external (injection) signal locks the frequency of the oscillator to the frequency of the external signal. This form of synchronization is relatively straightforward to implement because it does not require specially organized feedback as is the case with phase locked loop. Circuits that exploit IL can have very simple designs and be applied to a broad range of applications, such as to synchronize frames and lines in early television sets, to synchronize lasers, and to function as ac voltmeters, field-intensity meters, amplifier-limiters and AM and FM detectors. However, the focus of this article is the recent application of IL to magnetic field sensors. This novel application highlights the potential benefits of the IL approach but also some of the complexities and opportunities for further development. As with all measurement systems, the consideration of noise is paramount in the design of magnetic sensors. Noise reduction and mitigation strategies are essential. IL can be employed as a noise mitigation strategy in magnetometers that utilize self-oscillations as part of their detection paradigm; it can stabilize the oscillation frequency, potentially simplifying the measurement circuitry, and in some circumstances improve the signal-to-noise ratio. Here we review some magnetometers that have successfully exploited IL principles and highlight design options. We also propose a new circuit that is simple to implement and more straightforward to analyze
Phase locking below rate threshold in noisy model neurons
The property of a neuron to phase-lock to an oscillatory stimulus before adapting its spike rate to the stimulus frequency plays an important role for the auditory system. We investigate under which conditions neurons exhibit this phase locking below rate threshold. To this end, we simulate neurons employing the widely used leaky integrate-and-fire (LIF) model. Tuning parameters, we can arrange either an irregular spontaneous or a tonic spiking mode. When the neuron is stimulated in both modes, a significant rise of vector strength prior to a noticeable change of the spike rate can be observed. Combining analytic reasoning with numerical simulations, we trace this observation back to a modulation of interspike intervals, which itself requires spikes to be only loosely coupled. We test the limits of this conception by simulating an LIF model with threshold fatigue, which generates pronounced anticorrelations between subsequent interspike intervals. In addition we evaluate the LIF response for harmonic stimuli of various frequencies and discuss the extension to more complex stimuli. It seems that phase locking below rate threshold occurs generically for all zero mean stimuli. Finally, we discuss our findings in the context of stimulus detection
Interaction between counter-propagating quantum Hall edge channels in the 3D topological insulator BiSbTeSe
The quantum Hall effect is studied in the topological insulator BiSbTeSe.
By employing top- and back-gate electric fields at high magnetic field, the
Landau levels of the Dirac cones in the top and bottom topological surface
states can be tuned independently. When one surface is tuned to the
electron-doped side of the Dirac cone and the other surface to the hole-doped
side, the quantum Hall edge channels are counter-propagating. The opposite edge
mode direction, combined with the opposite helicities of top and bottom
surfaces, allows for scattering between these counter-propagating edge modes.
The total Hall conductance is integer valued only when the scattering is
strong. For weaker interaction, a non-integer quantum Hall effect is expected
and measured
Paleo-Balkan and Slavic Contributions to the Genetic Pool of Moldavians
Moldova has a rich historical and cultural heritage, which may be reflected in the current genetic makeup of its population.
To date, no comprehensive studies exist about the population genetic structure of modern Moldavians. To bridge this gap
with respect to paternal lineages, we analyzed 37 binary and 17 multiallelic (STRs) polymorphisms on the non-recombining
portion of the Y chromosome in 125 Moldavian males. In addition, 53 Ukrainians from eastern Moldova and 54 Romanians
from the neighboring eastern Romania were typed using the same set of markers. In Moldavians, 19 Y chromosome
haplogroups were identified, the most common being I-M423 (20.8%), R-M17* (17.6%), R-M458 (12.8%), E-v13 (8.8%), RM269*
and R-M412* (both 7.2%). In Romanians, 14 haplogroups were found including I-M423 (40.7%), R-M17* (16.7%), RM405
(7.4%), E-v13 and R-M412* (both 5.6%). In Ukrainians, 13 haplogroups were identified including R-M17 (34.0%), I-M423
(20.8%), R-M269* (9.4%), N-M178, R-M458 and R-M73 (each 5.7%). Our results show that a significant majority of the
Moldavian paternal gene pool belongs to eastern/central European and Balkan/eastern Mediterranean Y lineages.
Phylogenetic and AMOVA analyses based on Y-STR loci also revealed that Moldavians are close to both eastern/central
European and Balkan-Carpathian populations. The data correlate well with historical accounts and geographical location of
the region and thus allow to hypothesize that extant Moldavian paternal genetic lineages arose from extensive recent
admixture between genetically autochthonous populations of the Balkan-Carpathian zone and neighboring Slavic group
Enhanced processing in arrays of optimally tuned nonlinear biomimetic sensors : a coupling-mediated Ringelmann effect and its dynamical mitigation
Inspired by recent results on self-tunability in the outer hair cells of the mammalian cochlea, we describe an array of magnetic sensors where each individual sensor can self-tune to an optimal operating regime. The self-tuning gives the array its “biomimetic” features. We show that the overall performance of the array can, as expected, be improved by increasing the number of sensors but, however, coupling between sensors reduces the overall performance even though the individual sensors in the system could see an improvement. We quantify the similarity of this phenomenon to the Ringelmann effect that was formulated 103 years ago to account for productivity losses in human and animal groups. We propose a global feedback scheme that can be used to greatly mitigate the performance degradation that would, normally, stem from the Ringelmann effect
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