500 research outputs found
Determining the size of the proton
A measurement of the Lamb shift of 49,881.88(76) GHz in muonic hydrogen in
conjunction with theoretical estimates of the proton structure effects was
recently used to deduce an accurate but rather small radius of the proton. Such
an important shift in the understanding of fundamental values needs
reconfirmation. Using a different approach with electromagnetic form factors of
the proton, we obtain a new expression for the transition energy, , in muonic hydrogen and deduce
a proton radius, fm.Comment: 20 pages LaTe
Chaotic dynamics and fractal structures in experiments with cold atoms
We use tools from nonlinear dynamics to the detailed analysis of cold atom
experiments. A powerful example is provided by the recent concept of basin
entropy which allows to quantify the final state unpredictability that results
from the complexity of the phase space geometry. We show here that this enables
one to reliably infer the presence of fractal structures in phase space from
direct measurements. We illustrate the method with numerical simulations in an
experimental configuration made of two crossing laser guides that can be used
as a matter wave splitter
Using the basin entropy to explore bifurcations
Bifurcation theory is the usual analytic approach to study the parameter
space of a dynamical system. Despite the great power of prediction of these
techniques, fundamental limitations appear during the study of a given problem.
Nonlinear dynamical systems often hide their secrets and the ultimate resource
is the numerical simulations of the equations. This paper presents a method to
explore bifurcations by using the basin entropy. This measure of the
unpredictability can detect transformations of phase space structures as a
parameter evolves. We present several examples where the bifurcations in the
parameter space have a quantitative effect on the basin entropy. Moreover, some
transformations, such as the basin boundary metamorphoses, can be identified
with the basin entropy but are not reflected in the bifurcation diagram. The
correct interpretation of the basin entropy plotted as a parameter extends the
numerical exploration of dynamical systems
Data-driven estimation of the instantaneous reproduction number and growth rates for the 2022 monkeypox outbreak in Europe
Objective: To estimate the instantaneous reproduction number and the epidemic growth rates for the 2022 monkeypox outbreaks in the European region.
Methods: We gathered daily laboratory-confirmed monkeypox cases in the most affected European countries from the beginning of the outbreak to September 23, 2022. A data-driven estimation of the instantaneous reproduction number is obtained using a novel filtering type Bayesian inference. A phenomenological growth model coupled with a Bayesian sequential approach to update forecasts over time is used to obtain time-dependent growth rates in several countries.
Results: The instantaneous reproduction number for the laboratory-confirmed monkeypox cases in Spain, France, Germany, the UK, the Netherlands, Portugal, and Italy. At the early phase of the outbreak, our estimation for , which can be used as a proxy for the basic reproduction number , was ( CI ) for Spain, ( CI ) for France, ( CI ) for Germany, ( CI ) for the UK, ( CI ) for the Netherlands, ( CI ) for Portugal, ( CI ) for Italy. Cumulative cases for these countries present subexponential rather than exponential growth dynamics.
Conclusions: Our findings suggest that the current monkeypox outbreaks present limited transmission chains of human-to-human secondary infection so the possibility of a huge pandemic is very low. Confirmed monkeypox cases are decreasing significantly in the European region, the decline might be attributed to public health interventions and behavioral changes in the population due to increased risk perception. Nevertheless, further strategies toward elimination are essential to avoid the subsequent evolution of the monkeypox virus that can result in new outbreaks.Non
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Intermediate progenitors support migration of neural stem cells into dentate gyrus outer neurogenic niches.
The hippocampal dentate gyrus (DG) is a unique brain region maintaining neural stem cells (NCSs) and neurogenesis into adulthood. We used multiphoton imaging to visualize genetically defined progenitor subpopulations in live slices across key stages of mouse DG development, testing decades old static models of DG formation with molecular identification, genetic-lineage tracing, and mutant analyses. We found novel progenitor migrations, timings, dynamic cell-cell interactions, signaling activities, and routes underlie mosaic DG formation. Intermediate progenitors (IPs, Tbr2+) pioneered migrations, supporting and guiding later emigrating NSCs (Sox9+) through multiple transient zones prior to converging at the nascent outer adult niche in a dynamic settling process, generating all prenatal and postnatal granule neurons in defined spatiotemporal order. IPs (Dll1+) extensively targeted contacts to mitotic NSCs (Notch active), revealing a substrate for cell-cell contact support during migrations, a developmental feature maintained in adults. Mouse DG formation shares conserved features of human neocortical expansion
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