356 research outputs found
How can a 22-pole ion trap exhibit 10 local minima in the effective potential?
The column density distribution of trapped OH ions in a 22-pole ion trap
is measured for different trap parameters. The density is obtained from
position-dependent photodetachment rate measurements. Overall, agreement is
found with the effective potential of an ideal 22-pole. However, in addition we
observe 10 distinct minima in the trapping potential, which indicate a breaking
of the 22-fold symmetry. Numerical simulations show that a displacement of a
subset of the radiofrequency electrodes can serve as an explanation for this
symmetry breaking
Aggregation of log-linear risks
In this paper we work in the framework of a k-dimensional vector of log-linear risks. Under weak conditions on the marginal tails and the dependence structure of a vector of positive risks, we derive the asymptotic tail behaviour of the aggregated risk and present an application concerning log-normal risks with stochastic volatility
Formation of ultracold LiCs molecules
We present the first observation of ultracold LiCs molecules. The molecules
are formed in a two-species magneto-optical trap and detected by two-photon
ionization and time-of-flight mass spectrometry. The production rate
coefficient is found to be in the range 10^{-18}\unit{cm^3s^{-1}} to
10^{-16}\unit{cm^3s^{-1}}, at least an order of magnitude smaller than for
other heteronuclear diatomic molecules directly formed in a magneto-optical
trap.Comment: 8 pages, 2 figure
The Visibility Graph: a new method for estimating the Hurst exponent of fractional Brownian motion
Fractional Brownian motion (fBm) has been used as a theoretical framework to
study real time series appearing in diverse scientific fields. Because its
intrinsic non-stationarity and long range dependence, its characterization via
the Hurst parameter H requires sophisticated techniques that often yield
ambiguous results. In this work we show that fBm series map into a scale free
visibility graph whose degree distribution is a function of H. Concretely, it
is shown that the exponent of the power law degree distribution depends
linearly on H. This also applies to fractional Gaussian noises (fGn) and
generic f^(-b) noises. Taking advantage of these facts, we propose a brand new
methodology to quantify long range dependence in these series. Its reliability
is confirmed with extensive numerical simulations and analytical developments.
Finally, we illustrate this method quantifying the persistent behavior of human
gait dynamics.Comment: 5 pages, submitted for publicatio
Bedeutung der radiolytischen Selbstzersetzung von Uranhexafluorid bei der Anreicherung von Uran-235 nach dem Trennduesenverfahren
Asymptotic normality of quadratic forms of martingale differences
We establish the asymptotic normality of a quadratic form QnQn in martingale difference random variables ηtηt when the weight matrix A of the quadratic form has an asymptotically vanishing diagonal. Such a result has numerous potential applications in time series analysis. While for i.i.d. random variables ηtηt, asymptotic normality holds under condition ||A||sp=o(||A||)||A||sp=o(||A||), where ||A||sp||A||sp and ||A|| are the spectral and Euclidean norms of the matrix A, respectively, finding corresponding sufficient conditions in the case of martingale differences ηtηt has been an important open problem. We provide such sufficient conditions in this paper
A planar multipole ion trap
We report on the realisation of a chip-based multipole ion trap manufactured
using micro-electromechanical systems (MEMS) technology. It provides ion
confinement in an almost field-free volume between two planes of radiofrequency
electrodes, deposited on glass substrates, which allows for optical access to
the trap. An analytical model of the effective trapping potential is presented
and compared with numerical calculations. Stable trapping of argon ions is
achieved and a lifetime of 16s is measured. Electrostatic charging of the chip
surfaces is studied and found to agree with a numerical estimate
Gaucher Disease in Bone: From Pathophysiology to Practice
Gaucher disease (GD) is a rare, genetic lysosomal disorder leading to lipid accumulation and dysfunction in multiple organs. Involvement of the skeleton is one of the most prevalent aspects of GD and a major cause of pain, disability, and reduced quality of life. Uniform recommendations for contemporary evaluation and management are needed. To develop practical clinical recommendations, an international group of experienced physicians conducted a comprehensive review of 20 years' of the literature, defining terms according to pathophysiological understanding and pointing out best practice and unmet needs related to the skeletal features of this disorder. Abnormalities of bone modeling, reduced bone density, bone infarction, and plasma cell dyscrasias accompany the displacement of healthy adipocytes in adult marrow. Exposure to excess bioactive glycosphingolipids appears to affect hematopoiesis and the balance of osteoblast and osteoclast numbers and activity. Imbalance between bone formation and breakdown induces disordered trabecular and cortical bone modeling, cortical bone thinning, fragility fractures, and osteolytic lesions. Regular assessment of bone mineral density, marrow infiltration, the axial skeleton and searching for potential malignancy are recommended. MRI is valuable for monitoring skeletal involvement: It provides semiquantitative assessment of marrow infiltration and the degree of bone infarction. When MRI is not available, monitoring of painful acute bone crises and osteonecrosis by plain X-ray has limited value. In adult patients, we recommend DXA of the lumbar spine and left and right hips, with careful protocols designed to exclude focal disease; serial follow-up should be done using the same standardized instrument. Skeletal health may be improved by common measures, including adequate calcium and vitamin D and management of pain and orthopedic complications. Prompt initiation of specific therapy for GD is crucial to optimizing outcomes and preventing irreversible skeletal complications. Investing in safe, clinically useful, and better predictive methods for determining bone integrity and fracture risk remains a need. © 2019 The Authors. Journal of Bone and Mineral Research Published by Wiley Periodicals Inc
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