909 research outputs found
Kongenitale Nävi im Kindesalter
Zusammenfassung: Nävi stellen kongenitale hamartomatöse Fehlbildungen unterschiedlicher Bestandteile der Haut dar. Am häufigsten treten kongenitale melanozytäre Nävi (CMN) auf, gefolgt von Nävi epithelialen Ursprungs (epidermale und organoide Nävi). Insbesondere große CMN können zu schwerwiegenden Komplikationen führen, und das Management der Betroffenen stellt ab Geburt eine Herausforderung dar. Entgegen früheren Annahmen ist das Risiko einer malignen Entartung von CMN insgesamt als eher gering anzusehen, steigt jedoch in speziellen Situationen relevant an. Nicht zu vernachlässigen sind mögliche extrakutane Symptome im Falle einer ZNS-Beteiligung, und frühe bildgebende Untersuchungen gehören heute zur Routinediagnostik. Chirurgische Maßnahmen haben noch immer einen hohen Stellenwert in der Behandlung von CMN, die Indikation dazu ist jedoch von Fall zu Fall individuell abzuwägen. Nicht zuletzt leiden die Patienten häufig stark an der ästhetischen Beeinträchtigung durch ihr Muttermal, sodass in der Behandlung auch diesem Punkt Rechnung getragen werden muss. Der Naevus sebaceus ist der häufigste Vertreter der epithelialen Nävi. In 2-13% treten darin Zusatztumoren auf, und eine frühe chirurgische Exzision ist in den meisten Fällen nicht zuletzt auch aus ästhetischen Überlegungen sinnvoll. Epidermale Nävi erfordern bei generalisierter Ausdehnung Zusatzuntersuchungen zum Ausschluss von assoziierten ophthalmologischen, kardialen oder neurologischen Fehlbildunge
Detecting periodicity in experimental data using linear modeling techniques
Fourier spectral estimates and, to a lesser extent, the autocorrelation
function are the primary tools to detect periodicities in experimental data in
the physical and biological sciences. We propose a new method which is more
reliable than traditional techniques, and is able to make clear identification
of periodic behavior when traditional techniques do not. This technique is
based on an information theoretic reduction of linear (autoregressive) models
so that only the essential features of an autoregressive model are retained.
These models we call reduced autoregressive models (RARM). The essential
features of reduced autoregressive models include any periodicity present in
the data. We provide theoretical and numerical evidence from both experimental
and artificial data, to demonstrate that this technique will reliably detect
periodicities if and only if they are present in the data. There are strong
information theoretic arguments to support the statement that RARM detects
periodicities if they are present. Surrogate data techniques are used to ensure
the converse. Furthermore, our calculations demonstrate that RARM is more
robust, more accurate, and more sensitive, than traditional spectral
techniques.Comment: 10 pages (revtex) and 6 figures. To appear in Phys Rev E. Modified
styl
Test your surrogate data before you test for nonlinearity
The schemes for the generation of surrogate data in order to test the null
hypothesis of linear stochastic process undergoing nonlinear static transform
are investigated as to their consistency in representing the null hypothesis.
In particular, we pinpoint some important caveats of the prominent algorithm of
amplitude adjusted Fourier transform surrogates (AAFT) and compare it to the
iterated AAFT (IAAFT), which is more consistent in representing the null
hypothesis. It turns out that in many applications with real data the
inferences of nonlinearity after marginal rejection of the null hypothesis were
premature and have to be re-investigated taken into account the inaccuracies in
the AAFT algorithm, mainly concerning the mismatching of the linear
correlations. In order to deal with such inaccuracies we propose the use of
linear together with nonlinear polynomials as discriminating statistics. The
application of this setup to some well-known real data sets cautions against
the use of the AAFT algorithm.Comment: 14 pages, 15 figures, submitted to Physical Review
National survey in Switzerland calls for improved diagnosis and treatment in children with scabies
AIM OF THE STUDY: The global prevalence of scabies is estimated to be up to 200 million cases annually, with young children particularly affected. In Europe, most cases are thought to originate in migrant populations. Scabies management is challenging in children. To identify knowledge gaps and research needs, we aimed to descriptively evaluate the management of children with scabies by different Swiss healthcare providers.
METHODS: An invitation for an anonymous online survey (36 questions) was sent to members of Swiss societies of dermatologists, general practitioners, paediatricians, paediatric dermatologists, paediatric infectious diseases specialists, and tropical medicine specialists, inviting clinicians to participate from 25th May to 8th August 2020. One reminder invitation was sent. Hospital pharmacies and the distributor of permethrin were contacted to report consumption trends of scabicides in 2018 and 2019.
RESULTS: The survey was completed by 248 clinicians: 146 (59%) paediatricians, 47 (19%) dermatologists, 28 (11%) general practitioners, 6 (2%) paediatric dermatologists, 13 (5%) paediatric infectious diseases specialists, and 8 (3%) tropical medicine specialists. Most consulted up to 10 scabies cases within a 16-month period, with similar numbers in migrant and Swiss children. Dermoscopy was used by 24% of non-dermatologists. Non-dermatologists did not consider co-treatment of close contacts in up to 59% of cases. While permethrin was the first-line treatment, treatment failures were frequently reported in children aged <5 years. Up to 67% of paediatric dermatologists regularly used oral ivermectin off-label in children weighing <15 kg. None of the paediatric dermatologists, 15% of the dermatologists, and 9% of the non-dermatologists used only one treatment cycle.Scabicide consumption increased. Treatment studies on ivermectin use in children weighing <15 kg had the highest research priority.
CONCLUSION: In Switzerland, scabies is a frequent dermatosis in migrant and Swiss children. While accessible, optimal diagnostics are underutilised, and treatment is suboptimal. Permethrin resistance appears to be an increasing problem. Dermatologists regularly use ivermectin off-label in children weighing <15 kg. Treatment studies on ivermectin use in children weighing <15 kg, user-friendly diagnostic tools, new treatment protocols, and child-friendly dosage forms are needed to improve the diagnosis and treatment of children with scabies
A Robust Method for Detecting Interdependences: Application to Intracranially Recorded EEG
We present a measure for characterizing statistical relationships between two
time sequences. In contrast to commonly used measures like cross-correlations,
coherence and mutual information, the proposed measure is non-symmetric and
provides information about the direction of interdependence. It is closely
related to recent attempts to detect generalized synchronization. However, we
do not assume a strict functional relationship between the two time sequences
and try to define the measure so as to be robust against noise, and to detect
also weak interdependences. We apply our measure to intracranially recorded
electroencephalograms of patients suffering from severe epilepsies.Comment: 29 pages, 5 figures, paper accepted for publication in Physica
Magnitude and Sign Correlations in Heartbeat Fluctuations
We propose an approach for analyzing signals with long-range correlations by
decomposing the signal increment series into magnitude and sign series and
analyzing their scaling properties. We show that signals with identical
long-range correlations can exhibit different time organization for the
magnitude and sign. We find that the magnitude series relates to the nonlinear
properties of the original time series, while the sign series relates to the
linear properties. We apply our approach to the heartbeat interval series and
find that the magnitude series is long-range correlated, while the sign series
is anticorrelated and that both magnitude and sign series may have clinical
applications.Comment: 4 pages,late
Predicting the Detectability of Thin Gaseous Plumes in Hyperspectral Images Using Basis Vectors
This paper describes a new method for predicting the detectability of thin gaseous plumes in hyperspectral images. The novelty of this method is the use of basis vectors for each of the spectral channels of a collection instrument to calculate noise-equivalent concentration-pathlengths instead of matching scene pixels to absorbance spectra of gases in a library. This method provides insight into regions of the spectrum where gas detection will be relatively easier or harder, as influenced by ground emissivity, temperature contrast, and the atmosphere. Our results show that data collection planning could be influenced by information about when potential plumes are likely to be over background segments that are most conducive to detection
The Necessity for a Time Local Dimension in Systems with Time Varying Attractors
We show that a simple non-linear system of ordinary differential equations
may possess a time varying attractor dimension. This indicates that it is
infeasible to characterize EEG and MEG time series with a single time global
dimension. We suggest another measure for the description of non-stationary
attractors.Comment: 13 Postscript pages, 12 Postscript figures (figures 3b and 4 by
request from Y. Ashkenazy: [email protected]
Statistics of finite-time Lyapunov exponents in the Ulam map
The statistical properties of finite-time Lyapunov exponents at the Ulam
point of the logistic map are investigated. The exact analytical expression for
the autocorrelation function of one-step Lyapunov exponents is obtained,
allowing the calculation of the variance of exponents computed over time
intervals of length . The variance anomalously decays as . The
probability density of finite-time exponents noticeably deviates from the
Gaussian shape, decaying with exponential tails and presenting spikes
that narrow and accumulate close to the mean value with increasing . The
asymptotic expression for this probability distribution function is derived. It
provides an adequate smooth approximation to describe numerical histograms
built for not too small , where the finiteness of bin size trimmes the sharp
peaks.Comment: 6 pages, 4 figures, to appear in Phys. Rev.
Critical and Near-Critical Branching Processes
Scale-free dynamics in physical and biological systems can arise from a
variety of causes. Here, we explore a branching process which leads to such
dynamics. We find conditions for the appearance of power laws and study
quantitatively what happens to these power laws when such conditions are
violated. From a branching process model, we predict the behavior of two
systems which seem to exhibit near scale-free behavior--rank-frequency
distributions of number of subtaxa in biology, and abundance distributions of
genotypes in an artificial life system. In the light of these, we discuss
distributions of avalanche sizes in the Bak-Tang-Wiesenfeld sandpile model.Comment: 9 pages LaTex with 10 PS figures. v.1 of this paper contains results
from non-critical sandpile simulations that were excised from the published
versio
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