Background
Dengue is an arbovirosis affecting nearly 4 billion people worldwide. Since 2018, dengue has been re‐emerging in Reunion Island. The incidence of mucocutaneous manifestations varies ...according to the studies and is generally called ‘rash’.
Objectives
To assess the prevalence of different mucocutaneous symptoms and describe the characteristics of patients developing these symptoms and the clinical signs associated with severe dengue.
Methods
A prospective study was conducted in 2019 at the University Hospital of La Réunion, in patients presenting a positive PCR for dengue. Descriptive analyses were performed. All cases in the prospective study were examined by a dermatologist.
Results
A total of 163 cases were included. The prevalence of mucocutaneous signs was 80.4%. A pruritus was reported in 33.7% cases, an erythematous rash in 29.4% and a mouth involvement including lip, tongue, cheek, angular cheilitis, pharyngitis, mouth ulcer and gingivitis in 31.3%. Most of symptoms appeared in the first days, but some of them could disappear only after the 3rd week. Mucocutaneous signs were not associated with a severe dengue fever (p = 0.54), but ecchymotic purpura was (p = 0.037). In multivariate analysis, skin involvement was associated with flu‐like syndrome (headache, pharyngitis, rachis pain) and patient required rehydration but not invasive reanimation.
Conclusion
This work confirms the high prevalence of skin symptoms in dengue disease, but also their wide diversity. The mucocutaneous involvement of dengue fever appears to be accompanied by a pronounced flu‐like syndrome in people without severity, but careful examination to identify ecchymotic purpura or sign of dehydration in the mucous membranes would better identify cases that may worsen.
We consider parametric exponential families of dimension
K
on the real line. We study a variant of
boundary crossing probabilities
coming from the multi-armed bandit literature, in the case when the ...real-valued distributions form an exponential family of dimension
K
. Formally, our result is a concentration inequality that bounds the probability that
B
ψ
(
θ̂
n
,
θ
*) ≥
f
(
t
/
n
)/
n
, where
θ
* is the parameter of an unknown target distribution,
θ̂
n
is the empirical parameter estimate built from
n
observations,
ψ
is the log-partition function of the exponential family and
B
ψ
is the corresponding Bregman divergence. From the perspective of stochastic multi-armed bandits, we pay special attention to the case when the boundary function
f
is logarithmic, as it is enables to analyze the regret of the state-of-the-art KL-ucb and KL-ucb+ strategies, whose analysis was left open in such generality. Indeed, previous results only hold for the case when
K
= 1, while we provide results for arbitrary finite dimension
K
, thus considerably extending the existing results. Perhaps surprisingly, we highlight that the proof techniques to achieve these strong results already existed three decades ago in the work of T. L. Lai, and were apparently forgotten in the bandit community. We provide a modern rewriting of these beautiful techniques that we believe are useful beyond the application to stochastic multi-armed bandits.
Timing performance of a multi-pad PICOSEC-Micromegas detector prototype Aune, S.; Bortfeldt, J.; Brunbauer, F. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
03/2021, Letnik:
993, Številka:
C
Journal Article
Recenzirano
Odprti dostop
The multi-pad PICOSEC-Micromegas is an improved detector prototype with a segmented anode, consisting of 19 hexagonal pads. Detailed studies are performed with data collected in a muon beam over four ...representative pads. We demonstrate that such a device, scalable to a larger area, provides excellent time resolution and detection efficiency. As expected from earlier single-cell device studies, we measure a time resolution of approximately 25 picoseconds for charged particles hitting near the anode pad centres, and up to 30 picoseconds at the pad edges. Here, we study in detail the effect of drift gap thickness non-uniformity on the timing performance and evaluate impact position based corrections to obtain a uniform timing response over the full detector coverage.
The PICOSEC Micromegas detector can time the arrival of Minimum Ionizing Particles with a sub-25 ps precision. A very good timing resolution in detecting single photons is also demonstrated in laser ...beams. The PICOSEC timing resolution is determined mainly by the drift field. The arrival time of the signal and the timing resolution vary with the size of the pulse amplitude.
Detailed simulations based on GARFIELD++ reproduce the experimental PICOSEC timing characteristics. This agreement is exploited to identify the microscopic physical variables, which determine the observed timing properties. In these studies, several counter-intuitive observations are made for the behavior of such microscopic variables. In order to gain insight on the main physical mechanisms causing the observed behavior, a phenomenological model is constructed and presented. The model is based on a simple mechanism of “time-gain per interaction” and it employs a statistical description of the avalanche evolution. It describes quantitatively the dynamical and statistical properties of the microscopic quantities, which determine the PICOSEC timing characteristics, in excellent agreement with the simulations. In parallel, it offers phenomenological explanations for the behavior of these microscopic variables. The formulae expressing this model can be used as a tool for fast and reliable predictions, provided that the input parameter values (e.g. drift velocities) are known for the considered operating conditions.
•Dengue fever is an arbovirosis expanding worldwide and in Reunion Island, whose main treatment is oral hydration in primary care.•Oral hydration of Reunionese patients was higher than the ...recommendations of the World Health Organization.•Drinking at least 5 glasses of liquid in the previous 24 hours was significantly associated with fewer clinical warning signs (p = 0.044).•Adequate hydration could reduce the severity of dengue in primary care.
Dengue fever is an arbovirosis expanding worldwide, for which hydration has been reported to reduce the risk of hospitalization. Our objective was to estimate the volume of hydration in Reunionese patients with dengue.
A prospective observational study included patients presenting with a ‘dengue-like’ syndrome in ambulatory care. General practitioners recruited patients during consultation, and beverage consumption over the previous 24 hours was reported at two different times. Warning signs were defined according to the 2009 WHO guidelines.
GPs included 174 patients from April to July 2019. Average oral hydration volume was 1863 mL and 1944 mL, at the 1st and 2nd medical consultations, respectively. Water was the most wide consumed liquid. Drinking at least 5 glasses of liquid was significantly associated with fewer clinical warning signs at the 1st medical consultation (p = 0.044).
Sufficient hydration volume could prevent dengue warning signs. Further studies with standardized measurement of hydration would be needed.
This contribution describes the PICOSEC-Micromegas detector which achieves a time resolution below 25ps. In this device the passage of a charged particle produces Cherenkov photons in a radiator, ...which then generate electrons in a photocathode and these photoelectrons enter a two-stage Micromegas with a reduced drift region and a typical anode region. The results from single-channel prototypes (demonstrating a time resolution of 24ps for minimum ionizing particles, and 76ps for single photoelectrons), the understanding of the detector in terms of detailed simulations and a phenomenological model, the issues of robustness and how they are tackled, and preliminary results from a multi-channel prototype are presented (demonstrating that a timing resolution similar to that of the single-channel device is feasible for all points across the area covered by a multi-channel device).
The PICOSEC detection concept consists in a “two-stage” Micromegas detector coupled to a Cherenkov radiator and equipped with a photocathode. A proof of concept has already been tested: a ...single-photoelectron response of 76ps has been measured with a femtosecond UV laser at CEA/IRAMIS, while a time resolution of 24ps with a mean yield of 10.4 photoelectrons has been measured for 150GeV muons at the CERN SPS H4 secondary line. This work will present the main results of this prototype and the performance of the different detector configurations tested in 2016–2018 beam campaigns: readouts (bulk, resistive, multipad) and photocathodes (metallic+CsI, pure metallic, diamond). Finally, the prospects for building a demonstrator based on PICOSEC detection concept for future experiments will be discussed. In particular, the scaling strategies for a large area coverage with a multichannel readout plane, the R&D on solid converters for building a robust photocathode and the different resistive configurations for a robust readout.
Micromegas for beam loss monitoring Segui, L; Alves, H; Aune, S ...
Journal of physics. Conference series,
04/2020, Letnik:
1498, Številka:
1
Journal Article
Recenzirano
Odprti dostop
The early detection of beam losses and the alarm to the machine protection system in accelerators are crucial for the safe operation of the machine. In the low energy region of the hadron ...accelerators, only neutrons and photons are produced in the case of a beam loss. However, photons are also emitted by electrons at the RF cavities, becoming a natural background for losses identification. A new kind of beam loss monitors have been conceived to extend the sensitivity to the low energy region of the high intensity hadron accelerators. They are based on Micromegas detectors sensitive to fast neutrons. The appropriate configuration of the Micromegas operating conditions will allow a fast response, a sensitivity to small beam losses and a suppressed sensitivity to photons. In this paper the operation principle and the system developed for the European Spallation Source will be presented, with focus on the results obtained at different irradiation facilities. First time proof of operation in real conditions, with the detection of beam losses, will be also shown with measurements performed at LINAC4 (CERN).
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