Clinical description and outcome of overall varicella-zoster virus-related organ dysfunctions admitted in intensive care units: the VAZOREA cohort study.

BACKGROUND: Due to aging population and increasing part of immunocompromised patients, a raise in life-threatening organ damage related to VZV can be expected. Two retrospective studies were already conducted on VZV in ICU but focused on specific organ injury. Patients with high-risk of VZV disease still must be identified. The objective of this study was to report the clinical features and outcome of all life-threatening VZV manifestations requiring intensive care unit (ICU) admission. This retrospective cohort study was conducted in 26 French ICUs and included all adult patients with any life-threatening VZV-related event requiring ICU admission or occurring in ICU between 2010 and 2019. RESULTS: One-hundred nineteen patients were included with a median SOFA score of 6. One hundred eight patients (90.8%) were admitted in ICU for VZV disease, leaving 11 (9.2%) with VZV disease occurring in ICU. Sixty-one patients (51.3%) were immunocompromised. Encephalitis was the most prominent organ involvement (55.5%), followed by pneumonia (44.5%) and hepatitis (9.2%). Fifty-four patients (45.4%) received norepinephrine, 72 (60.5% of the total cohort) needed invasive mechanical ventilation, and 31 (26.3%) received renal-replacement therapy. In-hospital mortality was 36.1% and was significantly associated with three independent risk factors by multivariable logistic regression: immunosuppression, VZV disease occurring in ICU and alcohol abuse. Hierarchical clustering on principal components revealed five phenotypically distinct clusters of patients: VZV-related pneumonia, mild encephalitis, severe encephalitis in solid organ transplant recipients, encephalitis in other immunocompromised hosts and VZV disease occurring in ICU. In-hospital mortality was highly different across phenotypes, ranging from zero to 75% (p < 0.001). CONCLUSION: Overall, severe VZV manifestations are associated with high mortality in the ICU, which appears to be driven by immunosuppression status rather than any specific organ involvement. Deciphering the clinical phenotypes may help clinicians identify high-risk patients and assess prognosis.

In situ compression of micropillars under coherent X-ray diffraction: a case study of experimental and data-analysis constraints.

Micropillar compression is a method of choice to understand mechanics at small scale. It is mainly studied with electron microscopy or white-beam micro-Laue X-ray diffraction. The aim of the present article is to show the possibilities of the use of diffraction with a coherent X-ray beam. InSb micropillars in epitaxy with their pedestals (i.e. their support) are studied in situ during compression. Firstly, an experiment using a collimated beam matching the pillar size allows determination of when the sample enters the plastic regime, independently of small defects induced by experimental artefacts. A second experiment deals with scanning X-ray diffraction maps with a nano-focused beam; despite the coherence of the beam, the contributions from the pedestal and from the micropillar in the diffraction patterns can be separated, making possible a spatially resolved study of the plastic strain fields. A quantitative measurement of the elastic strain field is nevertheless hampered by the fact that the pillar diffracts at the same angles as the pedestal. Finally, no image reconstructions were possible in these experiments, either in situ due to a blurring of the fringes during loading or post-mortem because the defect density after yielding was too high. However, it is shown how to determine the elastic bending of the pillar in the elastic regime. Bending angles of around 0.3° are found, and a method to estimate the sample's radius of curvature is suggested.

Into the wild of nonlinear electromagnetism-a course on nonlinear electromagnetism, not quite from scratch, part I: tutorial.

This tutorial is aimed at introducing in a natural fashion the propagation equations system governing the scattering of an electromagnetic wave by a nonlinear medium. The purpose is first to obtain the equations showing the most common nonlinear effects such as the Kerr effect or second and third harmonic generation by avoiding conventional recipes and trying to arrive at these equations with a minimum of assumptions. For this, we start from the general Maxwell's equations involving the fields E, B, D, and H and rigorously provide all the hypotheses needed to attain the nonlinear systems of PDEs involving the different complex amplitudes of the different fields associated with the different frequencies at stake. In part II, the difficult question of energy transfer between fields emitted at the various frequencies involved is discussed in detail. We then examine the tensorial nature of susceptibilities and, using Neumann's principle, show how the number of their independent components can be significantly reduced. In part III, numerical examples of scattering by nonlinear materials are given and discussed.

Into the wild of nonlinear electromagnetism-a course on nonlinear electromagnetism, not quite from scratch, part III: tutorial.

This tutorial is aimed at introducing in a natural fashion the propagation equations system governing the scattering of an electromagnetic wave by a nonlinear medium. The purpose is first to obtain the equations showing the most common nonlinear effects such as the Kerr effect or second and third harmonic generation by avoiding conventional recipes and trying to arrive at these equations with a minimum of assumptions. For this, we start from the general Maxwell's equations involving the fields E, B, D, and H, and we rigorously provide all the hypotheses needed to attain the nonlinear systems of partial differential equations involving the different complex amplitudes of the different fields associated with the different frequencies at stake. In part II, the difficult question of energy transfer between fields emitted at the various frequencies involved is discussed in detail. We then examine the tensorial nature of susceptibilities and, using Neumann's principle, show how the number of their independent components can be significantly reduced. In part III, numerical examples of scattering by nonlinear materials are given and discussed.

Noise models for low counting rate coherent diffraction imaging.

Coherent diffraction imaging (CDI) is a lens-less microscopy method that extracts the complex-valued exit field from intensity measurements alone. It is of particular importance for microscopy imaging with diffraction set-ups where high quality lenses are not available. The inversion scheme allowing the phase retrieval is based on the use of an iterative algorithm. In this work, we address the question of the choice of the iterative process in the case of data corrupted by photon or electron shot noise. Several noise models are presented and further used within two inversion strategies, the ordered subset and the scaled gradient. Based on analytical and numerical analysis together with Monte-Carlo studies, we show that any physical interpretations drawn from a CDI iterative technique require a detailed understanding of the relationship between the noise model and the used inversion method. We observe that iterative algorithms often assume implicitly a noise model. For low counting rates, each noise model behaves differently. Moreover, the used optimization strategy introduces its own artefacts. Based on this analysis, we develop a hybrid strategy which works efficiently in the absence of an informed initial guess. Our work emphasises issues which should be considered carefully when inverting experimental data.