Towards performing high-resolution inelastic X-ray scattering measurements at hard X-ray free-electron lasers coupled with energetic laser drivers

High-resolution inelastic X-ray scattering is an established technique in the synchrotron community, used to investigate collective low-frequency responses of materials. When fielded at hard X-ray free-electron lasers (XFELs) and combined with high-intensity laser drivers, it becomes a promising technique for investigating matter at high temperatures and high pressures. This technique gives access to important thermodynamic properties of matter at extreme conditions, such as temperature, material sound speed, and viscosity. The successful realization of this method requires the acquisition of many identical laser-pump/X-ray-probe shots, allowing the collection of a sufficient number of photons necessary to perform quantitative analyses. Here, a 2.5-fold improvement in the energy resolution of the instrument relative to previous works at the Matter in Extreme Conditions (MEC) endstation, Linac Coherent Light Source (LCLS), and the High Energy Density (HED) instrument, European XFEL, is presented. Some aspects of the experimental design that are essential for improving the number of photons detected in each X-ray shot, making such measurements feasible, are discussed. A careful choice of the energy resolution, the X-ray beam mode provided by the XFEL, and the position of the analysers used in such experiments can provide a more than ten-fold improvement in the photometrics. The discussion is supported by experimental data on 10 µm-thick iron and 50 nm-thick gold samples collected at the MEC endstation at the LCLS, and by complementary ray-tracing simulations coupled with thermal diffuse scattering calculations.

High-resolution inelastic x-ray scattering at the high energy density scientific instrument at the European X-Ray Free-Electron Laser

We introduce a setup to measure high-resolution inelastic x-ray scattering at the High Energy Density scientific instrument at the European X-Ray Free-Electron Laser (XFEL). The setup uses the Si (533) reflection in a channel-cut monochromator and three spherical diced analyzer crystals in near-backscattering geometry to reach a high spectral resolution. An energy resolution of 44 meV is demonstrated for the experimental setup, close to the theoretically achievable minimum resolution. The analyzer crystals and detector are mounted on a curved-rail system, allowing quick and reliable changes in scattering angle without breaking vacuum. The entire setup is designed for operation at 10 Hz, the same repetition rate as the high-power lasers available at the instrument and the fundamental repetition rate of the European XFEL. Among other measurements, it is envisioned that this setup will allow studies of the dynamics of highly transient laser generated states of matter.

An approach for the measurement of the bulk temperature of single crystal diamond using an X-ray free electron laser

We present a method to determine the bulk temperature of a single crystal diamond sample at an X-Ray free electron laser using inelastic X-ray scattering. The experiment was performed at the high energy density instrument at the European XFEL GmbH, Germany. The technique, based on inelastic X-ray scattering and the principle of detailed balance, was demonstrated to give accurate temperature measurements, within [Formula: see text] for both room temperature diamond and heated diamond to 500 K. Here, the temperature was increased in a controlled way using a resistive heater to test theoretical predictions of the scaling of the signal with temperature. The method was tested by validating the energy of the phonon modes with previous measurements made at room temperature using inelastic X-ray scattering and neutron scattering techniques. This technique could be used to determine the bulk temperature in transient systems with a temporal resolution of 50 fs and for which accurate measurements of thermodynamic properties are vital to build accurate equation of state and transport models.

[Association between screen time and sleep habits in 11-to-12-year-old French middle school students]

BACKGROUND

Screen media usage has become increasingly commonplace in daily life with children initiating themselves to screen media at an early age. Given the high prevalence of screen viewing among children worldwide, its impact on children's health has become a cause for concern. Unfortunately, little information on the independent association between sleep habits and screen time in French children is currently available. The main aim of this study was to assess possible relationships between screen time and sleep habits (quality, duration, etc.) among young middle school students in France.

METHODS

A total of 448 (55 % girls) 11-to-12-year-olds from 5 schools were included. Body weight and height were measured according to standard procedures and BMI percentiles were determined based on international reference values. Sleep parameters were obtained by sleep diaries and visual estimations. A sleep diary was maintained for one week to record sleeping and waking times and related information. Information on lifestyle habits (sedentary behaviours, physical activity, and dietary intake) was obtained via standardised questionnaires.

RESULTS

Participants were 11.5 (±0.4) years of age. From total sample, 25.5 % reported screen time ≥2hours/d during school days and 62.7 % during school-free days. High screen time was associated with significantly poorer sleep habits and these results remained valid after adjustment for several confounding factors (body mass index, sex, center and parental level of educational attainment) (P<0.05).

CONCLUSION

This study highlights an association between longer screen time and shorter sleep duration in French middle school students aged 11 to 12 years. Preventive measures on use of and exposure to screens are called for. Further studies are necessary to confirm our findings.

[Study of practices: What do general practitioners first propose when faced with asymptomatic lower extremity peripheral artery disease?]

INTRODUCTION

Peripheral artery disease of lower limbs (PAD) can be discovered at an asymptomatic stage by the realization of systolic pressure indices. The 2006 recommendations of the French National Authority for Health on AOMI encourage the systematic prescription of antiplatelet agents; the 2012 recommendations on the proper use of antiplatelet agents no longer encourage it in the case of asymptomatic PAD. These two recommendations still coexist. Our objective was to determine the management of an asymptomatic PAD by general practitioners.

METHODS

Descriptive and analytical epidemiological study, with analysis of practices, prospectively addressed by postal questionnaire to a randomized sample of 220 GPs practicing in the European Metropolis of Lille between December 15, 2016 and February 15, 2017. The question was: "if an asymptomatic PAD is discovered in a 50-year-old patient who is otherwise in good general condition, what do you generally do?"

RESULTS

Our sample was 92 general practitioners (42% participation). Of these, only 6 were practicing HPIs. Before an asymptomatic PAD, management included an opinion from an angiologist (84%) and/or a cardiologist (75%) before the drug was prescribed (antiplatelet agent for 57%, statin for 33% and ACE inhibitor for 14%).

CONCLUSION

The extension assessment was carried out in more than 8 out of 10 cases. The use of antiplatelet antiaggregants was significant, which can be explained by the coexistence of divergent recommendations. The rapid clarification of recommendations is essential with the evolution of scientific data.

Toward quasi-DC conductivity of warm dense matter measured by single-shot terahertz spectroscopy

We present an experimental setup capable of measuring the near DC conductivity of laser generated warm dense matter using single-shot terahertz time-domain spectroscopy. The setup uses a reflective echelon and balanced detection to record THz waveforms with a minimum detectable signal of 0.2% in a single laser pulse. We describe details of the experimental setup and the data analysis procedure and present single-shot terahertz transmission data on aluminum that has been laser heated to an electron temperature of 0.5 eV.

Setup for meV-resolution inelastic X-ray scattering measurements and X-ray diffraction at the Matter in Extreme Conditions endstation at the Linac Coherent Light Source

We describe a setup for performing inelastic X-ray scattering and X-ray diffraction measurements at the Matter in Extreme Conditions (MEC) endstation of the Linac Coherent Light Source. This technique is capable of performing high-, meV-resolution measurements of dynamic ion features in both crystalline and non-crystalline materials. A four-bounce silicon (533) monochromator was used in conjunction with three silicon (533) diced crystal analyzers to provide an energy resolution of ∼50 meV over a range of ∼500 meV in single shot measurements. In addition to the instrument resolution function, we demonstrate the measurement of longitudinal acoustic phonon modes in polycrystalline diamond. Furthermore, this setup may be combined with the high intensity laser drivers available at MEC to create warm dense matter and subsequently measure ion acoustic modes.

How nanoparticles encapsulating fluorophores allow a double detection of biomolecules by localized surface plasmon resonance and luminescence

The paper shows how polysiloxane particles encapsulating fluorophores can be successfully used to detect biotin-streptavidin binding by two types of technique. After functionalization of the particles by streptavidin, the fixation of the biomolecule can indeed be detected by a shift of the localized surface plasmon resonance of the biotinylated gold dots used as substrate and by the luminescence of the fluorophores evidenced by scanning near-field optical microscopy. The development of particles allowing such a double detection opens a route for increasing the reliability of biological detection and for multi-labelling strategies crossing both detection principles.

Ethics and law in the field of medical care for the elderly in France

The authors discuss law and ethics when medical decisions are to be taken by patients who are unable in any valid sense to express their own wishes. The main problem in legal terms is to protect an individual's free will as far as possible and ensure that his or her wishes, if known, are respected. If a patient's independent wishes cannot be known, then we must at least ensure that nothing is imposed which is not in his interest. Legal measures, however, are far from adequate in resolving all the concrete problems that emerge. The field of ethics does bring some better adapted solutions, but none is laid down in law. One such approach, involving a multidisciplinary advisory group in a department of geriatrics, is discussed.

[Lymphocyte macrophage activation factor. Comparison of the mode of production in man and mice]

A macrophage activating factor (MAF) has been previously described in mixed lymphocyte cultures (MLC) between the donor and the recipient of a mouse skin allograft. This factor can render macrophages cytotoxic against mouse mastocytoma targert cells. The present work demonstrates the production of a similar factor in the human, using macrophages from uremic patients treated with peritoneal dialysis. There is, however, an apparent difference between mouse and human MAF. In the mouse the production of MAF in primary MLC is inconsistent, late and weak, while it is regularly found in large amounts in MLC between a donor and a recipient of a skin allograft. Conversely, in the human, MAF is consistently found in primary MLC as well as in MLC between two individuals previously sensitized to each other by a skin allograft followed by repeated white blood cell injections.