A biological nanofoam: The wall of coniferous bisaccate pollen.

The outer layer of the pollen grain, the exine, plays a key role in the survival of terrestrial plant life. However, the exine structure in different groups of plants remains enigmatic. Here, modern and fossil coniferous bisaccate pollen were examined to investigate the detailed three-dimensional structure and properties of the pollen wall. X-ray nanotomography and volume electron microscopy are used to provide high-resolution imagery, revealing a solid nanofoam structure. Atomic force microscopy measurements were used to compare the pollen wall with other natural and synthetic foams and to demonstrate that the mechanical properties of the wall in this type of pollen are retained for millions of years in fossil specimens. The microscopic structure of this robust biological material has potential applications in materials sciences and also contributes to our understanding of the evolutionary success of conifers and other plants over geological time.

X-ray optics and beam characterization using random modulation: theory.

X-ray near-field speckle-based phase-sensing approaches provide efficient means of characterizing optical elements. Presented here is a theoretical review of several of these speckle methods within the framework of optical characterization, and a generalization of the concept is provided. As is also demonstrated experimentally in a parallel paper [Berujon, Cojocaru, Piault, Celestre, Roth, Barrett & Ziegler (2020), J. Synchrotron Rad. 27, (this issue)], the methods theoretically developed here can be applied to different beams and optics and within a variety of situations where at-wavelength metrology is desired. By understanding the differences between the various processing methods, it is possible to find and implement the most suitable approach for each metrology scenario.

X-ray optics and beam characterization using random modulation: experiments.

A parallel paper [Berujon, Cojocaru, Piault, Celestre, Roth, Barrett & Ziegler (2020), J. Synchrotron Rad. 27, 284-292] reviewed theoretically some of the available processing schemes for X-ray wavefront sensing based on random modulation. Shown here are experimental applications of the technique for characterizing both refractive and reflective optical components. These fast and accurate X-ray at-wavelength metrology methods can assist the manufacture of X-ray optics that transport X-ray beams with a minimum amount of wavefront distortion. It is also recalled how such methods can facilitate online optimization of active optics.

Wavefront sensing at X-ray free-electron lasers.

Here a direct comparison is made between various X-ray wavefront sensing methods with application to optics alignment and focus characterization at X-ray free-electron lasers (XFELs). Focus optimization at XFEL beamlines presents unique challenges due to high peak powers as well as beam pointing instability, meaning that techniques capable of single-shot measurement and that probe the wavefront at an out-of-focus location are desirable. The techniques chosen for the comparison include single-phase-grating Talbot interferometry (shearing interferometry), dual-grating Talbot interferometry (moiré deflectometry) and speckle tracking. All three methods were implemented during a single beam time at the Linac Coherent Light Source, at the X-ray Pump Probe beamline, in order to make a direct comparison. Each method was used to characterize the wavefront resulting from a stack of beryllium compound refractive lenses followed by a corrective phase plate. In addition, difference wavefront measurements with and without the phase plate agreed with its design to within λ/20, which enabled a direct quantitative comparison between methods. Finally, a path toward automated alignment at XFEL beamlines using a wavefront sensor to close the loop is presented.

Guideline-Based Clinical Assessment Versus Procalcitonin-Guided Antibiotic Use in Pneumonia: A Pragmatic Randomized Trial.

STUDY OBJECTIVE: Efforts to reduce unnecessary and unnecessarily long antibiotic treatment for community-acquired pneumonia have been attempted through use of procalcitonin and through guidelines based on serial clinical assessment. Our aim is to compare guideline-based clinical assessment- and procalcitonin algorithm-guided antibiotic use among patients with community-acquired pneumonia. METHODS: We performed a pragmatic, randomized, multicenter trial from November 2012 to April 2015 at 12 French hospitals. We included emergency department (ED) patients older than 18 years with community-acquired pneumonia. Patients were randomly assigned to either the procalcitonin-guided or clinical assessment group. In accordance with past studies, we hypothesized that serial clinical assessment would be superior to procalcitonin-guided care. The primary outcome was antibiotic duration, and secondary outcomes included rates of antibiotic duration less than or equal to 5 days, and clinical success and combined serious adverse outcomes at 30 days in the intention-to-treat population. RESULTS: Of 370 eligible patients, 285 (77%) were randomly assigned to either clinical assessment- (n=143) or procalcitonin-guided care (n=142). Median age was 67 years (range 18 to 93 years) and 40% of patients were deemed to have Pneumonia Severity Index class IV or V. Procalcitonin algorithm adherence was 76%. Antibiotic duration was not significantly different between clinical assessment- and procalcitonin-guided groups (median 9 versus 10 days, respectively). Clinical success rate was 92% in each group and serious adverse outcome rates were similar (15% versus 20%, respectively). CONCLUSION: Guideline-based serial clinical assessment did not reduce antibiotic exposure compared with procalcitonin-guided care among ED patients with community-acquired pneumonia. The strategies were similar in terms of duration of antibiotic use and clinical outcomes.