PINK: a tender X-ray beamline for X-ray emission spectroscopy.

A high-flux beamline optimized for non-resonant X-ray emission spectroscopy (XES) in the tender X-ray energy range has been constructed at the BESSY II synchrotron source. The beamline utilizes a cryogenically cooled undulator that provides X-rays over the energy range 2.1 keV to 9.5 keV. This energy range provides access to XES [and in the future X-ray absorption spectroscopy (XAS)] studies of transition metals ranging from Ti to Cu (Kα, Kß lines) and Zr to Ag (Lα, Lß), as well as light elements including P, S, Cl, K and Ca (Kα, Kß). The beamline can be operated in two modes. In PINK mode, a multilayer monochromator (E/ΔE ≃ 30-80) provides a high photon flux (1014 photons s-1 at 6 keV and 300 mA ring current), allowing non-resonant XES measurements of dilute substances. This mode is currently available for general user operation. X-ray absorption near-edge structure and resonant XAS techniques will be available after the second stage of the PINK commissioning, when a high monochromatic mode (E/ΔE ≃ 10000-40000) will be facilitated by a double-crystal monochromator. At present, the beamline incorporates two von Hamos spectrometers, enabling time-resolved XES experiments with time scales down to 0.1 s and the possibility of two-color XES experiments. This paper describes the optical scheme of the PINK beamline and the endstation. The design of the two von Hamos dispersive spectrometers and sample environment are discussed here in detail. To illustrate, XES spectra of phosphorus complexes, KCl, TiO2 and Co3O4 measured using the PINK setup are presented.

Ruthenium 4d-to-2p X-ray Emission Spectroscopy: A Simultaneous Probe of the Metal and the Bound Ligands.

Ruthenium 4d-to-2p X-ray emission spectroscopy (XES) was systematically explored for a series of Ru2+ and Ru3+ species. Complementary density functional theory calculations were utilized to allow for a detailed assignment of the experimental spectra. The studied complexes have a range of different coordination spheres, which allows the influence of the ligand donor/acceptor properties on the spectra to be assessed. Similarly, the contributions of the site symmetry and the oxidation state of the metal were analyzed. Because the 4d-to-2p emission lines are dipole-allowed, the spectral features are intense. Furthermore, in contrast with K- or L-edge X-ray absorption of 4d transition metals, which probe the unoccupied levels, the observed 4p-to-2p XES arises from electrons in filled-ligand- and filled-metal-based orbitals, thus providing simultaneous access to the ligand and metal contributions to bonding. As such, 4d-to-2p XES should be a promising tool for the study of a wide range of 4d transition-metal compounds.

Effects of periodontal treatment on the C-reactive protein levels in hemodialysis patients: A systematic review and meta-analysis.

AIM: This systematic review provides a summary of the scientific evidence concerning effects of periodontal treatment on the C-reactive protein (CRP) levels in hemodialysis patients. MATERIAL AND METHODS: Eight databases were accessed until May 2020 for interventional studies which evaluated CRP levels in hemodialysis patients before and after periodontal treatment. Inclusion criteria were studies involving hemodialysis patients with gingivitis or periodontitis, without restriction of year, language, and publication status. Random effects meta-analysis was performed. The risk of bias in eligible studies was assessed using the Joanna Briggs Institute's Critical Appraisal tools for use in systematic reviews. Certainty of evidence was also evaluated using GRADE approach. RESULTS: The search in the databases resulted in 326 records, from which only seven met the eligibility criteria and therefore were submitted to qualitative evaluation. The meta-analysis revealed that, in general, the reduction in CRP levels had moderate and statistically significant effect size (standardized mean difference [SMD] = 0.45; confidence interval [CI] 95% = 0.25, 0.65; p < .001). Statistical heterogeneity was low (I2  = 0.0%; p = .771). Most studies showed moderate risk of bias. CONCLUSION: Based on low certainty of evidence, the results suggest that periodontal treatment can significantly contribute to reduce CRP levels among hemodialysis patients. However, more randomized clinical studies, with follow-up longer than 12 months, using standardized diagnostic methods and controlling confounding factors, should be performed to strengthen the evidence.