Finding intersections between electronic excited state potential energy surfaces with simultaneous ultrafast X-ray scattering and spectroscopy

Light-driven molecular reactions are dictated by the excited state potential energy landscape, depending critically on the location of conical intersections and intersystem crossing points between potential surfaces where non-adiabatic effects govern transition probabilities between distinct electronic states. While ultrafast studies have provided significant insight into electronic excited state reaction dynamics, experimental approaches for identifying and characterizing intersections and seams between electronic states remain highly system dependent. Here we show that for 3d transition metal systems simultaneously recorded X-ray diffuse scattering and X-ray emission spectroscopy at sub-70 femtosecond time-resolution provide a solid experimental foundation for determining the mechanistic details of excited state reactions. In modeling the mechanistic information retrieved from such experiments, it becomes possible to identify the dominant trajectory followed during the excited state cascade and to determine the relevant loci of intersections between states. We illustrate our approach by explicitly mapping parts of the potential energy landscape dictating the light driven low-to-high spin-state transition (spin crossover) of [Fe(2,2′-bipyridine)3]2+, where the strongly coupled nuclear and electronic dynamics have been a source of interest and controversy. We anticipate that simultaneous X-ray diffuse scattering and X-ray emission spectroscopy will provide a valuable approach for mapping the reactive trajectories of light-triggered molecular systems involving 3d transition metals

Contrast-Enhanced Ultrasound: Development of Syllabus for Core Theoretical and Practical Competencies

Contrast-enhanced ultrasound (CEUS) is dependent on the observer's competencies, and thus, appropriate education and testing of individual competency is essential. The current international curriculum in CEUS is methodologically weak and lacks validated competency assessment tests. In this study, we aimed to develop a syllabus for core competencies in CEUS using the Delphi process and an international panel of experts. A core writing group constructed an initial draft of the syllabus based on the existing literature. Eight international experts in CEUS or medical education were recruited as Delphi panelists. The draft underwent iterative and anonymous Delphi rounds until a pre-defined level of consensus was reached. The final syllabus consisted of 16 items, which were indexed in two main domains and in procedural order. An expert-generated proposal for a syllabus of core CEUS competencies has been constructed via the Delphi process and may serve as framework for future development of a CEUS curriculum, including competency assessment tests

Tracking the picosecond deactivation dynamics of a photoexcited iron carbene complex by time-resolved X-ray scattering

Recent years have seen the development of new iron-centered N-heterocyclic carbene (NHC) complexes for solar energy applications. Compared to typical ligand systems, the NHC ligands provide Fe complexes with longer-lived metal-to-ligand charge transfer (MLCT) states. This increased lifetime is ascribed to strong ligand field splitting provided by the NHC ligands that raises the energy levels of the metal centered (MC) states and therefore reduces the deactivation efficiency of MLCT states. Among currently known NHC systems, [Fe(btbip)2]2+ (btbip = 2,6-bis(3-tert-butyl-imidazol-1-ylidene)pyridine) is a unique complex as it exhibits a short-lived MC state with a lifetime on the scale of a few hundreds of picoseconds. Hence, this complex allows for a detailed investigation, using 100 ps X-ray pulses from a synchrotron, of strong ligand field effects on the intermediate MC state in an NHC complex. Here, we use time-resolved wide angle X-ray scattering (TRWAXS) aided by density functional theory (DFT) to investigate the molecular structure, energetics and lifetime of the high-energy MC state in the Fe-NHC complex [Fe(btbip)2]2+ after excitation to the MLCT manifold. We identify it as a 260 ps metal-centered quintet (5MC) state, and we refine the molecular structure of the excited-state complex verifying the DFT results. Using information about the hydrodynamic state of the solvent, we also determine, for the first time, the energy of the 5MC state as 0.75 ± 0.15 eV. Our results demonstrate that due to the increased ligand field strength caused by NHC ligands, upon transition from the ground state to the 5MC state, the metal to ligand bonds extend by unusually large values: by 0.29 Å in the axial and 0.21 Å in the equatorial direction. These results imply that the transition in the photochemical properties from typical Fe complexes to novel NHC compounds is manifested not only in the destabilization of the MC states, but also in structural distortion of these states

Intrapleural fibrinolysis and DNase versus video-assisted thoracic surgery (VATS) for the treatment of pleural empyema (FIVERVATS) : protocol for a randomised, controlled trial – surgery as first-line treatment

Introduction: Pleural empyema is a frequent disease with a high morbidity and mortality. Current standard treatment includes antibiotics and thoracic ultrasound (TUS)-guided pigtail drainage. Simultaneously with drainage, an intrapleural fibrinolyticum can be given. A potential better alternative is surgery in terms of video-assisted thoracoscopic surgery (VATS) as first-line treatment. The aim of this study is to determine the difference in outcome in patients diagnosed with complex parapneumonic effusion (stage II) and pleural empyema (stage III) who are treated with either VATS surgery or TUS-guided drainage and intrapleural therapy (fibrinolytic (Alteplase) with DNase (Pulmozyme)) as first-line treatment. Methods and analysis: A national, multicentre randomised, controlled study. Totally, 184 patients with a newly diagnosed community acquired complicated parapneumonic effusion or pleural empyema are randomised to either (1) VATS procedure with drainage or (2) TUS-guided pigtail catheter placement and intrapleural therapy with Actilyse and DNase. The total follow-up period is 12 months. The primary endpoint is length of hospital stay and secondary endpoints include for example, mortality, need for additional interventions, consumption of analgesia and quality of life. Ethics and dissemination: All patients provide informed consent before randomisation. The research project is carried out in accordance with the Helsinki II Declaration, European regulations and Good Clinical Practice Guidelines. The Scientific Ethics Committees for Denmark and the Danish Data Protection Agency have provided permission. Information about the subjects is protected under the Personal Data Processing Act and the Health Act. The trial is registered at www.clinicaltrials.gov, and monitored by the regional Good clinical practice monitoring unit. The results of this study will be published in peer-reviewed journals and presented at various national and international conferences. Trial registration number: NCT04095676

Ammonium alters creatine transport and synthesis in a 3D culture of developing brain cells, resulting in secondary cerebral creatine deficiency

Hyperammonemic disorders in pediatric patients lead to poorly understood irreversible effects on the developing brain that may be life-threatening. We showed previously that some of these NH4+-induced irreversible effects might be due to impairment of axonal growth that can be protected under ammonium exposure by creatine co-treatment. The aim of the present work was thus to analyse how the genes of arginine:glycine amidinotransferase (AGAT) and guanidinoacetate methyltransferase (GAMT), allowing creatine synthesis, as well as of the creatine transporter SLC6A8, allowing creatine uptake into cells, are regulated in rat brain cells under NH4+ exposure. Reaggregated brain cell three-dimensional cultures exposed to NH4Cl were used as an experimental model of hyperammonemia in the developing central nervous system (CNS). We show here that NH4+ exposure differentially alters AGAT, GAMT and SLC6A8 regulation, in terms of both gene expression and protein activity, in a cell type-specific manner. In particular, we demonstrate that NH4+ exposure decreases both creatine and its synthesis intermediate, guanidinoacetate, in brain cells, probably through the inhibition of AGAT enzymatic activity. Our work also suggests that oligodendrocytes are major actors in the brain in terms of creatine synthesis, trafficking and uptake, which might be affected by hyperammonemia. Finally, we show that NH4+ exposure induces SLC6A8 in astrocytes. This suggests that hyperammonemia increases blood-brain barrier permeability for creatine. This is normally limited due to the absence of SLC6A8 from the astrocyte feet lining microcapillary endothelial cells, and thus creatine supplementation may protect the developing CNS of hyperammonemic patients