Publications by authors named "Robert Richter"

We report a study of the electronic and nuclear relaxation dynamics of the photoexcited RNA base uracil in the gas phase using time-resolved core-level photoelectron spectroscopy together with high-level calculations. The dynamics was investigated by trajectory surface hopping calculations, and the core ionization energies were calculated for geometries sampled from these. The molecule was excited by a UV laser and dynamics probed on the oxygen, nitrogen, and carbon sites by core electron spectroscopy.

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The photofragmentation of halothane (CFCHBrCl) was studied with synchrotron radiation by photoionization efficiency (PIE) measurements and photoelectron-photoion coincidence (PEPICO) experiments, as well as by a theoretical exploration of potential energy surfaces. Among the other fragments, the formation of the CHClF and CHBrF ions, which involves the transfer of a F atom between the two moieties of the parent molecule, was observed. To understand the mechanisms leading to the halogen migration, a detailed theoretical study of the production of CHClF, / 67, based on DFT calculations and natural bond orbital (NBO) analysis was conducted.

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The reversible photoisomerization of 1,2-dihydro-1,2-azaborinines (BN benzenes) to their Dewar isomers (2-aza-3-borabicyclo[2.2.0]hex-5-enes) provides a promising platform for molecular solar thermal (MOST) energy conversion, storage, and release.

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A combined experimental and computational approach aimed at systematically exploring unimolecular reaction channels of ionized gas-phase systems-including rearrangements, intramolecular bonds formation, and fragmentation-has been applied to 5- and 6-benzyluracil (5BU and 6BU) molecules, which are used as molecular models of photo-induced interactions between nucleobases and aromatic aminoacids. Photoelectron-photoion coincidence experiments offer a unique view of energy-selected fragmentation channels, while ab initio molecular dynamics of the ionic system, performed with semi-empirical potentials and for long simulation times, can extensively explore possible unimolecular reactive pathways, revealing the detailed molecular identity of the products. Results show that, at lower binding energies, ionized 5- and 6-benzyluracil molecules do not fragment but may nevertheless rearrange to give, mainly in 6BU, cross-linked products.

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Macrophages are key players in host defense and lung injury, and their crosstalk with other cells dictates the course of the inflammatory response and tissue remodeling. Here, we present a protocol for isolating extracellular vesicles (EVs) from human bronchoalveolar lavage fluid (BALF) and for generating EVs from primary human or murine alveolar macrophages following stimulation by cigarette smoke extract. Furthermore, we describe how to measure matrix metalloproteinase (MMP)-12 activity on macrophage-derived EVs using a Förster resonance energy transfer assay.

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We report a nickel-catalyzed stereoselective [2 + 2 + 2] cycloaddition between norbornadienes and benzocyclobutanones via C-C activation. This transformation generates four stereocenters, producing nortricyclane scaffolds that introduce three-dimensional architecture. The reaction proceeds with high stereoselectivity while allowing precise steric control of the reaction site, offering a versatile approach for constructing intricate stereochemical frameworks.

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Small extracellular vesicles (EVs) derived from neutrophils play an important role in the remodeling of extracellular matrices in human health and disease. Here, we present a protocol for isolating EVs secreted from human neutrophils either ex vivo or within circulation. We describe steps for neutrophil and plasma isolation, neutrophil activation, and EV isolation and enumeration.

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The valence and core electronic structure of three non-steroidal anti-inflammatory drugs (methyl salicylate, fenoprofen and ketoprofen) have been studied by photoelectron and soft X-ray absorption spectroscopy, supported by theoretical calculations of the molecular and electronic structure. The conformational landscape has been explored for sixteen low-energy conformers of fenoprofen and ketoprofen, and the energies of both compounds fall into two groups with steric similarities, separated by about 3 kJ mol. Valence band photoelectron spectra agree with previous results, and the spectra have been calculated using two approaches.

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The exposure of molecules to attosecond extreme-ultraviolet (XUV) pulses offers a unique opportunity to study the early stages of coupled electron-nuclear dynamics in which the role played by the different degrees of freedom is beyond standard chemical intuition. We investigate, both experimentally and theoretically, the first steps of charge-transfer processes initiated by prompt ionization in prototype donor-π-acceptor molecules, namely nitroanilines. Time-resolved measurement of this process is performed by combining attosecond XUV-pump/few-femtosecond infrared-probe spectroscopy with advanced many-body quantum chemistry calculations.

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Background: Coronary atherosclerotic plaques susceptible to acute coronary syndrome have traditionally been characterized by their surrounding cellular architecture. However, with the advent of intravascular imaging, novel mechanisms of coronary thrombosis have emerged, challenging our contemporary understanding of acute coronary syndrome. These intriguing findings underscore the necessity for a precise molecular definition of plaque stability.

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Background: Sustainability has become a ubiquitous imperative across all sectors of society, including healthcare. Building on the broader discourse on sustainable development, sustainability is used in relation to social, ecological, and economic concerns with varying degrees of emphasis and often related to a sense of durability.

Objective: To provide a detailed analysis of the concept of sustainability in current physical therapy literature and advance its deliberate future implementation.

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Heparan sulfate (HS) in the vascular endothelial glycocalyx (eGC) is a critical regulator of blood vessel homeostasis. Trauma results in HS shedding from the eGC, but the impact of trauma on HS structural modifications that could influence mechanisms of vascular injury and repair has not been evaluated. Moreover, the effect of eGC HS shedding on endothelial cell (EC) homeostasis has not been fully elucidated.

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We report the x-ray absorption spectrum (XAS) of the tert-butyl radical, C4H9. The radical was generated pyrolytically from azo-tert-butane, and the XAS of the pure radical was obtained by subtraction of spectra recorded at different temperatures. The bands in the XAS were assigned by ab initio calculations that are in very good agreement with the experimental data.

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The goals of this work are to attempt to decipher if an aniline dication can isomerize to a picoline dication in a given astrochemical environment and if the dissociation of such dications could be a source of kinetically hot fragment ions, some of which could be of significance in the interstellar medium. Toward this purpose, the VUV-induced dication dissociation was investigated experimentally using ion-ion coincidence and computationally by optimizing various pathways. Contrary to previous reports, we show here that the dication of aniline is structurally too weak to retain its ring structure while following the dissociation pathways.

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Molecular solar thermal systems (MOST) represent an auspicious solution for the storage of solar energy. We report silver salts as a unique class of catalysts, capable of releasing the stored energy from the promising 1,2-dihydro-1,2-azaborinine based MOST system. Mechanistic investigations provided insights into the silver catalyzed thermal backreaction, concurrently unveiling the first crystal structure of a 2-aza-3-borabicyclo[2.

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The electronic structure of ammonia-borane (NHBH) has been investigated by using valence and core photoelectron spectroscopy and near-edge X-ray absorption fine structure spectroscopy at the nitrogen and boron K edges. The first two valence ionic states display vibronic structure, in agreement with the published results for the first ionic state. Analysis of the vibrational frequency of the second state yields an assignment which is consistent with the calculated molecular orbital character reported in the literature.

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Refractory vasodilatory shock (RVS) following massive calcium channel blocker (CCB) overdose remains a challenging clinical entity. Peripheral venoarterial extracorporeal membrane oxygenation (ECMO) has proven useful in several cases of CCB intoxication, however, its use in the pediatric population poses unique challenges given the generally small size of pediatric peripheral vasculature in comparison to the high flow rates necessary for adequate mechanical circulatory support. As a result of these challenges, our group has adopted a "primary" central ECMO cannulation approach to the treatment of children and adolescents admitted to our center with profound RVS after CCB ingestion.

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The dissociative double photoionization of isoxazole molecules has been investigated experimentally and theoretically. The experiment has been carried out in the 27.5-36 eV photon energy range using vacuum ultraviolet (VUV) synchrotron radiation excitation combined with ion time-of-flight (TOF) spectrometry and photoelectron-photoion-photoion coincidence (PEPIPICO) technique.

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Introduction: Plasma levels of syndecan-1 (Sdc-1), a biomarker of endothelial glycocalyx (EG) damage, correlate with worse outcomes in trauma patients. However, EG injury is not well characterized in injured older adults (OA). The aims of this study were to characterize Sdc-1 shedding in OA trauma patients relative to younger adults (YA) and determine associations with putative regulators of EG sheddases.

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In search of the cause behind the similarities often seen in the fragmentation of PANHs, vacuum ultraviolet (VUV) photodissociation of two pairs of isomers quinoline-isoquinoline and 2-naphthylamine-3-methyl-quinoline are studied using the velocity map imaging technique. The internal energy dependence of all primary fragmentation channels is obtained for all four target molecules. The decay dynamics of the four molecules is studied by comparing their various experimental signatures.

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Critical physiotherapy has been a rapidly expanding field over the last decade and could now justifiably be called a professional sub-discipline. In this paper we define three different but somewhat interconnected critical positions that have emerged over the last decade that share a critique of physiotherapy's historical approach to health and illness, while also diverging in the possibilities for new forms of practice and thinking. These three positions broadly align with three distinctive philosophies: approaches that emphasize lived experience, social theory, and a range of philosophies increasingly referred to as the "posts".

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Background: Sepsis-associated destruction of the pulmonary microvascular endothelial glycocalyx (EGCX) creates a vulnerable endothelial surface, contributing to the development of acute respiratory distress syndrome (ARDS). Constituents of the EGCX shed into circulation, glycosaminoglycans and proteoglycans, may serve as biomarkers of endothelial dysfunction. We sought to define the patterns of plasma EGCX degradation products in children with sepsis-associated pediatric ARDS (PARDS), and test their association with clinical outcomes.

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Severe acute respiratory distress syndrome in children, or PARDS, carries a high risk of morbidity and mortality that is not fully explained by PARDS severity alone. Right ventricular (RV) dysfunction can be an insidious and often under-recognized complication of severe PARDS that may contribute to its untoward outcomes. Indeed, recent evidence suggest significantly worse outcomes in children who develop RV failure in their course of PARDS.

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Helium nanodroplets are ideal model systems to unravel the complex interaction of condensed matter with ionizing radiation. Here we study the effect of purely elastic electron scattering on angular and energy distributions of photoelectrons emitted from He nanodroplets of variable size (10-10 atoms per droplets). For large droplets, photoelectrons develop a pronounced anisotropy along the incident light beam due to a shadowing effect within the droplets.

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The behavior of nitrosyl chloride (ClNO) exposed to ionizing radiation was studied by direct probing valence-shell electrons in temporal coincidence with ions originating from the fragmentation process of the transient ClNO. Such a molecular dication was produced by double photoionization with synchrotron radiation in the 24-70 eV photon energy range. The experiment has been conducted at the Elettra Synchrotron Facility of Basovizza (Trieste, Italy) using a light beam linearly polarized with the direction of the polarization vector parallel to the ClNO molecular beam axis.

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