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The beamline optics and endstations at branch B of the Versatile Soft X-ray (VerSoX) beamline B07 at Diamond Light Source are described. B07-B provides medium-flux X-rays in the range 45-2200â eV from a bending magnet source, giving access to local electronic structure for atoms of all elements from Li to Y. It has an endstation for high-throughput X-ray photoelectron spectroscopy (XPS) and near-edge X-ray absorption fine-structure (NEXAFS) measurements under ultrahigh-vacuum (UHV) conditions. B07-B has a second endstation dedicated to NEXAFS at pressures from UHV to ambient pressure (1â atm). The combination of these endstations permits studies of a wide range of interfaces and materials. The beamline and endstation designs are discussed in detail, as well as their performance and the commissioning process.
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OBJECTIVES: To evaluate the advantages of adding acupuncture to standard postoperative pain management for open radical prostatectomy (RP). MATERIALS AND METHODS: A randomized controlled trial (1:1:1) comparing routine postoperative analgesic care (control [CON]) vs the addition of press tack needle acupuncture (ACU) or press tack placebo acupressure (SHAM) for pain management after open RP was performed. A total of 126 patients were enrolled between February 2020 and April 2021. After open RP, the CON group received standard postoperative analgesia, the ACU group received long-term acupuncture with press tacks at specific points (P-6, Shenmen and SP-6) along with standard analgesia, and the SHAM group received placebo press tacks at the same acupuncture points alongside standard analgesia. The primary endpoint was postoperative pain measured on a numeric rating scale, the NRS-11, calculated as the area under the curve. The cumulative use of routine postoperative analgesics, time to first defaecation, and quality of life were analysed using the Kruskal-Wallis rank sum test, Fisher's exact test, and Pearson's chi-squared test. RESULTS: The ACU group reported significantly less postoperative pain compared to the SHAM (P = 0.007) and CON groups (P = 0.02). There were no significant difference in median (interquartile range) cumulative pain medication usage, time to first defaecation (CON: 37 [33, 44] h; SHAM: 37 [33, 42] h; ACU: 37 [33, 41] h; P > 0.9), or health status at discharge (EuroQol five-dimension, five-level general health assessment questionnaire: CON: 70 [65-83]; SHAM: 70 [60-80]; ACU: 70 [50-80]). CONCLUSION: Incorporating acupuncture into postoperative pain management can improve patient postoperative outcomes.
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Dor Pós-Operatória , Prostatectomia , Humanos , Prostatectomia/efeitos adversos , Prostatectomia/métodos , Masculino , Dor Pós-Operatória/etiologia , Pessoa de Meia-Idade , Idoso , Terapia por Acupuntura/métodos , Medição da Dor , Manejo da Dor/métodos , Neoplasias da Próstata/cirurgia , Analgesia por Acupuntura/métodos , Qualidade de VidaRESUMO
It is important to be able to identify the precise position of H-atoms in hydrogen bonding interactions to fully understand the effects on the structure and properties of organic crystals. Using a combination of near-edge X-ray absorption fine structure (NEXAFS) spectroscopy and density functional theory (DFT) quantum chemistry calculations, we demonstrate the sensitivity of core-level X-ray spectroscopy to the precise H-atom position within a donor-proton-acceptor system. Exploiting this sensitivity, we then combine the predictive power of DFT with the experimental NEXAFS, confirming the H-atom position identified using single-crystal X-ray diffraction (XRD) techniques more easily than using other H-atom sensitive techniques, such as neutron diffraction. This proof of principle experiment confirms the H-atom positions in structures obtained from XRD, providing evidence for the potential use of NEXAFS as a more accurate and easier method of locating H-atoms within organic crystals.
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The intermolecular interactions in concentrated (5 M) aqueous imidazole solutions have been investigated by combining neutron diffraction with isotopic substitution, total X-ray scattering and empirical potential structure refinement (EPSR) simulations using a box containing 5530 water and 500 imidazole molecules. The structural model with the best fit was used to generate radial distribution functions and spatial density functions. The local volume surrounding imidazole molecules is dominated by water, due to strong hydrogen-bonding between the nitrogen moieties of imidazole and water molecules; within a radius of 6.4 Å from the central imidazole molecule there are, on average, 17 water and only 3 imidazole molecules. Even though imidazole interacts with water it appears to disrupt hydrogen bonding in the surrounding water network only minimally. Hydrogen-bonding between imidazole molecules is negligible. The most probable positions of imidazole nearest-neighbours are above and below the plane of the aromatic ring. At low distances (up to â¼3.5-3.8 Å) these nearest neighbours were found to prefer parallel orientation of the molecular planes, indicating hydrophobic (π-π) stacking. At longer distances (up to â¼5 Å), imidazole neighbours assume both parallel and edge-to-face orientations. Overall, hydrated imidazole molecules are the most probable structural motif in aqueous solutions, with very few direct imidazole-imidazole interactions.
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Short, strong hydrogen bonds (SSHBs) have been a source of interest and considerable speculation over recent years, culminating with those where hydrogen resides around the midpoint between the donor and acceptor atoms, leading to quasi-covalent nature. We demonstrate that X-ray photoelectron spectroscopy (XPS) and near-edge X-ray absorption fine structure (NEXAFS) spectroscopy provide deep insight into the electronic structure of the short OHN hydrogen bond of 3,5-pyridinedicarboxylic acid, revealing for the first time distinctive spectroscopic identifiers for these quasi-symmetrical hydrogen bonds. An intermediate nitrogen (core level) chemical shift occurs for the almost centrally located hydrogen compared to protonated (ionic) and non-ionic analogues, and it reveals the absence of two-site disorder. This type of bonding is also evident through broadening of the nitrogen 1s photoemission and 1s â 1π* peaks in XPS and NEXAFS, respectively, arising from the femtosecond lifetimes of hydrogen in the potential wells slightly offset to either side of the centre. The line-shape of the core level excitations are thus related to the population occupancies, reflecting the temperature-dependent shape of the hydrogen potential energy well. Both XPS and NEXAFS provide a distinctive identifier for these quasi-symmetrical hydrogen bonds, paving the way for detailed studies into their prevalence and potentially unique physical and chemical properties.
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We report the results of a Versailles Project on Advanced Materials and Standards interlaboratory study on the intensity scale calibration of x-ray photoelectron spectrometers using low-density polyethylene (LDPE) as an alternative material to gold, silver, and copper. An improved set of LDPE reference spectra, corrected for different instrument geometries using a quartz-monochromated Al Kα x-ray source, was developed using data provided by participants in this study. Using these new reference spectra, a transmission function was calculated for each dataset that participants provided. When compared to a similar calibration procedure using the NPL reference spectra for gold, the LDPE intensity calibration method achieves an absolute offset of â¼3.0% and a systematic deviation of ±6.5% on average across all participants. For spectra recorded at high pass energies (≥90 eV), values of absolute offset and systematic deviation are â¼5.8% and ±5.7%, respectively, whereas for spectra collected at lower pass energies (<90 eV), values of absolute offset and systematic deviation are â¼4.9% and ±8.8%, respectively; low pass energy spectra perform worse than the global average, in terms of systematic deviations, due to diminished count rates and signal-to-noise ratio. Differences in absolute offset are attributed to the surface roughness of the LDPE induced by sample preparation. We further assess the usability of LDPE as a secondary reference material and comment on its performance in the presence of issues such as variable dark noise, x-ray warm up times, inaccuracy at low count rates, and underlying spectrometer problems. In response to participant feedback and the results of the study, we provide an updated LDPE intensity calibration protocol to address the issues highlighted in the interlaboratory study. We also comment on the lack of implementation of a consistent and traceable intensity calibration method across the community of x-ray photoelectron spectroscopy (XPS) users and, therefore, propose a route to achieving this with the assistance of instrument manufacturers, metrology laboratories, and experts leading to an international standard for XPS intensity scale calibration.
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BACKGROUND: Diabetic peripheral neuropathy (DPN) is the most common complication of diabetes mellitus with significant clinical sequelae that can affect a patient's quality of life. Metabolic and microvascular factors are responsible for nerve damage, causing loss of nerve function, numbness, painful sensory symptoms, and muscle weakness. Therapy is limited to anti-convulsant or anti-depressant drugs for neuropathic pain and paresthesia. However, reduced sensation, balance and gait problems are insufficiently covered by this treatment. Previous data suggests that acupuncture, which has been in use in Traditional Chinese Medicine for many years, may potentially complement the treatment options for peripheral neuropathy. Nevertheless, more objective data on clinical outcome is necessary to generally recommend acupuncture to the public. METHODS: We developed a study design for a prospective, randomized (RCT), placebo-controlled, partially double-blinded trial for investigating the effect of acupuncture on DPN as determined by nerve conduction studies (NCS) with the sural sensory nerve action potential amplitude as the primary outcome. The sural sensory nerve conduction velocity, tibial motor nerve action potential amplitude, tibial motor nerve conduction velocity, the neuropathy deficit score, neuropathy symptom score, and numeric rating scale questionnaires are defined as secondary outcomes. One hundred and eighty patients with type 2 diabetes mellitus will be randomized into three groups (needle acupuncture, verum laser acupuncture, and placebo laser acupuncture). We hypothesize that needle and laser acupuncture have beneficial effects on electrophysiological parameters and clinical and subjective symptoms in relation to DPN in comparison with placebo. DISCUSSION: The ACUDIN trial aims at investigating whether classical needle acupuncture and/or laser acupuncture are efficacious in the treatment of DPN. For the purpose of an objective parameter, NCS were chosen as outcome measures. Acupuncture treatment may potentially improve patients' quality of life and reduce the socio-economic burden caused by DPN. TRIAL REGISTRATION: German Clinical Trial Register (DRKS), No. DRKS00008562 , trial search portal of the WHO ( http://apps.who.int/trialsearch/ ).
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Terapia por Acupuntura , Diabetes Mellitus Tipo 2/terapia , Neuropatias Diabéticas/terapia , Humanos , Ensaios Clínicos Controlados Aleatórios como AssuntoRESUMO
The mechanism of the Brust-Schiffrin gold nanoparticle synthesis has been investigated through the use of ion transfer voltammetry at the water/1,2-dichloroethane (DCE) solution interface, combined with X-ray absorption fine structure (XAFS) of the reaction between [AuCl4](-) and thiol (RSH) in homogeneous toluene (TL) solution. Ion transfer calculations indicate the formation of [AuCl2](-) at RSH/Au ratios from 0.2-2 with a time-dependent variation observed over several days. At RSH/Au ratios above 2 and after time periods greater than 24 h, the formation of Au(I)SR is also observed. The relative concentrations of reaction products observed at the liquid/liquid interface are in excellent agreement with those observed by XAFS for the corresponding reaction in a single homogeneous phase. BH4(-) ion transfer reactions between water and DCE indicate that the reduction of [AuCl4](-) or [AuCl2](-) to Au nanoparticles by BH4(-) proceeds in the bulk organic phase. On the other hand, BH4(-) was unable to reduce the insoluble [Au(I)SR]n species to Au nanoparticles. The number and size of the nanoparticles formed was dependent on the concentration ratio of RSH/Au, as well as the experimental duration because of the competing formation of the [Au(I)SR]n precipitate. Higher concentrations of nanoparticles, with diameters of 1.0-1.5 nm, were formed at RSH/Au ratios from 1 to 2.
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Through X-ray absorption and emission spectroscopies, the chemical, electronic and structural properties of organic species in solution can be observed. Near-edge X-ray absorption fine structure (NEXAFS) and resonant inelastic X-ray scattering (RIXS) measurements at the nitrogen K-edge of para-aminobenzoic acid reveal both pH- and solvent-dependent variations in the ionisation potential (IP), 1sâπ* resonances and HOMO-LUMO gap. These changes unequivocally identify the chemical species (neutral, cationic or anionic) present in solution. It is shown how this incisive chemical state sensitivity is further enhanced by the possibility of quantitative bond length determination, based on the analysis of chemical shifts in IPs and σ* shape resonances in the NEXAFS spectra. This provides experimental access to detecting even minor variations in the molecular structure of solutes in solution, thereby providing an avenue to examining computational predictions of solute properties and solute-solvent interactions.
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X-ray absorption/emission spectroscopy (XAS/XES) at the N K-edge of iron protoporphyrin IX chloride (FePPIX-Cl, or hemin) has been carried out for dissolved monomers in DMSO, dimers in water and for the solid state. This sequence of samples permits identification of characteristic spectral features associated with the hemin intermolecular bonding. These characteristic features are further analyzed and understood at the molecular orbital (MO) level based on the DFT calculations.
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Hemina/química , Soluções/química , Animais , Bovinos , Dimerização , Dimetil Sulfóxido/química , Teoria Quântica , Água/química , Espectroscopia por Absorção de Raios XRESUMO
Significant elemental segregation is shown to exist within individual hollow silver-gold (Ag-Au) bimetallic nanoparticles obtained from the galvanic reaction between Ag particles and AuCl4(-). Three-dimensional compositional mapping using energy dispersive X-ray (EDX) tomography within the scanning transmission electron microscope (STEM) reveals that nanoparticle surface segregation inverts from Au-rich to Ag-rich as Au content increases. Maximum Au surface coverage was observed for nanoparticles with approximately 25 atom % Au, which correlates to the optimal catalytic performance in a three-component coupling reaction among cyclohexane carboxyaldehyde, piperidine, and phenylacetylene.
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The properties of nitrogen centres acting either as hydrogen-bond or Brønsted acceptors in solid molecular acid-base complexes have been probed by N 1s X-ray photoelectron spectroscopy (XPS) as well as (15)N solid-state nuclear magnetic resonance (ssNMR) spectroscopy and are interpreted with reference to local crystallographic structure information provided by X-ray diffraction (XRD). We have previously shown that the strong chemical shift of the N 1s binding energy associated with the protonation of nitrogen centres unequivocally distinguishes protonated (salt) from hydrogen-bonded (co-crystal) nitrogen species. This result is further supported by significant ssNMR shifts to low frequency, which occur with proton transfer from the acid to the base component. Generally, only minor chemical shifts occur upon co-crystal formation, unless a strong hydrogen bond is formed. CASTEP density functional theory (DFT) calculations of (15)N ssNMR isotropic chemical shifts correlate well with the experimental data, confirming that computational predictions of H-bond strengths and associated ssNMR chemical shifts allow the identification of salt and co-crystal structures (NMR crystallography). The excellent agreement between the conclusions drawn by XPS and the combined CASTEP/ssNMR investigations opens up a reliable avenue for local structure characterization in molecular systems even in the absence of crystal structure information, for example for non-crystalline or amorphous matter. The range of 17 different systems investigated in this study demonstrates the generic nature of this approach, which will be applicable to many other molecular materials in organic, physical, and materials chemistry.
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Prótons , Benzenossulfonatos/química , Benzoatos/química , Ácido Cítrico/química , Cristalografia por Raios X , Fumaratos/química , Glutaratos/química , Ácido Clorídrico/química , Ligação de Hidrogênio , Malonatos/química , Modelos Moleculares , Estrutura Molecular , Ácido Oxálico/química , Teoria Quântica , Salicilatos/química , Espectrofotometria , Raios XRESUMO
The outcome of synthetic procedures for crystalline organic materials strongly depends on the first steps along the molecular self-assembly pathway, a process we know as crystal nucleation. New experimental techniques and computational methodologies have spurred significant interest in understanding the detailed molecular mechanisms by which nuclei form and develop into macroscopic crystals. Although classical nucleation theory (CNT) has served well in describing the kinetics of the processes involved, new proposed nucleation mechanisms are additionally concerned with the evolution of structure and the competing nature of crystallization in polymorphic systems. In this Review, we explore the extent to which CNT and nucleation rate measurements can yield molecular-scale information on this process and summarize current knowledge relating to molecular self-assembly in nucleating systems.
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[This corrects the article DOI: 10.1021/acs.macromol.3c00585.].
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In situ small-angle X-ray scattering (SAXS) is a powerful technique for characterizing block-copolymer nano-object formation during polymerization-induced self-assembly. To work effectively in situ, it requires high intensity X-rays which enable the short acquisition times required for real-time measurements. However, routine access to synchrotron X-ray sources is expensive and highly competitive. Flow reactors provide an opportunity to obtain temporal resolution by operating at a consistent flow rate. Here, we equip a flow-reactor with an X-ray transparent flow-cell at the outlet which facilitates the use of a low-flux laboratory SAXS instrument for in situ monitoring. The formation and morphological evolution of spherical block copolymer nano-objects was characterized during reversible addition fragmentation chain transfer polymerization of diacetone acrylamide in the presence of a series of poly(dimethylacrylamide) (PDMAm) macromolecular chain transfer agents with varying degrees of polymerization. SAXS analysis indicated that during the polymerization, highly solvated, loosely defined aggregates form after approximately 100 s, followed by expulsion of solvent to form well-defined spherical particles with PDAAm cores and PDMAm stabilizer chains, which then grow as the polymerization proceeds. Analysis also indicates that the aggregation number (Nagg) increases during the reaction, likely due to collisions between swollen, growing nanoparticles. In situ SAXS conducted on PISA syntheses using different PDMAm DPs indicated a varying conformation of the chains in the particle cores, from collapsed chains for PDMAm47 to extended chains for PDMAm143. At high conversion, the final Nagg decreased as a function of increasing PDMAm DP, indicating increased steric stabilization afforded by the longer chains which is reflected by a decrease in both core diameter (from SAXS) and hydrodynamic diameter (from DLS) for a constant core DP of 400.
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Using operando X-ray absorption spectroscopy in a continuous-flow microfluidic cell, we have investigated the nucleation of platinum nanoparticles from aqueous hexachloroplatinate solution in the presence of the reducing agent ethylene glycol. By adjusting flow rates in the microfluidic channel, we resolved the temporal evolution of the reaction system in the first few seconds, generating the time profiles for speciation, ligand exchange, and reduction of Pt. Detailed analysis of the X-ray absorption near-edge structure and extended X-ray absorption fine structure spectra with multivariate data analysis shows that at least two reaction intermediates are involved in the transformation of the precursor H2PtCl6 to metallic platinum nanoparticles, including the formation of clusters with Pt-Pt bonding before complete reduction to Pt nanoparticles.
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Process analytical technologies are widely used to inform process control by identifying relationships between reagents and products. Here, we present a novel process analytical technology system for operando XAS on multiphase multicomponent synthesis processes based on the combination of a conventional lab-scale agitated reactor with a liquid-jet cell. The preparation of sulfonate-stabilized CaCO3 particles from polyphasic Ca(OH)2 dispersions was monitored in real time by Ca K-edge XAS to identify changes in Ca speciation in the bulk solution/dispersion as a function of time and process conditions. Linear combination fitting of the spectra quantitatively resolved composition changes from the initial conversion of Ca(OH)2 to the Ca(R-SO3)2 surfactant to the ultimate formation of nCaCO3·mCa(R- SO3)2 particles. The system provides a novel tool with strong chemical specificity for probing multiphase synthesis processes at a molecular level, providing an avenue to establishing the relationships between critical quality attributes of a process and the quality and performance of the product.