Ammonia is an important nutrient for the growth of plants. In industry, ammonia is produced by the energy expensive Haber-Bosch process where dihydrogen and dinitrogen form ammonia at a very high ...pressure and temperature. In principle one could also reduce dinitrogen upon addition of protons and electrons similar to the mechanism of ammonia production by nitrogenases. Recently, major breakthroughs have taken place in our understanding of biological fixation of dinitrogen, of molecular model systems that can reduce dinitrogen, and in the electrochemical reduction of dinitrogen at heterogeneous surfaces. Yet for efficient reduction of dinitrogen with protons and electrons major hurdles still have to be overcome. In this tutorial review we give an overview of the different catalytic systems, highlight the recent breakthroughs, pinpoint common grounds and discuss the bottlenecks and challenges in catalytic reduction of dinitrogen.
Catalytic reduction of dinitrogen with protons and electrons is a very challenging alternative to the energy expensive Haber-Bosch reaction.
Support effects in supported metal catalysts are well studied for thermocatalytic reactions, but less studied for electrocatalytic reactions. Here, we prepared a series of Pt supported on carbon ...nanofiber catalysts which vary in their Pt particle size and the content of oxygen groups on the surface of the CNF. We show that the activity of these catalysts for electrocatalytic glucose oxidation relates linearly with the content of support oxygen groups. Since the electronic state of Pt (XAS) and Pt surface structure (CO-stripping) were indistinguishable for all materials, we conclude that sorption effects of glucose play a crucial role in catalytic activity. This was further confirmed by establishing a relation between the annulus of the Pt particles and the activity.
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•Pt/CNF were used for the electrocatalytic oxidation of glucose.•Oxygen content on the CNF was varied.•Support oxygen groups in the annulus of the Pt particles enhance catalytic activity.
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The dissolution of noble‐metal catalysts under mild and carbon‐preserving conditions offers the possibility of in situ regeneration of the catalyst nanoparticles in fuel cells or other applications. ...Here, we report on the complete dissolution of the fuel cell catalyst, platinum nanoparticles, under very mild conditions at room temperature in 0.1 M HClO4 and 0.1 M HCl by electrochemical potential cycling between 0.5–1.1 V at a scan rate of 50 mV s−1. Dissolution rates as high as 22.5 μg cm−2 per cycle were achieved, which ensured a relatively short dissolution timescale of 3–5 h for a Pt loading of 0.35 mg cm−2 on carbon. The influence of chloride ions and oxygen in the electrolyte on the dissolution was investigated, and a dissolution mechanism is proposed on the basis of the experimental observations and available literature results. During the dissolution process, the corrosion of the carbon support was minimal, as observed by X‐ray photoelectron spectroscopy (XPS).
Platinum recovery: Noble metal catalyst nanoparticles are typically used as electrocatalysts in fuel cells. The main problem of these catalysts is their degradation during operation, making their recovery after use an important issue. We present an in situ strategy to recover platinum from a fuel cell catalyst under mild conditions by electrochemical potential cycling, with minimal corrosion of the carbon support and possibility of the catalyst regeneration.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Microemulsions are exciting systems that are promising as tuneable self-assembling templating reaction vessels at the nanoscale. Determination of the nano-structure of microemulsions is, however, not ...trivial, and there are fundamental questions regarding their design. We were able to reproduce experimental data for an important microemulsion system, sodium-AOT-n-heptane-water, using coarse-grained simulations involving relatively limited computational costs. The simulation allows visualization and deeper investigation of controversial phenomena such as bicontinuity and ion mobility. Simulations were performed using the Martini coarse-grained force field. AOT bonded parameters were fine-tuned by matching the geometry obtained from atomistic simulations. We investigated several compositions with a constant ratio of surfactant to oil while the water content was varied from 10 to 60% in weight. From mean square displacement calculation of all species, it was possible to quantify caging effects and ion mobility. Average diffusion coefficients were calculated for all charged species and trends in the diffusion coefficients were used to rationalize experimental conductivity data. Especially, the diffusion coefficient of charged species qualitatively matched the variation in conductivity as a function of water content. The scattering function was calculated for the hydrophilic species and up to 40% water content quantitatively matched the experimental data obtained from small angle X-ray scattering measurements. For higher water contents, discrepancies were observed and attributed to a nearby phase separation. In particular, bicontinuity of water and oil was computationally visualized by plotting the coordinates of hydrophilic beads. Equilibrated coarse-grained simulations were reversed to atomistic models in order both to compare ion mobility and to catch finer simulation details. Especially, it was possible to capture the intimate ion pair interaction between the sodium ion and the surfactant head group.
To develop a nationwide, evidence-based framework to support prenatal counseling in extreme prematurity, focusing on organization, decision-making, content, and style aspects.
A nationwide ...multicenter RAND-modified Delphi method study was performed between November 2016 and December 2017 in the Netherlands. Firstly, recommendations were extracted from literature and previous studies. Secondly, an expert panel (
= 21) with experienced parents, obstetricians, and neonatologists rated the recommendations on importance for inclusion in the framework. Thirdly, ratings were discussed in a consensus meeting. The final set of recommendations was approved and transformed into a framework.
A total of 101 recommendations on organization, decision-making, content, and style were included in the framework, including tools to support personalization. The most important recommendations regarding organization were to have both parents involved in the counseling with both the neonatologist and obstetrician. The shared decision-making model was recommended for deciding between active support and comfort care. Main recommendations regarding content of conversation were explanation of treatment options, information on survival, risk of permanent consequences, impossibility to predict an individual course, possibility for multiple future decision moments, and a discussion on parental values and standards. It was considered important to avoid jargon, check understanding, and provide a summary. The expert panel, patient organization, and national professional associations (gynecology and pediatrics) approved the framework.
A nationwide, evidence-based framework for prenatal counseling in extreme prematurity was developed. It contains recommendations and tools for personalization in the domains of organization, decision-making, content, and style of prenatal counseling.
BACKGROUND:A survival estimation for patients with symptomatic long bone metastases (LBM) is crucial to prevent overtreatment and undertreatment. This study analyzed prognostic factors for overall ...survival and developed a simple, easy-to-use prognostic model.
METHODS:A multicenter retrospective study of 1,520 patients treated for symptomatic LBM between 2000 and 2013 at the radiation therapy and/or orthopaedic departments was performed. Primary tumors were categorized into 3 clinical profiles (favorable, moderate, or unfavorable) according to an existing classification system. Associations between prognostic variables and overall survival were investigated using the Kaplan-Meier method and multivariate Cox regression models. The discriminatory ability of the developed model was assessed with the Harrell C-statistic. The observed and expected survival for each survival category were compared on the basis of an external cohort.
RESULTS:Median overall survival was 7.4 months (95% confidence interval CI, 6.7 to 8.1 months). On the basis of the independent prognostic factors, namely the clinical profile, Karnofsky Performance Score, and presence of visceral and/or brain metastases, 12 prognostic categories were created. The Harrell C-statistic was 0.70. A flowchart was developed to easily stratify patients. Using cutoff points for clinical decision-making, the 12 categories were narrowed down to 4 categories with clinical consequences. Median survival was 21.9 months (95% CI, 18.7 to 25.1 months), 10.5 months (95% CI, 7.9 to 13.1 months), 4.6 months (95% CI, 3.9 to 5.3 months), and 2.2 months (95% CI, 1.8 to 2.6 months) for the 4 categories.
CONCLUSIONS:This study presents a model to easily stratify patients with symptomatic LBM according to their expected survival. The simplicity and clarity of the model facilitate and encourage its use in the routine care of patients with LBM, to provide the most appropriate treatment for each individual patient.
LEVEL OF EVIDENCE:Prognostic Level IV. See Instructions for Authors for a complete description of levels of evidence.
Background
The HEART score is a validated risk stratification tool for chest pain patients presenting to the emergency department and was recently investigated for implementation in a pre-hospital ...setting. Fingerstick (capillary blood) point-of-care (POC) troponin testing enables quick measurements outside the hospital and seems easier to implement than the current venous blood sampling techniques. This study investigates the diagnostic accuracy of the modified HEART score, integrating fingerstick POC troponin testing, in ruling out acute coronary syndrome (ACS).
Methods
The data of 96 patients with chest pain, included in a study investigating a novel POC troponin device under development at the cardiac emergency department, were analysed retrospectively. Based on the patients’ admission data and capillary POC high-sensitivity troponin I (hs-cTnI) results, the modified HEART score was determined. The outcome measure, for evaluating the diagnostic accuracy of the modified HEART score, was the occurrence of ACS.
Results
Of the total study population, 33 patients (34%) were diagnosed with ACS. Seventeen patients (18%) were classified as low risk (0–3 points) and one patient (6%) in this group was diagnosed with ACS. The sensitivity and negative predictive value of the modified HEART score was 97.0 and 97.6%, respectively.
Conclusion
The modified HEART score, integrating capillary POC hs-cTnI results, is a promising tool for ruling out ACS in patients with chest pain presenting to the cardiac emergency department. These results encourage prospective investigation into the integration of fingerstick POC troponin testing in the modified HEART score in a pre-hospital setting.
The present work deals with the Cd²⁺ sorption studies on iron coated silica synthesized by sol-gel method. The coated media has been characterized before and after the adsorption of cadmium by ...surface area measurement, scanning electron microscopy (SEM), energy dispersive X-ray (EDX), Fourier transform infrared spectroscopy (FTIR), point of zero charge (PZC) and X-ray diffraction (XRD). X-ray diffraction patterns confirm the amorphous nature of the coated oxide. The uptake of Cd²⁺ ions is found to increase with increasing concentration, pH and temperature of solution. The Langmuir model is used to interpret sorption of cadmium ions on the solid surface. The values of both ΔH and ΔS are found to be positive, which explains the sorption process to be endothermic and spontaneous in nature. The silica dissolved from the solid surface plays a key role in the in the formation of ligand like surface ternary complexes.
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To understand the role of interfacial resistance to water transport in a system geometry comparable to that of a PEM fuel cell, water sorption kinetics in carbon-supported Nafion thin-films has been ...studied at different relative humidities at 20 °C while varying the membrane thickness. We have found anomalous water sorption kinetics at short time scales, i.e. deviation from the Fickian diffusion characteristic of these systems. We observe two different time scales with a delayed onset to Fickian behaviour that can be understood as the existence of two regimes with different diffusion coefficients. We attribute them to an interfacial diffusivity, Di, and a bulk diffusivity, Db. The onset delay is relatively more pronounced on thinner films due to increased interfacial resistance. Here, we show with a simple mathematical model based on Crank’s solution to Fick’s second law, that the presence of two regimes where water transport at the interface is orders of magnitude slower than at the bulk can simulate the anomalous behaviour in sorption curves. Experimental estimations of the onset time show it decays rapidly with increasing thickness of the films and scales linearly with the resistance to water transport.
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•Anomalous water sorption is observed at the MEA interface due to increased interfacial resistance.•Water transport resistance is higher at the vapour/membrane interface.•Water transport resistance decreases with hydration of the membrane.•Water transport (diffusivity) improves with thickness of the membrane.•A systematic method that disentangles interfacial and bulk contributions is proposed. MEA.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The cross-linking behavior of mussel adhesive protein Mefp-1 was studied by measuring the rate of aggregation of the protein by photon correlation spectroscopy. To be able to calculate the ...aggregation numbers, the hydrodynamic radius of monomer Mefp-1 (10 nm) was determined under reducing conditions. The aggregation is controlled by the redox potential of the solution, and the aggregation number varied, independent of pH, over a factor 2 within the experimentally accessible redox potential window. A kinetic model for cross-linking, based on the intricate interplay of the oxidation and auto-oxidation of the hydroquinones of Mefp-1, is proposed. The oxidation rate strongly depends on redox potential. The cross-linking rate is taken to be proportional to the rate of auto-oxidation. The model correctly predicts the experimentally observed phenomena. When the oxidation rate is slower than the auto-oxidation rate, cross-linking is efficient and controlled by the oxidation rate. When the rate of auto-oxidation rate is slower than the oxidation rate, the cross-linking is inefficient due to the quick exhaustion of the hydroquinones. The experimentally determined rate constant for cross-linking is found to be much smaller than those found for auto-oxidation of hydroquinones because of the excluded volume interactions imposed by the protein backbone. Tuning the interplay between oxidation and auto-oxidation presents the potential of controlling cross-linking density independent of the density of reactive groups.
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