A surface oxidised Fe-S catalyst for the liquid phase hydrogenation of CO₂

Rapidly increasing anthropogenic carbon dioxide (CO_{2}) emissions, coupled with irreversible climate change and depleting fossil fuel reserves, have significantly increased the drive for CO_{2} utilisation. Iron sulfide as a catalyst for the hydrogenation of CO_{2} has been discussed in the literature for decades, especially in an origin-of-life context, but little experimental evidence exists in the literature for its feasibility. Here we report the catalytic properties of pyrrhotite (Fe_{1−x}S) for the hydrogenation of CO_{2} into formate. Advanced material characterisation methods in combination with computational studies have allowed us to identify surface S–Fe–O moieties as active sites for the reaction

Reconsidering Calcium Dehydration as the Rate-Determining Step in Calcium Mineral Growth

The dehydration of cations is generally accepted as the rate-limiting step in many processes. Molecular dynamics (MD) can be used to investigate the dynamics of water molecules around cations, and two different methods exist to obtain trajectory-based water dehydration frequencies. Here, these two different post-processing methods (direct method versus survival function) have been implemented to obtain calcium dehydration frequencies from a series of trajectories obtained using a range of accepted force fields. None of the method combinations reproduced the commonly accepted experimental water exchange frequency of 10–8.2 s–1. Instead, our results suggest much faster water dynamics, comparable with more accurate ab initio MD simulations and with experimental values obtained using neutron scattering techniques. We obtained the best agreement using the survival function method to characterize the water dynamics, and we show that different method combinations significantly affect the outcome. Our work strongly suggests that the fast water exchange kinetics around the calcium ions is not rate-limiting for reactions involving dissolved/solvated calcium. Our results further suggest that, for alkali and most of the earth alkali metals, mechanistic rate laws for growth, dissolution, and adsorption, which are based on the principle of rate-limiting cation dehydration, need careful reconsideration

The role of surface oxidation and Fe-Ni synergy in Fe-Ni-S catalysts for CO2 hydrogenation.

Increasing carbon dioxide (CO2) emissions, resulting in climate change, have driven the motivation to achieve the effective and sustainable conversion of CO2 into useful chemicals and fuels. Taking inspiration from biological processes, synthetic iron-nickel-sulfides have been proposed as suitable catalysts for the hydrogenation of CO2. In order to experimentally validate this hypothesis, here we report violarite (Fe,Ni)3S4 as a cheap and economically viable catalyst for the hydrogenation of CO2 into formate under mild, alkaline conditions at 125 °C and 20 bar (CO2 : H2 = 1 : 1). Calcination of violarite at 200 °C resulted in excellent catalytic activity, far superior to that of Fe-only and Ni-only sulfides. We further report first principles simulations of the CO2 conversion on the partially oxidised (001) and (111) surfaces of stoichiometric violarite (FeNi2S4) and polydymite (Ni3S4) to rationalise the experimentally observed trends. We have obtained the thermodynamic and kinetic profiles for the reaction of carbon dioxide (CO2) and water (H2O) on the catalyst surfaces via substitution and dissociation mechanisms. We report that the partially oxidised (111) surface of FeNi2S4 is the best catalyst in the series and that the dissociation mechanism is the most favourable. Our study reveals that the partial oxidation of the FeNi2S4 surface, as well as the synergy of the Fe and Ni ions, are important in the catalytic activity of the material for the effective hydrogenation of CO2 to formate

Relation between physical activity and cerebral small vessel disease: A nine-year prospective cohort study.

BACKGROUND AND AIMS: Given the unexplored potential of physical activity to reduce the progression of cerebral small vessel disease (cSVD, the purpose of this study was to prospectively (across nine-year follow-up) examine the relation between (baseline) physical activity and the (clinical and imaging) consequences of the whole spectrum of cerebral small vessel disease. METHODS: Five hundred and three patients with cerebral small vessel disease from the RUNDMC study were followed for nine years. Physical activity was assessed using a questionnaire in 2006, 2011, and 2015. Clinical events (i.e. all-cause mortality, cerebrovascular events (by stroke subtype)) were collected with a structured questionnaire. Patients underwent magnetic resonance imaging scanning for the assessment of magnetic resonance imaging markers of cerebral small vessel disease (i.e. white matter hyperintensities, lacunes, and microbleeds) and microstructural integrity of the white matter at three timepoints. RESULTS: The mean age at baseline was 66 (SD 9.0) years; 44% were women. A higher baseline physical activity level was independently associated with a lower all-cause mortality (HR: 0.69, 95%CI: 0.49-0.98, p = 0.03) and incidence of cerebrovascular disease (HR: 0.58, 95%CI: 0.36-0.96, p = 0.03). However, we found no relation between physical activity and incident lacunar stroke or progression of magnetic resonance imaging markers of cerebral small vessel disease. CONCLUSIONS: Whilst regular physical activity was not related to the progression of magnetic resonance imaging markers of cerebral small vessel disease across a nine-year follow-up, results from our study prove that high levels of physical activity in patients with cerebral small vessel disease are associated with a lower all-cause mortality and lower incidence of cerebrovascular events

Surface Oxidized Fe-S catalyst for the Liquid Phase Hydrogenation of CO2

Rapidly increasing anthropogenic carbon dioxide (CO2) emissions, coupled with irreversible climate change and depleting fossil fuels reserves, has significantly increased the drive for CO2 utilization. Iron sulfide as a catalyst for the hydrogenation of CO2 has been discussed in the literature for decades, especially in an origin-of-life context, however little experimental evidence exists in the literature for its feasibility. Here we report the catalytic properties of pyrrhotite (Fe1-xS) for the hydrogenation of CO2 into formate under mild, alkaline conditions at 125 oC and 20 bar (CO2:H2, 1:1). Controlled surface oxidation of pyrrhotite, via high temperature calcination, increased the surface oxygen species that in turn resulted in an increased catalytic activity, with the optimum calcination temperature being 200 oC. X-ray based characterisation methods in combination with computational studies, allowed us to identify surface S-Fe-O moieties as active sites for the reaction

Accelerated development of cerebral small vessel disease in young stroke patients.

OBJECTIVE: To study the long-term prevalence of small vessel disease after young stroke and to compare this to healthy controls. METHODS: This prospective cohort study comprises 337 patients with an ischemic stroke or TIA, aged 18-50 years, without a history of TIA or stroke. In addition, 90 age- and sex-matched controls were included. At follow-up, lacunes, microbleeds, and white matter hyperintensity (WMH) volume were assessed using MRI. To investigate the relation between risk factors and small vessel disease, logistic and linear regression were used. RESULTS: After mean follow-up of 9.9 (SD 8.1) years, 337 patients were included (227 with an ischemic stroke and 110 with a TIA). Mean age of patients was 49.8 years (SD 10.3) and 45.4% were men; for controls, mean age was 49.4 years (SD 11.9) and 45.6% were men. Compared with controls, patients more often had at least 1 lacune (24.0% vs 4.5%, p < 0.0001). In addition, they had a higher WMH volume (median 1.5 mL [interquartile range (IQR) 0.5-3.7] vs 0.4 mL [IQR 0.0-1.0], p < 0.001). Compared with controls, patients had the same volume WMHs on average 10-20 years earlier. In the patient group, age at stroke (β = 0.03, 95% confidence interval [CI] 0.02-0.04) hypertension (β = 0.22, 95% CI 0.04-0.39), and smoking (β = 0.18, 95% CI 0.01-0.34) at baseline were associated with WMH volume. CONCLUSIONS: Patients with a young stroke have a higher burden of small vessel disease than controls adjusted for confounders. Cerebral aging seems accelerated by 10-20 years in these patients, which may suggest an increased vulnerability to vascular risk factors.This is the final version of the article. It first appeared from Wolters Kluwer via https://doi.org/10.​1212/​WNL.​0000000000003123

Looking for interaction: quantitative measurement of research utilization by Dutch local health officials

Background: In the Netherlands, local authorities are required by law to develop local health memoranda, based on epidemiological analyses. The purpose of this study was to assess the actual use of these epidemiological reports by municipal health officials and associated factors that affect this use.Method: Based on a conceptual framework, we designed a questionnaire in which we operationalized instrumental, conceptual, and symbolic use, the interaction between researchers and local health officials, and four clusters of barriers in this interaction process. We conducted an internet survey among 155 Dutch local health officials representing 35% of all Dutch municipalities. By means of multiple regression analyses, we gained insight into the related factors for each of the three types of research utilization.Results: The results show that local health officials use epidemiological research more often in a conceptual than an instrumental or symbolic way. This can be explained by the complexity of the local policy process which is often linked to policies in other areas, and the various policy actors involved. Conceptual use was statistically associated with a presentation given by the epidemiologist during the policy process, the presence of obstructions regarding the report's accessibility, and the local official's personal belief systems and interests originating from different professional values and responsibilities. Instrumental and symbolic use increased with the involvement of local officials in the research process.Conclusions: The results of this study provide a partial solution to understanding and influencing research utilization. The quantitative approach underpins earlier qualitative findings on this topic. The outcomes suggest that RPHS epidemiologists can use different strategies to improve research utilization. 'Blurring the boundaries', and the enhancement of interfaces between epidemiologists and local health officials, like direct interactions into each other's work processes, is expected to create better possibilities for optimizing research use

The quark anti-quark potential and the cusp anomalous dimension from a TBA equation

We derive a set of integral equations of the TBA type for the generalized cusp anomalous dimension, or the quark antiquark potential on the three sphere, as a function of the angles. We do this by considering a family of local operators on a Wilson loop with charge L. In the large L limit the problem can be solved in terms of a certain boundary reflection matrix. We determine this reflection matrix by using the symmetries and the boundary crossing equation. The cusp is introduced through a relative rotation between the two boundaries. Then the TBA trick of exchanging space and time leads to an exact equation for all values of L. The L=0 case corresponds to the cusped Wilson loop with no operators inserted. We then derive a slightly simplified integral equation which describes the small angle limit. We solve this equation up to three loops in perturbation theory and match the results that were obtained with more direct approaches.Comment: 63 pages, 12 figures. v2: references added, typos correcte