A mechanistic study of the Fischer-Tropsch synthesis using transient isotopic tracing. Part-1: Model identification and discrimination

A steady state isotopic transient kinetic anal. (SSITKA) of the Fischer-Tropsch synthesis over Co/Ru/TiO2 catalyst is reported by using 13CO and D2. Besides a qual. interpretation of the transients, model identification and discrimination are mainly based on numerical modeling. From this, it is concluded that two single-C species are present on the catalyst surface, Ca,ads and Cb,ads. These species both participate in the formation of methane and of higher hydrocarbons. The heterogeneity of the catalyst surface is limited to these two single-C species. Only one type of chain-growth site is present in a low concn. compared to the surface concns. of COads, Ca,ads, and Cb,ads. The H-content of Ca,ads and Cb,ads is assessed by comparing the simulated transient for the incorporation of the D-labeling into methane with expts. In case the stepwise hydrogenations of Cads to CH4 are irreversible, Ca,ads and Cb,ads are H-free species. In case these reactions are reversible, the H-exchange between Cads, CHads, CH2,ads, and CH3,ads is fast compared to the net formation of methane, and the H-content of Ca,ads and Cb,ads cannot be assessed. The most probable mechanism for the Fischer-Tropsch reaction resulting from this study is used in a next paper (Part 2) for the quantification of the kinetic parameters. In that paper, a systematic anal. of these parameters yields detailed mechanistic insight into the Fischer-Tropsch synthesis reaction. [on SciFinder (R)

Efficacy of Biphasic Calcium Phosphate Ceramic With a Needle-shaped Surface Topography Versus Autograft in Instrumented Posterolateral Spinal Fusion: A Randomized Trial

Study Design. A multicenter randomized controlled noninferiority trial with intrapatient comparisons. Objective. The aim of this study was to determine noninferiority of a slowly resorbable biphasic calcium phosphate with submicron microporosity (BCP15% inferiority with binomial paired comparisons of the fusion performance score per treatment side. Results. Of the 100 patients (57 ± 12.9 y, 62% female), 91 subjects and 128 segments were analyzed. The overall posterolateral fusion rate per segment (left and/or right) was 83%. For the BCP<μm side only the fusion rate was 79% versus 47% for the autograft side (difference of 32 percentage points, 95% CI, 23-41). Analysis of the primary outcome confirmed the noninferiority of BCP<μm with an absolute difference in paired proportions of 39.6% (95% CI, 26.8-51.2; p < 0.001). Conclusion. This clinical trial demonstrates noninferiority and indicates superiority of MagnetOs Granules as a standalone ceramic when compared to autograft for posterolateral spinal fusion. These results challange the belief that autologous bone is the most optimal graft material

The effectiveness of a protocol without routine radiographs for follow-up of adolescent idiopathic scoliosis patients (CURVE): a study protocol

Background and purpose: Current follow-up protocols for adolescent idiopathic scoliosis (AIS) are based on consensus and consist of regular full-spine radiographs to monitor curve progression and surgical complications. Consensus exists to avoid inappropriate use of radiographs in children. It is unknown whether a standard radiologic follow-up (S-FU) approach is necessary or if a patient-empowered follow-up (PE-FU) approach can reduce the number of radiographs without treatment consequences. Methods and analyses: A nationwide multicenter pragmatic randomized preference trial was designed for 3 follow-up subgroups (pre-treatment, post-brace, post-surgery) to compare PE-FU and S-FU. 812 patients with AIS (age 10–18 years) will be included in the randomized trial or preference cohorts. Primary outcome is the proportion of radiographs with a treatment consequence for each subgroup. Secondary outcomes consist of the proportion of patients with delayed initiation of treatment due to non-routine radiographic follow-up, radiation exposure, societal costs, positive predictive value, and interrelation of clinical assessment, quality of life, and parameters for initiation of treatment during follow-up. Outcomes will be analyzed using linear mixed-effects models, adjusted for relevant baseline covariates, and are based on intention-to-treat principle. Study summary: (i) a national, multicenter pragmatic randomized trial addressing the optimal frequency of radiographic follow-up in patients with AIS; (ii) first study that includes patient-empowered follow-up; (iii) an inclusive study with 3 follow-up subgroups and few exclusion criteria representative for clinical reality; (iv) preference cohorts alongside to amplify generalizability; (v) first study conducting an economic evaluation comparing both follow-up approaches