Evaluation of appendicitis risk prediction models in adults with suspected appendicitis

Background Appendicitis is the most common general surgical emergency worldwide, but its diagnosis remains challenging. The aim of this study was to determine whether existing risk prediction models can reliably identify patients presenting to hospital in the UK with acute right iliac fossa (RIF) pain who are at low risk of appendicitis. Methods A systematic search was completed to identify all existing appendicitis risk prediction models. Models were validated using UK data from an international prospective cohort study that captured consecutive patients aged 16–45 years presenting to hospital with acute RIF in March to June 2017. The main outcome was best achievable model specificity (proportion of patients who did not have appendicitis correctly classified as low risk) whilst maintaining a failure rate below 5 per cent (proportion of patients identified as low risk who actually had appendicitis). Results Some 5345 patients across 154 UK hospitals were identified, of which two‐thirds (3613 of 5345, 67·6 per cent) were women. Women were more than twice as likely to undergo surgery with removal of a histologically normal appendix (272 of 964, 28·2 per cent) than men (120 of 993, 12·1 per cent) (relative risk 2·33, 95 per cent c.i. 1·92 to 2·84; P < 0·001). Of 15 validated risk prediction models, the Adult Appendicitis Score performed best (cut‐off score 8 or less, specificity 63·1 per cent, failure rate 3·7 per cent). The Appendicitis Inflammatory Response Score performed best for men (cut‐off score 2 or less, specificity 24·7 per cent, failure rate 2·4 per cent). Conclusion Women in the UK had a disproportionate risk of admission without surgical intervention and had high rates of normal appendicectomy. Risk prediction models to support shared decision‐making by identifying adults in the UK at low risk of appendicitis were identified

Effect of lattice shrinking on the migration of water within zeolite LTA

\u3cp\u3eWater adsorption within zeolites of the Linde Type A (LTA) structure plays an important role in processes of water removal from solvents. For this purpose, knowing in which adsorption sites water is preferably found is of interest. In this paper, the distribution of water within LTA is investigated in several aluminum-substituted frameworks ranging from a Si:Al ratio of 1 (maximum substitution, framework is hydrophilic) to a Si:Al ratio of 191 (almost pure siliceous framework, it is hydrophobic). The counterion is sodium. In the hydrophobic framework, water is found in the large α-cages, whereas in the most hydrophilic frameworks, water is found preferably in the small β-cages. For frameworks with moderate aluminum substitution, β-cages are populated first, but at intermediate loading water favors α-cages instead. Framework composition and pressure therefore drive water molecules selectively towards α- or β-cages.\u3c/p\u3

Nucleation of zeolitic imidazolate frameworks: from molecules to nanoparticles

We have studied the clusters involved in the initial stages of nucleation of Zeolitic Imidazolate Frameworks, employing a wide range of computational techniques. In the pre-nucleating solution, the prevalent cluster is the ZnIm4 cluster (formed by a zinc cation, Zn2+, and four imidazolate anions, Im−), although clusters such as ZnIm3, Zn2Im7, Zn2Im7, Zn3Im9, Zn3Im10, or Zn4Im12 have energies that are not much higher, so they would also be present in solution at appreciable quantities. All these species, except ZnIm3, have a tetrahedrally coordinated Zn2+ cation. Small ZnxImy clusters are less stable than the ZnIm4 cluster. The first cluster that is found to be more stable than ZnIm4 is the Zn41Im88 cluster, which is a disordered cluster with glassy structure. Bulk-like clusters do not begin to be more stable than glassy clusters until much larger sizes, since the larger cluster we have studied (Zn144Im288) is still less stable than the glassy Zn41Im88 cluster, suggesting that Ostwald's rule (the less stable polymorph crystallizes first) could be fulfilled, not for kinetic, but for thermodynamic reasons. Our results suggest that the first clusters formed in the nucleation process would be glassy clusters, which then undergo transformation to any of the various crystal structures possible, depending on the kinetic routes provided by the synthesis conditions. Our study helps elucidate the way in which the various species present in solution interact, leading to nucleation and crystal growth

Understanding the stability and structural properties of ordered nanoporous metals towards their rational synthesis

Peer reviewed: TrueOrdered Nanoporous Metals (ONMs) form a new family of nanoporous materials composed only of pure metals. The expected impact is considerable from combining the ordered nanopore structure of MOFs, zeolites and carbon schwartzites with the robustness and electronic conductivity of metals. Little is known about their stability and structural features. Here we address these points to provide clues toward their rational synthesis, introducing an automatic atomistic design that uses model building and molecular dynamics structural relaxation, and is validated against the experimentally known ONMs. Analysing the properties of the 10 stable structures out of the 17 studied (14 of which are designed in this work) using four noble metals (Pt, Pd, Au and Ag), we have deciphered some key elements and structural descriptors that provide guidelines for the experimental synthesis of ONMS. The long-lived metastability of the stable ONMs is evidenced by the high free energy landscape, computed via Metadynamic simulations. The new ONMs permit molecular diffusion of various molecules of industrial relevance, increasing the expectation for their use in catalysis, separation, nanofiltration, batteries, fuel cells, etc. Stable low-cost ONMs are predicted using Earth-abundant Ni metal, which maintains the main features of their relative noble metal forms.</jats:p

Zeolites for CO\u3csub\u3e2\u3c/sub\u3e-CO-O\u3csub\u3e2\u3c/sub\u3e separation to obtain CO\u3csub\u3e2\u3c/sub\u3e-neutral fuels

\u3cp\u3eCarbon dioxide release has become an important global issue due to the significant and continuous rise in atmospheric CO\u3csub\u3e2\u3c/sub\u3e concentrations and the depletion of carbon-based energy resources. Plasmolysis is a very energy-efficient process for reintroducing CO\u3csub\u3e2\u3c/sub\u3e into energy and chemical cycles by converting CO\u3csub\u3e2\u3c/sub\u3e into CO and O\u3csub\u3e2\u3c/sub\u3e utilizing renewable electricity. The bottleneck of the process is that CO remains mixed with O\u3csub\u3e2\u3c/sub\u3e and residual CO\u3csub\u3e2\u3c/sub\u3e. Therefore, efficient gas separation and recuperation are essential for obtaining pure CO, which, via water gas shift and Fischer-Tropsch reactions, can lead to the production of CO\u3csub\u3e2\u3c/sub\u3e-neutral fuels. The idea behind this work is to provide a separation mechanism based on zeolites to optimize the separation of carbon dioxide, carbon monoxide, and oxygen under mild operational conditions. To achieve this goal, we performed a thorough screening of available zeolites based on topology and adsorptive properties using molecular simulation and ideal adsorption solution theory. FAU, BRE, and MTW are identified as suitable topologies for these separation processes. FAU can be used for the separation of carbon dioxide from carbon monoxide and oxygen and BRE or MTW for the separation of carbon monoxide from oxygen. These results are reinforced by pressure swing adsorption simulations at room temperature combining adsorption columns with pure silica FAU zeolite and zeolite BRE at a Si/Al ratio of 3. These zeolites have the added advantage of being commercially available.\u3c/p\u3