The separation of molecules with similar size and shape is an important technological challenge. For example, rare gases can pose either an economic opportunity or an environmental hazard and there ...is a need to separate these spherical molecules selectively at low concentrations in air. Likewise, chiral molecules are important building blocks for pharmaceuticals, but chiral enantiomers, by definition, have identical size and shape, and their separation can be challenging. Here we show that a porous organic cage molecule has unprecedented performance in the solid state for the separation of rare gases, such as krypton and xenon. The selectivity arises from a precise size match between the rare gas and the organic cage cavity, as predicted by molecular simulations. Breakthrough experiments demonstrate real practical potential for the separation of krypton, xenon and radon from air at concentrations of only a few parts per million. We also demonstrate selective binding of chiral organic molecules such as 1-phenylethanol, suggesting applications in enantioselective separation.
A chemoselective spectroscopic method for measuring CO2 sorption isotherms at pressures up to 14 MPa (140 bar) is validated against manometric measurements and molecular simulations, giving insights ...into the preferred sorption sites in various crystalline porous organic cages.
We report two isoreticular 3D peptide‐based porous frameworks formed by coordination of the tripeptides Gly‐L‐His‐Gly and Gly‐L‐His‐L‐Lys to CuII which display sponge‐like behaviour. These porous ...materials undergo structural collapse upon evacuation that can be reversed by exposure to water vapour, which permits recovery of the original open channel structure. This is further confirmed by sorption studies that reveal that both solids exhibit selective sorption of H2O while CO2 adsorption does not result in recovery of the original structures. We also show how the pendant aliphatic amine chains, present in the framework from the introduction of the lysine amino acid in the peptidic backbone, can be post‐synthetically modified to produce urea‐functionalised networks by following methodologies typically used for metal–organic frameworks built from more rigid “classical” linkers.
Motion capture: Sponge‐like behaviour in isoreticular Cu(Gly‐His‐X) (X=Gly or Lys) peptide‐based porous materials is enabled by the rich conformational flexibility accessible to tripeptides (see figure).
Summary
Context
Evidence‐based clinical guidelines in endocrinology attempt to improve and standardize patient care. There has been an expansion in guideline production although some of the ...heterogeneous methods used to assess the quality of the underlying evidence base might limit interpretation and implementation.
Design
Current and archived guidelines from major endocrine organizations were accessed. The organizations used six different methods to rate underlying evidence, including Grading of Recommendations Assessment, Development and Evaluation (GRADE). To allow direct comparison between guidelines produced by different organizations, the levels of evidence used to generate them were graded according to the standardized system: ‘high’ based on randomized, controlled trials and meta‐analyses, ‘moderate’ based on nonrandomized studies and ‘low’ based on expert opinion.
Results
There was an increase in guideline production over time (1995–2000 = 9, 2001–2005 = 12, 2006–2011 = 36). Three guidelines were updated with an average delay of 4·3 years and an increase in recommendations per guideline (21·1%). Encouragingly, whilst updates had similar levels of ‘high’‐quality evidence, there was increased reliance on ‘moderate’‐category evidence and less on ‘low’‘‐quality evidence’ (‘high’, 6·3% vs 6·5%; ‘moderate’, 46·1% vs 59·1%; ‘low’, 47·7% vs 34·4%). A high proportion of ‘low’‐category evidence was seen throughout all organizations. Rarer conditions and recommendations concerning treatment efficacy were particularly reliant on ‘low’‐category evidence.
Conclusions
The level of evidence underpinning current guidelines highlights areas in need of well‐designed, collaborative clinical research. Furthermore, criteria to define when guideline updates are necessary are currently lacking. A standardized method of assessment, such as GRADE, would promote understanding and compliance by guideline users with the ultimate aim of enhancing patient care.
A chemoselective spectroscopic method for measuring CO
2
sorption isotherms at pressures up to 14 MPa (140 bar) is validated against manometric measurements and molecular simulations, giving insights ...into the preferred sorption sites in various crystalline porous organic cages.
A spectroscopic method for measuring CO
2
sorption isotherms at high pressure is validated for crystalline porous organic cages.
It is over 10 years since the first ACPGBI Position Statement on the management of anal fistula was published in 2007. This second edition is the result of scrutiny of the literature published during ...this time; it updates the original Position Statement and reviews the published evidence surrounding treatments for anal fistula that have been developed since the original publication.
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