Review: Marine natural products

This review covers the literature published in 2003 for marine natural products, with 619 citations (413 for the period January to December 2003) referring to compounds isolated from marine microorganisms and phytoplankton, green algae, brown algae, red algae, sponges, coelenterates, bryozoans, molluscs, tunicates and echinoderms. The emphasis is on new compounds (656 for 2003), together with their relevant biological activities, source organisms and country of origin. Biosynthetic studies or syntheses that lead to the revision of structures or stereochemistries have been included (78), including any first total syntheses of a marine natural product

Coerced Mechanical Coarsening of Nanoparticle Assemblies

Coarsening is a ubiquitous phenomenon [1-3] that underpins countless processes in nature, including epitaxial growth [1,3,4], the phase separation of alloys, polymers and binary fluids [2], the growth of bubbles in foams5, and pattern formation in biomembranes6. Here we show, in the first real-time experimental study of the evolution of an adsorbed colloidal nanoparticle array, that tapping-mode atomic force microscopy (TM-AFM) can drive the coarsening of Au nanoparticle assemblies on silicon surfaces. Although the growth exponent has a strong dependence on the initial sample morphology, our observations are largely consistent with modified Ostwald ripening processes [7-9]. To date, ripening processes have been exclusively considered to be thermally activated, but we show that nanoparticle assemblies can be mechanically coerced towards equilibrium, representing a new approach to directed coarsening. This strategy enables precise control over the evolution of micro- and nanostructures

Broken symmetry and the variation of critical properties in the phase behaviour of supramolecular rhombus tilings

The degree of randomness, or partial order, present in two-dimensional supramolecular arrays of isophthalate tetracarboxylic acids is shown to vary due to subtle chemical changes such as the choice of solvent or small differences in molecular dimensions. This variation may be quantified using an order parameter and reveals a novel phase behaviour including random tiling with varying critical properties as well as ordered phases dominated by either parallel or non-parallel alignment of neighbouring molecules, consistent with long-standing theoretical studies. The balance between order and randomness is driven by small differences in the intermolecular interaction energies, which we show, using numerical simulations, can be related to the measured order parameter. Significant variations occur even when the energy difference is much less than the thermal energy highlighting the delicate balance between entropic and energetic effects in complex self-assembly processes

An interlaboratory comparison of X-ray computed tomography measurement for texture and dimensional characterisation of additively manufactured parts

Abstract This paper presents the results of the CT-STARR (CT-Surface Texture for Additive Round Robin) Stage 1 interlaboratory comparison. The study compared the results obtained for the extraction of areal surface texture data per ISO 25178-2 from five X-ray computed tomography (CT) volume measurements from each of four laboratories. Two Ti6Al4V ELI (extra-low interstitial) components were included in each of the CT acquisitions. The first component was an additively manufactured (AM) cube manufactured using an Arcam Q10 electron beam melting (EBM) machine. Surface texture data was extracted from CT scans of this part. The values of selected parameters per ISO 25178-2 are reported, including Sa, the arithmetic mean height, for which the values from the Nikon MCT 225 metrology CT measurements were all within 0.5% of the mean reference focus variation measurement. CT resolution requirements are discussed. The second component was a machined dimensional test artefact designed to facilitate independent analysis of CT global voxel scaling errors and surface determination errors. The results of mathematical global scaling and surface determination correction of the dimensional artefact data is reported. The dimensional test artefact errors for the XT H 225 commercial CT for length, outside diameter and inside diameter reduced from -0.27%, -0.83% and -0.54% respectively to less than 0.02% after performing mathematical correction. This work will assist the development of surface texture correction protocols, help define surface-from-CT measurement envelope limits and provide valuable information for an expanded Stage 2 interlaboratory comparison, which will include a more diverse range of CT systems and technologies, further expanding the surface-from-CT knowledge base

Height dependent molecular trapping in stacked cyclic porphyrin nanorings

Stacked layers of cyclic porphyrin nanorings constitute nanoscale receptacles with variable height and diameter which preferentially adsorb sublimed molecules. Using scanning tunnelling microscopy we determine the filling capacity of these nanoring traps, and the dependence of adsorbate capture on stack height and diameter

Can increased primary care access reduce demand for emergency care? Evidence from England's 7-day GP opening

Restricted access to primary care can lead to avoidable, excessive use of expensive emergency care. Since 2013, partly to alleviate overcrowding at the Accident & Emergency (A&E) units of hospitals, the UK has been piloting 7-day opening of General Practitioner (GP) practices to improve primary care access for patients. We evaluate the impact of these pilots on patient attendances at A&E. We estimate that 7-day GP opening has reduced A&E attendances by patients of pilot practices by 9.9% with most of the impact on weekends which see A&E attendances fall by 17.9%. The effect is non-monotonic in case severity with most of the fall occurring in cases of moderate severity. An additional finding is that there is also a 9.9% fall in weekend hospital admissions (from A&E) which is entirely driven by a fall in admissions of elderly patients. The impact on A&E attendances appears to be bigger among wealthier patients. We present evidence in support of a causal interpretation of our results and discuss policy implications

The incidence of ventilator-associated pneumonia using the PneuX System with or without elective endotracheal tube exchange: A pilot study

<p>Abstract</p> <p>Background</p> <p>The PneuX System is a novel endotracheal tube and tracheal seal monitor, which has been designed to minimise the aspiration of oropharyngeal secretions. We aimed to determine the incidence of ventilator-associated pneumonia (VAP) in patients who were intubated with the PneuX System and to establish whether intermittent subglottic secretion drainage could be performed reliably and safely using the PneuX System.</p> <p>Findings</p> <p>In this retrospective observational study, data was collected from 53 sequential patients. Nine (17%) patients were initially intubated with the PneuX System and 44 (83%) patients underwent elective exchange to the PneuX System. There were no episodes of VAP while the PneuX System was <it>in situ</it>. On an intention to treat basis, the incidence VAP was 1.8%. There were no complications from, or failure of, subglottic secretion drainage during the study.</p> <p>Conclusions</p> <p>Our study demonstrates that a low incidence of VAP is possible using the PneuX System. Our study also demonstrates that elective exchange and intermittent subglottic secretion drainage can be performed reliably and safely using the PneuX System.</p