Structure determination of a 4-pyrone from the liverwort <i>Plagiochila bifaria</i> (Sw.) Lindenb. (Plagiochilaceae)

The centenary of the presentation in 1907 of the "polyketide" hypothesis by Collie, along with his use of a 4-pyrone as an example, is marked by reporting the discovery and isolation of 2-(3,4-dimethoxyphenethyl)-6-methyl-4-pyrone from &lt;i&gt;Plagiochila bifaria&lt;/i&gt;. This compound dominates the phytochemical profile of the deuteriochloroform extract of a Venezuelan specimen of &lt;i&gt;P. bifaria&lt;/i&gt; and the structure was determined using spectroscopic techniques, especially 2D NMR. This natural product is novel because it contains what appears to be the first example of a monocyclic 4-pyrone that has a polyketide origin. The hypothetical pathway for cyclization of a triketocarboxylic acid to a 4-pyrone was known to be applicable to model systems but no examples of natural products from this route were known. This compound is the same as one of a series of compounds observed previously in an extract of a Brazilian specimen of &lt;i&gt;P. bifaria&lt;/i&gt;; the working structures that were proposed earlier require revision. The mass spectral characteristics are the same as those reported (parent and base peak) in 1987 for the major component observed in the GC-MS profile of an extract of a specimen of &lt;i&gt;P. bifaria&lt;/i&gt; from Peru. The roles played by Birch and Robinson in the renaissance of the polyketide hypothesis almost fifty years after its initial launch are considered. Based on evidence from their publications, they worked independently of each other. It appears Robinson always had knowledge of Collie's hypothesis when developing ideas about structural relations of natural products whereas Birch initially was unaware of both Collie's and Robinson's ideas on the subject

Haydn's Welsh songs: George Thomson's musical and literary sources / Caneuon Cymreig Haydn: Ffynonellau Cerddorol a Llenyddol George Thomson

No abstract available

Electromagnetic atmosphere-plasma coupling: the global atmospheric electric circuit

A description is given of the global atmospheric electric circuit operating between the Earth’s surface and the ionosphere. Attention is drawn to the huge range of horizontal and vertical spatial scales, ranging from 10−9 m to 1012 m, concerned with the many important processes at work. A similarly enormous range of time scales is involved from 10−6 s to 109 s, in the physical effects and different phenomena that need to be considered. The current flowing in the global circuit is generated by disturbed weather such as thunderstorms and electrified rain/shower clouds, mostly occurring over the Earth’s land surface. The profile of electrical conductivity up through the atmosphere, determined mainly by galactic cosmic ray ionization, is a crucial parameter of the circuit. Model simulation results on the variation of the ionospheric potential, ∼250 kV positive with respect to the Earth’s potential, following lightning discharges and sprites are summarized. Experimental results comparing global circuit variations with the neutron rate recorded at Climax, Colorado, are then discussed. Within the return (load) part of the circuit in the fair weather regions remote from the generators, charge layers exist on the upper and lower edges of extensive layer clouds; new experimental evidence for these charge layers is also reviewed. Finally, some directions for future research in the subject are suggested

Re-Framing the knowledge to action challenge through NIHR knowledge mobilisation research fellows. Comment on “CIHR Health System Impact Fellows: Reflections on ‘Driving Change’ Within the Health System"

The ambition of the Canadian Institutes for Health Research (CIHR) Health Service Impact (HIS) Fellowship initiative to modernise the health system is impressive. Embedded researchers who work between academia and non-academic settings offer an opportunity to reframe the problem of evidence uptake as a product of a gap between those who produce knowledge and those who use it. As such, there has been an increasing interest in the potential of people in embedded research roles to work with stakeholders in the co-production of knowledge to address service challenges. In this commentary, we draw on research and experiential evidence of an embedded researcher initiative, which has similar intentions to the HIS Fellowships programme: the National Institute for Health Research (NIHR) Knowledge Mobilisation Research Fellowship (KMRF) scheme. We outline the similarities and differences between the two schemes, and then consider the work, characteristics and skills, and organisational arrangements evident in operationalising these types of roles

Editorial

No abstract availabl

Density-equalizing maps for simply-connected open surfaces

In this paper, we are concerned with the problem of creating flattening maps of simply-connected open surfaces in $\mathbb{R}^3$. Using a natural principle of density diffusion in physics, we propose an effective algorithm for computing density-equalizing flattening maps with any prescribed density distribution. By varying the initial density distribution, a large variety of mappings with different properties can be achieved. For instance, area-preserving parameterizations of simply-connected open surfaces can be easily computed. Experimental results are presented to demonstrate the effectiveness of our proposed method. Applications to data visualization and surface remeshing are explored

Differential-activity driven instabilities in biphasic active matter

Active stresses can cause instabilities in contractile gels and living tissues. Here we describe a generic hydrodynamic theory that treats these systems as a mixture of two phases of varying activity and different mechanical properties. We find that differential activity between the phases provides a mechanism causing a demixing instability. We follow the nonlinear evolution of the instability and characterize a phase diagram of the resulting patterns. Our study complements other instability mechanisms in mixtures such as differential growth, shape, motion or adhesion

Optimizing intermittent water supply in urban pipe distribution networks

In many urban areas of the developing world, piped water is supplied only intermittently, as valves direct water to different parts of the water distribution system at different times. The flow is transient, and may transition between free-surface and pressurized, resulting in complex dynamical features with important consequences for water suppliers and users. Here, we develop a computational model of transition, transient pipe flow in a network, accounting for a wide variety of realistic boundary conditions. We validate the model against several published data sets, and demonstrate its use on a real pipe network. The model is extended to consider several optimization problems motivated by realistic scenarios. We demonstrate how to infer water flow in a small pipe network from a single pressure sensor, and show how to control water inflow to minimize damaging pressure gradients

Resonances of the Earth-ionosphere Cavity Observed at Cambridge, England.

Comparison of atmospheric electric field in 1 to 30 c/s band and resonant frequencies of modes of electromagnetic field in earth-ionosphere cavity excited by radiation from lightning discharge