An alternative synthesis of cycloalkyl-substituted CPA catalysts and application in asymmetric protonation reactions

LAM thanks the EPSRC (grant number EP/S027165/1) for postdoctoral funding.An alternative synthesis of cycloalkyl-substituted CPA catalysts is reported. A Negishi coupling offers improved yields and purity of the necessary 1,3,5-tri(cycloalkyl)benzenes. Limitations in the use of commercial organozinc reagents have been identified and a robust procedure for the preparation of these reagents is detailed. Similarly, a robust procedure for the key Kumada coupling is also provided. The route is demonstrated by preparation of three different tri(cycloalkyl)aryl-substituted CPAs and the utility of these catalysts in asymmetric protonation reactions is shown.Publisher PDFPeer reviewe

Asymmetric synthesis of heterocyclic chloroamines and aziridines by enantioselective protonation of catalytically generated enamines

L.A.M. and J.W.B.F. thank EPSRC for postdoctoral funding (EP/S027165/1; EP/R025754/1). J.W.B.F. thanks the Leverhulme Trust for postdoctoral funding (RPG-2018-362). M.W.A. thanks the University of St Andrews for a PhD studentship.We report a method for the synthesis of chiral vicinal chloroamines via asymmetric protonation of catalytically generatedprochiral chloroenamines using chiral Brønsted acids. The processis highly enantioselective, with the origin of asymmetry and catalystsubstituent effects elucidated by DFT calculations. We show theutility of the method as an approach to the synthesis of a broadrange of heterocycle-substituted aziridines by treatment of thechloroamines with base in a one-pot process, as well as the utility ofthe process to allow access to vicinal diamines.Publisher PDFPeer reviewe

Assessing the potential of autonomous submarine gliders for ecosystem monitoring across multiple trophic levels (plankton to cetaceans) and pollutants in shallow shelf seas

A combination of scientific, economic, technological and policy drivers is behind a recent upsurge in the use of marine autonomous systems (and accompanying miniaturized sensors) for environmental mapping and monitoring. Increased spatial–temporal resolution and coverage of data, at reduced cost, is particularly vital for effective spatial management of highly dynamic and heterogeneous shelf environments. This proof-of-concept study involves integration of a novel combination of sensors onto buoyancy-driven submarine gliders, in order to assess their suitability for ecosystem monitoring in shelf waters at a variety of trophic levels. Two shallow-water Slocum gliders were equipped with CTD and fluorometer to measure physical properties and chlorophyll, respectively. One glider was also equipped with a single-frequency echosounder to collect information on zooplankton and fish distribution. The other glider carried a Passive Acoustic Monitoring system to detect and record cetacean vocalizations, and a passive sampler to detect chemical contaminants in the water column. The two gliders were deployed together off southwest UK in autumn 2013, and targeted a known tidal-mixing front west of the Isles of Scilly. The gliders’ mission took about 40 days, with each glider travelling distances of >1000 km and undertaking >2500 dives to depths of up to 100 m. Controlling glider flight and alignment of the two glider trajectories proved to be particularly challenging due to strong tidal flows. However, the gliders continued to collect data in poor weather when an accompanying research vessel was unable to operate. In addition, all glider sensors generated useful data, with particularly interesting initial results relating to subsurface chlorophyll maxima and numerous fish/cetacean detections within the water column. The broader implications of this study for marine ecosystem monitoring with submarine gliders are discussed

Jet stream position explains regional anomalies in European beech forest productivity and tree growth

The mechanistic pathways connecting ocean-atmosphere variability and terrestrial productivity are well-established theoretically, but remain challenging to quantify empirically. Such quantification will greatly improve the assessment and prediction of changes in terrestrial carbon sequestration in response to dynamically induced climatic extremes. The jet stream latitude (JSL) over the North Atlantic-European domain provides a synthetic and robust physical framework that integrates climate variability not accounted for by atmospheric circulation patterns alone. Surface climate impacts of north-south summer JSL displacements are not uniform across Europe, but rather create a northwestern-southeastern dipole in forest productivity and radial-growth anomalies. Summer JSL variability over the eastern North Atlantic-European domain (5-40E) exerts the strongest impact on European beech, inducing anomalies of up to 30% in modelled gross primary productivity and 50% in radial tree growth. The net effects of JSL movements on terrestrial carbon fluxes depend on forest density, carbon stocks, and productivity imbalances across biogeographic regions

Chemoselective sequential click ligations directed by enhanced reactivity of an aromatic ynamine

Aromatic ynamines or N-alkynylheteroarenes are highly reactive alkyne components in Cu-catalyzed Huisgen [3 +2] cycloaddition (“click”) reactions. This enhanced reactivity enables the chemoselective formation of 1,4-triazoles using the representative aromatic ynamine N-ethynylbenzimidazole in the presence of a competing aliphatic alkyne substrate. The unique chemoselectivity profile of N-ethynylbenzimidazole is further demonstrated by the sequential click ligation of a series of highly functionalized azides using a heterobifunctional diyne, dispelling the need for alkyne protecting groups

Experimental Platform to Facilitate Novel Back Brace Development for the Improvement of Spine Stability

The spine or ‘back’ has many functions including supporting our body frame whilst facilitating movement, protecting the spinal cord and nerves and acting as a shock absorber. In certain instances, individuals may develop conditions that not only cause back pain but also may require additional support for the spine. Common movements such as twisting, standing and bending motions could exacerbate these conditions and intensify this pain. Back braces can be used in certain instances to constrain such motion as part of an individual’s therapy and have existed as both medical and retail products for a number of decades. Arguably, back brace designs have lacked the innovation expected in this time. Existing designs are often found to be heavy, overly rigid, indiscrete and largely uncomfortable. In order to facilitate the development of new designs of back braces capable of being optimised to constrain particular motions for specific therapies, a numerical and experimental design strategy has been devised, tested and proven for the first time. The strategy makes use of an experimental test rig in conjunction with finite element analysis simulations to investigate and quantify the effects of back braces on flexion, extension, lateral bending and torsional motions as experienced by the human trunk. This paper describes this strategy and demonstrates its effectiveness through the proposal and comparison of two novel back brace designs

Tele-Operated Lunar Rover Navigation Using Lidar

Near real-time tele-operated driving on the lunar surface remains constrained by bandwidth and signal latency despite the Moon s relative proximity. As part of our work within NASA s Human-Robotic Systems Project (HRS), we have developed a stand-alone modular LIDAR based safeguarded tele-operation system of hardware, middleware, navigation software and user interface. The system has been installed and tested on two distinct NASA rovers-JSC s Centaur2 lunar rover prototype and ARC s KRex research rover- and tested over several kilometers of tele-operated driving at average sustained speeds of 0.15 - 0.25 m/s around rocks, slopes and simulated lunar craters using a deliberately constrained telemetry link. The navigation system builds onboard terrain and hazard maps, returning highest priority sections to the off-board operator as permitted by bandwidth availability. It also analyzes hazard maps onboard and can stop the vehicle prior to contacting hazards. It is robust to severe pose errors and uses a novel scan alignment algorithm to compensate for attitude and elevation errors

The assessment of mitral valve disease: a guideline from the British Society of Echocardiography.

peer reviewedMitral valve disease is common. Mitral regurgitation is the second most frequent indication for valve surgery in Europe and despite the decline of rheumatic fever in Western societies, mitral stenosis of any aetiology is a regular finding in all echo departments. Mitral valve disease is, therefore, one of the most common pathologies encountered by echocardiographers, as both a primary indication for echocardiography and a secondary finding when investigating other cardiovascular disease processes. Transthoracic, transoesophageal and exercise stress echocardiography play a crucial role in the assessment of mitral valve disease and are essential to identifying the aetiology, mechanism and severity of disease, and for helping to determine the appropriate timing and method of intervention. This guideline from the British Society of Echocardiography (BSE) describes the assessment of mitral regurgitation and mitral stenosis, and replaces previous BSE guidelines that describe the echocardiographic assessment of mitral anatomy prior to mitral valve repair surgery and percutaneous mitral valvuloplasty. It provides a comprehensive description of the imaging techniques (and their limitations) employed in the assessment of mitral valve disease. It describes a step-wise approach to identifying: aetiology and mechanism, disease severity, reparability and secondary effects on chamber geometry, function and pressures. Advanced echocardiographic techniques are described for both transthoracic and transoesophageal modalities, including TOE and exercise testing

Field Testing of Utility Robots for Lunar Surface Operations

Since 2004, NASA has been working to return to the Moon. In contrast to the Apollo missions, two key objectives of the current exploration program is to establish significant infrastructure and an outpost. Achieving these objectives will enable long-duration stays and long-distance exploration of the Moon. To do this, robotic systems will be needed to perform tasks which cannot, or should not, be performed by crew alone. In this paper, we summarize our work to develop "utility robots" for lunar surface operations, present results and lessons learned from field testing, and discuss directions for future research