Teaching the Doppler Effect in Astrophysics

The Doppler effect is a shift in the frequency of waves emitted from an object moving relative to the observer. By observing and analysing the Doppler shift in electromagnetic waves from astronomical objects, astronomers gain greater insight into the structure and operation of our universe. In this paper, a simple technique is described for teaching the basics of the Doppler effect to undergraduate astrophysics students using acoustic waves. An advantage of the technique is that it produces a visual representation of the acoustic Doppler shift. The equipment comprises a 40 kHz acoustic transmitter and a microphone. The sound is bounced off a computer fan and the signal collected by a DrDAQ ADC and processed by a spectrum analyser. Widening of the spectrum is observed as the fan power supply potential is increased from 4 to 12 V.Comment: 9 pages, 5 figures, published in Eur. J. Phy

Thallium 201 Myocardial Imaging

In recent years technological advancements in nuclear medicine have resulted in increasing interest in the use of radioisotope techniques in the evaluation of cardiac disease, and cardiovascular nuclear medicine has developed into a useful noninvasive tool in clinical cardiology. Myocardial infarct imaging with technetium-99m pyrophosphate has been demonstrated to be a reliable method in the diagnosis of suspected myocardial infarction. Radioisotope cardiac flow studies are useful in the diagnosis and follow-up of congenital heart disease, and gated cardiac blood pool imaging is emerging as an important technique in the evaluation of left ventricular function and ejection fraction. One of the more promising recent applications of nuclear medicine in cardiology has been the development of myocardial perfusion imaging in the evaluation of coronary artery disease. Thallium 201 is the major radioisotope employed in myocardial perfusion imaging and this report will review its basic properties and its use in the diagnosis of ischemic heart disease

Aluminium-mediated carbon–carbon coupling of an isonitrile

Cp*Al reacts with diphenylacetylene to form a Cp*-substituted 1,4-dialuminacyclohexene, which mediates the coupling of isonitriles to form a new zwitterionic diamide ligand with a carbocationic backbone.</p

Using electric network theory to model the spread of oak processionary moth, Thaumetopoea processionea, in urban woodland patches

Context: Habitat fragmentation is increasing as a result of anthropogenic activities, especially in urban areas. Dispersal through fragmented habitats is key for species to spread, persist in metapopulations and shift range in response to climate change. However, high habitat connectivity may also hasten the spread of invasive species. Objective: To develop a model of spread in fragmented landscapes and apply it to the spread of an invasive insect in urban woodland. Methods: We applied a patch-based model, based on electric network theory, to model the current and predicted future spread of oak processionary moth (OPM: Thaumetopoea processionea) from its source in west London. We compared the pattern of ‘effective distance’ from the source (i.e. the patch ‘voltage’ in the model) with the observed spread of the moth from 2006 to 2012. Results: We showed that ‘effective distance’ fitted current spread of OPM. Patches varied considerably in their ‘current’ and ‘power’ (metrics from the model), which is an indication of their importance in the future spread of OPM. Conclusions: Patches identified as ‘important’ are potential ‘pinch points’ and regions of high ‘flow’, where resources for detection and management will be most cost-effectively deployed. However, data on OPM dispersal and the distribution of oak trees limited the strength of our conclusions, so should be priorities for further data collection. This application of electric network theory can be used to inform landscape-scale conservation initiatives both to reduce the spread of invasives and to facilitate large-scale species’ range shifts in response to climate change

Aluminum-Catalyzed Hydroboration of Alkenes

The aluminum-catalyzed hydroboration of alkenes with HBpin is reported using simple commercially available aluminum hydride precatalysts [LiAlH₄ or sodium bis­(2-methoxyethoxy)aluminum hydride (Red-Al)]. Good substrate scope and functional group tolerance is demonstrated for alkene hydroboration, and the protocol was also applied to the hydroboration of ketone, ester, and nitrile functional groups, showing the potential for wider application. The aluminum-catalyzed hydroboration is proposed to proceed by alkene hydroalumination, which generates an alkyl aluminum species that undergoes σ-bond metathesis with HBpin to drive turnover of the catalytic cycle