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

Right Atrial Metastatic Melanoma with Unknown Primaries

A 54-year-old male with history of anemia and rheumatoid arthritis presented with a three-month history of dyspnea on exertion and lower extremity edema. Patient was referred for a transthoracic echocardiogram that revealed a large right atrial mass with reduced ejection fraction of 40% and an incidental large liver mass. Subsequent cardiac MRI revealed a lobulated right atrial mass measuring 5.4 cm * 5.3 cm with inferior vena cava compression and adjacent multiple large liver lesions confirmed to be malignant melanoma through biopsy. Interestingly, no primaries were found in the patient. PET/CT imaging displayed hypermetabolic masses within the right atrium and liver that likely represent metastases, as well as bilateral pleural effusions, most likely due to heart failure. Preoperative coronary angiogram demonstrated perfusion to the mass by a dense network of neovasculature arising from the mid right coronary artery. The cardiac melanoma was surgically removed, and the right atrium was reconstructed with a pericardial patch. After surgery, all cardiac chambers appeared normal in size and function with associated moderate tricuspid regurgitation. The patient is currently being administered ipilimumab for systemic therapy of metastatic melanoma

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

Skeletal Muscle Function, Morphology, and Biochemistry in Ts65Dn Mice: A Model of Down Syndrome

A common clinical observation of persons with Down syndrome at all developmental stages is hypotonia and generalized muscle weakness. The cause of muscle weakness in Down syndrome is not known and there is an immediate need to establish an acceptable animal model to explore the muscle dysfunction that is widely reported in the human population. Using a combination of functional, histological, and biochemical analyses this dissertation provides the initial characterization of skeletal muscle from the Ts65Dn mouse, a model of Down syndrome. The experiments revealed that Ts65Dn muscle over-expresses SOD1 protein but this did not lead to oxidative stress. Ts65Dn soleus muscles displayed normal force generation in the unfatigued state, but exhibited muscle weakness following fatiguing contractions. We show that a reduction in cytochrome c oxidase expression may contribute to the impaired muscle performance in Ts65Dn soleus. These findings support the use of the Ts65Dn mouse model of Down syndrome to delineate mechanisms of muscle dysfunction in the human condition

A comment on the relation between diffraction and entropy

Diffraction methods are used to detect atomic order in solids. While uniquely ergodic systems with pure point diffraction have zero entropy, the relation between diffraction and entropy is not as straightforward in general. In particular, there exist families of homometric systems, which are systems sharing the same diffraction, with varying entropy. We summarise the present state of understanding by several characteristic examples.Comment: 7 page

Investigating the role of the imprinted Grb10 gene in the regulation of maternal nutrient transfer

Imprinted genes are a subset of loci, positioned on autosomes and the X-chromosome, which are expressed monoallelically in a parent-of-origin specific manner. The influence of such genes on the regulation of embryonic growth and postnatal energy homeostasis is well established. The parental conflict hypothesis predicts that, in utero, paternally-expressed genes will promote maternal resource acquisition and thus growth, whereas maternally-expressed genes will oppose this action, restricting resource investment in a single brood in the interests of the lifetime reproductive success of the mother. Grb10 is an imprinted gene which encodes the cytoplasmic adaptor protein Growth factor receptor bound protein 10. In the majority of tissues, Grb10 is expressed from the maternally-derived chromosome. Consistent with conflict theory, transgenic mice inheriting a disrupted Grb10 allele through the maternal line (Grb10Δ2-4m/+) exhibit embryonic overgrowth, although the mechanisms and signalling pathways responsible for this effect are unclear. Grb10Δ2-4m/+ mice also demonstrate enhanced insulin signalling and improved whole body glucose clearance, consistent with the established role of imprinted genes in the regulation of postnatal metabolism. An integrated LacZ gene-trap in the Grb10Δ2-4 allele failed to fully recapitulate endogenous Grb10 expression, notably within the central nervous system. To address this issue, a second transgenic mouse line, Grb10KO, was created. This allele produced strong LacZ reporter expression in the central nervous system, but only when transmitted through the paternal line (Grb10KO+/p), establishing Grb10 as the only known imprinted gene with a reciprocal imprinting profile between the central nervous system and peripheral tissues. Grb10KO+/p mice exhibit a social dominance phenotype, suggesting distinct roles for maternally- and paternally-expressed Grb10, consistent with their respective sites of expression. The current study characterised the Grb10KO allele at the genetic level, and in doing so, revealed a phenotypic difference between Grb10KOm/p and Grb10Δ2-4m/p mice for which a possible explanation was provided. Importantly, with this knowledge, the current study elucidated the genetic and molecular basis for inconsistencies in reporter expression between the two transgenic lines, identifying a novel tissue-specific enhancer element at the locus. In addition to the central nervous system, this enhancer appeared to be active in the mammary epithelium, identifying a novel site of Grb10 expression, which was pregnancy-dependent and specifically from the maternally-inherited chromosome. Characterisation of the functional significance of expression in this tissue revealed that maternally-expressed Grb10 mediates a supply/demand system between lactating mother and suckling pup, acting as a supply promoter and demand suppressor. This role is inconsistent with conflict theory, but suggests the maintenance of the Grb10 imprint in the mammary epithelium might be associated with improved coadaptiveness between mother and offspring. Intriguingly, in utero, Grb10 is both a demand and supply suppressor. When considered together, these findings suggest a wider role for maternally-expressed Grb10 in the homeostatic control of growth and achievement of optimal fitness.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

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