Quantum cascade laser light propagation through hollow silica waveguides

In this paper, the transmission characteristics of hollow silica waveguides with bore diameters of 300 and 1000 μm are investigated using a 7.8-μm quantum cascade laser system. We show that the bore diameter, coiling and launch conditions have an impact on the number of supported modes in the waveguide. Experimental verification of theoretical predictions is achieved using a thermal imaging camera to monitor output intensity distributions from waveguides under a range of conditions. The thermal imaging camera allowed for more detailed images than could be obtained with a conventionally used beam profiler. The results show that quasi-single-mode transmission is achievable under certain conditions although guided single-mode transmission in coiled waveguides requires a smaller bore diameter-to-wavelength ratio than is currently available. Assessment of mode population is made by investigating the spatial frequency content of images recorded at the waveguide output using Fourier transform techniques

Integrating cavity based gas cells: a multibeam compensation scheme for pathlength variation

We present a four beam ratiometric setup for an integrating sphere based gas cell, which can correct for changes in pathlength due to sphere wall contamination. This allows for the gas absorption coefficient to be determined continuously without needing to recalibrate the setup. We demonstrate the technique experimentally, measuring methane gas at 1651nm. For example, contamination covering 1.2% of the sphere wall resulted in an uncompensated error in gas absorption coefficient of ≈41%. With the ratiometric scheme, this error was reduced to ≈2%. Potential limitations of the technique, due to subsequent deviations from mathematical assumptions are discussed, including severe sphere window contamination

The effect of oestrogen on excitation and contraction mechanisms in the heart

Post-menopausal women have an enhanced risk of developing cardiovascular disease and disturbances of cardiac rhythm, that have been attributed to declining oestrogen levels during menopause. This highlights the requirement to understand the effect of declining oestrogen levels and oestrogen signalling on cardiac structural remodelling and electrophysiology. This thesis addressed the hypotheses that cardiomyocytes undergo remodellingin response to long-term oestrogen withdrawal following ovariectomy (OVx) that may contribute to altered excitation-contraction (EC) coupling in the heart that such changes may involve the G protein-coupled oestrogen receptor 1 (GPER). OVx or sham surgeries were performed in female guinea pigs. Left ventricular cardiomyocytes were isolatedfor experimental use. Cellular t-tubule network and structural integrity were assessed using membrane staining and scanning ion conductance microscopy. Electrophysiological, fluorescence imaging and molecular biology techniques were utilised to investigate the effect of oestrogen withdrawal and GPER signalling on EC coupling. GPER was targeted with the agonist, G-1 or antagonist G36. Following OVx, t-tubule density decreased by 13% and these cells presented with larger Ca2+transients, prolonged action potential duration(APD) as well as increased spontaneous Ca2+activity and abnormal depolarisations that led to the formation of a pro-arrhythmic substrate. GPER localised to the t-tubules and its expressionincreased by32% in OVx. GPER activation reduced Ca2+transient amplitude (by 40%), shortened the APD (by 22%) and near abolished the formation of early after-depolarisations (by >96%). GPER appears to mediate these cardioprotective changes via the downstream effectors cAMP and eNOS, which were both upregulated in the presence of G-1. In an animal species with comparable steroidogenesis and cardiac physiology to humans, it is shown that adverse remodelling and Ca2+signalling occurred in cardiomyocytes following oestrogen deficiency. GPER activation induced negative inotropic responses and anti-arrhythmogenic behaviours, indicating the potential benefits of targeting oestrogenic signalling.Open Acces

Lochner as Literature: Weighing the Paternalism of Progressivism

In order to add a depth of understanding to the Lochner v. New York debate interpretation, this Comment utilizes an interdisciplinary approach by blending literary critique, legal analysis, and historical context to revisit Justice Peckham’s opinion. The context of the Progressive Era and the application of the law as literature movement framework reveal a critical subtext of the opinion, one which relies heavily on Paternalistic aspirations to assimilate immigrants. This Comment offers a unique perspective on Lochner v. New York while simultaneously providing a framework for future opinion analyses to aid attorneys best harness the power of metaphor in appellate argument

A 50-Million-Year-Old Fossil Forest from Strathcona Fiord, Ellesmere Island, Arctic Canada: Evidence for a Warm Polar Climate

The remains of a fossil forest are buried within a sedimentary sequence of Eocene age (approximately 50 million years old) near Strathcona Fiord, Ellesmere Island. Large petrified tree stumps are preserved in their original growth positions in coals of the Eureka Sound Group, a sequence of sandstones, siltstones and coals deposited in a delta/floodplain environment. The dimensions of 83 stumps were recorded and their positions plotted on a plan of the exposed area of coal. The fossil stumps are roughly conical in shape, up to 1.8 m high and with roots spreading up to 5 m in diameter. They are closely spaced on the coal, some only 1 m spart. A density of 1 stump in 27 sq. m (367 stumps/Ha) was calculated for this forest. The stumps represent large forest trees that grew in freshwater, swampy conditions between large river channels. Their buttressed roots provided extra support in the waterlogged peats. The rivers periodically shifted their courses, flooding the forest and burying them under silts and sands. Wide growth rings in the fossil wood, in addition to evidence from associated sediments and vertebrate faunas, indicate favourable growing conditions in a mild, cool/warm temperate climate with high rainfall. Palaeolatitude studies suggest that the forest lay close to its present high-latitude position during the Euocene. Such a forest is therefore evidence that the Eocene polar climate was much warmer than today and that the trees were able to tolerate polar sunlight regime of continuous summer sunlight followed by months of winter darkness.Key words: fossil forest, Tertiary, Canadian Arctic, palaeoclimate, Ellesmere Island, petrified wood, Eureka Sound GroupMots clés: forêt fossilisée, tertiaire, Arctique canadien, paléoclimat, île Ellesmere, bois pétrifié, groupe d’Eureka Soun

Sensitive detection of methane at 3.3 μm using an integrating sphere and interband cascade laser

Detection of methane at 3.3μm using a DFB Interband Cascade Laser and gold coated integrating sphere is performed. A 10cm diameter sphere with effective path length of 54.5cm was adapted for use as a gas cell. A comparison between this system and one using a 25cm path length single-pass gas cell is made using direct TDLS and methane concentrations between 0 and 1000 ppm. Initial investigations suggest a limit of detection of 1.0ppm for the integrating sphere and 2.2ppm for the single pass gas cell. The system has potential applications in challenging or industrial environments subject to high levels of vibration

Child Survival, Poverty and Policy Options from DHS Surveys in Kenya: 1993-2003

This paper analyses multidimensional aspects of child poverty in Kenya. We carry out poverty and inequality comparisons for child survival and also use the parametric survival model to explain childhood mortality using DHS data. The results of poverty comparisons show that: children with the lowest probability of survival are from households with the lowest level of assets; and poverty orderings for child survival by assets are robust to the choice of the poverty line and to the measure of wellbeing. Inequality analysis suggests that there is less mortality inequality among children facing mortality than children who are better off. The survival model results show that child and maternal characteristics, and household assets are important correlates of childhood mortality. The results further show that health care services are crucial for child survival. Policy simulations suggest that there is potential for making some progress in reducing mortality, but the ERS and MDG targets cannot be achieved.Child survival, multidimensional poverty, inequality, stochastic dominance, childhood mortality, asset index, Kenya