A high stability optical shadow sensor with applications for precision accelerometers

Displacement sensors are found in a variety of applications including gravitational wave detectors, precision metrology, tissue imaging, gravimeters, microscopy, and environmental monitoring. Most of these applications benefit from the use of displacement sensors that offer both high precision and stability. This is particularly the case for gravimetry where measurements are often taken over multi-day timescales. In this paper we describe a custom-built microcontroller-based displacement sensor that has been utilized in a micro-electromechanicalsystem gravimeter. The system runs off battery power and is low-cost, portable, and lightweight. Using an optical shadow sensor technique, and by designing a digital lock-in amplier based around a dsPIC33 microcontroller, we demonstrate a displacement sensitivity of 10 nm/Hz down to 300 s, and an rms sensitivity of 1 nm over timescales of one day. The system also provides real time monitoring/control of temperature, using an AD7195 ratiometric bridge to provide mK control of three separate PT100 sensors. Furthermore, a tilt sensor conditioning circuit is incorporated to drive a pair of electrolytic tilt sensors, resulting in the ability to monitor 2 axis tilt at the level of 1 microradian over approximately 1 day. The sensor system described is thus multifunctional and capable of being incorporated into precision accelerometers/gravimeters, or indeed other applications where long term displacement/temperature monitoring is necessary

Field tests of a portable MEMS gravimeter

Gravimeters are used to measure density anomalies under the ground. They are applied in many different fields from volcanology to oil and gas exploration, but present commercial systems are costly and massive. A new type of gravity sensor has been developed that utilises the same fabrication methods as those used to make mobile phone accelerometers. In this study, we describe the first results of a field-portable microelectromechanical system (MEMS) gravimeter. The stability of the gravimeter is demonstrated through undertaking a multi-day measurement with a standard deviation of 5.58 × 10−6 ms−2 . It is then demonstrated that a change in gravitational acceleration of 4.5 × 10−5 ms−2 can be measured as the device is moved between the top and the bottom of a 20.7 m lift shaft with a signal-to-noise ratio (SNR) of 14.25. Finally, the device is demonstrated to be stable in a more harsh environment: a 4.5 × 10−4 ms−2 gravity variation is measured between the top and bottom of a 275-m hill with an SNR of 15.88. These initial field-tests are an important step towards a chip-sized gravity senso

Microelectromechanical system gravimeters as a new tool for gravity imaging

A microelectromechanical system (MEMS) gravimeter has been manufactured with a sensitivity of 40 ppb in an integration time of 1 s. This sensor has been used to measure the Earth tides: the elastic deformation of the globe due to tidal forces. No such measurement has been demonstrated before now with a MEMS gravimeter. Since this measurement, the gravimeter has been miniaturized and tested in the field. Measurements of the free-air and Bouguer effects have been demonstrated by monitoring the change in gravitational acceleration measured while going up and down a lift shaft of 20.7 m, and up and down a local hill of 275 m. These tests demonstrate that the device has the potential to be a useful field-portable instrument. The development of an even smaller device is underway, with a total package size similar to that of a smartphone

Power scalable TEM(oo) CW Nd: YAG laser with thermal lens compensation

We present finite-element analyzes and experimental results to validate our approach for building high-power single-mode Nd:YAG lasers. We show that the thermooptical and thermomechanical properties of a slab laser can be controlled. This is essential for the use of the proposed unstable resonator. We include demonstration of an efficient subscale laser operating at 20 W TEM00.D. Mudge, M. Ostermeyer, P. J. Veitch, J. Munch, B. Middlemiss, D. J. Ottaway and M. W. Hamilto

Energy and symmetry of dddd excitations in undoped layered cuprates measured by Cu L3L_3 resonant inelastic x-ray scattering

We measured high resolution Cu $L_3$ edge resonant inelastic x-ray scattering (RIXS) of the undoped cuprates La$_2$CuO$_4$, Sr$_2$CuO$_2$Cl$_2$, CaCuO$_2$ and NdBa$_2$Cu$_3$O$_6$. The dominant spectral features were assigned to $dd$ excitations and we extensively studied their polarization and scattering geometry dependence. In a pure ionic picture, we calculated the theoretical cross sections for those excitations and used them to fit the experimental data with excellent agreement. By doing so, we were able to determine the energy and symmetry of Cu-3$d$ states for the four systems with unprecedented accuracy and confidence. The values of the effective parameters could be obtained for the single ion crystal field model but not for a simple two-dimensional cluster model. The firm experimental assessment of $dd$ excitation energies carries important consequences for the physics of high $T_c$ superconductors. On one hand, having found that the minimum energy of orbital excitation is always $\geq 1.4$ eV, i.e., well above the mid-infrared spectral range, leaves to magnetic excitations (up to 300 meV) a major role in Cooper pairing in cuprates. On the other hand, it has become possible to study quantitatively the effective influence of $dd$ excitations on the superconducting gap in cuprates.Comment: 22 pages, 11 figures, 1 tabl

Foreign policy beliefs and support for Stephen Harper and the Conservative Party

Similar to other recent Canadian elections, foreign policy did not feature prominently in the 2011 federal election campaign. In fact, many doubt Canadian public opinion on international affairs is linked to the actions taken by recent Governments. In this paper, we examine Canadian public opinion toward a range of foreign policy issues and argue that the survey questions measure two latent dimensions —militarism and internationalism. Our survey evidence indicates the existence of an “issue public” which is prepared to endorse military action and is skeptical of human rights and overseas aid programs, and this group is far more supportive of Prime Minister Harper and the Conservative Party than other Canadians. The absence of an elite discussion, either among politicians or between media elites, about the direction of Canadian foreign policy does not prevent the Canadian voter from thinking coherently about questions pertaining to this issue domain and employing these beliefs to support or oppose political parties and their leaders

Characterizing the energy use of disabled people in the European Union towards inclusion in the energy transition

Designing environmental policy to take account of social difference is increasingly recognized as essential to address both effectiveness and justice concerns. So far there is limited research on the experiences of disabled people in the environmental literature, amounting to a failure to recognize this substantial constituency. Here we compare disabled households’ embodied energy use, income, risk of poverty and energy poverty, and other socio-demographics with other households in the European Union. We find that households including an economically inactive disabled person earn less and consume 10% less energy than other households, and are more likely to experience energy poverty. Disabled households have lower consumption than other households in most categories, with the exception of basic consumption such as food, energy at home (gas and electricity), water and waste services: in effect they have less—and sometimes inadequate—access to resources. We conclude that more attention should be paid to disabled households needs to ensure a just energy transition

A study of fuel poverty and low-carbon synergies in social housing

This socio-technical pilot involved qualitative interviews with social housing tenants, combined with basic energy modelling of the individual dwellings to estimate the carbon emissions of that house. The study aimed to investigate the relationship between fuel poverty and carbon-saving synergies in the UK domestic housing stock. Fuel poverty, the circumstance where a household spends more than 10% of its income on energy bills, is predicted as being 21% of the entire domestic stock. The fuel poor behaviours described in this study, including frugality and rationing of energy use, may become more common, and even be seen as the “norm”. If domestic energy bills increase with predictions, the number of fuel poor households will continue to rise. It is likely that their practices will become more diverse. This diversity is important as it will affect not only the choice of measures for reducing energy consumption but also the likely post-measure “rebound effect”, where a perceived energy saving might not be achieved as households increase their energy use directly, or indirectly, as a result of having lower energy bills. The study found that “electricity as entertainment” is very apparent in low-income homes, particularly those with children. This can have a significant impact on the household’s fuel poverty status. It is important not to discount this effect as the choices for reducing fuel poverty may not only be related to building refurbishment. This study concludes that lack of energy inefficiency is not the main driver of fuel poverty in the UK. Small changes in the efficiency of the UK stock have had minimal impact on fuel poverty numbers because this is driven by gas prices. But if large-scale changes were made to such homes then it may be possible to ameliorate the effect of rising fuel prices, though without eliminating fuel poverty altogether. The work ascertained that the fuel poor do not recognise themselves as living ‘low-carbon lifestyles’ but it seems likely that they do from the frugal responses that our sample display. Helping those in fuel poverty to recognise this, and rewarding this through policy, could be a positive way of encouraging continued action If a substantial impact to both fuel poverty and domestic carbon emissions is to be made, large-scale changes to buildings are necessary. Existing energy behaviour, energy frugality (as governed by income) and the response of the occupant to any potential energy-saving improvement will not be universal across the stock. Given the fuel poverty context, the authors suggest that the proposed 2011 Energy Act Green Deal is not suitably structured for achieving large-scale reductions in fuel poverty and domestic carbon emissions. The provision intends to provide loans of up to £6.500 to eliminate the need to pay upfront for energy efficiency measures. The cost of repayment should be covered by electricity bill savings. If large-scale measures are needed to have a genuine, and long lasting, effect, then £6,500 per home is not likely to be sufficient for fuel poor social housing tenants to rise out of fuel poverty. It is currently unclear whether the Energy Company Obligation (ECO) will be sufficient to compensate for any of the weaknesses of the Green Deal when applied to fuel poor homes. ECO will place one or more obligations on energy companies requiring them to facilitate the installation of energy efficiency measures in homes

Continuous cultivation of photosynthetic microorganisms: approaches, applications and future trends

The possibility of using photosynthetic microorganisms, such as cyanobacteria and microalgae, for converting light and carbon dioxide into valuable biochemical products has raised the need for new cost-efficient processes ensuring a constant product quality. Food, feed, biofuels, cosmetics and pharmaceutics are among the sectors that can profit from the application of photosynthetic microorganisms. Biomass growth in a photobioreactor is a complex process influenced by multiple parameters, such as photosynthetic light capture and attenuation, nutrient uptake, photobioreactor hydrodynamics and gas-liquid mass transfer. In order to optimize productivity while keeping a standard product quality, a permanent control of the main cultivation parameters is necessary, where the continuous cultivation has shown to be the best option. However it is of utmost importance to recognize the singularity of continuous cultivation of cyanobacteria and microalgae due to their dependence on light availability and intensity. In this sense, this review provides comprehensive information on recent breakthroughs and possible future trends regarding technological and process improvements in continuous cultivation systems of microalgae and cyanobacteria, that will directly affect cost-effectiveness and product quality standardization. An overview of the various applications, techniques and equipment (with special emphasis on photobioreactors) in continuous cultivation of microalgae and cyanobacteria are presented. Additionally, mathematical modelling, feasibility, economics as well as the applicability of continuous cultivation into large-scale operation, are discussed.This research work was supported by the grant SFRH/BPD/98694/2013 (Bruno Fernandes) from Fundacao para a Ciencia e a Tecnologia (Portugal). The authors thank the FCT Strategic Project PEst-OE/EQB/LA0023/2013. The authors also thank the Project "BioInd Biotechnology and Bioengineering for improved Industrial and Agro-Food processes, REF. NORTE-07-0124-FEDER-000028" Co-funded by the Programa Operacional Regional do Norte (ON.2-O Novo Norte), QREN, FEDE