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

Detailed modelling of a large sample of Herschel sources in the Lockman Hole: identification of cold dust and of lensing candidates through their anomalous SEDs

We have studied in detail a sample of 967 SPIRE sources with 5σ detections at 350 and 500 μm and associations with Spitzer-SWIRE 24 μm galaxies in the HerMES-Lockman survey area, fitting theirmid- and far-infrared, and submillimetre, spectral energy distributions (SEDs) in an automatic search with a set of six infrared templates. For almost 300 galaxies,we havemodelled their SEDs individually to ensure the physicality of the fits. We confirm the need for the new cool and cold cirrus templates, and also of the young starburst template, introduced in earlier work. We also identify 109 lensing candidates via their anomalous SEDs and provide a set of colour–redshift constraints which allow lensing candidates to be identified from combined Herschel and Spitzer data. The picture that emerges of the submillimetre galaxy population is complex, comprising ultraluminous and hyperluminous starbursts, lower luminosity galaxies dominated by interstellar dust emission, lensed galaxies and galaxies with surprisingly cold (10–13 K) dust. 11 per cent of 500 μm selected sources are lensing candidates. 70 per cent of the unlensed sources are ultraluminous infrared galaxies and 26 per cent are hyperluminous. 34 per cent are dominated by optically thin interstellar dust (‘cirrus’) emission, but most of these are due to cooler dust than is characteristic of our Galaxy. At the highest infrared luminosities we see SEDs dominated by M82, Arp 220 and young starburst types, in roughly equal proportions

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

The effect of crystal orientation on the cryogenic strength of hydroxide catalysis bonded sapphire

Hydroxide catalysis bonding has been used in gravitational wave detectors to precisely and securely join components of quasi-monolithic silica suspensions. Plans to operate future detectors at cryogenic temperatures has created the need for a change in the test mass and suspension material. Mono-crystalline sapphire is one candidate material for use at cryogenic temperatures and is being investigated for use in the KAGRA detector. The crystalline structure of sapphire may influence the properties of the hydroxide catalysis bond formed. Here, results are presented of studies of the potential influence of the crystal orientation of sapphire on the shear strength of the hydroxide catalysis bonds formed between sapphire samples. The strength was tested at approximately 8 K; this is the first measurement of the strength of such bonds between sapphire at such reduced temperatures. Our results suggest that all orientation combinations investigated produce bonds of sufficient strength for use in typical mirror suspension designs, with average strengths >23 MPa

Art and authority : aspects of Russian art since 1917

From Introduction: The Artist was denied any role in Plato's Republic because of his ability to impair reason by imitating reality through his works. Aristotle, however, welcomed the artist because of his ability to express ideas about society through artistic form. Ernst Fischer agrees with the latter view, "Art enables man to comprehend reality, and not only helps him to bear it but increases his determination to make it more human and more worthy of mankind. Art is itself a social reality, society needs the artist ... and it has a right to demand of him that he should be conscious of his social function" (Fischer: 1963:46). Fischer adds to Aristotle's view by stating that society has a right to demand a social function from the artist. This issue has been the subject of controversial debate throughout the history of art. In a society based on class, the classes try to recruit art to serve their particular purposes. Art is seen by some as a powerful weapon - a means by which people can be swayed towards certain ideals. At the time of the Counter Reformation Italian artists were given strict instructions by the Jesuits on how to persuade and educate the people with their paintings. Napoleon urged his men of letters, painters and architects to refer to the classical ideals of ancient Greece and Rome to shape the emergent French Republic. The French philosopher, Dennis Diderot, stressed the futility of art unless it expressed great prinCiples or lessons for the spectator. Ideals of justice, courage and patriotism were embodied in the Neo-Classical movement. The didactic paintings of Jacques Louis David portray the above ideals. History records several attempts by those in power to coerce artists into conforming to their idea of society, indicating that authoritative manipulation of the arts is not purely a twentieth century phenomenon. This thesis intends to examine aspects of Russian art since 1917. Because Soviet art was dominated by policies which enabled authorities to determine its content, its history raises ideological issues which are relevant to the study of art. The theories of Suprematism, Constructivism and Socialist Realism will be discussed and conclusions will be drawn as to whether these theories succeeded as art movements which were ostensibly designed for the improvement of mankind. Present attitudes toward the visual arts in Russia will also be examined. However, in order to examine the above it is necessary to place the development of art into historical perspective

A SCUBA Scanmap of the HDF: Measuring the bright end of the sub-mm source counts

Using the 850 micron SCUBA camera on the JCMT and a scanning technique different from other sub-mm surveys, we have obtained a 125 square arcminute map centered on the Hubble Deep Field. The one-sigma sensitivity to point sources is roughly 3 mJy and thus our map probes the brighter end of the sub-mm source counts. We find 6 sources with a flux greater than about 12 mJy (>4 sigma) and, after a careful accounting of incompleteness and flux bias, estimate the integrated density of bright sources N(>12 mJy)= 164 (+77/-58) per square degree (68 per cent confidence bounds).Comment: 5 pages, 2 figures, Accepted for publication in MNRA