Thermoelastic dissipation in inhomogeneous media: loss measurements and displacement noise in coated test masses for interferometric gravitational wave detectors

The displacement noise in the test mass mirrors of interferometric gravitational wave detectors is proportional to their elastic dissipation at the observation frequencies. In this paper, we analyze one fundamental source of dissipation in thin coatings, thermoelastic damping associated with the dissimilar thermal and elastic properties of the film and the substrate. We obtain expressions for the thermoelastic dissipation factor necessary to interpret resonant loss measurements, and for the spectral density of displacement noise imposed on a Gaussian beam reflected from the face of a coated mass. The predicted size of these effects is large enough to affect the interpretation of loss measurements, and to influence design choices in advanced gravitational wave detectors.Comment: 42 pages, 7 figures, uses REVTeX

Effect of heat treatment on mechanical dissipation in Ta2_2O5_5 coatings

Thermal noise arising from mechanical dissipation in dielectric reflective coatings is expected to critically limit the sensitivity of precision measurement systems such as high-resolution optical spectroscopy, optical frequency standards and future generations of interferometric gravitational wave detectors. We present measurements of the effect of post-deposition heat treatment on the temperature dependence of the mechanical dissipation in ion-beam sputtered tantalum pentoxide between 11\,K and 300\,K. We find the temperature dependence of the dissipation is strongly dependent on the temperature at which the heat treatment was carried out, and we have identified three dissipation peaks occurring at different heat treatment temperatures. At temperatures below 200\,K, the magnitude of the loss was found to increase with higher heat treatment temperatures, indicating that heat treatment is a significant factor in determining the level of coating thermal noise.Comment: accepted Classical and Quantum Gravity 201

Infrared single spike pulses generation using a short period superconducting tape undulator at APEX

We report on the possibility of constructing an infrared FEL by combining a novel design super-conducting undu-lator developed at LBNL with the high brightness beam from the APEX injector facility. Calculations show that the resulting FEL is expected to deliver a saturated power of over a MW within a ∼4 m undulator length when operating in Self-Amplified-Spontaneus-Emission mode, with a single-spike of coherent radiation at ∼ 2 μm wavelength. The sub-cm undulator periods, associated with the relatively low energy of the APEX beam (20-25 MeV), forces the FEL to operate in a regime with unusual and interesting characteristics. The alternative option of laser seeding the FEL is also briefly examined, showing the potential to reduce the saturation length even further

UNITED STATES-LATIN AMERICAN TRADE RELATIONS: IMPORTANCE TO U.S. AGRICULTURAL POLICY DECISIONS

International Relations/Trade,

Renal homotransplantation in pediatric patients.

Fifty-seven patients were treated with renal homotransplantation from 1½ to 7⅔ years ago; 23 patients were 12 years or younger and the other 34 patients were 13 to 18. Family members (usually parents) were the primary donors in 45 cases. Unrelated volunteers or cadavers donated the other 12 homografts. Immunosuppression was with azathioprine and prednisone, and in some cases also with ALG. Forty-two of the 57 recipients survived for at least 1 year. Additional deaths occurred at 17½ and 19 months leaving 40 recipients (70.2%) alive. Six survivors had successful retransplantation following late failure of their original homografts. Control of rejection was not particularly different than in adult cases. “Homograft glomerulonephritis” was found in chronically tolerated transplants, but no more frequently than in older patients. Many postoperative problems in the pediatric age group were the consequence of retardation of growth caused either by pre-existing uremia or by the need for high dose postoperative steroid therapy, orthopedic accidents such as femoral and vertebral fractures, and psychiatric complications which led to two suicides. In spite of these difficulties, the meaningful rehabilitation that was obtained in the chronic survivors makes us regard pediatric patients as favorable candidates for therapy with renal transplantation

Triboluminescent Materials for Smart Optical Damage Sensors for Space Applications

There is a need to develop a new technique of damage detection for composites, which could detect cracking or delamination from any desired location within a material structure in real time. Recently, triboluminescent materials have been proposed as smart sensors of structural damage. To sense the damage, these materials can be epoxy bonded, coated in a polymer matrix, or embedded in a composite host structure. When the damage or fracture takes place in the host structure, the resultant fracture of triboluminescent crystals creates a light emission. This will warn in real time that structural damage has occurred. The triboluminescent emission of the candidate phosphor has to be bright enough that the light reaching from the point of fracture to the detector through a fiber optic cable is detectable. There are a large number of triboluminescent materials, but few satisfy the above criterion. The authors have synthesized an organic material known as Europium tetrakis (dibenzoylmethide) triethylammonium (EuD4TEA), which is a potential candidate for application as a damage sensor and could be made into a wireless sensor with the addition of microchip, antenna, and electronics. Preliminary results on the synthesis and characterization of this material are presented

Measurements of a low temperature mechanical dissipation peak in a single layer of Ta2O5 doped with TiO2

Thermal noise arising from mechanical dissipation in oxide coatings is a major limitation to many precision measurement systems, including optical frequency standards, high resolution optical spectroscopy and interferometric gravity wave detectors. Presented here are measurements of dissipation as a function of temperature between 7 K and 290 K in ion-beam sputtered Ta2O5 doped with TiO2, showing a loss peak at 20 K. Analysis of the peak provides the first evidence of the source of dissipation in doped Ta2O5 coatings, leading to possibilities for the reduction of thermal noise effects

Very high quality factor measured in annealed fused silica

We present the results of quality factor measurements for rod samples made of fused silica. To decrease the dissipation we annealed our samples. The highest quality factor that we observed was $Q=(2.03\pm0.01)\times10^8$ for a mode at 384 Hz. This is the highest published value of $Q$ in fused silica measured to date.Comment: 8 pages, 2 figure

Technical assistance, neo-colonialism or mutual trade? The experience of an Anglo/Ukrainian/Russian social work practice learning project

Since the collapse of the Soviet Union there has been a steady stream of Western consultants ready to work in Eastern Europe and Russia and share professional and academic expertise and experience. Social work, unknown as a discrete discipline or profession in the Soviet Union, has been a growth area with funding from a variety of sources to help promote East-West partnerships.Social work theory and practice emphasises critical appraisal of policy and embraces issues of power, discrimination and oppression. Social work educators should therefore be especially alert to the complex ethical questions which these kinds of collaborations raise, and adept at finding practical solutions or workable compromises. This article explores these ethical and political issues with reference to a project to develop social work practice learning in a Russian oblast' (region). The project was an ambitious partnership of British, Ukrainian and Russian educators, involving numerous Russian social work and related agencies, and four Russian universities and colleges in one oblast'. The authors use a series of vignettes to help the reader achieve insights into these East-West transactions. The article concludes with a discussion of different interpretations of these dealings, using three prisms: technical assistance, neo-colonialism and mutual trade

Augmented reality meeting table: a novel multi-user interface for architectural design

Immersive virtual environments have received widespread attention as providing possible replacements for the media and systems that designers traditionally use, as well as, more generally, in providing support for collaborative work. Relatively little attention has been given to date however to the problem of how to merge immersive virtual environments into real world work settings, and so to add to the media at the disposal of the designer and the design team, rather than to replace it. In this paper we report on a research project in which optical see-through augmented reality displays have been developed together with prototype decision support software for architectural and urban design. We suggest that a critical characteristic of multi user augmented reality is its ability to generate visualisations from a first person perspective in which the scale of rendition of the design model follows many of the conventions that designers are used to. Different scales of model appear to allow designers to focus on different aspects of the design under consideration. Augmenting the scene with simulations of pedestrian movement appears to assist both in scale recognition, and in moving from a first person to a third person understanding of the design. This research project is funded by the European Commission IST program (IST-2000-28559)