High-sensitivity tool for studying phonon related mechanical losses in low loss materials

Fundamental mechanical loss mechanisms exist even in very pure materials, for instance, due to the interactions of excited acoustic waves with thermal phonons. A reduction of these losses in a certain frequency range is desired in high precision instruments like gravitational wave detectors. Systematic analyses of the mechanical losses in those low loss materials are essential for this aim, performed in a highly sensitive experimental set-up. Our novel method of mechanical spectroscopy, cryogenic resonant acoustic spectroscopy of bulk materials (CRA spectroscopy), is well suited to systematically determine losses at the resonant frequencies of the samples of less than 10^(-9) in the wide temperature range from 5 to 300 K. A high precision set-up in a specially built cryostat allows contactless excitation and readout of the oscillations of the sample. The experimental set-up and measuring procedure are described. Limitations to our experiment due to external loss mechanisms are analysed. The influence of the suspension system as well as the sample preparation is explained.Comment: 4 pages, 3 figures, proceedings of PHONONS07, submitted to Journal of Physics: Conference Serie

Conservative-dissipative approximation schemes for a generalized Kramers equation

We propose three new discrete variational schemes that capture the conservative-dissipative structure of a generalized Kramers equation. The first two schemes are single-step minimization schemes while the third one combines a streaming and a minimization step. The cost functionals in the schemes are inspired by the rate functional in the Freidlin-Wentzell theory of large deviations for the underlying stochastic system. We prove that all three schemes converge to the solution of the generalized Kramers equation

Spin Glass and antiferromagnetism in Kondo lattice disordered systems

The competition between spin glass (SG), antiferromagnetism (AF) and Kondo effect is studied here in a model which consists of two Kondo sublattices with a gaussian random interaction between spins in differents sublattices with an antiferromagnetic mean Jo and standard deviation J. In the present approach there is no hopping of the conduction electrons between the sublattices and only spins in different sublattices can interact. The problem is formulated in the path integral formalism where the spin operators are expressed as bilinear combinations of Grassmann fields which can be solved at mean field level within the static approximation and the replica symmetry ansatz. The obtained phase diagram shows the sequence of phases SG, AF and Kondo state for increasing Kondo coupling. This sequence agrees qualitatively with experimental data of the Ce_{2} Au_{1-x} Co_{x} Si_{3} compound.Comment: 7 pages, 1 figure, submitted to EPJ

For To All Those Who Have, More Will be Given: The Matthew Effect, Nonprofit Organizations, and the Adoption of Internet Technology

This study assesses the adoption of Internet-based communication by nonprofit organizations. The research literature posits that the Internet may serve as a ‘leveler’ between rich and poor organizations by lowering the transaction costs of communication, by lowering costs of access to information and by reducing the scale-economy advantages that larger and well-resourced organizations usually enjoy. This literature contrasts with Robert Merton’s Matthew Effect, in which the better-resourced advance and the lesser resourced do not (Merton and Zuckerman 1973(1968)). This study attempts to determine what characteristics distinguish the nonprofit organizations that adopt Internet technologies. This study uses a multi-method approach to ascertain these structural and financial characteristics (Campbell and Fiske 1959; Brewer and Hunter 1989; Judd, Smith et al. 1991). The data collected during this research include case studies of Roman Catholic higher education institutions, content analysis of institutional WWW sites, and a large-scale national survey of randomly chosen nonprofit organizations as a baseline data set on adoption and usage of the Internet among v nonprofit organizations. Results of these analyses suggest that while earlier patterns of adoption perdure in some nonprofit organizations and other organizations have Internet connectivity, as of the year 2000—some six years after the general availability of WWWbased technologies—the adoption of some of these technologies has already occurred, calling into question the Matthew Effect and comparable concerns about a “Digital Divide.” Nearly 90 percent of nonprofit organizations use electronic mail and have access to the Internet as of July 2000. However, only two-thirds of nonprofit organizations have WWW sites and only 20 percent of organizations use their respective WWW sites for electronic fundraising. Regression analysis suggests a positive correlation between the use of Internet technologies and the variables: organization size, assets, information technology (IT) investment, IT personnel, and history of innovation adoption. The same analysis finds a negative correlation between Internet usage and available financial resources

Cryogenic Q-factor measurement of optical substrates for optimization of gravitational wave detectors

Future generations of gravitational wave interferometers are likely to be operated at cryogenic temperatures because one of the sensitivity limiting factors of the present generation is the thermal noise of end mirrors and beam splitters that occurs in the optical substrates as well as in the dielectric coatings. A possible method for minimizing thermal noise is cooling to cryogenic temperatures, maximizing the mechanical quality factor Q, and maximizing the eigenfrequencies of the substrate. We present experimental details of a new cryogenic apparatus that is suitable for the measurement of the temperature-dependent Q-factor of reflective, transmissive as well as nano-structured grating optics down to 5 K. In particular, the SQUID-based and the optical interferometric approaches to the measurement of the amplitude of vibrating test bodies are compared and the method of ring-down recording is described

Regulatory Effectiveness in The Electric Utility Industry: An Empirical Analysis

An established result in the theory of the regulated firm is that an effective rate-of-return constraint induces the firm to employ larger proportions of capital inputs to noncapital inputs than would be the case in the absence of the regulatory constraint. This overcapitalization, often referred to as the Averch-Johnson effect, has been the subject of several recent empirical studies of the electric utility industry. The present study adds to this body of literature. It seeks to test for the effectiveness of utility regulation in the context of a cost minimization model which includes the allowed rate of return as an explanatory variable and permits arbitrary elasticities of substitution for any pair of inputs