The origin of Sr segregation at La1-xSrxMnO3 surfaces

A uniform distribution of La and Sr in lanthanum-strontium manganites would lead to charged crystal planes, a charged surface, and arbitrarily large surface energy for a bulk crystal. This divergent energy can be eliminated by depleting the La concentration near the surface. Assuming an exponential form for segregation suggested by experiment, the total electrostatic energy is calculated, depending only upon the decay length and on an effective charge Z* associated with the La ion. It is found to be lower in energy than neutralization of the surface by changing Mn charge states, previously expected, and lower than simply readjusting the La concentration in the surface plane. The actual decay length obtained by minimizing this electrostatic energy is shorter than that observed. The extension of this mechanism to segregation near the surface in other systems is discussed

Spillover effects from London and Frankfurt to Central and Eastern European stock markets

This paper investigates comovement in stock markets between the emerging economies of Central and Eastern Europe (CEE) and the developed markets of Western Europe. Three approaches are employed to examine this issue. The first two approaches, time-varying realised correlation ratios and cointegration statistics, use a two-step technique to derive timevarying estimates of the comovement between returns on CEE and EU stock exchanges. The first step uses common factor analysis to define the factors driving CEE stock exchanges, while the second step evaluates the relationship between the leading principal factor for CEE countries and the DAX and FTSE using time-varying realised correlation and rolling cointegration statistics. The third approach employs multivariate GARCH techniques to obtain estimates of mean and variance spillover effects

Stock market co-movement in the Caribbean

This paper investigates co-movement in five Caribbean stock markets (Barbados, Jamaica and Trinidad and Tobago, The Bahamas and Guyana) using common factor analysis. The common factors are obtained using principal component analysis and therefore account for the maximum portion of the variance present in the stock exchanges investigated. We break our analysis down and test for co-movement in different periods so as to ascertain any changes that have taken place from one period to the next. In particular we examine 10-year, 5-year and 3-year periods. We also specify a vector autoregression model and test for co-movement between the five markets during the sample period through impulse response functions. Both of our tests fail to find any evidence of co-movement between the exchanges over the entire sample period. However, we find evidence of periodic co-movement, particularly between exchanges in Barbados, Jamaica and Trinidad and Tobago

The Abrikosov Flux Lattice in Planar Crystals of YBaCuO

Anisotropic London Theory is used to predict the Abriskosv flux lattice in planar crystals of YBaCuO. By taking into account the orientation of the flux lattice as a function of applied field it is shown that the vortex chain state is observed in Bitter pattern experiments.Comment: 17 pages, Late

Self-consistent energy balance simulations of hole dynamics in SiGe/Si THz quantum cascade structures

Analysis of hole transport in cascaded p-Si/SiGe quantum well structures is performed using self-consistent rate equations simulations. The hole subband structure is calculated using the 6×6 k·p model, and then used to find carrier relaxation rates due to the alloy disorder, acoustic, and optical phonon scattering, as well as hole-hole scattering. The simulation accounts for the in-plane k-space anisotropy of both the hole subband structure and the scattering rates. Results are presented for prototype THz Si/SiGe quantum cascade structures. © 2004 American Institute of Physic

Experimental Methods and the Welfare Evaluation of Policy Lotteries

Policies impose lotteries of outcomes on individuals, since we never know exactly what the effects of the policy will be. In order to evaluate alternative policies, we therefore need to make some assumptions about individual preferences, even before social welfare functions are applied. Instead of making a priori assumptions about those preferences that are likely to be wrong, there are two broad ways in which experimental methods are used to evaluate policy. One is to use experiments to estimate individual preferences, valuations and beliefs, and use those estimates as priors in the evaluation of policy. The other approach is to undertake deliberate randomization, or exploit accidental or natural randomization, to infer the effects of policy. The strengths and weaknesses of these approaches are reviewed, and their complementarities identified.

Advanced refractory alloy corrosion loop program Quarterly progress report, 15 Apr. - 15 Jul. 1967

Fabrication and evaluation of Rankine system refractory alloy corrosion test loo

Advanced refractory alloy corrosion loop program Quarterly progress report no. 2, 15 Jul. - 15 Oct. 1965

Advanced refractory alloy corrosion loo

Advanced refractory alloy corrosion loop program Quarterly progress report no. 4, Jan. 15 - Apr. 15, 1966

Refractory alloy materials procurement and evaluation for potassium corrosion loop progra

Advanced refractory alloy corrosion loop program Quarterly progress report no. 3, period ending Jan. 15, 1966

Purification of alkali metals for use in advanced refractory alloy corrosion loo