Molecular dynamics calculation of mean square displacement in alkali metals and rare gas solids and comparison with lattice dynamics

Molec ul ar dynamics calculations of the mean sq ua re displacement have been carried out for the alkali metals Na, K and Cs and for an fcc nearest neighbour Lennard-Jones model applicable to rare gas solids. The computations for the alkalis were done for several temperatures for temperature vol ume a swell as for the the ze r 0 pressure ze ro zero pressure volume corresponding to each temperature. In the fcc case, results were obtained for a wide range of both the temperature and density. Lattice dynamics calculations of the harmonic and the lowe s t order anharmonic (cubic and quartic) contributions to the mean square displacement were performed for the same potential models as in the molecular dynamics calculations. The Brillouin zone sums arising in the harmonic and the quartic terms were computed for very large numbers of points in q-space, and were extrapolated to obtain results ful converged with respect to the number of points in the Brillouin zone.An excellent agreement between the lattice dynamics results was observed molecular dynamics and in the case of all the alkali metals, e~ept for the zero pressure case of CSt where the difference is about 15 % near the melting temperature. It was concluded that for the alkalis, the lowest order perturbation theory works well even at temperat ures close to the melting temperat ure. For the fcc nearest neighbour model it was found that the number of particles (256) used for the molecular dynamics calculations, produces a result which is somewhere between 10 and 20 % smaller than the value converged with respect to the number of particles. However, the general temperature dependence of the mean square displacement is the same in molecular dynamics and lattice dynamics for all temperatures at the highest densities examined, while at higher volumes and high temperatures the results diverge. This indicates the importance of the higher order (eg. ~* ) perturbation theory contributions in these cases.

The effects of moisture, cation concentration, temperature, density and composition of soils on their electrical resistivity

The effects. of moisture, cation concentration, dens ity , temper~ t ure and grai n si ze on the electrical resistivity of so il s are examined using laboratory prepared soils. An i nexpen si ve method for preparing soils of different compositions was developed by mixing various size fractions i n the laboratory. Moisture and cation c oncentration are related to soil resistivity by powe r functions, whereas soil resistiv ity and temperature, density, Yo gravel, sand , sil t, and clay are related by exponential functions . A total of 1066 cases (8528 data) from all the experiments were used in a step-wise multiple linear r egression to determine the effect of each variable on soil resistivity. Six variables out of the eight variables studied account for 92.57/. of the total variance in so il resistivity with a correlation coefficient of 0.96. The other two variables (silt and gravel) did not increase the · variance. Moisture content was found to be - the most important Yo clay. variable- affecting s oil res istivi ty followed by These two variables account for 90.81Yo of the total variance in soil resistivity with a correlation ~oefficient ·.of 0 . 95. Based on these results an equation to ' ~~ed{ ct soil r esist ivi ty using moisture and Yo clay is developed . To t est the predicted equation, resistivity measurements were made on natural soils both in s i tu a nd i n the laboratory. The data show that field and laboratory measurements are comparable. The predicted regression line c losely coinciqes with resistivity data from area A and area B soils ~clayey and silty~clayey sands). Resistivity data and the predicted regression line in the case of c layey soils (clays> 40%) do not coincide, especially a t l ess than 15% moisture. The regression equation overestimates the resistivity of so i l s from area C and underestimates for area D soils. Laboratory prepared high clay soils give similar trends. The deviations are probably caused by heterogeneous distribution of mo i sture and difference in the type o f cl ays present in these soils.

The green movement in Canada

The green movement has evolved over the last twenty years from various social, peace and ecology activist organizations into direct political participation in parliamentary institutions through the Green Party. Although there is no definable theory of green politics, the culmination of interacting social movements as well as feminist, decentralist and in many cases, left wing political ideology, has produced a specific kind of political direction for the Greens internationally. As a result of the increased a ttention and awareness given to ecological issues , combined with the heightened evidence of large scale environmental deterioration, public attitudes and government decisions on development and natural resource management have been significantly altered. The Green Party of Canada is still r elatively young in comparison to its European counterparts, although ecologica l awareness and interest in t he green movement in Canada is strong, as reflected not only in support on a political level for the Canadian Greens I but for environmental issues and a ctivism in general. For this reason it s important to determine whether or not the Green Party is a significant aspect of the Canadian green movement, and if in fact its representation is necessary as an active participant in the Canadian political system . The Green Party of Canada, as a vital aspect of the Canadian green movement, and its connection to international green organizations can be examined primarily through the examp l es of both the Canadian Greens and the Green party of Ontario , by using original party documents and literature, information gained through Green party meetings and discussions with members, and commentary by Green theorists where app licable. As well, the influence on the Canadian green movement by the German Green Party is outlined , again mainly through party literature, documents and critiques of the party's experiences. This study reveals several existing and potential problems fo r t he Green Party in Canada, and the political fut ure of the Canadian green movement in general. Some, such as the real i ties of the Canadian political system are external to the movement, and may be overcome with adjustments in goals and methods, and a realization of the changing attitude towards environmental issues in a political context . On the other hand, internal party disfunctions in both organization and direction, caused mainly by the indefinite parameters of green ideology, threaten to exploit the already problematic aspects evident in t he Green Party . Aside from its somewhat slow beginnings, the Green Party in Canada has developed into a strong grassroots social movement, not however from its political visibility but from the steady growth in the popul ari ty of ecological pol i t ics in Canada. Due to the seeming enormity of the obstacles facing the Greens in their effort 4 to achieve electoral success, it is doubtful that Parliamentary representation will be achieved without a major re-orientation of party organization and methods. UI timately the strength of the Green Party in Canada will be based upon its ability to survive as a significant movement, and its willingness to continue to challenge political thought and practice.

The origins of federal public enterprises in Canada: an appraisal of two approaches

The Green Party of Canada, as a vital aspect of the Canadian green movement, and its connection to international green organizations can be examined primarily through the examp l es of both the Canadian Greens and the Green party of Ontario , by using original party documents and literature, information gained through Green party meetings and discussions with members, and commentary by Green theorists where app licable. As well, the influence on the Canadian green movement by the German Green Party is out lined , again mainly through party literature, documents and critiques of the party's experiences. This study reveals several existing and potential problems fo r t he Green Party in Canada, and the political fut ure of the Canadian green movement in general. Some, such as the real i ties of the Canadian political system are external to the movement, and may be overcome with adjustments in goals and methods, and a realization of the changing attitude towards environmental issues in a political context . On the other hand, internal party disfunctions in both organization and direction, caused mainly by the indefinite parameters of green ideology, threaten to expl oi t t he al ready problematic aspects evident in t he Green Party . Aside from its somewhat slow beginnings, the Green Party in Canada has developed into a strong grassroots social movement, not however from its political visibility but from the steady growth in the popul ari ty of ecological pol i t ics in Canada . Due to the seeming enormity of the obstacles facing the Greens in their effort 4 to achieve electoral success, it is doubtful that Parliamentary representation will be achieved without a major re-orientation of party organization and methods. UI timately the strength of the Green Party in Canada will be based upon its ability to survive as a significant movement, and its willingness to continue to challenge political thought and practice.