Reviews

Review of Exploring the Underground Economy: Studies of Illegal and Unreported Activity, Human Resource Management: a Critical Text, Personnel Management: a Comprehensive Guide to Theory and Practice in Britain and Reform at Work: Workplace Change and the New Industrial Order and Workplace Reform and Enterprise Bargaining: Issues, Cases and Trend

Discrimination of soil phases by dual energy x-ray tomography

Numerous soil ecological functions are influenced by soil structure through its impact on spatial and temporal distributions of soil particles, water, and air within the soil profile. The nondestructive technique of x‐ray computed tomography (CT) was used for studying soil structure. X‐ray attenuation determined for two energy levels (80 kV and 120 kV) was used to calculate distributions of water, air, and solids, as well as the voxel dry bulk density for two silt loam subsoils. The spatial resolution during scanning was 0.25 mm in the horizontal and 1 mm in the vertical direction. For different voxel sizes, the weighted mean of the derived volumetric water, air, and solid contents, and the dry bulk densities agreed with the sample's phase composition and dry bulk density obtained by weighing. The use of dual energy scanning to study the heterogeneity of soil structure and the spatial distribution of water, air, and solids is discussed

Journey of an Arctic ice island

In August 2010, a 253 km2 ice island calved from the floating glacial tongue of Petermann Glacier in Northwest Greenland. Petermann Ice Island (PII)-B, a large fragment of this original ice island, is the most intensively observed ice island in recent decades. We chronicle PII-B’s deterioration over four years while it drifted more than 2,400 km south along Canada’s eastern Arctic coast, investigate the ice island’s interactions with surrounding ocean waters, and report on its substantial seafloor scour. Three-dimensional sidewall scans of PII-B taken while it was grounded 130 km southeast of Clyde River, Nunavut, show that prolonged wave erosion at the waterline during sea ice-free conditions created a large underwater protrusion. The resulting buoyancy forces caused a 100 m × 1 km calving event, which was recorded by two GPS units. A field team observed surface waters to be warmer and fresher on the side of PII-B where the calving occurred, which perhaps led to the accelerated growth of the protrusion. PII-B produced up to 3.8 gigatonnes (3.8 × 1012 kg) of ice fragments, known hazards to the shipping and resource extraction industries, monitored over 22 months. Ice island seafloor scour, such as a 850 m long, 3 m deep trench at PII-B’s grounding location, also puts subseafloor installations (e.g., pipelines) at risk. This long-term and interdisciplinary assessment of PII-B is the first such study in the eastern Canadian Arctic and captures the multiple implications and risks that ice islands impose on the natural environment and offshore industries

Superconducting instability in the Holstein-Hubbard model: A numerical renormalization group study

We have studied the d-wave pairing-instability in the two-dimensional Holstein-Hubbard model at the level of a full fluctuation exchange approximation which treats both Coulomb and electron-phonon (EP) interaction diagrammatically on an equal footing. A generalized numerical renormalization group technique has been developed to solve the resulting self-consistent field equations. The $d$-wave superconducting phase diagram shows an optimal T_c at electron concentration ~ 0.9 for the purely electronic Hubbard system. The EP interaction suppresses the d-wave T_c which drops to zero when the phonon-mediated on-site attraction $U_p$ becomes comparable to the on-site Coulomb repulsion $U$. The isotope exponent $\alpha$ is negative in this model and small compared to the classical BCS value $\alpha_{BCS} = 1/2$ or compared to typical observed values in non-optimally doped cuprate superconductors.Comment: 4 pages RevTeX + 3 PS figures include

Effects of hydrostatic pressure on the magnetic susceptibility of ruthenium oxide Sr3Ru2O7: Evidence for pressure-enhanced antiferromagnetic instability

Hydrostatic pressure effects on the temperature- and magnetic field dependencies of the in-plane and out-of-plane magnetization of the bi-layered perovskite Sr3Ru2O7 have been studied by SQUID magnetometer measurements under a hydrostatic helium-gas pressure. The anomalously enhanced low-temperature value of the paramagnetic susceptibility has been found to systematically decrease with increasing pressure. The effect is accompanied by an increase of the temperature Tmax of a pronounced peak of susceptibility. Thus, magnetization measurements under hydrostatic pressure reveal that the lattice contraction in the structure of Sr3Ru2O7 promotes antiferromagnetism and not ferromagnetism, contrary to the previous beliefs. The effects can be explained by the enhancement of the inter-bi-layer antiferromagnetic spin coupling, driven by the shortening of the superexchange path, and suppression, due to the band-broadening effect, of competing itinerant ferromagnetic correlations.Comment: 11 pages, 4 figure

The Isotope Effect in d-Wave Superconductors

Based on recently proposed anti-ferromagnetic spin fluctuation exchange models for $d_{x^2-y^2}$-superconductors, we show that coupling to harmonic phonons {\it{cannot}} account for the observed isotope effect in the cuprate high-$T_c$ materials, whereas coupling to strongly anharmonic multiple-well lattice tunneling modes {\it{can}}. Our results thus point towards a strongly enhanced {\it{effective}} electron-phonon coupling and a possible break-down of Migdal-Eliashberg theory in the cuprates.Comment: 12 pages + 2 figures, Postscript files, all uuencoded Phys. Rev. Lett. (1995, to be published

Pinning of stripes by local structural distortions in cuprate high-Tc superconductors

We study the spin-density wave (stripe) instability in lattices with mixed low-temperature orthorhombic (LTO) and low-temperature tetragonal (LTT) crystal symmetry. Within an explicit mean-field model it is shown how local LTT regions act as pinning centers for static stripe formation. We calculate the modulations in the local density of states near these local stripe regions and find that mainly the coherence peaks and the van Hove singularity (VHS) are spatially modulated. Lastly, we use the real-space approach to simulate recent tunneling data in the overdoped regime where the VHS has been detected by utilizing local normal state regions.Comment: Conference proceedings for Stripes1

Project manager-to-project allocations in practice: an empirical study of the decision-making practices of a multi-project based organization

Empirical studies that examine how managers make project manager-to-project (PM2P) allocation decisions in multi-project settings are currently limited. Such decisions are crucial to organizational success. An empirical study of the PM2P practice, conducted in the context of Botswana, revealed ineffective processes in terms of optimality in decision-making. A conceptual model to guide effective PM2P practices was developed. The focus of this study is on deploying the model as a lens to study the PM2P practices of a large organization, with a view to identify and illustrate strengths and weaknesses. A case study was undertaken in the mining industry, where core activities in terms of projects are underground mineral explorations at identified geographical regions. A semi-structured interview protocol was used to collect data from 15 informants, using an enumeration. Integrated analysis of both data types (using univariate descriptive analysis for the quantitative data, content and thematic analysis for the qualitative data) revealed strengths in PM2P practices, demonstrated by informants’ recognition of some important criteria to be considered. The key weaknesses were exemplified by a lack of effective management tools and techniques to match project managers to projects. The findings provide a novel perspective through which improvements in working practices can be made