Characterization of six-coordinated iron (V) in an oxide lattice

On the basis of a discussion of the correlations between the stability of the d³ configuration and the symmetry and size of the cation site, six-coordinated iron (V) has been stabilized in the La₂LiFeO₆ perovskite-type oxide and characterized by magnetic susceptibility, Mössbauer resonance and EPR measurements.     

Déplacements engendrés par des ondes élastiques incidentes sur une sphère multi-couches

In an infinite space, we study the propagation of elastic spherical waves emitted by a source point placed outside a given finite set of concentric elastic spherical layers. The exact solution (displacements fields) of this problem is determined by a new method which avoids solving the totality of equations and boundary conditions. From these results we deduce those corresponding to some particular cases.     

The Effect of Solute Content on the Slip Behavior in 7XXX Series Aluminum Alloys

The microstructures of three high strength, high purity Al-Zn-Mg-Cu alloys, in the T6 temper, were characterized extensively using quantitative optical metallography and quantitative transmission electron microscopy. Only the solute content (Mg + Zn) of these alloys was varied for this study. These alloys were shown to be identical in grain size and shape, dispersoid (E-phase) and grain boundary precipitate (ν) populations, and precipitate free zone widths. The matrix microstructures consisted of ordered GP zones and ν′ and differed only in the volume fraction of these strengthening precipitates. The higher solute alloys had the higher yield strengths and volume fractions of matrix precipitates. Subsequent slip behavior analysis of prestrained tensile specimens demonstrated that slip band spacings and slip step heights increased with increasing solute content for the same macroscopic strain (ε_p = 0.02). A work softening model by Hornbogen and Gahr was shown to predict this tendency toward increased strain localization with higher solute levels. Formerly a Research Assistant at Carnegie-Mellon University     

On a new structural type of fluorine compounds : Crystal and magnetic structures of a high pressure form of PdF2

A new structural type of MF₂ fluorine compounds has been studied using neutron diffraction. The structure of the high pressure form of Pd difluoride has been shown to derive from the fluorite type by a rhombohedral distortion of the cubic environment of the cations. The coordination number of the cations is VI + II : the six nearest neighbor fluorine atoms form a distorted octahedron with $\text{M}\text{?}\text{F}{}_1\text{? 2.18}\text{A}\text{?}$, while two further anions correspond to $\text{M}\text{?}\text{F}{}_2\text{? 3.17}\text{A}\text{?}$. Distances and angles have been compared with those of other Pd compounds. The structure of the high pressure form of PdF₂ has been refined via neutron diffraction ($\text{a}\text{= 5.329}\text{A}\text{?}$, space group Pa3 or P2₁3). This phase orders antiferromagnetically below 190 ± 5 K and the magnetic structure has been determined on the basis of both collinear and noncollinear models. The magnetic data have been compared with results obtained for other d⁸ or d⁹ difluorides.     

The effects of atomic force microscopy upon nominated living cells

This work describes a system for precise re-location of cells within a monolayer after atomic force imaging. As we know little about probe interaction with soft biological surfaces any corroborative evidence is of great importance. For example, it is of paramount importance in living cell force microscopy that interrogated cells can be re-located and imaged by other corroborative technologies. Methodologies expressed here have shown that non-invasive force parameters can be established for specific cell types. Additionally, we show that the same sample can be transferred reliably to an SEM. Results here indicate that further work with live cells should initially establish appropriate prevailing force parameters and that cell damage should be checked for before and after an imaging experiment.     

Severe accidents in the energy sector: comparative perspective

This paper addresses one of the controversial issues in the current comparative studies of the environmental and health impacts of energy systems, i.e. the treatment of severe accidents. The work covers technical aspects of severe accidents and thus primarily reflects an engineering perspective on the energy-related risk issues, though some social implications are also touched upon. The assessment concerns fossil energy sources (coal, oil and gas), nuclear power and hydro power. The scope is not limited to the power production (conversion) step of these energy chains but, whenever applicable, also includes exploration, extraction, transports, processing, storage and waste disposal. With the exception of the nuclear chain the focus of the work has been on the evaluation of the historical experience of accidents. The basis used for this evaluation is a comprehensive database ENSAD (Energy-related Severe Accident Database), established by the Paul Scherrer Institut (PSI). For hypothetical nuclear accidents the probabilistic technique has also been employed and extended to cover the assessment of economic consequences of such accidents. The broader picture obtained by coverage of full energy chains leads on the world-wide basis to aggregated immediate fatality rates being much higher for the fossil chains than what one would expect if only power plants were considered. Generally, the immediate fatality rates are for all considered energy carriers significantly higher for the non-OECD countries than for OECD countries. In the case of hydro and nuclear the difference is in fact dramatic. The presentation of results is not limited to the aggregated values specific for each energy chain. Also frequency-consequence curves are provided. They reflect implicitly the ranking based on the aggregated values but include also such information as the observed or predicted chain-specific maximum extents of damages. This perspective on severe accidents may lead to different system rankings, depending on the individual risk aversion.     

Sorption of phenanthrene to environmental black carbon in sediment with and without organic matter and native sorbates

Strong sorption to soot- and charcoal-like material (collectively termed black carbon or BC) in soils and sediments is possibly the reason for recent observations of elevated geosorbent-water distribution ratios, slow desorption, limited uptake, and restricted bioremediation. We evaluated the role of environmental BC in the sorption of phenanthrene (PHE) to a polluted lake sediment from a Rhine River sedimentation area. Sorption isotherms were determined over a wide concentration range (0.0005-6 microg/ L) for the original sediment (with organic matter or OM, native sorbates, and BC), sediment from which we had stripped > 90% of the native sorbates (only OM and BC), and sediment combusted at 375 degrees C (only BC). The sorption isotherms of the original and stripped sediments were almost linear (Freundlich coefficient or n(F) > 0.9), whereas the isotherm of the BC remaining after the sediment combustion was highly nonlinear (n(F) = 0.54). At low concentrations (ng/L range), PHE sorption to BC in the combusted sediment was found to exceed the total PHE sorption in the original and stripped sediments. This implies that it may not be possible to use a BC-water sorption coefficient measured in combusted sediment to estimate total sorption to the original sediment. This "intrinsic" BC-water sorption coefficient after combustion was calculated to be 9 times larger than the "environmental" one in the untreated sediment. Competition between the added PHE and the native PAHs and/or OM may explain this difference. It appears that, at low aqueous PHE concentrations (ng/L and below), BC is the most important geosorbent constituent with respect to sorption. At higher concentrations (microg/L), BC sorption sites become saturated and BC sorption is overwhelmed by sorption to the other OM constituents. Because sorption is a central process affecting contaminant behavior and ecotoxicity, understanding this process can strongly contribute to risk assessment and fate modeling.     

No interference of task complexity with circadian rhythmicity in a constant routine protocol

Time course in task performance has been studied extensively. In particular, the investigation of circadian rhythmicity in task performance that varied in complexity. However, these studies disclosed heterogeneous outcomes. This could be the result of confounding exogenous factors, the use of diverse tasks, as well as accumulating sleepiness interfering with the underlying circadian drive. The present study varied task demands systematically within a single task and a dual task, using a constant routine protocol to examine the unmasked influence of the endogenous circadian oscillator on the periodicity of performance. Moreover, the subjects were divided into an early-start and a late-start group to estimate the potential interaction of circadian rhythmicity with the duration of prior wakefulness. The results revealed a distinct congruence in the circadian rhythms of all performance measures, with which prior wakefulness (< 40 h) did not interact. Also, single-task as well as dual-task complexity did not interfere with circadian rhythmicity. In conclusion, when sufficiently controlled for masking exogenous factors, task complexity is removed from the underlying circadian rhythms.     

Motion retargeting and evaluation for VR-based training of free motions

Virtual reality (VR) has emerged as one of the important and effective tools for education and training. Most VR-based training systems are situation based, where the trainees are trained for discrete decision making in special situations presented by the VR environments. In contrast, this paper discusses the application of VR to a different class of training, for learning free motion, often required in sports and the arts. We propose a VR-based motion-training framework that contains an intuitive motion-guiding interface, posture-oriented motion retargeting, and an evaluation and advice scheme for corrective feedback. Applications of the proposed framework to simple fencing training and a dance imitation game are demonstrated.     

Generalized Lorenz-Mie theory for a spheroidal particle with off-axis Gaussian-beam illumination

The beam-shape coefficients of arbitrary off-axis Gaussian beams in spheroidal coordinates are evaluated with a generalized Lorenz-Mie theory. The light-scattering properties of absorbing and nonabsorbing homogeneous spheroidal particles, such as the angular distribution of scattered intensity for a wide range of particles sizes and different complex refractive indices versus the magnitude and location of the beam waist, are investigated.