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Doping of SrFe12O19 with 0.3 mol per unit of Ga3+ or In3+ ions causes a division in the 12K octahedral subspectrum. The splitting occurs due to a magnetic exchange interaction of some of the 12k2 Fe3+ ions. The random changes in the exchange interactions do not influence the 12k splitting.

Presents information on a study which investigated the chemical composition of mineral specimens of the mixed-valence solid ilvaite iron compound using x-ray diffraction, magnetic susceptometry, ...iron Mossbauer spectroscopy and electrical conductivity. Experimental details; Results and discussion.

Presents a study which determined the influence of pressure on the Möbauer spectrum of a nearly stoichiometric sample of Fe[sub3]O[sub4] that exhibits no isomer shift induced splitting of the B-site patterns of the spectrum at 300 K. Procedure used to obtain the spectra; Basis for the adequacy of the fits; Factor attributed to the components of the B site.

Presents a study which investigated the influence of heat treatments on order-disorder phenomena in a naturally occurring manganese-ferrite. Experimental procedures; Results and discussion; Conclusion.

Presents a study that investigated the unusual behavior of the 12k site in SrGa[subx]Fe[sub12-x]O[sub19] (0.3≤x≤6.0) and SrIn[subx]Fe[sub12-x]O[sub19] (0.3≤x≤1.4) by means of [sup57]Fe M&oml;ssbauer spectroscopy at 298 Kelvin. Lattice constants of substituted SrFe[sub12]O[sub19]; Description of the bifurcation of the 12k M&oml;ssbauer subspectrum; Factors that affect splitting of the 12k magnetic hyperfine spectrum.

Presents a study which determined the influence of each of the iron (Fe) sites on the bulk magnetic properties of the different MFe[sub12]O[sub19] compounds. Dynamical aspects of the hyperfine interactions; Magnitude of the hyperfine interactions of a given Fe; Structure of the M-type hexaferrites MFe[sub12]O[sub19].

Presents a study that examined the magnetic properties, compositions and microstructures of high-energy product strontium hexaferrites. Details of the experiment; Results; Conclusions.

Presents a study which examined the crystal/chemical structures and magnetic properties of naturally occurring manganese[sub1.7]iron[sub1.3]oxygen[sub4]. Investigation of the thermodynamic equilibrium of the crystal/chemical structrues of manganese ferrite iwakiite under conditions of regional metamorphism; Experimental details; Results and discussion.

We describe a new octoploid species of African clawed frog ( Xenopus) from the Lendu Plateau in the northern Albertine Rift of eastern Democratic Republic of the Congo. This species is the sister taxon of Xenopus vestitus (another octoploid), but is distinguished by a unique morphology, vocalization and molecular divergence in mitochondrial and autosomal DNA. Using a comprehensive genetic sample, we provide new information on the species ranges and intra-specific diversity of African clawed frogs from the Albertine Rift, including the details of a small range extension for the critically endangered Xenopus itombwensis and previously uncharacterized variation in Xenopus laevis. We also detail a new method for generating cytogenetic preparations in the field that can be stored at room temperature for up to 3 weeks. While extending our understanding of the extant diversity in the Albertine Rift, this new species highlights components of species diversity in ancestral African clawed frogs that are not represented by known extant descendants. [ABSTRACT FROM AUTHOR]

The BLOODHOUND SSC project was publicly announced in October 2008, with a primary engineering objective of designing, constructing, and running a vehicle capable of achieving a speed of 1,000 miles per hour on land. The aerodynamic design of this vehicle is to be accomplished using computational simulation only, and this article describes the development and application of the approach adopted. The computational model employs a cell vertex finite volume algorithm for the solution of compressible viscous flow problems on unstructured hybrid meshes. A one-equation turbulence model is adopted, and the solution of the steady flow equations is obtained by explicit relaxation. For the combination of high Mach number, complex geometry, and complex boundary conditions involving rotating surfaces and a rolling ground, a consistent Harten, Lax van Leer Contact (HLLC) wave numerical flux function is adopted to ensure a stable procedure. To illustrate the impact of the approach upon the final configuration, a number of simulations undertaken to aid the aerodynamic design are described. [ABSTRACT FROM AUTHOR]

We investigated the influence of lighting on performance at activities of daily living in 24 older people with low vision from cataract and/or macular degeneration. Participants carried out four everyday tasks, each at three illuminances: 50 lux, 200 lux, and 800 lux. Both objective performance and subjective preference were recorded. Subjects tend to perform better under brighter conditions, but the average results masked large individual variations. Indeed, most participants showed a large effect of lighting on performance in at least one task, but the optimal light level varied idiosyncratically from one subject to another. The best approach to provide optimal lighting for older people with low vision may be to individually assess their preference and performance at different light levels. [ABSTRACT FROM AUTHOR]

High-temperature oxide-melt calorimetry and Rietveld refinement of powder X-ray diffraction patterns were used to investigate the energetics and structure of the hematite–corundum solid solution and ternary phase FeAlO3 (with FeGaO3 structure). The mixing enthalpies in the solid solution can be described by a polynomial ΔHmix= WXhem(1− Xhem) with W=116 ± 10 kJ mol−1. The excess mixing enthalpies are too positive to reproduce the experimental phase diagram, and excess entropies in the solid solution should be considered. The hematite–corundum solvus can be approximately reproduced by a symmetric, regular-like solution model with Δ Gexcess=( W H− TW S) Xhem Xcor, where WH= 116 ± 10 kJ mol−1 and W S=32 ± 4 J mol−1 K−1. In this model, short-range order (SRO) of Fe/Al is neglected because SRO probably becomes important only at intermediate compositions close to Fe:Al=1:1 but these compositions cannot be synthesized. The volume of mixing is positive for Al-hematite but almost ideal for Fe-corundum. Moreover, the degree of deviation from Vegard's law for Al-hematite depends on the history of the samples. Introduction of Al into the hematite structure causes varying distortion of the hexagonal network of oxygen ions while the position of the metal ions remains intact. Distortion of the hexagonal network of oxygen ions attains a minimum at the composition (Fe0.95Al0.05)2O3. The enthalpy of formation of FeAlO3 from oxides at 298 K is 27.9 ± 1.8 kJ mol−1. Its estimated standard entropy (including configurational entropy due to disorder of Fe/Al) is 98.9 J mol−1 K−1, giving the standard free energy of formation at 298 K from oxides and elements as +19.1 ± 1.8 and −1144.2 ± 2.0 kJ mol−1, respectively. The heat capacity of FeAlO3 is approximated as C p( T in K)= 175.8 − 0.002472 T − (1.958 × 106)/ T 2− 917.3/ T 0.5+(7.546 × 10−6) T 2 between 298 and 1550 K, based on differential scanning calorimetric measurements. No ferrous iron was detected in FeAlO3 by Mössbauer spectroscopy. The ternary phase is entropy stabilized and is predicted to be stable above about 1730 ± 70 K, in good agreement with the experiment. Static lattice calculations show that the LiNbO3-, FeGaO3-, FeTiO3-, and disordered corundum-like FeAlO3 structures are less stable (in the order in which they are listed) than a mechanical mixture of corundum and hematite. At high temperatures, the FeGaO3-like structure is favored by its entropy, and its stability field appears on the phase diagram. [ABSTRACT FROM AUTHOR]

Concentration upon aggregate levels of voting behaviour and the two party system have obscured the persistence of electoral co-operation in multi-party systems in British local politics. This article examines the factors contributing to successful electoral co-operation, particularly, a favourable local political culture and elite interaction. This article shows such co-operation to be unstable in the long run. The focus for the study is the Bolton and Huddersfield constituencies. [ABSTRACT FROM AUTHOR]

A recent double-masked placebo-controlled trial has confirmed that some children experience a reduction in symptoms of eyestrain and headache when they read through individually prescribed coloured filters and has shown that this benefit cannot be solely attributed to a placebo effect. People who are helped by coloured filters in this way have been described as having 'Meares-lrlen syndrome'. We investigated the mechanism of this benefit by studying the optometric and visual perceptual characteristics of the children in the double-masked study. This population had normal refractive errors and heterophorias (none of the subjects had strabismus). They demonstrated slightly, but significantly, reduced amplitudes of accommodation and vergence and poor stereo-acuity. However, these factors seemed to be correlates of Meares-lrlen syndrome rather than the underlying cause. Pattern glare, a sensitivity to striped patterns (e.g. lines of text), was prevalent in our sample and was significantly associated with the subjects' symptoms. The spatial contrast sensitivity function was normal. Copyright © 1996 The College of Optometrists. Published by Elsevier Science Ltd [ABSTRACT FROM AUTHOR]

Dyslexia has conventionally been attributed to a left hemisphere deficit affecting language skills. However, it has recently been suggested that two-thirds of dyslexic people have a lesion of the right posterior parietal lobe (RPPL) resulting in poor oculo-motor control. It has been reported that neurological patients with RPPL lesions commonly manifest a neglect of the left side of space and this has also been described in clinical observations of 'visual dyslexies'. We investigated this hypothesis with a sample of 53 dyslexic children and 53 controls using a line-bisection task. In the horizontal test condition both groups tended to transect slightly to the left of the midpoint (mean displacement 0.14 mm for controls; 0.4 mm for dyslexies). The result suggests a small right side neglect which, contrary to one report in the literature, is found here in developmental dyslexies as well as controls, and leads to the conclusion that RPPL lesion is unlikely to be a common feature of dyslexia. [ABSTRACT FROM AUTHOR]

Research by Evans et al. (Ophthal. Physiol. Opt. 15, 481-487, 19956) has demonstrated a correlation between visual processing and ocular motor factors in people with specific reading difficulties (dyslexia). In addition, research by Wilkins et al. (Ophthal. Physiol. Opt. 14, 365-370, 1994) has shown that some people with dyslexia will benefit from a reduction of perceptual symptoms of discomfort and distortion if they use individually prescribed coloured filters. Three examples of the dyslexic patients who attend at the Institute of Optometry clearly demonstrate the importance of full investigation of ocular function, including the assessment of the effect of colour on visual perception. All three patients presented with similar symptoms of asthenopia when reading. Symptoms were alleviated for the first patient by use of orthoptic treatment of an exotropia with intermittent suppression. With the second patient, ocular motor functions were found to be within acceptable limits and relief of symptoms was obtained by the prescribing of lenses of a specific chromaticity. For the third patient, both orthoptic intervention and the use of specifically tinted lenses were necessary to relieve the visual difficulties that were being experienced. By taking advantage of recent research and developments in optometric instrumentation, it is possible for some of those with dyslexia to receive considerable benefit from optometric intervention. [ABSTRACT FROM AUTHOR]