55,944 research outputs found
A qualitative study of adjustment to caring for an older spouse with psychiatric illness
An understanding of ways in which older carers' perceptions of their marital relationship and duty to their spouse underlie adjustment to care-giving is required for the development of acceptable and efficacious services for spouse carers. With this aim we conducted qualitative interviews with 20 spouses Of older people with a mental illness identified in a representative community study. While carers acknowledged distressing changes in their spouse, a history of reciprocity and intimacy emerged, comprising positive themes and perceived continuity which favourably influenced adjustment to care-giving. Those who still experience closeness in the relationship see themselves as coping and are reluctant to accept formal help. Others describe long-term unhappiness in marriage and experience feelings of entrapment in the role of carer. They require early and comprehensive services. Hypotheses regarding these themes are proposed
Travelling waves in a tissue interaction model for skin pattern formation
Tissue interaction plays a major role in many morphogenetic processes, particularly those associated with skin organ primordia. We examine travelling wave solutions in a tissue interaction model for skin pattern formation which is firmly based on the known biology. From a phase space analysis we conjecture the existence of travelling waves with specific wave speeds. Subsequently, analytical approximations to the wave profiles are derived using perturbation methods. We then show numerically that such travelling wave solutions do exist and that they are in good agreement with our analytical results. Finally, the biological implications of our analysis are discussed
Extent of stacking disorder in diamond
Hexagonal diamond has been predicted computationally to display extraordinary
physical properties including a hardness that exceeds cubic diamond. However, a
recent electron microscopy study has shown that so-called hexagonal diamond
samples are in fact not discrete materials but faulted and twinned cubic
diamond. We now provide a quantitative analysis of cubic and hexagonal stacking
in diamond samples by analysing X-ray diffraction data with the DIFFaX software
package. The highest fractions of hexagonal stacking we find in materials which
were previously referred to as hexagonal diamond are below 60%. The remainder
of the stacking sequences are cubic. We show that the cubic and hexagonal
sequences are interlaced in a complex way and that naturally occurring
Lonsdaleite is not a simple phase mixture of cubic and hexagonal diamond.
Instead, it is structurally best described as stacking disordered diamond. The
future experimental challenge will be to prepare diamond samples beyond 60%
hexagonality and towards the so far elusive 'perfect' hexagonal diamond
Advanced General Aviation Turbine Engine (GATE) concepts
Concepts are discussed that project turbine engine cost savings through use of geometrically constrained components designed for low rotational speeds and low stress to permit manufacturing economies. Aerodynamic development of geometrically constrained components is recommended to maximize component efficiency. Conceptual engines, airplane applications, airplane performance, engine cost, and engine-related life cycle costs are presented. The powerplants proposed offer encouragement with respect to fuel efficiency and life cycle costs, and make possible remarkable airplane performance gains
Research and Teacher Education: The BERA-RSA inquiry. Policy and Practice within the United Kingdom.
Across the four jurisdictions of the United Kingdom (England, Northern Ireland, Scotland and Wales) initial teacher education (ITE) is under active development, with its content, location, control and quality often the focuses of sustained debate. Statutory and professional requirements for the sector inevitably reflect differing assumptions about teaching, teacher knowledge and governance. In exploring ITE across the four jurisdictions, this paper reviews policies and practices through two major focuses: first, the relationships between the declared teacher standards (competencies/competences) and research-informed teacher education provision; second, the ‘turn or (re)turn to the practical’ in teacher education, including policy declarations, changes in practices, and emphases and effects of the discourse(s) of relevance
Sequential pattern formation in a model for skin morphogenesis
During morphogenesis regular patterns often develop behind a frontier of pattern formation which travels across the prospective tissue. Here the authors consider the propagating patterns exhibited in a two-dimensional domain by a tissue interaction mechanochemical model for skin pattern formation. It is shown that the model can exhibit travelling waves of complex spatial pattern formation. Two alternative mechanisms that can produce such sequential patterning are presented. In particular, it is demonstrated that the specification of a simple quasi-one-dimensional pattern is all that is required to determine a complex two-dimensional pattern. Finally, the model solutions are related to actual pattern propagation during chick feather primordia initiation
Network formation of tissue cells via preferential attraction to elongated structures
Vascular and non-vascular cells often form an interconnected network in
vitro, similar to the early vascular bed of warm blooded embryos. Our
time-lapse recordings show that the network forms by extending sprouts, i.e.,
multicellular linear segments. To explain the emergence of such structures, we
propose a simple model of preferential attraction to stretched cells. Numerical
simulations reveal that the model evolves into a quasi-stationary pattern
containing linear segments, which interconnect above the critical volume
fraction of 0.2. In the quasi-stationary state the generation of new branches
offset the coarsening driven by surface tension. In agreement with empirical
data, the characteristic size of the resulting polygonal pattern is
density-independent within a wide range of volume fractions
Angular Momentum Transfer in the Binary X-ray Pulsar GX 1+4
We describe three presentations relating to the X-ray pulsar GX 1+4 at a
workshop on magnetic fields and accretion at the Astrophysical Theory Centre,
Australian National University on 1998, November 12-13. Optical and X-ray
spectroscopy indicate that GX 1+4 is seen through a cloud of gravitationaly
bound matter. We discuss an unstable negative feedback mechanism (originally
proposed by Kotani et al, 1999), based on X-ray heating of this matter which
controls the accretion rate when the source is in a low X-ray luminosity state.
A deep minimum lasting ~6 hours occurred during observations with the RXTE
satellite over 1996, July 19-21. The shape of the X-ray pulses changed
remarkably from before to after the minimum. These changes may be related to
the transition from neutron star spin-down to spin-up which occurred at about
the same time. Smoothed particle hydrodynamic simulations of the effect of
adding matter with opposite angular momentum to an existing disc, show that it
is possible for a number of concentric rings with alternating senses of
rotation to co-exist in a disc. This could provide an explanation for the
step-like changes in Pdot which are observed in GX 1+4. Changes at the inner
boundary of the disc occur at the same timescale as that imposed at the outer
boundary. Reversals of material torque on the neutron star occur at a minimum
in L_X.Comment: 10 pages, 5 figures; accepted for publication by PAS
Causality Violations in Cascade Models of Nuclear Collisions
Transport models have successfully described many aspects of intermediate
energy heavy-ion collision dynamics. As the energies increase in these models
to the ultrarelativistic regime, Lorentz covariance and causality are not
strictly respected. The standard argument is that such effects are not
important to final results; but they have not been seriously considered at high
energies. We point out how and why these happen, how serious of a problem they
may be and suggest ways of reducing or eliminating the undesirable effects.Comment: RevTeX, 23 pages, 9 (uuencoded) figures; to appear in Phys. Rev
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