Positive effective Q12 electrostrictive coefficient in perovskites

It is demonstrated that for classical perovskites such as BaTiO3, SrTiO3 and PbTiO3 electrostrictive strain induced by an electric field may not obey traditionally considered "extension along the field, contraction perpendicular to it" behavior if a sample is cut obliquely to the cubic crystallographic directions

Packet utilisation definitions for the ESA XMM mission

XMM, ESA's X-Ray Multi-Mirror satellite, due for launch at the end of 1999 will be the first ESA scientific spacecraft to implement the ESA packet telecommand and telemetry standards and will be the first ESOC-controlled science mission to take advantage of the new flight control system infrastructure development (based on object-oriented design and distributed-system architecture) due for deployment in 1995. The implementation of the packet standards is well defined at packet transport level. However, the standard relevant to the application level (the ESA Packet Utilization Standard) covers a wide range of on-board 'services' applicable in varying degrees to the needs of XMM. In defining which parts of the ESA PUS to implement, the XMM project first considered the mission objectives and the derived operations concept and went on to identify a minimum set of packet definitions compatible with these aspects. This paper sets the scene as above and then describes the services needed for XMM and the telecommand and telemetry packet types necessary to support each service

A Typology of Corrupt Transactions in Developing Countries

Summary Economic theory has attempted to identify the conditions under which corruption has particularly harmful effects. This article evaluates these theories and argues that the classifications offered are misleading. Very successful interventionist states have suffered from corruption just as much as very unsuccessful ones. Policy responses to corruption require an understanding of the effects of corruption and the determinants of these effects. The fact which appears to have a strong effect in determining the harmfulness of corruption is the balance of power between the state and its clients. An alternative classification of the effects of corruption is suggested on this basis

The modalities of Iranian soft power: from cultural diplomacy to soft war

Through exploring Iran's public diplomacy at the international level, this article demonstrates how the Islamic Republic's motives should not only be contextualised within the oft-sensationalised, material or ‘hard’ aspects of its foreign policy, but also within the desire to project its cultural reach through ‘softer’ means. Iran's utilisation of culturally defined foreign policy objectives and actions demonstrates its understanding of soft power's potentialities. This article explores the ways in which Iran's public diplomacy is used to promote its soft power and craft its, at times, shifting image on the world stage

Polarization of tightly focused laser beams

The polarization properties of monochromatic light beams are studied. In contrast to the idealization of an electromagnetic plane wave, finite beams which are everywhere linearly polarized in the same direction do not exist. Neither do beams which are everywhere circularly polarized in a fixed plane. It is also shown that transversely finite beams cannot be purely transverse in both their electric and magnetic vectors, and that their electromagnetic energy travels at less than c. The electric and magnetic fields in an electromagnetic beam have different polarization properties in general, but there exists a class of steady beams in which the electric and magnetic polarizations are the same (and in which energy density and energy flux are independent of time). Examples are given of exactly and approximately linearly polarized beams, and of approximately circularly polarized beams.Comment: 9 pages, 6 figure

Simulation as a Disruptive Innovation in Advanced Practice Nursing Programs: A Report from a Qualitative Examination

Simulation as a pedagogy is used extensively to educate healthcare professionals in both academic and clinical arenas with the intent to improve the delivery of care and patient outcomes. Advanced practice nursing (APN) programs use simulation as a pedagogy even though APN accreditation and certification organizations prohibit substituting simulation hours for the minimum 500 clinical hours. The purpose of this qualitative study was to explore faculty perceptions of educating APN students using simulation. Focus groups were conducted with a convenience sample of APN simulation faculty. Disruptive innovation theory was used by the researchers to guide the data analysis. Themes emerging during analysis included: 1) extrinsic tension and pressure in the midst of chaos, 2) internal vulnerability, and 3) passion and tenacity to remain resilient. The study results provide clarity to understand integration of APN simulation in the current environment, and introduce the impact of simulation as a disruptive innovation

Optimal configuration of microstructure in ferroelectric materials by stochastic optimization

An optimization procedure determining the ideal configuration at the microstructural level of ferroelectric (FE) materials is applied to maximize piezoelectricity. Piezoelectricity in ceramic FEs differ significantly from that of single crystals because of the presence of crystallites (grains) possessing crystallographic axes aligned imperfectly. The piezoelectric properties of a polycrystalline (ceramic) FE is inextricably related to the grain orientation distribution (texture). The set of combination of variables, known as solution space, which dictates the texture of a ceramic is unlimited and hence the choice of the optimal solution which maximizes the piezoelectricity is complicated. Thus a stochastic global optimization combined with homogenization is employed for the identification of the optimal granular configuration of the FE ceramic microstructure with optimum piezoelectric properties. The macroscopic equilibrium piezoelectric properties of polycrystalline FE is calculated using mathematical homogenization at each iteration step. The configuration of grains characterised by its orientations at each iteration is generated using a randomly selected set of orientation distribution parameters. Apparent enhancement of piezoelectric coefficient $d_{33}$ is observed in an optimally oriented BaTiO$_3$ single crystal. A configuration of crystallites, simultaneously constraining the orientation distribution of the c-axis (polar axis) while incorporating ab-plane randomness, which would multiply the overall piezoelectricity in ceramic BaTiO$_{3}$ is also identified. The orientation distribution of the c-axes is found to be a narrow Gaussian distribution centred around ${45^\circ}$. The piezoelectric coefficient in such a ceramic is found to be nearly three times as that of the single crystal.Comment: 11 pages, 7 figure

An experiment on the shifts of reflected C-lines

An experiment is described that tests theoretical predictions on how C-lines incident obliquely on a surface behave on reflection. C-lines in a polarised wave are the analogues of the optical vortices carried by a complex scalar wave, which is the usual model for describing light and other electromagnetic waves. The centre of a laser beam that carries a (degenerate) C-line is shifted on reflection by the well-known Goos-H\"anchen and Imbert-Fedorov effects, but the C-line itself splits into two, both of which are shifted longitudinally and laterally; their shifts are different from that of the beam centre. To maximise the effect to be measured, internal reflection in a glass prism close to the critical angle was used. In a simple situation like this two recently published independent theories of C-line reflection overlap and it is shown that their predictions are identical. The measured differences in the lateral shifts of the two reflected C-lines are compared with theoretical expectations over a range of incidence angles.Comment: 9 pages, 2 figure

Electromagnetic wave scattering by a superconductor

The interaction between radiation and superconductors is explored in this paper. In particular, the calculation of a plane standing wave scattered by an infinite cylindrical superconductor is performed by solving the Helmholtz equation in cylindrical coordinates. Numerical results computed up to $\mathcal{O}(77)$ of Bessel functions are presented for different wavelengths showing the appearance of a diffraction pattern.Comment: 3 pages, 3 figure