Enhancement of dielectric constant and associated coupling of polarization behavior in thin film relaxor superlattices

Thin film capacitor structures in which the dielectric is composed of superlattices of the relaxors [0.2Pb(Zn1/3Nb2/3)O- 3-0.8BaTiO(3)] and Pb(Mg1/3Nb2/3)O-3 have been fabricated by pulsed laser deposition. Superlattice wavelength (Lambda) was varied between similar to3 and similar to 600 nm, and dielectric properties were investigated as a function of Lambda. Progressive enhancement of the dielectric constant was observed on decreasing Lambda, and, in contrast to previous work, this was not associated with the onset of Maxwell-Wagner behavior. Polarization measurements as a function of temperature suggested that the observed enhancement in dielectric constant was associated with the onset of a coupled response. The superlattice wavelength (Lambda =20 nm) at which coupled functional behavior became apparent is comparable to that found in literature for the onset of coupled structural behavior (between Lambda =5 nm and Lambda =10 nm). (C) 2001 American Institute of Physics.

Scaling of domain periodicity with thickness measured in BaTiO3 single crystal lamellae and comparison with other ferroics

The focused ion beam microscope has been used to cut parallel-sided {100}-oriented thin lamellae of single crystal barium titanate with controlled thicknesses, ranging from 530 nm to 70 nm. Scanning transmission electron microscopy has been used to examine domain configurations. In all cases, stripe domains were observed with {011}-type domain walls in perovskite unit-cell axes, suggesting 90 degrees domains with polarization in the plane of the lamellae. The domain widths were found to vary as the square root of the lamellar thickness, consistent with Kittel's law, and its later development by Mitsui and Furuichi and by Roytburd. An investigation into the manner in which domain period adapts to thickness gradient was undertaken on both wedge-shaped lamellae and lamellae with discrete terraces. It was found that when the thickness gradient was perpendicular to the domain walls, a continuous change in domain periodicity occurred, but if the thickness gradient was parallel to the domain walls, periodicity changes were accommodated through discrete domain bifurcation. Data were then compared with other work in literature, on both ferroelectric and ferromagnetic systems, from which conclusions on the widespread applicability of Kittel's law in ferroics were made.

Extension of the Ye and Shreeve group contribution method for density estimation of ionic liquids in a wide range of temperatures and pressures

An extension of the Ye and Shreeve group contribution method [C. Ye, J.M. Shreeve, J. Phys. Chem. A 111 (2007) 1456–1461] for the estimation of densities of ionic liquids (ILs) is here proposed. The new version here presented allows the estimation of densities of ionic liquids in wide ranges of temperature and pressure using the previously proposed parameter table. Coefficients of new density correlation proposed were estimated using experimental densities of nine imidazolium-based ionic liquids. The new density correlation was tested against experimental densities available in literature for ionic liquids based on imidazolium, pyridinium, pyrrolidinium and phosphonium cations. Predicted densities are in good agreement with experimental literature data in a wide range of temperatures (273.15–393.15 K) and pressures (0.10–100 MPa). For imidazolium-based ILs, the mean percent deviation (MPD) is 0.45% and 1.49% for phosphonium-based ILs. A low MPD ranging from 0.41% to 1.57% was also observed for pyridinium and pyrrolidinium-based ILs.

Hydrodynamic cavitation in micro channels with channel sizes of 100 and 750 micrometers

Decreasing the constriction size and residence time in hydrodynamic cavitation is predicted to give increased hot spot temperatures at bubble collapse and increased radical formation rate. Cavitation in a 100 x 100 mu m(2) rectangular micro channel and in a circular 750 mu m diameter milli channel has been investigated with computational fluid dynamics software and with imaging and radical production experiments. No radical production has been measured in the micro channel. This is probably because there is no spherically symmetrical collapse of the gas pockets in the channel which yield high hot spot temperatures. The potassium iodide oxidation yield in the presence of chlorohydrocarbons in the milli channel of up to 60 nM min(-1) is comparable to values reported on hydrodynamic cavitation in literature, but lower than values for ultrasonic cavitation. These small constrictions can create high apparent cavitation collapse frequencies.

Dis)Harmony in Illyria: Music, Order, and Time in Twelfth Night:Music, Order, and Time in Twelfth Night

This paper considers the integral aspect of music as performed in Shakespeare's Twelfth Night. It posits that music is that which orders and structures time in its interplay throughout the play.

Community identity as resource and context: A mixed method investigation of coping and collective action in a disadvantaged community

Community identities enhance well-being through the provision of social support and feelings of collective efficacy as well as by acting as a basis for collective action and social change. However, the precise mechanisms through which community identity acts to enhance well-being are complicated by stigmatisation which potentially undermines solidarity and collective action. The present research examines a real-world stigmatised community group in order to investigate: (1) the community identity factors that act to enhance well-being, and (2) the consequences of community identity for community action. Study 1 consisted of a household survey conducted in disadvantaged areas of Limerick city in Ireland. Participants (n=322) completed measures of community identification, social support, collective efficacy, community action, and psychological well-being. Mediation analysis indicated that perceptions of collective efficacy mediated the relationship between identification and well-being. However, levels of self-reported community action were low and unrelated to community identification. In Study 2, twelve follow–up multiple-participant interviews with residents and community group workers were thematically analysed, revealing high levels of stigmatisation and opposition to identity-related collective action. These findings suggest the potential for stigma to reduce collective action through undermining solidarity and social support.

City of Dreams? Belfast, planning and the ‘myth’ of development

The future of Belfast is found in its plans – beginning with 1945 planning proposals to the recently adopted Belfast Metropolitan Area Plan, these documents have aimed to encourage and channel urban development processes to secure collective outcomes that enhance the public interest. Central to this objective has been the idea of ‘development’ and in this paper we interrogate the representation of this concept in the urban discourse of Belfast. We seek to do this by first exploring how ‘development’ and associated concepts are articulated in key spatial policy documents and then contrast these with examples of some of the key physical, spatial outcomes of economic processes that have occurred in the last ten years. The paper will review the dominant trajectories of urban change in Belfast, consider their implications and relate these to the official goals and aspirations represented in planning strategies and regeneration visions for the city. In doing this we draw on the recent work of Marcuse (2015) to identify how ideas of ‘development’ and ‘growth’ have been used to anonymise, harmonize and homogenise the outcomes of these spatial processes. The paper will conclude by considering how Belfast’s urban discourse acts to suppresses alternative visions of the city and explores the potential consequences of this for the new governance arrangements for planning in Belfast.

City Profile: Erbil

Erbil (Hawler in Kurdish), is the capital and the largest city of Iraqi Kurdistan. Having been continuously inhabited for about 6000 years, the city has recently been regarded by UNESCO World Heritage as one of the world’s oldest urban settlements. The city is witnessing remarkable urban growth and rapid spatial expansion compounded by a dramatic increase in population due to emigration from the countryside and rural areas over the last three decades. Following the changing geopolitical landscape of post-war Iraq, urban changes and socio-political transformation are largely driven by Erbil’s growing autonomous status as the capital of northern region of Kurdistan since 2003. This paper explores the layers of historical, spatial and social developments of the contemporary urban context of Kurdistan in general and of Erbil in particular as a reflection of the changing status of the city, as well as the polarization of Iraq and the emergence of neoliberal urbanism. The tension between the global and modern from one side and traditional and authentic from another is ever present and evident in everyday challenges in the planning of the city. In large part, Erbil’s built fabric embodies the dichotomy of identity and contests between its past and future, in which the present remains a transition between two disconnected realities.

King David’s City at Khirbet Qeiyafa: Results of the Second Radiocarbon Dating Project

Fifteen samples of burnt olive pits discovered inside a jar in the destruction layer of the Iron Age city of Khirbet Qeiyafa were analyzed by accelerator mass spectrometry (AMS) radiocarbon dating. Of these, four were halved and sent to two different laboratories to minimize laboratory bias. The dating of these samples is ~1000 BC. Khirbet Qeiyafa is currently the earliest known example of a fortified city in the Kingdom of Judah and contributes direct evidence to the heated debate on the biblical narrative relating to King David. Was he the real historical ruler of an urbanized state-level society in the early 10th century BC or was this level of social development reached only at the end of the 8th century BC? We can conclude that there were indeed fortified centers in the Davidic kingdom from the studies presented. In addition, the dating of Khirbet Qeiyafa has far-reaching implications for the entire Levant. The discovery of Cypriot pottery at the site connects the 14C datings to Cyprus and the renewal of maritime trade between the island and the mainland in the Iron Age. A stone temple model from Khirbet Qeiyafa, decorated with triglyphs and a recessed doorframe, points to an early date for the development of this typical royal architecture of the Iron Age Levant.