Competition between memory-keeping and memory-erasing decoherence channels

We study the competing effects of simultaneous Markovian and non-Markovian decoherence mechanisms acting on a single spin. We show the existence of a threshold in the relative strength of such mechanisms above which the spin dynamics becomes fully Markovian, as revealed by the use of several non-Markovianity measures. We identify a measure-dependent nested structure of such thresholds, hinting at a causality relationship among the various non-Markovianity witnesses used in our analysis. Our considerations are then used to argue the unavoidably non-Markovian evolution of a single-electron quantum dot exposed to both intrinsic and Markovian technical noise, the latter of arbitrary strength. 

Cyclic nanoindentation and nano-impact fatigue characterisation of functionally graded TiN/TiNi shape memory film

This paper investigates the mechanism of nanoscale fatigue of functionally graded TiN/TiNi films using nano-impact and multiple-loading-cycle nanoindentation tests. The functionally graded films were deposited on silicon substrate, in which TiNi films maintain shape memory and pseudo elastic behavior, while a modified TiN surface layer provides tribological and anti-corrosion properties. Nanomechanical tests were performed to comprehend the localized film performance and failure modes of the functionally graded film using NanoTestTM equipped with Berkovich and conical indenter between 100 μN to 500 mN loads. The loading mechanism and load history are critical to define film failure modes (i.e. backward depth deviation) including the shape memory effect of the functionally graded layer. The results are sensitive to the applied load, loading type (e.g. semi-static, dynamic) and probe geometry. Based on indentation force-depth profiles, depth-time data and post-test surface observations of films, it is concluded that the shape of the nanoindenter is critical in inducing the localized indentation stress and film failure, including shape recovery at the lower load range. Elastic-plastic finite element (FE) simulation during nanoindentation loading indicated that the location of subsurface maximum stress near the interface influences the backward depth deviation type of film failure. A standalone, molecular dynamics simulation was performed with the help of a long range potential energy function to simulate the tensile test of TiN nanowire with two different aspect ratios to investigate the theory of its failure mechanism.

The Landscape of Differences: Contact and Segregation in the Everyday Encounters

The article examines everyday life in Northern Ireland’s segregated communities and focus on a neglected empirical dimension of ethnic and social segregation developed within the socio-spatial relations between people and their built environment. It shows how the everyday urban encounters are reproduced through negotiating differences and the ways in which living in divided communities lead to social inequality and imbalanced use of space. The article employed qualitative research methods with individuals and community groups from the Fountain estate, a small Protestant enclave in Derry/Londonderry. Their stories were replete with cases of injustice and insights into the daily struggles that have generally occurred within theories of contact and social segregation as a whole. In fact, people in the Fountain presented their own intertextual references on what was more significant for them as a matter of routine survival and belonging, which allowed them to be more constructive about themselves. While segregation has persisted for multiple decades; time is believed to be the factor most likely to change it, as it is hoped that the younger generation will provide lasting change to Northern Ireland and eventual peace between currently segregated communities.

Post-Conflict Performance, Film and Visual Arts:Cities of Memory

This book examines how contemporary theatre, performance, film and the visual arts respond to the post-conflict condition. The contents of the volume focus on a range of post-conflict cities, encouraging interdisciplinary discussion on the role of the arts and its relation to issues of testimony, witnessing, forgetting, representation, healing, reconciliation, agency, and metaphor. Contributors include: Thomas Elsaesser, Jane Taylor, Marvin Carlson, Rob Stone, Laurel Borisenko, Katarzyna Puzon, Miriam Paeslack, Emma Grey, Paula Blair, Zoran Poposki, Marija Todorova, Elena Carduro, and Paul Devlin.

Software-Managed Energy-Efficient Hybrid DRAM/NVM Main Memory

This paper evaluates the viability of user-level software management of a hybrid DRAM/NVM main memory system. We propose an operating system (OS) and programming interface to place data from within the user application. We present a profiling tool to help programmers decide on the placement of application data in hybrid memory systems. Cycle-accurate simulation of modified applications confirms that our approach is more energy-efficient than state-of-the- art hardware or OS approaches at equivalent performance. Moreover, our results are validated on several candidate NVM technologies and a wide set of 14 benchmarks.
The key observation behind this work is that, for the work- loads we evaluated, application objects are too short-lived to motivate migration. Utilizing this property significantly reduces the hardware complexity of hybrid memory systems.

On the complexity of solving polytree-shaped limited memory influence diagrams with binary variables

Influence diagrams are intuitive and concise representations of structured decision problems. When the problem is non-Markovian, an optimal strategy can be exponentially large in the size of the diagram. We can avoid the inherent intractability by constraining the size of admissible strategies, giving rise to limited memory influence diagrams. A valuable question is then how small do strategies need to be to enable efficient optimal planning. Arguably, the smallest strategies one can conceive simply prescribe an action for each time step, without considering past decisions or observations. Previous work has shown that finding such optimal strategies even for polytree-shaped diagrams with ternary variables and a single value node is NP-hard, but the case of binary variables was left open. In this paper we address such a case, by first noting that optimal strategies can be obtained in polynomial time for polytree-shaped diagrams with binary variables and a single value node. We then show that the same problem is NP-hard if the diagram has multiple value nodes. These two results close the fixed-parameter complexity analysis of optimal strategy selection in influence diagrams parametrized by the shape of the diagram, the number of value nodes and the maximum variable cardinality.

Solving Limited Memory Influence Diagrams

We present a new algorithm for exactly solving decision making problems represented as influence diagrams. We do not require the usual assumptions of no forgetting and regularity; this allows us to solve problems with simultaneous decisions and limited information. The algorithm is empirically shown to outperform a state-of-the-art algorithm on randomly generated problems of up to 150 variables and 10^64 solutions. We show that these problems are NP-hard even if the underlying graph structure of the problem has low treewidth and the variables take on a bounded number of states, and that they admit no provably good approximation if variables can take on an arbitrary number of states.

Solving Limited Memory Influence Diagrams

We present a new algorithm for exactly solving decision making problems represented as influence diagrams. We do not require the usual assumptions of no forgetting and regularity; this allows us to solve problems with simultaneous decisions and limited information. The algorithm is empirically shown to outperform a state-of-the-art algorithm on randomly generated problems of up to 150 variables and 10^64 solutions. We show that the problem is NP-hard even if the underlying graph structure of the problem has small treewidth and the variables take on a bounded number of states, but that a fully polynomial time approximation scheme exists for these cases. Moreover, we show that the bound on the number of states is a necessary condition for any efficient approximation scheme.

Patterning and switching of nano-size ferroelectric memory cells

A "top-down" approach using a-beam lithography and a "bottom-up" one using self-assembly methods were used to fabricate ferroelelectric Pb(Zr,Ti)O-3, SrBi2Ta2O9 and BaTiO3 nanostructures with lateral sizes in the range of 30 nm to 100 nm. Switching of single sub-100 nm cells was achieved and piezoelectric hysteresis loops were recorded using a scanning force microscope working in piezoresponse mode. The piezoelectricity and its hysteresis acquired for 100 nm PZT cells demonstrate that a further decrease in lateral size under 100 nm appears to be possible and that the size effects are not fundamentally limiting on increase density of non-volatile ferroelectric memories in the Gbit range.

Families and Poverty: Everyday life on a low income

The recent radical cutbacks of the welfare state in the UK have meant that poverty and income management continue to be of great importance for intellectual, public and policy discourse. Written by leading authors in the field, the central interest of this innovative book is the role and significance of family in a context of poverty and low-income. Based on a micro-level study carried out in 2011 and 2012 with 51 families in Northern Ireland, it offers new empirical evidence and a theorisation of the relationship between family life and poverty. Different chapters explore parenting, the management of money, family support and local engagement. By revealing the ordinary and extraordinary practices involved in constructing and managing family and relationships in circumstances of low incomes, the book will appeal to a wide readership, including policy makers.

Film, History and Memory

Film, History and Memory examines the relationship between film and history, exploring the multiplicity of ways in which films depict, contest, reinforce or subvert historical understanding. This volume broadens the focus from 'history', the study of past events, to 'memory', the processes – individual, generational, collective or state-driven – by which meanings are attached to the past. This approach acknowledges how the significance of the historical film lies less in its empirical qualities than in its powerful capacity to influence public thinking and discourses about the past, whether by shaping collective memory, popular history and social memory, or by retrieving suppressed or marginalized histories. This study aims to contribute to the growing literature on history and film through the breadth of its approach, both in disciplinary and geographical terms. Contributors are drawn not only from the discipline of history but also film studies, film practice, art history, languages and literature, and cultural studies.