Controlling the divergence of high harmonics from solid targets: a route toward coherent harmonic focusing

Harmonic generation from relativistically oscillating plasma surfaces formed during the interaction of high contrast lasers with solid-density targets has been shown to be an efficient source of extreme ultraviolet (XUV) and X-ray radiation. Recent work has demonstrated that the exceptional coherence properties of the driving laser can be mirrored in the emitted radiation, permitting diffraction limited performance and attosecond phase locking of the harmonic radiation. These unique properties may allow the coherent harmonic focusing (CHF) of high harmonics generated from solid density targets to intensities on the order of the Schwinger limit of 10(29) W cm(-2) with laser systems available in the near future [Phys. Rev. Lett. 93, 115002 (2004)] and thus pave the way for unique experiments exploring the nonlinear properties of vacuum on ultra-fast timescales. In this paper we investigate experimentally as well as numerically the prospect of focusing high harmonics under realistic experimental conditions and demonstrate, using particle in cell (PIC) simulations, that precise control of the wavefronts and thus the focusability of the generated harmonics is possible with pre-shaped targets.

Scaling of proton acceleration driven by petawatt-laser-plasma interactions

The possibility of using high-power lasers to generate high-quality beams of energetic ions is attracting large global interest. The prospect of using laser-accelerated protons in medicine attracts particular interest, as these schemes may lead to compact and relatively low-cost sources. Among the challenges remaining before these sources can be used in medicine is to increase the numbers and energies of the ions accelerated. Here, we extend the energy and intensity range over which proton scaling is experimentally investigated, up to 400 J and 6 x 10(20) W cm(-2) respectively, and find a slower proton scaling than previously predicted. With the aid of plasma-expansion simulation tools, our results suggest the importance of time-dependent and multidimensional effects in predicting the maximum proton energy in this ultrahigh-intensity regime. The implications of our new understanding of proton scaling for potential medical applications are discussed.

On the Qualitative Comparison of Decisions Having Positive and Negative Features

Making a decision is often a matter of listing and comparing positive and negative arguments. In such cases, the evaluation scale for decisions should be considered bipolar, that is, negative and positive values should be explicitly distinguished. That is what is done, for example, in Cumulative Prospect Theory. However, contrary to the latter framework that presupposes genuine numerical assessments, human agents often decide on the basis of an ordinal ranking of the pros and the cons, and by focusing on the most salient arguments. In other terms, the decision process is qualitative as well as bipolar. In this article, based on a bipolar extension of possibility theory, we define and axiomatically characterize several decision rules tailored for the joint handling of positive and negative arguments in an ordinal setting. The simplest rules can be viewed as extensions of the maximin and maximax criteria to the bipolar case, and consequently suffer from poor decisive power. More decisive rules that refine the former are also proposed. These refinements agree both with principles of efficiency and with the spirit of order-of-magnitude reasoning, that prevails in qualitative decision theory. The most refined decision rule uses leximin rankings of the pros and the cons, and the ideas of counting arguments of equal strength and cancelling pros by cons. It is shown to come down to a special case of Cumulative Prospect Theory, and to subsume the “Take the Best” heuristic studied by cognitive psychologists.

'Just be Brave' - The Experiences of Young Witnesses in Criminal Proceedings in Northern Ireland

The last three decades have witnessed considerable interest in the position of children and young people acting as witnesses in criminal cases and on how best to facilitate them to give their best evidence and minimise the trauma involved. This paper presents the findings of a small-scale study in Northern Ireland examining the experiences of young witnesses pre-trial, during the trial and post-trial. Interviews were carried out with 37 young witnesses and 33 parents, and a questionnaire was completed by 16 volunteers and practitioners working in a local young witness support scheme. The findings indicate that the prospect and actuality of giving evidence in a criminal trial are anxiety-provoking and stressful for the majority of young witnesses. Particular issues identified are delay, both in terms of cases coming to court and in waiting times at court, the availability of pre-trial preparation and support, facilities at court buildings and the treatment of young people during cross-examination by defence lawyers. The paper concludes that there is a continuing need to strive for improvement, and that this necessarily involves reviewing the experiences of young witnesses and seeking their views on measures designed to enable them to give their best evidence. Copyright © 2013 John Wiley & Sons, Ltd.

The End of the Urban-Rural Divide?

The urban-rural divide in China was an entrenched feature of Chinese society in the Maoist era. This divide generated and continues to generate inequality as between the rural population and the urban population. In post-Deng China, legal and administrative distinctions between urban and rural have become blurred, especially with the development of rural-urban migration. Nevertheless, the urban-rural divide still exists, and the income of farmers is below that of urban residents. In this paper, it is argued that the emergence of the phenomenon of “quasi-commons” in rural China, crossing the “borders” of the urbanrural divide, may increase farmers’ income in the future and bridge this divide. The paper focuses on different forms of “quasi-commons” (the sharing and use of communal land) emerging in rural areas, including the farmland shareholding cooperatives and transforming rural land management rights into shares in joint ventures. There are divergent views held by Chinese academics and policy makers about “quasi-commons” in rural China, as well as the direction of change in the rural land system. However, most of the proposals for reform have been polarized between nationalization and privatization of rural land. Looking beyond this “boundary thinking” and drawing on the discourses of “the commons” (for example, the writings of Hardin, Heller and Ostrom), this paper analyses the theoretical models of both the nationalization and privatization schemes and their shortcomings. The present essay also analyses the prospect for, and the barriers to the emerging commons in rural China.

Controlling magnetoelectric coupling by nanoscale phase transformation in strain engineered bismuth ferrite

The magnetoelectric coupling in multiferroic materials is promising for a wide range of applications, yet manipulating magnetic ordering by electric field proves elusive to obtain and difficult to control. In this paper, we explore the prospect of controlling magnetic ordering in misfit strained bismuth ferrite (BiFeO3, BFO) films, combining theoretical analysis, numerical simulations, and experimental characterizations. Electric field induced transformation from a tetragonal phase to a distorted rhombohedral one in strain engineered BFO films has been identified by thermodynamic analysis, and realized by scanning probe microscopy (SPM) experiment. By breaking the rotational symmetry of a tip-induced electric field as suggested by phase field simulation, the morphology of distorted rhombohedral variants has been delicately controlled and regulated. Such capabilities enable nanoscale control of magnetoelectric coupling in strain engineered BFO films that is difficult to achieve otherwise, as demonstrated by phase field simulations.

Connectivity Mapping for Candidate Therapeutics Identification Using Next Generation Sequencing RNA-Seq Data

The advent of next generation sequencing technologies (NGS) has expanded the area of genomic research, offering high coverage and increased sensitivity over older microarray platforms. Although the current cost of next generation sequencing is still exceeding that of microarray approaches, the rapid advances in NGS will likely make it the platform of choice for future research in differential gene expression. Connectivity mapping is a procedure for examining the connections among diseases, genes and drugs by differential gene expression initially based on microarray technology, with which a large collection of compound-induced reference gene expression profiles have been accumulated. In this work, we aim to test the feasibility of incorporating NGS RNA-Seq data into the current connectivity mapping framework by utilizing the microarray based reference profiles and the construction of a differentially expressed gene signature from a NGS dataset. This would allow for the establishment of connections between the NGS gene signature and those microarray reference profiles, alleviating the associated incurring cost of re-creating drug profiles with NGS technology. We examined the connectivity mapping approach on a publicly available NGS dataset with androgen stimulation of LNCaP cells in order to extract candidate compounds that could inhibit the proliferative phenotype of LNCaP cells and to elucidate their potential in a laboratory setting. In addition, we also analyzed an independent microarray dataset of similar experimental settings. We found a high level of concordance between the top compounds identified using the gene signatures from the two datasets. The nicotine derivative cotinine was returned as the top candidate among the overlapping compounds with potential to suppress this proliferative phenotype. Subsequent lab experiments validated this connectivity mapping hit, showing that cotinine inhibits cell proliferation in an androgen dependent manner. Thus the results in this study suggest a promising prospect of integrating NGS data with connectivity mapping. © 2013 McArt et al.

Deriving the Edge: What's in a phase?

This article offers a critical conceptual discussion and refinement of Chomsky’s (2000, 2001, 2007, 2008) phase system, addressing many of the problematic aspects highlighted in the critique of Boeckx & Grohmann (2007) and seeking to resolve these issues, in particular the stipulative and arbitrary properties of phases and phase edges encoded in the (various versions of the) Phase Impenetrability Condition (PIC). Chomsky’s (2000) original conception of phases as lexical subarrays is demonstrated to derive these properties straightforwardly once a single assumption about the pairwise composition of phases is made, and the PIC is reduced to its necessary core under the Strong Minimalist Thesis (SMT)—namely, the provision of an edge. Finally, a comparison is undertaken of the lexical-subarray conception of phases with the feature-inheritance system of Chomsky 2007, 2008, in which phases are simply the locus of uninterpretable features (probes). Both conceptions are argued to conform to the SMT, and both converge on a pairwise composition of phases. However, the two conceptions of phases are argued to be mutually incompatible in numerous fundamental ways, with no current prospect of unification. The lexical-subarray conception of phases is then to be preferred on grounds of greater empirical adequacy.

De-linkage Processes and Grassroots Movements in Transitional Justice

Transitional justice literature has highlighted a negative relationship between enforced disappearances and reconciliation in post-conflict settings. Little attention has been paid to how human rights issues can become stepping-stones to reconciliation. The article explains the transformation of the Cypriot Committee on Missing Persons (CMP) from an inoperative body into a successful humanitarian forum, paving the way for the pro-rapprochement bi-communal grassroots mobilization of the relatives of the missing. By juxtaposing the experience of Cyprus with other societies confronting similar problems, the article shows how the issue of the missing can become a driving force for reconciliation. The findings indicate that a policy delinking humanitarian exhumations from the prospect of a wider political settlement facilitates positive transformation in protracted human rights problems and opens up a window of opportunity to grassroots actors.

Inhuman and Degrading Punishment, Dignity, and the Limits of Retribution

The recent judgment of the Grand Chamber of the European Court of Human Rights (ECtHR) in Vinter and others v United Kingdom provides a much needed clarification of the parameters of the prohibition on inhuman and degrading punishment under Article 3 of the European Convention on Human Rights (ECHR) as it applies to whole life orders of imprisonment under mandatory life sentences – essentially, life imprisonment without parole. The Grand Chamber’s judgment refines Strasbourg doctrine on life imprisonment and the prospect of release and illuminates key principles concerning inhuman and degrading punishment under Article 3 of the ECHR. This article considers the judgment’s profound significance in relation to both human rights and penology.

What’s in a (Party) Name?: Examining preferences, discipline, and social identity in a parliamentary free vote

In trying to understand the effects of political parties on shaping the voting behaviour of legislators, research has attempted the difficult task of separating the effects of preferences from rules used by party leaders to enforce discipline. However, little research has explored the prospect that party labels also reflect a social identity that is independent of legislators’ preferences and the rules used by party leaders to enforce discipline. In this study we examine that possibility, employing a data set that permits us to control both for leadership-based effects and legislator preferences on a 2000 free vote dealing with stem cell research. Using the British Representation Studies 1997 – which interviewed Members of Parliament regarding their preferences on several key issues related to the bill – we find significant evidence that party-as-identification plays a role in shaping how legislators vote, even after preferences and discipline are accounted for.

Universal tight binding model for chemical reactions in solution and at surfaces. II. Water

A revised water model intended for use in condensed phase simulations in the framework of the self consistent polarizable ion tight binding theory is constructed. The model is applied to water monomer, dimer, hexamers, ice, and liquid, where it demonstrates good agreement with theoretical results obtained by more accurate methods, such as DFT and CCSD(T), and with experiment. In particular, the temperature dependence of the self diffusion coefficient in liquid water predicted by the model, closely reproduces experimental curves in the temperature interval between 230 K and 350 K. In addition, and in contrast to standard DFT, the model properly orders the relative densities of liquid water and ice. A notable, but inevitable, shortcoming of the model is underestimation of the static dielectric constant by a factor of two. We demonstrate that the description of inter and intramolecular forces embodied in the tight binding approximation in quantum mechanics leads to a number of valuable insights which can be missing from ab initio quantum chemistry and classical force fields. These include a discussion of the origin of the enhanced molecular electric dipole moment in the condensed phases, and a detailed explanation for the increase of coordination number in liquid water as a function of temperature and compared with ice-leading to insights into the anomalous expansion on freezing. The theory holds out the prospect of an understanding of the currently unexplained density maximum of water near the freezing point. 

The Changing Context for Planning Education in the UK and the Prospects for Research-Led, Practice-Engaged Teaching

The UK’s Royal Town Planning Institute (RTPI) celebrates its centenary in 2014, marking 100 years of close relationships between university-based Planning Schools and a professional body focussed on planning practice. During this period, the context for university education and the very idea of planning has changed dramatically contributing to a continual renegotiation of the relationships between the planning profession and the educational institutions it accredits. These changes have been particularly acute in the last ten years where a number of factors have forced a rapid change in the nature of planning education in the UK. This has included a boom and then slump in the number of planning students linked to the national economic situation, a reorganisation of many planning schools and their merger with cognate disciplines such as geography and an increased focus of research output, rather than professional engagement the key institutional indicator of success. This last factor adds a particularly new dimension to the profession-university relationship, which could potentially lead to either a straining of tensions or a synergy through research-led teaching that could significantly benefit both.

This paper will briefly review the evolution of UK planning schools and the co-evolution of the main ideas informing planning education. It will then describe the current profile of UK planning schools, based on an extensive national survey conducted on behalf of the Royal Town Planning Institute. The paper will then critically review the main challenges and opportunities facing UK Planning Schools in the context of changes in both planning practice and higher education. It will then move on to the concept of research-led teaching, drawing on current practice in the UK and review how well this concept serves students and the idea of developing reflective planning practitioners. Finally, the paper will seek to draw broad lessons from the experience of the UK and reflect on the type of planning education that can best serve planning professions in a variety of international contexts in the future.