461 research outputs found
Orbital photogalvanic effects in quantum-confined structures
We report on the circular and linear photogalvanic effects caused by
free-carrier absorption of terahertz radiation in electron channels on
(001)-oriented and miscut silicon surfaces. The photocurrent behavior upon
variation of the radiation polarization state, wavelength, gate voltage and
temperature is studied. We present the microscopical and phenomenological
theory of the photogalvanic effects, which describes well the experimental
results. In particular, it is demonstrated that the circular (photon-helicity
sensitive) photocurrent in silicon-based structures is of pure orbital nature
originating from the quantum interference of different pathways contributing to
the absorption of monochromatic radiation.Comment: 8 pages, 5 figures, two culumne
25 jaar moord in Nederland: Een trendanalyse van geslacht en leeftijd van slachtoffers van moord.
Deze studie beschrijft de trend in slachtofferschap van moord in Nederland in deperiode 1992-2016. Hierbij is gebruik gemaakt van de Dutch Homicide Monitor. Debevindingen laten zien dat het moordcijfer sinds de jaren negentig aan het dalen is.Deze daling is het grootst onder mannelijke en vrouwelijke slachtoffers in de leeftijd van20 tot en met 39 jaar. Dit onderzoek benadrukt het belang om de discussie rondom dedalende moordtrend te verschuiven naar een verdiepende analyse van geslacht en leeftijdbij slachtoffers.Security and Global Affair
The future of social is personal: the potential of the personal data store
This chapter argues that technical architectures that facilitate the longitudinal, decentralised and individual-centric personal collection and curation of data will be an important, but partial, response to the pressing problem of the autonomy of the data subject, and the asymmetry of power between the subject and large scale service providers/data consumers. Towards framing the scope and role of such Personal Data Stores (PDSes), the legalistic notion of personal data is examined, and it is argued that a more inclusive, intuitive notion expresses more accurately what individuals require in order to preserve their autonomy in a data-driven world of large aggregators. Six challenges towards realising the PDS vision are set out: the requirement to store data for long periods; the difficulties of managing data for individuals; the need to reconsider the regulatory basis for third-party access to data; the need to comply with international data handling standards; the need to integrate privacy-enhancing technologies; and the need to future-proof data gathering against the evolution of social norms. The open experimental PDS platform INDX is introduced and described, as a means of beginning to address at least some of these six challenges
Forecasting in the light of Big Data
Predicting the future state of a system has always been a natural motivation
for science and practical applications. Such a topic, beyond its obvious
technical and societal relevance, is also interesting from a conceptual point
of view. This owes to the fact that forecasting lends itself to two equally
radical, yet opposite methodologies. A reductionist one, based on the first
principles, and the naive inductivist one, based only on data. This latter view
has recently gained some attention in response to the availability of
unprecedented amounts of data and increasingly sophisticated algorithmic
analytic techniques. The purpose of this note is to assess critically the role
of big data in reshaping the key aspects of forecasting and in particular the
claim that bigger data leads to better predictions. Drawing on the
representative example of weather forecasts we argue that this is not generally
the case. We conclude by suggesting that a clever and context-dependent
compromise between modelling and quantitative analysis stands out as the best
forecasting strategy, as anticipated nearly a century ago by Richardson and von
Neumann
Socially sensitive lactation: Exploring the social context of breastfeeding
Many women report difficulties with breastfeeding and do not maintain the practice for as long as intended. Although psychologists and other researchers have explored some of the difficulties they experience, fuller exploration of the relational contexts in which breastfeeding takes place is warranted to enable more in-depth analysis of the challenges these pose for breastfeeding women. The present paper is based on qualitative data collected from 22 first-time breastfeeding mothers through two phases of interviews and audio-diaries which explored how the participants experienced their relationships with significant others and the wider social context of breastfeeding in the first five weeks postpartum. Using a thematic analysis informed by symbolic interactionism, we develop the overarching theme of ‘Practising socially sensitive lactation’ which captures how participants felt the need to manage tensions between breastfeeding and their perceptions of the needs, expectations and comfort of others. We argue that breastfeeding remains a problematic social act, despite its agreed importance for child health. Whilst acknowledging the limitations of our sample and analytic approach, we suggest ways in which perinatal and public health interventions can take more effective account of the social challenges of breastfeeding in order to facilitate the health and psychological well-being of mothers and their infants
Data, ideology, and the developing critical program of social informatics
The rapidly shifting ideological terrain of computing has a profound impact on Social Informatics's critical and empirical analysis of computerization movements. As these movements incorporate many of the past critiques concerning social fit and situational context leveled against them by Social Informatics research, more subtle and more deeply ingrained modes of ideological practice have risen to support movements of computerization. Among these, the current emphasis on the promises of data and data analytics presents the most obvious ideological challenge. In order to reorient Social Informatics in relation to these new ideological challenges, Louis Althusser's theory of ideology is discussed, with its implications for Social Informatics considered. Among these implications, a changed relationship between Social Informatics's critical stance and its reliance on empirical methods is advanced. Addressed at a fundamental level, the practice of Social Informatics comes to be reoriented in a more distinctly reflective and ethical direction
Generations of interdisciplinarity in bioinformatics
Bioinformatics, a specialism propelled into relevance by the Human Genome
Project and the subsequent -omic turn in the life science, is an
interdisciplinary field of research. Qualitative work on the disciplinary
identities of bioinformaticians has revealed the tensions involved in work in
this “borderland.” As part of our ongoing work on the emergence of
bioinformatics, between 2010 and 2011, we conducted a survey of United
Kingdom-based academic bioinformaticians. Building on insights drawn
from our fieldwork over the past decade, we present results from this survey
relevant to a discussion of disciplinary generation and stabilization. Not only
is there evidence of an attitudinal divide between the different disciplinary
cultures that make up bioinformatics, but there are distinctions between the
forerunners, founders and the followers; as inter/disciplines mature, they face
challenges that are both inter-disciplinary and inter-generational in nature
Datatrust: Or, the political quest for numerical evidence and the epistemologies of Big Data
Recently, there has been renewed interest in so-called evidence-based policy making. Enticed by the grand promises of Big Data, public officials seem increasingly inclined to experiment with more data-driven forms of governance. But while the rise of Big Data and related consequences has been a major issue of concern across different disciplines, attempts to develop a better understanding of the phenomenon's historical foundations have been rare. This short commentary addresses this gap by situating the current push for numerical evidence within a broader socio-political context, demonstrating how the epistemological claims of Big Data science intersect with specific forms of trust, truth, and objectivity. We conclude by arguing that regulators' faith in numbers can be attributed to a distinct political culture, a representative democracy undermined by pervasive public distrust and uncertainty
Electronic structure of the MO oxides (M=Mg, Ca, Ti, V) in the GW approximation
The quasiparticle band structures of nonmagnetic monoxides, MO (M=Mg, Ca, Ti,
and V), are calculated by the GW approximation. The band gap and the width of
occupied oxygen 2p states in insulating MgO and CaO agree with experimental
observation. In metallic TiO and VO, conduction bands originated from metal 3d
states become narrower. Then the partial densities of transition metal e_g and
t_2g states show an enhanced dip between the two. The effects of static
screening and dynamical correlation are discussed in detail in comparison with
the results of the Hartree-Fock approximation and the static Coulomb hole plus
screened exchange approximation. The d-d Coulomb interaction is shown to be
very much reduced by on-site and off-site d-electron screening in TiO and VO.
The dielectric function and the energy loss spectrum are also presented and
discussed in detail.Comment: 10 pages, 5 figure
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