3,922 research outputs found
Origin of spectral broadening in pi-conjugated amorphous semiconductors
We present a study of the picosecond fluorescence dynamics of pi-conjugated semiconducting organic dendrimers in the solid state. By varying the degree of branching within the dendrons, referred to as the dendrimer generation, a control of intermolecular spacing of the emissive core and therefore of the lattice parameter for Forster-type energy transfer is achieved. This allows a distinction between spectral diffusion and excimer formation as the two main sources of spectral broadening in organic semiconductors. Whereas Forster-type dispersive spectral relaxation is independent of temperature but strongly dependent on the interchromophore distance, excimer formation is also strongly thermally activated due to temperature-dependent conformational changes and the influence of thermally activated dynamic disorder. The rapid spectral diffusion allows a determination of the excimer rise in the emission, which is shown to have a profound impact on the steady state luminescence properties of dendrimer films. We show that the dendrimer generation not only allows a microscopic control of intermolecular interactions but also a direct control of the rate of spectral diffusion. Implications for the design of novel materials for optoelectronic devices are discussed
Data informed learning: A next phase data literacy framework for higher education
This poster was presented at the Association for Information Science and Technologyâs (ASIS&T) Annual Meeting in St. Louis, MO on November 9, 2015. Accessing, using and managing data is increasingly recognized as an important learning outcome in higher education. Approaches to data literacy have typically been informed by information literacy. New approaches to information literacy have emerged that address how information is used in the different disciplinary contexts in which people learn and work. Successful approaches to data literacy will also need to address contextual concerns. Informed learning is an approach to information literacy that purposefully addresses contextual concerns by suggesting pedagogic strategies for enabling students to use information in ways that support discipline-focused learning outcomes. As part of an ongoing investigation, we advance data informed learning as a framework for data literacy in higher education that emphasizes how data are used to learn and communicate within disciplinary learning contexts. Drawing from informed learning, we outline principles and characteristics of data informed learning, and suggest future directions to investigate ways that data are used in real-world environments
New UltraCool and Halo White Dwarf Candidates in SDSS Stripe 82
A 2.5 x 100 degree region along the celestial equator (Stripe 82) has been
imaged repeatedly from 1998 to 2005 by the Sloan Digital Sky Survey. A new
catalogue of ~4 million light-motion curves, together with over 200 derived
statistical quantities, for objects in Stripe 82 brighter than r~21.5 has been
constructed by combining these data by Bramich et al. (2007). This catalogue is
at present the deepest catalogue of its kind. Extracting the ~130000 objects
with highest signal-to-noise ratio proper motions, we build a reduced proper
motion diagram to illustrate the scientific promise of the catalogue. In this
diagram disk and halo subdwarfs are well-separated from the cool white dwarf
sequence. Our sample of 1049 cool white dwarf candidates includes at least 8
and possibly 21 new ultracool H-rich white dwarfs (T_eff < 4000K) and one new
ultracool He-rich white dwarf candidate identified from their SDSS optical and
UKIDSS infrared photometry. At least 10 new halo white dwarfs are also
identified from their kinematics.Comment: 10 pages, 5 figures, published in MNRAS, minor text changes, final
versio
Spin relaxation dynamics of radical-pair processes at low magnetic fields
We report measurements of room-temperature spin-relaxation times and
of charge-carrier spins in a -conjugated polymer thin film under
bipolar injection and low (1\mbox{ mT}\lesssim B_0\lesssim 10\mbox{ mT})
static magnetic fields, using electrically detected magnetic resonant Hahn-echo
and inversion-recovery pulse sequences. The experiments confirm the correlation
between the magnetic-field sensitive observables of radical-pair processes,
which include both the spin-dependent recombination currents in organic
semiconductors and the associated spin-relaxation times when random local
hyperfine fields and external magnetic fields compete in magnitude. Whereas a
striking field dependence of spin-lattice relaxation exists in the low-field
regime, the apparent spin decoherence time remains field independent as the
distinction between the two is lifted at low fields.Comment: Manuscript: 14 pages, 4 figures; Supplemental Material: 13 pages, 7
figure
Size Acceptance: A Discursive Analysis of Online Blogs
This document is an Accepted Manuscript of an article published by Taylor & Francis Group in Fat Studies on 25 May 2018, available online at: https://doi.org/10.1080/21604851.2018.1473704. Under embargo until 25 May 2019.Dominant discourses of âfatnessâ and âfat peopleâ have implications for physical and mental health. Although alternative discourses such as âsize acceptanceâ exist, there has been little consideration of the ways in which these alternative arguments (and speakers) may be positioned to be heard. Using a discursive thematic analysis, the authors demonstrate that size acceptance online bloggers have created a community online that enables them to persuasively provide alternative claims to âexpertise,â which positions their views as credible and legitimate alternatives to those of more established authority figuresâsuch as health professionals. This has implications not only for the lived experience of fat people, but also for researchers by emphasizing the importance of exploring not just what is said, but how, if we are to understand how different articulated positions are to be persuasive.Peer reviewe
Prevention is better than cure, but...: Preventive medication as a risk to ordinariness?
Preventive health remains at the forefront of public health concerns; recent initiatives, such as the NHS health check, may lead to recommendations for medication in response to the identification of 'at risk' individuals. Little is known about lay views of preventive medication. This paper uses the case of aspirin as a prophylactic against heart disease to explore views among people invited to screening for a trial investigating the efficacy of such an approach. Qualitative interviews (N=46) and focus groups (N=5, participants 31) revealed dilemmas about preventive medication in the form of clashes between norms: first, in general terms, assumptions about the benefit of prevention were complicated by dislike of medication; second, the individual duty to engage in prevention was complicated by the need not to be over involved with one's own health; third, the potential appeal of this alternative approach to health promotion was complicated by unease about the implications of encouraging irresponsible behaviour among others. Though respondents made different decisions about using the drug, they reported very similar ways of trying to resolve these conflicts, drawing upon concepts of necessity and legitimisation and the special ordinariness of the particular dru
Morphology effects on spin-dependent transport and recombination in polyfluorene thin films
We have studied the role of spin-dependent processes on conductivity in
polyfluorene (PFO) thin films by conducting continuous wave (c.w.) electrically
detected magnetic resonance (EDMR) spectroscopy at temperatures between 10 K
and 293 K using microwave frequencies between about 100 MHz and 20 GHz as well
as pulsed EDMR at X-band. Variable frequency EDMR allows us to establish the
role of spin-orbit coupling in spin-dependent processes, pulsed EDMR probes
coherent spin motion effects. We used PFO for this study in order to allow for
the investigation of the effects of microscopic morphological ordering since
this material can adopt two distinct intrachain morphologies: an amorphous
(glassy) phase, and an ordered (beta) phase. In thin films of organic
light-emitting diodes (OLEDs) the appearance of a particular phase can be
controlled by deposition parameters, and is verified by electroluminescence
spectroscopy. We conducted multi-frequency c.w. EDMR, electrically detected
Rabi spinbeat experiments, Hahn-echo and inversion-recovery measurements.
Coherent echo spectroscopy reveals electrically detected electron spin-echo
envelope modulation (ESEEM) due to the precession of the carrier spins around
the protons. Our results demonstrate that while conformational disorder can
influence the observed EDMR signals, including the sign of the current changes
on resonance as well as the magnitudes of local hyperfine fields and charge
carrier spin-orbit interactions, it does not qualitatively affect the nature of
spin-dependent transitions in this material. At 293 K and 10 K, polaron-pair
recombination through weakly spin-spin coupled intermediate charge carrier pair
states is dominant, while at low temperatures, additional signatures of
spin-dependent charge transport through the interaction of polarons with
triplet excitons are seen in the half-field resonance of a triplet spin-1
species.Comment: 27 pages, 2 tables, 11 figures, full abstract in articl
M-health and health promotion: the digital cyborg and surveillance society
The new mobile wireless computer technologies and social media applications using Web 2.0 platforms have recently received attention from those working in health promotion as a promising new way of achieving their goals of preventing ill-health and promoting healthy behaviours at the population level. There is very little critical examination in this literature of how the use of these digital technologies may affect the targeted groups, in terms of the implications for how individuals experience embodiment, selfhood and social relationships. This article addresses these issues, employing a range of social and cultural theories to do so. It is argued that m-health technologies produce a digital cyborg body. They are able to act not only as prostheses but also as interpreters of the body. The subject produced through the use of m-health technologies is constructed as both an object of surveillance and persuasion and as a responsible citizen who is willing and able to act on the health imperatives issuing forth from the technologies and to present their body/self as open to continual measurement and assessment. The implications of this new way of surveilling the bodyâs health are discussed
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