8,960 research outputs found
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Room reflections and constancy in speech-like sounds: within-band effects
The experiment asks whether constancy in hearing precedes or follows grouping. Listeners heard speech-like
sounds comprising 8 auditory-filter shaped noise-bands that had temporal envelopes corresponding to those
arising in these filters when a speech message is played. The âcontextâ words in the message were ânext youâll
get _to click onâ, into which a âsirâ or âstirâ test word was inserted. These test words were from an 11-step
continuum that was formed by amplitude modulation. Listeners identified the test words appropriately and quite
consistently, even though they had the âroboticâ quality typical of this type of 8-band speech. The speech-like
effects of these sounds appears to be a consequence of auditory grouping. Constancy was assessed by comparing
the influence of room reflections on the test word across conditions where the context had either the same level
of reflections, or where it had a much lower level. Constancy effects were obtained with these 8-band sounds,
but only in âmatchedâ conditions, where the room reflections were in the same bands in both the context and the
test word. This was not the case in a comparison âmismatchedâ condition, and here, no constancy effects were
found. It would appear that this type of constancy in hearing precedes the across-channel grouping whose
effects are so apparent in these sounds. This result is discussed in terms of the ubiquity of grouping across
different levels of representation
Controlling the polarisation correlation of photon pairs from a charge-tuneable quantum dot
Correlation between the rectilinear polarisations of the photons emitted from
the biexciton decay in a single quantum dot is investigated in a device which
allows the charge-state of the dot to be controlled. Optimising emission from
the neutral exciton states maximises the operating efficiency of the biexciton
decay. This is important for single dot applications such as a triggered source
of entangled photons. As the bias on the device is reduced correlation between
the two photons is found to fall dramatically as emission from the negatively
charged exciton becomes significant. Lifetime measurements demonstrate that
electronic spin-scattering is the likely cause.Comment: 3 figure
Cortical excitability and the shape of the haemodynamic response
Individual differences in the temporal dynamics of the haemodynamic response can reflect cortical excitation and can reveal underlying cortical physiology. Here, we show differences in the shape of the haemodynamic response that are dependent on stimulus parameters. Two sets of visual stimuli were used varying in parameters that are known to manipulate the haemodynamic response in the visual cortex. We measured the oxyhaemoglobin response using near infrared spectroscopy. The first set of stimuli comprised chromatic square-wave gratings that varied with respect to the separation in the CIE UCS chromaticities of the alternating bars. The gratings with large separations in chromaticity evoked an oxyhaemoglobin response with greater amplitude, consistent with greater activation of the visual cortex. The second set of stimuli comprised horizontal achromatic gratings that (1) were static, (2) drifted at a constant velocity towards fixation, or (3) reversed direction every half spatial cycle to create a vertical vibrating motion. Although the three types of grating had a similar effect on the amplitude of the oxyhaemoglobin response, the moving gratings (2 and 3) evoked a steeper decrease in oxyhaemoglobin concentration after stimulus-offset. The steeper slope appears to reflect the post-stimulus undershoot and the slope may provide a correlate of cortical excitability when the amplitude of the haemodynamic response has saturated
Inversion of exciton level splitting in quantum dots
The demonstration of degeneracy of exciton spin states is an important step toward the production of entangled photon pairs from the biexciton cascade. We measure the fine structure of exciton and biexciton states for a large number of single InAs quantum dots in a GaAs matrix; the energetic splitting of the horizontally and vertically polarized components of the exciton doublet is shown to decrease as the exciton confinement decreases, crucially passing through zero and changing sign. Thermal annealing is shown to reduce the exciton confinement, thereby increasing the number of dots with splitting close to zero
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Measuring velocity and turbulent diffusivity in wall-flow filters using compressed sensing magnetic resonance
Gas-phase compressed sensing magnetic resonance methods have been used to image gas flow velocity and turbulent diffusivity in wall-flow particulate filters. Two-dimensional magnetic resonance velocity imaging was used to observe the local distribution of gas velocity in the direction of superficial flow (z) in the entrance and exit regions of the filter at an in-plane spatial resolution of 140 ”m (x) à 140 ”m (y) and 140 ”m (x) à 390 ”m (z) perpendicular to and parallel with the direction of superficial flow, respectively. Images were acquired in 14 min. Three-dimensional images of the turbulent diffusivity were acquired at a spatial resolution of 280 ”m (x) à 280 ”m (y) à 1250 ”m (z) for channel Reynolds numbers, Rec, of 210, 360, 720 and 1140. These data provide evidence of regions of turbulence inside the filter that has not been predicted by earlier numerical simulations. For Rec = 1140, a three-dimensional velocity image was also obtained at the same spatial resolution as the image of turbulent diffusivity; the data acquisition time was 2 h. Co-registration of these two images enables visualisation of the spatial extent and magnitude of these two characteristics of the flow field.JDC would like to thank Johnson Matthey and the EPSRC for a CASE award (award reference 1628588)
Charitiesâ use of Twitter : exploring social support for women living with and beyond breast cancer
Twitter is one social media platform that enables those experiencing breast cancer to access support from others. This study explores how cancer charities provide support to women living with and beyond breast cancer (LWBBC) through their Twitter feeds. Seven hundred and seventy-two tweets from seven purposively sampled cancer charities were used to explore Twitter posts made relating to social support. Two questions were posed: (1) what type of support is positioned by cancer charities on Twitter for women LWBBC and (2) what themes emerge from tweet content pertaining to support for women LWBBC? Using a peer-reviewed typology of âsocial supportâ [Rui, J., Chen, Y., & Damiano, A. (2013). Health organizations providing and seeking social support: A twitter-based content analysis. Cyberpsychology, Behavior, And Social Networking, 16(9), 669â673. doi:10.1089/cyber.2012.0350], a deductive content analysis was utilised to identify informational, instrumental or emotional social support tweets (nâ=â199). Over half (56%) of tweets offered informational support; 27% provided or sought instrumental support and 18% related to emotional support. Interestingly, 74.3% (nâ=â573) of tweets were not related to providing or seeking social support. An inductive qualitative thematic analysis of the 199 tweets identified the focus (i.e., themes) of support. Three themes were identified: (1) raising awareness, (2) focusing on the future and (3) sharing stories. Cancer charities predominantly use Twitter to signpost women to informational resources and to seek instrumental support to meet charitable objectives. As the number of women LWBBC continues to increase, this study provides valuable insight into how charities represent themselves on Twitter in relation to the social support needs of women LWBBC
Physical activity, sedentary time and physical capability in early old age: British birth cohort study
To investigate the associations of time spent sedentary, in moderate-to-vigorous-intensity physical activity (MVPA) and physical activity energy expenditure (PAEE) with physical capability measures at age 60-64 years
Participation in Free and Open Source Communities: An Empirical Study of Community Membersâ Perceptions
Although the defining factors of Free and Open Source Software (FOSS) are generally seen as the availability and accessibility of the source code, it is what these facilitate that is perhaps of more significance. Source code availability allows the sharing of code, skills, knowledge, and effort, focused on a particular piece of software under development. The result of this is the FOSS community, which although often perceived as a single group, is actually many small groups, each bound by a common interest in a particular piece of software and using the Internet as a communication medium. Although there have been studies focusing on the motivation of FOSS developers to contribute to software, there has been little investigation into the motives, attitudes, and the culture within the communities as a whole. There is much more to most of these communities than software development. Many also have extensive support networks for the use of software, portals for research, and social facilities. This paper describes the results of an investigation into how FOSS community members perceive the communities that they belong to, their reasons for being in the community, and the manner in which they participate
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