33 research outputs found
Adoption and Diffusion of Group Support Systems in Tanzania
No full textTechnology, Policy and Managemen
Scour depth development at piles of different height under the action of cyclic (tidal) flow
No full textThe impact of cyclic (tidal) flow on scour at cylindrical monopiles in the live-bed regime has been examined on the basis of results from mobile sand bed flume experiments. Four tests were conducted with four 0.114 m diameter piles of differing stickup height placed across the 4 m wide test section of the Fast Flow Facility. The tidal tests Tide01, Tide02 and Tide03 had the same peak current speed in forward and reverse direction with different cycle periods to examine the role of cycle length on scour. The period in Tide01 was approximately halved in Tide02 and doubled in Tide03. A unidirectional test Uni01 was run for comparative purposes. The results have shown how the cycle length adopted in testing has a key controlling effect on the scour achieved in a fixed number of cycles. The scour data measured on two sides of the piles at 1 Hz are plotted both in time-series format and pairwise to illustrate the cyclic nature of the scour development and recycling of sediment within the scour hole. The effective work method of Link et al. (2016) provides a good correlation for the dimensionless scour depth. The cyclic behaviour of the scour difference across the pile diameter has been analysed in terms of a basal slope and the magnitude of the scour depth, akin to geotechnical testing of monopile response to cyclic loads. Comparison with field measurements of scour shows that the cyclic tests can achieve non-dimensional scour depths found in the field. A progressive reduction in the slope angle is demonstrated for increasing number of cycles but further investigation of the different angle observed in field and laboratory is required. Finally the effect of pile stickup height is evaluated using both published and the current data, and a modified value of the Sumer and Fredsøe coefficient is proposed for undirectional and tidal scour
The Neural Correlates of Declining Performance with Age: Evidence for Age-Related Changes in Cognitive Control
No full textThe neural system involved in cognitive control includes the anterior cingulate cortex (ACC) and the lateral prefrontal cortex (PFC). Neural activity within these structures is sensitive to aging. We investigated the hypothesis that decline in performance with age results in increased cognitive control, as indexed by greater activity within the ACC and lateral PFC. Using positron emission tomography we measured neural activity during a range of verbal decision-making tasks in 16 subjects aged 37–83 years. Conditions were separated behaviorally on the basis of their sensitivity to aging. This allowed the comparison of age-dependent and age-independent conditions, revealing the neural correlates of age-dependent decline in performance. We then modeled the relationship between age, decision type, performance, and frontal lobe activity. ACC activity was independently predicted by age and decision-making accuracy, indicating that in older individuals ACC response is more sensitive to declining performance. We also found strong functional connectivity between the ACC and lateral PFC and observed that activation of the lateral PFC was qualitatively different over time in different age groups. Thus, the ACC and lateral PFC show distinct responses to age-related decline in decision-making performance. This suggests that greater cognitive control is employed as individuals age and their performance declines
The Pathways for Intelligible Speech: Multivariate and Univariate Perspectives
No full textAn anterior pathway, concerned with extracting meaning from sound, has been identified in nonhuman primates. An analogous pathway has been suggested in humans, but controversy exists concerning the degree of lateralization and the precise location where responses to intelligible speech emerge. We have demonstrated that the left anterior superior temporal sulcus (STS) responds preferentially to intelligible speech (Scott SK, Blank CC, Rosen S, Wise RJS. 2000. Identification of a pathway for intelligible speech in the left temporal lobe. Brain. 123:2400-2406.). A functional magnetic resonance imaging study in Cerebral Cortex used equivalent stimuli and univariate and multivariate analyses to argue for the greater importance of bilateral posterior when compared with the left anterior STS in responding to intelligible speech (Okada K, Rong F, Venezia J, Matchin W, Hsieh IH, Saberi K, Serences JT,Hickok G. 2010. Hierarchical organization of human auditory cortex: evidence from acoustic invariance in the response to intelligible speech. 20: 2486-2495.). Here, we also replicate our original study, demonstrating that the left anterior STS exhibits the strongest univariate response and, in decoding using the bilateral temporal cortex, contains the most informative voxels showing an increased response to intelligible speech. In contrast, in classifications using local "searchlights” and a whole brain analysis, we find greater classification accuracy in posterior rather than anterior temporal regions. Thus, we show that the precise nature of the multivariate analysis used will emphasize different response profiles associated with complex sound to speech processin
Lexical retrieval constrained by sound structure: The role of the left inferior frontal gyrus
No full textContains fulltext :
17163.pdf (Publisher’s version ) (Closed access)Positron emission tomography was used to investigate two competing hypotheses about the role of the left inferior frontal gyrus (IFG) in word generation. One proposes a domain-specific organization, with neural activation dependent on the type of information being processed, i.e., surface sound structure or semantic. The other proposes a process-specific organization, with activation dependent on processing demands, such as the amount of selection needed to decide between competing lexical alternatives. In a novel word retrieval task, word reconstruction (WR), subjects generated real words from heard non-words by the substitution of either a vowel or consonant. Both types of lexical retrieval, informed by sound structure alone, produced activation within anterior and posterior left IFG regions. Within these regions there was greater activity for consonant WR, which is more difficult and imposes greater processing demands. These results support a process-specific organization of the anterior left IFG
Emotional avatars:videos of animated emotional facial expressions
No full textThis collection of videos depicts emotional facial expression animations which were used as part of a doctoral research project. The animations include individual universal expressions of emotion, as well as transitions between emotions, where the timing of movements have been manipulated. These videos are being made freely available for use in other projects and research under a creative commons licence (CC BY-NC-ND-3.0) See http://creativecommons.org/licenses/by-nc-nd/3.0/. If the videos are used as part of any activity that leads to publication, you are requested to credit the author. The videos were discussed in: Sloan, R.J.S., Robinson, B., Scott-Brown, K., Moore, F. and Cook, M. 2010. Choreographing emotional facial expressions. Journal of Computer Animation and Virtual Worlds, 21(3-4), pp.203-213. DOI: 10.1002/cav.339
Emotional avatars:videos of animated emotional facial expressions
No full textThis collection of videos depicts emotional facial expression animations which were used as part of a doctoral research project. The animations include individual universal expressions of emotion, as well as transitions between emotions, where the timing of movements have been manipulated. These videos are being made freely available for use in other projects and research under a creative commons licence (CC BY-NC-ND-3.0) See http://creativecommons.org/licenses/by-nc-nd/3.0/. If the videos are used as part of any activity that leads to publication, you are requested to credit the author. The videos were discussed in: Sloan, R.J.S., Robinson, B., Scott-Brown, K., Moore, F. and Cook, M. 2010. Choreographing emotional facial expressions. Journal of Computer Animation and Virtual Worlds, 21(3-4), pp.203-213. DOI: 10.1002/cav.339
Reading fluent speech from talking faces: Typical brain networks and individual differences
No full textListeners are able to extract important linguistic information by viewing the talker's face—a process known as “speechreading.” Previous studies of speechreading present small closed sets of simple words and their results indicate that visual speech processing engages a wide network of brain regions in the temporal, frontal, and parietal lobes that are likely to underlie multiple stages of the receptive language system. The present study further explored this network in a large group of subjects by presenting naturally spoken sentences which tap the richer complexities of visual speech processing. Four different baselines (blank screen, static face, nonlinguistic facial gurning, and auditory speech) enabled us to determine the hierarchy of neural processing involved in speechreading and to test the claim that visual input reliably accesses sound-based representations in the auditory cortex
Be concrete to be comprehended:consistent imageability effects in semantic dementia for nouns, verbs, synonyms and associates
No full textThere are two contrasting views on the nature of comprehension impairment in semantic dementia: (a) that it stems from degradation of a pan-modal "hub" that represents core conceptual knowledge or (b) that it results from degradation of modality-specific visual feature knowledge. These theories make divergent predictions regarding comprehension of concrete versus abstract words in the disorder. The visual hypothesis predicts that concrete words should be particularly impaired because they depend heavily on visual information. In contrast, the pan-modal hub hypothesis holds that all types of knowledge are affected but predicts less severe impairment of concrete words because they have richer and more detailed semantic representations than abstract words. We investigated concreteness effects in the comprehension of six SD patients. Across nouns, verbs, synonymous and associative relationships, a clear and consistent pattern emerged: concrete words were always comprehended more successfully than abstract words. These findings extend those of previous studies and suggest that conceptual impairment in SD is not confined to concepts that rely on visual information. Instead, all types of knowledge are affected by the progressive deterioration of modality-invariant representations (required for coherent pan-modal concepts). Concrete words succumb less quickly by virtue of their richer and more detailed semantic representations.</p
